External Review Draft No. 1
April 1980
Draft
Do Not Quote or Cite
Air Quality Criteria
for Participate Matter
and Sulfur Oxides
Volume
Welfare Effects
NOTICE
This document is a preliminary draft. It has not been formally released by EPA and should not at this stage be
construed to represent Agency policy. It is being circulated for comment on its technical accuracy and
policy implications.
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
-------
External Review Draft No. 1
April 1980
Draft
Do Not Quote or Cite
Air Quality Criteria
for Particulate Matter
and Sulfur Oxides
Volume
Welfare Effects
NOTICE
This document is a preliminary draft. It has not been formally released by EPA and should not at this stage be
construed to represent Agency policy. It is being circulated for comment on its technical accuracy and policy
implications.
Environmental Criteria and Assessment Office
Office of Health and Environmental Assessment
Office of Research and Development
U.S. Environmental Protection Agency
Research Triangle Park, N.C. 27711
-------
Preface to Volume III
A concern for human welfare implies a concern for the biological and
physical realms of man's environment. This volume assesses the effects of
sulfur oxides and particulate matter on human welfare by examining four
specific topics: effects on vegetation and ecosystems (Chapter 7), acidic
precipitation (Chapter 8), visibility and climate (Chapter 9), and materials
(Chapter 10).
Sulfur oxides and particulate matter induce a variety of specific
symptoms in vegetation. These effects range from visible injury to latent
declines in yield or, conversely, beneficial effects under certain conditions.
Several variables influence these outcomes, including pollutant concentration,
mode of exposure, ambient conditions, and various characteristics of the
vegetation itself. In addition, the specific form of particulate matter is,
of course, an important variable.
As the level of SCL increases, plants develop more predictable and
visible symptoms of injury. In research tests, important agricultural crops
such as alfalfa, timothy, range grasses, soybean, barley, wheat, cabbage,
lettuce, spinach, tobacco, cucumber, eggplant, pea, and kidney bean suffered
necrotic leaf injury or reduced yield.
Acidic precipitation is relevant to an evaluation of the impact of sulfur
oxides on human welfare. The pH of precipitation in various regions appears
to have declined (become more acidic) in recent history. An increase in the
acidity of rain and snow has serious implications for terrestrial and aquatic
ecosystems. Thus, in this volume, the effects of acidic precipitation on
aquatic organisms and terrestrial vegetation and soils are considered in some
detail. In addition, the causes and characteristics of acidic precipitation
are examined.
iii
-------
The precipitation (wet deposition) of acidic oxides of sulfur and
nitrogen is only one aspect of atmospheric deposition. Dry deposition also
distributes similar chemical substances in gases, aerosols, and particulate
matter. Thus, the biological effects of acidic precipitation or dry
deposition are chemically indistinguishable. But geographically, acidic
precipitation has been associated with regions in which man-made emissions of
sulfur and nitrogen oxides are highest. The combustion of fossil fuels,
certain industrial processes (such as smelting of ore), auto exhausts, and
nitrogen fertilizers used in agricultural and forest lands are primary -
man-made sources of acidic precipitation pollution.
The reduction (or extinction) of fish populations in hundreds of
Minnesota, New York State, and Canadian lakes is believed to be associated with
aquatic acid stress. Similar reports concern lakes and streams in other U.S.
and Canadian regions.
One of the most conspicuous effects of air pollution, especially
particulate matter, is the degradation of man's view of his environment.
Atmospheric particles scatter and absorb light, creating haze which reduces
the clarity and range of vision and which distorts aesthetic features of the
landscape. In addition, atmospheric particles can potentially affect meteoro-
logical conditions, including precipitation quantity and quality, cloudiness,
and solar radiation.
Sulfates primarily exist in the atmosphere as fine particles. Being
hygroscopic (able to absorb moisture from the air), their effect on visibility
varies with degrees of humidity. This complicates predicting the effect of
sulfates on visibility reduction. Increasing emissions of sulfur oxides have,
however, been linked with similar increases in haziness.
IV
-------
Do increased concentrations of airborne participate warm or cool
the earth? There is little agreement on an answer to that question.
However, in urban areas, inadvertent changes in cloudiness have been
well established. Haze is also strongly suspected (though it is not yet
proved) to affect agricultural productivity by causing solar radiation
decreases.
Finally, this volume examines the tangible effects of sulfur oxides
and particulate matter on man's artifacts. The corrosion and the soiling
of materials are damaging processes that can have significant economic
implications. For example, corrosion of specific metal coatings, such as
zinc (as in galvanized metal), is accelerated by sulfur dioxide
(S02) and acid sulfates. Experiments indicate that one part SCL will
react with iron and form about 40 parts of rust.
Sulfur oxides and particulate matter also deteriorate and soil
buildings and painted surfaces. Deterioration of limestone and marble
is evident, but the economic loss, especially to works of art, is difficult
to assess.
-------
CONTENTS
7 EFFECTS ON VEGETATION 7-1
7.1 GENERAL INTRODUCTION AND APPROACH 7-1
7.1.1 Origin and Distribution of Particles 7-1
7.1.2 Phytotoxic Forms of Particles 7-2
7.1.3 Origins and Distribution of Sulfur 7-3
7.1.4 Phytotoxic Forms of Sulfur 7-3
715 Relationships Between Particles and Sulfur 7-5
7. 2 SYMPTOMATOLOGY OF SOp-INDUCED PLANT INJURY 7-6
7.2.1 Introduction 7-6
7.2.2 Cellular and Biochemical Changes 7-8
7.2.3 Growth and Yield Effects Without Expression of
Visible Symptoms 7-10
7.2.4 Chronic Injury Due to S02 Exposure 7-17
7.2.5 Acute Injury Due to SO, Exposure 7-19
7.2.6 Classification of Plant Sensitivity 7-19
7.2.6.1 Introduction 7-19
7.2.6.2 Plant Sensitivity to SO, 7-20
7.3 DOSE-RESPONSE RELATIONSHIPS—SO, 7-22
7.4 PLANT EXPOSURE TO SULFUR DIOXIDE 7-51
7.4.1 Deposition Rates of Sulfur Compounds 7-51
7.4.1.1 Dry Deposition 7-51
7.4.1.2 Wet Deposition 7-51
7.4.2 Routes and Methods of Entry Into the Plant 7-53
7.4.3 Beneficial Effects 7-56
7.4.4 Tissue Concentration 7-57
7.5 INTERACTIVE EFFECTS ON PLANTS WITH THE ENVIRONMENT—SO, 7-58
7.5.1 Physical Factors 7-58
7.5.1.1 Temperature 7-58
7.5.1.2 Relative Humidity 7-59
7.5.1.3 Light 7-59
7.5.1.4 Edaphic Factors 7-60
7.5.2 Biotic Factors 7-61
7.6 INTERACTIVE EFFECTS OF SO, WITH OTHER POLLUTANTS INCLUDING
PARTICULATE MATTER 7-65
7.6.1 Introduction 7-65
7.6.1.1 Sulfur Dioxide and Ozone 7-65
7.6.1.2 Sulfur Dioxide and Nitrogen Dioxide 7-71
7.6.1.3 Sulfur Dioxide and Hydrogen Fluoride 7-72
7.6.1.4 Sulfur Dioxide, Nitrogen Dioxide, and
Ozone 7-72
7.6.2 Particles in Combination with Other Pollutants 7-74
7.7 SYMPTOMATOLOGY OF PARTICLE-INDUCED INJURY 7-75
7.7.1 Dusts 7~75
7.7.2 Heavy Metals, Arsenic, and Boron - • • '~''
7.7.2.1 Arsenic '~'1
7.7.2.2 Cadmium '~/y
-------
7.7.2.3 Copper 7-79
7.7.2.4 Lead 7-79
7.7.2.5 Nickel 7-79
7.7.3 Classification of Plant Sensitivity-Particles 7-80
7. 8 DOSE-RESPONSE RELATIONSHIPS—PARTICULATE MATTER 7-82
7.9 PLANT EXPOSURE TO PARTICULATE MATTER 7-86
7.9.1 Deposition Rates 7-86
7.9.2 Routes and Methods of Entry Into Plants 7-86
7.9.2.1 Direct Entry Through Foliage 7-86
7.9.2.2 Indirect Entry Through Roots 7-88
7.10 INTERACTIVE EFFECTS ON PLANTS WITH THE ENVIRONMENT--
PARTICULATE MATTER 7-88
7.10.1 Biotic Interactions 7-88
7.11 EFFECTS OF SULFUR DIOXIDE AND PARTICULATE MATTER ON
NATURAL ECOSYSTEMS 7-89
7.11.1 Introduction 7-89
7.11.2 Sulfur in Natural Ecosystems 7-94
7.11.2.1 The Sulfur Cycle in Natural Ecosystems 7-94
7.11.3 Ecosystem Responses to Sulfur Dioxide 7-95
7.11.3.1 Kaybob I and II Gas Plants, Fox Creek,
Alberta, Canada 7-95
7.11.3.2 West Whitecourt Gas Plant, Whitecourt,
Alberta, Canada 7-99
7.11.3.3 Montana Grasslands 7-102
7.11.4 Response of Producers, Consumers and Decomposers
to Sulfur Dioxide 7-106
7.11.4.1 Response of Producers to Sulfur Dioxide.... 7-106
7.11.4.2 Response of Consumers and Decomposers to
Sulfur Dioxide 7-122
7.11.4.3 Response of Natural Ecosystems to the
Interaction of S0£ With Other Pollutants... 7-124
7.11.5 Response of Natural Ecosystems to Particulate Matter. 7-126
7.11.6 Discussion and Conclusions 7-134
7.12 EXECUTIVE SUMMARY 7-143
7.13 REFERENCES 7-151
VII
-------
LIST OF TABLES
Page
7-1 Relationships between certain biochemical effects and plant
injury 7-11
7-2 Partial list of plants known to be sensitive to S0? under field
exposure conditions 7-21
7-3 Progressive increase in the degrees of injury of radish with
increasing SCL concentrations 7-26
7-4 Sulfur dioxide concentrations causing visible injury to various
sensitivity groupings of vegetation 7-28
7-5 Dose-response information summarized from literature pertaining
to cultivated agronomic crops as related to foliar, yield, and
specific effects induced by increasing S0? dose 7-29
7-6 Dose-response information summarized from literature pertaining
to forest tree species as related to foliar, yield, and specific
effects induced by increasing SC^ dose 7-40
7-7 Dose-response information summarized from literature pertaining
to native plants as related to foliar, yield and specific effects
induced by increasing S0? dose 7-45
7-8 Results of several experimental investigations of SCL deposition
by various scientists 7-52
7-9 Effects of sulfur dioxide on plant diseases 7-62
7-10 Relative sensitivities of some microorganisms to gaseous sulfur
dioxide 7-64
7-11 Effects of sulfur dioxide alone and in combination with other
pollutants on selected plants at 0.50 ppm or less 7-66
7-12 Some reported toxic effects (visual symptoms) of heavy metals,
arsenic, and boron following accumulations in soils 7-78
7-13 Plants sensitive to heavy metals, arsenic, and boron as accu-
mulated in soils following potential atmospheric depositions 7-81
7-14 Effect of cement kiln dust on bean leaves as determined by obvious
tissue damage and C02 exchange 7-84
vm
-------
2 2
7-15 Effect of a dust containing cadmium (5.2 mg/m,,), lead (488 mg/m ),
copper (20.8 mg/m ), and manganese (72.8 mg/m ) (total
application) on yield (dry weight) and foliar/flower injury
after application once a week for 4 weeks 7-85
7-16 Examples of ecosystem benefits that either directly affect human
welfare or underlie the more demonstrable economic and esthetic
products derived from natural ecosystems 7-93
7-17 Comparison of global land sulfur cycle with regional sulfur cycle
of northeastern United States (10 tons of SO./year) 7-97
7-18 Documented direct S0? effects on individual plants 7-108
7-19 Summary of the effects of selected abiotic stresses on natural
ecosystems 7-136
7-20 Conceptual scheme for categorizing ecosystem-level responses to
S0? as a function of stress level and subsequent plant community
response 7-139
7-21 Fate and distribution of SO* and its derivatives in natural
ecosystems 7-141
-------
LIST OF FIGURES
Number Page
7-1 Flow diagram shows the tropospheric sulfur cycle 7-4
7-2 Conceptual model shows factors involved in air pollution
effects (dose-response) on vegetation 7-24
7-3 Nutrient cycles and energy are closely interrelated as
this model indicates 7-91
7-4 Schematic diagram shows sources and sinks of atmospheric
sulfur compounds 7-96
-------
CONTENTS
8. ACIDIC PRECIPITATION 8-1
8.1 INTRODUCTION 8-1
8.2 EFFECTS OF ACIDIC PRECIPITATION 8-9
8.2.1 Ecosystems 8-9
8.2.2 Aquatic Ecosystems 8-17
8.2.3 Effects on Fish 8-19
8.2.4 Effects on Aquatic Ecosystem Dynamics 8-28
8.2.4.1 Effect on Primary Production and Food Web . . 8-28
8.2.4.2 Effects on Decomposition 8-34
8.2.4.3 Effects on Vertebrates Other Than Fish. . . . 8-42
8.2.4.4 Water Chemistry 8-44
8.2.4.5 Metal Concentrations in Acidified Waters. . . 8-49
8.2.4.6 Effects on Human Health 8-51
8.2.5 Acidification of Lakes 8-54
8.3 SENSITIVE AREAS 8-58
8.3.1 Aquatic Ecosystems 8-58
8.3.2 Terrestrial Ecosystems 8-65
8.3.3 Aquatic and Terrestrial 8-68
8.4 EFFECTS ON TERRESTRIAL ECOSYSTEMS 8-71
8.4.1 Effects of Acidic Precipitation on Vegetation 8-72
8.4.1.1 Direct Damage to Tissues 8-72
8.4.1.2 Leaching of Nutrients 8-75
8.4.1.3 Indirect Effects on Plants 8-76
8.4.2 Precipitation as a Source of Nutrients 8-92
8.5 THE VALUE OF A NATURAL ECOSYSTEM 8-102
8.6 EFFECTS OF ACIDIC PRECIPITATION ON MATERIALS 8-108
8.7 ACIDIC PRECIPITATION 8-112
8.7.1 Causes of Acidic Precipitation 8-112
8.7.2 Formation and Composition 8-117
8.7.3 Long Term Trends 8-123
8.7.4 Seasonal Variations in pH 8-126
8.7.5 Geographic Extent of Acidic Rain 8-136
8.7.6 Sulfur and Nitrogen Oxides and the Formation of
Acidic Precipitation 8-142
8.7.7 Seasonal Variations in Sulfate and Nitrates 8-155
8.8 REFERENCES 8-158
XI
-------
LIST OF FIGURES
Figures page
8-1 Law of tolerance 8-11
8-2 Frequency distribution of pH and fish population status'in
Adirondack Mountain lakes greater than 610 meters elevation.
Fish population status determined by survey gill netting during
the summer of 1975 8-20
8-3 Frequency distribution of pH fish population status in 40
Adirondack lakes greater than 610 meters elevation, surveyed
during yhe period 1929-1937 and again in 1975 8-20
8-4 Pathways among the producers and consumers of an ecosystem . . . 8-30
8-5 Generalized scheme of food relationships in a lake. Efficiency
in a lake. Efficiency in utilization of food increases in the
higher consumer levels 8-36
8-6 The number of species of crustacean zooplankton observed in 57
lakes during a synoptic survey of lakes in southern Norway . . . 8-38
8-7 Cumulated mortality of Gammarus lacustris adults at several pH
levels 8-40
8-8 8-60
8-9 Equivalent percent composition of major ions in Adirondack lake
surface waters (215 lakes) sampled in June 1975 8-62
8-10 Percent frequency distribution of sulfate concentrations in
surface water from lakes in sensitive regions 8-63
8-11 Relationship between precipitation excess sulfate and lake
excess sulfate for lakes in Norway and the Adirondacks.
(A = mean lake and precipitation sulfate for the Adirondack
region) 8-64
8-12 Soils of the Eastern United States sensitive to acid rainfall. . 8-69
8-13 Showing the exchangeable ions of a soil with pH~7, the^ soil
solution composition, and the replacement of Na by H from
acid rain 8-83
8-14 The weighted annual average of NO., concentration in bulk
precipitation at Ithaca, N. Y. as a function of time 8-94
8-15 Trajectory map indicating source strengths for S0? emissions
affecting the eastern United States. Emission rates of S02
are shown by shading of the map. 500 mbar trajectory corridors
from Cogbill and Likens are superimposed on the map to indicate
directions of movement of air masses at ca. 5500 m altitude
for several days preceding specific rain events at Ithaca,
New York. The numbers between the lines are mean pH values
for rain events associated with each trajectory corridor .... 8-114
8-15a 8-115
8-15b 8-116
8-16 The weighted annual average pH of precipitation in the eastern
U.S. in 1955-56, 1965-66, and 1972-73 8-121
8-17 Spread of acid rain, 1975-76 8-122
8-18 Cation inputs in precipitation at Hubbard Brook, New Hampshire.
(A) Annual input of hydrogen ion, 1964-73; (B) Annual precipita-
tion, 1964-1973; (C) Comparison of annual input of hydrogen ion
and annual input of total cations less hydrogen ion plotted
against amount of annual precipitation 8-125
xii
-------
Figure Page
8-19 History of acidic precipitation at various sites in and adjacent
to State of New York 8-127
8-20 Location of acidic precipitation monitoring stations 8-129
8-21 Sulfate monthly weighted ion concentrations 8-133
8-22 Seasonal variations in pH (A) and ammonium and nitrate
concentrations (B) in wet-only precipitation at Gainesville,
Florida. Values are monthly volume-weighted averages of levels
in rain from individual storms 8-134
8-23 Seasonal variation of precipitation pH in the New York
Metropolitan Area 8-135
8-24 Theoretical relationship between major chemical ions in
precipitation (see text). Any lack of equivalence between
aniorps and cations can be envisioned to exist as a misestimate
of H concentration 8-137
8-25 Hydrogen ion deposition in precipitation plotted against (A)
nitrate deposition and (B) sulfate deposition. Data from
Hubbard Brook, New Hampshire, 1964-1973 8-145
8-26 Trends in mean annual concentrations of sulfate, ammonia, and
nitrate in precipitation. (A), (B), and (C) present long-term
data for Ithaca, New York; (D) presents data for eight years
averaged over eight sites in New York and one in Pennsylvania.
One point in (A), for 1946-47, is believed to be an anomaly
(see Likens for discussion) 8-147
8-27 Comparison of weighted mean monthly concentrations of sulfate
in incident precipitation collected in Walker Branch Watershed,
Tenn. (WBW) and four MAP3S precipitation chemistry monitoring
stations in New York (<>, 0), Pennsylvania (A), and Virginia
(n) 8-157
xm
-------
LIST OF TABLES
Table Page
8-1 Components of the environment of a terrestrial organism,
vegetation, or biological community . . . 8-15
8-2 Summary of effects of pH changes on fish . . . . . . ...... 8~22
8-3 Approximate pH at which fish in the LA Cloche Mountain Lakes,
Canada, stopped reproduction 8-26
8-4 Changes in aquatic biota likely to occur with increasing
acidity 8-45
8-5 Summary of effects on aquatic organisms with decreasing pH . . . 8-46
8-6 Chemical composition (mean ± standard deviation) of acid lakes
(pH <5) in regions receiving highly acidic precipitation (pH
<4.5), and of soft-water lakes in areas not subject to highly
acidic precipitation (pH >4.8) less s w = concentrations after
subtracing the seawater contribution according to the procedure
explained in the text 8-48
8-7 Chemical composition of four acid lakes and non-polluted lakes
in a remote area of N.W. Ontario. Range in brackets 8-50
8-8 Lead and copper concentration and pH of water from pipes
carrying outflow from hinckley basin and hanns and steele creek
basin 8-53
8-9 Maximum pH concentration producing injury to vegetation after
direct contact with simulated acidic precipitation 8-74
8-10 The sensitivity to acid precipitation baseijl on: Buffer
capacity against pH-change, retention of H , and adverse effects
on soils 8-85
8-11 Potential effects of acid precipitation on soils 8-86
8-12 Sources of nitrogen and phosphorus for various lakes as
percentages of the total annual input 8-93
8-13 Compsotion of rain and hoarfrost at heading!ey, leeds 8-111
8-14 Stations in the precipitation pH monitoring network 8-130
8-15 Weighted precipitation chemistry and predicted pH for locations
in eastern United States during 1972 to 1973 8-139
8-16 Acidic sulfate and nitrate salts sources of acidity in
precipitation 8-143
8-17 Hydrochloric, sulfuric, and nitric acids are strongest of
several potentially important proton donors in rain and snow . . 8-144
8-18 Deposition of sulfuric and nitric acids in precipitation in
eastern North America 8-149
8-19 Correlation coefficients for various parameters quantified as u
equivalents in individual rainfall samples in central Minnesota
during 1976 and 1977 8-151
8-20 Mean pH values in the New York Metropolitan Area (1975-1977) . . 8-152
8-21 Storm type classification 8-152
8-22 Temporal variations of constituents in rain storms in
Gainesville, Florida, 1976 8-153
xiv
-------
CONTENTS
EFFECTS ON VISIBILITY AND CLIMATE 9-1
9.1 INTRODUCTION 9-1
9.2 EFFECTS ON VISIBILITY 9-2
9.2.1 Fundamentals of Atmospheric Visibility 9-4
9.2.1.1 Summary 9-10
9.2.2 Measurement Methods 9-10
9.2.2.1 Observer (Total Extinction) 9-10
9.2.2.1.1 Method 9-10
9.2.2.1.2 Problems 9-12
9.2.2.2 Contrast Telephotometry (Total Extinction) 9-12
9.2.2.2.1 Method 9-12
9.2.2.2.2 Problems 9-13
9.2.2.3 Long-path Extinction (Total Extinction) 9-14
9.2.2.3.1 Method 9-14
9.2.2.3.2 Problems 9-14
9.2.2.4 Nephelometer (Scattering) 9-15
9.2.2.4.1 Method 9-15
9.2.2.4.2 Problems 9-16
9.2.2.5 Light Absorption Coefficient 9-16
9.2.3 Role of Particulate Matter in Visibility Impairment 9-17
9.2.3.1 Rayleigh Scattering 9-17
9.2.3.2 Nitrogen Dioxide Absorption 9-18
9.2.3.3 Particle Scattering 9-18
9.2.3.4 Particle Absorption 9-29
9.2.3.5 Summary , 9-29
9.2.4 Chemical Composition of the Light-Scattering Aerosol 9-29
9.2.5 Historical Patterns of Visibility 9-36
9.2.5.1 Summary 9-47
9.3 SOLAR RADIATION 9-47
9.3.1 Spectral and Directional Quality 9-50
9.3.2 Total Solar Radiation: Local to Regional Scale 9-57
9.3.3 Radiative Climate: Global Scale 9-59
9.4 CLOUDINESS AND PRECIPITATION 9-61
9.5 SUMMARY 9-65
9.6 REFERENCES 9-70
xv
-------
LIST OF FIGURES
Figure
9-1. Map shows median yearly visual range (miles) and isopleths
for suburban/nonurban areas, 1974-76 9-3
9-2. (A) A schematic representation of atmospheric extinction,
illustrates (i) transmitted, (ii) scattered, and (iii) absorbed
light. (B) A schematic representation of daytime visibility
illustrates: (i) residual light from target reaching observer,
(ii) light from target scattered out of observer's line of
sight, (iii) air light from intervening atmosphere and (iv) air
light constituting horizon sky 9-5
9-3. The apparent contrast between object and horizon sky decreases
with increasing distance from the target 9-7
9-4. Measured apparent contrast of farthest visibility marker was
identified in 1000 determinations of visual range by 10
observers 9-9
9-5. Inverse proportionality between visual range and the scattering
coefficient, b t, was measured at the point of observation 9-11
9-6. For a light-scattering and absorbing particle, the scattering per
volume has a strong peak at particle diameter of 0.5 pm(m=1.5-
0.05; wavelength = 0.55pm) 9-20
9-7. (A) Calculated scattering cross-section per unit mass at a wave-
length of 55 pm for absorbing and nonabsorbing materials is shown
a function of diameter for single-sized particles. (B) Calculated
absorption cross-section per unit mass at 0.55 pm for single-
sized particles of carbon and iron (C) Calculated extinction
cross-section per unit mass at 0.55 pm for single-sized particles
of carbon, iron, silica and water 9-21
9-8. For a typical aerosol volume (mass) distribution, the calculated
light-scattering coefficient is contributed almost entirely by
the size range 0.1-1.0 pm 9-23
9-9. Scattering-to-volume ratios are given for various size
distributions 9-24
9-10. Simultaneous monitoring of b . and fine-particle mass in
St. Louis in April 1973 showlaaa high correlation coefficient of
0.96, indicating that b . depends primarily on the fine
particle concentration 9-26
xvi
-------
9-11. Aerosol mass distributions, normalized by the total mass, for
New York aerosol at different levels of light-scattering
coefficient show that at high background visibility, the fine-
particle mass mode is small compared with the coarse-particle
mode 9-28
9-12. Chemical-mass balance was determined for fine and coarse
particles collected in Charleston, West Virginia 9-31
9-13. Normalized mass distribution functions of some species found in
New York City aerosol show that sulfate and ammonium were
found in the most efficient light-scattering size range (0.2-0.7
urn) 9-32
9-14. In this humidogram for laboratory HpSO. aerosol and for the
reaction product of this ^SO. and NH-,, the ordinate is the
ratio of light-scattering coefficient due to particulate matter
at the given relative humidity [b (RH)] to the light-scattering
coefficient at 30 percent P 9-35
9-15. Historical trends in hours of reduced visibility at Phoenix
and Tucson are compared with trends in SO emissions from
Arizona copper smelters * 9-37
9-16. Seasonally adjusted changes in sulfate during the copper strike
are compared with the geographical distribution of smelter SO
emissions 9-39
9-17. Seasonally adjusted percent changes in visibility during the
copper strike compared with the geographical distribution of
smelter SO emissions 9-41
9-18. Compared here are summer trends of U.S. coal consumption and
Eastern United States average extinction coefficient 9-43
9-19. In the 1950's the seasonal coal consumption peaked in the winter
primarily because of increased residential and railroad use.
By 1974, the seasonal pattern of coal usage was determined by the
winter and summer peak of utility coal usage 9-43
9-20. In 1974, the U.S. winter coal consumption was well below, while
the summer consumption was above the 1943 peak. Since 1960, the
average rate of summer consumption was 5.8 percent per year, while
winter consumption increased at only 2.8 percent per year 9-44
9-21. Trends in coal consumption in the continental United States
are shown by region 9-45
9-22. Trends in the light extinction coefficient (b .) in the Eastern
United States are shown by region 9-46
xvi i
-------
9-23. The spatial distribution of 5-year average extinction
coefficients shows the substantial increases of third-quarter
extinction coefficients in the Carolines, Ohio River Valley and
Tennessee-Kentucky area 9-48
9-24. Solar radiation intensity spectrum at sea level in cloudless sky
peaks in the visibile window, 0.4-0.7 urn wavelength range, shows
that in clean remote locations, direct solar radiation
contributes 90 percent and the skylight 10 percent of the
incident radiation on a horizontal surface 9-49
9-25. Extinction of direct solar radiation by aerosols is depicted 9-51
9-26. On a cloudless but hazy day in Texas, the direct solar radiation
intensity was measured to be half that on a clear day, but
most of the lost direct radiation has reappeared as skylight 9-52
9-27. To interpret these monthly average turbidity data in terms of
aerosol effects on transmission of direct sunlight, use the
expression 1/1Q = 10 , where B is turbidity and 1/1Q is the
fraction transmitted 9-55
9-28. Seasonal turbidity patterns for 1961-66 and 1972-75 are shown for
selected regions in the Eastern United States 9-56
9-29. Analysis of the hours of solar radiation since the 1950's shows
a decrease of summer solar radiation over the Eastern United
States 9-60
9-30. Numbers of smoke, haze days are plotted per 5 years at Chicago,
with values plotted at end of 5-year period 9-63
xv m
-------
LIST OF TABLES
Table Page
9-1. Light scattering per unit mass of fine aerosol 9-25
9-2. Empirical extinction efficiencies of specific
aerosol fractions 9-34
9-3. Correlation/regression analysis between airport extinction and
copper smelter SO emissions :.... 9-38
9-4. Some solar radiation measurements in the Los Angeles area 9-58
xix
-------
CONTENTS
10.1 INTRODUCTION 10-1
10. 2 SULFUR OXIDES '.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'.'. '.'/.'.'.'.'. 10-2
10.2.1 Corrosi on of Exposed Metals 10-2
10.2.1.1 Physical & Chemical Considerations............ 10-2
10.2.1.1.1 Relative Humidity & Corrosion Rate 10-4
10.2.1.1.2 Influence of Rainfall on
Corrosion 10-9
10.2.1.1.3 Influence of Temperature
on Corrosion 10-10
10.2.1.1.4 Hygroscopicity of Metal Sulfate 10-11
10.2.1.1.5 Electronic Conductivity of Rust 10-12
10.2.1.1.6 Cathodic Reduction of SO. 10-12
10.2.1.1.7 Cathodic Reduction of RuSt 10-12
10.2.1.1.8 Corrosion-Protective Properties
of Sul fate i n Rust 10-13
10.2.1.2 Effects of Sulfur Oxide Concentrations on the
Corrosion of Exposed Metals 10-14
10.2.1.2.1 Ferrous Metals 10-15
10.2.1.2.2 Laboratory & Field Studies
Emphasizing Ferrous Metals 10-16
10.2.1.2.2.1 Laboratory Studies 10-17
10.2.1.2.2.2 Field Studies 10-19
10.2.1.2.3 Nonferrous Metals 10-28
10.2.2 Protective Coatings 10-32
10.2.2.1 Zinc-Coated Materials 10-32
10.2.2.2 Paint Technology and Mechanisms
of Damage 10-39
10.2.3 Fabrics 10-47
10.2.4 Building Materials 10-48
10.2.4.1 Stone 10-49
10. 2.4. 2 Cement and Concrete 10-50
10.2.5 Electrical Equipment and Components 10-51
10. 2. 6 Paper 10-51
10.2.7 Leather 10-52
10.2.8 Elastomers and Plastics 10-53
10.2.8.1 Elastomers 10-53
10.2.8.2 Plastics 10-53
10. 2. 9 Works of Art 10-54
10. 3 PARTICULATE MATTER 10-55
10. 3.1 Corrosion and Erosion 10-55
10.3.2 Soiling and Discoloration 10-57
10.3.2.1 Building Materials 10-57
10. 3.2. 2 Fabrics 10-58
10.3.2.3 Household and Industrial Paints 10-58
xx
-------
10.4 ECONOMIC DAMAGES OF AIR POLLUTION TO
MATERIALS—SO AND PM 10-60
10.4.1 Corrosion of Metals 10-61
10.4.2 Exterior Household Paints 10-66
10.4.3 Fibers 10-67
10.4.4 Masonry, Cement, and Building Stone 10-69
10.4.5 Soiling 10-70
10.4.6 Damage Functions 10-80
10. 5 SUMMARY 10-82
10. 6 REFERENCES 10-93
xxi
-------
LIST OF TABLES
Tables Page
10-1 Some Empirical Expressions for Corrosion of Exposed Ferroalloys.10-25
10-2 Critical Humidities for Various Metals 10-29
10-3 Experimental Regression Coefficients 10-35
10-4 Corrosion Rates of Zinc or Galvanized Steel Products 10-38
10-5 Paint Erosion Rates and T-Test Probability Data 10-45
10-6 Soiling of Building Materials As A Function of Suspended
Particulate Dose 10-59
10-7 Summation of Annual Extra Losses Due to Corrosion Damage 10-63
10-8 Costs Attributable to S02 and Particulate Contaminants 10-65
10-9 Amounts of Cotton Fiber Used for Various Outdoor Purposes 10-69
10-10 Cleaning and Maintenance Tasks 10-71
10-11 Pollution and Cleaning and Painting Expenditures for
Philadelphia Annual Expenditures of E-• 10-72
10-12 Reported Gain to Consumers from Reducing Particulate Matter ....10-74
10-13 Relationship of Cleaning and Maintenance to Air
Particulate Levels 10-75
10-14 Summary of Property Value Studies 10-78
10-15 Physical Damage Functions for Materials 10-83
10-16 Economic Damage Functions on Materials 10-84
xxn
-------
LIST OF FIGURES
Figures Page
10-1 Steel corrosion behavior is shown as a function of average
relative humidity at three average concentration levels of
sulfur dioxide 10-5
10-2 Steel corrosion behavior is shown as a function of average
sulfur dioxide concentration and average relative humidity (RH)..10-6
10-3 Empirical relationship between average relative humidity and
fraction of is shown for a wet zinc sheet specimen 10-8
10-4 Relationship between corrosion of mild steel and corresponding
mean S0? concentration is shown for seven Chicago sites 10-21
10-5 Effects of particles on the rate of iron corrosion shown for:
1. charcoal alone; 2. ammonium sulfate alone; 3. 0.01 percent
S0?; 4. charcoal + 0.01 percent S0?; 5. ammonium sulfate + 0.01
percent S02; 6. charcoal + 0. 01 percent S02 10-27
10-6 Adsorption of sulfur dioxide on polished metal surfaces is shown
at 90 percent relative humidity 10-30
10-7 There is a clear relationship between maintenance frequency for
exterior repainting and particulate concentration 10-68
xxm
-------
CONTRIBUTORS AND REVIEWERS
Mr. John Acquavella
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Roy E. Albert
Institute of Environmental Medicine
New York University Medical Center
New York, New York 10016
Dr. Martin Alexander
Department of Agronomy
Cornell University
Ithaca, New York 14850
Dr. A. P Altshuller
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. David S. Anthony
Department of Botany
University of Florida
Gainesville, Florida 32611
Mr. John D. Bachmann
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Allen C. Basala
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Neil Berg
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Michael A. Berry
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxiv
-------
Mr. Francis M. Black
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Joseph Blair
Environmental Division
U. S. Department of Energy
Washington, D.C. 20545
Dr. Edward Bobalek
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Ms. F. Vandiver P. Bradow
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Ronald L. Bradow
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Robert Bruce
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Angelo Capparella
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Robert Chapman
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Robert J. Char!son
Department of Environmental Medicine
University of Washington
Seattle, Washington 98195
Dr. Peter Coffey
New York State Department of Environmental Conservation
Division of Air Resources
Albany, New York 12233
Mr. Chatten Cowherd
Midwest Research Institute
425 Volker Boulevard
Kansas City. Missouri 64110
XXV
-------
Dr. Ellis B. Cowling
School of Forest Resources
North Carolina State University
Raleigh, North Carolina 27650
Mr. William M. Cox
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. T. Timothy Crocker
Department of Community and Environmental Medicine
Irvine, California 92664
Mr. Stanley T. Cuffe
Emission Standards and Engineering Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Thomas C. Curran
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Michael Davis
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Gerrold A. Demarrais
National Oceanic and Atmospheric Administration
U. S. Department Of Commerce
Dr. Jerrold L. Dodd
Natural Resources Ecology Laboratory
Colorado State University
Fort Collins, Colorado 80523
Dr. Thomas G. Dzubay
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Thomas G. Ellestad
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. John Evans
School of Public Health
Harvard University
Boston, Massachusetts 02115
xxvi
-------
Dr. Lance Evans
Department of Energy and Environment
Brookhaven National Laboratory
Upton, New York 11973
Mr. Douglas Fennel!
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Benjamin G. Ferris, Jr.
School of Public Health
Harvard University
Boston, Massachusetts 02115
Mr. Patrick Festa
New York Department of Environmental Conservation
Division of Fish and Wildlife
Albany, New York 12233
Mr. Terrence Fitz-Simmons
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Christopher R. Fortune
Northrop Services, Inc.-Environmental Sciences
P. 0. Box 12313
Research Triangle Park, North Carolina 27709
Dr. Robert Frank
Department of Environmental Health
University of Washington
Seattle, Washington 98195
Dr. Warren Galke
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Phil Galvin
New York Department of Environmental Conservation
Division of Air Resources
Albany, New York 12233
Dr. Donald Gardner
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. J.H.B. Garner
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxvi
-------
Dr. Donald Gillette
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Judy Graham
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Lester D. Grant
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Armin Gropp
Department of Chemistry
University of Miami
Miami, Florida 33124
Dr. Jack Hackney
Rancho Los Amigos Hospital
Downey, California 90242
Mr. Bertil Hagerhall
Ministry of Agriculture
Pack
S-163 20 Stockholm
Sweden
Dr. Douglas Hammer
2910 Wycliff Road
Raleigh, North Carolina 27607
Mr. R. P. Hangebrauck
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Thomas A. Hartlage
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Victor Hasselblad
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Thomas R. Hauser
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxvm
-------
Dr. Carl Hayes
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Fred H. Haynie
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Walter Heck
Department of Botany
North Carolina State University
Raleigh, North Carolina 27650
Dr. Howard Heggestad
USDA-SAE
The Plant Stress Laboratory
Plant Physiology Institute
Beltsville, Maryland 20705
Dr. George R. Hendrey
Department of Energy and Environment
Brookhaven National Laboratory
Upton, New York 11973
Dr. Ian Higgins
Department of Epidemiology
School of Public Health
University of Michigan
Ann Arbor, Michigan 48109
Mrs. Patricia Hodgson
Editorial Associates
Chapel Hill, North Carolina 27514
Mr. George C. Holzworth
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Robert Horton
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Steven M. Horvath
Institute of Environmental Stress
University of California
Santa Barbara, California 93106
xxnx
-------
Dr. F. Gordon Hueter
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Janja Husar
CAPITA
Washington University
St. Louis, Missouri 63130
Dr. Rudolf Husar
Department of Mechanical Engineering
Washington University
St. Louis, Missouri 63130
Dr. William T. Ingram
Consulting Engineer
7 North Drive
Whitestone, New York 11357
Dr. Patricia M. Irving
Argonne National Laboratory
9700 South Cass Avenue
Argonne, Illinois 60439
Dr. Jay Jacobson
Boyce Thompson Institute
Cornell University
Ithaca, New York 14850
Mr. James Kawecki
Biospherics, Inc.
4928 Wyaconda Road
Rockville, Maryland 20852
Dr. Sagar V. Krupa
Department of Plant Pathology
University of Minnesota
St. Paul, Minnesota 55108
Dr. Edmund J. LaVoie
Section of Metabolic Biochemistry
American Health Foundation
Dana Road
Valhalla, New York 10592
Dr. Michael D. Lebowitz
Arizona Health Sciences Center
1501 North Campbell
Tucson, Arizona 85724
xxx
-------
Dr. Robert E. Lee
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Allan H. Legge
Environmental Science Center
University of Calgary
Calgary, Alberta, Canada T2N 1N4
Ms. Peggy Le Sueur
Atmospheric Environment Service
Downsview, Ontario, Canada M3H5T4
Dr. Morton Lippmann
Institute of Environmental Medicine
New York University
New York, New York 10016
Dr. James P. Lodge
385 Broadway
Boulder, Colorado 80903
Dr. Gory J. Love
Institute of Environmental Studies
University of North Carolina
Chapel Hill, North Carolina 27514
Dr. David T. Mage
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Delbert McCune
Boyce Thompson Institute
Cornell University
Ithaca, New York 14850
Mr. Frank F. McElroy
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. David J. McKee
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Thomas McMullen
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxxi
-------
Dr. Daniel B. Menzel
Department of Pharmacology
Duke University Medical Center
Durham, North Carolina 27710
Dr. Edwin L. Meyer
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Fred Miller
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. John 0. Mil liken
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Jarvis Moyers
Department of Chemistry
University of Arizona
Tucson, Arizona 85721
Dr. Thaddeus J. Murawski
New York State Department of Health
Empire State Plaza
Albany New York 12337
Dr. David S. Natusch
Department of Chemistry
Colorado State University
Fort Collins, Colorado 80523
Dr. Stephen A. Nielsen
Environmental Affairs
Joyce Environmental Consultants
414 Live Oak Boulevard
Casselberry, Florida 32707
Dr. Kenneth Noll
Department of Environmental Engineering
Illinois Institute of Technology
Chicago, Illinois 60616
Mr. John R. O'Connor
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxxii
-------
Mr. Thompson G. Pace
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Jean Parker
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Nancy Pate
Strategies and Air Standards Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Thomas W. Peterson
Department of Chemical Engineering
University of Arizona
Tucson, Arizona 85721
Mr. Martin Pfeiffer
New York State Department of Environmental Conservation
Bureau of Fisheries
Raybrook, New York 12977
Dr. Marlene Phillips
Atmospheric Chemistry Division
Environment Canada
Downsview, Ontario, Canada M3H5T4
Dr. Charles Powers
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
Mr. Larry J. Purdue
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. John C. Puzak
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxx m
-------
Dr. Otto Raabe
Radiobiology Laboratory
University of California
Davis, California 95616
Mr. Danny Rambo
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
Mr. Kenneth A. Rehme
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Elmer Robinson
Department of Chemical Engineering
Washington State University
Pullman, Washington 99163
Mr. Charles E. Rodes
Environmental Monitoring Systems Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Douglas R. Roeck
GCA Corporation
Technology Division
Burlington Road
Bedford, Massachusetts 01730
Mr. J. C. Romanovsky
Environmental Sciences Research -Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. August Rossano
University of Washington
Seattle, Washington 98195
Mr. Joseph D. Sableski
Control Programs Development Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Dallas Safriet
Monitoring and Data Analysis Division
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
xxxiv
-------
Dr. Victor S. Salvin
University of North Carolina at Greensboro
Greensboro, North Carolina 27408
Dr. Shahbeg Sandhu
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. Joseph P. Santodonato
Life and Material Sciences Division
Syracuse Research Corporation
Merrill Lane
Syracuse, New York 13210
Dr. Herbert Schimmel
Neurology Department
Albert Einstein Medical College
26 Usonia Road
Pleasantville, New York 10570
Dr. Carl L. Schofield
Department of Natural Resources
Cornell University
Ithaca, New York 14850
Dr. David Shriner
Environmental Sciences Division
Oak Ridge National Laboratory
Ms. Donna Sivulka
Environmental Criteria and Assessment Office
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. John M. Skelly
Department of Plant Pathology and Physiology
Virginia Polytechnic Institute
Blacksburg, Virginia 24061
Mr. Scott Smith
Biospherics, Inc.
4928 Wyaconda Road
Rockviell, Maryland 20852
Ms. Elaine Smolko
Department of Pharmacology
Duke University Medical Center
Durham, North Carolina
xxxv
-------
Dr. Frank Speizer
School of Public Health
Harvard University
Boston, Massachusetts 02115
Or. John D. Spengler
School of Public Health
Harvard University
Boston, Massachusetts 02115
Mr. Robert K. Stevens
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. George E. Taylor, Jr.
Environmental Sciences Division
Oak Ridge National Laboratory
Oak Ridge, Tennessee 37830
Dr. Larry Thibodeau
School of Public Health
Harvard University
Boston, Massachusetts 02115
Dr. W. Gene Tucker
Industrial Environmental Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. D. Bruce Turner
Environmental Sciences Research laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. James B. Upham
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. Robert Waller
Toxicology Unit
St. Bartholomew's Hospital
London, England
Mr. Stanley Wall in
Warren Spring Laboratory
Department of Industry
Stevenage, Hertfordshire SGI 2BX
England
xxxvi
-------
Dr. Joseph F. Walling
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. James Ware
School of Public Health
Harvard University
Boston, Massachusetts 02115
Dr. David Weber
Office of Air, Land, and Water Use
U.S. Environmental Protection Agency
Washington, D. C. 20460
Dr. Jean Weister
Health Effects Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Mr. R. Murray Wells
Radian Corporation
8500 Shaol Creek Boulevard
Austin, Texas 78766
Dr. Kenneth T. Whitby
Mechanical Engineering Department
University of Minnesota
Minneapolis, Minnesota 55455
Dr. Warren White
CAPITA
Washington, University
St. Louis, Missouri 63130
Dr. Raymond Wilhour
Environmental Research Laboratory
U.S. Environmental Protection Agency
Corvallis, Oregon 97330
Dr. William E. Wilson
Environmental Sciences Research Laboratory
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. John W. Winchester
Department of Oceanography
Florida State University
Tallahassee, Florida 32306
xxxvii
-------
Mr. Larry Zaragoza
Strategies and Air Standards Division,
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina 27711
Dr. William H. Zoller
Chemistry Department
University of Maryland
College Park, Maryland 20742
We wish to thank everyone who contributed their efforts to the preparation of
this document, including the following staff members of the Environmental
Criteria and Assessment Office, U.S. Environmental Protection Agency, Research
Triangle Park, North Carolina:
Mrs. Dela Bates
Ms. Hope Brown
Ms. Diane Chappell
Ms. Deborah Doerr
Ms. Mary El ing
Ms. Bettie Haley
Mr. Allen Hoyt
Ms. Susan Nobs
Ms. Evelynne Rash
Ms. Connie van Oosten
Ms. Donna Wicker
The final draft of this document will cite the many persons outside of the
Environmental Criteria and Assessment Office who have assisted in its pre-
paration.
xxxvi
-------
7. EFFECTS ON VEGETATION
7.1 GENERAL INTRODUCTION AND APPROACH
This chapter reviews pertinent and useful literature on the effects
of particulate matter and sulfur oxides on all forms of plant life.
Information of only historical interest has been kept to a minimum and
emphasis has been given to more recent studies that have employed modern
technologies and statistical procedures. Information on each pollutant
is presented separately since few interactive effects have been demonstrated
Interactions that have been reported are covered in the appropriate
chapter section.
7.1.1 Origin and Distribution of Particles
Particles are defined as solid particles or liquid droplets ranging
in diameter from 0.00 to 500 ym (134). The size limits are arbitrary
but are meant to indicate that particles can be as small as a cluster of
several molecules or as large as a visible dust unit. Particles constitute
a significant fraction of the atmospheric air pollutants. This chapter
discusses all types of particles other than acidic rain and biological
particles (fungal spores, bacteria, viruses, etc.).
Particles have been classified as fine (<2 ym in diameter) and
coarse (>2 ym in diameter) (470). Very fine particles exhibit Brownian
motion, follow fluid streamlines, and can coagulate and condense. Larger
particles are strongly influenced by gravity and seldom coalesce or
condense (134). The chemical behavior of particles may be determined by
the composition of the particles themselves and by the gases adsorbed on
their surfaces.
7-1
-------
Particles are generally categorized as primary and secondary.
Primary particles are usually 2 to 20 \\m in size and are injected directly
into the atmosphere by chemical or physical processes. Secondary particles
are produced by chemical reactions in the atmosphere. They are smaller
than primary particles and can be classified as sulfates, nitrates, or
hydrocarbons.
There is increasing evidence that particles and gases that produce
particles when injected into the atmosphere in one location can be deposited
several hundred miles away from this source. According to Whitby (470),
"It is now well established that a significant fraction of sulfur,
emitted into the atmosphere either as a primary aerosol or as a product
of gas to particle phase conversion, ends up in the atmosphere as stable
sub-micron aerosol." At present, the heaviest concentrations of particles
seem to be located along the coastline and in the heavily industrialized
Mid-Central States.
7.1.2 Phytotoxic Forms of Particles
The effects of air pollutants on vegetation can be considered in terms
of source, transport, deposition, and plant uptake. Except where the residence
time of the pollutant in the air is very short, chemical transformation of
the pollutant may be involved. There are exceptions, in which effects may occur
without significant uptake, as is the case with certain types of water-insoluble
particles.
Particles may affect vegetation directly or indirectly through changes
in soil chemistry and physics, or both.
The surfaces of vegetation provide a major collection surface for the
transfer of particles to the biosphere (401). The capacity of plants to act
as a sink for air contaminants has been reviewed by several investigators
(31, 68, 181, 403).
7-2
-------
Toxic effects result when the rates of exposure or deposition and
accumulation exceed the rates of detoxification through metabolism. Phytotoxic
forms of both inorganic and organic chemical species occur as particles.
Among the constituents of inorganic particulates, the following elements are
considered to be phytotoxic: Al, As, B, Cd, Cu, Pb, Mg, Mn, Hg, K, Na, Zn, and
F. In addition, acid (H2$04.HN03) and saline (NaCl) aerosols are phytotoxic.
Organic particles such as herbicides are phytotoxic to target, as well as
to nontarget, organisms when air drift occurs (370).
7.1.3 Origins and Distribution of Sulfur
Sulfur in the atmosphere has been found in as many as 23 different
chemical forms (70). Of all sulfur compounds directly emitted into the
atmosphere through man's activities, sulfur dioxide is emitted in the largest
quantity (325).
Hydrogen sulfide is believed to be emitted into the atmosphere in large but
uncertain quantities, mainly from natural sources such as swamps and estuaries.
Most of it is rapidly oxidized to S0? and sulfuric acid (64). Charlson
et al. (70) proposed a flow diagram for the cycling of sulfur compounds
through the atmosphere (Figure 7-1). The likelihood of simultaneous
coexistence of several sulfur-containing species (possibly in different
oxidation states) in single or separate atmospheric particles may further
confuse evaluation of cause and effect relationships in plant response.
7.1.4 Phytotoxic Forms of Sulfur
In laboratory and field tests, the following sulfur compounds have been
shown to be phytotoxic at appropriate doses: sulfur dioxide, hydrogen sulfide,
and sulfuric acid as mist, submicron aerosol, or in aqueous solution. At other
concentrations, over time, these sulfur compounds have demonstrated
stimulatory or beneficial effects.
7-3
-------
O HICOONIZABIE INTITIEt IN THE ATMOSPHERE
£ PflOCEKES HAVING SINOLE DIRECTION OF MATERIAL PLOW
0 HEVEHSIBLE FftOCEBES
• SOURCES
k SINKS
• OAS TO-PARTICLE CONVERSIONS
t SORPTION
• DELIQUESCENCE
« IFFLOftEKCNCE
f HAOULT-S EQUILIBRIUM
It HEACTION IN CONCENTRATED »OLUTION DROfLET
I MUCLEATION AND CONDENSATION OF WATER
| EVAPORATION
k CAPTURE OF AEROSOL IV CLOUD DROPS
I REACTION IN DILUTE SOLUTION
m MAIN
n FREEZING OF SUPERCOOLED DROP BY ICE NUCLEUS
• MELTING
» DIRECT SUBLIMATION OF ICE NUCLEUS
« PRECIPITATION
r ORGANIC RADICAL
OASES • AEROSOL
MIECUF1SORS
LOW RH AEROSOL
H2S, RSH
RSR
H3
(NH4I2SO4
MgSO4. Ni2SO4. ZnSO» C.SO4
ADSORBED CASEOUS SPECIES
H^. Hi'
Hsoj A «o;
H'.WH* \/ N.*
HIGH • MM AEROSOL
WARM CLOUDS
ICE CLOUDS
Figure 7-1. Flow diagram shows the tropospheric sulfur cycle.
Source: Charlion et »l. (1978).
7-4
-------
The phytotoxic effects of SCL have been studied since 1871 (410). In
recent years, some effort has been directed towards the understanding of
the direct effects of other sulfur compounds such as hydrogen sulfide,
carbonyl sulfide, sulfates or sulfuric acid aerosols, and sulfuric acid in
aqueous media (447).
7.1.5 Relationships Between Particles and Sulfur
No comprehensive summary of the chemical composition and size
distribution of sulfur-containing primary particles is available. Several
reports have emphasized the interrelationships of sulfur compounds and
particles.
Studies on the chemical composition of fly ash as a function of particle
size show that toxic elements such as lead, cadmium, manganese, and arsenic
increase markedly in concentration with decreasing particle size (108, 259).
Dzubay and Stevens (123) found that in urban aerosols, 75 percent of the
sulfur along with zinc, bromine, selenium, and lead occurred in fine particles.
Sulfur dioxide in a point-source plume is considered to be converted to
particulate sulfur at the rate of 0.5 to 4 percent per hour (199).
It is believed that solid phases containing sulfur are numerous.
Particulate matter such as ferric oxide, manganese oxide, and carbon can
capture S02 by physical absorption, as well as by catalyzed oxidation (79, 215,
398). The principal sulfur compounds include (NH4)2S04, (NH4)3H(S04)2> NH
CaS04, MgS04, and Na2S04, sulfates of transition metals, and organic sulfur
compounds (refer to Atmospheric Environment, vol. 12, 1978). Dry and wet
removal of sulfur from the atmosphere is considered to be important relative
to ground-level effects. Because the chemical composition of particles and
their effects on vegetation are very varied (263), published literature on
the interactive effects of particles and other air pollutants is scarce
(235, 236, 474).
7-5
-------
7.2 SYMPTOMATOLOGY OF S02-INDUCED PLANT INJURY
7.2.1 Introduction
Exposure to S02 may cause visible injury to a plant. Below the threshold
for visible damage, S02 causes physiological injury that is not visible
but is nonetheless real. Such injury has been called "latent," "hidden,"
"invisible," "physiological" and "subtle"; the term "latent" is used here.
For example, exposure to SOp concentrations that cause no visible effects
may depress growth and reduce the yield of the usable part of the plant.
In evaluating the impact of a pollutant on vegetation, latent injury
may be more important than visible injury (24, 222, 237, 353).
When preclinical visible injury is manifested as yellowing of tissues,
pigmentation, or visible stunting of growth, then chronic injury has occurred.
If plant death does occur under such exposure conditions, other mitigating
factors may also be involved, i.e., abiotic or biotic disease inducing
agents or insect attack.
However, once a sufficient dose of pollutant has occurred to induce
necrosis of individual cells, tissues, organs, or entire plants then acute
injury has occurred and irreversible effects may be observed. Plant death
may result from continual exposure to high pollutant doses.
Latent injury involves effects on the normal physiological activity
of the plant without manifestation of visible symptoms. Chronic injury is
detectable visually but does not involve necrosis and acute injury entails
death of tissues. Depending upon the plant species, exact conditions of the
seasonal stage of crop growth, pollutant dose and environmental conditions,
many forms of injury may take place and their relative impact may vary.
Symptoms of acute and chronic injury may occur on a given plant simultaneously.
The distinction between latent and acute or chronic injury may
not always be clear. Dead cells (acute injury) have been found in
S02-exposed soybean leaves in the absence of visible (unaided eye)
7-6
-------
foliar injury (207). Under the definitions set forth herein, such
injury could still be classified as acute since it is visible and need
not be compared with an unexposed plant to be detected.
Three terms have frequently been used to describe the effects of air
pollutants on vegetation: injury, damage, and impact. These are herein
defined for purposes of this chapter as follows:
Injury - one or more physiological effects as manifested by one of the
symptoms discussed above or direct yield losses in specific vegetation
species. No economic value incurred £r_ no economic value loss estimates
made and available.
Damage - injury (as defined above) that results in measurable
economic losses to specific crops, i.e., yield reduction in soybeans;
radial increment decreases in forest trees, and visible injury to
orchids and ornamental quality from an esthetic sense of value.
Impact - the total influence (detrimental or beneficial) of air
pollutants on all aspects of vegetation as used for food, fiber, and
esthetic considerations. Impact on a forest may include ecosystem
shifts, watershed effects, and recreational value due to reductions in
visibility; impact in crop situations may include indirect losses such
as shifts in planted species, farm machinery purchase as part of new
crop production, or land-use values as reduced or increased by pollutant
loading in the area.
Many reviews of SCL effects on vegetation have been prepared (58,
97, 159, 202, 272, 318, 325, 434, 442, 447, 452). Additional reports of
SOp effects on plants for use in diagnostic situations have also been
prepared (103, 104, 248, 396, 444).
7-7
-------
7.2.2 Cellular and Biochemical Changes
There is evidence that the anions formed from SCL affect the membranes
of chloroplasts and other organelles (154). Fisher et al. (136) found
that in leaves of Vicia faba exposed to S09, granulation of the stroma
- L.
and swelling of the fret membranes of the chloroplasts were the first
observable changes at the ultrastructural level. Wellburn et al. (464),
using Vicia faba, also observed a swelling of the fret membranes and
granal compartments of the chloroplasts. This swelling was more extensive
for higher concentrations and for longer durations. It was followed by the
swelling of the chloroplast and degradation of the chloroplast envelope.
In the final stages of response, the density of the cell contents increased,
with an aggregation of cellular material, although the granal membranes
persisted for a long period of time.
Sulfur dioxide has been shown to increase or decrease stomatal
resistance and thus affect the photosynthetic performance (164). When
it enters the leaf, SO^ is readily dissolved in the water surrounding
the mesophyll cells and is then converted into bisulfite, sulfite, and
sulfate. Silvius et al. (395) exposed isolated spinach chloroplasts to
0.5 mM concentrations of either SOp, sodium bisulfite, sodium sulfite, or
sodium sulfate, and measured oxygen evolution as an indicator of photosynthesis,
Photosynthesis was inhibited most by sulfite, bisulfite, and S02, and least by
SO^. No inhibition of photosynthesis was observed when the chloroplasts
were exposed to hydrochloric acid at comparable mM concentrations. Silvius
et al. (395) also observed that all of the compounds they tested inhibited
ATP formation.
7-8
-------
More recently, Legge et al. (260) showed a direct but reversible
decrease in ATP levels in lodgepole x jack pine with exposures to ambient
S02 below 0.20 ppm for 15 min. These same levels of S02, however, did
not produce measurable changes in the photosynthetic rates in this study.
Horsman and Well burn (190) prepared the most complete listing of
reported metabolic or enzymatic effects of S02 on plants or plant tissues.
In only one of ten studies was an increase in photosynthesis (14C02 fixation)
in response to the exposure to S02 or its derivatives reported; in five
of seven studies listed however, ATP concentrations dropped after exposure
to S02. Ziegler (495) showed an inhibition of the enzyme ribulose-1,5,-
diphosphate carboxylase in isolated spinach chloroplasts, and Horsman
and Wellburn (189) found a slight reduction in the activity of the same
enzyme in pea seedlings at a concentration of 0.20 ppm S02. Since
ribulose-l,5-diphosphate carboxylase fixes C02 in the pentose pathway,
any reduction in its activity would be reflected in reduced photosynthetic
rates.
Recent studies have shown a variety of S02-induced biochemical effects:
enzyme inhibition (343, 344, 495); interference with respiration (162);
energy transduction (18, 395); lipid biosynthesis (286); alterations in
amino acid content and quality (151); increase in phenolic compounds
and soluble sugars (157); altered mineral nutrients status (261); and
chlorophyll loss (260, 366). Pahlich (345) has rationalized some of this
diverse list of effects in terms of sulfite and sulfate accumulation by
the exposed plant tissue. However, it is not clear what these biochemical
responses mean in terms of visible injury or growth and productivity effects.
7-9
-------
Vogl et al. (455) have attempted to integrate the biochemical response
and the type and magnitude of the resultant plant effect (Table 7-1).
Development of models is necessary to relate changes in physiology
(biochemical responses) of specific plant species to altered growth and
productivity of that species relative to chronic, long-term exposures to
fluctuating SO,, concentrations. Thus frequent simultaneous measurements
of the pollutant concentration and a number of physiological parameters
are required to interpret plant response to the stress (226).
7.2.3 Growth and Yield Effects Without Expression of Visible Symptoms
Invisible injury was originally associated with (1) reduced photosynthesis,
(2) early senescence, (3) an overall unthrifty appearance without actual
lesions on the leaves, (4) reduced growth and yield, and (5) increased suscep-
tibility to disease (411). Respiration of spruce was inhibited but there
was not visible injury to the leaves (411). A later review defined invisible
injury as interference with growth, photosynthesis, respiration, reproduction,
enzyme function, or demonstrable increase in susceptibility to disease
without lesions or discoloration of leaves, stems, or roots of the plant (419).
New techniques and instrumentation have aided the demonstration of
physiological effects without visible symptoms for many crops. Ryegrass
(S23) exposed to ambient air in a greenhouse weighed between 16 and 57
percent less than plants grown in similar air that had been passed through
a water scrubber to remove SCL. However, lack of continuous S0? concentrations
(0.067 ppm S02) for a 26-week exposure period reduced the growth of (S23)
ryegrass and led to a 52 percent reduction in dry-weight production over
control-treated plants which received an average of 0.005 ppm S02 for the same
period. The plants exposed to S02 were slightly chlorotic, but it is
doubtful whether the symptom could have been detected in the absence of control
plants.
7-10
-------
TABLE 7-1. RELATIONSHIPS BETWEEN CERTAIN BlULHhMlLAL
AND KLANI IINOUKT
Degree
of
Injury
Visible
symptoms
Symptoms of biochemical
injury in leaf cells
Description of injury
Injury to:
Assimilation
organs Whole plant
Ability to
Assimilation
organs
recover in:
Whole plant
None
Not detectable
Loss of assimi-
lation capa-
city through:
(1) premature
death of
assimila-
tion organs
(leaves,
needles)
(2) diminished
growth of
new tissues
(shorter
needles,
etc.)
Necrosis of the
assimilating and
active plant tis-
sues
Destruction
of all im-
portant
assimilatory
plant tissues
Stress on
buffer systems
Photosynthesis
adversely af-
fected, dimin-
ished assimila-
tion rate
Diminished ac-
tivity of
enzymes
Effect on
chlorophyll
Death of cells
through protein
and enzyme de-
gradation
Death of organs
None
Temporary
reduction of
gaseous ex-
change
Prolonged
impedance of
gaseous ex-
change
None
Not detectable Very quick,
completely
Reduced growth
(deficiency
conditions)
Irreversible
injury: necro-
sis of some
assimilatory
organs or parts
thereof
Irreversible
injury to all
assimilation
organs
Loss of assimi-
lation capabi-
lity
Destruction
of assimila-
tion capability
Slowly, com-
pletely
Slowly, com-
pletely for
perennials
Quickly, not
completely;
sometimes, not
at all
for isolated
tissues
Not any more
Slowly, com-
pletely for
perrennials
Sometimes (for
isolated tissues)
source: Vogel et al., 1965 (455).
-------
Detached leaves of pea (Pisum sativum) were exposed to 0.05, 0.10, and
0.25 ppm S0? and resulting changes in photosynthetic rates were measured
(10, 25, and 50 percent, respectively) (62). The SO,, at first stimulated
and later inhibited photosynthesis but there was no visible injury to the
leaves. Pea plants were continuously exposed to 0.1, 0.15, and 0.25 ppm
S0? for 18 days (204). Accumulation of inorganic sulfur, a reduced buffer
capacity of the cells, and a stimulation of glutamate dehydrogenase
activity were reported. There was a decrease in fresh and dry weight of
plants exposed to the lower concentrations, and visible signs of injury
on older leaves. The same effects were noted at 0.25 ppm SO,, but were
accompanied by considerable necrosis.
Soybeans (cultivar wells) in field plots exposed to fluctuating con-
centrations of S02 for 4 to 4.5 hr daily for 24 and 18 days in 1977 and
1978, respectively, gave reduced yields but showed no visible injury to
the leaves (311, 407). Mild symptoms were noted only on the plants
exposed to high S02 concentrations, but reduced yields were recorded for
all of the fumigated plots. Yield reductions resulted mainly from
decreases in seed size, numbers of filled seeds per pod, and number of
pods per plant. In 1977, photosynthesis was reduced by as much as 63
percent at the highest concentrations, and a short-lived stimulation of photo-
synthesis was noted occasionally at the lowest levels of SO,, (311).
Photosynthesis in barley and oat plant canopies was reduced in response
to a 2-hr exposure to 0.20 ppm S02, but no leaf damage was observed (30).
The yield of durum wheat and barley exposed to SO,, concentrations of 0.03,
0.05, 0.10, and 0.15 ppm SO,, for 3 consecutive days per week for 12 weeks
7-12
-------
of the 1977 growing season was reduced by as much as up to 44 percent in
the 0.10- and 0.15-ppm treatment (473). The yield of spring wheat was un-
affected by similar treatments. Shorter exposures of 3 hr per week to 1.20
ppm S02 had no effect on yield.
Leaf injury and radial growth were evaluated on Douglas fir (Pseud-
otsugae menziesii) and yellow pine (Pinus ponderosa) growing in nursery plots
exposed to sulfur dioxide (S02) in controlled fumigations (221). Slightly
injured yellow pine (0.10 percent foliar symptoms) exhibited no significant
deviations in growth while slightly injured Douglas fir (0.10 percent foliar
symptoms) showed a definite growth retardation when compared with control
plants. The growth retardations were evident for 3 years after S02 exposure,
followed by substantial recovery.
Piskornik (354) exposed six tree species (Quercus robur, Aesculus hip-
pocastanum, Acer pseudoplatanus, Fraximus excelsior, Betula verrucosa, and
Acer platanoides) to 0.10, 0.40, and 1.30 ppm S02 for 24 hr. Exposure to 0.10
ppm S0? resulted in a significant reduction in photosynthesis only in the
oak (Quercus robur), with no visible symptoms. At 0.40 ppm, all species
had reduced photosynthesis (36, 60, 86, 16, 24, and 26 percent, respectively),
and a few symptoms appeared on planetree maple (Acer pseudoplatanus),
some on oak, and some on horsechestnut (Aesculus hippocastanum). A
decrease in the rate of photosynthesis (measured by carbon dioxide assimi-
lation) occurred even in leaves that did not exhibit any visible injury, and
premature aging of some leaves and decreased water content of tissues was
also noted.
Spruce may respond to low S02 concentrations by metabolic changes and
increased susceptibility to other pests and parasites without visible symp-
toms (296); losses in growth under such conditions have been reported to amount
to 10 percent. Significant reductions in the growth of trees in Austrian
forests occurred in response to a variety of pollutants at relatively low
7-13
-------
concentrations (117). Radial increment studies revealed growth reductions
in many trees, some of which exhibited no typical macroscopic visible symptoms.
Growth in a mixed white pine stand and a yellow poplar (Liriodendron
tulipifera) stand near a source of S0? and nitrogen oxides was examined
using a simple linear regression analysis to evaluate the relationship be-
tween annual radial increment (1936-71) and annual industrial production
level (amount of coal burned) (412). A significant inverse relationship be-
tween growth and air pollution was demonstrated in both white pine and yellow
poplar. Experiments were extended to three stands of loblolly pine, using
multiple linear regression analysis, annual radial increment growth being
the dependent variable and annual industrial production level (SCX, and N0x
pollution), total annual rainfall, annual seasonal rainfall, and age as in-
dependent variables to evaluate pollution impact (352). A significant
(p = 0.01) inverse relationship was demonstrated between annual radial in-
crement and industrial production level. The eastern white pine stand pre-
viously studied (412) was reexamined for growth reduction in trees of dif-
fering classes of symptom versus pollutant sensitivity (353). Regression
analysis revealed no significant differences in growth rate between symptom
classes (ranging from asymptomatic to greater than 25 percent of the needles
tipburned) and industrial production peaks; that is, the growth of asymptomatic
trees was reduced as much as growth of trees with symptoms during the time of
sampling (1935-74). Unfortunately, the researchers evaluated the trees at
the end of each period, and did not document that the then asymptomatic
trees were asymptomatic during previous periods of high pollution levels.
Growth as measured by radial increment in this eastern white pine stand has
continued to increase since 1972 as a result of reduced levels of industrial
production and concurrent pollution-abatement efforts at the major sources
of S02 and nitrogen oxides (331).
7-14
-------
Eastern white pine in the field exhibited increased height growth after
a power plant smokestack was made higher, which effectively removed the
air pollutants from the immediate vicinity of the pines (120). The in-
crease in height growth was detectable 2 years after construction of the
taller stack and the amount of increase decreased with distance from the
source.
Continuous exposures of Norway spruce (Picea abies) to 0.05, 0.10,
and 0.20 ppm S02 from April through July 1976 caused significant depres-
sions in carbon dioxide uptake long before visible symptoms occurred (225).
Increasing S02 levels caused a decrease in width of annual rings with par-
ticular effects to summer wood formation following the springtime fumiga-
tion. Industries selling wood on a weight basis therefore may suffer addi-
tional losses through decreased production of the denser summer wood. Con-
tinuous exposure to 0.10 or 0.20 ppm S0~ for 10 weeks caused significant
depression in photosynthesis of silver fir (Abies alba) needles in the
absence of foliar symptoms (223). Exposure of spruce to 0.05 ppm S0? for 9
months decreased the buffering capacity and increased the activity of peroxidase
(222). Low S0? concentrations for several summer weeks significantly depressed
photosynthesis in pine. The viability of fir pollen was reduced if the plants
were exposed to S02 during the winter (222).
Wintertime exposures to S02 killed terminal buds of beech (Fagus
sylvatica) and caused increases in sulfur compounds in leaf tissues flushed
from surviving buds (224). Norway spruce, beech, and black pine were more
sensitive to frost injury after continuous exposure to 0.05, 0.10, 0.15,
and 0.20 ppm SO- for 2.5 to 4.0 months. These data help explain the more
frequent occurrence of frost damage in polluted areas.
7-15
-------
The effects of ambient levels of pollutant (mainly SCL) on cone, seed, and
pollen characteristics were examined on eastern white pine (Pinus strobus) and red
pines (P_. resinosa) growing in areas of high and low pollution (194).
Significantly lower values were found for seeds per cone, 100-seed weight, and
percent pollen germination for white pine in the high-pollution area. Sig-
nificantly lower values for cone length, 100-seed weight, percent filled seed,
percent seed germination, and pollen tube length were found in red pine.
None of the trees exposed to S02 showed leaf injury symptoms.
Scotch pine, known to be relatively resistant to SO^ damage following
continuous long-term exposure (average 0.07 ppm, maximum 0.24 ppm), suffered
decreases in cone yield, cone length, seed yield, and seed weight with an
increase in field S02 concentrations (317). The germination rate of the
seed and the growth and development of 1-year seedlings grown from the seeds
were not significantly affected. The trees were also grouped by height classes.
As the concentration decreased, the number of trees that bore fruit in-
creased for all height classes.
Elevated S02 content in the atmosphere around the Urals significantly
weakened Scotch pine stands, thereby lowering the reproductive capacity of
the trees (287). The number of seeds per cone decreased, and the ratio of
male to female cones changed in favor of the females. The cone size of the
trees in the smoke-damaged areas also decreased. The quality of the seeds
and pollen grains from trees growing in the smoke-damaged areas was sig-
nificantly lower than that of pollen and seeds from trees in undamaged stands.
Exposures of cotyledon-stage red pine seedlings under continuous field
fumigation adversely influenced seedling development and regeneration of
pine communities. Somewhat high concentrations were used (0.5, 1.0, 3.0, and
4.0 ppm SOp) for periods of 15, 30, 60, or 120 min. Visible injury occurred
only with the high concentrations of S02 at longer exposure periods (78).
7-16
-------
Research published in the early 1970s has demonstrated effects within
plants of low continuous exposure to SCL. Many of the effects occur in the
absence of visible foliar injury, but can lead to reductions in growth and
yield. The few studies that have associated decreased photosynthetic rates
with yield reductions (225, 237, 272) support the contention that reduced
photosynthetic rates lead to reduced growth. The demonstrated effects of
SC^ on reproductive systems (cone size and number, seed size and germination
capacity, pollen germination and growth) (197, 222, 287, 317) could
have an impact on the competitive ability of some species. The reported
increases in susceptibility to biotic and abiotic (296) factors of the en-
vironment brought about by SCL may also be of importance to the growth and
survival of plants. Metabolic changes may indicate not only growth losses
but also losses in quality of the plant product. Many important economic
and ecologic effects could therefore be occurring as a result of SCL that
are not obvious even to the trained observer.
7.2.4 Chronic Injury Due to S(L Exposure
Plant injury that is visible but does not involve collapse and ne-
crosis of tissues is termed chronic injury. This type of visible injury
is usually the result of short-term, high-concentration or long-term low-
concentration exposures to SCL. It has also been referred to as being
"sulfate injury" since a slow accumulation of sulfate is the end result of
such exposures (97). As with most air pollutants, SCL enters plants pri-
marily through stomata during normal gas exchange functions. Once within
the substomatal cavities, S02 reacts with intercellular water to quickly
form sulfite and bisulfite, which are slowly oxidized to sulfate which is
approximately 30 times less toxic than sulfite and bisulfite (418). The
capacity of the plant tissues to convert sulfite and bisulfite to sulfate may
7-17
-------
never be exceeded and as such only latent injury may occur with no
further expression of symptoms. In some studies sulfate levels in
plants exposed to S0? have been demonstrated to be several times greater
than those in controls (269). However, if sulfite and bisulfite ions
are formed, and sulfate accumulates to phytotoxic levels, then chronic
symptoms first appear as various forms of chlorotic (yellowing) patterns.
As sulfite and bisulfite ions accumulate after exposure to high levels
of SCL, destruction of individual chloroplast membranes or a reduction
of chlorophyll production ensues. Accumulation of toxic levels of
sulfate induce reddening or bleaching of cells without causing death.
Following such accumulations, there is a fine distinction between chronic
and acute symptom expressions.
In broadleaf plants, chronic injury is usually expressed in tissues found
between the veins, with various forms of chlorosis predominating. Chlorotic
spots or chlorotic mottle may persist following exposure or may subside and
disappear following removal of the pollutant or as a result of changing en-
vironmental conditions. A yellowing of lower leaf surfaces of cotton was found
to follow exposure to SCL; symptoms progressed to the upper leaf surface as
exposure to low concentrations continued (57). Later the symptoms progressed
to bleaching or a brownish-red coloration, but the tissues remained turgid.
The chronic effects of SO,, in perennial conifers are generally first
expressed on older needles (270). Chlorosis of tissues visible as spots or
mottle progresses down the needle from the oldest to youngest tissues.
Advanced symptoms may follow, involving reddening of affected tissues. Houston
(193) found that symptoms were initiated in eastern white pine seedlings
following a 6-hr fumigation with 0.05 ppm S0-
7-18
-------
7.2.5 Acute Injury Due to SCL Exposure
Acute injury usually results from exposure to high concentrations of
S02. Such symptoms are easily recognized in most plant species. Acute in-
jury from rapid absorption of a toxic dose of SCL causes marginal and inter-
costal necrotic areas which at first have a dull dark-green, watersoaked
appearance. After desiccation and bleaching of the tissues, the affected
areas become light ivory to white in most broadleaf plants. However, some
species show darker colors, brown or red, but there is characteristically
an exact line of demarcation between symptomatic and asymptomatic portions
of leaf tissues. Bifacial necrosis is common (444).
In conifers, acute symptoms are expressed as needle-tip necrosis that
has progressed from banding (necrosis) of distinct areas of affected
tissues. Recently incurred injury is light colored, but later, bright
orange or red colors are typical for the banded areas and tips. As
needle tips die, they become brittle and break or whole needles drop from
the tree. Pine needles are most sensitive to SCL during the period of rapid
needle elongation, but injury may also occur on mature needles (104).
In summary, the response of plants to sulfur dioxide may take the form of
latent injury only, or of visible injury; the latter may take chronic or
acute forms. The response of individual plants or plant communities may be
governed by the dose of pollutant, the number of exposures, the season of
exposure, or any one or a group of environmental and biological factors that
influence basic physiological functions.
7.2.6 Classification of Plant Sensitivity
7.2.6.1 Introduction—Because of space limitation, it is not possible to list
all plants that are known to be sensitive to various doses of S02. Further-
7-19
-------
more, in a listing of sensitive plants, the evidence collected should also
indicate the environmental, genetic, and cultural considerations that may
in fact determine such sensitivities. It has also been demonstrated that
plant response to air pollutants varies at the genus, species, variety, and
cultivar levels.
Lists of plant sensitivities have been prepared on the basis of the
expression of visible symptoms by any given plant. Injury expressed by
growth or yield losses has not been considered in the preparation of such
lists.
7.2.6.2 Plant Sensitivity to S02--Jacobson and Hill (202) included a list-
ing of plants sensitive to the major phytotoxic air pollutants. Other compi-
lations have been presented. The report of Davis and Wilhour (105) pro-
vides information on an international basis. Specific reports have been pre-
pared for vegetation native to the south-western deserts of the United States
(182). Table 7-2 provides a partial listing of more common plants found to be
sensitive to SO,,.
Extensive efforts have been made to develop certain plant species as
bioindicators. Perhaps the most extensively examined plants for this use are
eastern white pine (Pinus strobus) and numerous species of lichens. The white
pine literature has been reviewed (145, 330) and the most recent review of
lichen bioindicators was prepared by LeBlanc and Rao (256).
Other recent reports have been prepared for various ornamentals (96,
177, 349), bluegrass cultivars (320), scotch pine (109), loblolly pine (236),
hybrid poplar (113), and trembling aspen (218). These represent examples of
the continued efforts to identify sensitive plants suitable for use as bio-
indicators.
7-20
-------
TABLE 7-2. PARTIAL LIST OF PLANTS KNOWN TO BE SENSITIVE TO
S00 UNDER FIELD EXPOSURE CONDITIONS
Cultivated Crops:
A1
L.
Alfalfa - Medicago sativa L
Barley - Hordeum vulgare L.
Bean - Phaseolus vulgaris L.
Bluegrass - Poa annuaL.
Cabbage - Brassica oleracea L
Cucumber - Cucumis" sativus L.
Oats - Avena sativa L.
Pea - Pi sum sativum L.
Radish - Raphanus sativus L.
Rhubarb - Rheum rhaporiticum L
Rye - Secalecefeale L.
Soybean - Glycine max Merr.
Spinach - Spinaciaoleracea L.
Tobacco - Nicotiana tobacum L.
Weed Species:
Forest Trees
Big-leaved aster - Aster macrophyllum
Bindweed - Convolvulus arvensis
Blueberry - Vaccinium angustifolium
Curly dock - Rijmex^ crispus
Dandelion - Taraxacum officinale
Fleabane - Erigeron canadensis
Lambsquarter - Chenopodium album
Pigweek - Amaranthus retroflexus
Plantain -
Ragweed
Plantago major
- Ambrosia spp.
Raspberry -
Smartweed -
Wildgrape -
Rubus spp,
Polygonum
Vitis spp.
spp.
grandidentata
Ash, white - Fraxinus americana
Aspen, large tooth - Popul
Birch - Betula spp.
Elm - Ulmus spp.
Fir, Douglas - Pseudotsuga menziesii
Hybrid poplar - Populus
Larch - Larix spp.
Maple - Acer spp.
Mountain ash - Sorbus aucuparia
Pine, jack - Pinus banksiana
Pine, ponderosa - Pinus ponderosa
Pine, eastern white - Pinus stroFus
Willow - Salix spp.
Ornamentals and Flowers:
Aster - Aster bigelovii
Azalea - Rhododpndron spp.
Bachelor's button
Begonia - Begonia spp.
Cosmos - Cosmos^ bipinnatus
- Centarea cyanus
Four-o'clock - Mirabilis jalapa
Morning glory - Pipmpea purpurea
Petunia - Petunia hybrida
Sweet pea - Lathyrus odoratus
Verbena - Verbena canadensis
Violet - Viola spp.
Zinnia - Zinnea elegans
7-21
-------
Detection of symptoms similar to S02 injury on sensitive species will pro'
vide additional evidence in diagnostic procedures. However, other causes may
induce injury symptoms that mimic those of SCL, and several bioindicators are
desirable for evaluation in any given area. In addition, individual species
and more complicated plant bioindicator systems are not as effective for
detecting SCL at low concentrations as are sophisticated instruments.
7.3 Dose-Response Relationships—SCL
Dose may simply be defined as concentration of pollutant(s) times the
duration of the exposure period without further consideration of any environ-
mental or biological influences. The response of any individual plant may be
evaluated in light of influencing physical and biotic factors. Dose-response,
therefore, is a term used to define and characterize the reaction of any
given plant to various doses and the specific reaction may be enhanced or
mitigated by a complexity of factors within the exposure conditions.
Plant responses induced by low-dose exposures (as usually characterized
by low concentrations over short or long periods of time) involve the expres-
sion of latent symptoms that may lead to growth and yield effects or overt
symptoms that seldom become more serious than those associated with chronic
injury.
Plant responses induced by high-dose exposures (as characterized by high
concentrations for short or peak periods of time or longer periods) usually
involve the expression of symptoms leading to the necrosis of cells, tissues,
entire organs, or plants and plant communities. Such symptoms usually de-
velop rapidly following high-dose exposures and are usually described as acute
injury.
Response may be characterized by a measurable change in any parameter.
Induced changes have been measured in biochemical pathways, gas exchange
rates, photosynthetic rates, physiological functions, degree of
7-22
-------
visibly recognizable leaf injury, or subsequent growth and yields. The
latter two effects have most commonly been expressed as quantitative changes.
Results such as those obtained by Horsman et al. (186) are not easily
tabulated into dose-response tables. They provided strong evidence that
high doses of SCL were responsible for a population differentiation within
perennial ryegrass, favoring a few, more tolerant, clones within those
receiving high doses.
Numerous physical and biotic factors must be considered in evaluating
dose-response data. Changes in exposure conditions, differences in exposure
methodology, efficiency of monitoring equipment, and consistency of
measurements within a study and between studies on the same plant will directly
influence results (Figure 7-2; Heck and Brandt, ref 173).
Several attempts have been made to characterize dose-response relationships
in a mathematical sense using monitored concentrations, exposure times,
and injury thresholds as modified by physical and biotic factors expressed as
constants.
O'Gara (341) derived the following formula from short-term fumigations
of alfalfa; (C - C.) t = K. In this function, concentration (C) and exposure
time (t) are directly proportional. The value C, is the threshold concentration
at which no injury occurs, even under long-term exposures. As C approaches
C., t approaches infinity.
After extensive experimentation with S0?, the equation has been modified
so that the pollutant dose that causes a particular degree of injury can be
predicted (422). For example, under conditions of extreme plant sensitivity,
7-23
-------
NUMBER OF
EXPOSURES
CLIMATIC FACTORS.
EOAPHIC FACTORS
BIOTIC FACTORS'
ACUTE
POLLUTANT
CONCENTRATION
DOSE
PLANT RECEPTOR
MECHANISM OF ACTION
EFFECTS
CHRONIC
DURATION OF
EACH EXPOSURE
GENETIC MAKEUP
STAGE OF PLANT
DEVELOPMENT
SUBTLE
Figure 7-2. Conceptual model shows factors involved in air pollution
effects (dose-response) on vegetation. Subtle effects are called "latent
effects" in this chapter.
Source: Heck and Brandt (1977).
7-24
-------
the following values are given:
(C - 0.24)t = 0.94, slight necrosis
(C - 1.40)t = 2.10, 50 percent necrosis
(C - 2.60)t = 100 percent necrosis
Zahn (494) developed an equation for the function of the threshold concentration
for short-term exposure to high SO,, concentrations resulting in acute injury:
1 + 0.5c
* = C(C - a)
where a = threshold concentration, b = measurable resistance factor
incorporating influences of environmental conditions, C = monitored
concentration, and t = time of exposure.
However, studies on the influence of concentration (C) and exposure
time (t) have shown that dose-response induced by SOp does not always conform
to such simple computations. Van Haut (451) demonstrated that injury to
radish increased progressively with increased S0? concentrations even though
time was correspondingly reduced, that is, the product of concentration and
time was held constant (Table 7-3).
According to Larsen and Heck (250): (1) a constant percentage of leaf
surface will be injured by an air pollutant concentration that is inversely
proportional to the exposure duration raised to an exponent, and (2) for a
given exposure duration, the percent leaf injury as a function of pollutant
concentration tends to fit a log-normal frequency distribution.
The following exponential function has been developed which takes
into account the particular risks of high SO,, concentrations (250):
t - tp - (e-a(c - C)r)K
where t is exposure time, t is the threshold time minus minimum exposure
time required to cause injury, C = pollutant concentration, C is the
threshold concentration minus the minimum concentration required to cause
7-25
-------
TABLE 7-3 PROGRESSIVE INCREASE IN THE DEGREES OF IN-
JURY OF RADISH WITH INCREASING
S00 CONCENTRATIONS
S02 ppm
concentration
C
i
1.15
2.3
3.4
4.6
Exposure time in
hours
C
12
6
4
3
Ct
36
36
36
36
Area of leaf
injury
%
2
20
40
77
a Converted from mg/m to ppm (2.62 mg/m = 1 ppm) at 25° C,
760 mm Hg.
Source: Van Hart (451).
7-26
-------
injury, a is an internal and external growth parameter, and K is growing
time. Larsen and Heck used this approach to predict the dose-response
relationship for SCL on Norway maple, gingko, pin oak, and Chinese elm.
The latter species mentioned was the most sensitive, being injured by
S02 doses of 3.5 ppm for 1 hr, 0.46 ppm for 3 hr, and 0.07 ppm for 8 hr.
The authors used such data to develop an effects model.
Information on S02 doses causing acute injury on sensitive plant species
is summarized in Table 7-4. When evaluating the material presented in the
table, the reader must remember that demonstration of an effect in terms of
injury does not necessarily indicate an effect in terms of damage. Damage
always implies injury; injury may occur, however, without damage. (See
section 7.2.1 for a further explanation of this consideration.)
Tables 7-5, 7-6, and 7-7 present salient information taken from numerous
reports of S02-induced effects to field crops, forest trees, and other forms
of vegetation, respectively. Many of these reports have been reviewed in
more detail elsewhere in this chapter; several more have been added here
to emphasize the total number of studies available for review. The tables
have been arranged on the first-order basis of increasing concentrations
of S0~, and increasing lengths of exposure times have been used as a second-
order breakdown under concentrations. For the sake of brevity, only common
names of plants have been presented. Latin binomials of all plants used with-
in this table may be found in the composite listing in appendix A of this
chapter. The conditions of exposure refer to the location of the experiment
as to field or indoor tests and the type of fumigation systems used. Effects
examined are indicated by an (X) as the designation of foliar or yield effects
being examined; the (X) does not indicate that such effects were found. The
effects listed are those considered to be the most important findings from
the research data presented in original articles. Each effect has been located
7-27
-------
TABLE 7-4. SULFUR DIOXIDE CONCENTRATIONS CAUSING VISIBLE INJURY TO
VARIOUS SENSITIVITY GROUPINGS OF VEGETATION5
(ppm S00)
Maximum
average
Sensitivity grouping
concentration Sensitive
Peak 1.0-1.5
1-hr 0.5-1.0
3-hr 0.3-0.6
Ragweeds
Legumes
Blackberry
Southern pines
Red and black
oaks
White ash
Sumacs
Intermediate
1.5-2.0
1.0-2.0
0.6-0.8
Maples
Locust
Sweetgum
Cherry
Elms
Tuliptree
Many crop and
garden species
Resistant
>2.0
>2.0
>0.8
White oaks
Potato
Upland cotton
Corn
Dogwood
Peach
Based on observations over a 20-year period of visible injury occurring
on over 120 species growing in the vicinities of coal-fired power
plants in the southeastern United States.
Source: Jones et al. (213).
7-28
-------
TABLE 7-5. DOSE-RESPONSE INFORMATION SUMMARIZED FROM LITERATURE PERTAINING TO CULTIVATED AGRONOMIC CROPS AS RELATED TO FOLILAR,
YIELD, AND SPECIFIC EFFECTS INDUCED BY INCREASING S02 DOSE
IS)
10
Cone,
ppm
0.01
0,01
0.015
0.02
0.035
0.02
0.05
0.10
0.03-
0.10
0.3-
0.06
0.10
0.15
0.20
0.035
1.75
0.05
Exposure
time
10 m1n
Growing season
Growing season
10 m1n
3 hr for 8 exp,
growing season
Growing season
(2 year)
72 hr/wk for
growing season
24 hr/day
for 30
days
8 hr
10 min
Exposure.
condition
EC
EC
F/CC
F-ZAP
F/CC
F/CC
EC/SD
EC
Effects on
Plant0 Foliar Yield
Corn
Oats X
Wheat X
Bean
Wheat
Winter wheat
Prairie June grass
Barley X
Durham wheat
Spring wheat
Winter wheat X
ev. Yamhill
ev. Ilyslop X
Broadbean
Broadbean
Species Effect0
Stomata open wider
Light leaf Injury
15S decrease 1n grain weight yield
Stomata open wider
No effect on apparent photosynthesis, no
effect on the average head length or
number of grains per head
S content increased with increase 1n SOp
concentration; digestibility of dry
matter was reduced by 2 years of treat-
ment; crude protein content in winter
wheat decreased significantly
No effect on yield
0.03 ppm Increased yield 27%
0.06-0.15 ppm, no effect
0.06 ppm decreased yield 22%)
0.20 ppm decreased yield 70%
Depressed photosynthesis
Stomata open wider; threshold 0.02 ppm for
10 m1n
Reference
448
159
159
448
394
473
473
473
40
37
-------
TABLE 7-5 (continued)
Cone,
ppm
0.05
0.05
0.10
0.25
Exposure
time
Exposure.
condition
5 hr/day; 5 day/wk EC/SO
for 4 wk
4 hr
EC/SO
Plantc
Alfalfa
Tobacco
Oats
Radish
Soybean
Tobacco
Effects on
Foliar
YieTJ
Species Effect0
26% decrease in foliage dry weight
49% decrease in root dry weight
22% decrease in leaf dry weight
No foliar injury
Reference
430
431
OJ
o
0.05
0.20
0.06
0.065
0.13
0.26
0.10
0.10
0.10
8 hr/day
5 days/wk
for 18 days
68 days
1-55 days
EC/SD
EC/SD
GC
20 min
1 hr
8 hr
EC
EC
GH
Soybean
Alfalfa
Cabbage
Chinese cabbage
Cucumber
Eggplant
Lettuce
Spinach
Bean
Corn
Bean
Tobacco
No effect on top fresh or dry weight; root
fresh or dry weight; plant height; shoot/
root fresh or dry weight ratio
28% decrease in foliage stubble, 45% decrease
root dry weight
21% decrease in total protein content, amino
acid content, total nonstructured carbohy-
drates, symbiotically fixed nitrogen 327
Foliage injury threshold 0.13x27 days 140
Foliage injury threshold 0.26x55 days
Foliage injury threshold 0.13x26 days
Foliage injury threshold 0.13x11 days
Foliage injury threshold 0.13x15 days
Foliage injury threshold 0.13x1 day
Other parameters measured such as plant height,
number of leaves, top fresh weight, number of
flowers, fresh weight vs. dry weight of roots
were not found to be significantly different
from controls
Stomata open wider, effect also shown to occur 448
in dark
Stomata open wider, water-stressed plant had 448
wider opening of stomata compared with
controls
Foliar injury threshold for development of 283
fleck-like lesions
-------
Cone,
ppm
0.10
0.10
0.10
0.125-
1.0
0.15
0.15
0.25
0.11
Exposure
time
6 hr/day
for 133 days
18 days
6 hr/day
43 days
92 days
133 days
1-3 hr
18 days
72 hr/wk for
growing season
18 days
Exposure,
condition
F/CC
GC
F/OT
EC/SD
GC
F/CC
GC
103.5 hr/wk
for 20 wk
GC
Plantc
Soybean
Pea
Effects on
Foliar
Yield
Soybean
Oats
Radish
Sweet pea
Swiss chard
Pea
Barley
Durham wheat
Spring wheat
Pea
Cocksfoot
Meadowgrass
Italian ryegrass
Timothy
Species Effect0 Reference
No significant effect on growth or yield; 169
92nd-day defoliation was 12% greater;
135th-day seed weight was 1% reduced from
control
3% decrease in fresh weight of shoot 204
5% decrease in dry weight of shoot
4% decrease in total nitrogen
30% decrease in H (buffer capacity)
10% increase glutamate dehydrogenase activity
110% increase in inorganic sulfur content
No significant effect on foliar injury, defolia- 171
tion fresh weights, seeds/plant, or weight
of seeds/plant
No foliar injury 32
3% decrease in fresh weight of shoot 204
8% decrease in dry weight of shoot
2% decrease in to£al nitrogen
35% decrease in H (buffer capacity)
32% increase in glutamate dehydrogenase activity
140% increase in inorganic sulfur content
42% decreased yield in Durham wheat; 44% 473
decreased yield in barley; no effect on
spring wheat
32% decrease in fresh weight of shoot 204
26% decrease in dry weight of shoot
24% decrease in total nitrogen
42% decrease in H (buffer capacity)
80% increase in glutamate dehydrogenase activity
150% Increase in inorganic sulfur content
40% decrease in total dry weight 13,14
28% decrease in total dry weight
Nonsignificant
51% decrease in total dry weight
(Yield reductions were related to decrease In
leaf areas)
-------
Cone,
ppm
0.15
0.15-
0.30
0.15
0.17
0.20
0.25
0.25
0.20
0.30
0.40
0.50
0.60
0.70
0.20
0.20
0.218
Exposure
time
24 hr
7 days
14 days
2 hr
1 hr
2 hr
2 hr
15 days
To maturation
4.5 hr/day
for 4 days
Exposure.
condition
EC/SO
EC/SD
GH
EC/SD
EC/SD
GC
GC
EC/SD
F-ZAP
Plantu
Corn
Rice
Barley
Bean
Corn
Celery
Big plantain
Bean
Big mallow
Broadbean
Alfalfa
Alfalfa
Barley
Oats
Alfalfa
Barley
Tomato
Kidney bean
Soybean
TABLE 7-5 (continued)
Effects on
Foliar
Yield
Species Effect0 Reference
Absorbed S0? remained in water-soluble 490
form and very difficult to assimilate to
protein
Severe foliar injury 288
No injury
Severe foliar injury
Increased peroxldase activity, caused 356
chlorosis of leaves
Increased peroxidase activity, decreased
buffering capacity of cells, caused
necrotic leaf injury
Caused necrotic leaf injury
Caused necrotic leaf injury
Decreased photosynthetic rate, decreased 39
stomatal resistance if RH 3 40%, increased
stomatal resistance if RH < 40%
No effect on photosynthesis 471
Threshold dose for inhibition of photosynthesis 30
No effects at these doses
, ,
Threshold dose for initial symptom of tissue
death, decrease or change in vitamin B,
Bg, and nicotinic add content
15% decrease in total yield
No visible damage
20% decrease in yield
30
449
33
201
-------
Cone,
ppm
0.23
Exposure
time
14 days
Exposure.
condition
Planr
GH Buckwheat
Lucerne
Red clover
Little stinging nettle
Ryegrass
TABLE 7-5 (continued)
Effects on
Foliar Yield
X
X
X
0.25
0.25
0.25
0.40
0.80
1.20
0.25
0.25
0.25
0.25
0.25
0.40
0.80
1.20
0.25
0.25
0.29
1 hr
2 hr
Once every wk
(3 hr) to once
in 5 wk (3 hr)
4 hr
8 hr
24 hr
1 hr
3 hr every
2 wk for
growing season
Unknown
Unknown
15 days
F/CC
EC/SD
EC/SD
GC
EC
F/CC
EC
EC
GC
Broadbean
Broadbean
Alfalfa
Barley
Durham wheat
Spring wheat
Broccoli
Tobacco, Bel B,
Tobacco
Broadbean
Begonia
Alfalfa
Barley
Durham wheat
Spring wheat
Pea
Sunflower
Morning glory
Corn
Sorghum
Lettuce
Species Effect0 Reference
Caused necrotic leaf injury 356
Caused necrotic leaf injury
Caused necrotic leaf injury
Increased peroxidase activity
Increased S content in leaves
Slight swelling of stroma thylakoids of 464
chloroplast, effect reversible
Stroma thylakoids spread to granum
thylakoids, effect reversible
No effect on yield 473
H leaf injury 432
6% leaf injury
Chlorophyll a decreased more sharply than
chlorophyll b 40
Stomata opened faster and wider 1n light 286
condition; stomata opened longer in darkness
Foliar Injury 431
No effect on yield 473
50* decrease in net photosynthesis 62
10% decrease in photosynthetic rate 450
20-30% decrease in photosynthetic rate
No effect
No effect
Foliar injury, 30% decrease in thiamine content 449
-------
Cone,
ppm
0.30
0.35
0.35
Exposure
time
5 hr/day
6 day/wk
12 days
26 days
1 hr
21 days
Exposure.
condition
EC/SD
EC/SD
EC/SD
PlantL
Barley
Bean
Sunflower
Barley
Alfalfa
Pea
TABLE 7-5 (continued)
Effects on
FoTTaT TTeTJ
0.38
1.15
1/90
0.40
0.40
0.50
0.60
0.40
0.40
0.45
0.46
0.50-
6.00
14 days
3 hr
4 hr
6 hr
6 hr/2 wk
(1-2 exposures)
3 hr for 7
exposures for
growing season
7 hr
30 min
0
EC/SD
EC/SD
EC/SD
F/CC
EC
F/CC
Radish
Oats
Tomato
Apples
Alfalfa
Cotton
Pecan
Pepper
Wheat
Buckwheat
Soybean
X
X
X
X
Species Effect0 Reference
11% foliar injury; 38% decrease in 292
dry weight shoot
1% foliar injury; 38% decrease in
dry weight shoot
5% foliar injury; 41% decrease in
dry weight shoot
21% foliar injury; 26% decrease in
dry weight shoot
2% foliar injury; 15% decrease in dry
weight shoot
16% foliar injury; 29% decrease in
dry weight shoot
80% decrease in apparent photosynthesis 472
Increase in glutamine content, decrease 205
in glutamic acid and protein content
inorganic S accumulated
Necrosis and growth inhibition at 0.35
x 14 days
Decrease injury at 0.38 and above, inhibited 111
seed germination, formation of green leaf-
lets of sprouts, and root growth
Threshold for leaf injury 174
Increase accumulation total and soluble 29
S content
No effect 227
No difference found in total N, protein/total 424
N ration, chlorophyll, all plants, all
treatments
No accumulative effect on yield, no effect on
average head length or number of grains/head 394
Injury threshold
Very significant negative linear relation-
ship between percent leaf area destroyed
and percent crop loss; 0.66% yield loss
for every 1% increase in foliar injury;
asymtomatic plots increased yield oy
6.02% over controls
498
102
-------
lABLt /-b (continued)
Cone,
ppm
0.50
0.50
0.50
Exposure
time
1.5 hr
1.5 hr
2 hr
Exposure.
condition
EC/SO
EC
Plant0
Soybean
Oats
Begonia
Petunia
Coleus
Effects
Foliar
X
on
Yield
X
X
X
0.50
0.50
0.50
0.50
0.50
2 hr
4 hr
4 hr
4 hr/day
for 14 days
5 hr/day
6 days/wk
for 12 days
26 days
EC
EC/SD
EC/SD
EC/SD
Snapdragon
Grape
Alfalfa
Broccoli
Radish
Tobacco
Tomato
Oats
Radish
Soybean
Tobacco
X
X
X
X
X
X
Oats
Barley
Bean
Sunflower
Barley
Bean
Sunflower
Species Effect0 Reference
7% decrease in short fresh weight; 172
trace foliar injury
Inition of leaf injury 174
No effect
30% decrease in flower number; 152 2
decrease in shoot weight
No effect; 12% decrease in shoot weight
11% decrease in number of flowers; no
effect
190% Increase in stomatal resistance 371
19% leaf injury
4% leaf injury 431
1% leaf injury
1% leaf injury
1% leaf injury
Foliar injury occurred to all crops 441
32% decrease top dry weight; 13% decrease 175
1n root dry weight; number of heads
unchanged
24% foliar injury; 42% decrease in dry 292
weight shoot
7% foliar injury; 31% decrease in dry
weight shoot
18% foliar injury;
weight shoot
36% foliar injury;
weight shoot
12% foliar injury;
44% decrease in dry
45% decrease in dry
34% decrease in dry
weight shoot
26% foliar injury; 35% decrease 1n dry
weights shoot
-------
Cone,
ppm
0.50
1.00
1.50
0.50
0.50
0.56
0.77
0.92
0.60
0.60
0.70
0.70
0.75
0.80
0.80-
2.00
0.80-
2.00
Exposure
time
4 hr
Exposure^
condition
GC/G
6/12, 24 hr/day EC
1-7 days
3 hr EC/SD
2 hr
4 hr, 20 min F/ZAP
4 hr, 20 min F/ZAP
PlantL
Red Clover
Effects on
Foliar
Yield
5 hr/day
6 days/ week
for 14 days
6 days
4 hr
6 hr
6 hr/day
5 days/week
for 14 days
8 hr/day for
3 days
EC
0
EC/SD
EC/SD
EC/SD
EC/SD
Broadbean
Sunflower
Tobacco
Pea
Cucumber
Apples
Soybean
White bean
Broadbean
Bean
Alfalfa
Alfalfa
Soybean
Soybean
Species Effect Reference
Increase in vitamin A, fat, protein content 196
Significant change in plant nutritional
components
Under drought conditions exposure caused 379
wider opening of stomata, no effect on
diffusive resistance
Increased glutamate dehydrogenase; increased 465
peroxidase activity
Accumulation of significant total and soluble 29
sulfur
7.3% increase in foliage injury; 5% increase 227
leaf abscission
No effects
Bifacial necrotic lesion on mature leaves 183
20% decrease in photosynthesis after 2 hr
fumigation; after 3-day fumigation, 1 24
hr to full recovery in light condition;
no foliage injury
Increase in total amino acids and ammonium,
decrease in aspartic acid glutamic acid
and protein synthesis, all before visible
injury present
No injury developed 192
Threshold dose for foliar necrosis; 25-50% 30
decrease in net photosynthesis
4.5% decrease in yield at 1,4 ppm
11% decrease in yield at 1.7 ppm 310
15% decrease in yield at 2.0 ppm
Epidermal and mesophyll cell death, the number
of dead mesophyll cells highly correlated
with increase in S02
Highest SO- concentration, significant decrease
in seed yield
-------
TABLt /-b (continued)
Cone,
ppm
0.90
1.00
1.00
1.00
1.00
1.00
1.0
1.0
1.00
1.50
1.50
Exposure
time
2 hr
2 hr
3 hr
3 hr
2 hr
Exposure.
condition
EC/SO
4 hr
1 hr/2 days
for 4 days
6 hr/day
for 3 days
1.5 hr
3 hr
0.75-3 hr
3 hr
GC
EC/SO
EC
EC/SD
EC/SO
EC/SD
EC/SD
EC/SD
EC/SD
Plant0 1
Broadbean
Barley
Poinsettia
eight cultivars
Alfalfa
Begonia
Petunia
Coleus
Snapdragon
Broccol i
Bromegrass
Cabbage
Lima bean
Radish
Spinach
Tomato
Geranium
Strawberry
Soybean
Soybean
Alfalfa
Effects on
•oliar
X
X
X
X
X
X
X
X
X
X
X
X
X
Yield
X
X
X
X
X
X
Species Effect0
26% decrease in net photosynthesis under
saturated light conditions; 52% decrease
in net photosynthesis under nonsaturated
light conditions
Threshold dose for foliar necrosis; 30-60
decrease in net photosynthesis
No effect
Leaf necrosis at 315 ppm CO- was 2.8x that
induced under 645 ppm C02
No effect
in flower number
Reference
39
30
177
192
19% decrease in
19% decrease in
16% decrease in
30% decrease
shoot weight
27% decrease in flower number
shoot weight
14% decrease in flower number
shoot weight
38% leaf injury
65% leaf injury 431
70% leaf injury
25% leaf injury
46% leaf injury
49% leaf injury
33% leaf injury
Rapid closing of stomata in low-RH air after
exposure; slow closing in high-RH conditions, 47
stomata remained open
No effect on growth and development
Necrotic lesions, lower leaf surface 358
9% decrease in shoot fresh weights, 4% leaf
injury 21%-29% decrease in shoot fresh weight 172
24-94% decrease in shoot fresh weight; 63-93% 172
foliar injury
Leaf necrosis at 315 ppm C0? was 2.5x that
induced under 645 ppm CO- 192
-------
OJ
00
Cone,
ppm
1.50
2.00
2.0
2.5
3.0
4.00
Exposure
time
To maturation
Exposure.
condition
EC/SD
Plantc
Kidney bean
/-;> ^continued;
Effects on
Foliar
2 hr
EC
3 hr
6 hr
hr
hr
hr
2 hr
GC
EC/SD
GC
GC
GC
EC
Begonia
Petunia
Coleus
Snapdragon
Poinsettia
eight cultivars
Apples
Yield
X
X
Poinsettia
eight cultivars
Begonia
Petunia
Coleus
Snapdragon
X
X
X
Species Effect0 Reference
20% decrease 1n root dry weight; 14%
decrease in legume dry weight;
17% decrease in seed dry weight; 33
10-30% decrease in apparent photo-
synthesis. Increase in chlorophyll
a and b content
14% decrease flower number; 22% decrease 2
in shoot weight
32% decrease in flower number; 24$ decrease
in shoot weight
30% decrease in flower number; 20% decrease
in shoot weight
15% decrease in flower number; 15% decrease
in shoot weight
0-18.3% foliar injury 177
17% increase in foliar injury; 62% increase 227
in lead abscission; 19% decrease in shoot
growth
0.13.8% foliar injury 177
1.8-26.8% foliar injury
18.8-96.5% foliar injury
33% decrease
32% decrease
21% decrease in
27% decrease in flower number;
in shoot weight
42% decrease in flower number;
in shoot weight
30% decrease in flower number,
shoot weight
20% decrease in flower number; 19% decrease in
shoot weight
Table arranged by increasing SO, concentration as first-order and exposure time as second-order divisions. Doses within a single study that
did not induce specifically different effects are listed along with the lowest SO. concentration that induced said effect.
F = field or forest surveys
F/CC = Field, closed chambers
D/OT = Field, open-top chambers
F/ZAP = Field, zonal air pollution system
G = Greenhouse
GC = Growth chambers
EC = Exposure chambers
EC/SD = Exposure chamber, special design
0 = Other
csee Appendix A for most scientific latin binomials of plants.
-------
U)
<£>
TABLE 7-5 (continued)
X Indicates study examinated foliar and/or yield effects. The X does not necessarily imply that an effect was found.
eMost prominent or significant effect reported.
-------
TABLE 7-6. ^E-RESPONSEJNFORMTION^UMMARIZED FROM LITERATURE PERTAINING TO FOREST TREE SPECIES AS RELATED TO FOLIAR, YIELD,
Cone,
ppm
0.001
0.003-
0.09
0.09-
0.12
0.004
0.35
0.006
0.007-
0.01
0.007-
0.01
0.008
0.011
0.017
0.015
0.019
0.023
0.025
Exposure
time
10 yr avg.
Annual avg
Annual avg
Annual avg
Annual avg
(exposed 5 mo)
Growing season
Annual avg
Annual avg
10 yr avg
Growing season
10 yr avg
Annual avg
Annual avg
Annual avg
6 hr
Exposure,
condition
F
F
F
F
F
F
F
F
F
F
F
F
EC/SO
Plant0
Forest trees
Scotch pine
Eastern white pine
White birch
Fir forests
Fir forests
Forest trees
White birch
Forest trees
Conifers
Conifers
Conifers
Eastern white pine
Effects on
Foliar Yield
X X
X X
X
X X
X X
X
X X
X
X
X
X
Species Effect0
No injury
Reference
Decreased photosynthesis leading to the
death of tree
No significant difference in S content of
foliage
No effect on foliar S content
20 +; 5% growth increase
20 +_ 5% growth decrease
Premature defoliation
Very little chronic foliar injury
Increased foliar 5 content; trace to light
foliar injury
Mostly chronic foliar injury; some acute injury
30% decrease in growth 454
52% decrease in growth 454
54% decrease in growth 454
355
369
273
297
296
273
Threshold dose for needle damage; most
sensitive clones only
193
-------
TABLE 7-6 (continued)
Cone,
ppm
0.025-
0.037
0.026
0.026-
0.037
0.035
0.038-
0.057
Exposure
time
Annual avg
Growing season
Annual avg
5 mo
Annual avg
Exposure.
condition
F
F
F
F
F
Plantc
Fir
White birch
Fir
Eastern white pine
Scotch pine
Effects
Foliar
X
X
X
X
on
Yield
X
X
X
0.045
0.045
0.048
0.05
0.15
0.05
0.05
0.05
0.10
0.20
0.05
0.05-
0.10
0.05
0.10
0.20
Growing season
10 yr avg
Growing season
6 hr
49 days
10 wk
5 mo
9 mo
9 mo
9 mo
F
F
F
EC/SD
F/CC
F/CC
F/CC
F/CC
F/CC
Jack pine
Forest trees
White birch
Eastern white pine
Norway spruce
Spruce
Beech
Spruce
Scotch pine
Fir
X
X
X
X
X
X
Species Effect Reference
Death of groups of trees 297
Moderate to severe foliar Injury 273
Rapid death of groups of trees 296
Foliar injury 369
Species occurrence negatively correlated 133
with SO^ ambient cone.; foliar S content
positively correlated with SO, ambient
cone.; foliar S content positively
correlated with SO- ambient cone.; by
distance from source
Reduced chlorophyll content, tissue death 273
Acute and chronic foliar injury -H-&
Severe foliar injury; foliar S concentration 273
3x normal
60% of tolerant clones foliar injury 193
developed
Foliar injury 491
No effects 224
Increase in S concentration proportional 223
to increase in SO,, exposure cone.;
terminal bud deatn
Decreased foliar buffering capacity; in- 222
peroxidase activity
Decreased photosynthesis 222
Decreased pollen viability 222
-------
TABLE 7-6 (continued)
Cone,
ppm
0.069
0.07
0.10
0.20
0.10
0.15
0.30
0.18-
0.20
0.20-
1.00
Exposure
time
Annual avg
3 days
10 wk
76 days
9 wk
24 hr
1 hr
Exposure.
condition
F
EC
F/CC
Plantc
Conifer
Eastern white pine
Spruce
Black alder
Poplar
Jack pine
Azalea
Firethorn
White ash
White birch
Effects on
Foliar
Yield
X
0.20
0.20
0.025
0.25
0.27
0.35
0.40
0.50
12 hr/day
for 7 wk
110 days
2 hr
2 hr
3 mo
3 hr
74 hr
EC/SD
EC/SD
EC/SD
EC
EC/SD
EC
Hybrid poplar
English birch
Eastern white pine
Jack pine
Red pine
Loblolly pine
Short! eaf pine
Slash pine
Virginia pine
Pin oak
White birch
Trembling aspen
Yellow pine
Fastprn whitp n-lno
X
X
X
X
X
X
X
X
Reference
454
19
223
Species Effect0
70% decrease in growth
Chlorotic spotting and death of needle tips
Decreased C0? uptake; positive correlation
between CO- uptake and cambium growth;
increase in cone, induced annual ring
width
Increase phenoloxidase activity 491
Decreased leaf area index and foliar 209
growth
Inhibited foliar lipid synthesis, inhibition 286
reversible; increase in dose = increase in
recovery time
No appreciable effect on foliar sorption of SO,, 367
Slightly decreased height; decreased relative 208
growth rate, relative leaf growth rate, and
relative leaf area expansion rate
No effect on phenyloxidase activity 491
6.5% foliar injury 34
4.5% foliar injury
0.5% foliar injury
All equally sensitive; most sensitive period 35
8-10 wk of age or older
45% decrease in height growth 368
107% increase in height growth
2% foliar Injury 217
Chlorophyll content varied inversely with 100
concentration
-------
TABLE 7-6 (continued)
Cone,
ppm
0.45
0.45
0.5
Exposure
time
6 hr
9 hr/day
for 8 wk
15 min
30 min
60 min
120 min
Exposure.
condition
EC/SO
EC
Plant0
Eastern white pine
Ponderosa pine
Red pine
Effects
Foliar
X
X
on
Yield
0.50
0.50
0.50
1.00
1.07-
6.41
1.83
2 hr
3 hr
5 hr
8 hr
30 min
to 6 hr
50 min
EC/SD
EC/SD
GC
Eastern white pine
Jack pine
Red pine
Trembling aspen
Austrian, Ponderosa
Scotch pine, Balsam,
Fraser, White fir
Blue, White spruce
Douglas fir
Scotch pine, Balsam,
Fraser, White fir,
White spruce, Douglas
fir
EC American elm
0 Scotch pine
P. pinea
F. nigra
0 Pine
Spruce
0.50
0.65
1.00
30 day
3 hr
4 hr
GC
EC/SD
GC
Chinese elm
Gingko
Norway maple
Pin oak
Trembling aspen
Austrian, Ponderosa,
X
X
X
X
X
X
Species Effect0 Reference
All tolerant clones developed foliar 193
injury
Severe needle tip chlorosis and necrosis 128
Decreased primary needle chlorophyll con- 78
tent.
Decrease dry weight of primary needles and
cotyledons
Further increase of all of above effects
12% foliar injury 34
11% foliar injury
2% foliar injury
11% foliar injury 217
No injury 399
Severe chlorosis and necrosis 416
Moderate marginal chlorosis
Moderate marginal chlorosis
Slight overall chlorosis
23% foliar injury 217
Less than 4% foliar injury all species 399
Inhibition of stomatal closing 335
Visible injury was proportional to foliage 65
S content
S0« absorbed by exposed foliage in winter- 298
time; S stored in new shoots
-------
TABLE 7-6 (continued)
Cone, Exposure Exposure, Effects on
ppm t1me condition0 Plant0 FbTTar TTeTd" Species Effect0 Reference
'°° 2 hr CG Austrian, Ponderosa X No foliar injury on Douglas fir, firs, 399
Scotch pine, Balsam, spruce
Eraser, White fir. Blue, Pine foliar injury threshold, necrotic
white spruce, Douglas fir tips
2-00 6 hr GC American elm X X Induce severe foliar injury; defoliation in 76
older leaves; significant reduced expansion
of new leaves; number of emerging leaves
and root dry weight reduced
2-00 6 nr GC American elm No significant reduction in lipid content; 79
significant decrease in new leaf protein
content; significant decrease in leaf,
stem, root carbohydrate content
2-°° 6 hr GC Chinese elm X 100% leaf necrosis 416
2-°° 6-5 nr 0 Ginkgo Water-stressed plant increased uptake 335
of S02
2-0(-1 12 nr 0 American elm Induced stomatal closing; S content 416
increased in plants fumigated in
light
3-°° 6 hr GC Ginkgo X 50% leaf necrosis 416
Norway maple
Table arranged by increasing SO concentration as first-order and exposure time as second-order divisions. Doses within a single study
that did not induce specifically different effects are listed along with the lowest S02 concentration that induced said effect.
F = field or forest surveys
F/CC = field, closed chambers
D/OT = field, open-top chambers
G/ZAP = field, zonal air pollution system
G = greenhouse
GC = growth chambers
EC = exposure chambers
EC/SO = exposure chamber, special design
0 = other
cSee Appendix A for most scientific latin binomials of plants
-------
0.14
0.02
0.02
0.03
0.04
0.08
0.15
0.03
0.04
0.04
0.15
0.05
TABLE 7-7 DOSE-RESPONSE INFORMATION SUMMARIZED FROM LITERATURE PERTAINING TO NATIVE PLANTS AS RELATED TO FOLIAR, YIELD
AND SPECIFIC EFFECTS INDUCED BY INCREASING S02 DOSE
Species Effect0
Loss of chlorophyll, decreased growth
Elimination of many lichen species
Decreased lichen diversity
Elimination of species
No effect on net photosynthesis, dark respira-
tion, transpiration coefficients, number of
tillers and yield
As above effects except visible foliar injury
and reduction of specific leaf area
Cone,
ppm
0.006
0.018
0.01-
0.02
0.015
0.017
0.02
Exposure
time
6 mo
Annual avg
Annual avg
6 mo
29 days
Exposure.
condition
F
F
F
F
GC
Plantc
Lichens
Lichens
Bryophytes
Lichens
Bryophytes
Ryegrass
Effects on
Foliar Yield
X
X
GC
Ryegrass
22 days in
2 consecutive
growing seasons
29 days
22 days in 2
consecutive growling
seasons
85 days GC Ryegrass
Growing season GC Ryegrass
10 wk GC Ryegrass
6 mo F Lichens
51 days GC Ryegrass
Growing season GC Ryegrass
Increased organic S content
Increased organic and inorganic S content
Alleviated S deficiency
Alleviated S deficiency
Alleviated S deficiency
Reduction in yield without symptoms
Tissue death
Decreased concentration glycine and serine;
inhibited photorespiration pathway
Alleviated S deficiency symptoms
Reference
255
256a
397
147
87
89
86
277
256a
234
86
-------
TABLE 7-7 (continued)
Cone,
ppm
0.06
0.067
0.073
0.074
0.08
0.09
(peak)
0.11
0.11
0.11
0.12
0.13
0.25
0.50
1.00
0.13
Exposure
time
Growing season
26 wk
26 wk
Exposure.
condition" Plant0
Ryegrass
4 wk
103 5 hr/wk
for 20 wk
9 wk
6 wk
6 wk
GC
EC
EC
Effects on
Foliar Yield
X
Ryegrass
Ryegrass
18 nr
13 hr/day for
28 days
115 days
4 wk
0
EC
F/CC
0
Spiderwort
Foxtail grass
Ryegrass
Cocksfoot
X
X
EC
EC/SD
Ryegrass
Grass
Ryegrass
Ryegrass
EC/SD Ryegrass
Species Effect0 Reference
Increase in photosynthesis, respiration 135
and chlorophyll content; light increase
in productivity
Increase 1n dry weight of leaves, number 24
of tillers, dry weight of stubble and
leaf area; 51% decrease in yield
50% decrease in shoot dry weight 24% 25
decrease in chlorophyll a content;
26% decrease in chlorophyll b content
Increase in chromosome aberration rate of 282
germinating pollen
Foliar injury as caused by heavy metals was 236
increased by SO- exposure
Decrease in weight; accelerated leaf 42
senesence
30% decrease in leaf area; 45% decrease 12
in dry weight; decrease in number tillers;
decrease in number of green leaves;
decrease root/shoot ratios
20% decrease in leaf area; 40% decrease in 14
dry weight; decreased root/shoot ratio
Significant decrease in leaf area and all dry 13
weight fractions; decrease in number of leaves
and tillers
Decrease in dry weight of leaves, number 24
of tillers, dry weights of stubble and
leaf area; 46% decrease in yield
Foliar necrotic lesions and decrease in 135
net primary productivity at 0.13 ppm
and above
Decreased productivity 135
-------
TABLE 7-7 (continued)
Cone,
ppm
0.15
0.15
0.15
0.20
0.20
(peak)
0.25
0.27
0.27
0.38
(peak)
0. 50-
lL 00
0.71
2.00-
0.00
3.50
Exposure
time
6 wk
51 days
Growing season
2 hr
55 days
5 wk
14 days
8 wk
6-43 wk
2 hr
1 hr
2 hr
5 hr
8 hr
1 hr
Exposure,
condition
GC
GC
F/CC
EC/SD
EC/SD
EC/SD
EC/SD
F/CC
EC/SD
EC/SD
0
Plant0
Duckweed
Duckweed
Ryegrass
Kentucky
bluegrass
Ryegrass
Ryegrass
Ryegrass
Ryegrass
Ryegrass
87 Desert
species
Lily
Dij>lacus
meteromeles
Acacia
Effects on
Foliar Yield
X
X
X
X X
X
X
X
X
X
Species Effect0
Reference
Decrease in starch content and size of 131
fronds
Decrease in starch content and growth; 131
decrease in surface area dry weight
Alleviated S deficiency symptoms; increase 85
in S content of foliage, free amino acid
content, and N/S ratio
Visible foliar injury 320
Decrease in weight; accelerated leaf sensence 42
No effect on number of tillers; 17% decrease 188
in yield
Increase in free amino acid content 11
38% decrease in green weight; 30% decrease 188
in total dry weight; no reduction in
number of tillers; 2x senesence
36% decrease in total dry weight 93
Most plants required more than 2.00 ppm 182
S0_ to produce foliar injury
Inhibited pollen tube elongation at all 294
exposure durations
Increase in SO- dose induced a progressive 478
decrease in photosynthesis and transpiration
Foliar Injury 337
-------
TABLE 7-7 (continued)
« *l fif>st-order and exposure time as second-order divisions. Doses within a single study
effects are listed along with the lowest S02 concentration that induced said effect.
F = field or forest surveys
F/CC = field, closed chambers
D/OT = field, open-top chambers
G/2AP = field, zonal air pollution system
G = greenhouse
GC = growth chambers
EC = exposure c,~-?.mbers
EC/SD = exposure chamber, special design
0 = other
See Appendix A for most scientific latin binomials of plants.
-------
spatially in reference to dose. However, if no difference in response was
obtained within plant species or groups of plants exposed to a series of doses
as reported in a single publication, then all effects data have been summarized
at the point in the tables of lowest sequence in dose.
The concept of dose-response can be demonstrated by a synthesis of data
presented in Tables 7-5, 7-6, 7-7. The following conclusions were developed
by summarizing the dose-response data without regard to confounding environ-
mental variables:
(1) Yield of economically important agricultural species can be signifi-
cantly suppressed by SCL concentrations in the range of 0.05 to 0.06 ppm if the
exposure period is sufficiently long, i.e., 2 weeks in length. Both crop
quality and quantity can be negatively affected.
(2) Fluctuating, long-term (seasonal, annual) S0? exposures averaging
0.05 ppm or less can cause economically and ecologically undesirable effects to
productivity and stability of range and forest ecosystems.
(3) As S02 concentrations increase to 0.25 ppm, a variety of agricultural
crops such as alfalfa, timothy, range grasses, soybean, barley, wheat, cabbage,
lettuce, spinach, tobacco, cucumber, eggplant, pea, and kidney bean responded
with necrotic foliar injury or suppressed yield. Approximately 70% of the
cultivated agronomic crop species exposed to 0.25 ppm or less S0? responded
to the treatment with changes in stomatal aperture, foliar injury, or yield
effects. Foliar injury on vegetables and yield suppression are directly related
to economic value.
(4) Forest tree species representing coniferous and deciduous forest
ecosystems such as pine, spruce, fir, beech, alder, and poplar responded to
0.25 ppm or less S02. Approximately 90% of the species tested in this range of
S0? concentrations responded with physiological modifications, suppressed
7-49
-------
photosynthesis, foliar injury, death of buds, or suppressed foliar or woody
growth.
(5) Non-woody components of native ecosystems such as lichens and grasses
also responded to SCL concentrations up to 0.025 ppm. Responses included suppressed
growth, death, and reduced diversity in lichen populations, and suppressed photo-
synthesis and growth of leaves, tillers and stubble of grasses.
(6) At S02 concentrations between 0.25 and 0.50 ppm, less than 50% of the
agronomic species tested responded negatively to the SC^ treatments. A compar-
ison of this 70% species response to the 90% response at S02 concentrations
less than 0.25 ppm might be taken to suggest that plant response is not positively
correlated with dose. This is not the case; exposure durations used at the
higher range S0? studies generally ranged 1-8 hours while multiple day exposures
were frequently at the lower SO- concentrations. Above 0.50 ppm SCL the expected
trend is apparent—greater sensitivity at increased SCL concentrations. All
agronomic species responded to SCL exposures at 0.50 ppm for exposure durations
ranging from 1.5 to 5 hours. A variety of responses occurred, including physio-
logical modifications, foliar injury, and suppressed growth.
These trends imply that as S0? concentrations are increased:
(1) shorter exposure duration is sufficient to elicit the same or greater
plant response which occurred at a lower concentration;
(2) responses become more severe;
(3) plants tolerant at lower concentrations become sensitive.
For additional information on dose-response relationships the reader is
referred to the sections in this document on the interactive effects of S02 and
particulates with other air pollutants.
7-50
-------
7.4 PLANT EXPOSURE TO SULFUR DIOXIDE
7.4.1 Deposition Rates of Sulfur Compounds
Deposition processes limit the lifetime of sulfur compounds in the
atmosphere, control the distance traveled before deposition, and limit the
atmospheric concentrations of the pollutant (142). As previously mentioned,
sulfur dioxide and particulate sulfate are the predominant forms of sulfur
in the atmosphere of developed countries.
7.4.1.1 Dry Deposition—There have been several studies of the deposition
of particulate material to natural surfaces (68, 276a, 382). Very large
particles are chiefly deposited by sedimentation. Particles in the range of
1-100 ym are also borne towards the surface by turbulence where sedimentation
is supplemental to impaction on rough surfaces. Submicron particles (sulfuric
acid aerosols) diffuse by Brownian motion through the thin laminar layers
close to the surface elements. This may be followed by active uptake in the
case of plant leaves. The mean SO^ deposition velocities are surprisingly
similar for a wide range of deposition surfaces (Table 7-8).
Dry deposition is capable of removing significant amounts of the
larger particles from the atmosphere within 2 or 3 days but would require
several weeks to remove the submicron fraction.
7.4.1.2 Wet Desposition--Both S0? and sulfate may contribute significantly
to the amount of dissolved sulfur in rain. Hogstrom (184) found that sulfur
emitted by a point source in Sweden was deposited during rain with a removal
time of 1 to 2 hr. However, Granat and Rodhe (155) found that less than
6 percent of sulfur emitted from the tall stacks of a power-generating
station was removed within 15 km of travel distance. Dissolved SO^ in
7-51
-------
TABLE 7-8 RESULTS OF SEVERAL EXPERIMENTAL INVESTIGATIONS OF
S02 DEPOSITION BY VARIOUS SCIENTISTS3
Surface
Calcareous soil
Acid soil
Calcareous soil
Grass
Grass
Short grass
Medium grass
Medium grass
Cotton (sedgemoor)
Wheat
Wheat
Soybean
Pine forest
Pine forest
Method, Conditions
Laboratory, mass
balance
Laboratory, mass
balance
Gradient, field
Gradient, field
Summer
Autumn
35CO tracer,
SU2field
Gradient, field
Gradient, field
Tracer, field
Gradient, field
Gradient, field
Tracer
Tracer
Mean
v r
9' 9'
cm/sec sec/cm
1.2 0.83
0.8
0.3
0.8
0.85 1.2
0.89 0.46
0.19 0.38
0.7
0.74
0.44 0.28
1.25 0.11
0.1-0.6 0.1
1.0
r
s1
sec/cm
0.24-0.39
1.2-3.8
0.01
0.8
3.0
0.34
0.66
0.45
--
1-2.5
2.0
0.69
1.5-5.0
S0~ deposition expressed in terms of deposition velocity relative to 1 m.
r = gas plus resistance, rx = surface resistance.
Source: Garland (1978) (143).
7-52
-------
rainwater in England was about 3 mg/liter when the corresponding air
concentration was about 100 ug/m (101).
Sulfur dioxide removal from the atmosphere may be characterized (142)
as follows:
(1) SOp is removed by dry deposition with a deposition velocity of
approximately 0.8 cm/sec for most surfaces.
(2) The deposition velocity of sulfate aerosol is no greater than
0.1 cm/sec.
(3) Sulfate is removed by rain with a time constant on the order of
10"4/sec.
(4) S02 removal by rain is about an order of magnitude less efficient
than that for sulfate.
7.4.2 Routes and Methods of Entry Into the Plant
The stomata of leaves have been demonstrated to be the major avenue of
S02 entrance into plants. Although this is a widely accepted conclusion that
has been presented in numerous reviews (159, 219, 420, 421, 442), there is
still a controversy as to the role of stomata in plant sensitivity. Many
factors that govern the mechanism of stomatal opening and closing have been
determined to be independent of S0? concentrations. The physical factors
such as light, leaf surface moisture, relative humidity, and soil moisture
availability may actually play a major role in plant sensitivity as related
to initial passive entry of S02 into the leaf (114, 307, 383, 405, 497).
7-53
-------
There is reported to be no linear relationship between stomatal pore
size and permeability of leaves to gases (427). The diffusion of a gas through
the stomata is a dynamic process that depends upon the diffusion coefficient of
the gas, the partial pressure difference between the atmosphere and the inside
of the leaf, the leaf or stomatal resistance, and the boundary layer resistance
(159). When the other factors are held constant or are of known predictable
variations, then the importance of the stomatal resistance can be estimated
in relation to the entry of pollutants. Although several methods of measuring
stomatal resistance have been reported (91, 428), as have methods of deter-
mining the number and distribution of stomata (258), the influence of actual
pore radius may also be of importance (159). The numerous independent physical
factors that influence stomatal opening and closing must therefore be
considered when determining plant sensitivity or tolerance to the entry of
so2.
The absorption rate of SCL into plants varies not only with species,
but also with previous exposure to SCL. Bigtooth aspen (Populus grandidentata)
had a higher SCL absorption rate during exposure to 2.75 ppm SCL for 2 hr
than white ash (Fraxinus americana) or yellow birch (Betula jflleghaniensis)
when they were exposed to 0 to 6 hr of prefumigation with 0.75 ppm SCL(210).
However, after 20 to 36 hr of the prefumigation treatment, the rate of S02
absorption during the 2.75 ppm S02 exposure was greater for the birch and ash.
The sulfur content of the foliage increased in all species. Eight days after
35
fumigation with S02 varying amounts were translocated throughout the plants
including roots (210).
Sulfur dioxide induced the closure of Pelargonium hortorum stomata
especially when they had been fully opened before the exposure. However,
large stomata still remained 50 percent open and necrosis was not averted
(46). Kodata and Inoue (233) demonstrated that S02 entered leaves of Pinus
7-54
-------
resinosa through stomata and that it accumulated in the cells around the
stomata for some time before diffusing inward through the leaf. They reported
that lateral diffusion was slower.
Once SCL has entered, it may itself induce stomata to remain open for
longer periods of time or to open wider than before fumigation. Exposure
to SCL when relative humidities were above 40 percent caused an increase in
stomatal opening, but a depression of stomatal opening at lower relative
humidities (285, 290). A 3-min fumigation with 2.5 ppm S02 increased carbon
dioxide uptake and stomatal opening in Sinapsis alba plants. However,
with the same concentration suppressed carbon dioxide uptake and stomatal
closure were noted (63). Potted sunflower, broadbean, tobacco, bean, barley,
and corn plants maintained under drought conditions and treated with 0.5 ppm
S02 for 5 hr over several days showed a wider stomatal opening than plants
supplied with adequate moisture (390).
Stomatal opening of the leaves of many crops may be increased by
ambient S02 levels, possibly inducing two undesirable consequences (448).
Increased transpiration rates would lead to earlier and more severe water
stress in periods of prolonged drought and therefore restricted growth.
Induced opening of stomata would also increase the access of other toxic
gases or pathogens to the underlying susceptible mesophyll tissues.
Increasing the S02 concentration evenly up from zero reduced stomatal
resistance in beans (Vicia faba) and corn (Zea mays) at 0.02 and 0.01 ppm,
respectively, with young leaves exhibiting the lowest resistances. The
effect of S0? on stomatal resistance was greater on leaves of water-
stressed plants (448).
The effects of low concentrations of S0? on Vicia faba include larger
and more rapid stomatal opening in older leaves exposed to 290 yg/m (37).
Stomatal resistance of leaves exposed to up to 0.5 ppm S02 decreased by
20 percent, and it was estimated that response to SO should increase the
7-55 2
-------
transpiration rate by 32 percent for single leaves in a growth chamber
and by 23 percent for a field situation (37).
Uptake of SCL through the cuticle of the leaf surface has been
suggested. Sulfur could be washed from pine shoots shortly after exposure,
and thus SCL uptake by the cuticle may be a reversible reaction (143).
Uptake of SCL by wheat plants during periods of stomatal closure was
considerably enhanced by dew since there was considerable surface resistance
during periods of no dew (137).
It has been suggested by Keller (221) that pollutants such as S02
and hydrogen fluoride may enter through bud scales or lenticels of
certain hardwood species. The percent bud kill in beech following
winter fumigation with low increasing SCL concentration lends support to
this avenue of ingress over long periods of exposure.
7.4.3 Beneficial Effects
Under certain conditions, atmospheric SCL can have beneficial
effects on vegetation. This subject has been recently reviewed (334).
Sulfur requirements to maintain high crop production range from 10 to 40
kg/ha per year. A decline in the use of sulfur-containing fertilizers
in recent years has placed a greater dependency on the atmosphere as a
source of supplemental sulfur to meet the needs of vegetation.
Cowling et al. (86) found beneficial effects of S02, such as increases
in yield and sulfur content, in perennial ryegrass that was grown with an
inadequate supply of sulfur to the roots.
Faller (129) conducted a series of experiments to determine the effects
of varying atmospheric concentrations of SO^ on sunflower, corn, and tobacco.
In these studies, the plants were grown in nutrient media containing adequate
supply of all essential elements, but no sulfur.
Plants grown in the atmosphere without S0? developed sulfur deficiency
7-56
-------
symptoms within a few days. In other treatments, total plant yield increased
to some extent with increasing concentrations of atmospheric SCL. For tobacco,
the total dry weight increased by up to 48 percent. The yield of leaves
and stems alone increased by 80 percent, while increments in the dry
weights of tobacco occurred even at the highest SCL concentration used
o
(1.5 mg/m ); sunflower and corn had their highest biomass at SCL concentrations
3
of 1.0 and 0.5 mg/m , respectively. Beyond these concentrations, visible
injury was observed. Additional studies by Faller (129) with S suggest
that up to 90 percent of the plant sulfur can originate from the atmosphere
under the specific experimental conditions.
Recently, Noggle and Jones (334) conducted a 2-year study using S to
determine the contributions of soil and atmospheric sulfur to the sulfur
requirements in cotton and fescue. Cotton was more efficient than fescue
in accumulating sulfur from the atmosphere. The amount of sulfur accumulated
from the atmosphere was apparently influenced by the amount of sulfur supply
in the soil relative to the sulfur requirements of the plant. A crop
grown in a sulfur-deficient soil will accumulate more sulfur from the
atmosphere than the same crop grown in a soil that has an adequate
supply of sulfur. Noggle and Jones (334) showed that cotton grown in
the vicinity of certain coal-fired power plants accumulated significant
amounts of atmospheric sulfur (as S02) and produced significantly more
biomass than that grown at a location remote to the industrial source of
sulfur. Thus, under appropriate conditions, such as with sulfur-deficient
soils, the atmosphere can be an important source of sulfur for plant
requirements.
7.4.4 Tissue Concentration
Studies of sulfur accumulation after exposure to a constant dose
consisting of different concentrations and exposure times have shown that
after short-term exposures to SO,, concentrations sufficient to cause injury,
7-57
-------
sulfur content of exposed tissue is relatively low. In this case, it is not
the amount of sulfur absorbed but the rate of absorption that is the deciding
factor. High concentrations of S02 can cause acute necrosis on fast-growing
plants under conditions of high light and humidity and favorable temperature
at levels of absorbed sulfur that are difficult to detect (59). In polluted
areas, high concentrations of atmospheric S02 occur in combination with low
concentrations. Because of the comparatively high contribution of low
SCL concentrations to the total frequency of occurrence, chemical analysis
of leaves for the detection of sulfur accumulation is less problematic at
higher pollutant loads. Sulfur content in plant organs, therefore, can be
used as a diagnostic tool to determine the effects of atmospheric SCL on
vegetation, but is not useful to establish air quality criteria.
Several reports in the literature show that plants resistant to SCL
injury can accumulate more sulfur than sensitive plant species growing under
the same conditions. In interpreting the sulfur analysis of foliage for
diagnostic purposes, consideration should be given to the geographic
location, the state of plant growth, the relationship between visible
injury and pollutant or biological causes, the sulfur content of the soil,
and atmospheric SCL concentrations.
7.5 INTERACTIVE EFFECTS ON PLANTS WITH THE ENVIRONMENT—SO-
7.5.1 Physical Factors
Environmental factors are unstable and highly variable, and therefore
no generalized statements can be made about long-term effects over large
geographic areas. However, environment plays an extremely important role
in plant response to SCL.
7.5.1.1 Temperature—Temperature plays an important part not only in
determining the metabolic rate of the plant, but in determining (with moisture,
fertility, and light) the species diversity and richness of a given ecosystem
7-58
-------
(325). The primary path of entry of SO- into the leaf is through the stomata.
Temperature exerts an effect on the guard cells that control the stomatal opening
and closing and thus the entry of SCL. Temperature regimes that increase the
physiological activity of the plant also increase the plant response to SCL
(363). It is generally believed that plant sensitivity increases with temper-
ature over a wide range, from about 4 to 35°C (159). Several studies suggest
greater resistance of conifers to SCL in the winter, attributed to lower rate
of physiological activity (325). However, there is some conflicting evidence.
According to Guderian and Stratmann (161), in areas with S0? emissions, winter
wheat and winter rye are more severely injured than the summer varieties. Guderian
(159) interpreted this to be due to gas exchange taking place through the stomata
at temperatures as low as -2°C.
7.5.1.2 Relative Humidity—Relative humidity is another factor that controls
stomatal opening and thus plant sensitivity to SCL. Although plant sensitivity
increases with relative humidity, once above a relative humidity of 40 percent,
changes of 20 percent or more are required to cause changes in plant sensitivity
(383). According to Zimmerman and Crocker (498), although relative humidity is
important in governing sensitivity and consequently the susceptible population,
it is not as important as the tissue turgidity. Based on the water relation in
trees, Halbwachs (163) has rated plants as sensitive, intermediate, and tolerant
at relative humidities of over 75 percent, 50 to 75 percent, and below 50 percent,
respectively.
7.5.1.3 Light—Light also controls stomatal opening and thus the plant sensi-
tivity. Plants are more tolerant when fumigated in darkness with S0? or when
held in the dark for a few hours before exposure (498). This relationship is
complex, since injury is greater if the night exposure follows daylight (325).
Setterstrom and Zimmerman (383) observed that buckwheat grown at a
light intensity of 35 percent or less of full sunlight was more sensitive to
7-59
-------
SO than when grown under full sunlight. Other investigators have found that
injury was more severe when tomato stems and foliage were fumigated on clear
days than it was on cloudy days (325).
Plants seem to be more sensitive from midmorning to midafternoon, in
spite of a high light intensity that might continue after midafternoon (363,
421). At the same time, plants may be more sensitive in the morning during
good weather, but may become more sensitive if temperature and light increase
in late afternoon (452).
7.5.1.4 Edaphic Factors—Soil factors influence directly and indirectly the
responses of plants to S02. Soil fertility, moisture, and soil physics directly
influence plant sensitivity to S02 (325). Adequate soil moisture and the
resultant stomatal opening result in plant sensitivity, whereas wilting
conditions confer tolerance (383, 493, 498). As long as plants are grown with
an adequate supply of water, they are much more sensitive to S02 than are plants
grown with an inadequate supply, even though the moisture content of the soil
is the same at the time of fumigation (383). Therefore, sudden changes in soil
moisture at particular growth stages will probably have little influence on
sensitivity to S02 injury (325), although withholding water from some crops
during periods of high pollution risk has been suggested (56). According to
Brandt and Heck (56), sensitivity is less for plants grown in heavy soils than
it is for those grown in sandy soils. Obviously, heavy soils have better
water retention capacity than sandy soils. This may also be related to
differences between the two soils in the oxygen tension.
Soil fertility has a significant influence on plant response to S02.
Some plants become more tolerant to S02 upon its application (126, 493). On the
contrary, with eastern white pine, increased nitrogen, phosphorus, and potassium
concentrations in the greenhouse raised tolerance (decreased needle
necrosis) in sensitive clones, but did not prevent chlorotic banding in the
field (81). Nitrogen and sulfur deficiencies were correlated with decreased
7-60
-------
tolerance to SCL in tobacco and tomato (262). Conversely, nutrient deficiencies
increased S02 sensitivity in alfalfa (383). Fertilization of several dicotyledons
with a complete fertilizer has been effective in decreasing their sensitivity
to SCL, but similar treatment of monocotyledons like oats and barley have been
ineffective (452, 493).
7.5.2 Biotic Factors
Plant disease is caused by the interaction of a plant and a pathogen acting
under suitable environmental conditions. The influence of SCL directly on any
given plant and pathogen has been difficult to investigate. Whenever the
variables of the physical environment are added to such experimental sequences,
the subject becomes even more difficult to examine. Heagle (170) has
provided the most recent review of the interaction between air pollutants
and plant parasites (Table 7-9).
The powdery mildew fungus (Microsphaera alni) is often sparse in sites
exposed to urban air pollutants. Although the fungus is tolerant of ozone,
infection was reduced by acute and chronic doses of SCL. Previously fumigated
leaves became infected, which indicated that SCL was directly fungicidal to
M_. alni rather than being toxic to the plant and thereby making it less
susceptible to infection (180). Such interactions do not always take place,
as was reported by Majernik (284) in studies of barley and the powdery mildew
fungus Erysiphe graminis. He could show no relationship between S02 fumigation
and disease development even though infection by £. graminis enhanced
stomatal closing and SOp stimulated stomatal opening. Fumigation with
sulfur dioxide is a well-known treatment to prevent mold and rot of
grapes during storage and shipment (328, 329, 375).
Relatively low concentrations of SO- (0.20 ppm) reduced the germination of
uredospores and thereby reduced the incidence and severity of bean rust caused
by Uromyces phaseol i (463). Exposure of the bean plants to sulfur dioxide
''•SI
-------
(ABLE /-y. L-H-hClS OK SULI-UR DIOXIDE ON PLANT DISEASES.
Pollutant and
disease affected
Wheat stem rust
Tree rusts
Wood rots
Needle cast on juniper
Needle cast on
larch and pine
Rhytisma on maple
Hysterium on alder
and birch
Apple scab
Oak powdery mildew
Lilac powdery mildew
Rose black spot
Rose black spot
Dwarf mistletoe on
larch and pine
Armillaria in trees
Hood rots
Needle cast on
spruce
Effects
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Decreased incidence
Smaller lesion
Decreased incidence
Increased incidence
Increased incidence
Increased incidence
Pollutant
dose
Ambient
Ambient
Ambient
Ambient
Ambient
Ambient
Ambient
Ambient
Ambient
Ambient
Ambient
0.04 ppm for 48 hr
Ambient
Ambient
Ambient
Ambient
Location
Sweden
Canada
Czechoslovakia
England
Canada
England
Sweden
Poland
Austria
U.S.A.
England
England
Canada
Canada
Czechoslovakia,
Poland, Germany
Czechoslovakia
Poland
Source:Heagle (170).
-------
before inoculation was most effective in reducing disease.
Concentrations of 0.01 ppm SCL for 2 days after inoculation slightly
favored disease development on roses inoculated with Diplocarpon rosae, but
0.04 ppm S02 reduced the disease (375).
Decreased parasitism by several pathogenic fungi has been noted on
trees injured by SCL (377). Smelter emissions decreased the incidence of
rust (caused by Cronartium ribicola); less heart rot was found in white pines
located close to a source of S0? (269).
Sulfur dioxide, like other harmful agents, weakens plants and permits
many organisms to invade. Such is the suspected reason for increased incidence
and severity of attack by Armillaria mellea in trees weakened by SO- (116, 206,
245).
The effects of S0? on infection by organisms other than fungi have also
been studied. Abies concolor and A_. vertchi were severely attacked by plant
lice in an environment of high SCL, but Pinus strobus was attacked less and _P_.
griffithi and P_. sylvestris were not attacked at all (409).
The sensitivity of plant nematodes to SO- and ozone varies with species
and feeding habits (461). When plants were exposed to 0.25 ppm ozone and S0?
singly and in combination for 4-hr periods three times per week, the ozone
and the mixture of ozone and sulfur dioxide inhibited the development of
Heterodera glycines and the reproduction of Trichodoris christiei. Sulfur
dioxide treatment alone increased the reproduction of Pratylenchus penetrans.
No direct effects of S0? on plant pathogenic bacteria have been reported,
but Heagle (170) presented a brief review of the indirect effects of S0? in
relation to the acidity of soil and nutrient exchange. Table 7-10 groups a
number of microorganisms, most of which are known to be pathogenic, according
to their sensitivity to S0?.
As with higher plants, a direct influence of SCL on plant pathogenic
7-63
-------
TABLE 7-10. RELATIVE SENSITIVITIES OF SOME MICROORGANISMS
TO GASEOUS SULFUR DIOXIDE
Groupc
Organism
Extremely sensitive
Very sensitive
Sensitive
Less sensitive
Some yeasts, Displocarpon rosae, Sclerotinia delphinii,
Rhizoctonia tuliparum, Venturia inaegualT?
Phytophthora infestans, Rhytisma acerinum, Botrytis
cinerea, Botrytis sp., Sphaerotheca pannosa,
Melampsora cerastii, Didymellina macrospora,
Alternaria sp., Microsphaera alphitoides
Sclerotinia fructicola, Pestalotia stellata, Glomeralla
cinguluta, Macrosporium sarcinaeforme, Puccini a
graminis, Puccinia striiformis, Puccini astrum sp.,
Coleosporium sp., Cronartium sp., Phragmidium sp.,
Alternaria brassicicola
Ceratostomella ulmi, anaerobic yeasts, Aspergillus
niger, Penicillium sp.
These are arbitrary ratings based on field surveys (presence or absence of
organism) and supported by extrapolations from fumigation trials and
germination tests (inhibition > 76 percent).
Source: Saunders (1973) (376)
7-64
-------
organisms has been demonstrated. In addition, the indirect influence of
SCL on the process of pathogenesis through increasing the host's
susceptibility to attack by biotic pathogens has also been shown to occur.
The frequency of these events under natural conditions has been difficult
to study, and therefore estimates of the importance of such occurrences are
lacking.
7.6 INTERACTIVE EFFECTS OF S02 WITH OTHER POLLUTANTS INCLUDING PARTICULATE
MATTER
7.6.1 Introduction
Ambient atmospheres usually contain more than one specific air pollutant.
Long-distance transport of photochemical oxidants and oxidant precursors
(200, 441), the demonstration of acidic rainfall over large areas of the eastern
United States (74), and atmospheric monitoring suggest that emissions from
specific sources are mixed with ambient concentrations of one or more associated
pollutants. Extrapolation from results of single pollutant effects on vegetation
under ambient field conditions must be approached with caution. Reactions to
pollutant combinations may be additive, less than additive, more than additive,
or antagonistic. Reinert (360) and Reinert et al. (362) have prepared the
most recent reviews of this area of investigation. In addition, a compilation
of studies using ^0.50 ppm S0? in combination with other pollutants is
presented in Table 7-11.
7.6.1.1 Sulfur Dioxide and Ozone--A more than additive reaction on vegetation
was first noted with ozone and SO,, (308). Tobacco was severely injured by
0.03 ppm ozone and 0.24 ppm SO^ when the pollutants were combined for
either 2 or 4 hr, whereas when used alone, neither pollutant produced
foliar symptoms.
Since that first report, the interactive effects of ozone and S02 have
been studied using a variety of plant species. Radish and alfalfa plants
showed more than additive foliar injury from a 4-hr exposure to a mix of
7-65
-------
TABLE 7-11. EFFECTS OF SULFUR DIOXIDE ALONE AND IN COMBINATION WITH
OTHER POLLUTANTS ON SELECTED PLANTS AT 0.50 PPM OR LESS
Species
Exposure
Duration
Result
Pea
Alfalfa
Alfalfa
Alfalfa
Alfalfa
Radish
0.05 ppm Sg 1 hr
0.05 ppm N02
0.15 ppm S02 1 hr
0.15 ppm N0?
0.15 ppm S02
0.15 ppm N02
0.30 ppm S02
0.10 ppm 0,
(03) 3
0.15 ppm S02
0.15 ppm N02
0.15 ppm S02
0.10 ppm N02
Pinto bean 0.05 ppm S02
0.05 ppm N02
Radish 0.05 ppm S0?
+ ^
0.05 ppm N02
Oats 0.05 ppm S02
0.05 ppm N09
1 hr
1 hr
2 hr
4 hr
4 hr
4 hr
4 hr
Significantly decreased net
photosynthesis.
Inhibited photosynthesis; percent
of reduction not stated, but
authors state synergistic effect
most marked at this concentration.
Greater than additive inhibition
(7%) of photosynthesis (as
measured by C02 uptake). Similar
results at 0.25 ppm for both
gases.
Additive inhibition of photosyn-
thesis (11% +_ 3%) measured by
C02 uptake. Some tissue damage.
7% reduction in apparent photo-
synthesis. Some tissue death.
17% leaf injury, lower leaf
surface. 0.5 ppm S0? alone
= threshold; 2 ppm of alone
= threshold.
2% leaf injury measured as pig-
mented lesion, tissue death,
loss of chlorophyll.
Tissue death and loss of chloro-
phyl1.
Tissue death and loss of chloro-
phyll.
7-66
-------
TABLE 7-11 (continued).
Species
Exposure
Duration
Result
Eastern 0.05 ppm S0
white pine +
0.05 ppm )o
Radish
0.10 ppm S0?
+ L
0.10 ppm 03
4 hr
4 hr
Severe needle injury (2-3 cm leaf
tip injured) on new needles,
expressed most vividly 72
hr after exposure
50/o leaf injury
Cabbage
Tomato
Radish
Alfalfa
Cabbage
Broccoli
0.10 ppm S0?
+
0.10 ppm 0
4 hr
Broccoli 0.10 ppm SO,
0.10 ppm 0,,
0.10 ppm S0?
+
0.10 ppm 03
0.10 ppm S0?
+ ^
0.10 ppm 03
0.10 ppm „
+ *-
0.10 ppm 0
0.50 ppm S0?
+
0.05 ppm 03
0.05 ppm S02
0.05 ppm 0
4 hr
4 hr
4 hr
4 hr
4 hr
4 hr
22% leaf injury. 0.10-0.5
ppm S00 alone = no foliar
injury! 0.05 ppm 03 alone
= 1% foliar injury.
34% leaf injury. 0.05 ppm
S02 alone = 4% leaf injury; 0.10
ppm 0- alone = 1% leaf
injury.
50% leaf injury.
50% leaf injury.
24% leaf injury.
4% leaf injury. 0.10-0.05 ppm
SO- alone = no leaf injury;
0.05 On alone = no leaf
injury.
17% leaf injury. 0.5 ppm
SO- alone = 4% leaf injury;
0.10 ppm On alone =
1% leaf injury.
7-67
-------
TABLE 7-11 (continued).
Species
Exposure
0.50 ppm S02
0.05 ppm 03
0.10 ppm S02
0.10 ppm 03
0.05 ppm S02
0.10 ppm 0-,
O
0.10 ppm S02
0.10 ppm 03
0.15 ppm S02
0.10 NO
0.14 ppm S02
0.05 ppm 03
0.10 ppm N02
Duration
Result
Radish
Peas
Peas
Peas
Loblolly
pine (2 wk
old) Syca-
more (1 wk
old) seed-
1 ings
4 hr
5 hr
5 hr
5 hr
6 days
24 hr/day
(144 hr)
6 hr/day
for 23 days
(168 hr)
Scotch
pine
Norway ppm S0?
spruce
Douglas fir 0.01 ppm N00
Frazier fir 0.07 ppm HP
0.05 ppm 0.
4-month J
average during
growing season
less than 0.01 Growing season
7% leaf injury.
14.6% damage. Leaf surface
destruction more severe on
lower leaves. Ash-colored
spots on intermediate
leaves and veins.
9% visible injury. Upper leaves
showed ozone injury; lower
leaves shosed ozone leaf surface
destruction. Author calls
this response synergy.
14.6% leaf tissue death
15% reduction in RDP enzymes.
Snyergism at metabolic
levels.
Significant growth reduction
(measured as height) com-
pared to either ozone alone
or ozone and sulfur dioxide
combined. Needles were signifi-
cantly shorter than for any
other exposure. This study
is an example of growth
reduction with slight leaf
symptoms. Leaf symptoms
most sensitive in early
July.
Growth abnormalities, needle
loss, and tissue death.
7-68
-------
TABLE 7-11 (continued).
Species
Lichens
Exposure Duration Result
0.041 ppm Monthly Lichens completely absent.
plus dust at
g/m ambient
Source: Montana Air Quality Bureau (1978).
7-69
-------
0.10 ppm 0 +0.10 ppm SO- (432), but less than additive growth reduction
(top and root weights) from an 8 hr per day, 5-week exposure to a mix of
0.05 ppm 03 + 0.05 ppm S02 (429, 430). Greater than additive foliar injury
effects have also been reported for broccoli and tobacco, while additive or
less than additive effects have been noted for cabbage, tomato, lima bean,
bromegrass, spinach, onion, and soybean (432). Soybean has exhibited less
than additive foliar injury effects (432) while exhibiting greater than
additive growth effects (433).
As can be seen from the preceding research, plant species vary in
their expression of interactive effects, and the type of interactive effect
(additive, less than additive, greater than additive) may depend on the
parameter measured.
Field-grown soybeans (cv. Dare) exposed to 0.10 ppm 0, alone or 0.10 ppm
0^ + 0.10 ppm SO,, for 6 hr/day for 133 days in field chambers exhibited injury
and defoliation. Increased injury and decreased yield due to the mixture was
evident but not significantly different from the ozone treatment (171). Two
cultivars of bean exposed to sulfur dioxide and ozone showed interactive effects
between these two gases, but the magnitude and direction of the effects
depended on the cultivar and on the pollutant concentrations (203).
Alfalfa exposed in closed field chambers to low levels of ozone and
sulfur dioxide singly and in combination for varying periods of time exhibited
significant reductions in yield, quality, and nitrogen fixation compared
with the control plants, but there were no significant interactive effects (327).
Many studies have been conducted on the interactive effects of sulfur
dioxide and ozone on eastern white pine (Pinus strobus L.) (19, 80, 112, 193,
195). Genetic control of sulfur dioxide and ozone tolerance in this species
has been demonstrated for low concentrations of S02 (0.25 ppm) and 03 (0.05 ppm)
for only 6 hr with consistent injury to the exposed sensitive clones (195).
Houston (193) later used mixtures of sulfur dioxide and ozone and doses to
7-70
-------
simulate actual field conditions and reported that even the lowest concentra-
tions of CL (0.05 ppm) and S02 (0.025 ppm) in mixture caused more serious damage
than that resulting from either pollutant alone at similar concentrations.
Loblolly pine and American sycamore exposed to 0.05 ppm 0^ and 0.14 ppm S0?,
6 hr/day for 28 consecutive days, showed more than additive foliar injury in
the mixture (239, 240). Height growth reductions were greatest with the
mixture, but not significantly greater than with S02 alone. A less than additive
effect on foliar injury was noted when Scotch pine trees were exposed to 0.25 ppm
S02 and/or 0.14 ppm or 0.29 ppm Oo> 6 hr/day for varying time periods (332).
Histological examination of ponderosa pine needles injured by 3 weeks of
exposure to 0.45 ppm 0., and/or 0.45 ppm S02 for 9 hr/day revealed some
differences in the tissues injured (128). Different parts of the needles were
affected (the tip for S02, the middle for ozone) initially, so the potential for
interactive effects may exist.
Exposure of aspen clones to 0.05 ppm 0- and/or 0.20 ppm S02 for 3 hr
resulted in a more than additive number of plants in the mix exhibiting foliar
injury (217).
7.6.1.2 Sulfur Dioxide and Nitrogen Dioxide—The occurrence of sulfur dioxide
and nitrogen dioxide has been associated with power-plant plumes as well as
mobile sources. However, ambient concentrations of nitrogen dioxide seldom
reach the injury threshold, and the literature for that pollutant suggests that
any injury associated with nitrogen dioxide results from interactions with
other pollutants.
No injury occurred to oats, beans, soybeans, radish, tomato, or tobacco
following exposure for 4 hr to up to 2 ppm N02 or 0.50 ppm S02 (431). However,
at 0.10 ppm of each gas, injury was noted on all species; at 0.05 ppm of each
gas, injury was noted on all species except tomato. A greater than additive
suppression of the apparent photosynthetic rate of alfalfa was obvious when
7-71
-------
exposed to 0.25 ppm of S02 and/or N02 for 2 hr (472). At 0.15 ppm of each
gas singly, there were no measurable effects, but a 7 percent suppression of
apparent photosynthetic rate was noted in the mixture (472).
Field exposure of seven different species of plants indigenous to the
cold desert areas of the Southwestern United States to 0.50-11.0 ppm S02 or
0.10-5.00 ppm N02 and combinations thereof in 2 hr fumigations resulted in no
evidence of more than additive foliar injury (182).
More than additive foliar injury was noted on radish leaves exposed for
1 hr to 0.50 ppm S02 and/or 0.50 ppm N02- No interactive effects were found
for other plants tested (oats, Swiss chard, and pea). More than additive
effects have been noted for the enzyme activity in pea plants exposed to
0-0.20 ppm S02 and/or 0-0.10 ppm N02 for 6 days. Peroxidase activity was
increased and ribulose-l,5-diphosphate carboxylase activity was decreased
(189).
7.6.1.3 Sulfur Dioxide and Hydrogen Fluoride—Linear growth and leaf area
suppressions (in the absence of foliar injury) of Koethen orange plants
exposed to S0? (0.80 ppm) and/or hydrogen fluoride (2.3-19.4 ppb) for 23
days were no greater than additive. Satsuma mandarin plants exposed to
the same conditions for 15 days exhibited only additive foliar injury
effects, and no growth suppressions at all (299). Greater than additive
foliar injury was exhibited by barley and sweet corn exposed to 0.06-
0.08 ppm S02 and/or 0.60-0.90 ppb hydrogen fluoride for 27 days (288).
Using higher concentrations of S02 for only 7 days resulted in simply
additive foliar injury effects. Pinto beans were not injured in any of
the treatments.
7.6.1.4 Sulfur Dioxide, Nitrogen Dioxide, and Ozone--Fujiwara et al. (140)
combined SO,,, i'iCL, and 0^ at concentrations ranging from 0 to 0.2 ppm in an
L. *L O
artificially controlled environment and exposed peas and spinach for 5 hr.
'ie was ^,e most injurious, S0? was next, and N02 elicited only minor injury
7-72
-------
More than additive foliar injury followed exposure to SCL + CL, but only
additive effects were observed with SCL + NCL or NCL + 0~. The addition of
N02 to the 03 + S02 had little effect on foliar injury. Reinert (361)
exposed two cultivars of cotton and one cultivar each of radish, snap bean,
tomato, pepper, soybean, and tobacco to pollutant mixtures of N0? + SCL + CL,
NCL + SCL, and SCL + CL and each single gas for 3 or 6 hr. Gas concentrations
varied from 0.10 to 0.60 ppm. Injury from the N02 + S0? mixture was greater
than that induced by either pollutant alone, and except for snap bean, injury
from the S02 + 03 and N02 + S02 + 0^ exposures was greater than injury from
DO alone. All plant species were injured by the NO,, + S02 + 03 mixture at
0.25 ppm.
Loblolly pine and American sycamore exposed to 0.14 ppm S0?, 0.10 ppm
NCL, and 0.05 ppm CL singly and in combination for 6 hr/day for 28 consecutive
days exhibited significant height growth suppressions when exposed to 0^ + S02
compared to CL alone (239, 240). Growth reductions of 21 and 26 percent were
observed in the CL + S0? and S0? + N02 + 0^ treatments, respectively, for
loblolly pine. American sycamore height growth was suppressed 32 and 45 percent,
respectively, for the CL + S0? and CL + S02 + N0? treatments. A slight
stimulatory effect on growth was noted with N0~ alone. There was no foliar
injury on sycamore and less than 1 percent foliar injury on pine in any of the
treatments.
In addition to pollutant combinations under controlled conditions
as presented in the above-cited reports, the interaction of constantly changing
environmental factors and fluctuating pollutant doses must be further evaluated
before a conclusive statement of the importance of such interactions can be made.
Further research is needed in order to determine the influence of pollutant
sequencing during combination exposures, meteorological influences, the effect
of various cultural practices, and many other variables in relation to vegetation
7-73
-------
effects induced by S0? combined with other pollutants.
7.6.2 Particles in Combination with Other Pollutants
Few investigations have attempted to relate particulate depositions and
accumulations on and within plants in combination with gaseous air pollutants
to a specific response in plants.
Ricks and Williams (365) presented evidence obtained with the scanning
electron microscope that partial occlusion of stomata by particles was
responsible for decreased diffusion resistance of oak leaves at night. They
further reported that overall water loss rates were not seriously increased
by the reduction in stomatal diffusion resistance at night, but uptake of
gases such as SCL appeared to be enhanced. This fact may explain the increased
sulfur level in tissues of oak leaves collected in polluted areas. Sprugel
et al. (407) suggested that S0? fumigations influenced the accumulation of
elements from the soil (increased zinc, copper, manganese, and calcium;
decreased magnesium and boron) in field-exposed soybean. Evidence of direct
relationships between lowered pH of soil and elevated levels of foliar
manganese in lodgepole x jack pine trees has been reported (261). Foliar
manganese was found to decrease dramatically with increasing distance from
the source and the known transmission corridor. Site variability did not
modify the observed effect. Other elements that did not follow this same
trend (i.e., they were site related) were phosphorus, potassium, iron,
magnesium, zinc, calcium, and aluminum. Similarly, Krause (235) showed
that exposure to low concentrations of S02 increased zinc and cadmium
phytotoxicity to bean plants.
More recently, evaluations of the combined effects of several heavy
metals and sulfur dioxide have been made in relation to ion uptake through
leaves, yield, and foliar injury (236). Lactuca sativa L. Raphanus sativus
oleifera L., Raphanus sativus radicula L., Setaria italica L., and Tagetus
7-74
-------
spp. were dusted with a mixture of cadmium oxide, lead dioxide, cupric oxide,
and manganese dioxide once a week for 4 weeks while being exposed over the
o
28 days to 0.21 mg/m of S02 (approximately 0.08 ppm). Exposure to SO- did
not influence the uptake or translocation of the heavy metals. The heavy metal
treatment reduced yield in all plant species, and this was not influenced by
the SO- exposure. However, SO- exposure resulted in a more than additive
increase in the amount of foliar injury.
Guderian et al. (160) investigated the phytotoxic effects of complex
pollutant conditions consisting of combined gaseous and particulate components
under experimental conditions similar to an actual field situation in West
Germany. There was a general yield reduction with all the plant species used,
and this reduction in yield increased progressively as the number of chemical
components used in the treatments increased. Maximum yield loss from the
interactive effects of SO- and multiple particulates was 30 percent of the
control.
7.7 SYMPTOMATOLOGY OF PARTICLE-INDUCED INJURY
Particulate-induced injury to plants has most often been associated with
sustained accumulation of particles such as dust or fly ash. Few investigations
have dealt with direct or indirect chemical interactions at the plant surface
or subsequent effects. The toxicity of accumulated heavy metals in soils has
been established for several plant species.
The various forms of particulates and their associated impacts on plants
have been reviewed (99, 263, 440, 445). Krupa et al. (243) have also prepared
an extensive review of various forms of heavy metal depositions and impact.
Tolerance of plants for heavy metals has been reviewed, and fine particles of
0.01 to 2.0 urn and their bioenvironmental impacts have also been reviewed (443).
7.7.1 Dusts
The chemistry of this form of particulate matter has been poorly defined
7-75
-------
in relation to plant effects, and therefore indirect effects have been
considered to occur primarily from a mechanical basis. Heavy metals, arsenic,
and boron have been identified as constituents of various kinds of particles
and, as such, have become of interest to the understanding of subsequent plant
effects following dust deposition.
Dusts directly affect plants by coating all exposed plant parts, including
leaves, stems, flowers, and fruits (207, 220, 271). Depending on the chemical
nature of the particles and environmental conditions, deposits may accumulate
as dry dusts, as encrustations in the presence of free moisture, or as greasy
films or tars. Encrustations on leaves result in reduced gas exchange, increased
temperatures, reduced photosynthesis, and eventual yellowing and tissue
desiccation (94, 346).
Terminal growth is greatly reduced in length in hemlocks with heavy dust
deposits. Chlorosis of 2-year-old needles is also reported. In addition,
changes in microflora of needles compared with control plants has been reported,
with fungal propagules increasing and bacterial numbers decreasing (289). Brandt
and Rhoades (54) reported long-term changes in plant community structure
and species composition, and later indicated that radial growth rates were
reduced in the species involved (55). On the exposed site they demonstrated
a 19 percent reduction in radial growth of red maple, chesnut oak, and red oak
but a 76 percent increase in radial growth of tulip poplars as compared with
representatives of these species growing on a similar but nonexposed site.
Deposition rates averaged 824 yg/m3 of suspended particulates during a
February-March (1970) monitoring period. The deposition of limestone dusts
has caused substrate pH changes followed by lichen community changes namely
replacement of acid-loving communities of lichens by more alkaline-loving
species. A reversal of this trend occurred in areas where S0? was of
importance prior to limestone dust emission. No exact pollutant doses of
7-76
-------
either limestone dusts or SCL were reported. Winter S0? levels were estimated
to average 65 pg/m .
Cement kiln dusts have been collected from precipitators and applied to
vegetation. Visible effects were demonstrated on beans following application
? ?
of particles of >10 pm at rates of 0.05 mg/cm /day to 0.38 mg/cm /day for
2-3 days. The lower dose induced a slight reduction in carbon dioxide exchange,
and the two higher doses reduced carbon dioxide uptake by 16-32 percent (99).
The accumulation of dust caused increased reflection of solar radiation
in wavelengths of 400 to 750 nm and has been demonstrated to reduce photo-
synthesis (365). Conversely, increased absorption of solar radiation by dusted
leaves at wavelengths 750-1350 nm has been demonstrated to lead to heat stresses
within the leaf tissues (406).
Growth and yield effects induced by the accumulation of dust have recently
been reviewed (443). Conflicting reports of yield increases and decreases from
such accumulation appear to be caused by variations in doses applied, substrate
nutrient balances and pH, and other specific physiological interferences with
processes such as pollination of fruit trees (7).
Dusts, therefore, have only been considered of importance to vegetation
growing near emission sources. Accumulation of dusts has been demonstrated to
reduce photosynthesis and radial-increment growth of some forest tree species
but has increased them in other species.
7.7.2 Heavy Metals, Arsenic, and Boron
The phytotoxicity of these elements has been demonstrated after accumulations
in soils and subsequent uptake by plants. Table 7-12 presents a summation of
toxic effects of individual elements (246). Published reports of direct effects
on plants from specific sources are discussed in the following paragraphs.
7.7.2.1 Arsenic—No evidence is available to show foliar uptake of airborne
arsenic. Arsenic sprays have been applied to the foliage of many plants to
7-77
-------
TABLE 7-12 SOME REPORTED TOXIC EFFECTS (VISUAL SYMPTOMS) OF
HEAVY METALS, ARSENIC, AND BORON FOLLOWING ACCU-
MULATIONS IN SOILS
Element
Symptoms
Reference
Arsenic
Boron
Cadmium
Copper
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Zinc
Reduced germination of seeds, rotting of
roots, leaf wilt, brown to red coloration
of leaves, reduced yield in fruit trees,
death.
Yellowing of leaf tips, necrosis between
lateral veins and midrib of monocotyledons,
marginal leaf scorch, downward cupping of
leaves, reduced flowering, fruit lesions.
Reduced root elongation, general growth
retardation.
Stunted root development, chlorotic leaves,
reduced vegetative growth.
Stunted root growth, shoot retardation, in-
creased leaf abscission, reduced yields.
Leaf rolling, spiral ing inhibition of leaf
emergence. Narrow leaf development
Necrotic spots on leaves, necrosis of in-
ternal bark, marginal leaf yellowing , in-
curling of leaf margins
Possible reduced growth
Repression of vegetative growth, leaf
chlorosis, white or light yellow and
green striping.
Fruit coarseness and leaf necrosis,
leaves curl downward, marginal leaf
necrosis, intervene! chlorosis, plant
dieback.
Uniform chlorosis, reduced terminal
growth, twig dieback, chlorotic striping
of leaves, stems stiff and erect.
Liebig (265;
Bradford (52)
Krupa and Kohut
(244)
Yopp et al. (492)
Yopp et al. (492)
Reuther and
Labanauskas
(346)
Yopp et al. (42)
(492)
Embleton (125)
Yopp et al. (492)
Labanauskas
Lagerwerff, (249)
Vanselow (453)
Ulrich and Ohki
Chapman (69)
Source: Adapted from Krupa et al. (ref 246).
7-78
-------
hasten fruit maturation by causing premature defoliation and chemical changes
in the fruit. For example, lead arsenate sprayed on grapefruit trees caused
a "fruit gumming" reminiscent of boron deficiency (265). Boertitz (44) reported
that arsenic deposited at 22 mg/kg soil reduced the yield of wheat, rye, winter
rape, and red clover by 25, 8, 0, and 6 percent respectively.
7.7.2.2 Cadmium--Most of the biologically active cadmium enters plants through
root uptake (214). Small oxide particles (0.01 to 0.03 ym) may enter leaves
through stomata, but it is thought that the oxides remain largely inert.
Cadmium accumulated by apple leaves may be translocated and incorporated into
fruit as they develop (492).
7.7.2.3 Copper--Wu and Bradshaw (489) demonstrated a selection of individual
plants of Agrostis stolonifer growing near metal smelters, thus indicating
an indirect effect of within-species simplification within a population
through selection.
7.7.2.4 Lead--Davis and Barnes (107) reported reduced growth of loblolly
pine and red maple seedlings in pots of two forest soils treated with
4 -2
2 x 10 to 2 x 10 M lead chloride. Lead toxicity symptoms may include fewer
and smaller leaves, reduced plant size, leaf yellowing, and necrosis of
elder, sugar beet, squash, and bush bean (378a). Plants growing in soils
already high in these metals tended to be more sensitive to the addition of
metals by air pollution.
7.7.2.5 Nickel—The phytotoxic effects of nickel may be insignificant even
though plants can absorb and translocate airborne nickel salts (324). Once
inside the plant, nickel affects photosynthesis and other processes such
as stomatal function (23). In cases of incipient nickel toxicity to
vegetation, no definite symptoms have been observed other than the repression
of growth. In cases of moderate or acute nickel toxicity, chlorosis resembling
symptoms of iron deficiency is common (6, 9).
7-79
-------
7.7.3 Classification of Plant Sensitivity—Particles
Coarse participates have not been shown to elicit responses in plants
in a manner to allow plants to be placed into sensitivity classes similar to
those developed for gaseous pollutants. Accumulations of particulate matter
such as roadside dusts, cement, quarry particle emissions, or other forms
of deposits such as fly ash, are deposited on all surfaces and induce responses
discussed under the symptom portion of this chapter. However, heavy metals do
elicit differential responses in plants, and therefore it is possible to
develop lists of particularly sensitive plants.
Heavy metals are constituents of many coarse particles emitted from
various sources. To our knowledge, there has not been an organized effort
to establish under field conditions the toxicity of specific chemical
constituents of particulates in relation to sensitivity groupings of
vegetation. Table 7-13 lists plants that may be sensitive to component
heavy metals following deposition.
7-80
-------
TABLE 7-13. PLANTS SENSITIVE TO HEAVY METALS, ARSENIC, AND BORON
AS ACCUMULATED IN SOILS FOLLOWING POTENTIAL ATMOSPHERIC DEPOSITIONS
Metal
Plant
Arsenic Snap bean, lima bean, onion, pea, cucumber, alfalfa, legumes, sweet
corn, strawberry (on light and sandy soils) (246)
Boron Barley, var. Atlas 46; lima bean, var. Henderson; kidney bean, var.
Navel; oats, var. Riverside; onion, var. Cabot; pea, var Alaska; peach,
var. J.H. Hale; persimmon, var. Kaki; rose, var. Snow White; soybean,
var. Wilson, var O'Tootan; wheat, var. Opal; yellow zinnia (406)
Cadmium Red oak, birch, trembling aspen (Jordan, 1975); beet, carrot, celery,
green pepper, lettuce, radish, soybean, Swiss chard, tomato, winter
wheat (406)
Copper Bean, citrus fruits, corn, mustard (291)
Lead Bean dwarf French, var. Carters, beet, corn, fescue, lettuce, lupine,
loblolly pine, red maple (406)
Magne-
sium
Manga-
nese
Potas-
sium
Zinc
Orange (only case known from published literature) (214)
Alfalfa, broadbean, cabbage, cauliflower, cereals, citrus, clover,
lespedeza, pineapple, potato, tobacco, tung (243); Barley, var. Atlas
46, var. Herta; yellow birch, cranberry, peanut, potato, var. Kesweck
(406); alfalfa, apple, apricot, barley, bean, brussels sprout, carrot,
clover, cotton, lettuce, medic, orange, peas, potato, sugar beet, vetch,
wheat (265)
Mercury Broadbean, oxalis, sunflower (406), bean, butterfly weed, cinquefoil,
fern, Hydrangea, Mimosa, Oxa 1is, privet, sunflower, willow (99)
Nickel Citrus fruits (378a), alfalfa, oats, var. Victory; pear (406)
Orange, tung (only case known from published literature) (346)
Oats, orange, tung (6); barley, var. Trail; corn, var. Whatley's
Prolific, var. Ida Hybrid 330; cowpea, var. Suwannee; wheat, var.
Gaines (406); barley, citrus, oats, sugarbeet (6)
7-81
-------
7.8 DOSE-RESPONSE RELATIONSHIPS--PARTICULATE MATTER
Review of the published literature suggests that it is not possible at
present to give even generalized dose-response relationships for the effects
of particulate air pollutants on plants. Many reports deal only with gross
visible effects or tissue accumulation of one or more constituents of the
particulates. The emphasis of research has been on settleable coarse particles.
Since these are conglomerates of several pollutants, their chemical constitution
is frequently not defined properly; however, their source is often identified.
Little information could be found on the effects of fine particles on vegetation.
Most of the sulfate and about half of the nitrate, metals, and metalloids are
found in fine particles.
Where cause-and-effect relationships have been established, generally no
information is presented on the actual concentration, particle size, and
frequency distributions. Deposition rates and plant effects vary significantly
with particle size. Few studies are available where two independent scientists
have evaluated the effects of particles on vegetation with closely comparable
physical and chemical properties under reproducible conditions.
Much of the literature refers to particulates from point and line sources,
and their accumulation in or on soils and vegetation. Tissue accumulation of
a given element or elements must be considered as a plant response. Soil
scientists have contributed much of the information on plant toxicity symptoms
that has been obtained under laboratory conditions. Since many of the plant
effects observed are due to the accumulation of elements up to toxic concentrations
the prior tissue concentrations will affect the amount and elemental composition
of particulates that plants can tolerate, that is, the dose-response relationship.
The dose-response relationship is therefore conditioned by the back-ground
concentrations of various elements in the soil where the plant is growing.
7-82
-------
The effects of surface accumulation of cement kiln dust on bean leaves
o
have been investigated by Barley (99). Doses of 0.6-3.8 g/m per day were
applied for 2 or 3 days, and foliar injury and reductions in carbon dioxide
exchange were observed. Reductions in carbon dioxide exchange of up to 33 percent
were noted in the absence of foliar injury (Table 7-14). Bean leaves dusted with
2
cement kiln dust at the rate of 4.7 g/m per day for 2 days and then exposed to
dew developed leaf rolling and interveinal necrosis (263). Leaves not exposed
to dew following the dust treatments remained asymptomatic.
Reduced yields and injury to leaves and flowers of several plant species
were observed when the plants were exposed once a week for 4 weeks to a dust
containing cadmium, lead, copper, and manganese (236). Yield reductions of up
to 36 percent were noted (Table 7-15).
Plants accumulate different elements at differing rates. Tissue concen-
trations of some elements (particles) are known to be significantly higher in the
vicinity of a source for those elements (particles) in comparison with background
or baseline concentrations. This elevated tissue concentration may be due to
direct foliar uptake or uptake from the pollutant accumulations in the soil.
In many of these cases, elevated tissue concentrations of a given metal or
metalloid are not paralleled by visible injury.
Demonstration of injury symptoms on vegetation under field conditions
as a result of accumulation of metals or metalloids is rare. These demonstrated
cases are for such cases as strip mine wastes. Predicted effects from atmos-
pheric deposition include plant community changes, chronic long-term physiological
changes, and indirect effects through modification of response to other types
of stress. Thus, the state of our knowledge concerning the effects of
particles on vegetation is inadequate at this time and does not allow the develop-
ment of accurate dose-response curves.
7-83
-------
TABLE 7-14. EFFECT OF CEMENT KILN DUST ON BEAN LEAVES AS DETERMINED BY OBVIOUS
TISSUE DAMAGE AND CO, EXCHANGE
I
00
Dust Dosage, No. of Water added
no. g/m /day days dusted to leaves
I 1.5 est.
1.5 est.
1.5 est.
Pretreatment
3.0 est.
0.6
1.0
2 1.5
1.8
3.8
3 2.2
2
2
2
--
3
2
3
3
2
2
2
X
X
—
Dry plants
Wet plants
--
X
X
-
Wet all plants
X
X
X
X
Average C02 exchange,
ppm/cm
Tissue
damage
None
None
None
None
None
--
Margins
necrotic
None
None
None
None
Necrosis,
leaf roll
3%
5%
13%
26%
Necrosis,
leaf roll
13%
16%
20%
29%
None
Control
0.225
0.221
—
0.196
0.181
0.189
0.213
(Lowest value
leaf)
0.200
0.238
0.236
0.229
0.216
0.7143
(Single
--
--
--
--
0.157
(Single
--
--
--
—
0.196
F
Damage di
0.189
0.170
--
0.196
0.181
0.205
0.114
for single
0.053
0.221
0.157
0.161
0.146
0.1603
dusted leaves
0.204
0.160
0.138
0.140
0.085
dusted leaves
0.091
0.097
0.072
0.083
0.142
'ercent
fference
-16
-23
--
0
0
+9
16
-73
-7
-32
-33
-32
-8
+17
-8
-21
-20
-46
-42
-38
-54
-47
-27
aCarbon dioxide exchange measured on third day after end of dusting.
Source: Darley (99).
-------
TABLE 7-15.„ EFFECT OF A DUST CONTAINING CADMIUM (5.2 mg/m2) LEAD
(488 mg/ni ), COPPER (20.8 mg/rrT), AND MANGANESE (72.8 mg/rrT)
(TOTAL APPLICATION) ON YIELD (DRY WEIGHT) AND FOLIAR FLOWER
INJURY AFTER APPLICATION ONCE A WEEK FOR 4 WEEKS
Relative yield depression and
% injured leaves/flowers
Plant species
Lactuca sativa L. ,
leaf
Raphanus sativus
oleifera L. , leaf
Setaria italica L. ,
leaf
Raphanus sativus
radicula L. , root
Tagetus spp. ,
f 1 owers
Treatment
Control
Dust
Control
Dust
Control
Dust
Control
Dust
Control
Dust
Total ,
yield,
%
100.0
94.4
100.0
86.4
100.0
63.8
100.0
85.3
Injured
leaves/flowers,
%
0.0
20.2
0.0
54.3
1.0
32.9
0.0
18.4
Source: Adapted from Krause and Kaiser (1977) (236).
7-85
-------
7.9 PLANT EXPOSURE TO PARTICIPATE MATTER
7.9.1 Deposition Rates
Deposition of particles is strongly dependent on particle size.
Most sulfates and nitrates are found in the size range of 0.1 to 1.0 ym,
and very little information is available on the deposition rate for
these particles. Shinn (387) divided participate deposition into three
categories based on particle size:
CATEGORY 1. Particles more than 10 ym in diameter; includes dust
and spores.
CATEGORY 2. Particles between 1 ym and 10 ym in diameter where
the collection efficiency is highly dependent on the
particle diameter.
CATEGORY 3. Submicron particles between 0.1 and 1.0 ym in diameter,
which have a nearly constant collection efficiency.
Current experimental data suggest that collection efficiencies in
category 3 are at least 10 times less than in category 2 (387). The collective data
indicate that the efficiency of collection increases as the particle size
increases. According to Clough (72a), in the range of wind speeds normally
encountered, the larger particles in the atmosphere are much more efficiently
collected than the smaller fraction.
Little (276) evaluated the effect of leaf surface texture on the deposition
of monodisperse polystyrene aerosols on the leaf surfaces. Rough and hairy
leaf discs collected 5.0 ym particles up to seven times more efficiently
than did smooth leaves. Very large differences in particle deposition velo-
cities were observed between the laminas, petioles, and stems of each species.
The velocity of deposition of particles to plant surfaces was proportional
to both wind speed and particle size.
7.9.2 Routes and Methods of Entry Into Plants
7-9-2.1 Direct Entry Through Foliage—Foliage is continuously subjected to
natural and manmade coarse particles that are insoluble or sparingly soluble in
7-86
-------
water. Coarse particles in general are too large to enter leaves through stomata.
In certain cases, such as with cement kiln dusts (263) and other types of
aggregate particles (401), a limited amount of stomatal clogging can occur.
This is apparently dependent on the statistical probability of the particulate
matter falling on the stomata, the size of the particle, and the stomatal
aperture. In many plants, the stomatal opening is on the lower surface. Cement
kiln dust forms a crust on leaves, twigs, and flowers. According to Czaja (94),
crusts of this type form because some portion of the settling dust consists of
calcium aluminosilicates typical of the clinker from which cement is made.
Hydration of the dust on the leaf surface results in the formation of a gelatin-
ous calcium aluminosilicate hydrate which later crystallizes and solidifies to a
hard crust.
When coarse particles are water soluble or have some water-soluble com-
ponents, plant uptake of ions from the leaf surface does occur. Because of
analytical difficulties, the exact magnitude of the uptake is difficult to
measure. Since it is not possible to predict the efficiency of any washing
procedure used to remove particles from the leaf surface, it is difficult to
separate the concentration of a given element on the leaf surface from its
concentration inside the tissue. In addition, leaching of elements from within
the tissue is known to occur during the washing (275).
Smith (399b) evaluated metal contamination of urban woody plants by using a
variety of washing procedures. Indirect evidence from all these studies strongly
suggests that a variable concentration of metals originating from coarse particulates
can accumulate in plant foliar tissue through direct uptake.
At this time, one of the significant problems in deriving conclusions
concerning the magnitude of direct foliar deposition and uptake of atmospheric
particulates is the lack of coordinated data on size and frequency distribution
7-87
-------
of the particles and their chemistry, rates of deposition, and dose in conjunction
with changes in tissue concentrations over time relative to background conditions.
This is an area of research where there is definite need for further information.
7.9.2.2 Indirect Entry Through Roots—Many of the inorganic constituents of
particulate air pollutants occur naturally in the soil. Deposition of these
pollutants may increase the soil concentrations of the chemical species in question
Some of the chronic effects caused by particulate air pollutants may result from
changes in soil physics and chemistry and from increased plant uptake of either
the added particles themselves or some other soil-borne elements made more
available by the influence of the deposited particles.
It should be recognized that only a portion of the total elemental
content of the soil is available at a given time for plant absorption (53).
As uptake of elements proceeds, there may be a redistribution of nutrients
or toxicants in the soil. Excess magnesium and potassium are the only
macronutrients from particles that are considered phytotoxic.
The availability of nutrients or other chemical elements from the soil
is strongly influenced by type, chemical composition, and acidity of the soils.
Plant nutrients, when present in optimal amounts, are usually available at a
neutral pH; however, when the soil becomes acidic, toxic elements such as aluminum
become available.
7.10 INTERACTIVE EFFECTS ON PLANTS UITH THE ENVIRONMENT—PARTICULATE MATTER
7.10.1 Biotic Interactions
Few studies have examined the influence of dusts or heavy-metal-containing
particles on the interactions between organisms capable of causing disease and
the predisposition of the host plant to the disease process.
Infection due to Cercospora spp. increased on sugar beet leaves exposed to
cement dust of 36 percent calcium oxide and 15 percent silica (378). Increased
7-88
-------
occurrence of fungus-induced leaf spots on wild grape and sassafras have been
observed near a source of heavy emissions of limestone dust (289). After
examining 40 leaves in each of five locations exposed and not exposed to the
dust accumulations, disease development was two to three and six to seven times
greater, respectively, for the two diseases in the exposed areas.
Natural exposure to combustion nuclei from automobile exhaust which
supplied increased levels of Aitken nuclei and atmospheric lead reduced germina-
tion of uredospores of Puccini a striiformis (stripe rust of wheat); in situ
development of disease was prolonged about 4 days. Similar studies at a
nonexposed site did not result in decreased spore germination (384,385).
The influence of heavy metals on microbes has been investigated; some
studies deal with toxicity effects related to pesticides (373), and others deal
with the ability of microbes to accumulate metals and serve as potential
bioindicators (1).
7.11 EFFECTS OF SULFUR DIOXIDE AND PARTICULATE MATTER ON NATURAL ECOSYSTEMS
7.11.1 Introduction
The ecosystem is the basic functional unit of ecology since it includes
both the living organism (biotic) and the non-living (abiotic) environment in
which these organisms live. Odum (379) has defined an ecosystem as
...any unit that includes all of the organisms in a
given area interacting with the physical environment so
that a flow of energy leads to clearly defined trophic
structure, biotic diversity, and material cycling witin
the system.
Due to the inseparable nature and interdependence of the components of
ecosystems, any change that occurs in one component of the system potentially
affects all the components of that ecosystem. Generally, the higher the
diversity, the more numerous the interrelationships within the ecosystem, and
therefore, the more stable it is (Jernelov & Rosenberg, ref 211). As a result,
7-89
-------
agricultural ecosystems are considered very susceptible to any external stresses;
the diversity of the producers in the ecosystem is reduced to one or two species
and thus restricts the other trophic levels of the system.
Agricultural ecosystems, or agro-ecosystems, have been extensively studied
because of their great economic importance to man, and, as a result, can be
managed. Natural ecosystems have also been studied but are not fully understood,
primarily because of their extremely complex nature.
It is, therefore, not possible to predict exactly how a natural ecosystem
will react to a pollutant stress. In addition, it must be remembered that
very little is known about the effects of atmospheric pollutants such as SO,,,
NO , 07, and PAN on natural vegetation and wild animals, since most of the work
A O
has been performed on crops and domestic species.
In an ecosystem the flow of energy and the cycling of nutrients are of
paramount importance because they link the biotic and abiotic components.
Energy flow and nutrient cycling are closely interrelated. Energy flow,
however, is unidirectional. Light energy from the sun is converted by
producers (green plants) through the process of photosynthesis to chemical
energy. Chemical energy moves to herbivores when they consume vegetation and
to carnivores when they eat herbivores. Further transfer of energy occurs when
producer-decomposer organisms feed on the remains of plants and animals to
obtain their energy (see Figure 7-3). Energy flow through an ecosystem is
mediated at the level of the individual organism. At each trophic (feeding)
level some energy is lost in respiration so that less energy is available to
the organsims at each trophic level. Interference with or removal of a particular
trophic level in one part of an ecosystem will potentially affect the movement
of energy elsewhere.
Nutrients are cycled from living organisms to the non-living environment
7=90
-------
Nutrient
FIGURE 7-3. Nutrient cycles and energy are closely interrelated,
as this model indicates. It also stresses the face that energy
flow is unidirectional, whereas nutrient flow is cyclic. (R-Respiration
Source: Adapted from Smith (399a).
7-91
-------
and back to living components of the ecosystem. In this way, plants and animals
obtain the nutrients mecessary to their well-being. Some of the elements, the
macro-elements, are required by plants and animals in relatively large
quantities. Micronutrients, or trace elements, are required in smaller or
minute amounts. Though required in minute amounts, the micronutrients are just
as essential as macro-nutrients. Neither plants nor animals can exist without
them. Micronutrients, however, in too large an amount are toxic. Many of the
pathways followed by nutrients parallel those of energy flow and this reflects
the interrelatedness of energy utilization and materials cycling.
This network of interactions, which dictates an ecosystem structure and
function, determines how the ecosystem responds to stress. A perturbation at
one site not only affects proximal structures and functions but also induces
effects elsewhere in the system. The complexity of ecosystems coupled with
the attribute of self-maintenance makes specific predictions of reversible and
irreversible effects difficult. This is particularly so for stresses of varying
intensity and stressors capable of being assimilated by the ecosystem. Chronic
stress may result in significant ecosystem responses due to the slow accumula-
tion over time of many small alterations. Consequently, visible modifications
in the functioning of the ecosystem may not be apparent until a long time after
the stress was initiated.
Natural ecosystems are integral to the maintenance of the biosphere.
They are the support system of all life on earth. The most obvious ecosystem
benefits derived by man are recreational (e.g., hunting, fishing, hiking) and
economic (e.g., forest products); however, a variety of more subtle benefits
are important for human welfare (Table 7-16). These include regional and local
control of ambient air temperature, prevention of erosion, recharging of
grcundwater supplies, modulation of stream flow, and cleansing of water and
7-92
-------
TABLE 7-16. EXAMPLES OF ECOSYSTEM BENEFITS THAT EITHER DIRECTLY AFFECT HUMAN WELFARE OR UNDERLIE
THE MORE DEMONSTRABLE ECONOMIC AND ESTHETIC PRODUCTS DERIVED FROM NATURAL ECOSYSTEMS
Benefit of ecosystem function
Source of benefit
Consequency
Temperature control of local
and regional climate
Light-reflective capacity
of foliage
Moderation of temperature via
removal or actual or potential
heat energy
Control of hydrological cycle
Transpiration
Water retention
capacity of soils
Reduced stream flow
Reduced erosion
Recharged groundwater supplies
UD
CO
Control of atmospheric chemistry
Filtration of soil water
(upper soil horizons)
Temperal stability of water
chemistry leaving ecosystem
despite variable chemistry of
incident precipitation
Control of water chemistry
Deposition (wet and dry)
of particles and gaseous
materials
Clearer air
Source:Bormann (ref. 48).
-------
air resources (48). The net effect of summing these subtle benefits is a
predictable environment that is pleasing to man and accommodating to his
culture and technology. Furthermore, these benefits are provided cost-free to
man since natural ecosystems are self-maintaining units.
The following discussion addresses the response of terrestrial ecosystems
to sulfur dioxide and particulate matter. Although the focus is on natural
ecosystems, managed ecosystems are also mentioned. The importance of acidic
and acidifying precipitation is acknowledged, but discussion of effects of
acidic precipitation on ecosystems is found in Chapter 8.
For simplification, the discussion that follows has been divided into a
number of separate categories. These categories are related to the function
and trophic level of the organisms in the ecosystem. All organisms referred
to as producers, consumers, and decomposers perform the same basic functions
in an ecosystem. Due to the inseparability and the interdependence of the
components of an ecosystem, any change that takes pla^e in the producer,
consumer, or decomposer categories will result in a change in the other categories
and therefore, in the processes of energy flow and mineral nutrient cycling.
7.11.2 Sulfur in Natural Ecosystems
7.11.2.1 The Sulfur Cycle in Natural Ecosystems—Sulfur is an element that is
essential for the normal growth and development of plants. It is a basic constit-
uent of protein and is required in large amounts by some plants. Under normal
circumstances sulfur in rainwater and in soil organic matter is sufficient to
meet the plant requirements. Excessive sulfur in the form of sulfur dioxide
can be toxic to plants. The phytotoxic forms of sulfur, routes of entry into
plants, and the symptomatology of S02 injury to plants have been discussed in the
preceding sections.
Within any ecosystem, nutrients occur in the atmosphere in living and dead
7-94
-------
organisms, and as available and unavailable salts in the soil and rocks. Air
pollution, however, can influence nutrient cycling by altering the amounts in,
and the rate of flow among, ecosystem compartments (400).
The biogeochemical cycle of sulfur is both sedimentary and gaseous. Sulfur
in the longterm sedimentary phase is tied up in organic and inorganic deposits
in the soil. Weathering and decomposition permit sulfur to enter into solution
and to be carried into aquatic and terrestrial ecosystems. In its gaseous state,
sulfur is circulated on a global scale (Figure 7-4).
Although major sources, sinks, and pathways of sulfur flux are accurate,
estimates of the relative importance of the various cycle components vary (359).
Estimates of the manmade contribution to the atmosphere (versus that released
naturally by microbial activity) in the early 1970s ranged from 50 percent (226)
to 70-90 percent (336, 359). Kellogg et al. (226) conclude that manmade sulfur
emissions will actually exceed natural emissions in the northern hemisphere by
the year 2000.
The influence of man on the sulfur cycle is best seen when studied on a
regional basis (154) as Shinn and Lynn (388) have done for the northeastern
United States. Atmospheric sulfur is not deposited equally over the global
land areas (Table 7-17). The emission of sulfur from manmade sources results
in greater deposition occurring on and adjacent to industrialized areas. In
the northeastern United States, the deposition of atmospheric sulfur is 28.4
times greater than would be expected if emissions were uniformly distributed
on a global basis. Globally, natural processes far exceed human contributions.
7.11.3 Ecosystem Responses to Sulfur Dioxide
7.11.3.1 Kaybob I and II Gas Plants, Fox Creek, Alberta, Canada (475.476,477)—
The Kaybob gas plants, which emit S0? during the removal of hydrogen sulfide
from natural gas, are located within transition montane-boreal forest
dominated by a mixed assemblage of deciduous and coniferous trees. White spruce
(Picea glauca) stands predominant in successional areas on well drained soils.
7-95
-------
—I
I
Ch
SO4-PARTICLES IN THE LOWER STRATOSPHERE GROW BY
11 COAGULATION AND SETTLE OUT OR MIX DOWNWARD
II (1 TO 2 YEARS RESIDENCE TIME)
LSEA SA
BIOLOGICAL
PROCESSES
IN
COASTAL
LT | PRECIPITATION] *«EAS
PLANT ANAEROBIC
BURNING UPTAKE BACTERIAL
FOSSIL AND DRY AND PLANT
FUELS | PRECIPITATION | UbPOSI 1 ION EMISSION | VOLCANOES]
XSO. SO,. XSO. H,S SO, SO,, XSO. "o0 Xe0 ' H-S.SU H,S, SO,. XSO.
424 2 224 *>*J0, AOU^ z f. z 2 4
t
130
1 t t 1 1 1 t I
217 SO, * 150 258 45 30 * 2
Ml I 1 1 1
OCEANS II
so,
S H,S
t 4
/ LAND
^S/ RIVER RUNOFF
^*
* TOTAL - 262
F igure 7-4. Schematic diagram shows sources and sinks of atmospheric sulfur compounds. Units are
106 metric tons (109 kg) per year calculated as sulfate.
Source: Adapted from Kellogg (1972).
-------
TABLE 7-17. COMPARISON OF GLOBAL LAND SULFUR CYCLE WITH REGIONAL SULFUR
CYCLE OF NORTHEASTERN UNITED STATES (106 tons of S04/year)
Northeastern United States
Cycle component Global By land area3 Experimental Data
(A)
(B)
(C)
Atmospheric inputs
Manmade S0?
Microbial sulfur
Terrestrial inputs
Deposition (wet and dry)
Fertilizer
Weathering
Terrestrial export
Stream
Air
150
210
360
33
42
250
0
0.88
1.23
2.11
0.19
0.25
1.32
0
2.5
2.0
13.0
1.0
1.0
15.0
10.0
aFigures for "By land area" were calculated to illustrate what the various
component figures would be regionally if sulfur inputs and outputs were
distributed evenly over all global land areas.
Source: Adapted from Shinn and Lynn (ref. 388).
7-97
-------
Since these £_. glauca forests have less species variation than other sites,
they were selected for analysis along a transect showing decreasing SO,, stress
and ranging in elevation from 600 to 1075 m. Since edaphic factors were
responsible, in part, for the observed differences in plant communities, they
were considered to be unimportant (475). The facility began operation in 1968,
and the field study was completed in 1976. Field measurements of ambient
atmospheric conditions were not made although the nature of the technological
process would necessitate S02 emission products (260). From 1973 to 1975, it
is estimated that the Kaybob facility emitted approximately 71,000 kg/day of
so2.
Relative species diversity showed no gradient pattern of response to S02;
however, percent coverage for all understory plants, including vascular species
and mosses, showed a marked increase with distance from the source (476). A
comparable pattern for the canopy was not recorded even though reproductive
effort represented by seedling number in white spruce populations close to the
refinery was reduced. Changes in moss communities were conspicuous and included
decreasing values for moss canopy coverage, moss carpet depth, dry weight,
capsule number, and frequency of physiologically active versus inactive moss
plants. Close to the source, there were no mosses at all (475). These results
suggest that species diversity, particularly in the mosses, has changed as a
consequence of sulfur gas emissions. As noted by the authors, the decreased
coverage of producer species close to the source was associated with an actual
increase in species diversity (Shannon Weaver Index). The significance of this
phenomenon is that qualitative changes in species composition have occurred as a
consequence of sulfur emissions, and this has important ramifications
for functional processes of energy flow and nutrient cycling.
7-98
-------
In a subsequent study of the ecological fate of sulfur emissions in the
same white spruce forests, Winner et al. (477) found an association between
sulfur accumulation in foliage and the vertical location of the organism in the
forest's stratification. Specifically, the sensitivity of mosses versus
understory and canopy species was attributed to the greater sulfur accumulation
derived solely from sulfur emitted from the Kaybob facility. This conclusion
was based on tracer experiments ( S: S) which unequivocally assessed the fate
of emitted sulfur (41). This condition of enhanced moss sensitivity has ecological
consequences since mosses serve several unique functions within a forest. These
include water storage, soil formation, erosion prevention, and nutrient cycling;
therefore, any stress (e.g., light, temperature, SCL) that affects the performance
of mosses is likely to induce changes throughout the ecosystem. This research
is of particular relevance since it shows that species biomass is not necessarily
a good indicator of ecological importance.
7.11.3.2 West Whitecourt Gas Plant, Whitecourt, Alberta, Canada (260)--The
effects of chronic sulfur gas emissions in a forested ecosystem were investi-
gated in a region experiencing effluents from a natural gas-processing facility.
Ecological observations were coupled with physiological investigations, the goal
being to explain changes in ecosystem structure and function by alterations in
physiology. The processing plant began operation in 1961, and field studies
were conducted in 1975 within a 120-year-old lodgepole x jackpine forest (£_.
contorta x banksiania) characterized by a bearberry-blueberry understory.
Results of an air-monitoring program in 1975 within the pine forest showed SO^
levels to be variable but not exceeding the Alberta air quality criteria
standard of 0.2ppm/0.5 hr/24 hr. Measurable quantities of S02 (0.01 ppm detection
level of the instrument) were recorded on 40 out of 46 days. On an average day
detectable levels of S02 remained in the forest for four hours; however, over 46
percent of all hours monitored were characterized by pollutant levels below 0.05
7-99
-------
ppm. The highest instantaneous level was 0.45 ppm. In general, pollution
levels in the forest were greater during daylight hours. These data depicting
the ambient SO- exposure for the forest are specific for 1975. Differences
in exposure are documented for different years, although the general trends are
consistent.
Two locations were selected based upon their similarity in many edaphic,
climatic, and biological indices, but differing in their proximity to the source.
Studies of structural changes induced by SCL at the ecosystem level were limited
to studies of basal-area increments and biomass of the dominant pines in both
the reference and SCL-stressed location. Using basal-area increments as an
example (Legge et a!., ref 260), differences between sites were dramatic,
with trees nearer the source showing smaller incremental additions, beginning in
1971 and continuing through 1975. Statistically significant differences were
obtained in 1964 through 1975. In addition to these data, tracer techniques
( S: S) coupled with atmospheric profile, micrometeorological studies showed
that the pine canopy was acting as a sink for the sulfur emitted from the pro-
cessing facility.
This evidence of changes induced by SOp in the dominant producer species
led to physiological and biochemical experiments designed to investigate the
mechanisms of growth inhibition. Controlled field exposures revealed no effect
of SO^ on photosynthesis of lodgepole/jackpine; however, laboratory studies
indicated that the pine population inhabiting the stressed site had a lower
rate of photosynthesis than that from the "reference" location. Other physio-
logical investigations showed increased sulfate levels in pine needles through-
out the growing season, decreased foliar retention of potassium and phosphorus,
and lower soil pH.
Further evidence at the biochemical level pointed to S02 effects. These
results included changes in plant pigment level, phenolic content, and adenosine
7-100
-------
triphosphate (165). The authors remarked that "vegetation along the downwind
path of SCL emissions is adversely affected on a molecular level,ri and this may
be one of the causes underlying decreased basal-area increments.
The movement of materials within the forest also showed signs of SCL-induced
modification (260). This phase of the study compared indices of changes
in a series of sites selected for their similarity in vegetation and in soil
properties but varying in their exposure to SCL. As expected, sulfur distribu-
tion in the soils and vegetation varied with distance and direction from the
source. In lodgepole x jackpines sulfate levels in leaves in three successive
years decreased with increasing distance along the corridor of SO- stress.
Seasonal variation in sulfate in the leaves of tamarisk (Larix larincinia),
aspen (Populus tremuloides), and lodgepole x jackpine was recorded, with pro-
gressive sulfur loading from June through September annually. Among the dominant
producer species, foliar sulfate levels were higher in the deciduous forest
trees than in the pine. Finally, sulfate in the leaves of forest canopy near
the source decreased downward through the canopy.
The status of soil sulfur also reflected the direction and distance of the
sample site from the source. Total soil sulfur generally decreased with distance
along the downwind corridor of SO- stress. Along the corridor, consistently
higher sulfur levels were found in the upper 2 cm of the soil, which also had
the highest organic content. These data support the hypothesis that humus
material is a major reservoir of soil sulfur. Finally, the acidity of the top 2
cm of soil varied as a function of S02 stress; higher acidity was recorded
proximal to the source of S0?.
Pollutant-induced modifications of the biogeochemical cycles were not
restricted to sulfur alone but were also evident in a variety of other inorganic
elements. The most striking and consistent pattern was recorded with manganese
7-101
-------
distribution. Over 4 successive years, the manganese content of
lodgepole x jackpine needles decreased with increasing distance away from the
source. The authors noted the concordant changes in soil pH, a factor known .to
affect the availability of soil ions to plants. The potential importance of
this effect lies in the fact that elevated manganese levels elicit iron defi-
ciencies which, in turn, are known to affect the regeneration of pine forests.
In addition, the recorded iron deficiency might explain, in part, the pattern of
chlorosis observed in pines as well as the depressed photosynthetic rates. The
distribution of other elements along the corridor also exhibited patterns associated
with the level of SCL exposure: lodgepole x jackpine foliar concentrations
of potassium, zinc, phosphorus, and iron were consistently lower in SCL-exposed
versus "reference" locations.
In summary, atmospheric emissions of SCL modified the forest ecosystem in
2
an area of approximately 454 km , principally along a downwind corridor of
decreasing SCL exposure. The atmospheric level of S0? is described as producing
chronic injury to sensitive producer species. However, the authors contend that
in terms of forest ecology, S02 foliar uptake and subsequent injury are less
important as a mechanism responsible for ecological modification than deposition
on the ground. Numerous SC^-associated changes are recorded, and collectively
they represent pollutant-induced modification of the rates and pathways traveled
by nutrients moving among the atmosphere, soil, water, and vegetation components
of the ecosystem. These modifications occur through direct and indirect pol-
lutant effects, and collectively they interfere with physiological activities in
producer organisms. These changes, however, are not viewed as being ecologically
irreversible.
7.11.3.3 Montana Grasslands — In the near future, the grasslands of the upper
plains will be subject to S02 emissions from the new coal-burning power facilities
7-102
-------
that are being constructed in areas rich in coal reserves (122). There are
insufficient data to evaluate accurately the ecological consequences of elevated
atmospheric sulfur levels in grasslands, and the uniqueness of grass-dominated
systems precludes extrapolating freely from results in forested or agricultural
ecosystems impacted by SCL (485). To address this problem, plots of Montana
grasslands were exposed to SCL during growing seasons of successive years. The
exposure levels averaged 0, 0.02 (52 yg/m ), 0.05 (105yg/m ), and 0.15 ppm
(183 yg/m ) S0? and were delivered by a zonal air pollution system, or ZAPS (257).
Field observations over 3 years verified that these concentrations were not suf-
ficient to elicit any leaf lesions characteristic of acute S0? injury (253). Ambient
pollutant concentrations were typically greater at night, and the concentration
decreased rapidly from the interface of turbulent air and grass canopy downward
to the soil (357). This pattern of decreasing pollutant concentration within a
canopy is common for any gas being deposited on or assimilated by a surface.
The most prevalent producer species within the grassland is a perennial,
Agrypyron smithii. In populations sampled over the growing season in each of
the exposure regimes, SO- induced a variety of changes in biochemical indices of
plant performance. Monthly samples of tillers and leaves showed a positive
correlation of foliar sulfur (as sulfate) with time of exposure and canopy-level
SOp concentrations (251). This relationship was most conspicuous with the two
higher exposure regimens, and total foliar sulfate in the highest exposure plot
was three times greater than that in vegetation sampled from control locations
(253). As the sulfur content of leaf tissue increased, the ratio of nitrogen to
sulfur decreased (178), as did the levels of crude protein and digestability
(380).
This array of biogeochemical changes in the major producer species was
mirrored by other modifications in plant performance. In /\. smithii populations
7-103
-------
exposed to 52 yg/m SCL over the growing season the functional leaf life (the
period of active photosynthesis) was increased by several weeks while the same
2
index of plant performance was shortened by 2 weeks at 105 and 183 yg/m SCL.
Parallel increases and decreases in chlorophyll content at the low and high S02
levels, respectively, were also recorded. Finally, with increasing SO^ exposure
plants stored less photosynthate in rhizome tissue (178).
Dominant producers were not the only flora exhibiting sensitivity to SC^.
In simulated pollutant exposure using a bisulfate solution, Sheridan (386)
showed that nitrogenase activity in a major component of the lichen flora (Collema
tenex) was reduced. Although the applicability of the data must be validated
through field studies, the potential for such an effect must be recognized,
particularly in light of the importance of soil lichens in regulating nitrogen
fixation in the grasslands (386).
The significance of pollutant-induced changes in producers lies with the
importance of these organisms in defining the structure and function of the
grasslands. For example, a decrease in herbage quality (e.g., crude protein or
digestibility) of a dominant grass may alter the potential of the grasslands for
cattle grazing. In terms of the flux of energy and nutrients within the system,
any factor affecting the rate at which consumers devour producers will have
repercussions throughout the ecosystem (380).
Further evidence of SO^-associated effects on the grasslands is recorded in
both consumer and decomposer populations. The density of grasshoppers, a major
consumer of A., smithii foliage, decreased with increasing SOp stress in two
successive seasons (Laurenroth and Heasley, ref 253). Decomposition rates were also
altered with less decomposition in SO^-exposed plots. The mechanism involves a
direct pollutant effect on decomposer activity rather than an indirect effect,
such as elevated sulfur levels in the litter (253).
7-104
-------
Larger consumers also exhibited responses reflecting the presence of SCL in
the atmosphere; however, the responses were not dose dependent (71). Peromyscus
maniculatus, prairie deer mouse, is a common and active vertebrate in grassland
communities. Over one exposure season, the frequency of £. mam'culatus in
control plots increased, implicating an SO^-induced behavioral response
(habitat preference) whereby individuals seek habitats free of the pollutant.
The speed of the response (within one season) suggests a direct, adverse
effect of S02 on the animal's health.
Any summary of SCL effects on grasslands must be tentative since the research
effort is not completed. At the reported exposure levels, SCL does induce
changes in the performance of producers, consumers, and decomposers. Many of
the responses are individually small, but collectively over time they are gradually
modifying the structure and function of the grasslands (357).
The results of these studies, particularly the West Whitecourt and Montana
grasslands studies, document the usefulness of addressing ecosystem-level
responses to SCL from a multidisciplinary approach incorporating investigations
of physiology, autecology, synecology, geology, meteorology, and modeling. The
results confirm that producers are sensitive to direct SCL effects as evidenced
by S02-associated changes in cell biochemistry, physiology, growth, development,
survival, fecundity, and community composition. Such responses are not unexpected.
An equally important point of agreement among the different research efforts is
the potential for ecological modification resulting from either direct SCL
effects on nonproducer species or direct changes in habitat parameters, which in
turn affect an organism's performance. Changes in biogeochemistry, particularly
in the soil compartment, are notably responsive to chronic SCL exposure.
7-105
-------
7.11.4 Response of Producers, Consumers, and Decomposers to Sulfur Dioxide
7.11.4.1 Response of Producers to Sulfur Diox1de--In both natural and agroeco-
systems, producers are indispensable. They alone are capable of converting
solar energy into a chemical form that is subsequently the energy source for the
remainder of the ecosystem's organisms. Secondly, this flow of energy originating
in producers and continuing throughout the ecosystem provides the pathway and
driving force for the ecosystem's other major function—the cycling of materials.
Finally, producers are commonly integral to the system's physical structure,
providing a framework in the soil and above the ground. In so doing, producers
collectively modify the environment, and create a variety of habitats for other
producers, consumers, and decomposers. Thus, the interest in producers and
their response to SO- are justified.
Vegetation is notably responsive to most environmental stimuli, including
SOp. This responsiveness is a consequence, in part, of the gas-exchange process
in leaves whereby any gas in ambient air (e.g., CCL, SCL, ozone) exhibiting a
concentration gradient will diffuse into the leaf interior. However, this
predisposition to absorb pollutants is not the sole factor governing plant sus-
ceptibility; internal biochemical factors are also important. Sulfur is an
element required for normal growth and development; however, in excessive amounts
it is detrimental. Therefore, the concept of "cardinal points" (20) applies:
a range of sulfur levels in plants is considered essential for optimal physiological
activity, but either deficient or toxic levels reduce growth to levels below
optimal. The interplay between differential pollutant uptake (gas-exchange
process) and variation in sulfur metabolism underlies the great and confusing
variation in plant response to S0?.
7-106
-------
In the literature there are many examples of producer responses to
SCL, and most describe how individual plants respond to artificially
elevated S02 levels in controlled exposures. Seldom have in situ field
studies been reported in which atmospheric pollutant levels are monitored
throughout the course of study; thus the results must be interpreted
with caution. From an ecological perspective, each report is of limited
value, but collectively they are a valuable source of information on (1)
S0? levels at which responses occur and (Z) potential mechanisms underlying
ecosystem-level modifications (436).
At the individual plant level, S0? has pronounced effects on a
variety of vegetative and reproductive characters ranging from alterations
in a cell's biochemical status to responses at the whole-plant level.
Examples of these responses for species occurring in agricultural and
natural ecosystems were outlined in Tables 7-5 and 7-6, respectively.
The range of SCL doses at which changes are detected indicates that the
lack of necrosis or chlorosis does not indicate absence of injury.
Furthermore, even though the site of SCL toxicity is the leaf, pollutant-
induced perturbation of physiological processes in the leaf can affect
vegetative and reproductive activities that depend on the assimilatory
capacity of the leaf.
In reviewing Tables 7-5 and 7-6 from an ecological perspective, the
responses may be grouped according to how SCL affects the organism's
ability to survive and reproduce as well as the importance of the response
from the point of view of nutrient cycling (Table 7-18). Survival
depends on the plant's autotrophic output remaining higher than its
maintenance expenditures, hence the category entitled "net productivity."
In this respect, two processes of obvious importance are the rate of
photosynthesis and respiration, the difference being net photosynthesis.
7-107
-------
TABLE 7-18. DOCUMENTED DIRECT S09 EFFECTS ON INDIVIDUAL PLANTS.'
Survival and reproduction
Nutrient cycling
o
co
A. Net productivity
1. Photosynthesis
CO assimilation rate
Chlorophyll content
Photosynthetically active tissue
2. Respiration
3. Cell maintenance
Buffer capacity
pH
Lipid synthesis
Membrane permeability
ATP levels
B. Growth and development
1. Vegetative processes
Terminal buds
Carbon allocation
Senescence
Shoot biomass
Root btomass
2. Reproductive processes
Flower number
Pollen germination
Fertilization
Seed quantity
Seed quality
A. Sulfur in vegetation
Dry deposition
Plant sulfur levels
(root, stem, and leaf)
Organic to inorganic sulfur ratio
Sulfur metabolism
B. Nitrogen
Nitrogen: sulfur ratio
N0? emissions
Nitrogen fixation
C. Water
Transpiration
D. Carbon
Digestability
E. Miscellaneous
Plant levels of potassium
magnesium, phosphorus, calcium
Production of leaf litter
aEffects are generalized from those summarized in Tables 7
level processes is indicated according to their impact on
•5, 7-6, and 7-7. Their relevancy to ecosystem-
survival and reproduction or the cycling of nutrients.
-------
As an example of the response of these three categories to S0?, the
effects of the pollutant on net photosynthesis are discussed.
The rate of carbon dioxide assimilation by foliage in controlled environ-
ments is responsive within minutes to elevated S0? levels. In barley (Medicago
sativa). exposure to 0.25 and 0.40 ppm S02 reduced carbon dioxide uptake
within 15 min to levels of 98 and 93 percent of the controls, respectively (29).
Within 20 min the corresponding rates were 94 and 86 percent, and remained un-
changed for the remainder of the 2-hr exposure. Once S02 was removed, (XL uptake
rate returned gradually within 2 hrs to that exhibited by "control" plants. A
similar pattern of photosynthetic depression at elevated S02 levels (1.0 ppm)
is reported for Phaseolus vulgaris (21). In both high (84 percent) and low
humidity (44 percent), C02 uptake was reduced within 10 min and, at the higher
humidity, was completely suppressed. In a comparison of the response of
photosynthesis to S0? in a deciduous (Diplacus aurantiacus) and an evergreen
(Heteromeles arbutifolia) shrub, Winner and Mooney (479) found that the magnitude
of depression depended strongly on concentration. Using a range of S02 concen-
trations from 0.25 to 1.71 ppm for 8 hr, net photosynthesis (as a percentage of
the controls) decreased linearly with time, and the slope became more negative
with increasing concentration. In both species and at all concentrations,
photosynthetic rates returned to normal within 3 to 7 days after S02 exposure
ceased.
The S02 response of net photosynthesis in three evergreen forest species
(Abies alba, Picea abies, and Pinus sylvestris) was investigated at S02 con-
centrations of 0.0, 0.05, 0.1, and 0.2 ppm delivered continuously over a
10-week period (223). Exposures were conducted in either the spring, summer,
or fall. Regardless of the species or season, increased S02 concentration
and duration led to progressive reduction in photosynthesis. This response
occurred even in the absence of visible needle injury and was common for all
three seasons.
7-109
-------
These studies highlight the sensitivity and responsiveness of photosynthesis
to S09; however, the implications of the results for an assemblage of plants
(e.g., crop canopy or forest stand) is difficult to assess, as was demonstrated
by Black and Unsworth (39). Vicia faba plants were individually exposed to a
range of low SCL concentrations (0-0.175 ppm) in a controlled environment
designed to mimic conditions characteristic of agroecosystems in Great Britain.
The levels of S0? used in the study were common ambient concentrations in that
country. Whenever SO- levels exceeded 0.035 ppm, net photosynthesis of
individual leaves decreased according to the amount of light irradiance. In
light-saturated leaves (upper canopy), photosynthetic response was concentration-
dependent, whereas the corresponding response with lower light irradiance was
depressed equally whenever SO^ levels exceeded 0.035 ppm. When SOp exposure
ceased, photosynthesis rapidly returned to control levels within 1 to 12 hr.
Dark respiration was notably increased (71 percent with low S0? levels), and this
may explain the decrease in net photosynthesis.
The implications of these results for crop physiology and yield were
discussed using a model of crop photosynthesis (39). The study indicates that
the experimental results derived from individual plants studies are valuable
in assessing crop-level response, but that direct extrapolation may not be
accurate. This conclusion is derived from the understanding that physical
associations among plants (in agricultural and natural ecosystems) create
canopies that modify an array of habitat factors, including S02 levels (28).
For example, light levels are attenuated vertically through the canopy so that
lower leaves are not light saturated, and, as demonstrated by the authors
(39), this factor modified the photosynthetic response. In a similar analytical
fashion, Black and Unsworth showed that crop net photosynthesis is inhibited
at a given low S02 concentration, but the response for the entire crop is not
concentration-dependent since the majority of canopy foliage experiences less
7-110
-------
0
27.9
-5.6
22.3
0.035
17.4
-9.5
7.9
0.088
16.4
-9.5
6.9
0.175
15.4
-9.5
5.9
than light-saturated irradiance levels. Model calculations (39) of dry
matter accumulation (grams of dry matter per square meter ground) for a
hypothetical crop of V_. faba were as follows:
Sulfur dioxide concentration (ppm)
Day (14 hr)
Night (10 hr)
Net total
production
(24 hr)
At SOp levels exceeding 0.035 ppm, net dry matter accumulation during daylight
hours decreased only slightly, which reflects the fact that most foliage was
below light saturation. During the evening, some of the photosynthate was
consumed in dark respiration, which increased uniformly at S02 levels above
0.035 ppm. As a consequence, net accumulation of dry matter per day for a given
area of ground decreased 65, 69, and 74 percent with increasing S0? levels.
Therefore, dry matter production in this hypothetical crop does not respond to
S0? in a concentration-dependent manner but rather is uniformly depressed above
S02 levels of 0.035 ppm. These results are relevant to understanding the manner
in which S02 impacts agricultural and natural ecosystems, and further
experimental study is warranted.
The open system of plant growth and development suggests that changes
in productivity should affect vegetative and reproductive processes. Furthermore,
the concept of "cardinal points" dictates that the S02 response be a function
of the plant's sulfur requirement and its ability to assimilate the S02
derived from the atmosphere. Results from a variety of research efforts support
this assessment.
7-111
-------
The response of plants to SO- may be interpreted as positive ("beneficial"),
negative ("detrimental"), or undetectable. When sulfur levels in the plant
are suboptimal, sulfur derived from SCL can remedy the deficiency, and thus
enhance growth and yield (4, 138, 417). In a variety of plant species found in
intensely managed agroecosystems (e.g., pastures, monocultured forests, croplands)
such beneficial responses are reported (88, 130, 264, 334).
Conversely, elevated SO- levels may reduce growth and development. Exposure
of poplar clones (Populus deltoides x P_. trichocarpa) to 0.25 ppm S02 for
6 weeks caused leaf injury which was, in time, associated with reduced growth
in height (113). Pinus sylvestris seedlings were exposed to 0.06 ppm SO,,
for 25 weeks in both summer and winter (132). Measures of growth (including
stem and root dry weight) were reduced in both seasons, and the response was
attributed to reduced COp assimilation and subsequent effects on photosynthate
allocation. Similar S02-associated growth effects are reported in the Biersdorf
area of Germany, which experienced chronic SO- levels (161). In the first 10
years of elevated SO- levels, several indices of growth in beech (Fagus
sylvatica), pine (Pinus sylvestris), and larch (Larix europaea) showed
reductions associated with the level of SO- stress. Although several growth
indices were studied, the most reliable were the ratio of thickness growth to
shoot length, and new shoot number and length.
Keller (224) documented changes in shoot growth of two deciduous tree
species (Ulmus scrabra and Robinia pseudoacacia) and attributed the response
to S02 inhibition of terminal bud growth. Furthermore, the response was
recorded after wintertime exposures when foliage was absent. Following
controlled exposures to S02 concentrations ranging from 0.01 to 0.2 ppm, the
number of buds failing to renew growth the following spring increased with
S0 concentration.
7-112
-------
Similar S0?-induced changes in growth of meristematic tissue are reported
for reproduction. In red (Pinus resinosa) and white (P_. strobus) pines growing
in a region experiencing elevated SCL levels emitted from a coal-burning power
plant, several indices of impaired reproductive success (e.g., number seeds per
cone, seed weight, and percent pollen germination) were associated with increasing
sulfur levels in the atmosphere (194).
Evidence that SCL modifies the distribution of elements in individual
plants may have implications for ecosystem-level nutrient cycles. With increasing
atmospheric concentrations of SCL, sulfur levels in vegetation rise accordingly;
the significance of this for the ecosystem's sulfur cycle is discussed
elsewhere (section 7.11.2). Concomitant effects of SCL on other elements are
also observed. Materna (295) found that the concentrations of potassium,
calcium, magnesium, and phosphorus increased in fir needles following controlled
exposures to SOp over several consecutive growing seasons. The pollutant con-
centrations never exceeded 0.38 ppm and were routinely less than 0.19 ppm.
Water-use efficiency in producers is also responsive to SOp. In Vicia faba,
an agriculturally important crop, exposure to 0.11 ppm SOp for a full day
reduced stomatal resistance to water vapor flux by 25 percent (37); the
authors estimate that an equivalent response in the field would increase the
amount of water transpired by 23 percent. Finally, many reports describe
pollutant-induced changes in a variety of proteins. Recently, Klepper (232)
found that hydrated SOp derivatives were responsible for N02 emissions
from foliage.
The response of plant populations and communities to elevated S0? levels
is not documented as well as that for individuals. From an ecological perspective
7-113
-------
this is unfortunate because single plant responses under controlled
conditions may not necessarily be the same as a population or community-level
effect. The response of populations is particularly relevant to intensely
managed ecosystems (e.g., pastures, croplands, forests) in which a single or
a few species dominate. Discussion of community responses is more appropriate
to natural ecosystems.
The dilemma of extrapolating from SO- effects on individual plants to
higher levels of organization is less difficult for populations than for com-
munities, especially intensely managed agroecosystems. Typically, producers
are genetically similar and experience comparable environments. The resulting
physiological uniformity requires that most individuals respond to environmental
stress in a comparable manner.
Managed agroecosystems are potentially very susceptible to SCL stress
for several reasons. First, plants exhibiting distinctly seasonal growth
and thriving in well-watered habitats maintain extremely high rates
of gaseous exchange, which encourages SO- influx. Some evidence indicates
that rapidly growing foliage (i.e., foliage with high intrinsic photosynthetic
rates) is very sensitive to S02, gauged according to leaf injury (466) and
reduced carbon dioxide assimilation (478). Furthermore, crops are commonly
harvested for their reproductive effort, a process notably responsive to S02
(via altered photosynthate allocation). Finally, the developmental uniformity
of single-species crops means that elevated S02 levels during a particularly
sensitive stage of growth (e.g., flowering) will affect most individuals in the
population with concomitant effects on yield. A more detailed discussion of
stress response in managed agroecosystems is provided by Loucks (280).
7-114
-------
From another perspective, agricultural ecosystems in sulfur-deficient
areas (e.g., southeastern United States) may benefit from elevated SCL levels
(334) if the exposure does not exceed the crop's ability to assimilate the
pollutant. This assumes that the level of sulfur in the plant is suboptimal.
This situation is strictly applicable to agricultural areas where soil sulfur
retention is extremely poor because of the depletion of litter, which is the
soil component most responsible for controlling the release of plant-available
sulfur (176, 216, 301).
In 1950, Dunn hypothesized that elevated atmospheric levels of smog in
the Los Angeles Basin were differentially affecting individuals in populations
of native plants and that differential selection was gradually changing the
genetic structure of the populations toward greater smog resistance. In
recent years, this population phenomenon has been documented in many native
species thriving in areas impacted by S0? (24, 187, 191). One example is the
evolution of SO- resistance in populations of Lolium perenne in grasslands
of Great Britain (187). These results indicate that at least some populations
are experiencing gene pool shifts as a consequence of prolonged exposure to
low-level SOp stress. The capacity to evolve resistance, which would
ameliorate some of the adverse pollutant effects, is likely to be more
common in naturally occurring species than in crop plants since the latter lack
the inherent intraspecific variation upon which selection can act (187).
The significance of the induction of gene pool shifts by S02 is difficult
to assess from an ecological perspective. Greater resistance may be beneficial
to sensitive populations. Conversely, if increased resistance is associated
with lower photosynthetic rates (478), slower intrinsic growth (466), or
decreased water-use efficiency (182), selection of S02 resistance would lead
to populations possessing a new set of ecologically important traits that might,
in turn, redefine the species' niche (325).
7-115
-------
Community-level responses resulting from prolonged exposures to S02
are not well documented; however, a theoretical basis from which to evaluate
effects is emerging. This conceptual effort is exemplified by the development
of a generalized forest growth model (50) that was designed to assess the
consequences of perturbation on plant communities (49, 392). This model has
been applied to the response of a mixed-species, deciduous forest in the
southeastern United States to differential levels of growth reduction (0, 10,
and 20 percent) following air pollution stress (468). Over several decades,
simulated pollution stress altered dramatically the relative biomass importance
of the major tree species within the forest; some species populations increased
while others decreased in importance. This suggests that the qualitative
composition of producer species changes in response to pollution stress, and
since community structure is coupled to the flow of energy and materials,
dependent processes within the ecosystem will necessarily be modified. The
mechanism underlying community-level changes is twofold. First, the growth and
reproduction of populations of sensitive species is impaired as a direct con-
sequence of SOp toxicity. Second, since community composition is determined
in part by species interactions (e.g., competition, symbiosis), the ecological
importance of resistant species whose prominence in the community is determined
by an interaction with sensitive species will be altered (468). The direction
of this indirect response depends on the nature and extent of the interaction.
An understanding of this governing role of species interactions is essential
to predicting how ecosystems respond to low levels of pollution (49). This is
also the justification for not extrapolating freely the results from intensely
managed forest and agroecosystems to predict how a mixed-species community
(e.g., natural forests or grasslands) will respond to a comparable perturbation
(229, 313).
7-116
-------
Modeling predicts that SCL affects species' performance directly through
inhibition of growth and reproduction or indirectly by changing a population's
relationship to other species. How does this conclusion compare with empirical
data?
The results from community-level studies in acutely stressed areas such
as Trail, British Columbia (326), lend credence to the modeling effort.
Regardless of the region and intensity of SCL stress, patterns of plant community
response are repeated. These include: (1) the species number decreasing
toward the source, (2) a parallel pattern of decreasing importance of canopy
species, (3) increasing prominence of ground vegetation toward the source,
and (4) profusion of opportunistic SCL-resistant species in areas vacated by
SCL-sensitive plants (483). The most likely explanation for these patterns is
that SCL directly inhibits either growth or reproduction of many species
populations. Following the decline of these SCL-sensitive plants, SCL-resistant
species flourish as they invade areas previously occupied by competitors
(483). The results from these acutely stressed locations indicate that the
SCL-susceptibility of individual species populations plays a greater role in
determining community response than does species interaction.
This conclusion is not appropriate to regions experiencing lower levels
of SCL. Guderian (158), using communities consisting of only two or three
different species, analyzed community-level responses to SCL and their underlying
causes. Each community, which was typical of those purposely planted for
fodder, was exposed to graduated levels of SCL for varying periods of time.
Several key observations were reported. First, changes in community composition
following exposure were a function of SCL dose, so that the higher the dose, the
greater the community change. Second, altered community composition was
attributed to both direct SCL effects on sensitive species populations and
7-117
-------
indirect changes in species interactions. This is exemplified by the increased
prominence of SCL-resistant populations which outcompeted the SC^-affected
plants. Community biomass exhibited little quantitative change despite striking
differences in species composition. The same conclusion was reached by another
researcher in a similar study of artificial exposure to S02 in an old field
in New England (73); it is also comparable to the conclusion achieved through
the modeling effort (468).
This understanding of community-level responses was achieved through
modeling and controlled exposures of intensely managed ecosystems. The results,
however, are applicable to field studies of regions experiencing prolonged
SCL stress (161, 372). As an example, Rosenberg et al. (372) assessed the
species composition in 27 stands of natural regrowth northern hardwood forest
dominated by oaks (Quercus spp.). white pine (Pinus strobus), and hemlock
(Tsuga canadensis). The stands, which varied in their distance from a 25-year-
old coal-burning power plant, exhibited no obvious a priori compositional
differences. Atmospheric pollutant levels were not reported, although foliar
symptoms typical of SCL toxicity were recorded on several occasions. In both
upwind and downwind directions, the number of vascular plant species (canopy,
understory, and ground) per unit area (species richness) increased with distance
from the source. A similar distance-dependent response was recorded for
species diversity using the Shannon-Weiner index. Both indices of plant
community response approached asymptotic values with increasing distance,
which implicates the facility as the cause of the response pattern. The
more rapid approach to the asymptote in the upwind direction supports
the hypothesis of an atmospheric pollutant affecting vegetation.
In spite of these S02-induced changes in community composition, an index
of above ground biomass (basal area of overstory species) showed no variation
among stands (372). Among the vascular plants, shrub and ground vegetation
was more responsive (in diversity and richness) than the overstory to SCL stress,
7-118
-------
and this enhanced susceptibility of the lower strata was attributed to the
intense competition, unique population biology attributes, and microhabitat
factors that tend to increase SCL levels close to the ground.
Among the most notable examples of S02 affecting plant communities is the
response of cryptogamic flora (lichens and mosses); several reviews are
available (110, 167). A map of epiphytic lichen communities for England and
Wales has been devised that associates progressive shifts in species composition
with SO- levels (168). In general, the higher ambient S0? levels were consistently
associated with fewer species and an increasing relative frequency of crustose
versus foliose or fruticose forms. The fidelity with which community composition
changes in accordance with SCL has led to the suggestion that analyses of
lichen communities be used as a natural bioassay to estimate ambient S0? levels
(168).
Similar mapping efforts are reported for several regions of North America.
In a rural area of Ohio surrounding a coal-burning power station (emitting
1025 tons SOp/day), the distribution of two corticolose lichens, Parmelia
caperata and P. ruderta, was markedly affected by elevated S0? levels (389).
Both species were absent from regions experiencing an annual average SCL level
exceeding 0.020 ppm. The distribution of more resistant lichens was not
noticeably affected until S02 levels exceeded 0.025 ppm (annual average).
Somewhat lower levels were projected by LeBlanc and Rao (255) to affect the ability
of sensitive lichen species to survive and reproduce. Using lichen transplants
along a gradient of decreasing S02 levels in the Sudbury region of Canada,
they estimated that acute and chronic symptoms of S02 toxicity in epiphytic
lichens occur when annual averages of S02 exceed 0.03 and 0.006-0.03 ppm,
respectively.
7-119
-------
The depauperate nature of cryptogamic flora in urban areas is well documented
(254, 480), and SCL is implicated most often as the principal abiotic factor
responsible for the change in species composition. Mosses and lichens have a
predisposition to altered growth and reproduction in polluted atmospheres
(146, 321, 322, 437).
The decline of cryptogamic flora in atmospheres containing elevated S02
levels is typically rapid. For example, LeBlanc and Rao (255) reported impaired
growth in several transplanted lichens within 6 months. This rapid decline
is in sharp contrast to the time required for lichen recolonization in the
event of a restoration of clean air. Using simulation modeling to project
reinvasion time by a common urban lichen (Lecanora mural is), Henderson-Sellers
and Seaward (179) reported a minimum of 5 years. In addition, even though the
rate of decline was a function of SCL concentration, cleaner air was only partly
responsible for the recolonization rate.
In addition to their importance in energy flow and material cycling in
ecosystems, producers also serve as hosts for a variety of microflora and
fauna. The nature of these interactions, which commonly involve fungi, bacteria
and viruses, ranges from being mutually beneficial (e.g. mycorhizae) to
antagonistic. It is the latter interactions, principally parasitic diseases,
that we know to be affected by elevated S02 levels. The mechanism of sulfur
dioxide's effect is either a modification of the virulence of the parasite or the
susceptibility of the host (435). Modification of the virulence of microorganisms
by S02 is well documented, for example, in the development of pollutant susceptibility
rankings for many common microflora (376). In general, spore germination is
the most sensitive stage of development. In light of the extensive interspecific
variation among microflora in response to S02, Saunders (376) hypothesized
that prolonged exposure would lead to the selective elimination of S02-sensitive
species.
7-120
-------
Evidence in nature that virulence is modified by SCL is provided by the
study of the distribution of Rhytisima acerinium, a leaf fungus responsible
for tar spot disease in sycamore trees (36). Along a gradient of decreasing
atmospheric S02 levels in Great Britain, the frequency of tar spot disease
increased. Whenever SCL levels exceeded 0.034 ppm (annual average), the fungus
was absent from sycamore foliage. This indicates that SOp prevented the spread
of the fungus and, as a consequence, the disease. In a review of this subject,
Heagle (170) concluded that documented cases of SOp inhibition of parasitic
infestations are more common than the converse.
In a review of parasites in European pine forest experiencing chronic
exposure to atmospheric pollutants, Sierpinski (393) found that infestations,
particularly of beetles, were more prevalent in chronically impacted forests
than elsewhere. The author hypothesized that the initial decline of producers
was attributable to the pollutants but that subsequent infestation of "weakened"
trees resulted in death. A comparable interaction between polluted air and
beetle infestations is offered to explain the loss of pines in the San Bernardino
National Forest, which has experienced chronic and acute pollution stress for
several decades (312). The consensus of these studies is that pollutant-
parasite interactions are principally governed by changes in the susceptibility
of the host rather than the virulence of the microbe. Donnabauer (115) and
Treshow (435) arrived at similar conclusions, and the former extends his
analysis by highlighting the potential consequences for forest growth. He
concluded that emissions may "...act as a stimulus for the development of
parasites and thus lead to subsequent damage that is entirely disproportionate
to the intensity of the emissions" (translated from the German).
7-121
-------
7.11.4.2 Response of Consumers and Decomposers to Sulfur Dioxide—The network
of biotic-abiotic interactions characteristic of managed and natural ecosystems
leads to the hypothesis that S0? effects on producers must have repercussions
at other trophic levels. Analysis of such responses, however, is difficult
experimentally, and an accurate assessment of the importance of SO,, in eliciting
the response is plagued by the often complex relationships among producers,
consumers, and decomposers.
This mechanism of response of consumers and decomposers to SOp via producers
does not preclude a direct, adverse effect of the pollutant in a manner analogous
to physiological injury in plants. Elevated atmospheric levels of S02 are
particularly harmful to soil organisms (16) since soils are preferential sulfur
accumulation sites. This focus on soil organisms takes on even more relevance
since the rhizosphere is not only biologically active but also responsible for
selectively fractionating sulfur derivatives (82, 260).
In forested areas experiencing prolonged elevations of atmospheric
S02 levels, the species composition of soil microflora shifted toward a greater
number and frequency of species capable of utilizing the sulfur additions
(457). Specifically, the levels of thiobacilli and sulfur-oxidizing fungi were
positively correlated with levels of S02 stress, soil depth (Wainwright, ref 457)
and extent of tree canopy. In areas impacted by S02, the greatest concentration of
thiobacilli and sulfur-oxidizing fungi were isolated from the upper 0 to 20 mm
of soil. The importance of canopy was most conspicuous, for the absence of
a litter on the forest floor reduced dramatically the number of "sulfur-loving"
microflora. Comparable results were reported for an area in which the
annual average S02 level exceeded 0.048 ppm (458). This study confirmed
7-122
-------
the dual importance of litter layer and upper soil profiles in determining the
microfloral distribution in SO^-polluted areas and, in addition, documented
an apparent S0?- induced decrease and increase in the total numbers of heterotrophic
bacteria and fungi, respectively.
Since prolonged S0~ exposure tends to increase soil acidity concentration,
acidification may be the predominant change in soil chemistry that elicits a
response in the microfloral community. In native soils of Canada acidified to
a pH of 3.0 due to their proximity to a sulfur-emitting "sour gas" processing
facility, bacterial numbers (particularly heterotrophic forms) were reduced
(59). Artificially acidified soils in "reference" locations responded in an
analogous manner. Since the activity of heterotrophs contributes to nutrient
cycling, this pollutant-induced modification could have adverse ecological
consequences (59).
There is further evidence of SCL effects on soil nutrient levels as a
consequence of pollutant-induced changes in soil microflora for nitrogen,
although the applicability of the data to natural soils needs to be assessed.
Soil exposed continuously to atmospheric S0? levels at 5-10 ppm showed changes
in levels of ammonia, nitrate, and nitrite (247). Blue-green algae were found
to be extremely sensitive to bisulfite (482), and since these organisms are
the principal nitrogen fixers in several agricultural and natural ecosystems,
their susceptibility warrants further study (16, 150, 247). Finally, the ability
of heterotrophic bacteria to decompose organic substrate was inhibited during
exposures to high S0? levels (156). The authors conclude that this response may be
appropriate to acutely stressed areas but not to regions experiencing prolonged
exposure at low S0? levels.
7-123
-------
These experimental studies coupled with the understanding that S02
derivatives have pronounced effects on soil chemistry (268, 456) suggest that the
rhizosphere is a potential site for pollutant-induced modifications that have
far reaching ecological consequences. Nutrient cycling appears to be notably
responsive. Unfortunately, few research efforts have focused on soil-pollutant
interactions, particularly as regards the selective accumulation over time of
pollutant derivatives in the rhizosphere and its influence of soil microbiota.
Coleman et al. (75) postulated that root exudation of organics during active
root growth is a bacterial stimulant. This response in turn elicits feeding
by a variety of soil microfauna including nematodes and amoebae. This sequence
of events is tightly linked to the mobilization of carbon, nitrogen, and
phosphorus. Since SCL is known to affect root growth at levels that do not
induce foliar injury, this may be a mechanism whereby SCL indirectly modifies
nutrient cycling events in the soil even though pollutant derivatives do not
accumulate.
7.11.4.3 Response of Natural Ecosystems to the Interaction of S00 with Other
Pollutants—Sulfur dioxide is commonly associated with many other stresses,
principally gaseous pollutants (including ozone, nitrogen oxides, PAN, hydrogen
sulfide, and fluoride) and particulates.
The Copper Basin of Tennessee has received an array of stresses since the
initiation of smelting operations in the 1850s, and foremost among these
have been logging, fire, and acute levels of S02. The effect is dramatically
evident over 6.2 x 106 ha, of which 1.8 x 106 ha are devoid of vegetation,
and the remainder are covered by a grass region merging into forest (198).
Prior to the stresses, the area was a natural mixed-species forest consisting
of oak, white pine, sourwood, tupelo, and dogwood.
Even though the peak of logging and S02 emissions was around 1900, the
veqetational component of the ecosystem continued to show pronounced effects in
7-124
-------
the 1940s (198). In comparison to the surrounding forests, the soil and
atmospheric environment of the grasslands and inner barren zone was different in
air and soil temperature, evaporation, wind velocity, and rainfall. Furthermore,
the denuded zone was continuing to increase in area as erosion gullies cut deeper
into the sparsely vegetated terrain. Additional evidence of the lingering
impact of the multiple stresses was exemplified by the study of factors limiting
revegetation (481). Isolated plots of kudzu have been established successfully;
however, expansion of the vegetation islands was limited to several meters
since nutrients, particularly phosphorus and nitrogen, became limiting.
Several studies in regions surrounding zinc and copper smelters have
reported effects attributed to the combined toxicity of heavy metals and SO-.
The pattern of community response in a desert ecosystem receiving episodic
emissions of copper and sulfur dioxide over a 47-year period did not differ
from that observed in areas stressed acutely by SO- alone (484). Along a
gradient originating at the source, gradual increases in species number,
vegetation density, species diversity, and percentage cover were recorded (484).
Similar results are reported from Trail, British Columbia (326), WaWa (152)
and Sudbury (153), Ontario, Canada.
Research addressing the effects of gaseous pollutant interactions on an
individual's performance is receiving increased attention; however, comparable
emphasis at the community and ecosystem level are wanting. Sulfur dioxide, nitro-
gen dioxide, and a combination of the two decreased the expansion rate of new leaves
in American elm (Ulmus americana). The combined exposure caused the greatest
suppression of growth (76). In intensely managed pastures dominated by several
competing grasses, a combination of sulfur dioxide and nitrogen dioxide caused a
much greater loss in dry weight and leaf area than did either pollutant alone (14).
Predicting the effects of prolonged exposure of the grasslands to these mixtures
7-125
-------
is further complicated by the interspecific and intraspecific variation in
response to SCL and NO- alone and in combination. "Final" community composition
will likely reflect competitive interactions between species and the respective
levels of each pollutant in the atmosphere (14).
7.11.5 Response of Natural Ecosystems to Particulate Matter
The atmosphere contains a great variety of particulate matter, both
natural and manmade (415). As discussed in Section 7.7, the heterogeneous
physical and chemical nature of particulates presents problems in addressing
the significance of elevated atmospheric particulate levels for natural and
agroecosystems. From an ecological perspective this hindrance is particularly
acute since terrestrial ecosystems are major sites for deposition and accumulation
of many elements associated with manmade particles.
Wet and dry deposition are the two processes by which particulates are
transferred from the atmosphere to the landscape. In wet deposition, water
solubility of the particulate is of paramount importance since precipitation
scavenging is the flux vector. In contrast, dry depositional flux is controlled
by wind speed, particle size, and the physical properties of the receptor. In
terrestrial ecosystems, the receptor is typically foliage since it provides an
extensive, multi-tiered array of surfaces extending from the uppermost parts of
the canopy down to the forest floor. However, the capacity of foliage to serve
as a receptor varies with surface area (67, 462), location in the canopy (276),
concentration of particulate matter in the atmosphere (460), and leaf pubescence
(276, 462). The importance of pubescence is illustrated by the sevenfold
greater flux of aerosols to a heavily pubescent (Helianthus annus) versus a
smooth (Liriodendron tulipifera) leaf (462). This difference indicates that
deposition rates will differ for different plant communities experiencing
equivalent particulate exposure.
7-126
-------
The fate of particles deposited on foliar surfaces depends on the
solubility of the chemical in constituents, the occurence of precipitation, and
the sorptive capacity of the leaf (275). Furthermore, many elements commonly
associated with particulates are essential for plant metabolism (e.g., zinc
and phosphorus) and, as a consequence, absorption may be a means by which the
plant can supplement its nutrient supply (231,305). Some elements, once deposited,
are tightly bound to the surface through chemical interactions; even rainfall may not
be effective in removing all of the material. A good example is lead, which can
be absorbed into the leaf tissue, sequestered in cellular organelles (496), held
to the leaf surface by electrostatic charges (276), or washed off by rain. Since
the leaf retains approximately 30-70 percent of the deposited lead, the element
accumulates in vegetation to levels that far exceed those in the atmosphere or
soil (72). This fate and distribution pattern is unique for lead; other elements
associated with particulates may behave differently (231,275).
Vegetation may be only a transitory site for particulate matter and
its associated constituents. If not retained by the leaf, material is washed
off by rain or removed by litterfall and ultimately transferred to the forest
floor. The net effect of these processes is to funnel leaf surface deposits
to the litter-soil complex. This conclusion is verified for many atmospherically
derived elements deposited in natural ecosystems: fluoride in a coniferous forest
(423); cadmium, zinc, and copper in a deciduous forest (333); lead along a roadway
(460); mercury in an urban ecosystem (278); and lead, zinc, cadmium, and copper in
diverse hardwood forest (84). The tendency for the forest floor to serve as a
sink for these atmospherically derived elements is further accentuated in the
tendency of most heavy metals to remain solely in the upper soil profiles rather
than being leached.
7-127
-------
This retention of heavy metals in upper soil horizons is of potential
ecological significance, particularly in areas near sources of emissions con-
taminated with heavy metals. The accumulation has not been fully explained,
although several key factors have been identified (340, 431). First, if litter
decomposition occurs faster in uncontaminated than in contaminated plant remains,
then the heavy metal concentration will rise. Second, detritus is an effective
sink for a variety of cations, and heavy metals are easily bonded to the negatively
charged organic groups in detritus. The capacity of these processes to cause an
accumulation of heavy metals is remarkably great. In a nonpolluted location, lead
levels in detritus were four to five times higher than those in the living plant
canopy; the corresponding value for comparable detritus sampled from a heavily
polluted environment was 20 to 25 (340). The point at which equilibrium is
attained between heavy metal inputs and outputs for the detritus is not known
(340, 438).
These results, showing preferential retention of heavy metals in the
soil-litter layer, follow a general characteristic of element cycling in
ecosystems: even though most elements move throughout the entire system, the
distribution of each is not uniform. Specific components (e.g., atmosphere,
soil, plants) tend to serve as pools or reservoirs for individual elements, and
as a consequence a disproportionate fraction of elemental inputs will be sequestered
in one or several components of the ecosystem. Some of the best evidence supporting
this observation is from regions acutely stressed by particulates containing high
levels of heavy metals. Given the regional character of low-level particulate
emissions, particularly along the east coast (446), the applicability of this
conclusion to more moderate pollution levels needs to be assessed.
This concern has been addressed for a deciduous forest in the southeastern
United States (267). Wet and dry deposition of aerosols, gases, precipitation, and
7-128
-------
large particles were major sources of trace element input to the forest floor,
including 99 percent for lead, 44 percent for zinc, 42 percent for cadmium,
39 percent for sulfate, and 14 percent for manganese. These seemingly large
percentages are typical for rural or remote areas even though three major coal-
burning power plants (total coal consumption of 7 x 10 tons/year) were within
20 km of the forest. The deposition patterns throughout the year indicate that
the atmospheric chemistry is determined by regional source and transport phenomena
rather than local emission sources, except during air stagnation.
Regardless of the source of particulates deposited in the forest, the
atmosphere contributed a major portion of the trace element inputs (267). Uater
solubility was critical since insoluble constituents associated with the
particles were not readily mobilized within the forest. Any event promoting
solubilization (e.g., aerosol formation, rainfall scavenging, moisture formulation
on leaves) enhanced an element's mobility. One example of the potential ecological
significance of solubilization is the nontoxic accumulation of dry-deposited
material on a leaf surface followed by a brief shower, a common summer condition.
Following the rain, surface droplets of water should exhibit high concentrations
of solutes resulting from rainfall scavenging and from solubilization of the dry
deposits. Evaporation further enriches the concentration of these solutes, yielding
concentrations from 100 to 1000 times greater than that in incident precipitation.
Calculations using typical rainfall data and dry deposition rates for a Tennessee
forest indicate that pH values of droplets on the leaf surface may often drop below
2.0.
This study confirms the hypothesis that regardless of the deposition
rates, elements tend to become enriched in certain components. The behavior
7-129
-------
of each element within a given ecosystem is unique, so specific accumulation
sites and enrichment dynamics may not be comparable.
The consequences of particle deposition for natural ecosystems and
agroecosystems are not simply identified. This dilemma results from the complex
chemical variability of the particulate matter (88, 263), mobilization capacity
of the associated constituents (267), size of accumulation, inherent response
variation of the bioreceptor (303), and the importance of the receptor in ecosystem
structure and function (263,303, 496).
The hypothesis that deposition of particles alone, regardless of the
toxicity of its constituents, can adversely affect an ecosystem when deposition
rates are high is well documented (408) and intuitively obvious, given the
diversity of plant physiological responses elicited by particle deposits (see
section 7.7).
A mixed hardwood-conifer forest of southwestern Virginia has been
impacted by limestone dust for a maximum of 25 years, and pronounced structural
changes in the producer community are evident. Crust formation on foliage of
both deciduous hardwoods and conifers was reported to be responsible for the 18
percent reduction in lateral stem growth of Acer rubrum, Quercus prunus, and
5.- rubra (54). The reduction was not clearly associated with the initiation of
quarry activities but rather increased progressively with time as if the effects
were cumulative. Not all trees were affected adversely; Liriodendron tulipifera
increased its lateral growth by 76 percent indicating that local inhabitant
conditions became more favorable for growth of this species. This growth
stimulation is attributed to either a change in species interaction favoring
the growth of J_. tulipifera or a "fertilizer effect," that is, emissions provided
7-130
-------
some element that was in limited supply (305). In hemlock populations within
the same region, Manning (289) noted a striking reduction in terminal growth
and increasing needle chlorosis of pines. Brandt and Rhoades (55) maintained
that all acidophilic species (including conifers) were the least resistant of
the producers to the emissions. A similar hypothesis is offered to explain
the replacement of conifers by deciduous tree species in a region experiencing
heavy deposition of particulate matter (high fluoride levels) in Newfoundland
(423). The effect of limestone dust on species survival was also responsible
for changes in leaf microflora where some species declined while others in-
creased in prominence (289).
The deposition of material on leaf surfaces can have ecological effects
in addition to producer-level responses. In particular, organisms that inhabit
the leaf surface or consume the foliage may be affected (185), and the magnitude
of the response is correlated with the toxicity of the soluble constituents.
Smith (402) hypothesized that the accumulation of metallic elements on leaf
surfaces results in toxicity to the leaf surface microbial community. To
support his contention, he reported growth inhibition of the phylloplane fungus
Platanus acerifolia by several common cations (including nickel, zinc, lead,
aluminum, iron, and manganese) that are associated with particles. Since
deposition of these constituents on the leaf surface in a water-soluble form
constitutes a pronounced habitat change for the microbes, competitive interactions
will be affected and result in community composition shifts. This same rationale
is reported to be responsible for outbreaks of black pineleaf scale in pine and
Douglas fir forests (124). The mechanism whereby emissions affect scale frequency
7-131
-------
is complex and involves the particle-induced extinction of a parasitic species
that regulates the size of the scale population. In forests exposed to dust
emissions, the parasite's decline effectively modifies the "predator-prey-
relationships between these two species. Other examples of pollution-induced
habitat changes that in turn affect insects are reported to be responsible for
the distribution pattern of ladyspot, Adalia bipunctata. in Great Britain (92)
and atypical behavioral activity of two moths, Biston betularia and Gonodontis
bidentata (38).
The implications for herbivores of particle deposition on plant
surfaces in natural ecosystems is not well documented, even though food chain
pathways suggest concern particularly for constituents that can be assimilated and
concentrated in body tissues (231,340). In a study of this exposure pathway,
Chamberlain (66) calculated that in comparison with inhalation of airborne
particulates, ingestion of contaminated foliage by herbivores can be 350 times
more effective as an exposure pathway. Evidence in support of this mechanism
for livestock is reviewed by Chamberlain (66), Daessler (95), and Philips (351).
Comparable results from natural ecosystems are only scattered (139, 281).
The leaf surface is not the only accumulation site for particles and
their associated constituents. Through precipitation scavenging of particles
in air, washoff of surface deposits, or litterfall, particulate material is
transferred to the soil, where it is tightly bound to decaying organic matter.
For producers, this retention of toxic substances in the upper soil horizons
may explain in part the differences in zinc tissue levels in shallow-rooting
versus deep-rooting species in an area near a smelter (275). Because of their
surface-rooting characteristics, herbs may experience greater soil levels of
soluble particulate materials than do deep-rooting trees (275).
7-132
-------
The upper soil horizon, including decaying organic material, is a
region of intense biological activity as a result of the degradation of litter,
remineralization of the bound materials and root uptake of the nutrients available
to plants. These processes are mediated by a variety of decomposers (bacteria,
fungi, detritovores), and their presence fosters a hierarchy of primary,
secondary, and tertiary consumers. Consequently, particulate emissions that
interfere with microbial activity can have delayed effects on primary producers
(438) and soil consumers. Evidence supporting decreasing decomposition rates
with increasing emission levels are most demonstrable in acutely stressed
regions. In woodlands near a lead-zinc-cadmium smelter, Coughtrey et al. (84)
reported that 90 percent of the heavy metal burden in the environment was in
the soil-litter component and that this accumulation was responsible for
consistently greater amounts of standing litter. The authors attributed this
increase to sustained leaf fall together with impaired decomposition rates.
Toxic effects of heavy metals in soils on fungi and bacteria involved in
decomposition are reported (374) and this effect may be propagated to other
soil organisms (22,413).
In summary, particulate matter emissions, by influencing atmospheric
chemistry, impact on terrestrial ecosystems. These effects are most apparent near
large emission sources, but ecosystems within the same geographic region may also
be the site of deposition. Foliar surfaces are the most probable site for initial
dry and wet deposition; however, most material is eventually transferred to the soil
Particulate matter alone constitutes an ecological problem only where deposition
rates are high. Conversely, since many toxic elements (e.g., heavy metals,
polycyclic aromatic hydrocarbons) are commonly associated with particles,
7-133
-------
ecological modifications may arise even if deposition rates are not high. In
this regard, regional atmospheric chemistry is important. Solubility of
participate constituents is a critical factor, since water-insoluble elements
are not mobile within the ecosystem. One common characteristic of particulates is
their tendency to accumulate selectively within a given environmental component.
One transitional site of accumulation is foliage where wet- and dry-deposited
material becomes highly concentrated during brief precipitation events. Un-
fortunately, the physiological effects of concentrated solubles is not fully
resolved. Soils are long-term sites for the retention of may constituents
found in particles. This accumulation in the soil-litter layer has demonstrated
consequences for ecological processes, notably decomposition, mineralization,
nutrient cycling, and primary production.
7.11.6 DISCUSSION AND CONCLUSIONS
In spite of their overt differences in biota, most terrestrial ecosystems
are driven by comparable processes that control energy flow and nutrient cycling.
These similarities have fostered the development of conceptual models to explain
the movement of energy and materials in ecosystems.
One example of ecosystem performance supporting this conclusion is
the common pattern of response in different ecosystems to acute and prolonged
abiotic stress (486) such as ionizing radiation (487) and multiple perturbations
near smelter operations (152,153). Woodwell (486) argued that regardless of the
stress and the successional trends of the ecosystem, changes imposed by the
stress were broadly predictable and included biotic simplification, reordering
of energy flow, and modification of nutrient cycles. This simplification is
characterized by the initial loss of stress-sensitive species followed by the
progressive loss of vegetational strata in the sequence of canopy > subcanopy >
understory > forest floor. With increasing stress, energy utilization is altered,
7-134
-------
with a greater amount diverted to maintenance and less allocated to net photosynthate.
This shift in net productivity decreases standing crop biomass which, in turn,
reduces the capacity of vegetation and soils to store nutrients. As a consequence,
nutrient cycles that develop during succession toward efficient redistribution of
essential nutrients are broken, leading to a net export of materials in streamflow.
In general, the inventory of organisms, energy, and nutrients is reduced, and this
simplification effectively inhibits restoration.
This analysis of ecosystem response is applicable to systems experiencing
prolonged exposure to acute levels of atmospheric pollutants. Wolak (483)
predicted four disciimax communities in order of decreasing stress intensity:
biological desert, grasslands, shrubs, and forest. Since the interplay of
successional processes and stress intensity determines which zone will prevail,
Wolak designated the equilibrium community as the "industrioclimax."
In contrast to responses to acute stress, patterns of ecosystem
modification following low-level or chronic exposures are not easily identified.
Table 7-19 outlines some examples of ecosystem response to an array of abiotic stresses,
including radiation, nutrient subsidies, gaseous pollutants, pesticides, and
species removal. The most common response is a change in species composition of
the community. Initially, stress-sensitive species decline, followed by a
corresponding increase in competitor species. This consequence of species
interaction- is not restricted to populations within one trophic level, but may be
propagated between and among producers, consumers, and decomposers. Finally,
in an analogous fashion, the fate and distribution of nutrients is also modified.
In ecosystems experiencing a prolonged stress (e.g., oxidants) or the
lingering effects of a stress (e.g., species removal or radiation), a unique
7-135
-------
TABLE 7-19. SUMMARY OF THE EFFECTS OF SELECTED ABIOTIC STRESSES ON NATURAL ECOSYSTEMS
Stress
Cpmmuni ty
Effect
Mechanism
Reference
Radiation
Oxidant
^ Nutrients
OJ
Herbicide
Fire
Species
removal
Old field
Old field
Forest
Old field
Grasslands
Old field
Old field
Forest
Old field
Forest
Change in community composition:
Loss of some species,
increased importance of
others
Establishment of a new
equilibrium
Change in community composition:
Demise of ponderosa pine,
increased importance of
others
Change in community composition:
Demise of some species,
increased importance of
others
Change propagated to other
trophic levels
Primary production increased
Change in community composition:
Increased diversity and
species richness
Primary production unchanged
Interrupts and renews succes-
sion
Composition altered, primary
production recovered
Change in water cycling rates
Radiation sensitivity
Species interaction
Oxidant sensitivity
Species interactions
Nutrient sensitivity
Species interactions
Species interactions
Species interactions
Species interactions
Fire sensitivity plus species
interactions
Species interactions
98
10
312
17, 252
197
17
459
488
-------
response emerges: as a consequence of succession, a new equilibrium between the
stress and the ecosystem is achieved. However, in the process the ecosystem
develops a new biotic diversity and concordant functional attributes unlike those
of its predecessor. This is well documented in the response of old fields to
ionizing radiation (10), projected successional changes for the San Bernardino
National Forest experiencing elevated oxidant levels for several decades (312),
and the modified water cycle that developed in 15 years following the conversion
of a southeast watershed from a canopy of deciduous hardwoods to conifers (414).
What factors influence the response of ecosystems to chronic and low
levels of abiotic stress? Ultimately the issues of ecosystem stability and
complexity are of central importance; however, the relationship between the
two is enigmatic (302, 342). In particular, theory predicts that increasing
complexity imparts stability whereas experimental data, mostly from the tropics,
demonstrate the fragility of complex communities (302). It is clear that
monocultures are at greater risk of deterioration when subjected to stress (323)
than their multispecies counterparts. In these low-diversity communities,
population responses govern, to a large extent, the fate of the ecosystem (342).
This same hypothesis of the central importance of population response is
extended to natural ecosystems in the event of stress sensitivity being exhibited
by species having pivotal functional roles in the ecosystem (51, 211,350,436).
In this situation sensitivity predisposes the system to respond, while the final
outcome is determined by species interactions.
In summary, the response of terrestrial ecosystems to assorted stresses,
particularly at low and chronic levels, is not totally predictable since the response
is governed by the nature and magnitude of the stress and its effect on the
performance of the plant-animal community (3). As regards a pollutant stress,
7-137
-------
its fate, distribution and toxicity are important. Any stress that is
selectively fractionated within the environment or the biota has the potential
for unexpected ecological impact, since ambient atmospheric levels do not
accurately reflect concentrations in the ecosystem. Furthermore, stress assim-
ilation by the biota may involve detoxification; therefore, the ecosystem
response is determined by the ratio of the rates of application versus assimi-
lation and detoxification. This latter factor is critical to gauging the effects
of S0? on agricultural and natural ecosystems. The influence of the biotic communi-
ty in determining stress responses lies in the resistance level of sensitive species
as well as the integration of the species into the structural and functional sta-
bility of the system.
In a conceptual approach to the response of natural ecosystems to air
pollution stress alone, Smith (400) outlined three categories of response de-
pending on the level of pollution stress (Table 7-20). Acute pollutant
levels for prolonged time periods lead to extensive simplification of the
ecosystem as all life forms are adversely affected. The most conspicuous examples
are areas near smelter operations, although the magnitude of deterioration can-
not be attributed to air pollution alone since a multitude of other stress-
factors (e.g., fire, logging, heavy metals) may also be important. At more
moderate levels of pollution, only sensitive species are differentially affected;
however, the impact is propagated to other species as a consequence of trophic
and nutrient cycling interactions. With time, the stress and the ecosystem will
establish a new equilibrium, seen especially as shifts in species composition.
More subtle modifications of trophic relationships and nutrient cycling underlie
these overt changes. Finally, when pollutant levels are low, effects are more
difficult to predict and detect. Many pollutants tend to exhibit patterns of
7-138
-------
TABLE 7-20. CONCEPTUAL SCHEME FOR CATEGORIZING ECOSYSTEM-LEVEL RESPONSES TO SO
STRESS LEVEL AND SUBSEQUENT PLANT COMMUNITY RESPONSE
AS A FUNCTION OF
Class of
response
Level of S0?
stress
Plant community response Ecosystem response
Example
High
II
Intermediate
III
Low
Growth and reproduction of
most species affected
leading to local extinction of
many species
Growth and reproduction of
only S02-sensitive species
initially affected; subse-
quent changes as a conse-
quence of species interactions
Effect on growth and
reproduction cumulative
over time
Simplification of
Structure:
Reduced diversity
Altered climate
and hydrology
Increased soil loss
Function:
Net nutrient loss
Reduced energy flow
Modification of:
Structure:
Changes in species
composition
Function:
Altered flux of
energy and materials
Structure:
Changes unknown
Function:
Sulfur incorporated
into exciting pathways
and sinks leading to
progressive accumulation
of sulfur in vegetation
and soils
152, 133, 198, 326
253,260,275,276,477
253,260,275.276,477
Source: Smith (400).
-------
accumulation within one or several fractions of the biotic or abiotic components
of the ecosystem. As a consequence, overt modifications will be gradual and
lag several years behind the initiation of the stress. Although Table 7-20
shows a difference between ecological effects of intermediate and low pollu-
tion levels, this distinction is artificial since stress levels fluctuate and
ecosystems vary in their susceptibility. Examples of ecosystems exhibiting
class II and III responses include Kaybob, Whitecourt, and the Montana grass-
lands (see section 7.11.3).
The preceding material provides a framework for evaluating the impact
of SCL and particles on terrestrial ecosystems. The gradient of responses
included in classes II and III are areas of concern from an ecological perspec-
tive. This conclusion is most relevant in regional terms, since high SCL
levels for prolonged time periods (class I) are precluded by pollution controls
and atmospheric injection of point-source emissions well above the vegetation
canopy. With subsequent atmospheric turbulence and transport, SCL products
are mixed with other pollutants and distributed throughout the region. As a
consequence, deposition of SCL, which may be simultaneous with other gaseous
and particulate pollutants, occurs at sites distant from the emission source.
The effect on biota will vary depending on the rate of deposition and sensi-
tivity of the biota. Episodes in which S02 levels are sufficient to induce ex-
tensive necrotic lesions are likely to be less important than variable-dose
situations in which chronic levels during air stagnations are intermixed with
the more common periods of low-level deposition rates (229).
In an attempt to pinpoint regions that are likely to experience pollution
episodes (short-term high levels), Miller and McBride (313) devised a map
that overlays the boundaries of 10 forested ecosystems with projections of the
7-140
-------
TABLE 7-21. FATE AND DISTRIBUTION OF S02 AND ITS DERIVATIVES IN NATURAL ECOSYSTEMS
Source
Fate
Mechanism
Ecological concern
Atmosphere
Vegetation
Soil
Water
Transport out of region
Deposition to landscape
A. Vegetation
B. Soil
C. Water
Retention on surface
Assimilation
Soil
Soil organic fraction
Soil inorganic fraction
Water
Transport out of region
Atmospheric transport
and dispersion
Wet and dry deposition
Adsorption
Sulfur metabolism
Washoff and litterfall
Detrital adsorption and
litterfall
Microbial decomposition
Leaching
Stream flow
Contribution to another region
pollution burden
Accumulation of S0? derivatives in
and on foliage
Increasing levels of SO-
Derivatives in soil
and water (e.g., H+ and SO.)
Altered leaf surface chemistry
(e.g., H+ increase, cationic
leaching)
Physiological effects
including chronic and
physiological injury
Change in soil chemistry:
A. Selective accumulation
of S0? derivatives
B. Acidification
C. Cationic leaching
Lake and stream acidification
-------
number of atmospheric forecast days. The highest potential for air pollution epi-
sodes was found along the Pacific coast, while a second focus of episode inten-
sity was within the interior of the middle and southern Atlantic States, including
parts of West Virginia, Virginia, Kentucky, Tennessee, Georgia, and Alabama.
Concern for SCL impacts along the Pacific Coast is limited to single sites near
smelters. Conversely, in the East, high emission rates are common from the
northeast southward to the Gulf States. Therefore, concern for air pollution
episodes during which S02 concentrations increase in the atmosphere centers
primarily along a broad band of insular regions of the Atlantic States. This
region is dominated by the eastern deciduous forest.
There are problems in relying solely on the overlay of projected frequency
of SCL episodes with natural ecosystems (313). This technique only projects
the frequency of atmospheric conditions conducive to SO- build-up, not eco-
system response. Many biotic and abiotic factors mitigate or potentiate the
response, including topographic features, local emission sources, biotic
sensitivity, and environmental conditions.
Given the scenario of projected SO,, levels, what ecological effects are
likely? Based on Table 7-20, gradual shifts in community composition in some com-
munities are expected as are elevated levels of sulfur throughout the ecosystem.
A more detailed accounting of the fate and distribution of S0? in the environ-
ment as well as its effects on biota is outlined also in Table 7-21. Within
the environment S02 is highly reactive with a variety of elements, and many of
these derivatives are ecologically important. Once absorbed by foliage, S02
is oxidized to sulfites and sulfates, while absorption to the leaf surface
and subsequent solubilization produce sulfate and hydrogen ions. In soils,
sulfur occurs as both inorganic and organically bound sulfur. Many of these de-
rivatives are selectively accumulated in different parts of the ecosystem and for
varying time periods that range from hours (leaf surface) to seasons (internal
7-142
-------
leaf tissue) to years (soils). The accumulation of SCL derivatives to toxic
levels impairs physiological processes. In plants, net photosynthesis is
notably responsive, whereas in the soil the microbiota exhibits shifts in
species composition with increasing levels of sulfate and acidity. The
SO^-induced changes in the composition of the primary producer community are
considered major criteria for judging pollutant effects on ecosystems; however,
this overt response reflects an extensive and subtle modification of the
ecosystem.
A similar analysis of particles must realistically assess the ecological
importance of the water-soluble consituents more than that of the particulate
matter. Once deposited, particles, inorganic elements, and organic molecules
are mobilized within the system and either directly affect biota or tend to
accumulate. Given the diversity of chemicals associated with particulate
matter, a full accounting of the fate, distribution, and ecological impact of
each chemical is beyond the scope of this document.
7.12 SUMMARY
The widespread occurrence of particulate matter and sulfur dioxide in the
atmosphere frequently results in terrestrial vegetation being exposed simul-
taneously to these two pollutants and other phytotoxic pollutants. More is
known about the effects of sulfur dioxide than about the effects of particulate
matter, as the former has been studied more. Studies of the effects of particulate
matter have generally focused on the effects of heavy accumulations and the
reduction in the photosynthesis resulting from these accumulations. The more
subtle effects of particulate matter on vegetation have not been extensively
investigated and are, therefore, not well understood. Even less information
is available concerning plant response following exposure to sulfur oxides and
particulate matter in combination.
Sulfur dioxide must enter a plant through leaf openings termed stomata to
cause injury. Sulfur dioxide entering plant stomata (leaf openings) is converted
7-143
-------
to sulfite and bisulfite, which may then be oxidized to sulfate. Sulfate is
about 30 times less toxic than sulfite and bisulfite. As long as the absorption
rate of S0? in plants does not exceed the rate of conversion to sulfate, the
only effects of exposure may be changes in opening or closing of stomata or
changes in biochemical or physiological systems. Such effects may abate if
S0? concentrations are reduced. Both negative and positive influences on crop
productivity have been noted following low-dose exposures.
Symptoms of 50,,-induced injury in higher plants may be classified as
preclinical or clinical. The former term refers to alterations in plant
metabolism or physiology that may or may not develop into visible (clinical)
symptoms. Reduced growth and yield and/or increased susceptibility to other
biotic or abiotic stress-inducing agents may occur if alterations in plant
metabolism or physiology persist for a period of time. Significant reductions
in the growth and yield of major forest tree species and agronomic crops have
been reported without the presence of visible symptoms.
Chronic injury symptoms include plant responses that usually involve
chlorophyll disruption followed by a condition of chlorosis or yellowing of
tissues. Pigmentation changes resulting in stippling or general discoloration
characterize this type of injury. Chronic injury results from either high-dose
or low-dose exposure; high-dose exposure may lead rapidly to acute injury.
Acute injury includes necrosis or death of cells, tissues, organs, or the
entire plant.
Clinical or visible symptoms result from both chronic and acute injury,
and refer to plant response rather than to the exposure conditions and the
dose received. Dose-response functions concern the interactions of the exposed
plant, its biological response systems, and the environment with the dose of
the pollutant.
Many species of plants are sensitive to low levels of S02. Some of these
plants, listed in Table 7-2, may serve as bioindicators in the vicinity of
7-144
-------
major sources of SO-. Even these sensitive species may be asymptomatic,
however, depending on the environmental conditions before, during, and after
S02 exposure. Of the plants listed in Table 7-2, various species of lichens
may be among the most sensitive. However, no plant species is equal in sensi-
tivity to sophisticated monitoring equipment designed to detect parts-per-bil1 ion
concentrations of S0?.
The dose-response information presented in this chapter relates the
length of exposure and pollutant concentration to plant response. Dose is
defined as the concentration of pollutant multiplied by the length of the
exposure period. Unfortunately, variations in exposure regiment and response
measurements make it difficult to conpare the results of different studies.
The concept of dose-response can be demonstrated by a synthesis of the
data presented in Tables 7-5, 7-6, and 7-7. The following conclusions were
formed by summarizing the dose-response data without considering confounding
environmental variables: (1) Yield of economically important agricultural
species can be significantly suppressed by S0? concentrations in the range of
0.05 to 0.06 ppm if the exposure period is sufficiently long (2 weeks). Both
crop quality and quantity can be negatively affected. (2) Fluctuating,
long-term (seasonal, annual) SO,, exposures averaging 0.05 ppm or less can
cause economically and ecologically undesirable effects to productivity and
stability of range and forest ecosystems. (3) As S0? concentrations increase
to 0.25 ppm, a variety of agricultural crops such as alfalfa, timothy, range
grasses, soybean, barley, wheat, cabbage, lettuce, spinach, tobacco, cucumber,
eggplant, pea, and kidney bean respond with necrotic foliar injury or suppressed
yield. Approximately 70 percent of the cultivated agronomic crop species
exposed to 0.25 ppm or less respond to the SO,, treatment with changes in
stomatal aperature (leaf openings), foliar injury, or yield effects. Foliar
injury on vegetables and suppression of yield are directly related to economic
values. (4) Forest trees species such as pine, spruce, fir, beech, alder and
7-145
-------
poplar, representing coniferous and deciduous forest ecosystems respond to
0.25 ppm or less of SCL. Approximately 90 percent of the species tested in
this range of SO,, concentrations responded with physiological modifications,
suppressed photosynthesis, foliar injury, death of buds, or suppressed foliar
or woody growth. (5) Non-woody components of native ecosystems such as
lichens and grasses respond to SO,, concentrations below 0.025 ppm. Responses
include suppressed growth, death, and reduced diversity in lichen populations
and suppressed photosynthesis and growth of leaves, tillers, and stubble of
grasses. (6) At S02 concentrations between 0.25 and 0.50 ppm, less than 50
percent of the agronomic species tested responded negatively to the sulfur
dioxide treatments. At S02 concentrations less than 0.25 ppm, 90 percent of
the species responded negatively. A comparison of the species response to the
treatments at the concentrations ranging between 0.25 to 0.50 ppm with the
response to concentrations below 0.25 ppm might be interpreted as suggesting
that plant response is not positively correlated with dose. This is not the
case. Exposure durations used in the studies at the higher S0? concentrations
generally ranged from 1 to 8 hours while multiple-day exposures were frequently
used at the lower concentrations of S0?. All agronomic species responded to a
concentration of 0.50 ppm at expo'sure durations ranging from 1.5 to 5 hours.
A variety of responses occurred, including physiological modifications, foliar
injury, and suppressed growth. These trends suggest that as S0? concentrations
are increased (a) a shorter exposure duration is sufficient to elicit a plant
response equal to or greater than that which occurred at a lower concentration;
(b) responses become more severe; and (c) plants tolerant at lower concen-
trations become sensitive.
The lack of short- or long-term monitoring data makes assessment of the
results of dose-response studies in the field difficult. When data are not
available to determine whether short-term spike concentrations occurred, then
only long-term averages have been used to define the dose. Obvious differences
7-146
-------
between forests in areas with high S02 concentrations have been observed,
There is usually no exact dose information for short-term influences. There-
fore, in most field studies, only long-term averages are used to define the
dose.
As the dose of SO,, increases, plants develop more predictable and more
obvious visible symptoms. Foliar symptoms advance from chlorosis or other
types of pigmentation changes to actual necrotic areas, and the extent of
necrosis increases with exposure. Studies of the effects of SCL on growth and
yield have demonstrated a reduction in the dry weight of foliage, shoots,
roots, and seeds, as well as a reduction in the number of seeds. At still
higher doses, reductions in growth and yield increase. Extensive mortality
has been noted in forests continuously exposed to SCL for many years.
The amount of sulfur accumulated from the atmosphere by leaf tissues is
influenced by the amount of sulfur in soil relative to the sulfur requirement
of the plant. After low-dose exposure to SCL, plants grown in sulfur-deficient
soils have exhibited increased productivity.
Sulfur dioxide and particulate sulfate are the main forms of sulfur in
the atmosphere, and a plant may be exposed to these pollutants in several
different ways. Dry deposition of particulate malter and wet deposition of
gases and particles bring sulfur compounds into contact with plant surfaces
and soil substrates. The effects of such exposure are more difficult to
assess than those associated with the entry of SCL through plant stomata.
Plant response to dynamic physical factors such as light, leaf surface moisture,
relative humidity, and soil moisture may influence stomatal opening and closing,
and hence play a major role in determing sensitivities of species and cultivars
or the time of sensitivity of each on a seasonal basis. Dose-response relation-
ships are significantly conditioned by environmental conditions before, during,
and following exposure to SC^.
Measuring sulfur accumulation in plants has been suggested as a tool for
7-147
-------
determining the levels of sulfur in the atmosphere of a given area over time.
Such data, however, cannot accurately define the dose received by a plant.
Very few studies have been conducted to determine the sensitivity of
microorganisms to SCL or to explore the interactions of S02 with plant pathogens
such as fungi, nematodes, or bacteria. Both inhibition and enhancement of
disease processes have been reported, but more data are needed to provide
reliable information on trends.
In ambient atmospheres SCL and other pollutants usually exist as diverse
mixtures in which a multiplicity of chemical combinations can take place.
Therefore, with the possible exception of a point source in which vegetation
is exposed to a high dose of SCL, the direct and indirect influences of other
air pollutants in combination with SCL must be considered. Major phytotoxic
air pollutants that have been studied in combination with SCL include ozone,
oxides of nitrogen, and hydrogen fluoride. The interactions of SCL and CL
have been most extensively investigated because of the incursions of ozone and
other oxidant precursors into many rural areas, as well as their presence in
urban areas. Many studies have demonstrated more than additive effects in
symptom expressions, but relatively few studies have attempted to evaluate the
impacts on growth and yield. Additionally, pollutant combinations with SCL
have caused less than additive and/or additive effects depending upon doses
applied. The influence of various physical and biological factors of the
environment increase in complexity as the pollutants are combined together
during exposures.
A few studies have reported that combinations of particulate matter and
S02 or particulate matter and other pollutants increase foliar uptake of S02,
increase foliar injury of vegetation by heavy metals, and reduce growth and
yield. Because of the complex nature of particulate pollutants, conventional
methods for assessing pollutant injury to vegetation, such as dose-response
relationships are poorly developed. Studies have generally reported vegetation
7-148
-------
responses relative to a given source and the physical size or chemical composition
of the particles. For the most part, studies have not focused on effects
associated with specific ambient concentrations. Coarse particles such as
dust directly deposited on the leaf surfaces results in reduced gas exchange,
increased leaf surface temperature, reduced photosynthesis, chlorosis, reduced
growth, and leaf necrosis. Heavy metals deposited either on leaf surfaces or
on the soil and subsequently taken up by the plant can result in the accumulation
of toxic concentrations of the metals within the tissue.
Particulate matter is heterogeneous in size and composition ranging in
mean diameter from <0.005 urn (molecular clusters) to >100 urn (visible dust
particles). Particles occur in both solid and liquid phases and vary in
chemical composition from a single chemical species (e.g., hLSCL) to complex
combinations of chemical species. They are produced directly from stationary
and mobile sources and are also formed secondarily in the atmosphere through
chemical reactions.
While coarse particles (>2.0 urn in mean diameter settle rapidly, fine
particles (<2.0 urn in mean diameter) have prolonged atmospheric residence
times and are not influences by gravity. Because of the complex nature of
particulate matter, doseresponse studies are very difficult to conduct and
data, therefore, are not available for making generalized statements. Reports
of the effects of particulate matter on vegetation have usually dealt with
response to a given source or the physical size and/or chemical composition of
the particles rather than mentioning concentrations. Coarse particles (dusts,
etc.) directly deposited on the leaf surfaces result in reduced gas exchange,
increased leaf surface temperature, reduced photosynthesis, chlorosis, necrosis,
and reduced growth. Heavy metals deposited on either leaf surfaces or the soil
and subsequently taken up by the plant can accumulate to toxic concentrations.
Particulate matter is heterogeneous in size and composition ranging in
mean diameter from <0.005 urn (molecular clusters) to >100 urn (visible dust
7-149
-------
particles). Particles occur in both solid and liquid phases and vary in
chemical composition from a single chemical species (e.g., H2$04) to complex
combinations of chemical species. They are produced directly from stationary
and mobile sources and are also formed secondarily in the atmosphere through
chemical reactions.
While coarse particles (>2.0 urn in mean diameter) settle rapidly, fine
particles (<2.0 pm in mean diameter) have prolonged atmospheric residence
times and are not influenced by gravity. Because of the complex nature of
particulate matter, dose-response studies are very difficult to conduct and
data, therefore, are not available for making generalized statements. Reports
of the effects of particulate matter on vegetation have usually dealt with
response to a given source or the physical size and/or chemical composition of
the particles rather than mentioning concentrations. Coarse particles (dusts,
etc.) directly deposited on the leaf surfaces result in reduced gas exchange,
increased leaf surface temperature, reduced photosynthesis, chlorosis, necrosis,
and reduced growth. Heavy metals deposited on either leaf surfaces or the
soil and subsequently taken up by the plant can accumulate to toxic concentra-
tions.
Natural ecosystems are integral to the maintenance of the biosphere.
They are the support system for all life on earth. Disruption of ecosystem
functions can have long range effects which cannot be predicted. Approxi-
mately 60 percent of the atmospheric sulfur in the northeastern United States
is deposited on terrestrial and aquatic ecosystems; however, the subsequent
distribution of sulfur through the ecosystems is not fully understood. The
sulfur may reach the ecosystems through dry or wet deposition. (The wet depositor!
of sulfur compounds is discussed in Chapter 8 under acidic precipitation). The
effects of the dry deposition of sulfur, principally as SOp, on terrestrial
ecosystems has been studied only in a few widely divergent areas of North
7-150
-------
America. Though the effects of dry deposition have been emphasized in these
studies, wet deposition has also occurred.
Vegetation within terrestrial ecosystems is sensitive to direct S0?
toxicity, as evidenced by changes in physiology, growth, development, sur-
vival, fecundity, and community composition. Responses of individual organisms
reflect both direct or indirect effects. Habitat modification by SCL results
in indirect effects occurring. Nutrient cycling appears to be a sensitive
indicator of subtle, yet important, environmental modification.
At the community level, chronic exposure to SCL may result in a shift in
the species composition due to the elimination of individuals or populations
sensitive to the pollutant. The tendency for S02 derivatives to accumulate in
the soil may have consequences for the microbiota inhabiting the upper soil
horizons. The gradual accumulation of pollutant derivatives may cause a
change in soil chemistry and influence nutrient cycling and ecosystem pro-
ductivity.
Particulate emissions have their greatest impact on terrestrial ecosystems
near large emission sources. However, other ecosystems within the same geo-
graphic region may also be affected. Most of the material deposited by wet
and dry deposition on foliar surfaces in vegetated areas is transferred to
the soil. Ecological modifications may occur if the particles contain toxic
elements, even though deposition rates are moderate. Particulate matter in
itself constitutes a problem only in those areas where deposition rates are
high. Solubility of particle constituents is critical, since water-insoluble
elements are not mobile within the ecosystem. Foliage may serve as a
transitional site of accumulation if previously deposited dry material
becomes highly concentrated during precipitation. Soils are long-term sites
for the retention of many constituents found in particulate matter. Accumu-
lation in the soil-litter layer influences ecological processes such as
decomposition, mineralization, nutrient cycling, and primary production.
7-151
-------
7.3 REFERENCES
1 Abeles, F. B., L. E. Craker, L. E. Forrence, and G. R. Leather. Fate
of air'pollutants: removal of ethylene, sulfur dioxide and nitrogen
dioxide by soil. Science 173:914-916, 1971.
2. Adedipe, N. 0., R. E. Barrett, and D. P. Ormrod. Phototoxicity and
growth response of ornamental bedding plants to ozone and sulfur dioxide.
J. Amr. So. Hortic. Sci. 97:341-345, 1972.
3. Allen, E. B., and R. T. T. Forman. Plant species removal and old-field
community structure and stability. Ecology 57:1233-1243, 1976.
4. Alway, F. I., A. W. Marsh, and W. J. Methley. Sufficiency of atmospheric
sulfur for maximum crop yield. Proc. Soil Sci. Soc. 2:229-238, 1937.
5. Amdur, M. 0. Effects of sulfur oxides on animals. Sulfur in the
Environment. J. 0. Nriagu, ed., John Wiley and Sons, New York, 1978.
pp. 61-74.
6. Anderson, A. J. , D. R. Meyer, and F. K. Mayer. Heavy metal toxicities:
levels of nickel, cobalt, and chromium in the soil and plants associated
with visual symptoms and variation in growth of an oat corp. Aust. J.
Agric. Res. 24:557-571, 1973.
7. Anderson, P J. The effect of dust from cement mills on the setting of
fruits. Plant World 17:57-68, 1914.
8. Antonovics, J. Metal tolerance in plants: perfecting an evolutionary
paradigm. In: Symposium Proceeding of International Conference on
Heavy Metals in the Environment, vol. 2. National Research Council of
Canada, Ottawa, 1975.
9. Atonovics, J., A. D. Bradshaw, and R. G. Turner. Heavy metal tolerance
in plants. Adv. Ecol. Res. 7:1-85, 1971.
10. Armentano, T. V., and G. M. Woodwell. The production and standing crop
of litter and humus in a forest exposed to chronic gamma irradiation
for 12 years. Ecology 57:350-366, 1976.
11. Arndt, U. Concentration changes of free amino acids in plants under
the effect of hydrogen fluoride and sulfur dioxide. Staub-Reinhalt
30:28-32, 1970.
12. Ashenden, T. W. Growth reductions in Cocksfoot (Dactyl is golmerata L.)
as a result of S02 pollution. Environ. Pollut. 15:161-166, 1978.
13. Ashenden, T. W. The effects of long-term exposures to S0? and N09
pollution on the growth of Dactyl is golmerata L. and Poa pratensiS L.
Environ. Pollut. 18:249-258, 1979.
7-152
-------
14. Ashenden, T. W., and T. A. Mansfield. Influence of wind speed on
the sensitivity of ryegrass to S02. J. Exp. Bot. 28^727-735, 1977.
15. Ashenden, T. W., and T. A. Mansfield. Extreme pollution sensitivity
of grasses when S0? and N09 are present in the atmosphere together.
Nature 273_: 142-1437 1978.
16. Babich, H., and G. Stotzky. Air pollution and microbial ecology.
CRC Crit. Rev. Environ. Control 4_:353-421, 1974.
17. Bakelaar, R. G., and E. P. Odum. Community and population level
responses to fertilization in an old-field ecosystem. Encology
59:660-665, 1978.
18. Ballentyne, D. J. Sulfite inhibition of ATP formation in plant mitro-
chondria. Phytochemistry 12_: 1207-1209, 1973.
19. Banfield, W. M. Sulfur dioxide-ozone synergism on eastern white
pine. Phytopathology 62_:493, 1972.
20. Bannister, P. Introduction to Physiological Plant Ecology. John
Wiley Sons, New York, 1979.
21. Barton, J. R., S. B. Mclaughlin, and R. K. McConathy. The effects
of S02 on components of leaf resistance to gas exchange. Environ.
Pollut., in press, 1980.
22. Bassus, W. Uber Wirkungen von Indutrieexhalaten auf der Nematodent
Besatz in Boden von Kiefernwaldern. Pedogiologia 8^:288-295,
1968.
23. Bazzaz, M. B., and Govindjee. Effects of lead chloride on chloroplast
reactions. Environ. Lett. 6_: 175-191, 1974.
24. Bell, J. N. B., and W. S. Clough. Depression of yield in ryegrass exposed
to sulfur dioxide. Nature 241:47-49, 1973.
25. Bell, J. N. B., and C. H. Mudd. Sulfur dioxide resistance in plants:
a case study of Lolium perene. In: Effects of Air Pollutants
on Plants. T. A. Mansfield, ed., Cambridge University Press,
1976. pp. 87-103.
26. Benedict, H. M., and W. H. Breen. The use of weeds as a means of evaluating
vegetation damage caused by air pollution. In: Proceedings of the
Third National Air Pollution Symposium. Sponsored by Stanford
Research Institute, Los Angeles, 1955. pp. 177-190.
27. Bennett, J. H. Inhibition of apparent photosynthesis of air
pollutants. J. Environ. Qua!. 2^:526-530, 1973.
28. Bennett, J. H., and A. C. Hill. Absorption of gaseous air pollutants
by a standardized plant canopy. J. Air Pollut. Control Assoc.
23:203-206, 1973.
7-153
-------
29. Bennett, J. H., and A. C. Hill. Acute inhibition of apparent
phytosynthesis by air pollutants. J. Environ, qua!. 2^:526-
530, 1973.
30. Bennett, J. H., and A. C. Hill. Acute inhibition of apparent photosyn-
thesis by phytotoxic air pollutants. Am. Chem. Soc. Symp. Ser.
3.: 115-127, 1974.
31. Bennett, J. H., and A. C. Hill. Interactions of air pollutants with
canopies of vegetation. In: Responses of Plants to Air
Pollution. J. B. Mudd and T. T. Kozlowski, eds., Academic
Press, 1975. pp. 273-306.
32. Bennett, J. H., A. C. Hill, A. Soleimani, and W. H. Edwards. Acute
effects of combination of sulfur dioxide and nitrogen dioxide
on plants. Environ. Pollut. JJ: 127-132, 1975.
33. Berigari, M. S., C. F. Jordan, and C. A. Feickert. The Effect of
Sulfur Dioxide on Yield and Growth of Kidney Beans (Phaseolus
vulgaris L.). Radiol. Environ. Res. Div. Ann. Rep., Argonne Natl.
Laboratory, 1974.
34. Berry, C. R. Relative sensitivity of red, jack, and white pine
seedlings to ozone and sulfur dioxide. Phytopathology 64:231-232,
1971.
35. Berry, C. R. Age of pine seedlings with primary needles affects
sensitivity to ozone and sulfur dioxide. Phytopathology
6i:207-209, 1974. . !
36. Bevan, R. J., and G. N. Greenhalgh. Rhytisma acerinum as a biological
indicator of pollution. Environ. Pollut. Kh 271-285, 1976.
37- Biscoe, P. V., M. H. Unsworth, and H. R. Pickney. The effects of low
concentrations of sulfur dioxide on stomatal behavior in Vicia
faba. New Phytol. 7^:1299-1306, 1973.
38. Bishop, J. A., L. M. Cook, J. Muggleton, and M. R. D. Seaward.
Moths, lichens and air pollution along a transect from
Manchester to North Wales. J. Appl. Ecol. JL2_: 83-95, 1975.
39. Black, V. J., and M. H. Unsworth. A system for measuring effects of
sulfur dioxide on gas exchange of plants. J. Exp. Bot. 30:81-88,
1979. ~~
40. Black, V. J., and M. H. Unsworth. Effects of low concentrations of
sulfur dioxide on net photosynthesis and dark respiration of
Vicia faba. J. Exp. Bot. 30:473-483, 1979.
41. Black, V. J., and M. H. Unsworth. Effects of low concentrations of
sulfur dioxide on net photosynthesis and dark respiration of
Vicia faba. J. Exp. Bot. 30:1-11, 1979.
7-154
-------
42. Bleasdale, J. K. A. Atmospheric pollution and plant growth. Nature
241:376-377, 1952.
43. Bleasdale, J. K. A. Effects of coal-smoke pollution gases on the
growth of ryegrass (Lolium perenne L.). Environ. Pollut 5:272-285,
1973.
44. Boertitz, S., H. G. Daessler, and E. Friedrich. Effect of metallurgical
dust on agricultural plants. Tech. Umweltschutz J^:247-254, 1976.
45. Bohn, H. L. Soil absorption of air pollutants. J. Environ. Qua!.
1:372-377, 1972.
46. Bonte, J. , L. DeCormis, and P. Louguet. Effect of sulfur dioxide
pollution on the degree of opening of Pelargoniurn x hortorum
stomata. C. R. Hedb. Sciences Acad. Sci. Ser. D 280:2377-2380, 1975
47. Bonte, J., and P. Louguet. Interrelations between the pollution with
sulfur dioxide and the movements of stomata in Pelargonium
hortorum: effect of the relative humidity and the air content
in carbon dioxide. Physiol. Veg. 13:527-537, 1975.
48. Bormann, F. H. An inseparable linkage: conservation of natural
ecosystems and the conservation of fossil energy. Bioscience
2^:754-760, 1976.
49. Botkin, D. B. The role of species interactions in the response of
a forest ecosystem to environmental perturbation. Systems
Analysis and Simulation in Ecology, vol. IV. B. C. Patten,
ed., Academic Press, New York, 1976. pp. 147-173.
50. Botkin, D. B., J. F. Janak, and J. R. Wallis. Some ecological conse-
quences of a computer model of forest growth. J. Ecol. 60:849-872,
1972.
51. Bourdeau, P., and M. Treshow. Ecosystem response to pollution.
j_n_: Principles of Ecotoxicology. G. C. Butler, ed., John
Wiley & Sons, New York, 1978 pp. 313-330.
52. Bradford, G. R. Boron. In: Diagnostic Criteria for Plants and Soils.
H. G. Chapman, ed., University of California, 1966. pp. 33-61.
53. Brady, N. C. The Nature and Properties of Soils 8th edition. McMillan
Publishing Co., New York, 1974. 639 pp.
54. Brandt, C. J., and R. W. Rhoades. Effects of limestone dust accumu-
lation on composition of a forest community. Environ. Pollut.
3^:217-225, 1972.
55. Brandt, G. J. and R. W. Rhoades. Effects of limestone dust accumulation
on lateral growth of forest trees. Environ. Pollut. 4_:207-213,
1973.
56. Brandt, C. S., and W. W. Heck. Effects of air pollutants on vegetation.
In: Air Pollution, vol. I: Air Pollution and Its Effects.
A7 C. Stern, ed., Academic Press, New York, 1968. pp. 401-443.
7-155
-------
57. Brisley, H. R., C. R. Davis, and J. A. Booth. Sulfur dioxide fumigations
of cotton with special reference to its own effect yield. Agron.
J. 51:77-80, 1959.
58. Brown, H. D., P. R. Miller, J. M. Skelly, C. E. Carlson, and D. B.
Drummond. Air Pollution Impact on Forests of the United States
and the Role of Forest Insect and Disease Management. U.S.
Dept. of Agriculture Forest Service Task Force Report, In press,
1979.
59. Bryant, R. D., E. A. Gordy, and E. J. Laishley. Effect of soil
acidification on the soil microflora. Water Air Soil Pollut.
11:437-445, 1979.
60. Buchauer, M. J. Effects of zinc smelter emissions on tree reproduction
and post-fire succession. Bull. Ecol. Soc. Am. 5^:33, 1973.
61. Buchauer, M. J. Effects of zinc smelter emissions on forest soil
microflora. Bull. Ecol. Soc. Am. 54:33, 1973.
62. Bull, J. N., and T. A. Mansfield. Photosynthesis in leaves exposed to
S02 and No2- Nature ^50:443-444, 1974.
63. Buron, A., and G. Comic. Effect of sulfur dioxide on gas exchange
in white mustard (Si naps is alba). Bull. Soc. Vaudoise Sci.
Natur. 71:451-461, 1973.
64. Cadle, R. D. The sulfur cycle In: Sulfur in the Environment. Missouri
Botanical Garden, St. Louis, 1975. p.189.
65. Caput, C., Y. Belot, D. Auclair, and N. Decourt. Absorption of sulfur
dioxide by pine needles leading to acute injury. Environ.
Pollut. 16:3-15, 1978.
66. Chamberlain, A. C. Deposition and uptake by cattle of airborne
particles. Nature ^25_:99-100, 1970.
67. Chamberlain, A. C. Interception and retention of radioactive aerosols
by vegetation. Atmos. Environ. 4^57-77, 1970.
68. Chamberlain, A. C. The movement of particles in plant communities.
ln_: Vegetation and the Atmosphere, vol. 1. J. L. Monteith,
ed. Academic Press, London, New York, San Francisco, 1975.
pp. 155-204.
69. Chapman, H. D. Zinc. In: Diagnostic Criteria for Plants and Soils.
H. D. Chapman ed., University of California pp. 484-499.
70. Charlson, R. J., D. S. Covert, T. V. Larson, and A. P. Waggoner.
Chemical properties of tropospheric sulfur aerosols. Atmos.
Environ. 12; 39-54, 1978.
71. Chilgren, J. D. The response of prairie deer mice to a field S09 gradient,
In: Proc. 4th Joint Conf. Sensing of Environmental Pollutants.
American Chemical Society, Washington, D.C., 1978. pp. 61-65.
7-156
-------
2. Chow. T. J. Lead accumulation in roadside soil and grass. Nature 225:
295-296, 1970.
!!a. Clough, W. S. The deposition of particles on moss and grass surfaces.
Atmos. Environ. 9^1113-1119, 1975.
"3. Cocking, W. D. Plant Community Damage and Reparability Following
Sulfur Dioxide Stress on an Old-Field Ecosystem. Ph.D. Thesis,
Rutgers University, New Brunswick, NO, 1973.
i'4. Cogbill, C. V. The history and character of acid precipitation in
eastern North America. In: Proc. 1st International Symposium
on Acid Precipitation and the Forest Ecosystem. U.S. Dept.
of Agriculture Forest Service, Gen. Tech. Rep. N-23, 1975.
i75. Coleman, D. C., C. V. Cole, H. W. Hunt, D. A. Klein. Trophic interactions
in soils as they affect energy and nutrient dynamics. I.
Introduction. Microb. Ecol. 4_:345-349, 1978.
!76. Constantinidou, H. A., and T. T. Kozlowski. Effects of sulfur dioxide
and ozone on Ulmus americana seedlings. I. Visible injury
and growth. Can. J. Bot. 5^:170-175, 1979.
\11. Constantinidou, H. A., and T. T. Kozlowski. Effects of sulfur dioxide
and ozone on Ulmus americana seedlings. II. Carbohydrates,
proteins, and lipids. Can. J. Bot. 5^:176-184, 1979.
!78. Constantinidou, H. A., T. T. Kozlowski, and K. Jensen. Effects of sulfur
dioxide on Pinus resinosa seedlings in the cotyledon state. J.
Environ. Qual. 5;141-144, 1976.
179. Corn, M., and R. T. Cheng. Interactions of sulfur dioxide with insoluble
suspended particulate matter. J. Air Pollut. Contra!. Assoc. 22:
807-975, 1972.
:JO. Costonis, A. C. Injury to eastern white pine by sulfur dioxide and
ozone alone and in mixtures. Eur. J. For. Pathol. _3:50-55, 1973.
:J1. Cotrufo, C., and C. R. Berry. Some effects of a soluble NPK fertilizer
on sensitivity of eastern white pine to injury from S0? air
pollution. For. Sci. 16:72-73, 1970. "
:J2. Coughenour, M. B. Grasslands Sulfur Cycle and Ecosystem Response
to Low-Level S0?. Ph.D. Thesis Colorado State University, Fort
Collins, 1978. 353 p.
i!3. Coughenour, M. B., W. J. Parton, W. K. Lauenroth, J. L. Dodd, and R. G.
Woodmansee. Simulation of a grassland sulfur cycle. Ecol.
Modi., in press, 1980.
!!4. Coughtrey, P. J., C. H. Jones, M. H. Martin, and S. W. Shales.
Litter accumulation in woodlands contaminated by PG, Zn, Cd and
Cu. Oecologia 39.:51-60, 1979.
7-157
-------
85. Cowling, D. W., and A. W. Bristow. Effects of SOp on sulfur and nit-
rogen fractions and on free amino acids in perennial ryegrass. J.
Sci. Food Agric. 30:354-360, 1979.
86. Cowling, D. W., L. H. P. Jones, and D. R. Lockyer. Increased yield
through correction of sulfur deficiency in ryegrass exposed to
sulfur dioxide. Nature 243:479-480, 1973.
87- Cowling, D. W., and M. J. Koziol. Growth of ryegrass (Lolium perenne L.
exposed to S0?. I.Effects on photosynthesis and respiration.
J. Exp. Bot. 29_: 1029-1036, 1978.
88. Cowling, D. W., and D. R. Lockyer. Growth of perennial ryegrass
(Lolium perenne L.) exposed to a low concentration of sulfur
dioxide. J. Exp. Bot. 27_:411-417, 1976.
89. Cowling, D. W., and D. R. Lockyer. Growth of perennial ryegrass
(Lolium perenne L.) exposed to a low concentrations of sulfur
dioxide. J. Exp. Bot. 27_:411-417, 1977.
90. Cowling, D. W., and D. R. Lockyer. The effect of S0? on Lolium
perenne L. grown at different levels of sulfur and nitrogen
nutrition. J. Exp. Bot. 29_:257-265, 1978.
91. Coyne, P- I., and G. E. Bingham. Phytosynthesis and stomatal light
responses in snap bean exposed to hydrogen sulfide and ozone.
JAPCA 28:1119-1123, 1978.
92. Creed, E. R. Two spot ladybirds as indicators of intense local air
pollution. Nature 249_:390-392, 1974.
93. Crittenden, P. D., and D. J. Read. II. Growth studies with Lolium
perenne L. New Phytol. 80:49-62, 1978.
94. Czaja, A. T. Zementstaubwir-Kungen auf pflanzen: Die enstehung der
Zementkrusten. Qual. Plant Mater. Veg. 8:201-238, 1961.
95. Daessler, H. Vegetationsschaden als Folge de Luftverschmutzung.
Wiss. Z. Tech. Univ. Dresden. 2£: 1171-1173, 1971.
96. Daessler, H. G., J. Ranft, and K. H. Rehn. The susceptibility of woody
plants exposed to fluorine compounds and sulfur dioxide. Flora
(Jean) 161:289-302, 1972.
97. Daines, R. H. Sulfur dioxide and plant response. J. Occup. Med. _10_:
516-534, 1968.
98. Daniel, C. F., and R. B. Platt. Direct and indirect effects of short-
term ionizing radiation on old field succession. Ecol. Monogr.
38;1-29, 1968.
99. Darley, E. F. Studies on the effect of cement-kiln dust on vegetation.
J. Air Pollut. Control Assoc. 16:145-150, 1966.
7-158
-------
100. Davidson, J. W. Reactions of white pine and yellow poplar to sulfur
dioxide. In: Organisms and Biological Communities as Indicators
of Environmental Quality. Ohio State University, Columbus, OH,
1975. pp. 21-23.
101. Davies, T. D. Precipitation scavenging of sulfur dioxide in an in-
dustrial area. Atmos. Environ. _1(D:879-890, 1976.
102. Davis, C. R. Sulfur dioxide fumigation of soybeans: effect of yield
J. Air Pollut. Control Assoc. 22_:964-966, 1972.
103. Davis, D. D. Sulfur Dioxide and Deciduous Plants. Air Pollution and
Plants Series. PA. Coop. Ext. Ser. U. Ed. 3-17, 1972. 2pp.
104. David, D. D. Sulfur Dioxide and Evergreens. Air Pollution and Plants
Series. Pa. Coop. Ext. Serv. U. Ed. 3-526, 1972. 2pp.
105. David, D. D., and H. D. Gerhold. Selection of Trees for Tolerance of
Air Pollutants. Better Trees for Metropolitan Landscapes Symp.
Proc. U.S. Dept. of Agriculture Forest Service Gen. Tech. Rep.
NE-22:61-66, 1976.
106. Davis, D. D. , and R. G. Wilhour. Susceptibility of woody plants to
sulfur dioxide and photochemical oxidants: a literature review.
Ecol. Res Ser., 1976. 71 pp.
107. Davis, J. B., and R. L. Barnes. Effects of soil-applied fluoride and
lead on growth of loblolly pine and red maple. Environ. Pollut.
5_:35-44, 1973.
108. Davidson, R. L., D. F. S. Natusch, J. R. Wallace, and C. A. Evans,
Jr. Trace elements in fly ash. Environ. Sci. Technol. 8_:
1107-1113, 1974.
109. Demeritt, M. E., Jr., W. M. Chang, J. D. Murphy, and H. D. Gerhold.
Selection system for evaluating resistance of Scots pine seedlings
to ozone and sulfur dioxide. ]j]_:Proc. 19th Northeastern For. Tree
Improvement Conf., 1971.
110. DeSloover, J., and F. LeBlanc. Mapping of atmospheric pollution on
the basis of lichen sensitivity. In: Proc. Symp. Recent Adv.
Trop. Ecol. R. Misra and B. Gopal eds. The International Society
for Tropical Ecology. Varanashi-5, India, 1968.
111. Dobrovolskyi, I. A., and Yo. A. Strikha. Study of the Phytotoxicity
of Certain Components of Industrial Air Pollution. U.S. Army
Foreign Service and Technology Center. FSTC-ET-23-2264-72,
1970. 8 pp.
112. Dochinger, L. S., and W. W. Heck. An ozone-sulfur dioxide synergism
produces symptoms of chlorotic dwarf disease of eastern white pine
Phytopathology 59^:399, 1969.
7-159
-------
113. Dochinger, L. S., and K. F. Jensen. Effects of chronic and acute
exposure to sulfur dioxide on the growth of hybrid poplar cuttings.
Environ. Pollut. 9.:219-229, 1975.
114 Domes, W. Uterschiedliche C0?-Abhangigkeit des Gasaustaushes beider
Blattseiten von Zea Mays: PIanta 98:186-189, 1971.
115. Donaubauer, E. Secondary damages to forests caused by industrial
exhausts. Mitt. Forstl. Vers. Aust. 73^:101-110, 1966. (Translated
from German)
116. Donaubauer, E. Sekundarshaden in Osterreichischen Rauchschadensgegieten.
Schwierigkeiten der Diagnose and Bewertung. Niedzynarodoweg Konf.
Wplyw Zanieczyszczen Powietrza na Lasy, 6th., Katowice, Poland,
1968.
117. Donaubauer, E. Tree ring analysis as a means of diagnosis and evaluation
of pollutant effect. Abstract No. 0991. J_n_: Abstracts of Papers,
2nd International Congress of Plant Pathology, Sept. 5-12 1973,
Minneapolis, MN, American Phytopathological Society, St. Paul,
MN, 1973.
118. Dreisinger, B. R. Sulfur dioxide levels and the effects of the gas
on vegetation near Sudbury, Ontario, Paper No. 65-121. Presented
at the 58th Annual Meeting of the Air Pollution Control
Association, 1951. 21 pp.
119. Dreisinger, R. B., and P. C. McGovern. Monitoring atmospheric sulfur
dioxide and correlating its effects on crops and forests in the
Sudbury area. In: Impact of Air Pollution on Vegetation Conf.
S. N. Linzon, ed., Ontario Dept. of Energy and Resource
Management, Toronto, 1970. 122 pp.
120. Drummond, D. B., and F. A. Wood. Recovery of eastern white pine
following reduction in levels of ambient air pollution.
Phytopathology 57_:810, 1967. (Abstr. )
121. Dunn, D. B. Some effects of air pollution on Lupinus in the Los
Angeles Area. Ecology 40_:621-625, 1959.
122. Durran, D. R., M. J. Meldgin, M. Liu, T. Thoem, and D. Henderson.
A study of long-range air pollution problems related to coal
development in the northern Great Plains. Atmos. Environ. 13:
1021-1037, 1979.
123. Dzubay, T. G., and R. K. Stevens. Ambient air analysis which dichotomous
sampler and x-ray fluorescence spectrometer. Environ. Sci.
Technol. 9^:663-668, 1975.
124. Edmunds, G. F., Jr. Encology of black Pineleaf schale (Homoptera:
Diaspididae). Environ. Entomol. 2;765-777, 1973.
125. Embleton, T. W. Magnesium. JJT_: Diagnostic Criteria for Plants
and Soils. H.D. Champman, ed., University of California,
1966. pp. 225-263.
7-160
-------
126. Enderlein, H., and W. Kastner. Welchen Einfluss hat der Mangel eines
Nahrstoffes auf die S0?-Resistenz Ijahriger kiefern. Arch.
Forstwes. 16^:431-435, 1976.
127- Enke, M., H. Matschiner, and M. K. Achtzehn. Heavy metal enrichment
in mushrooms. Nahrung 2^:331-334, 1977.
128. Evans, L. S., and P. R. Miller. Histological comparison of single and
additive 0^ and S0~ injuries to elongating ponderosa pine needles.
Am. J. BotT 62:416-421, 1975.
129. Faller, N. Effects of atmospheric S09 on plants. Sulfur Inst. J.
i:5-7, 1970. *
130. Faller,-N., K. Herwig, and H. Kuhn. Die Aufnahme von Schwefeldioxd
(S 0?) ausder Luft I. Einfluss auf den Pflanzlichen Ertrag.
Plant Soil 33.: 177-191, 1970.
131. Fankhauser, N. C. Brunold, and K. N. Erisman. The influence of sublethal
concentrations of sulfur dioxide on morphology, growth and production
yield of the duckweed Lemne minor L. Oecologia (Berlin) 23^201-208, 1976
132. Farrar, J. F., J. Relton, and A. J. Rutter. Sulfur dioxide and
the growth of Pinus sylvestris. J. Appl. Ecol. 14_:861-875, 1977-
133. Farrar, J. F., J. Relton, and A. J. Rutter. Sulfur dioxide and the
scarcity of Pinus sylvestris in the industrial Pennines. Environ.
Pollut. L4:63-68, 1977.
134. Fennelly, P. E. The origin and influence of airborne particles. Am.
Sci. 64_:46-56, 1976.
135. Ferenbaugh, R. W. Effects of prolonged exposure of Oryzopsis
hemenoides to S02- Water Air Soil Pollut 1£:27-31, 1978.
136. Fisher, F., D. Kramer, and H. Ziegler. Elektronenmikroskopische
Untersuchungen S0?-begaster Blatter vaon Vicia faba. I.
Beobachtungun am chloroplasten mit akuter Schadigung. Protoplasma
76:83-96, 1973.
137. Fowler, D. Uptake of Sulfur Dioxide by Crops and Soil. Ph. D.
Thesis, University of Nottingham, England, 1976.
IL37a. Flower, D., and M. H. Unsworth. Dry deposition of sulfur dioxide
on wheat. Nature 249:389-390, 1974.
138. Fried, M. The absorption of sulfur dioxide by plants as shown
by the use of radioactive sulfur. Proc. Soil Sci. Am. 13:
135-138, 1948.
139. Frietag, R., and L. Hastings. Kraft mill fallout and ground beetle
populations. Atmos. Environ. 7^:587-588, 1973.
7-161
-------
140. Fujiwara, T., T. Umezawa, and H. Ishikawa. Effects of mixed air pol-
lutants on vegetation. I. Effects of combinations of S0?,
No- and CL. Cent. Inst. of Elec. Power. Res. Rep. 72007; Inst.
of Agric. Electricity, 1973.
141. Galbally, J. E. , J. A. Garland, and M. J. G. Wilson. Sulfur uptake
from the atmosphere by forest and farmland. Nature 280:49-50,
1979.
142. Garland, J. A. Dry and wet removal of sulfur from the atmosphere.
Atmos. Eviron. 12:349-362, 1978.
143. Garland, J. A., and J. R. Branson. The deposition of sulfur dioxide
to pine forest assessed by a radioactive method. Tellus 29:
445-454, 1977.
144. Garland, J. A., W. S. Clougahnd, and D. Flower. Deposition of
sulfur dioxide on grass. Nature 24^:256-257, 1973.
145. Gerhold, H. D. Effect of air pollution on Pinus strobus L. and genetic
resistance. Report No. EPA-600/3-77-002. Con/all is Environ.
Res. Lab., Corvallis, OR, 1977. 45 pp.
146. Gilbert. 0. L. Further studies on the effect of sulfur dioxide on
lichens and bryophytes. New Phytol. 69.:605-627, 1970.
147. Gilbert, 0. L. An alkaline dust effect on epiphytic lichens. Lichenolo-
gist 8:173-178, 1976.
148. Gilbert 0. L. The establishment and subsequent growth of planted
trees in polluted atmospheres. In: Proc. Knopid Meeting
of Plant Damages Caused by Air Pollution, L. Karenlampi ed.,
1976. pp. 126-132.
149. Ginevan, M. E., and D. D. Lane. Effects of sulfur dioxide in air on
the fruit fly, Drosophila melanograster. Environ. Sci. Technol.
1^:828-831, 1978.
150. Glass, N. R., and D. T. Tingey. Effects of air pollution on ecological
processes. In: Radiation Research, O.F. Nygaard, H. I. Adler,
W. K. Sinclair, eds., Academic Press, New York, 1975.
151. Godzik, S., and H. F. Linskens. Concentration changes of free amino
acids in primary bean leaves after continuous and interrupted S02
fumigation and recovery. Environ. Pollut. 7:25-28, 1974.
7-162
-------
152. Gordon, A. G., and E. Gorham. Ecological aspects of air pollution
from an iron-sintering plant at Wawa, Ontario. Can. J. Bot.
41:1063-1078, 1963.
153. Gorham E., and A. G. Gordon. Some effects of smelter pollution
northeast of Falconbridge, Ontario. Can. 0. Bot. 38:307-312,
1960. ~~
154. Granat, L., H. Rehe, and R. 0. Hallberg. The global sulfur cycle.
Ecol. Bull. (Stockholm) 22_:89-134, 1976.
155. Granat, L., and R. Rodhe. Study of fallout by precipitation
around an oil-fired power plant. Atmos. Environ. 2:781-792,
1973.
156. Grant, I. F., K. Bancroft, and M. Alexander. Effect of S02 and bisulfite
on heterotrophic activity in an acid soil. App. Environ. Microbiol.
38:78-83, 1979.
157. Grill, D., H. Esterbauer, and G. Beck. Untersuchungen an phenolischen
Substanzen und Glukose im S09 -geschadigten Fichtennadeln. Phyto-
path I. 8^:182-184, 1975. ^
158. Guderian, R. Reaktione von Fflanzer Gemeinschaften des Fesluffer-
baues auf Schwefeldioxideinwirkungen. Essen: Girardet-Verlag,
Schriftenr. Landesnst. Immisions-Bodennutsungssch. d. Landes
Nordrheim-Westfalen 4^80-100, 1967.
159. Guderian, R. Air pollution: phytotoxicity of acidic gases and its
significance in air pollution control. Springer-Verlag, Berlin,
1977. 127 pp.
160. Guderian, R., G. H. M. Krause, and H. Kaiser. Utersuchungen zur
kombinationswirkung von schefeldioxide and Schwermetall-haltigen
stauben auf Pflanzen. Schriftenreihe der Landesaustalt fur
Immissionsschutz des Landes Nordrhein-westfalen. Essen 40:23-30,
1978.
161. Guderian R., and H. Stratmann. Freilandversuche zur Ermittlung von
Schwefeldioxidwirkungen auf die Vegetation. III. Grenzewerte
schadlicher S0?-Immissionen fur Obst-und Forstkulturen Sowie
fur land wirtschaftliche and gratnerische Pflanzenarten. Forschunsber,
Landes Nordrhein-West-falen Nr. 1920. Westdeutscher Verlag, Cologne,
1968. 113 pp.
162. Haisman, D. R. The effect of sulfur dioxide on oxidizing enzyme
systems in plant tissue. J. Sci. Food Agric 25^:803-810, 1974.
163. Halbwachs, G. Der Wasserhaushalt rauchgeschadigter Holzgewasche.
Allg. Forstz. 78^:196-197, 1976.
164. Hallgren, J-E. Physiological and biochemical effects of sulfur
dioxide on plants. In: Sulfur in the Environment vol. 2.
J. 0. Nriagu, ed., John Wiley & Sons, New York, 1978. 163-210.
7-163
-------
165. Harvey, G. W., and A. H. Legge. The effect of sulfur dioxide
on the metabolic level of adenosine triphosphate. Can.
J. Bot. 57_:759-764, 1979.
166 Hasan, S. M., R. L. Fox, and C. C. Boyd. Solubility and
availability of sorbed sulfate in Hawaiian soils. Proc.
Soil Sci. Soc. Am. 34:987-901.
167. Hawksworth, D. L. Lichens as litmus for air pollution: a
historical review. Int. J. Environ. Stud. ^:281-296,
1971.
168. Hawksworth, D. L., and F. Rose. Qualitative scale for estimating
sulfur dioxide air pollution in England and Wales using
epiphytic lichens. Nature 227_: 145-148, 1970.
169. Heagle, A. S. Effect of ozone and sulfur dioxide on injury,
growth and yield of soybeans. Phytopathology 62:763,
1972.
170. Heagle, A. S. Interactions between air pollutants and plant
parasites. Annu. Rev. Phytopathol. ri_:365-388, I973-
171. Heagle, A. S., D. E. Body, and G. E. Neely. Injury and yield
responses of soybean to chronic doses of ozone and sulfur
dioxide in the field. Phytopathology 64:132-136, 1974.
172. Heagle, A. S., and J. W. Johnston. Variable responses of
soybeans to mixtures of ozone and sulfur dioxide. J. Air
Pollut. Control Assoc. 29^:729-732, 1979.
173. Heck, W. W., and C. S. Brandt. Effects on vegetation: native,
crops, forest. In: Air Pollution. A. C. Stern, ed.,
Academic Press, New York, 1977, pp. 157-229.
174. Heck, W. W., and J. A. Dunning. Effects of Sulfur Dioxide
and/or Ozone on Two Oat Varieties. Interim report prepared
by North Carolina State University, Raleigh, for Office
of Research and Development, 1976. 60 pp.
175. Heck, W. W., J. A. Dunning, H. Mamann, and F. Greisbrecht.
The Effects of Sulfur Dioxide on Carolee Oat and Ozone on
Ladino Clover. Interim report, Natl. Ecol. Res. Lab.,
Nat!. Environ. Res. Center, Corvallis, Or, 1979. 60 pp.
176. Heese, P. R. Sulfur and nitrogen changes in forest soils of
east Africa. Plant Soil 9^:86-96, 1957.
177. Heggestad, H. E., K. L. Tuthill, and R. N. Stewart. Differences
among poinsettias in tolerance to sulfur dioxide. Hort.
Sci. 8^:377-338, 1973.
178. Heitschmidt, R. K., W. K. Lauenorth, and J. L. Dodd. Effects
of controlled levels of sulfur dioxide on western wheatgrass
in a southeastern Montana grassland. J. Appl. Ecol.
11:859-868, 1978.
179. Henderson-Sellers, A., and M. P. D. Seaward. Monitoring
lichen reinvasion of ameliorating environments. Environ.
Pollut. 10-207-213, 1979.
— 7-164
-------
180. Hibben, C. R., and M. P. Taylor. Ozone and sulfur dioxide
effects on the lilac powdery mildew fungus. Environ.
Pollut. .9:107-114, 1975.
181. Hill, A. C. Vegetation: sink for atmospheric pollutants. J.
Air Pollut. Control Assoc. 21^:342-346, 1971.
182. Hill, A. C., S. Hill, Lamb, and T. W. Barrett. Sensitivity of
native desert vegetation to S0? and S02 and N0? combined.
J. Air Pollut. Control Assoc. 24_:153-157, 19747
183. Hofstra, G., and D. P. Ormrod. 1977. Ozone and sulfur dioxide
interaction in white bean and soybean. Can. J. Plant
Sci. 57^1193-1198, 1977.
184. Hogstrom, U. Residence times of sulfurous air pollutants from
a local source during precipitation. Ambio 2^37-41,
1973.
185. Holdgate, M. W. Targets of pollutants in the atmosphere.
Phil. Trans. R. Soc. Londser A 290:591-601, 1979.
186. Horsman, D. C., T. M. Roberts, and A. D. Bradshaw. Evolution
of sulfur dioxide tolerance in perennial ryegrass.
Nature 276;493-494, 1978.
187. Horsman, D. C., T. M. Roberts, and A. D. Bradshaw. Studies on
the effect of sulfur dioxide on perennial ryegrass
(Lolium perenne). II. Evolution of sulfur dioxide
tolerance. J. Exp. Bot. 3_0:495-501, 1979.
188. Horsman, D. C., T. M. Roberts, M. Lambert, and A. D. Bradshaw.
Studies on the effect of sulfur dioxide on perennial
ryegrass (Lolium perenne L.) I. Characteristics of fumigation
system and preliminary experiments. J. Exp. Bot. 30:485-
493, 1978.
189. Horsman, D. C., and A. R. Wellburn. Synergistic effect of S02
and N0? polluted air upon enzyme activity in pea seedlings.
Envirofi. Pollut. 8:123-133, 1975.
190. Horsman, D. C., and A. R. Wellburn. Appendix II. Guide to
metobolic and biochemical effects of air pollutants on
higher plants. In: Effects of Air Pollutants on Plants,
T. A. Mansfield, ed., Cambridge University Press, Cambridge,
1976. pp. 185-199.
191. Horsman, D. C., and A. R. Wellburn. Effect of SO^-polluted
air upon enzyme activity in plants originating from areas
with different annual mean atmospheric S0? concentrations.
Environ. Pollut. 13^:33-39, 1977.
192. Hou, L-Y., A. C. Hill, and A. Soleimani. Influence of C02 on
the effects of S0? and N0? on alfalfa. Environ. Polfut.
1_2:7-16, 1977. ^
193. Houston, D. B. Response of selected Pinus strobus L. clones
to fumigation with sulfur dioxide and ozone. Can. J.
For. Res. 4.:65-68, 1974.
7-165
-------
194. Houston, D. B. and L. S. Dochinger. Effects of ambient air
pollution on cone, seed and pollen characteristics in
eastern white and red pines. Environ. Pollut. ^2.: 1-5,
1977.
195. Houston, D. C., and G. R. Stairs. Genetic control of sulfur
dioxide and ozone tolerance of eastern white pine. For.
Sci. 19:267-271, 1973.
196. Howell, R. K. Ozone and sulfur dioxide—their effect on nutrient
composition of forages. Conf. Rumen. Funct. Rep., 1975.
pp. 4-5.
197. Hurd, L. E., M. 0. Mellinger, L. L. Wolf, and S. J. McNaughton.
Stability and diversity at three trophic levels in terrestrial
successional ecosystems. Science 173:1134-1136, 1971.
198. Hursh, C. R. Local climate in the Copper Basin of Tennessee
as modified by removal of vegetation. U.S. Dept. of
Agriculture Circ. 774, 1948. 38 pp.
199. Husar, R. B., D. E. Patterson, J. D. Hausar, N. V. Gillani,
and W. E. Wilson, Jr. Sulfur budget of a power plant
plume. Atmos. Environ. 1^:549-568, 1978.
200. Hausar, R. B., D. E. Patterson, C. C. Paley, and N. V. Gillani.
Ozone in hazy air masses. I_n_: International Congress on
Phytochemical Oxidant Pollution and Its Control. Proc.
Vol. II, Rept. No. EPA 600/377-0016, Ecol. Res. Sereis.
U.S. Environmental Protection Agency, Research Triangle
Park, NC., pp. 275-282.
201. Irving, P. M., D. J. Martinson, and J. E. Miller. A histological
study of soybeans injured by exposure to sulfur dioxide.
Radiol. Environ. Res. Div. Ann. Rep., Argonne Natl.
Lab., ANL-78-65. Part III, 1979.
202. Jacobson, J. S., and A. C. Hill. Recognition of Air Pollution
Injury to vegetation: A Pictorial Atlas. Air Pollution
Control Association, Pittsburgh, PA, 1970.
203. Jacobson, J. S., and L. J. Colavito. The combined effect of
sulfur dioxide and ozone on bean and tobacco plants.
Environ. Exp. Bot. j^:177-185, 1976.
204. Jager, J. H., and H. Klein. Biochemical and physiological
detection of sulfur dioxide injury to pea plants (Pisum
sativum). J. Air Pollut. Control Assoc. 27:464-466,
1977. —
205. Jaeger, H. J., E. Pahlich, and L. Steubing. The effect of
sulfur dioxide on the content of amino acids and protein
in pea seedlings. Angew. Bot. _4J5:199-211, 1972.
206. Jancraik, V. Vyskyt drevokaznych hub v hourem poskozovani
oblasti Krusnych hor. Lesnictvi 7^:677-692, 1961.
207. Jennings, 0. E. Smoke injury to shade trees. Natl. Shade
Tree Conf. Hh44-48, 1934.
7-166
-------
208. Jensen, K. F. Effect pf air pollution on leaf area partitioning.
U.S.D.A. Forest Service, NE Forest Exp, Stat., Delaware,
OH, 1978. CMimeograph)
209. Jensen, K. F., and L. F. Hanks. Growth analysis of poplar
cuttings fumigated with SO,, Proc. Atn. Phytopathol. Soc.
3.:306, 1976. *
210. Jensen, K. R., and T. T. Kozlowski. Absorption and translocation
of sulfur dioxide by seedlings of four forest tree species.
J. Environ. Qual. ^:379-382, 1975.
211. Jernelov, A-, and R. Rosenberg. Stress tolerance of ecosystems.
Environ. Conserv. 3^:43-46, 1976.
212. Johnson, D. W., and G. S. Henderson. Sulfate adsorption and
sulfur fractions in a highly weathered soil under a mixed
deciduous forest. Soil Sci. .128^34-40, 1979.
213. Jones, H. D., D. Weber, and D. Balsillie. Acceptable limits
for air pollution dosages and vegetation effects: sulfur
dioxide. Presented at the 67th Annual Meeting, Air
Pollution Control Association, Denver, Co, 1974. Paper
No. 74-225.
214. Jordan, M. Effects of zinc smelter emissions and fire on a
chestnut oak woodland. Ecology j>6_:78-91, 1975.
215. Judeikis, H. S., and S. Siegal. Particle-catalzyed oxidation
of atmospheric pollutants. Atmos. Environ. 7_:619-631 ,
1973.
216. Kamprath, E. J. Possible effects from sulfur in the atmosphere.
Combustion 44_: 16-17, 1972.
217. Karnosky, D. F. Threshold levels for foliar injury to Populus
tremuloides by sulfur dioxide and ozone. Can. J. For.
Res. 6^:166-169, 1976.
218. Karnowsky, D. F. Evidence for genetic control of response to
sulfur dioxide and ozone in Populus tremuloides. Can. J.
For. Res. 7_:437-440, 1977.
219. Katz, M. Sulfur dioxide in the atmosphere and its relation to
plant life. Ind. Eng. Chem. 41:2350-2465, 1949.
220. Katz, M. Effect of contaminants other than sulfur dioxide on
vegetation and animals. In: Pollution and Our Environment
Conf., Background Paper A4-2-2, Vol. 1, Council Res.
Ministers, Montreal, Can. 1967. pp. 1-18.
221. Katz, M., and A. W. McCallum. The effect of sulfur dioxide on
conifers. Proc. U.S. Tech. Conf. Air Pollution, 1952.
pp. 84-96.
222. Keller, T. Begriff und bedeutung der "latenten immissions -
schadigung." (Definition and importance of "laten"
injury by air pollution.) Allg. Forst. Jagdzyg 148:115-
120, 1977.
7-167
-------
223. Keller, T. The effect of long duration, low SCL concentrations
upon phytosynthesis of conifers. In: Proc. 4th Int.
Clean Air Congress, 1977- pp. 81-83.
224. Keller, T. Wintertime atmospheric pollutants—do they effect
the performance of deciduous trees in the ensuing growing
season. Environ. Pollut. 1^:243-247, 1978.
225. Keller, T. The effect of a continuous springtime fumigation
with SCL and C02 uptake and structure of the annual ring
in spruce. Environ. Pollut., in press, 1979.
226. Kellogg, W. W., R. D. Cradle, E. R. Allen, A. L. Lazrus, and
E. A. Martell. The sulfur cycle. Science 175:587-596,
1972.
227- Kender, W. J., and F. H. F. G. Spierings. Effects of sulfur
dioxide, ozone, and their interactions on "Golden delicious"
apple trees. Neth. J. Plant Pathol. 81.: 149-151, 1975.
228. Kercher, J. R. Grow 1: A Crop Growth Model for Assessing
Impacts of Gaseous Pollutants from Geothermal Technologies.
UCRL-52247, Lawrence Livermore Laboratory, Livermore,
Calif., 1977. 33 pp.
229. Kickert, R. N., and P. R. Miller. Responses of ecological
systems. In: Methodology for the Assessment of Air
Pollution Effects on Vegetations, W. W. Heck, S. V.
Krupa, and S. N. Linzon, Air Pollution Control Association,
1979.
230. Kirschbaum, U., R. Klee, and L. Stenbing. Lichens as indicators
for emission load in the urban region of Frankfurt. M.
Staub-Reinhalt. Luft. 31,:28-31, 1971.
231. Kalke, A. Lead-zinc-cadmium-enrichment in soils and plants.
Staub Reinhaltung der Luft 3^:20-24, 1974.
232. Klepper, L. A. Author's reply. Atmos. Environ. JJ:1475,
1979.
233. Kodata, M., and T. Inous. Invading path of sulfur dioxide
into pine leaves as revealed by microradioauthography.
J. For. Soc. 5^:207-208, 1972.
234. Koziol, M. J., and D. W. Cowling. Growth of ryegrass (Lolium
perenne L.) exposed to S0?. II. Changes in the distribution
of photoassimilated 14. J. Exp. Bot. 29:1431-1440,
1978. c ~~
235. Krause, G. H. M. Phytoxosche Wechselwirkungen zwischen Schwefeldioxid
und den schwermetallen zink and Cadmium. Schriftenreihe
der Landesanstalt fur Immissions and Bodennutzugsschutz
des Landes N. Rhein-Westf. 34_: 86-91, 1975.
236. Krause, G. H. M., and H. Kaiser. Plant response to heavy
metals and sulfur dioxide. Environ. Pollut. 12:63-71,
1977.
7-168
-------
237. Kress, L. W. Growth Impact of CL, S0? and N0? Singly and in
Combination on Loblolly pine (Pinus taeda L.) and American
Sycamore (Platanus occidentjalis L.). Ph. D. Thesis,
Virginia Polytechnic. Institute and State University,
Blacksburg, Va, 1978. 102 pp.
238. Kress, L. W., and J. M. Skelly. The interaction of 0.,, S0?
and NCL and its effects on the growth of two forest tree
species. In: Proc. Cottrell Centennial Symp. Air Pollution
and Its Impact on Agriculture. California State College,
Stanislaus, CA, 1976.
239. Kress, L. W., and J. M. Skelly. The interaction (L, SO. and
NO^ and its effect on the growth of two forest tree
species. In: Proc. Cottrell Centennial Symp: Air
Pollution and Its Impact on Agriculture, Stanislaus, CA,
1977. pp. 128-152.
240. Kress, L. W., and J. M. Skelly. Pinus taeda L. and Platanus
occidental's L. seedling height growth suppression in
response to long term-low levels of 03, ^ and/or S0?.
Proc. 3rd International Congress on Plant Pathology,
Munich, in press.
241. Krouse, H. R. Sulfur isotope abundance elucidate uptake of
atmospheric sulfur emissions by vegetation. Nature
2jx5:46, 1977.
242. Krupa, S. V. Impact of air pollutants on terrestrial vegetation.
In: The Role of Disease in Environmental and Ecological
Management of National Parks, vol. 2. F. A. Wood ed.,
Annual Report to National Park Service, U.S. Dept. of the
Interior, 1976. 221 pp.
243. Krupa, S. V., B. I. Chevone, S. Fagerlie, F. Russo, and D. S.
Lang. Impact of air pollutants on terrestrial vegetation -
a literature survey. State of Minnesota Environ. Qua!.
Council, 1976. 470 pp.
244. Krupa, S. V., and R. J. Kohut. Impact of stark emissions from
the NSP-SHERCO power plant on terrestrial vegetation.
Annual Report, Northern States Power Co., Minneapolis,
MM, 1976.
245. Kudela, M., and E. Novakova. Lesnf skudci a skody zeri v
lesich poskozovanych Kourum. Lesnictvi 6^:493-502, 1962.
246. Labanauskas, C. K. Manganese. In: Diagnostic Criteria for
Plants and Soils. H. D. Chapman, ed., University of
California, 1966. pp. 264-285.
247. Labeda, D. P., and M. Alexander. Effects of SO and NO on
nitrification in soil. J. Environ. Qual. _7:523-526,
1978.
7-169
-------
248. Lacasse, N. L. and W. J. Moroz. Handbook of effects assessment;
vegetation damage. CAES. Pennsylvania State University,
University Park, PA 1969.
249. Lagerwerff, J. V. Lead, mercury, and cadmium as environmental
contaminants. In: Micronutrients in Agriculture. J. J.
Mortuedt, P. M. Giodana, and W. L. Lindsay, ed., Soil
Science Society of America, Madison, WI, 1972. pp. 593-
636.
250. Larsen,
m, R. I., and W. W. Heck. An air quality data analysis
system for interrelating effects, standards, and needed
source reduction: Part 3. Vegetation injury. J. Air
Pollut. Control Assoc. 26_:325-333, 1976.
251. Lauenroth, W. K., C. J. Bicak, and J. L. Dodd. Sulfur accumulation
in western wheatgrass exposed to three controlled SCL
concentrations. Plant Soil, in press, 1980.
252. Lauenroth, W. K., and J. L. Dodd. The effects of water- and
nitrogen-induced stresses on plant community structure in
a semiarid grassland. Oecologia 36_:211-222, 1978.
253. Lauenroth, W. K. and J. E. Heasley. Impact of atmospheric
sulfur deposition on grassland ecosystems. In: Atmospheric
Sulfur Deposition: Environmental Impacts and Health
Effects. D. S. Shriner, A. Richmond and S. E. Lindbergh,
eds., Ann Arbor Science Publishers, in press, 1980.
254. LeBlanc, F., and J. DeSloover. Relation between industrialization
and the distribution and growth of epiphytic lichens and
mosses in Montreal. Can. J. Bot. 48:1485-1496, 1970.
255. LeBlanc, F., and D. N. Rao. Effects of sulfur dioxide on
lichen and moss transplants. Ecology 5^:612-617, 1973.
256. LeBlanc, F., and D. N. Rao. Effects of air pollutants on
lichens and bryophytes. In: Responses of Plants to Air
Pollution. J. B. Mudd and T. T. Kozlowski, eds., Academic
Press, New York, 1975. 383 pp.
256a. LeBlanc, F., D. N. Rao, and G. Comeau. The epiphytic vegetation
of Populus balsamifera and its significance as an air
pollution indicator in Subdury, Ontario. Can. J. Bot.
50:519-528, 1972.
257- Lee, J. J., E. M. Preston, and R. A. Lewis. A system for the
experimental evaluation of the ecological effects of
sulfur dioxide. Proc. 4th Joint Conf. Sensing of Environmental
Pollutants. American Chemical Society, Washington, D.C.,
1978. pp. 49-53.
258. Lee, R., and D. M. Gates. Diffusion resistance in leaves and
related to their stomatal anatomy and microstructure.
Am. J. Bot. 51:963-975, 1964.
7-170
-------
259. Lee, Jr., R. E., and D. J. von Lehmden. Trace metal pollution
in the environment. J. Air Pollut. Control Assoc. 23_:853-
857, 1973.
260. Legge, A. H., C. W. Harver, P. F. Lester, D. R. Jaques, H. R.
Krouse, J. Mayo, A. P. Hartgerink, R. G. Amundson, and R.
B. Walker. Quantitative assessment of the impact of
sulfur gas emissions on a forest ecosystem. Final report
submitted to Whitecourt Environmental Study Group.
Environmental Sciences Centre, Kananskis, The University
of Calgary, Alberta, 1976.
261. Legge, A. H., D. R. Jaques, G. W. Harvey, H. R. Krause, H. M.
Brown, E. D. Rhodes, M. Nosal, H. W. Schellhase, J. Mayo,
A. P. Hartgerink, P. F. Lester, R. G. Amundson, and R. B.
Walker. Sulfur gas emissions in the Boreal forest—the
West Whitecourt Case Study. Kananaskis Centre for Environ.
Res., The University of Calgary, Alberta, 1978. 615 pp.
262. Leone, I. A., and E. Brennan. Modification of sulfur dioxide
injury to tobacco and tomato by varying nitrogen and
sulfur nutrition. J. Air Poll. Control Assoc. 22:544-
547, 1972.
263. Lerman, S. L., and E. F. Darley. Particles. In: Responses
of Plants to Air Pollution. J. B. Mudd and T. T. Kozlowski
eds., Academic Press, New York, 1975. pp. 141-158.
264. Libera, W., H. Ziegler, and I. Ziegler. Stimulation of Hill-
reaction and CCL function in isolated spinach chloroplasts
by low concentrations of S02. Planta ^09^:269-279, 1973.
265. Liebig, G. F. Arsenic. In: Diagnostic Criteria for Plants
and Soils. H. D. Chapman, eds., University of California,
1966. pp 13-23.
266. Likens, G. E., F. H. Borman, R. S. Pierce, J. S. Eaton, and N.
M. Honson. Biogeochemistry of a Forested Ecosystem.
Springer-Verlag, New York, 1977.
267. Lindberg, S. E. Effects of airborne sulfur pollutants on
plants. In: Sulfur in the Environment. J. 0. Nriagu
eds., John Wiley & Sons, 1978. pp. 109-162.
268. Lindberg, S. E., A. C. Harriss, R. R. Turner, D. S. Shriner,
and D. D. Huff. Mechanisms and rates of atmospheric
deposition of selected trace elements and sulfate to a
deciduous forest watershed. Pub. No. 1299, Oak Ridge
National Laboratory, Oak Ridge, TN, 1979.
269. Linzon, S. N. The influence of smelter fumes on the growth
of white pine in the Sudbury region. Can. Dep. Agr.
Publ., Ontario Dep. Lands Forests, 1958. 45 pp.
7-171
-------
270. Linzon, S. N. Damage to eastern white pine by sulfur dioxide,
semimature tissue needles blight and ozone. J. Air
Pollut. Control Assoc. 16.: 140-144, 1966.
271. Linzon, S. N. Some effects of particulate matter on vegetation.
.In.: Ontario Proc. 3rd International Clean Air Congress,
Dusseldorf, West Germany, 1973. pp. A118-A120.
272. Linzon, S. N. Effects of airborne sulfur pollutants on plants.
In: Sulfur in the Environment: Part II, Ecological
Impacts. J. 0. Nriagu, ed., John Wiley & Sons. New York,
1978. pp. 109-162.
273. Linzon, S. N., P. L. Temple, and R. G. Pearson. Sulfur concentration
in plant foliage and effects. Presented at the 71st
Annu. Meet, of the Air Pollution Control Assoc., Houston,
TX, 1978.
274. Linzon, S. N., P. J. Temple, and R. G. Pearson. Sulfur concentrations
in plant foliage and related effects. J. Air Pollut.
Control Assoc. 29.:520-525, 1979.
275. Little, P- A study of heavy metal contamination of leaf
surfaces. Environ. Pollut. 5;159-172, 1973.
276. Little, P. Deposition of 2.75, 5.0 and 8.5ym particles to
plant and soil surfaces. Environ. Pollut. 12:293-305,
1977.
276a. Little, P., and R. D. Wiffen. Emission and deposition of
petrol engine exhaust Pb-1. Deposition of exhaust Pb.
Atmos. Environ. U_:437-447, 1977.
277- Lockyer, D. R., D. W. Cowling, and L. H. P. Jones. A system
for exposing plants to atmospheres containing low concen-
trations of sulfur dioxide. J. Exp. Bot. 27_:397, 1976.
278. Lodenius, M., and K. Laaksovirta. Mercury content of Hypogymnia
physodes and pine needles affected by a chlor-alkali
works at Kuusankoski, SE Finland. Ann. Bot. Fenn. 16:7-
10, 1979.
279. Loman, A. A., R. A. Bauel, and D. Hocking. Sulfur dioxide and
forest vegetation. N. For. Res. Centre Inf. Report NOR-
X-49. Edmonton, Alberta, 1972. 22 pp.
280. Loucks, 0. L. Emergence of research on agroecosystems. Annu.
Rev. Ecol. Syst. 8.: 173-192, 1977.
281. Lower, W. R. Gene frequency differences in Drosophila melanogaster
associated with lead smelting operations. Mutat. Res.
31:315, 1975.
282. Ma, T., D. Isbandi, S. N. Kahn, and Y. S. Tseng. Low level
of SO^-enhanced chromatid aberrations in tradescantia
pollen tubes and seasonal variation of the aberration
rates. Mutat. Res. 21:93-100, 1973.
7-172
-------
283. MacDowall, F. D. N., and A. F. W. Cole. Threshold and synergistic
damage to tobacco by ozone and sulfur dioxide. Atmos.
Environ. 5_:553-559, 1971.
284. Majernik, 0. Physiological study of the effects of sulfur
dioxide pollution, phenylmercuric acetate sprays, parasitic
infection of stomatal behavior and aging in barley.
Phytopathology 72.:255-268, 1971.
285. Majernik, 0., and T. A. Mansfield. Direct effect of So2
pollution on the degree of opening of stomata. Nature
227.: 377-378, 1970.
286. Malhortra, S. S., and A. A. Kahn. Effects of sulfur dioxide
fumigation on lipid biosynthesis in pine needles. Phytochemistry
17_:241-244, 1978.
287. Mamajev, S. A., and 0. D. Shkarlet. Effects of air and soil
pollution by industrial waste on the fructification of
scots pine in the Urals. Mitt. Frost!. Bundesverschanst.,
Wien 97.: 443-450, 1972.
288. Mandl, R. H., L. H. Weinstein, and M. Keveny. Effects of
hydrogen fluoride and sulfur dioxide alone and in combination
on several species of plants. Environ. Pollut. 9_:133-
143, 1975.
289. Manning, W. J. Effects of limestone dust on leaf condition,
foliar disease incidence, and leaf surface microflora of
native plants. Environ. Pollut. 2^:69-76. 1971.
290. Mansfield. T. A., and 0. Majernik. Can stomata play a part in
protecting plants against air pollution? Environ. Pollut.
1:149-154, 1970.
291. Mansfield, T. A., and 0. Majernik. Effects of S02 pollution
on stomatal movements in Vicia faba. Phytopathology
2.:71;123-128, 1971.
292. Markowski, A., S. Grzesiak, and M. Schramel. Indexes of
susceptibility of various species of cultivated plants to
sulfur dioxide action. Bulletin de L'Academie Polanaise
des Sciences 23_(9): 637-646, 1975.
293. Martin, A., and F. R. Barber. Some measurements of loss of
atmospheric sulfur dioxide near foliage. Atmos. Environ.
^:345-352, 1971.
294. Masaru, N., F. Syozo, and K. Saburo. Effects of exposure to
various injurious gases on germination of lily pollen.
Environ. Pollut. U.:181-187, 1976.
295. Materna, J. Einfluss niedriger Schwefledioxyd Konzentrationen
ouf die Fichte. Mittl. Forstl. Bundesversuchsanst. Wien
97_:219-232, 1972.
7-173
-------
296. Materna, J. Criteria for characterization of pollution damages
in forests. Proc. 3rd Int. Clean Air Congress, Dusseldorf,
West Germany, 1973. pp. A121-A123.
297. Materna, J., J. Jirgle, and J. Kucera. Vysledky mereni koncentraci
lyclicniky siricitheo v. lesich krusnych hor. (Measurement
results of sulfur dioxide concentrations in the Ore
Mountain Forests.) Ochrana Oyzdusi. _l(6):84-92, 1969.
298. Materna, J., and R. Knout. The absorption of sulfur dioxide
by spruce and pine trees. Naturwissenshaften 50(11):407,
1969.
299. Matsushima, J., and R. R. Brewer. Influence of sulfur dioxide
and hydrogen fluoride as a mix or reciprocal exposure on
citrus growth and development. J. Air Pollut. Control
Assoc. 22^:710-713, 1972.
300. May, P. F., and A. M. Downes. Nutrient cycling in grazed
pastures. I. A preliminary investigation of the use of
6 S gypsum. Aust. J. Agric. Res. _19_: 531-543, 1968.
301. May, P. £„ A. R. Till, and M. J. Cumming. Systems analysis
of sulfur kinetics in pastures grazed by sheep. J.
Appl. Ecol. 9_:25-49, 1972.
302. May, R. M. Stability in ecosystems: some comments. In:
Unifying Concepts in Ecology. W. H. van Dobben and R. H.
Lowe-McConnel, eds., Junk, The Hague, 1975. pp. 161-167.
303. McCune, D. C., D. H. Silberman, R. H. Mandl, L. H. Weinstein,
P. C. Freudenthal, and P- A. Giardina. Studies on the
effects of saline aerosols of cooling tower origin on
plants, J. Air Pollut. Control Assoc. 27_:319-324, 1977.
304. McGovern, P. C. Air quality assessment studies in the Wawa
area, 1975. Ontario Ministry of Environment, 1976. pp.
1-51.
305. McLay, C. L. Windblown dust as a source of nutrients for
aquatic plants. Environ. Pollut. 5^:173-180, 1973.
306. McMahon, T. A., and P. J. Deaison. Epirical atmospheric
deposition parameters—a survey. Atmos. Environ. 13:571-
583, 1979. ~~
307. Meidner, H., and T. A. Mansfield. Physiology of stomata.
McGraw-Hill, Great Britian, 1968. 128 pp.
308. Menser, H. A., and H. E. Heggestad. Ozone and sulfur dioxide
synergism: injury to tobacco plants. Science 153:424-
425, 1966.
309. Meszaros, E., G. Varhelyi, and L. Haszpra. On the atmospheric
sulfur budget over Europe. Atmos. Environ. 12:2273-2277,
1978.
7-174
-------
310. Miller, J. E., H. J. Smith, P. G. Sprugel, and P. B- Xerikos.
Yield response of field-grown soybeans to an acute SCL
exposure. Radiol. Environ. Res. Div. Annu. Rep., Argonne
Natl. Lab., ANL-78-65, Part III, 1979.
311. Miller, J. E., and D. G. Sprugel. Some preliminary notes
concerning the impact of fossil fuel combustion on crop
plants. Argonne Natl. Lab., U.S. Dept. of Energy Contract,
Report W-31-109-Eng-38, 1979. 4 pp.
312. Miller, P. Oxidant-induced community change in a mixed conifer
forest. Adv. Chem. Ser. JL22.:107-117, 1973.
313. Miller, P., and J. R. McBride. Effects of air pollutants on
forest. _In_: Response of Plants to Air Pollution. J. B.
Mudd and T. T. Kozlowski, eds., Academic Press, New York,
1975. pp. 195-235.
314. Montana Air Quality Bureau. Environmental impact statement:
Montana Air Qual. Standards Study, M. D. Roach Proj.
Director. Helena, MT, 1978.
315. Moss, M. R. Spatial patterns of sulfur accumulation by vegeta-
tion and soils around industrial centres. J. Biogeorg.
2^:205-222, 2975.
316. Moss, M. R. Biogeochemical cycles as integrative and spatial
models for the study of environmental pollution (the
example of the sulfur cycle). Int. J. Environ. Sutd.
9.:209-216, 1976.
317. Mrkva, R. Influence of industrial air pollution on the quality
of Pinus sylvestris L. seed in the region of the Breclav
forest enterprise (S. Moravia). Acta Univ. Agr. Brno
(Fac. SiIvicult.) 38:345-360, 1969.
318. Mudd, J. B. Sulfur dioxide. In: Responses of plants to air
pollution. J. B. Mudd and T. T. Kozlowski, eds., Physio-
logical Ecol Mono. Series, Academic Press, Inc., New
York 1975. pp. 9-22.
319. Murphy, C. E., Jr., T. R. Sinclair, and K. R. Knoerr. An
assessment of the use of forests as sinks for the removal
of atmospheric sulfur dioxide. J. Environ. Qual. 6^:388-
396, 1977.
320. Murray, J. J., R. K. Howell, and A. C. Wilton. Differential
response of 17 Poa pratensis cultivars to ozone and
sulfur dioxide. Plan Dis. Rep. 59_:852-854, 1975.
321. Nash, T. H. III. Sensitivity of lichens to sulfur dioxide.
Bryologist _3:333-339, 1973.
322. Nash, T. H., and E. H. Nash. Sensitivity of mosses to sulfur
dioxide. Oecologia r/_:257-263, 1974.
7-175
-------
323. National Academy of Sciences. Principles for Evaluating
Chemicals in the Environment. National Academy of
Sciences, Washington, DC, 1975. ,
324. National Academy of Sciences. Nickel, Series on medical and
biological effects of environmental pollutants. National
Academy of Sciences, Washington, DC, 1975. 277 pp.
325. National Academy of Sciences. Sulfur oxides. Board on Toxi-
cology and Environ. Health Hazards. U.S. Environmental
Protection Agency Contract. Report No. 68-01-4655, 1978.
326. National Research Council of Canada. Effect of Sulfur Dioxide
on Vegetation. Prepared for the Associate Committee on
Trail Smelter Smoke of the National Research Council of
Canada. Ottawa. NRCC NO. 1117, 1939.
327. Neely, G. E., D. T. Tingey, and R. G. Wilhour. Effects of
ozone and sulfur dioxide singly and in combination on
yield, quality and N-fixation of alfalfa. Proc. International
Conference on Photochemical Oxidant Pollution and Its
Control. EPA-600/3-77-001b, 1977- pp. 663-673.
328. Nelson, K. E. Some studies of the action of sulfur dioxide in
the control of Botrytis rot of tokay grapes. Proc. Am.
Soc. Hortic. Sci. 71:183-189, 1958.
329. Nelson, K. E., and M. Ahmedullah. Effect of type of in-
pagkage sulfur dioxide generator and packaging materials
on quality of stored table grapes. Am. J. Enol. Viti-
culture 23j78-85, 1972.
330. Nicholson, C. R. The response of 12 clones of eastern white
pine (Pinus strobus) to ozone and nitrogen dioxide. M.S.
Thesis, Virginia Polytechnic Institute and State Univer-
sity, Blacksburg, VA, 1977. 141 pp.
331. Nicholson, C. R., and J. M. Skelly. An Update of the Annual
Radial Increment Growth Analysis of Eastern White Pine
Stand #2 at the Radford Army Amnunition Plant, Progress
Report. Virginia Polytechnic Institute and State Univ.,
Blacksburg, VA, 1976.
332. Nielson, D. G., L. E. Terrell, and T. C. Weidensaul. Phyto-
toxicity of ozone and sulfur dioxide to laboratory fumi-
gated Scots pine. Plant Dis. Rep. 61:699-703, 1977.
333. Nishimoto, T., K. Jujita, H. Furakawa, and M. Yoshimoto.
Accumulation of heavy metals (cadmium, zinc and copper)
from smeltery on forest ecosystem and their uptake by
shiitakejnushroom (Lentinus ecodes) and Nameko mushroom
(Pholiota glutinosa) through polluted bed bogs. Bull.
Gov. For. Exp. Stn. (Tokyo) 298:1-38, 1978.
7-176
-------
334. Noggle, J. C., and H. C. Jones. Accumulation of atmospheric
sulfur by plants and sulfur-supplying capacity of soils.
U.S. Environmental Protection Agency Publication. EPA-
600-7-79-109, 1979.
335. Noland, T. L., and T. T. Kozlowski. Effect of S02 on stomatal
aperature and sulfur uptake of woody angiosperm seedlings.
Can. J. For. Res. ^:57-62, 1979.
336. Nriagu, J. 0., and R. D. Coker. Isotopic composition of
sulfur in precipitation within the Great Lakes Basin.
Tellus 30:365-375, 1978.
337. O'Connor, J. A., D. G. Parbery, and W. Strauss. The effect of
phytotoxic gases on native Australian plant species:
Part I. Acute effects of sulfur dioxide. Environ.
Pollut. 7.:7-23, 1974.
338. Odum, E. P. The strategy of ecosystem development. Science
164: 262-269, 1969.
339. Odum, E. P. Fundamentals of Ecology, 3rd ed. W. B. Saunders,
Co., Philadelphia, 1971. 570 pp.
340. Odum, W. E., and J. E. Drifmeyer. Sorption of pollutants by
plant detritus: a review. Environ. Health Perspect.
27_:133-137, 1978.
341. O'Gara, P. J. Sulfur dioxide and fume problems and their
solutions. In: 14th Semiannual Meeting of the American
Institute of Chemical Engineers. J. Ind. Eng. Chem.
11:744, 1922.
342. Orians, G. H. Diversity, stability and maturity in natural
ecosystems. In: Unifying Concepts in Encology. W. H.
van Dobben and R. H. Lowe-McConne, eds., Junk, The Hague,
1975. pp. 139-140.
343. Palich, E. Allosterische Regulation der Aktivitat der Glutamat-
dehydrogenase aus Erbsenkeimlingen durch das Substrat L-
Ketoglutarsaure. Planta (Berline) HW:222-227, 1971.
344. Palich, E. Uber den Hemm-Mechanismus mitochondriater Glutamat-
oxalacetat-transaminase in S09-begaster Erbsen. Planta
(Berlin) JLIO.:267-278, 1973. e~
345. Palich, E. Effect of S02-pollution on cellular regulation. A
general concept of the mode of action of gaseous air
contamination. Atmos. Environ. 9;.261-263, 1975.
346. Parish, S. B. The effect of cement dust on citrus trees.
Plant World 13:288-291, 1910.
7-177
-------
347. Parker, G. G., S. E. Lindberg, and 0. M. Kelly. Atmosphere/canopy
interaction of sulfur in the southeastern United States.
In: Atmospheric Sulfur Deposition: Environmental Impacts
and Health Effects, Shriner, D. S., A. Richmond and S.
Lindberg, eds., Ann Arbor Science Publishers, Ann Arbor,
MI, in press, 1980.
348. Payrissat, M., and S. Beilke. Laboratory measurements of the
uptake of sulfur-dioxide by different European soils.
Atmos. Environ. 9_:211-217, 1975.
349. Pelz, E. The individual smoke resistance of spruce. Wiss. 2.
Tech Univ., Dresden 1^:3:595-600, 1962.
350. Perozzi, R. E., and F. A. Bazzaz. The response of an early
successional community to shortened growing season.
Oikos 31:89-93, 1978.
351. Phillips, P- H. The effects of air pollutants on farm animals.
_In_: Air Pollution Handbook. Magi 11 and Hoi den eds.,
McGraw-Hill, New York, 1956.
352. Phillips, S. 0., J. M. Skelly, and H. E. Burkhart. Growth
fluctuations of loblolly pine (Pinus taeda L.) proximal
to a periodic source of air pollution. Phytopathology
67:716-720, 1977.
353. Phillips, S. 0., J. M. Skelly, and H. E. Burkhart. Inhibition
of growth in asymptomatic white pine exposed to fluctuating
levels of air pollution. Phytopathology 67:721-725,
1977.
354. Piskornik, Z. Effect of industrial polluted air on photosynthesis
of deciduous trees. Bull. Zakl. Brdan. Nauk. Gog. PAN
121:155-178, 1969.
355. Podzorov, N. V. Photosynthesis and respiration of Scots pine
in relation to the degree of atmospheric pollution.
Trydy Glav Geofiz Observ. 238:232-235, 1971.
356. Posthumus, A. C. New results from S09 fumigation of plants.
VDI-Berichte NR. 314/1978, 1975. pp. 225-230.
357. Preston, E. M. The ecological implications of chronic sulfur
dioxide exposure for native grasslands. Presented at the
72nd Annual Meeting Air Pollution Control Association,
Cincinnati, OH, 1979.
358. Rajput, C. B. S., D. P. Ormrod, and D. W. Evans. The resistance
of strawberry to ozone and sulfur dioxide. Plant Dis.
Rep. 61:76-79, 1977.
359. Rasmussen, K. H., M. Taheri, and R. Kabel. Global emissions
and natural processes for removal of gaseous pollutants.
Water Air Soil Pollut. i:33-64, 1975.
360. Reinert, R. A. Pollutant interactions and their effects on
plants. Environ. Pollut. 9.:115-116, 1975.
7-178
-------
361. Reinert, R. A. Exposure of various plant species to N02> SO-
and On singly and in combination. Proc. Am. Phytopathof.
Soc. £:87, 1977.
362. Reinert, R. A., A. S. Heagle, and W. W. Heck. Plant response
to pollutant combinations. In: Responses of Plants to
Air Pollution. J. B. Mudd and T. T. Koslowski, eds.,
Academic Press Inc., 1975. pp. 159-177.
363. Rennie, P. J., and R. L. Halstead. The effects of sulfur on
plants in Canada. In: Sulfur and its Inorganic Derivatives
in the Canadian Environment. Nat. Res. Council Canada,
NRCC No. 15015:69-180, 1977/
364. Reuther, W., and C. K. Labanauskas. Copper. In: Diagnostic
Criteria for Plants and Soils, H. D. Chapman, eds.,
University of California, 1966. pp. 157-179.
365. Ricks, G. R., and J. H. Williams. Effects of atmospheric
pollution on deciduous woodland. Part 2: Effects of
particulate matter upon stomatal diffusion resistance in
leaves of Quercus petraea (Mattuschka) Liebl. Environ.
Pollut. 6_:87-109, 1974.
366. Roa, D. N., and F. LeBlanc. Effect of sulfur dioxide on the
lichen algae with special reference to chlorophyll.
Bryologist 69_:69-75, 1965.
367- Roberts, B. R. Foliar sorption of atmospheric sulfur dioxide
by woody plants. Environ. Pollut. 7^:133-140, 1974.
368. Roberts, B. R. The effect of sulfur dioxide concentration on
growth of .potted white birch and pin oak seedlings in the
field. J. Am. Hortic. Sci. H)0;640-642, 1975.
369. Roberts, B. R. The response of field-grown white pine seedlings
to different sulfur dioxide environments. Environ.
Pollut. 1^:175-180, 1976.
370. Robinson, E., and L. L. Fox. 2,4-D herbicides in central
Washington. In: Proc. 70th Annual Meet. Air Pollution
Control Assoc. 77_:45.4:1/16, 1977-
371. Rosen, P. M., R. C. Musselman, and W. J. Kender. Relationships
of stomatal resistance to sulfur dioxide and ozone injury
in grapevines. Sci. Hortic. 8^:137-142, 1978.
372. Rosenberg, C. R., R. J. Hutnik, and D. D. David. Forest
composition of varying distances from a coal-burning
power plant. Environ. Pollut. 14:307-317.
373. Ros, I. S. Some effects of heavy metals on fungal cells.
Trans. Br. Mycol. Soc. 64_: 175-193, 1975.
374. Ruhling, A., and G. Tyler. Heavy metal pollution and decomposition
of spruce needle litter. Oikos 2^:402-416, 1973.
7-179
-------
375. Saunders, P. J. The toxicity of sulfur dioxide to Deplocarpon
rosae Wolf causing blackspot of roses. Ann. Appl. Biol.
58:103, 1966.
376. Saunders, P. J. W. Effects of atmospheric pollution of leaf
surface microflora. Pestic Sci. 4-589-594, 1973.
377. Scheffer, T- C., and G. G. Hedgcock. Injury to northwestern
forest trees by sulfur dioxide from smelters. U.S.D.A.
Tech. Bull 1117, 1955. 49 pp.
378. Schoenbeck, H. Beobachtungen zur Frage des einflusses von
industriellen immissionen auf die drankheit bereitschaft
der Pflanze. Benchte der Landesanstalt fur Bodennutzungschertz
1:89-98, 1960.
378a. Shoenbeck, H. Detection of heavy metal-containing air pollutants
by selected plant indicators. Ver. Dtsch. Ing. 203:75-
85, 1973.
379. Schramel, M. Influence of sulfur dioxide on stomatal apertures
and diffusive resistance of leaves in various species of
cultivated plants under optimum soil moisture and drought
conditions. Bull. Acad. Polon. Sci. Ser. Sci. Biol.
13:57-63, 1975.
380. Schwartz, C. C., W. K. Lauenroth, R. K. Heitschmidt, and J. L.
Dodd. Effects of controlled levels of sulfur dioxide on
the nutrient quality of western wheatgrass. J. Appl.
Ecol. JJK869-874, 1978.
381. Schwela, D. H. An estimate of deposition velocities of several
air pollutants on grass. Ecotoxic. Environ. Safety
1:174-189, 1979.
382. Sehmel, G. A., and W. A. Hodgson. Predicted dry deposition
velocities. In: Atmosphere-surface exchange of particulate
and gaseous pollutants symposium. Conf-74092. Richland,
WA, 1974. pp. 399-422.
383. Setterstrom, C., and P. W. Zimmerman. Factors influencing
susceptibility of plants to sulfur dioxide injury.
Contrib. Boyce Tompson Inst. _10_:155-186, 1939.
384. Sharp, E. L. Atmospheric ions and germination of uredospores
of Purcinia striiformis. Science 156_: 1359-1360, 1967.
385. Sharp, El. Relation of air ions to air pollution and some
biological effects. Environ. Pollut. 1:227-239, 1972.
386. Sheridan, R. P. Impact of emissions from a coal-fired electricity
generating facilties on N -fixing in lichens. Bryologist
82:54-58, 1979. 2
7-180
-------
387. Shin, J. H. A critical survey of measurements of foliar
deposition of airborne sulfates and nitrates. Ann. Air
Pollut Control Assoc. 78:1-16, 1978.
388. Shinn, J. H., and S. Lynn. Do manmade sources affect the
sulfur cycle of northeastern states? Environ. Sci.
Technol. 13:1062-1067, 1979.
389. Showman, R. E. Linchens as indicators of air quality around a
coal-fired power generating plant. Bryologist 78;1-6,
1975.
390. Shramel. M. Influence of sulfur dioxide on stomatal apertures
and diffusive resistance of leaves in various species of
cultivated plants under optimum soil moisture and drought
conditions. Bull. Acad. Pol. Sci. Ser. Sci. Biol. 23:57-
63, 1975.
391. Shriner, D. S., and G. S. Henderson. Sulfur distribution and
cycling in a deciduous forest watershed. J. Environ.
Qual. "7:392-397, 1978.
392. Shugart, H. H., and D. C. West. Development of an Appalachian
deciduous forest succession model and its application to
assessment of the impact of the Chestnut Blight. J.
Environ. Manag. 5^:161-179, 1977.
393. Sierpinski, Z. Die Bedeutung der sekundaeren Kiefernschaedlinge
in Gibieten chronischer Einwirkuny industrieller Luftverunre-
inigungedn. M1H1. Forstl. Bundesversuchsanst. Wien
97.:609-615, 1972.
394. Sij, J. W., E. T. Kanemasu, and S. M. Goltz. Some preliminary
results of sulfur dioxide effects on phytosynthesis and
yield in field-grown wheat. Tans Kans. Acad. Sci. 76:199-
297, 1974.
395. Silvius, J. E., M. Ingle, and C. H. Baer. Sulfur dioxide
inhibition of photosynthesis in isolated spinach chlorosplasts.
Plant Physio!. 56_:434-437, 1975.
396. Skelly, J. M., and R. C. Lambe. Diagnosis of air pollution
injury to plants. Va. Coop. Ext. Serv. Publ. No. 586.
Blacksburg, Va, 1974. 14 pp.
397. Skye, E. The influence of air pollution on the fruticolous
and foliaceous lichen flora around the shale-oil works at
Kvarntorp in the province of Nirke. Sven. Bot. Tidskr.
52_:133-190, 1958. (In Swedish)
398. Smith, B. M., J. Wagman, and B. R. Fish. Interaction of
airborne particles with gases. Environ. Sci. Technol.
3_:558-562, 1969.
399. Smith, H. J., and D. D. Davis. Susceptibility of conifer
cotyledons and primary needles to acute doses of sulfur
dioxide. Hortic. Sci. 13:703-704, 1978.
7-181
-------
399a. Smith, R. L. Ecology and Field Biology. 2nd ed. New York,
Harper and Row. 1974. 850 p.
399b Smith, W. H. Metal contamination of urban woody plants.
Environ. Sci. Technol. 7_:631-636, 1973.
400 Smith", W. H. Air pollution—effects on the structure and
function of the temperate forest ecosystem. Environ.
Pollut. 6;111-129, 1974.
401. Smith, W. H. Removal of atmospheric particles by urban vegeta-
tion: implications for human and vegetative health.
Yale J. Biol. Med. 50^:185-197, 1977.
402. Smith, W. H. Influence of heavy metal leaf contaminants on
the vitro growth of urban-tree phylloplane-fungi. Microb.
Ecol. 3^:231-239, 1979.
403. Smith, W. H., and L. S. Dochinger. Capability of metropolitan
trees to reduce atmospheric contaminants. In: Proc.
Better Trees for Metropolitan Landscapes Symp. H. Gerold,
F. Santamore, and S. Little eds., USDA For. Ser. Gen.
Tech. Rep. No. NE-22, 1976, pp. 49-59.
404. Soto, A. EM., A. Pinto de Torres, and E. L. Cancino. Preventing
control of postharvest rotting of table grapes. Agr.
Tec. (Santiago de Chile), 33:176-182, 1973.
405. Speeding, D. J. Uptake of sulfur dioxide by barley leaves at
low sulfur dioxide concentrations. Nature 224:1229-1231,
1969.
406. Spinka, J. Effects of polluted air on fruit trees and legumes.
Ziva 19:13-15, 1971.
407- Sprugel, D. G., J. E. Miller, P. B. Zerikos, and H. J. Smith.
Effect of chronic sulfur dioxide fumigation on development
of yield and seed quality of field-grown soybeans: a
summary of 1977 and 1978 experiments. Radiol. and Environ.
Res. Div. Annu. Rep. Argonne Natl. Lab. ANL-78-65-III,
1978.
408. Steinhubel, G., and L. Halas. The destruction and formation
of dry matter of elevated temperatures induced in the
leaves of trees by dust emissions. Lesnick Casopis
11:265-382, 1967.
409. Stewart, D., M. Treshow, and F. M. Harner. Sulfur dioxide and
hydrogen fluoride emissions in regard to phytopathology.
Can. J. Bot. 51_:983-988, 1973.
410. Stoeckhardt, A. Utersuchungen uber de schaediliche Einwirkung
des huettenund Steinkohlenrauches auf das Wachstum der
Pflanzen, Inbesondere der Fichte und Tanne. Tharandt.
Forst. Jahrb. 21: 218-254, 1971.
7-182
-------
411. Stoklasa, J. Die Beschadigung der Vegetation curch Rauchgase
und Fabriksexhalationen. Urban and Schwartzenberg Verlag,
Berlin and Vienna, 1973. 487 pp.
412. Stone, L. L. and J. M Skelly. The growth of two forest tree
species adjacent to a periodic source of air pollutants.
Phytopathology 64_: 773-778.
413. Strojan, C. L. The impact of zinc smelter emissions on forest
litter arthropods. Oikos 31:41-46, 1978.
414. Swank, W. T., and J. E. Douglass. Streamflow greatly reduced
by converting deciduous hardwood stands to pine. Science
185: 857-859, 1974.
415. Swank, W. T., and G. S. Henderson. Atmospheric input of some
cations and anions to forest ecosystems in North Carolina
and Tennessee. Water Res. Res. 12_:541-546, 1976.
416. Temple, P. J. Dose-response of urban trees to sulfur dioxide.
J. Air Pollut. Control Assoc. 22_:271-274, 1972.
417. Terman, G. L. Atmospheric sulfur - the agronomic aspects.
Tech. Bull. 23, The Sulfur Institute. Washington, DC,
1978.
418. Thomas, M. D. Gas damage to plants. Ann. Rev. Plant Physiol.
1:293-322, 1951.
419. Thomas, M. D. The invisible injury theory of plant damage.
Pollut. Control Assoc. 5_:205-208, 1956.
420. Thomas, M. D., and R. H. Hendricks. Effect of air pollution
on plants JJT_ Air Pollution. World Health Organization
Monograph Ser. No. 46., Columbia University Press, New
York, 1951. pp. 233-278.
421. Thomas, M. D., and R. H. Hendricks. Effect of air pollution
on plants In: Air Pollution Handbook. PI. L. Magill et
al. eds., New York, 1956. pp. 9:1-44.
422. Thomas, M. D., and G. R. Hill, Jr. Absorption of sulfur
dioxide by alfalfa and its relation to lead injury.
Plant Physiol. 10^:291-307, 1935.
423. Thompson, L. K., S. S. Sidhu, and B. A. Roberts. Fluoride
accumulations in soil and vegetation in the vicinity of a
phosphorus plant. Environ. Pollut. 1*3:221-234, 1979.
424. Throneberry, G. 0., J. A. Booth, D. Kasunic, and H. McKinney.
Nitrogen and chlorophyll in crop plants exposed to sulfur
dioxide. Bull. N. M. Agric. Exp. Sta. , 1978. 9 pp.
7-183
-------
425. Till, A. R. Nutrient cycling in grazed pastures. IV- The
fate of sulfur-35 following its application to a small
area in a grazed pasture. Aust. J. Agric. Res. 22_:391-
400, 1971.
426. Till, A. R., and P. F. May. Nutrient cycling in grazed pastures
II. Further observations with S gypsum. Aust J.
Agric. Res. 21:253-260, 1970.
427. Ting, I. P-, and W. M- Dugger. Factors affecting ozone sensitivity
and susceptibility of cotton plants. J. Air Pollut.
Control Assoc. jj.:810-313, 1968.
428. Ting, I. P., M. L. Thompson, and W. M. Dugger. Leaf resistance
to water vapor transfer in succulent plants: effect of
thermoperiod. Am. J. Bot. 54_: 245-251, 1967-
429. Tingey, D. T., W. W. Heck, and R. A. Reinert. Effect of low
concentrations of ozone and sulfur dioxide on foliage,
growth, and yield of radish. J. Am. Soc. Hort. Sci.
915:369-371, 1971.
430. Tingey, D. T., and R. A. Reinert. Effect of ozone and sulfur
dioxide singly and in combination on plant growth.
Environ. Pollut. 1:117-125, 1975.
431. Tingey, D. T., R. A. Reinert, J. A. Dunning, and W. W. Heck.
Vegetation injury from the interaction of nitrogen dioxide
and sulfur dioxide. Phytopathology 61.: 1506-1511, 1971.
432. Tingey, D. T., R. A. Reinert, J. A. Dunning, and W. E. Heck.
Foliar injury responses of 11 plant species to ozone/
sulfur dioxide mixtures. Atmos. Environ. 2_: 201-208, 1973.
433. Tingey, D. T., R. A. Reinert, C. Wickliff and W. W. Heck.
Chronic ozone or sulfur dioxide exposures or both affect
the early vegetative growth of soybean. Can. J. Plant
Sci. 53_: 87 5-879, 1973.
434. Treshow, M. Environment and plant response. McGraw-Hill Book
Co., New York, 1970. 422 pp.
435. Treshow, M. Interactions of air pollutants and plant diseases.
ln_: Responses of Plants to Air Pollution. J. B. Mudd and
T. T. Kozlowski eds., Academic Press, New York, 1975.
pp. 307-334.
436. Treshow, M. Terrestrial plants and plant communities. J_n:
Principles of Ecotoxicology. G. C. Bulter ed., John
Wiley and Sons, New York, 1978. pp. 223-237.
7-184
-------
437. Tuerk, R., V. Wirth, and 0. L. Lange. C02-Gasvvechsel-Untersuchungen
zur S09-Resistenz yon Flechten. Oecologia 15:33-64,
1974. ^ ~~
438. Tyler, G. Heavy metals pollute nature, may reduce productivity.
Ambio 1:53-59, 1972.
439. Ulrich, A., and K. Ohki. potassium, jn.: Diagnostic Criteria
for Plants and Soils, H. D. Chapman, ed., University of
California, 1966. pp. 157-179.
440. U.S. Department of Health, Education, and Welfare. Air Quality
Criteria for Particulate Matter. PHS, EHS, Natl. Air
Pollut. Control Admin., Washington, DC. 1969.
441. U.S. Environmental Protection Agency. Mount Storm, West
Virginia -Gorman, Maryland, and Luke, Maryland - Keyser,
West Virginia Air Pollution Abatement Activity, 1971. 67
pp.
442. U.S. Environmental Protection Agency. Effects of Sulfur
Oxides in the Atmosphere on Vegetation, Report No. EPA-
R3-73-030. Natl. Environ. Res. Center, U.S. Environmental
Protection Agency, Raleigh, NC, 1973. 43 pp.
443. U.S. Environmental Protection Agency. The Bioenvironmental
Impact of Fine Particulates: A Critical Review and
Summary. USEPA/CERL Report, 1975. Mimeo, 49 pp.
444. U.S. Environmental Protection Agency. Diagnosing Vegetation
Injury Caused by Air Pollution. D. R. Hicks, ed., EPA
Cont. Pub. No. 68-02-1344, 1976.
445. U.S. Environmental Protection Agency. Airborne Particles.
Env. Health Eff. Series, Rep. No. EPA-600/1-77-053, 1977.
555 pp.
446. U.S. Environmental Protection Agency. National Air Quality,
Monitoring, and Emission Trends Report. Research Triangle
Park, NC 1977.
447- U.S. Environmental Protection Agency. Emission of Sulfur-
Bearing Compounds from Motor Vehicle and Aircraft Engines.
A Report to Congress. EMSL Report EPA-600/9-78-028,
1978. 437 pp.
448. Unsworth, M. H., P. V. Biscoe, and H. R. Pickney. Stomatal
response to sulfur dioxide. Nature 239_:458-459, 1972.
449. Unzicker, H. J., H. J. Jager, and L. Steubing. Influence of
S02 on von Pfanzen.) Agnew. Bot. 49_:131-139, 1975.
450. Ushijima, T., and T. Tazaki. The influence of sulfur dioxide
on the photosynthetic and transpiration rate in several
higher plants 1st Int. Clean Air Congr. Proc. 4^84-87,
1977.
7-135
-------
451 Van Haut, H. Die analyse von Schwefeldioxydwirkungen auf
Pflanzen im Laboratoriumsversuch. (Laboratory Experiments
on the Effect of S02 on Plants.) Stub 21:52-56, 1961.
452 Van Haut, H., and H. Stratmann. Farbtfelatlas uber Schwefeldioxid-
wirkugen and Pflanzen. (Color-Plate Atlas of the Effects
of Sulfur Dioxide on Plants.) Verlag W. Girardet, Essen,
West Germany, 1970. 206 pp.
453 Vanselow, A. P- Nickel. In.: Diagnostic Criteria for Plants
and Soil, H. D. Chapman, ed., University of California,
1966. pp. 302-309.
454. Vins, B., and R. Mrkva. The diameter increment losses of pine
stands as a result of injurious emissions. Acta Univ.
Agric-Brno Ser. C 42:(1):25-46, 1973.
455. Vogl, M., S. Bortitz, and H. Polster. Physiological and
biochemical contributions to research of fume damage.
6th report. Definitions of degrees of damage and forms of
resistance against the S0? Component of injurious fumes.
Biol. Zentralb. 84:763-777, 1965.
456. Wainwright, M. Sulfur-oxidizing micro-organisms on vegetation
and in soils exposed to atmospheric pollution. Environ.
Pollut. 17:167-174, 1978.
457. Wainwright, M. Distribution of sulfur oxidation products in
soils and on Acer pseudoplatanus L. growing close to
sources of atmospheric pollution. Environ. Pollut.
17_:153-160, 1978.
458. Wainwright, M. Microbial S-oxidation in soils exposed to
heavy atmospheric pollution. Soil Biol. Biochem. 11:95-
98, 1979. ~
459. Wakefield, N. G., and G. W. Barrett. Effects of positive and
negative nitrogen perturbations on an old-field ecosystem.
Midi. Nat. 101-159-169, 1979.
460. Ward, N. I., R. R. Broks, and R. D. Reeves. Effect of lead
from motor vehicle exhausts on trees along a major thorough-
fare in Palmerston North, New Zealand. Environ. Pollut.
6.:149-158, 1974.
461. Weber, D. E., R. A. Reinert, and K. R. Barker. The effects of
ozone and sulfur dioxide on selected species of plant
parasitic nematodes. Proc. Am. Phytopathol. Soc. 1:133,
1974. ~
462. Wedding, J. B., R. W. Carlson, J. J. Stukel, and E. A. Bazzaz.
Aerosol deposition on plant leaves. Water Soil Air
Pollut. 7_:555-561, 1977.
7-186
-------
463. Weinstein, L. H., D. C- McCune, A. L, Aluisio, and P. Van
Leuken. Effect of sulfur dioxide on the incidence and
severity of bean rust and early blight of tomato. Environ.
Pollut. 1:145-155, 1975.
464. Wellburn, A. R., 0. Majernick, and F. A. M. Wellburn. Effects
of S0? and N0?, polluted air on the ultrastructure of
chloroplasts. Environ. Pollut. 1:37-49, 1972.
465. Wellburn, A. R., T. M. Capron, H. S. Chan, and D. C. Horsman.
Biochemical effects of atmospheric pollutants on plants.
466. Wentzel, K. F. Gibt es immissionsfeste oder raucharte Baeume?
Forstarchiv 35_:49-51, 1964.
467. Wesely, M. L., and B. B. Hicks. Some factors that affect the
deposition rates of sulfur dioxide and similar gases on
vegetation. J. Air Pollut. Control. Assoc. 27_:1109-1116,
1979.
468. West, D. C., S. B. Mclaughlin, and H. H. Shugart. Simulated
forest response to chronic air pollution stress. J.
Environ. Qua!., in press, 1979.
469. Whelpdale, D. M., and R. W. Shaw. Sulfur dioxide removal by
turbulent transfer over grass, snow, and water surfaces.
Tellus 2^:196-205, 1974.
470. Whitby, K. T. The physical characteristics of sulfur aerosols.
Atmos. Environ. _12:135-160, 1978.
471. White, K. L. Synergistic inhibition of apparent photosynthesis
rate of alfalfa by combinations of sulfur dioxide and
nitrogen dioxide, M.S. Thesis, University of Utah, Salt
Lake City, UT, 1976.
472. White, K. L., A. C. Hill, and J. H. Bennett. Synergistic
inhibition of apparent photosynthesis rate of alfalfa by
combinations of sulfur dioxide and nitrogen dioxide.
Environ. Sci. Techno!. 8:574-576, 1974.
473. Wilhour, R. G./f &m^tf>fesponse of sele&tedismal!
&$/*&<*-> foliage cco-ps to sulfur d i oxide.71 tl.lT. Environmental
Protection Agency-&ERL Report, 19/8. -M4ffloo. <\ p-p
474. Williams, R. J. H.', M. M. Lloyd, and G. R. Ricks. Effects of
atmospheric pollution on deciduous woodland. I: Some
effects on leaves of Quercus petreaea (Mattuschka) Leibl.
Environ. Pollut. .2:57-68, 1971.
475. Winner, W. E., and J. D. Bewley. Terrestrial mosses as bioindicators
of SO- pollution stress. Synecological analysis and the
index of atmospheric purity. Oecologia 35^221-230, 1978.
7-187
-------
476. Winner, W. E., and J. D. Bewley. Contrasts between bryophyte
and vascular plant synecological responses in an S02-
stressed white pine association in central Alberta.
Oecologia 33_:311-325, 1978.
477 Winner, W. E., 0. D. Bewley, H. R. Krouse, and H. M. Brown.
Stable sulfur isotope analysis of S02 pollution Impact on
vegetation. Oecologia 36:351-361, 1978.
478.
Winner, W. E., and H. A. Mooney. Ecology of SCL resistance:
I. Effects of fumigations on gas exchange of deciduous
and evergreen shrubs. Oecologia .39:4-6, 1979.
479. Winner, W. E., and H. A. Mooney. Ecology of S02 resistance:
II. Photosynthetic changes of shrubs in relation to S02
absorption and stomatal behavior. Oecologia, in press,
1979.
480. Wirth, V., and B. Brinckmann. Statistical analysis of the
lichen vegetation of an avenue in Freiburg (Southwest
Germany), with regard to injurious anthropogenous influences.
Oecologia 28:87-101, 1977-
481. Witkamp, M., M. L. Frank, and J. L. Shoopman. Accumulation
and biota in a pioneer ecosystem of kudzu vine at Copperhill,
TN. J. Appl. Ecol. 3_:383-391, 1966.
482. Wodzinski, R. S., D. P. Labeda, and M. Alexander. Toxicity of
S02 and N02: selective inhibition and blue-green algae
by bisulfite and nitrite. J. Air Pollut. Control Assoc.
21:891-893, 1977.
483. Wolak, J. Studies on the industrioclimax in Poland. Mittl.
Forstl. Bundesuersuchsanst. Wien J92_:233-244, 1971.
(Translated from German)
484. Wood, C. W., Jr., and T. N. Nash III. Copper smelter effluent
effects on Sonoran desert vegetation. Ecology 57:1311-
1316, 1976. ~~
485. Woodmansee, R. G. Sulfur in grassland ecosystems. In:
Sulfur in the Environment. Missouri Botanical Garden,
St. Louis, MO, 1975. pp. 134-140.
486. Woodwell, G. M. Effects of pollution on the structure and
physiology of ecosystems. Science 168:429-433, 1970.
487- Woodwell, G. M. and R. H. Whittaker. Effects of chronic gamma
irradiation on plant communities. Rev. Biol. 43:42-55,
1968. ~~
488. Wright, H. E., Jr. Landscape development, forest fires, and
wilderness management. Science 186:487-494, 1974.
-------
489. Wu, L., and A. D. Bradshaw. Aerial pollution and the rapid
evolution of copper tolerance. Nature 238;167-169, 1972.
490. Yamazoe, F., and H. Mayumi. Vegetation injury from interaction
of mixed air pollutants. In: Proc. 4th Int. Clean Air
Congress, 1977. P. 1-30.
491. Yee-Meiler, D. Der Einfluss von kontinuierlichen, niedrigen
S02-begasungen auf den Phenolgehalt und die Phenoloxidase-
Aktivitat in Blattern einiger Waldbaumarten. (Influence
of continuous fumigation by low levels of S0? on the
phenolic contents and phenoloxidase activities in leaves
of forest trees.) Eur. J. For. Pathol. .8:14-20, 1978.
492. Yopp, J. H., W. E. Schmid, and R. W. Hoist. Determination of
maximum permissible levels of selected chemicals that
exert toxic effects on plants of economic importance in
Illinois. Illinois Inst. for Environ. Qual. NTIS PB-
237654, 1974. 272 pp.
493. Zahn, R. Uber den Einfluss verschiedener Umweltfaktoren auf
die Pflanzenempfindlich-keit gegenuber Schwefeldioxyd.
Z. Pflanzenkr. (Pflanzenpathol.) Pflanzenschutz 70:81-
95, 1963.
494. Zahn, R. Utersuchungen uber die Bedeutung Kontinuierlicher
and intermittierender Schwefeldioxideinwirkung fuer die
Pflanzenreaktion. (Invest!ations on plant reaction to
continuous and/or intermittent sulfur dioxide exposure.)
Stub. 23.:334-352, 1963.
o
495. Ziegler, I. The effect of SO, on the ability of ribulose-
1,5-disphosphate carboxyfase in insulated spinach chloroplasts
Planta (Berlin) 103:155-163, 1972.
496. Zimdahl, R. L. Entry and movement in vegetation of lead
derived from air and soil sources. J. Air Pollut. Control
Assoc. 26.: 655-660, 1976.
497. Zimmerman, P. W. Impurities in the air and their influence on
plant life. _In_: Proc. 1st Natl. Air Pollut. Symp, 1950.
pp. 135-141.
498. Zimmerman, P. W., and W. Crocker. Toxicity of air containing
sulfur dioxide gas. Contrib. Boyce Thompson Inst. 6^:445-
470, 1954.
7-189
-------
Note to Reader
Chapter 8: Acidic Precipitation
The story of acidic precipitation is an everchanging one. New infor-
mation concerning its far-reaching effects is forthcoming nearly every day.
The Environmental Protection Agency, therefore, is continually revising its
data base as new information becomes available. The International Conference
on the Ecological Impact of Acidic Precipitation, sponsored by the SNSF Projct
of the Agricultural Research Council of Norway, was held March 11-14, 1980 at
Sandjeford, Norway, to discuss the latest discoveries concerning the effects
of acidic precipitation at about the time the chapter that follows was being
completed. It was, therefore, not possible to incorporate the information
presented at the conference into the chapter. Several areas in the present
chapter which will receive expanded treatment in the next version due to new
information are: (1) problems associated with the liming of lakes, streams,
and forests; (2) the short-term beneficial effects of sulfur oxide deposition
on nitrogen deficient forest soils and the long-term detrimental effects; (3)
additional information on the role of aluminum in causing the death of fish;
(4) the detrimental effects of aluminum in the soil on root hairs of plants;
(5) the role of acidic precipitation in lowering the pH and increasing the
aluminum content of ground water.
The economic import of acidic precipitation as present in the chapter is
very preliminary. It is based on some early studies made by the State of
8-a
-------
New York. The Environmental Protection Agency is currently involved in a
study to determine as accurately as possible the cost of acidic precipitation
effects. EPA believes the costs will run much higher than those cited in the
present chapter. Swedish studies estimate the cost of liming their acidified
lakes, streams, forests, and soils would run from 50 to 100 million dollars.
8-b
-------
8. ACIDIC PRECIPITATION
8.1 INTRODUCTION
Acidic precipitation is a major environmental concern in many regions of
the United States, Canada, northern Europe, and Japan. It has caused measurable
damage to aquatic ecosystems in Scandanavia, eastern Canada, and the northeastern
United States. Acidic precipitation has, by acidifying lakes, induced the
extinction of fish, caused the breakdown of nutritional food webs, and reduced
life in lakes to a few acid tolerant species. Acidic precipitation, in addition,
has the potential for damaging national monuments and buildings made of stone,
for degrading natural terrestrial ecosystems, for impoverishing sensitive soils,
and for causing damage over the long-term (over several decades) to forest eco-
systems.
Precipitation, more specifically rain, has long been considered bene-
ficial to all life. Rain falling on forest, field, lake, and stream brings to
earth not only the water of life but also elements essential for the existence
of plants and animals. Has precipitation changed? How? Why is it acidic?
Precipitation acts as a scavenger, bringing to earth substances present
in the atmosphere. The composition of rain, therefore, depends on the substances
present in the atmosphere. Among the substances present in the atmosphere are
emissions from both natural and anthropogenic sources. On a global scale
natural emissions of sulfur oxides exceed man's contributions; however, man-made
emissions are localized in specific geographic areas, where they may be concen-
trated in the atmosphere or transported meteorologically to other areas downwind
(see Chapter 4).
8-1
-------
In an atmosphere relatively free of natural or man-made emissions of
oxides of sulfur and nitrogen, precipitation would be expected to have a pH of
5.6 due to carbon dioxide in the atmosphere dissolving in water vapor to form
carbonic acid. The chemistry of precipitation has changed, however, due
chiefly to the emission of large amounts of sulfur and nitrogen oxides being
released from the combustion of fossil fuels (particularly coal and oil). In
addition, precipitation is acidified by transformation products of other
gases, aerosols, and particulate matter from natural and man-made sources,
such as the smelting of ores and the use of nitrogen fertilizers of agricultural
and forest land.
Sulfur and nitrogen oxides are transformed in the atmosphere to sulfates
and nitrates. Sulfates and nitrates upon hydrolysis in the atmosphere con-
tribute hydrogen ions (H ). If hydrogen ions are present in significant
quantities, precipitation becomes acidic. The acidity of precipitation is a
reflection of the balance between the major cations and anions in precipi-
tation. It is essential that in addition to all the major anions and cations,
particularly H+, NH4+, N03, and S042, that K+, Na+, Ca+, Cl, C032~, and P043"
ions should also be measured. Currently, the acidity of precipitation in the
northeastern United States is between 4.0 and 5.0.
The ratio of sulfuric to nitric acids in precipitation varies from time
to time and place to place. In much of the eastern United States, the average
annual ratio of sulfuric to nitric acids is currently 2:1; however, nitric
acid is becoming progressively more important as a contributor of hydrogen
ions.
The tall stacks (some as high as 1200 ft.) from power plants have de-
creased local pollution problems but increased the widespread wet and dry
deposition of sulfur and nitrogen oxides by permitting them to be carried long
8-2
-------
distances by air streams. Analysis of air-mass movements and chemical transfor-
mations in the atmosphere indicates that acidic precipitation in one state or
region of the United States or Canada results in large part from emissions
which enter the atmosphere in other states or regions, often many hundreds of
miles from the original source.
Acidic precipitation is only one special feature of the general phenome-
non of atmospheric deposition. There is in addition to precipitation (wet
deposition) also dry deposition. The major anions and cations that are trans-
ferred into ecosystems via acidic precipitation (wet deposition) are also
present in the gases, aerosols, and particulate matter that are transferred
into ecosystems by dry deposition when it is not raining or snowing. It is,
therefore, impossible to distinguish chemically the biological effects of
acidic precipitation from the biological effects of dry deposition.
In addition to the direct wet and dry deposition of acidic substances
into ecosystems, some substances in ionic form (notably various complexes of
ammonium and sulfate ions), although chemically neutral or nearly so, are
acidifying in their effects when taken up by plants and animals. Thus, the
concept of "acidifying precipitation" must be added to the concept of "acid
precipitation".
Included in wet and dry deposition, besides the acidic substances, are
certain organic or inorganic substances which are potentially injurious to the
ecosystems into which they are introduced. Among the inorganic substances
are: manganese, zinc, copper, iron, boron, flourine, bromine, aluminum, lead,
iodine, nickel, cadmium, vanadium, mercury, and arsenic. The underlined
elements in the list above are essential micronutrients that are required by
plants in small amounts. However, at concentrations above the amount required,
8-3
-------
these same elements, can be toxic to plants and animals. The non-essential
elements can also be toxic to plants or animals when present in large amounts
or when their mobility and solubility is increased due to soil acidity. Also
the deposition of these metallic substances in precipitation can affect the
foliage and roots of plants and injure microorganisms or animals that may
ingest the plants. In addition, these substances can harm animals (including
man) which may drink water containing these elements as well as aquatic animals
(especially fish) that live in the water.
The increased deposition of acidic substances into aquatic ecosystems
has, as of 1979, caused hundreds of lakes in the Adirondack Mountain region of
New York State, certain lakes in northern Minnesota, and many hundreds of
lakes in various parts of southern Ontario and Quebec to show acid stress.
Reduction or extinction of fish and other plant and animal populations has
occurred. Lakes and streams in other regions of the United States and Canada
are also potentially vulnerable to stress by acidic precipitation. Damage or
injury to aquatic or terrestrial organisms is most likely to occur when a
particularly sensitive life form or life stage (one with a narrow range of
tolerance) developing in poorly buffered waters or soils coincides in time
and/or space with major episodic injections of acidic precipitation or other
injurious substance.
An example of a major episodic injection of acids and other soluble
substances occurs when these substances present in polluted snow are released
as polluted meltwater during warm periods in winter or early spring. The
release of pollutants can cause major and rapid changes in acidity and chemical
properties of stream and lake waters. Fish kills are a dramatic consequence
of such episodic injections into aquatic ecosystems.
8-4
-------
Equally dramatic long-term changes in aquatic ecosystems also occur from
the wet and dry deposition of acidic substances because the chemical compo-
sition of precipitation and dry deposition determine in part the chemical
composition of lake, stream, and ground waters. The terrestrial watershed
also plays a significant role as the chemical composition of precipitation is
modified by chemical and biological weathering and exchange processes which
take place as precipitation washes over vegetation, percolates through the
soil and interacts with the underlying bedrock of the drainage basin in which
the precipitation occurs. The situation is analogous to a gigantic, regional
scale titration with the lakes and streams acting as receiving vessels for
acidic additions from the atmosphere. The titration end point of each lake is
predetermined by its hydrology and the capacity of the soils in the drainage
basin to assimilate the incoming acid. If the soils and drainage basin can no
longer assimilate the incoming acids, the lake and stream waters are changed
from conditions that are favorable for fish and other aquatic organisms to
conditions that inhibit reproduction and/or recruitment of populations of fish
and other aquatic organisms, some of which are food for fish.
Studies indicate that at pH's between 6.0 and 5.0, reproduction of many
species of aquatic organisms is inhibited and at a pH below 5.0 populations of
many fresh-water fish become extinct. Interference with normal reproductive
processes in fish occurs not only because of acidity itself but also due to
increased concentrations of certain metallic cations, notably aluminum, which
become mobilized in acidified lakes and streams.
Terrestrial and aquatic ecosystems are so intimately linked that it is
unrealistic to consider the effects of acidic precipitation in aquatic ecosystems
without considering its effects on terrestrial vegetations, soils, and the
geology of the drainage basin.
8-5
-------
The dry deposition of toxic gases, aerosols, and participate matter causes
substantial damage to crops in certain regions of the United States. The
possible effects of acid deposition must be considered together with the
serious economic damage occurring to crops caused by sulfur dioxide, ozone,
oxides of nitrogen, fluoride, and hydrogen chloride.
Direct and indirect injury to crops and forests have been reported based
on laboratory, greenhouse, and field experiments in which simulated acidic
rains were used. The following biological effects were observed:
o Formation of necrotic lesions and spots on foliage.
o Accelerated erosion of waxes on leaf surfaces.
o Loss of nutrients due to leaching from exposed plant surfaces.
o Inhibition of nodulation of legumes leading to decreased nitrogen
fixation by symbiotic bacteria.
o Reduced yield of marketable crops.
o Reduced rates of leaf litter decomposition leading to decreased
mineralization of organically-bound nutrients.
Soils differ by orders of magnitude in their susceptibility to acidifi-
cation. Acidic additions are unlikely to damage calcareous (calcium carbonate)
soils, but metal deposition may. Soils with very low cation exchange capacities
are very susceptible to increased acidification. In addition, the conse-
quences of acidic additions to soils vary greatly, depending upon the rates ,
and recent history of acidic injections, the character of the vegetation,
natural rates of acid formation in the soil, and the physical-chemical pro-
perties of the parent material of the soil.
Acidic precipitation may indirectly influence plant productivity by
altering the supply and availability of soil nutrients. Increased additions
8-6
-------
of hydrogen ions may result in a gradual acidification of the soil. Soil
acidification increases leaching of plant nutrients such as calcium, magnesium,
potassium, iron, and manganese and increases the rate of weathering of most
minerals. It also makes phosphorous less available to plants. Acidification
also decreases the rate of many soil microbiological processes such as nitrogen
fixation and the breakdown of organic matter. Various processes important in
nutrient cycling and critical in most ecosystems are known to be inhibited by
increasing the soil acidity. Included among these processes are: nitrogen
fixation by Rhizobium bacteria on legumes and by the free-living Azotobacter;
mineralization of nitrogen from forest litter; nitrification of ammonium
compounds; and overall decay rates of forest floor litter.
Acidic precipitation increases the solubility and mobility of many cations
in the soil thus increasing the concentration of toxic metal cations such as
aluminum, manganese, and zinc in soil solutions. Solubility and mobility of
other heavy metals is also enhanced. These toxic or nutrients ions leached
from the soil are transferred into surface and ground waters from which they
may enter lakes or streams and drinking water. Plant nutrients leached in the
same way are lost to vegetation.
Large quantities of hydrogen ions are added to soils as acidic precipitation
and as a result of soil amendment and fertilization practices. Acidification
by these processes can be readily controlled through normal soil management
practices such as liming. Large areas of the United States, however, are not
cultivated and have soils that are poorly buffered. These soils are sus-
ceptible to further acidification. Many of these sour soils occur in forest
and wilderness areas. Some of these soils could be helped by the significant
quantities of plant nutrients, including nitrogen and sulfur that are being
8-7
-------
added to soil in precipitation and by dry deposition. In some ecosystems
these additions may be important in the overall nutrient budgets; however, the
additions are subject to the vagaries of wind and weather.
Though various specific biological effects of simulated acidic rain have
been demonstrated in controlled field and laboratory experiments, reliable
evidence of economic damage to agricultural crops, forests, and other natural
vegetation and to biological processes in soil by naturally occurring acidic
precipitation has been reported very rarely.
Acidic precipitation plays an important role in the deterioration of
stone buildings, cultural monuments, and a variety of materials. Stone has
traditionally been considered one of the most durable building materials used
by man. What is forgotten is that the structures built with stone which were
not durable have long since disappeared.
High acidity promotes corrosion because hydrogen ions act as a sink for
the electrons liberated during the critical corrosion process. Acidic preci-
pitation forms a layer of moisture on the surface of material and by adding
hydrogen and sulfate ions increases corrosion. Atmospheric sulfur compounds
react with the carbonates in limestone and dolomites, calcareous sandstone, and
mortars to form calcium sulfate. Blistering, scaling, and loss of surface
cohesion occurs, which in turn induces similar effects in neighboring materials
not in themselves subject to direct attack. Acid rain may also leach ions
from stonework just as acidic runoff and ground water leaches ions from soil
bedrock.
The discussion which follows is EPA's most up-to-date review of acidic
precipitation. Though the emphasis in this chapter is on the environmental
effects resulting from air pollution causing acidic precipitation, it should
8-8
-------
be noted that the substances which are transferred from the atmosphere onto
the earth when it is raining or snowing also come to earth as dry deposition
in the form of gases, aerosols, and participate matter. Because ecosystems are
subjected to both wet and dry deposition, it is impossible to attribute all of
the observed biological effects to acidic precipitation alone. Likewise,
since both sulfur and nitrogen oxides are involved in the formation of acidic
precipitation, it is necessary to look at the whole picture rather than attempting
to limit the effects to sulfur oxides, the principal subject of this document.
Chapter 7 emphasizes the effects of the dry deposition of sulfur oxides
and particulate matter on vegetation and ecosystems. The sources and emissions
of sulfur oxides are discussed in Chapter 4 and those of nitrogen oxides in
Air Quality Criteria for Oxides of Nitrogen. Chapter 6 discusses the trans-
formation, transport and removal of sulfur oxides. Ambient air concentrations
are discussed in Chapter 5.
8.2 EFFECTS OF ACIDIC PRECIPITATION
8.2.1 Ecosystems
The effects of acidic precipitation on individual organisms, populations,
communities and ecosystems can be better understood if the biological principles
which govern the responses of organisms to their environment are elucidated.
The discussion which follows outlines the principles which are mentioned in
more detail when the effects on specific organisms or ecosystems are discussed.
Climatic, physicochemical, or biological changes in the environment,
regardless of the source, affect the functioning of organisms and the eco-
system of which they are a part. Acidic precipitation, by changing the chemical
environment of a variety of organisms, has already caused measurable damage
to aquatic ecosystems and possesses the potential for causing injury to terrestrial
ecosystems.
8-9
-------
Organisms vary in their ability to withstand environmental changes. At
any moment in time an organism is the product of the interaction of its total
environmental history and its inherited genetic code. Organism-environment
relationships are governed by certain ecological principles. Three of these
which help to explain the effects of acidic precipitation are: (1) the principle
of limiting factors, (2) the principle of the holocoenotic (holistic) environ-
ment, and (3) the principle of trigger factors.
The ability of an organism to withstand injury from polluted air, weather
extremes, changes in the acidity of the environment, or other disturbances is
dependent on its "range of tolerance", that is, the range between too much or
too little, within which an organism can survive and function (also termed
"law of tolerance" (Figure 8-1)). Organisms vary in their susceptibility to
injury by polluted air, climate, or other disturbances due to their genetic
make up. The range of tolerance of organisms also varies depending on their
age, stage of growth, or growth form. Highly specialized organisms usually
have a narrow range of tolerance (or adaptability) and are either reduced in
numbers or eliminated by environmental changes. Limiting factors are, therefore,
factors which, when scarce or overabundant, limit the growth, reproduction,
and distribution of an organism. Acidic precipitation is such a factor since
it changes the acidity of the environment in which an organism exists.
If or when one limiting factor is removed, another immediately takes its
place. No barriers exist between the various environmental factors or between
an organism or biotic community and its environment. The environment is a
complex of interacting factors. If one factor is changed almost all will
change eventually. Organismal- or community-environmental relationships are
8-10
-------
ZONE OF
INTOLERANCE
LOWER LIMITS
OF TOLERANCE
ZONE OF
PHYSIOLOGICAL
STRESS
TOLERANCE RANGE
RANGE OF OPTIMUM
trrix LIMITS
BF 70lE«»HC£
ZONE OF
PHYSIOLOGICAL
STRESS
ZONE OF
INTOLERANCE
ORGANISMS
INFREQUENT
ORGANISMS
ABSENT
GREATEST
ABUNDANCE
ORGANISMS
INFREQUENT
ORGANISMS
ABSENT
LOW«-
•GRADIENT-
•+HIGH
Figure 8-1. Law of tolerance.
8-11
-------
holocoenotic, that is, "The ecosystem reacts as a whole. It is practically impossible
to wall off a single factor or organism in nature and control it at will
without affecting the rest of the ecosystem." In other words, everything in
our world, is related to everything else. "Any
change no matter how small is reflected in some way throughout the ecosystem:
no 'walls' have yet been discovered that prevent these interactions from
taking place.' The chain reaction caused by acidic precipitation in aquatic
ecosystems illustrates this principle.
Acidic precipitation may also be termed a "trigger factor". As indicated
above, the removal of a limiting factor usually creates a far-reaching chain
reaction in an ecosystem and occasionally may be the cause of one ecosystem
replacing another. The addition of a new substance to the environment, such
as acidic precipitation, may also be a trigger factor. Trigger factors may
act quickly or slowly and almost imperceptibly and require centuries before
changes are noted. The migration of the alewife (Alosa pseudoharengus) and
the sea lamprey (Pentromyzon marinus) into the Great Lakes through the Erie and
Welland Canals illustrates how slowly trigger factors may act. The Erie Canal
was opened in 1819 and the Welland in 1829. The migration of the alewife into
the lakes via the Erie Canal was not observed until 1873, while the presence of
the sea lamprey was first observed in Lake Ontario only in the 1880s. It was
first caught in 1921 in Lake Erie which it entered by the Welland Canal. The
invasion of both of these species of fish has had catastrophic effects on the
populations of native and economically important fish species.3 Regardless of
whether the trigger is a new factor which has been added or a limiting factor
which has been removed, life in the affected ecosystem is never again the same.
8-12
-------
Ecosystem diversity and structure are usually changed the most by a
limiting or trigger factor, such as acidic precipitation, due to the sensitive
species of flora and fauna being eliminated. In a forest ecosystem the selective
removal of the larger overstory plants favors plants of small stature.4'5 The
result is a shift from the complex forest community toward the less complex
hardy shrub and herb communities. The opening of the forest canopy changes
the environmental stresses on the forest floor causing differential survival
and, consequently, changed gene frequencies in subcanopy species.
Associated with the reduction in diversity and structure in an ecosystem
is a shortening of food chains, a reduction in the total nutrient inventory,
and a return to a simpler successional stage. ' In addition, in forest
ecosystems the pollutants often act as predisposing agents; thus, an increase
4 6
in the activity of insect pests and certain diseases may occur. ' Ecosystems
are usually subjected to a number of stresses at the same time, not a single
perturbation, so the effects of any particular stress will be exacerbated or
mitigated by interaction with the other stresses acting upon the ecosystem.
Plants, animals, and microorganisms usually do not live alone but exist
as populations living and interacting with each other and the environment.
Populations live together and interact as communities. Communities, because
of the interactions of their populations and of the individuals that comprise
them, respond to pollutant stress or other perturbations differently from
individuals. Man is an integral part of these communities and, as such, is
directly involved in the complex ecological interactions that occur within the
communities and within the ecosystem of which they are a part.
An ecosystem (e.g., the planet earth, a forest, a pond, lake or stream,
old field, or a fallen log) is an ecological unit comprised of living (biotic)
8-13
-------
and physical (abiotic) components through which the cycling of energy
and nutrients occurs (Table 8-1). The relationship between the various components
is a structured rather than a haphazard one. The biotic units are linked
together by functional interdependence, while the abiotic units comprise the
totality of physical factors and chemical substances that interact with the
biotic units. The processes occurring within the biotic and abiotic units and
1 8
the interactions between them are subject to environmental influences. '
Ecosystems tend to change with time, and it is usually possible to recognize
sequential changes in the types of populations within a community. Adaptation,
adjustment, and evolution are constantly taking place as the biotic component,
the populations, and communities of living organisms interact with the abiotic
components in the environment. The interaction and exchange of energy and
nutrients over time result in sequential or, in some cases, cyclic or
telescoped changes in populations and communities. The sequential replacement
of one population by another in a continual series, going from pioneer (first
and less diversified) populations to so-called climax (mature and more diversified)
1 Q
communities, is termed succession. ' Climax communities are structurally
complex and more or less stable, and are held in a steady state through the
operation of a particular combination of biotic and abiotic factors. Man
1 8
often is a factor as, for example, when his grazing cattle maintain a pasture. '
It is obvious once the cattle are removed that the pasture will change. New
plant and animal species will come in and there will be a transition toward a
different climax community. The disturbance or destruction of a climax community
or ecosystem results in its being returned to a simpler and less stable stage.4'
The simpler or successional stages are less stable, as the variety of species
necessary to develop the interspecific relationships and environmental
8-14
-------
TABLE 8-1. COMPONENTS OF THE ENVIRONMENT OF A TERRESTRIAL
ORGANISM, VEGETATION, OR BIOLOGICAL COMMUNITY
Source Domain
Physical Components
Biological Components
Universal Space
Universal "space-
time" gravity
Meteorites and
"space dust"
Primary cosmic
radiation particles
Solar radiation
electromagnetic
particles
Atmosphere
Secondary, tertiary,
etc. cosmic
radiation
Sky, reflected, and
thermal radiation
Radioactivity
including fallout
Atmospheric gases
Pressure
Wind
Water (vapor, cloud,
and precipitation)
Heat and temperature
Fire
Pollutants
Plants
Animals
Microorganisms
Man
DNA
Lithosphere
Rock and soil
particles
Minerals
Water
Radioactivity
Heat and
temperature
Gases
Topography (indirect)
Plants
Animals
Microorganisms
Man
DNA
Earth Mass
Gravity
For aquatic plants or community, interpose a liquid water course domain
between atmosphere and lithosphere of substitute it for thejitho-
sphere in deep water. This aquatic source domain will provide many of
the same components included in the atmosphere and lithosphere - but
not all. Table is adapted from Billings (1974).
8-15
-------
interactions necessary for stability are not present. Therefore, simple
communities, such as agricultural monocultures or natural communities which
are in transition, are more subject to change due to disturbances of biotic or
abiotic factors than are the structurally complex communities where intricate
energy and nutrient exchange relationships make the breaking down of the
system difficult. It is easier to keep the weeds out of a cornfield than out
of the pasture.
Woodwell has suggested that the possible effects of pollutants on
ecosystems fall into two categories: short-term and long-term effects. In
most terrestrial ecosystems, short-term effects are dominated by the conse-
quences of differential species sensitivity to environmental change. The
long-term effects are established by those same consequences, plus effects on
reproductive capacity and genetic characteristics. Existing studies indicate
that changes occurring within ecosystems, in response to pollution or other
disturbances, follow definite patterns that are similar even in different
ecosystems. It is, therefore, possible to predict broadly the basic biotic
3 4 7 9 10
responses to the disturbance of an ecosystem. ' ' ' ' These responses to
disturbances are:
1. Reduction in standing crop, i.e., the number of plants and animals
which make up the species structure of an ecosystem.
2. Inhibition of growth or reduction in productivity, i.e., reproduction,
3. Differential kill (removal of sensitive organisms at the species and
subspecies level).
4. Food chain disruption.
5. Successional setback, i.e., return to an earlier more simple stage.
6. Changes in nutrient cycling rates.
8-16
-------
Mature ecosystems, because of their greater diversity, are less suscepti-
ble to the disruption of their normal structure and function by any type of
perturbation. For example, a forest ecosystem in which the communities are
composed of many species would show less immediate damage by stress than
successional stages having only a few species. Even greater damage would be
anticipated in an agroecosystem, which may be considered the simplest of
successional stages, since often a single producer species is present.
Ecosystems are dynamic systems. Energy flow and nutrient cycling are
constantly occurring. The sources of energy are external to the ecosystem and
energy flow is unidirectional through the system. Nutrients, however, are
continuously cycled through the system. The concept of balance is associated
with the flow of energy and nutrients. Theoretically, it is possible for the
composition and cycling of energy and materials to remain essentially the same
for long periods of time so that a steady state is achieved. Very few ecosystems
actually ever reach this condition. Environmental changes, removal of limiting
factors, or the presence of trigger factors usually prevent an ecosystem from
achieving a steady state. It should be noted, however, that an ecosystem is
in delicate balance. Any change, natural or manmade, may lead to a result
I p O "I 1
that cannot be forseen or predicted. ' ' ' The following sections discuss
ecosystem changes resulting from acidification of the local environment.
8.2.2 Aquatic Ecosystems
The disappearance of natural fish populations from acidified freshwater
lakes and streams in southern Norway was first noted during the 1920's.
During the past 50 years, the problem has become more severe. The effect on
inland fisheries became serious during the 1940's and 1950's with the disappear-
ance of the brown trout (Salmo trutta L.) populations from an increasing
12
number of lakes in Stfrlandet (southern Norway). The cause of the
8-17
-------
acidification remained a mystery until the late 1950's as the increase in
acidity of lakes and streams could not be related to industrial, municipal, or
agricultural effluents, or to the draining of bogs and peatlands. Acidic
13
precipitation was postulated by Dannevig in 1959 as the cause of acidifica-
tion of freshwaters in southern Norway when data from the European Atmospheric
Chemistry Network in the late 1950's revealed that the precipitation falling
on southwestern Scandinavia was acidic with a pH <4.7. Acidic precipitation
12
was, therefore, indirectly the cause of fish having been eliminated.
Laboratory and field experiments have shown that acidification of lakes
and streams is the reason for fish disappearing. Many studies have shown that
12
the reproductive stages are most sensitive to changes in water chemistry.
Increased acidity in freshwater ecosystems is the trigger factor which
causes many changes to occur within the communities of organisms living there.
Most of the changes cause decreases in biological activity and limit nutrient
cycling. Decrease in biological activity is due to a decrease in numbers of
individuals in a number of groups of organisms. Disturbances occur at all
trophic (food) levels. Phytoplankton, zooplankton, bottom fauna, and a number
of other groups of organisms decrease, greatly affecting the variety of food
for fish and other animals. Shifts in plant communities occur. Higher plants
disappear, and mosses take their place. Shifts in plant communities influence
nutrient cycling and lead to a reduction in the activity of microorganisms
involved in decomposition. In addition to the direct results occurring
from acidification, mobilization of heavy metals often occurs. Pertinent
details of the effects are described in the following sections.
8-18
-------
8.2.3 Effects on Fish
The decline of fish populations in acidified lakes and streams has been
1 ? 14 1 fi 1R m 99 97 1Q
reported from Norway, ''' Sweden, 1D'^>" Canada, and the United
20
States. Surveys in southern Norway indicate that fish populations, especially
trout and salmon, have been affected by acidification in 20 percent of the
waters lying south of latitude 63°N. As mentioned previously, the disappear-
ance of fish was initially noted 50 years ago. However, there has been a
sharo increase in the rate of disappearance during the past 15 years, a period
that coincides with increases in fossil fuel combustion. While the salmon
catch for the entire country shows no decrease, records for 79 Norwegian
rivers since the late 1800's show that nine rivers in Stfrlandet declined
22 15 23
rapidly between 1885 and 1925. Similar changes have been observed in Sweden '
where it is estimated that 10,000 lakes have been acidified to a pH value less
than 6.0 and 5,000 below a pH of 5.0. The acidification of lakes and the loss
of fish in the Sudbury, Ontario, region have been well documented by Beamish
19 24
and his coworkers. ' In the northeastern United States, a survey in the
Adirondack Mountains of New York has revealed that 50 percent of the lakes
above 610 m elevation have pH values below 5.0, and that 90 percent of those
lakes are devoid of fish (Figure 8-2). A similar survey in the 1929 to 1937
period showed that only 4 percent of the same lakes had a pH <5 or were devoid
of fish (Figure 8-3).21 The State of New York has identified 170 lakes and
ponds in the Adirondack Park which have been acidified to a point where they
pr
no longer support viable sport fish populations. In Pennsylvania, 314
different bodies of water or locations within streams for which pH and
alkalinity data were available at intervals of at least one year were examined
to determine pH. Of these, 107 (34 percent) showed decreases in pH, alkalinity,
8-19
-------
«/> 70
a
u>
a>
1 1 NO FISH PRESENT
ES FISH PRESENT
Figure B-2. Frequency distribution of pH and fish
population status in Adirondack Mountain lakes
greater than 610 meters elevation. Fish population
status determined by survey gill netting during the
summer of 1975.21
20
10
CD
»-
m
10
197i>
1830
46
PH
I 1 NO »!Sn
E3 flSH PRESIN1
Figure 8-3. Frequency distri-
bution of pH fish population
status in 40 Adirondack lakes
greater than 610 meters eleva-
tion, surveyed during the
period 192^1937 and again
in 1975.21
8-20
-------
or both. The average decrease in pH was 0.4 units and in alkalinity it was
15.1 mg/1 as CaCO,. The average span of time between earliest and most recent
samples was 8.5 years. In seventy-one of the 107 sites showing pH decreases,
fish collection data indicate that in 41 cases (58 percent) there had been a
decrease in the number of fish species. a The current trend needs to be
documented with further data.
Because of their economic and recreational value, the death of fish in
acidified freshwater lakes and streams has been more thoroughly studied than
12 22
any other aspect of lake and stream acidification. Field surveys in Norway, '
15 34 21
Sweden, Canada, and the United States indicate that most fish species
disappear from acidified lakes when the pH drops below 5. Disappearance of
the fish is usually not due to massive fish kills, but due to reproductive
•10 pi pp p7_op
inhibition at a pH between 5 and 6 (Table 8-2). ' -L'"^' ^ Laboratory
experiments indicate that fish eggs and fry are first affected by acidic
18 18
water. Jensen and Snekvik report that the lower limit for normal reproduc-
tion for salmon is pH 5.0 to 5.5; for sea trout, pH 4.5 to 5.0; and for brown
trout, approximately pH 4.5.
32 12
Field surveys in New York State and Norway indicate that most fish
species disappear from acidified lakes when the pH drops below 5. Both inhibition
24 27 12 29 30
of gonad maturation ' and mortality of eggs and larvae ' ' can contribute
12 23
to reproductive failure in populations inhabiting acidified water. '
Reduction of egg deposition is due to disrupted spawning behavior or effects
on the reproductive physiology of maturing adults. Females failed to release
ova even though the ovaries were mature prior to the normal spawning period.
The ova became flaccid and watery, and the material from the ovaries appeared
8-21
-------
TABLE 8-2. SUMMARY OF EFFECTS OF pH CHANGES ON FISH
pH Effects
11.5 - 11.0 Lethal to all fish.
11.5 - 10.5 Lethal to salmonids; lethal to carp, tench, goldfish,
pike if prolonged.
10.5 - 10.0 Roach, salmonids survive short periods, but lethal
if prolonged.
10.0 - 9.5 Slowly lethal to salmonids.
9.5 - 9.0 Harmful to salmonids, perch if persistent.
9.0 - 6.5 Harmless to most fish.
6.5 - 6.0 Not harmful unless >100 ppm CCy
Significant reductions in egg hatchability and
growth in brook trout under continued exposure.
6.0 - 5.0 Not harmful unless >20 ppm C02, or high concentrations
of iron hydroxides present.
Rainbow trout do not occur. Small populations of
relatively few fish species found. Fathead
minnow spawning reduced. Molluscs rare.
Declines in a salmonid fishery can be expected.
High aluminum concentrations may be present in
certain waters causing fish toxicity.
5.0 - Tolerable lower limit for most fish.
5.0 - 4.5 Harmful to salmonid eggs and fry; harmful to common
carp; tolerable lower limit for most fish.
4.5 - 4.0 Harmful to salmonids, tench, bream, roach, goldfish,
common carp; resistance increases with age. Pike can
breed, but perch, bream, and roach cannot.
4.0 - 3.5 Lethal to salmonids. Roach, tench, perch; pike survive.
3.5 - 3.0 Toxic to most fish; some plants and invertebrates survive.
Modified and updated from ref. 34
8-22
-------
to be resorbed by the fish. This process was reported as the primary cause
for failure of fish populations to reproduce in the Sudbury area lakes in
Ontario, Canada, while studies conducted in Norway, Sweden, and the United
States suggest that eggs and newly hatched larvae are the most vulnerable
stages in the fish life history (see Table 8-2).21'31'35
The disappearance of fish from lakes and streams usually follows two
general patterns. One pattern results from the long-term decrease in the pH
33
of the water and the other when sudden short-term shifts in pH occur. Based
on field observations, prolonged acidity interferes with reproduction and
spawning so that changes in the structure of the population occur over time.
These changes include a decrease in population density and a shift in size and
19
age of the population to one consisting primarily of older and larger fish.
This pattern has been observed in Norway, ' Sweden, Canada ' and the
20 21
United States. ' The process is insidious, and effects on yield are often
delayed and not recognizable until the population is close to extinction.
This is true particularly for late maturing species with long lives. Large
increases in the mortality rate are not necessary to bring about population
extinction. Even small increases (5 to 50 percent) in mortality of fish eggs
21
and fry can decrease yield and bring about population extinction.
Acid shock, i.e., sudden short-term changes in pH, may cause fish mortality
Sudden decreases in pH cause severe physiological stress that may cause fish
21 22 33
kills at pH concentrations above those normally toxic to fish. ' ' Sudden
decreases in pH often occur in early spring when melting of the snowpack
releases the acid pollutants accumulated during the winter. In Norway the pH
in the Frafjord River ranged from 3.9 to 4.2 during a period of mild weather
in the winter of 1948. In the spring of 1975 a similar episode occurred in
8-23
-------
the Tovdal River.33 For salmonid fishes the yolk-stage, which appears to be
the most sensitive portion of the life cycle, occurs in the spring and is,
therefore, the stage which is likely to be subjected to the most acidic conditions.33
Species of fish vary in their ability to resist acidic shocks.
Physiologic stress resulting from osmoregulatory dysfunction (body salt
regulating mechanism) at low pH and low calcium concentration has been identified
12 21 23 37
as a primary source of mortality in dilute acidified waters. ' ' ' The
physiological mechanisms involved in mortality of fish in acidic waters may
vary in response to different levels of acidity and the presence of such
synergistic components as heavy metals and carbon dioxide. At the pH concentra-
tion of 4 to 5 usually encountered in the acidified lakes, disturbance of
1 c pi
normal ion and acid-base balance is the most likely cause of mortality. '
Laboratory experiments using several species of salmonid fish demonstrate that
in water with a low pH and salinity, sodium uptake is inhibited. Increasing
the salt concentration of water effectively lowers the lethal pH level. ' '
Field observations corroborate these results, in that fish populations tend to
1 fi ?l
disappear from the most dilute lakes first. ' The laboratory experiments
also explain why fish kills occur at pH concentrations higher than those
21 37
normally considered toxic to fish. ' In general, indications are that it
is interference with osmo- and ionic regulation mechanisms in fish which
causes mortality at the pH concentration range experienced when freshwater
35 37
bodies become acidified. '
Studies indicate that in the Adirondacks the mobilization of toxic metals,
particularly aluminum, is an additional factor which occurs at low pH values. '
Soil leaching and mineral weathering by acidic precipitation results in high
concentrations of dissolved aluminum in surface and ground waters. The increased
aluminum in water at concentrations of approximately 0.2 mg/liter or higher
8-24
-------
can lead to fish mortality. Increased transport of aluminum into aquatic
systems may affect phosphorus availability.
Biotic, physical, and chemical factors affect the tolerance of fish to
acidic waters. Biotic factors determining tolerance are: (a) species, (b)
strain, and (c) age and size of fish. Species, as well as different strains
of species, vary in their tolerance to low pH. A fairly well established
order of tolerance exists among salmonid species. Rainbow trout are most
sensitive, salmon are next, and brown and brook trout follow. Among other
European species, minnow and roach are most sensitive, while eel and pike are
most tolerant. The data available are based on experiments in which fish
have been maintained at a constant pH. Data are not available on species'
response to transient changes of pH.
Strains of the same species have shown different survival times. The
differences in some cases have been shown to be based on genetics; in others
they are based on differences in acclimative ability. Different strains of
the same species can spawn at different times of the year (± 1 or 2 months)
and thus miss the acidic episodes. Based on laboratory data, larger fish
are more tolerant than those at younger stages. The sensitivity of eggs also
varies with the species of fish. Table 8-3 lists some of the different
24
species of fish and the pH at which they are sensitive. Beamish noted that
fish populations in the acidic La Cloche Mountain lakes of Canada appeared to
be affected in the pH range of 4.5 to 6.0. The most sensitive species of fish
(smallmouth bass, walleye, and lake trout) were also the most desired sport
fish. Reproduction appeared to be the most sensitive major physiological
process critical to the survival of the species.
8-25
-------
TABLE 8-3. APPROXIMATE pH AT WHICH FISH
IN THE LA CLOCHE MOUNTAIN LAKES, CANADA, STOPPED REPRODUCTION
pH
6.0 + to 5.5
5.5 to 5.2
5.2 to 4.7
4.7 to 4.5
Species
Smallmouth bass
Micropterus dolomieui
Walleye
Stizostedion vitreum
Burbot
Lota lota
Lake trout
Salve! inus namaycush
Troutperch
Percopsis omiscomaycus
Brown Dull head
Ictalurus nebulosus
White sucker
Catostomus commersoni
Rock bass
Ambloplites rupestris
Lake herring
Coregonus artedii
Yellow perch
Perca flavescens
Lake chub
Couesius plumbeus
Family
Centrarchidae
Percidae
Gadidae
Salmonidae
Percopsidae
Ictaluridae
Catostomidae
Centrarchidae
Salmonidae
Percidae
Cyprinidae
From Ref. 24
8-26
-------
Temperature, season, and hydrology are physical factors influencing the
survival rate of fish. Laboratory bioassays indicate that the higher the
temperature, the shorter the survival time. Thus, acid episodes occurring at
different water temperatures may differ in toxicity. Survival of a species
has also been found to vary with the season. It has been suggested that
survival may be related to changes in the nutritional and physiological condition
35
(e.g., total salt content) of fish. Water quality exhibits considerable
temporal and spatial variations. Water quality in streams usually shows
greater fluctuations than lakes fed by the same streams. The chemistry of
surface waters over short time periods can be altered by meteorological conditions.
Chemical factors influencing fish survival include the ionic composition
of water, synergism or antagonism of toxic ions, and toxic organics. Calcium
has been shown to be important in enhancing fish survival at low pH. Physiologically
calcium reduces the permeability of the gill membrane to both sodium and
hydrogen ions. Magnesium does not prolong survival when present as the only
non-hydrogen cation; however, when it is added to water in which other ions
are present, it can have an ameliorating effect thus indicating that ions
behave differently when present alone or in combination with other ions.
Aluminum has been observed to be toxic at pH values as low as 4.0. The
solubility of aluminum increases below the pH of 4.0, but toxicity ceases due
to a change in the chemical form of aluminum. Gill damage has been said to be
a symptom of aluminum toxicity. However, it is not specific to aluminum, and
it is not clear whether it is the mechanism causing mortality. Manganese also
is released from minerals in acidic waters and is suspected of being toxic,
35
but its effect at low pH is yet unknown.
8-27
-------
Data on the toxicity of organic acids are not available at present. It
is thought that the presence of organic acids may be protective since they may
chelate some of the harmful ions (aluminum and manganese) and reduce the
effective concentrations. Calcium, however, could also be made less available.
The availability of ions to the physiological mechanisms of fish is more
important than their overall concentration.
8.2.4 Effects on Aquatic Ecosystem Dynamics
The elimination of fish populations is the most obvious biological effect
of the acidification of fresh water lakes and streams. Less obvious, but of
equal if not greater importance, are the effects which occur to other aquatic
organisms. Organisms at all trophic (feeding) levels are affected. Species
are reduced in number, alteration of the biomass (total amount of living
organic material) occurs, and primary production and decomposition are
impaired.15'16'21'24'23'40-42
8.2.4.1 Effect On Primary Production and Food Web--0rgam'sms in aquatic
habitats obtain their food (energy) directly or indirectly from solar energy.
Sunlight, carbon dioxide, and water are used by producers (phytoplankton,
other algae, mosses, and macrophytes) in the process of photosynthesis to form
sugars which are used by the plants or stored as starch. The stored energy may
be used by the plants or pass through the food chain or web. Energy in any
food chain or web passes through several trophic levels. (Transfer of energy,
usually as food, from one organism to another is termed a trophic level.)
Energy moves unidirectionally along two main pathways, the grazing food chain
and the detrital food chain. ' Green plants are the food base in the grazing
food chain in which plants are eaten by animals and animals by other animals,
etc. ' In the detrital food chain, the base is dead organic matter. Decom-
posers (bacteria, fungi, and some protozoa) use dead plant and animal matter
8-28
-------
as food and release minerals and other compounds back into the environment '
(see Figure 8-4). Energy flow and nutrient cycling are two processes which
occur in all ecosystems. Disruption of either of these processes illustrates
the holocoenotic nature of the ecosystem relationships by creating a chain
reaction which disrupts the whole ecosystem.
A change in pH causes changes to occur in the composition of the aquatic
44
plant communities involved in primary production. Kwiatkowski and Roff
noted in the lakes they studied in Ontario that the increased hydrogen ion
concentrations were progressively reflected in changes "in the species
composition, standing crop and production of the phytoplankton community." In
the highly acidic lakes, many of the phytoplankton species common in the more
neutral lakes were either eliminated or appeared only occasionally. Of the
lakes studied, the pH in Daoust Lake ranged from 6.32 to 7.15 while in Ruth
and Roy Lake it ranged from 4.05 to 4.6. In these lakes the species of
Chlorophyta (Green Algae) were reduced from 26 to 5, the Chrysophyta (Golden
Brown) from 22 to 5 species, and the Cyanophyta (Blue-Green) from 22 species to
10.44
The relative dominance of the algal flora also changed. The Chlorophyta
comprise between 40 and 50 percent of the total algae population and the
Cyanophyta approximately 30 percent in more neutral lakes. In acidified
lakes, the Chlorophyta population is reduced to 25 percent and the Cyanophyta
increased to 60 percent. In addition, as the H+ concentration increased, new
45
species of Chlorophyta appeared. The studies of Brock suggest that at pH 4.0
the Cyanophyta are reaching the lower limits of their growth range.
Primary productivity in lake water is generally thought to be limited by
the nutrients, phosphorus and nitrogen. In the lakes studied by Kwiatkowski
and Roff, the difference in nutrient levels were not sufficient to account for
8-29
-------
HERBIVORES
CARNIVORES
(C.l-IC.l-lC.l
PRODUCERS
DETRITUS
FEEDERS
DECOMPOSERS
Figure 8-4. Pathways among the producers and consumers of an ecosystem. 43
8-30
-------
the differences in productivity rates. Acidity appeared to be the limiting
factor. Primary productivity increased as the pH of the lakes approached
44
neutrality.
A study of the phytoplankton populations of 115 lakes in the west coast
region of Sweden supports the findings in Ontario. On the average, the
biomass of all algal groups was equally distributed at pH 6 or above. The
critical pH range appeared to lie between pH 5 and 6. Below 5.0 most of the
diatoms and green algal species disappear, but as the pH increases toward 5.8
there is an increase in number. The species composition of lakes with a pH
lower than 5 lacked diversity, and the size of the population was limited.
Similar phenomena were observed in a regional survey of 55 lakes in
southern Norway and in a study of four lakes in Ontario, Canada.
Phytoplankton biomass was low (<1 mg/liter) in these acidic lakes and was
correlated with the concentration of phosphorus which generally decreased at a
lower pH. In the Ontario lakes, phytoplankton biomass at pH values near 4.5
was only one-ninth to one-third as much as when the pH was near 6.5. Van
47
and Stokes, however, on the basis of experimental studies conducted by
varying the pH ui situ of an already acidic lake feel that phytoplankton
species number and community structure are more sensitive indicators of lake
acidification than phytoplankton community biomass. Further, their studies
suggest that continued addition of acid into the Canadian lakes with low
buffering capacities will ultimately result in major shifts in the
phytoplankton community structure of these lakes.
Diatoms (Chrysophyta) are important components of the phytoplankton. They
form assemblages of species which are broadly characteristic of the aquatic
environment in which they are growing; therefore, changes in water quality
8-31
-------
parameters, such as pH, can be investigated by analyzing diatom communities. 6
Samples of periphytic diatoms collected at seven locations in Norway in 1949
were compared with samples collected from the same sites in 1975. Qualitatively
the species were similar; however, changes had occurred in the proportions of
the various species present. A shift toward the more acid tolerant species
had occurred.
In all of the lakes investigated, the species composition of the phyto-
plankton was less diverse and reduced in population size in acidic lakes when
compared with neutral oligotrophic lakes and a reduction in primary production
usually resulted.
Acidification of lakes also reduces the species diversity of the macrophyte
community and reduces productivity. Studies of the succession of macrophyte
communities in six lakes in Sweden indicate that in 5 of the 6 lakes Lobelia
40 42
Isoetes communities were being replaced by Sphagnum. ' In the most acidic
lakes (pH 4.5), the Sphagnum covers approximately 70 to 80 percent of the lake
bottom at the 0 to 2 m depth. In the least acidic lake (pH 5.5), coverage is
42
approximately 50 percent. The rate of Sphagnum invasion has been greatest
in the shaded and sheltered areas of the lake and at a depth of 4 to 6 m. The
abundance of Sphagnum mats in the different lakes is positively correlated
with the lowering of the pH. The consequences of the Sphagnum occupying ever
larger areas of the lake bottoms are that several base ions (e.g., Ca++)
necessary for biological production are bound to the mass tissue due to its
strong ion exchange capacity and are, therefore, not available to other organisms,
There is also a deterioration of the benthic habitat because moss is a very
poor substrate for bottom fauna. Under these conditions two filamentous
algae, Mougeotia (a Green alga) and Batrochospermum (a Red alga), in addition
8-32
-------
to Sphagnum, become important components of the benthic communities. In Lake
Oggevatn, a clear-water lake in southern Norway with a pH of 4.6, not only is
Sphagnum beginning to choke out Lobelia dortmana and Isoetes lacustris, but
41
these macrophytes have been observed to be festooned with filamentous algae.
Experimental studies by Leivestad et al. support the findings of Grahn
41 42
et al. and Grahn as discussed above. Sediment cores containing Lobelia
dortmanna L. were incubated at three different pH concentrations. The rate of
growth was less at pH 4.0 when compared to the higher pH values and flowering
time was delayed. Mougeotia spp. began to grow upon the Lobelia after 30 to
40 days at pH 4.O.16
Heavy growths of filamentous algae and mosses not only occur in acidified
lakes, but also have been reported in Norwegian streams affected by acidification
In experiments conducted in artificial stream channels in which water and
naturally seeded algae from an acidified brook (pH 4.3 to 5.5) were used,
increasing the acidity to a pH of 4 through the addition of sulfuric acid led
to an increased accumulation of algae, when compared with that in an unmodified
40 48
control. ' The flora was dominated by Binuclearia tatrana, Mougeotia spp.,
Eunotia lunaris, Tabellaria flocculosa, and Dinobryon spp., each accounting
40
for at least 20 percent of the flora at one time or another.
Root systems of higher plants are important in supplying oxygen to lake
sediments. A reduction in oxygen supply due to reduction in viability of
macrophytes could affect the decomposer organisms in the sediments.
Simplification of the vegetational communities in lakes and streams
involved in primary production reduces the variety of food available to the
next trophic level and therefore reduces energy flow within the ecosystem.
Changes in plant communities also cause a reduction in nutrient supply. A
reduction in both energy flow and nutrient supply limits the number of organisms
which can exist within that system.
8-33
-------
8.2.4.2 Effects On Decomposition—Acidification of lakes reduces microbial
activity causing a reduction of the processes of decomposition and an
accumulation of organic matter in aquatic ecosystems. An abnormal
accumulation of coarse organic matter (detritus) was observed on the bottoms
of six Swedish lakes where a decrease in pH by 1.4 to 1.7 units occurred during
the last 30 to 40 years. Layers of leaves and the remains of Sphagnum and
41
other macrophytes covered large areas of the lake bottoms. In Cardsjon, 85
percent of the lake bottom in the zone 0-2 m deep was covered with a thick
felt of fungus. Bacterial activity had apparently decreased and the minerali-
zation of organic matter was being accomplished by fungi at a very slow rate.
Liming raised the pH of the lake and caused the rapid decomposition of the
organic litter and a great reduction in the fungal felt, thus indicating that
bacterial activity had been inhibited at a low pH. ' A similar
neutralization of acidified lakes in Canada resulted in a significant increase
in aerobic heterotrophic bacteria in the water. Results from field and
laboratory experiments with litterbags in Norwegian lakes indicated reduced
40
decomposition of leaves in acidic water. In laboratory experiments con-
ducted at pH 6 and pH 4, decomposition of the leaves was significantly higher
at pH 6 after 1 year of exposure. Similar results were obtained when experi-
ments were conducted in lakes and brooks.
The organic matter in lakes is either produced there through the process
of photosynthesis (autochthonous) or enters from outside the lake dissolved in
rain, via wind or streams flowing into the lake (allochthonous). The relative
importance of each of the sources varies greatly from lake to lake.38'39
Organic litter from land sources (allochthonous detritus) is an important
source of energy for bottom-dwelling invertebrates. In fact, detritus plays a
8-34
-------
15 16 40-42 44 48-51
centra] role in the energetics of lake ecosystems. ' ' ' ' ' The
metabolism of detrital organic matter is an integral part of the complex
carbon cycles that dominate both the structure and function of aquatic ecosystems
and provide, according to Wetzel, a fundamental stability to the system.
Detritus in aquatic ecosystems may be defined as nonliving particulate (>0.45
urn particle diameter) organic matter together with the associated microbiota
52 53
(e.g., fungi, bacteria, protozoa, and other microinvertebrates). ' Organic
52
matter smaller than 0.45 urn is classified by Boling et al. as dissolved
52
organic matter. The biochemical transformations of particulate and dissolved
organic matter via microbial metabolism are fundamental to the dynamics of
nutrient cycling and energy flux. The trophic relationships within lake
systems are almost entirely dependent on detrital structure. A generalized
scheme of food relationships in a lake is shown in Figure 8-5.
From Figure 8-5, it may be noted that bacteria are central to the food
relationships in a lake. Experiments have demonstrated that a shift in the
populations of decomposer organisms from bacteria to fungi occurs with a
lowering of the pH. ' Accompanying the shift in populations was a decrease
40
in the zooflagellate fauna. In addition, laboratory studies have shown the
inhibition of biochemical processes as well as a decrease in the total cell
count and species number of ciliate protozoa. '
Interference with nutrient cycling through the disruption of the detrital
trophic structure is a major consequence of changes occurring in microdecomposer
40
populations brought about by acidification. Accumulation of organic litter
and the formation of extensive mats of fungal hyphae as observed in Swedish
lakes ' causes the sealing off of mineral sediments from interaction with
the overlying water, and holds organically bound nutrients that would otherwise
8-35
-------
RADIATION
OUTION
fOMOWIIDS (MACROPHYTES)
Figure 8-5. Generalized scheme of food relationships in a lake. Efficiency in utilization
of food increases in the higher consumer levels.43
8-36
-------
41
become available if normal decomposition occurred. The reduction in nutrient
availability can be expected to have a negative feedback effect on the micro-
organisms, further inhibiting their activities. The reduction of nutrient
supplies to the water column from the sediments, because of the physical
covering, and from reduced mineralization of organic materials in the water
itself, will lead to reduced phytoplankton productivity.
Reduction of microdecomposer activities can have a direct effect on
invertebrates. Although some benthic invertebrates appear to feed directly on
the allochtonous detritus material, it seems that "conditioned" material (that
colonized by microorganisms) is preferred and that the nutritive value of the
52
detritus is highly increased by the conditioning process.
Bacteria and detrital organic matter are a source of food for filter-
feeding zooplankton. An inhibition of the microbiota or a reduction in
microbial decomposition processes has a direct impact on the non-predatory
detrital pathways and on animal communities in lakes.
Invertebrate communities are affected by acidification of freshwater
bodies. ' ' Surveys at many sites in Norway, Sweden, and North America
have shown that lakes and streams affected by acidic precipitation have fewer
33 46 49 54
species of benthic invertebrates than waters with a higher pH. ' ' '
Zooplankton analyzed from net samples collected from 84 lakes in Sweden
showed that acidification caused limitation of many species and led to simpli-
fication of zooplankton communities. Crustacean zooplankton were sampled in
57 lakes during a Norwegian lake survey in 1974 and the number of species
observed was found to be related to the pH (see Figure 8-6). The distributions
and associations of crustacean zooplankton in 47 lakes of a region of Ontario
affected by acid precipitation were strongly related to the pH and to the
8-37
-------
u
$ 3
Z 2
z
HfTEftVAL
WUMiCHO* LAfttl
Figure 8-6. The number of species of crustacean zooplankton observed in 57 lakes during a
synoptic survey of lakes in southern Norway.40
8-38
-------
the number of fish species in the lakes. However, fish and zooplankton were
each correlated with the same limnologic variables, especially pH. As
acidity increases, the complexity of zooplankton communities decreases.
Sprules found that many species of zooplankton did not occur below a pH of
5. At a pH of 5 an abrupt change from complex to simple zooplankton communities
occurred. Lakes with a pH >5 had 9 to 16 zooplankton species, while lakes
with a pH <5 had fewer than 7 species. In some lakes only a single species
was found. Reduced diversity in zooplankton communities affects the food
supply, feeding habits of consumer populations, and thus causes changes in the
community structure of organisms dependent on the zooplankton as a food source.
Gastropods are also adversly affected by acidic waters. In 832 Norwegian
lakes, no snails were found where the pH was below 5.2; snails were rare at a
pH of 5.2 to 5.8, and they occurred less frequently at a pH of 5.8 to 6.6 than
in more neutral or alkaline water. ' The amphipod Gammarus lacustris, an
important element in the diet of trout in Norwegian lakes where it occurs, is
not found in lakes with a pH less than 6.0. ' ' Experimental investi-
gations have shown that the adults of this species cannot tolerate 2 days of
exposure to a pH of 5.0 ' (see Figure 8-7). Eggs were reared in water at 6
different pH levels ranging from 4.0 to 6.8. Below a pH of 5.5 a majority of
the animals died within 48 hours. The short-term acidification which often
occurs during the spring melt of snow could eliminate these species from small
lakes.
In the River Duddon in England, acid from precipitation is the overriding
factor that prevents permanent colonization of the upper acidified reaches of
the river by a number of species of benthic invertebrates, primarily herbi-
vores.59 In the more acidic tributaries (pH <5.7), the epiphytic algal
8-39
-------
100
10
40
Figure 8-7. Cumulative mortality of Gammarus lacustris adults at several pH levels.
8-40
-------
flora was reduced (in contrast with increases noted in Norway), and leaf
litter decomposition was retarded. The food supply of the herbivores was
apparently decreased, and this may have played a role in the simplification of
the benthic fauna.
As mentioned previously, macrophyte communities of Lobelia and Isoetes in
41 42
some Swedish and Norwegian lakes ' are heavily overgrown with filamentous
algae and are being choked out by dense mats of Sphagnum. Under these con-
ditions, benthic invertebrate populations will be depleted by starvation,
evacuation, or extinction due to the loss of preferred habitat. Chironomids
and other benthic invertebrates will, in many situations, be affected by
altered decomposition cycles and variations in available foods caused by
increased acidification.
The tolerance of aquatic invertebrates to low pH varies during their life
cycles. Adult insects seem to be particularly sensitive at emergence. Broadly
speaking, the percentage of aquatic insects which emerge successfully decreases
as the pH of the water decreases. Bell, in studies with Epimeroptera
found emergence patterns to be affected at pH of 5.3 to 5.5 for extended
periods of time (greater than 30 days). Trichoptera, however, are very tolerant
of low pH. In general, aquatic insects differ markedly in pH tolerance, but
based on available data, a value of pH 5.5 or higher is necessary for 50
percent successful emergence.
Many species of aquatic insects emerge early in the spring through cracks
in the ice and snow cover. Because the spring meltwater is often contaminated
by atmospheric pollutants, these early emerging insects are in many cases
exposed to the least desirable conditions.
8-41
-------
Damage to invertebrate communities influences other components of food
chains. Benthic invertebrates assist with the essential function of removing
dead organic material. In experiments in which litterbags were used, leaf
decomposition by invertebrates was much greater at a higher pH than at a low
pH.^ The accumulation of attached algae in acidified lakes and streams may
result from a reduction in the number of grazing benthic invertebrates.
In unstressed lake ecosystems, a continuous emergence of different insect
species is available to predators from spring to autumn. In acid-stressed
ecosystems the variety of prey is reduced, and periods may be expected to
occur in which the amount of prey available to fish (and waterfowl) is diminished.
8.2.4.3 Effects On Vertebrates Other Than Fish—Amphibians may be the vertebrate
animals most directly affected by acidic precipitation. Amphibians' reproductive
habits make them susceptible to changes in pH of the ponds which they lay
their eggs. Frogs, toads, and approximately half of the terrestrial salamanders
in the United States lay eggs in ponds. Not only do these vertebrates breed
in water, but many species breed in ephemeral pools. These temporary pools
are usually completely dry during some period of the year and are refilled by
rain or snow shortly before the amphibians enter them to lay their eggs.
These pools depend on rain, drainage water, or snow melt to fill them. Because
these pools are small and collect drainage from a small area, and because no
buffering occurs since they are filled before deciduous trees have sprouted
leaves, the acidity of the water in the pools is strongly influenced by the pH
of the precipitation that fills them.65
Frog embryos have observed to develop abnormally when the pH range is
between 3.7-4.6. A pH of <4.0 is usually lethal.66
8-42
-------
Spotted salamander reproduction is impaired by an increase in the acidity
of the breeding pools. Rough and Wilson, in a study of the effects of pH on
salamanders, observed that spotted and Jefferson salamanders tolerated pH
values of 5 to 10 and 4 to 6, respectively. Young hatched best when the pH
range was 7 to 9 for the spotted salamander and 5 to 6 for the Jefferson's. A
pH lower than 6.0 can inhibit the development and increase the egg mortality
of spotted salamanders. Based on the data available, it appears that in
ro
amphibians, as in fish, a lowering of the pH first affects reproduction.
Frog populations in Tranevatten, a lake near Gothenberg, Sweden, acidified
69
by acidic precipitation were investigated. The lake has a pH ranging from
4.0 to 4.5. All fish have disappeared, and frogs belonging to the species
Rana temporaria and Bufo bufo are being eliminated. At the time of the study
(1977) only adult frogs 8 to 10 years old were found. Many egg masses of Rana
temporaria were observed in 1974, but few were found in 1977, and the few
larvae observed at that time died.
Frogs and salamanders are important predators on invertebrates, such as
The}
67
38
mosquitos and other pest species, in pools, puddles and lakes. They also are
themselves important prey for high trophic levels in an ecosystem.
The elimination of fish and vegetation from lakes by acidification will
have an indirect effect on a variety of vertebrates. Species of birds, e.g.,
the bald eagle, loon and osprey, and fish-eating mammals such as mink and
otter will be affected. It has been estimated that 70 percent of the Canadian
population of the common loon and hooded merganser and 50 percent of the range
of the bald eagle lies within the affected area. Dabbling ducks which feed on
vegetation also will be affected. In fact, any animals which depend on aquatic
organisms (plant or animal) for a portion of their food will be affected.
8-43
-------
Increasing acidity in freshwater habitats results in shifts in species, popula-
tions, and communities. Virtually all trophic levels are affected.
A summary of the changes which are likely to occur in aquatic biotia with
decreasing pH is listed in Table 8-4 while a summary of the effects of decreasing
pH on aquatic organisms is listed in Table 8-5.
8.2.4.4 Water Chemistry—The discussion in the previous section suggests that
the increasing acidity of freshwater lakes and streams appears to be the chief
environmental factor stressing aquatic ecosystems in certain regions of the
United States,20'21'74 Canada,19'24 Norway,12'14'18 and Sweden.15'23'33 The
pH appears to be the limiting factor which has triggered the major ecological
changes that have taken place.
Wide variations in relative acidity and alkalinity occur in natural
waters not only in the amount of dissolved materials producing the acidity or
alkalinity but also in actual pH values. Dilute concentrations of alkalines
and alkaline earth compounds of bicarbonates, carbonates, sulfates, and chlorides
dominate the ionic composition of fresh waters. The concentrations of four
major cations, Ca , Mg , Na , K and four major anions HC03", C03~, SO." and
Cl , usually constitute the total ionic salinity of water. Ionized components
of nitrogen (N), phosphorus (P), iron (Fe), and numerous minor elements are of
great biological importance, but from the standpoint of the chemical composition
of water, their concentrations are not as important.51 Salinity is the chemical
term for the ionic composition expressed in mg/1 or mg/1, which units are
essentially equivalent as mass or volume in dilute solutions. The chemical
composition of open lakes with an outlet is governed largely by the composition
of influents from precipitation and the drainage basin.51
8-44
-------
TABLE 8-4. CHANGES IN AQUATIC BIOTA LIKELY TO OCCUR WITH INCREASING ACIDITY
1. Bacterial decomposition is reduced and fungi dominate saprotrophic
communities. Organic debris accumulates rapidly.
2. The ciliate fauna is greatly inhibited.
3. Nutrient salts are taken up by plants tolerant of low pH (mosses, fila-
mentous algae) and by fungi. Thick mats of these materials may develop
which inhibit sediment-to-water nutrient exchange and choke out other
aquatic plants.
4. Phytoplankton species diversity, biomass, and production are reduced.
5. Zooplankton and benthic invertebrate species diversity and biomass are
reduced. Remaining benthic fauna consists of tubificids and Chironomus
(midge) larvae in the sediments. Some tolerant species of stone flies
and mayflies persist as does the alderfly. Air-breathing bugs (water-
boatman, backswimmer, water strider) may become abundant.
6. Fish populations are reduced or eliminated.
7. Changes in populations and communities occur at virtually all trophic
levels.
From reference 38
8-45
-------
TABLE 8-5. SUMMARY OF EFFECTS ON AQUATIC ORGANISMS WITH DECREASING pH
8.0-6.0
6.0-5.5
5.5-5.0
5.0-4.5
4.5 and
below
Long-term changes of less than 0.5 pH units in the range 8.0 to
6.0 are likely to alter the biotic composition of freshwaters to
some degree. The significance of these slight changes is, however,
not great.
A decrease of 0.5 to 1.0 pH units in the range 8.0 to 6.0 may cause
detectable alterations in community composition. Productivity of
competing organisms will vary. Some species will be eliminated.
Decreasing pH from 6.0 to 5.5 will cause a reduction in species
numbers and, among remaining species, significant alterations in
ability to withstand stress. Reproduction of some salamander
species is impaired.
Below pH 5.5, numbers and diversity of species will be reduced.
Many species will be eliminated. Crustacian zooplankton, phy-
toplankton, molluscs, amphipods, most mayfly species, and many
stone fly species will begin to drop out. In contrast, several
pH-tolerant invertebrates will become abundant, especially the
air-breathing forms (e.g., Gyrinidae, Notonectidae, Corixidae),
those with tough cuticles which prevent ion losses (e.g.,
Si all's lutaria), and some forms which live within the sediments
(Oligochaeta, Chiromomidae, and Tubificidae). Overall, inver-
tebrate biomass will be greatly reduced.
Below pH 5.0, decomposition of organic detritus will be severely
impaired. Autochthonous and allochthonous debris will accumulate
rapidly. Most fish species will be eliminated.
Below pH 4.5, all of
and all fish will be
species.
the above changes will be greatly exacerbated,
eliminated. Lower limit for many algal
Modified from reference.
38
8-46
-------
Soft waters contain low concentrations of salinity and are usually de-
rived from drainage of acidic igneous rocks while hard waters contain large
concentrations of alkaline earths derived from the drainage of calcareous
deposits.
The major ion chemistry of acid lakes has been studied in southern
Norway, the west coast and west-central regions of Sweden, the La Cloche
24 73
Mountains of southeastern Ontario, and Sudbury, Ontario, Canada. The
data obtained in these studies as well as data from unacidified lakes in
west-central Norway and the Experimental Lakes Area of northwestern Ontario,
74
Canada, are listed in Table 8-6. Data from these indicate that the un-
affected soft-water lakes are calcium-magnesium bicarbonate waters while the
water in acid lakes is dominated by hydrogen-calcium-magnesium sulfate.
Sulfate in these lakes comes from man-made sources and seawater. The sul-
fate coming from seawater can be estimated, if it is assumed that all of the
chloride comes from seawater and that the amount of sulfate attributable to
sea salts is proportional to the sulfate/chloride ratio in seawater. The
contribution of saltwater to the concentration of other ions can also be
estimated in a similar way. Because of their proximity to the ocean, coastal
lakes receive more ions from sea spray than inland lakes.
In acidified lakes sulfate replaces bicarbonate as the major
anion. ' ' Since the bicarbonate lost in acidified lakes has been re-
placed by an equivalent amount of sulfate, the concentration of excess sulfate
serves as an index of the amount of acidification that has taken place. The
pH of natural water is governed to a large extent by the interaction of
8-47
-------
TABLE 0-6 CHEMICAL COMPOSITION (MEAN t STANDARD DEVIATION) OF ACID LAKES (pH 4.8) LESS s w = CONCENTRATIONS AFTER SUBTRACING THE SEAWATER
CONTRIBUTION ACCORDING TO THE PROCEDURE EXPLAINED IN THE TEXT
CO
1
-p>
co
Region
I. LAKES IN ACID AREAS
Scandinavia
Southernmost
Norway
Westcoast
Sweden
West-central
Sweden
North America
La Cloche Mtns,
Ontario
Sudbury, Ontario
No. of
lakes
Measured 26
Less s w
Measured 12
Less s w
Measured 6
Less f v
Measured 4
Less s w
Measured 4
Less s v
uS/cn
at 20»C
27110
72«
47123
3818
120140
H (pH)
18111 (4.76)
18
43« (4.37«)
43
22115 (4.66)
22
2019 (4.7)
20
3615 (4.5)
36
Na
70140
9
330
-50
1651120
20
2614
9
100130
50
K
513
4
20
13
1518
12
1013
10
40110
40
Ca
56135
50
-
75110
70
150125
150
4501180
450
Mg
41116
25
-
80140
50
7518
65
3101120
300
M*q/l
HCOj
11126
11
0
0
-
-
0
0
812
8
HCI
711 45
0
440
0
170190
0
2216
0
50120"
0
SO,
100133
92
200
155
200170
180
290140
290
800*290
800
NO,
412
4
B
8
1914
19
-
-
-
-
I cations
189
106
673
-
360
175
280
255
9*0
880
I anlons
186
107
648
-
390
200
310
290
850
800
Reference
71
72
41
24
74
II. LAKES IN UNAFFECTED AREAS
Scandinavia
West-central
Norway
North Anerlca
Experimental Lakes
Area, Ontario
Measured 23
Less t w
1313
612 (S.2)
6
50120
9
Measured 40 19
Less s H
0.2-2 (5.6-6.7) 40
0.2-2 4
311
3
10
10
1819
16
80
80
1615
7
75
65
1318
13
60
60
46121
0
40
0
3318
30
60
55
512
5
93
41
200
160
97
48
160
120
71
74
•Data for 112 lakes
•'Measured after chealcal treatment of the lakes
From reference 75, Wright and Gjessing, 1976.
-------
H ions resulting from the dissociation of H?CO, and from OH ions that result
24
from the hydrolysis of bicarbonate. Beamish noted that the high sulfate
concentrations in the lakes were found in association with low pH and by
balancing anions and cations, it can be demonstrated that part of the sulfate
ion is balanced with the H ion, indicating the low pH results from the presence
of HpSO^. Comparison of the major ions found in four of the acidified lakes
in Ontario with unacidified lakes indicated that, except for H and sulfate
24 75
ions, the ionic compositon was similar. Wright and Gjessing also noted
that in lakes with a low pH (<5) sulfate is the major anion, while in lakes
with a pH >5 bicarbonate is the major ion.
8.2.4.5 Metal Concentrations in Acidified Waters—Significant changes in the
concentrations of heavy metals in acidified lakes have been observed. ' '
(Table 8-7.) Increased concentrations of aluminum, manganese, zinc, copper,
cadmium, and nickel have been reported. ' ' Mobility of all of these
24
metals is greatly increased at low pH concentrations. Beamish suggested
that in Canada the increased concentrations of nickel and copper were probably
the result of precipitation loading; however, copper concentrations in acidified
lakes were not significantly greater than in non-acidified lakes. Zinc con-
centrations were much higher in the acidified lakes but when compared to the
average concentration obtained from the analysis of more than 1500 samples
24
from waters within the United States, they were normal. Zinc concentrations
were similar to those found in acidified lakes in Sweden. Manganese concentra-
tions also were similar to those noted in Sweden. Increase in the concentrations
of aluminum, manganese, and zinc are associated with increased leaching from
•7Q
soils and lake sediments. Schofield noted high concentrations of aluminum in
8-49
-------
TABLE 8-7. CHEMICAL COMPOSITION OF FOUR ACID LAKES AND NON-POLLUTED LAKES IN A REMOTE
AREA OF N.W. ONTARIO. RANGE IN BRACKETS
PH _!
Sulfate mgl ,
Chloride mgl
Na mgl.
Ca mgl ,
Mg mg].
K mgl ,
Hardness (as CaCO,) mgl ,
Total dissolved solids mgl...
Total suspended solids mgl
Bicarbonate alkalinity
(as CaCO,) mgl"1 ..
Conductivity pmho cm
Fe pg ,
Ni P9 .7
Cu pg _:
Zn pg ,
Cd pg "f
Pb pg ~\
Mn pg ~l
O.S.A.
4.5(4.4-4.9)
15(14-17)
K<1-1)
0.6(0.6-0.8)
3.2(2.9-3.7)
0.9(0.7-1.0)
0.4(0.3-0.5)
11(10-14)
23(7-59)
1(0-2)
0.5
48(46-53)
23(18-29)
11(8-13)
4(2-6)
36(30-48)
<1
4(2-6)
Muriel
4.7(4.5-4.8)
15(14-15)
-------
stream runoff at the time of snow melts. Leaching of aluminum from watersheds
83
has also been reported.
Aluminum concentrations in acidified waters in regions where acidic
79
precipitation occurs are characteristically high. Aluminum concentrations
75 8^
in acidified lakes in southern Norway, Sweden, and the northeastern United
•yr oo
States ' are five to ten times higher than aluminum concentrations in
circumneutral waters from these same regions. Aluminum appears to be the
primary element mobilized by strong acids from acidic precipitation in regions
oo
where the watershed is characterized by acidic, base deficient soils. In
the acidified soft surface waters of the Adirondack Mountains of New York
State, aluminum is highly variable in concentration and form. a Organically
complexed aluminum is the dominant form. Labile inorganic aluminum appears to
be the form toxic to fish. Temporal changes in concentration of hydrogen
ions and organic carbon appear to have a significant effect on the chemistry
of aluminum in these aqueous systems. a
The increased concentrations of heavy metals in acidified lakes are not
only the result of direct deposition of these metals in precipitation, particu-
larly, in areas such as Sudbury, Ontario which are near metal smelters, but
also the result of mobilization and enhanced solubility of these metals in
watersheds and sediments as a result of the acidification of precipitation.
8.2.4.6 Effects on Human Health—Indirect effects of acidification that are
potentially of concern to human health is the possible contamination by toxic
84 87 82 85
metals of edible fish and of water supplies. Studies in Sweden, ' Canada, '
op
and the United States have revealed high mercury concentrations in fish from
acidified regions. Methylation of mercury to monomethyl mercury occurs at low
8-51
-------
oc
pH while dimethyl mercury forms at higher pH. Monomethyl mercury in the
water passing through the gills of fish reacts with thiol groups in the hemoglobin
of the blood and is then transferred to the muscle. Methyl mercury is eli-
minated very slowly from fish, therefore, it accumulates with age.
09
Tomlinson reports that in the Bell River area of Canada precipitation
is the source of mercury. Both methyl mercury and inorganic mercury were
found in precipitation. The source of mercury in snow and rain was not known
at the time of the study.
Zinc, manganese, and aluminum concentrations also increase as the acidity
21
of lakes increases. The ingestion of fish contaminated by the metals is a
distinct possibility.
Another human-health aspect is the possibility that, as drinking-water
reservoirs acidify, owing to acid precipitation, the increased concentrations
of metals may exceed the public-health limits. The increased metal concentra-
tions in drinking water are caused by increased watershed weathering and
increased leaching of metals from household plumbing. Indeed, in New York
State, water from the Hinckley Reservoir has acidified to such an extent that
"lead concentrations in water in contact with household plumbing systems
exceed the maximum levels for human use recommended by the New York State
R7
Department of Health." The lead and copper concentrations in pipes which
have stood over night (U) and those in which the water was used (F) are depicted
in Table 8-8.
8-52
-------
TABLE 8-8. LEAD AND COPPER CONCENTRATION AND pH OF WATER FROM PIPES
CARRYING OUTFLOW FROM HINCKLEY BASIN AND HANNS AND STEELE CREEK BASIN
Collection site
and date
Hinckley Dam
Nov. 21, 1974
Nov. 21, 1974
Nov. 7, 1974
Nov. 7, 1974
Oct. 1, 1974
Oct. 1, 1974
Aug. 15, 1974
Aug. 15, 1974
Amsterdam
Jan. 6, 1975
Jan. 6, 1975
Pipe ,
condition
U
F
U
F
U
F
U
F
U
F
Copper
(M9/D
600
20
460
37
570
30
760
40
2900
80
Lead
(M9/D
66
2
40
6
52
5
88
2
240
3
pH
—
7.4
6.3
6.3
6.8
7.1
6.3
6.3
4.5
5.0
U, unflushed; (water stands in pipes all night) F, flushed
From reference 88
8-53
-------
8.2.5 Acidification of Lakes
Precipitation enters lakes directly or as runoff from the watersheds
which surround the lakes. The relative magnitude of the influents from the
two sources is dependent on the surface area and volume of the lake, the size
78
of the watershed, and the type of soil. The watershed plays a dominant role
in determining the composition of water entering the lake when the watershed
is large and the lake area and volume are small. Precipitation plays a dominant
role when lake areas are large in comparison to the size of the watershed.
However, watersheds with poor soil and vegetational cover usually have little
78
influence on the composition of the influents.
The acidity of freshwater lakes reflects both the acidity of precipitation
and the capability of the watershed and the lake itself to neutralize the
75 32 79
incoming acid. Schofield ' has pointed out that the situation is analogous
to a gigantic, regional-scale titration with the lakes serving as the receiving
vessels for the acidity coming from the atmosphere. The titration endpoint of
each lake is predetermined by its hydrology and the capacity of the soils in
35
the drainage basin to assimilate the incoming acid. Hardness of water is
closely correlated with alkalinity and, therefore, with the capacity of
water to neutralize (buffer) the acidity of precipitation entering a lake.
Chemical weathering and ion exchange are two processes in watersheds that act
to neutralize incoming acidic precipitation. In soils, the cation exchange
capacity and the buffering capacity are closely related. The rate at which
the two processes take place depends on the physical and chemical nature of
the bedrock, the overburden, and the soils. In areas with no appreciable
amounts of carbonate-bearing materials, for example large parts of southern
Norway, chemical weathering and ion exchange processes proceed too slowly to
neutralize all of the incoming acid.
8-54
-------
Bicarbonate provides most of the buffering capacity in soft water lakes.
The concentration of bicarbonate in these waters is highly pH dependent.
Therefore, as pH of runoff and lake waters decreases the bicarbonate concentration
decreases. Sulfate, supplied by acidic precipitation replaces bicarbonate and
becomes the major ion. In areas where the watersheds and lakes do not have
the capability of neutralizing the incoming acid, acidic precipitation causes
the pH of lakes to drop below 5.0. Bicarbonate in these lakes is essentially
eliminated and no effective buffer system remains. These waters are, therefore,
subject to large fluctuations in acidity in response to episodic injections of
acidic pollutants such as those occurring the snowpack melts.
Melting of the ice and snowpack on lakes and streams can result in a
32 37 75 79 80
large influx of acidic pollutants. ' ' ' ' streams, rivers, and small
ponds, which usually are only slightly acidic or may even be alkaline, are
subject to sharp increases in acidity for brief periods during the late winter
32 79
and early spring thaws. ' These episodes of high acidity result from the
81
release of acids stored in the winter snowpack. Galvin and Cline measured
anions in the snow cover of the Adirondack Mountains and noted nitrates and
sulfates were the only ones present in appreciable quantities. The concentrate
of nitrates was greater than sulfate. The absence of chloride indicated that
80
the sources of nitrate and sulfate were inland. Hagen and Langeland also
noted the snow covering Norwegian lakes and brooks in winter and spring contained great
quantities of SO^, NO^, Zn and Pb, and were associated with high acidity.
While studying the effect of the pH of snow and ice on lakes in Norway, it was
observed that no change in either acidity or conductivity occurred between
January and March, but in April and early May the pH decreased from 5.4 to 4.2 and
the conductivity increased from 15 to 40. After the ice had melted at the end
of May, the pH distribution returned to a normal 6.0.
8-55
-------
Water from the snowmelt in the early stages percolates down through the
snowpack and leaches the stored acids. The first flush of melt water is
typically a highly concentrated, acid solution having pH levels of 3.0 to
3.5.79 As the thaw ends, most of the pollutants have been removed from the
remaining snow and the dilute melt water approaches the composition of
distilled water with pH in the range of 5 to 6.
pp
Tomlinson studied the effects of the spring thaw of snow on the Bell
River, a tributary of the Nottaway River, which flows into the Hudson Bay in
Northern Quebec Province. The Bell River is a soft water river, and it was
noted that its pH changed with the seasons. Throughout most of the year the
pH values range from 6.1 to 6.5, but in the spring the values decrease due to
melting snow. On april 19, 1977, the pH of two small creeks that flow into
the Wedding River was 4.0 and 3.8, respectively while the pH of the Wedding
River which flows into the Bell River, was 5.7. The pH of the Bell River was
6.1. By the following week (April 25, 1977), the ph of the Bell River had
dropped to 5.6 while that of the creeks had moderated and was now 4.9 and 4.8,
respectively. The pH of the Wedding River was 5.8. It was noted that the pH
of precipitation occurring in the thinly wooded area surrounding the Bell
River ranged from 4.1 to 4.7. The seepage of the acid through the snow results
in the first runoff in the spring usually being somewhat lower in pH.
Laboratory and lysimeter experiments comparing the melting of snow with
the time of release of 14 chemical elements in the snowpack conducted in
Norway showed that the first 30 percent of meltwater contained 44 to 97 percent
of the total amount of chemicals measured. No significant loss of water of or
H , SO^, N03, NH^, and Pb ions occurred during the winter. Observations
indicated that a snowpack with a bulk pH of 4.4 could give rise to an initial
8-56
-------
meltwater "wave" of pH 4.1. In lakes, the meltwater changes not only the pH,
89
but the chemical composition, also.
Strong acids, such as sulfuric and nitric are not the only acids contributing
to lake acidification. Concentrations of weak and strong acids in the surface
waters of the Tovdal River were measured during snowmelt. Though the strong
acid anions, sulfate, and nitrate come largely from precipitation, the weak
90
acids, humic and fulvic, are produced by biodegradation of vegetable material.
Inorganic weak acids based on hydrated alumininum, iron, and species of silica
are also present. The presence of the weak acids is significant because they
contribute to the hydrogen ion concentration and because they give an indication
90
of the ground interaction effects.
Sudden episodic drops in pH due to snowmelt and the injection of large
concentrations of H ions are the cause of massive fish kills which often
occur at that time; fish are unable to adapt to the sudden pH
change.16)20'32'33'75'76'80 The sudden influx of H+ ions also causes changes
in pH and chemical composition of lakes for a short period of time even though
they may normally have a circumneutral pH.
In general, acidification of surface waters by acidic precipitation in
geologically sensitive regions is a continuous process involving water quality
changes. The process which is analogous to the acidimetric-titration of a
bicarbonate solution can be divided into three broad states that define the
94
nature extent of water quality change and the associated biological inpacts.
In the initial stage, a decrease in alkalinity occurs, but the pH remains
above 6.0 and bicarbonate buffering is maintained. The second stage is charac-
terized by a loss of bicarbonate buffering and severe temporal pH fluctuations
occur. Reproductive inhibition and episodic fish kills may initiate the
8-57
-------
failure of recruitment and the eventual extinction of fish populations may
begin at this stage. The third and final stage is characterized by a chronically
depressed pH and an increase in concentrations of toxic metals. Fish have
94
usually disappeared from waters when this stage of acidification is reached.
8.3 SENSITIVE AREAS
8.3.1 Aquatic Ecosystems
Why do some lakes become acidified by acidic precipitation and others
not? What determines susceptibility? Are terrestrial ecosystems likely to be
susceptible; if so, which ones?
The sensitivity of lakes to acidification is determined by: (1) the
acidity of both wet (precipitation) and dry deposition, (2) the hydrology of
the lake, (3) the soil system and canopy effects, and (4) the surface water.
Given acidic precipitation, the soil system and associated canopy effects are
most important. The hydrology of lakes includes the sources, amounts and
pathways of water entering and leaving a lake, while the capability of a lake
and its drainage basin to neutralize acidic contributions as well as the
mineral content of its surface water is largely governed by the composition of
51 75 92
the bedrock of the watershed ' 'as the chemical weathering of the watershed
strongly influences the salinity (ionic composition) and the alkalinity (hardness
51 75 9?
and softness) of the surface water of a lake. ' ' The cation exchange
capacity of the watershed and the alkalinity of the surface water determine
the ability of a lake to neutralize the acidity of precipitation.
Lakes vulnerable to acidic precipitation have been shown to have watersheds
whose geological composition is highly resistant to chemical weathering. ''
In addition, the watersheds of the vulnerable lakes usually have thin, poor
soils and are poorly vegetated. The cation exchange capacity of such soils is
poor and, therefore, its buffering capacity is poor.32'92
8-58
-------
92
Wright and Henriksen point out that the chemistry of Norwegian lakes
could be accounted for primarily on the basis of bedrock geology. They examined
155 lakes and observed that 59 of them lay in granite or felsic gneiss basins.
Water in the lakes was low in most major ions and had low electrical conductivity
(The fewer the minerals in water the poorer its conductivity. ) The waters
qp
in the lakes surveyed were "among the softest waters in the world.1 Sedi-
mentary rocks generally weather readily, whereas igneous rocks are highly
01 00
resistant. The Adirondacks, as pointed out by Schofield, ' have granite
bedrock with much of the area covered with a mantle of mixed gneisses. Shallow
soils predominate in the area.
Limestone terrains are capable of buffering intense concentrations of
acids and glacially derived sediment has been found to be more important than
93
bedrock in assimilating acidic precipitation in the Canadian Shield area.
Generally, however, bedrock geology is the best predictor of the sensitivity
94
of aquatic ecosystems to acidic precipitation.
Areas with aquatic ecosystems that have the potential for being sensitive
to acidic precipitation are shown in Figure 8-8. In Figure 8-8, the shaded
areas on the map indicate that the bedrock is composed of igneous or metamorphic
rock while in the unshaded areas it is of calcareous or sedimentary rock.
Metamorphic and igneous bedrock weathers slowly, therefore, lakes in areas
with this type of bedrock would be expected to be dilute and of low alkalinity
7ft
(<0.5 meq HCCL/liter). Galloway and Cowling verified this hypothesis by
compiling alkalinity data. The lakes having low alkalinity were concurrent
78
with the regions having igneous and metamorphic rock.
Henriksen has developed a lake acidification "indicator model" using
pH-calcium and calcium-alkalinity relationships as an indicator for determining
8-59
-------
Figure 8-8. Regions in North America with lakes that are sensitive to acidification by acid
precipitation.78
8-60
-------
sensitive lake districts. The indicator is based on the observation that in
pristine lake environments (e.g., NW Norway or the Experimental Lakes Area in
NW Ontaria, Canada) calcium is accompanied by a proportional amount of bicarbonate,
because carbonic acid is the primary chemical weathering agent. The pH - calcium
relationship found for such regions is thus defined as the reference level for
unacidified lakes. Acidified lakes (e.g., SE Norway and the Adirondack region)
will exhibit lower pH than the reference lakes, at comparable calcium levels,
due to the replacement of bicarbonate by strong acid anions.
Schofield has illustrated the use of Henriksen's model by using data
from Norway, the Adirondacks and the Experimental Lakes Area of Ontario,
Canada. In the acidified lakes sulfate replaces bicarbonate as the major
anion present (Figures 8-9 and 8-10) and is derived primarily from precipitation
(Figure 8-11). Since the bicarbonate lost in acidified lakes has been replaced
by an equivalent amount of sulfate, the concentration of excess sulfate serves
as an index of the amount of acidification that has taken place. Henriksen
compared estimated acidification in Norwegian lakes to the pH and sulfate
concentrations in the prevailing precipitation and concluded that significant
lake acidification had occurred in areas receiving precipitation with an
annual average (volume weighted) pH below 4.6 to 4.7 and sulfate concentrations
above 1 mg/liter. This approximate threshold of precipitation acidity may be
applicable to sensitive lake districts in other regions as well. For reference,
the estimated annual, bulk deposition sulfate loading levels for the acidified
lake districts in the Adirondacks and southern Norway are approximately 30 to
60 kg SO./ha. , as compared with only 5 - kg SO./ha. in the reference areas of
northern Norway and the Experimental Lakes Area in Ontario. A comparison of
lake pH with regional sulfate loading levels in Sweden suggests that critical
loading levels for sensitive lakes are in the range of 15 to 20 kg SO^/ha./yr.
8-61
-------
UJ
o
a:
UJ
o.
o
UJ
O
UJ
EC
40 60
EQUIVALENT PERCENT
80
Ca*2
Al
+3
HC03-1
Figure 89. Equivalent percent composition of major ions in Adirondack lake
surface waters (215 lakes) sampled in June 1975.76
8-62
-------
10
z
UJ
O 0
cc
01
CL
10
20
NW Norway
(58)
SE Norway
(57)
Adirondacks
(184)
ELA
(102)
50
100 150
804, /J eq/liter
200
250
Figure 8-10. Percent frequency distribution of sulfate concentrations in surface
water from lakes in sensitive regions.76
8-63
-------
0.15
0.10
fc
.t
I
E
5
V)
v>
V)
UJ
u
X
UJ
0.05
Y*-0.86* 1.94 X
r« 0.823. p--0.001
• o
0 0.025 0.050 0.075
PRECIPITATION EXCESS SC-4, m eq/liter
Figure 8-11. Relationship between precipitation excess sulfate and lake excess
sulfate for lakes in Norway and the Adirondacks. (A = mean lake and precipi-
tation sulfate for the Adirondack region.)76
8-64
-------
Though bedrock geology generally is a good predictor of the susceptibility
of an area to acidification due to acidic precipitation, other factors also
have an influence. Florida, for example, is underlaid by highly calcareous
and phosphate rock suggesting that acidification of lakes and streams is
highly unlikely. Many of the soils, however, (particularly in northern Florida)
are very mature, have been highly leached of calcium carbonate, and, as a
94
result, some lakes in which groundwater inflow is minimal have become acidified.
Conversely, there are areas in Maine with granitic bedrock where lakes have
not become acidified despite receiving precipitation with an average pH of
approximately 4.3 because the drainage basins contain lime-bearing till and
95
marine clay. Small amounts of limestone in a drainage basin exert a strong
influence on water quality in terrain which would otherwise be vulnerable to
acidification. Soils in Maine in the areas where the pH of lakes has decreased
due to acidic precipitation are immature, coarse, and shallow and are derived
largely from granitic material and commonly have a low capacity for assimilating
95a
hydrogen ions from leachate and surface runoff in lake watersheds. Consequently,
when predicting vulnerability of a particular region to acidification, a
careful classification of rock mixtures should be made. Rock formations
should be classified according to their potential buffering capacity and the
type of soil overlying the formations should be noted.
8.3.2 Terrestrial Ecosystems
Predicting the sensitivity of terrestrial ecosystems to acidic precipi-
tation is much more difficult than for aquatic ecosystems. With aquatic
ecosystems it is possible to compare affected ecosystems with unaffected and
note where the changes have occurred. With terrestrial ecosystems, comparisons
are difficult to make because the effects of acidic precipitation have been
difficult to detect. Therefore, predictions regarding the sensitivity of
8-65
-------
terrestrial ecosystems must, as much as possible, use the data which links the
two ecosystems, bedrock geology. Since, in most regions of the world, bedrock
is not exposed but is covered with soil, it is the sensitivity of different
types of soil which must be assessed. Therefore, the first step is to define
"sensitivity" as it is used here in relation to soils and acid precipitation.
Sensitivity of soils to acidification, alone, though it may be the most important
long-term effect, is too narrow a concept. Soils influence the quality of
waters in associated streams and lakes and may be changed in ways other than
simple pH-base saturation relationships, e.g., microbiological populations of
the surface layers, accelerated loss of aluminum by leaching. Therefore,
criteria need to be used that would relate soil "sensitivity" to any important
97
change brought about in the local ecosystem by acid precipitation.
Soils are the most stable component of a terrestrial ecosystem. Any
changes which occur to this component would probably have far-reaching effects.
97
McFee has listed four parameters which are of importance in estimating the
sensitivity of soils to acidic precipitation. They are:
1. The total buffering or cation exchange capacity which is provided
primarily by clay and soil organic matter.
2. The base saturation of that exchange capacity which can be estimated
from the pH of the soil.
3. The management system imposed on the soil, is it cultivated and
amended with fertilizers, lime, renewed by flooding or by other
additions?
4. The presence or absence of carbonates in the soil profile.
In order that the factors listed above could be used in broad scale
mapping of soils, McFee evaluated them for wide applicability and ready
availability. In natural soils the most serious effects would be caused by
changes in pH or due to leaching of soil minerals. Susceptibility of soils to
8-66
-------
changes in either of these categories is most closely associated with the
cation exchange capacity (CEC). Soil with a low CEC and a circumneutral pH is
likely to have the pH rapidly reduced by an influx of acid. Soils with a high
CEC, however, are strongly buffered against pH changes or changes in the
composition of the leachate. Acid soils with a pH near that of acidic precipi-
tation will not rapidly change pH due to acidic precipitation, but will probably
+3 97
release AL ions into the leachate. Soils having low CEC's are usually low
in plant nutrients, therefore, significant changes in their productivity could
97
occur with only a slight loss of nutrients.
Even though CEC or buffering capacity does not completely define soil
sensitivity to possible influents of acid, for the reasons given above it was
the primary criterion used by McFee for the regional mapping of soil sensitivity
to acidic precipitation in the eastern United States. Further, though it is
frequently stated in much of the literature that soils with low CEC or sandy
soils having low organic matter are likely to be most susceptible to effects
of acidic precipitation, the "low CEC" values are not quantified. To develop
a working set of classes, it was necessary to make certain assumptions and
"worst case" calculations. Since soils in general are rather resistant to
change due to additions of acid, a fairly high addition of acid was assumed
and the question asked, "What is the maximum effect that it can have on soil,
97
and how high would the CEc have to be to resist that effect?"
To determine sensitivity of a soil, McFee arbitrarily chose a span of 25
years. It was hypothesized that a significant effect could occur if the
maximum influx of acid (100 cm of precipitation at pH 3.7 per annum) during
that period equaled 10 to 25 percent of the cation exchange capacity in the
top 25 cm of soil. Soils are considered slightly sensitive if the top 25 cm
of soil has an average CEC of 6.2 to 15.4 me/100 g (also assumes a bulk density
8-67
-------
of 1.3 g/cc). If the same influx of acid exceeds 25 percent of the CEC in the
top 25 cm, i.e., when the CEC is less than 6.2 me/100 g, the soils are considered
sensitive.
Based on the above concepts, the soils of the eastern United States
including farm effects were mapped (Figure 8-12) by McFee. The areas containing
most of the soils potentially sensitive to acidic precipitation are in the
upper coastal plains and Piedmont regions of the southeast, along the Appalachian
Highlands, through the east central and northeastern areas, and in the Adirondack
Mountains of New York. The present limited state of knowledge regarding the
effects of acidic precipitation on soils makes a more definitive judgment of
the location of areas with the most sensitive soils difficult at the present
time.
8.3.3 Aquatic and Terrestrial
The Boundary Waters Canoe Area Wilderness (BWCAW) and the Voyageurs
National Park of Minnesota lies along 176 km (110 miles) of the Minnesota-Ontario
border. It varies from 16 to 48 km (10 to 30 miles) in width and includes
439,093 ha (1,085,000 acres) of typical northwoods terrain with more than one
qo
third of the area composed of island-studded lakes. Glass and Loucks assessed
the BWCW-Voyageurs National Park area in order to predict the sensitivity of
the region to emission from a major coal-fired power plant. Though Glass and
go
Loucks were concerned with the effects of all emissions from the power
plant, one portion of their report estimates the sensitivity of the area to
acidic deposition. To estimate the probable impact of acidic precipitation,
Glass and Loucks used the basic concepts regarding sensitivity of aquatic
ecosystems as discussed previously in this section on sensitivity. Taking
the findings associated with the acidification of aquatic ecosystems in north-
' 68
-------
REGIONS WITH SIGNIFICANT
AREAS OF SOILS THAT ARE
n NON SENSITIVE
SLIGHTLY SENSITIVE
Eg SENSITIVE
WITHIN THE EASTERN U S
Figure 8-12. Soils of the Eastern United States sensitive to acid rainfall.97
8-69
-------
eastern North America and Europe and applying these to the ecological receptors
in the BWCA-Voyageurs National Park region they arrived at certain conclusions
regarding the aquatic and terrestrial ecosystems in the area. They felt that
1) the vulnerable lakes in the region (poorly buffered headwater lakes with
small watersheds and shallow soils of low buffering capacity) are already
being affected by acidity from atmospheric sources. 2) Given the probable
changes in the acidity of water, the responses of the biota in the aquatic
ecosystem will result in changes similar to those seen in the acidified lakes
of the eastern United States and Canada. These changes will occur over different
time spans: for some lakes, several years; for others, several decades. 3)
Probable increases in the acidity of the water will increase the severity of
seasonal events such as acid flushing in the spring due to snow melt. 4)
Increased acidity is likely to result in detrimental levels of aluminum and of
other trace elements in the lake water by increasing leaching and creating
more toxic forms of these elements.
The possible impact on the terrestrial ecosystems are more nebulous than
for the aquatic areas. The structure of the soils in the region (mostly
shallow (0 to 46 cm), of glacial origin, coarse textured, derived from granites
and other acid bedrock types, low in cations and available nitrogen, and low
in percentage base saturation suggests that acidic precipitation could result
in the mobilization of elements toxic to terrestrial vegetation. Runoff
wastes could also carry the same elements into small lakes. Small additions
of acidity to the thin, rocky soils common in the BWCA, coupled with the
geochemical weathering changes that are probable can be expected to have
relatively rapid and irreversible effects on outputs from the nutrient cycles
of these ecosystems. These changes will affect groundwater quality and produce
8-70
-------
soil-mediated changes in cycling rates within the ecosystems. Although the
net changes in cation leaching due to lowered soil pH are difficult to predict,
H+ additions to some soils will facilitate leaching of essential plant nutrients.
Lichens are an important part of the BWCA-VNP biota and make up the
principal plant cover on 5 percent of the land area. Lichen species also have
been shown to be an important source of nitrogen (through N fixation) in a
number of nitrogen-limited coniferous forest areas. Acidic precipitation, as
well as, sulfur oxides, could result in injury to these plants.
no
The conclusions reached by Glass and Loucks can only be verified by
long-term studies of the area.
8.4 EFFECTS ON TERRESTRIAL ECOSYSTEMS
Determining the effects of acidic precipitation on terrestrial ecosystems
is not an easy task. In aquatic ecosystems it has been possible to measure
change in pH that occur in acidified waters and then observe the response of
aquatic ecosystems to the shifts in pH. In the case of terrestrial ecosystems
the situation is more complex since no component of terrestrial ecosystems
appears to be as sensitive to acidic precipitation as poorly buffered aquatic
ecosystems.
Acidic precipitation may produce a direct effect on plants and the ecosystem
in general or the effects may be indirect. Direct effects frequently will
also result in many indirect effects. At the present time it has not been
possible to observe or measure changes in naturally occurring terrestrial
ecosystems which can be attributed directly to acidic precipitation. This
does not mean that effects do not exist, rather that the capability of observing
and measuring them is limited.
8.4.1 Effects of Acidic Precipitation on Vegetation
The atmosphere, as well as the soil, is a source of nutrients for plants.
Chemical elements reach the plant surface via wet and dry deposition. Sulfates
8-71
-------
and nitrates are not the only components of precipitation falling onto the
plant surface. Other chemical elements at least partially soluble in water
are deposited on the surface of vegetation and may be assimilated by it,
usually through the leaves. An average rain drop deposited on trees in a
typical forest washes over three tiers of foilage before it reaches the soil.
The effects of acidic precipitation may be beneficial or deleterious depending
on its chemical composition, the species of plant on which it is deposited and
7ft
the physiological condition and maturity of the plant.
It has generally been assumed that the free hydrogen ion concentration in
acidic precipitation is the component that is most likely to cause direct,
99
harmful effects on vegetation. Experimental studies support this assumption;
however, to date, there are no confirmed reports of exposure to ambient
acidic precipitation causing foliar symptoms on field grown vegetation in the
99
continental U.S.
8.4.1.1 Direct Damage to Tissues—The formation of lesions or zones of dead
tissues on the upper epidermis at the bases of trichomes, in guard cells and
in epidermal cells above veins is the most frequently reported response to
qq -i 07
experimental exposure with simulated acidic rain. ' A large percentage of
the leaf area may exhibit lesions after repeated exposures to simulated acid
rain at pH concentrations of 3.0, 2.7, 2.5 and 2.3.102'108 Pinto bean leaves
which have reached full expansion exhibited the greatest amount and most
pronounced visible leaf injury.100"102 Most injury to foliage by simulated
acidic rain occurs on expanding or recently expanded leaves. Birch seedlings
104 _
ngs.
14 days old are more sensitive than six-weeks-old seedlings.104 Evans et
al. using six clones of Populus spp. hybrids have shown that leaves that
had just reached full expansion were more sensitive to simulated acidic rain
8-72
-------
than were unexpanded or those which were fully expanded. On two of the clones,
gall formation due to abnormal cell proliferation and enlargement occurred.
109
Hindawi and Ratsch demonstrated that needle elongation will be inhibited if
simulated acid rain solutions are applied to immature pine fasicicles.
In leaves injured by simulated acidic rain, collapse and distortion of
epidermal cells on the upper surface is frequently followed by injury to the
palisade cells and ultimately both leaf surfaces are affected. Reductions
in growth and yield have not been unequivocally associated with leaf injury.
Premature abscission of leaves of bean plants has been associated with simulated
acid rain.
Foliar response to acidic precipitation is dependent on the temporal and
physical characteristics of the events. Duration and frequency of exposure,
length of time between rain events and intensity of rainfall all influence the
99a
development of foliar symptoms. The acid content and size of rain drops
may be of importance in producing effects. Environmental conditions during
and after a precipitation event effect the response of plants by altering
physiological processes, the degree of contact with rainfall, the amount of
liquid remaining on leaf surface, or the rate of evaporation after rainfall
99a
has terminated. Table 8-9 summarizes the foliar effects of simulated
acidic precipitation.
8.4.1.2 Leaching of NutrientsLeaching of chemical elements from exposed plant
surfaces is one of the more important effects rain, fog, mist and dew have on
vegetation. Substances leached include a great diversity of materials. All
of the essential minerals, amino acids, carbohydrate growth regulators, free
sugars, pectic substances, organic acids, vitamins, alkaloids and alleopathic
113
substances are among the materials which have been detected in plant leachates.
8-73
-------
TABLE 8-9. MAXIMUM pH CONCENTRATION PRODUCING INJURY TO VEGETATION AFTER DIRECT
CONTACT WITH SIMULATED ACIDIC PRECIPITATION
Effect
Foliar lesions
Foliar aberrations
decrease in growth
Foliar lesions,
Receptor
Eastern white
pine
Bean
Bean
pH value
2.3
2.5
2.5
Reference
108
103
108
plasmolysis of
cells, reduction
in dry weight
Foliar necrotic spots
Necrotic lesions and
chlorotic areas in
leaves
Foliar lesions, decrease
in growth
Foliar lesions
Bifacial necrosis
Foliar lesions
Foliar lesions
Reduction in dry weight
Scots pine birch 2.5
(Betula pubescens
Ehrb)
Soybean 3.0
Yellow birch 3.1
(Betula alleg-
haniensis Britt)
Bean, sunflower 3.1
Oak (Quercus 3.2
phellos)
Hybrid poplar 3.4
Sunflower 3.4
Bean 4.0
112
106
104
102
109a
101
99
111
8-74
-------
Many factors influence the quantity and quality of the substances leached from
foliage. They include factors associated directly with the plant as well as
those associated with the environment. Not only are there differences among
species with respect to leaching, but individual differences also exist among
individual leaves of the same crop and even the same plant, depending on the
physiological age of the leaf. Young, actively growing tissues are relatively
immune to leaching of mineral nutrients and carbohydrates, while mature tissue
which is approaching senescence is very susceptible. The stage of plant
development, temperature, and rain water falling on foil age and running down
plant stems or tree bark influences leaching. Rainwater, which naturally has
a pH of about 5.6, washing over vegetation may become enriched with substances
114
leached from the tissues.
Leaching of organic and inorganic materials from vegetation to the soil
is part of the normal functioning of terrestrial ecosystems. The nutrient
flow from one component of the ecosystem to another is an important phase of
nutrient cycling. ' Plant leachates have an effect upon soil texture,
aeration, permeability, and exchange capacity. Leachates, by influencing the
number and behavior of soil microorganisms, affect soil-forming processes,
soil fertility, susceptibility or immunity of plants to soil pests and plant
113
chemical interactions.
It has been demonstrated that precipitation of increased acidity can
increase the leaching of various cations and organic carbon from the tree
canopy. ' Foliar losses of potassium, magnesium, and calcium from bean
plants and maple seedlings were found to increase as the acidity of an artificial
mist was increased. Below a pH of 3.0 tissue damage occurred, however, signifi-
cant increases in leaching were measured at a pH 3.3 and 4.0 with no observable
8-75
-------
tissue damage.1 Hindawi et al. also noted that as the acidity of acid
mist increased so did the foliar leaching of nitrogen, calcium, phosphorous,
and magnesium. Potassium concentrations were not affected while the concentra-
118
tion of sulfur increased. Abrahamsen and Dollard in experiments using
Norway spruce (Picea abies (L.) Karst.) observed that despite increased leaching
at the most acid treatment, there was no evidence of change in the foliar
cation content. Wood and Bormann using Eastern white pine (Pinus strobus
L. ) also noted no significant changes in calcium magnesium and potassium
content of needles. Tukey states that increased leaching of nutrients from
foilage can accelerate nutrient uptake by plants. No injury will occur to the
plants as long as roots can absorb nutrients to replace those being leached.
To date, the effects of the increased leaching of substances from vegetation
by acidic precipitation remains unclear.
8.4.1.3 Indirect Effects on Plants—Acidic precipitation can have beneficial
effects on plants. Wood and Bormann reported an increase in needle length
and the weight of seedlings of Eastern white pine with increasing acidity of
simulated precipitation where sulfuric and nitric acid were used to acidify
the mist. Increased growth was attributed to increased N0~ application.
o
119
Irving and Miller observed that the acidic simulant had a positive effect
on productivity of field-grown soybeans as reflected by seed growth. Increased
growth was attributed to a fertilizing effect extending the pod-filling period.
119
Irving and Miller, in the same study, also exposed soybeans to S02 and
acidic precipitation. No visible injury was apparent in any of the plots,
however, a histological study revealed significant increases in the number of
dead mesophyll cells in all plots when compared to the control. The proportion
of dead mesophyll cells of plants exposed to acid rain and S02 combined was
more than the additive when compared to the effects of each taken singly.
8-76
-------
120
Shnner studied the effect of acidic precipitation on host-parasite
interactions. Simulated acid rain with a pH of 3.2 inhibited the development
of bean rust and production of telia (a stage in the rust life cycle) by the
oak-leaf-rust fungus Cronartrium fusiforme Hedge and Hung. It also inhibited
reproduction of root-knot nematodes and inhibited or stimulated development of
halo blight of bean seedlings depending on the time in the disease cycle
120
during which the simulated acidic rain was applied. Shriner also observed
that root nodulation by Rhizobium on common beans and soybeans was inhibited
by the simulated acidic rain.
Plants such as mosses and lichens are particularly sensitive to changes
in precipitation chemistry because many of their nutrient requirements are
obtained directly through precipitation. These plant forms are typically
absent from regions with high chronic S0? air pollution and acidic precipitation.
121 122
Gorham and Giddings and Galloway have written reviews concerning this
problem. Most investigations on the effects of air pollution on epiphytes
have dealt with gaseous pollutants. Very few studies have considered acidic
122a
precipitation. Denison et al. however, did observe that the nitrogen-fixing
ability of the epiphytic lichen Lobaria oregana was reduced when treated with
simulated rainfall with a pH of 4.0 and below. Investigations concerning the
effects of acidic precipitation on epiphytic microbial populations are very
few.118
Limited fertilization could occur in the bracken fern Pteridium aqui1inum
under conditions of acidic precipitation (pH and sulfate concentrations) that
123
prevail in the northeastern United States. Evans and Bozzone, using buffered
solutions to simulate acidic precipitation, observed that flagellar movement of
sperm was reduced at pH levels below 5.8. Longevity of motility was reduced so
8-77
-------
that no movement was observed 8 to 10 and 5 to 7 minutes after exposure to pH 5.6
and 5.2, respectively. Gametophyte survival and development was not affected by
solutions of pH 5.8 to 2.2, however, fertilization was reduced after exposure to
pH's below 4.2. Sporophyte production was also reduced by 50 percent at pH levels
below 4.2 when compared to 5.8. Addition of sulfate (86 uM) decreased fertilization
at least 50 percent at all pH concentrations observed.
124
In another study, Evans and Bozzone observed that additions of one or
more anions produced additive effects at all pH concentrations. Both sperm
motility and fertilization in gametophyte of Pteridium aquilinum were reduced
when anions of sulfate, nitrate, and chloride were added to buffered
solutions, sulfate alone at 43.3 uM (equivalent to the sulfate concentration
in rain in the northeastern United States) decreased sperm motility approxi-
mately 40 percent when compared with plants exposed to solutions without
sulfate.
The effects of acidic precipitation on forest tree growth has been
investigated in experiments using simulated acidic rain, and by comparing
development of tree rings in the past with present ring formation in areas
with different amounts of hydrogen ion deposition or in areas assumed to have
-I -| O
different sensitivities to acidic precipitation. Using the tree ring
method, Jonsson and Sundberg analyzed forest growth in southern Sweden from
1896 to 1965 and observed a 2 to 7 percent decrease in growth between 1950 and
1965. They attributed the reduction in growth to acidification. Similar
studies in North America and Norway have not produced similar results.112'125'126
Acidifying already acid forest soils by acidic precipitation or air
pollutants is a slow process. Growth effects probably could not be detected
for a long time. To identify the possible effects of acidification on poor
8-78
-------
127
pine forests, Tarn et al. conducted experiments using 50 kg and 100 kg of
sulfur per hectare as dilute sulfuric acid (0.4 percent) applied annually with
and without NPK (nitrogen, phosphorous, potassium) fertilizer. Nitrogen was
found to be the limiting factor at both experimental sites. Acidification
produced no observable influence on tree growth. Lysimeter and soil incubation
experiments conducted at the same time as the experiments described above
suggest that even moderate additions of sulfuric acid or sulfur added to soil
affect soil biological processes, particularly nitrogen turnover. The soil
incubation studies indicated that additions of sulfuric acid increased the
amount of mineral nitrogen but lowered the amount of nitrate.
Simulated acidic precipitation was observed to increase the growth of
-] -| O
Scots pine saplings in experiments conducted in Norway. Saplings in plots
watered with acid rain of pH 3.0, 2.5, and 2.0 grew more than the control
plots. The application of acid rain increased the nitrogen and sulfur content
of the needles. As the acidity of the artificial rain was adjusted using
sulfuric acid only, the increased growth was probably due to increased nitrogen
uptake.
Increasing acidic precipitation may cause a decrease in the fertility of
1 OQ
forest soils. Laboratory investigations by Overrein have demonstrated that
leaching of potassium, magnesium and calcium, all important plant nutrients,
is accelerated by increased acidity of rain. Field studies in Sweden correlate
129
decreases in soil pH with increased additions of acid. On the other hand,
soil fertility may increase as a result of acidic precipitation as nitrate and
sulfate ions, common components of chemical fertilizers, are deposited; however,
the advantages of such additions are likely to be short-lived as depletion of
nutrient cations through accelerated leaching should eventually retard growth.
8-79
-------
Another major uncertainty in estimating effects of acidic rain on forest
productivity is the capacity of forest soils to buffer against leaching by
hydrogen ions. Where the evidence is strongest for a direct effect of acidic
precipitation on forest growth (e.g., Sweden), the soils are already highly
leached, and the buffering capacity has been reduced. For much of the eastern
United States, however, the soils still retain the major portion of their
natural buffering capacity. This may explain why effects are not yet apparent
in this region. In addition, forest canopies have been found to filter 90
percent of the hydrogen ions from rain (pH 4.0) falling on the landscape during
the growing season. As a result, solutions reaching the forest floor are less
132
acidic (ph 5.0). Mayer and Ulrich, however, point out that for most elements
the addition by precipitation (wetfall plus dryfall) to the soil beneath the
tree canopy is considerably larger than that by precipitation to the canopy
surface as measured by rain gauges on a non-forested area. The leaching of
metabolites, mainly from leaf surfaces, and the washing out from leaves,
branches, and stems of airborne particles and atmospheric aerosols intercepted
by trees from the atmosphere are suggested as the reason for the mineral
increase. Using element balance data, Mayer and Ulrich came to the following
conclusions regarding the effect of acidic precipitation on a forest ecosystem:
"The buffering of protons, and to a minor extent accumulation
of Fe in the mineral soil, is balanced by the loss of Al , Mn
and, to a smaller extent, Na, K, Ca and Mg. This is possible
by the weathering of silicates, or, as in the case of K, Ca
and Mg, by desorption from the exchangeable fraction.
These processes definitely change the soil chemical
conditions in the uppermost 1 to 2 cm of the soil. While tree
growth is probably not affected by the acidification of this
layer, a disturbance of all plants rooting very close to the
In addition, the acidification of soil and the associated loss of magnesium may
become a problem in the supply of this nutrient element in the near future.
Many needle and leaf analyses indicated this possibility. The same is true
for manganese.
8-80
-------
A forest ecosystem is a complicated biological organization. Acidic
precipitation will produce some responses within the ecosystem even though it
is not possible at present to evaluate the changes which occur. The deter-
mination as to whether the changes are harmful or beneficial can only be
determined with certainty over a long period of time.
8.4.2 Effects of Acidic Precipitation on Soils
The active factor in the acidification of soils is the hydrogen ion (H ).
133
In the soil hydrogen ions are derived from the following sources:
1. nutrient uptake by plants. The root acidoids adsorb cation
nutrients and desorb H ;
2. COp produced by plant roots and micro-organisms;
3. oxidation of NH. and S, FeSp, and H?S to HN03 and HpSO.;
4. very acid litter in coniferous forests, the main acidifying
source for the A and horizons;
5. atmospheric deposition of HpSO. and some HN03, NO , HC1 and
NH4+ (after nitrification to HN03).
A gradual acidification of the soil may result from an increased influx
of H ions. Soils become acidic when large numbers of the exchangeable cations
are hydrogen (H ) and various forms of aluminum. Most acid soils develop due
to leaching. As water containing hydrogen cations (usually from weak acids)
moves through the soil, some of the hydrogen cations replace adsorbed exchange-
able cations, such as Ca , Mg , K and Na . (See Figure 8-13). The removed
cations are then carried deep into the soil profile or into the ground water.
In addition to the acidifying factors listed above the use of ammonium
fertilizers also adds hydrogen cations to the water solution. Ammonium
fertilizers are oxidized by bacteria to form nitrate (N03 ) and hydrogen ions
8-81
-------
(Many areas of the United States now use anhydrous ammonia as fertilizer
to prevent soils from becoming acid.) Increased leaching causes soils to
become lower in the basic Ca++, Mg , Na and K cations. Sensitivity to
leaching is according to the following sequence: Na » K > Mg > Ca .
All soils are not equally susceptible to acidification. Sensitivity to
leaching and to loss of buffering capacity varies according to the type of
parent material from which a soil is derived. Buffering capacity is greatest
in soils derived from sedimentary rocks, especially those containing carbonates,
and least in soils derived from hard crystalline rocks such as granites and
quartzites. Soil buffering capacity varies widely in different regions of
the country (Figure 8-8.) Unfortunately, many of the areas now receiving the
most acidic precipitation also are those with relatively low natural buffering
capacities.
The buffering capacity of soil depends on mineralogy, texture, structure,
organic matter, pH, base saturation, salt content and soil permeability.
Above a pH of 5.5 virtually all of the H ions, irrespective of source are
retained by ion exchange and chemical weathering. Below pH 5.5, the retention
of the H ion decreases with the soil pH in a manner determined by the composi-
134
tion of the soil. With a successive drop in the soil pH below 5.0, an
increasing proportion of hydrogen ions (H+) and deposited sulfuric acid will
pass through the soil and acidify run off water.134 The sensitivity of
different soils based on pH, texture and calcite content is summarized in
Table 8-10.
-I oc
Norton has reviewed the potential effects of acidic rain on soils
(Table 8-11). Most of the available information is from northern latitudes;
much less in known about soils of temperate regions, where the largest
8-82
-------
SOIL PARTICLES
ACID RAIN
I
SOIL SOLUTION
_
•
WEATHERING—^
-
*
*
Ca24
K4
Na4— T
NH;
so2-
HoPO"
*•
Ca24
Mg24
*H
K4
Na4
NOJ
so?-
*f'\rL
CAN BE LEACHE
Figure 8-13. Showing the exchangeable
ions of a soil with pH'^'7, the soil solu-
tion composition, and the replacement
of Na"1" by H+ from acid rain.133
8-83
-------
increases in rainfall acidity are presently occurring. The types of effects
that have been observed are destabilization and solution of clay minerals,
loss of cation exchange capacity, increased rates of mineral losses and,
128
consequently, increased rates pf podzolization. Overrein has conducted
extensive studies of effects of acidic precipitation on soils. Both accelerated
leaching of calcium and loss of the capacity of the soil to buffer pH have
been observed in lysimeter studies. Malmer is in agreement with Overrein's
findings. In field studies in Southern Sweden he noticed that increased
leaching of calcium from the soil resulted when the acidity of the rain falling
through the canopy decreased. He also mentioned that the buffering capacity
of a soil may be better correlated with the base saturation than with cations
exchange capacity and clay content.
Wiklander notes that in humid areas leaching leads to a gradual decrease
of plant nutrients in available and mobilizable forms. The rate of nutrient
decrease is determined by the buffering capacity of the soil and the amount
and composition of precipitation (pH and salt content). Leaching sooner or
later leads to soil acidificaiton unless the buffering capacity of the soil is
strong and/or the salt concentration of precipitation is high. Soil acidifica-
tion influences the amount of exchangeable nutrients and is also likely to
affect various biological processes in the soil.
Acid precipitation increases the amounts of SO2' and NO ~ entering the
soils. Nitrate is easily leached from soil, however, because it is usually
deficient for both plants and soil microorganisms, it is retained within
71 11? T1R
the soil-plant system. ' x'» ^° Retention of sulfate in soils appears
to depend on the amount of hydrous oxides of iron and aluminum present. The
amounts of these compounds present varies with the soil type. In significant
8-84
-------
TABLE 8-10. THE SENSITIVITY TO ACID PRECIPITATION BASED ON: BUFFER
CAPACITY AGAINST pH-CHANGE, RETENTION OF H , AND ADVERSE EFFECTS ON SOILS
Noncalcareous
Buffering
H retention
Adverse
effects
Calcareous
soils
Very high
Maximal
None
clays
pH > 6
High
Great
Moderate
sandy soils
pH > 6
Low
Great
Considerable
Cultivated
soils
pH > 5
High
Great
None -
s 1 i ght
Acid
soils
pH < 5
Moderate
Slight
Slight
Ref. 133
8-85
-------
TABLE 8-11. POTENTIAL EFFECTS OF ACID PRECIPITATION ON SOILS
Effect
Comment
Increased mobility of
most elements
Increased loss of
existing clay minerals
A change in cation
exchange capacity
A general propor-
tionate increase in
the removal of all
cations from the soil
An increased flux in
nutrients through the
ecosystem below the
root zone
Mobility changes are essentially
in the order: monovalent,
divalent, trivalent cations.
Under certain circumstances may
be compensated for by production
of clay minerals which do not
have essential (stoichiometric)
alkalies or alkali earths.
Depending on conditions, this
may be an increase or a decrease.
In initially impoverished or
unbuffered soil, the removal
may be significant on a time
scale of 10 to 100 years.
SOURCE: Ref. 136.
8-86
-------
amounts of the hydrous oxides of iron and aluminum are found in organic soils
I ~] Q
and therefore, sulfate retention is low. Mineral soils vary in their sulfate
retaining ability. Those with iron and aluminum hydroxides in their B horizons
appear to retain the largest amounts of sulfate.
Leaching of soil nutrients is efficiently inhibited by vegetation growing
on it. Plant roots take up the nutrients frequently in larger amounts than
required by the plants. Large amounts of these nutrients will later be
deposited on the soil surface as litter or as leachate from the vegetation
118
canopy.
In lysimeter experiments in Norway plots with vegetation cover were used.
One plot had a dense layer of the grass, Deschampsia flexuosa V(L) Trin. and
2-
the other a less dense cover. The soil retained 50 percent of the SO. added
to it. The greatest amount was retained by in the lysimeters covered with
grass and the relative retention increased with increasing additions of
n ft
sulfate. Leaching of cations from the soil was reduced by the retention of
2- 2+ 2+
the SO. , however, leaching of Ca and Mg increased significantly as the
acidity of the simulated rain increased. In the most acid treatment leaching
of Al was highly significant. The behavior of K , NO., and NH. was different
in the two lysimeter series. These ions were retained in the grass-covered
lysimeters whereas these was a net leaching of K and N03 in the other series.
Statistically significant effects were obtained only when the pH of the simulated
11 ft
rain was 3.0 or lower.
The Scandinavian lysimeter experiments appear to demonstrate that the
relative rate of adsorption of sulphate increases as the amounts applied are
8-87
-------
increased. In control lysimeters the output/input ratio was approximately
one. These results are in agreement with results of watershed studies which
frequently appear to demonstrate that on an annual basis, sulfate outflow is
equal to or greater than the amounts being added. ' Increased outflow may
be attributed to dry deposition and the weathering of sulfur bearing rocks.
The increased deposition of sulfate via acidic precipitation appears to have
increased the leaching of sulphate from the soil. Together with the retention
of hydrogen ions in the soil this results in an increased leaching of the
+ o+ 2+ 118
nutrient cations K , Ca , Mg , Mn.
The effects of acidic precipitation on soils are potentially long-lasting.
138
Oden has estimated that rainfall at pH 4.0 would be the cation equivalent
+2
of 30 kg Ca /ha, which represents a considerable potential loss of cations
139
essential for plant growth. McFee et al. calculated that 1000 cm of rainfall
at pH 4.0 could reduce the base saturation of the upper 6 cm of a midwestern
United States forest soil by 15 percent and lower the pH of the Al (A-One)
horizon (the surface layer in most agricultural soils) by 0.5 units if no
countering forces are operating in the soil. They note, however, that many
counteracting forces could reduce the final effect of acidic precipitation,
including the release of new cations to exchange sites by weathering through
nutrient recycling by vegetation.
Lowered soil pH also influences the availability and toxicity of metals
to plants. In general, potentially toxic metals become more available as pH
decreases. Ulrich reported that aluminum released by acidified soils could
be phytotoxic if acidic rain continued for a long period. The degree of ion
8-88
-------
leaching increased with decreases in pH, but the amount of cations leached was
far less than the amount of acid added. Baker et al. found that sulfur
dioxide in precipitation increased the extractable acidity and aluminum and
decreased the exchangeable bases, especially calcium and magnesium. Although
dilute sulfuric acid in sandy podsolic soils caused a significantly decreased
pH of the leached material, the amount of acid applied (not more than twice
the yearly airborne supply over southern Scandinavia) did not acidify soil as
127
much as did nitrate fertilizer. Highly acidic rainfall, frequently with a
pH less than 3.0, in combination with heavy metal particulate fall-out has
caused soils to become toxic to seedling survival and establishments according
142
to observations by Hutchinson and Whitby. Very low soil pH's are associated
with mobility of toxic aluminum compounds in the soils. High acidity, high
sulfur and heavy metals in the rainfall have caused fundamental changes in the
structure of soil organic matter. The sulfate and heavy metals were borne by
air from the smelters in the Sudbury area of Ontario and brought to earth by
dry and wet deposition. Among the metals deposited in rainfall and dustfall
were: nickel, copper, cobalt, iron, zinc, and lead. Most of these metals are
retained in the upper layers of soil except in very acid or sandy soils.
The accumulation of metals is mainly an exchange phenomenon. Organic
143
components of litter, humus and soil may bind heavy metals as stable complexes.
The heavy metals when bound may interfere with litter decay, nutrient cycling
143
and in this manner interfere with ecosystem functioning. Acidic precipitation
by altering the equilibria of the metal complexes through mobilization may
have a negative effect upon the residence time of the heavy metals with soil
and litter.143' 144
8-89
-------
Biological processes in the soil necessary for plant growth can be
affected by soil acidification. Nitrogen fixation, decomposition of organic
material, mineralization, especially of nitrogen, phosphorus and sulfur might
be affected.118' 127' 137' 145 Nearly all of the nitrogen, most of the
phosphorus and sulfur as well as other nutrient elements in the soil are bound
in organic combination. In this form, the elements are largely or entirely
145
unavailable for utilization by higher plants. It is only through the
activity of heterotrophic microorganisms that nitrogen and phosphorus and
sulfur are made available to higher plants. Thus, the microbial processes
that lead to the conversion of the organic forms of these elements to the
inorganic state are crucial for maintaining plant life in natural or
agricultural ecosystems. The key role of these degradative processes is the
fact that nitrogen is limiting for food production in much of the world and
145
governs primary productivity in many terrestrial habitats.
Many, and probably most, microbial transformations in soil may be brought
about by several populations. Therefore the elimination of one population is
not necessarily detrimental inasmuch as a second population not affected by
the stress may fill the partially or totally unfilled niche. For example, the
conversion of organic nitrogen compounds to inorganic forms is characteristically
catayzed by a number of species, often quite dissimilar, and a physical or
chemical perturbation affecting one of the species may not seriously alter the
rate of the conversion. On the other hand, a few processes are in fact carried
out, so far as it is now known, by only a single population, and elimination
of that species could have serious consequences. Examples of this are the
nitrification process, in which ammonium is converted to nitrate, and the
nodulation of leguminous plants, for which the bacteria are reasonably
specific according to the leguminous host.145
8-90
-------
The nitrification processes is one of the best indicators of pH stress
because the responsible organisms, presumably largely autotrophic bacteria,
are sensitive both in culture and in nature to increasing acidify. Although
nitrification will sometimes occur at pH values below 5.0, characteristically
the rate decreases with increasing acidity and often is undetectable much
below pH 4.5. Limited data suggest that the process of sulfate reduction to
147
sulfide in soil is markedly inhibited below a pH of 6.0 and studies of the
presumably responsible organisms in culture attest to the inhibition linked
145
with the acid conditions.
Blue-green algae have been found to be absent from acid soils even though
they have both adequate moisture and exposure to sunlight. Studies by Wodzinki
148
et al. attests to the sensitivity of these organisms to acidity. Inhibition
of the rates of both CO- afixation and nitrogen fixation were noted.
Studies concerned with the acidification of soil by nitrogen fertilizers
or sulfur amendments as well as comparisons of the microbial populations in
soils with dissimilar pH values attest to the sensitivity of bacteria to
increasing hydrogen ion concentrations. Characteristically, the numbers of
these organisms decline and not only is the total bacterial community reduced
145
in numbers but individual physiological groups are also reduced. The
actinomycetes (taxonomically considered to be bacteria) also are generally
less abundant as the pH decreases, while the relative abundance of fungi
146
increases, possibly due to a lack of competition from other heterotrophs.
The pH of soil not only influences the microbial community at large but also
145
those specialized populations that colonize the root surfaces.
It is difficult to make generalizations concerning the effects of soil
acidification on microorganisms. Many microbial processes that are important
for plant growth are clearly suppressed as the pH declines, however, the
8-91
-------
inhibition noted in one soil at a given pH may not be noted at the same pH in
another soil.''"4 The capacity of some microorganisms to become acclimated to
changes in pH suggests the need to study this phenomenon using environments
that have been maintained at different pH values for some time. Typically the
studies have been done with soils maintained only for short periods at the
greater acidity. The consequences of increased acidity in the subterranean
ecosystem are totally unclear.
8.4.2 Precipitation as a Source of Nutrients
Precipitation is a major source of nutrients in terrestrial and aquatic
78 149
ecosystems. '
The majority of the nutrients for lakes where the watershed is undisturbed
149
and the ratio of lake surface area to drainage area is large come from
precipitation. Precipitation may be the source of 40 to 55% of the phosphorus
and 45 to 75% of the inorganic nitrogen in some oligotrophic (low nutrient)
lakes. The direct contribution of nutrients by precipitation to lakes is
particularly important in areas with granite geological substrates. This is
particularly true if the ratio of lake surface area to the watershed area is
large. In ecosystems where the watersheds are disturbed by man, the
contributions from runoff is increased and the direct contribution of
precipitation becomes less important (Table 8-12). Precipitation is having
an even greater impact on aquatic ecosystems in undisturbed areas (those
having no local anthropogenic source of sewage or industrial wastes). Fossil
fuel combustion and long range atmospheric transport of its volatile combustion
products has resulted in the ionic composition of precipitation in remote
78 -
areas increasing. For example, the concentration of NO," in precipitation
in the Ithaca, N.Y., has increased by a factor of approximately 4-5 from
1915-1976. (Figure 8-14) The increased nitrogen in precipitation increases
8-92
-------
Table 8-12. SOURCES OF NITROGEN AND PHOSPHORUS FOR VARIOUS LAKES AS PERCENTAGES OF THE TOTAL ANNUAL INPUT
Sources
Phosphorus
Precipitation
Urban runoff and waste water
oo Rural runoff and ground water
00 Nitrogen
Precipitation
Urban runoff and waste water
Rural runoff and ground water
Fixation
Lake
Mendota
6
35
59
17
11
66
7
Di
Lake
Rotorua
2
14
83
6
11
83
7
sturbed Watersheds
Lake
Malaren
4
39
57
4
25
71
Lake Cayuga
Canandaigua Lake
2 2
46
98a
52
3 7
6
93a
91
• *
Undisturbed Watersheds
Clear Rawson Mirror Dogfish
Lake Lake Lake Lake
61 50 17 82
39 50 83 18
75 50 78
25 50 22
.
aThis value is a total for both "urban runoff and waste water" and "rural runoff and ground water."
Ref.149
-------
1915 20 25 30 35 40 45 SO 55 60 65 70 75 80
Figure 8-14. The weighted annual average of NO3 concentration
in bulk precipitation at Ithaca, N. Y. as a function of time.
8-94
-------
the fertilization effect of precipitation into undisturbed aquatic ecosystems,
however, because the increased N0_ concentration is associated with an increase
+ 7ft
in the H concentration an acidification of sensitive lakes also results.
This effect is significant because aquatic ecosystems which previously because
of their remoteness had remained pristine are now being influenced by man as a
7ft
result of the increasing contamination of precipitation on a regional basis.
Adding nitrate and other forms of nitrogen from the atmosphere to
ecosystems is an integral function of the terrestrial nitrogen cycle. Higher
plants and microorganisms can assimilate the inorganic forms rapidly. The
contribution of inorganic nitrogen in wet precipitation (rain plus snow) is
usually equivalent to only a few percent of the total nitrogen assimilated
annually by plants in terrestrial ecosystems; however total nitrogen con-
tributions, including organic nitrogen, in bulk precipitation (rainfall plus
dry fallout) can be significant, especially in unfertilized natural systems.
Atmospheric contributions of nitrate can range from less than 0.1 kg
N/ha-yr in the Northwest152 to 4.9 kg N/ha-yr in the eastern United States.153'
154
Inorganic nitrogen (ammonia-N plus nitrate-N) additions in wet precipitation
155
ranged from less than 0.5 kg/ha-yr to more than 3.5 kg/ha-yr in Junge's
study of rainfall over the United States. On the other hand, total nitrogen
loads in bulk precipitation range from less than 5 kg/ha-yr in desert regions
of the West to more than 30 kg/ha-yr near barnyards in the Midwest. Total
contributions of nitrogen from the atmosphere commonly range from about 10 to
20 kg N/ha-yr for most of the United States.156
In comparison, rates of annual uptake by plants range from 11 to 125 kg
N/ha-yr in ecosystems selected from several bioclimatic zones. Since the
lowest additions are generally associated with desert areas, where rates of
uptake by plants are low, and the highest additions usually occur in moist
8-95
-------
areas where high plant uptake is high, the contributions of ammonia and nitrate
from rainfall to terrestrial ecosystems are equivalent to about 1 to 10 percent
of annual plant uptake. The typical additions of total nitrogen in bulk
precipitation, on the other hand, represent from about 8 to 25 percent of the
annual plant requirements in eastern deciduous and western coniferous forest
ecosystems. Although these comparisions suggest that plant growth in terrestrial
ecosystems depends to a significant extent on atmospheric deposition, it is
not yet possible to estimate the importance of these contributions by comparing
them with the biological fixation and mineralization of nitrogen in the soil.
In nutrient-impoverished ecosystems, such as badly eroded abandoned croplands
or soils subjected to prolonged leaching by acid precipitation, nitrogen
additions from atmospheric depositions are certainly important to biological
productivity. Such sites, however, are relatively limited in extent. In
largely unperturbed forests, recycled nitrogen from the soil organic pool is
the chief source of nitrogen for plants, but nitrogen to support increased
production must come either from biological fixation or from atmospheric
contributions. It seems possible, therefore, that man generated contributions
could play a significant ecological role in a relatively large portion of the
forested areas near industrialized regions.
Sulfur, like nitrogen, is essential for optimal plant growth. Plants
usually obtain sulfur from the soil in the form of sulfate. The amount of
mineral sulfur in soils is usually low and its release from organic matter
during microbial decomposition is a major source for plants. Another major
source is the wet and dry deposition of atmospheric sulfur.134' 157' 158
In agricultural soils crop residues, manure, irrigation water and
fertilizers and soil amendments are important sources. The amounts of sulfur
entering the soil system from atmospheric sources is dependent on proximity to
8-96
-------
industrial areas, the sea coast and marshlands. The prevailing winds and the
amount of precipitation in a given region are also important. Near fossil
fueled power plants, and industrial installations the amount of sulfur in
1 *ift
precipitation may be as much as 150 pounds per acre or more. By contrast,
in rural areas the amount of sulfur in precipitation is generally well below
the average 15 pounds per acre. Approximately 5 to 7 pounds per acre per year
were reported for Oregon in 1966. Shinn and Lynn have estimated that in
the northeastern United States, the area where precipitation is most acidic,
approximately 5 x 10 tons of sulfate per year is removed by rain. Hoeft
et al. estimated the overall average sulfur as sulfate deposition as 26
pounds of sulfur/acre per year (30 kg S/ha per year). Estimates for rural
areas were 14 pounds of sulfur per acre per year (16 kg/ha). Approximately 40
to 50 percent of the sulfur additions occurred from November to February.
-1 CO
Tabatabai and Laflin found that SO.-S deposition in Iowa was greatest in
fall and winter when precipitation was low. They also estimated that the
additions of sulfur by precipitation were the same in for Ames in 1976 as were
reported for 1923, approximately 15 Ibs/acre. The average annual additions of
sulfur by precipitation is similar to that reported for rural Wisconsin by
Hoeft et al.161
Experimental data have shown that even though plants are supplied with
adequate soil sulfate they can absorb 25-35 percent of their sulfur from the
157
atmosphere. Particularly if the soil sulfur is low and the atmosphere
sulfur high, most of the sulfur required from the plant can come from the
atmosphere. Atmospheric sulfur would be of benefit chiefly to plants
growing on marginal lands with a low sulfur content, assuming of course that
the sulfur was not leached before it could be absorbed by the plants or the
deposition did not occur during the winter when in northern climes the uptake
8-97
-------
activity of evergreens is low and crops are not grown. In addition, the fact
that rainfall is highly variable within geographical areas, as well as the
previously mentioned fact that rainfall does not fall uniformly throughout the
year, may prevent nutrients being added to an ecosystem when their need is
greatest.163
When discussing the effects of acidic precipitation, or the effects of
sulfates or nitrates on soils, a distinction should be made between managed
and unmanaged soils. There appears to be general agreement that managed,
agricultural soils are less susceptible to the influences of acidic
precipitation than are unmanaged forest or rangeland soils because fertilizers
increase soil acidity much more than precipitation does. Ammonium fertilizers
usually as ammonium sul fate (NH.)? SO- or ammonium nitrate, NH. N03 (All
ammonium fertilizers are acid forming. Only anlydrous ammonia is not.) are
O-
oxidized by bacteria to form sulfate (SO. ) or nitrate (NOO and hydrogen
+ 134 157
ions (H ). ' The release of hydrogen ions into the soils causes the soil
to become acidified. This is the same process that occurs when acidic
precipitation by contributing hydrogen ions to the soil becomes "acidifying
precipitation." Strongly acid soils are not productive for most crops for one
of the following reasons:
1 Aluminum toxicity.
2 Manganese toxicity.
3 Iron toxicity in a few soils.
4 Calcium deficiency.
5 Magnesium deficiency.
6 Molybdenum deficiency.
7 Very slow organic matter decomposition.
8-98
-------
These are the same reasons, as has already been mentioned, that apply for
uncultivated soils. The acidifying effects of fertilization or acidic
precipitation is countered in managed soils through the use of lime. Liming
tends to raise the pH and thereby eliminate most major problems associated
130 134 149
with acids soils. ' ' Costs of liming all natural soils would be
prohibitive as well as extremely difficult to carry out.
Precipitation may add many chemicals not necessarily beneficial to
terrestrial, aquatic ecosystems and agricultural ecosystems. In addition to
sulfur and nitrogen, the biologically most important because they often limit
149
biological productivity, are phosphorus and potassium. Other chemicals of
varying biological importance found in precipitation over North America are
the following: chlorine, sodium, calcium, magnesium, iron, nickel, copper,
zinc, cadmium, lead, manganese, >1^,lb,3 mercup^1^ anc| cobalt. Rain over
121
Britain and the Netherlands, according to Graham contained the following
elements not found in North American precipitation: aluminum, arsenic,
beryllium, cerium, chromium, cesium, antimonry, scandium, selinium, thorium
and vanadium. Again it is obvious that many of these elements will be found
in precipitation in highly industrialized areas and will not be of bio-
logical importance until they enter an ecosystem where they may come into
contact with some form of life as in the case of heavy metals in the waters
and soils near Sudbury. Ontario. The chemical elements in the above list
which are essential in small amounts for the growth of plants are underlined;
however, at high concentrations these elements, as well as the other heavy
metals, can be toxic to plants and animals. Furthermore, the acidity of
precipitation can affect the solubility, mobility and toxicity of these
elements to the foliage or roots of plants and to animals or micro-organisms
8-99
-------
which may ingest or decompose these plants. Water in which these elements are
soluble could be toxic to the animals living in it or to animals (including
man) which may drink it.
Acidity is a critical factor in the behavior of natural or agricultural
soils. Soil acidity influences the availability of plant nutrients and
various microbiological processes which are necessary for the functioning of
terrestrial ecosystems, therefore, there is concern that acidic precipitation
over time could have an acidifying effect on soils through the addition of
hydrogen ions. A number of observations can be made regarding the effects of
acidic precipitation on soils.
Wiklander has pointed out that based on the ion exchange theory, ion
exchange experiments, and the leaching of soil samples, the following conclusions
can be drawn about the acidifying effect on soils through the atmospheric
deposition of mineral acids.
1. At a soil pH > 6.0 acids are fully neutralized by decomposition of
CaC03 and other unstable minerals and by cation exchange.
2. At soil pH < 5.5 the efficiency of the proton to decompose minerals
and to replace exchangeable Ca , Mg , K and Na+ decreases with the
soil pH. Consequently, the acidifying effect of mineral acids on
soils decreases, but the effect on the runoff water increases in the
very acid soils.
3. Salts of Ca , Mg , K and NH4+ in the precipitation counteract the
absorption of protons and, in that way, the decrease of the base
saturation. A proportion of the acids percolate through the soil
and acidify the runoff.
The sensitivity of various soils to acid precipitation depends on
the soil buffer capacity and on the soil pH. Noncalcareous sandy soils with
pH > 5 are the most sensitive, irrespective of soil type.
8-100
-------
Very acid soils are less sensitive to acidic precipitation because they
are already adjusted by soil formation to acidity and are therefore more
stable. In these soils easily weatherable minerals have disappeared, base
saturation is low and the pH of the soil may be less than that of precipitation
The low nutrient level is a crucial factor in these soils. Even a slight
decrease by leaching may have a detrimental effect on plant yield. Ferti-
lization appears to be the only preventive measure.
In properly managed cultivated soils, acidic precipitation should cause
only a slight increase in the lime requirement with the cost compensated for
by the supply of sulfur, nitrogen, magnesium, potassium, and calcium made
available to plants.
All of the major anions and cations transferred into ecosystems when it
is raining or snowing (wet deposition) also are contained in the gases,
aerosols, and particulate matter that are transferred from the atmosphere into
ecosystems when it is not raining or snowing (dry deposition). Thus, in a
chemical mass balance sense, it is both impossible and unrealistic to
distinguish the biological effects of "acid precipitation" (wet deposition)
from the biological effects of dry deposition.
In addition to the direct deposition of acidic substances into ecosystems
as wet and dry deposition, some ionic materials (notably various complexes of
ammonium and sulfate ions) although chemically neutral (or nearly so) are
acidifying in their effects when they are taken up by plants and animals.
Thus, the concept of "acidifying precipitation" must be added to the concept
of "acid precipitation".
The injurious substances in dry and wet deposition include not only
acidic substances but also certain volatile organic substances as well as
various other inorganic substances and heavy metals such as Mn, Zn, Cu, Fe,
Mo, B, F, Br, Al, Pb, I, Ni, Cd, and V.
8-101
-------
The elements underlined in the list above are essential elements required
in small amounts by plants. At high concentrations, however, these same
elements can be toxic to plants and animals. In addition, the acidity of
precipitation can affect the solubility, mobility and toxicity of these
elements when they contact the foliage or roots of plants, and are ingested by
microorganisms during decomposition of plant parts or by animals eating the
plants. When in water they can be toxic to animals, including man, which may
drink the water containing these elements or to the animals (fish and other
aquatic organisms) that inhibit the waters in which these elements are
dissolved.
8.5 THE VALUE OF A NATURAL ECOSYSTEM
Ecosystems are evaluated by modern man solely on the basis of their
economic value to him as expressed in dollars and cents. The basis of this
evaluation depends on the extent to which man can manipulate the ecosystem for
his own purpose. This single-purpose point of view makes it difficult to
explain the many benefits of a natural ecosystem to man's welfare in terms of
conventional cost-benefit analysis. Natural forests are among the most
efficient in the use of solar energy. By comparison, agriculture is
inefficient in fixing (using) solar energy; however, agriculture is emphasized
because its benefits as food production for man is much more readily quan-
titled.170
Attempts have been made to quantify the cost of lake acidification and
the loss of fisheries resources of the Adirondacks to the state of New York.
The Adirondacks service the outdoor recreational needs of local residents as
well as those of vacationers from other states, New York City and the urban
centers of the Hudson and Mohawk Valleys. These resources also contribute
significantly to the economy of local communities. According to a 1973
survey, during 2 million fishing trips, anglers spent an estimated 26 million
8-102
-------
dollars for bait, tackle, lodging and transportation. Acidic precipitation,
therefore, has a potential for significantly affecting the economic base of
the region.
There are two obvious approaches to the management of acidified waters:
1) change the water to suit the fish, or 2) change the fish to suit the
water. The first approach involves increasing the pH of the lakes to the
point where existing or newly-stocked fish populations can survive. The
second, the development of strains of fish tolerant to acid waters. Both
approaches have their limitations. The first approach is to lime the lakes.
Since the mid-19501s, the New York State Bureau of Fisheries has added lime to
51 ponds at an average cost of $15 to $30 per acre of water per year depending
on the accessibility of the lake or pond. The emphasis was on maintaining
genetically unique fish populations or stocks having especially high
recreational importance. In some instances, a single lime treatment has
permitted reestablishment and maintenance of populations for three to four
years. Under appropriate watershed conditions, liming not only increases the
survival rate of fish in otherwise acid waters but can promote growth of
invertebrate forage populations. Liming, however, is no easy chore. More
than a ton of lime may have to be applied to each acre of water to obtain
acceptable results. The application of lime to inaccessible Adirondack ponds
is a difficult logistical exercise requiring the cooordination of truck,
helicopter and ground crews. In practical terms, liming whole bodies of water
is a feasible treatment only for smaller ponds which have low flushing rates.
Refuge liming, or applying lime to less than the whole lake surface, is a
possible option for larger waters. This involves liming littoral areas or
tributary areas to provide a "safety zone" for fish during periods of high
8-103
-------
acid input. These episodes are often associated with spring snowmelt.
Further study is required on the feasibility and methodology of this approach.
A treatment program covering all Adirondack waters presently known to be out
of production would require an estimated 150,000 dollars per year in material
and labor costs alone. Not quantified are the cost of inventorying and
monitoring of the lakes to determine their potential for acidification and
assessing the fish populations. It was estimated in 1978 that the cost of
surveying 100 waters per year over the next five years would cost
approximately $70,000 a year.
The cost of the second approach, developing species of fish tolerant to
acidic water conditions has not been as well quantified. The possibility
exists of maintaining fish populations in some brook trout waters by stocking
strains of trout that can survive conditions which are intolerable to native
populations or the strains of brook trout presently being stocked. This
approach has potential only for those marginal waters which have maintained a
forage base capable of sustaining reasonable growth of stocked trout, and may
be used to extend the effective life of lime applications.
Liming of acidified lake ecosystems was first used in Scandanavia and was
1 -79
found to produce beneficial effects in some lakes. Wright reviewed an
early attempt in which addition of chalk to Swedish lakes increased pH and led
to increased phytoplankton growth and improved fish survival. Addition of
CaC03 and Ca(OH2) to two acidic lakes in Sudbury, Ontario, increased pH, de-
creased heavy metal concentrations, and caused a temporary decline in
chlorophyll. Reviews of liming experiments in Norway, cited by Wright
concluded that this practice would be feasible only for small ponds and
8-104
-------
streams. One disadvantage of liming is that when the pH reaches the 5.0 to
6.0 range aluminum in waters with high concentrations becomes toxic.
The Boundary Waters Conoe Area occupies over a million acres of lakes and
streams and complementing it is Ontario's Quetico Provincial Park of 1,120,000
acres. The cost of liming the lakes and streams over such a large area can
only be imagined.
In Sweden, the cost of lost productivity of fish-stocks has been
estimated at 16.5 million dollars per year solely in terms of the expected
market value of commercially utilized species. Loss of income associated with
tourism and recreational fishing is estimated to be in the range of 50 to 100
million dollars annually.
The previous discussion has dealt only with the estimatable costs for
reclaiming a few lakes and streams. Many functions and benefits of natural
ecosystems to man are unknown to the decision makers. In an attempt to
quantify the values of natural ecosystems Gosselink, Odum and Pope have used a
tidal marsh as an example. They have placed a value on a tidal marsh by
assigning monetary values to the multiple contributions to man's welfare such
as fish nurseries, food suppliers, and waste-treatment functions of the marsh.
They estimate the total social values to range from $50,000 to $80,000 per
acre.
174
Using four different categories, Gosselink, Odum and Pope, developed a
step-wise means of assessing the true value of natural tidal marshes to
society as a whole. The value was based on commercial usage, social usage and
the monetary value of natural ("undeveloped") estuarine environments.
8-105
-------
The categories or levels of marshlands to which monetary values were
assigned are: (1) commercial and recreational use, e.g., shell fish produc-
tion and sport fishing; (2) potential for development, e.g., aquaculture,
draining for industrial use; (3) waste assimailation or treatment, e.g.
tertiary sewage treatment; and (4) total life support values, e.g., global
cycling of nitrogen and sulfur, as protective "breakwaters." The round-figure
values calculated in terms of (a) annual return and (b) an income-capitalized
value were: (1) a. $100; b. $2,000; (2) a. $1,000; b. $20,000; (3) a. $2,500;
b. $50,000; and (4) a. $4,100; b. $82,000.
The foregoing estimates for category (1) were based on identifiable 1974
commercial and recreational uses for which monetary values could be determined
rather well. For category (2) the income-capitalization approach was used to
estimate the values for development potential and for aquaculture. The
estimates for tertiary sewage treatment (3) and life support (4) represent
estimates of what man would have to pay for this useful work that is now per-
formed by an acre of estuary were it not available to do this work.
Shortcomings exist in evaluating the environment solely in terms of
direct uses or products. "Such cost-accounting ignores the extremely valuable
life-support work that natural areas carry on without any development or
direct use by man. It is this 'free work of nature1 that is grossly under-
valued, simply because it has always been taken for granted or assumed to be
unlimited in capacity." Development by man of a salt marsh may adversely
affect its functioning in tertiary sewage treatment or as a life support
system, therefore, it is important to evaluate it before deciding what kind of
development, if any, is in the long-term best interest of both the environment
and the economy.
8-106
-------
Westman also evaluated the benefits of natural ecosystems by
estimating the monetary costs associated with the loss of the free services
(absorption of air pollution, production of oxygen, regulation of global
climate and radiation balance, and soil binding) provided by the ecosystems.
Westman estimated that the oxidant damage to the San Bernardino National
Forest could result in a cost of $27 million per year (1973 dollars) for
sediment removal alone due to erosion as long as the forest remained in the
early stages of succession.
Estimates of the cost in currency of the values of items and qualities
such as clean air and water, untamed wildlife, and wilderness, once regarded
as priceless, are an attempt to rationalize the activities of civilization.
When estimating the monetary cost in currency of the values lost through the
damaging of ecosystems, the assumption is usually made that the decision
makers will choose the alternative which is most socially beneficial as in-
dicated by costs compared to benefits. As Westman points out, the
assumption "that decisions that maximize benefit cost ratios simultaneously
optimize social equity and utility" are based on certain inherent corollaries
These are:
"(1) The human species has the exclusive right to use and
manipulate nature for its own purposes. (2) Monetary units are
socially acceptable as means to equate the value of natural
resources destroyed and those developed. (3) The value of
services lost during the interval before the replacement or
substitution of the usurped resource has occurred is included
in the cost of the damaged resource. (4) The amount of
compensation in monetary units accurately reflects the full
value of the loss to each loser in the transaction. (5) The
value of the item to future generations has been judged and
included in an accurate way in the total value. (6) The
benefits of development accrue to the same sectors of society,
and in the same proportions, as the sectors on whom the costs
are levied, or acceptable compensation has been transferred.
Each of these assumptions, and others not listed, can and have
been challenged."
8-107
-------
In the case of (4) above, for example, the losses incurred when the develop-
ment of natural ecosystems are involved, include species other than man.
These losses are seldom, if ever, compensated. The public at large also is
usually not consulted to determine whether the dollar compensation is adequate
and acceptable. Frequently, there is no direct compensation. Corollary (5)
can never be fulfilled because it is impossible to determine accurately the
value to future generations.
It should be remembered that ecosystems are life support systems and
therefore their worth, in the final analysis, cannot be valued in dollars and
cents.
8.6 EFFECTS OF ACIDIC PRECIPITATION ON MATERIALS
Acidic precipitation can damage the abiotic as well as the biotic com-
ponents of an ecosystem. Of particular concern in this section are the
deteriorative effects of acidic precipitation on materials and cultural
artifacts of man-made ecosystems. The dominant factor in the formation of
acidic precipitation is sulfur, usually as sulfur dioxide. ' Because of
this fact, it is difficult to isolate the effect of acidic precipitation from
changes induced by sulfur pollution in general. (The effects of sulfur
compounds on materials is discussed in Chapter 10.) High acidity
promotes corrosion because the hydrogen ions act as a sink for the
electrons liberated during the critical corrosion process. Precipitation
as rain affects corrosion by forming a layer of moisture on the surface of the
material and by adding hydrogen (H+) and sulfate (SO- ) ions as corrosion
stimulators. Rain also washes out the sulfates deposited during dry deposition
and thus serves a useful function by removing the sulfate and stopping
corrosion. Rain plays a critical role in the corrosive process because in
8-108
-------
areas where dry deposition predominates the washing effect is greatest, while
in areas where the dry and wet deposition processes are roughly equal, the
corrosive effect is greater. The corrosion effect in areas where the pH of
precipitation is very low, particularly of certain metals, may be greatly
inhanced by precipitation. In a Swedish study the sulfur concentration of
2
precipitation, expressed as meg/m per year, was found to correlate closely
with the corrosion rate of steel. The metals most likely to be corroded by
precipitation with a low pH are those whose corrosion resistance may be
ascribed to a protective layer of basic carbonates, sulfates or oxides, as
used on zinc or copper. The decrease in pH of rainwater to 4.0 or lower may
accelerate the dissolution of the protective coatings.
Materials reported to be affected by acid precipitation in addition to
steel are: copper materials, linseed oil, alkyd paints on wood, antirust
paints on steel and accelerated deterioration of limestone, sandstone,
concrete and both cement-lime and lime plaster.
Stone is one of the oldest building materials used by man and has
traditionally been considered one of the most durable because structures, such
as the pryamids, which have survived since antiguity are made of stone. What
is usually forgotten is that the structure built with stone which was not
durable has long since disappeared.
Atmospheric sulphur compounds (mainly sulphur dioxide, with subsidiary
amounts of sulphur trioxide and ammonium sulphate) react with the carbonates
in limestone and dolomites, calcareous sandstone and mortars to form calcium
sulphate (gypsum). The results of these reactions is blistering, scaling, and
loss of surface cohesion which in turn induces similar effects in neighboring
materials not in themselves susceptible to direct attack.
8-109
-------
-I CO
Sulphates have been implicated by Winkler as very important in the
disintegration of stone. The surface flaking on the Egyptian granite obelisk
(Cleopatra's Needle) in Central Park, NY is cited as an example. The
deterioration accurred within two years of its erection.
A classic example of the effects of the changing chemical climate on the
stability of stone is the deterioration of the Madonna at Herten Castle, near
Recklinghousen, Westphalia in Germany. The sculpture of porous Baumberg
sandstone was erected in 1702. Pictures taken of the Madonna in 1908 shows
slight to moderate damage during the first 206 years. The features of the
Madonna, eyes, nose, mouth and hair are readily discernable. In pictures
taken in 1969 after 267 years, no features are visible.
It is not certain in what form sulfur is absorbed into stone, as a gas
(S0?) forming sulphurous or sulphuric acid or whether it is deposited in rain.
Rain and hoarfrost both contain sulfur compounds. Schaffer compared the
sulphate ion in both rain and hoarfrost (Table 8-13) and showed that the
content of hoarfrost was approximately 7 times greater than rain at
Heachingley, Leeds, England in 1932. Wet stone surfaces unquestionably
increase the condensation or absorption of sulphates. Stonework kept dry and
shielded from rain, condensing dew or hoarfrost will be damaged less by S0?
pollution than stone surfaces which are exposed.167
Acid rain may leach ions from stonework just as acidic runoff and ground
water leaches ions from soils or bedrock, however, at the present time it is
not possible to attribute the deleterious effects of atmospheric sulphur
pollution to specific compounds.
8-110
-------
TABLE 8-13. COMPOSITION OF RAIN AND HOARFROST AT HEADINGLEY, LEEDS
Suspended matter
Tar
Ash
Acidity
Sulphur as SO,
Sulphur as SO^
Total sulphur
Chlorine
Nitrogen as NH3
Nitrogen as N?0r
Nitrogen as albuminoid
Average rain
parts per mill ion
115
15
28
1.9
22
5.7
27.7
7.3
1.98
0.196
0.434
Hoarfrost
parts per million
4620
158
67
102.9
148
41.0
189.0
94.6
8.57
0.0
1.618
Ref.169
8-111
-------
8.7 ACIDIC PRECIPITATION
8.7.1 Causes of Acidic Precipitation
Several lines of evidence suggest that the widespread acidification of
rain began no earlier than 1950-1955. Athough this shift has been linked with
changes in the amounts of S0~ and NO emissions, the precise causes are still
^ j{
?f)fi
unclear. Likens and Bormann suggested that acidification was partially a
consequence of the decrease in emissions of alkaline fly ash from coal-burning
power plants, coupled with increasing emissions of SO,, and NO (from power
£ /^
plants, smelters, and industrial processes), and Likens noted that the
trend toward higher smokestacks to disperse pollutants may be responsible in
part for the widening geographic extent of the acid deposition problem. The
taller smokestacks are associated with a shift in the usage of coal from
residential heating and railroads to use by the electric utilities to fire
224
power generators. Despite the shift, the actual amount of coal used does
not show a great increase when figures for 1918-1928 are compared to those for
1979. Approximately 550 MM tons were used during 1918-1928 compared to 672
225
MM tons during 1979. There was, however, a seasonal shift in the pattern
of coal consumption. Summer coal consumption has increased since 1960 while
winter consumption has decreased due to increased summer usage by the electric
utilities.
182
Cogbill and Likens associated acidic rainfall in New York with high
altitude air masses transported into the region from the Midwest, implying
that the SO^ and N0x that cause acidic rain may be transported distances of
300 to 1500 km. A report by Miller et al.202 dealing with the origin of air
masses producing acidic precipitation at Ithaca, New York, points to the
trajectories from the southwest sector as being the source of acidic precipi-
tation. The trajectories from the southwest were high in sulfuric, nitric and
8-112
-------
202
hydrochloric acids. The report by Miller et al. supports the study made by
182
Cogbill and Likens which also concluded that precipitation was more acidic
when upper level trajectories originated from the southwest (Figure 8-15).
Emissions of sulfur and nitrogen oxides for the United States are depicted in
Figures 8-15a, 8-15b.
226
Gatz suggested that if trajectories of low altitude air masses are
used to trace the source of acids in rainfall the major source of rainfall
acidity in the Northeast is the Ohio River Valley of Ohio, Pennsylvania, West
Virginia, plus Maryland, a region of large S02 emissions (Figure 8-15).
195
Galvin et al. also point to the Ohio River Valley as the source of trajectories
passing Schoharie and Holland, New York. These air streams contained large
amounts of sulfate.
Evidence from northern Europe also supports the idea that acidic rainfall
is a large-scale regional problem involving long distances between emission
sources and deposition of acidic rain. The acidic rains that have received
intensive study in southern Scandinavia have been shown to result primarily
from emissions of sulfur and nitrogen oxides in Great Britain and the industrial
178
regions of continental Western Europe (e.g., Holland, Belgium, West Germany).
198
Nisbet compared estimated total SOp emissions with total deposition of
sulfate in precipitation in eastern North America for the years 1955-1956,
1965-1966, and 1972-1973. Only 30 to 38 percent of the emitted sulfur could
be accounted for by rainfall deposition. The fate of the remainder is uncertain;
presumably some was deposited as dry fallout within the region studied and the
rest was transported eastward over the Atlantic Ocean.
Transformation and transport of S02 and sulfate aerosol is discussed in
Chapter 6 of this document, however, the following conclusions regarding the
8-113
-------
Figure 8-15. Trajectory map indicating source strengths for S02 emissions
affecting the eastern United States.206 Emission rates of S02 are shown by
shading of the map. 500 mbar trajectory corridors from Cogbill and Likens182
are superimposed on the map to indicate directions of movement of air masses
at ca. 5500 m altitude for several days preceding specific rain events at Ithaca,
New York. The numbers between the lines are mean pH values for rain events
associated with each trajectory corridor.
8-114
-------
Figure 8-15a. SO emissions over 100 tons per year from NEDS.
A
-------
CO
I
CTi
OO.OQO row) ni T(M
Figure 8-15b. NO emissions over 100 tons per year from
NEDS,
-------
large scale movements of pollutants within the United States and across national
boundaries have been presented in the document, "The Long-Range Transport of
Air Pollutants (LRTAP) in North America."227
"The meteorological regime in eastern North America is conducive
to long-range transport and transboundary transport in both directions
across the Canada-United States border.
The large-scale movement of pollutants does occur within the
United States and within Canada, as well as across the Canada-United States
border, and poses an environmental problem.
The net flux of sulfur compounds is from south to north across
the border. The northward movement of sulfur is comparable in
magnitude to the internal emissions in Canada, whereas, the southward
flux is substantially less than domestic United States emissions.
The greater portion of total sulfur deposition in each country
is probably the result of domestic emissions. The contribution of
neighbour-country emissions is relatively greater in the case of
United States emissions being deposited in Canada. However, the
crucial aspect is the magnitude of deposition of acid species on
sensitive ecosystems within the United States and Canada.
Preliminary estimates suggest that two-thirds of the sulfur
emitted into the atmosphere of eastern North America is probably
deposited there with the remainder leaving the atmosphere of the
region, primarily to the east."
8.7.2 Formation and Composition
Precipitation is that portion of the global water cycle by which water
vapor from the atmosphere is converted to rain or snow and then is deposited
p
on earth. Water by evaporation and transpiration (water vapor lost by
vegetation) moves into the atmosphere. Once it reaches the atmosphere, the
water vapor is cooled, then condenses on solid particles and soon reaches
equilibrium with atmospheric gases. One of the gases is carbon dioxide. As
carbon dioxode dissolves in water carbonic acid (^COg) is formed. Carbonic
acid is a weak acid and in distilled water only dissociates slightly yielding
hydrogen ions and bicarbonate ions (HC03 ). At normal atmospheric concen-
trations and pressures of carbon dioxide, the pH of rain and snow is 5.6.
8-117
-------
The pH of precipitation may vary and become more basic or more acidic
depending on substances in the atmosphere. Dust and debris may be swept
from the ground in small amounts and into the atmosphere where it can be
involved in the rain. Soil particles are usually slightly basic in distilled
2+ 2+
water and release positive ions, such as calcium (Ca ), magnesium (Mg ),
potassium (K+), and sodium (Na ) into solution. Bicarbonate usually is the
corresponding negative ion. Decay organic matter adds gaseous ammonia to
the atmosphere. Ammonia gas in rain or snow forms ammonium ions (NH^ ) and
tends to increase the pH. In coastal areas sea spray plays a strong role in
the chemistry of precipitation. The important ions entering into precipi-
tation, sodium, magnesium, calcium, potassium, and the anions chloride
(Cl ) and sulfate (SO. +) are the ones most abundant in the ocean.
Other gases, in addition to CO^, which enter precipitation are sulfur
dioxide ($02), hydrogen sulfide (^S) the nitrogen oxides. The sulfur gases
originate from such natural sources as volcanoes and swamps. In the atmos-
phere both of these gases can be oxidized to sulfuric acid. Nitrogen oxides
in the atmosphere are converted to nitric acid. If the two acids are pre-
sent in significant amounts, the acidity of precipitation can go below a pH
of 5.6. The acidity of precipitation, however, is a reflection not only of
sulfuric, nitric, hydrochloric and organic acids but also of the total ionic
balance between all cations and anions in precipitation.
The amounts of the various substances in the atmosphere originating from
seawater, desert sands, volcanic islands or vegitated land influence the
chemistry of natural precipitation. In regions with calcareous soils,
calcium and bicarbonate may enter precipitation and presumably as a result of
the dust being incorporates, the pH of rain or snow is usually above 6.0.
8-118
-------
The precipitation that fell before the Industrial Revolution and was
preserved in glaciers and continental ice sheets has been analyzed, and it
generally has a pH above 5.0. In Greenland,, the pH of ice that had originated
as snow approximately 180 years ago, was measured by Swiss scientists and
found to have a pH ranging from 6.0 to 7.6
Combustion of fossil fuels and the smelting of sulfide ores in the
heavily industrialized and urbanized regions of the north temperate zone
have changed the picture. Evidence exists that during the past two decades
the emission of large amounts of sulfur and nitrogen oxides (See Chapter 4)
have caused the strong inorganic acids, sulfuric (H9SO.) and nitric (HNOO
L* ^ *J
to appear in increasing amounts in the precipitation in many of the areas
surrounding the industrial regions of the world. ' ' Strong
acids dissociate completely in dilute aqueous solutions and lower the pH
to less than 5.6 Acidic precipitation is rain or snow with a pH below
5 678,130,176
Continuous sampling and analysis of precipitation over northern Europe
since the mid-19501s have revealed that there has been a steady increase in
acidity from a range in pH of 6.0 to 5.5 in 1956 to one of 4.5 to 4.0 in
1966. ' The pH rainfall throughout southern Scandinavia is less than 4.5,
and the hydrogen ion content of precipitation in some parts of Scandinavia has
increased 200-fold (a change of 2.3 pH units) in the past two decades. '
Studies to date in the northeastern United States have also demonstrated a
trend toward a decrease in the pH of rain and snow as well as an expansion of
the area receiving precipitation with a decreasing pH (Figures 8-16,
8_17) 98a,130,151,176,177,181-186
8-119
-------
The continuing occurrence of acidic rainfall and snow over large areas of
the eastern United States, Canada and northern Europe has received increasing
attention in recent years.98a>13°.151>176~186 Currently the average annual pH
of precipitation in the northeastern United States is between 4.0 and 5.0.
Average pH values around 4.5 have been reported as far south as northern
Florida,151'185 from Illinois,187 the Denver area of Colorado,188 the San
189 190 191
Francisco Bay Area of California, ' Pasadena, Ca. , the Puget Sound
-iqo 98a 192 193
area of Washington and from eastern Canada. '
It is clear from recent studies that acidic rainfall is a manmade problem
(See Chapter 4 and 5). Such acidification has the potential for causing
serious ecological effects over widespread geographic areas. Especially note-
worthy in this connection are the observations showing the acidity of rainfall
to be many times higher downwind from major industrial areas than
elsewhere. ' Several aspects of the problem, however, remain subject
to debate because existing data are ambiguous or inadequate. Important issues
include: (1) the rate at which rainfall is becoming more acidic and the rate
at which the problem is becoming geographically more widespread; (2) the
quantitative contributions of various acids to the overall acidity of rainfall;
(3) the relative extent to which the acidity of rainfall in a region depends
on local emissions of sulfur and nitrogen oxides versus emissions transported
from distant sources; (4) the relative importance of changes in total mass
emission rates compared to changes in the nature of the emission patterns
(ground level versus tall stacks) in contributing to regional acidification of
precipitation; and (5) the biological/ecological effects on terrestrial
ecosystems.
8-120
-------
A IKS M
s.eo
B IMS M
C 1972-73
7*0
•J«
8*3
»00
MILES
• 50 100 200 300
Figure 8-16. The weighted annual average pH of precipitation in the eastern U. S. in 1955-56,
1965-66, and 1972-73.151
8-121
-------
25 66
100 S.O
250 46
600 4.3
750 412
Figure 8-17. Spread of acid rain, 1975-76.176
8-122
-------
The following sections discuss evidence related to the first four issues
while the ecological effects have been discussed in the preceeding sections of
this chapter. The emissions of sulfur oxides from both natural and man-made
sources are set forth in Chapter 4, ambient concentrations of sulfates, S02
and nitrate aerosols are described in Chapter 5 while transformation of SOp
and the transmission of particles are explained in Chapter 6. The ecological
effects resulting from the acidification and the possibility of effects due to
the long term acidification of terrestrial ecosystems if the present trends
continue is cause for concern. An understanding of the factors involved in
the formation of acidic precipitation is essential if the trends are to be
ameliorated.
8.7.3 Long Term Trends
In northern Europe and the northeastern United States rainfall has become
more acidic. For Europe the data obtained from long-term
studies15'16'179'180'181 shows conclusively that since the 1950's, the acidity
of precipitation has increased. The United States is not so fortunate. Be-
latedly an atmospheric deposition network has been established to aid in
78
determing trends in precipitation acidity as well as the composition. Lack-
ing such a system it has been necessary to extrapolate long-term trends from
such data as are available.
The isopleth maps of rainfall pH presented in Figure 8-15 indicate that
the acidity of rainfall over the eastern United States has increased during
the past 20 years, but the rate of change at a given location is difficult to
quantify, largely because historical data on the pH of rainfall are extremely
rare. Even where fairly long-term records are available (e.g., measurements
have been made since 1964 at Hubbard Brook, New Hampshire), values are
8-123
-------
197
scattered over a wide range. Likens et al., reported that the weighted
annual average pH ranged from 4.03 to 4.21 between the years 1965 and 1973-74.
(A weighted average considers the amount of rain as well as its composition.)
No statistically significant trend was noted, however, when concentrations
were multiplied by the amount of precipitation to give areal deposition rates
(equivalents of H+/ha-yr), a trend of increasing H deposition (a 36 percent
increase over the decade) was noted [Figure 8-18 (A)]. Increases in the
annual amount or frequency of precipitation will increase the rate of
deposition in the same way that increases in acidic emissions will; and as
Figure 8-16 (B) shows, the annual amount of rainfall at Hubbard Brook
increased significantly over the decade. However, deposition rates for
cations other than H at the same site were not related to the annual amount
of precipitation [Figure 8-16 (C)]. The amount of annual rainfall is one of
the factors influencing H deposition and may help to explain the increase in
H deposition over time. The acidity of pH in Florida has resulted in the
isopleths for that state to move farther south (Figure 8-17) than in Figure 8-16(C),
The change reflects the availability of more accurate data.
183
Cogbill reviewed the temporal trends and the geographic distribution
of rainfall acidity in the northeastern United States, and summarized the
sparse information on rainfall pH available prior to the 1960s. He found that
the acidity of rainfall at nine stations near the periphery of the central
isopleth in 1955-1956 (see Figure 8-17) showed an average increase of 12 ug
H /I by 1965-1966. Data for two of the stations near the northern limit of
the acidic region showed an apparent stabilization in rainfall pH after the
initial decrease in the 1960s. At Caribou, Maine, the pH values for 1955 to
8-124
-------
120
110
_ A
I 90
•
I 80
I 70
60
I I
/
I L
I I
I
I
I
I
I
I
I
1964 '65 '66 '67 '68 '69 70 "71 72 73 74 75
YEAR
Z
o
a.
5
ai
cc
a
D
Z
Z
200
180
160
140
120
100
80
t
0
120
100
I
I
I
I I
I
I I
I I I
_B
i i i
j i
j i
I
1964 '65 '66 '67 '68 '69 70 71 72 73 74 75
YEAR
a. CM
Z E
9. I
80
» 60
< = 40
I 'i
I 20
_ c
I J 1 J
80
100
120
140
160
180
200
ANNUAL PRECIPITATION, cm
Figure 8-18. Cation inputs in precipitation at Hubbard Brook, New
Hampshire. (A) Annual input of hydrogen ion, 1964-73; (B) Annual
precipitation, 1964-1973; (C) Comparison of annual input of hydro-
gen ion and annual input of total cations less hydrogen ion plotted
against amount of annual precipitation. 197
8-125
-------
1956, 1965-1966, and 1972-1973 were 4.94, 4.63, and 4.76, respectively, and at
Sault Ste. Marie, Michigan, the pH values for the same years were 5.76, 4.76,
•I QO
and 4.69, respectively. Other reviews of available data suggest that the
average pH is decreasing in the most affected areas, from about 4.4 in the
1950s to 4.0 to 4.1 in the 1970s, ' but quantitative inferences should be
made cautiously.
Acidic precipitation has been a reality in New York State for an undeter-
mined period of time. The data collected by the United States Geological
iqq
Survey over a ten year period which documents this statement is presented
in Figure 8-19. These curves represent the pH of precipitation at eight
different locations in New York State and one location in Pennsylvania. Each
of these locations (Figure 8-20) represents an area within a given watershed,
Table 8-14. Because the pH of precipitation has remained nearly at the same
general average during the entire ten year period, it is obvious that precipi-
tation was probably acidic in nature more than ten years before this fact was
noted. Since data for the years prior to 1965 are lacking, it is difficult to
1 qq
determine when the pH in precipitation first began to decrease.
8.7.4 Seasonal Variations in pH
Seasonal variations in pH measured at several sites in New York during
182
1970 to 1971 were erratic and site-specific, but pH values tended to be
lower in summer than in winter.182 Hornbeck et al.200 reported that
precipitation at nine stations in the northeastern United States was most
acidic during the growing season (May to September) and least acid during
winter (December to February). At Hubbard Brook, New Hampshire, the mean H+
8-126
-------
ALBANY. NEW YORK
ALLEGHENY STATE PARK, NEW YORK
0.0 I ""••• i • i il • i i i i • i i i i i I i i i i i u i i • i 1 i i i i 11 i i i i i I. i i i i i i i i i 11 i 111 i 11 u i il i i j i 11 i i i i 111 i i i i • i i i i i I i i i i i i ] i i i i
I I 1 J 1111 11 1 111
1965 1966
1973
1967 1968 1969 1970 1971 1972
YEAR
Figure 8-19. History of acidic precipitation at various sites in and adjacent to State of New York.199
8-127
-------
7.0
6.0
S.O
4.0
0.0 U.
HINCKLEY. NEW YORK
i in i
MAYS POINT. NEW YORK
MINEOLA. NEW YORK
7.0
6.0
S.O
4.0
0.0-n...1.1.nilii
6.0
T 6.0
4.0
ROCK HILL. NEW YORK
1.0 I i i i i 11 i i i 111 i 11 i i i 11 i i 11 i 11 i i . i i i 11 I i i i i 11 i i i i 11
0.0
UPTON. NEW YORK
5.0
I 4.0
«i n' 11 i i i i I i i i 11 I I m I n I i i i 1 I i I i i i i i i i i I , i i i i ...,
i il i i i . i ii i i i il . ' i n i i i i i il I I I in i
I
11' 11. -11
1965 19G6 1967
1968 1969
YEAR
1970 1971
1872 1973
Figure 8-19 (cont'd). History of acidic precipitation at various sites in and adjacent to State
of New York. 199
8-128
-------
1. Albany. N.Y.
2. Allegheny State Park, N.Y.
3. Athens. Pa.
4. Canton, N.Y.
5. Hinctcley.N.Y.
6. Mays Point, N.Y.
7. Mineola, N.Y.
8. Rock Hill, N.Y.
9. Upton, N.Y.
N
SYRACUSE
BUFFALO 6 •
BINGHAMTON
•
ALBAN
•
1
SCALE
_• 3
0 60 100
MILES
Figure 8-20. Location of acidic precipitation monitoring stations. 199
d-129
-------
TABLE 8-14. STATIONS IN THE PRECIPITATION pH MONITORING NETWORK
Station Location Watershed
1. Albany Albany County Hudson River
2. Alleghany State Park Cattaraugus County Alleghany River
3. Athens, Pennsylvania Bradford County Susquehanna
4. Canton St. Lawrence County St. Lawrence River
5. Hinckley Oneida County Upper Hudson River
6. Mays Point Wayne County Lake Ontario
7. Mineola Nassau County Long Island
8. Rock Hill Sullivan County Lower Hudson River
9. Upton Suffolk County Long Island
1. At U.S. Weather Bureau Station at Albany Municipal Airport, 0.5 mile north of
new State Highway 155.
2. At U.S. Weather Bureau Station in Alleghany State Park, 100 feet west of
Park Administration Building, 300 feet west of Park Highway 1 and 0.6 miles
south of Salamanca, N.Y.
3. At U.S. Weather Bureau Station, 300 feet west of U.S. Highways 220 and 309,
0.6 mile west of the mouth of the Chemung River, 2.0 miles south of Athens, Pa.
and 5.1 miles south of the New York-Pennsylvania state line.
4. At U.S. Weather Bureau Station at the Canton State University Farm on State
Highway 68, 2.5 miles of U.S. Highway 11 and Canton, N.Y.
5. At U.S. Weather Bureau Station at Hinckley Dam on West Canada Creek on Cody
Road in Hinckley, N.Y.
6. At U.S. Weather Bureau Station at Lock 25, Erie (Barge) Canal and State Highway
89 at Mays Point, 6.2 miles south of Savannah, N.Y.
7. At U.S. Weather Bureau Station 1 W on roof of U.S. Geological Survey office,
at 1505 Kellum Place, Mineola, N.Y.
8-130
-------
TABLE 8-14 (continued)
8. On North Shore Road, just north of Wanaksink Lake, 0.9 mile east of Rock
Hill and 3.5 miles northwest of U.S. Weather Bureau, Rock Hill 35 W
station and 6.5 miles southeast of Monticello, N.Y.
9. At U.S. Weather Bureau Station at Brookhaven National Laboratory weather
tower about 2 miles east of main entrance at Upton, N.Y.
8-131
-------
content of precipitation was 46 ug/1 (pH = 4.34) in winter, and 102 ug/1 (pH =
3.99) in summer. The seasonal trends in pH were mirrored by seasonal trends
in sulfate content of precipitation, and the trends in both components could
be explained by the lower efficiency of snow (compared to rain) in scavenging
201
substances from the atmosphere. Analyses by Pack of the MAPgS (Multi-State
Atmospheric Power Production Pollutant Study) data for 1976 to 1977 of H+,
p_
SO. and NO, concentrations in precipitation from five sites in the eastern
*T «J
United States between Virginia and upstate New York supports the seasonal
variation of sulfates in precipitation (Figure 8-21) as does the study by
20? 201 2~
Miller et al. Pack noted that the consistency of the SO^ correlations
p-
over the network's entire range suggested that the SO. concentrations were
the result of long range transport and mixing. Nitrates, however, showed a
definite decrease with increasing distance. The H ion was significantly
correlated between sites out to 600 km site separation, a value which was
2-
intermediate between SO. and NO., .
No significant seasonal trends were noted in pH of bulk precipitation
rainfall at Gainesville, Florida, during 1976 to 1977, but wet-only deposition
showed a trend of highest pH in fall and winter months and lowest pH in spring
ono
months (see Figure 8-22).
The mean pH of precipitation falling on the New York Metropolitan Area
during a 2-year (1975 to 1977) study was 4.28; however, a pronounced seasonal
variation was observed (Figure 8-23). The minimum pH at all sites except
Manhattan occurred during July to September while the maximum occurred during
October to December. The minimum pH in Manhattan, however, occurred January
to March and then gradually increased through the year. The lowest mean pH of
4.12 for the New York Metropolitan area occurred during the summer months.
8-132
-------
O P£NN STATE
D U OF VIRGINIA
ITHACA
• WHITEFACE MTN
SONDJFMAMJ JASON
1976 1977
Figure 8-21. Sulfate monthly weighted ion concentrations.201
8-133
-------
4.80
4.60
1. 4.40
4.20
0.40
0.30
z
g
< s
^ E
£*
Sf
o
u
0.20
0.10
I I I I I I I I I I
I I
N
M
M
I I I I I I I I I I I
A S 0
1976
N
M A
-1977-
M
MONTH
Figure 8-22. Seasonal variations in pH (A) and ammonium and
nitrate concentrations (B) in wet-only precipitation at Gainesville,
Florida. Values are monthly volume-weighted averages of levels
in rain from individual storms.202
8-134
-------
4.4
4.5
4.4
4.5
4.2
4. I
4.0 JFM AMJ
MONTHS OF THE
WAS ONO
(IST5 «»'0«f»>
Figure 8-23. Seasonal variation of precipitation pH in the
New York Metropolitan Area. 203
G-135
-------
In general the pH of rain is usually lower in the summer than in the winter
and is associated with the high summertime sulfate concentrations. In addition,
the lowest pH's were associated with cold fronts and air mass type precipitation
events. These events occur more frequently during the summer months. The
lower pH's also occurred on west or southwest winds.
Precipitation associated with cold fronts generally occurs when the heaviest
cold air behind the front lifts the warmer less dense air which precedes the
front off the ground. The warmer air is usually the trailing edge of the
backside of a high-pressure system. As a result, both the air mass and the
204
frontal type events generally occur in a polluted air mass.
8.7.5 Geographic Extent of Acidic Rain
As indicated earlier, there appears to be no published data dealing with
precipitation chemistry that includes pH measurements for the northeastern
one 9f)fi
United States prior to 1962. ' However, data that shows measureable
CaCOo alkalinity in precipitation is available from central New York and
182 207
Tennessee prior to 1930. Landsberg in a 1954 publication mentions that
the pH of individual raindrops 17 km west of Boston, Massachusetts, during
1ft?
1952 to 1953 averaged approximately 4.0. Cogbill and Likens point out that
208
according to Granat, a stoichiometric relationship exists for the major
chemical ions in precipitation (Figure 8-24).
"Certain cation equivalents come from sea-salt particles and
ar§ effectively neutralized by corresponding anions. We have used
Na as a basis for sea-salt measurement, since its dominant source
is the o^ggn. Then the ratio of Na to other ions in seawater
[Gya.nat,++ ] is u|ed to predict the equivalent amounts of SO. , Cl",
Mg , Ca , and K expected to orginate from the sea. When the
ratio of Cl:Na is Iess2than that of seawater, Cl" is used as the
basis [Junge and Werby ]. Such cases, howevcg, are rare in recent
samples in the northeastern United States. '
8-136
-------
AMONS
CATIONS
1 1
r> ACiD
* FORMING
n
r>
Li
J
< N
NEUTRALIZED
vl
1
1
SEA SALT
J
i
c so4 NO;
L
J2rtl__
CL"
H*
NH^. CA**,
CA-.VG^.K*
NA^
1
Figure 8-24. Theoretical relationship between major chemical ions
in precipitation (see text). Any lack of equivalence between anions
and cations can be envisioned to exist as a misestimate of H+ con-
centration. 182
8-137
-------
Remaining anions (SO. , NO., , and sometimes Cl ), commonly
called 'excess' ions, are assumed to originate from terrestrial
sources. A certain amou^ of £hjs e_xcess is neutralized by other
cations (particularly Mg , Ca , K , and NH. ), which probably
originate from soil or_other_particulate matter. Equal proportions
of thos.e remaining SO. , NO., , and Cl equivalents are associated
with H , since the calculations are in equivalents. Each SO. is
associated with two hydrogen ions, and each NO, or Cl is associated
with one. The sum of these hydrogen ion equivalents gives a predicted
hydrogen ion concentration or pH (due to H^SO., HNO^, or HC1) that
can be compared to the measured pH."
To substantiate the assumptions that a stoichiometric balance exists
+ 2- -
between ion equivalents as well as the association of H with SO. , N03 and
182
Cl and the overall predictability of acidity, Cogbill and Likens compared
the weighted average precipitation chemistry of samples collected on a storm-by-
storm basis with the predicted pH (see Table 8-15). A statistically significant
relationship (correlation coefficient r = 0.96) between predicted and actual
pH was observed based on actual storm-by-storm samples collected in the eastern
United States. Measured and predicted values appeared to be within 0.1 of a
pH unit.
Using the ionic relationship to predict pH, and the chemical data from
pin ?n.Q 189
Junge"lu and Junge and Werby^U3 for 1955 to 1956, Cogbill and Likens10^
predicted the annual average pH for the eastern United States. Using the same
7~\ 1
method and data from Lodge et al. for the U.S. during 1960 to 1966, Gambell
205
and Fisher for North Carolina and Virginia during 1962 to 1963 and Pearson
and Fisher for New England and New York, 1965 to 1966, Cogbill and Likens182
predicted the pH for 1965 to 1966. Based on the data obtained from their
1 pp
calculations, Cogbill and Likens developed the maps shown in Figure 8-16 A
and B.
The isopleth maps in Figure 8-16, based on the predicted annual average
pH for 1955 to 1956 and 1962 to 1963, illustrates that a significant increase
8-138
-------
TABLE 8-15. WEIGHTED PRECIPITATION CHEMISTRY AND PREDICTED pH FOR LOCATIONS
IN EASTERN UNITED STATES DURING 1972 TO 1973
00
CO
VO
Location
Ithaca, N.Y.
Aurora, N.Y.
Geneva, N.Y.
Hubbard Brook, N.H.
Gatlinburg, Tenn.
Location
Ithaca,
Aurora,
Geneva,
Hubbard
N.Y.
N.Y.
N.Y.
Brook, N.H.
Gatlinburg, Tenn.
Cl
Period
Sep. 1972 to Aug. 1973
Sep. 1972 to Aug. 1973
Sep. to Aug. 1973
June 1973 to Aug. 1973
June 1973 to Aug. 1973
NH4+,
mg/1
0.
0.
0.
0.
0.
47
47
37
15
15
mg/1
0.
0.
0.
0.
0.
32
40
42
37
19
Na+
mg/1
0.15
0.08
0.10
0.07
0.05
Water
cm/area
90.04
98.07
91.34
7.95
38.15
K+
mg/1
0.09
0.07
0.09
0.07
0.07
S04 , N03",
mg/1 mg/1
4.96 2.88
4.51 2.72
4.58 3.27
4.77 1.92
3.19 1.24
Ca++,
mg/1
0.83
0.45
0.73
0.24
0.20
Mg++,
mg/1
0.08
0.07
0.13
0.05
0.03
pH
4.05
4.05
4.09
4.05
4.19
Predicted
pH
4.05
4.02
4.09
4.03
4.20
Ref. 182
-------
in the area affected by acidic rainfall has occurred during the past 20 years
and that it now covers nearly all of the United States east of the Mississippi
River. Controversy exists over this apparent trend due to the fact that the
pH values in the 1955 to 1956 and 1965 to 1966 maps are computed rather than
measured and in addition it has been suggested that the number of sampling
stations is too small for accurate placement of the isopleths in all of the
maps. It has also been suggested that the accuracy of the method used by
182
Cogbill and Likens may overestimate the accuracy of data from most routine
monitoring programs.
The controversy regarding the number of data points used to draw isopleths
is illustrated by the fact that the pH 5.00 isopleth was drawn through the
border between North and South Carolina in the first two maps in Figure 8-15,
but in Likens' map for the early 1970s the pH 5.00 line was moved to central
Florida. This change was based on recent acquisition of data for two Florida
cities, Tallahassee and Gainesville, in a region where pH measurements had not
previously been made, and it does not necessarily imply a rapid expansion of
the acidic rainfall area.
Despite the cautions mentioned above regarding the rate of expansion of
acidic precipitation, as more and more evidence accumulates indications are
that the area, both east and west of the Mississippi receiving acidic precip-
1 07
nation is increasing. Reports from both Minnesota and Illinois indicate
precipitation events which are acidic. Data from the San Francisco Bay area
indicate that precipitation has become more acidic in that region since 1957
-i on
to 1958. The pH has decreased from 5.9 in 1957 to 1958 to 4.0 in 1974, and
1 on
seems to be related to the N03 concentration. Another report, using data
from the California Air Resources Board (CARB)190 states that acidic precipi-
tation has been reported from such widespread areas as Pasadena, Palo Alto,
8-140
-------
Davis and Lake Tahoe. Due to the geological composition of the soil, the
areas most likely to be affected by acidic precipitation are the national
forests, state parks and preserves, Bureau of Land Management forested areas,
many national parks and private forest holdings concentrated in the southern
California mountains, the western slope of the Sierra Nevada and the Coast
Range. All of the areas have acidic soils and are being adversely affected by
photochemical oxidant air pollutants at the present time. '
The increasing acidity of precipitation has also been noticed in Colorado.
188
Lewis and Grant, based on the collection of bulk precipitation in Boulder
County, Colorado, over a three year period, report a decline in pH of 0.80
units, from 5.43 to 4.63. The downward trend in pH appears to cut across
seasons and across years with very different weather patterns. No evidence
exists for the exclusive association of declining pH with upstate weather, as
would be expected if the decline were caused exclusively by direct movements
1RR
of pollutants from Denver over the station.
215
Studies in the Great Smoky Mountain National Park indicate a downward
trend in pH has occurred there over the past twenty years. There has been a
drop in pH from a range of 5.3-5.6 to 4.3 in 1979.
The absence of a precipitation monitoring network throughout the United
States in the past makes determination of trends in pH extremely difficult and
a controversial topic. This shortcoming has been rectified recently through
the establishment of the National Atmospheric Deposition Program. Under the
program, monitoring stations collect precipitation samples, determine their pH
and then send the samples to the Central Analytical Laboratory to be
analyzed. The network plans to have 75 to 100 collection sites throughout the
U.S.
8-141
-------
8.7.6 Sulfur and Nitrogen Oxides and the Formation of Acidic Precipitation
The generally held hypothesis is that sulfur and nitrogen compounds are
9-1 c
largely responsible for the acidity of precipitation. Jacobson et al.
analyzed the contribution of the sulfate and nitrate anions to precipitation
by collecting the wet deposition from 58 events from January through December
1971, in the area of Yonkers, New York. The sulfate anion was generally in
greatest concentration, but in some samples the concentration of the nitrate
anion was greater.
Likens has pointed out that although sulfuric acid has been by far the
dominant acid in precipitation at the Hubbard Brook Experimental Forest in New
Hampshire for the past decade, the increased deposition of hydrogen ion has
been due chiefly to an increase in the amount of nitric acid in the precipi-
tation (rain and snow) falling there. The components in precipitation and
their contribution to acidity in precipitation are listed in Tables 8-16 and
8-17.
The acidity of precipitation is a reflection of the balance of the major
cations and anions in precipitation. The contribution of sulfate and nitrate
anions has changed with time and analysis indicates that the nitrate anion ion
makes up an ever-increasing fraction of the total negative ion equivalents.
208 197 +
Following the reasoning of Granat, Likens et al. found, (assuming 2H
2- + 9-
per S04 ion as in H2$04 or one H ion per SOt as in NH4$04) that the con-
tribution of sulfate to acidity declined from 83 to 66 percent of the total
acidity between 1964 to 1974 at Hubbard Brook, and the contribution of nitrate
increased from 15 to 30 percent of the total during the same period. Further-
more, increased annual input of H was closely correlated with increased input
of nitrate, but there was little correlation between H input a.nd sulfate
input (Figure 8-25). Hendry203 found that sulfate contributed 69 percent,
8-142
-------
TABLE 8-16. ACIDIC SULFATE AND NITRATE SALTS
SOURCES OF ACIDITY IN PRECIPITATION
Concen- Contri-
tration in bution to
precipitation free acidity3
(mg per (microequiv-
Substance liter) alents per liter)
H2C03
NH4
Al , dissolved
Fe, dissolved
Mn, dissolved
Total organic acids
HN03
H2S04
TOTAL
0.62C
0.92
0.05d
0.04d
0.0005d
0.34
4.40
5.10
0
0
0
0
0
2.4
39
57
98
Contri-
bution to .
total acidity
(microequiv-
alents per liter)
20
51
5
2
0.1
4.7
39
57
179
jAt pH 4.01.
In a titration to pH 9.0.
•Equilibrium concentration.
Average value for several dates.
Note: Data from a sample of rain collected at Ithaca, N.
Ref. 151.
. , on Oct 23, 1975.
8-143
-------
TABLE 8-17. HYDROCHLORIC, SULFURIC, AND NITRIC ACIDS ARE
STRONGEST OF SEVERAL POTENTIALLY IMPORTANT PROTON
DONORS IN RAIN AND SNOW
Acid Relative strength (pK _)
HC1 —3
H2S04 -3
HN03 -1
S02*H20 1.9
HS04 2.0
Fe(H20)6+3 2.2 to ~3
FH 3.2
Organic acids 3 to 7
A1(H20)6+3 4.9
H2C03 6.3
HS03 7.2
HN4+ 9.3
10.3
j
Ref 151.
8-144
-------
120
110
» 100
i
5 to
o
>•
z
•o
70
I
o o
I
120
100
M
•0
40
10 20 30 40 60
NITRATC INPUT, millMqunlltnti/m2/yr
—I 0
60 0
I
I
O
o
20 40 M SO 100
f ULFATE INPUT, mHlwqu™«l«nti/mr/yf
120
Figure 8-25. Hydrogen ion deposition in precipitation plotted against (A) nitrate deposition and (B)
sulfate deposition. Data from Hubbard Brook, New Hampshire, 1964-1973.197
3-145
-------
nitrate 22 percent, and chloride 6 percent of the free acidity in rainfall at
216 217
Gainesville, Florida, during 1976. On the other hand, Gorham ' reported
that hydrochloric acid was the dominant acid in urban precipitation in Great
Britain. Coal used in Great Britain is high in chloride, but low in sulfur.
Data for nitrate, ammonia and sulfate in rain at Ithaca and Geneva, New York,
constitute the longest record of precipitation chemistry in the United States
184
according to Likens.
Data are available from 1915 to the present, but long gaps exist in the
measurements, especially at the Geneva site. Figures 8-26 (A) to (C) show that
marked changes in composition have occurred at Ithaca: a gradual decline in
ammonia, an increase in nitrate beginning around 1945, and a marked decrease
in sulfate starting between 1945 and 1950. Early data for Ithaca showed
higher concentrations of sulfate in winter than in summer, presumably because
of greater local burning of coal in winter. Data for 1971 showed the reverse
trend, however, with nearly half the annual sulfate input occurring during the
184
months of June to August. Likens concluded that, despite deficiencies in
the historical data and questions concerning their reliability, the trends are
real and can be explained by changes in fuel consumption patterns; i.e.,
natural gas began to replace coal for home heating near the time of the shifts
in precipitation chemistry. Likens reported a sharp increase in nitrate
concentrations in New York state during the past decade (Figure 8-26 [D]), on
the basis of United States Geological Survey data for nine stations.
Data for eastern North America indicate a roughly three-fold increase in
nitrate in rainfall since 1955, whereas sulfate in rain has roughly doubled in
this period. According to Nisbet,198 sulfate/nitrate ratios in rainfall
averaged about 4 in the eastern United States in 1955-1956, but the average
ratio had fallen to about 3 in 1972-1973. Nisbet calculated that the fraction
8-146
-------
10
I
I I I
1920 1930 1940 1950 1960 1970
YEAR
1920 1930 1940 1950 1960 1970
YEAR
<
2
1920 1930 1940 1950 1960 1970
YEAR
0.6
w 0.5
*
2 0.4
I
uj" 0.3
| 0.2
z
0.1
0
1968 1970 1972 1974
YEAR
SOURCE: (A), (B), and (C) modified from Likens;183 (D) modified from Likens.151
Figure 8-26. Trends in mean annual concentrations of sulfate, ammonia, and nitrate in precipitation.
(A), (B), and (C) present long-term data for Ithaca, New York; (D) presents data for eight years
averaged over eight sites in New York and one in Pennsylvania. One point in (A), for 1946-47, is be-
lieved to be an anomaly (see Likens183 for discussion).
8-147
-------
of H+ deposition attributable to nitrate assuming nitric acid rose from 19
percent in 1955-1956 to 24 percent in 1972-1973 (Table 8-18). He also
projected trends in acid deposition for 1970 to 1980 for a number of scenarios
assuming continued control of SOp emissions, but no controls on projected NO
emissions. Even if S02 emissions were held constant by source controls on new
power plants, a small increase in acidity would be likely because of increase
in NO emissions.
A
219 2- +
Lindberg et al. noted that SO. and H were by far the dominant
constituents of precipitation at the Walker Branch Watershed, Tennessee.
Comparison with the annual average concentration of major elements in rain at
the Walker Branch Watershed on an equivalent basis, indicates that H constitutes
approximately 50 percent of the cationic strength and trace elements account
2-
for only 0.2 percent. SO. constituted approximately 65 percent of the anionic
strength and on an equivalent basis was 3.5 times more concentrated than NO., ,
the next most abundant anion. The incident precipitation for the 2 year
(1976-1977) period was described "as a dilute mineral acid solution," primarily
HpSO., at a pH approximating 4.2 and containing relatively minor amounts of
219
various trace salts.
It is becoming increasingly clear that there are significant spatial and
temporal variations and differences in the chemistry of rain in the United
States. The pH of rain varied from 4.2 to a high of 7.5 in central Minnesota
212
during 1976 and 1977. The following parameters were quantified in samples
without dead volume, and obtained during individual rain falls: free, total,
strong and non-volatile weak acids as well as NH* SO?", and HQ~ No chloride
was detected in any of these samples. Statistical analyses of the data indicated
no single parameter to be dominant in predicting free acid concentrations.
All the parameters quantified in the study has some influence on the rain pH.
8-148
-------
TABLE 8-18. DEPOSITION OF SULFURIC AND NITRIC ACIDS IN
PRECIPITATION IN EASTERN NORTH AMERICA
Percent
1955-56 1972-73 change 1956-73
Total deposition of
acid (as H )
Estimated deposition
as sulfuric acid
(percent of total)
expressed as sulfate
Estimated deposition
4.0
3.2 (80)b
0.76 (19)b
10.8
7.9 (73)b
2.60 (24)b
+170
+150
+240
as nitric acid
(percent of total)
expressed as nitrate
Total deposition 16.4 31.8 +94
of sulfates
Sulfuric acid as % 19.7 24.8 +27
of sulfates
Deposition rates are expressed as multiples of the chemical equivalent
weight, so that raj.es for different chemical species can be compared
directly. 1 ton H is equivalent to 49 tons sulfuric acid or to 63
tons nitric acid.
A small but increasing fraction of the acid in precipitation is attribut-
able to hydrochloric acid.
SOURCE: Modified from Ref. 198.
8-149
-------
Table 8-19 shows correlation coefficients between the different parameters
measured. Based on these results it can be concluded that on a comparative
basis sulfate and nitrate are more highly correlated with ammonium ion than
with the hydrogen ion. This is consistent with the results of Weiss et al.
who reported that a significant portion of the sulfate aerosol in the midwest
is associated with the ammonium ion. This may be more true for nitrate [(NhL
+ HN03 -»• NH.N03)] in certain geographic areas of the United States such as
Minnesota. The averate p equivalents of ammonium ion could account for 83
percent of the average u equivalents of SO. + NO,.
The pH of rainfall varies from event to event, from locality to locality
204 204
and from storm to storm. Wolff et al. noted that there was some site to
site variability among the eight sites they studied in the Manhattan area
(Table 8-20). They also noted that the pH varied according to storm type
(Table 8-21). Storms with a continental origin have a lower pH than storms
originating over the ocean. The storms with trajectories from the south and
southwest had the lowest pH's, while those from the north and east had the
highest pH's. The lowest pH's were associated with cold front air mass type
204
precipitation and high summertime sulfate concentrations.
203 221
Hendry and Seymour et al. have also studied variations in the
content of elements in single precipitation events. Hendry collected 5-minute
segments within three individual rain storms. The temporal variations of
constituents in rain storms at Gainesville, Florida in 1976 are listed in
221
Table 8-22. Seymour et al. sampled rain water during five rainfall events
during July and August, 1977 in Tucson, Arizona. Variations in H+, SOJj~,
N03, and NH^ concentrations were observed. Initially the concentration of
ions was low, then increased rapidly as a function of time until a maximum was
reached, and then fell off. The ionic strengths were noted to attain maximum
8-150
-------
TABLE 8-19. CORRELATION COEFFICIENTS FOR VARIOUS PARAMETERS
QUANTIFIED AS u EQUIVALENTS IN INDIVIDUAL RAINFALL SAMPLES IN CENTRAL
MINNESOTA DURING 1976 AND 1977.
Dependent
Variable
S04 + N03
N03
S04 + N03
so4
so4
FA
N03
S04 + N03
so4
HT
S04 + N03
N03
so4
Independent
Variable
NH4
NH4
FA + NH4
NH4
N03
NH4
FA
HT
HT
NH4
FA
HT
FA
Correlation
Coefficient
0.746
0.723
0.708
0.532
0.469
0.343
0.282
0.252
0.245
0.221
0.215
0.197
0.054
FA = Free acid, HT = total acid
Where S0?~ concentrations were below the limits of detection, they were
assumed to be half of the minimum limit of quantification.
Cation/anion balance was achieved in these samples.
From Ref. 219.
8-151
-------
TABLE 8-20. MEAN pH VALUES IN THE NEW YORK METROPOLITAN
AREA (1975-1977)
Site
Caldwell, N.J.
Piscataway, N.J.
Cranford, N.J.
Bronx, N.Y.
Manhattan, N.Y.
High Point, N.J.
Queens, N.Y.
Port Chester, N.Y.
All sites
Mean pH
4.32
4.25
4.34
4.31
4.29
4.25
4.63
4.60
4.28
SD
0.26
0.36
0.34
0.37
0.25
0.30
0.35
0.19
0.32
No. obsd
50
64
48
57
39
25
20
21
72
Range
3.35-5.60
3.57-5.50
3.44-5.95
3.42-5.75
3.80-5.50
3.74-4.90
3.98-5.28
4.00-5.10
3.50-5.16
From Ref. 204
TABLE 8-21. STORM TYPE CLASSIFICATION
Type
1
2
3
4
5
6
7
8
Description of dominant storm
system
Closed low-pressure system which formed
over continental N. Amer.
Closed low-pressure system which formed in
Gulf of Mexico or over Atlantic Ocean
Closed low which passed to W or N of N.Y.C.
Closed low which passed to S or E of N.Y.C.
Cold front in absence of closed low
Air mass thunderstorm
Hurricane Belle
Unclassified
No.
obsd
22
21
26
17
16
5
1
6
Mean
pH
4.35
4.43
4.39
4.39
4.17
3.91
5.16
4.31
From Ref. 204.
8-152
-------
TABLE 8-22. TEMPORAL VARIATIONS OF CONSTITUENTS IN RAIN STORMS IN GAINESVILLE, FLORIDA, 1976
00
I
>—•
en
CO
Date
Sept. 19
Oct. 16
Oct. 26
Collection
(min)
0-5
5-10
11-15
15-end
0-5
5-10
10-15
15-20
20-25
25-end
0-5
5-10
10-15
15-20
20-end
TKN
1.09
1.10
0.63
0.60
1.35
1.11
1.02
0.80
0.69
0.41
1.41
1.03
0.83
0.65
0.70
NH4-N
0.23
0.11
0.07
0.03
0.44
0.16
0.07
0.05
0.01
0.01
0.24
0.09
0.12
0.03
0.02
N03-N
0.60
0.22
0.14
0.07
0.75
0.25
0.16
0.15
0.11
0.10
0.55
0.50
0.31
0.24
0.11
Ortho P
0.060
0.030
0.030
0.005
0.024
0.016
0.006
0.003
0.005
0.005
0.045
0.008
0.005
<.005
<.005
Total P
0.125
0.082
0.035
0.010
0.160
0.095
0.050
0.009
0.005
0.805
1.215
0.150
0.075
0.680
0.040
Na
0.88
0.31
0.14
0.04
1.03
0.28
0.21
0.11
0.08
0.07
1.45
1.05
0.85
0.30
0.35
K
0.23
0.20
0.19
0.20
0.28
0.21
0.17
0.11
0.08
0.07
0.35
0.10
0.15
0.14
0.10
Ca
1.50
0.75
0.55
0.36
1.95
1.23
0.84
0.72
0.43
0.30
1.55
1.90
0.95
0.65
0.70
Mg
0.30
0.04
0.01
0.01
0.38
0.10
0.09
0.09
0.06
0.03
0.45
0.35
0.13
0.00
0.10
Cl
1.95
1.10
0.95
0.60
1.95
1.23
0.84
0.72
0.43
0.30
2.40
1.65
1.55
1.05
0.90
SO,
5.15
2.50
1.90
1.25
5.80
4.03
2.88
2.60
1.68
1.60
7.35
5.43
4.23
2.34
1.45
PH
4.38
4.19
4.15
4.29
4.65
4.42
4.51
4.32
4.49
4.37
4.68
4.45
4.27
4.36
4.38
All values in mg/1 except pH.
-------
values in the course of a single precipitation event. The variations in the
concentrations of H+ and NH. were observed to be closely followed by changes
2- + + 2-
in the concentrations of the anions, N03 and SO^ . H , NH^, SO^ and N03
were the principal ionic constituents of a single precipitation event. Dissolved
221
C0? from the atmosphere was also noted.
9?~\ a
Stensland has compared the precipitation chemistry for 1954 and 1977
at a site in central Illinois. The precipitation samples for 1954 were more
basic than those of 1977, due mainly to high concentrations of sulfate and
nitrate. The corrected pH for 1954 was 6.05. The pH for 1977 was 4.1. The
author suggests that the higher pH in 1954 is due to atmospheric dust because
of drought in the area. He also concludes that further data is needed to
determine the effect of sample handling on the calcium and magnesium values.
Scavenging by rainfall produces large changes in atmospheric contaminant
concentrations during a given rainfall event. The decline in constituent
levels is usually rapid, at least in localized convective showers, and low,
steady-state concentrations are usually reached within the first half hour of
a rain event.
The variability of rainfall volume within small geographic areas over
short periods of time and on a year-to-year basis for larger geographic regions
is well known. Variations of up to 50 percent of the long-term average amount
of precipitation are relatively common for any given year. Large annual
differences in rainfall amounts can also occur within small geographic regions
2
of 10 to 50 km , but this variability is probably more pronounced in areas
where convective rain showers predominate.
Nearly all of the nitrate in rainfall is formed in the atmosphere from
N0x, and little is derived from wind erosion of nitrate salts in soils.
Similarly, nearly all of the sulfate in rainfall is formed in the atmosphere
from S02- The reactions that produce nitrate and sulfate from NO and S02 are
8-154
-------
generally known and result in the production of equivalent amounts of hydrogen
ion, regardless of the reaction mechanism:
OH + N02 -> HN03, or
N205 + H20 •* 2HN03, and
S02 + 1/2 02 •* S03 + H20 •» H2S04.
Thus, all atmospherically derived nitrate and sulfate contribute to the
acidification of rainfall, since H is associated stoichiometrically with the
formation of each. A second stoichiometric process that affects the acidity
of rain is the reaction of nitric and sulfuric acids with ammonia or other
alkaline substances (e.g., dust particles) in the atmosphere to form neutral
nitrate and sulfate aerosols. To the extent that such neutralization occurs,
222 22"?
the free acidity of rainfall will be reduced. Reuss noted, however,
that even ammonium (NH^ )in rain can contribute to the acidification of soil,
since ammonium that enters the soil may be oxidized, resulting in the formation
of nitric acid.
8.7.7 Seasonal Variations in Sulfate and Nitrates
Many workers have reported that the sulfur content as well as the pH of
2- +
precipitation shows seasonal fluctuations. In general SO. and H concentrations
in precipitation in the eastern United States are higher in the summer than in
204
the winter. Wolff et al. found this to be true for the New York Metropolitan
200 202
Area. Hornbeck and Miller et al. both stated that a summer maximum for
sulfate for pH exists in upstate New York, the Hubbard Brook Experimental
201
Forest in New Hampshire and in portions of Pennsyvania. Pack, using data
from the four original MAP3S (Multistate Atmospheric Power Production Pollution
Study) precipitation chemistry network, plotted the weighted monthly sulfate
ion concentrations (Figure 8-21). Maximum sulfate concentrations occurred
219
from June through August. Lindberg et al. studying wetfall deposition of
8-155
-------
2+
sulfate in the Walker Branch Watershed also noted summer maxima for SO. and
H+. Using the same MAP3S data as did Pack they plotted weighted mean con-
centrations of sulfate in rain collected from November, 1976 through November
1977. This information is depicted in Figure 8-27. The concentrations at
Walker Branch Watershed, Tennessee, are lower than all of the stations except
remote Whiteface Mountain, New York. The regional nature of the wet deposition
of sulfate is apparent. Reasons for the existence of the high summer maxima
of sulfate for the eastern United States is discussed in some detail in Chapter
5, Section 5.2.2.1 (Ambient Sulfates). Ambient nitrate aerosols also are
discussed in Chapter 5, Section 5.2.2.2. Information concerning nitrates in
the atmosphere is limited. Data from studies prior to 1977 are in doubt
because of artifact formation on filters. Aerosol nitrate is now believed to
be in the form of ammonium nitrate.
8-156
-------
ID
44
12
10
^
J 8
c/>
6
4
4
2 '
<
0
C
1 1 1 1 1 1 1 1 1 I 1 '
• WBW 9
_ 0 WHITEFACE 1 /',
0 ITHACA MAP3S
A PFMM CTATF PRECIPITATION ; \
A PENN STATE NETWORK
D VIRGINIA J ; •
lt\
. i •
l'\\
c '/'VJ if
Q 1 1 *\ ' M
r\ if •• i .i
_ ;/^. /f(< • j: .' \ _
•7 W^\fe ^
^•^. 0 ./fAVX VV\ ~
?&£%ytffi' \ ~
l ^ T l l l l i l l i l
'ND'JFMAMJJASOr-
1976 I 1977
Figure 8-27. Comparison of weighted mean monthly concentrations of sulfate
in incident precipitation collected in Walker Branch Watershed, Tenn. (WBW)
and four MAP3S precipitation chemistry monitoring stations in New York
(C> 0), Pennsylvania (A), and Virginia (D}.219
8-157
-------
8.8 REFERENCES
1. Billings, W. D. Plants and the Ecosystem. 3rd ed. pp. 1-62. Wadsworth
Publishing Company, Inc. Belmont, PA., 1978. 177 p.
2. Smith, R. L. Ecology and Field Biology, 2nd ed., p. 170. New York,
Harper and Row, 1974. 850 p.
3. Aron, W. I., and S. H. Smith. Ship Canals and Aquatic Ecosystems.
Science 174:13-20, 1971.
4. Woodwell, G. M. Effects of pollution on the structure and physiology of
ecosystems. Science. 168:429-433, 1970.
5. Woodwell, G. M. The ecological effects of radiation. Scientific American.
208:40-49, 1963.
6. Sinclair, W. A. Polluted air: Potent new selective force in forest. J.
Forestry. 67:305-309, 1969.
7. Woodwell, G. M. Effects of ionizing radiation on terrestrial ecosystems.
Science. 138:572-577, 1962.
8. Boughey, A. S. Fundamental Ecology. Scranton, Pa. , Intex Educational
Publishers, 1971. p. 11-50.
8a. Billings (1974).
9. Odum, E. P. Summary. In: Ecological Effects of Nuclear War. G. M.
Woodwell (ed.). Brookhaven National Lab. 917 (C-43). 1965.
10. Garrett, A. Compositional changes of ecosystem during chronic gamma
irradiation. In: Symposium on Radioecology. Proc. Second National
Symposium, Ann~^rbor, Mich., May 15-17, 1967.
11. Odum, E. P Fundamental of Ecology 3 ed. W. B. Saunders Co. Philadelphia,
1971. p. 5, 8-139.
12. Wright, R. F. , and E. Snekvik. Acid precipitation: Chemistry and fish
populations in 700 lakes in southernmost Norway. Verh. Int. Ver. Theor.
Angew. Limnol. 20:765-775, 1978.
13. Donnevig, A. Influence of precipitation on the acidity of water courses
and on fish stocks. Jeger og Fisker. 3:116-118, 1959 (in Norwegian
cited in Wright #12).
14. National Research Council. Sulfur Oxides. National Academy of Sciences.
Washington, D. C. Chapter 5. Effects of Sulfur Oxides on Aquatic Ecosystems
1978.
15. Aimer, B. , W. Dickson, C. Ekstrom, E. Hornstrom, and U. Miller. Effects
of acidification on Swedish lakes. Ambio 3:30-36, 1974.
8-158
-------
16. Leivestad, H. , G. Hendrey, I. P. Muniz, and E. Snekvik. Effects of acid
precipitation on freshwater organisms, pp. 87-111. In: Impact of Acid
Precipitation on Forest and Freshwater Ecosystems in^orway, F. H. Braekke,
ed., Research Report FR 6/76, 1432 Aas-NLH, Norway: SNSF Project Secretariat,
1976.
17. Report from the International Conference on the Effects of Acid Precipitation
in Telemark, Norway, June 14-19, 1976. Ambio 5:200-201, 1976.
18. Jensen, K. W. , and E. Snekvik. Low pH Levels Wipe Out Salmon and Trout
Populations in Southernmost Norway. Ambio 1:223-225, 1972.
19. Beamish, R. J. , and H. H. Harvey. Acidification of the La Cloche Mountain
Lakes, Ontario and resulting fish mortalities. Jour. Fisheries Res. Board
Canada. 29:1131-1143, 1972.
20. Schofield, C. L. Lake acidification in the Adirondack Mountains of
New York: Causes and consequences. In: Proceedings of the First
International Symposium on Acid Precipitation and the Forest Ecosystem,
May 12-15, 1975, Columbus, Ohio, L. S. Dochinger and T. A. Seliga, eds.,
U.S. Forest Service General Technical Report NE-23, U.S. Department of
Agriculture, Forest Service, Northeastern Forest Experiment Station,
Upper Darby, PA, 1976. p. 477. (Abstract)
21. Schofield, C. L. Acid precipitation: Effects on fish. Ambio. 5:228-230,
1976.
22. Wright, R. F. , T. Dale, E. T. Gjessing, G. R. Hendry, A. Henriksen,
M. Johannessen, and I. P. Muniz. Impact of Acid Precipitation on Freshwater
Ecosystems in Norway. Water, Air and Soil Poll. 6:483-499, 1976.
23. Dickson, W. The acidification of Swedish lakes. In: Fishery Board of
Sweden, Institute of Freshwater Research, Drottningfiolm, Sweden. Report
No. 54, Lund, Sweden: Carl Bloms Boktryckeri A.-B, 1975. pp. 8-20.
24. Beamish, R. J. Acidification of Lakes in Canada By Acid Precipitation and
the Resulting Effects of Fish. Water, Air and Soil Poll. 6:501-514, 1976.
25. Omang, J. Acid Rain: Push Toward Coal Makes Global Pollution Worse. Wall
Street Journal, Sunday, December 30, 1979. p. 1 and A8.
26. Pfeiffer, M. List and Summary of Acidified Adirondack Waters Based on
Data Available as of April 1979. New York State Department of Environmental
conservation. Albany, New York, May 1979.
26a. Arnold, D. E., R. W. Light, and V. J. Dymond. Probable Effects of Acid
Precipitation on Pennsylvania Waters. EPA 600/3-80-D12. January 1980.
EPA Corvallis, OR. 19 p.
27. Beamish, R. J., W. L. Lockhart, J. C. Van Loon, and H. H. Harvey.
Long-term acidification of a lake and resulting effects on fishes.
Ambio 4:98-102, 1975.
8-159
-------
28. Menendex, R. Chronic effects of reduced pH on brook trout (Salvelinus
fontinalis). J. Fish. Res. Board Can. 33:118-123, 1976.
29. Trojnar, J. R. Egg and larval survival of white suckers (Catostomus
commersoni) at low pH. J. Fish. Res. Board Can. 34:262-266, 1977.
30. Trojnar, J. R. Egg hatchability and tolerance of brook trout (Salvelinus
fontinalis) fry at low pH. J. Fish. Res. Board Can. 34:574-579, 1977.
31. Schofield, C. L. Lake Acidification in the Adirondack Mountains of New
York: Causes and Consequences. Presented at the First International
Symposium on Acid Precipitation and the Forest Ecosystem, May 12-15,
1975, Columbus, Ohio. Sponsored by U.S.D.A. Forest Service, Northeastern
Forest Experiment Station and Ohio State University Atmospheric Science
Program, p. 25.
32. Schofield, C. L. The Acid Precipitation Phenomenon and Its Impact in
the Adirondack Mountains of New York State. In: Scientific Paper from
the Public Meeting on Acid Precipitation, May~4~-5, 1978, Lake Placid,
New York, published by Science and Technology Staff, New York State
Assembly, Albany, NY, March, 1979. p. 86-91.
33. Hendrey, G. R., and R. F. Wright. Acid precipitation in Norway: Effects
on aquatic fauna. J. Great Lakes Res. 2(Suppl 1):192-207, 1976.
34. European Inland Fisheries Advisory Committee (EIFAC). Water quality
criteria for European freshwater fish. Report on extreme pH values and
inland fisheries. Water Res. 3:593-611, 1969.
35. Potts, W. T. W., and D. J. A. Brown. Study Group 5 Discussions. D.5.1-D.5.5.
In: Wood, M. J. (ed). Ecological Effects of Acid Precipitation. Report
oT workshop held at Cally Hotel, Gatehouse-of-Fleet, Galloway, U.K. 4-7
Sept. 1978. EPRI SOA77-403, Electric Power Res. Institute, 3412 Hillview
Ave., Palo Alto, California 94303, 1979.
36. Cronan, C. S., and C. L. Schofield. Aluminum Leeching Response to Acid
Precipitation: Effects on High-Elevation Watersheds in the Northeast.
Science 204:304-305, 1979.
37. Leivestard, H. , and I. P. Muniz. Fish Kill at Low pH in a Norwegian River.
Nature 259:391-392, 1976.
37a. Driscoll, C. T., Jr., J. P. Baker, J. I. Bisogin, Jr., and C. Schofield.
Aluminum Speciation in Dilute Acidified Waters and Its Effects on Fish.
Nature (In Press).
38. Hendrey, George. Aquatics Task Force on Environmental Assessment of the
Atikokan Power Plant: Effects on Aquatic Organisms. Land and Fresh Water
Environmental Sciences Group, Department of Energy and Environment.
Brookhaven National Laboratory Associated Universities, Inc. Lipton, NY
BNL 50932. November 1978. 16 p.
8-160
-------
39. Hendrey, G., and F. W. Barvenik. Impact of Acid Precipitation on Decomposition
and Plant Communities in Lakes. In: Scientific Papers from the Public
Meeting on Acid Precipitation, May 4-5, 1978, Lake Placid, New York, published
by Science and Technology Staff, New York State Assembly, Albany, NY
March, 1979. p. 92-103.
40. Hendrey, G. R., K. Baalstrud, T. S. Traaen, M. Laake, and G. Raddum.
Acid precipitation: Some hydrobiological changes. Ambio 5:224-227,
1976.
41. Grahn, 0., H. Hultberg, and L. Landner. Oligotrophication--a self-accelerating
process in lakes subjected to excessive supply of acid substances. Ambio
3:93-94, 1974.
42. Grahn, 0. Macrophyte succession in Swedish lakes caused by deposition of
airborne acid substances, pp. 519-530. _In: Proceedings of the First
International Symposium on Acid Precipitation and the Forest Ecosystem,
L. S. Dochinger and T. A. Seliga, eds., Ohio State University, May 12-15,
1975. U.S.D.A. Forest Service General Technical Report NE-23. Upper
Darby, Pennsylvania. Forest Service, U.S. Department of Agriculture,
Northeastern Forest Experiment Station, 1976.
43. Reid, G. K., and R. D. Wood. Ecology of Inland Waters and Estuaries.
2nd ed. D. Von Nostrand Co. New York, 1976. p. 261-319.
44. Kwiatkowski, R. E., and J. C. Roff. Effects of acidity on the phytoplankton
and primary productivity of selected northern Ontario lakes. Can. J.
Bot. 54:2546-2561, 1976.
45. Brock, Thomas D. Lower pH Limit for the Existence of Blue-Green Algae:
Evolutionary and Ecological Implications. Science 179:480-483, 1973.
46. Conroy, N., K. Hawley, W. Keller, and C. Lafrance. Influences of the
atmosphere on lakes in the Sudbury area. J. Great Lakes Res.
2(Suppl.l):146-165, 1976.
47. Yan, N. D. , and P. Stokes. Phy to plankton of an Acidic Lake, and Its
Responses to Experimental Alterations of pH. Environ. Conservation
5:93-100, 1978.
48. Hendrey, G. R. Effects of pH on the Growth of Periphytic Algae in Artificial
Stream Channels. Research Report IR 25/76. 1432 Aas-NLH, Norway: SNSF
Project Secretariat, 1976. 50 pp.
49. Andersson, I., 0. Grahn, H. Hultberg, and L. Landner. Jamfbrande undersbkning
av olika tekniker for aterstallande av fbrsurade sjbar. STU Report
73-3651. Stockholm: Institute for Water and Air Research, 1975. Cited
in: National Research Council, Sulfur Oxides, National Academy of Sciences,
Washington, DC, 1978. 118 pp.
50. Scheider, W., J. Adamski, and M. Paylor. Reclamation of Acidified Lakes
Near Sudbury, Ontario. Rexdale, Ontario, Canada: Ontario Ministry of
the Environment, 1975. 129 pp.
8-161
-------
51. Wetzel, R. G. Limnology, p. 287-621, W. B. Saunders Co., Philadelphia,
PA, 1975. 743 pp.
52. Boling, R. H. , Jr., E. D. Goodman, J. A. VanSickle, J. 0. Zimmer, K. W.
Cummins, R. C. Petersen, and S. R. Reice. Toward a model of detritus
processing in a woodland stream. Ecology 56:141-151, 1975.
53. Minshall, G. W. Role of Allochtronous detritus in the trophic structure
of a woodland springbrook community. Ecology 48:139-149, 1967.
54. Borgstrom, R., J. Brittain, and A. Lillehammer. Evertebrater og surt
vann: Oversikt over innsamlingslokaliteter. Research Report IR 21/76.
1432 Aas-NLH, Norway: SNSF Project Secretariat, 1976. Cited in: National
Research Council, Sulfur Oxides, National Academy of Sciences, Washington,
DC, 1978. 33 pp.
55. Sprules, G. W. Midsummer crustacean zooplankton communities in acid-stressed
lakes. J. Fish Res Board Can. 32:389-395, 1975.
56. 0akland, J. Distribution and ecology of the freshwater snails Gastropoda)
of Norway. Malacologia 9:143-151, 1969.
57. 0akland, K. A. On the distribution and ecology of Gammarus lacustris, G.
0. Sars in Norway, with notes on its morphology and biology.Norw. J.
Zool. 17:111-152, 1969.
58. Borgstrom, R., and G. R. Hendrey. pH Tolerance of the First Larval
Stages of Lepidurus arcticus (Pallas) and Adult Gammarus lacustris G. 0.
Sars. Research Report IR 22/76. 1432 Aas-NLH, Norway: SNSF Project
Secretariat, 1976. Cited in: National Research Council, Sulfur Oxides,
National Academy of Sciences, Washington, DC, 1978. 37 pp.
59. Sutcliffe, D. W., and T. R. Carrick. Studies on mountain streams in the
English Lake District I. pH, calcium, and the distribution of invertebrates
in the River Duddon. Freshwater Biol. 3:437-462, 1973.
60. Oliver, D. R. Life history of the Chironomidae. Ann. Rev. Entomol.
16:211-230, 1971.
61. Bell, H. L. Effect of low pH on the survival and emergence of aquatic
insects. Water Res. 5:313-319, 1971.
62. Hagen, A., and A. Langeland. Polluted snow in southern Norway and the
effect of the meltwater on freshwater and aquatic organisms. Environ.
Pollut. 5:45-57, 1973.
63. Henriksen, A., and R. F. Wright. Effects of acid precipitation on a
small acid lake in southern Norway. Nord. Hydrol. 8:1-10, 1977.
8-162
-------
64. Hultberg, H. Thermally stratified acid water in late winter - A key
factor inducing self-accelerating processes which increase acidification
p. 503-517. In: Proceedings of the First International Symposium on Acid
Precipitation and the Forest Ecosystem, May 12-15, 1975, Columbus, Ohio,
L. S. Dochinger and T. A. Seliga, eds., U.S. Forest Service General Technical
Report NE-23, Upper Darby, Pennsylvania, Forest Service, U.S. Department of
Agriculture, Northeastern Forest Experiment Station, 1976.
65. Pough, F. H., and R. E. Wilson. Acid precipitation and reproductive
success of Ambystoma salamanders, pp. 531-544. In: Proceedings of the
First International Symposium on Acid Precipitation and the Forest Ecosystem,
Ohio State University, May 12-15, 1975. U.S. For. Serv. Gen. Tech. Rep.
NE-23, 1976.
66. Gosner, K. L. , and I. H. Black. The effects of acidity on the
development and hatching of New Jersey frogs. Ecology 38:256-262, 1957.
67. Pough, F. H. Acid precipitation and embryonic mortality of spotted
salamanders, Ambystoma maculatum. Science 192:68-70, 1976.
68. Impacts of Cool-Fired Power Plants on Fish, Wildlife, and their Habitats.
U.S. Department of the Interior, Fish and Wildlife Service. FWS/OBS-78/29,
March, 1978. p. 64-70.
69. Hagstrbm, T. 1977. Grodornas forsvinnande i an forsurad sjo. Sveriges
Natur 11/77:367-369. In: op cit # 38.
70. Johnson, Arthur H. Evidence of Acidification of Headwater Streams in the
New Jersey Pinelands. Science 206:834-839, 1979.
71. Gjessing, E. T. , A. Henriksen, M. Johannessen, and R. F. Wright. Changes
in the Chemical Composition of Lakes, pp. 65-85. Jji: Impact of Acid
Precipitation on Forest and Freshwater Ecosystems in Norway, F. H.
Braekke, ed., Research Report FR 6/76, 1432 Aas-NLH, Norway: SNSF Project
Secretariat, 1976.
72. Hornstrom, E., C. Ekstrbm, U. Miller, W. Dickson, Forsurnings inverkan
pa vastkustsjb'ar (Effects of the Acidion Lakes in the Swedish West Coast
Region) Statens Naturvardsverk, Slona, Sweden, Publikationer 1973: 7
(in Swedish, summary in English). Cited in: Wright, R. F., and Engil. T.
Gjessing. Changes in the chemical composition of lakes. Ambio. 5:
219-223, 1976.
73. Scheider, W., J. Adamski, and M. Paylor. Reclamation of Acidified Lakes
Near Sudbury, Ontario (Ontario Ministry of the Environment, Rexdale, Ontario,
Canada, 1975. Cited in: Wright, R. F. , and Egil. T. Gjessing. Changes in
the chemical composition of lakes. Ambio. 5:219-223, 1976.
74. Armstrong, F. A. J., and D. W. Schindler. Jour. Fish. Research Board,
Canada 28:171-, 1971.
75. Wright, R. F., and Egil. T. Gjessing. Changes in the chemical composition
of lakes. Ambio. 5:219-223, 1976.
8-163
-------
76. Schofield, C. Effects of Acid Rain on Lakes. Presented at the American
Society of Civil Eng. Convention, Boston. April 2, 1979. 13 pp.
77. Beamish, R. J. , and H. H. Harvey. 1972. Acidification of the La Cloche
Mountain Lakes, Ontario, and resulting fish mortalities. J. Fish. Res.
Board Can. 29:1131-1143.
78. Galloway, J. N., and E. B. Cowling. The effects of precipitation on
aquatic and terrestrial ecosystems: A proposed precipitation network.
JAPCA 28:229-235, 1978.
79. Schofield, C. L. Acid precipitation's destructive effects on fish in the
Adirondacks. N.Y. Food Life Sci. Q. 10(3):12-15, 1977.
80. Hagen, A., and A. Langeland. Polluted Snow In Southern Norway and the
Effect of the Meltwater on Freshwater and Aquatic Organisms. Environ.
Pollut. 5:45-57, 1973.
81. Galvin, P. J., and J. A. Cline. Measurement of Anions In the Snow Cover
of the Adirondack Mountains. Atoms. Envt. 12:1163-1167, 1978.
82. Tomlinson, G. H. Acidic Precipitation and Mercury In Canadian Lakes and
Fish. Scientific Paper From the Public Meeting on Acid Precipitation,
May 4-5, 1978. Lake Placid, N.Y. Sponsored by The Committee on Environmental
Conservation, New York State Assembly. Pub. by Science and Technology
Staff, New York State Assembly, p. 104-118. March 1979.
83. Cronan, C. S., and C. L. Schofield. Aluminum Leaching Response to Acid
Precipitation: Effects on High-Elevation Watersheds in the Northeast.
Science 204:304-305, 1979.
84. Landner, L., and P. 0. Larsson. Biological Effects of Mercury Fall-Out
Into Lakes from the Atmosphere, IUL Report B115. Stockholm: Institute
for Water and Air Research, 1972. 18 pp. (in Swedish, translated by H.
Altosaar, Domtar Research Centre, December 23, 1975)
85. Brouzes, R. J. P., R. A. N. McLean, and G. H. Tomlinson. Mercury - the
Link Between pH of Natural Waters and the Mercury Content of Fish. Paper
presented at a meeting of the Panel on Mercury of the Coordinating Committee
for Scientific and Technical Assessments of Environmental Pollutants,
National Academy of Sciences, National Research Council, Washington, DC,
May 3, 1977. Montreal, Quebec: Domtar Research Center, 1977.
86. Fagestrb'm, T. , and A. Jernelb'v. Some Aspects of the Quantitative Ecology
of Mercury. Water Res. 6:1193-1202, 1972.
87. Turk, J. T. , and N. E. Peters. Acid-rain weathering of a metasedimentary
rock basin, Herkimer County, New York. U.S. Geol. Surv. Open file Report
77-538, 1977. 14 pp.
8-164
-------
88. Turk, J. T., and N. Peters. Acid-rain Weathering of a Metasedimentary
Rock Basin, Herkimer County, New York. Scientific Paper From the Public
Meeting on Acid Precipitation, May 4-5, 1978. Lake Placid, N.Y. Sponsored
by The Committee on Environmental Conservation, New York State Assembly.
Pub. by Science and Technology Staff, New York State Assembly, p 136-145
March 1979.
89. Johannessen, M. , and A. Henriksen. Chemistry of Snowmelt water: Changes
in Concentration During Melting. SNSF Research Report 11/77. Oslo.
90. Glover, G. M., and A. H. Webb. Weak and Strong Acids in The Surface
Waters of The Tovdal Region in S. Norway. Water Res. 13:781-783, 1979.
91. Chin, C. W. , S. Gherini, and R. A. Goldstein. Modelling The Lake Acidifi-
cation Process. 5:1-43. I_n: Wood, M. J. (ed). Ecological Effects of
Acid Precipitation. Report of workshop held at Cally Hotel, Gatehouse-of-
Fleet, Galloway, U.K. 4-7 Sept. 1978. EPRI SOA77-403, Electric Power
Res. Institute, 3412 Hillview Ave., Palo Alto, California 94303, 1979.
92. Wright, R. F., A. Henrksen. Chemistry of small Norwegian lakes with
special reference to acid precipitation. Limnol. Oceanog. 23:487-498,
1978. ~~
93. Kramer, J. R., Geochemical and Lithological Factors in Acid Precipitation.
p. 611-618. In: Proceedings of the First International Symposium on
Acid Precipitation and the Forest Ecosystem, May 12-15, 1975, Columbus,
Ohio, L. S. Dochinger and T. A. Seliga, eds. , U.S. Forest Service General
Technical Report NE-23, Upper Darby, Pennsylvania, Forest Service, U.S.
Department of Agriculture, Northeastern Forest Experiment Station, 1976.
94. Hindrey, G. R., J. N. Galloway, S. A. Norton, C. L. Schofield, P. W.
Shaffer and D. A. Burns. Geological and Hydrochemical Sensitivity of
the Eastern United Stated to Acid Precipitation. Report prepared for
Ecological Effects Division, Corvallis Environmental Research Laboratory,
U.S. Environmental Protection Agency under EPA-DOE Interagency Agreement
79-D-X0672. EPA-600/3-80-024. January 1980.
95. National Atmospheric Deposition Program. 1979. NADP First data report:
July 1978 through February 1979: Natural Resource Ecology Laboratory,
Colorado State University.
95a. Davis, R. B. , M. 0. Smith, J. H. Baily, and S. A. Norton. Acidification
of Maine (U.S.A.) Lakes By Acidic Precipitation. Verh. Internet. Verein
Limnol. 20:532-537, 1978.
96. Henriksen, A. Acidification of Freshwaters: A Simple Approach for
Identification and Quantification. Nature 278:542-545, 1979.
97. McFee, W. W. Sensitivity of Soil Regions To Long Term Acid Precipitation.
p. 131. Corvallis Environmental Research Laboratory, U.S. Environmental
Protection Agency, Corvallis, OR. EPA-600/3-80-013, January 1980.
8-165
-------
98. Glass, G. E., and 0. L. Loucks (sds). Impacts of Air Pollutants on
Wilderness Areas of Northern Minnesota, pp. 188. Environmental Research
Laboratory-Duluth, ORD, U.S. Environmental Protection Agency, Duluth,
Minnesota, October
1979.
98a. Glass, N. R., G. E. Glass, and P. I. Rennie. Effects of Acid Precipitation.
Environ. Sci. and Tech. 13:1350-1355, 1979.
99. Jacobson, J. S. Experimental studies on the phytotoxicity of acidic
precipitation: The United States experience. Paper presented at N.A.T.O.
Advanced Research Institute, Effects of Acid Precipitation on Terrestrial
Ecosystems, Toronto, May 22-26, 1978. In Press.
99a. Jacobson, J. S., and P. van Leuken. Effects of acidic rain on vegetation.
Proc. Fourth Intern. Clean Air Congress, pp. 124-127. 1977.
100. Evans, L. S., and T. M. Curry. Differential responses of plant foilage
to simulated acid rain. Amer. J. Bot. 66:953-962, 1979.
101. Evans, L. S., N. F. Gmur, and F. DaCosta. Foliar response of six clones
of hybrid poplar to simulated acid rain. Phytopathology 68:847-856,
1978.
102. Evans, L. S. , N. F. Gmur, and F. DaCosta. Leaf surface and histological
perturbations of leaves of Phaseolus vulgaris and Helianthus annuus
after exposure to simulated acid rain"Amer. J. Bot. 64:903-913, 1977.
103. Ferenbaugh, R. W. Effects of simulated acid rain on Phaseolus vulgaris
L. (Fabaceae). Amer. J. Bot. 63:283-288, 1976.
104. Wood, T. , and F. H. Bormann. The effects of an artificial acid mist
upon the growth of Betula alleghaniensis. Brit. Environ. Pollut. 7:259-268,
1974.
105. Jonsson, B. , and R. Sundberg. Has the acidification by atmospheric
pollution cause a growth reduction in Swedish forests? Rep. Notes No.
20. Stockholm, Sweden: Royal College of Forestry, 1972.
106. Irving, P. M. Induction of Visible Injury in Chamber-Grown Soybeans
Exposed to Acid Precipitation. RER Division Annual Report, ANL-78-65-III,
Argonne, IL, 1978.
107. Wood, T., and F. H. Bormann. Short-term effects of a simulated acid
rain upon the growth and nutrient relations of Pinus strobus L. Water,
Air Soil Pollut. 7:479-488, 1977.
108. Hindawi, I. J., J. A. Rea, and W. L. Griffis. Response of bush bean
exposed to acid mist. 70th Annual Meeting of the J. Air Pollut. Control
Assoc. Abstract 77-30.4, 1977.
8-166
-------
109. Hindawi, I. J., and H. C. Ratsch. Growth Abnormalities of Christmas Trees
attributed to Sulfur Dioxide and Particulate Aerosol. Presented at the 67th
Annual Meeting of the Air Poll. Control Assoc. Abstract Number 74-252, 1974
109a.D. S. Lang, D. S. Shriner, and S. V. Krupa. Injury to vegetation incited by
sulfuric acid aerosols and acidic rain. Paper 78-7.3, 71st Annual Meeting,
Air Pollution Control Association, Houston, Texas, 1978.
110. Evans, K. S. , N. F. Gmur, and J. J. Kelsch. Perturbations of upper leaf
surface structures by simulated acid rain. Environ and Exptl. Bot.
17:145-149, 1977.
111. D. S. Shriner. Chapter 11. Atmospheric deposition: monitoring the
phenomenon; studying the effects. In: Handbook of Methodology for the
Assessment of Air Pollutant Effects on Vegetation. W. W. Heck, S. V. Krupa,
and S. N. Linzon, Editors. Air Pollution Control Association, Pittsburgh,
Pennsylvania, 1979.
112. Abrahamsen, G. , K. Bjor, R. Horntvedt, and B. Tveite. Effects of
acid precipitation on coniferous forest. In: F. H. Braekke, ed. ,
Research Report FR-6. SNSF Project, NISK,~A"as, Norway, 1976.
pp 37-63.
113. H. B. Tukey, Jr. The leaching of substances from plants. Ann.
Review of Plant Physiology. 21:305-324, 1970.
o
114. Nihlgard, B. Precipitation, its chemical composition and effect on
soil water in a beech and a spruce forest in south Sweden, Oikos,
21:208-217, 1970.
115. Comerford, N. b. and White, E. H. , 1977, Nutrient content of throughfall
in paper birch and red pine stands in northern Minnesota, Can. J.
For. Res., 7, (4), pp. 556-551.
116. Eaton, J. S., G. E. Likens, and F. H. Bormann. Throughfall and
Stemflow Chemistry in a Northern Hardwood Forest. J. Ecol. 61:495-
508, 1973.
117. Wood, T., and F. Bormann. Increases in foliar leaching by acidification
of an artificial mist. Ambio 4:169-171, 1975.
118.
119.
Abrahamsen, G., and G. J. Bollard. Effects of Acid Deposition on
Forest Vegetation. In: Wood, M. J. (ed.). Ecological Effects of
Acid Precipitation. "Report of workshop held at Calley Hotel,
Galloway, U.K., 4-7 Sept. 1978. ERRI SOA77-
Res. Institute, 3412 Hillview Ave., Palo Alto,
Gatehouse-of-Fleet,
403, Electric Power
California 94303, 1979.
Irving, P., and J. E. Miller. The Effects of Acid Precipitation
Alone and in Combination with Sulfur Dioxide on Field-Grown Soybeans
RER Division Annual Report, ANL-78-65-III, Argonne, IL, 1978.
8-167
-------
120. Shriner, D. S. Effects of simulated rain acidified with sulfuric
acid on host-parasite interactions. In: Proceedings of the First
International Symposium on Acid Precipitation and the Forest Ecosystem,
May 12-15, 1975, Columbus, Ohio, L. S. Dochinger and T. A. Seliga,
eds., U.S. Forest Service General Technical Report NE-23, U.S.
Department of Agriculture, Forest Service, Northeastern Forest
Experiment Station, Upper Darby, PA, 1976. pp. 919-925.
121. Gorham, E. Acid precipitation and its influence upon aquatic
ecosystems—an overview. In: Proceedings of the First International
Symposium on Acid Precipitation and the Forest Ecosystem, May 12-
15, 1975, Columbus, Ohio, L. S. Dochinger and T. A. Selinga, eds.,
U.S. Forest Service General Technical Report NE-23, U.S. Department
of Agriculture, Forest Service, Northeastern Forest Experiment
Station, Upper Darby, PA, 1976. pp. 425-458.
122. Giddings, J., and J. N. Galloway. The Effects of Acid Precipitation
on Aquatic and Terrestrial Ecosystems. Literature Reviews on Acid
Precipitation, EEP-2. Cornell University, Ithaca, NY, 1976.
122a. Denison, R., Caldwell B.,, Bormann, B. , Eldred, L., Swanberg, C., and
Anderson, S. The effects of acid rain on nitrogen fixation in western
Washington coniferous forests. Water, Air and Soil Pollution 8:(1), 1977,
pp. 21-34.
123. Evans, L. S. , and D. M. Bozzone. Effect of buffered solutions and
sulfate on vegetative and sexual development in gametophytes of
Pteridium aquilinum. Amer. J. Bot. 64:897-902, 1977.
124. Evans, L. S., and D. M. Bozzone. Effect of buffered solutions and
various anions on vegetative and sexual development in gamelophytes
of Pteridium aquilinum. Canadian Jour. Bot. 56:779-785, 1978.
125. Cogbill, C. V. The effect of acid precipitation on tree growth in
eastern North America, Water, Air and Soil Pollution, 8, pp. 89-93,
1977.
126. Abrahamsen, G., Horntvedt, R., and Tveite, B. Impacts of acid
precipitation on coniferous forest ecosystems, Water, Air and Soil
Pollution, 8, pp. 57-73, 1977.
127. Tamm, Co. 0., Wiklander, G., adn Popovie, B. Effects of application
of acid to poor pine forests, Water, Air and Soil Pollution, 8, pp.
75-87, 1977.
128. Overrein, L. N. Sulphur pollution patterns observed; leaching of
calcium in forest soil determined. Ambio. 1:145-147, 1972.
129. Oden, S. , R. Andersson, and M. Barting. The long-term changes in
the chemistry of soils in Scandanavia due to acid precipitation.
In: Supporting Studies to air Pollution Across National Boundaries.
THe impact on the environment of sulfur in air and precipitation,
B. Bolin, ed., Sweden's case study for the United Nations conference
on the human environment, Royal Ministry of Foreign Affairs., Royal
Ministry of Agriculture, Stockholm, Sweden, 1972. p. 20.
8-168
-------
130. Wood, T. Acid Precipitation. Jm: Sulfur in the Environment.
Missouri Botanical Garden in cooperation with Union Electric Company,
St. Louis, MO, 1975. pp. 39-50.
131. Eaton, J. S., G. E. Likens, and F. H. Bormann. Throughfall and
stemflow chemistry in a northern hardwood forest. J. Ecol. 61-ASS-
SOB, 1973. —
132. Mayer, R. , and B. Ulrich. Acidity of Precipitation as Influenced
by the Filtering of Atmospheric Sulphur and Nitrogen Compounds-Its
Role in the Element Balance and Effect on Soil. Water, Air, and
Soil Poll. 7:409-416, 1977.
133. Wiklander, L. Teaching and Acidification of Soils. In: Wood, M.
J. (ed.). Ecological Effects of Acid Precipitation. Report of
workshop held at Cally Hotel, Gatehouse-of-Fleet, Galloway, U.K.
4-7 Sept. 1978. EPRI SOA77-403, Electric Power Res. Institute, 3412
Hillview Ave., Palo Alto, California 94303, 1979.
134. Donahue, R. L. , R. W. Miller, and J. C. Shickluna. Soils. An introduction
to soils and plant growth. 4th ed. p. 244-248. Prentice-Hall,
Inc. Englewood Cliffs, NJ 07632, 1977.
135. Gorham, E. The influence and importance of daily weather conditions
in the supply of chloride, sulfate and other ions to fresh waters
from atmospheric precipitation. Phil. Trans. Roy. Soc. (London) B.
247:147-178.
136. Norton, S. A. Changes in Chemical Processes in Soils Caused by
Acid Precipitation. Water, Air and Soil Poll. 7:389-400, 1977.
137. Malmer, N. Acid precipitation: Chemical changes in the soil.
Ambio 5:231-234, 1976.
138. Oden, S. Acidification by atmospheric precipitation—A general
threat to the ecosystem. In: Acidification of the Biological
Environment, I. Mysterus, ed". , Translation Series No. 2564, Fisheries
Research Board of Canada. Ottawa, Canada, 1971.
139. McFee, W. W., J. M. Kelly, and R. H. Beck. Acid precipitation:
Effects on soil base pH and base saturation of exchange sites. Iji:
Proceedings of the First International Symposium on Acid Precipitation
and the Forest Ecosystem, May 12-15, 1975, Columbus, Ohio, L. S.
Dochinger and T. A. Seliga, eds., U.S. Forest Service General
Technical Report NE-23, U.S. Department of Agriculture, Forest
Service, Northeastern Forest Experiment Station, Upper Darby, PA,
1976. pp. 725-735.
140. Ulrich, B. Die Umweltbeeinflussung des Nahrstoffhaushaltes eines
bodensauren Buchenwalds. Forstwiss. Centralbl. 94:280-287, 1975.
8-169
-------
141. Baker, J., D. Hocking, and M. Nyborg. Acidity of open and intercepted
precipitation in forests and effects on forest soils in Alberta,
Canada. In: Proceedings of the First International Symposium on
Acid Precipitation and the Forest Ecosystem, May 12-15, 1975,
Columbus, Ohio, L. S. Dochinger and T. A. Seliga, eds., U.S. Forest
Service General Technical Report NE-23, U.S. Department of Agriculture,
Forest Service, Northeastern Forest Experiment Station, Upper
Darby, PA, 1976. pp. 779-790.
142. Hutchinson, T. C., and L. M. Whitby. The effects of acid rainfall
and heavy metal particulates on a boreal forest ecosystem near the
Sudbury smelting region of Canada. In: Proceedings of the First
International Symposium on Acid Precipitation and the Forest Ecosystem,
May 12-15, 1975, Columbus, Ohio, L. S. Dochinger and T. A. Seliga,
eds., U.S. Forest Service General Technical Report NE-23, U.S.
Department of Agriculture, Forest Service, Northeastern Forest
Experiment Station, Upper Darby, PA, 1976. pp. 745-765.
143. Tyler, G. Heavy metals pollute nature, may reduce productivity,
Ambio, 1, (2), pp. 52-59, 1972.
144. Tyler, G. Leaching rates of heavy metal ions in forest soil,
Water, Air and Soil Pollution, 9, pp. 137-148, 1977.
145. Alexander, M. Effects on acidity on microorganisms and microbial
processes in the soil. p. 341-362. In: Effects of Acid Precipitation
on Terrestrial Ecosystems. T. C. HutcTinson and M. Havas (eds.)
Plenum Press, NY, 1978.
146. W. S. Dancer, L. A. Peterson, and G. Chesters, Soil Sci. Soc. Am.
Proc. 37, 67, 1973.
147. W. E. Connell, and W. H. Patrick, Jr., Science 159, 86, 1968.
148. R. S. Wodzinski, D. P. Labeda, and M. Alexander, J. Air Pollut.
Control Assoc. 27, 891, 1977.
149. Likens, G. E. , J. S. Eaton, and J. N. Galloway. Precipitation as a
Source of Nutrients for Terrestrial and Aquatic Ecosystems. Precipitation
Seevenging (1974). Proc. of a Symposium held at Champaign, 111.
Oct. 14-18, 1974. Illinois State Water Survey. Publ. Tech. Information
Center, ERA. CONF-741003, 1977. p. 552-570.
150. Likens, G. E., and F. H. Bormann. Linkages Between Terrestrial and
Aquatic Ecosystems. BioScience 24:447-456, 1974.
151. Likens, G. E. Acid precipitation. Chem. Eng. News 54:(48)29-44,
1976. ~~
152. Fredricksen, R. L. Nutrient budget of a Douglas-fir forest on an
experimental watershed in western Oregon. Pages 115-131, Research
on Coniferous and R. H. Waring. Portland, Oreg.: Pacific Northwest
Forest and Range Experiment Station, 1972.
8-170
-------
153. Likens, G. E., G. H. Bormann, N. M. Johnson, D. W. Fisher, and R.
S. Pierce. Effects of cutting and herbicide treatment on nutrient
budgets in the Hubbard Brook Watershed - ecosystem. Ecol. Monoqr
40:23-47, 1970.
154. Henderson, G. S., and W. F. Harris. An ecosystem approach to
characterization of the nitrogen cycle in a deciduous forest watershed.
Pages 179-193, Forest Soils and Forest Soils Conference, edited by
B. Bernier and C. H. Winget. Quebec, Canada: Les Presses de
VUniversite Laval, 1975.
155. Junge, C. E. The distribution of ammonia and nitrate in rainwater
over the United States. Trans. Amer. Geophys. Union 39:241-248,
1958. —
156. The National Research Council, Scientific and Technical Assessments
of Environmental Pollutants. Nitrates: An Environmental Assessment.
National Academy of Scineces, Washington, D.C., 1978.
157. Brady, N. C. The Nature and Property of Soils. McMillan Publishing Co.,
New York. p. 464-472, 1974.
158. Jones. M. B. Sulfur in Agricultural Lands, p. 146-158. I_n:
Sulfur in the Environment. Missouri Botanical Garden in cooperation
with Union Electric Company, St. Louis, Mo., July, 1975.
159. Shinn, J. H. , and S. Lynn. Do man-made sources affect the sulfur
cycle of northeastern states? Environ. Sci. and Tech. 13:1062-
1067, 1979.
160. Halsteand, R. L., and P. J. Rennie. Effects of Sulphur on Soils in
Canada. 181-220. In: Sulphur and its Inorganic Derivatives in
the Canadian Environment. Nat. Res. Council of Canada. NRC Assoicate
Committee on Scientific Criteria for Environmental Quality. Ottawa,
Canada, 1977.
161. Hoeft, R. G., D. R. Kieney, and L M. Walsh. Nitrogen and Sulphur
in Precipitation and Sulfur Dioxide in the Atmosphere in Wisconsin.
J. Environ. Quality. 1:203-208, 1972.
162. Tabatabai, M. A., and J. M. Laflen. Nitrogen and Sulfur Content
and pH of Precipitation in Iowa. J. Environ. Quality. 5:108-112,
1976.
163. Brezonik, P. L Nutrients and Other Biologically Active Substances
in Atmospheric Precipitation. Proc. First Specialty Symposium on
Atmospheric Contribution to the Chemistry of Lake Waters. Internat.
Assoc. Great Lakes Res. Sept. 28-Oct. 1, 1975. p. 166-186.
164. Nriagn, J. Deteriorative Effects of Sulfur Pollution on Materials.
pp. 2-59. In. Nriagn, J. ed. Sulfur in the Environment Part II:
Ecological Imports, pp. 482. John Wiley and Sons, New York,
1978.
8-171
-------
165. Cowling, E. B., and L. S. Dochinger. The Changing Chemistry of
Precipitation and Its Effects on Vegetation and Materials. AICHE
Symposium Series. Control and Dispersion of Air Pollutants: Emphasis
on NO and Particulte Emissions. 7:134-142, 1978.
A
166. Kucera, V. Effects of Sulfur Dioxide and Acid Precipitation on
Metals and Anti-Rust Painted Steel. Ambio 5:243-248, 1976.
167. Sereda, P. J. Chapter 8. Effects of Sulphur on Building Materials.
p. 359-426. In: Sulphur and its Organic Derivatives in the Canadian
Environment. "Rat. Res. Council of Canada. NRC Associate Committee
on Scientific Criteria For Environmental Quality. Ottawa, Canada,
1977.
168. Winkler, E. M. Important Agents of Weathering For Building and
Monumental Stone. Eng. Geol. 1:381-400, 1966.
169. Schaffer, R. J. The weathering of natural building stones. Spec.
Ref. No. 18, London, HMSO. 149 pp. Cited in #167. Sereda, etc.
170. Woodwell, G. M. Eco-forum: Paradigms Lost. Bulletin on the
Ecolgical Soc. of Am. 59:136-140, 1978.
171.
172.
173.
174.
175.
176.
177.
178.
In:
Ray
Festa, P. Acid Waters and Declining Fisheries—The Next Step.
Scientific Paper from the Public Meeting on Acid Precipitation,
4-5, 1978, Lake Placid, New York, Published by the Science and
Technology Staff, New York State Assembly, Albany, NY, March, 1979.
p. 7-14.
Wright, R. F. Acid precipitation and its effects on freshwater
ecosystems: an annotated bibliography. In: Proceedings of First
International Symposium on Acid Precipitation and the Forest Ecosystem,
May 12-15, 1975, Columbus, Ohio, L. S. Dochinger and T. A. Seliga,
eds., U.S. Forest Service General Technical Report NE-23, U.S.
Department of Agriculture, Forest Service, Northeastern Forest
Experiment Station, Upper Darby, PA, 1976. pp. 619-678.
Michalski, M. F. P., and J. Adamski. Restoration of acidified
lakes Middle and Lohi in the Sudbury area. J_n: Proceedings of the
Ontario Industrial Wastes Conference, 1974. pp. 163-175. Cited in 172.
Gosselink, J. G. , E. P. Odum, and R. M. Pope. The Value of the
Tidal Marsh. Louisiana State Univ. Publication No. LSU-SG-74-03,
1975,
Westman, W. E. How much are nature's services worth? Science.
197:960-964, 1977.
LiKens, G. E., R. F. Wright, J. N. Galloway, and T. J. Butler.
Acid Rain. Scientific American. 241:43-51, 1979.
Likens, G. W., F. H. Bormann, and N. M. Johnson. Acid rain.
Environment 14:33-40, 1972.
Brasset, C. Airborne acid. Ambio 22-8, 1973.
8-172
-------
179. Oden, S. The acidity problem—An outline of concepts. In: Proceedings
of the First International Conference on Acid Precipitation and the
Forest Ecosystem. May 12-15, 1975, Columbus, Ohio, L. S. Dochinger
and T. A. Seliga, eds., U.S. Forest Service, General Technical
Report NE-23, U.S. Department of Agriculture, Forest Service,
Northeastern Forest Experiment Station, Upper Darby, PA, August
1976. pp. 1-36.
180. Oden, S. Acid precipitation: A world concern. In: Proceedings
of the Conference on Emerging Environmental Problems, Acid Precipitation,
May 19-20, 1975, The Institute on Man and Science, Rensselaerville,
N.Y. U.S. Environmental Protection Agency, Region II. Water
Resources and Marine Sciences Center, Cornell Univeristy and Center
for Environmental Quality Management, Cornell University, EPA-
902/9-75-001, November 1975. pp. 5-44.
181. Braekke, F. H. , ed. Impact of Acid Precipitation on Forest and
Freshwater Ecosystems in Norway. SNSF Project, Research Report FR 6/76,
Oslo, Norway, 1976.
182. Cogbill, C. V., and G. E. Likens. Acid precipitation in the northeastern
United States. Water Resour. Res. 10:1133-1137.
183. Cogbill, C. V. The history and character of acid precipitation in eastern
North America. In: Proceedings of the First International Conference on
Acid Precipitation and the Forest Ecosystem, May 12-15, 1975, Columbus,
Ohio, L. S. Dochinger and T. A. Seliga, eds., U.S. Forest Service General
Technical Report NE-23, U.S. Department of Agriculture, Forest Service,
Northeastern Forest Experiment Station, Upper Darby, PA, 1976. pp.
363-379.
184 Likens, G. E. The Chemistry of Precipitation in the Central Finger
Lakes Region. Technical Report No. 50. Water Resources and Marine
Science Center, Cornell University. Ithaca, NY, 1972.
185. National Research Council. Air Quality and Stationary Source Emission
Control. A report prepared by the Commission on Natural Resources,
National Academy of Sciences, for the Committee on Public Works, U.S.
Senate, 94th Congress, 1st Session, Committee Serial No. 94-4, U.S.
Government Printing Office, Washington, DC, 1975.
186. Matheson, D. H. , and F. C. Elder, eds. Proceedings of symposium on
atmospheric contribution to chemistry of lake waters. J. Great Lakes
Res. 2, Suppl. 1:1-225, 1976.
187. Irving, P. Rainfall Acidity at Argonne. RER Division Annual Report,
Argonne National Laboratory, Argonne, IL, ANL-78-65-III, 1978.
188. Lewis, W. M., Jr., and M. C. Grant. Acid Precipitation in the Western
U.S. Science 207:176-177, 1980.
8-173
-------
189.
190.
191.
McColl, J. G., and D. S. Bush.
in the San Francisco Bay Area.
Precipitation and throughfall chemistry
J. Environ. Qua! 7:352-357, 1978.
Williams, Wayne T.
Better Environment.
Acid Rain: The California Context. Citizens for
Environmental Review, May 1978. p. 6-8, 10.
Liljestrand, H., and J. J. Morgan.
Precipitation in Pasadena, Calif.
1978.
Chemical Composition of Acid
Environ. Sci. and Tech. 12:1271-1273,
191a. Larson, T. V., R. J. Charlson, E. J. Knudson, G. D. Christian, and H.
Harrison. The influence of a sulfur dioxide point source on the rain
chemistry of a single storm in the Puget Sound region. Water Air Soil
Pollut. 4:319-328, 1976.
192. Dillon, P. J., D. S. Jeffreis, W. Snyder, R. Reid, N. D. Van, D. Evans,
J. Moss, and W. A. Scheider. J. of Fish. Res. Board Can. 35:809-815,
1978.
193. Summers, P. W., and D. M. Whelpdale. Acid Precipitation in Canada. In:
Proceedings of the First International Conference on Acid Precipitation
and the Forest Ecosystem, May 12-15, 1975, Columbus, Ohio, L. S. Dochinger
and T. A. Seliga, eds., U.S. Forest Service General Technical Report
NE-23, U.S. Department of Agriculture, Forest Service, Northeastern
Forest Experiment Station, Upper Darby, PA, 1976. pp. 411-421.
194. Miller, J. M., J. N. Galloway, G. E. Likens. Origin of air masses
producing acid precipitation at Ithaca, N.Y., A preliminary report.
Geophysical Research Letters. 5:757-769, 1978.
195. Galvin, P. J., P. J. Samson, P. E. Coffey, and D. Romeno. Transport of
sulfate to New York State. Environ. Sci. and Tech. 12:580-584, 1973.
196. Pack, D. H., G. J. Ferber, J. L. Heffter, K. Telegadas, J. K. Angel 1, W.
H. Hoecker, and L. Machta. Meterology of Long-Range Transport. Atmos.
Envt. 12:425-444, 1978.
197. Likens, G. E. , F. H. Bormann, J. S. Eaton, R. S. Pierce, and N. M. Johnson.
Hydrogen ion input to the Hubbard Brook Experimental Forest, New Hampshire,
during the last decade. Jji: Proceedings of the First International
Symposium on Acid Precipitation and the Forest Ecosystem, May 12-15,
1975, Columbus, Ohio. L. S. Dochinger and T. A. Seliga, eds., U.S.
Forest Service General Technical Report NE-23. U.S. Department of
Agriculture, Forest Service, Northeastern Forest Experiment Station,
Upper Darby, PA, 1976. pp. 397-407.
198. Nisbit, I. C. T. Sulfates and acidity in precipitation: Their relationship
to emissions and regional transport of sulfur oxides. Jji: Air Quality
and Stationary Source Emission Control. A report prepared by the Commission
on Natural Resources, National Academy of Sciences for the Committee on
8-174
-------
Public Works, U.S. Senate, 94th Congress, 1st Session. Committee Serial
No. 94-4, U.S. Government Printing Office, Washington, D.C., 1975. pp.
199. Harr, T. E., and P. E. Coffey. Acid Precipitation in New York State.
Technical Paper No. 43. New York State Department of Environmental
Conservation, Albany, NY. pp. 21-29, 1975.
200. Hornbeck, J. W. , G. E. Likens, and J. S. Eaton. Seasonal patterns in
acidity of precipitation and their implications for forest stream ecosystems
In: Proceedings of the First International Conference on Acid Precipitation
and the Forest Ecosystem, May 12-15, 1975, Columbus, Ohio. L. S. Dochinger
and T. A. Seliga, eds. U.S. Forest Service General Technical Report
NE-23, U.S. Department of Agriculture, Forest Service, Northeastern
Forest Experimental Station, Upper Darby, PA, 1976. pp
201. Pack, D. W. Sulfate behavior in eastern U.S. precipitation. Geophysical
Res. Letters. 5:673-674, 1978.
202. Miller, J. M. , J. N. Galloway, G. E. Likens. Origin of air masses producing
acid precipitation at Ithaca, NY, A preliminary report. Geophysical
Research Letters 5:757-769, 1978.
203. Hendry, C. Chemical composition of rainfall at Gainesville, Florida.
M.S. Thesis. Department of Environmental Engineering Sciences, University
of Florida, Gainesville, 1977.
204. Wolff, G. T. , P. J. Lioy, H. Golub, and J. S. Hawkins. Acid precipitation
in the New York Metropolitan Area: Its relationship to meteorological
factors. Env. Sci. and Tech. 13:209-212, 1979.
205. Gambell, A. W., and D. W. Fisher. Chemical composition of rainfall in
eastern North Carolina and southeastern Virginia. U.S. Geol. Surv. Water
Supply Pop. 1535K, 1-41, 1966.
206. Likens, G. E. , and F. H. Bormann. Acid rain: A serious regional environ-
mental problem. Science 184:1176-1179, 1974.
207. Landsberg, H. E. Some observations of the pH of Precipitation Elements.
Arch. Meteorol. Geophys. Bioklimator., Serv. A, 7:219-226, 1954.
208. Granat, L. On the relationship between pH and the chemical composition
in atmospheric precipitation. Tellus 24:550-560, 1972.
209. Junge, C. E., and R. T. Werby. The concentration of chloride, sodium,
potassium, calcium and sulfate in rainwater over the United States. J.
Meteorol. 15:417-425, 1958.
210. Junge, C. E. The distribution of ammonia and nitrate in rain water over
the United States. Eos. Trans. Ag.V. 39:241-248, 1958.
8-175
-------
211. Lodge, J. R. , Jr., J. B. Pate, W. Basbergill, G. S. Swanson, K. C. Hill,
E. lorange, and A. L. Lazrus. Chemistry of United States Precipitation.
Final Report, National Precipitation Sampling Network. Boulder, Colo.:
National Center for Atmospheric Research. 1968.
212. Krupa, Sagar. Acidic Rain: Its Chemistry and Effects on Terrestrial
Vegetation. Proc. 3rd International Congress of Plant Pathology, Munich,
West Germany, August 1978. p. 345 (Abstract).
213. Miller, P. R., M. H. McCutchan, and H. P. Milligan. Oxidant air pollution
in the Central Valley, Sierra Nevada foothills, and Mineral King Valley
of California. Atmos. Environ. 6:623-633, 1972.
214. Air Quality Criteria for Ozone and Other Photochemical Oxidants. U.S.
EPA-600/8-78-004. Research Triangle Park, N.C. April 1978.
215. Lipske, M. Sour Rain, Deadly Rain. Defenders. 55:2-5, 1980.
216. Jacobson, J. S., L. J. Heller, and P. Van Lenken. Acidic precipitation
at a site within the northeastern concentration. Water, Air and Soil
Poll. 6:339-349, 1976.
217. Gorham, E. On the acidity and salinity of rain. Geochim. Cosmochim.
Acta. 7:231-239, 1955.
218. Gorham, E. Atmospheric pollution by hydrochloric acid. Quart. J. Royal
Meteorol. Soc. 84:274-276, 1958.
219. Lindberg, S. E. , R. C. Harriss, R. R. Turner, D. S. Shriner, and D. D.
Huff. Mechanisms and rates of atmospheric deposition of selected trace
elements and sulfate to a deciduous forest watershed. ORNL/TM 6674,
Environmental Sciences Division Pub. No. 1299, 1979. pp. 514.
220. Weiss, R. E., A. P. Waggoner, R. J. Charlson, and N. C. Ahlquist. Sulfate
aerosol: Its geographic extent in the midwestern and southern United States,
Science 195:979-981.
221. Seymour, M. D. , S. A. Schubert, J. W. Clayton, Jr., and Q. Fernando.
Variations in the acid content of rain water in the course of a single
precipitation. Water, Air and Soil Poll. 10:147-161, 1978.
221a. Stensland, G. J. A Comparison of Precipitation Chemistry Data At A Central
Illinois Site in 1954 and In 1977. Presented at 71st Annual Meeting of
the Air Poll. Control. Assoc., Houston, TX. June 25-26, 1978.
222. National Research Council. Scientific and Technical Assessments of
Environmental Pollutants. Nitrates: An Environmental Assessment.
National Academy of Sciences, 1978. p. 275-317.
223. Reuss, J. 0. Chemical/Biological Relationships Relevant to Ecological
Effects of Acid Rainfall. Ecological Research Series, Report No.
EPA-660/3-75-032, Office of Research and Development. U.S. Environmental
Protection Agency. Corvallis, OR, 1975.
8-176
-------
224. National Research Council. Sulfur Oxides. Chapter 4. National Academy
of Sciences. Washington, D.C. 1978.
225. Hamilton, W. C. Estimate by the National Coal Association. Personal
communication. Jan. 1980.
226. Gatz, D. F. Comment on 'Acid precipitation in the northeastern United States
by Charles V. Cogbill and Gene E. Likens. Water Resour. Res. 12:569-570,
1976.
227. The LRTAP Problem in North America: a preliminary overview. Prepared
the United States-Canada Research Consultation Group on the Long-Range
transport of Air Pollutants. A. P. Altshuler and G. A. McBean, Co-
Chairman, 1979. pp. 48.
8-177
-------
9. EFFECTS ON VISIBILITY AND CLIMATE
9.1 INTRODUCTION
Haze particles are the most conspicuous trace constituents of the atmosphere;
their presence can be detected from afar by the unaided eye. Particles scatter
and absorb visible radiation, redirecting a portion of it to form "air light,"
which obscures distant objects. Section 9.2 of this chapter discusses the
effects of particles on visibility.
Particles also indirectly affect the properties of the atmosphere. For
example, essentially all water vapor condensation occurs by nucleation, that is,
water deposition onto cloud condensation nuclei or ice nuclei. Addition of such
particles to the atmosphere therefore affects cloudiness, which in turn influ-
ences insolation. Section 9.3 of this chapter discusses the effects of particles
on solar radiation.
The incorporation of aerosols into cloud and fog droplets can change the
quality as well as the quantity of precipitation. The mechanisms and effects of
acid precipitation are discussed in chapter 8.
In 1977, the National Science Foundation Workshop on Inadvertent Weather
Modification (Robinson, 1977) identified five major areas in which effects on
the atmosphere can be attributed to presence of particles: visibility, solar
radiation/sunshine, cloudiness, precipitation quantity, and precipitation
quality. On the basis of current scientific knowledge, weather phenomena were
assessed to determine the likelihood and qualitative scale of their inadvertent
modification by human activities. Major inadvertent effects are considered
scientifically established for changed precipitation quality, increased haze,
and increased cloudiness. Moderate inadvertent effects are established for
decreases in solar radiation and sunshine and for urban-scale increases in
9-1
-------
quantity of precipitation and thunderstorms. Probable but not yet firmly
established inadvertent changes include mesoscale increases in cloudiness and
thunderstorms.
9.2 EFFECTS ON VISIBILITY
The term "visibility" is used colloquially to refer to various characteristics
of the optical environment, such as the clarity with which distant details can
be resolved and the trueness of their apparent coloration. These and other
aspects of visibility are addressed in an EPA report to Congress (U.S.
Environmental Protection Agency, 1979). Daytime visibility is normally
taken to mean visual range, or the greatest distance at which a large black
object can be distinguished against the daytime horizon sky. The National
Weather Service (NWS), however, uses the term prevailing or horizontal
visibility, which is the greatest visability which is attained or
surfaced throughout at least half of the horizon circle not neccessarily
continuous.
An insight into general visibility conditions in the United States can be
obtained by examining available regional airport visibility data. Figure 9-1
(Trijonis and Shapland, 1978) shows isopleths of median visibility, a statistic
that is insensitive to the site-specific availability of markers as long as the
farthest markers consistently reported lie beyond the median visibility. The
data represent midday visual ranges for 1974-76 from 100 suburban/nonurban
locations. Visibilities at 93 of the locations were determined from airport
observations, usually by NWS. Instrumental visibility measurements from seven
sites in the Southwest are also included. Although some uncertainties arise from
the use of airport visibility observations, there is reasonably good consistency
among airport observations within regions and between airport and instrumental
results in the Southwest.
The best visibility (70+ miles, 110+ km) occurs in the mountainous Southwest.
Visibility is also quite good (45-70 miles, 70-110* km) north and south of that
9-2
-------
VO
CO
P: BASED ON PHOTOGRAPHIC
PHOTOMETRY DATA
N BASED ON NEPHELOMETRY DATA
•: BASED ON UNCERTAIN EXTRAPOLATION
OF VISIBILITY FREQUENCY DISTRIBUTION
Figure 9-1. Map shows median yearly visual range (miles) and isopleths for suburban/nonurban areas,
197476.
Source: Trijonisand Shapland (1978).
-------
region, but sharp gradients occur to the east and west. Most of the area east of
the Mississippi and south of the Great Lakes has a median visibility of less than
15 miles (24 km). Within the East, the lowest visibilities occur along the
heavily industrialized Ohio River Valley.
Although natural sources of visibility impairment are undoubtedly an important
factor in producing these geographical and seasonal patterns, analysis of visibility
trends and other information discussed in later sections suggests that manmade
air pollution has a significant impact. It is also important to note that the
regions with the best existing visibility levels are the most sensitive to additional
impairment and most responsive to incremental pollution reductions. The reasons
for this are discussed in the next section.
9.2.1 Fundamentals of Atmospheric Visibility
The effect of the intervening atmosphere on the visual properties of distant
objects (e.g., the horizon sky, mountains, and clouds) can be determined if the
concentration and characteristics of air molecules, aerosols, and nitrogen
dioxide along the line of site are known. The rigorous treatment of visibility
requires a mathematical description of the interaction of light with the atmos-
phere, known as the radiative transfer equation. The description presented here
is intended to provide a qualitative understanding of the underlying theory.
Detailed treatments are available in a number of publications (Middleton, 1952;
Chandrasekhar, 1960).
Figure 9-2a shows the simple case of a beam of light (e.g., from the sun or
a searchlight) transmitted horizontally through the atmosphere. The intensity
of the beam in the direction of the observer, I(x), decreases with distance from
the source as light is absorbed or scattered out of the beam. Over a short
interval, this decrease is proportional to the length of the interval and to the
intensity of the beam at that point:
9-4
-------
Figure 9-2. (A) A schematic representation of atmospheric extinction,
illustrates (i) transmitted, (ii) scattered, and (iii) absorbed light. (6) A
schematic representation of daytime visibility illustrates: (i) residual
light from target reaching observer, (ii) light from target scattered
out of observer's line of sight, (iii) air light from intervening atmos
phere, and (iv) air light constituting horizon sky. (For simplicity,
"diffuse" illumination from sky and surface is not shown.) The
extinction of transmitted light attenuates the "signal" from the tar
get at the same time as the scattering of air light is increasing the
background "noise."
9-5
-------
-dl - bext Idx
where dl is the decrease in intensity, bgxt is the extinction coefficient, I is
the original intensity of the beam, and x is the path length. The extinction
coefficient b t has units of inverse distance. The extinction coefficient is
determined by the scattering and absorption of particles and gases and varies
with pollutant concentration and wavelength of light.
Consider an observer looking at a distant target in the daytime (Figure 9-
2b). Just as a beam is attenuated by the atmosphere, the light from the target
reaching the observer is also diminished by absorption and scattering. The
reduced brightness of distant objects is not usually the primary factor limiting
their visibility, however; if it were, the stars would be visible around the
clock, since their light must traverse the same atmosphere night and day. In
addition to light originating at the target, the observer receives extraneous
light scattered into the line of sight by the intervening atmosphere. It is
this air light that we describe as haze.
The effect of extinction and added air light on the perceived brightness of
visual targets is shown graphically in Figure 9-3. At increasing distances,
both bright and dark targets are "washed out" and approach the brightness
of the horizon. Thus, the contrast of an object relative to the horizon
(and other objects) decreases.
The limiting distance at which a target can be distinguished from the
horizon sky is the distance at which its apparent contrast (target brightness
minus horizon brightness, divided by horizon brightness) drops to the observer's
/.
threshold of detection. In a uniform atmosphere, the apparent contrast between
a target and the horizon sky decays exponentially with observer-target distance x
(Middleton, 1952):
C = CQ exp(-bext x) (9-1)
9-6
-------
Z
o
E
CD
LIGHT INTENSITY OF HORIZON
•LACK OBJECT
OBJECT-OBSERVER DISTANCE
Figure 9-3. The apparent contrast between object and horizon sky
decreases with increasing distance from the target. This is true for
both bright and dark objects.
9-7
-------
where C is the initial contrast at x = 0. The maximum distance at which a
given large target can be distinguished from the horizon is therefore Inversely
proportional to the extinction coefficient:
log |C0| - log |e| (g_2)
y = ———————————— * '
max .
bext
where e is the observer's contrast threshold.
The proportionality factor, log |Cg| - log |e| in equation 9-2, depends on the
target's intrinsic contrast with the horizon and on the observer's contrast
threshold. For a black target, CQ = -1, so that log |CJ = 0 and the propor-
tionality factor reduces to -log |e|. The visual range (V) in a uniform atmosphere is
thus given by the Koschmieder formula:
v = -log |e| (9-3)
bext
The observer's contrast threshold, e, is of course no universal constant.
It varies with apparent target size and overall illumination, and it varies with
observer (Figure 9-4; Middleton, 1952). However, it enters equation 9-3 only
logarithmically, so that the relationship of visual range to extinction is not
unduly sensitive to the psychophysiology of the observer. A sevenfold increase
in e, for example, does not quite double -log |e|. The conventional choice
of |e| for a "standard" observer is 0.02, which yields V = 3.9/b ,.
Little error is introduced into the determination of visual range by using
as targets such nonblack features as dark forests and deep shadows. For a
target whose intrinsic brightness is as much as 30 percent that of the horizon
sky. for example, the limiting distance given by equation 9-2 is within 10
percent of the visual range. On the other hand, the intrinsic brightness of
sunlit objects can approach that of the horizon sky, in which case their use as
targets can lead to large underestimates of visual range.
9-8
-------
>
u
D
O
220 |
200
180
160
140
120
100
80
60
40
20
0
—
—
^^
^M
•M
••M
•M
^m
1 1 1
-
-
N - 1000
—
^H
—
MI
-
•n _
_ —
Tin
1 H Un-i-i
00
05
10
15
20
L_
4.6
CONTRAST.|6|
J I I
3.0 2.3
LOG CONTRAST. K
V?
1.6
Figure 9-4. Measured apparent contrast of farthest visibility marker
was identified in 1000 determinations of visual range by 10 observ-
ers. Scatter is due to both the variability of observer thresholds and
the discrete nature of the marker set. The corresponding value for
the Koschmieder constant, K * -log e, is 3.2 ± 0.6.
Source: From Middleton (1952).
9-9
-------
The Koschmieder formula's neglect of pollution gradients and the
earth's curvature limits its applicability near sources of primary
particulate matter and in very clean air. Where visibility 1s restricted
by diffuse haze, however, equation 9-3 performs well. Comparisons of
daytime visual range, as measured by a human observer, and extinction
from scattering, as measured instrumentally at a single point, show
visual range to correlate with the reciprocal of extinction, as illustrated
in Figure 9-5 (Horvath and Noll, 1969; Samuels et al., 1973). The
correlation coefficients are commonly in the neighborhood of 0.9, which
is quite good considering that the point measurement of extinction is
being extrapolated along a sight path several kilometers long.
9.2.1. Summary—Visibility is inversely proportional to the atmospheric
extinction coefficient.
9.2.2 Measurement Methods
The extinction coefficient introduced in section 9.2.1 represents a
summation of contributions from scattering and absorption by air and by
pollutants: bgxt = bRg + bag + b$cat + babs, where bRg is Rayleigh
scattering by air molecules; ba is absorption by nitrogen dioxide gas;
ag
bscat is Scatterin9 by particles; and b . is absorption by particles.
There are several methods for measuring total extinction and its various
components, as discussed below.
9.2.2.1 Observer (Total Extinction)
9.2.2.1.1 Method. Contrast of an object is reduced as range increases as:
C = CQ exp(-bext x) (9-4)
For a black object viewed against the horizon, CQ = -1 and a 0.02 contrast
detection limit for the observer.
V - 3.91
" bext <9-5>
9-10
-------
0.50
0.40
0.30
0.20
u
o
8 0.10
0.05
0.03
I IT T
I I I I 1
I I
I I I
10 20
VISUAL RANGE, km
50
100
Figure 9-5. Inverse proportionality between visual range and the scat
tering coefficient, bltat, was measured at the point of observation.
The straight line shows the Koschmieder formula for nonabsorbing
(bext - b$cat) media. V « 3.9/bcr.Tfhe linear correlation coefficient
for Vand
i$0.89.
scat
Source: Horvath and Noll (1969).
9-11
-------
For the ideal case of a large black object and spatially uniform aerosol
and illumination, V will be independent of sun angle. Prevailing visibility is
normally observed over half of the horizon circle. A somewhat different v will
result if the observation is based on detecting fine spatial contrast detail
instead of a large black object (Henry, 1977).
9.2.2.1.2 Problems. This method is labor intensive and requires black objects
at several distances to provide gradation in measured visibility as b .
changes.
Few sites are suited for visibility observations over a visual range
greater than 50 km. For reflecting targets, such as snow-covered mountaintops,
the distance at which they can be detected under constant extinction can change
from the visual range or somewhat greater under clear skies and high sun eleva-
tions to less than one-fourth the visual range for evenly overcast skies. The
contrast between the horizon and the target is a function of sun angle except
for ideal black targets.
To detect changes in visual range, targets are required at a range of
distances. For example, Tombach and Chan (1977) reported on a visibility
measurement program consisting of about 1 year of weekly observations. In all
observations, the most distant target at 120 km was visible. The site used was
not well suited because targets were not available at various distances near the
mean visual range. In some places, topography or earth curvature prevent the
establishment of appropriate markers at V =250 km.
9.2.2.2 Contrast Telephotometry (Total Extinction)
9.2.2.2.1 Method. The brightness (usually luminance or radiance at various
wavelengths) of a black object at a distance much less than the visual range is
measured and expressed as ratio to the same brightness of the nearby horizon.
9-12
-------
Either photographic or photoelectric sensing is used. The extinction coefficient
is obtained from equation 9-4, which gives
x ln (§0> ' -bext (9-6)
Black targets must be used unless CQ is known for other targets, and the
wavelength of operation must be chosen. The obvious choice of photopic response
to match an observer is probably not the best choice in clean sites. Tombach
and Chan (1977) and Trijonis and Yuan (1978a) have shown that visual range or
extinction is at times largely determined by the molecular (Rayleigh) scattering
in the atmosphere. Therefore, there will be a color shift between the horizon
and the air light that is detected by looking at a nearby black object (Middleton,
1952). Measurements should be made by using narrowband radiance rather than
broadband luminance detectors to avoid errors in measurement of extinction.
Telephotometers may be useful for characterizing plumes in terms of their
brightness or contrast relative to sky or terrain background. Simple contrast
measurement of distant visible objects may be useful even if it is not possible
to reduce the observations to extinction.
9.2.2.2.2 Problems. At some sites there may be relatively few days on which
telephotometers are useful because clouds (on the horizon or above the path to
the nearby black object) introduce errors. The use of equation 9-6 to reduce
contrast measurements to extinction coefficients requires uniform illumination
of both measurement paths and assumes that the horizon is optically thick hori-
zontally. This means that visual range is limited by optical extinction and
reduced contrast and not by the earth's curvature. This last assumption is not
true in clean locations where visual range is largely limited by molecular
scatter. The error from this assumption will increase calculated extinction,
particularly at longer wavelengths.
9-13
-------
Although it is possible to design automatic, low-maintenance telephotometers
that can scan selected targets, no instrument of this type is now available.
Therefore this measurement is labor intensive, requiring an operator. Even with
an automated instrument, accuracy requires that the sight path and horizon be
cloud-free, and this check may be difficult to automate. Photographic measure-
ments minimize capital investment but increase operator cost and decrease
accuracy.
9.2.2.3 Long-Path Extinction (Total Extinction)
9.2.2.3.1 Method. The most direct way to measure extinction is simply to
measure the decrease in intensity of a beam of light as a function of range:
T0 = exP('bext x)
x 1n T0 = bext
This method has great appeal in that no assumptions are involved and it measures
average extinction over the path.
Experimentally, a source (either incoherent or laser) is observed at a
large distance by using collecting optics plus a photomultiplier light detector
and an optical band-limiting filter. The source and detector may be at opposite
ends of the path or at the same end, with a distant mirror used to reflect the
beam.
9.2.2.3.2 Problems. The calibration of a long-path transmissometer is difficult
for these reasons: (1) the outgoing optical energy is usually not well known;
(2) the distant mirror or other retroreflector has unknown divergence and
reflectivity; (3) the receiver sensitivity, including the collecting optics and
filter transmissions, is unknown; and (4) 1 through 3 can change with time.
9-14
-------
Hall and Riley (1976) have measured extinction by observing the same source
at two ranges. Any decrease in intensity with range in excess of the inverse-
square decrease is due to extinction. This method avoids any need for absolute
calibration, since only the ratio of intensities at two ranges need be measured.
This method as used by Hall and Riley is labor intensive but has been demon-
strated in clean and urban environments during night operation. A mercury arc
light probably would allow daytime operation.
Systems that do not use multiple path lengths require another calibration
method that must be stable over long periods and be accurate enough to permit
aerosol extinction comparable to or less than Rayleigh scattering to be quantified.
It is not clear how this can be done.
9.2.2.4 Nephelometer (Scattering)
9.2.2.4.1 Method. The integrating nephelometer was developed around 1943 as a
simple means of measuring visual range, and the principle has been used widely
for about 25 years (Middleton, 1952). The configuration of this instrument
gives an integration-over-scattering angle such that the scattering component
of the extinction, b „,«., can be measured. By subtracting the Rayleigh scattering,
sea u
bD , a measurement of b _ is possible with an accuracy in most cases of about 10
Kg sp
percent of the reading (Ensor and Waggoner, 1970; Rabinoff and Herman, 1973).
This measurement is made at a point in an internal sample volume. This closed
system allows both humidity control and the calibration with particle-free gases
such as carbon dioxide or Freon-12. Since these gases are widely available and
are inexpensive, calibration is simple. The instrument is commercially avail-
able from both U.S. and foreign manufacturers. The U.S. version was developed
under Federal Government support (Public Health Service, National Air Pollution
Control Administration, Environmental Protection Agency, and National Science
Foundation). Other versions are available that differ in sensitivity and
9-15
-------
wavelength response. The most sensitive instruments are capable of measuring
aerosol particle scattering extinction, b at or below 10 percent of Rayleigh
scatter (i.e., at b =0.1 bR ). Thus, adequate sensitivity is available for
class I regions.
The nephelometer can be used to measure the scattering coefficient at the
same point where samples are taken for mass or chemical determination. Most of
the data relating cause and effect (i.e., particle concentration or composition
and optical effect) have been acquired with the integrating nephelometer.
Agreement between the nephelometer and the long-path transmissometer has been
demonstrated (Waggoner and Charlson, 1976; Weiss, 1978).
9.2.2.4.2 Problems. The instrument measures optical properties at a point,
which may limit its application to cases where there is spatial uniformity of
atmospheric optical properties. There may be errors introduced by differences
in humidity inside the instrument relative to ambient conditions. The instru-
ment will have two types of error if atmospheric optical properties are con-
trolled by particles larger than 3 ym such as in fog or dust storms: (1) coarse
particles will be excluded by impaction on the sampling ductwork; and (2) the
angular integration suffers from truncation at low scattering angles and in fog
will underestimate the actual scattering coefficient by as much as a factor of
2.
9.2.2.5 Light Absorption Coefficient—Without doubt, the absorption component
of extinction, b , is the most difficult to measure. As yet, no single method
has proven to be the most effective. Were it not for the fact that graphitic
carbon as soot is a dominant species in cities and industrial regions, b
would be inconsequentially small. However, even a few percent of the submicron
mass as soot produces a significant effect on ban or b .. The methods that
flp CX u
have so far been used to evaluate b include: (1) determining the difference
9-16
-------
between bgxt and b by combining long-path transmissometer with nephelometer
(Weiss, 1978); (2) determining absorption on Nuclepore filters with scattered
light removed by an integrating plate of opal glass (Weiss, 1978); (3) deter-
mining absorption on Millipore filters (Rosen -dfra fevakov-. 1979-); (4) deter-
mining the reflectivity of a white powder with aerosol mixed Into it, called the
Kubelka-Monk method (Lindberg and Lande, 1974); (5) determining absorption of
light by a sample of particles inside a white sphere (integration sphere)
(Fischer, 1975); (6) estimating an imaginary refractive index from regular
scattering or polarization and size distribution (Eiden, 1971); (7) measuring
the amount of graphitic carbon and its size distribution and then calculating
V
To date, none of these methods has been characterized well enough to permit
making a clear-cut choice.
9.2.3 Role of Particulate Matter in Visibility Impairment
As noted in section 9.2.2, the extinction coefficient comprises contri-
butions from gas and aerosol scattering and absorption:
bext = bRg + bag + bscat + babs
This section discusses the relative magnitudes of these contributions.
9.2.3.1 Rayleigh Scattering—The particle-free molecular atmosphere at sea
level has an extinction coefficient of about 12 x 10" m" for green light
(wavelength 0.55 ym), limiting visual range to about 320 km. The coefficient
bn decreases with altitude. In some areas of the Western United States, the
Rg
extinction of the atmosphere is at times essentially that of the particle-free
atmosphere (Charlson et al., 1978). Rayleigh scattering thus amounts to a
simply definable and measurable background level of extinction with which other
extinction components (such as those caused by manmade pollutants) can be
9-17
-------
compared. Rayleigh scattering decreases with the fourth power of wavelength,
and contributes a strongly wavelength-dependent component to extinction. When
Rayleigh scattering dominates, dark objects viewed at distances over several
kilometers appear behind a blue haze of scattered light, and bright objects on
the horizon (such as snow, clouds, or the sun) appear reddened at distances
greater than about 30 km.
9.2.3.2 Nitrogen Dioxide Absorption—Of all gaseous air pollutants, only
nitrogen dioxide has a significant absorption band in the visible part of the
spectrum. Nitrogen dioxide absorbs strongly in the blue and can color plumes
red, brown, or yellow. The effects of nitrogen dioxide on visibility are dis-
cussed in the criteria document for oxides of nitrogen. Its contribution to
total extinction is in general minor.
9.2.3.3 Particle Scattering—As the particle concentration increases from very
low levels, where Rayleigh scattering dominates, the particle scattering coeffi-
cient, bscat» increases until eventually bscat is greater than bR . At 40-km
visibility, for example, Rayleigh scattering contributes about one-eighth of the
total extinction. At this point, the visual quality of air is controlled by
particle scattering. Two principal problems in understanding the degradation of
the visual quality of air have been: (1) defining the size range and other
physical characteristics of particles most effective in causing scatter; and
(2) defining the chemical composition and thus identifying the source of particle
in this size range (Charlson et al., 1978).
Size, refractive index, and shape are the most important parameters in
relating particle concentration and particle-related extinction coefficients,
bscat and babs' If these Pr°Pert1'es are established, the light scattering and
absorption can be calculated. Alternatively, the extinction coefficient asso-
ciated with an aerosol can be measured directly.
9-18
-------
From the point of view of aerosol optics, a key question is whether an
aerosol particle is spherical. For such particles, rigorous Mie theory (Mie,
1908) is applicable, and the optical properties can be readily calculated from
their size and refractive index. Measurements in St. Louis by Allen et al.
(1978) show that in the fine mode less than 5 percent of the aerosol popula-
tion is nonspherical. Pueschel and Wollman (1978) found that spherical particles
also dominate fine-mode aerosols near Cedar Mountain.
Coarse particles are almost exclusively nonspherical; using the Mie theory
to calculate their optical properties will therefore give only a crude approxima-
tion. There is, however, an extensive body of experimental data on the optical
properties of the nonspherical particles (e.g., Pinnick et al., 1976).
Charlson et al. (1978) used Mie theory to calculate the light-scattering
and absorption efficiency per unit volume of particles for a typical aerosol con-
taining some light-absorbing soot (Figure 9-6). As illustrated in the figure,
particles of 0.1 to 1 ym are the most efficient light scatterers. The remark-
ably high scattering efficiencies of these particles are illustrated by the
following examples: a given mass of aerosol of 0.5-pm diameter scatters about a
billion times more light than the same mass of air; a 1-mm-thick sheet of trans-
parent material, if dispersed as 0.5-pm particles, would be sufficient to scatter
99 percent of the incident light, that is, to completely obscure vision across
such an aerosol cloud.
Atmospheric particles or aerosols are made up of a number of chemical com-
pounds. All of these compounds exhibit a peak scattering efficiency in the
same diameter range (0.1 to 1.0 urn) calculated to be optically important for the
typical aerosol in Figure 9-6. However, because of differences in refractive
index, the values of the peak efficiency and the particle size at which it
occurs vary considerably among the compounds (Figure 9-7; Faxvog, 1975).
9-19
-------
E
a.
1. 5
"o
I ' "M
SCATTERING
10
2
10
-1
4.00
DIAMETER,
Figure 9-6. For t light scattering and absorbing particle, the scatter-
ing per volume has a strong peak at particle diameter of 0.5 pm (m =
1.5 - 0.05i; wavelength = 0.55 jjm). However, the absorption per
aerosol volume is only weakly dependent on particle size. Thus the
light extinction by particles with diameter less than 0.1 pm is primar-
ily due to absorption. Scattering for such particles is very low. A
black plume of soot from an oil burner is a practical example.
9-20
-------
100
•
A
s;
I 2
0.01
1.0
10.0
0.01
1.0
10.0
DIAMETER. Jim
Ftgur* 97 (A) Calculated turorinf cro«-*tction p*r unit m*u it *
w«v*l*ngTh of 55 urn for absorbing and nonabiorbmg mattnali n
ihown n * function of «rt u**d arbon (m •
V96-0.66i. d • 2.0). iron (m • 3.51 3.9V d • 7.86). ulica (m - 1.55.
d- 2.66). and w*ttr (m • 1 33. d - 1.0).
-------
Measured particle size distributions can be used in conjunction with Mie
theory calculations for single particles to determine the contribution of dif-
ferent size classes to extinction. The results of this kind of calculation are
shown in Figure 9-8. The peak in single-particle scattering per unit volume
is at 0.3 urn, so that the fine particles dominate extinction in almost all
cases.
Because the peak and shape of the bimodal particle mass distribution curve
can vary, the light-scattering characteristics of a given particle mass might
also be expected to vary. However, as noted by Charlson et al. (1978), for the
observed range of atmospheric particle distributions, the calculated scattering
coefficient per unit mass is relatively uniform. Latimer et al. (1979) have
determined the scattering efficiency per unit volume for several aerosol dis-
tributions. The calculated coefficient changes by no more than 40 percent in
the size range of 0.2 to 1.0 urn (Figure 9-9; Latimer et al., 1979).
The relative consistency of calculated light scattering per unit mass over
a range of particle distributions and the dominant influence of fine particles
suggest that reasonably good approximations of light-scattering coefficients can
be obtained by measurements of fine-particle mass. Indeed, agreement from
simultaneous monitoring of the two parameters at a number of sites has been
found by several investigators. Measurements by Weiss (1978), Patterson and
Wagman (1977), Macias et al. (1975), and Samuels et al. (1973) at various sites
showed scattering per unit mass ratios of 3-5 x 10 m~ /(yg/m ). Correlations
between the fine-particle mass and b . are consistently high (Table 9-1).
frjfc{(M!C^ (
-------
u a.
3 J
o <
> GC
HJ LU
» i
K 3
VOLUME
s
C r
*
0.01
0.1 1.0
PARTICLE DIAMETER,
10
Figure 9-8. For a typical aerosol volume (mass) distribution, the cal
culated light-scattering coefficient is contributed almost entirely by
the size range 0.1-1.0/jm. The total bscat and total aerosol volume
are proportional to the area under the respective curves.
9-23
-------
10
I
a.
V0
0.1
0.1
i i , , I ml
1.0
MASS MEDIAN DIAMETER
10.0
Figure 9-9. Scattering-to-volume ratios are given for various size
distributions.
9-24
-------
TABLE 9-1. LIGHT SCATTERING PER UNIT MASS OF FINE AEROSOL
bscat/mass,
Location 10 m" /(yg/m ) r N Reference3
Mesa Verde, CO
Seattle, WA (residential)
Seattle, WA (industrial)
Puget Island, WA
Portland, OR
New York, NY
St. Louis, MO
Los Angeles, CA
Oakland, CA
Sacramento, CA
2.9
3.1
3.2
3.0
3.2
5.0
5.0
3.7
3.2
4.4
0.95
0.97
0.97
0.95
--
0.96
0.83
0.79
0.98
5
58
64
26
108
--
72
39
20
6
1
1
1
1
1
2
3
4
4
4
a
1, Waggoner and Weiss (W-9); 2, derived by Charlson et al. (1978) from
Patterson and Wagman (1977); 3, Macias et al. (1975); 4, Samuels et al. (1973),
9-25
-------
«
60
40
0.2
0.1
I
4/17 4/18 4/19 4/20
TIME, d«ys
4/21
4/22
Figure 910. Simultaneous monitoring of bscat and firte-particle mass
in St. Louis in April 1973 showed a high correlation coefficient of
0.96, indicating that bKat depends primarily on the fine-particle
concentration.
Source: Macias et al. (1975).
9-26
-------
This was documented in an experiment conducted by Patterson and
Wagman (1977), who monitored the ambient aerosol size distribution by a set of
four cascade impactors in the New York metropolitan area. The first impactor
was operated only when the light-scattering coefficient was between 0 and 0.15
km" . Impactor A was operated at 0.15-0.3; impactor B at 0.3-0.45; and impactor
C at 0.45. The measured mass distributions (Figure 9-11; Patterson and Wagman,
1977) show that at good background visibility levels, the mass concentration was
largely (70 percent) contributed by coarse particles. At the low visibility
level C, however, over 60 percent of the total mass was contributed by fine
particles. Thus, visibility in the New York metropolitan area was found to be
lowest when the concentration of fine particles reached a maximum.
It is conceivable that in the arid West the aerosol refractive index and
relative amounts of coarse and fine particles are so different that the scat-
tering mass ratios quoted above would not be applicable. However, preliminary
results from project VISTTA (Macias et al., 1978) suggest that bc/./fine mass
scat
ratios in the Southwest are 3 x 10 m /(pg/m ), as measured elsewhere.
In clean areas where fine-particle levels are low, coarse particles may
contribute to light scattering. Coarse dust particles are much less efficient
scatterers per unit mass (Figure 9-6; Charlson et al., 1978), however, so that
much higher mass concentrations are required to produce a given optical effect.
In windblown dust, for example, Patterson and Gillette (1977) reported values
of the ratio of light scattering to mass that were more than an order
of magnitude lower than those noted above for fine particles.
The wavelength dependence of light scattering ranges from the very strong
blue scattering of air molecules (Rayleigh particles < 0.05 ym) to wavelength-
independent or "white" scattering for coarse particles of >5 urn.
9-27
-------
2.0
1.5
1.0
0.5
Ililllill I Illllii i |il
_ BACKGROUND VISIBILITY
"tot"40 Mi/1"3
_
— ^^^ /
,^^^^1* $
4l r ^fc^ -—^ A^AlMH
^•"i i i i inn k i i i
A
n
^H
i
i
i
i
i
1 1 1
—
_
i
t
\ —
\
\
\ ~
\
»
N Ml
0.1 0.2 0.5 1
10 20
50 100
Z.b
2.0
1.5
1.0
0.5
Ililllill | 1 1 1 | | I 1 III
VISIBILITY LEVEL A
1 U . 7«i na/rn3
-
1
_ /
1
— nr
h
\
|
—
i ^^B**i. __
v _U-P'^ 1 ^*.
nn" i i i 1 1 11 I i T*rT--—
0.1 0.2
0.5
10 20
60 100
I 25
< 2.0
1.5
1.0
0.5
1 I 1 I I Nil
I I II I I I I II I
VISIBILITY LEVEL B
3
i i i M mi
I NUT
1.0 0.2 0.5
10 20
50 100
2.0
1.5
1.0
0.5
1 1 1 1 1 III! I 1 I I 1 1 1 1 1 III
_ VISIBILITY LEVEL C _
_
t
t
1
1
™" A
x» —
i
I
1
x''i i , ,
—
\
v _
•— A^^^ ^*t^^==~Y* ** ^ ^
1 1 II 1 1 1 1 1 1 1 1 1 1 i ~l"l*»
0.1 0.2 0.5
12 5 10 20
DIAMETER, pm
50 100
Figure 9-11. Aerosol mass distributions, normalized by the total
mass, for New YorV aerosol at different levels of light-scattering
coefficient show that at high background visibility, the fine-particle
mass mode is small compared with the coarse-particle mode. At the
low visibility level, e. 60 percent of the mass is due to fine particles.
Source: Patterson and Wagman (1977).
9-28
-------
In pristine areas, when Rayleigh scattering dominates (bD = 2 x 10 m~ ),
Kg
addition of about 4 pg/m of fine particles (b „ . = 13 x 10" m ) would cause
scat
substantial "whitening" of the natural blue Rayleigh haze and the horizon sky
(Charlson et al., 1978). At a fine-particle level of 30 pg/m3 (0.1 km"1), the
wavelength-dependent scatter would be controlled by the aerosol itself.
9.2.3.4 Particle Absorption—Particle absorption (b , ) appears to be on the
aos
order of 10 percent of particle scattering (br/>a.) in low-background areas such
SCa L
as Bryce Canyon (Weiss, 1978). Its contribution may rise to 50 percent of br_3,
SCa t
in urban areas such as Phoenix, although values of 10 to 25 percent would be
more typical (Weiss, 1978). The amount of absorption per unit mass depends on
^^~
chemical composition and particle size distribution (Waggoner,^ 1973; Bergstrom,
1973). The most important contributor to this absorption in cities appears to
be graphitic carbon in the form of soot (Hansen et al., 1978). The source of
this highly absorbing submicron soot appears to be the combustion of liquid
fuels, particularly in diesel engines; coal combustion may not be a major
contributor (Charlson et al., 1978).
9.2.3.5 Summary--The extinction of light in polluted air is generally dominated
by particle scattering. On a regional scale, almost all of the particle scat-
tering is contributed by fine particles. Extinction due to scattering
is roughly proportional to the fine-particle mass concentration, with
-fi — 1 "\
extinction/mass ratios in the range of 3-5 x 10" m" /(yg/m ).
9.2.4 Chemical Composition of the Light-Scattering Aerosol
The preceding section showed that identifying the sources of light-
scattering aerosols largely reduces to determining the sources of fine-particle
mass. In this regard, a critical observation is that sulfates (sulfate and
associated cations) often account for 40 to 60 percent of the mass in
the fine-particle mode.
9-29
-------
Separate chemical mass balances for fine and coarse particles in
Charleston, WV, were conducted by Lewis and Macias (1979) (Figure 9-12). Of the
fine-particle mass (33 ug/m ), about 30 percent was sulfate, 13 percent was
ammonium, 18 percent was carbonaceous material, and the rest consisted of trace
constituents and undetermined species (including water). Thus, sulfate accounted
for a substantial part of fine-particle mass, with over 80 percent of the total
aerosol sulfate residing within the fine-particle mode.
A more detailed size-chemical composition distribution was reported by
Patterson and Wagman (1977) for the New York metropolitan area aerosol (Figure
9-13). Sulfate and ammonium ions, alone among the species measured, were con-
centrated in the size range between 0.2 and 0.7 ym. Comparison with Figure 9-6
(Charlson et al., 1978) shows that the size range in which sulfate and ammonium
occur is also the window of peak light-scattering efficiency per unit mass.
Consistent with their distribution with respect to particle size, sulfates
appear to contribute disproportionately to the degradation of visibility.
Sulfates have been found to be strongly associated with reduced visibility and
increased light scattering in Europe and the United States (Rodhe et al., 1972;
Eggleton, 1969; Barnes and Lee, 1978; Husar et al., 1979; Waggoner et al.,
1976).
Sulfates correlate with reduced visibilities even when the remainder of the
aerosol is taken into account. White and Roberts (1977) used multivariate
analysis to estimate the relative contributions of sulfates, nitrates, organic
compounds, and the remainder of the particulate mass to the measured light-
scattering coefficient in the Los Angeles area. Sulfates appeared to contribute
about twice as much extinction per unit mass as the average for the aerosol.
Similar findings have been reported by Cass (1979), Trijonis and Yuan (1978a,b),
9-30
-------
10
U)
AL-O-. C»O. F«.O,
O 2 3 2 3
OTHER
FINE PARTICLES
MASS-33.4 jg/m3
COARSE PARTICLES
MASS-27.1
VALUES IN PERCENT
Figure 9-12. Chemical-mass balance was determined for fine and coarse particles collected in Charleston.
WV.
Source: Lewis and Macias (1979).
-------
uo
to
2.0
1.0
2.0
1.0
0.1
1.0 10
PARTICLE DIAMETER. D it*
100
Fijur» 9-13. Normditcd mm dittnbulion functiom of torn* tp*cwi
found in H»* York City Mroiol thow th«t lulfitt ind ammonium
w«r« found in tto mo it tfficwnt light Kan«fing tut nngt (0.2-0.7
J
-------
Grosjean et al. (1976), and Leaderer et al. (1978). As summarized in Table 9-2,
empirically derived extinction/mass ratios for sulfate compounds are typically
?+i _6 i 3
ft4-[10 m /(yg/m )] at 70 percent relative humidity. In the Los
Angeles basin, Cass (1979) has further shown that the periods of highest
light scattering per unit sulfate occur on days of high sulfate mass
concentration.
Researchers (Charlson et al., 1974, Figure 9-14) recognize that the
major atomspheric sulfate species are hygroscopic and their light-scattering-
to-dry-mass ratio is a function of relative humidity. The light scattering
of some sulfate species (e.g. H,,S04 and NH4HS04) increases smoothly with
increasing humidity; other species (e.g. (NH^SO^) exhibit sudden particle
size growth at or above certain relative humidities and a subsequent two-to-three
fold increase in light scattering. The light scattering to humidity response
of atmospheric sulfate aerosols in highly dependent on size distribution and
molecular composition, which are difficult or almost impossible to measure
with sufficient resolution and accuracy. Thus, visibility cannot always
be accurately predicted using measurements of sulfate loadings or fine
particle mass loadings.
To the extent that particulate nitrates are secondary aerosols formed in
the size range of 0.2 to 1.0 pm, it is to be expected that they, too, are effi-
cient light scatterers. Since ammonium nitrate is hygroscopic, the scattering/
mass ratio for particulate nitrate could be comparable to that for sulfates. As
Table 9-2 shows, there is some statistical support for this hypothesis. However,
even if nitrates scatter efficiently, their absolute contributions to extinction
may be small because concentrations of particulate nitrates in most locations
may be low. As discussed in chapter 5, these conjectures cannot be satisfac-
torily tested with the existing data on particulate nitrate.
9-33
-------
TABLE 9-2. EMPIRICAL EXTINCTION EFFICIENCIES OF SPECIFIC AEROSOL FRACTIONS
vo
t*»
Efficiency,
Los Angeles, Phoenix, Salt Lake City, Columbus, Charlotte, Lexington, Cleveland, Newark,
CAL
AZ1
OH1
NC1
KY1
NJ1
Sul fates
30% RH
50% RH
70% RH
Nitrates
30% RH
50% RH
70% RH
Other, all RH
Fraction of variance
accounted for (r )
3.3
6.2
2.7 4.5
3.5
4.7
2.2
0.93 0.76
3.1
4.3
7.1
7.2
10.1
16.9
0.3
0.66
5.8 5.8
8.2 8.2
13.6 13.6
2.8
3.9
6.5
0.81 0.53
3.0
4.3
7.1
1.7
0.52
3.3
4.6
7.7
0.52
3.3
4.6
7.7
1.2
0.50
Efficiencies represent statistical increment in total scattering or extinction coefficient (10" m ) per increment
in individual compound (including cation) concentration (ug/m ). Efficiencies not differentiated by RH are entered
^nearest the average RH for the data set.
White and Roberts (1977), from 2-hr average nephelometer and total filter data.
' Trijonis and Yuan (1978a,b), from 9-hr daytime airport visibilities and 24-hr high-volume-filter data.
Visibilities are converted to extinction coefficients here via Koschmieder formula (see section 9.2.1) with
contrast threshold of 0.031 (Figure 9-4).
-------
I I 1
so
RELATIVE HUMIDITY. RH%
100
Figure 9-14. In this humidogram for laboratory H2SO4 aerosol and
for the reaction product of this H2S04 and NH3, the ordinate is the
ratio of light-scattering coefficient due to paniculate matter at the
given relative humidity [bjp (RH)] to the light-scattering coefficient
at 30 percent.
Source: Charlson et at. (1974).
9-35
-------
9.2.5 Historical Patterns of Visibility
Records of visual range can be used to gain insight into the effects
of changing emission patterns on visibility. As one example Marians and
i
Trijonis (1978) have derived statistical relationships between light extinction
(computed from visibility data) and historical emission trends. Yearly values
of extinction from four Arizona airports were regressed against statewide
emissions of smelter SO , nonsmelter SO , NO , and RHC. Smelter SO was found
/\ y\ /\ A
to be the most significant variable. Particularly close relationships between
Arizona smelter SO and visibility at Tucson and Phoenix are shown in Figure
A
9-15.
Table 9-3 summarizes the results of the correlation/regression analysis
between yearly airport extinction (visibility) data and Arizona smelter SO
A
emissions. The correlation coefficients and Student's t-statistics indicate
significant statistical relationships at high confidence levels. The regression
(extinction/emission) coefficients of 0.04 +_ 0.005 (10 m) /(1000 tons per day
of SO ) are remarkably consistent from site to site and represent the change in
/\
yearly median extinction associated with a given change in SO emissions; that is,
A
adding 1000 tons per day of SO tended to increase yearly median extinction by
y\
approximately 0.04 (10 m) .
Perhaps the best example of changed emission patterns is a strike that shut
down the copper industry over a 9-month period in 1967-68. In the Southwest at
this time, copper production accounted for over 90 percent of the SO emissions,
less than 1 percent of the N0x emissions, and less than 10 percent of the con-
ventional particulate emissions (Marians and Trijonis, 1978), and should there-
fore have affected visibility primarily through its contribution to sulfate
loadings. Substantial decreases in sulfate occurred at five locations (Tucson,
Phoenix, Maricopa County, White Pine, and Salt Lake City) within 12 to 70
miles of copper smelters as shown in Figure 9-16. More notably, sulfates
9-36
-------
V)
80
gg 60
I VI
£ > 40
O K
H 3
55 20
o 5
TUCSON
50
I
6000 g
5000 K i
4000 g; i
5 S
3000 5 m
2000 "* O
55
60 65
YEAR
70
75
X 80
K ««
» u
M - 7°
ec ^
O § 60
I VI
OK 50
uj CD 40
O
- I
PHOENIX
I ~
I
I
S
6000 m 2
i o
5000 ^ |
O v>
4000 S m
3000 | »
5 ^
5 m
2000
18
50
55
60 65
YEAR
70
75
Figure 9-15. Historical trends in hours of reduced visibility at
Phoenix and Tucson are compared with trends in SOX emissions
from Arizona copper smelters. Data points represent yearly percent
of hours with reduced visibility. The Tucson observation site moved
in 1958; although this move did not produce a statistically significant
change in reported visibilities, open dots are used to distinguish data
prior to 1958. Lines represent yearly SOX emissions from Arizona
copper smelters.
Source: Marians and Trijonis (1979).
9-37
-------
TABLE 9-3. CORRELATION/REGRESSION ANALYSIS BETWEEN AIRPORT
EXTINCTION AND COPPER SMELTER SO EMISSIONS
Data set
VO
I
OJ
rr>
Tucson
Tucson
Phoenix
Wins low
Prescott
Prescott
(1950-75)
(1959-75)
(1959-75)
(1948-73)
(1948-75)
(1948-69)
Correlation
coefficient
0.91
0.88
0.81
0.68
0.70
0.70
Regression coefficient
extinction/emissions,
(1(T m)"V(1000 TPD)
0.035
0.038
0.041
0.047
0.031
0.039
t-statistic
(t = 1.7 for 95% confidence)
(t = 2.5 for 99% confidence)
11.1
7.2
5.4
4.5
5.0
4.4
-------
VD
I
CO
(£1
• -260 TONS/DAY SO.
SCALE, mitot
Figure 9-16. Seasonally adjusted changes in sulfate during the copper strike are compared with the
geographical distribution of smelter SOX emissions.
Source: Trijonis and Yuan (1978a).
-------
dropped by about 60 percent at Grand Canyon and Mesa Verde; these remote
sites are located 200 to 300 miles from the main smelter area in southeast
Arizona. Comparing measurement during the strike with those during the
surrounding 4 or 6 years, Trijonis and Yuan (1978a) found a large decrease
in Phoenix sulfate loadings, accompanied by a substantial improvement in
visibility (Figure 9-17).
Visibility improved at almost all locations during the strike, with
the largest improvements occurring near and downwind (north) of the
copper smelters in southeast Arizona and near the copper smelters in
Nevada and Utah. The nine locations showing statistically significant
improvements are all within 150 miles of a copper smelter. Attributing
the improvement in visibility entirely to the drop in sulfate levels
—fi -1 "3
yields an estimated extinction efficiency of 3.9 x 10" m~ /(mg/m ).
Altshuller (1973) has noted an increase over the past decade in
sulfate concentration at nonurban sites in the Eastern United States,
which is not inconsistent with the decreasing trend in nonurban site
median visibilities noted by Trijonis and Yuan (1978b). Unfortunately,
the historical record of sulfate concentrations extends back only to the
mid-1960's. Within the Eastern United States, over 90 percent of the
SO emissions are associated with the combustion of coal and oil. One
A
apparent conclusion is that visibility reduction is currently due in
large part to sulfate aerosol, which is formed primarily from coal
combustion-related SO,, emissions, than examination of the trends and
changing spatial distributions of coal use should be similar the light
extinction coefficient.
Air pollutants emitted over the Eastern United States result mainly
from the combustion of fossil fuels—coal, oil products, and gas. The
great spatial and seasonal variability of haziness (inverse of visibility)
prompted Husar et al. (1979) to examine the patterns of coal consumption
in the Eastern United States over the past few decades.
9-40
-------
o
260 TONS/DAY SO
URBAN AIRPORTS
NOMURBAN AIRPORTS
0
I
100
I
SCALE, mitot
200
Figure 9-17. Seasonally adjusted percent changes in visibility during the copper strike are compared
with the geographical distribution of smelter SOX emissions.
Source: Trijonis and Yuan (1978a).
-------
Figure 9-18 (U.S. Bureau of Mines, 1933-74) illustrates the striking
similarity between summertime average haziness and coal use within the Eastern
United States over the past three decades.
Further support for the relationship between coal consumption and haziness
is given in Figure 9-19.
For comparison with coal consumption estimates, visibility data are expressed
in terms of a light extinction coefficient, b ., via the Koschmieder formula:
b
ext
As shown in Figure 9-19, in 1951 the haziness was most pronounced in the
wintertime, when the coal consumption was the highest. By 1974, there was a
shift toward a summer peak, coincident with the increasing summer use of coal.
Such coincident behavior alone cannot establish cause-effect relationships. It
is nevertheless instructive to examine the more detailed spatial and temporal
patterns of coal use and haziness.
Since 1940, the trend in coal consumption has been more pronounced in the
summer than in the winter (Figure 9-16; U.S. Bureau of Mines, 1933-74); since
1960 summer coal use has grown by about 5.8 percent per year compared with 2.8
percent per year for winter coal demand. The monthly coal combustion peaked in
the winter in the early 1950' s, but the seasonal pattern had shifted to a summer
peak by 1974 (Figure 9-20).
More instructive is examination of the State-by-State spatial trend of
yearly coal consumption (Figure 9-21; U.S. Bureau of Mines, 1933-74). The
corresponding regional trends of haziness in the Eastern United States (Figure
9-22; Husar et al., 1979) exhibit changes similar to those of coal combustion.
In the Ohio River Valley region, the winter (quarter 1) average extinction
decreased slightly, whereas the spring (quarter 2) average increased. The
sumsner (quart?*- 3) haziness increased from roughly 2.5 in the 1950's (a visibility
of 10 mile:) to about 4 in the 1970's (a visibility of less than 6 miles). Fall
(quarter 4) haziness remained essentially unchanged. The summer average
9-42
-------
1M
c
•s
100
8 "
TlIIIIIIIIII
I I I I I I i
1
4.0
3.0
2.5 I
10
1.5
1.0
0.5
1MO 1MO 1MO 1970 1MO IflW 2000
YEAR
Figure 9-18. Compared here in summer trends of U.S. coal con-
sumption and Earam United States average extinction coefficient.
Source: Adapted from Hutu et al. (1979).
I I I I I I
ILICTHIC UTILITIi
ILICTKIC UTILITIES
11 ill II I 111 I till
JFMAMJJASONO JFMAMJ JASONO
X
o
Figure 9-19. In the 1950't trie Miionel coel contumption peeked in
ttie winter primarily beceuie of incruwd reudential and railroad uu.
By 1974. the leeional pattern of coal usage wn determined by the
winter end lonvner peak of utility coel 111398. The shift awey from a
winter peak toward a summer peak in coal consumption is consistent
with a shift in extinction coefficient from a winter peak to a summer
peek in Dayton, OH, for 1948 52.
Source: U.S. Bureau of Minei Yearbooks 1933-74.
9-43
-------
175
vo
i
O
z
O
1C
O
«/>
z
O
175
150 -
125 -
100
1940
I960
Ml| II III I II I |ll I I |l II l|l ' II I M I I
1940
1980
Figure 9-20. In 1974, the U.S. winter coal consumption was well below, while the summer consumption
was above, the 1943 peak. Since 1960 the average growth rate of summer consumption was 5.8 percent
per year, while the winter consumption increased at only 2.8 percent per year.
Source: U.S. Bureau of Mines. Minerals Yearbooks 1933-1974.
-------
VD
MONTANA
IDAHO
WYOMING
NEVADA
UTAH
COLORADO
ARIZONA
NEW ME XI
CALIFORNIA
OREGON
'WASHINGTON
\
m M -
ARKANSAS
OKLAHOMA
"LOUISIANA
TEXAS I
FLORIDA
GEORGIA
\
N. CAROLINA
S. CAROLINA
TENNESSEE
ALABAMA
MISSISSIPPI^
KENTUCKY
W. VIRGINIA
YCAM
TEAK
YCAM
TIM
Figure 9-21. Trends in coal consumption in the continental United States are shown by region.
Source: U.S. Bureau of Mines. Minerals Yearbooks 1933-1974.
-------
OHIO MIVER
MEW ENGLAND
1940 SO ~«0 70 90 90 1*40 50 90 70 90 90
NE. MEGALOPOLIS
1*40 50 *0 70 SO »0 1940 50 «0 70 »0 90
EASTERN SUNBELT
1640 50 *0 70 M 90 1940 SO 90 70 90 90
YEAR
1940 BO 90 70 M 90 1940 SO 90 70 90 90
IKY MOUNTAINS
J L
1940 BO 90 70 90 90 1940 BO 90 70 90 90
MIDWEST
o.u
oL. ...
1940 50 90 70 90 90 1940 M 90 70 90 90
YEAR
Figure 9 22. Trends in the light extinction coefficient (bext) in the Eastern United States are shown by
region.
Source: Husar et al. (1979).
9-46
-------
increased was from about 2 to 3, corresponding to a reduction in visibility
from 12 to 8 miles. The Northeast megalopolis region shows a general decline in
haziness during quarters 1 and 4, whereas quarters 2 and 3 display a slight
increase from b = 2.7 (9 miles) to 3 (8 miles). The Smoky Mountain region
displays a strong increase in the average summer quarter extinction coefficient
from about 1.6 to 4, corresponding to visibility deterioration from 15 to 6
miles. Smaller but still pronounced increases are noted for quarters 2 and 4.
Evidently the Smoky Mountains have become appreciably "smokier" over the past 20
summers. The Eastern Sunbelt region has an increased haziness for all quarters,
most pronounced being the summer quarter, with an increased from 2 (12 miles) to
3.5 (7 miles). Midwest quarter-1 extinction fluctuated slightly with no discernible
trend. The spring and fall quarters have increased appreciably, but summer
values have nearly doubled, from 1.5 to 3 (16 to 8 miles).
The spatial shifts of Eastern United States haziness are displayed in
greater detail in Figure 9-23 (Husar et al., 1979).
9.2.5.1 Summary—The impact of sulfates in reducing visual air quality in
individual plumes and on the regional scale of 1000 km is no longer a matter of
dispute. Considerable evidence from chemical mass balance methods indicates
that sulfates, which make up approximately 50 percent of the fine-aerosol mass,
contribute considerably more to visibility degradation than do other chemical
species. Finally, the 30-year record of the spatial and temporal trends of coal
combustion and visibility suggest that the increasing emissions of SO since
^
the 1950's have in fact been associated with similar increased in haziness.
9.3 SOLAR RADIATION
Incoming solar radiation is composed of the direct beam and the diffuse
skylight arising from the light-scattering atmosphere (Figure 9-24; Gates,
1966). The relative contribution of the skylight is least at noon and
greatest at sunrise and sunset. At sea level, and for a clean atmosphere,
skylight contributes at least 10 percent of the total radiation.
9-47
-------
1*46-52
1M044
197074
ec
O
c
O
r>
c
4
O
E
01
c
4
O
EXTINCTION
COEFFICIENT, km'1
VISIBILITY, milei
>0.36
<6.6
O.JO.36
6.68
0.24-0.30
810
0.18-0.24
10-13.3
<0.18
>13.3
Figure 9-23. The spatial distribution of 5-year average extinction coefficients shows the substantial
increases of third-quarter extinction coefficients in the Carolines. Ohio River Valley, and Tennessee-
Kentucky area. In the summers of 1948 52, a 1000 km size multistate region centered around Atlanta,
GA, had visibility greater than 15 miles; visibility has declined to less than 8 miles by the 1970's. The
spatial trend of winter (first quarter) visibility shows improvements in the Northeast megalopolis
region and some worsening in the Sunbelt region. Both spring and fall quarters exhibit moderate but
detectable increases over the entire eastern United States. '
-------
I I I
" M^MB^^^^^^HM^H^BBMMjM^»^^B^^^^M^MJ^^^MUK.Z^^^^^^Mj|^MiMlflM(^^^X^^3Hta^3
0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8
WAVELENGTH, pm
Figure 9-24. Solar radiation intensity spectrum tt tea level in
cloudless sky peaks in the visible window. 0.4-0.7 jim wavelength
range, shows that in clean remote locations, direct solar radiation
contributes 90 percent and the skylight 10 percent of the incident
radiation on a horizontal surface. The airmass, m, is a measure of the
•mount of air the direct solar beam has to pass through.
Source: Gates (1966).
9-49
-------
Aerosol layers in the atmosphere scatter and absorb solar radiation (Figure
9-25). Some of the scattered radiation is directed upwards and lost to space;
some is directed downwards to the earth's surface. Most of the solar radiation
eventually reaches the surface, but its spectral and directional composition,
that is, the "quality" of the solar radiation, may be changed by atmospheric
haze. A small fraction of the scattered radiation may also be lost back to
space, in which case the amount of energy reaching the surface is reduced,
contributing to the cooling at the earth's surface. A fraction of the
radiation may also be absorbed by aerosols, further reducing the amount of
radiation reaching the surface but at the same time heating the aerosol layer
itself.
It should be noted that because aerosols are not uniformly distributed in
the atmosphere, their effects are spatially nonhomogeneous. First, the hori-
zontal spatial scale encompassing aerosol source, transport, and removal in the
lower troposphere is variable but often about 1000 km. The vertical spatial
scale of noninfluenced aerosols is also quite variable, but often the particles
are concentrated in a layer from 500 to 2000 m deep. Hence, the aerosol effects
should be concentrated in the lowest layers of the atmosphere, especially in
industrial regions.
Global-scale effects might also occur. If the effects in industrial
regions are strong enough, then the heat balance of the entire earth could be
influenced. On the other hand, effects from long-lived aerosol, for example, in
the stratosphere, might lead to direct physical effects on a global scale.
9.3.1 Spectral and Directional Quality of Solar Radiation
The spectral quality of solar radiation on a clear day and on a hazy day in
Texas is shown in Figure 9-26 (McCree and Keener, 1974). On the hazy day, the
direct solar radiation is reduced to about one-half of that on a clear day, but
9-50
-------
Figure 9-25. Extinction of direct solar radiation by aerosols is
depicted.
9-51
-------
u
c
oc
0.5
1.0
0.5
0.3
1 I
SUN + SKY
0.4 0.5
WAVELENGTH,
0.6
0.7
Figure 9-26. On • cloudless but hazy day in Texas, the direct solar
radiation intensity was measured to be half that on a clear day, but
most of the lost direct radiation has reappeared as skylight. However,
there is about 20 percent of the solar radiation missing on the hazy
day, some absorbed, and some backscattered to space.
Sourc*: McCree and Keener (1974).
9-52
-------
most of the energy has reappeared as diffuse skylight. However, there is also
an overall loss of up to about 10 to 20 percent of the radiation reaching the
surface.
If we take the typical backscattered fraction for haze aerosols to be 10
percent and the absorption to be also about 10 percent, as suggested by the
data of Weiss (1978), then we can estimate the amount of energy lost from the
surface, the amount lost to space, and the amount absorbed by the atmosphere.
On a day with half of the direct beam transmitted, we conclude that 10 percent
of the other half, or 5 percent, is lost to space, and the other 5 percent
results in atmospheric heating. Together, these phenomena lead to a loss of 10
percent of the radiation. Although it is not possible to calculate accurately
the influence this loss might have on surface temperature, rate of thawing of
frozen ground, growing season, or other climatological measures, it is highly
probable that this loss cools the ground and heats the hazy lower layers of the
atmosphere. In turn, if this occurs, it must increase atmospheric stability,
decrease convective mixing, and therefore increase the rate at which pollutants
accumulate.
No detailed and routine measurements of the quality of solar radiation are
available for the United States. However, the total solar energy reaching the
surface is monitored routinely at many meteorological observation sites in the
United States and worldwide. Unfortunately, the large variability of such data
does not allow manmade aerosol effects to be distinguished from other natural
causes.
A data base that gives some information on the quality of solar radiation
is the U.S. turbidity network operated at about 40 stations in the country since
1961 (Flowers et al., 1969). If there are no clouds between the observer and
the sun, the intensity of direct solar radiation for a given solar elevation
9-53
-------
depends on the variable amount of dust, haze, and water vapor in the atmosphere.
The extinction produced by these constituents is called "atmospheric turbidity."
The seasonal pattern of atmospheric turbidity in the United States at 29 sites
for 1961-66 is shown in Figure 9-27 (Flowers et al., 1969). At all sites, the
highest turbidity occurs in the summertime and the lowest occurs in the winter,
which is consistent with the haziness pattern obtained from visibility observa-
tions (section 9.2.3). However, the turbidity of the atmosphere in the United
States has a strong spatial dependence. In the Southwestern States with an
annual turbidity coefficient of about 0.06, the incoming direct solar radiation
is attenuated by only 13 percent (mostly scattered) compared with Midwestern
State values of about 20 percent. The highest turbidity coefficients were
observed in the Eastern United States, where summer values of 0.2 and winter
values of 0.1 were typical. This means that in the summertime about 35 percent
of the direct solar beam is diverted to skylight, backscattered to space, or
absorbed. This means that about 3.5 to 7 percent is backscattered to space and
another 3.5 to 7 percent is absorbed into the atmosphere.
Since the first report of Flowers et al. (1969), the turbidity data have
been reported yearly by the World Meteorological Organization (WMO, 1977).
Comparison of the seasonal turbidity pattern for 1961-66 and 1972-75 is shown in
Figure 9-28. Since the mid-1960's there has been a further increase in Eastern
U.S. turbidity, particularly in the summer season. Currently the summer average
turbidity in the region including Memphis, TN, Oak Ridge, TN, Greensboro, NC,
and Baltimore, MD, is about 0.3. This corresponds to a 50 percent attenuation
of the direct solar beam on an average summer day. During hazy episodes, tur-
bidity coefficients of 0.6 to 1.0 are often reported, resulting in a condition
in which 75 to 90 percent of the solar radiation is removed from the direct
beam, 7.5 to 18 percent is lost to space, and 7.5 to 18 percent is lost as
9-54
-------
I
Ul
in
Figure 9-27. To interpret these monthly average turbidity data in terms of aerosol effects on transmis-
sion of direct sunlight, usa the expression I/IQ = 10"^, where B is turbidity and I/IQ is the fraction
transmitted.
Source: Flowersetal. (1969).
-------
I
.£
I
S
o
•g
•
IX)
(O
I
+«
i
.*:
•2
^
CD 0>
IS
co
^
9-56
-------
atmospheric heating. One of the consequences of such hazy atmosphere is the
disappearance of shadow contrasts. It is strongly suspected but has not yet
been proved that there are effects on agricultural productivity.
The spatial distribution and trends of regional-scale turbidity in the
Eastern United States are consistent with the observed pattern of haziness
obtained through visibility observations. Both the turbidity and visibility
reduction by haze in the Eastern United States can be attributed to manmade fine
particles, consisting mainly of sulfate and nitrate (section 9.2.4). Bolin and
Charlson (1976) suggest that many of these radiative effects are due to sulfates
and conclude that the magnitude of effects is comparable to that summarized
here.
9.3.2 Total Solar Radiation: Local to Regional Scale
Changes in the total radiant energy have been observed within urban areas.
Early measurements in central city locations, primarily in Europe, showed levels
typically 10 to 20 percent below surrounding rural areas. Robinson (1962)
discussed some observations made in London and in Vienna. In London the deficit
was considerably reduced after the implementation of a clean air act. Measure-
ments on 47 days in autumn 1973 in the Los Angeles area are summarized in Table
9-4 (Peterson and Flowers, 1977). In the St. Louis area, however, smaller
urban-rural differences were observed. On 12 cloudless days in summer 1972, the
average solar and UV fluxes at an urban site were only 3 and 8 percent, respec-
tively, below those at a rural site about 50 km from the city. The difference
between the St. Louis and Los Angeles and European urban areas appears to involve
both decreased urban and increased rural attenuation, and it may be that neither
the city of St. Louis nor its surroundings over a wide area modify solar radia-
tion in a manner typical of other locations.
9-57
-------
TABLE 9-4. SOME SOLAR RADIATION MEASUREMENTS IN
THE LOS ANGELES AREA3
Measurement Total UV
Minimum
Average
Maximum
4
11
20
15
29
44
Values for the daily average percentage
decrease of total and UV solar radiation
between El Monte (urban) and Mt. Dis-
appointment (rural).
Source: Peterson and Flowers (1977).
9-58
-------
Recently, Angell and Korshover (1975) analyzed the solar radiation
duration data (hours of sunshine) for the eastern half of the United
States. Data for the 1950-70 time period were obtained with on/off
detectors, and these data are believed to be more reliable for long-term
trend analysis than data from recorders of solar radiation intensity.
Angell and Korshover noted some marked trends: in the Southeast and
South Central United States, the solar radiation duration has decreased
by about 4 to 6 percent; however, the North Central is increasing (Figure
9-29; Angell and Korshover, 1975). Although the authors do not attribute
these trends to any specific cause, it should be noted that there has
been an increase in haziness within that time period in areas with decreased
solar radiation. It is conceivable, therefore, that increased haziness
causes sunshine-duration detectors to delay the turn-on time in the
morning and advance the turn-off time. It should also be stressed,
however, that changes in the solar radiation duration may be caused by
other natural or manmade phenomena.
9.3.3 Radiative Climate: Global Scale
The attenuation of solar radiation from scattering and absorption by
particles in the atmosphere is probably an important factor in climatic change
9-59
-------
20
18
16
14
Z
w 12
I «
ff
Z 8
o
5 6
3 4
111111111111111111 ii111111111111 j 1111111111111111* 11111111
1940 50 60 70 80 90 2000
YEAR
Figure 9-29. Analysis of the hours of solar radiation since the 1950'$
shows a decrease of summer solar radiation over the Eastern United
States. There may be several causes for this trend, including an
increase of cloudiness; some of the change may also be due to hue.
Source: Angell and Konjhover (1975).
9-60
-------
on all scales. On local scales associated with urban and industrial areas, any
significant attenuation of radiation by air pollution can, in addition to other
well-recognized factors, result in changes in local weather (e.g., Landsberg,
1970). It is possible that local- and regional-scale changes in solar radiation
caused by human activity may ultimately influence the heat and water vapor
contents of the atmosphere on very large scales, but solar radiation and aerosol
levels measured at stations remote from pollutant sources have not as yet dis-
played any trend that can be related to human causes (Fischer, 1967; Ellis and
Pueschel, 1971; Hodge et al., 1972).
Unfortunately, there is little agreement about whether the net effect of
increased airborne particulate concentrations is the warming or cooling of the
earth. Most models can predict either an increase or a decrease in the effective
albedo of the earth under cloudless skies, depending on which combination of
surface albedo, sun angle, particle size distribution, and particle refractive
index is assumed. The effects of clouds are very important, and the contribu-
tions from infrared radiation must be considered in order to obtain a complete
energy budget (Wesely and Lipschutz, 1976).
9.4 CLOUDINESS AND PRECIPITATION
The global cloud cover plays a vital role in the earth's radiative budget
in reflecting energy back to space, in absorbing both solar and longwave (ter-
restrial) radiation, and in emitting its energy downward and outward into space.
Changes in cloud cover, therefore, alter the global heat balance. Cloud- and
precipitation-forming processes may be divided into two broad classes:
(1) macrophysical processes, which affect the rise and descent of air currents
and the amount of water vapor available for condensation; and (2) microphysical
processes, which affect the nature of cloud particles formed during condensation.
9-61
-------
The role of atmospheric aerosols, primarily those that are strongly hygroscopic,
is to influence the microphysics of cloud formation.
On a global or even regional scale, the very small amounts of moisture that
man adds by land practices or combustion of fossil fuels are negligible in
comparison with global evaporation. On a regional scale, only one form of
increasing cloudiness suggests itself: the formation of aircraft contrails
(Machta and Telegadas, 1974). Aircraft contrail formation results mainly from
the injection of water vapor rather than of aerosols.
In urban areas, inadvertent changes of cloudiness as well as the quantity
of precipitation have been well established. Such urban impacts also include
the frequencies of thunderstorms and hail as well as total amounts of rain. In
a classical study, Changnon (1968) has reported a notable increase in days of
precipitation, thunderstorms, and hail occurring since 1925 at La Porte, IN.
Since La Porte is 30 miles east of the Chicago urban-industrial complex, he
proposed that the increased precipitation results from inadvertent manmade
modifications. Figure 9-30 (Changnon, 1968) shows the 5-year running totals of
days with smoke and haze restricted visibility in Chicago. This measure
of atmospheric pollution has a temporal distribution after 1930 rather
similar to the La Porte precipitation curve. A noticeable increase in
smoke-haze days began in 1935 and became more marked after 1940, when
the La Porte precipitation curve began its sharp increase. The specific
role of haze particles in causing the La Porte anomaly has not been
established.
As part of project Metromex, studies by the Illinois State Water Survey
suggest increases of about 30 percent in rain and 200 percent in thunderstorms
and hail at single gauging stations downwind of St. Louis, with increases of
about 10 percent over a two-county area. Here again, the physical causes of the
maxima are not well understood, but they do appear to be associated with
9-62
-------
HICAOO
SMOKE-
HAZE DAYS
OBSERVER i
CHANGES AT .'
LA PORTE '
1910 1920 1930 1940 1950 1960
ENDING YEAR OF 5 YEAR PERIOD
Figure 9 30. Numbers of smoke haze days are plotted per 5 years at
Chicago, with values plotted at end of 5-year period.
Source: Changrx>n (1968).
9-63
-------
perturbations of the planetary boundary layer and enhanced cloudiness, possibly
resulting from the addition of aerosols. It is regrettable that the complex
interactions of cloud- and precipitation-forming processes obscure the specific
role of manmade aerosols.
The incorporation of particles into rain and fog droplets can change the
"quality" of precipitation by changing its chemical composition. The most
important impact on precipitation water quality is probably that of "acid
rain," discussed in more detail in chapter 8.
9-64
-------
9.5 SUMMARY
The term visibility refers to various characteristics of the optical
environment such as clarity and trueness of color. Meteorologically,
visibility refers to the greatest distance at which a black object can
be distinguished against the horizon sky. The effects of the atmosphere
on visibility can be determined from the concentrations and characteristics
of atmospheric constituents, which scatter and absorb light. The scattering
and absorption are used to determine the extinction coefficient. The
combination of extinction and added air light (haze) washes out both
bright and dark objects, decreasing the contrast of an object to the
horizon.
The extinction of light in polluted air is generally dominated by
particle scattering. On a regional scale, almost all of the particle
scattering is contributed by fine particles in the accumulation mode.
Extinction due to scattering is roughly proportional to the fine-particle
mass concentration, with extinction/mass ratios in the range of 3-5 x
10"6 m'Vdjg/m3).
Sulfates (sulfate and associated cations) occur primarily in the
fine-particle accumulation mode. They appear to contribute disproportion-
ately to the degradation of visibility, with an empirical extinction/mass
*71~ I
ratio of !=&. [10 m /(yg/m )7at 70 percent relative humidity^:
The impact of sulfates in reducing visual air quality in individual
plumes and on the regional scale of 1000 km has been studied extensively.
Considerable evidence indicates that sulfates, which make up approximately
9-65
-------
50 percent of the fine-aerosol mass, contribute considerably more to
visibility degradation than do other chemical species. Finally, the
30-year record of the spatial and temporal trends of coal combustion
and visibility suggest that the increasing emissions of SO since the
n
1950s have in fact been associated with similar increases in haziness.
Several methods are used to measure extinction and its components.
In the observer method, a black object is viewed against the horizon.
These observations are reported commonly at weather stations. A composite
value of these observations is called "prevailing visibility", which in-
cludes the greatest distance around at least 180 degrees of the horizon,
no.t just for a single direction. This measurement procedure has certain
limitations. Few sites are suitable for observations greater than 50
km. Additionally, the visual range of reflecting objects, such as snow-
covered mountaintops, is influenced by the angle of the sun and sky
conditions, overcast or clear.
In contrast telephotometry, the brightness of a black object is
measured and expressed as a ratio to the same brightness of the nearby
horizon. This method may be useful for characterizing plumes in terms
of their brightness of contrast relative to sky or terrain background.
At some sites, however, telephotometers cannot be used often because clouds
on the horizon or above the path to the nearby black object cause errors.
Also the method requires an operator.
Long-path extinction, the most direct way to measure extinction, in-
volves measuring the decrease in intensity of a beam of light as a function
of range. Unfortunately, several problems exist in calibrating a long-path
transmissometer. A modification of this method has eliminated the need
for absolute calibration.
9-66
-------
The nephelometric method measures the scattering component of extinction.
Many nephelometers are capable of measuring aerosol particle scattering ex-
tinction at or below 10 percent of Rayleigh scatter. This sensitivity is
adequate for class I regions. The nephelometer can be used to measure the
scattering coefficient at the same point where samples are taken for mass or
chemical determination. Most of the data relating cause and effect (i.e.,
particle concentration or composition and optical effect) have been acquired
with the integrating nephelometer. The instrument measures optical properties
at a point, which may limit its application to cases where there is spatial
uniformity of atmospheric optical properties. There may be errors introduced
by differences in humidity inside the instrument relative to ambient con-
ditions. The instrument will have two types of error if atmospheric optical
properties are controlled by particles larger than 3 ym, such as in fog or
dust storms.
No single method has been proven totally effective in measuring light
absorption. The methods used thus far include determining the difference
between extinction and scattering by combining long-path transmissometer
with nephelometer, several filtering methods, and a refractive index method.
Pollutants released to the atmosphere alter the environment in ways
other than visibility reduction. They may lead to slow and subtle changes
in atmospheric composition and, possibly, climate. For example, a fraction
of the solar radiation may be absorbed by aerosols, further reducing the
amount of radiation reaching the earth's surface and, at the same time,
heating the aerosol layer itself. On a hazy day, the direct solar radiation
is reduced to about one-half of that on a clear day. but most of the energy
has reappeared as diffuse skylight. However, there is also an overall loss
of up to about 10 to 20 percent of the radiation reaching the surface.
9-67
-------
If there are no clouds between the observer and the sun, the intensity
of direct solar radiation for a given solar elevation depends on the variable
amount of dust, haze, and water vapor in the atmosphere. The extinction
produced by these constituents is called "atmospheric turbidity." During
hazy episodes, turbidity coefficients of 0.6 to 1.0 are often reported,
resulting in a condition in which 75 to 90 percent of the solar radiation
is removed from the direct beam, 7.5 to 18 percent is lost to space, and
7.5 to 18 percent is lost as atmospheric heating. One of the consequences
of such a hazy atmosphere is the disappearance of shadow contrast. It is
strongly suspected but has not yet been proved that there are effects on
agricultural productivity.
The attenuation of solar radiation from scattering and absorption by
particles in the atmosphere is probably an important factor in climatic change
on all scales. On local scales associated with urban and industrial areas,
any significant attenuation of radiation by air pollution can, in addition
to other well-recognized factors, result in changes in local weather. It
is possible that local- and regional-scale changes in solar radiation caused
by human activity may ultimately influence the heat and water vapor contents
of the atmosphere on very large scales, but solar radiation and aerosol
levels measured at stations remote from pollutant sources have not as yet
displayed any trend that can be related to human causes.
Cloud- and precipitation-forming processes may be divided into two
broad classes: (1) macrophysical processes, which affect the rise and
descent of air currents and the amount of water vapor available for con-
densation; and (2) microphysical processes, which affect the nature of
cloud particles formed during condensation. The role of atmospheric
9-68
-------
aerosols, primarily those that are strongly hygroscopic, is to influence
the microphysics of cloud formation. The incorporation of particles into
rain and fog droplets can change the "quality" of precipitation by chang-
ing its chemical composition. The most important impact on precipitation
water quality is probably that of "acidic precipitation."
9-69
-------
9.6 REFERENCES
Allen, J., R. B. Husar, and E. S. Macias. la: Aerosol Measurement. D. A.
Lundgren, ed., University Presses of Florida, Gainesville, FL, 1978.
Altshuller, A. P. Atmospheric sulfur dioxide and sulfate, distribution of
concentration at urban and nonurban sites in the United States. Environ,
Sci. Technol. 7.:709-713, 1973.
Angell, J. K., and J. Korshover. Variation in sunshine duration over the
contiguous United States between 1950 and 1972. J. Appl. Meteorol. 14_:
1174-1181, 1975.
Barnes, R. A., and D. 0. Lee. Visibility in London and atmospheric sulfur.
Atmos. Environ. 12.:791-794, 1978.
Bergstrom, R. W. Beitr. Phys. Atmos. 46_:223, 1973.
Bo!in, B., and R. J. Charlson. On the role of the tropospheric sulfur cycle
in the shortwave radiative climate of the earth. Ambio 5^47-54, 1976.
Cass, G. R. On the relationship between sulfate air quality and visibility
with examples in Los Angeles. Atmos. Environ. 13:1069-1084, 1979.
Chandrasekhar, S. Radiative Transfer. Dover Publishers, New York, 1960.
Changnon, S. A., Jr. The La Porte weather anomaly—fact or fiction? Bull.
Am. Meteorol. Soc. 49.:4-11, 1968.
Charlson, R. J., D. S. Covert, T. V. Larson, and A. P. Waggoner. Chemical
properties of tropospheric sulfur aerosols. Atmos. Environ. 12:39-53,
1978.
Charlson, R. J., A. H. Vanderpgl, D. S. Covert, A. P. Waggoner, and N. C.
Ahlquist. HpS04/(NH.)2S07 Background aerosol: optical detection in
St. Louis region. Atm6s. Environ. 8^1257-1268, 1974.
Eggleton, A. E. J. The chemical composition of atmospheric aerosols on
Tees-side and its relation to visibility. Atmos. Environ. 3:355-372,
1969.
Eiden, R. Determination of the complex index of refraction of spherical
aerosol particles. Appl. Opt. 10:749-754, 1971.
9-70
-------
9.6 REFERENCES
Allen, J., R. B. Husar, and E. S. Macias. I_n: Aerosol Measurement. D. A,
Lundgren, ed., University Presses of Florida, Gainesville, FL,. 1978.
Altshuller, A. P. Atmospheric sulfur dioxide and sulfate, distribution of
concentration at urban and nonurban sites in the United States. Environ.
Sci. Techno!. 7:709-713, 1973.
Angel!, J. K., and J. Korshover. Variation in sunshine duration over the
contiguous United States between 1950 and 1972. J. Appl. Meteorol. 14:
1174-1181, 1975. ~~
Barnes, R. A., and D. 0. Lee. Visibility in London and atmospheric sulfur.
Atmos. Environ. 12:791-794, 1978.
Bergstrom, R. W. Beitr. Phys. Atmos. 46:223, 1973.
Bolin, B., and R. J. Charlson. On the role of the tropospheric sulfur cycle
in the shortwave radiative climate of the earth. Ambio 5:47-54, 1976.
Cass, G..R. On the relationship between sulfate air quality and visibility
with examples in Los Angeles. Atmos. Environ. 13:1069-1084, 1979.
Chandrasekhar, S. Radiative Transfer. Dover Publishers, New York, 1960,
Changnon, S. A., Jr. The La Porte weather anomaly-fact or fiction? Bull.
Am. Meteorol. Soc. 49:4-11, 1968.
Charlson, R. J., D. S. Covert, T. V. Larson, and A. P. Waggoner. Chemical
properties of tropospheric sulfur aerosols. Atmos. Environ. 12:39-53,
1978.
Charlson, R. J., A. H. Vanderpo.1, D. S. Covert, A. P. Waggoner, and N. C.
Ahlquist. H^SO./CNhL^SO. Background aerosol: optical detection ir
St. Louis region". AtmSs. Environ. 8:1257-1268, 1974.
Eggleton, A. E. J. The chemical composition of atmospheric aerosols on
Tees-side and its relation to visibility. Atmos. Environ. 3:355-372,
1969.
Eiden, R. Determination of the complex index of refraction of spherical
aerosol particles. Appl. Opt. 10:749-754, 1971.
9-70
-------
Ellis, A. T., and R. F. Pueschel. Absence of air pollution trends at Mouana
Loa. Science 172:845-846, 1971.
Ensor, D., and A. P. Waggoner. Angular truncation error in the integrating
nephelometer. Atmos. Environ. 4:481-487, 1970.
Faxvog, F- R. Optical scattering per unit mass of single particles. Appl.
Opt. 14:269-270, 1975.
Faxvog, F- R., and D. M. Roessler. Carbon aerosol visibility vs. particle
size distribution. Appl. Opt. 17:2612-2616, 1978.
Fischer, W. H. Some atmospheric turbidity measurements in Antarctica. J.
Appl. Meteorol. 6:958-959, 1967.
Fischer, K. Mass absorption indices of various types of natural aerosol
particles in the infrared. Appl. Opt. 14:2851-2856, 1975.
Flowers, E. C., R. A. McCormick, and K. R. Kurfis. Atmospheric turbidity over
the United States, 1961-1966. J. Appl. Meteorol. 8:955-962, 1969.
Gates, D. M. Spectral distribution of solar radiation at the Earth's surface.
Science 151:523-529, 1966.
Grosjean, D. et al. Concentration, size, distribution and modes of formulation
of particulate nitrate, sulfate and ammonium compounds in the eastern part
of the Los Angeles air basin. Presented at the Annual Meeting of the Air
Pollution Control Association, 1976. Paper No. 76-20.3.
Hall, J. S., and L. A. Riley. Basic spectrophotometric measures of air
quality over long paths. In: Radiative Transfer and Thermal Control,
vol. 49: Progress in Astronautics and Aeronautics. A. M. Smith, ed.,
American Institute of Aeronautics and Astronautics, New York, 1976.
pp. 205-212.
Hansen, A. D. A., H. Rosen, R. L. Dod, and T. Novakov. Optical attenuation as
a tracer for the primary component of the carbonaceous aerosol. In: Pro-
ceedings of Conference on Carbonaceous Particles in the Atmosphere, Berkeley;
CA, 1978.
Henry, R. C. The application of the linear system theory of visual acuity to
visibility reduction by aerosols. Atmos. Environ. 11:697-701, 1977.
Hodge, P. W., N. Laulainen, and R. J. Charlson. Astronomy and air pollution.
Science 178:1123-1124, 1972.
Horvath, H. , and K. E. Noll. The relationship between atmospheric light
scattering coefficient and visibility. Atmos. Environ. 3:543-550, 1969.
9-71
-------
Husar, R. B., D. E. Patterson, J. M. Holloway, W. E. Wilson, and T. G. Ellestad.
Trends of eastern U.S. haziness since 1948. J.n: Proceedings of the Fourth
Symposium on Atmospheric Turbulence, Diffusion, and Air Pollution, American
Meteorological Society, Reno, NE, 1979. pp. 249-256.
Landsberg, H. E. Man-made climatic changes. Science 170:1265-1274, 1970.
Latimer, D. A., R. W. Bergstrom, S. R. Hayes, M.-K. Liu, J. H. Sunfield, G. Z.
Whitten, M. A. Wojcik, and M. J. Hillyer. The Development of Mathematical
Models for the Prediction of Anthropogenic Visibility Impairment. EPA-
450/3/78-llOa, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1979.
Leaderer, B. P. et al. Summary of the New York Summer Aerosol Study (NYSAS).
J. Air Pollut. Control Assoc. 28:3221-327, 1978.
Lewis, C. W., and E. S. Macias. Composition of size-fractioned aerosol in
Charleston, West Virginia. Submitted for publication, 1979.
Lindberg, J. D., and L. S. Lande. Measurement of the absorption coefficient
of atmospheric dust. Appl. Opt. 13:1923-1927, 1974.
Machta, L., and K. Telegadas. Inadvertent large-scale weather modification.
In: Weather and Climate Modification, W. N. Hess, ed. , John Wiley & Sons,
New York, 1974. pp. 687-725.
Macias, E. S., D. L. Blumenthal, J. A. Anderson, and B. K. Cantrell. Characteri-
zation of visibility. Reducing aerosols in the southwestern United States;
interim report on Project VISTTA. MRI Report 78 IR 15-85, Midwest Research
Institute, Kansas City, MO, 1978.
Macias, E. S., and R. B. Husar. A review of atmospheric particulate mass
measurement via the beta attenuation technique. In: Fine Particles,
B. Y. H. Liu, ed., Academic Press, New York, NY, 1976.
Marians, M., and J. Trijonis. Empirical Studies of the Relationship Between
Emissions and Visibility in the Southwest. Prepared under grant 802015 by
Technology Service Corp. U.S. Environmental Protection Agency, Cincinnati,
OH, 1979.
Marians and Trijonis 1979
McCree, K. J. , and M. E. Keener. Effect of atmospheric turbidity on the
photosynthetic rates of leaves. Agric. Meteorol. 13:349-357, 1974.
Middleton, W. E. K. Vision Through the Atmosphere. University of Toronto Press,
Toronto, Canada, 1952.
Mie, G. Am. Phys. 25:377, 1908.
Patterson, E. M., and D. A. Gillette. Measurements of visibility vs. mass-
concentration for airborne soil particles. Atmos. Environ. 11:193-196, 1977.
9-72
-------
Patterson, R. K., and J. Wagman. Mass and composition of an urban aerosol as a
function of particle size for several visibility levels. J. Aerosol Sci.
8:269-279, 1977.
Peterson, J. T., and E. C. Flowers. Interactions between air pollution and
solar radiation. Solar Energy 19:23-32, 1977.
Pueschel, R., and D. L. Wollman. On the nature of atmospheric background
aerosol. Presented at the 14th Conference on Agricultural and Forest
Meteorology. Minneapolis, MN, April 1978.
Pinnick, R. G., and D. E. Carroll, D. J. Hofmann. Polarized light scattered
from monodisperse randomly oriented nonspherical aerosol particles:
measurements. Appl. Opt. 15:384, 1976.
Rabinoff, R., and B. Herman. Effect of aerosol size distribution on the
accuracy of the integrating nephelometer. J. Appl. Meteorol. 12:184-186,
1973. ~
Robinson, G. D. Absorption of solar radiation by atmospheric aerosol, as revealed
by measurements at the ground. Arch. Meteorol. Geophys. Bioclimatol. Ser.
B 12:19, 1962.
Robinson, G. D. Inadvertent Weather Modification Workshop. Final Report to the
NAS; The Center for the Environment and Man (CEM) Report 4215-604, 1977.
Rodhe, H., C. Persson, and 0. Akesson. An investigation into regional transport
of soot and sulfate aerosols. Atmos. Environ. 6:675:693, 1972.
Rosen, H., A. D. A. Hansen, R. L. Dod, and T. Novakov. Soot in urban atmospheres:
determination by an optical absorption technique. Science 208:741-743,
1980.
Samuels, H. J., S. A. Twiss, and E. Wong. Visibility, Light Scattering, Mass
Concentration of Particulate Matter. Report of the California Tri-City
Aerosol Sampling Project of the State of California Air Resources Board,
1973.
Tombach, I. H., and M. W. Chan. Physical, chemical, and radiological
characterization of background particulate matter in northeastern
Utah. Presented at the Annual Meeting of the Air Pollution Control
Association, 1977. Paper No. 77-48.6.
Trijonis, J., and R. Shapland. Existing Visibility Levels in the U.S.: Isopleth
Maps of Visibility in Suburban/Nonurban Areas During 1974-1976. Final
report to EPA under Grant No. 802815, 1978.
Trijonis, J., arid K. Yuan. Visibility in the Southwest: an Exploration of
the Historical Data Base. EPA-600/3/78/039, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1978a.
Trijonis, J. , and K. Yuan. Visibility in the Northeast: Long Term Visibility
Trends and Visibility/Pollutant Relationships. EPA-600/3-78-075, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1978b.
9-73
-------
U.S. Bureau of Mines. Minerals Yearbook, Annual Publication, 1933-74. U.S.
Department of the Interior, Washington, D.C.
U.S. Environmental Protection Agency. EPA Report to Congress: Protecting
Visibility. EPA-450/5-79-008, U. S. Environmental Protection Agency,
Research Triangle Park, NC, 1979.
Waggoner, A. P., A. J. Vanderpol, R. J. Charlson, S. Larsen, L. Granat, and
C. Tragardh. Sulphate-light scattering ratio as an index of the role of
sulphur in tropospheric optics. Nature 261:120-122, 1976.
Waggoner, A. P., and R. J. Charlson. Measurement of aerosol optical parameters.
^n: Fine Particles, B. Y. H. Liu, ed. , Academic Press, New York, 1976.
Waggoner, A. P., and R. E. Weiss. Comparisons of fine particle mass concen-
tration and light scattering extinction in ambient aerosol. Atmos. Environ.
14:623-626, 1980.
Waggoner, A. P. et al. Optical absorption by atmospheric aerosols. Appl.
Opt. 12:896, 1973.
Waggoner 1973
Weiss, R. E. Ph. D. Dissertation, 1978.
Weiss, R. E. et al. Studies of the optical, physical, and chemical properties
of light-absorbing aerosols. In: Proceedings of the Conference on
Carbonaceous Particles in the Atmosphere, 1978. p. 257.
Wesely, M. L., and R. C. Lipschutz. An experimental study of the effects of
aerosols on diffuse and direct solar radiation received during the summer
near Chicago. Atmos. Environ. 10:981-987, 1976.
White, W. H., and P. T. Roberts. On the nature and origins of visibility reducing
aerosols in the Los Angeles Air Basin. Atmos. Environ. 11:803:812, 1977.
WMO/EPA/NOAA/UNEP. Global Monitoring of the Environment for Selected Atmospheric
Constituents 1975. Environmental Data Service National Climatic Center,
Asheville, NC, 1977.
9-74
-------
Ellis, A. T., and R. F. Pueschel. Absence of air pollution trends at Mouana
Loa. Science J72:845-846, 1971.
Ensor, D., and A. P. Waggoner. Angular truncation error in the Integrating
nephelometer. Atmos. Environ. 4_:481-487, 1970.
Faxvog, F. R. Optical scattering per unit mass of single particles. Appl.
Opt. _14:269-270, 1975.
Faxvog, F. R., and D. M. Roessler. Carbon aerosol visibility vs. particle
size distribution. Appl. Opt. 17:2612-2616, 1975.
Fischer, W. H. Some atmospheric turbidity measurements in Antarctica. J.
Appl. Meteorol. 6_:958-959, 1967.
Fischer, K. Mass absorption indices of various types of natural aerosol
particles in the infrared. Appl. Opt. .14_:2851-2856, 1975.
Flowers, E. C., R. A. McCormick, and K. R. Kurfis. Atmospheric turbidity over
the United States, 1961-1966. J. Appl. Meteorol. 8:955-962, 1969.
Gates, D. M. Spectral distribution of solar radiation at the Earth's surface.
Science .151.:523-529, 1966.
Grosjean, D. et al. Concentration, size, distribution and modes of formulation
of particulate nitrate, sulfate and ammonium compounds in the eastern part
of the Los Angeles air basin. Presented at the Annual Meeting of the Air
Pollution Control Association, 1976. Paper No. 76-20.3.
Hall, J. S., and L. A. Riley. Basic spectrophotometric measures of air
quality over long paths. In: Radiative Transfer and Thermal Control,
vol. 49: Progress in Astronautics and Aeronautics. A. M. Smith, ed.,
American Institute of Aeronautics and Astronautics, New York, 1976.
pp. 205-212.
Hansen, A. D. A., H. Rosen, R. L. Dod, and T. Novakov. Optical attenuation as
a tracer for the primary component of the carbonaceous aerosol. In: Pro-
ceedings of Conference on Carbonaceous Particles in the Atmosphere, Berkeley,
CA, 1978.
Henry, R. C. The application of the linear system theory of visual acuity to
visibility reduction by aerosols. Atmos. Environ. U_:697-701, 1977.
Hodge, P. W., N. Laulainen, and R. J. Charlson. Astronomy and air pollution.
Science 178^:1123-1124, 1972.
Horvath, H., and K. E. Noll. The relationship between atmospheric light
scattering coefficient and visibility. Atmos. Environ. 3_:543-550, 1969.
9-71
-------
Husar, R. B., D. E. Patterson, and J. M. Holloway. Trends of eastern U.S.
haziness since 1948. In: Proceedings of the Fourth Symposium on Atmospheric
Turbulence, Diffusion, and Air Pollution, American Meteorological Society.
Reno, NE, 1979. pp. 249-256.
Landsberg, H. E. Man-made climatic changes. Science 17£: 1265-1274, 1970.
Latimer, D. A., R. W. Bergstrom, S. R. Hayes, M.-K. Liu, J. H. Sunfield, G. Z.
Whitten, M. A. Wojcik, and M. J. Hillyer. The Development of Mathematical
Models for the Prediction of Anthropogenic Visibility Impairment. EPA-
450/3/78-110a, U.S. Environmental Protection Agency, Research
Triangle Park, NC, 1979.
Leaderer, B. P. et al. Summary of the New York Summer Aerosol Study (NYSAS).
J. Air Pollut. Control Assoc. 2^:3221-327, 1978.
Lewis, C. W., and E. S. Macias. Composition of size-fractioned aerosol in
Charleston, West Virginia. Submitted for publication, 1979.
Lindberg, J. D., and L. S. Lande. Measurement of the absorption coefficient
of atmospheric dust. Appl. Opt. JL3; 1923-1927, 1974.
Machta, L., and K. Telegadas. Inadvertent large-scale weather modification.
In: Weather and Climate Modification, W. N. Hess, ed., John Wiley > Sons,
New York, 1974. pp. 687-725.
Macias, E. S., D. L. Blumenthal, J. A. Anderson, and B. K. Cantrell. Characterization
of visibility. Reducing aerosols in the southwestern United States; interim
report on Project VISTTA. MRI Report 78 IR 15-85, Midwest Research
Institute, Kansas City, MO, 1978.
Macias et al. 1975
Marians, M., and J. Trijonis. Empirical Studies of the Relationship Between
Emissions and Visibility in the Southwest. Prepared under grant 802015 by
Technology Service Corp. U.S. Environmental Protection Agency, Cincinnati,
OH, 1978.
Marians and Trijonis 1979
McCree, K. J., and M. E. Keener. Effect of atmospheric turbidity on the
photosynthetic rates of leaves. Agric. Meteorol. 13^349-357, 1974.
t ~
Middleton, W. E. K. Vision Through the Atmosphere. University of Toronto Press,
Toronto, Canada, 1952.
Mie, G. Am. Phys. 25_:377, 1908.
Patterson, E. M., and D. A. Gillette. Measurements of visibility vs. mass-
concentration for airborne soil particles. Atmos. Environ. 11:193-196, 1977-
9-72
-------
Patterson, R. K., and J. Wagman. Mass and composition of an urban aerosol as a
function of particle size for several visibility levels. J. Aerosol Sci.
8:269-279, 1977.
Peterson, J. T., and E. C. Flowers. Interactions between air pollution and
solar radiation. Solar Energy Jjh23-32, 1977.
Pueschel, R., and D. L. Wollman. On the nature of atmospheric background
aerosol. Presented at the 14th Conference on Agricultural and Forest
Meteorology, Minneapolis, MN, April 1978.
Pinnick, R. G., and D. E. Carroll, D. J. Hofmann. Polarized light scattered
from monodisperse randomly oriented nonspherical aerosol particles:
measurements. Appl. Opt. j^:384, 1976.
Rabinoff, R., and B. Herman. Effect of aerosol size distribution on the
accuracy of the integrating nephelometer. J. Appl. Meteorol. 12:184-186,
1973. —
Robinson, G. D. Absorption of solar radiation by atmospheric aerosol, as revealed
by measurements at the ground. Arch. Meteorol. Geophys. Bioclimatol. Ser.
B 12.: 19, 1962.
Robinson, G. D. Inadvertent Weather Modification Workshop. Final Report to the
NAS; The Center for the Environment and Man (CEM) Report 4215-604, 1977.
Rodhe, H., C. Persson, and 0. Akesson. An investigation into regional transport
of soot and sulfate aerosols. Atmos. Environ. 6^:675:693, 1972.
Rosen and Novakov 1979
Samuels, H. J., S. A. Twiss, and E. Wong. Visibility, Light Scattering, Mass
Concentration of Particulate Matter. Report of the California Tri-City
Aerosol Sampling Project of the State of California Air Resources Board,
1973.
Tombach, I. H., and M. W. Chan. Physical, chemical, and radiological
characterization of background particulate matter in northeastern
Utah. Presented at the Annual Meeting of the Air Pollution Control
Association, 1977. Paper No. 77-48.6.
Trijonis, J., and R. Shapland. Existing Visibility Levels in the U.S.: Isopleth
Maps of Visibility in Suburban/Nonurban Areas During 1974-1976. Final
report to EPA under Grant No. 802815, 1978.
Trijonis, J.t and K. Yuan. Visibility in the Southwest: an Exploration of
the Historical Data Base. EPA-600/3/78/039, U.S. Environmental Protection
Agency, Research Triangle Park, NC, 1978a.
Trijonis, J., and K. Yuan. Visibility in the Northeast: Long Term Visibility
Trends and Visibility/Pollutant Relationships. EPA-600/3-78-075, U.S.
Environmental Protection Agency, Research Triangle Park, NC, 1978b.
9-73
-------
U.S. Bureau of Mines. Minerals Yearbook, Annual Publication, 1933-74. U.S.
Department of the Interior, Washington, D.C.
U.S. Environmental Protection Agency. EPA Report to Congress: Protecting
Visibility. EPA-450/5-79-008, U. S. Environmental Protection Agency,
Research Triangle Park, NC, 1979.
Waggoner, A. P., A. 0. Vanderpol, R. J. Charlson, S. Larsen, L. Granat, and
C. Tragardh. Sulphate-light scattering ratio as an index of the role of
sulphur in tropospheric optics. Nature 261:120-122, 1976.
Waggoner, A. P- et al. Optical absorption by atmospheric aerosols. Appl.
Opt. 12_:896, 1973.
Waggoner 1973
Weiss, R. E. Ph. D. Dissertation, 1978.
Weiss, R. E. et al. Studies of the optical, physical, and chemical properties
of light-absorbing aerosols. In: Proceedings of the Conference on
Carbonaceous Particles in the Atmosphere, 1978. p. 257-
Wesely, M. L., and R. C. Lipschutz. An experimental study of the effects of
aerosols on diffuse and direct solar radiation received during the summer
near Chicago. Atmos. Environ. Hh981-987, 1976.
White, W. H., and P. T. Roberts. On the nature and origins of visibility reducing
aerosols in the Los Angeles Air Basin. Atmos. Environ. ^803:812, 1977-
WMO/EPA/NOAA/UNEP- Global Monitoring of the Environment for Selected Atmospheric
Constituents 1975. Environmental Data Service National Climatic Center,
Asheville, NC, 1977.
9-74
-------
10. EFFECTS ON MATERIALS
10.1 INTRODUCTION
Sulfur oxides and particulate material damage materials. In general
terms, sulfur oxides accelerate the corrosion of metals and the erosion
of building stone, while airborne particles soil fibers and structures.
This chapter discusses the chemical and physical action of these air
pollutants on materials and identifies other environmental factors (e.g.,
moisture and sunlight) that play a role in the degradation process. Laboratory
and field studies are reviewed, describing the effects of single pollutants
and combinations of pollutants at various concentrations. Damage functions
developed from these data are provided when available in useable form.
Although physical damage functions for some pollutants are fairly well
developed, most are based on exposure data collected at relatively high
pollutant levels. Little information exists on effects of current levels,
which are generally lower.
Economic damage functions are discussed, and some equations are presented.
These functions are less well established than are the physical damage
functions, and since they are derived in part from data highly influenced
by socioeconomic factors, they should be applied cautiously.
The chapter summarizes published analyses of the cost of materials
damage, maintenance, protection, and repair associated with ambient sulfur
oxides and particulate matter. However, the chapter does not attempt to
integrate current air quality data, physical damage functions, and economic
damage functions to arrive at a total cost associated with these pollutants
10-1
-------
at current levels. The next draft of this chapter will address possible
approaches to the problem of integrating these data sets.
10.2 SULFUR OXIDES
10.2.1 Corrosion of Exposed Metals
Sulfur oxides present in the environment accelerate the corrosion of
metals. Several factors other than concentration of SO,, are important. These
will be discussed first.
10.2.1.1 Physical and Chemical Considerations—The corrosion of metals is a
diffusion-controlled electrochemical process. For electrochemical action to
take place, the following are necessary: (1) a potential difference between
points on the metal surface; (2) a mechanism for charge transfer between the
electronic conductors; and (3) a conduction path between the cathode and anode
reaction centers. Measurements of the rate of SO^-accelerated rusting of iron
vary greatly from site to site, despite careful monitoring of pollutant con-
centrations, a fact that has often puzzled researchers. The problem has been
addressed from the standpoint of several factors that might be responsible for
inconsistent results. These include: (1) the deposition rate of gaseous or
dissolved S02 and particles; (2) the variability in the electrochemical actions
that cause corrosion; (3) the influence of rust on the rate of corrosion; and
(4) the interaction between the effects of "wetness time" and of relative
humidity (RH) on surface electrolyte concentrations.
According to Nriagu (1978), once corrosion has begun, the progress of the
reaction is largely controlled by the sulfate ions formed from oxidation of
the adsorbed S02- The actual mechanism for the oxidation of S0? (and its
10-2
-------
hydrated products) at metal-water interfaces is little understood. Barton
(1973) proposed the following reaction:
S02 + 02 + 2e -> S0^~
or
4HSO~ + 302 + 4e -» 4SO^" + 2H20
The electron is provided by the oxidation of the metal (M):
M -» Mn+ + ne
Duncan and Spedding (1974), using an electrophoretic method, found that the
rates of sulfate formation on iron and zinc surfaces were similar; the
pseudo-first-order half-life was determined to be about 24 hr. Other workers
(Karraker 1963; Yoshihara et al., 1964) reported higher oxidation rates
(half-life, 10 to 100 min) in bulk solutions using Fe catalysts as summarized
in Nriagu (1978). Nriagu also noted that rust on iron and steel is first
restricted to localized sites or "nests" and then spreads across the entire
exposed surface. At an S0? concentration of about 260 |jg/m , corrosion products
were obvious on iron surfaces after 6 to 8 weeks, whereas at SOp concentrations
5 3
of 4 x 10 [jg/m , they could be seen after only a few hours.
Barton (1973) showed that the critical S0? flux for corrosion was 6 to
10
2 2
ug/m per year for steel and 18 to 20 (jg/m per year for zinc and copper. The
formation of rust drastically increases the adsorption rate for SO^. For
example, at an S0? concentration of >0.001 percent and relative humidity (RH)
of >96 percent, virtually all of the S0? that comes into contact with the
rusting surface is adsorbed.
10-3
-------
According to Nriagu (1978), Barton and Bartonova (1960) postulated the
following mechanism of steel corrosion:
Fe + H20 -»• Fe(OH~)ads + H+
Fe(OH")ads •* Fe(OH)ads + e
Fe(OH)ads + SO^" -»• FeS04 + OH" + e
The oxidative hydrolysis of ferrous sulfate leads to the formation of ferric
hydroxide and the regeneration of sulfate ions, which in turn initiate another
chain reaction:
FeS04 + 2H20 -» FeOOH + S04" + 3H+ + e
The supply of oxygen to the cathode must be maintained; rust films may therefore
differ from metal to metal, with a tightly packed film giving a low diffusion
rate.
10.2.1.1.1 Relative Humidity and Corrosion Rate. According to Schwarz (1972),
the corrosion rate of a metal should increase by 20 percent for each increase of
1 percent in the relative humidity (RH) above the critical RH value. It is
evident that relative humidity has a considerable influence on the corrosion
rate. This influence has been established in laboratory trials by Barton and
Bartonova (1969) and Sydberger and Ericsson (1976). It is apparent from
Figures 10-1 and 10-2 (Haynie and Upham, 1974) that the corrosion rate of
steel increases with increasing relative humidity as well as with increasing
S02 concentration.
The climate of an area is usually characterized by average relative
humidity rather than relative humidity distribution. Since average relative
humidity is calculated from the distribution, there should be an empirical
relationship between average relative humidity and the fraction of time some
10-4
-------
I
E
100
90
80
70
60
1
O
cr
8
6
o
40
30
20
10
0
1 I I I I I I I I
SO2 CONCENTRATION, p fl/m
0 10 20 30 40 50 60 70 80 90 100
AVERAGE RELATIVE HUMIDITY,%
Figure 10-1. Steel corrosion behavior is shown as a function of aver-
age relative humidity at three average concentration levels of sulfur
dioxide.
Source: Haynie and Upham (1974).
10-5
-------
is
1
cc
O
CO
O
cc
cc
O
O
6
O
D
UJ
100
90
80
70
60
50
40
30
20
10
I
I
RH _
55% RH
I
0 100 200 300 400
AVERAGE SULFUR DIOXIDE CONCENTRATION, y. g/m3
Figure 10-2. Steel corrosion behavior is shown as a function of aver-
age sulfur dioxide concentration and average relative humidity (RH).
Source: Haynie and Upham (1974).
10-6
-------
"critical humidity value" (minimum concentration of water vapor required for
corrosion to proceed) is exceeded. The fraction of time that the surface is
wet must be zero when the average relative humidity is zero and unity when the
average relative humidity is 100 percent. The simplest single-constant first-
order curve that can be fitted to observed data and that meets these conditions
is described by the equation f = [(1 - k)RH]/(100 - kRH), where f is the
fraction of time the relative humidity exceeds the critical value, RH is the
average relative humidity, and k is an empirical constant less than unity
(Haynie, 1980).
Ten quarter-year periods of relative humidity data from St. Louis Inter-
national Airport were analyzed and fitted by the least-squares method to the
above equation. The fraction of time the relative humidity exceeded 90 percent
gave a value of 0.86 for k. This fraction and the data points are plotted in
Figure 10-3 (Haynie, 1980).
When the temperature of a metal is below the ambient dewpoint, condensation
of water on the metal surface will take place. The metal temperature at which
condensation occurs will vary with heat transfer between ground and metal and
between air and metal. Condensation will occur when the relative humidity
adjacent to the surface exceeds a value in equilibrium with the vapor pressure
of a saturated solution on the surface. The solution may contain corrosion
products, other hygroscopic contaminants, or both. Temperature, wind, and
sunshine then become factors in establishing corrosion rates, since they
determine whether there will be sufficient dew condensation. Sayre (1973)
established a direct relationship between the amount of dew precipitated and
the corrosion rate of steel.
10-7
-------
10 20 30 40 50 60 70 80 90 100
AVERAGE RELATIVE HUMIDITY, %
Figure 10-3. Empirical relationship between average relative humid-
ity and fraction of time is shown for a wet zinc sheet specimen.
Source: Haynie (1980).
10-8
-------
Haynie (1980) reported on the relationship between diffusion theory and
thermodynamics for the observed effects of five variables: pollution level,
relative humidity, temperature, wind velocity, and surface geometry. He
observed that metals must be wet to corrode electrochemically. Surfaces are
wet from condensation much more than from precipitation.
10.2.1.1.2 Influence of Rainfall on Corrosion. Steel surfaces shielded from
the leaching effect of rain may corrode at a higher rate than those exposed to
rain. The sulfate content of rust has been identified as a dominant factor in
corrosion and is found at higher concentrations on surfaces sheltered from
rain than on exposed surfaces because soluble sulfate is leached from the
rust. However, sulfur deposition during rainfall must also be considered.
Haagen -Roodond Ottaz (1975) found that the effect of rain on corrosion
depends on the sulfate and sulfuric acid content of the rain.
As Kucera's (1976) review of this problem indicates, the mode of deposition
complicates the analysis of acidic precipitation's effects. For example, in
an area where dry deposits of hydrogen and sulfate ions exceeded deposits in
wet precipitation, flat steel plates corroded more rapidly on their undersides
than on their upper surfaces, suggesting that the rainfall had more of a
washing effect than a corrosive action. However, in other areas where wet and
dry deposition were about equal, the skyward sides of the plates corroded more
quickly, indicating that the corrosive effect of the rainfall predominated.
Other variables, including amount and frequency of precipitation, its pH
level, humidity, and temperature, also determine the impact of acidic pre-
cipitation (Kucera, 1976).
For a more thorough discussion of the effects of acid rain on corrosion,
see Chapter 8.
-------
10.2.1.1.3 Influence of Temperature on Corrosion. From chemical reaction
kinetics, one might expect corrosion rates to follow the Arrhenius law according
to which the logarithm of a reaction rate is inversely proportional to the
absolute temperature. However, this does not appear to be a major factor
controlling corrosion rates. In most cases, as discussed later, the reaction
rate is controlled by diffusion, either in the corrosion product film or in
the environment. In either case, the rate of diffusion is relatively insensitive
to changes in ambient temperature. A decrease in temperature raises the
relative humidity while decreasing diffusivity; thus, the normal temperature
range will most likely not observably affect the overall corrosion rate.
Freezing should produce a step decrease in the corrosion rate because diffusion
is then through a solid rather than a liquid.
Guttman (1968) and Haynie and Upham (1974), using statistical techniques
of multiple linear regression and nonlinear curve fitting, could not obtain
from their data a significant correlation between corrosion and temperature.
However, increased temperature decreases the solubility of oxygen in the
electrolyte. Moreover, temperature changes can cause condensation, and the
increased quantity of condensed droplets would affect the corrosion rate. In
addition, the rate of drying of a surface depends on both temperature and air
movement.
The diffusion rate of oxygen in the electrolyte increases with temperature,
and changes in temperature are expected to cause changes in the physical
structure and in the chemical composition of the rust layer, thereby affecting
its protective function and the diffusion rate of the reactants. Temperature
changes may indirectly affect the pH of the electrolyte. For example, the
loss of ammonia by evaporation from particulate ammonium sulfate would produce
a greater acidity.
10-10
-------
Guttman and Sereda (1968) made continuous measurements of sulfur oxides,
time of wetness, and temperature in their outdoor exposure tests. The
corrosion rate increased markedly with temperature, which may be attributed to
a speeding up of the electrochemical process. The effects are not simply
thermodynamic since there are other factors including evaporation of surface
electrolyte and decrease in the solubility of oxygen and gaseous pollutants.
Barton (1973) did find that the effect of increased temperature was more
pronounced when the rust contained little water and sulfate.
10.2.1.1.4 Hygroscopicity of Metal Sulfates. The sulfate in rust stimulates
further corrosion by a mechanism that is related to the critical relative
humidity at which an electrolyte film is formed. The hygroscopicity of iron
sulfates in the rust lowers the critical relative humidity for corrosion;
however, sulfates are not the most deliquescent salts. For example, chloride
and nitrate salts which have higher hygroscopicity than sulfates make corrosion
possible at lower humidities.
Surfaces contaminated by sea salt (mostly sodium chloride) are expected
to be wet when the relative humidity exceeds 75 percent. In contrast, calcium
chloride keeps surfaces wet at relative humidities as low as 30 percent. A
saturated solution of zinc sulfate at 20°C is in equilibrium at 90 percent
relative humidity. Thus, zinc corroded by sulfur dioxide is expected to be
wet when the relative humidity exceeds 90 percent (Haynie, 1980).
Some pollutants which react chemically with various materials and are
consumed produce catalytic effects. The following four mechanisms act to
increase corrosion rates without consuming the pollutants: (1) Hygroscopic
materials increase the amount of time that a corroding surface is wet. (2)
Conductivities of solutions and corrosion product films increase.
10-11
-------
(3) Pollutants form soluble intermediate reaction products or activated
complexes that destroy the protective nature of films. (4) Lowering the pH
usually increases the solubility of corrosion products.
10.2.1.1.5 Electronic Conductivity of Rust. Barton (1973) postulated that
sulfate ions influence the anodic dissolution of iron as a function of their
concentration at the steel-rust interface. The corrosion rate of the rust
layer is based in part on the high electronic conductivity of rust, which
allows the reduction of oxygen to occur within the rust layer. The rate is
also influenced by the porosity of rust, which permits rapid diffusion of
oxygen to the cathode.
In the presence of SCL, ferrous sulfate is formed before insoluble rust
develops. The amount of S02 required is small; each SO^ molecule can generate
20 to 30 molecules of rust. Once ferrous sulfate is formed, rusting can
continue even though S02 is no longer present in gaseous form.
10.2.1.1.6 Cathodic Reduction of SO.,. Under experimental conditions, an S02
3
concentration of 10 ppm (2620 ug/m ) has reportedly led to cathodic reduction
and depolarization, yielding sulfide-containing corrosion products (Sydberger
and Ericsson, 1976). However, at ambient air concentrations (0.01 to 0.2 ppm
3
or 26 to 520 pg/m in polluted areas), it would not be reasonable to expect
the electrolyte to contain enough SO- to affect the cathodic reaction.
10.2.1.1.7 Cathodic Reduction of Rust. Evans (1972) suggests that oxidative
hydrolysis of ferrous sulfate occurs slowly, and would be important only in
the initial stage of corrosion. He proposes that there is a rate-controlling
cathodic process. Thus, the corrosion products in the ferric state would be
converted to magnetite (Fe.^), by a reaction involving the reduction of
ferric oxyhydroxide (FeOOH):
Fe2+ + SFeOOH + 2e~ •» 3Fe304 + 4H£0
10-12
-------
10.2.1.1.8 Corrosion-Protective Properties of Sulfate in Rust. The rust
layer on steel is somewhat protective against further corrosion, though far
less so than the corrosion layer on zinc and copper. A limiting factor in
rust's protection of steel is the content of soluble sulfate in rust.
Rust samples investigated by Chandler and Kilcullen (1968) and by Stanners
(1970) contained 2 to 2.5 percent soluble sulfate and 3 to 6 percent total
sulfate. The outer rust layer contained a small amount (0.04 to 0.2 percent)
of soluble sulfate, compared with 2 percent in the inner rust layer. The
concentration of insoluble sulfate was fairly uniform throughout the rust
layers.
The emphasis on the composition of the rust layer has led to studies of
the corrosion-protective properties of rust as a function of exposure history
(Nriagu, 1978; Sydberger, 1976). Steel samples initially exposed to low
concentrations of sulfur oxides and then moved to sites of higher sulfur oxide
concentrations corroded at a slower rate than did samples continuously exposed
to the higher concentrations. Exposure tests started in summer showed slower,
corrosion rates during the first years of exposure than did those started in
winter.
The long-term corrosion rate of steel appears to depend on changes in the
composition and structure of the rust layer. During the initiation period,
which varies in length with the S0? concentration and other accelerating
factors, the rate of corrosion increases with time (Barton, 1973). Because it
is porous and nonadherent, the rust initially formed offers no protection; in
fact, it may accelerate corrosion by retaining hygroscopic sulfates and chlo-
rides, thus producing a microenvironment with a high moisture content (most
often reported in terms of percent relative humidity). After the initiation
10-13
-------
stage, the corrosion rate decreases as the protective properties of the rust
layer improve. Satake and Moroishi (1974) relate this slowing down to a
decrease in the porosity of the rust layer. During a third and final stage, a
stationary rate of corrosion is attained and the amount of sulfate rust is
proportional to atmospheric sulfur oxide concentrations. Where there is no
appreciable deposition of sulfur or chloride compounds, the corrosion of steel
is low, even with high atmospheric humidity and temperature (Haynie and Upham,
1974). The quantitative determination of corrosion rates becomes difficult
if it is not known how long the metal has a surface layer of electrolyte.
Variations in the "wet states" will occur with relative humidity, temperature,
rain, dew, fog, and evaporation caused by wind. The surface electrolyte layer
may form on a metal surface as a result of rain, dew, or adsorption of water
from the atmosphere. Capillary condensation in rust can be related to the
minimum atmospheric moisture content which allows corrosion to occur (i.e.,
critical relative humidity). Centers of capillary condensation of moisture on
metals can occur in cracks, on dust particles on the metal surface, and in the
pores of the rust (Tomashov 1966).
The water content of rust formed by laboratory exposure of steel samples
to various SCL concentrations was examined by Barton and Bartonova (1969).
They concluded that water content of rust increased with SCL in the atmosphere
The hygroscopic nature of soluble salts in rust is believed to be the prime
factor affecting water sorption by the rust layer.
10.2.1.2 Effects of Sulfur Oxide Concentrations on the Corrosion of Exposed
Metals--Most of the laboratory studies reviewed in this section have measured
corrosion rates related to exposure to sulfur dioxide alone or in combination
with other compounds. In field exposure studies, where sulfur oxides almost
10-14
-------
invariably occur in combination with other airborne pollutants, an attempt is
made, on the one hand, to assign separate values to sulfur oxides and, on the
other, to describe pollutant interactive effects on corrosion. The section
unavoidably overlaps somewhat with a later section on particles, since sulfur
oxides exist in particulate phase. Here, the emphasis is on the direct role
of sulfur oxides in the corrosion process (e.g., the oxidation of S0? with
moisture on a metal surface). In a later section, sulfur oxide particles are
discussed mainly in terms of their indirect role (e.g., their ability to
increase wetness time of a metal surface).
10.2.1.2.1 Ferrous Metals. Ferrous metal products and structures are exposed
widely to ambient pollutant levels. Rusting of these metals is the best
documented form of metallic corrosion affected by sulfur oxides. This subsection
reviews studies of rusting rates of ferrous metals, including iron, steel, and
steel alloys.
Addition of small amounts of certain elements, especially copper, improves
the corrosion resistance of mild steel. The American Society for Testing and
Materials (ASTM) has established this fact in an extensive series of exposure
tests (Guttman and Sereda, 1968). Larrabee (1959) showed that carbon steel,
copper steel, and a Cr/Si/Cu/P low-alloy steel used in an industrial environment
for 10 years were more resistant to corrosion than carbon steel. Stainless
steels contain more than 12 percent chromium and are widely used in outdoor
exposures; they are specified for use in many industrial processes in which
corrosive liquids rapidly attack ordinary steels.
The most important additive in low-alloy steels is copper. Larrabee and
Coburn (1961) established that the addition of 0.03 percent copper to steel
reduces corrosion losses in an industrial area by up to 70 percent. Low-alloy
10-15
-------
steels usually contain 0.2 to 0.5 percent copper. Other investigators, including
Schwenk and Ternes (1968) and Brauns and Kalla (1965), have also shown that
adding copper to steel at these levels will decrease metal loss in industrial
atmospheres.
Phosphorus is also effective in raising the corrosion resistance of
steel. Larrabee (1959) found less corrosion in copper alloy steels containing
0.05 to 0.1 percent added phosphorus.
The high corrosion resistance of stainless steels incorporating chromium,
molybdenum, and nickel, is attributed to the protective properties of the
oxide film formed on these alloys; however, in heavily polluted atmospheres,
this film is not completely protective. Particles in settled dust, including
sulfates and chlorides, can promote rupture of the oxide film and cause pitting
corrosion, which may be influenced by the surface finish (see section 10.3.1).
Smoothly polished or electropolished surfaces are less likely to retain solid
deposits originating from airborne particles (Larrabee, 1959).
Stainless-steel alloys contain chromium, molybdenum, and sometimes nickel.
The lowest alloyed types have little corrosion resistance; in particular, #13
Cr steel suffers pitting attack in industrial atmospheres. Evgang and Rockel
(1975) report that the austenitic steels of 18 percent Cr and 8 percent Ni are
reasonably resistant in urban atmospheres but have shown slight rusting in
industrial areas. The rusting is decreased when the steel surface is cleaned
of atmospheric deposits.
10.2.1.2.2 Laboratory and Field Studies Emphasizing Ferrous Metals. It is
useful to consider laboratory and field studies of corrosion effects separately
because the attribution of cause to effect is much clearer in laboratory
experiments; field studies are often beset with many "confounding variables."
10-16
-------
The following are included as examples of confounding variables associated
with field studies; organized as temporal and spatial.
o temporal fluctuations in temperature, wind moisture content,
insolation, rainfall and chemical characteristics (e.g.,
acidic rain) and atmospheric pollutant concentrations
o spatial differences such as aspect, altitude, electromagnetic
fields and indigenous microorganisms
10.2.1.2.2.1 Laboratory Studies. Spence and Haynie (1974) described the
design of a laboratory experiment to identify the effects of environmental
pollutants on various materials including ferrous metals. The environmental
system consisted of five exposure chambers to control temperature and humidity
and chill racks to simulate the formation of dew. Gaseous pollutants included
those usually monitored in field exposures: sulfur dioxide, nitrogen dioxide,
and ozone. Experiments were statistically designed for analysis of variance,
and a system was selected to study the interactive effects of pollutants and
other variables. The effect of particles was not included in the design. The
chambers were equipped with a xenon arc light to simulate sunlight. The
system was designed to maintain air contact with the various materials at
preselected temperatures, relative humidities, flow rates, and pollutant con-
centrations. A dew-light cycle was used; it produced faster deterioration
than did conditions of constant humidity and temperature.
Haynie et al. (1976) exposed weathering steel in the chamber study de-
scribed above and measured concentrations of sulfur dioxide, nitrogen dioxide,
and ozone in various combinations and at two levels of pollutant concentration
The corrosion rate was measured by loss in weight of the weathering steel (a
Cor Ten A product). Six panels were exposed under 16 polluted-air and 4
clean-air conditions, and measurements were taken at 250, 500, and 1000 hr of
exposure. The weight losses were converted to equivalent thickness loss
10-17
-------
values. As expected, corrosion was most severe at high SOp concentrations and
high humidity. The results of earlier field exposures (see following section)
had shown that the presence of high oxidant concentrations decreased
the corrosion rate. The chamber exposures showed that ozone neither inhibited
nor accelerated corrosion. The authors concluded that some other oxidant or
unmeasured factor that was covariant with ozone caused the inhibition effect.
However, if the data from the sites with high concentrations of oxidant in the
field exposure experiments were excluded, a damage function from the laboratory
study was an excellent predictor of the field results.
Sydberger and Ericsson (1976) studied the corrosion of mild steel at 1,
10, and 100 ppm (2620, 26,200, 262,000 ug/m ) S02 across the range of critical
humidities (80 to 96 percent RH). The flow rate of the SO^ atmosphere was varied,
and some samples were sprayed with water to simulate rain or condensation.
The chemical composition of the corrosion products was studied by X-ray
diffraction, infrared spectrometry, and electron spectroscopy for chemical
analyses (ESCA) techniques. The flow rates of the S02 atmospheres markedly
influenced the corrosion rates. It appears that corrosion rates are related
not only to the SOp concentration in the atmosphere, but also to the supply of
S02 per unit surface area and time. Spraying the samples with distilled water
at intervals substantially increased corrosion.
Sydberger and Ericsson's (1976) analysis of the corrosion product (rust
layer) was based on the concepts of Schwarz (1972) and Barton (1973) that
sulfate is the primary corrosion stimulant in rust formation. Anodic activity
is maintained by the concentration of ferrous sulfate in the electrolyte. An
2
S02 supply of 4 ug/cm /hr at the lowest humidity initiated corrosion at a low
rate. A rise above 50 percent RH increased corrosion markedly. Of particular
10-18
-------
interest was the finding that a variation of the flow rate at 1 ppm (2620
3
|jg/m ) SOp with 96 percent RH gave significant differences in corrosion rates.
This study of the effect of rust on corrosion showed that even at high humidity
and high sulfate content, the corrosion rate decreased to a low level when the
S0? concentration was low.
The reaction between S02 and wet metal surfaces was examined by Vannenberg
and Sydberger (1970). This laboratory study involved the exposure of copper,
aluminum, zinc, iron, 18/8 stainless steel, and rusted iron to SOp and oxygen at
high humidity. Under reflux conditions, the products of corrosion were leached
out into the reflux water where pH and conductivity were measured as a function
of time. The experiments with iron, stainless steel, and rust demonstrate
that iron oxides strongly catalyze the formation of sulfuric acid from S02-
With the samples of copper and aluminum, the increase in conductivity was
slight; it appears that these metals do not provide good surfaces for the
oxidation of S0?. Thus, copper and aluminum show better corrosion resistance
than do iron and zinc.
10.2.1.2.2.2 Field Studies. Sydberger, in his review of studies on
corrosion of steel by sulfur pollution, noted that Schikorr found a good
correlation between the corrosion rate and the amount of sulfur compounds
deposited on steel, zinc, and nickel. There was a clear relationship between
corrosion and SCL adsorption on iron samples exposed in the urban atmosphere
of Stuttgart. Several studies have established that adsorption on a rusty
steel surface did not depend on relative humidity or temperature. Schikorr
reported SO,, adsorption by the Liesegang-bell method (Sydberger, 1976).
For outdoor exposures, the primary rate-controlling factor in the delivery
of pollutants to a surface is eddy diffusion. This value is not constant and
10-19
-------
is a function of the horizontal wind velocity gradient away from the surface.
The transport of a pollutant to a surface is usually expressed as a "deposition
velocity" (u), defined as the flux to the surface divided by the ambient
pollution level at some specific measuring height. Reported deposition veloci-
ties for gaseous pollutants have usually been within an order of magnitude of
1 cm/sec. These values are consistent with calculated estimates based on an
analogy with momentum flux and measured wind velocity profiles.
The amount of S0? reaching a steel surface depends on wind direction,
wind velocity, and the orientation of the surface to the emission source. The
concept that S02 deposition varies with flow direction and velocity suggests
that data on concentration alone cannot be used to determine the supply of SOp
to metal surfaces, therefore surface adsorption methods like the Liesegang-bell
and the lead candle method may provide valuable information in relating supply
of sulfur oxides to metal surfaces (Sydberger, 1976). Upham's (1967) work
indicated, however, that corrosion of mild steel at seven Chicago sites
increased with time and with increasing mean S0? concentration (Figure 10-4).
Haynie and Upham (1971) continuously monitored urban pollutants including
SO^, nitrogen dioxide, and ozone (oxidants) to determine whether previously
unconsidered variables might affect steel corrosion. Their 5-year program,
begun in 1963, involved sites in Chicago, Cincinnati, New Orleans, Philadelphia,
San Francisco, Washington, Detroit, and Los Angeles. They studied three types
of steel expected to show different levels of resistance to atmospheric corro-
sion: (1) a plain carbon steel containing some copper (0.1 percent copper);
(2) a copper-bearing steel (0.22 percent copper); and (3) a low-alloy weather-
ing steel (0.4 percent copper with 0.058 percent phosphorus). The exposure
periods were 4, 8, 16, and 32 months. The same steels were exposed at rural
10-20
-------
18.0
tu 16.0
z
o.
(3
8
14.0
o 12.0
Z
(C
X
o
z
cc
o
C/9
in
O
u
10.0
8.0
6.0
4.0
2.0
3 (months)
I
I
I
I
I
I
I
0.02 0.04 0.06 0.08 0.10
(50) (100) (150) (210) (260)
0.12 0.14 0.16 0.18
(310) (360) (415) (470)
MEAN SO2 CONCENTRATION, ppm ( pig/m3)
Figure 10-4. Relationship between corrosion of mild steel and cor-
responding mean SO2 concentration is shown for seven Chicago sites.
Source: Upham (1967).
10-21
-------
sites as a control. The rural sites proved to have higher than expected
corrosion rates, presumably caused by the transport of SCL from the cities.
Pollution levels were not measured at these sites. Multiple regression
analysis was able to establish significant correlations between average SO,,
concentrations and corrosion of all three steels.
A first consideration was climatic conditions. For metallic corrosion to
occur, a certain level of wetness on the metal surface is required to provide
an electrolyte film in which electrochemical action can take place. The
average humidities recorded by Haynie and Upham were thought to be high enough
to produce this critical wetness threshold. Temperature was a statistically
insignificant variable, because the range of average temperatures was less
than 15 percent (Haynie and Upham, 1971).
Inspection of the monitored SOp and oxidant concentrations revealed wide
variations from site to site. Multiple-regression analysis showed that high
concentrations of oxidants correlated with lowered metallic corrosion rates.
Mansfeld (1980) made observations at nine test sites in and around St.
Louis for 30 months beginning in October, 1974, as part of the Environmental
Protection Agency's Regional Air Pollution Study to determine the effect of
airborne pollutants on galvanized steel, weathering steel, stressed aluminum,
marble, and house paint—essentially the same materials examined in the chamber
study reported by Haynie et al. (1976). During 1975 and 1976, atmospheric
corrosion monitors (ACM) of the type described by Mansfeld and Kenkel (1976)
were installed at four sites to measure time of wetness. Each ACM consists of
a copper-zinc or copper-steel couple that registers current flow when an
electrolytic path forms between the two plates as a result of deposition of
water from the air, dew, or rain on corrosion products. The ACM measures the
10-22
-------
time that the panel is wet enough for the electrochemical mechanism of corrosion
to occur. Parameters measured in Mansfeld's study included the following:
wind speed, wind direction, temperature, ozone concentration, total hydro-
carbon concentration, total sulfur and NO concentration, hydrogen sulfide
/\
concentration, sulfur dioxide concentration, relative humidity, sulfate
concentration, nitrate concentration, total suspended particle concentration,
and time of wetness. Mansfeld determined weight losses for galvanized steel,
weathering steel, house paint, and marble; he removed aluminum tension samples
after failure. Concentrations of SO,, measured by Mansfeld (1980) were generally
an order of magnitude lower than the 130 ppb concentrations reported by Upham
(1967) at urban sites in St. Louis.
Mansfeld's data show that damage to a particular material does not
necessarily occur at the same corrosion rate at each site. Preliminary
statistical analysis of the results failed to show significant correlation
between corrosivity and pollutant concentration. There was substantial error
in the measurement of relative humidity, an extremely important corrosion
variable. This makes data interpretation difficult; more sophisticated
statistical techniques are now being applied to the data.
In another study (1974), Haynie and Upham observed enameling steel
containing 0.019 percent carbon and 0.028 percent copper at 57 sites in the
National Air Sampling Network (NASN). They measured corrosion by weight loss
and quantitatively determined other pollutants, including gaseous sulfur
dioxide, total suspended particles, and the amount of sulfate and nitrate in
3
the particles. Sulfur dioxide levels ranged from 9 to 374 ug/m , total suspended
particles from 11 to 182 ug/m , and relative humidity from 29 to 76 percent.
The average temperature remained within a fairly narrow range and was considered
10-23
-------
constant. The temperature, the quantity of total particles, and the presence
of nitrate in the particles did not significantly affect the corrosion rate of
steel. The concentration of sulfur dioxide was significant only when sulfate
was not included in the regression analysis. At each site, sulfate content of
the particles and sulfur dioxide concentration were closely related; sulfate
content was used in the analysis of the data. On the basis of this study,
Haynie and Upham derived the following empirical expression to obtain the best
relationship between corrosion of enameling steel and atmospheric SC^ content:
COR = a t* e(a2sul"a2/RH) where COR = depth of corrosion (urn)
3
sul = average level of sulfate in particles (pg/m )
RH = average relative humidity (percent)
t = time a , a-,, a,,, are coefficients of determination.
Sulfate was considered a more accurate proxy for S0? because of the strong
covariance between sulfate and SO,,. Average relative humidity factor is a
substitute variable for the fraction of time the steel is wet.
Considerable effort has gone into isolating environmental variables that
would predict long-term corrosion rates. Empirical expressions for corrosion
of various steels exposed to the atmosphere (see Table 10-1) have been developed
by Oma et al. (1965), Chandler and Kilcullen (1968), Guttman and Sereda (1968),
and Haynie and Upham (1974). These equations may be used to relate reduction
in S02 and sulfates to reduction in corrosion of metals, serving as a basis
for a benefit appraisal. The effects of various particles containing S0? and
sulfate on the corrosion of iron are illustrated in Figure 10-5 (from Rosenfeld,
1973).
Matsushima et al. (1974), in studies of low-alloy weathering steels,
considered the impact of the washing action of rain, the ease with which water
10-24
-------
TABLE 10-1. SOME EMPIRICAL EXPRESSIONS FOR CORROSION
OF EXPOSED FERROALLOYS
Exposure
Material Site Duration Empirical Equation
Steel A Sheffield 1 year y = 0.51 + O.Olx
England
Parameter Units
y = corrosion rate
In nils/year ,
x = S0» In ug/m
Source
Chandler and
Kilcullen
(1968)
Note/Comments
Authors stated that SO. and smoke
has a Major Influence On the corrosion
rate of steel and accounted for about
50% of the variations found at the
different sites. Other factors, such
as time of wetness, were found equally
Important In determining the corrosion
rate of steel.
95X confidence limit * 0.75 mils for
any point on regression.
Steel B
Enameling
steel
Sheffield
England
NASN
sites
1 year
1-2
years
y = 0.82 + 0.006x
cor = aoV~t [e
-------
TABLE 10-1. (Continued)
Exposure
Material Site
Enameling NASN
steel sites
Steel Ottawa
Duration
1-2
years
1-12
•OS.
Empirical Equation Parameter Units
cor = 325 n t°-00275S02-<163-2/RH>Vameter units
same as for previous
equation
y = -0.572 + 1.69B + 0.215 C - 0.268B2 + 0.174AB
y = corrosion loss of
Source
Haynie and
Upham
(1974)
Guttman and
and Sereda
(1968)
Note/Comments
Sul and SO, relationship defined as
sul = 8.9 * 0.0429 SO,
± 2S = 8.2 *
Authors noted that this
equation and others derived fro«
the same base equation do "not
o
I
ro
steel in g/panel
A = (time of wetness,
days -14.3)75.0
B =temperature,
°F -5.25)/15.0
C = (SO,, ppm -0.0202)7
0.024 ^
enable one to identify the atmo-
spheric factor which exerts the aost
critical effect on corrosion or to
observe how the others modify this
effect".
-------
2.4
2.0
1.6
U
f
13
0.8
0.4
O 0.01% so2
Q AMMONIUM SULFATE ALONE
A AMMONIUM SULFATE + 0.01%
• CHARCOAL ALONE
g CHARCOAL + 0.01% SO.,
A CHARCOAL + 0.01% SO-
Ill
01530 506070809099
RH,%
1
0
1
10
I
20
I
30
I
40
I
50
I
60
I
70
I
80
I
90
I
100
EXPOSURE TIME, days
Figure 10-5. Effects of particles on the rate of iron corrosion are
shown for: 1, charcoal alone; 2, ammonium sulfate alone; 3, 0.01
percent SO2; 4, charcoal + 0.01 percent SO2; 5, ammonium sulfate
0.01 percent SO2; 6, charcoal + 0.01 percent SO2.
Source: Adapted from Rosenfeld (1973).
10-27
-------
would drain off the surface, and the drying effect of sunlight to determine
the effect of these variables on the retention of particles that influence the
electrolytic corrosion mechanism and the time of wetness. The authors hypoth-
esized that the geometry of unpainted weathering steels may not favor the
development of a protective oxide film of rust. The model structure used in
the exposure trials contained horizontal and inclined roofs, vertical wall
panels, and window frames. Two sites were chosen: an industrial location and
a residential site in the Kawasaki area, which has a cold, dry winter and a
hot, humid summer.
The results show that the successful use of weathering steel is related
not only to the severity of pollution but also to the specific interplay
between shelter and the uniform washing action of rain. Thus, for areas in
which the structural factors are unfavorable, the optimum rust film is slow to
form and may deteriorate. Rust films develop and are then destroyed, and the
surface never develops a protective film. Generally, boldly exposed surfaces
such as horizontal or inclined roofs show the least corrosion.
10.2.1.2.3 Nonferrous Metals. Sydberger and Vannenberg (1972) examined the
influence of relative humidity and rust on the adsorption of sulfur dioxide on
metal surfaces, using radioactive sulfur. The concentration of S0? was 0.1
ppm (262 ug/m ), and relative humidity was varied between 50 and 98 percent.
Polished and preexposed samples of iron, zinc, copper, and aluminum were
compared for their adsorption properties. Iron, zinc, and copper were pre-
exposed to S02 concentrations (0.01 percent or 2.6 x 105 pg/m3) at 98 percent
RH and 22°C for 3 hr. The aluminum samples were preexposed for 30 hr. The
principal corrosion product identified by X-ray diffractometry was hydrated
metal sulfate. Exposures were made in an atmosphere containing 1.0 x 10"5
10-28
-------
3
percent (262 |jg/m ) SCL at relative humidities ranging from 50 to 98 percent.
Adsorbed SCL was measured at 30-min intervals with a Geiger counter.
The corrosion rate at 90 percent RH was initially high for zinc and
copper but quite low for aluminum. Adsorption of S0? on preexposed iron
samples was high. At 80 percent RH, almost all of the S0? was adsorbed. The
high adsorption rate is perhaps explained by the rapid oxidation of adsorbed
sulfur dioxide caused by the catalytic effect of the rust. The initial rate
of adsorption on polished iron below 80 percent RH is related to the absence
of corrosion; however, at increased humidity, corrosion is initiated and the
adsorption rate increases.
Of particular significance is the observation that adsorption takes place
at humidities below the critical humidity (Sydberger and Vannenberg, 1972).
This finding suggests that SO,, will be adsorbed on a rusty iron surface during
periods of low humidity and will affect the corrosion rate as humidity rises.
The critical humidities for nonferrous metallic surfaces, as summarized from
Rosenfeld (1978) and MAS (1977), appear on Table 10-2. The corrosion products
of copper and aluminum have an extremely low adsorption capacity below 90
percent RH, confirming the lower sensitivity of these metals to corrosion by
S0? (see Figure 10-6, from Sydberger and Vannenberg, 1972).
TABLE 10-2. CRITICAL HUMIDITIES FOR VARIOUS METALS
Metal Critical humidity, % RH
Aluminum 75-80
Brass 60-65
Copper 65-70
Nickel 65-70
Zinc 70-75
10-29
-------
I
M 9
o 2
CD
OC
O
I I
I I
34567
EXPOSURETIME.hr
COPPER
ALUMINUM
10
Figure 10-6. Adsorption of sulfur dioxide on polished metal surfaces
is shown at 90 percent relative humidity.
Source: Adapted from Sydberger and Vannenberg (1972).
10-30
-------
Aluminum is generally considered to be corrosion resistant. It forms a
protective film of aluminum oxide which is not dissolved at low concentrations
of acid sulfate particles. When the film becomes contaminated with dirt and
soot particles, there is a change in surface appearance characterized by
mottling and pitting. Simpson and Horrobin (1970) reported that aluminum
undergoing long exposure in industrial areas displayed white areas of
crystalline corrosion products. Aluminum surfaces exposed for periods of more
3
than 5 years to a sulfate concentration of 0.14 ppm (550 ug/m ) had pits as
deep as 14 mils (0.36 mm).
Fink et al. (1971) summarized measured corrosion rates (mils per year)
3
and depth of pitting (mils) for rural, mild industrial (30 ug/m or 0.01 ppm
o
S0?), normal industrial (370 ug/m or 0.14 ppm SO,, and 80% RH), and severe
industrial areas. Their overall conclusion was that although some loss of
thickness occurred in the first 2 years, structures composed of aluminum and
its alloys are resistant to air pollutants.
In another study, Haynie (1976) found that stressed aluminum specimens
exposed to S0? at concentrations of 79 and 1310 ug/m (0.5 ppm) lost approxi-
mately 8.6 and 27.6 percent of their bending strength, respectively. He also
noted that 7005-T53 high-strength aluminum alloy tubing, which contains very
little copper, is susceptible to stress-corrosion cracking in industrial
environments.
Abe et al. (1971) exposed copper and copper alloys for 2 years in marine,
rural, highly industrial, and urban areas in which there was great variation
in pollutant and salt content. Analyses of the metallic surface deposits
showed the presence of basic sulfate, sulfide, and chloride of copper. The
10-31
-------
green patina on copper was analyzed and determined to be basic copper sulfate
in urban areas and basic copper chloride in seacoast areas. These surfaces
were protective against further corrosion.
The formation of these basic copper salts, according to Simpson and
Horrobin (1970), can take up to 5 years and will vary with the concentration
of sulfate or chloride particles, the humidity, and the temperature. They
reported the corrosion rate of copper to be 0.9 to 2.2 urn/year in industrial
atmospheres, compared with 0.1 to 0.6 urn/year in rural areas.
The high corrosion resistance of nickel and copper compared with unalloyed
steel is attributed by Sydberger (1976) to the ability of these metals to form
a layer of insoluble basic sulfate that protects the metal surface. Such
layer formation does not occur on steel because of the action of sulfuric acid
from the oxidation of S02 in an oxidative hydrolysis of ferrous sulfate.
10.2.2 Protective Coatings
Some materials are coated for protection against the effects of exposure.
The coatings provide either sacrificial protection or barrier protection. In
galvanization, zinc is applied to ferrous metal for sacrificial protection.
Thus, while the galvanized surface may suffer corrosion damage, it helps to
prevent rusting of steel products such as gutters, cables, wire fencing, and
building accessorites. Barrier protection is provided by varnishes, lacquers,
and paints by sealing the underlying surface material against intrusion by
moisture.
10-2.2.1 Zinc-Coated Materials—Zinc is used to protect steel because this
coating is fairly resistant to atmospheric corrosion. Zinc is anodic with
respect to steel; when zinc and steel are in contact with an electrolyte, the
electrolytic cell provides current to protect the steel from corrosion with
some oxidation of the zinc.
10-32
-------
Zinc is generally exposed as a protective coating in the form of galvanized
steel products such as gutters, cables, wire fencing, and building accessories.
It is used to protect steel since a zinc coating is fairly resistant to atmo-
spheric corrosion. Zinc is anodic with respect to steel; when zinc and steel
are in contact with an electrolyte, the electrolytic cell provides current to
protect the steel from corrosion with some oxidation of the zinc.
Guttman (1968) carried out a long-term exposure of zinc panels with
measurement of the atmospheric factors. He found that zinc is corroded by S0?
and that time of wetness and concentration of S0? are the major factors that
determine the rate of corrosion.
Kucera (1976) noted strong correlations between the corrosion rate and
(1) the adsorption of S0? on zinc surfaces and (2) the concentrations of S0?.
Fleetwood (1975) conducted 5-year exposure studies of zinc and iron in a
number of locations ranging from dry tropical to industrial. He estimated the
service life of galvanized steel to be 15 to 20 years in an industrial area
containing pollutants, and 300 years in a dry tropical unpolluted area.
Haynie and Upham (1970) exposed zinc panels in eight cities, continuously
monitoring SCL concentration and collecting meteorological data, including
temperature and relative humidity, from the nearest weather stations. They
developed the following empirical equation, which correlates corrosion rate
with average sulfur dioxide concentration and relative humidity: Y = 0.001028
(RH - 48.8) S02, where Y = zinc corrosion rate (um/yr), RH = average annual
3
relative humidity, and S0? = average SCL concentration (ug/m ). The regression
intercept indicated that no corrosion would occur below an average relative
humidity of 48.8 percent. This expression gave a reasonably good linear fit
with the experimental corrosion results obtained by Haynie and Upham for SO,,
10-33
-------
concentration and relative humidity. Based on the St. Louis study results
(Haynie, 1980), the corrosion of small steel specimens of zinc or galvanizing
steel follows the relationship:
C = 2.32 t + 0.134 v °'781 • S09 • t
Z w £- w
t = time-of-wetness in years,
w
v = wind velocity in m/s, and
S0£ = ug/m3 S02
A damage coefficient (for purposes of the chapter, damage = any measurable
adverse effect) for a pollutant can be calculated from the stoichiometry of a
reaction and the deposition velocity. For the reaction between SO^ and zinc
to form zinc sulfate, the coefficient is 0.045, when the zinc corrosion rate
is expressed in micrometers per year, SCL in micrograms per cubic meter, and
the deposition velocity (u) in centimeters per second. For a small zinc or
galvanized steel sheet specimen, the damage coefficient for S02 is calculated
n 7ft
to be 0.0123 cv . At a wind velocity of 4 m/sec, the value is 0.0363 (um/yr)/
3
(ug/m ). For the same conditions, a similar calculation for marble yields a
3
coefficient of 0.136 (um/yr)/(ug/m ).
Haynie (1980) restudied the results of six exposure investigations to
relate the corrosion of zinc and galvanized steel to the concentration of
sulfur dioxide. Each investigation was different and the data were evaluated
differently; thus, no direct comparison of the results as they were published
was possible. Haynie reevaluated the data from each study, using the same
technique in order to make comparisons.
The damage coefficients obtained from all of these studies are compared
in Table 10-3. The S02 coefficient for the chamber study is low, whereas the
analogous coefficients for the CAMP (Haynie and Upham, 1970) and ISP (Cavender
10-34
-------
et a "I., 1971) studies are high and agree with each other. The remaining three
SOp coefficients are in good agreement. The average of the time-of-wetness
coefficients are within a range of + 0.75 from a mean of 1.73 um/yr.
The specified thickness of galvanized coating varies with intended use.
Furthermore, the thickness of a particular coating varies considerably from
one point to another. Bird's measurements revealed that 5 percent of coating
thickness measurements varied from the mean by more than 46 percent (Bird, 1977).
TABLE 10-3. EXPERIMENTAL REGRESSION COEFFICIENTS WITH
ESTIMATED STANDARD DEVIATIONS FOR SMALL ZINC AND
GALVANIZED STEEL SPECIMENS OBTAINED FROM SIX
EXPOSURE SITES
Study
Time-of-wetness
coefficient,
um/yr
S09 coefficient,
(um/yr)/(ug/nO
Number of
data sets
CAMP (Haynie and
Upham, 1970)
ISP (Cavender et al.,
1.15 + 0.60
0.081 + 0.005
37
1971)
Guttman,
Guttman
1968
Chamber
et al. ,
St. Loui
1980)
1968
and Sereda,
study (Haynie
1976)
s (Mansfeld,
1.
1.
2.
1.
2.
05 +
79
47 +
53 +
36 +
0.
0.
0.
0.
96
86
39
13
0.
0.
0.
0.
0.
073
024
027
018
022
+ 0.
+ 0.
+ 0.
+ 0.
007
008
002
004
173
>400
136
96
153
10-35
-------
Haynie confirmed this variability with 475 thickness measurements on a single
galvanized steel sheet. The life of a coating is generally proportional to
its thickness; thus, rusting of the substrate steel will occur first at the
thinnest spots and last at the thickest spots.
The American Society for Testing and Materials (ASTM) as reported in
Haynie (1980) has observed rusting at thin spots on galvanized steel wire,
fencing, and sheet exposed to various types of atmospheres over many years.
Some of their exposures were started in 1916 and were continued until the test
could reveal no additional information. In the case of sheet, the product was
completely rusted and showed perforations. In general, the amount of corrosion
at each site varied linearly with time. Corrosion rates at each site were
calculated on the basis of time to first rust and time to complete rust for
various zinc thicknesses, assuming +40 percent thickness variability.
Originally, State College, Pa., was selected by ASTM as a control site
representing a "clean" rural environment; however, the corrosion is higher
there than at five other rural locations including the rural-marine environment
of Santa Cruz, Calif., where high relative humidities are expected to accelerate
corrosion. It is possible that the State College environment is influenced by
pollution from Altoona, which is 40 miles to the southwest (the prevailing
upwind direction). ASTM made no pollution measurements but recognized the
effects of "industrial" and "severe industrial" environments.
Zinc corroded nearly twice as fast on wire and fencing as it did on
sheet, a finding that is consistent with the theoretically predicted effects
of surface configuration on S02 deposition velocity. One would expect a
greater deposition velocity onto fencing than onto sheet material. ASTM noted
that fencing corrodes less near the ground than it does near the top because
10-36
-------
wind velocity increases with height, with a resultant increase in deposition
velocity.
The average corrosion rates shown in Table 10-4 correspond to actual
corrosion rates that are two to four times greater when the substrate is wet.
Theoretical calculations indicate that the average SCL levels at the Pittsburgh
site over the long period of exposure were between 350 and 700 ug/m . The
3
average at the Altoona site could have been as high as 1000 ug/m .
From the relationships between theoretical and experimental studies,
Haynie (1980) concluded the following:
1. Both short-term laboratory evidence and long-term exposure results
for galvanized steel are consistent with theoretical considerations.
2. Damage functions for some materials can be calculated from theoretical
relationships that consider factors controlling time of wetness and
pollutant fluxes.
3. Wind speed and material geometry should be considered in evaluating
atmospheric corrosion effects.
Marker et al. (1980) examined the variables controlling the corrosion of
zinc by S0? and sulfuric acid. They used an aerosol flow reactor. Under
steady-state conditions, they made the following measurements:
Environmental Measurements
o Percent RH and temperature (at two points)
o Average flow velocity (Pitot tube)
o Flow velocity profile (recorded when a steady state had been estab-
lished),
Aerosol Measurements
o Aerosol size distribution and number concentration determined at
intervals during test by TSI 3050 analyzer
o Two total-mass filter samples collected
o Total-deposition sample collected on aluminum foil throughout each
experiment
o TEM deposition grid samples collected continuously
o X-ray photoelectron spectroscopy samples (both zinc plate and aluminum
foil) collected continuously during experiment
10-37
-------
TABLE 10-4. CORROSION RATES OF ZINC ON GALVANIZED STEEL PRODUCTS EXPOSED TO
VARIOUS ENVIRONMENTS PRIOR TO 1954
Mean corrosion rate and estimated standard
deviation, (jm/year
Site
Sheet
Wire and fencing
Altoona, PA
Pittsburgh, PA
Sandy Hook, NJ
Bridgeport, CT
Lafayette, IN
Ithaca, NY
State College, PA
Ames, IA
College Station, TN
Santa Cruz, CA
Manhattan, KS
Davis, CA
7.57 + 0.54
5.63 + 0.34
2.74 + 0.30
1.27 + 0.29
10.86 + 1.02
4.37 + 0.45
4.25 + 0.44
2.94 + 0.34
2.68 + 0.42
2.48 + 0.24
1.68 + 0.19
1.22 + 0.43
0.83 + 0.26
0.79 + 0.27
0.76 + 0.42
Source: Haynie (1980)
10-38
-------
Corrosion rate measurements were recorded continuously by an ACM detector, which
had been pretreated with either 0.1 N sulfuric acid or ammonium sulfate.
Experimental conditions were selected from the following ranges:
Temperature, °C 12-20
Relative humidity, % 65-100
Mean flow velocity, m/sec 0.5-8
Sulfur dioxide concentration, ppb (volume) 46-216
Sulfate aerosol mass concentration, mg/m 1.2
Aerosol size distribution, urn diameter 0.1-1.0
The factors controlling the rate of corrosion in Marker's study were
relative humidity, pollutant flux, and chemical form of the pollutant. Cor-
rosion occurred only at relative humidities high enough (more than 60 percent)
to wet the surface; temperature did not appear to be a controlling factor
within the range 12-20°C. The rate of corrosion for S0? was about twice that
for sulfuric acid at an equivalent flux.
The investigators noted deposition velocities of 0.07 cm/sec for 0.1-1.0
urn sulfate aerosols and 0.93 cm/sec for SO,, at a velocity of 35 cm/sec. These
factors indicate that the effects of SOp will dominate the effects of HUSO, in
most urban areas.
10.2.2.2 Paint Technology and Mechanisms of Damage—The specific action of
SOp and particles in paint deterioration has received comparatively little
attention from the paint industry. There are at present no ASTM proce dures
for evaluating the effect of S0?, nitrogen dioxide, and/or ozone on paints.
Degradation by ultraviolet light has received major emphasis; outdoor test
stations have been located in Florida and in Arizona, where SOp levels are
low.
The erosion of paint is measured by loss of thickness of the paint layer,
which can result from the chemical action of S02 and the action of light and
ozone to cause degradation of the polymer. Film erosion rates are used by
paint manufacturers to determine the fail point for their formulations. Film
10-39
-------
formers have been developed that are resistant to acids, e.g., epoxies,
urethanes, vinyls, and chlorinated rubbers. Protective coatings for metals
are applied over primers that contain anticorrosive metallic compounds. Alkyd
is often used as the top coat. Oil-base and vinyl-acrylic latex paints contain
groups that may be more susceptible to sulfur acids.
In the formulation of paints, the ratio of pigments to film formers is of
importance in the overall properties of gloss, hardness, and permeability to
water. If the amount of film former is too low, soiling is increased and the
paint may lose the film flexibility needed for durability and become brittle.
Condensation of water on the surface to which the paint layer adheres
causes a separation (peeling) of the paint film from the surface. The
permeability of paints to water has been reported by Hay and Schurr (1971).
Pores occur in many kinds of film as a result of shrinkage of the resin on
setting, solvent or water evaporation, and leaching out of soluble chemicals
in the film. High-permeability films are desirable for surfaces that must
allow water to pass through, such as wooden exterior walls behind improperly
ventilated kitchens. Low-permeability coatings are needed to protect surfaces
that corrode when repeatedly kept moist. The low permeability of chlorinated
rubber is advantageous for use on concrete, an application it shares with
styrene-acrylic.
Hay and Schurr (1971) found that the use of primer and top coat having
the same low pigment volume concentration is effective in preventing rust.
When the relative amount of pigment and extender in the primer is increased,
its ability to diffuse water also increases. When the top coat retards the
diffusion of water out from the primer, the water in the primer is trapped and
tends to cause corrosion, mildew, peeling, and blistering.
10-40
-------
Paint films permeable to water are susceptible to penetration by sulfur
dioxide and sulfate aerosols. The absorption of S0? was observed by Holbrow
(1962), who found sulfites and sulfates in paint, and by Walsh et al. (1977),
who used radioactive SO,, to determine rates and saturation values for SCL
absorption. Paint absorbed S02 more readily than did wool carpeting or wallpaper,
Exposure to sulfur dioxide under laboratory conditions has been shown to
affect certain wet paint films. Holbrow (1962) found that the drying time of
linseed, tung, and certain castor oil paint films increased by 50 to 100
percent on exposure to 2620 to 5240 (jg/m (1 to 2 ppm) S0?. The touch-dry and
hard-dry times of alkyl and oleoresinous paints with titanium dioxide pigments
were also reported to increase substantially; however, the exposure time of
the wet films was not reported. Analysis of the dried films indicated that
S0? had chemically reacted with the drying oils, altering the oxidation-
polymerization process. It was therefore concluded that concentrations of SOp
encountered in fogs or near industrial sites can increase the drying and harden-
ing times of certain kinds of paints.
No studies have been reported on the effects of S02 on the drying of
latex paints, which account for more than 50 percent of exterior household
use. At the time of application, S0? may interfere with the evaporation of
water and the coalescence of the polymer-pigment particles. Water in the
coating reacts with SO,, to form sulfurous acid, which could cause instability
of the protective colloid around latex particles, resulting in flocculation.
Incomplete film formation is thus possible, leading to loss of protective and
esthetic value.
Holbrow (1962) also studied the effects of sulfur dioxide on dried paint
film. In these experiments, paint films were allowed to dry, refrigerated,
and exposed for 15 min to an atmosphere containing 1.2 percent sulfur dioxide.
10-41
-------
The paint films with condensed moisture were finally placed in an accelerated-
weathering chamber. For all paints except a pentaerythritol alkyd paint, the
gloss decreased significantly after 1 day in the accelerated-weathering chamber.
Without the accelerated weathering, the actions of sulfur dioxide and moisture
on the paint films produced only a slight reduction in gloss. Examination of
the films under the light microscope revealed very fine wrinkles. Holbrow
concluded that the sulfur dioxide had sensitized the film, permitting water to
be absorbed during the weathering cycle.
Bluing of Brunswick green paints has been observed during the early life of
the film. Holbrow (1962) reproduced this effect in the laboratory by exposing
the film to sulfur dioxide and moisture and then to warmth and moisture. The
bluing was probably caused by conversion of the lead chromate pigment of the
Brunswick green paints to lead sulfate. Exposure of the film to sulfur dioxide
and moisture only was not sufficient to produce the bluing. Holbrow concluded
that sulfur dioxide could be retained in paint films for a period of weeks;
however, damage (color change) would occur only when the film was exposed to
warmth and moisture.
Svoboda et al. (1973) compared pigmented and unpigmented paint film for SCL
permeability and found that the rate of penetration of SCL into a paint film was
related to the pigment content. Zinc oxide and titanium dioxide pigments caused
a 50 to 70 percent decrease in the rate of penetration of SCL into the paint
film.
Spence et al. (1975) carried out a chamber study of the effects of gaseous
pollutants on four classes of paints formulated for exterior exposure: oil-base
house paint, vinyl-acrylic latex house paint, vinyl coil coating, and acrylic
10-42
-------
coil coating. The house paints were applied to aluminum panels by spraying.
The vinyl- and acrylic-painted panels were cut from coil-painted commercial
stock. The oil-base paint film was 58 urn thick; the acrylic latex, 45 urn; the
vinyl coil coating, 27 urn; and the acrylic coil coating, 20 urn. The exposure
chambers controlled temperature, humidity, S0?, nitrogen dioxide, and ozone.
Each exposure chamber had a xenon arc lamp to provide ultraviolet radiation. A
dew/light cycle was included; light exposure time was followed by a dark period
wherein coolant circulated through racks holding the specimens, thereby forming
dew on the panels. Each dew/light cycle lasted 40 min and consisted of 20 min
of darkness with formation of dew, followed by 20 min under the xenon arc. The
total exposure time was 1000 hr. Damage was measured after 200-hr, 500-hr, and
1000-hr intervals by loss of weight and by loss of film thickness. In evaluating
the data, loss of weight was converted to equivalent loss of film thickness.
Visual examination of the panels coated with oil-base house paint revealed
that all exposure conditions caused considerable damage. The erosion rate
varied from 4.2 to 48.6 urn/year, with an average of 18.2 urn/year. The investi-
gators concluded that S0? and relative humidity markedly affected the rate of
erosion of oil-base house paint. The presence of nitrogen dioxide increased the
weight of the paint film. A multiple linear regression on SO^ concentration and
relative humidity yielded the following relation:
E = 14.3 + 0.0151 S02 + 0.388 RH,
where E = erosion rate in urn/year, SO,, = concentration of SO^ in ug/m , and RH
= relative humidity in percent. The authors reported the 95 percent tolerance
limits on 99 percent of the calculated rates to be ± 44 urn/year.
10-43
-------
The formation of blisters on acrylic latex house paint was noted at the
high S0? levels. The blisters resulted from a rather unexpected severe pitting
and buildup of aluminum corrosion products on the substrate. The paint acted
as a membrane retaining moisture under the surface and excluding oxygen which
would passivate the aluminum. The vinyl coating and the acrylic coating are
resistant to S0? and are used in protective coatings for metals. The visual
appearance of the vinyl coil coating showed no damage. The average erosion
rate was low, 3.29 urn/year. The average erosion rate for a clean air exposure
was 1.29 urn/year. Acrylic coil coating showed an average erosion rate of 0.57
urn/year.
A study of the effects of air pollutants on paint was conducted by Campbell
et al. (1974). The paints studied included oil and acrylic latex house paints,
a coil coating finish, automotive refinish and an alkyd industrial maintenance
coating. These coatings were exposed to clean air, S0? at 262 and 2620 ug/m
3
and ozone at 196 and 1960 ug/m (i.e., equivalent to 0.1 and 1.0 ppm of each
pollutant). Other controlled study variables included light, temperature, and
relative humidity. In addition, one-half of the coatings were shaded during
the laboratory exposures.
The laboratory exposure chamber operated on a 2-hour light-dew cycle
(i.e., 1 hour of xenon light at 70 percent RH and 66°C followed by 1 hour of
darkness at 100 percent RH and 49°C). Coating erosion rates were calculated
after exposure periods of 400, 700, and 1000 hours. Estimated erosion rates
and statistical characterizations of the data are summarized in Table 10-5.
As shown in the table, erosion rates at CL or S02 concentrations of 0.1
ppm were not significantly associated with clean air exposures. At 1 ppm
pollutant concentrations erosion rates were significantly increased with oil
10-44
-------
TABLE 10-5. PAINT EROSION RATES AND T-TEST PROBABILITY DATA
TABLE 10-5a. PAINT EROSION RATES AND T-TEST PROBABILITY DATA
FOR CONTROLLED ENVIRONMENTAL LABORATORY EXPOSURES (67)
Mean erosion rate (mil loss X 10 /hour with 95%
confidence limits) for unshaded panels and
probability that differences exit
Type of paint
House paint
oil
latex
Coil coating
Automotive refinish
Industrial maintenance
Clean air
control
20.1 + 7.2
3.5 + 1.5
11.9 + 2.3
1.8 + 0.8
18.6 + 5.1
SO
(1.0 pfrn)
141.0 + 19.0
99%
11.1 +1.0
99%
34.1 + 4.7
99 %
3.1 + 2.6
75%
22.4 + 7.0
66%
°3
(1.0 ppm)
44.7 + 10.5
99%
8.5 + 5.9
93%
14.9 + 2.5
94 %
5.1 + 1.3
99%
28.1 + 14.0
85%
TABLE 10-5b. PAINT EROSION RATES AND T-TEST PROBABILITY DATA
FOR FIELD EXPOSURES (67)
T5
Mean erosion rate (mil loss X 10 /month with 95%
confidence limits for panels facing south and %
probability that differences exist
Type of paint
House paint
oil
latex
Coil coating
Automotive refinish
Industrial maintenance
Rural
(clean air)
4.3 + 7.5
1.8 + 0.5
2.1 + 0.8
0.9 + 1.1
3.6 + 1.6
Suburban
14.8 +4.9
99.3%
3.0 + 0.7
99.2%
10.0 + 1.9
99.9%
2.3 + 0.7
97.6%
8.2 + 4.2
97.3%
Urban
(SO
dominant)
14.2 +4.9
98.1%
3.8 + 0.3
97.8%
9.5 + 0.8
99.9%
1.6 + 0.4
86.2%
6.6 + 3.9
91.2%
Urban
(oxidant
dominant)
21.0 + 6.2
99.2%
6.5 + 5.6
94.3%
8.8 + 1.7
99.9%
1.7 + 0.4
91.6%
7.8 + 2.4
99.7%
10-45
-------
based house paint experiencing the largest erosion rate increases, latex and
coil coatings moderate increases, and the industrial maintenance coating and
automotive refinish the smallest increases (TRC 1976; Yocom and Upham 1977;
and Campbell et al., 1974). Coatings that contained extender pigments, particu-
larly calcium carbonate, show the greatest erosion rates from the SOp exposures.
Results of field exposures also support these conclusions (Campbell et al.,
1974).
From the above discussion, the following observations can be made regarding
mechanisms of damage to painted surfaces:
1. The major cause of deterioration of paints is sunlight, with some
contribution from ozone.
2. S02 and particles accelerate deterioration of paints, particularly
at high humidity.
3. Laboratory exposures of paints to light, S0?, and humidity can
identify effects of resistant and nonresistant paint formulations,
but the particles and the degree of oxidation of S02 to sulfuric
acid remain undefined.
4. The effect of SO- in the mechanism by which light degrades the
polymeric paint film is not known.
5. Exterior house paints based on alkyds and latexes of vinyl acetate-
acrylic are esters and therefore subject to acid hydrolysis by SCL
and its derived sulfates. Pigment extenders, including calcium
carbonate, also make these paints susceptible to attack by acids.
6. The ease of application and the need for water permeability are the
bases for the continued use of alkyd and latex exterior house paints.
These paints are as a class vulnerable to S02 and particles.
10-46
-------
7. Although laboratory and service tests show a more severe change at
higher SOp concentrations, the action of S0? is primarily catalytic;
thus, SO^ is not consumed by chemical action but remains in the
paint layer.
8. The anticorrosive primers and paints recommended for use on steel
and zinc withstand long exposures.
10.2.3 Fabrics
Fibers that suffer destructive action upon exposure to acids derived from
S0? include (1) cellulosic fibers such as cotton and its close relative
viscose rayon, a regenerated cellulose, and cellulose acetate; and (2) polyamide
fibers such as nylon 6 and 66. Polyester, acrylic, and polypropylene fibers
are not damaged directly by SO,,. -Sulfate particles, which aro-mostly-ammefH-uffl-
•sulfato, damage these Tibet's by acid hydroly-54-s.
The effect of suIfuric acid on industrial fabrics, particularly those
exposed outdoors, is significant. Of the total quantity of fibers produced,
it is estimated that 15 to 20 percent are employed by industry in a wide range
of applications that has been reviewed by Gay and Terekevis (1970).
Brysson et al. (1967) exposed cotton fabrics at 12 different environmental
sites in St. Louis, MO. and Chicago, IL. for a period of up to one year
(1963-64). The seven sites in the St. Louis metropolitan area represented
industrial, urban, suburban, and rural-suburban environments. Four of the
Chicago sites represented downtown, industrial, commercial, and rural environments
An additional site 20 miles southwest of Chicago at Argonne National Laboratory
was also used.
Air pollution in the St. Louis area was assessed using periodic 24-hour
high volume air sampler runs measuring suspended particulate matter and sulfation.
10-47
-------
Sulfation values were determined by the lead peroxide candle method. Monthly
dustfall measurements were also used. Air pollution was determined at the
Chicago sites by two means; a high volume air sampler measured 24-hour total
particulate matter 3 days per week and S02 was monitored by bubble type absorbers
for 24 hours twice a week.
Two fabric types were exposed in this study, scoured cotton, print cloth
and army duck. Study results indicate that there is a significant relationship
between air pollution and strength degradation and degree of fabric soiling.
o
High pollutant levels (mean sulfation 5 mg S03/100 cm Iday and/or S02 concen-
trations of 0.2 ppm or 520 ug/m ) can reduce the effective life to one-sixth
2
when compared with low pollution sites (0.5 mg S03/100 cm Iday and/or 0.02 ppm
or 60 pg/m S02 concentrations). The relationship between suspended particulate
matter and fabric strangth degradation was not as good as that for SO,,. No
correlation between dustfall and strength degradation/effective life was
demonstrated by the study (Brysson et al. 1967).
In a review of the Brysson et al. (1967) study, Upham and Salvin (1975)
report a correlation coefficient of 0.95 for retention of breaking strength
versus sulfation was obtained for cotton duck cloth. The correlation coefficient
for the thinner cotton print was 0.96. Of all the pollutants measured, SO-
was most responsible for causing fabric damage (Upham and Salvin, 1975).
10.2.4 Building Materials
The deterioration of inorganic building materials occurs initially through
surface decay. Moisture and salts are the most important factors in building
material damage. The mechanism of damage from air pollution involves the
formation of salts from reactions in the material. Subsequently, these surface
salts dissolve in moist air and are washed away by rainfall. The components
10-48
-------
of inorganic building materials can react with sulfur dioxide, sufates, and
other particulate matter. The role and levels of these pollutants associated
with the deterioration is assessed in the following sections (Winkler, 1975;
Arnold et al. 1977).
10.2.4.1 Stone—Certain types of building stone adsorb sulfur dioxide and
undergo chemical changes that weaken the material and lead to erosion. Par-
ticles soil the stone surface and act as nuclei for absorption of sulfate
aerosols, which react chemically and produce efflorescence and spalling.
Calcium carbonate, a constituent of various stones including marble,
sandstone, and limestone, reacts to form calcium sulfate and carbon dioxide.
Magnesium carbonate reacts with SO- to form magnesium sulfate. The end products
are the relatively water-soluble calcium sulfate, magnesium sulfate, and
calcium bicarbonate.
Sengupta and DeGast (1972) noted that SCL adsorption also causes physical
changes in stone involving porosity and water retention. Removal of calcium
carbonate changes the physical nature of the stone surface. The hard, nonporous
layer that forms as a result of alternate freezing and thawing may blister,
exfoliate, and separate from the surface. If the stone contains some substances
that are unaffected by S0~, the surface deteriorates unevenly. The conversion
of calcium carbonate into calcium sulfate, which crystallizes to a product of
much greater volume, results in a type of efflorescence termed crystallization
spalling.
Acidic precipitation also contributes to the weathering process of building
stone in at least two ways, according to Gauri (1979). For example, marble
that is directly exposed to rainfall undergoes nearly continuous erosion as
the acid dissolves the calcium carbonate, allowing calcite granules to break
10-49
-------
away and wash off. Also, the sulfuric acid in acidic precipitation reacts
with the calcium carbonate and forms calcium sulfate, a corrosive salt in
itself. If, however, the marble is under a roof and not directly exposed to
rain, the calcium sulfate will form a hard crust on the surface, which is
often black because of soot in the atmosphere. The formation of a crusty
surface affords no real protection to the marble, however. Instead, the crust
merely allows sulfate salts and acidic moisture to penetrate even further into
the stone and continue the weathering action even longer than they would if
they were exposed to the open air. As a result, the crust and surface layer
of the stone eventually exfoliate.
10.2.4.2 Cement and Concrete—Cement is an alkaline material that reacts with
S0? and suffers erosion and spalling effects; it can be protected by paint.
Concrete is also subject to damage by sodium sulfate. Sulfate-resistant
cement is prepared by reducing the "calcium aluminate" content.
The chemical action of SCL or sulfates on cement and concrete is of a
dual nature. Calcium hydroxide in cement and concrete can be converted to
calcium sulfate, which reacts to form calcium sulfate aluminum hydrate (ettringite),
with a substantial increase in volume. Many dams and culverts are in continuous
contact with sulfate salts, derived from natural soil components. Cement for
dams and culverts requires special formulation for sulfate resistance when
exposed to sulfate concentrations > 200 ppm in water (Nriagu, 1978).
Portland cement, the major active constituent of concrete, is manufactured
by the high-temperature reaction of a mixture of limestone, alumina, silicates,
and iron salts found in clay. Litvin (1968) examined concrete samples containing
Portland cement and marble aggregate with sand at an industrial site in Buffington,
Indiana. Some changes were noted in the marble aggregate, but a more observable
10-50
-------
change was found in the cement portion. Sealants were evaluated as protective
coatings; their use was accompanied in some cases by surface efflorescence.
10.2.5 Electrical Equipment and Components
Robbins (1970) and ITT Electro-Physics Labs (1971) studied the damaging
effects of S02 and particles on electronic components and estimated the cost
of this damage. The report by ITT Electro-Physics Labs considered damage to
11 categories of electronic components for which a literature survey indicated
that sulfur dioxide pollution would be mainly responsible. However, information
gained directly from manufacturers indicated that particles were the major
factor in degradation and failure of electronic components and equipment. The
following five types of damage from particles were reported:
o Interference with the photoresist process to fabricate integrated
circuits.
o Release in a vacuum of gases adsorbed on particles.
o Spot formation on TV screens and cathode ray tubes.
o Creation of microscopic leakage paths in semiconductors and integrated
circuits.
o Creation of gross leakage paths in all electronic equipment.
Reduction of SOp and particulate concentrations would have little effect
on costs for the prevention of corrosion; low concentrations of pollutants
would still require essentially the same protective measures. Corrosion-
resistant metals are used even in environments where air pollution is minimal,
since their cost is far outweighed by the expense of equipment failure. But
at current precious metal prices, alternatives may be sought.
10.2.6 Paper
Modern papers are manufactured from wood pulp, which is
cellulose. On exposure to acids, paper is hydrolyzed and loses strength.
10-51
-------
Spedding et al. (1971), in work with radioactive labeling techniques, determined
that S0? is readily absorbed by paper and oxidized to sulfuric acid by the
metallic impurities in the paper. The reaction may also involve the lignins
in the paper, resulting in the formation of lignosulfonic acids. Walsh et al.
(1977) showed that SOp is rapidly absorbed by uncoated wallpaper and less
rapidly absorbed by vinyl-coated paper.
Sulfuric acid can accumulate in paper at concentrations of up to 5 percent
by weight, according to Ede (1979). Although most paper is used in objects
with a short service life, the preservation of documents has been of concern
in museums and archives. Coating paper with polymers impervious to gases is
an established process. It is, however, aimed more at preventing wear and
soil than at preventing SCL damage.
The preservation of books in libraries is of major concern. The extent
of the problem is emphasized by the estimate that 50 percent of the books
printed between 1900 and 1940 are in need of conservation. The New York
Public Library, conserves books by microfilming, lamination, and electrostatic
reproduction. The library spent $900,000 between 1952 and 1967 to microfilm
books which had deteriorated because of air pollution (Waddell, 1974).
10.2.7 Leather
Leather has a high capacity for absorbing SO^. Spedding et al. (1971)
reported that the rate of S02 diffusion to the leather surface is the control-
ling factor in SQ^ uptake. The formation, in the presence of water, of sulfuric
acid is followed by hydrolysis of the protein (collagen) of which leather is
principally composed.
The destruction of leather by absorption of S02 has long been known and
was described in detail by Prenderleith (1946). The buildup of sulfuric acid
10-52
-------
in aged leathers correlates with deterioration, which can be reduced by inactiva-
ting the sulfate ion and by pH buffering. Deterioration of leather is important
in bookbinding and in leather upholstery; the use of artificial leathers has
reduced damage costs.
10.2.8 Elastomers and Plastics
10.2.8.1. Elastomers—The deterioration of natural rubber and synthetic elas-
tomers under weathering conditions has been studied extensively. Heat, light,
oxygen, certain metallic ions, and particularly ozone cause deterioration, but
there is no mention in the literature of SCL damage to rubber. In fact,
rubber is used as an acid-resistant coating. The problem of determining
ambient air pollution effects on rubber is complicated by the presence of
ozone, which attacks the double bonds in both natural rubber and the synthe-
tics butadiene-styrene and butadiene-acrylonitrile.
Haynie et al. (1976) conducted a chamber study on rubber to determine the
effects of ozone, SO^, and nitrogen dioxide under controlled conditions of
temperature, humidity, and light. Exposures were made at concentrations of
0.1 and 1.0 ppm for each pollutant (in ug/m3; 262 and 2620 for SCk, 196 and
1960 for 0., and 188 and 1880 for NCL). As expected, ozone was responsible for
•3 £.
accelerated cracking of the rubber. Sulfur dioxide did not have any effect.
10.2.8.2 Plastics—Verdu (1974) presented a theoretical study of the effect
of air pollutants on the weathering of plastics. He attributed a direct
deteriorating effect on plastics to ozone and suggested that air pollutants
such as sulfur dioxide may form active compounds through photochemical reactions
leading to oxidation chain reactions. In light-exposure trials, SO^ increased
the rate of polymer degradation of polystyrene.
10-53
-------
10.2.9 Works of Art
The deteriorating effects of SCL and particles are well known to museum
conservators whose function is to preserve and restore works of art. The rate
of pollutant-related deterioration has increased markedly in the last 50
years. The damage is striking in Europe, where ancient buildings, paintings,
frescoes, bronze sculptures, stained glass windows, and marble statuary have
suffered deterioration. Damage occurring in Venice, Florence, Rome, Athens,
London, and Cologne has been attributed to the effect of SOp from industrial
areas in these cities (Yocom and Upham, 1977). The United States is also
concerned about the deterioration of public buildings and monuments. The
National Bureau of Standards was asked by the National Park Service to investi-
gate methods for preservation of stone after erosion was noted in the facade
of the Lincoln Memorial in Washington, DC (Sleater, 1977).
The damage to the Acropolis caused by S0? and SO,, has resulted in a
massive interdisciplinary effort by the Greek government to protect the ancient
buildings from further deterioration (Yocum, 1979). The dome of the cathedral
in Cologne,located in a highly polluted urban area, has suffered serious
erosion of its sandstone due to the reaction of sulfur acids with calcium
carbonate to form calcium sulfate, which is leached out by rain (Luckat,
1976).
Newton (1974) has investigated the cause of deterioration of medieval
stained glass windows. He found that the main cause of decay is the leaching
of potassium ions from the silicate glass by condensed water. Another cause
is S02, which produces opaque white crusts containing CaSO.-hLO and syngenate
(Ca-CaS04-K2S04-H20). The poor durability of medieval glass is due to its high
content of alkaline earths such as lime and magnesia.
10-54
-------
Riedeier (1974) conducted a study of the corrosion of bronze sculpture by
air pollutants. Sulfates were found in the corroded surfaces.
Sayre (1973) examined several cases of damage to Northern Italian frescoes
(paintings on lime plaster). The damage has become most evident in the 20th
century. The paintings show high levels of efflorescent material determined
to be calcium sulfate. Treatment with barium salts produces stable barium
sulfate which contains absorbed SO^. To protect the cleaned surfaces, waxes
were recommended.
Sleater (1977) investigated damage to stone from the action of S0~, salt,
sodium sulfate, and light. Conservation materials including epoxy resins,
fluorosilicates, and silicone resins were evaluated. The conservation methods
recommended to the National Park Service varied with the exposure conditions.
10.3 PARTICULATE MATTER
A report by the National Academy of Sciences (1977) on airborne particles
notes that deposition of dust and soot on building materials not only signifi-
cantly reduces the esthetic appeal of structures, but also, either alone or in
concert with other environmental factors, results in direct chemical attack.
It is difficult to determine the specific types of particles and chemical
constituents that have damaged or soiled a particular structure.
10.3.1 Corrosion and Erosion
Early studies indicated that suspended particulate matter played a signifi
cant role in metal corrosion. Sanyal and Singhania, writing in 1956, termed
the influence of suspended particulate matter "profound." They ascribed the
corrosive effects of particles to (1) electrolytic, hygroscopic, and/or acidic
properties and (2) their ability to sorb corrosive gases, i.e., sulfur dioxide.
It has been pointed out that it is quite difficult to predict corrosion rates
10-55
-------
separately for sulfur dioxide and particulate matter since they frequently
coexist at high levels (Chandler and Kilcullen, 1968). Other field studies
have established no conclusive correlation between total suspended particulate
matter and corrosion (Mansfeld, 1980; Haynie and Upham, 1974; and Upham,
1967), though further analysis of recent data is still under way.
Barton (1973) reported that dustfalls contribute to the initial stages of
corrosion but that their influence becomes less important as a layer of rust
forms. There are two classes of particulate matter that appear to be definitely
associated with corrosion: hygroscopic salts (including those of natural
origin such as sodium chloride, see previous subsection 10.2.1.1.4) and acid
smut.
A review of atmospheric factors affecting metal corrosion provided evidence
for a relationship between salinity and corrosion (Guttman and Sereda, 1968).
Corrosion of metals can be accelerated by deposition of particles due to their
hygroscopic nature. The hygroscopic influence on metal corrosion rates has
been previously discussed in section 10.2.1.1.4. Particles can also disrupt
the protective oxide films formed on metal surfaces such as aluminum and
stainless steel resulting in pitting (MAS, 1977).
Acid smut is highly corrosive, sticky material formed in and emitted
mainly from furnaces burning liquid fuels containing sulfur, notably in power
plants (Ireland et a!., 1968). This material would not usually be considered
suspended particulate matter, as it occurs as large particles or even large
masses which fall out close to the source.
Japanese investigators analyzed a large (>10 drums [sic]) sample of acid
smut and found the sulfuric acid content to be 30 percent (Oyama et al. ,
1974). Damage to painted surfaces, automotive finishes; and even agricultural
10-56
-------
crops can be substantive. As noted in a review of residual oil firing problems,
"public reaction can be quite severe" (Exley, 1970). A report on the status
of "public nuisances" in the electric power industry of Japan reported progress
in determining the cause of acid smut and in developing preventive techniques
(Overseas Public Nuisance Study Mission, 1965).
Tests of quartz particles on steel indicated that particles >5 urn cause
progressively more erosion damage until saturation is reached. Regardless of
particle attack angle erosion varied with a simple power of velocity--2.0 for
small particles and 2.3 for particles > 100 ug (MAS, 1977).
10.3.2 Soiling and Discoloration
Soiling is the accumulation of particulate matter on the surface of a
material. It produces a change in reflection from opaque materials and reduces
light transmission through transparent materials (Beloin and Haynie, 1975;
NAS, 1977).
Soiling due to airborne particles from manmade sources results in increased
cleaning costs for building and other materials and reduction in the useful
life of fabrics.
10.3.2.1 Building Materials—Under high wind conditions, large particles
entrained in the windstream actually result in a slow erosion of surfaces
similiar to sandblasting. Particles also fill surface pores of many sandstones
causing them to become uniformly darkened. Particles can contribute to chemical
decay of marble, limestone and dolomite stone work and concrete structures
because they carry acids and soluable salts (NAS, 1977). Dose-response relation-
ships were developed for suspended particulate matter and various building
materials by Beloin and Haynie (1975). These relationships were based on
exposure studies carried out at sites where suspended particulate levels
10-57
-------
3 3
ranged from an annual geometric mean of 60 ug/m to 250 |jg/m . The authors
suggest that the relationships shown in Table 10-6 can be used in the calcula-
tion of soiling costs due to suspended particulate matter (Beloin and Haynie,
1975).
10.3.2.2 Fabrics—Although particulate matter obviously soils fabrics, researchers
have noted that it is only damaging when the particles are highly abrasive and
the fabrics are frequently flexed. Curtains, hanging in open windows, serving
as filters in polluted areas provide a good example. Weakened as a result of
such exposure, curtains often split in parallel lines along the folds. The
more tightly woven the cloth, the more resistant it is to soiling this physical
damage (NAS, 1977).
Because of soiling, fabrics must be washed more often. Washing reduces
fabric strength, leading to loss of appearance and concomitantly results in
shortened life expectancy. However, other factors, sunlight, water vapor,
SO NO and ozone concentrations are believed to more significantly effect
/\ /\
service life of fabrics. Insolation decoloration is considered to be the most
important service life reduction factor (NAS, 1977). Effects of elevated
sulfur oxide concentrations has been previously discussed.
10.3.2.3 Household and Industrial Paints—Exterior paints can be soiled by
liquids and by solid particles composed of soot, tarry acids, and various
other constituents. Water-soluble chlorides and sulfates of iron, copper,
calcium, and zinc are commonly found in rainwater and in particulate samples
from urban areas. Holbrow (1962) examined the effects of small quantities of
these four salts during laboratory studies of the weathering of paint panels.
The presence of 0.1 ppm of iron in the test water produced yellow staining,
whereas 0.5 ppm of copper produced severe brown staining of the paint panels.
10-58
-------
TABLE 10-6. SOILING OF BUILDING MATERIALS AS A FUNCTION OF SUSPENDED PARTICULATE DOSE.
Material
Independent Variable N
2
Remarks
HI base paint VsP(ug/m3) x t(months) 400 89.43 -0.2768 0.0641 0.000069 7.6510 0.745
"int base paint
Ditto
heltered acrylic "
emulsion paint
crylie emulsion "
paint
hingles SP(|jg/m3) x t(years)
10
! Tingles
Concrete
Coated limestone
oUncoated limestone
c!n Coated red brick
Uncoated red brick
Coated yellow brick
Uncoated yellow brick
Glass
J) x t(months)
Ditto
VO
400
400
720
48
48
160
80
80
80
80
80
80
45
86.13
91.54
90.79
41.69
43.50
41.75
44.57
46.99
12.95
14.88
45.05
43.21
0.2806
-0.2618 0.0571 0.000061 6.8265 0.738
-0.593 0.1156 0.000123 13.8143 0.880
•0.4131 0.0497 0.000026 8.3791 0.902
•0.331 0.1895 0.000312 3.8685 0.884
-0.
-0.
+0.
-0.
-o.
-0.
-0.
-0.
+0.
199
0458
0779
0503
0296
0374
1133
1133
0314
0.
0.
0.
0.
0.
0.
0.
0.
0.
5771
1338
2464
1500
0223
0331
5337
2740
008077
0.
0.
0.
0.
0.
0.
0.
0.
0.
000258
000080
000164
000089
000013
000020
000317
000168
000007
7.
7.
6.
4.
0.
0.
14.
7.
0.
6992
5011
9046
2035
6255
9274
9533
6773
6851
0.
0.
0.
0.
0.
0.
0.
0.
0.
769
143
347
266
459
477
342
503
340
Excludes all dat<
beyond 12 month;
Ditto
Ditto
Excludes two 24
month Tarrant
readings
Ditto
Haze readings
including 3
periods for
right panes
prior to 12
months
Number of data sets (dependent upon the number of controlled variables in the factorial experiment).
Intercept of linear regression.
Slope of linear regression.
Estimated variance of intercept.
Estimated variance of slope.
N,
A,
B,
S '
'B.
3E2, Residual variance (error).
R , Correlation index (fraction of variability accounted for by regression).
Source: Beloin and Haynie, 1975.
-------
The conditions to which the paint panels were exposed and the types of paints
tested were not given. Holbrow stated, however, that the effects may be
expected during actual exterior exposure of paint films.
Finishes on automobiles parked near industrial sites have often been
severely damaged. Staining and even pitting of auto finishes have been traced
to iron particles from nearby industrial operations (Fochtman and Langer,
1957). Cars parked near brick buildings being demolished have been damaged by
alkali mortar dust during humid weather. Repainting of damaged auto finishes
was required because of color changes that were not reversible by washing or
polishing. The auto finishes damaged in these instances were probably of the
lacquer type.
Parker (1955) reported that large numbers of black specks collected on
freshly painted buildings in industrial areas. The exterior surfaces of these
buildings became distinctly soiled and required cleaning or repainting in 2 or
3 years, depending on the particulate concentration in the air. When particulate
matter became embedded in the paint film, the coating was physically and
esthetically damaged. Embedding of particles also provides nucleation sites
at which other pollutants can concentrate. For example, particles on a painted
surface can act as nuclei for absorption of aerosols containing dissolved
sulfates. Cowling and Roberts (1954) suggest that particles promote the
chemical deterioration of paint by acting as wicks to transfer the S0? corrosive
solution to the underlying surface.
10.4 ECONOMIC DAMAGE OF AIR POLLUTION TO MATERIALS—SULFUR OXIDES AND
PARTICULATE MATTER
Economic estimates of the costs attributable to some of the damaging
effects of sulfur oxides and particulate matter on materials are available
from the literature. Some of these estimates were derived directly from
10-60
-------
consumer or business surveys. Others were derived from estimates of maintenance
and replacement costs based upon available damage functions and ambient air
data. Extrapolation of these study results for application to the present
situation is not easily done, and in some cases cannot be done with accuracy,
since both fluctuations in the value of the dollar in the intervening years
and changes in air quality must be considered in any such adjustment of past
reported dollar cost of materials damage. Therefore, in the present document,
all dollar costs assigned to materials damage and soiling are given as reported.
Damage functions have been provided where available; ambient air qualtiy
trends are discussed in Chapter 5; no attempt has been made to perform integration
of the two data sets.
Salmon (1970) cites economic damage from sulfur oxides to the following
materials, listed in decreasing order of the extent of damage: metals, cotton,
finishes and other coatings, building stone, paints, paper, leather. Paint,
zinc, and cement/concrete account for 70 percent ($2.647 billion) of the
estimated annual economic loss of all major materials ($3.8 billion). Carbon
steel, which has virtually no resistance to SO- and sulfate, accounts for $54
million of the total loss. According to this estimate, the annual economic
loss of paint and zinc ($1.873 billion) far exceeds the corrosion costs of the
metal (carbon steel) that these coatings protect.
10.4.1 Corrosion of Metals
Realistic estimation of the economic damage to metals attributable to
sulfur oxides and particles must take into account several factors, including
the costs of specific protective treatment. For metals, these costs include
those for the use of anticorrosive primers, the practice of sandblasting
before painting, and the use of paints that are resistant to acid hydrolysis.
10-61
-------
A recent study published by the U. S. Department of Commerce (Bennett et
al., 1978) estimated that metallic corrosion cost $70 billion in the United
States in 1975. This study used a modified version of the Battelle Columbus
Laboratories National Input/Output Model, and the results were subjected to an
uncertainty analysis by the National Bureau of Standards. The model, which
incorporated a broad range of cost items (e.g., materials, labor, energy, and
technical capabilities), indicated a total annual corrosion cost of $82 billion.
About 40 percent of this cost, or $33 billion, was considered avoidable.
Avoidable costs were defined as those which could be reduced by the most economic
application of available corrosion technology. Adjusted for possible errors,
such as in the treatment of useful lives of automobiles, a total annual cost
of $70 billion was considered reasonable. Uncertainty in the total corrosion
cost figure was estimated at ±30 percent. Analysis suggested that avoidable
costs of metallic corrosion represent about 15 percent of the total, but could
range from 10 to 45 percent.
Roebuck and McCage (1974) estimated that $15 billion in corrosion losses
occur annually in the United States, largely from the corrosion of steel. The
National Commission on Materials Policy estimated that $5 billion could be
saved annually by using known procedures to decrease corrosion of industrial
steel, such as sandblasting the surface before painting and applying two coats
of paint, which would protect the metal for many years with little maintenance.
Fink et al. (1971) estimated that corrosion caused by air pollution of
external metal structures costs $1.45 billion annually, as shown in Table
10-7.
Another method for estimating the economic damage from corrosion is to
determine the annual cost of industrial paints used for anticorrosion systems.
10-62
-------
TABLE 10-7. SUMMATION OF ANNUAL EXTRA LOSSES DUE TO CORROSION DAMAGE BY AIR POLLUTION
TO EXTERNAL METAL STRUCTURES FOR 1970
Steel system or structure
Basis for calculation
Annual
loss in $1000
cr>
GJ
Steel storage tanks
Highway and rail bridges
Power transformers
Street lighting fixtures
Outdoor metal work
Pole-line hardware
Chain-link fencing
Galvanized wire and rope
Transmission towers
Maintenance
Maintenance
Maintenance
Maintenance
Maintenance
Replacement
Maintenance and replacement
Replacement
Maintenance
$ 46,310
30,400
7,450
11,910
914,015
161,000
165,800
111,800
1,480
$1,450,165
Source: Fink et al. (1971). Haynie (1974) estimated that 90 percent of the cost to prevent corrosion
damage cost was attributable to galvanizing expenses.
-------
This cost is estimated by totaling the costs of surface preparation, paint,
and labor. Coatings applied at this combined cost would protect metal structures
against corrosion for about 10 years, whereas "ordinary" coatings of paint
would provide protection for only 2 years.
Painting of structural steel in bridges was investigated by Moore and
O'Leary; the practice involves sandblasting the steel to produce a rust-free
surface and to remove mill scale. Without such surface preparation, water is
immediately absorbed and sets up a corrosion system, rusting occurs, and the
paint surface deteriorates in 2 to 3 years. The metal surface is protected by
a primer that inhibits rust formation, and the primer coat is covered with two
coats of SCL-resistant paint, such as vinyl resin, which is substantially more
expensive than household paint. Banov (1973) estimated the cost of sandblasting
2
at 25
-------
in these low-power circuits, according to Baker (1975). Corrosion failure of
electrical contacts is costly because of additional maintenance of equipment
and in time lost for equipment shutdowns. To reduce corrosion, contacts are
electroplated with corrosion-resistant metals such as gold, platinum, palladium,
and silver. Less expensive metals are susceptible to corrosion failure,
mostly from the action of SOp and HLS. Robbins estimated that 15 percent of
the gold and platinum used in the United States for electrical contacts in
1970 was for the specific purpose of combating SO,, corrosion, with the remainder
going for protection against other environmental pollutants. The use of
palladium in electrical components has presented a problem in that it acts on
compounds derived from plastics to catalyze the formation of an organic polymer
film which acts as an insulator.
In areas where electrical instrumentation and computers are used, air is
dehumidified and purified to help protect against corrosion. Robbins (1970)
suggested that the use of activated carbon filters and high-efficiency fine
particle filters represents a cost attributable to SO,, and particulate contaminants.
as itemized in Table 10-8.
TABLE 10.8. COSTS ATTRIBUTABLE TO S0? AND PARTICULATE CONTAMINANTS
IN THE ELECTRONIC COMPONENTS INDUSTRY
Millions of dollars
1970
Use of precious metals 20
Protective measures—filters and air conditioning 25
Loss due to failures 10
Research 5
Total £0
10-65
-------
10.4.2 Exterior Household Paints
Spence and Haynie (1972) presented a survey and economic assessment of
the deterioration of exterior paints ("trade paints") caused by air pollution.
Included in this category were both oil-base paints and latex paints containing
polyvinyl acetate-acrylic as the binder. The total annual economic damage to
exterior household paints was estimated at $540 million (1972 prices), including
paint loss and a labor factor of three times the cost of the paint.
Salmon (1970) estimated that the annual cost of soiling of household
paint would be $35 billion if surfaces were maintained as clean as they are
in a clean environment. The annual cost of deterioration damage to paints was
estimated to be $1.2 billion. A 1974 study by Midwest Research Institute
recalculated the annual cost of damage to be $22 billion for soiling and $753
million for deterioration. These figures appear to be based on Salmon's
hypothetical situation evaluation, which has been criticized as unrealistic.
With a total cost of $2.5 billion for annual production of household paints,
the damage far exceeds the production cost, even with a labor factor of 6 to 8.
Michelson and Tourin (1967) investigated the frequency of house repainting
as a function of suspended particulate concentration. Questionnaires were
sent to residents of three suburbs of Washington, DC (Suitland, Rockville, and
Fairfax) and two cities in the upper Ohio Valley (Steubenville and Uniontown).
Data were compiled from the questionnaires to show maintenance intervals for
exterior repainting in each of the five communities, but paint types were not
reported. In Steubenville, where the mean annual particulate concentration
was 235 ug/m , repainting occurred about every year. In Fairfax, where the
o
mean annual particulate concentration was 60 ug/m , repainting occurred every
4 years. Thus, maintenance frequency increased as particulate concentration
10-66
-------
increased, as shown in Figure 10-7 (Michelson and Tourin, 1967). A plateau at
the low and high extremes of particulate concentration should be expected.
The results of this investigation suggest that a significant relationship
exists between frequency of repainting and particulate concentration. However,
it would appear that additional maintenance data are needed, particularly for
3
cities with mean annual particulate concentrations greater than 150 ug/m , to
establish a more definite correlation. Any correlation of frequency of repaint-
ing with concentration of particulate matter must take into account the fact
that S02 is usually present in high concentration where particle counts are
high.
Booz Allen and Hamilton (1970), in a study conducted for EPA, reported on
painting maintenance frequencies in several zones of the Philadelphia metropoli-
tan area (see Table 10-11) with different population characteristics, climates,
and types of industry. Socioeconomic factors were delineated by pollution
zone; however, paint types were not reported. The percentage of households
with incomes of less than $6000 increased with pollution level, a finding that
partially explains why there was no statistically significant correlation
between painting frequency and particulate level.
10.4.3 Fibers
Cotton and nylon are subject to damage by acids derived from SOp. This
damage is of major importance to the military and to other users of industrial
2
fabrics. High pollutant levels (mean sulfation 5 mg S03/100 cm /day and/or
SOp concentrations of 0.2 ppm or 520 ug/m ) can reduce the effective life to
2
one-sixth when compared to low pollution sites (0.5 mg S03/100 cm /day and/or
o
0.02 ppm or 60 ug/m SOp concentrations) (Brysson et al. 1967).
10-67
-------
1.50
1.25
I
u
UJ
o
UJ
cc
LL
O
a.
UJ
tt
c
o
E
UJ
X
UJ
1.00
0.75
0.50
0.25
KTEUBENVILLE
UNIONTOWN
— FAIRFAX
SUITLAND
ROCKVILLE
I
I
I
I
0 50 100 150 200 250
ANNUAL MEAN PARTICULATE CONCENTRATION, jig/m3
Figure 10-7. There is a clear relationship between maintenance fre-
quency for exterior repainting and particulate concentration.
Source: Michelson and Tourin (1967).
10-68
-------
The magnitude of the cost of S0? damage to fibers can be developed by
comparing the total quantity of fibers used in industry to the amount with
outdoor exposure where SOp damage to cotton has been demonstrated. Of the
1.257 trillion pounds of fiber used for industrial purposes in 1965, the
Textile Organization reported that 583 million pounds were cotton and that 300
million pounds had the outdoor uses shown in Table 10-9.
TABLE 10-9. AMOUNTS OF COTTON FIBER USED FOR VARIOUS
OUTDOOR PURPOSES
Use Amount, 106 Ib
Automotive upholstery and
seat covers 56
Fire hose 20
Cordage 56
Tarpaulins, tents, awnings, etc. 70
Bags and bagging 63
Miscellaneous (agricultural cloth, flags) 35
Total 300
In a report of a telephone survey of consumer awareness of damage to
textiles due to air pollution, Upham and Salvin (1975) noted that Philadelphia
respondents did not perceive soiling of fabrics as a damage effect. There was
a reluctance to communicate this type of information, which is somewhat personal
10.4.4 Masonry, Cement, and Building Stone
Damage by S02 to masonry, concrete, and building stone containing calcium
compounds has been well established. In concrete, sulfur dioxide reacts with
alkaline conglomerates, resulting in spalling and efflorescence. Protection
against SOp and acidic rain requires treatment of the porous structure with
10-69
-------
special sealers and paints in order to preserve the appearance and prevent
crumbling of the stone. No monetary cost has been assigned to the erosion of
building stone.
10.4.5 Soiling
Studies on soiling have been limited to household cleaning costs. In a
study by Booz Allen and Hamilton (1970), $5 billion for annual household
cleaning costs was attributed to particulate pollution. This amount did not
include laundering, dry cleaning, and personal care items (i.e., face and
hair).
Watson and Jaksch (1978) estimated physical soiling and frequency-of-cleaning
functions for each of the five indoor and three outdoor cleaning and maintenance
tasks shown in Table 10-10, using the study of Beloin and Haynie (1975) to
establish the relationship between level of particulate matter and soiling
rate and the work of Esmen (1973) to estimate various levels of particulate
soiling for rural, suburban, and industrial locations. They determined frequency-
of-cleaning functions from the Booz Allen and Hamilton study (1970), which
surveyed 1090 households in the Philadelphia SMSA during 1969. Table 10-11
gives average pollution and total cleaning and painting expenditures for this
area, and Table 10-12 shows the consumers' gain in Philadelphia from reducing
airborne particle pollution.
From a range of 27 cleaning and maintenance operations, Watson and Jaksch
(1978) designated 11 as sensitive to airborne particle levels. Table 10-13
indicates which operations were emphasized as requiring special attention;
each of these is a low-cost, done-at-home cleaning procedure. Watson and
Jaksch concluded that the frequency of the low-cost cleaning operations depended
on the level of airborne particles but that the frequency of professional
house painting was unaffected by variation in airborne particle levels.
10-70
-------
A survey of commercial buildings occupied by stores was not useful, since
stores are cleaned on a contract basis and the work is done regardless of the
amount of soil that has collected.
The Booz Allen and Hamilton (1970) report has been criticized on the
basis that its analysis of the data did not include other sources of damage
TABLE 10-10. CLEANING AND MAINTENANCE TASKS3
Indoor Outdoor
Painting walls and ceilings Painting walls
Wallpapering Painting trim
Washing walls Washing windows
Washing windows
Cleaning Venetian blinds
Watson and Jaksch (1978)
10-71
-------
TABLE 10-lla.
POLLUTION AND CLEANING AND PAINTING EXPENDITURES FOR PHILADELPHIA
PERCENT OF HOUSEHOLDS IN ZONE PERFORMING TASKS3
o
i
ro
Pol lution
zone
1
2
3
4
1
2
3
4
Average par-
ticulate level ,
Hg/m
61
87
112
133
61
87
112
133
Percent of
households in
zone j out of
all house-
holds3
47.3
23.0
19.1
10.6
47.3
23.0
10.1
10.6
Indoor tasks
Painting
walls and
ceil ings
76.6
72.0
67.9
59.0
Painti
walls
38.6
28.5
11.4
10.4
Wall-
papering
36.9
45.4
43.1
52.6
Outdoor
ng Painti
trim
66.5
68.9
54.5
55.0
Washing Washing
windows walls
97.2 42.7
97.9 41.3
97.0 45.8
98.0 37.1
Tasks
ng Washing
wi ndows
89.5
89.5
86.3
89.3
Cleaning
Venetian
bl inds
34.0
48.2
62.5
59.4
Source: Watson and Jaksch (1978)
-------
TABLE 10-llb.
o
CO
POLLUTION LEVELS AND CLEANING AND PAINTING EXPENDITURES FOR PHILADELPHIA
ANNUAL EXPENDITURE OR E^, MILLIONS OF 1970 DOLLARS3
Pollution
zone
1
2
3
4
Average participate
level pg/m
61
87
112
133
Painting
walls and
ceilings
28.2
12.9
10.1
4.8
Wall-
papering
23.4
14.0
11.1
7.5
Indoor tasks
Washing
walls
9
4.4
3.6
2
Washing
windows
8.6
4.0
3.7
1.7
Cleaning
Venetian
blinds
3.2
2.2
2.4
1.2
Total expenditure or TE.
56
56
Outdoor tasks
19
18
1
2
3
4
Total expenditure or TE.
61
87
112
133
Painting
walls
20.2
7.2
2.4
1.2
31
Painting
trim
24.8
12.4
8.2
4.6
50
Washing
wi ndows
8.6
4.2
3.3
1.9
18
Annual expenditure or E.. is defined PH. PHT../IPH. • PHT-j . TE., where PH. is percent of households in zone j out
.of all households, PHT.l^is percent of households in zone j performing task^-M, and TE. is total expenditure for task i
Source is Booz Allen anii Hamilton (1970) for five of the tasks. Costs for the remaining three were derived as
follows: wallpapering costs are assumed to equal inside painting costs, Venetian blind cleaning costs are assumed
to equal one-half of window cleaning costs, and costs of cleaning windows are assumed to equal costs of cleaning
windows inside.
Source: Watson and Jaksch (1978)
-------
TABLE 10-12. REPORTED GAIN TO CONSUMERS FROM REDUCING PARTICULATE MATTER
(1970 dollars)
Total gain, $ million Gain per household, $
Primary Secondary Primary Secondary
Area standard standard standard standard
Philadelphia
a. = 0.35 14.4 27.5 10 19
a1 = 1.0 42.5 82.6 29 26
an- =2.0 93.2 195.2 63 132
123 SMSA's including
Philadelphia0
a. = 0.35
i
a. =1.0
ai = 2.0
537
1613
3816
919
2830
7268
14
43
101
24
75
192
For the primary standard, gain is from reducing particulate matter from
measured levels in 1970 down to 75 jjg/m . Similarly, for the secondary
standard, gain is from Deducing particulate matter from measured levels
in 1970 down to 60 ug/m . The gain in going from the primary to the
secondary standard is the difference between the primary and secondary
bgains.
Estimates for other SMSA's are made by assuming: (1) total expenditure
for each task in any other SMSA equals expenditure per household for
each task in the Philadelphia region times the number of households in
any other SMSA (the numbers of households by SMSA are taken from County
and City Book; (2) the fractional distribution of total expenditure
across pollution zone (i.e., E../TE.) is the same as that indicated for
Philadelphia; and (3) the distribution of particulate matter in any other
SMSA relative to its mean particulate level is the same as in the Philadelphia
region: AP. = (AP,ph:1]a/meanp ., ) mean. , where AP., is the average
parti cul ateJPeadingJ "in1'tfie jthr2ii)l and kth SMSA, andkmean. is the annual
geometric mean for suspended particulates in the kth SMSA
Source: Watson and Jaksch (1978).
10-74
-------
TABLE 10-13.
RELATIONSHIP OF CLEANING AND MAINTENANCE
TO AIR PARTICIPATE LEVELS
Relationship
Maintenance operation
Sensitive
Insensitive
Inside
Clean and oil air conditioners
Clean furnace
Clean Venetian blinds and shades
Dry clean carpeting
Dry clean draperies
Paint walls and ceilings
Replace air conditioner filter
Replace furnace filter
Shampoo carpeting
Shampoo furniture
Wallpaper walls
Wash floor surfaces
Wash walls
Wash windows (inside)
Wax floor surfaces
Outside
Clean and repair awnings
Clean and repair screens
Clean and repair storm windows
Clean gutters
Clean outdoor furniture
Maintain driveways and walks
Maintain shrubs, flowers, etc.
Paint outside trim
Paint outside walls
Wash automobiles
Wash windows
Wax automobiles
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Source: Watson and Jaksch (1978),
10-75
-------
that might be responsible for extra maintenance such as painting. There is
doubt as to which operations in Table 10-13 are really sensitive to air particu-
late levels. Also, the labor of the homemaker was not added to the cost of
the cleaning materials, and the number of urban homes surveyed was small.
Much effort has been expended on attempts to quantify the cost of soiling
attributable to S02 and particulates. The Beaver Report (1954) suggested an
annual total for damage by all forms of air pollution in Great Britain of 152
million pounds sterling in direct costs, of which 25 million was for laundry,
30 million for more frequent painting and decorating, and 20 million for
cleaning and depreciation of buildings other than houses; thus, about half the
total cost of pollution was attributed to soiling.
Michelson and Tourin (1967) compared the costs of air pollution in the
highly polluted area of Steubenville, Ohio, with those in the relatively clean
Uniontown, PA, area. The per capita costs for inside and outside maintenance
of houses (painting and cleaning), laundry, dry cleaning, and personal care
(hair and facial) were $84 higher in Steubenville than in Uniontown. Cost
figures were based on data obtained from questionnaires, but the results have
been questioned on the grounds that socioeconomic factors influenced responses
and that there were insufficient statistically reliable data.
Narayan and Lancaster (1973) conducted a questionnaire survey in a rural
area and a polluted area in New South Wales, Australia, to determine the
difference in cost of household upkeep. The cost of maintaining a house in
the polluted Mayfield area was about $90 per year higher than in the relatively
unpolluted Rotar area. This cost differential was attributed to the higher
levels of air pollution and airborne particulate matter in Mayfield; however,
the accuracy of the cost data was considered questionable, since the attitude
of the respondents could have introduced a biased point of view.
10-76
-------
Waddell (1974) in his review of the economic damage of air pollution
noted that the Michelson and Tourin (1967) and Booz Allen and Hamilton (1970)
studies considered principally the costs of household cleaning and maintenance.
He questioned the validity of extrapolating the Michelson and Tourin value of
$84 per capita because of insufficient information and socioeconomic problems
in obtaining defensible data. He further pointed out that the Booz Allen and
Hamilton report contradicts the intuitively recognized fact that there are
significant soiling costs associated with airborne particles. In particular,
he stated that soiling costs should include laundering, dry cleaning, hair and
facial care, washing of automobiles, and costs of cleaning commercial establish-
ments and public structures. Waddell (1974) concluded that there are insuffi-
cient data to assess these soiling costs though they "undoubtedly run into the
millions of dollars annually".
Waddell (1974) also reviewed the concept of property value as an estimator,
noting the assumption that the inconvenience of living in a polluted area with
soiling and odors leads to lower property values. He cited Jacksch and Stoevener's
(1970) study in Toledo, Oregon, using dustfall measurements as the variable. Their
hypothesis was that air pollution costs, though recognized, were not quanti-
tatively known, but that this cost was reflected in the value of property.
They found that reduction in property values from increasing air pollution was
greater in the higher priced, newer sections of town than in low-cost housing.
Table 10-14 summarizes the various property value studies that include the
effects of both S0? and particles on the market value.
The economic effects of soiling were examined by Liu and Yu (1976) in a
Midwest Research Institute project undertaken for the EPA's Corvallis Environ-
mental Research Laboratory. The objectives were to generate physical and
10-77
-------
TABLE 10-14. SUMMARY OF PROPERTY VALUE STUDIES
o
O3
Study
Ridker-Henm'ng
Zerbe
Anderson-Crocker
Crocker
Peckham
Spore
City
St. Louis
Toronto
Hamilton
St. Louis
Kansas City
Washington, DC
Chicago
Philadelphia
Pittsburgh
Pollution measure
Sulfation3
Sulfation
Sulfation3
Sulfation
Suspended particles
Sulfation
Suspended particles
Sulfation
Suspended particles
Sulfur dioxide
Suspended particles
Sulfation
Suspended particles
Sulfation
Dustfall
Pollution
coefficient
-0.12
-0.08
-0.10
-0.12*
-0.08
-0.09*
-0.07
-0.06**
0.06**
-0.40
-0.10
-0.12
-0.03*
-0.12
R2
0.94
0.92
0.76
0.82
0.70
0.77
0.76
0.81
Marginal
capitalized
damage
100b
97b
300-700°
470d
600-750°
150-2006
^Single pollution variable probably measures effect^of both sulfation and suspended particles.
Mean change in MPV per change of 0.1 mg SO-/100 cnu/day. ^
°Mean change in MPV per change of 0.1 mg SOV100 cm /day plus 10 |jg/m3/day change in suspended particles.
Mean change in MPV per change of 0.001 ppm/72 hr of SO^ plus 10 |jg/m /day change in suspended particles.
eMean change in MPV per change of 0.005 ppm/day of S0? plus a 5 tons/mi /month change in dustfall.
*Not significantly different from zero at the 0.01 level.
**Not significantly different from zero at the 0.05 level.
Source: Waddell (1974)
-------
economic damage functions, by receptor, for S0? and suspended particles and to
establish some cost/benefit relationships. The study included the effects of
air pollution damage on health, household soiling, materials, and vegetation.
Liu and Yu used the data of Booz Allen and Hamilton (1970) on soiling and
maintenance operations (Table 10-10) to identify and quantify soiling damage.
They surveyed costs for each of nine professional cleaning companies in Kansas
City, and developed a methodology that could be used on a nationwide basis for
estimating damage attributable to soiling by S02 and particles. They calculated
the gross cost of cleaning and the net (extra) cost from increases in suspended
particles using a formula they derived. For these calculations, a suspended
particulate level of 45 [jg/m was chosen as the level necessitating extra
cleaning.
Liu and Yu (1976) derived net and gross household cleaning costs for 65
large cities with populations greater than 500,000 and for 83 medium-size
cities of 200,000 to 500,000. For the nine cleaning operations, the extra
costs for Chicago, New York, and Los Angeles in 1970 were $516 million, $418
million, and $388 million, respectively. The costs for cleaning Venetian
blinds at a unit market value of $3.50 and washing outside windows at $1.50
gave total extra costs of $1.956 billion and $926 million, respectively, for
40 metropolitan areas. Per capita costs for household maintenance activities
ranged from $5 per person in San Antonio, Texas, to $104 per person in Cleveland,
Ohio. These per capita costs were estimated to be in the range of $200 by
Michelson and Tourin (1967), who added other soilage categories such as launder-
ing and personal care into their figures. The total net soilage cost for the
urban areas was $5.033 billion, and the gross soilage damage was $17.367
billion.
10-79
-------
The magnitude of economic damage attributed to soiling appears large.
Some European countries assess damage costs due to pollution as a percentage
of their gross national product. The following equations have been used in
their studies:
NSCO. = b. (TSP-45) • UC • U • HU, and
GSCOi = ai + b.(TSP-45) • UC • U • HU,
where NSCO. is the net (extra) soiling cost, GSCCK is the gross soiling cost,
a. and b. are related to the estimated coefficients for each cleaning task, UC
is the unit market value, U is the number of objects cleaned per house, HU is
the number of people per household, and TSP is the concentration of total
suspended particles. Liu and Yu (1976).
10.4.6 Damage Functions
A reasonable estimate of the economic damage to materials from sulfur
oxides and particulate matter depends on the validity of the physical damage
functions, the distribution of pollutant levels and receptors, and the dollar
value associated with the damaged material.
Gillette (1975) reported significant reductions in economic damage to
materials from sulfur oxides attributable to improvements in existing air
quality levels throughout the United States. Comparing annual S02 concentrations
from more than 200 monitoring sites with the estimated inventory of materials
exposed in the proximity of these sites, he decreased his nationwide estimate
of material damage from more than $900 million in 1968 to less than $100
million in 1972. These estimates, which are probably conservative, were
derived by carefully distinguishing between physical and economic losses and
by attributing current estimates of losses to current exposure levels.
10-80
-------
The distinction between physical and economic damage to materials was
based upon the concept of normal or economic use life of materials. Whereas
physical deterioration to materials may occur at relatively low exposure
levels, economic losses will occur only if the material requires early replacement
or increased maintenance before its normal or economic use life is spent.
Given the prevailing ambient concentrations observed, most materials were not
adversely affected economically except for metallic products which were subjected
to corrosion or paint damage. While material losses were much greater during
the early 1960's the losses in more recent years are substantially less and
reflect the considerable progress that has occurred in improving air quality.
(Gillette, 1975).
Beloin and Haynie (1975) proposed dose-response relationships between
concentration of airborne particulate matter and soiling of building material.
They noted that soiling is a continuous function of time and particulate
concentration; that is, particulate matter at any concentration will eventually
cause soiling.
Damage functions have been derived that indicate that reductions in SCL
and in particulate matter will decrease economic damage. In developing these
o
functions, a particulate matter concentration of 45 |jg/m was selected as the
concentration below which soiling costs would not be perceived as extra costs
from increased cleaning activities. For corrosion of metals, deterioration of
paint films, weakening of cotton fibers, and changes in masonry surfaces, the
catalytic action of sulfates makes it difficult to correlate SCL concentrations
with pollution damage; however, field trials under monitored conditions and
laboratory studies have shown that damage is less where SCL concentrations are
lower.
10-81
-------
The economic damage from S02 and participate matter has been recognized
by industry. The market response is empirical proof that pollution damage
must be counteracted by protective measures, such as controls or use of alternative
materials. In most cases, the cost of replacing a product that has suffered
premature damage is far greater than the cost of protective measures or of
alternative materials not damaged by SO,, and particulate matter.
Physical damage functions that have been reported for various metals and
paints are summarized in Table 10-15. Economic damage functions are presented
in Table 10-16.
10.5 SUMMARY
A principal deleterious effect of sulfur oxide pollution is the corrosion
of metals. SOp-accelerated rusting is an electrochemical process that results
in the formation of metal sulfates. Soluble sulfates in rust can stimulate
further corrosion because of their hygroscopicity and electrical conductivity;
however, insoluble sulfates in the rust layer provide corrosion protective
properties, particularly for steel.
Moisture is a key factor in the corrosion process. Corrosion rates of
metals increase rapidly with relative humidity. On the other hand, steel
surfaces shielded from rain may corrode at a higher rate than those exposed to
rain, which washes soluble sulfate from rust. The influence of temperature on
S02-assisted corrosion of metals is complex and has not been clearly defined.
Alloying steel with small amounts of copper, chromium, and phosphorus
improves corrosion resistance. The high corrosion resistance of stainless
steels incorporating chromium, molybdenum, and nickel is attributed to the
protective properties of the oxide film formed on these alloys. In heavily
10-82
-------
TABLE 10-15. PHYSICAL DAMAGE FUNCTIONS FOR MATERIALS
Material
Dose-Response relationships
oo
OJ
Metals
Steel
Carbon steel
Copper-bearing steel
Weathering steel A
Weathering steel B
Enameling steel A
Enameling steel B
Galvanized steel
Zinc
Paints
Oil-base house paint
Y = 9.013
Y = 8.341
Y = 8.876
F 0.00161 S0?~| r 0.7512 - 0.00582 OX~|
Le ZJ |14.768t) J
[."•
LV-
00161 SO
00171 SO
0045 SO
0.7512 - 0.00582 0
)
0.8151 - 0.00642 0
0.6695 - 0.00544 OX
•3
]
corr = 5.64 SOp + e
(55.44 - 31,150/RT)
w
corr = 183.5 /F,
f (0.06421 sul - 163.21/RHfl
corr = 325 /tie
(0.00275 S02 - 163.2/RH)~|
corr = 0.0187 S02 + e
(41.85 - 23,240/RT)
t
w
Y* = 0.001028 (RH - 48.8) SO,
Erosion rate = 14.323 + 0.01506 S02 + 0.3884 RH
0.91
0.91
0.91
0.91
0.91
0.92
0.61
33 3
corr = corrosion, (jm Y = corrosion, urn Y* = corrosion rate, um/yr SO^ in |jg/m OX = |jg/m Sul = ug/m sulfate
R gas constant (1.98 cal/gm mol/°K) RH in % T = OK t = time of exposure t = years
W
-------
TABLE 10-16. ECONOMIC DAMAGE FUNCTIONS ON MATERIALS3
SDCZ = -23,328.4 + 43.1 ME + 943.3 SO, + 148.1 TSP - 235.0 SUN
(19,929) (3.4)* (171.6)* ^ (356.0)* (1,820.4)
+ 2,679.3 RHM + 21.9 YP R2 = 0.64
(1,750.2) (18.9)
DDCZ = 7,562.2 + 1.4 ME + 30.5 SO, + 47.9 TSP - 76.2 SUN
(6,460.4) (0.1)* (5.5)* Z (11.5)* (59.0)
+ 86.8 RHM + 712.6 YP R2 = 0.63
(56.7) (615.5)
SDCP = -141,199.7 + 577.2 HU + 15.2 YP + 911.3 RHM + 69.1 S0
(259,861.3) (3.4)* (2.6)* (235.3)* (23.2)*
+ 305.3 SUN R2 = 0.995
(245.9)
DDCP = -4,820.1 + 19.7 HU + 0.5 YP + 31.1 RHM +2.3 S0? + 10.4 SUN
(887.2)* (0.1)* (0.08)* (8.0)* (0.8)* * (8.4)
R2 = 0.995
aThe values below the coefficients are standard errors, with * to indicate
that the coefficients are significant at the 1 percent level. -All
coefficients and standard errors are reduced by a factor of 10 .
SDCZ = soiling damage, cost of zinc
DDCZ = deteriorating damage, cost of zinc
SDCP = soiling damage, cost of paint
DDCP = deteriorating damage, cost of paint
ME = no. of manufacturing establishments in metropolitan area
= sulfur dioxide, in ug/m _
= total suspended particulate in mg/m
SUN = possible annual sunshine days
RHM = relative humidity
YP = per capita income
HU = number of households in metropolitan area
10-84
-------
polluted atmospheres, sulfate particles in settled dust can rupture this
surface film, causing pitting.
Many laboratory and field studies have investigated the corrosive effects
of sulfur dioxide and sulfates on ferrous metals. Haynie's chamber studies
confirmed that corrosion is most severe under conditions of high S02 concen-
tration and high humidity. Sydberger's laboratory experiments showed that
corrosion rates are related to the supply of SOp per unit surface area and
that a rise in humidity above 50 percent increases corrosion rates markedly.
Even at high humidity and high sulfate content, the corrosion rate decreased
to a low level when the SOp concentration was low. Sydberger and Vannenberg
established that at relative humidities ranging from 50 to 98 percent, the
principal corrosion product of iron, zinc, copper, and aluminum exposed to SOp
was hydrated metal sulfate. Some adsorption of SOp took place below the
critical humidities (60-80 percent) for all the metals investigated. In
general, copper and aluminum showed better corrosion resistance in the labora-
tory than did iron and zinc.
Sydberger reported good correlation between corrosion rates and the amount
of sulfur compounds on steel, zinc, and nickel during field exposures. The
correlation between ambient SO* and the amount of SOp deposited on metal
surfaces was dependent on both wind direction and velocity. Studies have
shown that eddy diffusion is another factor in SOp deposition. Haynie and
Upham found that the relationship between SOp concentrations and corrosion
rates of steel is complicated by climatic variables and special conditions at
particular sites. Temperature appeared to have little effect. Mansfeld's
10-85
-------
exposure studies with copper-zinc and copper-steel galvanic couples confirmed
the high variability of metallic corrosion rates from site to site and estab-
lished time of wetness as a critical parameter of corrosion.
Haynie and Upham derived a physical damage function relating depth of
steel corrosion to particulate sulfate level as a proxy for S02 and average
relative humidity as a proxy for time of wetness. Oma et al., Chandler and
Kilcullen, and Guttman and Sereda have also developed empirical expressions to
predict long-term corrosion rates of various steels exposed to the atmosphere.
These equations may be used to relate reduction in SCL and sulfate levels to
reduction in corrosion of metals, serving as the basis for a cost-benefit
appraisal. Matsushima et al. demonstrated that the corrosion of weathering
steel is related not only to the severity of pollution but also to the inter-
play of shelter and the washing action of rain.
Nickel and copper are more corrosion resistant than unalloyed steel.
Sydberger attributed this resistance to the ability of these nonferrous metals
to form layers of insoluble basic sulfates that protect their surfaces. Steel
is galvanized (coated with zinc) for corrosion resistance in applications such
as gutters, cables, wire fencing, and building accessories. The key factors
that determine the extent to which zinc is corroded by SO,, are time of wetness
and S02 concentration. Fleetwood estimated the expected service life of
galvanized steel at 15-20 years in a polluted industrial area and 300 years in
a dry, tropical, unpolluted area.
ASTM reported that zinc corroded nearly twice as fast on wire and fencing
than on sheets. Corrosion of the fencing was least severe near the ground.
Haynie (1980), in discussing these results, noted that these findings are
consistent with the predicted effects of surface configuration on S09
10-86
-------
deposition. Marker et al. examined the variables controlling the corrosion of
zinc by sulfuric acid and SO,,. They determined that relative humidity,
pollutant flux, and chemical form of the pollutant were most important. In
these studies, corrosion occurred only at relative humidities high enough
(>60%) to wet the surface. They concluded that S02 corrosion dominates over
H?SO. aerosol corrosion in most urban areas.
Aluminum is generally considered resistant to corrosion because it forms
a protective oxide film that is not dissolved at low concentrations of acid
sulfates or other aerosol particles. Copper corrodes slowly upon exposure to
S02, forming basic sulfates and sulfides in industrial areas, as well as
chlorides in seacoast locations. The resulting patina protects against further
corrosive action.
Many nonmetallic materials are also damaged by sulfur oxides and/or
soiled by particles. These materials include paints and other protective
coatings, fabrics, building materials, electrical components, paper, leather,
plastics, and works of art. The chemical action of SO^ erodes paint layers,
and light and ozone cause degradation of the polymer. Oil-base and vinyl
acrylic latex paints contain chemical groups that may be especially susceptible
to sulfuric acid. Paint films permeable to water may be penetrated by sulfur
dioxide and aerosols containing sulfuric acid, as observed by Holbrow. Holbrow
3
noted that drying times of certain paint films exposed to 2620 to 5240 ug/m
(1 to 2 ppm) SO,, increased by 50 to 100 percent because of a chemical altera-
tion of the polymerization process. Holbrow also found that SO,, could sensi-
tize dried paint film, permitting water to be absorbed during the weathering
cycle, especially at high humidity. Svoboda reported that SO^ penetrated
paint binder films pigmented with zinc oxide and titanium dioxide 50 to 70
percent faster than it did unpigmented films.
10-87
-------
Cotton, rayon, and nylon fabrics are damaged by acids derived from SC^.
Polyester, acrylic, and polypropylene fibers are damaged by ammonium sulfate
particles by acid hydrolysis. SC^-related damage to clothing is negligible
because the acids are neutralized during alkaline laundering. On the other
hand, deterioration of household furnishings such as curtains, draperies,
upholstery, and carpeting may be considerable. Sulfuric acid damages outdoor
industrial fabrics such as ropes, tarpaulins, awnings, banners, flags, tents,
and parachutes.
Certain types of building stone adsorb SCL and undergo chemical changes
which weaken the material and lead to erosion. The end products are the
relatively water-soluble calcium sulfate, magnesium sulfate, and calcium
dicarbonate. Sangupta and DeGast observed that SC^ adsorption on stone leads
to blistering, exfoliation, efflorescence, and spall ing. Concrete, which is
an alkaline material, reacts with SCL and suffers erosion and spall ing if not
protected by paint. Concrete is also subject to chemical damage by sodium
sulfate. Sulfate-resistant cement for use in dams and culverts is prepared by
reducing the proportion of calcium aluminate used in the mixture.
Sulfur dioxide and particles have deleterious effects on electrical con-
tacts in switches, relays, connectors, and computers. To reduce corrosion,
contacts are electroplated with corrosion-resistant metals such as gold,
platinum, palladium, and silver.
Sulfur dioxide is readily absorbed by paper and oxidized to sulfuric acid
by metallic impurities; the paper then hydrolyzes and loses strength. Leather
also has a high capacity for absorption of SCy The material is weakened by
hydrolysis of the proteins that make up the collagens in leather. Verdu
attributed the weathering of plastics in part to the joint action of S0? and
10-88
-------
light. He found that sulfur dioxide increased the rate of polymer degradation
of polystyrene in light-exposure trials.
The damaging effects of SOp and particles are well known to museum conserv-
ators whose function is to preserve and restore works of art. Action of S0?
has been implicated in the deterioration of the Acropolis in Greece and the
dome of a large cathedral in Cologne, Germany. Sulfate damage has been found
in medieval stained glass windows, bronze sculptures, marble and stone statues,
and Northern Italian fresco paintings on lime plaster.
Airborne particles aid corrosion by producing acid electrolytes; by
functioning as nuclei to promote the condensation of water containing S02 or
sulfates; and by forming a solid structure to retain active pollutants such as
chlorides, organic matter, and sulfates. Deposition of dust and soot on
building materials reduces the esthetic appeal of structures and can also
result in erosion and direct chemical attack. Periodic sandblasting is required
to renew the appearance. Cotton, rayon, and polyester fabrics soiled by
airborne particles require more frequent cleaning, which leads to increased
costs and reduces the useful life of fabrics.
Exterior paints are soiled by particles of soot, tarry acids, and various
other constituents such as sulfates of iron, copper, calcium, and zinc.
Staining and pitting of auto finishes has been traced to iron particles from
nearby industrial operations and to alkali mortar dust from buildings being
demolished. Parker reported that numerous black specks collected on freshly
painted buildings in industrial areas, distinctly soiling the exterior surfaces
and necessitating repainting in 2 or 3 years. Cowling and Roberts have suggested
that particles promote the chemical deterioration of paint by acting as wicks
to transfer SO^ to the underlying surface.
10-89
-------
Salmon cites economic damage from sulfur oxides to the following materials,
listed in decreasing order of the extent of damage: metals, cotton, finishes
and other coatings, building stone, paints, paper, leather. Paint, zinc, and
cement/concrete account for 70 percent ($2.647 billion ) of the estimated
annual economic loss of all major materials ($3.8 billion). Carbon steel,
which has virtually no resistance to SO,, and sulfate, accounts for $54 million
of the total loss. According to this estimate, the annual economic loss of
paint and zinc ($1.873 billion) far exceeds the corrosion costs of the metal
(carbon steel) that these coatings protect.
Estimates of the annual cost of corrosion of metals (mainly steel) in the
United States range from $1.5 billion to $85 billion. Robbins estimated in
1970 that $20 million is spent annually for precious metals to combat direct
S02 corrosion of electrical contacts and $40 million for indirect costs
associated with equipment failure and air cleaning. Costs of pollution-caused
soiling and deterioration damage to exterior household paints have been estimated
at $540 million to $36.2 billion (the latter figure has been criticized as
unrealistic).
A 1970 Booz Allen and Hamilton study attributed $5 billion for annual
household cleaning costs to particulate pollution, exclusive of laundering,
dry-cleaning, personal care items, and labor of the homemaker. Watson and
Jaksch, using data from the Booz Allen and Hamilton study, concluded that the
frequency of low-cost cleaning and maintenance operations depends on the level
of airborne particles and that the frequency of professional house painting is
unaffected by variations in air particle levels. Michelson and Tourin determined
that the annual per capita costs for painting and cleaning of houses, laundering,
dry-cleaning, and personal care (hair and facial) were $84 higher (1967 dollars)
10-90
-------
in the highly polluted area of Steubenville, Ohio, than in the relatively
clean city of Uniontown, PA. Their cost figures, based on data from question-
naires, have been questioned; critics suggest that socioeconomic factors
influenced responses and that there were insufficient statistically reliable
data. In a similar survey conducted in 1973, Narayan and Lancaster concluded
that the cost of maintaining a house in the polluted Mayfield area of New
South Wales, Australia, was about $90 per year higher than in the relatively
unpolluted Rotar area. This cost differential was attributed to differences
in airborne particulate matter in the two areas. Waddell reviewed the concept
of property value to estimate economic damage, noting that a polluted area
with soiling and odors may have lower property values. He cited the finding
of Jacksch and Stoevener that reduction in property values due to increasing
air pollutants was greater in the higher priced, newer sections of a city than
in areas of low-cost housing.
Liu and Yu examined the economic effects of soiling in an effort to
generate physical and economic damage functions and to establish some cost/benefit
relationships. The study included the effects of air pollution damage on
health, household soiling, materials, and vegetation. In 1970, extra costs
for nine selected cleaning operations in Chicago, New York, and Los Angeles
were $516 million, $418 million, and $388 million, respectively. The cleaning
costs for Venetian blinds and outside windows were $1.956 billion and $926
million, respectively, for 40 metropolitan areas. Annual per capita costs for
household maintenance activities ranged from $5 in San Antonio to $104 in
Cleveland. In urban areas, costs of soiling related to air pollution was
$5.033 billion, or 29 percent of the total soiling costs of $17.367 billion.
10-91
-------
Many physical and economic damage functions have been developed to estimate
materials damage from sulfur oxides and particulate matter. Their accuracy is
hampered by problems in identifying dose-response relationships for specific
damage from specific pollutants because of many variables influencing exposure
in the environment.
Damage functions indicate that reductions in SCL and particulate matter
will decrease economic damage. Because of the catalytic action of sulfates,
it is difficult to correlate SCL concentrations to deterioration of metal,
paint, cotton fiber, and masonry. Nevertheless, field trials under closely
monitored conditions and laboratory studies have shown that damage to these
materials is less severe where SCL concentrations are lower. In most cases,
the cost of replacing a product that has suffered premature damage is far
greater than the cost of using protective measures or alternative materials
resistant to damage from SCL and the particulate matter.
10-92
-------
10.6 REFERENCES
Abe, H., Y. Ishii, and H. Kato. Evaluation of atmospheric factors by analyses
of corrosion products and surface deposits on copper plates. Rail. Tech.
Res. Inst. 12:170-174, 1971.
Arnold, L., D. B. Honeyborne, and C. A. Price. Conversation of natural
stone. Chemistry and Industry, April 17, pages 345-347, 1976.
Baker, R. G. Corrosion and plating problems in electronic equipment for the
communications industry. Mater. Prot. Perform. 14:15-19, 1975.
Banov, A. Paintings and Coatings. Structures Publishing Co., Farmington, MI,
1973.
Barton, J. R. Protection Against Atmospheric Corrosion. John Wiley & Sons,
New York, 1973.
Barton, K., and Z. Bartonova. Auswertung dreijahneger atmospharischer Korrosion
versuche mit Eisen, Kupfer and Zink auf tschechoslowakischen Pref Stationen.
Werkst. Korros. 20:87-93, 1969. 1860?- p. 3.
Beaver, H. Committee on Air Pollution Report. H. M. Stationery Office,
London, 1954.
Beloin, N. J., and F. H. Haynie. Soiling of building materials. J. Air
Pollut. Control Assoc. 25:339, 1975.
Bennett, L. H., J. Kruger, R. L. Parker, E. Passaglia, C. Reimann, A. W.
Ruff, and H. Yakowitz. Economic Effects of Metallic Corrosion in the
United States, Part I, A Report to the Congress by the National Bureau of
Standards. NBS Special Publication 511-1, U. S. Department of Commerce,
National Bureau of Standards, Washington, D. C., May 1978.
Bird, C. E. Materials Protection and Performance, Vol. 16, No. 4, April 1977.
Booz Allen and Hamilton, Inc. Study to Determine Residential Soiling Costs of
Particulate Air Pollution. National Air Pollution Control Administration,
Raleigh, NC, October 1970.
Brauns, E., and U. Kail a. Korrosion 17:81, 1965.
Brysson, R. S., B. J. Trask, J. B. Upham, and S. G. Booras. The effects of
air pollution on exposed cotton fabrics. J. Air Pollut. Control Assoc.
17:294-298, 1967.
Campbell, G. G., G. G. Shurr, D. E. Slawikowski, and J. W. Spence. Assessing
air pollution damage to coatings. J. Paint Technol. 46:59-71, 1974.
Chandler, K. A., and M. B. Kilcullen. Survey of corrosion and atmospheric
pollution in and around Sheffield. Br. Corros. J. 3:80-84, 1968.
10-93
-------
Cowling, J. E. , and M. E. Roberts. Paints, varnishes, enamels, and lacquers.
J.TI: Deterioration of Materials. Causes and Preventive Techniques. G.
AT Greathouse and C. J. Wessel , eds. , Reinhold Publishing Corp., New
York, 1954. pp. 596-645.
Duncan, J. R. , and D. J. Spedding. The mode of material reaction of SOp at a
metal surface. Corros. Sci. 14:241-249, 1974.
Ede, 1979. p. 49.
Esmen (1973).
Evans, U.R. Mechanism of rusting under different conditions. Br. Corros. J.
7*10— 1ATQ79 - -d- * •-*$ rf ' —t~/ —$ rf
-Evgang, R. , and M. B. Rockel . Werkst. Kbrros. 26: 36? 1975. ^^, V
Exley, L. M. A practical review of residual oil firing problems and solutions.
Combustion 41:16-23, 1970.
Fink, F. W. , F. H. Buttner, and W. K. Boyd. Technical-Economic Evaluation of
Air-Pollution Corrosion Costs on Metals in the United States. Final
Report, prepared for the Air Pollution Control Office, Environmental
Protection Agency. Publication No. APTD-0654. Battelle Memorial Institute,
Columbus, OH, 1971.
Fleetwood, M. J. Corros ion Prev. 22:16-19, 1975.
Fochtman, E. G. , and G. Langer. Automobile paint damaged by airborne iron
particles. J. Air Pollut. Control Assoc. 6:243-247, 1957.
Gauri , K. L. Effect of acid rain on structures. In: Acid Rain, preprint
3598, Natl. Conv. Am. Soc. Civil Engineers, 1979, pp. 55-75.
Gerhard, J. and F. H. Haynie. Air pollution Effects on Catastrophic Failure
of Metals. EPA-650/3-74-009, U. S. Environmental Protection Agency,
Research Triangle Park, NC, November 1974.
Gay, R. S. , and J. A. Terekevis. Industrial applications of textiles. Text.
Prog. 2:1-64, 1970.
Gillette, D. G. S0? and material damage. J. Air Pollut. Control Assoc.
25:1238, 1975/
Guttman, J. Effects of atmospheric factors on the corrosion of rolled zinc.
Jji: Metal Corrosion in the Atmosphere, STP 435. American Society for
Testing and Materials, Philadelphia, PA, 1968.
Guttman, H. , and P. J. Sereda. Measurement of atmospheric factors affecting
the corrosion of metals. In: Metal Corrosion in the Atmosphere, STP
435. American Society for Testing and Materials, Philadelphia, PA, 1968,
pp. 325-359.
10-94
-------
Haagenrud, S. , and B. Ottar. In: Proc. of Seventh Scandinavian Corrosion
Congress. Trondheim, Norway, 1975.^5. 1Q2-115
/teJ%tt*>
, .
/ - ' ' ^~^ &X'jtL*Jr, 5~- ^¥3 "-S^Pi /V 7fo
Marker, A. B. , F. B. Mansfeld, D. R. StraussTand D. D LandYs. Mechanism of
S02 and HUSO. Aerosol Zinc Corrosion. EPA-600/3-80-018, U.S. Environmental
Protection Agency, Research Triangle Park, NC, January 1980.
Hay, T. K. , and G. G. Schurr. Moisture diffusion phenomena in practical paint
systems. Paint Technol. 43:63-72, 1971.
Haynie, F. H. Air pollution effects on stress induced intergranular corrosion
of 7005-T 53 aluminum alloy. In: Stress Corrosion - New Approaches.
ASTM STP 610, American Society for Testing and Materials, Philadelphia,
PA, 1976, pp. 32-43.
Haynie, F. H. Theoretical air pollution and climate effects on materials con-
firmed by zinc corrosion data. I_n: Durability of Building Materials and
Components. ASTM STP 691, P. J. Sereda and G. G. Levitan, eds. , American
Society for Testing and Materials, Philadelphia, PA, 1980, pp. 157-175.
Haynie, F. H. , J. W. Spence, and J. B. Upham. Effects of Gaseous Pollutants
on Materials—A Chamber Study. EPA-600/3-76-015. U.S. Environmental
Protection Agency, Research Triangle Park, NC. 1976.
Haynie, F. H. , J. W. Spence, and J. B. Upham. Effects of air pollutants on
weathering steel and galvanized steel: a chamber study (technical note).
Mater. Perform. 15:48, 1976.
Haynie, F. H. , and J. B. Upham. Correlation between corrosion behavior of
steel and atmospheric pollution data. In: Corrosion in Natural Environments,
STP 558. American Society for Testing and Materials, Philadelphia, PA,
1974.
Haynie, F. H. , and J. B. Upham. Effects of atmospheric pollutants on the
corrosion behavior of steels. Mater. Prot. Perform. 10:18-21, 1971.
Haynie, F. H. , and J. B. Upham. Effects of atmospheric sulfur dioxide on the
corrosion of zinc. Mater. Prot. Perform. 9:35, 1970.
Holbrow, G. L. Atmospheric pollution: its measurement and some effects on
paint. J. Oil Color Chem. Assoc. 45:701-718, 1962.
ITT Electro-Physics Laboratories, Inc. A Survey and Economic Assessment of
the Effects of Air Pollutants on Electrical Components. Prepared under
Contract CPA 70-72 for the U.S. Environmental Protection Agency, 1971.
Ireland, F. E. Pollution by Oxides of Sulfur. Che. Eng. (london) (221):
CE 261-CE262, 1968.
Jacksch and Stoevener. Effects of Air Pollution on Residential Property Value
in Toledo, Oregon. Special Report 304. Agricultural Experiment Station,
Oregon State University, Corvallis, Oregon, September, 1970.
10-95
-------
Karraker, D. G. J. Phys. Chem. 67:871-874. 1963.
Kucera, V. Effects of sulfur dioxide and acid precipitation on metals and
anti-rust painted steel. Ambio 5:243-248, 1976.
Larrabee, C. P. Mechanisms by which ferrous metals corrode in the atmosphere.
Corrosion 15:526, 1959.
Larrabee, C. P., and S. K. Coburn. Paper presented at the 1st International
Congress on Metallic Corrosion. Butterworths, London, 1961. p. 279.
Liu, B., and E. S. Yu. Physical and Economic Damage Functions for Air Pollutants
by Receptor. EPA 600/5-76-011, U. S. Environmental Protection Agency,
Corvallis, Oregon, September, 1976.
Litvin, A. Clear coatings for exposed architectural concrete. J. Portland
Cem. Assoc. 10:49-57, 1968.
Luckat, S. Air pollutant effects on dome at Cologne. Koeln Domblatt 38:39,
1976.
Mansfeld, F. B. Regional Air Pollution Study. Effects of Airborne Sulfur
Pollutants on Materials. EPA-600/4-80-007, U.S. Environmental Protection
Agency. Research Triangle Park, NC, January 1980.
Mansfeld, F., and J. V. Kenkel. Electrochemical monitoring of atmospheric
corrosion phenomena. Corros. Sci. 1^:111-122, 1976.
Matsushima, I., Y. Ishizu, T. Ueno, M. Kanazashi, and K. Horikawa. Effect of
structural and environmental factors on the practical use of low-alloy
weathering steel. Boshoku Gijutsu 23:177-182, 1974.
Michelson, I., and B. Tourin. Report on Study of Validity of Extension of
Economic Effects of Air Pollution Damage from Upper Ohio River Valley to
Washington, D.C. Area. Environmental Health and Safety Research Associa-
tion, August 1967.
Moore, J. C., and J. R. O'Leary. Evaluation of Structural Steel Coatings in
Relation to Industrial Atmospheric Conditions. PB 248 514 IBI PC AOJ MF
AOJ.
Narayan, R. L., and B. W. Lancaster. Household maintenance costs and particulate
air pollution. Clean Air 7:10-13, 1973.
National Academy of Sciences, National Research Council. Airborne Particles.
EPA 600/1-77-053, U. S. Environmental Protection Agency, Research
Triangle Park, NC, November 1977.
Newton, R. G. Cathedral chemistry-conserving the stained glass. Chem. Br.
10:89-91, 1974.
Nriagu, J. 0. Sulfur in the Environment. John Wiley & Sons, Toronto, Canada,
1978.
10-96
-------
Oma, K., T. Sugaro, T. Ueki, and Y. Hirai. Studies on atmospheric corrosion
of steels related to meteorological factors in Japan. II. Multiple
correlation of meteorological and atmospheric pollution substances on
corrosion of steel. Division of Building Research Technical Translation
1281. (transl. from Boshoku Gijutsu 14:16-19, 1965). National Research
Council of Canada, Ottawa, 1965.
Overseas Public Nuisance Study Mission. Present Status of Public Nuisance in
Electric Power Industry of Japan. Central Power Council, Tokyo, Japan,
September, 1965.
Oyama, M. , A. Moriyama, H. Miyazato, and H. Sakugawa. Examples on the acid-smut
fallout. Okinawa-ken Kogai Eisei Kenkysho-ho 8:32-33, 1974.
Parker A. 1955. p. 59. The Destructive Effects of Air Pollution on Materials.
Nat. Smoke Abatement Soc. , London, England, 1955.
Prenderleith, H. J. The Preservation of Leather Bookbindings. British Museum,
London, 1946.
Riederer, J. In: New Concepts in Air Pollution Research, Willums, ed., John
Wiley and Sons, New York, 1974. pp. 73-85.
Robbins, R. C. Inquiry into the Economic Effects of Air Pollution on Electrical
Contacts. Stanford Research Inst. Contract PH-22-68-35. April 1970.
Roebuck and McCage. 1974. p. 57.
Rosenfeld (1973).
'" / ' AT' t/P-/f / "
Rosenfeld, I. L. Atmospheric corrosion of metals. In: Sulfur in the Environment.
J. R. Nriagu, ed., John Wiley & Sons, New York, 1978. p. 18.
Salmon, R. L. Systems Analysis of the Effects of Air Pollution on Materials.
Final Report prepared for Economic Effects Research Division, National
Air Pollution Control Administration. Midwest Research Institute, Kansas
City, MO, 1970. 192 p.
Sanyal, B., and G. K. Singhania. Atmospheric corrosion of metals: Part I.
J. Sci. Indu. Res. Sect. 6.15:248-255, 1956.
Satake, J. , and T. Moroishi. In: Proceedings of the 5th International Congress
on Metal Corrosion, 1974. National Association of Corrosion Engineers,
Houston, TX. pp. 744-749.
Sayre, E. V. In: Application of Science in Examination of Works of Art. W.
J. Young, ed., Museum of Fine Arts, Boston, 1973. pp. 176-181.
Schwarz, H. Uber die Wirkung des Magetits beim atmosphaerischen Rosten und
beim unterrosten von Austrichen. Werkst. Korros. 23:648-663, 1972.
Schwenk, W. , and H. Ternes.^ Stahl risen 88:318, 1968.
10-97
-------
Sengupta, M., and A. K. DeGast. Environmental deterioration and evaluation
for dimension stone. Can. Min. Metal!. Bull. 65:54-58, 1972.
Simpson, J. W., and P. J. Horrobin, eds. The Weathering and Performance of
Building Materials. Wiley-Interscience', New York, 1970. p. 286.
SI eater, G. A. Stone Preservatives. Methods of Laboratory Testing and Pre-
liminary Performance Criteria. NBS Technical Note 941. National Bureau
of Standards, May 1977.
Spedding, D. J., P- P- Rowlands, and J. E. Taylor. Sorption of sulfur dioxide by
indoor surfaces: leather. J. Appl. Chem. Biotechnol. £1:68-70, 1971.
Spence, J. W., F. H. Haynie, and J. B. Upham. Effects of gaseous pollutants on
paints: A chamber study. J. Paint Techno!. 47:57-63, 1975.
Spence, J. W., and F. H. Haynie. Design of a laboratory experiment to identify
the effects of environmental pollutants on materials. In: Corrosion in
Natural Environments, STP 558. American Society for Testing and Materials,
Philadelphia, PA, 1974. pp. 279-291.
Spence, J. W., and F. H. Haynie. Paint Technology and Air Pollution: A Survey
and Economic Assessment. Publication No. AP-103. Environmental Protection
Agency, Research Triangle Park, NC, February 1972.
Stanners, J. F. Use of environmental data in atmospheric corrosion studies. Br.
Corros. J. 5:117-121, 1970.
Svoboda, M., B. Knapek, and H. Kilcoua. The effect of pigments on the penetra-
tion of sulfur dioxide into coatings. J. Oil Colour Chem. Assoc. 56:172174,
1973. ~~
Sydberger, T. Influence of Sulphur Pollution on the Atmospheric Corrosion of
Steel. University of Gothenburg, Department of Inorganic Chemistry,
Gothenburg, Sweden, 1976.
Sydberger, T., and R. Ericsson. Laboratory testing of the atmospheric corrosion
of steel. Werkst. Korros., 1976.
Sydberger, T., and N. G. Vannenberg. The influence of the relative humidity and
corrosion products on the adsorption of sulfur dioxide on metal surfaces.
Corros. Sci. 12:775-784, 1972.
The Textile Organization. 1965. p. 64.
Tomashov, N. D. The Science of Corrosion. The MacMillan Co., New York, 1966.
TRC--The Research Corporation of New England. Effects of Power Plant Emissions
on Materials. EPRI EC-139, Electric Power Research Institute, Palo Alto,
CA, July 1976.
10-98
-------
Turner, J. M. and R. S. Shelters. Laboratory Evaluation of the Sulfation
Plate for Estimation of Atmospheric Sulfur Dioxide. 6th Annual
Meeting, Air Pollution Control Association, Atlantic City, New Jersery,
June 27-July 2, paper no. 71-39.
Upham, J. B. Atmospheric corrosion studies in two metropolitan areas. J. Air
Pollut. Control Assoc. 17:398-402, 1967.
Upham, J. B. , and V. S. Salvin. Effects of Air Pollutants on Textile Fibers and
Dyes. Environmental Protection Agency, Office of Research and Development.
Ecological Research Series. Publication No. EPA-650/3-74-008. U.S.
Government Printing Office, Washington, D.C., 1975.
Vannenberg, N. G. , and T. Sydberger. Reaction between S0? and wet metal
surfaces. Corros. Sci. 10:1084, 1970.
Verdu. Effect of air pollutants on aging of plastic materials. Trib. CEBEDEAU
27:360-370, 1974.
Waddell, T. E. Economic damage of air pollution. NTIS PB 235 761 PGF. 1974.
Walsh, M. , A. Black, A. Morgan, and G. Crashaw. Sorption of S02 by indoor
surfaces including carpets, wallpaper, and paint. Atmos. Environ. 11:
1107-1111, 1977.
Watson and Jaksch, 1978. p. 65 and 67.
Winkler, E. M. Stone: Properties, Durability in Man's Environment.
Second revised edition, Springer-Verlag, New York, NY, 1975.
Yocum, J. E. Air pollution damage to buildings on the Acropolis. J. Air
Pollut. Control Assoc., 29:333-338, 1979.
Yocum, J. E. , and J. B. Upham. Effects on economic materials and structures.
J_n: Air Pollution Third Edition, Volume II, A. C. Stern, ed. , Academic
Press, Inc., New York, NY, 1977. pp. 65-116.
Yoshihara,,-K. , T. C, Huang, H. Ebihora, and H. Shibata. Chemical Effects of
the •3bCl(n,prD S Reaction. Radiochim. Acta 3:185-191, 1964.
10-99
-------
GLOSSARY
AaDCL: Alveolar-arterial difference or gradient of the partial pressure of
oxygen. An overall measure of the efficiency of the lung as a gas ex-
changer. In healthy subjects, the gradient is 5 to 15 mm Hg (torr).
A/PR/8 virus: A type of virus capable of causing influenza in laboratory
animals; also, A/PR/8/34.
Abscission: The process whereby leaves, leaflets, fruits, or other plant
parts become detached from the plant.
Absorption coefficient: A quantity which characterizes the attenuation with
distance of a beam of electromagnetic radiation (like light) in a substance
Absorption spectrum: The spectrum that results after any radiation has
passed through an absorbing substance.
Abstraction: Removal of some constituent of a substance or molecule.
Acetaldehyde: CH3CHO; an intermediate in yeast fermentation of car-
bohydrate ana in alcohol metabolism; also called acetic aldehyde,
ethaldehyde, ethanal.
Acetate rayon: A staple or filament fiber made by extrusion of cellulose
acetate. It is saponified by dilute alkali whereas viscose rayon remains
unchanged.
Acetylcholine: A naturally-occurring substance in the body which can
cause constriction of the bronchi in the lungs.
Acid: A substance that can donate hydrogen ions.
Acid dyes: A large group of synthetic coal tar-derived dyes which
produce bright shades in a wide color range. Low cost and ease
of application are features which make them the most widely used
dyes for wool. Also used on nylon. The term acid dye is derived
from their precipitation in an acid bath.
Acid mucopolysaccharide: A class of compounds composed of protein
and polysaccharide. Mucopolysaccharides comprise much of the
substance of connective tissue.
Acid phosphatase: An enzyme (EC 3.1.3.2) which catalyzes the disassociation
of phosphate (PO.) from a wide range of monoesters of orthophosphoric
acid. Acid phosphatase is active in an acidic pH range.
Acid rain: Rain having a pH less than 5.6, the minimum expected from
atmospheric C09.
G-l
-------
Acrolein: CH2=CHCHO; a volatile, flammable, oily liquid, giving off
irritant vapor. Strong irritant of skin and mucuous membranes. Also
called acrylic aldehyde, 2-propenal.
Acrylics (plastics): Plastics which are made from acrylic acid and are
light in weight, have great breakage resistance, and a lack of
odor and taste. Not resistant to scratching, burns, hot water,
alcohol or cleaning fluids. Examples include Lucite and Plexiglass.
Acrylics are thermoplastics and are softened by heat and hardened
into definite shapes by cooling.
Acrylic fiber: The generic name of man-made fibers derived from acrylic
resins (minimum of 85 percent acrylonitrite units).
Actinic: A term applied to wavelengths of light too small to affect
one's sense of sight, such as ultraviolet.
Actinomycetes: Members of the genus Actinomyces; nonmotile, nonspore-
forming, anaerobic bacteria, including both soil-dwelling saprophytes
and disease-producing parasites.
Activation energy: The energy required to bring about a chemical reaction.
Acute respiratory disease: Respiratory infection, usually with rapid
onset and of short duration.
Acute toxicity: Any poisonous effect produced by a single short-term
exposure, that results in severe biological harm or death.
Acyl: Any organic radical or group that remains intact when an organic
acid forms an ester.
Adenoma: An ordinarily benign neoplasm (tumor) of epithelial tissue;
usually well circumscribed, tending to compress adjacent tissue rather
than infiltrating or invading.
Adenosine monophosphate (AMP): A nucleotide found amoung the hydrolysis
products of all nucleic acids; also called adenylic acid.
Adenosine triphosphatase (ATPase): An enzyme (EC 3.6.1.3) in muscle
and elsewhere that catalyzes the release of the high-energy, ter-
minal phosphate group of adenosine triphosphate.
Adrenalectomy: Removal of an adrenal gland. This gland is located near
or upon the kidney and is the site of origin of a number of hormones.
Adsorption: Adhesion of a thin layer of molecules to a liquid or solid sur-
face.
Advection: Horizontal flow of air at the surface or aloft; one of the
means by which heat is transferred from one region of the earth
to another.
G-2
-------
Aerodynamic diameter: Expression of aerodynamic behavior of an irregularly
shaped particle in terms of the diameter of a sphere of unit density
having identical aerodynamic behavior to the particle in question.
Aerosol: Solid particles or liquid droplets which are dispersed or sus-
pended in a gas.
Agglutination: The process by which suspended bacteria, cells or similar
particles adhere and form into clumps.
Airborne pathogen: A disease-causing microorganism which travels in the
air or on particles in the air.
Air pollutant: A substance present in the ambient atmosphere, resulting
from the activity of man or from natural processes, which may cause
damage to human health or welfare, the natural environment, or
materials or objects.
Airway conductance: Inverse of airway resistance.
Airway resistance (R ): The pressure difference between the alveoli
and the mouth required to produce an air flow of 1 liter per second.
Alanine aminotransferase: An enzyme (EC 2.6.1.2) transferring amino
groups from L-alanine to 2-ketoglutarate. Also known as alanine
transaminase.
Albumin: A type of simple, water-soluble protein widely distributed
throughout animal tissues and fluids, particularly serum.
0
ii
Aldehyde: An organic compound characterized by the group -C-H.
Aldolase: An enzyme (EC 4.1.2.7) involved in metabolism of fructose
which catalyzes the formation of two 3-carbon intermediates in the
major pathway of carbohydrate metabolism.
Algal bloom: Sudden spurt in growth of algae which can affect water
quality adversely.
Alkali: A salt of sodium or potassium capable of neutralizing acids.
Alkaline phosphatase: A phosphatase (EC 3.1.3.1) with an optimum pH of
8.6, present ubiquitously.
Allergen: A material that, as a result of coming into contact with appro-
priate tissues of an animal body, induces a state of sensitivity result-
ing in various reactions; generally associated with idiosyncratic
hypersensitivities.
Alpha-hydroxybutyrate dehydrogenase: An enzyme (EC 1.1.1.30), present
mainly in mitochondria, which catalyzes the conversion of hydro-
xybutyrate to acetoacetate in intermediate biochemical pathways.
G-3
-------
Alpha rhythm: A rhythmic pulsation obtained in brain waves exhibited
in the sleeping state of an individual.
Alveolar capillary membrane: Finest portion of alveolar capillaries,
where gas transfer to and from blood takes place.
Alveolar macrophages (AM): Large, mononuclear, phagocytic cells found
on the alveolar surface, responsible for the sterility of the lung.
Alveolar oxygen partial pressure (PA02): Partial pressure of oxygen in the
air contained in the air sacs of the lungs.
Alveolar septa: The tissue between two adjacent pulmonary alveoli, con-
sisting of a close-meshed capillary network covered on both surfaces
by thin alveolar epithelial cells.
Alveolus: An air cell; a terminal, sac-like dilation in the lung. Gas
exchange (CL/CCL) occurs here.
Ambient: The atmosphere to which the general population may be exposed.
Construed here not to include atmospheric conditions indoors, or in
the workplace.
Amine: A substance that may be derived from ammonia (NhL) by the re-
placement of one, two or three of the hydrogen (H) atoms by hydro-
carbons or other radicals (primary, secondary or tertiary amines,
respectively).
Amino acids: Molecules consisting of a carboxyl group, a basic amino
group, and a residue group attached to a central carbon atom. Serve
as the building blocks of proteins.
p-Aminohippuric acid (PAH): A compound used to determine renal plasma
flow.
Aminotriazole: A systemic herbicide, CpH.N., used in areas other than
croplands, that also possesses some antithyroid activity; also called
amitrole.
Ammonification: Decomposition with production of ammonia or ammonium
compounds, esp. by the action of bacteria on nitrogenous organic
matter.
Ammonium: Anion (NH4) or radical (NHL) derived from ammonia by combination
with hydrogen. Present in rainwater, soils and many commercial ferti-
lizers.
Amnestic: Pertains to immunologic memory: upon receiving a second
dose of antigen, the host "remembers" the first dose and responds
faster to the challenge.
G-4
-------
Anaerobic: Living, active or occurring in the absence of free oxygen.
Anaerobic bacteria: A type of microscopic organism which can live in
an environment not containing free oxygen.
Anaphylactic dyspneic attack: Difficulty in breathing associated with
a systemic allergic response.
Anaphylaxis: A term commonly used to denote the immediate, transient
kind of immunological (allergic) reaction characterized by contraction
of smooth muscle and dilation of capillaries due to release of pharmacologically
active substances.
Angiosperm: A plant having seeds enclosed in an ovary; a flowering plant.
Angina pectoris: Severe constricting pain in the chest which may be
caused by depletion of oxygen delivery to the heart muscle; usually
caused by coronary disease.
o _o
Angstrom A: A unit (10 cm) used in the measurement of the wavelength
of light.
Anhydride: A compound resulting from removal of water from two molecules
of a carboxylic (-COOH) acid. Also, may refer to those substances
(anhydrous) which do not contain water in chemical combination.
Anion: A negatively charged atom or radical.
Anorexia: Diminished appetite; aversion to food.
Anoxic: Without or deprived of oxygen.
Anthraquinone: A yellow crystalline ketone, C,.HftO?, derived from
anthracene and used in the manufacture of dyes.
Anthropogenic: Of, relating to or influenced by man. An anthropogenic
source of pollution is one caused by man's actions.
Antibody: Any body or substance evoked by the stimulus of an antigen
and which reacts specifically with antigen in some demonstrable way.
Antigen: A material such as a foreign protein that, as a result of
coming in contact with appropriate tissues of an animal, after a latent
period, induces a state of sensitivity and/or the production of antibody.
Antistatic agent: A chemical compound applied to fabrics to reduce or
eliminate accumulation of static electricity.
Arachidonic acid: Long-chain fatty-acid which serves as a precursor
of prostaglandins.
G-5
-------
Area source: In air pollution, any small individual fuel combustion
or other pollutant source; also, all such sources grouped over a
specific area.
Aromatic: Belonging to that series of carbon-hydrogen compounds in
which the carbon atoms form closed rings containing unsaturated
bonds (as in benzene).
Arterial partial pressure of oxygen (PaCO: Portion of total pressure of
dissolved gases in arterial blood as measured directly from arterial
blood.
Arterialized partial pressure of oxygen: The portion of total pressure
of dissolved gases in arterial blood attributed to oxygen, as
measured from non-arterial (e.g., ear-prick) blood.
Arteriosclerosis: Commonly called hardening of the arteries. A condition
that exists when the walls of the blood vessels thicken and become
infiltrated with excessive amounts of minerals and fatty materials.
Artifact: A spurious measurement produced by the sampling or analysis
process.
Ascorbic acid: Vitamin C, a strong reducing agent with antioxidant proper-
ties.
Aspartate transaminase: Also known as aspartate aminotransferase
(EC 2.6.1.1). An enzyme catalyzing the transfer of an amine group
from glutamic acid to oxaloacetic, forming aspartic acid in the
process. Serum level of the enzyme is increased in myocardial in-
farction and in diseases involving destruction of liver cells.
Asphyxia: Impaired exchange of oxygen and carbon dioxide, excess of
carbon dioxide and/or lack of oxygen, usually caused by ventilatory
problems.
Asthma: A term currently used in the context of bronchial asthma in
which there is widespread narrowing of the airways of the lung.
It may be aggravated by inhalation of pollutants and lead to
"wheezing" and shortness of breath.
Asymptomatic: Presenting no subjective evidence of disease.
Atmosphere: The body of air surrounding the earth. Also, a measure of
pressure (atm.) equal to the pressure of air at sea level, 14.7 pounds
per square inch.
Atmospheric deposition: Removal of pollutants from the atmosphere onto
land, vegetation, water bodies or other objects, by absorption,
sedimentation, Brownian diffusion, impaction, or precipitation in rain,
G-6
-------
Atomic absorption spectrometry: A measurement method based on the
absorption of radiant energy by gaseous ground-state atoms. The
amount of absorption depends on the population of the ground state
which is related to the concentration of the sample being analyzed.
Atropine: A poisonous white crystalline alkaloid, C,7H?.,N03, from
belladonna and related plants, used to relieve spasms and to dilate
the pupil of the eye.
Autocorrelation: Statistical interdependence of variables being analyzed;
produces problems, for example, when observations may be related
to previous measurements or other conditions.
Autoimmune disease: A condition in which antibodies are produced against
the subject's own tissues.
Autologous: A term referring to cellular elements, such as red blood cells
and alveolar macrophage, from the same organism; also, something
natually and normally ocurring in some part of the body.
Autotrophic: A term applied to those microorganisms which are able to
maintain life without an exogenous organic supply of energy, or which
only need carbon dioxide or carbonates and simple inorganic nitrogen.
Autotrophic bacteria: A class of microorganisms which require only
carbon dioxide or carbonates and a simple inorganic nitrogen com-
pound for carrying on life processes.
Auxin: An organic substance that causes lengthening of the stem when
applied in low concentrations to shoots of growing plants.
Awn: One of the slender bristles that terminate the glumes of the
spikelet in some cereals and other grasses.
Azo dye: Dyes in which the azo group is the chromophore and joins
benzene or napthalene rings.
Background measurement: A measurement of pollutants in ambient air due
to natural sources; usually taken in remote areas.
Bactericidal activity: The process of killing bacteria.
Barre: Bars or stripes in a fabric, caused by uneven weaving, irregular
yarn or uneven dye distribution.
Basal cell: One of the innermost cells of the deeper epidermis of the
skin.
Benzenethiol: A compound of benzene and a hydrosulfide group.
6-7
-------
Beta (b)-lipoprotein: A biochemical complex or compound containing both
lipid and protein and characterized by having a large molecular
weight, rich in cholesterol. Found in certain fractions of human
plasma.
Bilateral renal sclerosis: A hardening of both kidneys of chronic
inflammatory origin.
Biomass: That part of a given habitat consisting of living matter.
Biosphere: The part of the earth's crust, waters and atmosphere where
living organisms can subsist.
Biphasic: Having two distinct successive stages.
Bleb: A collection of fluid beneath the skin; usually smaller than
bullae or blisters.
Blood urea: The chief end product of nitrogen metabolism in mammals,
excreted in human urine in the amount of about 32 grams (1 oz.)
a day.
Bloom: A greenish-gray appearance imparted to silk and pile fabrics
either by nature of the weave or by the finish; also, the creamy
white color observed on some good cottons.
Blue-green algae: A group of simple plants which are the only N?-fixing
organisms which photosynthesize as do higher plants.
Brightener: A compound such as a dye, which adheres to fabrics in order
to provide better brightness or whiteness by converting ultraviolet
radiation to visible light. Sometimes called optical bleach or
whitening agent. The dyes used are of the florescent type.
Broad bean: The large flat edible seed of an Old World upright vetch
(Vicia faba), or the plant itself, widely grown for its seeds and
for fodder.
Bronchi: The first subdivisions of the trachea which conduct air to
and from the bronchioles of the lungs.
Bronchiole: One of the finer subdivisions of the bronchial (trachea)
tubes, less than 1 mm in diameter, and having no cartilage in
its wall.
Bronchiolitis: Inflammation of the smallest bronchial tubes.
Bronchiolitis fibrosa obliterans syndrome: Obstruction of the bronchioles
by fibrous granulation arising from an ulcerated mucosa; the condition
may follow inhalation of irritant gases.
G-8
-------
Bronchitis: Inflammation of the mucous membrane of the bronchial tubes.
It may aggravate an existing asthmatic condition.
Bronchoconstrictor: An agent that causes a reduction in the caliber
(diameter) of a bronchial tube.
Bronchodilator: An agent which causes an increase in the caliber (diameter)
of a bronchus or bronchial tube.
Bronchopneumonia: Acute inflammation of the walls of the smaller bronchial
tubes, with irregular area of consolidation due to spread of the in-
flammation into peribronchiolar alveoli and the alveolar ducts.
Brownian diffusion: Diffusion by random movement of particles suspended
in liquid or gas, resulting from the impact of molecules of the
fluid surrounding the particles.
Buffer: A substance in solution capable of neutralizing both acids
and bases and thereby maintaining the original pH of the solution.
Buffering capacity: Ability of a body of water and its watershed to
neutralize introduced acid.
Butanol: A four-carbon, straight-chain alcohol, C.hLOH, also known as
butyl alcohol. 4 y
Butylated hydroxytoluene (BHT): A crystalline phenolic antioxidant.
Butylated hydroxyanisol (BHA): An antioxidant.
14
C labeling: Use of a radioactive form of carbon as a tracer, often
in metabolic studies.
14
C-proline: An amino acid which has been labeled with radioactive carbon.
Calcareous: Resembling or consisting of calcium carbonate (lime), or
growing on limestone or lime-containing soils.
Calorie: Amount of heat required to raise temperature of 1 gram of
water at 15°C by 1 degree.
Cannula: A tube that is inserted into a body cavity, or other tube
or vessel, usually to remove fluid.
Capillary: The smallest type of vessel; resembles a hair. Usually
in reference to a blood or lymphatic capillary vessel.
Carbachol: A chemical compound (carbamoylchol ine chloride, CgH-jtClNJDO that
produces a constriction of the bronchi; a parasympathetic Stimulant
used in veterinary medicine and topically in glaucoma.
G-9
-------
Carbon monoxide: An odorless, colorless, toxic gas with a strong affinity
for hemoglobin and cytochrome; it reduces oxygen absorption capacity,
transport and utilization.
Carboxyhemoglobin: A fairly stable union of carbon monoxide with hemo-
globin which interferes with the normal transfer of carbon dioxide
and oxygen during circulation of blood. Increasing levels of
Carboxyhemoglobin result in various degrees of asphyxiation, in-
cluding death.
Carcinogen: Any agent producing or playing a stimulatory role in the
formation of a malignancy.
Carcinoma: Malignant new growth made up of epithelial cells tending to
infiltrate the surrounding tissues and giving rise to metastases.
Cardiac output: The volume of blood passing through the heart per unit
time.
Cardiovascular: Relating to the heart and the blood vessels or the
circulation.
Carotene: Lipid-soluble yellow-to-orange-red pigments universally
present the photosynthetic tissues of higher plants, algae, and the
photosynthetic bacteria.
Cascade impactor: A device for measuring the size distribution of particulates
and/or aerosols, consisting of a series of plates with orifices of
graduated size which separate the sample into a number of fractions
of decreasing aerodynamic diameter.
Catabolism: Destructive metabolism involving the release of energy and
resulting in breakdown of complex materials in the organism.
Catalase: An enzyme (EC 1.11.1.6) catalyzing the decomposition of hydrogen
peroxide to water and oxygen.
Catalysis: A modification of the rate of a chemical reaction by some
material which is unchanged at the end of the reaction.
Catalytic converter: An air pollution abatement device that removes
organic contaminants by oxidizing them into carbon dioxide and
water.
Catecholamine: A pyrocatechol with an alkalamine side chain, functioning
as a hormone or neurotransmitter, such as epinephrine, morepinephrine,
or dopamine.
Cathepsins: Enzymes which have the ability to hydrolyze certain proteins
and peptides; occur in cellular structures known as lysosomes.
Cation: A positively charged ion.
G-10
-------
Cellular permeability: Ability of gases to enter and leave cells; a
sensitive indicator of injury to deep-lung cells.
Cellulose: The basic substance which is contained in all vegetable
fibers and in certain man-made fibers. It is a carbohydrate and
constitutes the major substance in plant life. Used to make cellulose
acetate and rayon.
Cellulose acetate: Commonly refers to fibers or fabrics in which the
cellulose is only partially acetylated with acetate groups. An
ester made by reacting cellulose with acetic anhydride with SO.
as a catalyst.
Cellulose rayon: A regenerated cellulose which is chemically the same
as cellulose except for physical differences in molecular weight
and crystallinity.
Cellulose triacetate: A cellulose fiber which is completely acetylated.
Fabrics of triacetate have higher heat resistance than acetate and
may be safely ironed at higher temperature. Such fabrics have improved
ease-of-care characteristics because after heat treatment during
manufacture, a change in the crystalline structure of the fiber
occurs.
Cellulosics: Cotton, viscose rayon and other fibers made of natural fiber
raw materials.
Celsius scale: The thermometric scale in which freezing point of water
is 0 and boiling point is 100.
Central hepatic necrosis: The pathologic death of one or more cells,
or of a portion of the liver, involving the cells adjacent to the
central veins.
Central nervous system (CNS): The brain and the spinal cord.
Centroacinar area: The center portion of a grape-shaped gland.
Cerebellum: The large posterior brain mass lying above the pons and
medulla and beneath the posterior portion of the cerebrum.
Cerebral cortex: The layer of gray matter covering the entire surface
of the cerebral hemisphere of mammals.
Chain reaction: A reaction that stimulates its own repetition.
Challenge: Exposure of a test organism to a virus, bacteria, or other
stress-causing agent, used in conjunction with exposure to a pollutant
of interest, to explore possible susceptibility brought on by the
pollutant.
G-ll
-------
Chamber study: Research conducted using a closed vessel in which pollutants
are reacted or substances exposed to pollutants.
Chemiluminescence: A measurement technique in which radiation is pro-
duced as a result of chemical reaction.
Chemotactic: Relating to attraction or repulsion of living protoplasm
by chemical stimuli.
Chlorophyll: A group of closely related green photosynthetic pigments
occurring in leaves, bacteria, and organisms.
Chloroplast: A plant cell inclusion body containing chlorophyll.
Chlorosis: Discoloration of normally green plant parts that can be
caused by disease, lack of nutrients, or various air pollutants,
resulting in the failure of chlorophyll to develop.
Cholesterol: A steroid alcohol C27H45OH5 tne most abundant steroid in
animal cells and body fluids.
Cholinesterase (CHE): One (EC 3.1.1.8) of a family of enzymes capable
of catalyzing the hydrolysis of acylcholines.
Chondrosarcoma: A malignant neoplasm derived from cartilage cells,
occurring most frequently near the ends of long bones.
Chromatid: Each of the two strands formed by longitudinal duplication
of a chromosome that becomes visible during an early stage of cell
division.
Chromophore: A chemical group that produces color in a molecule by absorbing
near ultraviolet or visible radiation when bonded to a nonabsorb-
ing, saturated residue which possesses no unshared, nonbonding valence
electrons.
Chromosome: One of the bodies (46 in man) in the cell nucleus that is the
bearer and carrier of genetic information.
Chronic respiratory disease (CRD): A persistent or long-lasting intermittent
disease of the respiratory tract.
Cilia: Motile, often hairlike extensions of a cell surface.
Ciliary action: Movements of cilia in the upper respiratory tract, which
move mucus and foreign material upward.
Ciliogenesis: The formation of cilia.
G-12
-------
Citric acid (Krebs) cycle: A major biochemical pathway in cells, in-
volving terminal oxidation of fatty acids and carbohydrates. It
yields a major portion of energy needed for essential body functions
and is the major source of CCL. It couples the glycolytic breakdown
of sugar in the cytoplasm witn those reactions producing ATP in the
mitochondria. It also serves to regulate the synthesis of a number
of compounds required by a cell.
Clara cell: A nonciliated mammalian cell.
Closing volume (CV): The lung volume at which the flow from the lower
parts of the lungs becomes severely reduced or stops during expiration,
presumably because of airway closure.
Codon: A sequence of three nucleotides which encodes information re-
quired to direct the synthesis of one or more amino acids.
Coefficient of haze (COH): A measurement of visibility interference in the
atmosphere.
Cohort: A group of subjects included in a test or experiment; usually
characterized by age, class or other characteristic.
Collagen: The major protein of the white fibers of connective tissue,
cartilage, and bond. Comprises over half the protein of the mammal.
Collisional deactivation: Reduction in energy of excited molecules
caused by collision with other molecules or other objects such
as the walls of a container.
Colorimetric: A chemical analysis method relying on measurement of the
degree of color produced in a solution by reaction with the pollutant
of interest.
Community exposure: A situation in which people in a sizeable area are
subjected to ambient pollutant concentrations.
Compliance: A measure of the change in volume of an internal organ (e.g.
lung, bladder) produced by a unit of pressure.
Complement: Thermolabile substance present in serum that is destructive
to certain bacteria and other cells which have been sensitized by
specific complement-fixing antibody.
Compound: A substance with its own distinct properties, formed by the
chemical combination of two or more elements in fixed proportion.
Concanavalin-A: One of two crystalline globulins occurring in the jack
bean; a potent hemagglutinin.
Conifer: A plant, generally evergreen, needle-leafed, bearing naked seeds
singly or in cones.
G-13
-------
Converter: See catalytic converter.
Coordination number: The number of bonds formed by the central atom in
a complex.
Copolymer: The product of the process of polymerization in which two or
more monomeric substances are mixed prior to polymerization. Nylon is
a copolymer.
Coproporphyrin: One of two porphyrin compounds found normally in feces
as a decomposition product of bilirubin (a bile pigment). Porphyrin
is a widely-distributed pigment consisting of four pyrrole nuclei
joined in a ring.
Cordage: A general term which includes banding, cable, cord, rope, string,
and twine made from fibers. Synthetic fibers used in making cordage
include nylon and dacron.
Corrosion: Destruction or deterioration of a material because of reaction
with its environment.
Corticosterone: A steroid obtained from the adrenal cortex. It induces
some deposition of glycogen in the liver, sodium conservation, and
potassium excretion.
Cosmopolitan: In the biological sciences, a term denoting worldwide
distribution.
Coulometric: Chemical analysis performed by determining the amount of a
substance released in electrolysis by measuring the number of
coulombs used.
Coumarin: A toxic white crystalline lactone (CnhL00) found in plants.
y D ^
Coupler: A chemical used to combine two others in a reaction, e.g. to
produce the azo dye in the Griess-Saltzman method for N0?.
Crevice corrosion: Localized corrosion occurring within crevices on metal
surfaces exposed to corrosives.
Crosslink: To connect, by an atom or molecule, parallel chains in a complex
chemical molecule, such as a polymer.
Cryogenic trap: A pollutant sampling method in which a gaseous pollutant
is condensed out of sampled air by cooling (e.g. traps in one method
for nitrosamines are maintained below -79 C, using solvents maintained
at their freezing points).
Cuboidal: Resembling a cube in shape.
Cultivar: An organism produced by parents belonging to different species
or to different strains of the same species, originating and persist-
ing under cultivation.
G-14
-------
Cuticle: A thin outer layer, such as the thin continuous fatty film
on the surface of many higher plants.
Cyanosis: A dark bluish or purplish coloration of the skin and mucous
membrane due to deficient oxygenation of the blood.
Cyclic GMP: Guanosine S'-phosphoric acid.
Cytochrome: A class of hemoprotein whose principal biological function
is electron and/or hydrogen transport.
Cytology: The anatomy, physiology, pathology and chemistry of the cell.
Cytoplasm: The substance of a cell exclusive of the nucleus.
Dacron: The trade name for polyester fibers made by E.I. du Pont de Nemours
and Co., Inc., made from dimethyl terephthalate and ethylene glycol.
Dark adaptation: The process by which the eye adjusts under reduced
illumination and the sensitivity of the eye to light is greatly in-
creased.
Dark respiration: Metabolic activity of plants at night; consuming oxygen
to use stored sugars and releasing carbon dioxide.
Deciduous plants: Plants which drop their leaves at the end of the grow-
ing season.
Degradation (textiles): The decomposition of fabric or its components
or characteristics (color, strength, elasticity) by means of light,
heat, or air pollution.
Denitrification: A bacterial process occurring in soils, or water, in
which nitrate is used as the terminal electron acceptor and is re-
duced primarily to N-. It is essentially an anaerobic process; it
can occur in the presence of low levels of oxygen only if the micro-
organisms are metabolizing in an anoxic microzone.
De novo: Over again.
Deoxyribonucleic acid (DMA): A nucleic acid considered to be the carrier
of genetic information coded in the sequence of purine and pyrimidine
bases (organic bases). It has the form of a double-stranded helix
of a linear polymer.
Depauperate: Falling short of natural development or size.
Derivative spectrophotometer: An instrument with an increased capability
for detecting overlapping spectral lines and bands and also for
suppressing instrumentally scattered light.
G-15
-------
Desorb: To release a substance which has been taken into another substance
or held on its surface; the opposite of absorption or adsorption.
Desquamation: The shedding of the outer layer of any surface.
Detection limit: A level below which an element or chemical compound
cannot be reliably detected by the method or measurement being used for
analysis.
Detritus: Loose material that results directly from disintegration.
DeVarda alloy: An alloy of 50 percent Cu, 45 percent Al, 5 percent Zn.
Diastolic blood pressure: The blood pressure as measured during the period
of filling the cavities of the heart with blood.
Diazonium salt: A+chemical compound (usually colored) of the general
structure ArNpCl", where Ar refers to an aromatic group.
Diazotizer: A chemical which, when reacted with amines (RNhL, for example),
produces a diazonium salt (usually a colored compound).
Dichotomous sampler: An air-sampling device which separates particulates
into two fractions by particle size.
Differentiation: The process by which a cell, such as a fertilized egg,
divides into specialized cells, such as the embryonic types that
eventually develop into an entire organism.
Diffusion: The process by which molecules or other particles intermingle
as a result of their random thermal motion.
Diffusing capacity: Rate at which gases move to or from the blood.
Dimer: A compound formed by the union of two like radicals or
molecules.
Dimerize: Formation of dimers.
1,6-diphosphofructose aldolase: An enzyme (EC 4.1.1.13) cleaving fructose
1,6-bisphosphate to dihydroxyacetone phosphate and glyceraldehyde-
3-phosphate.
D-2,3-diphosphoglycerate: A salt or ester of 2,3-diphosphoglyceric acid,
a major component of certain mammalian erythrocytes involved in the
release of Op from HbO^. Also a postulated intermediate in the bio-
chemical patnway involving the conversion of 3- to 2-phosphoglyceric
acid.
Diplococcus pneumoniae: A species of spherical-shaped bacteria belonging
to the genus Streptococcus. May be a causal agent in pneumonia.
G-16
-------
Direct dye: A dye with an affinity for most fibers; used mainly when
color resistance to washing is not important.
Disperse dyes: Also known as acetate dyes; these dyes were developed
for use on acetate fabrics, and are now also used on synthetic
fibers.
Distal: Far from some reference point such as median line of the body, point
of attachment or origin.
Diurnal: Having a repeating pattern or cycle 24 hours long.
DLCQ: The diffusing capacity of the lungs for carbon monoxide. The ability
of the lungs to transfer carbon monoxide from the alveolar air into the
pulmonary capillary blood.
Dorsal hyphosis: Abnormal curvative of the spine; hunch-back.
Dose: The quantity of a substance to be taken all at one time or in
fractional amounts within a given period; also the total amount of a
pollutant delivered or concentration per unit time times time.
Dose-response curve: A curve on a graph based on responses occurring
in a system as a result of a series of stimuli intensities or doses.
Dry deposition: The processes by which matter is transferred to ground
from the atmosphere, other than precipitation; includes surface ab-
sorption of gases and sedimentation, Brownian diffusion and impaction
of particles.
Dyeing: A process of coloring fibers, yarns, or fabrics with either
natural or synthetic dyes.
Dynamic calibration: Testing of a monitoring system using a continuous
sample stream of known concentration.
Dynamic compliance (C. . ): Volume change per unit of transpulmonary
pressure minus tneypYessure of pulmonary resistance during airflow.
Dynel: A trademark for a modacrylic staple fiber spun from a copolymer
of acrylonitrile and vinyl chloride. It has high strength, quick-
drying properties, and resistance to alkalies and acids.
Dyspepsia: Indigestion, upset stomach.
Dyspnea: Shortness of breath; difficulty or distress in breathing; rapid
breathing.
Ecosystem: The interacting system of a biological community and its
environment.
Eddy: A current of water or air running contrary to the main current.
G-17
-------
Edema: Pressure of excess fluid in cells, intercellular tissue or cavities
of the body.
Elastomer: A synthetic rubber product which has the physical properties
of natural rubber.
Electrocardiogram: The graphic record of the electrical currents that
initiate the heart's contraction.
Electrode: One of the two extremities of an electric circuit.
Electrolyte: A non-metallic electric conductor in which current, is carried
by the movement of ions; also a substance which displays these qualities
when dissolved in water or another solvent.
Electronegativity: Measure of affinity for negative charges or electrons.
Electron microscopy: A technique which utilizes a focused beam of electrons
to produce a high-resolution image of minute objects such as particu-
late matter, bacteria, viruses, and DNA.
Electronic excitation energy: Energy associated in the transition of
electrons from their normal low-energy orbitals or orbitals of higher
energy.
Electrophi1ic: Having an affinity for electrons.
Electrophoresis: A technique by which compounds can be separated from a
complex mixture by their attraction to the positive or negative
pole of an applied electric potential.
Eluant: A liquid used in the process of elution.
Elute: To perform an elution.
Elution: Separation of one material from another by washing or by dissolving
one in a solvent in which the other is not soluble.
Elutriate: To separate a coarse, insoluble powder from a finer one by
suspending them in water and pouring off the finer powder from the
upper part of the fluid.
Emission spectrometry: A rapid analytical technique based on measurement
of the characteristic radiation emitted by thermally or electrically
excited atoms or ions.
Emphysema: An anatomic alteration of the lung, characterized by abnormal
enlargement of air spaces distal to the terminal bronchioles, due
to dilation or destructive changes in the alveolar walls.
Emphysematous lesions: A wound or injury to the lung as a result of
emphysema.
6-18
-------
Empirical modeling: Characterization and description of a phenomena
based on experience or observation.
Encephalitis: Inflammation of the brain.
Endoplasmic reticulum: An elaborate membrane structure extending from the
nuclear membrane or eucaryotic cells to the cytoplasmic membrane.
Endothelium: A layer of flat cells lining especially blood and lymphatic
vessels.
Entropy: A measure of disorder or randomness in a system. Low entropy
is associated with highly ordered systems.
Enzyme: Any of numerous proteins produced by living cells which catalyze
biological reactions.
Enzyme Commission (EC): The International Commission on Enzymes, established
in 1956, developed a scheme of classification and nomenclature under
which each enzyme is assigned an EC number which identifies it by
function.
Eosinophils: Leukocytes (white blood cells) which stain readily with the
dye, eosin.
Epidemiology: A study of the distribution and determinants of disease
in human population groups.
Epidermis: The outermost living layer of cells of any organism.
Epididymal fat pads: The fatty tissue located near the epididymis. The
epididymis is the first convoluted portion of the excretory duct
of the testis.
Epiphyte: A plant growing on another plant but obtaining food from the
atmosphere.
Epithelial: Relating to epithelium, the membranous cellular layer which
covers free surfaces or lines tubes or cavities of an animal body,
which encloses, protects, secretes, excretes and/or assimilates.
Erosion corrosion: Acceleration or increase in rate of deterioration
or attack on a metal because of relative movement between a corrosive
fluid and the metal surface. Characterized by grooves, gullies, or
waves in the metal surface.
Erythrocyte: A mature red blood cell.
Escherichia coli: A short, gram-negative, rod-shaped bacteria common
to the human intestinal tract. A frequent cause of infections in
the urogenital tract.
-------
Esophageal: Relating to the portion of the digestive tract between the
pharynx and the stomach.
Estrus: That portion or phase of the sexual cycle of female animals
characterized by willingness to permit coitus.
Estrus cycle: The series of physiologic uterine, ovarian and other
changes that occur in higher animals.
Etiolation: Paleness and/or altered development resulting from the
absence of light.
Etiology: The causes of a disease or condition; also, the study of
causes.
Eucaryotic: Pertaining to those cells having a well-defined nucleus
surrounded by a double-layered membrane.
Euthrophication: Elevation of the level of nutrients in a body of water,
which can contribute to accelerated plant growth and filling.
Excited state: A state of higher electronic energy than the ground state,
usually a less stable one.
Expiratory (maximum) flow rate: The maximum rate at which air can be
expelled from the lungs.
Exposure level: Concentration of a contaminant to which an individual
or a population is exposed.
Extinction coefficient: A measure of the space rate of diminution, or
extinction, of any transmitted light, thus, it is the attenuation
coefficient applied to visible radiation.
Extramedullary hematopoiesis: The process of formation and development
of the various types of blood cells and other formed elements not
including that occurring in bone marrow.
Extravasate: To exclude from or pass out of a vessel into the tissues;
applies to urine, lymph, blood and similar fluids.
Far ultraviolet: Radiation in the range of wavelengths from 100 to 190
nanometers.
Federal Reference Method (FRM): For N02, the EPA-approved analyzers based
on the gas-phase chemiluminescent measurement principle and associated
calibration procedures; regulatory specifications prescribed in Title
40, Code of Federal Regulations, Part 50, Appendix F.
Fenestrae: Anatomical aperatures often closed by a membrane.
Fiber: A fine, threadlike piece, as of cotton, jute, or asbestos.
6-20
-------
Fiber-reactive dye: A water-soluble dyestuff which reacts chemically
with the cellulose in fibers under alkaline conditions; the dye
contains two chlorine atoms which combine with the hydroxyl groups of
the cellulose.
Fibrin: A white insoluble elastic filamentous protein derived from fibrino-
gen by the action of thrombin, especially in the clotting of blood.
Fibroadenoma: A benign neoplasm derived from glandular epithelium, in-
volving proliferating fibroblasts, cells found in connective tissue.
Fibroblast: An elongated cell with cytoplasmic processes present in
connective tissue, capable of forming collagen fibers.
Fibrosis: The formation of fibrous tissue, usually as a reparative or
reactive process and not as a normal constituent of an organ or
tissue.
Flocculation: Separation of material from a solution or suspension by
reaction with a flocculant to create fluffy masses containing the
material to be removed.
Fly ash: Fine, solid particles of noncombustible ash carried out of a
bed of solid fuel by a draft.
Folded-path optical system: A long (e.g. 8-22 m) chamber with multiple
mirrors at the ends which can be used to reflect an infrared beam through
an ambient air sample many times; a spectrometer can be used with such
a system to detect trace pollutants at very low levels.
Forced expiratory flow (FEF): The rate at which air can be expelled from
the lungs; see expiratory flow rate.
Forced expiratory volume (FEV): The maximum volume of air that can be
expired in a specific time interval when starting from maximal
inspiration.
Forced vital capacity (FVC): The greatest volume of air that can be
exhaled from the lungs under forced conditions after a maximum
inspiration.
Fractional threshold concentration: The portion of the concentration
at which an event or a response begins to occur, expressed as a
fraction.
Free radical: Any of a variety of highly-reactive atoms or molecules
characterized by having an unpaired electron.
Fritted bubbler: A porous glass device used in air pollutant sampling
systems to introduce small bubbles into solution.
G-21
-------
Functional residual capacity: The volume of gas remaining in the lungs
at the end of a normal expiration. It is the sum of expiratory
reserve volume and residual volume.
Gas exchange: Movement of oxygen from the alveoli into the pulmonary
capillary blood as carbon dioxide enters the alveoli from the blood.
Gas chromatography (GC): A method of separating and analyzing mixtures
of chemical substances. A flow of gas causes the components of a
mixture to migrate differentially from a narrow starting zone in a
special porous, insoluble sorptive medium. The pattern formed by
zones of separated pigments and of colorless substances in this
process is called a chromatogram, and can be analyzed to obtain the
concentration of identified pollutants.
Gas-liquid chromatography: A method of separating and analyzing volatile
organic compounds, in which a sample is vaporized and swept through
a column filled with solid support material covered with a nonvolatile
liquid. Components of the sample can be identified and their con-
centrations determined by analysis of the characteristics of their
retention in the column, since compounds have varying degrees of
solubility in the liquid medium.
Gastric juice: A thin watery digestive fluid secreted by glands in the
mucous membrane of the stomach.
Gastroenteritis: Inflammation of the mucous membrane of stomach and
intestine.
Genotype: The type of genes possessed by an organism.
Geometric mean: An estimate of the average of a distribution. Specifically,
the nth root of the product of n observations.
Geometric standard deviation: A measure of variability of a distribution.
It is the antilogarithm of the standard deviation of the logarithms
of the observations.
Globulins (a, b, q): A family of proteins precipitated from plasma (or
serum) by half-saturation with ammonium sulfate, or separable by
electrophoresis. The main groups are the a, b, q fractions, differ-
ing with respect to associated lipids and carbohydrates and in their
content of antibodies (immunoglobulins).
Glomular nephrotic syndrome: Dysfunction of the kidneys characterized
by excessive protein loss in the urine, accumulation of body fluids
and alteration in albumin/globulin ratio.
Glucose: A sugar which is a principal source of energy for man and other
organisms.
Glucose-6-phosphate dehydrogenase: An enzyme (EC 1.1.1.49) catalyzing
the dehydrogenation of glucose-6-phosphate to 6-phosphogluconolactone.
G-22
-------
Glutamic-oxaloacetic transaminase (SCOT): An enzyme (EC 2.6.1.1) whose
serum level increases in myocardial infarction and in diseases in-
volving destruction of liver cells. Also known as aspartate
aminotransferase.
Glutamic-pyruvic transaminase (SGPT): Now known as alanine aminotransferase
(EC 2.6.1.2), the serum levels of this enzyme are used in liver function
tests.
Glutathione (GSH): A tripeptide composed of glycine, cystine, and glutamic
acid.
Glutathione peroxidase: An enzyme (EC 1.11.1) which catalyzes the destruction
of hydroperoxides formed from fatty acids and other substances.
Protects tissues from oxidative damage. It is a selenium-containing
protein.
Glutathione reductase: The enzyme (EC 1.6.4.2) which reduces the oxidized
form of glutathione.
Glycolytic pathway: The biochemical pathway by which glucose is con-
verted to lactic acid in various tissues, yielding energy as a
result.
Glycoside: A type of chemical compound formed from the condensation of
a sugar with another chemical radical via a hemiacetal linkage.
Goblet cells: Epithelial cells that have been distended with mucin and when
this is discharged as mucus, a goblet-shaped shell remains.
Golgi apparatus: A membrane system involved with secretory functions
and transport in a cell. Also known as a dictyosome.
Grana: The lamellar stacks of chlorophyll-containing material in plant
chloroplasts.
Griege carpet: A carpet in its unfinished state, i.e. before it has
been scoured and dyed. The term also is used for woven fabrics
in the unbleached and unfinished state.
Ground state: The state of minimum electronic energy of a molecule or
atom.
Guanylate cyclase (GC): An enzyme (EC 4.6.2.1) catalyzing the trans-
formation of guanosine triphosphate to guanosine 3':5'-cyclic phosphate.
H-Thymidine: Ihymine deoxyribonucleoside: One of the four major nucleosides
in DNA. H-thymidine has been uniformly labeled with tritium, a radio-
active form of hydrogen.
Haze: Fine dust, smoke or fine vapor reducing transparency of air.
G-23
-------
Hemagglutination: The agglutination of red blood cells. Can be used as
as a measurement of antibody concentration.
Hematocrit: The percentage of the volume of a blood sample occupied by
cells.
Hematology: The medical specialty that pertains to the blood and blood-
forming tissues.
Hemochromatosis: A disease characterized by pigmentation of the skin
possibly due to inherited excessive absorption of iron.
Hemoglobin (Hb): The red, respiratory protein of the red blood cells,
hemoglobin transports oxygen from the lungs to the tissues as oxy-
hemoglobin (Hb02) and returns carbon dioxide to the lungs as hemoglobin
carbamate, completing the respiratory cycle.
Hemolysis: Alteration or destruction of red blood cells, causing hemoglobin
to be released into the medium in which the cells are suspended.
Hepatectomy: Complete removal of the liver in an experimental animal.
Hepatic: Relating to the liver.
Hepatocyte: A liver cell.
Heterogeneous process: A chemical reaction involving reactants of more
than one phase or state, such as one in which gases are absorbed into
aerosol droplets, where the reaction takes place.
Heterologous: A term referring to donor and recipient cellular elements
from different organisms, such as red blood cells from sheep and
alveolar macrophage from rabbits.
Hexose monophosphate shunt: Also called the phosphogluconate oxidative
pathway of glucose metabolism which affords a total combustion of
glucose independent of the citric acid cycle. It is the important
generator of NADPH necessary for synthesis of fatty acids and the
operation of various enzymes. It serves as a source of ribose and
4- and 7-carbon sugars.
High-volume sampler (Hi-vol): Device for taking a sample of the particulate
content of a large amount of_air, by drawing air through a fiber filter
at a typical rate of 2,000 m /24 hr (1.38 m /min), or as high as 2,880
rn/24 hr (2 in /min).
Histamine: An amine derived from the amino acid, histidine. It is a
powerful stimulant of gastric secretion and a constrictor of bronchial
smooth muscle. It is a vasodilator and causes a fall in blood
pressure.
G-24
-------
Homogenate: Commonly refers to tissue ground into a creamy consistency
in which the cell structure is disintegrated.
Host defense mechanism: Inherent means by which a biologic organism
protects itself against infection, such as antibody formation,
macrophage action, ciliary action, etc.
Host resistance: The resistance exhibited by an organism, such as man,
to an infecting agent, such as a virus or bacteria.
Humoral: Relating to the extracellular fluids of the body, blood and
lymph.
Hybrid: An organism descended from parents belonging to different
varieties or species.
Hydrocarbons: A vast family of compounds containing carbon and hydrogen
in various combinations; found especially in fossil fuels. Some
contribute to photochemical smog.
Hydrolysis: Decomposition involving splitting of a bond and addition
of the H and OH parts of water to the two sides of the split bond.
Hydrometeor: A product of the condensation of atmospheric water vapor (e.g.
fog, rain, hail, snow).
Hydroxyproline: An amino acid found among the hydrolysis products of
collagen.
Hygroscopic: Pertaining to a marked ability to accelerate the condensation
of water vapor.
Hyperplasia: Increase in the number of cells in a tissue or organ ex-
cluding tumor formation.
Hyperplastic: Relating to hyperplasia; an increase in the number of
cells.
Hypertrophy: Increase in the size of a tissue element, excluding tumor
formation.
Hypertension: Abnormally elevated blood pressure.
Hypolimnia: Portions of a lake below the thermocline, in which water
is stagnant and uniform in temperature.
Hypoxia: A lower than normal amount of oxygen in the air, blood or tissues
G-25
-------
Immunoglobulin (Ig): A class of structurally related proteins consist-
ing of two pairs of polypeptide chains. Antibodies are Ig's and
all Ig's probably function as antibodies.
Immunoglobulin A (IgA): A type of antibody which comprises approximately
10 to 15 percent of the total amount of antibodies present in normal
serum.
Immunoglobulin G (IgG): A type of antibody which comprises approximately
80 percent of the total amount of antibodies present in normal serum.
Subfractions of IgG are fractions G,, and G^.
Immunoglobulin M (IgM): A type of antibody which comprises approximately
5 to 10 percent of the total amount of antibodies present in normal
serum.
Impaction: An impinging or striking of one object against another; also,
the force transmitted by this act.
Impactor: An instrument which collects samples of suspended particulates
by directing a stream of the suspension against a surface, or into a
liquid or a void.
Index of proliferation: Ratio of promonocytes to polymorphic monocytes
in the blood.
Infarction: Sudden insufficiency of arterial or venous blood supply
due to emboli, thrombi, or pressure.
Infectivity model: A testing system in which the susceptibility of
animals to airborne infectious agents with and without exposure to air
pollutants is investigated to produce information related to the
possible effects of the pollutant on man.
Inflorescence: The arrangement and development of flowers on an axis;
also, a flower cluster or a single flower.
Influenza Ap/Taiwan Virus: An infectious viral disease, believed to
have originated in Taiwan, characterized by sudden onset, chills,
fevers, headache, and cough.
Infrared: Light invisible to the human eye, bgtween the wavelengths
of 7x10 and 10 m (7000 and 10,000,000 A).
Infrared laser: A device that utilizes the natural oscillations of atoms
or molecules to generate coherent electromagnetic radiation in the
infrared region of the spectrum.
Infrared spectrometer: An instrument for measuring the relative amounts
of radiant energy in the infrared region of the spectrum as a function
of wavelength.
6-Z6
-------
Ingestion: To take in for digestion.
In situ: In the natural or original position.
Instrumental averaging time: The time over which a single sample or
measurement is taken, resulting in a measurement which is an average
of the actual concentrations over that period.
Insult: An injury or trauma.
Intercostal: Between the ribs, especially of a leaf.
Interferant: A substance which a measurement method cannot distinguish
completely from the one being measured, which therefore can cause some
degree of false response or error.
Interferon: A macromolecular substance produced in response to infection
with active or inactivated virus, capable of inducing a state of
resistance.
Intergranular corrosion: A type of corrosion which takes place at and
adjacent to grain boundaries, with relatively little corrosion of
the grains.
Interstitial edema: An accumulation of an excessive amount of fluids
in a space within tissues.
Interstitial pneumonia: A chronic inflammation of the interstitial tissue
of the lung, resulting in compression of air cells.
Intraluminal mucus: Mucus that collects within any tubule.
Intraperitoneal injection: An injection of material into the serous
sac that lines the abdominal cavity.
In utero: Within the womb; not yet born.
In vitro: Refers to experiments conducted outside the living organism.
In vivo: Refers to experiments conducted within the living organism.
Irradiation: Exposure to any form of radiation.
Ischemia: Local anemia due to mechanical obstruction (mainly arterial
narrowing) of the blood supply.
Isoenzymes: Also called isozymes. One of a group of enzymes that are
very similar in catalytic properties, but may be differentiated by
variations in physical properties, such as isoelectric point or
electrophoretic mobility. Lactic acid dehydrogenase is an example
of an enzyme having many isomeric forms.
G-27
-------
Isopleth: A line on a map or chart connecting points of equal value.
Jacobs-Hochheiser method: The original Federal Reference Method for N02,
currently unacceptable for air pollution work.
Klebsiella pneumoniae: A species of rod-shaped bacteria found in soil,
water, and in the intestinal tract of man and other animals. Certain
types may be causative agents in pneumonia.
Kyphosis: An abnormal curvature of the spine, with convexity backward.
Lactate: A salt or ester of lactic acid.
Lactic acid (lactate) dehydrogenase (LDH): An enzyme (EC 1.1.1.27) with
many isomeric forms which catalyzes the oxidation of lactate to
pyruvate via transfer of H to NAD. Isomeric forms of LDH in the
blood are indicators of heart damage.
Lamellar bodies: Arranged in plates or scales. One of the characteristics
of Type II alveolar cells.
Lavage fluid: Any fluid used to wash out hollow organs, such as the lung.
Lecithin: Any of several waxy hygroscopic phosphatides that are widely
distributed in animals and plants; they form colloidal solutions in
water and have emulsifying, wetting and hygroscopic properties.
Legume: A plant with root nodules containing nitrogen fixing bacteria.
Lesion: A wound, injury or other more or less circumscribed pathologic
change in the tissues.
Leukocyte: Any of the white blood cells.
Lewis base: A base, defined in the Lewis acid-base concept, is a sub-
stance that can donate an electron pair.
Lichens: Perennial plants which are a combination of two plants, an alga
and a fungus, growing together in an association so intimate that they
appear as one.
Ligand: Those molecules or anions attached to the central atom in a
complex.
Light-fastness: The ability of a dye to maintain its original color under
natural or indoor light.
Linolenic acid: An unsaturated fatty acid essential in nutrition.
Lipase: An enzyme that accelerates the hydrolysis or synthesis of fats
or the breakdown of lipoproteins.
G-28
-------
Lipids: A heterogeneous group of substances which occur widely in bio-
logical materials. They are characterized as a group by their
extractability in nonpolar organic solvents.
Lipofuscin: Brown pigment granules representing lipid-containing residues
of lysosomal digestion. Proposed to be an end product of lipid
oxidation which accumulates in tissue.
Lipoprotein: Complex or protein containing lipid and protein.
Loading rate: The amount of a nutrient available to a unit area of body
of water over a given period of time.
Locomotor activity. Movement of an organism from one place to another
of its own volition.
Long-pathlength infrared absorption: A measurement technique in which a
system of mirrors in a chamber is used to direct an infrared beam
through a sample of air for a long distance (up to 2 km); the amount
of infrared absorbed is measured to obtain the concentrations of
pollutants present.
Lung compliance (C,): The volume change produced by an increase in a
unit change in pressure across the lung, i.e., between the pleural
surface and the mouth.
Lycra: A spandex textile fiber created by E. I. du Pont de Nemours & Co.,
Inc., with excellent tensile strength, a long flex life and high
resistance to abrasion and heat degradation. Used in brassieres,
foundation garments, surgical hosiery, swim suits and military and
industrial uses.
Lymphocytes: White blood cells formed in lymphoid tissue throughout the
body, they comprise about 22 to 28 percent of the total number of
leukocytes in the circulating blood and function in immunity.
Lymphocytogram: The ratio, in the blood, of lymphocyte with narrow
cytoplasm to those with broad cytoplasm.
Lysosomes: Organelles found in cells of higher organisms that contain
high concentrations of degradative enzymes and are known to destroy
foreign substances that cells engulf by pinocytosis and phyocytosis.
Believed to be a major site where proteins are broken down.
Lysozymes: Lytic enzymes destructive to cell walls of certain bacteria.
Present in some body fluids, including tears and serum.
Macaca speciosa: A species of monkeys used in research.
Macrophage: Any large, ameboid, phagocytic cell having a nucleus without
many lobes, regardless of origin.
G-29
-------
Malaise: A feeling of general discomfort or uneasiness, often the first
indication of an infection or disease.
Malate dehydrogenase: An enzyme (EC 1.1.1.37) with at least six isomeric
forms that catalyze the dehydrogenation of malate to oxaloacetate
or its decarboxylation (removal of a C02 group) to pyruvate. Malate,
oxaloacetate, and pyruvate are intermediate components of biochemical
pathways.
Mannitol: An alcohol derived from reduction of the sugar, fructose.
Used in renal function testing to measure glomerular (capillary)
filtration.
Manometer: An instrument for the measurement of pressure of gases or
vapors.
Mass median diameter (MMD): Geometric median size of a distribution of
particles based on weight.
Mass spectrometry (MS): A procedure for identifying the various kinds of
particles present in a given substance, by ionizing the particles
and subjecting a beam of the ionized particles to an electric or
magnetic field such that the field deflects the particles in angles
directly proportional to the masses of the particles.
Maximum flow (V ): Maximum rate or expiration, usually expressed at
50 or 25 percent of vital capacity.
Maximum mid-expiratory flow rate (MMFR): The mean rate of expiratory gas
flow between 25 and 75 percent of the forced expiratory vital capacity.
Mean (arithmetic): The sum of observations divided by sample size.
Median: A value in a collection of data values which is exceeded in
magnitude by one-half the entries in the collection.
Mesoscale: Of or relating to meteorological phenomena from 1 to 100
kilometers in horizontal extent.
Messenger RNA: A type of RNA which conveys genetic information encoded
in the DNA to direct protein synthesis.
Metaplasia: The abnormal transformation of an adult, fully differentiated
tissue of one kind into a differentiated tissue of another kind.
Metaproterenol: A bronchodilator used for the treatment of bronchial
asthma.
Metastases: The shifting of a disease from one part of the body to another;
the appearance of neoplasms in parts of the body remote from the seat
of the primary tumor.
G-30
-------
Meteorology: The science that deals with the atmosphere and its phenomena.
Methemoglobin: A+form of hemoglobin in which the normal reduced state
of iron (Fe ) has been oxidized to Fe . It contains oxygen in
firm union with ferric (Fe ) iron and is not capable of exchanging
oxygen in normal respiratory processes.
Methimazole: An anti-thyroid drug similar in action to propylthiouracil.
Methyltransferase: Any enzyme transferring methyl groups from one compound
to another.
Microcoulometric: Capable of measuring millionths of coulombs used in
electrolysis of a substance, to determine the amount of a substance
in a sample.
Microflora: A small or strictly localized plant.
Micron: One-millionth of a meter.
Microphage: A small phagocyte; a polymorphonuclear leukocyte that is
phagocytic.
Millimolar: One-thousandth of a molar solution. A solution of one-
thousandth of a mole (in grams) per liter.
Minute volume: The minute volume of breathing; a product of tidal volume
times the respiratory frequency in one minute.
Mitochondria: Organelles of the cell cytoplasm which contain enzymes
active in the conservation of energy obtained in the aerobic part
of the breakdown of carbohydrates and fats, in a process called
respiration.
Mobile sources: Automobiles, trucks and other pollution sources which are
not fixed in one location.
Modacrylic fiber: A manufactured fiber in which the fiber-forming sub-
stance is any long chain synthetic polymer composed of less than 85
percent but at least 35 percent by weight of acrylonitrite units.
Moeity: One of two or more parts into which something is divided.
Mole: The mass, in grams, numerically equal to the molecular weight of
a substance.
Molecular correlation spectrometry: A spectrophotometric technique which
is used to identify unknown absorbing materials and measure their
concentrations by using preset wavelengths.
Molecular weight: The weight of one molecule of a substance obtained
by adding the gram-atomic weights of each of the individual atoms
in the substance.
G-31
-------
Monocyte: A relatively large mononuclear leukocyte, normally constituting
3 to 7 percent of the leukocytes of the circulating blood.
Mordant: A substance which acts to bind dyes to a textile fiber of fabric.
Morphological: Relating to the form and structure of an organism or any
of its parts.
Moving average: A procedure involving taking averages over a specific
period prior to and including a year in question, so that successive
averaging periods overlap; e.g. a three-year moving average would
include data from 1967 through 1969 for the 1969 average and from
1968 through 1970 for 1970.
Mucociliary clearance: Removal of materials from the upper respiratory
tract via ciliary action.
Mucociliary transport: The process by which mucus is transported, by
ciliary action, from the lungs.
Mucosa: The mucous membrane; it consists of epithelium, lamina propria
and, in the digestive tract, a layer of smooth muscle.
Mucous membrane: A membrane secreting mucus which lines passages and
cavities communicating with the exterior of the body.
Murine: Relating to mice.
Mutagen: A substance capable of causing, within an organism, biological
changes that affect potential offspring through genetic mutation.
Mutagenic: Having the power to cause mutations. A mutation is a change
in the character of a gene (a sequence of base pairs in DNA) that
is perpetuated in subsequent divisions of the cell in which it occurs.
Myocardial infarction: Infarction of any area of the heart muscle usually
as a result of occlusion of a coronary artery.
Nares: The nostrils.
Nasopharyngeal: Relating to the nasal cavity and the pharynx (throat).
National Air Surveillance Network (NASN): Network of monitoring stations
for sampling air to determine extent of air pollution; established
jointly by federal and state governments.
Near ultraviolet: Radiation of the wavelengths 2000-4000 Angstroms.
Necrosis: Death of cells that can discolor areas of a plant or kill
the entire plant.
Necrotic: Pertaining to the pathologic death of one or more cells, or
of a portion of tissue or organ, resulting from irreversible damage.
G-32
-------
Neonate: A newborn.
Neoplasm: An abnormal tissue that grows more rapidly than normal; synonymous
with tumor.
Neoplasia: The pathologic process that results in the formation and
growth of a tumor.
Neutrophil: A mature white blood cell formed in bone marrow and released
into the circulating blood, where it normally accounts for 54 to 65
percent of the total number of leukocytes.
Ninhydrin: An organic reagent used to identify amino acids.
Nitramine: A compound consisting of a nitrogen attached to the nitrogen
of amine.
Nitrate: A salt or ester of nitric acid (NO- ).
Nitrification: The principal natural source of nitrate in which ammonium
(NH.+) ions are oxidized to nitrites by specialized microorganisms.
Other organisms oxidize nitrites to nitrates.
Nitrite: A salt or ester of nitrous acid (N0?~).
Nitrocellulose: Any of several esters of nitric acid formed by its action
on cellulose, used in explosives, plastics, varnishes and rayon;
also called cellulose nitrate.
Nitrogen cycle: Refers to the complex pathways by which nitrogen-containing
compounds are moved from the atmosphere into organic life, into the
soil, and back to the atmosphere.
Nitrogen fixation: The metabolic assimilation of atmospheric nitrogen by
soil microorganisms, which becomes available for plant use when the
microorganisms die; also, industrial conversion of free nitrogen into
combined forms used in production of fertilizers and other products.
Nitrogen oxide: A compound composed of only nitrogen and oxygen. Components
of photochemical smog.
Nitrosamine: A compound consisting of a nitrosyl group connected to the
nitrogen of an amine.
Nitrosation: Addition of a nitrosyl group.
N-Nitroso compounds: Compounds carrying the functional nitrosyl group.
Nitrosyl: A group composed of one oxygen and one nitrogen atom (-N=0).
Nitrosylhemoglobin (NOHb): The red, respiratory protein of erythrocytes
to which a nitrosyl group is attached.
G-33
-------
N/P Ratio: Ratio of nitrogen to phosphorous dissolved in lake water,
important due to its effect on plant growth.
Nucleolus: A small spherical mass of material within the substance of the
nucleus of a cell.
Nucleophilic: Having an affinity for atomic nuclei; electron-donating.
Nucleoside: A compound that consists of a purine or pyrimidine base com-
bined with deoxyribose or ribose and found in RNA and DMA.
5'-Nucleotidase: An enzyme (EC 3.1.3.5) which hydrolyzes nucleoside 5'-
phosphates into phosphoric acid (H3P04) and nucleosides.
Nucleotide: A compound consisting of a sugar (ribose or deoxyribose),
a base (a purine or a pyrimidine), and a phosphate; a basic structural
unit of RNA and DMA.
Nylon: A generic name chosen by E. I. du Pont de Nemours & Co., Inc.
for a group of protein-like chemical products classed as synthetic
linear polymers; two main types are Nylon 6 and Nylon 66.
Occlusion: A point which an opening is closed or obstructed.
Olefin: An open-chain hydrocarbon having at least one double bond.
Olfactory: Relating to the sense of smell.
Olfactory epithelium: The inner lining of the nose and mouth which contains
neural tissue sensitive to smell.
Oligotrophic: A body of water deficient in plant nutrients; also generally
having abundant dissolved oxygen and no marked stratification.
Oribitals: Areas of high electron density in an atom or molecule.
Orion: An acrylic fiber produced by E. I. du Pont de Nemours and Co., Inc.,
based on a polymer of acrylonitrite; used extensively for outdoor
uses, it is resistant to chemicals and withstands high temperatures.
Osteogenic osteosarcoma: The most common and malignant of bone sarcomas
(tumors). It arises from bone-forming cells and affects chiefly
the ends of long bones.
Ovarian primordial follicle: A spheroidal cell aggregation in the ovary
in which the primordial oocyte (immature female sex cell) is surrounded
by a single layer of flattened follicular cells.
Oxidant: A chemical compound which has the ability to remove electrons
from another chemical species, thereby oxidizing it; also, a substance
containing oxygen which reacts in air to produce a new substance, or
one formed by the action of sunlight on oxides of nitrogen and hydro-
carbons.
G-34
-------
Oxidation: An ion or molecule undergoes oxidation by donating electrons.
Oxidative deamination: Removal of the NH? group from an amino compound
by reaction with oxygen.
Oxidative phosphorylation: The mitochondrial process by which "high-
energy" phosphate bonds form from the energy released as a result of
the oxidation of various substrates. Principally occurs in the tri-
carboxylic acid pathway.
Oxyhemoglobin: Hemoglobin in combination with oxygen. It is the form
of hemoglobin present in arterial blood.
Ozone layer: A layer of the stratosphere from 20 to 50 km above the
earth's surface characterized by high ozone content produced by ultra-
violet radiation.
Ozone scavenging: Removal of 03 from ambient air or plumes by reaction with
NO, producing NOp and Op.
Paired electrons: Electrons having opposite intrinsic spins about their
own axes.
Parenchyma: The essential and distinctive tissue of an organ or an ab-
normal growth, as distinguished from its supportive framework.
Parenchyma 1: Referring to the distinguishing or specific cells of a
gland or organ.
Partial pressure: The pressure exerted by a single component in a mixture
of gases.
Particulates: Fine liquid or solid particles such as dust, smoke, mist,
fumes or smog, found in the air or in emissions.
Pascal: A unit of pressure in the International System of Units. One
pascal is equal to 7.4 x 10 torr. The pascal is equivalent to one
newton per square meter.
Pathogen: Any virus, microorganism, or other substance causing disease.
Pathophysiological: Derangement of function seen in disease; alteration
in function as distinguished from structural defects.
Peptide bond: The bond formed when two amino acids react with each other.
Percentiles: The percentage of all observations exceeding or preceding
some point; thus, 90th percentile is a level below which will fall 90
percent of the observations.
Perfusate- A liquid, solution or colloidal suspension that has been passed
over a special surface or through an appropriate structure.
G-35
-------
Perfusion: Artificial passage of fluid through blood vessels.
Permanent-press fabrics: Fabrics in which applied resins contribute to the
easy care and appearance of the fabric and to the crease and seam
flat-
ness by reacting with the cellulose on pressing after garment
manufacture.
Permeation tube: A tube which is selectively porous to specific gases.
Peroxidation: Refers to the process by which certain organic compounds
are converted to peroxides.
Peroxyacetyl nitrate (PAN): Pollutant created by action of sunlight on
hydrocarbons and NO in the air; an ingredient of photochemical smog.
pH: A measure of the acidity or alkalinity of a material, liquid, or solid.
pH is represented on a scale of 0 to 14 with 7 being a neutral state,
0 most acid, and 14 most alkaline.
Phagocytosis: Ingestion, by cells such as macrophages, of other cells,
bacteria, foreign particles, etc.; the cell membrane engulfs solid or
liquid particles which are drawn into the cytoplasm and digested.
Phenotype: The observable characteristics of an organism, resulting from
the interaction between an individual genetic structure and the
environment in which development takes place.
Phenylthiourea: A crystalline compound, CyHgN-S, that is bitter or tasteless
depending on a single dominant gene in the tester.
Phlegm: Viscid mucus secreted in abnormal quantity in the respiratory passages.
Phosphatase: Any of a group of enzymes that liberate inorganic phosphate
from phosphoric esters (E.G. sub-subclass 3.1.3).
Phosphocreatine kinase: An enzyme (EC 2.7.3.2) catalyzing the formation of
creatine and ATP, its breakdown is a source of energy in the contraction
of muscle; also called creatine phosphate.
Phospholipid: A molecule consisting of lipid and phosphoric acid group(s).
An example is lecithin. Serves as an important structural factor
in biological membranes.
Photochemical oxidants: Primary ozone, NO-, PAN with lesser amounts of
other compounds formed as products of atmospheric reactions involving
organic pollutants, nitrogen oxides, oxygen, and sunlight.
Photochemical smog: Air pollution caused by chemical reaction of various
airborne chemicals in sunlight.
Photodissociation: The process by which a chemical compound breaks down into
simpler components under the influence of sunlight or other radiant energy.
G-36
-------
Photolysis: Decomposition upon irradiation by sunlight.
Photomultiplier tube: An electron multiplier in which electrons released
by photoelectric emission are multiplied in successive stages by
dynodes that produce secondary emissions.
Photon: A quantum of electromagnetic energy.
Photostationary: A substance or reaction which reaches and maintains a
steady state in the presence of light.
Photosynthesis: The process in which green parts of plants, when exposed to
light under suitable conditions of temperature and water supply, produce
carbohydrates using atmospheric carbon dioxide and releasing oxygen.
Phytotoxic: Poisonous to plants.
Phytoplankton: Minute aquatic plant life.
Pi n bonds: Bonds in which electron density is not symmetrical about a
line joining the bonded atoms.
Pinocytotic: Refers to the cellular process (pinocytosis) in which the cyto-
plasmic membrane forms invaginations in the form of narrow channels
leading into the cell. Liquids can flow into these channels and the
membrane pinches off pockets that are incorporated into the cytoplasm
and digested.
Pitting: A form of extremely localized corrosion that results in holes in
the metal. One of the most destructive forms of corrosion.
Pituary: A stalk-like gland near the base of the brain which is attached
to the hypothalmus. The anterior portion is a major repository for
for hormones that control growth, stimulate other glands, and regulate
the reproductive cycle.
Placenta: The organ in the uterus that provides metabolic interchange between
the fetus and mother.
Plasmid: Replicating unit, other than a nucleus gene, that contains
nucleoprotein and is involved in various aspects of metabolism in
organisms; also called paragenes.
Plasmolysis: The dissolution of cellular components, or the shrinking
of plant cells by osmotic loss of cytoplasmic water.
Plastic: A plastic is one of a large group of organic compounds synthesized
from cellulose, hydrocarbons, proteins or resins and capable of being
cast, extruded, or molded into various shapes.
Plasticizer: A chemical added to plastics to soften, increase malleability
or to make more readily deformable.
G-37
-------
Platelet (blood): An irregularly-shaped disk with no definite nucleus;
about one-third to one-half the size of an erythrocyte and containing
no hemoglobin. Platelets are more numerous than leukocytes, numbering
from 200,000 to 300,000 per cu. mm. of blood.
Plethysmograph: A device for measuring and recording changes in volume of
a part, organ or the whole body; a body plethysmograph is a chamber
apparatus surrounding the entire body.
Pleura: The serous membrane enveloping the lungs and lining the walls of
the chest cavity.
Plume: Emission from a flue or chimney, usually distributed stream-like
downwind of the source, which can be distinguished from the surrounding
air by appearance or chemical characteristics.
Pneumonia (interstitial): A chronic inflammation of the interstitial tissue
of the lung, resulting in compression of the air cells. An acute, infec-
tious disease.
Pneumonocytes: A nonspecific term sometimes used in referring to types of
cells characteristic of the respiratory part of the lung.
Podzol: Any of a group of zonal soils that develop in a moist climate,
especially under coniferous or mixed forest.
Point source: A single stationary location of pollutant discharge.
Polarography: A method of quantitative or qualitative analysis based on
current-voltage curves obtained by electrolysis of a solution with
steadily increasing voltage.
Pollution gradient: A series of exposure situations in which pollutant con-
centrations range from high to low.
Polyacrylonitrile: A polymer made by reacting ethylene oxide and hydrocyanic
acid. Dynel and Orion are examples.
Polyamides: Polymerization products of chemical compounds which contain
amino (-NH-) and carboxyl (-COOH) groups. Condensation reactions
between the groups form amides (-CONH-). Nylon is an example of
a polyamide.
Polycarbonate: Any of various tough transparent thermoplastics characterized
by high impact strength and high softening temperature.
Polycythemia: An increase above the normal in the number of red cells in the
blood.
Polyester fiber: A man-made or manufactured fiber in which the fiber-
forming substance is any long-chain synthetic polymer composed of
at least 85 percent by weight of an ester of a dihydric alcohol and
terephthalic acid. Dacron is an example.
G-38
-------
Polymer: A large molecule produced by linking together many like molecules.
Polymerization: In fiber manufacture, converting a chemical monomer (simple
molecule) into a fiber-forming material by joining many like molecules
into a stable, long-chain structure.
Polymorphic monocyte: Type of leukocyte with a multi-lobed nucleus.
Polymorphonuclear leukocytes: Cells which represent a secondary non-
specific cellular defense mechanism. They are transported to the lungs
from the bloodstream when the burden handled by the alveolar macrophages
is too large.
Polysaccharides: Polymers made up of sugars. An example is glycogen which
consists of repeating units of glucose.
Polystyrene: A thermoplastic plastic which may be transparent, opaque,
or translucent. It is light in weight, tasteless and odorless, it
also is resistant to ordinary chemicals.
Polyurethane: Any of various polymers that contain NHCOO linkages and are
used especially in flexible and rigid foams, elastomers and resins.
Pores of Kohn: Also known as interalveolar pores; pores between air cells.
Assumed to be pathways for collateral ventilation.
Precipitation: Any of the various forms of water particles that fall from
the atmosphere to the ground, rain, snow, etc.
Precursor: A substance from which another substance is formed; specifically,
one of the anthropogenic or natural emissions or atmospheric constituents
which reacts under sunlight to form secondary pollutants comprising
photochemical smog.
Probe: In air pollution sampling, the tube or other conduit extending
into the atmosphere to be sampled, through which the sample passes
to treatment, storage and/or analytical equipment.
Proline: An amino acid, Cj-HgMOp, that can be synthesized from glutamate
by animals.
Promonocyte: An immature monocyte not normally seen in the circulating
blood.
Proteinuria: The presence of more than 0.3 gm of urinary protein in a
24-hour urine collection.
Pulmonary: Relating to the lungs.
Pulmonary edema: An accumulation of excessive amounts of fluid in the lungs.
G-39
-------
Pulmonary lumen: The spaces in the interior of the tubular elements of
the lung (bronchioles and alveolar ducts).
Pulmonary resistance: Sum of airway resistance and viscous tissue resistance.
Purine bases: Organic bases which are constituents of DNA and RNA, including
adenine and guanine.
Purulent: Containing or forming pus.
Pyrimidine bases: Organic bases found in DNA and RNA. Cytosine and
thymine occur in DNA and cytosine and uracil are found in RNA.
QRS: Graphical representation on the electrocardiogram of a complex of three
distinct waves which represent the beginning of ventricular contraction.
Rainout: Removal of particles and/or gases from the atmosphere by their
involvement in cloud formation (particles act as condensation nuclei,
gases are absorbed by cloud droplets), with subsequent precipitation.
Rayleigh scattering: Coherent scattering in which the intensity of the
light of wavelength g, scattered in any direction making an angle
with the incident direction, is.directly proportional to 1 + cos r
and inversely proportional to g .
Reactive dyes: Dyes which react chemically with cellulose in fibers under
alkaline conditions. Also called fiber reactive or chemically
reactive dyes.
Reduction: Acceptance of electrons by an ion or molecule.
Reference method (RM): For NO-, an EPA-approved gas-phase chemiluminescent
analyzer and associated calibration techniques; regulatory specifications
are described in Title 40, Code of Federal Regulations, Part 50,
Appendix F. Formerly, Federal Reference Method.
Residual capacity: The volume of air remaining in the lungs after a maximum
expiratory effort; same as residual volume.
Residual volume (RV): The volume of air remaining in the lungs after a
maximal expiration. RV = TLC - VC
Resin: Any of various solid or semi-solid amorphous natural organic sub-
stances, usually derived from plant secretions, which are soluble in
organic solvents but not in water; also any of many synthetic substances
with similar properties used in finishing fabrics, for permanent press
shrinkage control or water repellency.
Ribosomal RNA: The most abundant RNA in a cell and an integral constituent
of ribosomes.
G-40
-------
Ribosomes: Discrete units of RNA and protein which are instrumental in the
synthesis of proteins in a cell. Aggregates are called polysomes.
Runoff: Water from precipitation, irrigation or other sources that flows
over the ground surface to streams.
Sclerosis: Pathological hardening of tissue, especially from overgrowth
of fibrous tissue or increase in interstitial tissue.
Selective leaching: The removal of one element from a solid alloy by
corrosion processes.
Septa: A thin wall dividing two cavities or masses of softer tissue.
Seromucoid: Pertaining to a mixture of watery and mucinous material such
as that of certain glands.
Serum antiprotease: A substance, present in serum, that inhibits the activity
of proteinases (enzymes which destroy proteins).
Sigma (s) bonds: Bonds in which electron density is symmetrical about a
line joining the bonded atoms.
Silo-filler's disease: Pulmonary lesion produced by oxides of nitrogen
produced by fresh silage.
Single breath nitrogen elimination rate: Percentage rise in nitrogen fraction
per unit of volume expired.
Single breath nitrogen technique: A procedure in which a vital capacity
inspiration of 100 percent oxygen is followed by examination of nitrogen
in the vital capacity expirate.
Singlet state: The highly-reactive energy state of an atom in which certain
electrons have unpaired spins.
Sink: A reactant with or absorber of a substance.
Sodium arsenite: Na-AsO», used with sodium hydroxide in the absorbing solu-
tion of a 24-hour integrated manual method for N02-
Sodium dithionite: A strong reducing agent (a supplier of electrons).
Sodium metabisulfite: Na^O., used in absorbing solutions of N02 analysis
methods.
Sorb: To take up and hold by absorption or adsorption.
G-41
-------
Sorbent: A substance that takes up and holds another by absorption or
adsorption.
Sorbitol dehydrogenase: An enzyme that interconverts the sugars, sorbitol
and fructose.
Sorption: The process of being sorbed.
Spandex: A manufactured fiber in which the fiber forming substance is a
long chain synthetic elastomer composed of at least 85 percent of a
segmented polyurethane.
Spectrometer: An instrument used to measure radiation spectra or to deter-
mine wavelengths of the various radiations.
Spectrophotometry: A technique in which visible, UV, or infrared radiation
is passed through a substance or solution and the intensity of light
transmitted at various wavelengths is measured to determine the spectrum
of light absorbed.
Spectroscopy: Use of the spectrometer to determine concentrations of an
air pollutant.
Spermatocytes: A cell destined to give rise to spermatozoa (sperm).
Sphingomyelins: A group of phospholipids found in brain, spinal cord, kidney
and egg yolk.
Sphygomenometer: An apparatus, consisting of a cuff and a pressure gauge,
which is used to measure blood pressure.
Spirometry: Also called pneometry. Testing the air capacity of the lungs
with a pneometer.
Spleen: A large vascular organ located on the upper left side of the abdominal
cavity. It is a blood-forming organ in early life. It is a storage
organ for red corpuscles and because of the large number of macrophages,
acts as a blood filter.
Sputum: Expectorated matter, especially mucus or mucopurulent matter expec-
torated in diseases of the air passages.
Squamous: Scale-like, scaly.
Standard deviation: Measure of the dispersion of values about a mean
value. It is calculated as the positive square root of the average of
the squares of the individual deviations from the mean.
Standard temperature and pressure: 0°C, 760 mm mercury.
Staphylococcus aureus: A spherically-shaped, infectious species of bacteria
found especially on nasal mucous membrane and skin.
G-42
-------
c lung compliance (C,stat): Measure of lung's elastic recoil (volume
change resulting from CRSnge in pressure) with no or insignificant air-
Static lung compliance (C
chanc
flow.
Steady state exposure: Exposure to air pollutants whose concentration
remains constant for a period of time.
Steroids: A large family of chemical substances comprising many hormones and
vitamins and having large ring structures.
Stilbene: An aromatic hydrocarbon C,.H,0 used as a phosphor and in making
dyes. 14 "
Stoichiometric factor: Used to express the conversion efficiency of a non-
quantitative reaction, such as the reaction of N0? with azo dyes in air
monitoring methods.
Stoma: A minute opening or pore (plural is stomata).
Stratosphere: That region of the atmosphere extending from 11 km above the
surface of the earth to 50 km. At 50 km above the earth temperature
rises to a maximum of 0 C.
Streptococcus pyogenes: A species of bacteria found in the human mouth,
throat and respiratory tract and in inflammatory exudates, blood stream,
and lesions in human diseases. It causes formation of pus or even fatal
septicemias.
Stress corrosion cracking: Cracking caused by simultaneous presence of
tensile stress and a specific corrosive medium. The metal or alloy is
virtually unattached over most of its surface, while fine cracks progress
through it.
Strong interactions: Forces or bond energies holding molecules together.
Thermal energy will not disrupt the formed bonds.
Sublobular hepatic necrosis: The pathologic death of one or more cells, or
of a portion of the liver, beneath one or more lobes.
Succession: The progressive natural development of vegetation towards
a climax, during which one community is gradually replaced by others.
Succinate: A salt of succinic acid involved in energy production in the
citric acid cycle.
Sulfadiazine: One of a group of sulfa drugs. Highly effective against
pneumococcal, staphlococcal, and streptococcal infections.
Sulfamethazine: An antibacterial agent of the sulfonamide group, active
against homolytic streptococci, staphytococci, pneumococci and meningococci
Sulfanilimide: A crystalline sulfonamide (C.HgN 02$), the amide of sulfanilic
acid and parent compound of most sulfa flrugs.
G-43
-------
Sulfhydryl group: A chemical radical consisting of sulfur and hydrogen
which confers reducing potential to the chemical compound to which it is
attached (-SH).
Sulfur dioxide (S0?): Colorless gas with pungent odor released primarily from
burning of fossil fuels, such as coal, containing sulfur.
Sulfur dyes: Used only on vegetable fibers, such as cottons. They are
insoluble in water and must be converted chemically in order to be
soluble. They are resistant (fast) to alkalies and washing and fairly
fast to sunlight.
Supernatant: The clear or partially clear liquid layer which separates
from the homogenate upon centrifugation or standing.
Surfactant: A substance capable of altering the physiochemical nature of
surfaces, such as one used to reduce surface tension of a liquid.
Symbiotic: A close association between two organisms of different species in
which at least one of the two benefits.
Synergistic: A relationship in which the combined action or effect of two
or more components is greater than that of the components acting separately.
Systolic: Relating to the rhythmical contraction of the heart.
Tachypnea: Very rapid breathing.
12
Terragram (Tg): One million metric tons, 10 grams.
Teratogenesis: The disturbed growth processes resulting in a deformed
fetus.
Teratogenic: Causing or relating to abnormal development of the fetus.
Threshold: The level at which a physiological or psychological effect begins
to be produced.
Thylakoid: A membranous lamella of protein and lipid in plant chloroplasts
where the photochemical reactions of photosynthesis take place.
Thymidine: A nucleoside (cinH14N2°5^ that is cornP°sed of thymine and
deoxyribose; occurs as a structural part of DMA.
Tidal volume (V,.): The volume of air that is inspired or expired in a single
breath during regular breathing.
Titer: The standard of strength of a volumetric test solution. For example,
the titration of a volume of antibody-containing serum with another
volume containing virus.
G-44
-------
Tocopherol: a-d-tocopherol is one form of Vitamin E prepared synthetically.
The a form exhibits the most biological activity. It is an antioxidant
and retards rancidity of fats.
Torr: A unit of pressure sufficient to support a 1 mm column of mercury;
760 torr = 1 atmosphere.
Total lung capacity (TLC): The sum of all the compartments of the lung, or
the volume of air in the lungs at maximum inspiration.
Total suspended particulates (TSP): Solid and liquid particles present in
the atmosphere.
Trachea: Commonly known as the windpipe, a cartilaginous air tube extending
from the larnyx (voice box) into the thorax (chest) where it divides,
serving as the entrance to each of the lungs.
Transaminase: Aminotransferase; an enzyme transferring an ami no group from
an a-amino acid to the carbonyl carbon atom of an a-keto acid.
Transmissivity (UV): The percent of ultraviolet radiation passing through a
a medium.
Transmittance: The fraction of the radiant energy entering an absorbing
layer which reaches the layer's further boundary.
Transpiration: The process of the loss of water vapor from plants.
Triethanolamine: An amine, (HOChLCHO-N, used in the absorbing solution
of one analytical method for NOp.
Troposphere: That portion of the atmosphere in which temperature decreases
rapidly with altitude, clouds form, and mixing of air masses by convection
takes place. Generally extends to about 7 to 10 miles above the earth's
surface.
Type 1 epithelial cells: Squamous cells which provide a continuous lining
to the alveolar surface.
Type I pneumonocytes: Pulmonary surface epithelial cells.
Type II pneumonocytes: Great alveolar cells.
Ultraviolet: Light invisible0to the human eye of wavelengths between 4x10
and 5xlO~9 m (4000 to 50A).
Urea-formaldehyde resin: A compound composed of urea and formaldehyde in
an arrangement that conveys thermosetting properties.
G-45
-------
Urobilinogen: One of the products of destruction of blood cells; found in
the liver, intestines and urine.
Uterus: The womb; the hollow muscular organ in which the impregnated ovum
(egg) develops into the fetus.
Vacuole: A minute space in any tissue.
Vagal: Refers to the vagus nerve. This mixed nerve arises near the medulla
oblongata and passes down from the cranial cavity to supply the larynx,
lungs, heart, esophagus, stomach, and most of the abdominal viscera.
Valence: The number of electrons capable of being bonded or donated by
an atom during bonding.
Van Slyke reactions: Reaction of primary amines, including amino acids,
with nitrous acid, yielding molecular nitrogen.
Variance: A measure of dispersion or variation of a sample from its
expected value; it is usually calculated as the square root a sum of
squared deviations about a mean divided by the sample size.
Vat dyes: Dyes which have a high degree of resistance to fading by light,
NO and washing. Widely used on cotton and viscose rayon. Colors are
brilliant and of almost any shade. The name was originally derived
from their application in a vat.
Venezuelan equine encephalomyelitis: A form of equine encephalomyelitis
found in parts of South America, Panama, Trinidad, and the United States,
and caused by a virus. Fever, diarrhea, and depression are common. In
man, there is fever and severe headache after an incubation period of 2
to 5 days.
Ventilatory volume (Vp): The volume of gas exchanged between the lungs and
the atmosphere that occurs in breathing.
Villus: A projection from the surface, especially of a mucous membrane.
Vinyl chloride: A gaseous chemical suspected of causing at least one type
of cancer. It is used primarily in the manufacture of polyvinyl
chloride, a plastic.
Viscose rayon: Filaments of regenerated cellulose coagulated from a solution
of cellulose xanthate. Raw materials can be cotton 1 inters or chips
of spruce, pine, or hemlock.
o
Visible region: Light between the wavelengths of 4000-8000 A.
Visual range: The distance at which an object can be distinguished from
background.
Vital capacity: The greatest volume of air that can be exhaled from the
lungs after a maximum inspiration.
G-46
-------
Vitamin E: Any of several fat-soluble vitamins (tocopherols), essential
in nutrition of various vertibrates.
Washout: The capture of gases and particles by falling raindrops.
Weak interactions: Forces, electrostatic in nature, which bind atoms and/or
molecules to each other. Thermal energy will disrupt the interaction.
Also called van der Waal's forces.
Wet deposition: The process by which atmospheric substances are returned
to earth in the form of rain or other precipitation.
Wheat germ lipase: An enzyme, obtained from wheat germ, which is capable
of cleaving a fatty acid from a neutral fat; a lipolytic enzyme.
X-ray fluorescence spectrometry: A nondestructive technique which utilizes
the principle that every element emits characteristic x-ray emissions
when excited by high-energy radiation.
Zeolites: Hydrous silicates analogous to feldspars, occurring in lavas
and various soils.
Zooplankton: Minute animal life floating or swimming weakly in a body of water.
G-47
------- |