&EPA
United States
Environmental Protection
Agency
600884020A3
Environmental Criteria and
Assessment Office
Research Triangle Park NC 27711
June 1984
External Review Draft
Research and Development
Air Quality
Criteria for
Ozone and Other
Photochemical
Oxidants
Review
Draft
(Do Not
Cite or Quote)
Volume III of V
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.
-------
Draft EPA-600/8-84-020A
Do Not Cite or Quote June 1984
External Review Draft
Air Quality Criteria for
Ozone and Other
Photochemical Oxidants
Volume III of V
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, NC 27711
U S. Environmental Protection Agency
Region V, Library
, 230 South Dearborn Street •
/ Chicago, Illinois 60604 ^
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NOTICE
Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
f
Environmental Protection Agenctf *
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ABSTRACT
Scientific information is presented and evaluated relative to the health
and welfare effects associated with exposure to ozone and other photochemical
oxidants. Although it is not intended as a complete and detailed literature
review, the document covers pertinent literature through 1983 and early 1984.
Data on health and welfare effects are emphasized, but additional infor-
mation is provided for understanding the nature of the oxidant pollution pro-
blem and for evaluating the reliability of effects data as well as their
relevance to potential exposures to ozone and other oxidants at concentrations
occurring in ambient air. Separate chapters are presented on the following
exposure-related topics: nature, source, measurement, and concentrations of
precursors to ozone and other photochemical oxidants; the formation of ozone
and other photochemical oxidants and their transport once formed; the proper-
ties, chemistry, and measurement of ozone and other photochemical oxidants;
and the concentrations of ozone and other photochemical oxidants that are
typically found in ambient air.
The specific areas addressed by chapters on health and welfare effects
are the toxicological appraisal of effects of ozone and other oxidants; effects
observed in controlled human exposures; effects observed in field and epidemio-
logical studies; effects on vegetation seen in field and controlled exposures;
effects on natural and agroecosystems; and effects on nonbiological materials
observed in field and chamber studies.
0190LG/B May 1984
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CONTENTS
Page
VOLUME I
Chapter 1. Summary and Conclusions 1-1
VOLUME II
Chapter 2. Introduction 2-1
Chapter 3. Precursors to Ozone and Other Photochemical
Oxidants 3-1
Chapter 4. Chemical and Physical Processes in the Formation
and Occurrence of Ozone and Other Photochemical
Oxi dants 4-1
Chapter 5. Properties, Chemistry, and Measurement of Ozone
and Other Photochemical Oxidants 5-1
Chapter 6. Concentrations of Ozone and Other Photochemical
Oxidants in Ambient Air 6-2
VOLUME III
Chapter 7. Effects of Ozone and Other Photochemical Oxidants
on Vegetati on 7-1
Chapter 8. Effects of Ozone and Other Photochemical Oxidants
on Natural and Agroecosystems 8-1
Chapter 9. Effects of Ozone and Other Photochemical Oxidants
on Nonbiological Materials 9-1
VOLUME IV
Chapter 10. Toxicological Effects of Ozone and Other
Photochemical Oxidants 10-1
VOLUME V
Chapter 11. Controlled Human Studies of the Effects of Ozone
and Other Photochemical Oxidants 11-1
Chapter 12. Field and Epidemiological Studies of the Effects
of Ozone and Other Photochemical Oxidants 12-1
Chapter 13. Evaluation of Integrated Health Effects Data for
Ozone and Other Photochemical Oxidants 13-1
0190LG/B
IV
May 1984
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Chapter 7: Effects of Ozone and Other Photochemical Oxidants on Vegetation
Principal Authors
Dr. Richard M. Adams
Department of Agricultural and Resource Economics
Oregon State University
Con/all is, OR 97331
Dr. J. H. B. Garner
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Lance W. Kress
RER Division
Argonne National Laboratories
9700 Cass Avenue
Argonne, IL 60439
Dr. John A. Laurence
Boyce Thompson Institute for Plant Research
Tower Road
Cornell University
Ithaca, NY 14853
Mr. Ronald Oshima
State of California
Department of Food and Agriculture
Sacramento, CA 95814
Dr. Eva Pell
Department of Plant Pathology
Penn State University
University Park, PA 16802
Dr. Richard Reinert
Department of Plant Pathology
North Carolina State University
Raleigh, NC 27607
Dr. 0. C. Taylor
Department of Botany and Plant Sciences
University of California
Riverside, CA 92521
Dr. David T. Tingey
Environmental Research Laboratory
200 SW 35th Street
Corvallis, OR 97330
019DH/C 5/24/84
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Contributing Authors
Ms. Marcia Gumpertz
Northrop Services Institute
Environmental Research Laboratory
200 SW 35th Street
Corvallis, OR 97330
Dr. David S. Lang
Minnesota Environmental Quality Board
100 Capitol Square Bldg.
St. Paul, MN 55101
Reviewers
Authors also reviewed individual sections of the chapter. The following
additional persons reviewed this chapter at the request of the U.S. Environmen-
tal Protection Agency. The evaluations and conclusions contained herein,
however, are not necessarily those of the reviewers.
Dr. James Bennett
National Park Service
Air Quality Division
Box 25287
Denver, CO 80225
Dr. Harris M. Benedict
P.O. Box 50046
Pasadena, CA 91105
Dr. Donald D. Davis
Department of Plant Pathology and Center for Air Environment Studies
211 Buckhout Laboratory
University Park, PA 16802
Dr. Robert L. Heath
Department of Botany and Plant Sciences
University of California
Riverside, CA 92521
Dr. Allen Heagle
Field Air Quality Laboratory
North Carolina State University
Raleigh, NC 27606
Dr. Walter W. Heck
Department of Botany
North Carolina State University
Raleigh, NC 27606
VI
019DH/C 5/24/84
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Dr. Howard Heggestad
U.S. Department of Agriculture
ARS Beltsville Agricultural Research Center
Beltsville, MO 20205
Ms. Pamela Johnson
Office of Air Quality Planning and Standards
MD-12
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Robert Kohut
Boyce Thompson Institute for Plant Research
Tower Road
Cornell University
Ithaca, NY 14853
Dr. Jan G. Laarman
Department of Forestry
North Carolina State University
Raleigh, NC 27607
Dr. Allen S. Lefohn
A.S.L. & Associates
111 North Last Chance Gulch
Helena, MT 59601
Dr. David J. McKee
Office of Air Quality Planning and Standards
MD-12
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Lawrence 0. Moore
Department of Plant Pathology, Physiology and Weed Science
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061
Dr. John M. Skelly
Department of Plant Pathology
Penn State University
University Park, PA 16802
Dr. Boyd Strain
Department of Botany
Duke University
Durham, NC 27705
Mr. Robert Stricter
American Petroleum Institute
The Medicine and Biological Science Department
2101 L. Street, NW
Washington, DC 20037
vn
019DH/C 5/24/84
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Dr. Paul Teng
Department of Plant Pathology
University of Minnesota
St. Paul, MN 55108
Ms. Beverly Tilton
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Mr. Tom Walton
Office of Air Quality Planning and Standards
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Wayne T, Williams
The Black Apple Institute
920 St. Francis Drive
Petaluma, CA 94952
Dr. F. A. Wood
Institute of Food and Agricultural Science
1022 McCarty Hall
University of Florida
Gainesville, FL 32611
Mr. Laurence Zaragoza
Office of Air Quality Planning and Standards
MD-12
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
VI T 1
019DH/C 5/24/84
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Chapter 8: Effects of Ozone and Other Photochemical Oxidants
On Natural and Agroecosystems
Principal Authors
Dr. J. H. B. Garner
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. William H. Smith
School of Forestry and Environmental Studies
116 Greeley Memorial Laboratory
Yale University
370 Prospect Street
New Haven, CT 06511
Reviewers
Authors of Chapter 7 also reviewed this chapter. The following additional
persons reviewed this chapter at the request of the U.S. Environmental Protec-
tion Agency. The evaluations and conclusions contained herein, however, are
not necessarily those of the reviewers. .,
Dr. James Bennett
National Park Service
Box 25287
Denver, CO 80225
Dr. Donald D. Davis
Department of Plant Pathology and Center for Air Environment Studies
211 Buckhout Laboratories
University Park, PA 16802
Dr. Robert L. Heath
Department of Botany and Plant Sciences
University of California
Riverside, CA 92521
Dr. Allen Heagle
Field Air Quality Laboratory
North Carolina State University
Raleigh, NC 27606
Dr. Walter W. Heck
Department of Botany
North Carolina State University .
Raleigh, NC 27606
IX
019DH/C 5/24/84
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Dr. Robert Kohut
Boyce Thompson Institute for Plant Research
Tower Road
Cornell University
Ithaca, NY 14853
Dr. Allen S. Lefohn
A.S.L. & Associates
111 North Last Chance Gulch
Helena, MT 59601
Dr. Paul Miller
U.S. Forest Service Fire Laboratory
4955 Canyon Crest Drive
Riverside, CA 92507
Dr. Laurence 0. Moore
Department of Plant Pathology, Physiology and Weed Science
Virginia Polytechnic Institute and State University
Blacksburg, VA 24061
Dr. Eric Preston
Environmental Research Laboratory
200 SW 35th Street
Corvallis, OR 97330
Dr. Boyd Strain
Department of Botany
Duke University
Durham, NC 27705
Dr. John M. Skelly
Department of Plant Pathology
Penn State University
University Park, PA 16802
Mr. Robert Stricter
American Petroleum Institute
The Medicine and Biological Science Department
2101 L. Street, NW
Washington, DC 20037
Ms. Beverly Til ton
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
019DH/C 5/24/84
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Dr. David T. Tingey
Environmental Research Laboratory
200 SW 35th Street
Corvallis, OR 97330
Dr. David Weinstein
Ecosystems Research Center
Corson Hall
Cornell University
Ithaca, NY 14853
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019DH/C 5/24/84
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Chapter 9: Effects of Ozone and Other Photochemical Oxidants
On Nonbiological Materials
Principal Authors
Mr. James M. Kawecki
TRC Environmental Consultants
701 West Broad Street
Suite 401
Falls Church, VA 22046
Dr. Jan G. Laarman
Department of Forestry
North Carolina State University
Raleigh, NC 27607
Dr. Alexander R. Stankunas
930 Rockdale Dr.
San Jose, CA 95129
The following individuals reviewed the chapter at EPA's request:
Dr. Richard Adams
Department of Agricultural and Resource Economics
Oregon State University
Corvallis, OR 97331
Ms. F. Vandiver Bradow
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. J.H.B. Garner
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Mr. Fred Haynie
Environmental Sciences Research Laboratory
MD-84
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Dr. Bruce Jarvis
Department of Chemistry
University of Maryland
College Park, MD
019DH/C 5/24/84
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Mr. E. J. McCarthy
FRC Environmental Consultants
701 West Broad Street
Suite 401
Falls Church, VA 22046
Dr. James McNesby
Department of Chemistry
University of Maryland
College Park, MD
Mr. John Spence
Environmental Sciences Research Laboratory
MD-84
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Ms. Beverly Til ton
Environmental Criteria and Assessment Office
MD-52
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
Mr. Tom Walton
Office of Air Quality Planning and Standards
MD-12
U.S. Environmental Protection Agency
Research Triangle Park, NC 27711
XI 11
019DH/C 5/24/84
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TABLE OF CONTENTS
Page
LIST OF TABLES xix
LIST OF FIGURES xxi
LIST OF ABBREVIATIONS xxi i
7.0 EFFECTS OF OZONE AND OTHER PHOTOCHEMICAL OXIDANTS ON VEGETATION . 7-1
7.1 INTRODUCTION 7-1
7.2 METHODOLOGIES USED IN VEGETATION EFFECTS RESEARCH 7-5
7.2.1 Experimental Design and Statistical Analysis 7-5
7.2.2 Exposure Characteristics 7-7
7.2.2.1 Statistics Used to Characterize Seasonal
Exposures 7-8
7.2.2.2 Statistics Used to Characterize Short Exposures . 7-9
7.2.2.3 Exposure Statistics 7-10
7.2.3 Exposure Systems 7-11
7.2.3.1 Laboratory Systems 7-12
7.2.3.2 Greenhouse Exposure Systems 7-13
7.2.3.3 Field Exposure Systems 7-14
7.2.3.3.1 Field Chamber Systems 7-14
7.2.3.3.2 Field Exposure Systems Without
Chambers 7-16
7.2.4 The National Crop Loss Assessment Network 7-16
7.2.5 Determination of Yield and Crop Losses 7-18
7.3 MODE OF OZONE ACTION ON PLANTS 7-19
7.3.1 Biochemical and Physiological Responses to Ozone 7-21
7.3.1.1 Gas-Phase Movement into the Leaf
7.3.1.2 Transition Between Gas Phase and Liquid Phase
Movement i nto the Cel 1 7-23
7.3.1.3 Chemical and Biochemical Responses 7-23
7.3.1.4 Physiological Responses 7-25
7.3.1.5 Ti ssue and Organ Responses 7-29
7.3.1.6 Secondary Metabolic Responses 7-30
7.3.2 Factors That Modify Plant Response 7-31
7.3.2.1 Biological Factors 7-31
7.3.2.1.1 Genetic Factors 7-31
7.3.2.1.2 Developmental Factors 7-32
7.3.2.1.3 Pollutant - Plant-Pest Interactions .. 7-33
7.3.2.1.3.1 Pollutant-plant-
pathogen interactions ... 7-34
7.3.2.1.3.2 Effects of ozone on
pi ant-insect inter-
actions 7-41
7.3.2.1.3.3 Effects of pathogen
infection on plant
sensitivity to ozone .... 7-41
xiv
019DH/C 5/24/84
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TABLE OF CONTENTS (continued)
7.3.2.2 Physical factors /-44
7.3.2.2.1 Light 7-44
7.3.2.2.2 Temperature 7-45
7.3.2.2.3 Relative Humidity 7-45
7.3.2.2.4 Soil Moisture 7-47
7.3.2.2.5 Soil Fertility 7-49
7.3.2.3 Chemical Factors 7-50
7.3.2.3.1 Pollutant Interactions 7-50
7.3.2.3.1.1 Ozone and Sulfur
Dioxide 7-51
7.3.2.3.1.2 Ozone and Nitrogen
Dioxide 7-59
7.3.2.3.1.3 Ozone Plus Nitrogen
Dioxide and Sulfur
Dioxide 7-59
7.3.2.3.1.4 Ozone and Other
Pollutants 7-65
7.3.2.3.2 Chemical Sprays 7-66
7.4 OZONE EXPOSURE AND RESPONSE 7-70
7.4.1 Bioindicators of Ozone Exposure 7-75
7.4.1.1 Bioindicator Methods 7-77
7.4.1.2 Response of Indicator Species 7-77
7.4.1.3 Bioindicator Systems 7-78
7.4.1.4 Lichens as Bioindicators of Oxidant Pollution ... 7-83
7.4.1.5 Published Reports of Visible Injury of Plants
Due to Ambient Ozone in the United States 7-83
7.4.2 Microorganisms and Nonvascular Plant Response to Ozone
Exposure 7-84
7.4.2.1 Microorganisms 7-84
7.4.2.2 Lichens, Mosses, and Ferns 7-88
7.4.3 Losses in Vascular Plants Due to Ozone 7-89
7.4.3.1 Losses in Aesthetic Value and Foliar Yield 7-90
7.4.3.2 Yield Losses as Weight, Size, and Number 7-100
7.4.3.2.1 Ozone Addition Studies 7-100
7.4.3.2.1.1 Open-top chamber
studies 7-105
7.4.3.2.1.2 Other field studies 7-122
7.4.3.2.1.3 Greenhouse and indoor
chamber studies 7-122
7.4.3.2.1.4 Effects of ozone on
crop quality 7-134
7.4.3.2.1.5 Effects of ozone on
plant reproduction 7-137
7.4.3.2.1.6 Relationship between
foliar injury and yield
loss 7-137
7.4.3.2.2 Biomass and Yield Responses from
Ambient Exposures 7-140
XV
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TABLE OF CONTENTS (continued)
Page
7.4.3.3 Exposure-Response Relationships (Empirical
Model s) 7-148
7.4.3.3.1 Physiological Models 7-150
7.4.3.3.2 Injury Models 7-150
7.4.3.3.3 Growth Models 7-153
7.4.3.3.4 Yield and Loss Models 7-154
7.4.3.3.5 Interpreting Exposure Response
Models 7-160
7.5 ECONOMIC ASSESSMENTS OF OZONE EFFECTS 7-163
7.5.1 Economic and Methodological Issues in Performing
Assessments 7-163
7.5.2 Biological and Practical Issues in Performing
Assessments 7-166
7.5.3 A Review of Economic Assessments of Ozone Effects on
Agriculture 7-169
7.5.3.1 Regional Loss Estimates 7-170
7.5.3.2 National Loss Estimates 7-175
7.5.4 An Overview of Current Loss Assessments 7-178
7.6 MODE OF PEROXYACETYL NITRATE (PAN) ACTIONS ON PLANTS 7-180
7.6.1 Biochemical and Physiological Responses to PAN 7-181
7.6.1.1 Gas-Phase Movement Into the Leaf 7-183
7.6.1.2 Biochemical and Physiological Responses 7-183
7.6.2 Factors That Modify Plant Response to PAN 7-185
7.6.2.1 Biological Factors 7-185
7.6.2.2 Physical Factors 7-187
7.6.2.3 Chemical Factors 7-188
7.6.2.3.1 Pollutant Interactions 7-188
7.6.2.3.2 Chemical Sprays and Nutrients 7-189
7.7 PAN EXPOSURE AND RESPONSE 7-192
7.7.1 Bioindicators of PAN Exposure 7-195
7.7.2 Nonvascular Plant Response to PAN Exposure 7-196
7.7.3 Losses in Vascular Plants by PAN 7-197
7.7.3.1 Losses in Aesthetic Use and Foliar Yield 7-197
7.7.3.2 PAN Addition Studies 7-199
7.7.3.3 Biomass and Yield Responses from Ambient
Exposure 7-200
7.8 SUMMARY 7-203
7.9 REFERENCES 7-221
APPENDICES
A - Colloquial and Latin Names of Plants Discussed in the
Chapter A-l
B - Species That Have Been Exposed to Ozone to Determine
Differential Responses of Germplasm to Photochemical
Products B-l
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5/24/84
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TABLE OF CONTENTS (continued)
8. EFFECTS OF OZONE AND OTHER PHOTOCHEMICAL OXIDANTS ON
NATURAL AND AGROECOSYSTEMS 8-1
8.1 INTRODUCTION 8-1
8.2 ECOSYSTEMS: THE POTENTIAL FOR INDIRECT EFFECTS 8-1
8.2.1 Interwoven Structure, Boundaries, and Social Value 8-1
8.2.2 Ecosystem Components: Internal Structure 8-4
8.2.3 Response to Stress 8-5
8.3 RESPONSE TO OZONE 8-9
8.3.1 Effects on PI ant Processes 8-9
8.3.2 Effects on Species Composition and Succession 8-13
8.3.3 Effects on Tree Growth 8-20
8.3.4 Effects on Food Webs 8-30
8.3.4.1 Heterotrophs (Consumers) 8-30
8.3.4.2 Phytophagous Insects 8-31
8.3.4.3 Pathogens 8-32
8.3.4.4 Other Microorganisms, Symbionts and
Decomposers 8-33
8.3.5 Oxidant-Induced Effects on a Western Coniferous Forest
Ecosystem: The San Bernardino Study 8-37
8.3.5.1 Introduction 8-37
8.3.5.2 Effects Observed 8-37
8.4 INTERRELATED ECOSYSTEMS 8-39
8.4.1 Aquatic Ecosystems 8-39
8.4.2 Agricultural Ecosystems 8-40
8.5 ECOSYSTEM MODELING 8-40
8.6 VALUING ECOSYSTEMS: 8-41
8.7 SUMMARY 8-44
8.8 REFERENCES 8-50
9. EFFECTS OF OZONE AND OTHER PHOTOCHEMICAL OXIDANTS ON
NONBIOLOGICAL MATERIALS
9.1 INTRODUCTION 9-1
9.2 MECHANISMS OF OZONE ATTACK AND ANTIOZONANT PROTECTION 9-2
9.2.1 Elastomers 9-2
9.2.2 Textile Fibers and Dyes 9-7
9.2.3 Paint 9-9
9.2.4 Other Materials 9-9
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TABLE OF CONTENTS (continued)
Page
9.3 DOSE-RESPONSE DATA 9-10
9.3.1 Elastomers Cracking 9-11
9.3.2 Dye Fading 9-20
9.3.3 Fiber Damage 9-31
9.3.4 Paint Damage 9-36
9.4 ECONOMICS 9-39
9.4.1 Introduction 9-39
9.4.2 Methods of Cost Classification and Estimation 9-40
9.4.3 Aggregate Cost Estimates 9-41
9.4.4 Damage to Elastomers 9-44
9.4.5 Damage to Fibers and Dyes 9-45
9.4.6 Damage to Paint 9-47
9.5 SUMMARY AND CONCLUSIONS 9-48
9.6 REFERENCES 9-53
APPENDIX: CHEMICAL ABBREVIATIONS USED IN THE TEXT 9-57
xvm
019DH/C 5/24/84
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LIST OF TABLES
Table Page
7-1 Effect of ozone on photosynthesis 7-27
7-2 Plant and biotic pathogen interactions as influenced by various
doses of ozone under laboratory and field conditions 7-35
7-3 Response of plants to ozone as conditioned by humidity during
growth and exposure 7~46
7-4 Effects of soil moisture on response of selected plants to
oxidant 7-48
7-5 Summary effects of sulfur dioxide and ozone mixtures on foliar
injury 7-52
7-6 Foliar injury response of various plant species to ozone and
ozone plus sulfur dioxide 7-53
7-7 Growth response of selected plants to ozone and ozone plus
sulfur dioxide 7-55
7-8 Yield responses of various plant species to ozone and ozone
plus sulfur dioxide 7-56
7-9 The influence of mixtures of ozone and sulfur dioxide on yield
of soybean 7-57
7-10 Yield responses of selected tree species to ozone plus nitrogen
di oxi de 7-60
7-11 Yield of various plant species to ozone, sulfur dioxide, and
nitrogen dioxide 7-61
7-12 The effects of nitrogen dioxide, sulfur dioxide, or ozone or
both on radish root fresh weight (g) at three concentrations of
each gas 7-64
7-13 Protection of plants from oxidant injury by application of
protective chemicals 7-67
7-14 Concentration, time, and response equations for three suscepti-
bility groups and for selected plants or plant types with
respect to ozone 7-74
7-15 A partial listing of ambient ozone injury on sensitive
vegetation reported in the literature 7-85
7-16 Foliar symptom expression of various flower, ornamental tree,
shrub, turfgrass, and foliar crop species in response to ozone
exposure 7-91
7-17 Effects of short-term exposures on growth and yield of selected
plants 7-101
7-18 Effects of long-term, controlled ozone exposures on growth,
yield, and foliar injury to selected plants 7-102
7-19 Open-top chamber effects and Weibull parameters for individual
ozone dose-crop response data sets 7-108
7-20 Effects of ozone added to ambient air in open-top chambers on
the y i el d of sel ected crops 7-111
7-21 Effects of ozone added to filtered air in field chambers on the
yield of selected crops 7-123
7-22 Effects of ozone added to filtered air on the yield of selected
crops 7-125
7-23 Effects of ozone added to filtered air on the yield of selected
tree crops 7-130
7-24 Effects of oxidants (ozone) in ambient air on growth, yield,
and foliar injury in selected plants 7-141
xix
019DH/C 5/24/84
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LIST OF TABLES (continued)
Table Page
7-25 Effects of ambient air in open-top chambers, outdoor CSTR
chambers, or greenhouses on the growth and yield of selected
crops 7-143
7-26 Exposure-response functions relating ozone-dose to plant yield ... 7-146
7-27 Summary of models describing the relationship between foliar
injury and ozone exposure 7-151
7-28 Summary of models of ozone yield and loss 7-154
7-29 Summary of crop-loss models 7-158
7-30 Pre-1978 estimates of economic losses to crops and vegetation
attributable to ozone air pollution in the United States 7-164
7-31 Summary of recent regional ozone control benefits estimates 7-168
7-32 Summary of recent national damage estimates for ozone 7-176
7-33 Geographic occurrence of PAN (oxidant) injury on plants 7-182
7-34 Ozone concentrations for short-term exposures that produce 5 or
20 percent injury to vegetation grown under sensitive
conditions 7-209
7-35 Seven-hour seasonal average ozone concentrations at which yield
losses of 10 percent or 30 percent are predicted from exposure-
response models 7-210
7-36 Ozone concentrations that result in significant yield losses 7-216
8-1 Injury thresholds for 2-hour exposures to ozone 8-18
8-2 Average annual radial growth of 19 ponderosa pine trees in
two levels of oxidant air pollutants in the San Bernardino
National Forest, California 8-24
8-3 Annual mean radial growth increment (mm) based on the 24-year
period (1955 to 1978) for tree ozone sensitivity classes of
native eastern white pines (Pinus strobus L.) growing in ten
plots of three trees each along the Blue Ridge Mountains in
Virginia 8-25
8-4 Annual occurrences of ozone at hourly concentrations > 0.08 ppm
in the Knoxville, Tennessee area, and average length of needles
sampled during the 1979 growing season 8-28
9-1 Tire industry exposure tests 9-12
9-2 Effects of ozone on different SBR polymers containing
various antiozonant concentrations 9-15
9-3 Cracking rates of white sidewall tire specimens 9-15
9-4 Protection of tested rubber materials 9-17
9-5 Effect of ozone and humidity on interply adhesion 9-19
9-6 Effect of antiozonants, antioxidants, and fast-blooming
waxes on interply adhesion in natural rubber 9-20
9-7 Dose-response studies on effects of ozone on
el astomers 9-21
9-8 Colorfastness of test samples compared with color-fastness
of in-use carpeting 9-29
9-9 Summary of dye fading studies 9-32
9-10 Summary of damage costs to materials by oxidants 9-42
9-11 Summary of damage costs to rubber by ozone 9-46
xx
019DH/C 5/24/84
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LIST OF FIGURES
F i gure Page
7-1 Conceptual sequence of ozone-induced responses 7-3
7-2 Diagram of a typical dicot leaf (cross section) 7-20
7-3 Limiting values for foliar injury to trees and shrubs by ozone .... 7-72
7-4 Limiting values for foliar injury to agricultural crops by ozone .. 7-72
7-5 Ozone concentrations versus duration of exposure required to
produce 5 percent foliar injury in plants of three different
sensitivity groupings 7-73
7-6 Relation between ozone concentration, exposure duration, and
reduction in plant growth or yield 7-76
7-7 Ozone injury to Bel W-3 tobacco. Clear interveinal areas
represent necrotic tissue (fleck and bifacial necrosis) 7-79
7-8 Cross section of typical dicot leaf which shows ozone injury to
palisade cells and collapsed epidermal cells 7-79
7-9 Ozone injury to oats. Clear areas represent bleached and
necrotic tissue 7-80
7-10 Ozone injury to conifer needles. Clear areas represent injured
tissue (chlorotic mottle and tipburn) 7-80
7-11 States in which published reports of some ozone injury to
vegetation have been made 7-87
7-12 The effect of ozone exposures on the yield of various legumes 7-106
7-13 The effects of ozone exposure on yields of winter wheat and
field corn 7-114
7-14 The effects of ozone exposures on yields of spinach and lettuce ... 7-117
7-15 The effects of ozone exposures on turnip yields 7-120
7-16 PAN injury 7-191
7-17 Dose-response relationships and limiting values for foliar injury
to vegetation by PAN 7-193
7-18 Relative response of five major crop species as predicted from
the Weibul 1 model 7-215
8-1 The relationship of several managed ecosystems in terms of
degree of management and biological diversity 8-3
8-2 Conceptual sequence of levels showing continuum 8-10
8-3 Summation of abiotic and biotic agents involved in diseases
of trees, types of diseases, and functional parts of the
tree 8-21
8-4 Categories of factors influencing declines 8-22
8-5 Average annual growth of white pine trees in each of three
sensitivity classes expressed as increment in ring width
(A) and cross sectional area (B) 8-27
9-1 Postulated mechanism for damage to elastomers by oxygen 9-4
9-2 Postulated mechanism for damage to elastomers by ozone 9-5
9-3 Reaction of anthraquinone dyes with ozone and with nitrogen
oxi des 9-8
9-4 Relationship of cracking in natural rubber and ozone con-
centrati on 9-13
9-5 Relaxation of rubber compounds in ozone 9-18
9-6 The effects of relative humidity on the fading of C.I.
Disperse Blue 3 (CIDB-3) in Nylon 6 after exposure to
0.2 ppm of ozone is depicted 9-30
xx i
019DH/C 5/24/84
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7. EFFECTS OF OZONE AND OTHER PHOTOCHEMICAL OXIDANTS ON VEGETATION
7.1 INTRODUCTION
The effects of photochemical oxidants on vegetation were first observed
more than three decades ago in plants growing in localized areas of Los Angeles
County, California (Middleton et al., 1950). Foliar injury on vegetation was
one of the earliest and most obvious manifestations of the occurrence of photo-
chemical oxidant air pollution. Symptoms reported by Middleton et al. (1950)
included the glazing, silvering, and bronzing of lower leaf surfaces, and the
development of transverse bands of injury on leaves. Subsequently, Taylor
et al. (1960) showed that the injury reported by Middleton et al. (1950) was
caused by an unidentified component of smog known only as "compound X"
(Stephens et al., 1956). In 1960, Stephens et al. identified the compound
as peroxyacetyl nitrate (PAN), a minor but potent phytotoxicant present in
photochemical smog (see Chapters 5 and 6).
Injury to vegetation caused by 0- is distinguishable from that caused by
PAN. The first characteristic 0- injury observed in the field was reported
as "oxidant" stipple on grape vines (Richards et al., 1958). Similar symp-
toms in"tobacco as the result of 0^ exposure were reported subsequently by
Heggestad and Middleton (1959). Though these early reports were of vegeta-
tion injury in the oxiriant-polluted urban atmosphere of Los Angeles and its
environs, it is now recognized that vegetation at rural sites may be injured
by 0-, as well as PAN, transported long distances from urban centers (Edinger
et al., 1972; Heck et al. , 1969; Heck and Heagle, 1970; Kelleher and Feder,
1978; Miller et al. , 1972; Skelly et al., 1977; Skelly, 1980; see also chapters
4 and 6).
An analysis of photochemical oxidants in the ambient air has revealed
several phytotoxic components including NOp, 0,, and the peroxyacyl nitrates.
The phytotoxicity of nitrogen oxides is discussed in Ai r Qua1ity Criteria for
Oxides of Nitrogen (U.S. Environmental Protection Agency, 1982). Ozone, the
most prevalent photochemical oxidant, has been the most studied and its effects
are best understood. Ozone affects vegetation throughout the United States, im-
pairing crop production and affecting native vegetation and ecosystems more than
any other air pollutant (Heck et al., 1980). On a concentration basis, however,
the peroxyacyl nitrates are the most phytotoxic photochemical oxidants, but they
are less widely distributed than ozone and generally occur at lower concentra-
tions than ozone. The peroxyacyl nitrates are a homologous series of compounds,
several of which have been detected in the atmosphere. The most abundant member
019SX/B 7-1 5/4/84
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of this series, and often the only one detected in the atmosphere, even in
urban areas, is PAN. It has also received more study than the other peroxy-
acyl nitrates. The data in this chapter therefore focus primarily on the
effects of PAN on vegetation rather than on the effects of other peroxyacyl
compounds. Other phytotoxic compounds associated with the photochemical
complex may occur in the atmosphere, but the effects of such compounds on
vegetation have received very limited study and are not discussed in this
chapter.
The effects of CL and PAN on terrestrial vegetation may be envisioned as
occurring at several levels, ranging from the molecular to the organismal, and
then to the ecosystem level (Figure 7-1). The occurrence and magnitude of the
vegetational effects depend on the concentration of the pollutant, the duration
of the exposure, the length of time between exposures, and the various environ-
mental and biological factors that influence the response. The earliest
observable physiological effects include altered membrane permeability, decreased
carbon dioxide fixation (photosynthesis), and altered stomatal responses.
These initial physiological changes are followed by inactivation or activation,
or both, of specific enzymes, changes in metabolite pools, and alterations in
the translocation of photosynthate. Biochemical changes within the plants are
often expressed as visible foliar injury, premature senescence, increased leaf
abcission, and reduced plant growth and vigor. These changes at the individual
plant level lead to altered reproduction, changes in competitive ability, or
reduction of plant vigor. They subsequently are manifested by changes in
plant communities and, ultimately, change in ecosystems. The sequence of
topics in this chapter, which describes the effects of photochemical oxidant
on plants, is based on the logical hierarchical ordering of plant responses
depicted in Figure 7-1. The complexities of the entire subject are apparent
in the sections on factors affecting plant response and exposure-response
relationships. Effects on terrestrial ecosystems are discussed in Chapter 8.
The linkages relating altered biochemical processes, foliar injury, and
plant yield are not well understood. Likewise, no clear relationship exists
between foliar injury and reduced plant yield for species in which the foliage
is not part of the yield. The previous criteria document (U.S. Environmental
Protection Agency, 1978) focused primarily on the effects of 0., on physiologi-
cal processes, foliar injury, and plant growth and attempted to summarize the
literature by presenting limiting values (i.e., those concentrations below
019SX/B 7-2 4/12/84
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PRIMARY SECONDARY TERTIARY QUATERNARY
CHANGES IN PLANT
COMMUNITIES
AND ECOSYSTEMS
REDUCED PLANT GROWTH
REDUCED PLANT YIELD
ALTERED PRODUCT QUALITY
LOSS OF PLANT VIGOR
ALTERED ENZYME ACTIVITIES
ALTERED METABOLIC POOLS
ALTERED TRANSLOCATION
REDUCED PHOTOSYNTHESIS
INCREASE MEMBRANE PERMEABILITY
STRESS ETHYLENE
Figure 7-1. Conceptual sequence of ozone-induced responses.
Source: U.S. Environmental Protection Agency (1978).
7-3
-------
which foliar injury and, presumably, reduced growth and yield would not occur).
In this document, the results of previous work on physiological processes and
effects on foliar injury and growth will be briefly summarized, with major em-
phasis placed on the effects of photochemical oxidants on the intended use of
the plant. Such effects are those that have impact on the yield, quality, and
aesthetic value.
The number of scientific reports on the effects of photochemical oxidants
on vegetation has increased rapidly since the early 1950's. In reviewing this
extensive literature for the present revision, key references were selected
for in-depth examination. For the most part, materials selected for review
were publications that have appeared since the preparation of the 1978 criteria
document. Earlier information considered fundamentally important is discussed
and related to more recent studies. All primary references that relate expo-
sure-response information to yield loss or crop loss were cited directly, re-
gardless of their citation in the 1978 criteria document. In this revision,
crop loss refers to economic loss and yield loss relates to reduction in the
quality, quantity, aesthetic value, or intended use of the crop. Generally,
the papers cited included only published material that had undergone scientific
review.
Emphasis has been given to those studies that used pollutant concentra-
tions similar to those that occur in the ambient air of the United States. On
this basis, studies in which the lowest concentrations of 0, or PAN exceeded
1.0 ppm or 200 ppb, respectively, were not included unless the paper contained
unique data; e.g., documentation of a mechanism involved in a specific response.
In addition, when discussing exposure-response effects of 0- and PAN on plant
yield, the primary emphasis has been given to those studies reporting effects
at concentrations below 0.25 ppm for 0., and 40 ppb for PAN. (These units have
been used in the majority of the vegetational studies cited; conversion factors
are: 1 ppm 0- = 1960 ug/m and 1 ppb PAN = 4947 ug/m .) The scientific names
of the plants cited in this chapter are listed in Appendix A.
Data used in the development of this criteria document were derived from
a diverse range of studies that were conducted to determine the effects of 0.,
and PAN on various plant species and to characterize plant responses. The
studies used a range of plant species and various experimental conditions and
methodologies. Most important, these studies were generally conducted to test
specific biological hypotheses or to produce specific biological data rather
than to develop air quality criteria.
019SX/B 7-4 4/12/84
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This review of the effects of photochemical oxidants on vegetation and
the responses of vegetation to photochemical oxidants first discusses the
general methodologies used in studies of air pollution effects to provide a
basis for understanding the methods, approaches, and experimental designs used
in the studies discussed in this chapter. Ozone and PAN are discussed sepa-
rately, but the discussions of each will follow the same general outline,
which includes (1) mode of action of the pollutant; (2) physical, biological,
and chemical factors that alter plant response; and (3) primary emphasis on
the effects of the individual pollutants on the response of plants to various
concentrations and durations of exposure.
7.2 METHODOLOGIES USED IN VEGETATION EFFECTS RESEARCH
This section provides reference information that allows a better under-
standing of the studies discussed in the remainder of this chapter. The
section contains an evaluation of exposure methods, a discussion of the
strengths and limitations of various experimental designs and of the statis-
tics used to represent pollutant exposures, and a discussion of the defini-
tions of loss. These discussions emphasize the methodologies used in studies
cited in the chapter and do not reflect a general review of scientific litera-
ture. Changes in 0_ monitoring techniques, methods of calibration, quality
assurance procedures and their possible impacts on measured 0, concentrations
are discussed in Chapter 5.
7.2.1 Experimental Design and Statistical Analysis
The selection of an appropriate experimental design for specific objec-
tives is a critical step in determining the success of a study and the appli-
cation of the results. The number and kind of factors controlled, the patterns
of randomization, and the number of replicates used in an experiment determine
what treatment comparisons may be made, whether trends can be plotted and
curves fitted, the precision of estimates, and the range of conditions over
which inferences may be made. An experimental design focuses an experiment on
its specific objectives, but in doing so, limits the application of the results.
No experimental design has universal application.
Most experiments use traditional experimental designs amenable to the
analysis of variance, such as randomized-block and split-plot designs. When
019SX/B 7-5 4/12/84
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used in conjunction with treatment mean separation techniques, these designs
produce descriptive results that allow comparison of different treatments.
There are many different treatment mean separation techniques available, such
as Tukey's paired comparison procedure, Duncan's multiple range test, and
Dunnett's test for comparing several treatments with a control. The tests all
give slightly different results and have different powers. Some statisticians
recommend careful inspection of the treatment averages in relation to a refer-
ence distribution in addition to or in place of formal multiple comparisons
(Box et al., 1978). Few studies have attempted to partition interactions or
to analyze slope and curvature trends. In factorial experiments with more than
two factors, it has often been difficult to interpret the interactions fully.
Regression analyses are useful for many objectives, including the develop-
ment of empirical models. Care must be taken, however, to ensure that there
is no systematic deviation of the model from the observed data and to recognize
that, in general, results cannot be extrapolated beyond the range of pollutant
(e.g., ozone) concentrations used to construct the model. Both model valida-
tion (the testing of model fit to the experimental data) and applications
validation (testing the application of the model to a new population) are
appropriate precursors to model use.
In an experiment in which quantitative treatments are used and the treat-
ments have been replicated, both analysis of variance and regression analysis
may be used to analyze the data. The traditional approach is to use analysis
of variance to estimate the error variance and to determine whether there are
any differences among treatments; and then to break down the treatment effect
into regression components to test whether there are any linear or quadratic
trends as the treatment level changes (Cochran and Cox, 1957; Anderson and
McLean, 1974). This is equivalent to doing analysis of variance followed by
regression analysis. If a linear or quadratic equation does not fit the data
well, or if there is a theorized functional relationship between treatment and
response, nonlinear models may be fitted to the data at this point. Because
each mathematical function can assume only a limited range of shapes, it is
important to check for systematic lack of fit of the data. Ideally, confidence
bands would be provided with regression curves to show the variability of the
fitted curves. Confidence bands, however, are frequently omitted from
research papers because their computation is complicated and because it is
difficult to show more than one curve in a figure if confidence bands are
OJ9SX/B 7-6 4/12/84
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included. When confidence bands are not provided but results from similar
experiments are available, the reader can obtain an idea of the variability of
estimates by looking at the distribution of estimates from similar experiments.
This variability encompasses sources of error beyond a single experiment.
In most of the papers cited in this document, confidence bands for dose-
response curves were not provided. A 10 percent loss was considered to be a
significant agricultural loss; that is, one that would be important to a
grower. Therefore, a table of estimates from regression models of the (k
concentration at which a 10 percent yield loss would occur for all the culti-
vars and species studied is included in the summary so that the reader can
examine the range of estimates. On each graph of a fitted curve, the treat-
ment means are also plotted. More than one model was fitted to the data in
some cases. The reader may compare the results from the various models and
observe whether there is a systematic lack of fit between the data and the
curve. If a deviation is observed, the 0^ estimates may be biased.
The regression curves used in this document have either been calculated
from the original observations or from treatment means. This distinction is
noted in the figure legends whenever the method used is known. If the treat-
ment means are used rather than the original observations in a linear regres-
sion and there are equal numbers of observations in each treatment, the results
will be as follows: (1) the regression coefficients and estimated values will
be the same as if individual points had been used; (2) the coefficient of
2 2
variation (R ) will be greater than or equal to the R from individual points;
and (3) the variance of the regression coefficients will be about the same as
that computed from individual points if the variation of the means around the
line is similar to the variation of individual points around the treatment
means.
7.2.2 Exposure Characteristics
The occurrence of pollutants in the ambient environment is influenced by
many variables (see Chapters 3 and 4). Periods of significant air pollutant
episodes occur when meteorological conditions, pollutant precursors, and other
environmental conditions coincide. Ozone and PAN episodes usually occur
during the plant-growth season (Chapter 6). The episodes may vary in duration
from one to several days and occur at varying times of the day (Chapter 6).
Research has not yet clearly defined which components of an exposure are most
019SX/B 7-7 5/4/84
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important in causing vegetation responses. The characterization and represen-
tation of plant exposure to air pollutants has been and continues to be a
major problem. An appropriate summary statistic for one exposure duration
usually cannot be easily transformed to describe a different exposure duration
without access to the original aerometric data. In addition, statistics used
to represent extremely short exposures cannot be readily aggregated to provide
a representative summary statistic for plant responses resulting from an
extended exposure (for example, a growing season).
7.2.2.1 Statistics Used to Characterize Seasonal Exposures. To define the
problems associated with characterization and representation of plant exposures
necessitates consideration of the temporal resolution required. When plant
yield is considered, the ultimate impact of an air pollutant on yield depends
on the integrated impact of the pollutant exposures during the growth of the
plant. In this case, the temporal unit of interest becomes the plant growing
season, which varies with the geographic location, plant species, and cultivar
of interest. This period may be as short as 3 to 4 weeks for a crop such as
radish or as long as years for perennial plants such as trees. Plants may be
affected by exposures at several growth stages before harvest. Only a few
studies have investigated the influence of plant growth stage on plant response
to CL. Studies with white beans in areas affected by photochemical oxidants
indicated that crop maturity (plant growth stage) regulates the time of symptom
expression and that crop vigor regulates the severity of the symptom (Haas,
1970). Petunia hybrids were less sensitive to 0_ after the flower bud differen-
tiated (Hanson et al. , 1975). Ozone reduced radish hypocotyl growth the most
if the exposure occurred during the period of rapid hypocotyl growth (Tingey
et al., 1973a). A single exposure to ozone produced a 37 percent reduction in
hypocotyl growth in 14-day-old plants but less growth reduction in younger or
in older plants.
If it is necessary to characterize the temporal distribution of exposures
within a growing season to characterize a plant response adequately, it is
questionable whether the current exposure statistics used by researchers are
adequate. Such regimens do not characterize the effects of pollutant episodes
at specific and perhaps critical periods during plant growth. Statistics used
to describe cumulative seasonal exposures, such as a seasonal mean, do not
characterize the temporal distribution of the exposures within the season.
Lognormal (Larsen and Heck, 1976) and two-parameter Weibull (Georgopoulos and
019SX/B 7-8 4/12/84
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Seinfeld, 1982) functions have been utilized to characterize seasonal exposures.
These distribution functions are fitted to the frequency distribution of 0_
«J
concentration for the season without regard to their temporal order and there-
fore these functions, as well, do not characterize episodes within the season.
Percentiles (number of hours at a given concentration range) (Mclaughlin et
al., 1982) can also be used to summarize the seasonal distribution of concen-
trations but these likewise provide no means of characterizing when within a
season these episodes occur. The use of means (Heck et al., 1982a) (averages
of concentrations over specific time periods) and cumulative dose (Oshima et
al. , 1977 a,b) also ignores the episodic nature of seasonal exposures. Other
exposure representations based on a seasonal average time suffer from similar
inadequacies. The difficulty of selecting an appropriate statistic to charac-
terize plant exposure has been summarized by Heagle and Heck (1980). Ambient
and experimental 0.. exposures have been presented as (1) seasonal, monthly,
weekly, or daily means; (2) peak hourly means; (3) number of hours above a
selected concentration; or (4) number of hours above selected concentration
intervals. None of these statistics adequately characterizes the relationships
between ambient 0. concentration, exposure duration, and plant growth stages.
Until further research defines the influence on plant responses of temporal
fluctuations in ozone concentrations, which is characteristic of exposures to
ambient air, the selection of a summary statistic that characterizes ozone ex-
posures will continue to be discretionary. Unfortunately, the existing summary
statistics cannot be directly compared. Each is the result of calculations
from the original aerometric monitoring data and cannot be transformed to
another exposure statistic without the expensive and laborious task of return-
ing to the original data. Therefore, comparisons among studies that use
different summary statistics are difficult.
7.2.2.2 Statistics Used to Characterize Short Exposures. An experiment that
focuses on foliar injury or any other relatively short-term response may only
require short periods of exposure, which can be characterized by a simple
exposure statistic. When such results are evaluated, a problem occurs only if
the results of the short-term exposure experiment are extrapolated to evaluate
their significance in relation to long-term exposures. Mean and dose (concen-
tration times time) statistics from short-term exposures usually cannot be ag-
gregated to be representative of the temporal dynamics of long-term exposures.
019SX/B 7-9 4/12/84
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Although most short-term exposures are described by a concentration and
duration or dose, scientists point out that the correct exposure representation
is the amount of pollutant entering the plant, not the ambient air concentra-
tion to which it is exposed (Taylor et al . , 1982a; Tingey and Taylor, 1982).
Plants are affected only by the 03 or PAN that diffuses into the leaves. It
is difficult, however, to measure or quantify the relationship between the
concentration of pollutant in the air and the internal pollutant flux because
of the interactive effects of environmental and biological variables unique to
a specific set of environmental conditions. An interactive model that requires
variables describing the exposure, environmental condition, and species would
be necessary to relate internal pollution flux to ambient air levels.
7.2.2.3 Exposure Statistics. When pollutant concentrations exceed a given
level for a specific time period, plants will be affected by (k. Studies with
beans and tobacco (Heck et al . , 1966) showed that a dose over a short time
period (concentration times time) induced more injury than the same dose
distributed over a longer time period. Studies with tobacco showed that 0^
concentration was approximately twice as important as exposure duration in
causing foliar injury (Tonneijck, 1984). In this study, plants were exposed
to a range of 0_ concentrations (0.02 to 0.15 ppm) for 8 hr/day for 1 to 7
days. In beans foliar injury developed when the internal 0, flux exceeded
2 J
5500 fjg/m in 1 hr (Bennett, 1979). However, a single 3-hr exposure at approx-
imately half the concentration (0.27 compared to 0.49 ppm) required approximate-
ly a 64% greater internal 03 flux to cause the same amount of foliar injury as
the 1-hr exposure. The greater importance of concentration compared to exposure
duration has been reported by many authors (e.g., Heck and Tingey, 1971;
Henderson and Reinert, 1979; Reinert and Nelson, 1979).
Not only are concentration and time important but the dynamics of the 0,
exposure are also important; that is, whether the exposure is at a constant or
variable concentration. Musselman et al . (1983) recently showed that fixed
concentrations of 0_ cause the same pattern of responses as variable concentra-
tions at the equivalent dose. Fixed concentrations, however, had less effect
on plant growth responses than variable concentrations at similar doses.
Exposures of radishes to ambient 0- in open- top exposure chambers showed that
significant yield reductions occurred when the maximum 0- concentration ex-
ceeded 0.06 ppm at least 10% of the days when the crop was growing (Ashmore,
1984). Field studies with soybeans showed that reduced yield (weight/seed)
019SX/B 7-10 4/12/84
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was most closely correlated with the number of CL peaks in excess of 0.10 ppm
(Pratt, 1982). Similar results were previously reported for sulfur dioxide
(S02) (McLaughlin et al., 1979; Male et al., 1983). These results suggest
that the mechanisms causing the response are the same, but that exposures to
fixed concentrations underestimate the magnitude of plant growth responses.
The observations that the nature of the exposure influences plant response
is supported by other types of studies—for example, the study by Walmsley
et al. (1980) in which they exposed radishes to 0- continuously. During the
study period, the plants acquired some 0., tolerance. The acquired tolerance
displayed two components: (1) the exposed plants developed new leaves faster
than the controls and (2) there was a progressive decrease in the sensitivity
of the new leaves to 03- The newly formed leaves displayed a slower rate of
senescence. The observations by Elkiey and Ormrod (1981) that the CL uptake
decreased during a 3-day study period may provide an explanation for the
results with radish. Other research has suggested that plants exposed to low
levels of 0-. become more sensitive to subsequent exposures. For example,
studies with soybean (Johnston and Heagle, 1982), tobacco (Heagle and Heck,
1974) and bean (Runeckles and Rosen, 1977) showed that plants exposed to low
levels of 0- for a few days became more sensitive to a subsequent 0~ exposure.
Currently, there is no consensus as to the most appropriate summary sta-
tistic for representing plant exposure to photochemical oxidants. Consequently,
many different statistics are used, making direct comparisons between studies
extremely difficult. Further, there is some question as to the adequacy of
statistics used to characterize long exposures (season), since they do not
consider exposure dynamics within the period being represented. This question
cannot presently be resolved because research to date has not clearly deter-
mined whether stages of plant growth are differentially sensitive to exposures
relative to ultimate yield.
7.2.3 Exposure Systems
Research methods can be organized according to the means by which expo-
sures or environmental variables are controlled or characterized. Air pollu-
tion research often requires exposure chambers or other apparatus to maintain
controlled pollutant exposures. Exposure systems may range from sophisticated,
microprocessor-controlled cuvettes (Bingham and Coyne, 1977; Legge et al. ,
1979) to a series of tubes with calibrated orifices spatially distributed over
019SX/B 7-11 4/12/84
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a field to emit gaseous pollutants (Lee et al., 1978). Each of the types of
systems was designed for specific objectives and operates most efficiently
under the conditions for which it was intended. Each has advantages and
limitations and must be evaluated in terms of the objectives each was designed
to meet.
The exposure systems discussed in this section share many common charac-
teristics. Each uses a monitoring system that measures pollutant levels con-
tinuously during exposures or that incorporates a time-sharing system that
sequentially measures concentrations in chambers or at field sites. The
systems normally use inert Teflon tubing for sampling lines and continuous air
flow to reduce time lags. Additionally, many systems use EPA-approved monitor-
ing and detection systems (see chapter 5 for EPA equivalent and Federal refer-
ence methods). Recently, quality assurance programs were included in several
studies to ensure that high quality, standardized air monitoring data will be
available and readily comparable. The air pollutants are either generated
artifically and dispensed to exposure chambers or field plots, or proportional
activated-carbon filtration is used to provide different levels of ambient
pollutants.
The systems described in this section represent significant advances in
the methods used in air pollution research on vegetation. As systems that
utilize the latest technological advances evolve, it is easy to be caught in
the rapid progress of their evolution and lose sight of their limitations.
Even the most sophisticated and advanced systems are only as good as the
researcher who uses them. They do not insure that the research results will
be of superior quality. They only provide the potential for understanding
better the impact of air pollutants on vegetation.
The following discussion is limited to exposure systems used in air
pollution research and is not meant to be a detailed description of the system
components. These systems are described in greater detail in original publica-
tions and review articles (i.e., Heagle and Philbeck, 1979).
7.2.3.1 Laboratory Systems. Laboratory systems (Tingey et al., 1979; Winner
and Mooney, 1980) typically employ artificial lighting and controlled environ-
ments. Most are designed to identify and measure effects ranging from the
subcellular to the whole-plant level of biological organization. Although
results from these systems are difficult to relate directly to field studies,
they do contribute to an understanding of the mechanisms involved with air
019SX/B 7-12 4/12/84
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pollution effects. They provide useful information in explaining or inter-
preting responses. The stability of the well-controlled environmental condi-
tions characteristic of most laboratory systems allows precise measurement of
an array of plant responses. By altering only one variable and holding others
constant, one can define well and more easily understand responses. These
systems are powerful tools for increasing the understanding of the effects of
pollutants on the biological processes basic to plant growth.
The greatest drawback of laboratory systems relates to the general appli-
cability of final results. The precise environmental conditions that make the
systems valuable for defining responses also make the laboratory systems arti-
ficial. In comparison, ambient environmental conditions are complex and
dynamic.
7.2.3.2 Greenhouse Exposure Systems. Greenhouse systems are generally used
in studies to identify and quantify physiological, growth, and yield responses
at the organ and whole-plant level of biological organization. Plants are
usually grown in containers in greenhouses with charcoal-filtered air. Expo-
sures are conducted under natural or artificial lighting within chambers in
the greenhouse. Plants may be physically moved in and out of exposure chambers
and allowed to grow on greenhouse benches during interim periods. Normally, a
single plant or small groups of plants constitute the experimental unit.
While the environmental conditions of greenhouse exposure systems may more
closely approximate field than laboratory conditions, the plant cultural con-
ditions are more similar to those used in laboratory studies. Although related
to field studies, greenhouse studies differ sufficiently to make direct extra-
polations to field conditions difficult. It must be remembered, however, that
greenhouse conditions are the typical cultural environment for many floricul-
ture and ornamental plants. In this case, the use of greenhouse conditions is
appropriate and no extrapolation is necessary.
Greenhouse exposure systems usually consist of a series of chambers built
with a framework of various materials and covered with a transparent film.
The air exchange systems normally use a negative pressure, single directional
air flow, and employ an activated-charcoal filtration device at both air entry
and exhaust. Early systems were usually modifications of the system developed
by Heck et al. (1968), but a variety of designs were utilized. These systems
were all designed to meet common, desirable chamber characteristics (uniform
pollutant concentrations with minimal environmental alteration) and succeeded
019SX/B 7-13 4/12/84
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to varying degrees. The design of the continuous stirred-tank reactor (CSTR)
by Rogers et al. (1977) stimulated the development of exposure systems that
®
incorporated its desirable mixing properties and the use of FEP Teflon film
as an inert polymer film.
7.2.3.3 Field Exposure Systems. To assess economic impact or agricultural
productivity, it is desirable to minimize deviations from the ambient environ-
ment and to simulate as closely as possible the conditions characteristic of
agricultural systems or natural ecosystems. Field exposure systems range from
adaptations of the greenhouse and laboratory chamber designs to the use of
chemical protectants. In most greenhouse and field studies, the investigators
have attempted to ensure that soil moisture, plant nutrients, and other cultur-
al conditions did not limit growth.
7.2.3.3.1 Field Chamber Systems. The open-top chamber system (Heagle et al.,
1973; Mandl et al. , 1973) is the most popular field-exposure system presently
in use. Essentially upright cylinders with a clear polymer film as a covering
around the sides, these chambers have the advantage of portability, moderate
cost, and ease of maintenance. The size and shape of the chambers may be
modified for use with different plant types and sizes. The system uses a
high-volume flow of filtered air to reduce ambient pollutant influx through
the open top. Pollutants are added to the incoming air stream. Their rate of
addition is adjusted to control the pollutant concentration in the chambers.
Pollutants are usually measured just above canopy height. Studies of the 03
distribution within the chambers have shown it to be quite uniform. The
vertical variation of 0~ in the 2.44-m-high chambers was less than 6 percent
between 0.3 and 1.2 m and less than 19 percent between 1.2 and 1.8 m. The
2
horizontal variation over the 7.3 m of the chamber was 12 percent and 14
percent at heights of 1.2 and 1.8 m, respectively (Heagle et al., 1979d). The
portability of the system facilitates storage and maintenance during the
winter or in periods of inactivity and allows standard agricultural practices
to be carried out during field preparation, seeding, and early crop growth
before chambers are set in place. Open-top chambers and well-ventilated
closed-top chambers reduce temperature deviations from the ambient, allow
sufficient pollutant control for either single or mixed-gas exposures, and are
relatively inexpensive. They can be selectively placed in established fields
to avoid unacceptable soil types or to maximize soil uniformity in treatments.
019SX/B 7-14 4/12/84
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Most of the limitations of open-top chambers relate to air flow charac-
teristics. Air flowing from the lower portion of the chamber out through the
open top reduces the intrusion of outside air; this air flow pattern is differ-
ent, however, from that in the open field. Because plants in the chamber
experience a different air flow pattern than field-grown plants, concerns have
been expressed that this might alter the influence of CL on plants. However,
recent measurements of canopy resistance to CL uptake in open-top chambers by
-1
micrometeorological methods in the field yield similar results 73 and 84 s m ,
respectively (Unsworth et al. , 1984). This similarity led the authors to
conclude that crop exposure to gaseous pollutants in open-top chambers is
similar to that which would occur at the same concentrations in the field.
With open-top exposure chambers some intrusion of ambient air through the chamber
top is unavoidable, which can influence the concentration within the chamber
(Heagle et al., 1973; Unsworth et al., 1984). The amount of intrusion in-
creases with wind speed. Recent design innovations, however, have minimized
this (Kats et al. , 1976; Davis and Rodgers, 1980). For example, the addition
of a frustum (a truncated cone) to the top of the open-top chambers can reduce
the intrusion of ambient air by approximately 50% and also provided a more re-
producible environment for a given wind speed (Unworth et al., 1984). It should
be recognized that open-field environmental conditions cannot be exactly
duplicated by open-top exposure chambers (Heagle et al. , 1979d; Olszyk et al.,
1980) or any other pollutant exposure system presently available. In summa-
rizing studies of open-top exposure chambers, Heagle et al. (1979d) reported,
In our 7-yr experience, the open-top chambers caused plants to grow
slightly taller but rarely had significant effects on yield. Plants
often grew differently in different parts of the chambers but we did
not find significant interactions between chamber position and the
effects of 0-. The causes for chamber-induced growth effects may be
related to slower mean air velocity, slightly higher temperature, or
less light at some chamber locations than in the open.... There are
no reports, however, that environmental changes of the magnitude
caused by open-top chambers change plant sensitivity.
Other field-exposure systems use chambers of varying design, but have the
common characteristic of being fully enclosed by film (Thompson and Taylor,
1966; Oshima, 1978). These designs rely on high air-exchange rates to minimize
temperature alterations. Most of these designs are adaptations or alterations
of greenhouse exposure systems. Chamber shapes range from a square design
019SX/B 7-15 4/12/84
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originally developed by Heck et al. (1968), to the CSTR cylinder described by
Rogers et al. (1977).
7.2.3.3.2 Field Exposure Systems without Chambers. The desire to expose
large field plots to increase sample size and to remove environmental altera-
tions caused by enclosing plants in chambers led to the development of chamber-
free field exposure systems. The advantage of these systems (Lee et al.,
1978; deCormis et al. , 1975; Reich et al. , 1980; Laurence et al., 1982) is
that plants are exposed to pollutants under conditions similar to the ambient.
This advantage is offset to some extent by the disadvantage of losing some
control over the level of pollutants and the nature of the exposure. These
systems are highly influenced by wind speed direction, and are subject to
ambient air levels. There have been only limited 0- studies in these types of
systems.
7.2.4 The National Crop Loss Assessment Network
The National Crop Loss Assessment Network (NCLAN) was initiated in 1980
by EPA to estimate the magnitude of national crop losses caused by air pollu-
tion. Initial emphasis was placed on C> (Heck et al. , 1982). A research
management committee is responsible for the planning, management, and execution
of the program. The primary objectives of the NCLAN are:
1. To define the relationships between yields of major agricultural
crops and 0, exposure as required to support the needs of the eco-
nomic assessments and the development of NAAQS;
2. To assess national economic consequences resulting from the exposure
of major agricultural crops to 0.,; and
3. To advance the understanding of the cause and effect relationships
that determine crop responses to pollutant exposure.
NCLAN is a network of experimental field sites selected for (1) their
different climatological conditions, (2) their distribution of different crop
species, and (3) their proximity to established research groups with a history
of research on air pollutant effects on vegetation. The test species are
grown in the field under conditions approximating standard agronomic practices.
Efforts are made to minimize perturbations of the plant environment from the
exposure apparatus and to use realistic pollutant doses.
019SX/B 7-16 4/12/84
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The pollutant concentrations around crop plants in the field are control-
led and manipulated through the use of open-top chambers. Sufficient numbers
of chambers permit replicated experimental designs; this also permits the
development of empirical dose-response models. Models for test species and
cultivars are developed from data for several sites and for several years.
Within the open-top chambers, plants are exposed to a range of ozone con-
centrations. Daily variation in the 0_ concentration is determined in part by
changes in ambient CL concentrations at each site. The lowest CL level (con-
trol, charcoal filtered air) is 20 percent to 50 percnet of that in ambient
air; the 0, that is present enters the chamber mainly through the open top,
because the inlet air to the chamber is charcoal filtered. All other chambers
receive ambient air supplemented (7 hours per day) with enough 0 to provide
concentrations equal to those at field plots and three or four stepwise incre-
ments (0.02 to 0.03 ppm) above levels in ambient air. Ozone concentrations
within the chambers are measured at canopy height with time-shared monitors.
Plant yields are also measured for field plots of identical size exposed to
ambient (non-chamber) air to obtain an estimate of potential chamber effects.
Chamber fans are operational from 5:00 a.m. to 9:00 p.m. daily, and 0- is
O
added from 9:00 a.m. through 4:00 p.m. (local standard time) daily throughout
the growing season for the crop, except on rainy days.
A quality assurance program for the collection and measurement of air
quality and biological data is followed in NCLAN studies. Independent audits
of the pollutant monitors are conducted at each site.
The data are analyzed by both analysis of variance and by regression
analysis. The mean 7-hour daily concentration (9:00 - 4:00), averaged over
the growing season, is used for a seasonal exposure statistic. This is the
time period when 0_ is added to the chambers.
NCLAN has many strengths associated with a coordinated national multi-site
program. Perhaps its greatest strengths are the standardization of methods
for air monitoring, biological assessment, experimental design, pollutant
exposure regimes, summarization of exposures, and quality assurance. Addi-
tionally, the selection of agriculturally important crops for test species and
the use of close approximations of standard cultural practices ensure applica-
bility of experimental results. The development of empirical models interfaces
well with required economic inputs for a national economic assessment. Pre-
viously, very few biological models were available for economic assessments.
019SX/B 7-17 4/12/84
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NCLAN has limitations that must also be considered. The potential arti-
ficiality of the CL exposure treatments may complicate the application of
results. Further, the use of the seasonal 7-hour daily mean concentrations, a
relatively new exposure summary statistic, makes comparisons with previously
published studies difficult. It also does not accurately represent the temporal
exposure dynamics of ambient air. The lack of validation of the model predic-
tions is unsettling, but that is a common deficiency of all models to date and
is not unique to NCLAN. These limitations may also occur with other field
studies.
When viewed in perspective, NCLAN represents the state of the art for
documenting yield losses resulting from ozone and for providing compatible
data for economic assessments on a national scale.
7.2.5 Determination of Yield and Crop Losses
For the purposes of this chapter, yield loss is defined as reduction in
quantity, quality, aesthetic value, or any impairment of the intended use of a
plant. Thus, foliar injury on ornamental plants, detrimental responses in
native species, and reductions in fruit or grain production by agricultural
species are all considered yield loss. Crop loss, in contrast, is defined as
an economic or monetary loss and is not synonymous with yield loss. Crop loss
occurs at aggregative levels higher than the plant or plot. The transformation
of yield loss to crop loss incorporates economic considerations such as those
described in section 7.4.2.2.3.
Loss by definition implies some reduction from a reference zero-loss
level. When crop yields are considered, one must first establish a reference
in terms of quantitative yield units (grams, pounds, tons) and second, one
must transform reductions from that level into loss units (usually a proportion,
such as percentage). It is necessary to define adequately an appropriate
reference level from which loss is determined. When an empirical 0, yield-loss
model is used, the zero-loss reference yield should be representative of the
yield in the production area in question in the absence of 0.,. The reference
zero-loss level can be tested in conjunction with the model validation referred
to in section 7.2.1. Zadoks (1980) cites several definitions of yield that
can be used as a reference level for both biotic and abiotic crop losses.
019SX/B 7-18 4/12/84
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7.3 MODE OF OZONE ACTION ON PLANTS
Plant growth and yield are the culmination of many biochemical and physio-
logical processes. Plants absorb carbon dioxide from the atmosphere through
portals called stomata. Within the chloroplasts located in the mesophyll
cells of the leaf (Figure 7-2), the carbon dioxide is converted into carbohy-
drates in the presence of light (photosynthesis). Plants absorb the necessary
water and mineral nutrients for growth from the soil. Growth and yield depend
not only on the rate of photosynthesis and the uptake of water and nutrients,
but also on subsequent metabolic processes and the allocation of the photosyn-
thetic products to the rest of the plant. The uptake of carbon dioxide and
its subsequent metabolism and allocation within the plant is influenced by
various environmental conditions. The impairment of any of these processes
may affect plant growth and yield.
The responses of vascular plants to 03 may be viewed as the culmination
of a sequence of physical, biochemical, and physiological events. Ozone in
the ambient air is not directly phytotoxic, only the 03 that diffuses into the
plant. A phytotoxic effect will occur only if a sufficient amount of 03
reaches the sensitive cellular sites within the leaf. The 03 diffuses from
the ambient air into the leaf through the stomata, which can exert some control
on Oo uptake to the active sites within the leaf. Ozone injury will not occur
if 1) the rate of 03 uptake is sufficiently small so that the plant is able to
detoxify or metabolize 03 or its metabolites or 2) the plant is able to repair
or compensate for the 0^ impacts (Tingey and Taylor, 1982). The uptake and
movement of 03 to the sensitive cellular sites are subject to various physio-
logical and biochemical controls.
Ozone may diffuse into the leaf through stomata; and it should again be
noted that only the 03 diffusing into the leaf can affect plant growth and
yield. Once ozone enters the leaf through stomata it quickly dissolves in the
aqueous layer on the cells lining the air spaces. Ozone then diffuses through
the cell wall and membrane into the cell, where it may affect cellular or
organellar processes. Ozone flux (J) into the leaf may be represented by the
following equation (Tingey and Taylor, 1982);
J = AC/(Ra + Rs + Rr). (7-1)
019SX/B 7-19 5/4/84
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CUTICLE
VASCULAR
CELLS
LEAF
HAIR
EPIDERMIS
PHOTOSYNTHETIC
MESOPHYLL CELLS
INTERCELLULAR
SPACE
GUARD CELLS
STOMATA
Figure 7-2. Schematic cross section of a typical dicot leaf.
7-20
-------
Flux is directly proportional to the change in 03 concentration (AC) between
the ambient air and the leaf interior (gas-to-liquid transfer) and is in-
versely proportional to resistance to the mass transfer of gas. Resistance to
0, movement can be divided into components, including boundary layer (R ),
•j a
stomatal and intercellular space (R ), and liquid-phase (R ) resistances.
At any point along this pathway, 03 or its decomposition products may
react with cellular components. Altered cell structure and function may
result in changes in membrane permeability, carbon dioxide fixation, and many
secondary metabolic processes (Tingey and Taylor, 1982). The magnitude of
0 -induced effects will depend upon the physical environment of the plant,
including macro- and microclimate considerations; the chemical environment of
the plant, including other gaseous air pollutants and a variety of chemicals;
and biological factors, including genetic potential and developmental age of
the plant and interaction with plant pests. Cellular injury manifests itself
in a number of ways, including foliar injury, premature senescence, reduced
yield or growth, or both, reduced plant vigor, and sometimes death. Depending
upon the intended use of a plant species (viz., for food, forage, fiber,
shelter, or amenity), any of the effects discussed above could impact society
adversely.
In the following sections, selected references will be cited to describe
how CL induces some of its effects. Some of the physiological studies have
been conducted with 0., exposures that would rarely, if ever, be encountered in
ambient air. This literature can, however, serve as a tool for identifying the
potential sequence of the physiological and biochemical responses of plant
species, and for identifying potential metabolic sites of action that may or
may not be visibly expressed.
7.3.1 Biochemical and Physiological Responses to Ozone
Phytotoxic effects of air pollution on plant tissue will occur only when
sufficient concentrations of a gas diffuse into the leaf interior and pass
into the liquid phase of the cells. Once a gas is deposited on a wet cell
surface, it may move by diffusion or bulk flow to sites of action, such as the
interior of the cell membrane, the cytoplasm, or cellular organelles (Heath,
1980; Tingey and Taylor, 1982).
7.3.1.1 Gas Phase Movement into the Leaf. Ozone, as well as other gases,
diffuses from the atmosphere into the leaf through stomata. The stomata
019SX/B 7-21 4/12/84
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control the rate of 0_ uptake into the leaf and are influenced by various
plant and environmental stimuli. A variety of factors, including CL, have
O
been shown to induce stomatal closure. The previous criteria document (U.S.
environmental Protection Agency, 1978) cited a number of studies that directly
correlated 0- concentration and stomatal closure. Engle and Gabelman (1966)
reported that in the presence of 03 (0.3 ppm for 0.5 hours), stomata closed
more quickly in tolerant than in sensitive onion cultivars. Rich and Turner
(1972) found that when tobacco plants were exposed to 0.20 to 0.25 ppm 0, for
2 hours, leaf conductance (a measure of stomatal closure) decreased 32 percent
in a resistant cultivar and only 9 percent in a sensitive cultivar (no statis-
tics provided), suggesting possible differences in 0- uptake between cultivars.
More recently, Krause and Weidensaul (1978b) observed that geranium guard
cells, which control stomatal opening, ruptured after a 10-day exposure to 0-
O
at concentrations of 0.15 ppm for 6 hours per day. In contrast, when four
cultivars of peas were exposed to an 0., concentration of 0.15 ppm for 6 hours
per day and stomatal conductance was measured, the two more sensitive cul-
tivars had greater decreases in leaf conductance (85 percent and 86 percent)
than did the two more tolerant cultivars (62 percent and 69 percent) (Dijak
and Ormrod, 1982). Clearly, decreased conductance could not explain differen-
tial cultivar tolerance in this case. When they reviewed the 0, uptake litera-
ture, Tingey and Taylor (1982) found examples of species for which the 0.,
response was apparently limited by leaf conductance (i.e., 0, uptake) and
species for which 0,. response was not controlled by 0_ uptake but rather by
metabolic processes within the mesophyl1 cells.
Ozone flux into the leaf may also be regulated by stomatal density.
Butler and Tibbitts (1979a) correlated stomatal density directly with 0-.-
induced visible injury in bean plants, but Gesalman and Davis (1978) found no
such relationship for azalea cultivars. There was no apparent relationship
between stomatal frequency or guard-cell length and differential 0_ sensitivity
of two corn cultivars (Harris and Heath, 1981). They found that the leaf
water potential was poised near the point at which only a slight water loss in
the tolerant cultivar would induce stomatal closure. Hence, they suggested a
rapid stomatal closure in response to an 0,-induced water loss. In the 1978
criteria document (U.S. Environmental Protection Agency, 1978), equally dispa-
rate results were offered for several plant species. Dean (1972) reported
that tobacco cultivars that exhibited tolerance to oxidant-induced weather
019SX/B 7-22 4/12/84
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fleck in the field had lower stomatal density than did sensitive cultivars.
Evans and Ting (1974) found that the maximum Oo sensitivity of primary leaves
of bean could not be accounted for by stomatal density.
In summary, different plant responses to 0, are the result of the diffu-
sion of (L into the leaf interior. A knowledge of the (L uptake rate or
amount, however, is not sufficient for predicting subsequent responses for all
species. In some species, injury is apparently not directly related to 0,
uptake; while in others, there is a relationship between the quantity of 0,
entering the plant and the degree of subsequent injury. The physical and
chemical environment and biological potential of the plant influence stomatal
behavior and (L uptake, as will be documented in later sections. Once (L
enters the plant, there are potential reactions with many cellular constituents.
7.3.1.2 Transition between Gas-Phase and Liquid Phase Movement into the Cell.
Once it enters the intercellular spaces, ozone passes into the liquid phase at
the gas-liquid interface of the cell wall surface. The diffusive process is
dependent on physical, chemical, and biological factors that govern this
diffusive step (Tingey and Taylor, 1982). The solubility of 0^ is critical to
further reaction and depends on microclimatic factors, including temperature.
The rate at which gas diffusion occurs may also depend upon the internal
cell surface area exposed (Evans and Ting, 1974; Pell and Weissberger, 1976;
Uhring, 1978). Taylor et al. (1982b) reported that in soybean foliage, pollu-
tant flux was not regulated solely by the number of sites of 0., deposition.
When plants were exposed to 0, concentrations ranging between 0.25 and 0.58
ppm for 1 to 4 hours, uptake rates were higher and the ratio of internal/
external leaf area was lower for "Hood," a relatively resistant soybean culti-
var, than for "Dare," which was more susceptible. Athanassious (1980) did not
identify surface-volume ratio as a determinant of relative response of radish
mesophyll cells to 0, but suggested that differential suberization of cell
walls may explain relative sensitivity of parenchyma! tissue. This idea was
offered previously by Glater et al. (1962).
7.3.1.3 Chemical and Biochemical Response. When 0^ passes into the liquid
phase, it is likely that the molecule will rapidly undergo transformations
that yield a variety of free radicals, including superoxide and hydroxyl radi-
cals (Pryor et al., 1981; Hoigne and Bader, 1975; Tingey and Taylor, 1982).
Whether these chemical species result from decomposition of 0- or reactions
between 0,. and biochemicals in the extracellular fluid has not been determined.
019SX/B 7-23 5/4/84
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Ozone or its decomposition products, or both, will then react with cellular
components, resulting in structural or functional effects, or both.
The potential for 0.,, directly or indirectly, to oxidize biochemicals in
o
vitro has been demonstrated. Ozone can oxidize a number of biological mole-
cules, including reduced nicotinamide adenine dinucleotide (NADH), DMA, RNA,
purine, pyrimidines, indole acetic acid, some amino acids (including tryp-
tophan and methionine), many proteins (including glyceraldehyde-3-phosphate
dehydrogenase, catalase, peroxidase, papain, ribonuclease, and urease), and a
variety of lipids (Christensen and Geise, 1954; Todd, 1958; Ordin and Propst,
1962; Heath, 1975; Mudd, 1982). In these studies, and in similar ones, the
concentrations of 0., bubbled into the biochemical solutions were all very
high. It is difficult to compare the exposure to ozone in solution to the
ambient air exposure that plants experience. Coulson and Heath (1974) have
suggested, however, that solution and atmospheric exposures are not highly
dissimilar. They showed that most of the 0- bubbled into solutions exited
unreacted and that the 0, dose required to injure cells in solution was of a
magnitude similar to that required to injure intact plants exposed to atmos-
pheric 03. Todd (1958) predicted sensitivity within the plant by relating
concentrations of protein used i_n vitro to levels in the plant and extrapolated
to lower concentrations of 0... Similar comparisons could be made for other
biochemicals studied jji vitro. Because biochemicals are compartmentalized
within the plant, such calculations of potential sensitivity may deviate from
actual responses observed. Data acquired from i_n vitro studies are best
utilized to demonstrate that many cellular constituents are susceptible to
oxidation by 0~. Different approaches will have to be used to determine
which, in fact, are important i_n vivo.
The potential for biochemicals to be affected within the plant has been
explored by a number of researchers. Increases and decreases have been obser-
ved in the status of proteins, sulfhydryl residues, fatty acids, and sterols
(Pell, 1979; Trevathan et al. , 1979; Swanson et al. , 1973). Results vary
among laboratories. For example, Trevathan et al. (1979) observed a decrease
in fatty acids 3 days after tobacco plants were exposed to 0.24 ppm 03 for 6
hours, whereas Swanson et al. (1973) detected no change in fatty acid content
in the same species 2 hours after plants received 0.30 ppm 03 for 2 hours. It
is likely that Trevathan et al. (1979) were observing a late plant response
associated with injury and cell death while Swanson et al. (1973) provided
O
019SX/B 7-24 4/12/84
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evidence that lipids were not particularly sensitive to 0_. Similarly, Fong
and Heath (1981) were unable to detect any changes in either phospholipid
content or fatty acid composition of total polar lipids in bean leaves that
sustained mild visible injury after exposure to an 0_ concentration of 0.30
O
ppm for 1 hour. Changes in mono- and digalactolipids were observed after
severe injury was induced by a concentration of 0.50 ppm for 1 hour.
The examples above serve to underscore the importance of recognizing the
limitations of studies in which biochemical effects are determined for whole
leaf tissue rather than for organelles, or are determined in terms of cell
function. Such data neither describe the dynamics of injury development nor
identify the cellular site at which biochemical changes are occurring. This
kind of biochemical information is useful in characterizing the nature of a
response to CL as it relates to altered metabolism, in general, and to visible
foliar injury.
7.3.1.4 Physiological Responses. Physiological measurements have been more
useful than biochemical quantifications in characterizing cell responses to
oxidants. Many consider membranes to be the primary site of action of 0_
(Heath, 1980; Tingey and Taylor, 1982). The alteration in plasma membrane
function is an early event in the sequence of 0_-induced effects that eventu-
ally leads to leaf injury and subsequent yield loss. Changes in the semiper-
meability of the membrane are evidenced by changes in fluxes of carbohydrates,
amino acids, inorganic ions, and water (Heath, 1975, 1980; Tingey and Taylor,
1982). Whether the plasma membrane or some organelle membrane is the primary
site of 0, action is open to speculation (Tingey and Taylor, 1982). Mudd
(1982) suggested that 0-, may penetrate the plasma membrane and injure organ-
elles. A number of membrane-dependent functions of organelles can be altered
by 0_. MacDowall (1965) reported that oxidative phosphorylation was inhibited
when tobacco plants were exposed to 0, at concentrations from 0.6 to 0.7 ppm
for 1 hour. Photophosphorylation was inhibited in isolated spinach chloroplasts
exposed to 0, at a concentration of 400 ppm for 15 minutes (Coulson and Heath,
1974). Using the Bensen coefficient for 0_ and the partial pressure of the
gas above the aqueous solution, Coulson and Heath (1974) calculated the latter
dose to be equivalent to a concentration of 0.20 ppm in ambient air surrounding
a terrestrial plant.
Ozone can also affect biochemical functions not associated with membranes.
The activity of 1,5-ribulose bisphosphate (RuBP) carboxylase, an enzyme that
019SX/B 7-25 4/12/84
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catalyzes CCL fixation during photosynthesis, can be inhibited by 0-. For
example, 0.12 ppm for 2 hours inhibited the activity of RuBP carboxylase in
rice (Nakamura and Saka, 1978). Inhibition of RuBP carboxylase activity is a
relatively early event occurring several hours after conclusion of the 0_
exposure. Pell and Pearson (1983) observed 36, 68, and 80 percent decreases
in the concentration of 1,5-RuBP carboxylase in foliage of three alfalfa
cultivars that had been exposed to an 0_ concentration of 0.25 ppm for 2 hours.
Observations were made 48 hours after exposure on leaves that did not exhibit
macroscopic injury symptoms. Crystals observed in the chloroplast stroma of
beans and hybrid poplars exposed to 0_ were thought to be 1,5-RuBP carboxylase
(Thomson, 1975; Noble et al. , 1980).
In some of the studies cited above, researchers examined the specific
effects of 0 on key steps in photosynthesis. The effect of 0- on apparent
photosynthesis, a measure of CO- uptake or fixation or both, was measured for
many more plant species (Table 7-1). Reductions in apparent photosynthesis
may reflect the direct impairment of chloroplast function or reduced C0?
uptake, or both, resulting from 0.,-induced stomatal closure. Regardless of
the mechanism, a sustained reduction in photosynthesis will ultimately affect
growth, yield, and vigor of the plant.
When considering dose-response effects of G\ on plant yield in this docu-
ment, emphasis has been placed on studies in which 03 concentrations of 0.25
ppm or below were utilized (Table 7-1). Examples of 0.,-induced reduction in
apparent photosynthesis at concentrations exceeding 0.25 ppm are also presented
(Table 7-1). These data highlight the potential of 0~ to reduce primary
productivity. Several of the studies provide data more pertinent to the
ambient atmosphere. Barnes (1972a) examined the impact of 0- on seedlings of
three species of pine at concentrations of 0.05 or 0.15 ppm continuously for
19 days to 18 weeks. In younger seedlings of eastern white pine, which bore
only primary needles, 0_ had little influence on photosynthetic rate. In
older seedlings with secondary needles, photosynthesis was slightly depressed.
With seedlings of slash, eastern white, and loblolly pines, exposure at 0.15
ppm 0., had a relatively consistent depressing influence on photosynthesis of
o
all species. At 0.05 ppm, however, 0_ appeared to stimulate photosynthesis in
older secondary needles and depress photosynthesis in younger secondary needles.
Barnes (1972a,b) used a Mast meter to measure 0.,, which can underestimate the
0., concentration unless it is calibrated against a reference standard (chapter 5).
019SX/B 7-26 4/12/84
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TABLE 7-1. EFFECT OF OZONE ON PHOTOSYNTHESIS
Species
Loblolly pine
Slash pine
Bean
Alfalfa
Ponderosa pine
Eastern white pine
Eastern white pine
Sensitive
Tolerant
Bean
Black Oak
Sugar maple
White pine
Sensitive
Tolerant
Poplar hybrid
Ponderosa pine
._
Concentration
ppm
0.05
0.05
0.072
0.10
0.20
0.15
0.30
0.15
0.10
0.20
0.30
0.10
0.20
0.30
0.30
0.50
0.50
0.7 or 0.9
0.70 to 0.95
0.90
450, 700
800 ppm-hr
Exposure duration
18 weeks
continuously
18 weeks
continuously
4 hr/day for 18 days
1 hr
1 hr
9 hr daily/
60 days
9 hr daily/
30 days
19 days
4 hr/day for 50 days
4 hr/day for 50 days
4 hr/day for 50 days
4 hr/day for 50 days
4 hr daily/50 days
4 hr daily/50 days
3 hr
4 hr daily/2 days
4 hr daily/2 days
3.0 or 10
10/30 days
1.5 h
Cumulative
dose over
1,2,3 yr.
inhibition
15b
9b
18b
4b
10b
25C
67C
10C
24b
42b
51D
Not sig.
different
h
20b
22c
30 t 10d
21 ± 10d
K
100b
ob
60e
90b
Reference
Barnes, 1972a
Barnes, 1972a
Coyne and Bingham
Bennett and Hill ,
, 1978
1974
Miller et al. , 1969
Barnes, 1972a
Yang et al . , 1983
Pell and Brennan,
Carlson, 1979
Carlson, 1979
1973
Botkin et al. , 1972
Furukawa and Kadota, 1975
Coyne and Bingham
, 1981
P < 0.05.
CP < 0.01.
Standard deviation.
£
No statistical information.
7-27
-------
Also, the sample size used in these experiments was very small, four to nine
seedlings. It is possible that variation among samples may have masked poten-
tial effects in some of the experiments (Barnes, 1972a). More recently, Coyne
and Bingham (1978) exposed field-grown snap beans to an 0., concentration of
0.072 ppm (the 0.. monitor was calibrated by UV photometry; see chapter 5) for
4 hours per day for 18 days. Apparent photosynthesis was reduced 18 percent
in plants treated with 0_. Bennett and Hill (1974) reported that apparent
photosynthesis of alfalfa plants was depressed 4 percent and 10 percent when
0 concentrations were 0.1 and 0.2 ppm for 1 hour, respectively. Methods of
0- monitoring and calibration were not given by the authors.
Black et al. (1982) found a significant (p < 0.001) relationship (r =
-0.8) between net photosynthetic rate of broad bean and 4-hour exposures to
concentrations of 0_ from 0.05 to 0.30 ppm. Exposure to 0- concentrations of
less than 0.10 ppm resulted in a reversible depression of photosynthesis.
Twenty hours after exposure to 0- concentrations of 0.10, 0.20, and 0.30 ppm,
2
photosynthetic rate was depressed 0.037, 0.59 and 1.14 g CCL/m per hour,
2
respectively, when compared with an initial rate of approximately 2.1 g CO^/m
per hour (based on values presented for one example in the study). Miller et
al. (1969) found that 3-year-old ponderosa pine seedlings sustained a 25
percent reduction in apparent photosynthesis after a 60-day exposure to an 0.,
concentration of 0.15 ppm for 9 hours per day. Yang et al. (1983) exposed
three clones of white pine, classified by foliar response to 0^ as sensitive,
intermediate, and insensitive, to 0, concentrations of 0.10, 0.20, or 0.30
4 hours per day for 50 days in CSTR chambers. Net photosynthesis was reduced
in the foliage of sensitive and intermediate clones by 14 to 51 percent in
direct relation to 0_ dose and relative clonal sensitivity (Table 7-1). In
another study, Coyne and Bingham (1981) measured changes in gross photosynthe-
sis in needles of ponderosa pine trees of various sensitivities to 0.,. Needles
sustaining slight, moderate, and severe injury exhibited a 90 percent reduction
in gross photosynthesis after exposure to 800, 700, and 450 ppm-hours 0_,
respectively, in a 3-year time period (2 years for the most sensitive class of
trees). The percentage inhibition in gross photosynthesis was based on photo-
synthetic rates of newly emerged needles; no true controls were used in the
experiment. The authors emphasized that the decline in photosynthesis reflec-
ted the superimposition of 03 effects on normal aging.
019SX/B 7-28 4/12/84
-------
7.3.1.5 Tissue and Organ Responses. In addition to depressing photosynthesis
in the foliage of many plant species, 0~ inhibits the translocation of photo-
synthate (e.g., sucrose) from the shoots to the roots (Tingey, 1974; Jacobson,
1982). Tingey et al. (1971a) found that when radish plants were exposed to 03
(0.05 ppm for 8 hours, 5 days per week for 5 weeks), hypocotyl growth was
inhibited 50 percent, while foliage growth was inhibited only 10 percent (both
significant at p < 0.01). Walmsley et al. (1980) confirmed that radish plants
exposed to 03 (0.17 ppm continuously for 36 days) exhibited an altered pattern
of assimilation such that below-ground biomass was more severely affected than
foliage. Ponderosa pine exposed to 0.10 ppm 0.. for 6 hours per day for 20
weeks stored significantly less sugar and starch in their roots than did
control plants (Tingey et al. , 1976). Such an effect on translocation could
reduce root weight and directly affect the yield of a crop like radish or
carrot.
Snap beans exposed to 0- (0.30 ppm or 0.60 ppm for 1.5 hours) exhibited a
greater reduction in root than shoot growth (Blum and Heck, 1980). The root-
to-shoot ratio of crimson clover was suppressed 17 percent and 23 percent,
respectively, (p < 0.05) when plants were exposed to 0., at 0.03 and 0.09 ppm
for 8 hours per day for 6 weeks (Bennett and Runneckles, 1977). The root-to-
shoot ratio of rye grass was reduced 22 percent (p < 0.05) when plants were
exposed to 0.09 ppm with the same exposure regime. In other experiments, the
effects of 0., were measured on the partitioning of photosynthate in carrot,
parsley, sweet corn, cotton, and pepper (Oshima, 1973; Bennett and Oshima,
1976; Oshima et al., 1978; Oshima et al., 1979; Bennett et al. 1979). In each
of these experiments, plants were exposed to 0, concentrations of 0.12 to 0.25
ppm for 3 to 6 hours for 0.2 percent to 7 percent of the total growth period
of the plants. In all species but pepper, root dry weight was depressed much
more than leaf dry weight. For example, root dry weight of cotton was reduced
60 percent, whereas leaf dry weight was depressed only 17 percent by 0- (Oshima
et al., 1979). Ozone had virtually no effect on the dry weight of parsley
leaves, but it reduced root dry weight 43 percent (Oshima et al., 1978). The
photosynthetic rate of tomato plants exposed to 0~ (0.3 ppm for 3 hr) was
reduced 35% and the translocation of photosynthate from the leaves was reduced
29% (McCool and Menge, 1983). This combined reduction in photosynthate avail-
able for root growth can significantly affect plant growth. The reduction in
photosynthate translocation to roots and the resulting decrease in root size
019SX/B 7-29 4/12/84
-------
indicates that the plant had fewer stored reserves, rendering it more sensitive
to injury from cold, heat, or water stress.
When less carbohydrate is present in roots, less energy will be available
for root-related functions. In the 1978 criteria document (U.S. Environmental
Protection Agency, 1978), evidence was presented for 0~-induced reduction in
nodulation and nitrogen fixation in soybean and ladino clover. Blum and
Tingey (1977) reported that when 2-week old soybean plants were exposed to an
03 concentration of 0.50 ppm for 4 hr, nodulation was inhibited 60% (p <
0.05). Ensing and Hofstra (1982) measured nitrogenase activity in the roots
of red clover 1 and 6 days after the plants were exposed to 03 (0.20 ppm
16 hr/day for 4 days) in non-filtered open top chambers and found nitrogenase
activity was reduced 50 and 24% (p = 0.05), respectively, when compared to the
activity in plants growing in charcoal filtered open-top chambers. By 16 days
post- exposure, enzyme activity was comparable to other treatments. An ozone-
induced suppression of atmospheric nitrogen fixation by root nodules could
affect total biomass and agricultural yield, especially in areas where soil
nitrogen is low.
7.3.1.6 Secondary Metabolic Responses. In addition to the physiological
effects more directly related to productivity, there are many secondary meta-
bolic responses in a plant exposed to 0.,. While these responses do not explain
the initial reaction to 0.,, they may contribute to the manifestation of foliar
injury. Ethylene is an important stress metabolite produced by many plants
exposed to 03 (Tingey, 1980). Ozone at 0.15 ppm for 8 hours increased ethylene
evolution in beans (Stan et al. , 1981). Ethylene evolution ceased prior to
necrosis (visible injury). It has been proposed that ethylene may initiate
the observed stimulation of oxidizing enzymes such as phenylalanine lyase,
polyphenoloxidase, and peroxidase (Tingey et al., 1975). The accumulation of
phenols has been observed in many plant species in response to 0_ (Howell and
Kremer, 1973; Hurwitz et al. , 1979; Keen and Taylor, 1975; Koukol and Dugger,
1967). There appears to be a direct relationship between the concentration of
phenols detected in foliage and the extent of necrosis (visible injury) in-
duced by 0., (Hurwitz et al. , 1979). The pigmented lesions that are visible in
the leaf following 0~ exposure are thought to occur when phenols are oxidized
«5
and polymerized (Howell and Kremer, 1973).
Ozone enters the cell and initiates biochemical and physiological re-
sponses. Critical effects, including reduction in photosynthesis and a shift
019SX/B 7-30 4/12/84
-------
in the assimilation of photosynthate, will lead to reduced biomass, growth,
and yield. Visible injury, which results from 0.,-induced cell injury and
death, reflects the occurrence of both primary and secondary metabolic events.
Visible injury serves as an indicator of the presence of CL and reflects
potentially harmful effects on plant vigor.
7.3.2 Factors that Modify Plant Response
There is a great deal of variation in the magnitude of plant response to
OT. Biological, physical, and chemical variables influence plant response.
For example, trees in a stand of ponderosa pine will not respond equally to
exposure to (L because of genetic diversity in the sensitivity of individual
trees and because of environmental heterogeneity in the habitat. Plants at
different ages or at different temperatures, humidities, light intensities, or
soil moisture regimes will respond differently to an equivalent 0~ exposure.
The presence of several pollutants, chemical sprays, and biological pests all
will contribute to determining the magnitude of plant response to 0,. In
developing an understanding of 0^ effects, it is important to consider the (K
sensitivity of the plant and the environmental conditions it is likely to
experience during exposure. It is equally important to recognize that plants
at certain stages of development or under a given set of environmental condi-
tions may be differentially sensitive to 0,. The factors that modify plant
response are grouped into three categories: biological, physical, and chemical
factors.
7.3.2.1 Biological Factors
7.3.2.1.1 Genetic Factors. The genetic complement of a plant determines its
potential response to 0.,. Genetically controlled variation in response to CL
has been observed among species, cultivars, and individuals within a population.
Inherited variation in plant response to 0^ can be measured by using many
plant response variables. Most researchers have investigated relative CL
sensitivity by measuring foliar injury. Genetically controlled differences in
response to 03, however, are also reflected in differential yield and physio-
logical effects, as well. A list of the plant species studied that exhibited
differential ozone sensitivity within a species is presented in Appendix B.
The relative 0., sensitivity of cultivars can vary with dose and the
nature of the response measured (Tingey et al. , 1972; Heagle, 1979b). There
is also some disparity between the relative sensitivity ranking of cultivars
019SX/B 7-31 5/4/84
-------
from controlled CL exposures in a laboratory and exposure of the same cultivars
to ambient air oxidants in the field (Engle and Gabelman, 1966; Taylor, 1974;
Huang et al., 1975; Meiners and Heggestad, 1979; Hue! and Beyersdorf, 1982;
DeVos et al., 1983). The inconsistent results may be explained in part by
the nature of the inheritance of the 0., susceptibility. In the case of onion
and bean, one or a few gene pairs were associated with 0., susceptibility
(Engle and Gabelman, 1966; Butler et al., 1979); while for corn (Cameron,
1975), tobacco (Povilaitis, 1967; Sung et al., 1971; Aycock, 1972; Huang et
al., 1975), potato (DeVos et al., 1982) and petunia (Hanson et al., 1976),
several genes determine plant responses to (k. The apparent genetic complexity
explains the potential variability in plant response as gene expression changes
during plant development and with variations in the environment.
In agricultural ecosystems, tolerant germplasm is selected deliberately,
or inadvertently, in order to reduce the effects of (k. In natural ecosystems
in areas receiving long-term 0, stress, it is predictable that susceptible
individuals within a population may decline and be replaced by those more
tolerant to the pollutant (see chapter 8). Many stresses, including S02,
elicit this kind of response in populations in natural ecosystems (Taylor and
Murdy, 1975; Roose et al. , 1982). Narrowing of the gene pool creates the
potential for increased vulnerability of a plant population to various assaults,
including those of biotic pests.
It appears that as wide a range of susceptibility to 0~ exists among
plant species as within them. Ozone is prevalent in most agricultural regions
in the United States. Sensitive plant species are found throughout the country
and the environmental conditions that favor injury occur in many geographic
locations.
7.3.2.1.2 Developmental Factors. Plant foliage appears to be most sensitive
to 0., just prior to or at maximum leaf expansion (U.S. Environmental Protection
Agency, 1978). At this stage, stomata are functional, intercellular spaces are
expanded, and barriers to gas exchange such as internal cutin and secondary
thickening of cell walls are minimal (U.S. Environmental Protection Agency, 1978).
Blum and Heck (1980) analyzed the response of bean plants to 03 concentrations of
0.30 and 0.60 ppm for 1.5 hours at various stages during growth. The plants were
most sensitive to 03 early in development and just before senescence. Virginia
pine and petunia seem to be most sensitive to O, early in development as
described in the 1978 criteria document (U.S. Environmental Protection Agency,
019SX/B 7-32 5/4/84
-------
1978). Tolerance of foliage to 0_ increased at or just before appearance of
flower buds in plants from six F, hybrid multiflora petunia lines, at eight
physiological ages, that were exposed to 0, (0.20 ppm for 8 hours) (Hanson et
al., 1975). The effect of 0- on root dry weight of radish was related to
timing of the exposure (Tingey et al., 1973a). Plants exposed to an 0., con-
centration of 0.40 ppm for 1.5 hours at 7, 14, or 21 days from seeding, sus-
tained 25, 37, amd 15 percent (p < 0.05) inhibition of hypocotyl root dry
weight, respectively. Radish plants may be particularly sensitive to 0^ at 14
days because maximum root enlargement begins at that time.
One of the first observations of the effects of photochemical oxidants on
plants in the field was the development of leaf chlorosis followed by premature
leaf aging (senescence) and early leaf drop (abscission) (e.g., Richards et
al., 1958; Menser and Street, 1962). Ozone (0.05 or 0.10 ppm 6 hours per day
for 133 days) induced premature leaf drop in soybeans (Heagle et al., 1974).
The premature senescence and leaf drop increased throughout the study period.
Ozone-induced premature leaf senescence has been observed in both greenhouse
and field-grown potatoes (Heggestad, 1973; Pell et al., 1980). Field studies
with white beans (Hofstra et al., 1978) confirmed that 0- induced premature
leaf drop; the premature leaf drop was associated, in part, with the 0.,-induced
yield reductions. The photosynthetic rate of hybrid poplars exposed to 0^
(0.085 or 0.125 ppm for 5.5 hours/day for 65 days) decreased more rapidly with
age than unexposed plants, indicating that 0, induced a premature senescence
(Reich, 1983). Another study with hybrid poplar showed that 0^ (0.04 ppm
12 hour/day for 5 months) significantly increased leaf drop (Mooi, 1980). The
effects of 0, on the senescence process, regardless of time of initiation, may
be responsible for many of the documented reductions in yield.
7.3.2.1.3 Pollutant-Plant-Pest Interactions. Plant pests (pathogens and in-
sects) are normal components of both agro- and natural ecosystems. Crop
losses from pests can be significant and have been estimated at 20 to 30
billion dollars per year in the United States alone (James, 1980). When
considering the effects of 0,, on crop plants or forests, it is important to
realize that the pollutant does not occur alone, but rather in conjunction
with other stresses that are modifying the productivity of the system. The
purpose of this section is to indicate what is known about interactions between
0-, plants, and pests, and how these interactions might modify the effects of
0, on the quality, quantity, or the intended use of the plant.
019SX/B 7-33 4/12/84
-------
Disease is the result of a complex interaction between host plant, environ-
ment, and pathogen. In the context of this general discussion of biotic
stress, problems caused by pathogens and insects will both be termed disease.
To understand the ways in which CL, as a part of the environment, may modify
pest dynamics, it will be helpful to consider a generalized disease cycle.
The cycle begins with the arrival of the inoculum or pest at the plant
(host). Following deposition of the pest on the plant surface, in the pre-
sence of favorable conditions (temperature, moisture), penetration of the
plant (or insect feeding, or oviposition) may begin.
Host penetration may occur quickly or, in some cases, the pathogen may
live as a resident on the plant surface for a period of time. Once penetration
occurs, and favorable conditions are present, infection may occur that results
in an intimate relationship between plant and pathogen. Growth and development
or colonization by the pathogen or plant pest proceeds until the pest reaches
a reproductive stage. Propagules of the pest are formed and dispersed either
passively or actively.
At each stage of this cycle, (L may modify the success of the pest,
either directly through effects on the invading organisms, or indirectly,
through modification of the host plant. Similarly, the complex interaction
between plant and pest may alter the sensitivity of the plant to GV
7.3.2.1.3.1 Pollutant-plant-pathogen interactions. Most pollutant-plant-
pathogen interaction studies have been conducted under controlled laboratory
conditions, but a few field studies have been performed. This topic has been
reviewed recently (Heagle, 1973, 1982; Laurence, 1981; Manning, 1975; Treshow,
1980a; U.S. Environmental Protection Agency, 1978). The results of published
studies are summarized in Table 7-2.
Infection of plants by pathogens may be inhibited or stimulated by 03-
Manning et al. (1969; 1970a,b) found that potato and geranium leaves injured
by 03 (0.07 to 0.25 ppm, 6 to 10 hours) had a larger number of lesions caused
by Botrytis. Wukasch and Hofstra (1977a) found that field-grown (^-injured
onion plants developed twice as many Botrytis squamosa lesions as did uninjured
plants growing in charcoal-filtered air. The same authors (1977b) found fewer
natural B. squamosa lesions on plants treated with an antioxidant chemical.
Ambient air 0., concentrations exceeded 0.15 ppm for 4 hours and 0.08 ppm on
several occasions during the growing season. Bisessar (1982) found similar
results with the interaction of 03, potato, and Alternaria solani. The fungus
019SX/B 7-34 5/4/84
-------
TABLE 7-2. PLANT AND BIOTIC PATHOGEN INTERACTIONS AS INFLUENCED BY VARIOUS DOSES OF OZONE UNDER LABORATORY AND FIELD CONDITIONS
(MODIFIED FROM LAURENCE, 1981)
Plant/pathogen
Exposure
Experimental
conditions
Effect on disease
Effect on
pollutant injury
*
Reference
AGRONOMIC CROP/FUNGI
Pinto bean/root fungi
Barley/Erysiphe graminis
Wheat/Puccinia graminis
(V, Wheat/Puccinia graminis
cr.
Corn/Helminthosporium maydis
Oats/Puccinia coronata
Potato/Botrytis cinerea
Cabbage/Fusari urn oxysporium
Onion/Botrytis cinerea,
B. squamosa
0.10 ppm 03, 8 hr daily, 10 wk
0.15 ppm 03, 6 hr daily for 4, 6,
or 8 exposures after inoculation
0.06 to 0.18 ppm 03, 6 hr daily,
17 days after inoculation
0.1 ppm 03, 6 hr daily, 12 days
after inoculation
0.06 to 0.18 ppm 03 6 hr variable
days before and after inoculation
0.10 ppm 03, 6 hr/day 10 days after
inoculation
0.20 ppm 03/3 hr, 1 to 5 days after
inoculation
0.15 tn 0.25 ppm 03, 6 to 8 hr
0.10 ppm 03, 8 h>" daily, 10 wk
0.15 ppm 03, 4 hr
Potato/Alternaria solani 0.03 to 0.04 ppm 03 monthly
L Increased number fungal colonies NR
L Increased colony size NR
L Decreased hyphal growth, numbers Decreased
of spores, infection
L Reduced sporulation NR
L Increased lesion size, increased NR
number of spores produced at
highest concentration
L No effect on disease development NR
L Increased disease development NR
L Decreased disease development NR
FC Increased disease development NR
F Increased disease development NR
Manning et al. (1971b)
Heagle and Strickland
(1972)
Heagle and Key (1973a)
Heagle (1975)
Heagle (1977)
Heagle (1970)
Manning et al. (1969)
Manning et al. (1971b)
Wukasch and Hofstra
(1977a,b)
Bisessar (1982)
-------
TABLE 7-2. (cont'd). PLANT AND BIOTIC PATHOGEN INTERACTIONS AS INFLUENCED BY VARIOUS OZONE DOSES
UNDER LABORATORY AND FIELD CONDITIONS (MODIFIED FROM LAURENCE, 1981)
Plant/pathogen
Exposure
Experimental
conditions
Effect on disease
Effect on
pollutant injury
Reference
TREES AND ORNAMENTALS/FUNGI
White pine/Lophodermium
pinastri
Ponderosa, Jeffrey Pine/
Heterobasidion annosum
~~i Eastern white pine/
|o Verticicladiella procera
r>
Lilac/Microsphaera aim'
Poinsettla/Botrytis cinerea
Geranium/Botrytis cinerea
Geranium/Botrytis cinerea
Citrus/Glomus faciculatus
Tomato/Glomus faciculatus
0.07 ppm 03, 4.5 hr
0.18 ppm 03/12 hr
seasonal
0.045 ppm 03 monthly average
0.128 ppm monthly peak hourly
0.25 ppm 03, 72 hr
0.15 to 0.45 ppm 03, 4 hr
0.15 ppm 03, 6 hr, 2x at 24-hr
intervals after inoculation
0.07 to 0.10 ppm 03 10 hr daily for L
15 to 30 days
0.45 ppm 3 hr/day, 2 days/wk L
for 19 wks
0.30 or 0.60 ppm, 3 hr/wk L
for 8 wks
Slight increased disease
occurrence
Increased disease development
Increased colonization of stumps
Increased disease incidence
NR Costonis and Sinclair
(1972)
NR James et al. (1980a)
NR James et al. (1980b)
NR
No influence on germination, early NR
fungal development
No effect NR
Reduced sporulation; reduced NR
infection by exposed spores
Flocculent material produced
Increased disease development NR
when visible 03 injury evident
Decreased infection NR
Retarded infection NR
Skelly (1980)
Hibben and Taylor (1975)
Manning et al. (1972)
Krause and Weidensaul
(1978a)
Manning et al. (1970b)
McCool et al. (1979)
McCool et al. (1982)
-------
TABLE 7-2. (cont'd). PLANT AND BIOTIC PATHOGEN INTERACTIONS AS INFLUENCED BY VARIOUS OZONE DOSES
UNDER LABORATORY AND FIELD CONDITIONS (MODIFIED FROM LAURENCE, 1981)
Plant/pathogen
Exposure
Experimental Effect on
conditions Effect on disease pollutant injury
Reference
AGRONOMIC CROPS/VIRUS
Tobacco/tobacco mosaic
Tobacco/tobacco etch
^j Tobacco/tobacco streak
i
OJ
Tobacco-pinto bean/tobacco
mosaic
Pinto bean/bean common mosaic
Pinto bean/alfalfa mosaic
tobacco ringspot,
tobacco mosaic,
tobacco ringspot
Tomato/tobacco mosaic,
cucumber mosaic
0.30 ppm 03, 6 hr L
Seasonal maximum hour, 0.236 ppm 03 F
0.25 ppm 03,
inoculation
0.30 ppm 03,
0.35 ppm 03,
4
3
4
hr, once 9 days after L
hr for 1 or 2 days L
hr; 0
.25 ppm 03, L
NR < 03
< 03
NR < 03
NR > 03
NR < 03
injury
injury
injury
injury
injury
Brennan and Leone (1969)
Bisessar and Temple
(1977)
Moyer and Smith
(1975)
Reinert and Gooding
(1978)
Brennan (1975)
3 hr, respectively
0.25 ppm 03,
inoculation
0.25 ppm 03
inoculation
0.0 to 0.45
3 hr; 7 to
inoculation
4
4
hr, 5
hr, 5
ppm or 0
21
days
days after L
days after
to 0.90 ppm L
after
NR < 03
NR < 03
NR > 03
7
< 03
at
injury
injury
injury at
or 14 days
injury
21 days
Davis and Smith
Davis and Smith
Ormrod and Kemp
(1975)
(1976)
(1979)
Soybean/tobacco ringspot
0.35 to 0.40 ppm 03, 4 hr, once 6,
8, or 10 days before inoculation
NR
< 03 injury
Vargo et al. (1978)
-------
TABLE 7-2. (cont'd). PLANT AND BIOTIC PATHOGEN INTERACTIONS AS INFLUENCED BY VARIOUS OZONE DOSES
UNDER LABORATORY AND FIELD CONDITIONS (MODIFIED FROM LAURENCE, 1981)
Plant/pathogen
Exposure
Experimental Effect on
conditions Effect on disease pollutant injury
Reference
AGRONOMIC CROP/BACTERIA
Al falfa/Xanthomonas alfalfae
White bean/Xanthomonas phaseoli
Soybean/Pseudomonas glycinea
7"1 Ladino clover/Rhizobium sp.
Co
Soybean/Rhizobium japonicum
Wild strawberry/Xanthomonas
fragariae
NEMATODES
Soybean/cyst,
stubby root
Begonia/foliar
0.20 ppm 03, 4 hr at 24 hr before
or after 03 exposure
0.08 ppm 03, 11 hr average,
seasonal
0.08, 0.25 ppm 03, 4 hr
0.30 to 0.60 ppm 03, 2 times
to 2 hr
0.75 ppm 03, 1 hr
0.20 ppm 03, 3 hr before or after
inoculation
0.08 ppm (as above)
L Reduced disease development < 03 injury
Howell and Graham (1977)
F No effect < 03 injury
L Reduced disease incidence
L Reduced nodule number
Temple and Bisessar
(1979)
No effect
0.25 ppm 03, 4 hr/4 days before
inoculation. 3 days/wk for 4 hr/day
after inoculation until harvest
0.25 ppm 03, 4 hr at 3 days before
or after inoculation
(1977)
L Reduced growth and nodulation No effect
Reduced disease incidence No effect
Inconsistent results
L Reduced reproduction of nematode
L Reduced reproduction of nematode
Laurence and Wood (1978a)
Letchworth and Blum
Tingey and Blum (1973)
Laurence and Wood (1978b)
Weber et al. (1979)
Weber et al. (1579)
L - Laboratory, greenhouse, growth, or fumigation chamber studies; F = field studies; FC = chambers used in field studies.
> = Increased; < = decreased.
CNR = Not reported.
-------
colonized 0^-injured sites on potato leaves, and fewer lesions were present on
plants protected from (k with ethylene diurea (EDU), a compound developed to
reduce 0, injury (see Section 5.3.2.3.2). Ambient air 0, concentrations
exceeded 0.08 ppm during 68 hours, and the highest measured concentration was
about 0.14 ppm. Similar results were obtained by James et al. (1980a) in a
field study of Heterobasidion annosum (syn. Fomes annosus) infection of oxidant-
injured ponderosa and Jeffrey pines in the San Bernardino Mountains. They
found increased infection of the roots of severely affected trees. The results
of the field study were confirmed under controlled laboratory conditions.
They also found that the colonization of roots and freshly cut stumps of
ponderosa and Jeffrey pine was positively correlated with the severity of the
oxidant injury observed on needles. In laboratory studies, colonization of
both species was directly related to 0, exposure over the range of 0 to 0.45
ppm for 58 to 92 days (additional discussion in Chapter 8). Skelly (1980)
reported increased incidence of root disease caused by Verticicladiella procera
in oxidant-injured eastern white pines in Virginia.
Ozone can inhibit infection of plants by pathogens. In general, infection
by obligate parasites is inhibited in plants that have been exposed to elevated
concentrations of 03 (Heagle 1970, 1973, 1975, 1982; Heagle and Strickland,
1972; Heagle and Key, 1973a,b).
McCool et al. (1979) reported that infection of citrus by Glomus
fasciculatus, an endomycorrhizal fungus, was decreased by exposure to Cs (0.45
ppm, 3 hours per day, 2 days per week for 19 weeks). Exposure of tomato to
0.30 ppm OT for 3 hours once per week for 8 weeks retarded infection by the
same fungus (McCool et al., 1982). These exposures did not affect root growth
of the plants or sporulation by the fungus, but did reduce the number of
successful infections. Ozone reduced mycorrhizal infections of tomato roots
46 and 63% when the plants were 0.15 (3 h/exposure, twice weekly for 9 weeks)
or 0.30 ppm (3 h, once weekly for 9 weeks), respectively. Rhizobium, a nitrogen-
fixing bacterium of legumes, induced fewer nodules in soybean plants exposed
to 0.75 ppm Oo for 1 hour (Tingey and Blum, 1973) and in ladino clover exposed
to 0.3 or 0.6 ppm 0., twice for 2 hours each (Letchworth and Blum, 1977).
Infection of soybean by Pseudomonas glycinea was decreased when plants
were exposed to 0.08 or 0.25 ppm 0., for 4 hours at times ranging from 8 days
to 1 hour before inoculation. When exposures occurred more than one day after
inoculation, however, inhibition was not observed (Laurence and Wood, 1978a).
019SX/B 7-39 5/4/84
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Similar results were found with Xanthomonas fragariae and wild strawberry
(Fragaria virginiana) (Laurence and Wood, 1978b). Temple and Bisessar (1979),
however, did not find fewer Xanthomonas phaseoli lesions on 0.,-injured white
beans in the field.
In most cases, colonization of plant tissue by pathogens is assessed by
measuring lesion size. Lesions of obligate parasites are usually smaller on
plants exposed to 03 when compared to controls (Laurence, 1981). Heagle and
Strickland (1972), however, found larger colonies of Erysiphe graminis f. sp.
hordei on barley plants that were exposed repeatedly to low levels of 0., (up
O
to 0.15 ppm, 6 hours per day for 8 days).
Little is known about colonization of ozone-affected plants by facultative
parasites. Heagle (1977) inoculated corn plants with Helminthosporium maydis
race T and exposed them to 0., (0.06, 0.12, or 0.18 ppm) for 6 hours per day
for up to 7 days before inoculation, 9 days after inoculation, or combinations
of before and after. He found that lesion length was significantly increased
by 0., exposure (0.18 ppm) before and after inoculation, but was not affected
at other concentrations or time regimes.
Based on these few reports on the relationship of 0, to plant colonization
by pathogens, it is impossible to generalize and predict effects in particular
disease situations. It is apparent that the outcome of a pollutant-plant-
pathogen interaction depends on the particular plant and pathogen involved.
It also is affected by the environmental conditions and 0,, concentrations
before and after inoculation.
Rist and Lorbeer (1981) recently reviewed the effects of 03 on sporula-
tion of fungi. In axenic culture, sporulation and growth of fungi were almost
always inhibited or unchanged by exposure to 0.,. In a few studies, significant
inhibition of growth, sporulation, or germination has been observed following
exposures to concentrations as low as 0.10 ppm for 4 hours, but fungi often
are resistant to 1.0 ppm 0- for several hours. Germination of spores produced
during 0., exposure (0.15 or 0.30 ppm, 6 hours per day for 2 days) may also be
lower than that of controls (Krause and Weidensaul , 1978a,b). These spores
may subsequently be less successful in colonizing the leaf surface (Krause and
Weidensaul, 1978a,b). Both decreases and increases in sporulation have resul-
ted from 0_ exposure of infected plants (Laurence, 1981), and the particular
result seems to depend on the plant-pathogen combination and the specific 0~
exposure regime.
019SX/B 7-40 5/4/84
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In the case of bacterial diseases, reproduction of the pathogen is gener-
ally reflected in the size of lesions on the plant. Bacteria are generally
resistant to ambient concentrations of 0.,, but may be much more sensitive to
changes in plant metabolism induced by CL (Hughes and Laurence, 1984).
Reproduction of the soybean cyst nematode and the stubby root nematode
was reduced by exposure of infested soybean plants to 0.25 ppm 03 applied on
three alternate days a week for about 2 months (Weber et al., 1979). Similar
0., treatments also reduced the reproduction of a foliar nematode on begonia
plants. This reduction was related to the amount of (^-induced leaf injury
(Weber et al., 1979).
Only a few studies have been reported that relate the effects of 0_ in
combination with another pollutant (SOp) to disease development. Weidensaul
and Darling (1979) found that Scotch pines inoculated with Scirrhia acicola
and exposed to 03 (0.20 ppm for 6 hours) or 03 combined with S02 (0.20 ppm for
6 hours) had fewer lesions than controls, but did not differ from each other.
More lesions formed when inoculation preceded fumigation by 5 days than when
inoculation followed exposure by 30 minutes.
7.3.2.1.3.2 Effects of ozone on plant-insect interactions. The effects
of air pollutants on insect populations were reviewed recently (Alstad et al.,
1982). Very little is known about 03-insect interactions. Ozone-induced
injury in ponderosa pine has been shown to predispose trees to subsequent
invasion by several species of pine bark beetles (Stark et al., 1968). Elden
et al. (1978) found that 03 injury induced by exposures of 0.20 ppm for 4
hours had little or no effect on the development of pea aphids on alfalfa.
They did note that two of three varieties having higher levels of 03 resistance
also had greater resistance to pea aphid.
7.3.2.1.3.3 Effects of pathogen infection on plant sensitivity to 03-
Fungal, bacterial, or viral infections have been reported to provide some
protection to plants from the visible effects of 03> Although of interest
mechanistically, most of the studies have been conducted under controlled
conditions, and it is questionable whether they are relevant in field situa-
tions.
Yarwood and Middleton (1954) noted that pinto bean leaves infected by
Uromyces phaseoli were less sensitive to photochemical oxidants than were
uninfected leaves. Similar results have been observed with many pathogen-plant
combinations. The protection afforded by fungal and bacterial pathogens is
019SX/B 7-41 4/12/84
-------
usually localized at the margins of lesions, while virus infections can pro-
vide more generalized effects (Heagle, 1982).
Although bacterial pathogens often provide protection against (L injury
O
near lesions, they did not in the case of bacterial blight of soybean or
angular leafspot of strawberry (Laurence and Wood, 1978a,b). Pratt and Krupa
(1979), however, reported that in chlorotic soybean leaves Pseudomonas glycinej
infection did inhibit expression of CL symptoms. Temple and Bisessar (1979)
found less visible CL injury on Xanthomonas phaseoli-infected white beans in
the field in Ontario, Canada. Using the same species of bacterium, Olson and
Saettler (1979) observed no protection from 0 injury in controlled laboratory
experiments. Pell et al. (1977) investigated the interaction between 0... and a
species of Pseudomonas that caused a hypersensitive reaction in soybean. They
found that inoculation with the pathogen provided some protection from 0~ when
plants were inoculated 1 day before exposures to a relatively high concentra-
tion of the pollutant (0.35 ppm for 2 hours). The effect was not observed
when inoculation took place 4 hours before exposure.
Many reports have appeared on the effects of virus infection on plant re-
sponse to 0-, beginning with those of Brennan and Leone (1969) and Brennan
(1975). Davis and Smith (1975, 1976) reported protection of pinto bean leaves
following inoculation with common mosaic, tobacco ringspot, tomato ringspot,
alfalfa mosaic, and tobacco mosaic viruses. The protection depended upon an
establishment time of 4 to 5 days between inoculation and exposure, which is
apparently linked to the time required to attain sufficient virus titer to
afford protection. The protection was localized except in the case of tobacco
ringspot, in which a more general effect was observed. Tobacco etch virus
infection also protected tobacco plants from 0, injury (Moyer and Smith,
1975). All experiments were under controlled conditions with exposures of
0.25 ppm 0,, for 4 hours.
Virus infection in one part of a plant has also been shown to provide
protection against 0,. injury in other parts. Davis and Smith (1976) found
that inoculation of one primary leaf of a pinto bean plant resulted in some
degree of protection in the uninoculated leaf exposed to 0., (0.20 ppm for
4 hours), but was not effective at 0., concentrations greater than 0.20 ppm.
Varyo et al. (1978) found that sensitivity to 03 (0.35 to 0.4 ppm for 4 hours)
of the primary leaf opposite the leaf inoculated with tobacco ringspot virus
was decreased with increasing time after inoculation. They also found that as
virus-induced apical necrosis increased, less 0., injury occurred.
019SX/B 7-42 4/12/84
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Two recent reports show that 0_ injury may be increased following virus
infection. Reinert and Gooding (1978) found that tobacco plants systemically
infected with tobacco streak virus and exposed to 0-. (0.3 ppm for 3 hours on 1
or 2 days) 3 weeks after inoculation displayed more injury than the combined
injury of plants exposed to CL or virus. Ormrod and Kemp (1979) found both
increases and decreases in 0, sensitivity of tomato plants infected with cu-
cumber mosaic virus or tobacco mosaic virus or both, depending on the tomato
cultivar, 0- concentration, the virus, and the virus incubation period. Ozone
injury was observed more frequently on tobacco mosaic virus-infected plants
than on those inoculated with cucumber mosaic virus. They also observed that
increases in 03 injury usually occurred when 03 exposures (0.15 to 0.90 ppm
for 3 hours) occurred within 14 days of inoculation; 21 days after inoculation,
most of the differences observed were decreases in injury.
In the only field study reported, Bisessar and Temple (1977) found 60
percent less oxidant injury on tobacco plants infected with tobacco mosaic
virus than on uninfected plants. The ozone concentration exceeded 0.10 ppm
for 16 percent of the daylight hours during the study period.
The effects described in the above sections are not of commercial impor-
tance but the observations may provide some information as to the mode of
action of 0., in plants.
Ozone affects the development of disease in plant populations. Most
laboratory evidence indicates that 03 (at ambient concentrations or higher for
4 hours or more) inhibits infections by pathogens and subsequent disease
development; however, increases in disease development have been noted in
certain cases. Most often these increases occur with "stress pathogens" that
incite diseases such as Botrytis blight of potatoes or onions or Heterobasidion
annosum root rot of ponderosa and Jeffrey pine. Increases in disease develop-
ment have been observed in these host-parasite relationships under both labora-
tory and field conditions (plants exposed to ambient air levels of 03).
That ozone can also modify plant-insect relationships is best illustrated
by studies conducted in the San Bernardino Mountains that showed increased in-
vasion of 0.,-stressed pine trees by bark beetles.
The mode of action of 0,-plant-pest interaction probably involves indirect
effects on the pathogen or insect that are the result of the direct interaction
of 0- and the plant. Effects on disease development have been documented at
O
concentrations of 0., and durations of exposure that are considered to be low
019SX/B 7-43 4/12/84
-------
(i.e., < 0.10 ppm for a few hours). Thus, it would appear that 0., is affecting
plant metabolism at these low concentrations and short exposure durations.
7.3.2.2 Physical Factors. The environment of the plant is composed of various
biological, chemical, and physical factors that change throughout the plant
growth period. The physical factors (e.g., light, temperature, relative
humidity, soil moisture, and soil fertility) interact to provide the conditions
for and also govern plant growth. Short-term variations in one or several of
these environmental factors, if they coincide with a pollution episode, may
render the plant more or less sensitive to pollutant exposure.
Environmental conditions before and during plant exposure are critical to
the plant response, while postexposure conditions are less important. Although
the influence of physical factors on plant response to 0, has been studied
O
primarily under laboratory and greenhouse conditions, field observations have
often substantiated these results. Most studies have evaluated the effects of
a single environmental factor and have usually used foliar injury as the
measure of plant response. Information sufficient to make some generali-
zations about the influence of these factors on plant response to 0, is avail-
able, but for most factors, substantial uncertainty exists because of the
small number of species studied and the lack of information on the interactions
of the environmental factors. In this section, the various environmental fac-
tors will be discussed individually for organizational convenience, even
though these factors interact to influence plant growth and sensitivity to 0^.
7.3.2.2.1 Light. It was concluded in the 1978 criteria document (U.S. Environ-
mental Protection Agency, 1978) that a short photoperiod and a relatively low
light intensity during growth maximize O.-induced foliar injury. These results
were consistent across contrasting light regimes. For example, bean and
tobacco plants were more sensitive to 0., at 0.4 ppm for 1 hour if grown at 420
uE s"1 m"2 than if grown at 840 uE s m (Dunning and Heck, 1973). Cotton
_•» _ p
grown at 276 uE s m was less sensitive to 0, concentrations of 0.9 ppm for
-1 -?
1 hour than similar plants grown with 27.6 uE s m (Ting and Dugger, 1968).
Subsequently, Dunning and Heck (1977) demonstrated the complex nature of
environmental interactions. They reported that tobacco showed increased
sensitivity to an 0., concentration of 0.40 ppm for 1 hour when grown under
-1-2
high light intensity (840 pE s m ) and subsequently exposed at an interme-
-1 ~2
diate light intensity (420 uE s m ). In contrast, pinto bean leaves were
most sensitive when plants were grown at a lower light intensity (209 uE s
m ) and subsequently exposed at the high intensities cited above.
019SX/B 7-44 4/12/84
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The responsiveness of photosynthetic processes and stomatal function to
CL has already been noted. The importance of light to these physiological
functions may in part explain the influence of light on the (K response in
plants.
In the field, vegetation will not often be exposed to 0., at the low light
intensities and the short photoperiods (8 hours) used in simulations described
above. Therefore, special consideration of light may not be as relevant as
other environmental factors. There are, however, some cultural practices for
which light intensity and photoperiod are controlled. Shade-grown tobacco and
bedding plants (in the commercial floriculture industry) represent two examples
of production settings in which low light intensity is used and where losses
attributable to oxidants have been documented.
7.3.2.2.2 Temperature. The 1978 criteria document (U.S. Environmental Protec-
tion Agency, 1978) reported that there was no consistent pattern relating tem-
perature to plant response to (L. Radish was more sensitive to 0, if grown
under cool conditions, whereas snap bean, soybean, Bel W-3 tobacco, Virginia
pine, and white ash were sensitive if grown under warm conditions (U.S Environ-
mental Protection Agency, 1978). Miller and Davis (1981a) found that pinto
bean plants exposed to Oo at a concentration of 0.10 ppm for 3 hours at 15° or
32°C sustained more severe foliar injury than when the exposure temperature
was 24°C. Dunning and Heck (1977) also found that bean plants were more
sensitive to 03 when exposed at 16° or 32°C rather than at 21° or 27°C.
Tobacco behaved differently from bean, exhibiting less sensitivity to 0.40 ppm
03 for 1 hour when the exposure temperature was 32°C as opposed to 16°, 21°,
or 27°C.
The effects of temperature on plant response to 0~ are probably both
physical and biological. Temperature affects solubility of gases, enzymatic
reactivity, membrane conformation, and stomatal movement; the disparate 0, re-
sponses of various plant species at different temperature regimes may also
reflect morphological or biochemical differences or both.
7.3.2.2.3 Relative Humidity. It was concluded in the 1978 criteria document
(U.S. Environmental Protection Agency, 1978) that in general, plants seem to
be more sensitive to 0^ when growth or exposure, or both, occur under conditions
of high relative humidity (RH). Table 7-3 is a modification of a summary
table in the 1978 criteria document (U.S. Environmental Protection Agency,
1978). Dunning and Heck (1977) reported that the sensitivity of tobacco to 0.,
019SX/B 7-45 5/4/84
-------
TABLE 7-3. RESPONSE OF PLANTS TO OZONE AS CONDITIONED BY HUMIDITY DURING GROWTH AND EXPOSURE1
Plant species
Pine, Virginia
Bean, cultivar
Pinto
Tobacco,
cultivar Bel W.
•9
^j Ash, white
i
-p>
CTl
Tobacco ,
cultivar Bel W3
Bean, cultivar
Pinto
Bean cultivar
Pinto and
Tobacco, cultivar
Bel W-, averaged
Ozone
Concentration
ppm
0.25
0.25
0.25
0.40
0.40
0.25
0.30
0.20
0.40
Exposure
Duration
hr
4
4
4
1
1
4
1.5
1.5
1
Notesb
3-yr seedlings
Juveni le
Juvenile
8_hr PP; 420 uE s"1
m 2 control condi-
tions; 8 hr PP
8_hr PP; 420 \tfl
m z control condi-
ditions, 8 hr PP
1-yr seedlings
31°C
31°C
8 hr PP
8 hr PP
Growth or
exposure
Exposure
Growth
Exposure
Growth
Exposure
Growth
Exposure
Growth
Exposure
Post-exposure
Exposure
Exposure
Growth
45% EH
90% EH
Exposure
75% GH
60% RH
4
50
1
60% RH
66
52
60% RH
42
33
60% RH
33
38
36
26% RH
9
0
45% RH
36
73
41
Response % injury
85% RH
25
58
35
80% RH
78
67
80% RH
36
36
80% RH
46
41
41
51% RH 95% RH
39 50
0 55
60% RH 75% RH 90% RH
39 41 31
67 81 80
53 70 81
Modified from 1978 criteria document (U.S. Environmental Protection Agency, 1978); all the studies were conducted in controlled
environment facilities
PP = photoperiod, GH = relative humidity during growth, EH = relative humidity during exposure
Time when humidity treatment was applied
Relative humidity levels during growth or exposure as indicated
-------
(0.40 ppm for 1 hr) was not affected by the relative humidity during growth
until the level reached 90 percent RH, at which point plants became more
tolerant to 0.,. Mclaughlin and Taylor (1980) have demonstrated that in pinto
bean plants exposed to CL concentrations of 0.079 ppm for 2 hours, uptake of
the pollutant increased fourfold when the exposure RH was increased from 35
percent to 73 percent. At the low RH (35 percent), 03 uptake decreased when
the pollutant concentration exceeded 0.079 ppm, while at the higher RH (73
percent), CL uptake increased with increasing 03 concentration.
The influence of RH on stomatal function may help to explain the influence
of RH and plant responses to 0.,. As RH decreases, a water deficit can develop
in the guard cells, and stomatal closure occurs to minimize internal foliar
water deficit (Ludlow, 1980). Stomatal closure would reduce 03 flux into the
leaf. The influence of RH on plant sensitivity may explain important varia-
tions in plant response under field conditions. It is generally accepted that
plants in the eastern United States respond to lower concentrations of 0^ than
their counterparts in California (U.S. Environmental Protection Agency, 1978).
The low RH in the western United States compared to the high RH often found in
the eastern United States during the growing season could, at least in part,
explain differential plant responses.
7.3.2.2.4 Soil Moisture. Plant response to oxidants is modified by soil
moisture, probably through an influence on stomatal function. As soil moisture
decreases, water stress increases and there is a reduction in plant sensitivity
to Or In the previous criteria document (U.S. Environmental Protection Agency,
1978), the major studies on effects of soil moisture prior to 1978 were reviewed
and examples are shown in Table 7-4. More recently, Harkov and Brennan (1980)
demonstrated that potted hybrid poplar plants were more tolerant of 03 concen-
trations of 0.10 ppm after 6 to 9 days without water. Olszyk and Tibbitts (1981)
found that pea plants exposed to 03 concentrations of 0.23 ppm for 2 hours ex-
hibited less foliar injury when the plant water potential was -388 kPa than when
it was -323 kPa (reflecting relatively low and high soil moisture levels, respec-
tively).
It appears that the stomata of plants grown under soil moisture stress
close more rapidly in the presence of 0~ than stomata of plants under optimal
water availability (Tingey et al. , 1982; Olszyk and Tibbitts, 1981; U.S.
Environmental Protection Agency, 1978). Such a plant response would reduce 03
ingress and confer some resistance to CL injury.
019SX/B 7-47 5/4/84
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TABLE 7-4. EFFECTS OF SOIL MOISTURE ON RESPONSE OF SELECTED PLANTS TO OXIDANT
Ozone exposure
Plant species Concentration, ppm
Tomato, cultivar
Fireball 1.00
1.00
0.50
1.00
Beet, garden 0.00
0.20
^i
i
co
Bean, cultivar
Pinto 0.00
0.15
0.25
0.00
0.15
0.25
Duration
1.5 hr
1.0 hr
1.0 hr
1.0 hr
3 hr (daily
days)
2 hr/day (63
2 hr/day (63
2 hr/day (63
2 hr/day (63
for 38
days)
days)
days)
days)
Type of Response
Reduction in chlorophyll
Reduction in chlorophyll
Reduction in chlorophyll
Reduction leaf dry wt
Reduction in dry wt of
storage root from
nonsal ine control
Reduction in shoot dry
wt from nonsal ine
control
Reduction in root
dry wt from nonsal ine
control
Response,
%reduction fromucontrol
Moisture conditions"
High
90% turgidc
54
67
36
48
-40 kPa
0
40
-40 kPa
0
27
93
0
25
91
to
80% turgid0
10
24 d
(40)d
-440 kPa
24
52
-200 kPa
18
42
91
25
28
89
low
-840 kPa
68
69
-400 kPa
78
87
88
65
78
79
aModified from Table 11-9 in 1978 criteria document for ozone and other photochemical oxidants (U.S. Environmental Protection Agency, 1978).
Special soil moisture conditions are underlined; kPa = kilopascals.
GPercent turgid is a measure of the amount of water in the plant leaf.
A stimulation rather than a reduction.
-------
Tingey et al. (1982) found that when bean plants were water stressed,
their leaf conductance as compared with nonstressed plants, decreased, 24 hours
after the stress was applied. A coincident reduction in plant response to 0.,
(1 ppm for 1 hour) occurred. If plants were water stressed for 7 days and
then the water stress was relieved, leaf conductance and plant response to CL
both increased.
Plants subject to long-term soil moisture stress may also exhibit morpho-
logical or functional changes, or both, that could modify the 0_ response.
Drought or salt stress, which can confer long-term moisture stress, are more
limiting to plant health than the air pollution stress that they may modify;
hence, any of their protective effects are offset (U.S. Environmental Protec-
tion Agency, 1978).
It is important to recognize that plants grown under optimal soil moisture,
as in irrigated field or greenhouses, generally are particularly vulnerable to
CL injury. On this basis, vegetation in natural ecosystems would be expected
to be more sensitive to 0, in years of normal rainfall than in years of drought.
7.3.2.2.5 Soil Fertility. Nutrient balance is fundamental to plant growth;
any imbalance could lead to variations in the 03 response. Plant nutrients,
including nitrogen, phosphorus, potassium, and sulfur may all influence plant
response to 0~ (U.S. Environmental Protection Agency, 1978). Results of
studies cited in the 1978 criteria document (U.S. Environmental Protection
Agency, 1978) were inconsistent for a variety of reasons, including species
differences and differences in experimental protocols and designs. Since
then, additional data have appeared, but the relationship between soil fertil-
ity and 0- sensitivity has not been clarified. Harkov and Brennan (1980) grew
hybrid poplar seedlings in varied amounts of slow-release fertilizer, 18:16:12
(N:P:K), that yielded plants with foliar qontents of 1.53, 2.69, 3.12, or 3.47
percent nitrogen. Visible injury was greatest in leaves containing 2.69
percent nitrogen when plants were exposed to an 0_ concentration of 0.10 ppm
for 6 hours. Using a different N:P:K ratio (6:25:15), Heagle (1979a) found
that potted soybean plants exposed to an 03 concentration of 0.60 ppm for 1.5
hours were more sensitive when fertilized with 100 ml of N:P:K (6:25:15)
solution at a rate of 0 or 7.5 g fertilizer/3.8 liters of water than when 15
or 22.5 g/3.8 liter of water was used. Optimum soybean growth was observed at
fertilizer rates of 15.0 and 22.5 g/3.8 liters of water. Noland and Kozlowski
(1979) reported that silver maple became more sensitive to 0., (0.30 ppm for 6
019SX/B 7-49 5/4/84
-------
hours for 2 successive days) when grown with 117 ppm potassium as compared to
0 to 2 ppm potassium for 6.5 weeks. The authors suggested that potassium may
stimulate the guard cells to open, thereby increasing the uptake of 0~ by this
species. Dunning et al. (1974) found that pinto bean and soybean foliage were
injured more severely by 03 when plants were grown with low potassium levels
(105 meq/liter) rather than normal levels (710 meq/liter). Greenhouse studies
of tobacco showed a negative correlation between the calcium content of the
leaf tissue and (^-induced (0.25 ppm for 4 hours) foliar injury (Trevathan and
Moore, 1976). This result was observed at eight combinations of 0^ concentra-
tion and exposure duration. Additional explanations for the variable response
of plants to (k when grown with different fertility regimes have not been
formulated.
7.3.2.3 Chemical Factors. The chemical environment of plants (e.g., air
pollutants, herbicides, fungicides, insecticides, nematocides, antioxidants,
and chemical protectants) influences plant responses to CL. These factors may
be grouped into the subject areas of pollutant interactions and chemical
sprays.
7.3.2.3.1 Pollutant Interactions. Components of ambient atmospheres such as
SCL, NO,,, and other pollutants may change, modify, or alter plant sensitivity
to On. These substances all contribute to intensifying or reducing the effects
of (L on the quality, quantity, or intended use of the plant and must be
considered along with the discussion of biological (Section 7.3.2.1) and
physical (Section 7.3.2.2) factors that modify plant responses to 0,,. The
magnitude of these modifications depends on the plant species, cultivar,
pollutant concentration, duration and frequency of exposure, and the environ-
mental and edaphic conditions in which plants are grown.
The study of the effects of pollutant combinations on plants has evolved
from the basic premise that pollutants co-occur, and that together, therefore,
they may induce more plant damage than that induced by the individual pollutants.
Researchers have tried to develop terminology that is meaningful in evaluating
the effects of pollutant mixtures on plants (Reinert et al. , 1975; Ormrod,
1982; Ormrod et al., 1984). Two categories of plant response are possible
when the effects of two pollutants (A and B) are evaluated. When one pollutant
has no effect on plant response but the second one does, it is termed "no
joint action." Thus, the term "joint action" implies that both pollutants
have some effect on plant response. The concept of joint action can be further
019SX/B 7-50 5/4/84
-------
divided into subcategories that can be used to describe the response of plants
to pollutants, A and B:
1. Additive response: Effect.g = Effect A + Effect B
2. Interactive response: Effect.,, 1 Effect. + Effect.,
Mb rt u
The interactive response may be of two possible types:
1. Synergism: Effect.- > Effect. + Effect-
2. Antagonism: EffectAg < EffectA + Effectg
It is important to quantify interactive effects. It is equally important to
identify and quantify additive effects. It is the intent of this section to
discuss the effects of the joint action of SO- + CL, NO- + 0-, and NO- + SO- +
0 • and to identify the concentrations of 0,, alone or in combination with
other pollutants, that cause yield loss.
7.3.2.3.1.1 Ozone and sulfur dioxide. The joint action of 0., and SO-
has been extensively studied. The previous criteria document (U.S. Environmen-
tal Protection Agency, 1978) stated that mixtures of (k plus SO- were of
special interest because of the Menser and Heggestad (1966) study. In that
study, a sensitive 'Bel W~' cigar wrapper tobacco exposed to mixtures of 0,
(0.03 ppm) and SO- (0.25 ppm) for 2 or 4 hours sustained 23 percent and 48
percent foliar injury, respectively; but no visible injury was produced by the
same concentrations of the individual pollutants. The additive and frequently
synergistic foliar-injury response of tobacco has been reported to occur in
numerous tobacco cultivars and types. Menser and Hodges (1970), Grosso et al.
(1971), and Hodges et al. (1971) determined the response of several Nicotiana
species and various N. tabacum cultivars to SO- and 0_ mixtures. They found
that 0, and SO- acted synergistically and produced 0,-type symptoms on all
cultivars of burly and Havana tobacco. When plants were fumigated for 4 hours
with 0.03 ppm 0., alone or with 0.45 ppm SO- alone, no injury was observed.
When the gases were combined and the plants were exposed for the same length
of time, foliar injury, ranging from 5 percent to 15 percent was produced.
Tingey et al. (1973c) exposed 11 species of plants to different combinations
of 0- and SO-: either 0.05 or 0.1 ppm 0, and 0.1, 0.25, or 0.5 ppm SO- for 4
019SX/B 7-51 4/12/84
-------
hours. They observed additive and synergistic foliar-injury responses as
summarized for six of the species in Table 7-5.
TABLE 7-5. SUMMARY OF EFFECTS OF SULFUR DIOXIDE
AND OZONE MIXTURES ON FOLIAR INJURY
Plant species
Alfalfa
Broccoli
Cabbage
Radish
Tomato
Tobacco, Bel W3
Response
0.50/0.05
_
+
0
0
0
+
at stated ppm
0.50/0.10
+
0
+
0
+
S02/03 concentrations3
0.10/0.10 0.25/0.10
+ +
+ 0
0 0
0
0 +
Source: Tingey et al. (1973c)
+ = greater than additive; 0 = additive; - = less than additive
Foliar injury symptoms decrease the aesthetic value of various types of
woody ornamental and floriculture crop species (7.4.3). When foliage is the
marketable plant part, substantial losses in quality and marketability of the
crop result from the injury produced by the joint action of pollutants. The
amount of foliar injury affects the amount of photosynthate produced by the
plant. Thus, in many instances, foliar injury provides some indication of the
potential for loss in weight, size, and number (yield) of the marketable plant
part. Foliar-injury response from the joint'action of pollutants needs con-
tinued study.
Since 1978, researchers have continued to use foliar injury as an indica-
tor of the sensitivity of plant species and cultivars within a species to the
joint action of 0_ and S0?. Studies have included apple (Shertz et al. ,
1980), grape (Shertz et al. 1980b), radish, cucumber, and soybean (Beckerson
and Hofstra, 1979b), begonia (Reinert and Nelson, 1980), and pea (Olszyk and
Tibbitts, 1981). These results are summarized in Table 7-6. Although rela-
tively high 0- and SO- concentrations were used for only a few hours, most
species displayed a synergistic injury response from the joint effects of the
pollutants, supporting previous observations.
019SX/B
7-52
4/12/84
-------
TABLE 7-6. FOLIAR INJURY RESPONSE OF VARIOUS PLANT SPECIES TO OZONE AND OZONE PLUS SULFUR DIOXIDE
Concentration , ppm Exposure
Species 03 S02 durati'on Response Foliar injury ,%
Apple 0.40
(Vance Deli-
cious)
(Imperial
Mclntosh)
(Golden
Del icious)
Grape 0.40
(Ives)
(Delaware)
--J Radish 0.15
i
en
CO
Cucumber
Soybean
Begonia 0.25
(Schwaben-
land Red)
(Wisper '0'
Pink)
(Fantasy)
(Renaissance)
(Turo)
Pea 0.13
03 S02 S02 + 03
0.40 03-4 hr/day. Foliar injury 24 8 26
1 time
S02-4 hr/day,
1 time
30 9 22
27 19 19
0.40 03-4 hr/day, Foliar injury 27 18 47
1 time
S02-4 hr/day
1 1 4
0.15 03-6 hr/day, Foliar injury 13 1 30
5 days
S02-4 hr/day,
5 days
27 9 54
18 0 0
0.50 03-4 hr/day Foliar injury 54 2 67
every 6 days,
4 times
S02-4 hr/day 25 1 58
every 6 days
20 13
15 0 18
80 12
0.40 03-4 hr, Foliar injury 00 32
1 time
S02-4 hr,
1 time
Monitoring Calibration
method method
03-Mast KI
meter
S02-Not Permeation
given tubes
03-Mast meter KI
S02-Not Permeation
given tubes
03 -UV Not given
Dasibi
S02-Conduc- Not given
tivity
03-Chemilumi- Monitor
nescence Labs
S02-Flame Calibrator
photometry
03-Chemi lumi- KI
nescence
S02-Thermo- Gas-phase
electron titration
(S02)
Fumigation
facility
Controlled
envi ronment
chambers
Control led
environment
chambers
Exposure
chambers
in environ-
mentally
control led
room
CSTR in
greenhouse
Plexiglas
chamber
Reference
Shertz et al. (1980a)
Shertz et al . (1980b)
Beckerson and
Hofstra (1979)
Reinert and Nelson
(1980)
Olszyk and Tibbitts
(1981)
Where column entry is blank, information is the same as above.
Concentrations of the combination were the same as the single gases.
-------
The chronic effects of the joint action of 0 and S0? on the growth of
radish, alfalfa, soybean, and tobacco (Table 7-7) were summarized in 1978
(U.S. Environmental Protection Agency, 1978). These four species represent a
diverse group of plant species in terms of growth habit. Primary focus in
earlier studies was on weight changes during the vegetative stage of growth,
with the exception of one study (Heagle et al., 1974); however, radish root
(hypocotyl), tobacco leaf weight, and alfalfa foliage (top) weight are the
marketable portions of the plant. With the exception of alfalfa, the growth
of each plant species was reduced in an additive manner by the joint action of
the two pollutants. Soybean root (fresh weight) responded synergistically to
the joint action of CL and SO- in one study (Tingey et al., 1973d).
The above data were obtained in greenhouse studies (except for Heagle et
al., 1974). These data provided preliminary evidence that the joint action of
CL and S02 at concentrations of 0.05 ppm and greater caused an additive reduc-
tion in plant yield. Additional studies of the joint action of 0, and SO,, on
plant yield have been conducted since 1978 (Tables 7-8 and 7-9). More emphasis
has been given to the influence of pollutant combinations on yield (weight,
size, and numbers) as a measure of plant response, including the yield of
flower, fruit, and seed portions of the plant (Table 7-8). Shew et al. (1982)
exposed tomato to 0.2 ppm 03 and S0» alone and in mixture, two times per week,
2 hours each time for 8 weeks. They demonstrated that the joint action of 0^
and S0? was synergistic, decreasing the weight of the largest fruit in each
tomato cluster, but that the synergistic effects did not influence total fruit
weight per plant.
Reinert and Nelson (1980) exposed five cultivars of begonia to 0.25 ppm
0- and S0? alone and in combination for a total of 16 hours (4 hours per week)
over a 4-week period. The joint action of 0., plus SO- was antagonistic (cv.
Schwabenland Red) and additive (cv. Fantasy), respectively, in producing a
loss in flower weight. The mean yield (flower weight) from the joint effects
of 0^ and S0« ranged from 1 percent (Schwabenland Red) to 15 percent (Fantasy)
greater than the loss resulting from 0^ alone.
The joint action of 0., and SO- on the growth and yield components of tall
O £.
fescue was studied by Flagler and Younger (1982a). Fescue was exposed to 03
concentrations of 0.0, 0.1, 0.2, and 0.3 ppm and 0.0 and 0.1 ppm S02 for 6
hours per day, once a week for 12 weeks. The joint action of SO,, in the
presence of increasing concentrations of 0- caused additive decreases in
019SX/B 7-54 4/12/84
-------
TABLE 7-7. GROWTH RESPONSE OF SELECTED PLANTS TO OZONE AND OZONE PLUS SULFUR DIOXIDE
Concentration3, ppm Exposure
Species 03 S02 duration
Radish 0.05
(Cherry Belle)
Alfalfa 0.05
i (Vernal)
U1
en
Soybean 0.05
(Dare)
Soybean 0.10
(Dare)
Tobacco 0.05
(Bel-W3)
0.05 8 hr/day.
5 days/wk,
5 wks
0.05 8 hr/day.
5 days/wk
12 wk
0.05 7 hr/day,
5 days/wk
3 wk
0.10 7 hr/day,
5 days/wk,
until harvest
0.05 7 hr/day.
5 days/wk,
4 wk
Yield, %
reduction from control
(negative unless Monitoring
Response otherwise noted) Method
Oa S02
Top dry wt 10 0
Root dry wt 50 17
Top dry wt 12 26
Root dry wt 22 29
Top fresh wt 2 +5
Root frest wt 3 0
Top fresh wt 65 +3
Seed wt 54 4
Leaf dry wt 1 14
S02 + 03
10
55
18
24
12
24
52
63
30
03-Mast
meter
S02-Conduc-
t i v i ty
03-Mast
meter
S02-Conduc-
t i v i ty
03-Mast
meter
S02-Conduc-
tivity
03-Mast
meter
S02-Flame
photometry
03-Mast
meter
S02-Conduc-
tivity
Cal ibration
Method
KI
Colori-
metric
KI
Colori-
metric
KI
Colori-
metric
KI
Not given
KI
Colori-
metric
Fumigation
Facility
Chambers
in greenhouse
Chambers
in greenhouse
Chambers
in greenhouse
Field
chambers
Chambers
in greenhouse
Reference
Tingey
(1971)
Tingey
(1975)
Tingey
(1973d)
Heagle
(1974)
Tingey
(1975)
et al.
and Reinert
et al.
et al.
and Reinert
Concentrations of the combination were the same as the single gases.
-------
TABLE 7-8. YIELD RESPONSES OF VARIOUS PLANT SPECIES TO OZONE AND OZONE PLUS SULFUR DIOXIDE
Concentration , ppm Exposure
Species 03 S02 duration Response
Tomato
(Walter)
Begonia
(Schwaben-
land Red)
(Wisper '0'
-j-J Pink)
<_n (Fantasy)
crt
(Renaissance)
(Turo)
Snap bean
(BBL 290)
(BBL 274)
(Astro)
Tall fescue
(Alta)
Alfalfa
(Mesa-Si rsa)
0.20
0.25
0.25
0.25
0.25
0.25
0.065b
0.10
0.20
0.30
0.10
0.20
0.30
0.05
0.20
0.50
0.50
0.50
0.50
0.50
0.30
0.10
0.10
0.10
0.10
0.10
0.10
0.05
03-4 hr/day, Largest fruit
2 day/wk, 8 wk each cluster
S02-4 hr/day , Total fruit
2 day/wk, 8 wk
03-4 hr/day, Flower wt
every 6 days
for 4 times,
S02-4 hr/day
every 6 days
4 for times
Flower wt
Flower wt
Flower wt
Flower wt
03-11 hr/day Green pod wt
avg, 3 mo
S02-6 hr/day.
5 day/wk, 5 wk
03 and S02 No. of tillers
6 hr/day,
once a week
for 12 weeks
Top dry wt
03-6 hr/day, Foliage dry wt
68 days
S02-24 hr/day,
68 days
Yield, %
reduction from control
(negative unless Monitoring
otherwise noted) method
0, SO,
1 2
5 4
39 22
22 +16
6 9
55 43
+10 +11
2 16
+1 6
6 6
+5 6
+3 5
19 5
18 5
49
SO? + 0-,
18
4
38
28
21
54
4
44
4
+12
19
18
19
53
46
03-Chemi lumi-
nescence
S02-Flame
photometry
03-Chemilumi-
nescence
S02- Flame
photometry
03-Not given
S02-Pulse
fluorescence
03-UV
S02-Pulse
fluorescence
03 Mast
meter
Calibration Fumigation
method facility
Known source Chambers in
Permeation greenhouse
tube (CSTR)D
Known source Chambers in
Permeation greenhouse
tube (CSTR)
Not given Field chamber
Permeation (open top)
tube
UV photometry Chambers in
greenhouse
Permeation (CSTR)
tube
KI Field chamber
(closed top)
Reference
Shew et al. (1982)
Reinert and Nelson
(1980)
Heggestad and
Bennett (1981)
Flagler and Younger
(1982a)
Neely et al . (1977)
Concentrations of the combination were the same
CSTR = Continuous stirred tank reactor exposure
as the single gases.
chamber.
-------
TABLE 7-9. THE INFLUENCE OF MIXTURES OF OZONE AND SULFUR DIOXIDE ON
SOYBEAN YIELD (grams OF SEED)
Seasonal 7 hr/day Seasonal 4 hr/day
03 concentration, ppm S02 concentration, ppm
0.00
0.55
0.068
0.085
0.106
0.00
412
381
318
273
246
0.026
438
318
313
238
250
0.085
426
329
294
233
198
0.367
286
237
192
189
154
aEach value is the mean of eight 1-m-row samples.
Heagle et al., 1983a.
fescue total dry weight, root dry weight and root-to-shoot ratio. For example,
03 decreased total dry weight 49 percent at 0.3 ppm 03; in the presence of S02
there was an additional 11 percent loss in total dry weight. Ozone and S02
acted synergistically to decrease the number of tillers in fescue but the
synergism depended on the 0^ concentration. These studies were done in a
charcoal-filtered-air greenhouse in CSTR exposure chambers.
Recently, studies of the combined action of 03 and SO- have been conducted
in open-top field chambers (Heagle et al., 1983a; Heggestad and Bennett, 1981)
and large CSTR field chambers (Foster et al. , 1983b; and Oshima, 1978). In
these experiments, 0., levels near ambient, as well as increasing 0^ concentra-
tions above ambient, were used in combination with two or more concentrations
of S0?. Heagle et al. (1983a) exposed soybean to various concentrations of 0-j
for 7 hr daily and 4 concentrations of S0? for 4 hours per day. Both gases
were added for 111 days (Table 7-9). The high concentration of SO^ decreased
the amount of visible injury from increasing concentrations of 0,.. The joint
action of 0., and S0? on soybean seed weight per meter of row at lower concen-
trations appeared to be additive, but as the concentrations of both pollutants
increased there was an antagonistic 0» + SO^ interaction. The nature of the
joint action was similar to that for visible injury: as S0? increased to
0.365 ppm, the loss of seed weight from increasing 0_ concentrations was less
than at lower concentrations of S0?. For example, at 0.365 ppm S0« and 0.085
ppm 0., there was a 34 percent seed-weight loss compared to that at 0.365 ppm
019SX/B 7-57 4/12/84
-------
S02 alone. At 0.026 ppm S02 and 0.085 ppm 03 there was a 45 percent seed-
weight loss, compared to that at 0.026 ppm S02 alone (Table 7-8). The two
highest mean SO,, concentrations were higher than usually occur in the United
States (U.S. Environmental Protection Agency, 1983).
Heggestad and Bennett (1981) exposed three cultivars of bean to increasing
concentrations of S02 (0.06, 0.12, 0.3 ppm) for 6 hours per day in charcoal-
filtered and unfiltered ambient air, using open-top field chambers. The beans
were exposed daily 5 days per week, for 31 days. Sulfur dioxide (0.30 ppm)
reduced snap bean yields (all cultivars) in nonfiltered air (0_) by 44 percent
compared to a 16 percent reduction in charcoal-filtered air. At 0.06 ppm S0?,
the yield of cv. 'Astro' was reduced more in nonfiltered than in filtered air.
The S02 concentrations used in this study, however, were higher than typically
occur in the United States (U.S. Environmental Protection Agency, 1983).
In southern California, Oshima (1978) and Foster et al. (1983a,b) conduc-
ted studies to determine the joint action of S0? and photochemical oxidants.
A range of photochemical oxidant concentrations was obtained by combining
various proportions of charcoal-filtered ambient air containing oxidants
yielding various concentrations of oxidants in ambient air and charcoal-
filtered air which was added to the CSTR-type field exposure chambers. Sulfur
dioxide (0.0 or 0.1 ppm) was added to the chambers for 6-hour intervals approxi-
mately 47 times over a 76-day period for beans (Oshima, 1978) and 4 to 5 days
per week over a 10-week period for potato (Foster et al., 1983b). The kidney
bean yield was less in the presence of ambient oxidant plus SOp except at the
high oxidant concentrations, when the yields were more nearly similar. Similar
studies with potato exposed to S0? and partially filtered ambient air containing
03 resulted in no evidence of joint action on tuber yield (Foster et al. ,
1983b).
In summary, recent studies on the effects of 0., and S0? on the yield of
various plant species have found the effects of 0, and S09 to be additive for
«3 L.
begonia flower weight, fescue plant and root dry weight, soybean seed weight,
and snap bean and green bean yield. Synergistic interaction was identified
for the effects of 0., and SOp on the largest tomato fruit in each cluster, the
number of fescue tillers, and kidney bean yield. Examples of antagonistic
joint action occurred in one cultivar of begonia and in soybean seed weight at
the highest S02 concentration. These effects varied with the concentration of
pollutants, the plant response measured, species, and cultivar. Thus, observa-
tions were significant enough to propose the following general concepts:
019SX/B 7-58 4/12/84
-------
1. When concentrations of 03 and SCL are below or at the threshold for
visible injury, synergistic interaction may be a freqiJent occur-
rence.
2. As concentrations of 0., and SOp increase in mixture above the injury
threshold, yield loss from joint action may be additive.
3. When both pollutants are present in high concentrations, the joint
action of CL an
loss is miminal.
action of 0, and S0« may be antagonistic, such that further weight
O £-
4. An analysis of ambient air monitoring data at various locations
determined the frequency of the co-occurrence of pollutants pairs
(0-/S09, 07/NCU) during a 5-month summer season (May through
o u. *3 £.
September) (Lefohn and Tingey, 1984). Co-occurrence was defined as
the simultaneous occurrence of hourly averaged concentrations of
0.05 ppm for both pollutants of the pair, Applying this criterion,
most sites experienced 10 or fewer periods of co-occurrence during
the 5-month period.
7.3.2.3.1.2 Ozone and Nitrogen Dioxide. Although the effects of NOp and 03,
alone and in mixture, have not generally been studied, recent reports comparing
two- and three-pollutant mixture treatments include NO,, plus 0., combinations.
Kress and Skelly (1982) have studied the responses of seven tree species to
NO, (0.1 ppm) and 0, (0.1 ppm) alone and in mixture for 6 hours per day, for
L- «J
28 consecutive days (Table 7-10). Virginia and loblolly pine growth, as
measured by plant height, was significantly suppressed by the 0., + N0« treat-
ment, but not by the individual pollutants. Nitrogen dioxide alone signifi-
cantly suppressed root and total dry weight of sweetgum; however, the joint
action of 0- + N0? was antagonistic on sweetgum root and total dry weight and
white ash root dry weight.
7.3.2.3.1.3 Ozone plus nitrogen dioxide and sulfur dioxide. The previous
criteria document (U.S. Environmental Protection Agency, 1978) makes no refer-
ence to the effects of mixtures using three pollutants. Since then, however,
experiments have been designed to study the effect of increasing concentrations
of N0?, SO,.,, and 0- in mixture (Table 7-11). Reinert and Gray (1981) exposed
radish plants one time for 3 or 6 hours to 0.2 or 0.4 ppm of N0?, S0?, or 0->,
or combinations. They found no interaction for either two- or three-gas
019SX/B 7-59 4/12/84
-------
TABLE 7-10. YIELD RESPONSES OF SELECTED TREE SPECIES
TO OZONE PLUS NITROGEN DIOXIDE8
Species
Loblolly Pine
Loblolly Pine
(6-13 x 2-8)C
Pitch Pine
Virginia Pine
Sweetgum
White Ash
Green Ash
Willow Oak
Concentration
ppm Exposure
03 S02 Duration
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
0.10 0.10 6 hr/day,
28 days
Height and top dry wt
% reduction from control
(negative unless
Response otherwise noted)
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
Height Growth
Top Dry Wt
°s
17
19
25
9
14
+14
11
2
27
30
20
37
19
17
5
+1
N02
15
18
11
10
16
20
13
1
32
25
+5
1
+1
10
10
24
Oa' + N03
39
16
24
4
26
11
23
1
28
19
16
37
22
29
14
13
Source: Kress and Skelly, 1982
aPlants were exposed in continuously stirred tank reactor (CSTR) exposure chambers in a
greenhouse. Ozone and N02 were monitored using chemiluminescent analyzers which were
calibrated with known sources of each pollutant.
Concentrations of the combination were the same as the single gases.
""Indicates seeds were from a full-sibling collection.
019SX/B
7-60
5/4/84
-------
TABLE 7-11. YIELD OF VARIOUS PLANT SPECIES TO OZONE, SULFUR DIOXIDE, AND NITROGEN DIOXIDE
Species
Snap Bean
Marigold
Marigold
Radish
Radish
Azalea
Concentration3
ppm Exposure
03 S02 N02 duration
•
0.15 0.15 0.15 4 hr,
3 times/wk
4 wks
0.30 0.30 0.30 3 hr/day,
3 days/wk,
3 wks
0.30 0.30 0.30 3 hr/day.
3 days/wk,
1 wk
0.30 0.30 0.30 3 hr/day.
3 days/wk,
1 wk
0.40 0.40 0.40 3 hr + 6 hr
1 time
0.25 0.25 0.25 3 hr/day,
6 times in a
4-wk period
Yield, % reduction Monitoring
Response from control (negative unless otherwise noted) method
0, S02 N02 S02+N0, 03+S02 0,+N02 03+S02+N02
Green bean 27 9 +12 20 6 25 27 03, N02-
fresh wt chemi lumi-
nescence;
S02- flame
photometry
Flower wt 20 47 +16 13 23 +4 20 03, N02-
chemi lumi-
nescence;
S02- flame
photometry
Flower wt 41 49 23 47 25 39 20 03, N02-
chemi lumi-
nescence
S02 Flame
photometry
Hypocotyl 30 +21 +10 +16 43 33 65 03, N02-
chemi lumi-
nescence
S02-f lame
photometry
Hypocotyl 20 4 0 13 24 23 36 03 , N02-
chemi lumi-
nescence
S02- flame
photometry
Foliage 6 7 0 17 22 16 27 03, N02-
chemi lumi-
nescence;
S02- flame
photometry
Cal ibration
method
Known
source
Known
source
Known
source
Known
source
Known
source
Known
source
Fumigation .
faci 1 i ty
Chambers
in green-
house
(CSTR)
Chambers
in green-
house
(CSTR)
Chambers
in green-
house
(CSTR)
Chambers
in green-
house
(CSTR)
Chambers
in green-
house
(CSTR)
Chambers
in green-
house
(CSTR)
Reference
Reinert and
Heck
(1982)C
Reinert and
Sanders
(1982)
Sanders and
Reinert
(1982b)
Sanders and
Reinert
(19826)
Reinert and
Gray
(1981)
Sanders and
Reinert
(1982a)
-------
TABLE 7-11 (cont'd). YIELD OF VARIOUS PLANT SPECIES TO OZONE, SULFUR DIOXIDE, AND NITROGEN DIOXIDE
^1
1
CTl
ro
Concentration3
(ppm)
Species 03 S02 N02
Kentucky 0.15 0.15 0.15
bluegrass
(12 culti-
vars)
Red top 0.15 0.15 0.15
grass
Creeping 0.15 0.15 0.15
bentgrass
Colonial 0.15 0.15 0.15
bentgrass
Red Fescue 0.15 0.15 0.15
(2 culti-
vars)
Perennial 0.15 0.15 0.15
Ryegrass
Exposure ' Yield, % reduction
duration Response from control (negative unless otherwi
0, S02 N02 S02+N02 0.,+S02 01+N02
03-hr/day, 10 Leaf area 5 12 6 NTd NT NT
days S02-cont.
10 days N02-,
continuous,
10 days
SAA Leaf area 14 12 12 NT NT NT
SAAe Leaf area 7 18 8 NT NT NT
SAA Leaf area 15 6 13 NT NT NT
SAA Leaf area 16 0 0 NT NT NT
SAA Leaf area 20 +7 2 NT NT NT
Monitoring Calibration Fumigation
se noted) method method facility Reference
0,+S02+N02
16 03, UV Oasibi Not given Plexiglas EHiey
S02, phase exposure and
fluorescence chamber Ormrod
N02> chemi- (1980)
luminescence
28
26
27
22
13
Concentrations of the combinations were the same as two single gases, except for bean exposed at 0.05 (0 ), 0.1 or 0.15 (SO ) and 0.05 or 0.1 (N02).
CSTR = Continuous stirred tank reactor exposure chamber.
Derived from experimental data.
NT = Exposure combination not tested.
p
SAA = Exposure condition same as above.
-------
mixtures, even though the decrease in hypocotyl weight by 0_ was further
reduced by N0? alone, SOp alone, or N0» plus SOp, which suggests an additive
response. Reinert and Sanders (1982) and Sanders and Reinert (1982b) reported
similar results in radish following repeated exposures at different ages.
Marigold was exposed at different ages for 3 hours to 0.3 ppm of each
pollutant, three times per week for 1 week (Sanders and Reinert, 1982b).
Ozone alone decreased flower dry weight but the interaction of N0? or 0., with
S0? was apparently antagonistic. Similar results were reported for marigold
exposed repeatedly 3 days a week for 3 weeks. Reinert and Heck (1982) exposed
snap beans 27 times intermittently for 3 hours each time over 6.5 weeks to
increasing concentrations of SO^ (0.0, 0.1, 0.15 ppm) and N02 (0.0, 0.05, 0.1
ppm) in the presence of 0.05 ppm 03< Ozone alone decreased bean pod weight 10
percent, while N0? at 0.1 ppm, SO^ at 0.15 ppm, and at 03 0.05 ppm decreased
pod weight by 31 percent. Reinert and Heck (1982) exposed 16-day-old radish
plants one time for 3 hours to three concentrations (0.0, 0.2, and 0.4 ppm) or
(0.1, 0.2, and 0.4 ppm) of N02, S02, and 03 at all 27 (3 x 3 x 3) treatment
combinations (Table 7-12). In both experiments, the reduction in size of
radish hypocotyls was predominantly additive and linear within the range of
concentrations used. The above studies were conducted primarily under green-
house conditions but some of the species studied, such as marigold, tomato,
and azalea, are grown commercially in greenhouses. The concentrations of S0?
and N0? (^ 0.4 ppm) are below the concentration of each pollutant individually
(S0?, 0.5 ppm, and N0?, 1 to 2 ppm) that causes visible injury for a single
exposure (Tingey et al. , 1971b).
Several turf grass species and cultivars were exposed to 03, SO™, and NO^
individually, and the combination of the three pollutants combined to determine
the effects on leaf area (Elkiey and Ormrod, 1980). The three-pollutant
combination reduced the leaf area of only 4 of the 12 Kentucky bluegrass
cultivars. The three-pollutant combination had no significant effect on red
top, creeping bentgrass, and colonial bentgrass, but it did significantly
reduce the leaf area of perennial ryegrass and one of the two red fescue
cultivars.
The initial studies on the effects of mixtures of N0?) S0?, and 0~ have
involved the co-occurrence of these pollutants. The sequential effects of
pollutant mixtures need to be investigated. In addition, more monitoring data
are needed for each of the three pollutants so that realistic occurrences and
concentrations can be part of the experimental design for assessing plant
response.
019SX/B 7-63 4/12/84
-------
TABLE 7-12. THE EFFECTS OF NITROGEN DIOXIDE IN COMBINATION WITH SULFUR DIOXIDE
OR OZONE, OR BOTH, ON RADISH ROOT; FRESH WEIGHT (GRAMS) AT
THREE CONCENTRATIONS OF EACH GAS3
S02, ppm
03 ppm
Radish root fresh wt, g
Experiment 1
0.1
0.2
0.4
0.1
0.2
0.4
0.1
0.2
0.4
0.1
0.2
0.4
0.1
9.5
7.3
4.6
9.5
6.3
2.9
8.3
5.6
2.3
N02, ppm
0.2
8.8
7.7
3.0
9.5
5.3
3.3
6.6
5.0
3.0
0.4
8.4
4.6
2.9
6.2
5.1
2.7
4.9
3.9
3.0
Experiment 2
0 0
0.2
0.4
0.2 0
0.2
0.4
0.4 0
0.2
0.4
0.0
15.2
12.4
6.6
16.7
11.2
6.8
17.2
9.5
5.1
N0? , ppm
0.2
16.9
11.0
5.3
17.2
7.3
5.3
13.2
7.2
5.6
0.4
14.4
9.6
8.0
11.9
7.6
4.8
11.4
5.8
4.3
Source: Reinert and Heck (1982).
aMeans represent 20 (exp. 1) or 12 (exp. 2) plants. Plants were exposed once for
3 hr at 16 days from seed and were harvested at 23 days from seed.
019SX/B
7-64
4/12/84
-------
7.3.2.3.1.4 Ozone and other pollutants. Zinc and cadmium reacted syner-
gistically with 0,. in producing visible injury and chlorophyll loss in garden
cress and lettuce (Czuba and Ormrod, 1974). The combination of cadmium (Cd)
and 0^ induced earlier development of necrosis and chlorosis and the injury
was observed at lower CL plus cadmium levels than for the individual treatments
(Czuba and Ormrod, 1981). Cadmium and nickel (Ni) concentrations of 1, 10,
100 umol in the nutrient solution interacted to reduce root and shoot growth
of peas (Ormrod, 1977). Ozone exposure increased the Cd and Ni effects but
the increase was less than additive. Low concentrations of cadmium and nickel,
however, tended to enhance 0. phytotoxicity. The interaction of cadmium and
OT was influenced by both concentration and the environmental conditions.
Tomato plants grown at 0.25 and 0.75 mg Cd/ml developed only slight foliar
injury when exposed to 0., (0.20 ppm for 3 hours) under cloudy skies; whereas
the Cd treatment alone had no significant effect (Harkov et al., 1979). In
full sun there was extensive 0~ injury and the joint response was synergistic.
The changes in the cellular ultrastructure of pea leaves resulting from exposure
to ozone (0.50 ppm) increased when plants were grown in nutrient solutions
containing 100 jjmol nickel sulfate (Mitchell et al. , 1979).
The limited published data indicate that heavy metals can increase the
phytotoxic reactions of ozone. At the present time, it is not possible to
assess the risk from the joint action of gaseous and heavy metal pollutants to
vegetation. In industrial areas, along heavily travelled highways, and on
crop lands fertilized with sludge, however, there is the possibility for in-
teractive effects.
The results from pollutant interaction studies demonstrated that the
joint action of 0~ with SOp or NO^ or both decreased the yield of several
crop species more than 0., alone. Sulfur dioxide usually modified the response
to 0., in an additive way. Yield losses resulting from 0- exposure were fur-
ther decreased by SOp in radish (5 percent), alfalfa (6 percent), soybean seed
weight (9 percent) and tobacco (7 percent). These effects were at concentra-
tions of 0_ and SO,., £ 0.05 ppm and greater. At higher concentrations of 0,
«J £— ,j
and SO^ (0.2 to 0.5 ppm), yield losses from 0~ exposure were further reduced
by S02 in begonia flower weight 6 to 15 percent depending on the cultivar; in
kidney bean 11 to 28 percent, depending on the 0., concentration; in potato, 11
to 16 percent; in soybean seed weight, 11 to 12 percent; and fescue, < 24
percent. Additional information concerning pollutant dose and frequency of
exposure at which these effects take place is needed.
019SX/B 7-65 4/12/84
-------
7.3.2.3.2 Chemical Sprays. A variety of agricultural chemicals commonly used
by growers to control diseases and insects and other pests on crops, and re-
search plantings can modify vegetational response to air pollutants (Reinert
and Spurr, 1972; Sung and Moore, 1979). Certain fungicides, insecticides,
nematicides, and herbicides have been found to change the sensitivity of
plants to ozone.
Protection from or reduction of 0- injury to vegetation is significant to
growers of economically important crops in areas of high ozone concentrations.
In addition, the control of CL injury to plants in the field can be of assis-
stance to scientists attempting to determine how 0_ injures plants. The
•J
report by Kendrick et al. (1954) that fungicides used as sprays or dusts
protected pinto bean foliage from 0~-induced plant damage alerted the scienti-
fic community to the fact that agricultural chemicals could protect vegetation
from OT injury. Since that time, it has been shown that other chemicals, in-
cluding ascorbic acid sprays (Freebairn, 1963; Freebairn and Taylor, 1960),
antiozonants (Rich and Taylor, 1960), anti-transpirants (Gale and Hagan, 1966),
stomatal regulators (Rich, 1964), growth regulators (Cathey and Heggestad, 1973),
and some herbicides can offer some protection against ozone injury.
A comprehensive review of plant protectant sprays and their uses is found
in Ozone and Other Photochemical Oxidants (National Research Council, 1977).
The degree of plant protection obtained from 0, injury and the species tested
are listed in Table 7-13.
Nematicides increase the sensitivity of vegetation to 0.,, but nematicides
in combination with certain fungicides decrease sensitivity to 03_ Miller et
al. (1976) noted that pinto bean and tobacco growing in sand or soil treated
with the contract nematicides, phenamiphos, fensulfothion, aldicarb, and oxa-
fothion were more sensitive to 0.,. Adding benomyl or carboxin, both fungicides,
to the soil containing the contact nematicides caused the plants to become
highly resistant to 03 injury. Benomyl or carboxin used alone also induced
plant resistance to 03 injury.
The influence of selected herbicides on the 0^ sensitivity of tobacco and
other crop plants has been studied with differing results. Carney et al.
(1973) demonstrated that pebulate increased 03 injury to tobacco but that
benefin decreased 0, injury. The studies of Sung and Moore (1979), however,
•J
failed to confirm the observation that pebulate increases 03 sensitivity.
Sung and Moore suggested that the difference in results occurred either because
019SX/B 7-66 5/4/84
-------
TABLE 7-13. PROTECTION OF PLANTS FROM OXIOANT INJURY BY APPLICATION OF PROTECTIVE CHEMICALS
Plant species
Bean, cultivar Pinto
Petunia
Tobacco
Tobacco, cultivar White Gold
Tobacco, cultivar White Gold
Tobacco, cultivar White Gold
Bean, cultivar Pinto
Bean, cultivar Pinto
Azalea
Bean, cultivar Pinto
Radish
Poinsettia
Poinsettia
Bean, cultivar Pinto
Bean, cultivar Pinto
Bean and cucumber
Grape
Bean, cultivars Tempo and Pinto
Bean, cultivars Tempo and Pinto
Tobacco
Tobacco
Bean, cultivar Tempo
Grass, annual blue
Bean, cultivar Pinto
Bean, cultivar Pinto
Bean, cultivar White
Petunia
Tobacco
Tobacco
Tobacco
Pol lutant
protected from
Oxidant
Oxidant
Oxidant
Oxidant
Oxidant
Oxidant
Oxidant
Ozone
Oxidant
Ozone
Ozone
Ozone
Ozone (chronic)
Ozone
Ozone
Ozone
Ozone
Ozone
Oxidant
Ozone (0.50 ppm, 2 hr)
Ozone (0.35 ppm, 2 hr)
Oxidant
Ozone (0.25 ppm, 2 hr)
Ozone (0.30 ppm, 4 hr)
Ozone (0.25 ppm, 4 hr)
Ozone (0.13 to 0.50
ppm, 0.5 hr)
Oxidant
Oxidant
Oxidant
Ozone
Chemical (Concentration)3
K-Ascorbate (0.01 M)
K-Ascorbate (0.01 M)
Zn-ethylenebisdithiocarbamate
dust (variable)
Phygon XL (variable)
Phygon XL (variable)
4,4-Dioctyldiphenylamine in butyl
latex
Zineb (normal use)
Zineb (normal use)
Benomyl (60-ppm drench)
Carboxin (2.3 ppm in soil)
N-6-Benzyladenine (30-ppm spray)
Ancymidol (100-ppm spray)
Benomyl (500-ppm drench)
Folicote (0.5% spray)
Benomyl (5 ppm in nutrient
solution)
Benomyl (80 ppm in soil)
Benomyl (6.7 kg/ha, 6 times)
Benomyl (0.25 to 0.36%, 4 weekly
sprays)
Carboxin (10% granular as soil
amendment, 8 g/5-m row)
Piperonylbutoxide (2 mM solution)
Safroxane
Benomyl (0.24% spray)
Benomyl (60-ppm amendment)
Triarimol
Benomyl (1.60-ug/g soil amend-
ment)
Ascorbic acid
SAOH (0.5% spray)
Benomyl (25-ppm drench)
Benomyl (0.18% spray)
Peroxidase (0.10 ppm injected)
Type of protectant
Antioxidant
Antioxidant
Fungicide
Antioxidant
Antioxidant
Antioxidant
Fungicide
Fungicide
Fungicide
Fungicide
Growth substance
Growth retardant
Fungicide
Wax emulsion
Fungicide
Fungicide
Fungicide
Fungicide
Fungicide
Insecticide
Insecticide
Fungicide
Fungicide
Fungicide
Fungicide
Antioxidant
Growth retardant
Fungicide
Fungicide
Enzyme
Degree of .
protection, %
52
39
44
89
78
100
91
97
96
95
100
100
57
92
97
94
53
75
100
99
76 c
32 to 41C
85
81
98
75
82
68
59
89
Source: Modified from National Research Council, 1977.
These are applied as sprays unless otherwise noted.
Percent reduction in plant injury from ozone as a result of the protectant treatment.
Increase in yield by protectant application.
-------
the plants used were of different ages or because the CL concentrations used
in the respective experiments differed. Reilly and Moore (1982), however,
stated that pebulate had no consistent effect upon tobacco sensitivity to O-,.
Benomyl, specifically, and fungicides in general were discussed extensively
as plant protectants in the National Research Council report (1977) because
they have been the most widely studied protectants. Benomyl (methyl-1-butyl-
carbamoyl-2-bensimidazolecarbamate) has been used as a foliar spray, soil
drench, and a soil amendment (National Research Council, 1977) and was found
to reduce 0., injury in a wide range of plant species (Table 7-13). Benomyl,
while usually offering protection against CL injury, does not prevent PAN
injury (Pell, 1976; Pell and Gardner, 1975; Pell and Gardner, 1979).
Antioxidants, chemical compounds that prevent food spoilage and discolo-
ration and prevent rubber from reacting with 0-, have also been found to reduce
0~ injury in vegetation (Kendrick et al., 1962). In agricultural practice,
antioxidants are used as synergists with insecticides, herbicides, and fungi-
cides to increase in their effectiveness. For example, antioxidants increase
the potency of a certain insecticide by decreasing the rate at which insects
are able to detoxify it.
Piperonyl butoxide (a-[2-(2~butoxyethoxy)ethoxy]-4,5-methy1enedioxy-2-
propyltoluene), a synergist used with pyrethrum insecticides, is highly effec-
tive in protecting tobacco leaves from (L injury (Koiwai et al., 1974; Koiwai
and Kisaki, 1976; Koiwai et al., 1977). Koiwai et al. (1977) determined that
most compounds having a synergistic activity with pyrethrum insecticides are,
in general, effective in preventing ozone injury to tobacco leaves. Rubin et
al. (1980) tested the protective capability of piperonyl butoxide when applied
to navy bean cultivars '0686' and '0670' and found that both cultivars were
protected by piperonyl butoxide, but only if it was used as a spray, not as a
soil treatment. Piperonyl butoxide was slightly phytotoxic, but the symptoms
resulting from the spray were not similar to those characteristic of ozone
injury. Santoflex 13, (N-(l,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine),
an antioxidant, is used to protect rubber from ozone attack. Gilbert et al.
(1977) found that bean, muskmelon cultivar 'Delicious 51,' and tobacco cultivar
'Bel W-3' were protected by Santoflex dust against visible injury when they
were exposed to concentrations of 0, up to 0.35 ppm in chamber studies.
Ethylenediurea (EDU) [N-(2-(2-oxo-l-imidazolidinyl)ethyl)-N-phenylurea],
an antioxidant, has been widely used to reduced 0-3 injury to vegetation.
01900/A 7-68 5/4/84
-------
Pinto beans sprayed to run-off with 500 ug/ml EDU usually survived exposure to
0- at concentrations of 0.8 ppm for 150 minutes without visible injury
(Carnahan et al. , 1978). Untreated plants exposed under the same conditions
developed ozone injury symptoms over the entire surface area of the primary
leaves.
Hofstra et al. (1978) found EDU to be more effective than benomyl or car-
boxin in suppressing 0, injury on the highly sensitive navy bean growing in
the field. It reduced bronzing, delayed leaf drop, and increased the yield up
to 36 percent in plants exposed to hourly mean concentrations of 0_ at 0.1 to
0.3 ppm.
Pinto bean plants grown in pots received the greatest protection from 0.,
injury when treated with EDU 3 to 7 days before a 6-hour exposure to 0, concen-
trations of 0.10 to 0.76 ppm (Weidensaul, 1980). Plants received the most
effective protection by EDU when 0- concentrations were 0.41 ppm or higher.
Foliage that had not yet been formed at the time the chemical was applied was
not protected. The most extensive testing of the protective capabilities of
EDU has been done by Cathey and Heggestad (1982a,b,c), who studied the effects
of EDU (as either a foliar spray or soil drench) on the 0., sensitivity of
petunia (5 cultivars), chrysanthemum, and 44 other herbaceous species. In all
cases they found that treatment with EDU reduced the 0_ injury. In addition
to herbaceous species, EDU also reduced 0~ injury in woody vegetation
(McClenahan, 1979; Cathey and Heggestad, 1982c).
Legassicke and Ormrod (1981) showed the effectiveness of EDU in reducing
0- injury and increasing tomato yields in the field. For example, an EDU
treatment (spray) increased the number of fruit on the cultivar 'Tiny Tim' and
fruit size was increased in the cultivar 'New Yorker1 in the 0_ treatments.
In this study, the ambient 0- concentration exceeded 0.08 ppm for 15 days
during the growing season. A maximum of 0.14 ppm was recorded with a Oasibi
0- monitor.
In an attempt to quantify the yield losses of potato crops attributable
to 03, Clarke et al. (1983) grew three potato cultivars ('Norland,' 'Norchip,1
and 'Green Mountain') in the field for 2 years using standard commercial
practices (1978, 1980). Half of the plants grown were protected with a drench
of EDU at the rate of 6.7 kilograms of active ingredient gradient per hectare
every 3 weeks from June to September. Foliage was inspected weekly. The
order of foliar injury was 'Norland1 > 'Norchip1 > 'Green Mountain.1 The
01900/A 7-69 4/12/84
-------
percentage leaf injury increased as the season progressed, but EDU-treated
plants had significantly less injury than untreated plants. Oxidant concen-
trations were monitored continuously with a Mast meter. The effect of 0.. on
O
potato yield was determined by comparing the EDU-treated with the untreated
plants. Such a comparison indicated that in 1978, 'Norland' tuber yield was
reduced 25 percent; in 1980, yield was reduced 24 percent. The cumulative
oxidant dose (ppm-hr) for 1980 was nearly twice that of 1978. 'Norchip1
showed a 31 percent loss in yield in 1980 and a 10 percent loss in 1978.
'Green Mountain1 was relatively insensitive to 0, injury.
Farmers and others growing crops in areas where high 0~ concentrations
exist should be aware that agricultural chemicals commonly used to protect
plants from a variety of fungi, insects, and nematodes can modify the response
of the vegetation to 03 exposure. Antioxidants used in insecticides and
herbicides to increase their effectiveness can also change the way plants
respond to 0_ exposure. In general, nematicides seem to increase 0., sensitiv-
ity, while fungicides and antioxidants have a protective effect when sprayed
or drenched onto crops. Studies with herbicides have shown no general trend.
Because none of the chemical compounds that have been studied appear to func-
tion in the same way, it is not possible to generalize. At the present time,
none of the protectants appear to be cost-effective to the extent that they
can be generally prescribed for protecting plants from 0_ injury.
7.4 OZONE EXPOSURE AND RESPONSE
Plant responses to 0- may be manifested as biochemical, physiological,
visible injury, growth, yield, reproduction, and ecosystem effects. Biochemi-
cal and physiological alterations are the fundamental cause of all other
effects, and were briefly described in section 7.3. Visible foliar symptoms
are frequently the first indication of the effects of air pollution on vege-
tation, but they may be difficult to distinguish from other stress effects.
Although functional leaves are required for plant growth and yield, the loss
of leaf area is not always well correlated with yield reductions. This lack
of correlation may occur, if, for example, the plant has more leaf area than
required to maintain the yield, or if plant or environmental factors other
than leaf area limit yield. The lack of correlation between visible injury
and yield is most common when the plant foliage is not the usable or marketable
01900/A 7-70 4/12/84
-------
portion of the plant (yield). In this section, yield loss refers to the
impairment of the intended use of the plant as described in section 7.2.5.
Foliar injury on ornamental plants and leafy vegetables, effects on native
species, reductions in fruit, grain, foliage, or root production by agricul-
tural species and adverse changes in plant quality and aesthetic value are all
considered yield loss. Reproductive capacities may be altered as a result of
these responses. Effects on individual plants may lead to changes in popula-
tions and, eventually, ecosystem modification. The effects of 03 on ecosystems
are discussed in Chapter 8.
In the chapter on vegetational effects in the previous criteria document
(U.S. Environmental Protection Agency, 1978), emphasis was primarily on visible
injury and growth effects. Most of the growth effects discussed concerned
plant parts other than those of primary importance for yield. This emphasis
was dictated by the bulk of the data available at that time. The summary
figures and tables in the previous criteria document (U.S. Environmental
Protection Agency, 1978) emphasized foliar injury responses (Figures 7-3, 7-4,
7-5 and Table 7-14). The visible injury data were summarized by presenting
limiting values (Figures 7-3, 7-4) (i.e., those concentrations below which
visible injury was unlikely and presumably reduced growth and yield would not
occur). Another approach was to determine the 03 concentrations that would
produce a trace (5 percent) of foliar injury at various time intervals (Figure
7-5; Table 7-14). The limiting values shown in Figures 7-3 and 7-4, were
developed from a review of the literature available at that time (1976) and
represented the lowest concentration and time reported to cause visible injury
on various plant species. These data were based on more than 100 studies of
agricultural crops and 18 studies for tree species. In the figures, the
shaded areas represented the range of uncertainty in the data. Foliar injury
was considered unlikely at doses below and to the left of the shaded areas.
The limiting values were summarized as follows:
Agricultural crops:
0.20 to 0.41 ppm for 0.5 hour
0.10 to 0.25 ppm for 1.0 hour
0.04 to 0.09 ppm for 4.0 hour
01900/A 7-71 4/12/84
-------
0.5
£ 0.4
a
a
Z
O
§ 0.3
QC
I-
Z
ui
i 0.2
O
O
ui
1 0.1
o
I
a
Z
QC
z
ai
O
Z
o
o
LU
Z
o
N
O
III (Mil
T (ill
RANGE OF UNCERTAINTY FOR
SUSCEPTIBLE SPECIES
LIMITING VALUES FOR
TREES AND SHRUBS
I i I I M I I
O
800 o
Z
m
O
O
Z
o
m
33
400 §
O
t
ca
0.1 0.5 1 5
DURATION OF EXPOSURE, hours
Figure 7-3. Limiting values for foliar injury to trees and
shrubs by ozone.
Source: U.S. Environmental Protection Agency (1978).
*»* «
0,3
0.2
0.1
I I
RANGE OF
UNCERTAINTY FOR
SUSCEPTIBLE
SPECIES
I I I I
F
LIMITING VALUES FOR
AGRICULTURAL CROPS
I I I I I I I t
I I I I lln
400
O
N
O
z
m
O
O
Z
O
m
Z
O
z
(D
0.1
0.5 1
DURATION OF EXPOSURE hours
Figure 7-4. Limiting values for foliar injury to agricultural
crops by ozone,
Source: U.S. Environmental Protection Agency (1978).
7-72
-------
1.0
a 0.9
Z
2 0.8
a: 0.7
S 0.6
§ 0.5
2 0.4
O
g 0.3
0.2
0.1
TIME
0.5
1.0
2.0
4.0
8.0
CONCENTRATION, ppm
SENSITIVE
0.431 ± 0.044
0.218 ± 0.023
0.111 ± 0.020
0.058 ± 0.022
0.031 ± 0.023
INTERMEDIATE
0.637 ± 0.043
0.347 ± 0.020
0.202 ± 0.017
0.129 ± 0.019
0.093 ± 0.021
RESISTANT
0.772 ± 0.070
0.494 ± 0.028
0.355 ± 0.023
0.286 ± 0.026
0.251 ± 0.034
012345678
TIME, hours
Figure 7-5. Ozone concentrations versus duration of exposure required to
produce a 5 percent response in three different plant susceptibility group-
ings. The curves were generated by developing 95 percent confidence
limits around the equations for all plants in each susceptibility grouping
from Table 7-14. Curves: a = sensitive plants, b = intermediate plants, c =
resistant plants.
Source: U.S. Environmental Protection Agency (1978).
7-73
-------
TABLE 7-14. CONCENTRATION, TIME, AND RESPONSE EQUATIONS FOR THREE SUSCEPTIBILITY GROUPS AND FOR
SELECTED PLANTS OR PLANT TYPES WITH RESPECT TO OZONEa
Plants
Sensitive:
All plants
Grasses
Legumes
Tomato
Oat
Bean
Tobacco
Intermediate:
All Plants
Vegetables
Grasses
Legumes
Perennial
Clover
Wheat
Tobacco
Resistant:
All plants
Legumes
Grasses
Vegetables
Woody plants
Cucumber
Chrysanthemum
(C =
-0.0152
-0.0565
0.0452
-0.0823
-0.0427
-0.0090
0.0245
0.0244
-0.0079
0.0107
0.0116
0.0748
-0.0099
-0.0036
0.0631
0.1689
0.0890
0.1906
0.1979
0.2312
0.1505
0.2060
Ao + Atl + A
+0.00401
+0.00481
+0.00361
+0.00431
+0.00511
+0.00301
+0.00341
+0.00651
+0.00641
+0.00591
+0.00741
+0.00701
+0.00711
+0.00811
+0.00871
+0.00951
+0.01081
+0.01171
+0.01261
+0.00611
+0.01411
+0.00521
2T)b
+0.213/T
+0.291/T
+0.172/T
+0.243/T
+0.273/T
+0.164/T
+0.137/T
+0.290/T
+0.263/T
+0.292/T
+0.329/T
+0.237/T
+0.268/T
+0.302/T
+0.152/T
+0.278/T
+0.304/T
+0.263/T
+0.107/T
+0.208/T
+0.106/T
+0.256/T
R2c
0.57
0.74
0.46
0.50
0.76
0.58
0.52
0.74
0.79
0.82
0.81
0.77
0.95
0.88
0.78
0.51
0.82
0.55
0.70
0.45
0.83
0.40
Threshold .
concentration ppm
1 hr
0.22
0.26
0.24
0.18
0.26
0.17
0.18
0.35
0.29
0.33
0.38
0.35
0.29
0.34
0.26
0.50
0.45
0.51
0.38
0.47
0.33
0.49
4 hr
0.06
0.04
0.11
None
0.05
0.05
0.08
0.13
0.09
0.11
0.13
0.17
0.09
0.11
0.14
0.27
0.22
0.31
0.29
0.31
0.25
0.30
8 hr
0.03
0.01
0.09
None
0.02
0.03
0.06
0.09
0.06
0.09
0.09
0.14
0.06
0.08
0.13
0.25
0.18
0.20
0.20
0.30
0.23
0.27
Number
data
points
471
71
100
20
30
62
197
373
25
68
104
27
24
15
59
291
36
13
16
46
18
45
a
Mean values
Cone (C). ,
ppm
0.29
0.37
0.34
0.31
0.37
0.30
0.23
0.37
0.41
0.39
0.40
0.36
0.28
0.47
0.28
0.45
0.30
0.45
0.55
0.39
0.41
0.39
Time (T). , Response (I).
hr %
1.74
1.66
1.42
1.50
1.66
1.23
1.90
1.67
1.29
1.61
1.59
1.91
2.13
1.25
1.99
1.55
1.89
1.47
1.50
2.50
1.41
2.17
45.4
50.9
40.1
56.5
40.2
47.2
38.9
27.0
33.5
31.0
25.0
22.9
23.0
28.9
15.7
10.6
12.2
6.5
17.8
7.8
13.3
12.6
Dose,
ppm • hr
0.503
0.608
0.480
0.491
0.611
0.370
0.448
0.625
0.532
0.625
0.642
0.687
0.595
0.508
0.551
0.696
0.722
0.655
0.819
0.905
0.581
0.847
Equations were developed from exposures limited in time (0.5 to 8 hr except for 2 to 12 hr points in the sensitive group) and denote acute
responses of the plants. Concentrations range from 0.05 to 0.99 (1.0) ppm and responses from 0 to 99 (100)% of control (U.S. EPA, 1978).
C is ozone concentration in ppm. I is percent injury. T is time in hours, and A , At, and A2 are constants (partial regression
coefficients) that are specific for pollutant plant species or group of species, and environmental conditions used.
cMultiple correlation coefficient squared, which represents the percent variation explained by the model.
For 5 percent response in 1-, 4-, and 8-hr periods.
eFrom the computer analysis.
Source: U.S. Environmental Protection Agency (1978)
-------
Trees and shrubs:
0.20 to 0.51 ppm for 1 hour
0.10 to 0.25 ppm for 2 hour
0.06 to 0.17 ppm for 4 hour
A concept similar to the limiting values for foliar injury was developed
to present the 03 concentrations and durations which could potentially reduce
plant growth and yield (Figure 7-6). In the figure, the line displays the
boundary of mean 03 concentrations and exposure durations below which effects
on growth and yield were not observed. Most of the data points represented
effects on growth rather than yield, as defined in the present document (see
section 7.2.5). The graphical analysis indicated that the lower limit for
effects was a mean 0- concentration of 0.05 ppm for exposure durations greater
than 16 days. At exposure durations of less than 16 days, the 03 response
threshold increased to about 0.10 ppm at 10 days and 0.30 ppm at 6 days.
This revision of the criteria document will place greater emphasis on
yield loss rather than just injury. Visible foliar injury will be considered
for those plants in which the foliage is the marketable plant part (yield),
for plants used for aesthetic purposes, and for plants used as bioindicators.
In the following portions of Section 7.4, the use of plants as bioindica-
tors and effects on vascular and nonvascular plants will be discussed. Bio-
indicators are important, because they provide information about the site of
potential 0., impacts and may be useful in elucidating 03 as a causative factor
*D
in yield loss.
7.4.1 Bioindicators of Ozone Exposure
Plants are known to respond differentially to the characteristics of the
environments that they occupy (Treshow, 1980b). Temperature, moisture, solar
radiation, elevation, and soil quality are obvious environmental features that
affect the distribution and relative performance of vegetation. Because
established plants are confined to a particular location, they depend primarily
on that local environment to meet their requirements for growth and reproduc-
tion; therefore, plant growth and yield integrate all environmental factors.
Thus, vegetation can act as a biological indicator of the environment, which
includes air pollutants.
01900/A 7-75 4/12/84
-------
E
a
a.
<
cc
O
z
O
O
LLJ
z
O
N
O
1.0
0.1
0.01
TTT
47
21D 11D
\ 44* 19OP18
\
48-52
\
40
1514 30 59
V2 " 26 4'1
!ۥ OD29
^ 39
\
7 DO 20
H2439D9
\
\
) 33
54 ••55,56
3«
58
4* 57
38 •••34 •
53
EXPOSURE, hr/day
A ' 1.99
D 2 TO 3.99
O 4 TO 5.99
• ^ 6
NOS. = REF. NOS. ON TABLE 11-4
11
I I I I I I I I I
8 10
20 40 60 80 100
EXPOSURE PERIOD, days
200
400
Figure 7-6. Relationship between ozone concentration, exposure
duration, and reduction in plant growth or yield (see Table 7-18;
also U.S. EPA, 1978).
Source: U.S. Environmental Protection Agency (1978).
7-76
-------
Because organisms/plants growing in a particular environment are integrated
products of that environment, they can provide important information about air
pollution effects. A plant's response is the direct expression of the pollut-
ant in that specific environment; physical methods provide only a measure of
pollution occurrence and magnitude (Laurence, 1982). Therefore, bioindicators
provide a direct method for understanding the risk that pollution presents to
the biological components of the affected environment (Guderian, 1977). For
this reason, there is renewed interest in biological methods for determining
air pollution effects (Manning and Feder, 1980).
7.4.1.1 Bioindicator methods. As the use of plants to monitor air pollution
has increased, methods have changed to better relate plant response to pollu-
tion exposure. Manning and Feder (1980) have summarized the important attri-
butes of a bioindicator species. To perform predictably, the plants should be
sensitive to a specific pollutant, genetically uniform, native or adaptable to
the region, produce characteristic symptoms, grow indeterminately, and respond
proportionally to pollutant exposure. To further minimize natural variation,
efforts should be made to provide uniform soil and water conditions and ensure
observation by trained personnel (Oshima et al., 1976; Posthumus, 1976, 1980).
The aim of these measures is to standardize the plant and growing conditions
so that, effects of the pollutant are the major sources of variation in the
subsequent analysis (Teng, 1982). During the past 10 years, substantial
progress has been made towards improving our understanding of the variables
affecting the performance of indicator species. Specific examples of these
studies are summarized in this section.
7.4.1.2 Response of indicator species. Most early studies with indicator
species focused on visible symptoms, the most obvious reaction of a plant to
change in its environment. These responses included chlorosis or necrosis of
tissues and typically represented the effects of an acute exposure to a single
pollutant (Feder and Manning, 1979; Heck, 1966; Heggestad and Darley, 1969;
Laurence, 1982). With the identification and application of very sensitive
species such as Bel W~3 tobacco (Heggestad and Menser, 1962), means were
gained to predictably identify progressively lower concentrations of 03 (Feder,
1978). There is general agreement that this tobacco cultivar will predictably
respond to an 0., exposure above 0.04 ppm for 4 hr (Ashmore et al., 1978) when
environmental conditions are favorable.
01900/A 7-77 4/12/84
-------
The symptoms caused by exposure to 0~ differ on broad-leaved (dicotyle-
donous) and narrow-leaved (monocotyledenous) plants. The foliage of dicotyle-
donous plants initially appears water soaked due to injury to palisade cell
membranes (U.S. Environmental Protection Agency, 1976). These areas appear
shiny or oily within hours of the exposure and with characteristic flecks or
stipples when the water-soaked area dries (Figure 7-7). Flecks (Figure 7-8)
are small lesions formed when groups of palisade and/or mesophyll cells die
and the associated epidermal cells collapse (U.S. Environmental Protection
Agency, 1976). They may be yellow or tan, and if the injury is extensive, the
entire leaf surface may appear bronzed. Individual flecks may coalesce to
form bifacial lesions that appear on both leaf surfaces. "Stipples" (Figure
7-7) are small groups of red, purple, or black pigmented palisade cells (U.S.
Environmental Protection Agency, 1976). This symptom is viewed through the
uninjured epidermal layer of the upper leaf surface. The leaf veins are also
uninjured and form angular boundaries to the pigmented areas.
Monocotyledonous plants generally do not have differentiated mesophyll
tissue, and ozone injury typically appears as chlorotic spots or white flecks
between veins (U.S. Environmental Protection Agency, 1976). This injury may
extend to form long white or yellow streaks between the parallel veins of sen-
sitive plants and becomes most severe as leaf bands (Figure 7-9).
Ozone injury to the foliage of coniferous plants is described as chlorotic
mottle and tipburn (U.S. Environmental Protection Agency, 1976). Small patches
of needle tissue are injured and turn yellow. These areas are surrounded by
healthy green tissue and the needle appears mottled (Figure 7-10). When the
entire needle tip dies, it turns reddish brown and later gray. This tipburn
is also a characteristic of 0., injury. In both cases, it is usual for only
current-year needles to be affected after acute exposures to 0,.
Long-term exposure to low pollutant concentrations may adversely affect
plant health without producing visible symptoms. Chronic injury from this
type of exposure may be represented by reductions in growth or yield caused by
changes in photosynthesis, respiration, chlorophyl content, or other processes
(Dochinger et al. , 1970; Feder, 1978; Heck, 1966; Laurence, 1982; Posthumus,
1976).
7.4.1.3 Bioindicator Systems. Although many field biologists have identified
certain plants as indicators of pollutants, few have published documentation
of the sensitivity of specific plants to ambient 0_ in the field or in natural
01900/A 7-78 4/12/84
-------
Figure 7-7. Ozone injury to Bel W-3 tobacco. Clear interveinal
areas represent necrotic tissue (fleck and bifacial necrosis).
CUTICLE
ADAXIAL EPIDERMIS
PALISADE LAYER
SPONGY MESOPHYLL
STOMATA
ABAXIAL EPIDERMIS
Figure 7-8. Schematic cross section of typical dicot leaf
showing ozone injury to palisade cells and collapsed epider-
mal cells.
7-79
-------
Figure 7-9. Ozone injury to oats. Clear areas represent
bleached and necrotic tissue.
Figure 7-10. Ozone injury to needles of conifer. Clear areas
represent injured tissue (chlorotic mottle and tipburn).
7-80
-------
environments. Duchelle and Skelly (1981) characterized the response of milk-
weed to CL in both field and laboratory studies. This is a particularly
valuable study, because it defines the response of a plant that has been
classed as a sensitive bioindicator in the field and establishes a base line
sensitivity that can be reevaluated in the future to detect possible changes
in the frequency of sensitive individuals in the field. Benoit et al. (1982)
reported on the radial growth of eastern white pine as an indicator of CL
pollution. Similar results were obtained when ponderosa and Jeffrey pines
were used as bioindicators in the southern California mountains (Miller,
1973). Although a good relationship between radial growth and observed 0,
sensitivity exists, it is probably realistic to only use this procedure to
measure of long-term effects because of the detailed analyses of tree rings
and precipitation patterns required. They were able to identify three classes
of eastern white pine (sensitive, intermediate, and tolerant). Injury observed
on those sensitive species would serve to indicate the extent of CL pollution.
There have been several reports of the use of plants in systems designed
to detect the presence of elevated concentrations of ozone. Many early stud-
ies (Heck, 1966) were conducted to assess the spatial and temporal distri-
bution of smog by using sensitive indicator plants. In most cases, poor cor-
relations between measured oxidants and plant injury were found. With the
identification of Bel W-3 tobacco as a sensitive indicator of elevated ambient
CL concentrations (Heggestad and Menser, 1962), a new series of studies was
conducted (e.g., Heck et al., 1969, Heck and Heagle, 1970; Jacobson and Feder,
1974; Naveh and Chaim, 1978; Goren and Oonagi, 1979; Horsman, 1981; Ashmore et
al., 1978; 1980; Bell and Cox, 1975). The most widespread network established
to determine the spatial and temporal distribution of ambient oxidant induced
injury on Bel-W3 tobacco was that described by Jacobson and Feder (1974). The
bioindicators sites were located in nine states ranging from North Carolina to
Maine. The authors observed both temporal and spatical variations in 0,
injury and concluded that Bel-W3 could be used to indicate the present of 0_
but would not reliably indicate the 0, concentration. A major problem identi-
fied by the authors was the necessity of growing Bel W-3 plants under pollution-
free conditions prior to their use.
Oshima (1974b) devised a bioindicator system for use in California that
utilized pinto bean. In field trials, a strong and significant relationship
was found between injury observed on bean leaves and average weekly ambient 0,
01900/A 7-81 4/12/84
-------
dose. His measure of 0_ dose consisted of a censored sum (hours greater than
O
0.1 ppm) of ambient CL concentrations obtained from nearby physical monitors.
It would be feasible to use such a system on a large scale to at least quali-
tatively, if not quantitatively, assess spatial and temporal occurrence of
phytotoxic concentrations of 0,.
In the Netherlands, bioindicators of air pollution have been in continuous
use since 1954. Posthumus (1976) reported the results of a study to investi-
gate the occurrence and distribution of 0_ by using Bel W-3 tobacco at 31
sites throughout the country. He reported, "It is possible to determine the
place and time with the highest mean intensity or highest frequency of injury
by CL...". A '"fingerprint"' can be produced and, by comparing patterns from
year to year, specific trends in the occurrence of pollution may be identified.
He further concluded that, "The clear advantage of plants as indicators of air
pollution is that these show the result of the action of the pollutants on
living material", and added that, "In this way it could be a rather efficient
and relatively inexpensive manner to follow trends in air pollution and to
evaluate sanitation measures."
Nouchi and Aoki (1979) used morning glory as an indicator of photochemical
oxidants (primarily 0.,). In studies conducted both in the laboratory and
field, they were able to model the effects of C>3 on leaf injury, including the
effects of previously occurring exposures. Field verification of their model
showed that they were able to determine (within acceptable margins of error)
oxidant levels on a given day by using measurements of visible injury to
morning glory. They emphasized however, that the most valuable use of their
system was to characterize the frequency and spatial distribution of elevated
oxidant concentrations.
The common theme in all these studies is that a good understanding of the
occurrence of elevated 0, concentration can be obtained by using the visible
response of sensitive plants. While the methodology to biomonitor is still in
the early stages of development, bioindicators have a certain value as in-
tegrators, by providing information on where, when, and how often 03 concen-
trations may be reaching phytotoxic concentrations. The value of deploying
networks of bioindicators has been demonstrated in the early detection of
developing regional oxidant pollution problems, in identification of trends in
pollutant occurrence, and in supplementing physical monitoring networks to
provide additional information on the biological effects of pollution for the
assessment of crop loss (Laurence, 1982).
01900/A 7-82 4/12/84
-------
7.4.1.4 Lichens as bioindicators of oxidant pollution. Lichens have been
used extensively to index ambient air quality; there are many historic reports
describing the frequency and diversity of these plants as a function of distance
and direction from large sources of SCL and metal pollution (Guderian and
Schoenbeck, 1971; LeBlanc and Rao, 1973; Schoenbeck, 1969; Skye, 1979).
Because they lack roots and stomata, lichens depend more on and are more sub-
ject to the atmospheric component of their environment than are vascular
plants. For this reason, they are generally noted for their sensitivity to
air pollution (Laurence, 1982).
Until recently, there was little information describing the effects of 0,
on lichens in natural environments. Sigal and Nash (1983) have recently
conducted an extensive study of lichen distribution relative to oxidant air
pollution in southern California. Collections of lichens from regions of high
(1300 hr >0.09 ppm, 1968-1974, San Bernadino Mountains) and low (Cuyamaca
Rancho State Park) levels of oxidant pollution were compared with collections
made in 1913. The frequency and cover of the current lichen communities in
these regions were also compared with calculated levels of 0., associated with
injury to pines as reported earlier (National Research Council, 1977). Addi-
tionally, lichens from unaffected areas were transplanted to ecologically
similar sites in affected areas.
In this multidimensional study, the authors found consistently high
levels of injury to lichens in areas with high levels of 0,. In polluted
areas, only 8 of 16 previously reported species were still present, and 4 were
found only in trace amounts. This compared with 15 of 16 species still present
in areas with low levels of 0~. Transplanted lichens performed poorly in
areas where injury to pine was most extensive and calculated levels of 0, were
highest. The authors concluded that lichen communities in southern California
were not adversely affected if the cumulative oxidant dose level was below
about 300 ppm/hr per year. This dose was calculated with all concentrations
greater than 0.04 ppm 0, x time.
7.4.1.5 Published reports of visible injury of plants due to ambient ozone in
the United States. When the phytotoxicity of 0_ was first being discussed in
the late 1950's and early 1960's and when attempts to use plants as bioindica-
tors of 0., exposure were just beginning, many reports of ambient 0., injury to
plants were published. In the past 10 years, the number of published observa-
tions has decreased as scientists are reluctant to report "one more plant" or
01900/A 7-83 , 4/12/84
-------
"a new state" showing 03 injury, and journals are equally reluctant to publish
those reports.
There are published reports of 0~-induced visible injury to plants in at
least 27 states of the United States (Table 7-15 and Figure 7-11). In addition,
similar observations have been made for areas of Canada (Weaver and Jackson,
1968; MacDowell et al. , 1964) and Mexico (DeBauer, 1972). Combined with the
overseas reports previously mentioned, the magnitude of potential ozone pollu-
tion problems represented by injury to vegetation becomes apparent. There are
no reports of visible CL injury to vegetation in the Great Plains, parts of
the Rocky Mountain region, the Deep South, and a few states in the Northeast.
The areas in which vegetation injury has been reported are generally near
locations in which research is being conducted on the effects of air pollution
on vegetation. The absence of reported injury is probably the result of a
failure to look for it. It is quite likely that sensitive indicator plants
would be injured in many of those areas.
Plants have been used to index various characteristics of the environments
in which they grow. Ozone air pollution is an imposed environmental variable
that can be detected and sometimes quantified by observing the specific response
of sensitive plants. The occurrence of CL has been widely reported in the
United States, the Netherlands, Great Britain, Germany, Japan, Israel, and
Australia by observing foliar injury to selected sensitive species and cul-
tivars/subspecies.
Biological methods for assessing the extent and intensity of 03 air
pollution have value beyond that provided by physical measurements. Bioindi-
cators are integrators of their environment and can yield direct information
about the effect a given pollutant exposure has on vegetation, subject to
the joint influence of other environmental variables.
7.4.2 Microoorganism And Nonvascular Plant Response To Ozone Exposure
7.4.2.1 Microorganisms. Most studies with this group of organisms (bacteria
and fungi) have used 0- exposures that are higher than those that would be ex-
pected to occur in ambient air, often in excess of 1 ppm. Direct effects of
ozone on microorganisms and, in some instances, their capacity to incite plant
diseases have been reviewed by Laurence (1981) and Heagle (1973, 1982), and in
section 7.3.2.1.3 of this document.
01900/A 7-84 5/4/84
-------
TABLE 7-15. A PARTIAL LISTING OF AMBIENT OZONE INJURY ON SENSITIVE VEGETATION
REPORTED IN THE LITERATURE3
State
Arizona
Cal ifornia
Connecticut
Delaware
Florida
Georgia
11 1 inois
Indiana
Kentucky
Maine
Maryland
Massachusetts
Michigan
Minnesota
Mi ssouri
New Jersey
New York
North Carolina
Ohio
Pennsylvania
South Dakota
Tennessee
01900/A
Plant
Tobacco
Grape, bean, ponderosa pine
Tobacco
Tobacco
Tobacco
Tobacco
Soybean
White pine
Tobacco
Tobacco
Tobacco
Tobacco
Potato
Bean
Soybean
Tobacco
Tobacco
Tobacco
Tobacco
Tobacco
Tobacco
Tobacco
Tobacco
7-85
Reference
National Research Council,
1977
Richards et al . , 1958;
Oshima, 1974; Miller and
Millecan, 1971
Jacobson and Feder, 1974
Jacobson and Feder, 1974
Dean, 1963
Walker and Barlow, 1974
Kress and Miller, 1983
Usher and Williams, 1982
Menser, 1969
Jacobson and Feder, 1974
Jacobson and Feder, 1974
Jacobson and Feder, 1974
Hooker et al. , 1973
Olson and Saettler, 1979
Laurence et al . , 1977
Heck et al. , 1969
Jacobson and Feder, 1974
Jacobson and Feder, 1974
Jacobson and Feder, 1974
Heck and Heagle, 1970
Jacobson and Feder, 1974
Gardner, 1973
Menser, 1969
4/12/84
-------
TABLE 7-15. (continued)
State Plant Reference
Utah Tobacco Tingey and Hill, 1967
Virginia Milkweed Duchelle and Skelly, 1981
Potato Heggestad, 1973
Washington Tobacco National Research Council,
1977
West Virginia White pine Wood and Pennypacker, 1975
Wisconsin Pine Usher and Williams, 1982
aThis is a partial listing designed to show the nationwide distribution. It
is not complete in either the diversity of species injured or the number of
reports of injury.
01900/A 7-86 4/12/84
-------
I
CD
ON SENSITIVE
REPORTED IN
LITERATURE
..... .
published literature.
-------
The OT concentration required for direct impact on microorganisms may be
quite high. The data of Hibben and Stotsky (1969) are illustrative. These
investigators examined the response of detached spores of 14 fungi to 0.1 to
1.0 ppm of 0- for 1, 2, and 6 hr. The large pigmented spores of Chaetomium
sp. , Stemphylium sarcinaeforme, S. loti, and Alternaria sp. were not affected
by 1.0 ppm. Germination of Trichoderma viride, Aspergi1lus terreus, A. niger,
PenniciIlium egyptiacum, Botrytis a11i i, and Rhizopus strolonifera spores were
reduced by 0., exposure, but only at concentrations above 0.5 ppm. The germina-
tion percentages in the small colorless spores of Fusarium oxysporum, Colletotri-
chum largenarium, VerticiIlium albo-atrum, and V. dahliae were reduced by
0.5 ppm and occasionally by concentrations of 0.25 ppm of 0., for 4 to 6 hr;
lower doses stimulated spore germination in some cases. The ability of ozone
to reduce spore germination in fungi apparently depends on the species, spore
type, morphology, moisture, and substrate. Moist spores were more sensitive
than dry ones. Single-celled spores and those with thin cell walls were most
sensitive.
Hibben and Stotsky (1969) found 0_ toxic to moist fungus spores of some
species, even at concentrations of 0.1 ppm when applied for 28 hr. Exposure
to 0.5 and 1.0 ppm reduced or prevented germination of spores of all species
tested. Ozone at 0.1 ppm for 4 hr or at 1.0 ppm for 2 hr stopped apical cell
division of conidiophores of Alternaria solani and caused collapse of the
apical cell wall (Rich and Tomlinson, 1968).
Ozone can inhibit fungal growth on artificial media but rarely kills the
fungus even at high concentrations. Differences in species sensitivity are
known. In several fungi, exposure to 0_ (0.10 or 0.40 ppm for 4 hr) caused a
10 to 25 fold increase in sporulation (Heagle, 1973). The same author reported
the effects of low exposures to 0., on three obligate parasitic fungi. Germina-
tion of spores was not affected in any of these studies (Heagle, 1975).
Reduced sporulation, germination, and pathogenicity of Botrytis cinerea were
observed by Krause and Weidensaul (1978a,b) after exposure of the microorganism
ij} vitro and J_n vivo to 0.30 ppm of 03 for two 6-hr periods.
7.4.2.2 Lichens, mosses, and ferns. The effects of 0., on lichens are not
well known. Sigal and Nash (1983) recently completed a survey of lichens in
southern California and compared their results to a collection made early in
the 1900's. They found high levels of injury to pine trees. Lichen communi-
ties in non-polluted areas were similar in species composition to those ob-
served early in the century, but those in heavily polluted areas had only 8 of
01900/A 7-88 4/12/84
-------
16 previously reported species present. They concluded that lichens were not
adversely affected if the cumulative oxidant dose level was below about 300
ppm/hr.
In a laboratory study, Nash and Sigal (1979) fumigated two species of
lichen (Parmelia sulcata and Hypogymnia enteromorpha) with CL at concentrations
of 0.5 and 0.8 ppm for 12 hr. The former exhibited greater sensitivity than
the latter, as measured by a reduction in gross photosynthesis. £. sulcata,
which grows on black oak, is absent from the San Bernardino Mountains; H.
enteromorpha is present but apparently deteriorating. The authors noted that
for these species, the pattern observed in the laboratory is consistent with
that found in field observations in Southern California, where extensive CL
injury occurs. In another study (Ross and Nash, 1983), photosynthesis was
decreased at 0_ concentrations of 0.1, 0.25, and 0.50 ppm for 12 hr in Pseudo
parmelia caperata; however, effects were not found when Ramalina menziesei was
exposed to concentrations of 0- up to 0.5 ppm for 12 hr. Exposures of both
species to ozone at 0.10 ppm for 6 hr/day on 5 consecutive days resulted in
the same responses seen at the higher concentrations.
Very little is known about the responses of mosses and ferns to 0~. The
information in the previous EPA document (U.S. Environmental Protection Agency,
1978) indicates that, based on published information, significant effects
would not be expected at current ambient 0., levels.
The responses of nonvascular plants to ozone have received little study.
The study of Sigal and Nash (1983) is important, because it was performed
under ambient conditions and comparisons could be made to previous lichen
collections. Their data indicate that lichens are probably the most sensitive
of nonvascular plants to 0.,. In areas of high 0- pollution, many species
formerly present had been eliminated from the plant community, and lichens
that were transplanted into the area performed poorly. Reports indicate that
moist fungal spores were more sensitive to 0_ than dry spores, but these
experiments were conducted under laboratory conditions some years ago. Inhi-
bition of spore germination in the ambient environment has not been observed.
7.4.3 Losses in Vascular Plants Due to Ozone
This section will relate losses in plant yield to 0,. exposure. Exposures
will be described as duration and 0., concentrations, but the statistics used
to characterize the exposure will take several forms. Yield loss is defined
01900/A 7-89 4/12/84
-------
as the impairment of the intended use of the plant (see Section 7.2.5) and in-
cludes aesthetic values, foliar injury, plant appearance, and losses in terms
of number, size, or weight of the plant part that is normally harvested.
Yield loss can also be defined as a change in physical appearance, chemical
composition, or ability to withstand storage; collectively, these traits are
termed crop quality.
7.4.3.1 Losses in aesthetic value and foliar yield. Losses in aesthetic
value are difficult, if not impossible, to quantify. For example, because of
its aesthetic value, the loss of or adverse effects on a specimen tree or
shrub in a landscape planting will result in a much greater economic loss than
the same impact on a tree or shrub of the same or similar species growing as a
part of a natural plant community. Foliar symptoms which may decrease the
value of an ornamental crop may occur on various types of plants (e.g., turf-
grasses, floral foliage, ornamental trees, and shrubs) with or without concomi-
tant growth reductions. The occurrence of foliar injury on other crops in
which the foliage is the marketable plant part (e.g., spinach, cabbage, tobacco)
can substantially reduce marketability and constitute a yield loss in economic
(if not biologic) terms.
Petunia, geranium, and poinsettia were exposed to 0, (up to 0.10 to 0.12
ppm for 6 hr/day) for 9 days (petunia), 8 days (geranium), and 50 days (poin-
settia) (Cracker and Feder, 1972). Flower size was significantly reduced in
all three species at a concentration of 0.10 to 0.12 ppm. Ozone decreased
flower color in all three species: petunia (0.06 to 0.08 ppm), geranium (0.10
to 0.12 ppm), and poinsettia (0.02 to 0.04 ppm). All these changes in flower
appearance (yield) occurred without visible injury to the plant leaves. Five
begonia cultivars exposed to 0., (0.25 ppm for 4 hr/day for a total of 16 hr
over a 4-week period) varied in foliar injury from 2 to 54 percent (Table
7-16); flower size was also reduceo (Reinert and Nelson, 1980).
Ozone injury on the foliage of ornamental trees and shrubs impairs their
appearance and may reduce their value. Mean foliar injury on eight azalea
cultivars exposed to 0.25 ppm of 0, (six 3-hr fumigations) ranged from 0 to 24
percent (Sanders and Reinert, 1982a). Stem weight was significantly reduced
for three of the cultivars (Table 7-16). Tree and shrub species have developed
foliar injury following exposure to 0.20 ppm of 0_ for 5 hr (Davis et al.,
1981). Visible injury to black cherry foliage occurred following a 4-hr
exposure at 0.10 ppm and 2 hr at 0.19 ppm of 03 (Davis et al., 1981). In an
01900/A 7-90 4/12/84
-------
TABLE 7-16. FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE
Plant species
Begonia
(Schwabenland Red)
(Whisper '0' Pink)
(Fantasy)
: (Renaissance)
(Turo)
ORNAMENTAL TREES AND SHRUBS
Hybrid poplar
(Dorskamp)
(Zeeland)
Hinodegiri azalea
Black Cherry
American sycamore
Hybrid poplar
oa
concentration,
ppm
0.25
0.25
0.25
0.25
0.25
0.041
0.041
0.20
0.20
0.20
0.20
Percent
foliar Monitoring Calibrating Fumigation
Exposure duration injury method method facility Reference
4 hr/day, every 6th day, 54 (39%* dec. Chem not given GH-CSTR Reinert and
4 times in flower Nelson, 1980
wt)
25 (22%* dec.
in flower
wt)
2 (6%* dec.
in flower
wt)
15 (55%* dec.
in flower
wt)
8 (10% inc. in
flower wt)
12 hr/day, 23 wk not given Chem NBKI GH-CH Mooi , 1980
(1333%* inc
leaf drop)
not given
(692%* inc.
leaf drop)
5 hr 33 Chem NBKI GC Davis et al., 1981
27
26
20
-------
TABLE 7-16 (con't). FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE
Plant species
Yellow poplar
Black walnut
Delaware Valley
white azalea
Black elder
Spreading cotoneaster
Austrian pine
Eastern white pine
Virginia pine
Hinodegiri azalea
Korean azalea
Tree-of-heaven
Chinese elm
Mock-orange, sweet
Viburnum, tea
Viburnum, linden
American holly (<*)
American holly (9)
Amur privet
concentration,
ppm
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Percent
foliar Monitoring Calibrating Fumigation
Exposure duration injury method method facility Reference
19
12
12
11
4
0
0
0
8 hr 95 (Severity Chem NBKI GC Davis and
index ) Coppolino, 1974
70
65
24
17
5
2
0
0
0
-------
TABLE 7-16 (con't). FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE3
--J
I
i-D
03
concentration,
Plant species ppm
Black gum
Dense Anglogap yew
Mountain-laurel kalmia
Hete Japanese holly
Hybrid poplar
Azalea (Red Wing)
(Snow)
(Glacier)
(Hersey Red)
(Pink Gumpo)
(Mme. Pericat)
(Red Luann)
(Mrs. G.G. Gerbing)
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
0.25
Percent
foliar Monitoring Calibrating Fumigation
Exposure duration injury method3 method facility Reference
0
0
0
0
12 hr/day, 24 days not given Chem Known 0., GH-CSTR Noble and Jensen,
(50%* inc. source 1980
in leaf
abscission)
3 hr/day, 6 days ! 1
over 4 wk
0
24
21
0
4
8
9
(32%* dec. Chem Known 0- GH-CSTR Sanders and
stem dry source Reinert, 1982a
wt)
(44%* dec.
stem dry wt)
(25%* dec.
stem dry wt)
-------
TABLE 7-16 (con't) FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE3
•-J
I
03
concentration,
Plant species ppm Exposure duration
TURFGRASS
Turfgrass
(Meyer zoysiagrass)
(Tufcote bermudagrass)
(Merion bluegrass)
(Kenblue bluegrass)
(K-31 tall fescue)
(NK-100 ryegrass)
(Penncross bentgrass)
(Pennlawn red fescue)
(Annual bluegrass)
Kentucky bluegrass
(Newport)
(Sydsport)
(Merion)
(Fylking)
(Windsor)
(S. Dakota (certified)
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.20
0.10
0.10
0.10
0.10
0.10
0.10
2 hr
3.5 hr/day, 5 days
7 hr/day, 5 days
3.5 hr/day, 5 days
7 hr/day, 5 days
3. 5 hr/day, 5 days
7 hr/day, 5 days
3. 5 hr/day, 5 days
7 hr/day, 5 days
3.5 hr/day, 5 days
7 hr/day, 5 days
3.5 hr/day, 5 days
7 hr/day , 5 days
Percent
foliar Monitoring Calibrating Fumigation
injury method method facility Reference
0 Mast not given CH Richards et al.,
1980
0
0
2
7
9
14
17
20
0
5
5
12
9
14
9
14
7
15
10
17
-------
TABLE 7-16 (con't). FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE3
Plant species
(Kenblue)
Kentucky bluegrass
(Adelphi)
(Baron)
(Birka)
j (Cheri)
; (Fylking)
(Merion)
(Nugget)
1 (Plush)
(Skofti)
(Sydsport)
(Touchdown)
(Victa)
ted top
(Common)
03
concentration,
ppm Exposure duration
0.10 3.5 hr/day, 5 days
7 hr/day, 5 days
0.15 6 hr/day, 10 days
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
Percent
foliar Monitoring Calibrating
injury method3 method
12
17
6 UV not given
0
0
19
0
9
8 (8% dec.
in leaf area)
0
0
12
0
10
40
Fumigation
facility Reference
CH Elkiey and
Ormrod, 1980
Creeping bentgrass
(Penncross)
0.15
20
-------
TABLE 7-16 (con't). FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE3
concentration,
Plant species ppm
Colonial bentgrass
(Exetes)
Red fescue
(Highlight)
(Pennlawn)
i
^ Perennial ryegrass
FOLIAGE CROPS
Tobacco
(Bel B)
(White Gold)
Cabbage
(All Season)
Spinach
(Northland)
0.15
0.15
0.15
0.15
0.05
0.10
0.05
0.10
0.05
0.10
0.05
0.10
Percent
foliar Monitoring Calibrating Fumigation
Exposure duration injury method method facility Reference
6
2
6 (27%* dec.
in leaf area)
11 (20%* dec. in leaf
area)
4 hr 0 Mast NBKI GH-CH Tingeyetal.,
1973c
0
0
0
0
0
0
0
-------
TABLE 7-16 (con't). FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE
03
concentration
Plant species ppm
Spinach 0.13
(America)
(Winter Bloomsdale) 0.13
(Seven-R) 0.13
(Hybrid-424) 0.13
(Hybrid-7) 0.13
(Viking) 0.13
(Dark Green Bloomsdale) 0.13
(Viroflay) 0.13
(Chesapeake)
(Hybrid-612) 0.13
(Dixie Market) 0.13
Percent
, foliar Monitoring Cal ibratjng Fumigation
Exposure duration injury method method facility Reference
7 hr/day average for 49 (36%ng dec. Chem NBKI OT Heagleetal.,
30 days (0.08 ppm 03 in fresh wt) 1979b
ambient air each day)
52 (45%ng dec.
in fresh wt)
52 (55%ng dec.
in fresh wt)
54 (42%ng dec.
in fresh wt)
56 (43%ng dec.)
in fresh wt)
58 (44%ng dec.
in fresh wt)
58 (58%ng dec.
in fresh wt)
60 (33%ng dec.
in fresh wt)
63 (42%ng dec.
in fresh wt)
65 (61%ng dec.
in fresh wt)
65 (55%ng dec.
in fresh wt)
-------
TABLE 7-16 (con't). FOLIAR SYMPTOM EXPRESSION OF VARIOUS FLOWER, ORNAMENTAL TREE, SHRUB, TURFGRASS, AND
FOLIAR CROP SPECIES IN RESPONSE TO OZONE EXPOSURE
concentration,
Plant species ppm Exposure duration
Tobacco ambient air 11 wks
(GC-166) (Beltsville,
MD)
(CCC-E)
(GC-172)
(GC-169)
(GC-18)
^ (CCC-C)
g (GC-46)
(CCC-L)
(CCC-K)
(GC-50)
(CCC-M)
(CCC-J)
(CCC-S)
(Bel-C)
Percent
foliar Monitoring Calibrating Fumigation
injury method3 method facility Reference
1 Mast not given field Menser and
Hodges, 1972
1
2
6
7
10
10
11
11
11
15
18
25
55
aWhere a column entry is blank, the information is as above.
chem = chemiluminescence; Mast = Mast oxidant meter (coulometric); UV = ultraviolet spectrometry.
CNBKI = neutral buffered potassium iodide.
GH = greenhouse; GH-CSTR = continuous stirred tank reactor in a greenhouse; OT = open-top chamber; GC = growth chamber; CH = specially designed exposure
chamber other than CSTR; GH-CH = exposure chamber in a greenhouse.
severity index = [severity factor (0-5) x (% foliage injured) x (% population susceptible)] -=• 100.
significant at P = 0.05; ng = not given.
-------
earlier study, several species were exposed to 03 (0.25 ppm for 8 hr) and
evaluated for foliar injury (Davis and Coppolino, 1974). Some common ornamen-
tals (holly, privet, yew, laurel, linden) exhibited no foliar injury, but
others (azalea, tree-of-heaven, elm) appeared to be relatively sensitive
(Table 7-16).
For ornamental tree plantings, excessive leaf drop decreases the value
and thus can be considered a yield loss. Ozone has been shown to induce
significant defoliation in hybrid poplar. Mooi (1980) noted increases of
about 7 and 13-fold in leaf drop of two poplar cultivars exposed to 0.041 ppm,
12 hr/day, for 23 weeks (Table 7-16). Noble and Jensen (1980) reported a 50
percent increase in leaf drop of hybrid poplar exposed to 0.25 ppm of 03, 12
hr/day, for 24 days (Table 7-16).
Species and cultivars of turfgrass have exhibited foliar injury when
exposed to 0.15 ppm of 03 (6 hr/day, 10 days) (Elkiey and Ormrod, 1980). The
extent of foliar injury was usually greater than the resultant growth inhibi-
tion. Ozone concentrations of 0.10 ppm for 3.5 hr/day for 4 days or 0.20 ppm
for 2 hr were high enough to elicit injury in most turf grasses (Richards et
al. , 1980) (Table 7-16).
The appearance of the foliage on crops such as tobacco and spinach is
important to their value and may affect marketability. Tobacco and spinach
failed to exhibit visible injury after exposure to 0.05 or 0.10 ppm of 03 for
4 hr (Tingey et al., 1973c) (Table 7-16). Eleven spinach cultivars exhibited
49 to 65 percent mean foliar injury (and 33 to 61 percent mean fresh weight
reduction) when exposed in the field to a 7-hr seasonal mean 03 concentration
of 0.13 ppm (Heagle et al. , 1979b) (Table 7-16). The physical appearance of
cigar wrapper tobacco leaves may be very important to their value. Foliar in-
jury from 0- has been documented in the field (some cultivars are commonly
J
used as bioindicators) and in controlled fumigations. Plants of commercial
tobacco cultivars grown in ambient air at Beltsville, MD, exhibited 1 to 55
percent 0,. injury (Menser and Hodges, 1972) (Table 7-16). Ozone concentrations
O
of 0.10 ppm for 2 hr induced up to 20 percent foliar symptoms.
The above data are examples of 0~-induced impairments in the appearance
and aesthetic value of plants due to foliar injury. Such effects occur at
concentrations as low as 0.041 ppm for several weeks or 0.10 ppm for 2 hr, and
these effects can constitute a yield loss when marketability of the plants is
decreased. The actual amount of yield loss due to decreased aesthetic value
01900/A 7-99 4/12/84
-------
or appearance may be more difficult to quantify than yield loss in weight or
bulk. However, it is not unreasonable for such losses to be relatively greater
than those due to loss in weight even though there may not be as much physical
injury to the plant.
7-4.3.2 Yield Losses as Weight, Size, and Number. The previous criteria
document (U.S. Environmental Protection Agency, 1978) summarized the effects
of acute and chronic 0^ exposures with the primary focus on plant growth and a
few reports which specifically studied yield loss (Tables 7-17, 7-18). Growth
and yield reductions were observed in a diverse range of plant species at
various exposure durations and 03 concentrations. The majority of the studies
were conducted in greenhouse or controlled-environment chambers with only a
few studies conducted in the field. These data indicated that as the exposure
duration increased, the mean 0_ concentrations at which growth effects occurred
decreased. When the exposure duration exceeded 15 days (not continuous expo-
sures), mean 0 concentrations of 0.05 ppm and greater caused significant
growth and yield reductions. In field studies, significant growth and yield
reductions were observed in commercial varieties of sweet corn, soybean, and
pine seedlings (Heagle et al. , 1972; Heagle et al. , 1974; Wilhour and Neely,
1977) when the seasonal 6-hr 0, concentration was 0.10 ppm or greater. In
another field study, significant growth and yield reductions occurred in
alfalfa when the 7-hr seasonal mean 0~ concentration was 0.05 ppm or greater
(Neely et al., 1977).
Yield losses are summarized in the following sections in terms of weight
or size, and decrease in number from studies in which known amounts of 0, were
added to either charcoal-filtered or ambient air. The effects of ambient 0^
on yield are also presented.
7.4.3.2.1 Ozone addition studies. Ozone-induced yield-loss studies have used
a variety of experimental approaches. Some studies have attempted to ap-
proximate typical agronomic conditions, and others have deviated from typical
field practices in an attempt to have better control of the experimental
conditions. Open-top chamber data will be discussed first, because most of
these studies attempted to follow typical field practices. Results from
experiments conducted under more controlled conditions (greenhouses, indoor
chambers, potted plants) are discussed primarily as they relate to the field
studies.
01900/A 7-100 4/12/84
-------
TABLE 7-17. EFFECTS OF SHORT-TERM EXPOSURES ON GROWTH AND YIELD OF SELECTED PLANTS3
I
I—»
o
Plant Ozone concen-
species tration ppm
Begonia, cultivar
White Tausendschon
Petunia, cultivar
Capri
Coleus, cultivar
Scarlet Rainbow
Snapdragon, cultivar
Floral Carpet, mixture
Radish, cultivar
Cavalier Cherry Belle
Radish
Cucumber, cultivar
Ohio Mosiac
Potato, cultivar
Norland
Tomato, cultivar
Fireball
Tomato, cultivar
Fireball
Onion, cultivar
Spartan Era
Tobacco, cultivar
Bel W3
0.10
0.20
0.40
0.80
0.10
0.20
0.40
0.80
0.10
0.20
0.40
0.80
0.10
0.20
0.40
0.80
0.25
0.40
1.00
1.00
1.00
1.00
0.50
1.00
0.50
1.00
0.20
1.00
1.00
0.30
Exposure
time (hr)
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
p
1.5(1)'
1.5(2)=
1.5(3)c
1
4
* c
4(3)C
1
1
1
1
24
1
4
2
5,
10,
19,
38,
9,
11,
21,
31,
2,
17,
24,
39.
0,
6,
8,
16,
36,
38,
37.
63,
75,
19,
37,
0,
30,
15,
20,
15,
25,
0,
19,
49,
48,
Plant response, % reduction
from control
avg. of 3 growth responses: shoot wt,
flower wt, flower no.
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
avg. of same responses
top dry wt (Cavalier)
root dry wt (Cherry Belle)
root dry wt
root dry wt
root dry wt
top dry wt (1% injury)
top dry wt (18% injury)
tuber dry wt (no injury)
tuber dry wt (injury severe)
plant dry wt (grown in moist soil)
plant dry wt (grown in moist soil)
increase in plant dry wt (grown in dry soil)
increase in plant wt (grown in dry soil)
effect
plant dry wt (no injury)
plant dry wt
chlorophyll content
Taken from Ref. (U.S. Environmental Protection Agency, 1978).
b
Unless otherwise noted.
Number of exposures in parentheses.
-------
TABLE 7-18. EFFECTS OF LONG-TERM, CONTROLLED OZONE EXPOSURES ON GROWTH, YIELD,
AND FOLIAR INJURY TO SELECTED PLANTS3
I
I—>
o
Fig. 7-6b
Plant species Nos.
Lemna, duckweed
Carnation
Geranium
Petunia
Poinsettia
1
2
3
4
5
Ozone
concentration,
ug/m3 (ppm)
Exposure
196 (0.10) 5/day
98-177 (0.05-0.09) 24/day
137-196 (0.07-0.10) 9. 5/day
98-137 (0.05-0.07) 24/day,
196-235 (0.10-0.12) 6/day,
time
, 14 days
, 90 days
, 90 days
53 days
5 days/week,
Plant response, % reduction
from control
100,
50,
50,
50,
30,
39,
flowering; 36, flowering
(1 wk after exposure completed)
frond doubling rate
flowering (reduced vegetative
growth)
flowering (shorter flower
lasting time, reduced vegetative
growth)
flower fresh wt
bract size
10 weeks
Radish
6
98
(0.
05)
8/day
, 5
days/week,
5 weeks
98
(0.
05)
8/day
, 5
(mixture
Beet, garden
Bean, cultivar
Pinto
Bean, cultivar
Pinto
Bean, cultivar
Pinto
7
8
9
10
11
12
13
14
392
255
290
490
686
290
290
290
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
20)
13)
15)
25)
35)
15)
15)
15)
for
3/day
8/day
2/day
2/day
2/day
2/day
3/day
4/day
same
, 38
, 28
, 63
, 63
, 63
, 14
, 14
, 14
days/week
of 03 and S02
periods)
days
days
days
days
days
days
days
days
54,
20,
63,
22.
50,
79,
73,
70,
33,
95,
97,
8,
8,
23,
root fresh wt
leaf fresh wt
root fresh wt
leaf fresh wt
top dry wt
top fresh wt
root fresh wt
height
plant wt; 46,
plant dry wt;
plant dry wt;
leaf dry wt
leaf dry wt
pod
99,
100
leaf dry wt (Data
whole plants,
fresh wt
pod fresh wt
, pod fresh wt
available on
roots, leaves, injury,
and three levels
Bean, cultivar
Pinto
15
16
17
290
440
440
(0.
(0.
(0.
15)
225)
225)
6/day
2/day
4/day
, 14
, 14
, 14
days
days
days
49,
44,
68,
stress)
leaf dry wt
leaf dry wt
leaf dry wt (Data
whole plants,
of soil (moisture
available on
roots, leaves, injury,
and three levels of soil (moisture
18
588
(0.
30)
I/day
, 14
days
40,
stress)
leaf dry wt
-------
TABLE 7-18 (con't). EFFECTS OF LONG-TERM, CONTROLLED OZONE EXPOSURES ON GROWTH, YIELD
AND FOLIAR INJURY TO SELECTED PLANTS3
—i
i
o
OJ
Plant species
Tomato
Corn, sweet,
cultivar Golden
Jubilee
Wheat, cultivar
Arthur 71
Soybean
Soybean
Alfalfa
Grass brome
Alfalfa0
Alfalfac
Alfalfa
Pine, eastern
white
Fig. 7-6
Nos.
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
Ozone
concentration
ug/m3 (ppra)
588 (0.30)
392 (0.20)
686 (0.35)
392 (0.20)
686 (0.35)
392 (0.20)
98 (0.05)
196 (0.10)
196 (0.10)
290 (0.15)
390 (0.20)
290-647
(0.15-0.33)(varied)
196 (0.10)
98 (0.05)
98 (0.05)
196 (0.10)
Exposure time
3/day, 14 days
2.5/day, 3 days/week
14 weeks
2.5/day, 3 days/week,
14 weeks
3/day, 3 days/week
till harvest
3/day, 3 days/week
till harvest
4/day, 7 days
(anthesis)
8/day, 5 days/week
3 weeks
8/day, 5 days/week
(mixture of 03 and S02
for same periods)
8/day, 5 days/week
3 weeks
2/day, 21 days
2/day, 21 days
2 day, 21 days
4/day, 5 days/week
growing season
6/day, 70 days
7/day, 68 days
8/day, 5 days/week
12 weeks
4/day, 5 days/week
4 weeks (mixture of 03
and S02 for same periods)
76,
1,
45,
13,
24,
20,
54,
30,
13,
16,
20,
21,
9,
16,
26,
39,
83,
4,
20,
50,
30,
50,
18,
3,
16,
Plant response, % reduction
from control
leaf dry wt
yield; 32 top dry wt; 11,
root dry wt
yield; 72, top dry wt; 59,
root dry wt
kernel dry wt; 20, top dry wt;
root dry wt
kernel dry wt; 48, top dry wt;
root dry wt
yield
foliar injury
foliar injury
root dry wt
top dry wt
root dry wt
top dry wt
top dry wt
top dry wt
biomass
top dry wt, harvest 1
top dry wt, harvest 2
top dry wt, harvest 3
top dry wt, harvest 1
top dry wt, harvest 2
top dry wt
needle mottle
(over 2-3 days of exposure)
needle mottle
-------
TABLE 7-18 (con't). EFFECTS OF LONG-TERM, CONTROLLED OZONE EXPOSURES ON GROWTH, YIELD
AND FOLIAR INJURY TO SELECTED PLANTS3
I
I—»
o
Fig. 7-6
Plant species Nos.
Pine, ponderosa
Pine, ponderosa
Poplar, yellow
Maple, silver
Ash, white
Sycamore
Maple, sugar
Corn, sweet,
cultivar Golden
Midget0
Pine, ponderosac
Pine, western
white0
Soybean, cultivar
Darec
Poplar, hybrid
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Ozone
concentration
ug/m3 (ppm)
290 (0.15)
290 (0.15)
290 (0.15)
290 (0.15)
588 (0.30)
588 (0.30)
588 (0.30)
880-588 (0.30)
588-880 (0.45)
588 (0.30)
588 (0.30)
588 (0.30)
588 (0.30)
98 (0.05)
196 (0.10)
196 (0.10)
196 (0.10)
98 (0.05)
196 (0.10)
290 (0.15)
Exposure time
9/day, 10 days
9/day, 20 days
9/day, 30 days
9/day, 60 days
9/day, 10 days
9/day, 20 days
9/day, 30 days
9/day, 30 days
9/day, 30 days
13 weeks
8/day, 5 days/week
13 weeks
8/day, 5 days/week
13 weeks
8/day, 5 days/week
13 weeks
8/day, 5 days/week
13 weeks
6/day, 64 days
6/day, 64 days
6/day, 126 days
6/day, 126 days
6/day, 133 days
6/day, 133 days
8/day, 5 days/week
6 weeks
4,
25,
25,
34,
12,
50,
72,
85,
82,
50,
66,
0,
28,
9,
45,
12,
21,
13,
9,
3,
19,
55,
50,
47,
Plant response, % reduction
from control
photosynthesis
photosynthesis
photosynthesis
photosynthesis
photosynthesis
photosynthesis
photosynthesi s
photosynthesis
leaf drop; 0, height
leaf drop; 78, height
leaf drop; 0, height
leaf drop; 22, height
leaf drop; 64, height
kernel dry wt; 14, injury
(12, avg. 4 yield responses)
25, 35 for same responses
root length
stem dry wt; 26, root dry wt
foilage dry wt
stem dry wt
seed yield; 22, plant fresh wt;
injury, defoliation, no reduc-
tion in growth or yield
65, 37 for same responses
shoot dry wt; 56, leaf dry wt ;
root dry wt
aFrom Ref. (U.S. Environmental Protection Agency, 1978).
Numbers in this column are keyed to numbers in Fig. 7-6.
cStudies conducted under field conditions, except that plants were enclosed to ensure controlled pollutant doses.
Plants grown under conditions making them more sensitive.
-------
7.4.3.2.1.1 Open-top chamber studies. The data from experiments in
open-top chambers provide information on CL exposure-yield response relation-
ships for plants grown under near-normal field conditions. Each of the studies
described in this section used charcoal-filtered air as the lowest 0\ level
(control). To create a range of concentrations, CL was added to either charcoal-
filtered air or to unfiltered air. In summarizing the data, yield loss was
derived from the plant performance in charcoal-filtered air, although other
reference concentrations could have been used. One of the experimental objec-
tives of most of the studies was to develop exposure response relationships
among 0- concentration, exposure duration, and yield loss. To derive the
exposure response functions, various regression techniques have been used. To
estimate the impact of 0_ on yield at a common 0_ concentration for all the
studies, the derived equations were used to estimate the yield loss at a
particular exposure condition rather than individual means. Graphs of the
exposure response equations and the data used to derive them are presented to
show how well various models fit the experimental data.
The effects of 0., on the yield of five soybean cultivars exposed to
various 0, concentrations at different NCLAN sites during different years are
remarkably similar (Figure 7-12 A to D; Table 7-19). The yield reductions for
the soybean cultivar Davis (Heagle et a!., 1983a) were derived from a curvi-
linear (quadratic) regression approach which predicted a 24 percent reduction
in seed weight per meter of row at a 7-hr mean seasonal 0., concentration of
0.06 ppm and compared to a control of 0.025 ppm of 0., (Figure 7-12a). However,
this curve appears to overestimate the control yield. Based on interpolation
of the treatment means, the reduction at 0.06 ppm should be about 13 percent.
A yield reduction of 21 percent (0.06 ppm) was predicted for the soybean
cultivar Corsoy (control = 0.022 ppm of 0.,) based on a linear model (Figure
7-12d) (Kress and Miller, 1983). Plants infected with a virus appeared to be
more resistant to 0.,. However, no data from virus-free plants were used in
developing the equation. Earlier studies (1977, 1978) which used the cultivar
Davis grown in pots displayed smaller yield losses (Heagle and Heck, 1980;
Heck et al., 1982a) (Figure 7-12b,c). Linear regression equations predicted
yield reductions of 16 percent (0.06 ppm) (control = 0.025 ppm of 0~) in 1977,
and 13 percent (0.06 ppm) (control = 0.024 ppm of 03) in 1978. The apparent
lesser sensitivity of Davis soybean in 1977 and 1978 may have resulted from a
lower water availability, because the plants were grown in pots (Heagle et
al., 1983a).
01900/A 7-105 4/12/84
-------
t?
f
I'
o
oc
u.
O
E
"S
450
400
350
300
250
200
150
I I
DAVIS SOYBEAN
RALEIGH. 1981
'(A)
Y = 534.5 - 3988.6 ± 03 + 10960 ± 03SQ
: I I I
a.
"ft
O
a
LU
LU
CO
100
80
60
20
I I
DAVIS SOYBEAN (IN POTS)
RALEIGH, 1977
- O
(B)
Y = 96.6 - 385 ±03 R2 = .90
- I I I
0.00 0.05 0.10 0.15
0, CONCENTRATION, ppm
0.20
100,
a.
"S
ui
a
LU
LU
tO
80
60
40
20
I I I
DAVIS SOYBEAN (IN POTS)
RALEIGH, 1978
(C)
Y = 95.3 - 309 ±03 R2 = .99
: I I
3000
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
2500
I
D)
.X
Q
LU
2000
1500
1000
I
I I
CORSOY SOYBEAN
ARGON NE, 1980
(D)
Y = 3099.3 - 15135.0 ±03 R2 = .975
- I I I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
0.00 0.05 0.10 0.15
O, CONCENTRATION, ppm
0.20
Figure 7-12. Effect of O3 exposures on the yield of various legumes. O3 concentration
(ppm) is expressed as 7-hr seasonal mean, o indicates mean of plants in open top
chambers; X indicates mean of plants in ambient air, which were not used in the regres-
sion analysis. (A) Data and regression equation from Heagle et at., 1983a. Each point is
the mean of two plots; the regression equation was based on the individual plot values.
(B) and (C) Data are from Heck et al., 1982. Similar equations were published in Heagle
and Heck, 1980. Each point is the mean of two replications (chambers) with four plots per
replication. (D) Data and regression equation are from Kress and Miller, 1983. Data and
curve for yield in g/plant are also given in Heck et al., 1982. Each point is the mean of
four plots; the regression equation was based on individual plot values.
7-106
-------
160
120
80
O
o
Q.
40
PEANUT (NC-6)
RALEIGH, 1979
(E)
Y = 112-563 ±03 R2
.86
I
160
120
I 80
UJ
Q
2
40
I I
PEANUT (NC-6)
RALEIGH. 1980
0.00
0.05 0.10 0.15
03 CONCENTRATION, ppm
18
0.20
0
0.00
h (F)
1. Y = 173 - 1046 ±03 R2 = .96
2. Y = 142.3 IF 03 «.037
Y = 184.6 - 1160 + 03 IF 03 > .037
- I I | R2 = .99.
0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
\
a
16
14
12
10
I I I
KIDNEY BEAN (CALF LIGHT RED)
BOYCE THOMPSON INSTITUTE, 1980
_ O
(G)
17.44 - 35.51 + 03
I I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
Figure 7-12. (continued) (E) Data and regression equation from Heagle et al., 1983b. Each
point is the mean of two plots with 16 plants per plot. (F) Data and the straight line
equation are found in Heagle et al., 1983b, and Heck et al., 1982. The plateau-linear equa-
tion is from Heck et al., 1982. (G) Data and regression equation are from Kohut and
Laurence, 1983. The same data and another straight line regression are in Heck et al.,
1982. Each point is the mean of three plots. Regression was performed on treatment
means.
7-107
-------
TABLE 7-19. OPEN-TOP CHAMBER EFFECTS AND WEIBULL PARAMETERS FOR INDIVIDUAL OZONE DOSE-CROP RESPONSE
—i
i
o
oo
DATA SETS.'
Crop
Soybean
Corsoy
Davis6
Essex6 .
Hodgson (FK
Hodgson (P)
Williams6
Common Response (cv)
Corn
Coker 16
PAG 397
Pion. 3780
Common Response (cv)^'
Wheat
Blueboy II
Coker 47-27
Holly
Oasis
Common Response (cv)^
Peanut
NC-6
Cotton1
Acala SJ-2(I)
Kidney Bean
Calif. Lt. Red.
Lettuce
Empi re
Turnip
Just Right
Pu. Top W.G.
Shogoin
Tokyo Cr.
Chamber
Effect-62D
g/plant
-0.75
-2.26
7.51
1.28
0.14
3.49
18.3
13.0
5.9
0.93
0.70
0.75
0.32
(0.92)
(5.25)
(3.45)
(1.33)
(1.87)
(2.36)
(8
(7
(6
(0.
(0.
(0.
(0.
-48.1 (5.
-3.30 (3.
1.44 (1.
144 (181)
5.57
2.93
2.56
8.99
(0.
(0.
(0.
(2.
.67)
.38)
.28)
,27)**
.23)*
,25)*
,25)
80)**
72)
00)
70)**
45)**
38)**
09)**
Weibull
a
g/plant
15.6
31.1
18.7
15.2
15.5
19.4
240
166
149
5.88
5.19
4.95
4.48
(1.
(4.
(6.
(7.
(2.
(3.
(5.
(3.
(3.
(0.
(0.
(0.
(0.
148 (4.
41.5 (4.
16.5 (1.
1245 (530)
10.89
6.22
4.68
15.25
(0.
(0.
(0.
(1.
23)
63)
35)
63)
27)
77)
90)
80)
90)
22)
29)
17)
20)
70)
90)
10)
50)
35)
33)
30)
parameters for individual models
a, ppm
0.129
0.129
0.309
0.207
0.153
0.243
0.153
0.221
0.160
0.155
0.158
0.175
0.171
0.156
0.186
0.174
0.111
0.197
0.287
0.098
0.090
0.095
0.096
0.094
(0.01)
(0.02)
(0.37)
(0.14)
(0.03)
(0.17)
(0.007)
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
(0.
05)
00)
00)
00)
02)
02)
01)
04)
01)
(0.00)
(0.02)
(0.09)
(0.04)
(0.
(0.
(0.
(0.
003)
005)
006)
006)
1.70
0.91
0.76
0.50
1.57
0.94
1.26
4.46
4.28
3.11
3.53
3.22
2.06
4.95
3.20
2.90
2.21
1.12
1.77
1.22
3.05
2.51
2.12
3.94
c
(0.53)
(0.29)
(1.26)
(0.54)
(1.10)
(0.95)
(0.18)
(2.83)
(0.72)
(0.46)
(0.57)
(1.33)
(0.68)
(2.03)
(1.86)
(0.78)
(0.23)
(0.42)
(1.06)
(0.71)
(0.65)
(0.67)
(0.64)
(2.01)
Common Response
0.093 (0.003)
2.75 (0.57
-------
TABLE 7-19. OPEN-TOP CHAMBER EFFECTS AND WEIBULL PARAMETERS FOR INDIVIDUAL OZONE DOSE-CROP RESPONSE
DATA SETS3
I
I—'
o
Chamber.
effect-a2D
Crop (g/plant)
SpinachJ
America
Hybrid9
Viroflay
Winter Bloom.
Common Response (cv)^
Wei bull parameters
a
(g/plant)
21.
36.
41.
20.
2
6
1
8
(3.20)
(4.90)
(5.80)
(3.10)
0.
0.
0.
0.
0.
for individual models0
a (ppm)
,142
,139
,129
,127
,135
(0.
(0.
(0.
(0.
(0.
,021)
,017)
,017)
,017)
,008)
1.
2.
1.
2.
2.
,65
,68
,99
,07
,08
c
(0.98)
(1.70)
(1.06)
(1.17)
(0.51)
aTable from Heck et al., 1983. The Weibull model is Y = a exp [-(-)c] + e. The standard error (SE) is
shown in () for all data; all values are ±SE. The SE was calculated using the mean square error term
from the analysis of variance.
The a2 is the predicted chamber effect (g/plant), the significance of a2 was tested using a t-test; * and
**, significantly -different from zero at p=0.05 and p=0.01, respectively. Negative values correspond to
situations in which AA plot yields were greater than those from corresponding chambered plots and vice
versa.
GWeibull parameters: 5 is the predicted yield (g/plant) at zero 03; a is the predicted 03 concentration
(ppm) at 67% yield reduction; c is the predicted shape of the curve and has no dimensions; and a and c
are common for all cultivars that are combined, but a is different for each cv; Weibull parameters are
based on chambered plots only.
These estimates were based on yields corrected by a covariance analysis for the effects of a virus
infection and differ slightly from previously published information on this data set (Heck et al . , 1982).
For Davis, Essex, and Williams data sets, an S02 response was also measured.
The Hodgson data were obtained from two designs in 1981; a full plot harvest (F) and a partial plot
harvest (P), where some plants were removed before harvest.
^An F statistic was used as a test for the homogeneity of the proportional response part of the model, exp
[•(-) ]; none of the F values were significant at P = 0.05, thus they were all homogeneous.
(7
Coker 16 was not included in the "Common Response" because the use of the Coker 16 data resulted in a
highly significant F value (29.31), indicating a heterogeneous response.
The cotton experiment utilized an irrigated (I) and droughted (D) treatment. These two designs gave a
positive test for homogeneity using the Weibull function. However, the F statistic was large (3.2) and
the analysis of variance showed an 03 by soil moisture interaction. Thus, these data sets were not
combined.
AA plots were not used in this experiment.
•
-------
More recently, NCLAN has used the Weibull equation to estimate (L-induced
yield reductions (Heck et al., 1983). The predicted yield reductions at 0.06 ppm
were 18 percent (Essex), 18 to 22 percent (Hodgson), and 18 percent (Williams)
(Table 7-19). In fact, the responses of the five cultivars from these studies
were statistically homogeneous. Unfortunately, the raw data from which the
equations for Essex, Hodgson, and Williams were developed were not presented.
Peanuts are among the more sensitive crops thus far tested in the NCLAN
program (Heagle et al., 1983c). The peanut study was replicated over 2 years
(Figure 7-12 e,f). In the first year, a linear regression equation predicted
a 20 percent yield reduction (0.06 ppm) compared to a charcoal-filtered air con-
trol of 0.026 ppm 03 mean 7-hr seasonal concentration; however, the 0., effect was
statistically significant at only p = 0.13. In the second year (1980), a 25 per-
cent yield loss of marketable pod weight per plant (0.06 ppm), compared to a con-
trol concentration of 0.025 ppm, was predicted from the linear model. The authors
suggested that the 1979 peanut crop was under greater moisture stress because
of closer plant spacing, less irrigation, and constant air movement, which may
have depressed plant growth and rendered the plants less sensitive to Or The
data for 1980 were fit with linear, plateau-linear, and Weibull (Table 7-19)
models, which predicted similar yield losses.
Kidney bean (California Light Red) appeared to be considerably less
sensitive to 0^ than soybean (Kohut and Laurence, 1983). A linear regression
equation predicted bean weight/plant yield reductions of 7 percent (0.06 ppm)
compared to the control (0.025 ppm of 0.,) (Figure 7-19). The predicted yield
reductions from the Weibull equation (Heck et al., 1983) were similar, at 5 per-
cent (0.06 ppm) (Table 7-19).
Winter wheat yield appeared to be relatively sensitive to 0., based on the
yield reductions of four cultivars (Table 7-20). The yields of all four
cultivars were significantly reduced (11 to 25 percent) at 0.10 ppm of 0,,, but
only one cultivar was significantly affected (11 percent reduction) at 0.06 ppm
of 0., (Heagle et al. , 1979c). These data were subsequently re-evaluated using
quadratic (Heagle and Heck, 1980) and linear (Heck et al. , 1982) regression
models (Figure 7-13 a to d). Based on a visual inspection, the quadratic model
fit the data better than the linear model for all cultivars. A plateau-linear
model was used for one cultivar (Holly) but its fit did not appear better than
that of the quadratic. At a seasonal 7-hr mean 0.-, concentration of 0.06 ppm, the
model predicted yield losses of 0.0 to 11 percent for the four cultivars. The
yield reductions predicted by the Weibull equations were similar (Table 7-19).
01900/A 7~110 4/12/84
-------
TABLE 7-20. EFFECTS OF OZONE ADDED TO AMBIENT AIR IN OPEN-TOP CHAMBERS ON THE YIELD OF SELECTED CROPS
Plant species
Field corn
(Coker 16)
Field corn
(Coker 16)
(FR632 X FR619)
(H95 X FR64A)
Winter wheat
(soft red)
(Blueboy II)
(Coker 47-27)
(Holly)
(Oasis)
0, concentration,
ppra Exposure duration
0.02 Beginning 25 days after planting for 88
0.07 days, Seasonal 7-hr average (0830-1530 ST)
0.11
0.15
i 0.02 Beginning 25 days after planting for 88
0.15 days, Seasonal 7-hr average (0830-1530 ST)
0.02
0.15
0.02
0.15
0.03 Beginning when plants were 28 to 45 cm
0.06 tall for 53 days
0.10 Seasonal 7-hr average (0930-1530 ST)
0.13
0.03
0.06
0.10
0.13
0.03
0.06
0.10
0.13
0.03
0.06
0.10
0.13
Percent yield reduction Monitoring Calibration
from control method method Reference
Control Chem. 1% NBKI Heagle et
+3, seed wt/plant; +2, wt/seed al., 1979a
4, seed wt/plant; 1, wt/seed
16*, seed wt/plant; 9*, wt/seed
Control Chem. 1% NBKI Heagle et
12*. seed wt/plant; 15*. wt/seed al., 1979a
Control
37*. seed wt/plant; 25*. wt/seed
Control
40*, seed wt/plant; 30*. wt/seed
Control Chem. 1* NBKI Heagle etal.,
2, seed wt/plant 1979c
15*, seed wt/plant
31*, seed wt/plant
Control
11*, seed wt/plant
25*, seed wt/plant
43*, seed wt/plant
Control
1, seed wt/plant
11*, seed wt/plant
33*, seed wt/plant
Control
1, seed wt/plant
11*, seed wt/plant
26*, seed wt/plant
-------
TABLE 7-20 (con't). EFFECTS OF OZONE ADDED TO AMBIENT AIR IN OPEN-TOP CHAMBERS ON THE YIELD OF SELECTED CROPSd
0
Plant Species
Spinach
(America)
(Winter Bloomsdale)
(Hybrid 7)
(Viroflay)
Soybean (Pots)
(Forest)
(Ransom)
(Davis)
(Bragg)
, concentration
ppm
0.024
0.056
0.096
0.129
0.024
0.056
0.096
0.129
0.024
0.056
0.096
0.129
0.024
0.056
0.096
0.129
0.025
0.101
0.025
0.101
0.025
0.101
0.025
0.101
, Percent yield reduction Monitoring Calibration
Exposure duration from control method method Reference
Beginning 10 days after planting for 38 Control Chem. 1% NBKI Heagle et
days, Seasonal 7-hr average (0820-1520 ST) 23, fresh wt of shoots al., 1979b
39*, fresh wt of shoots
70*, fresh wt of shoots
Control
19, fresh wt of shoots
44*, fresh wt of shoots
73*, fresh wt of shoots
Control
4, fresh wt of shoots
35*, fresh wt of shoots
61*, fresh wt of shoots
Control
26, fresh wt of shoots
35*, fresh wt of shoots
72*, fresh wt of shoots
Beginning 25 days after planting for Control Chem. 1% NBKI Heagle and
116 days, Seasonal 7-hr average 32*. seed wt/plant Letchworth,
(0820-1520 ST) 1982
Control
20*, seed wt/plant
Control
34*, seed wt/plant
Control
+4, seed wt/plant
-------
TABLE 7-20 (con't). EFFECTS OF OZONE ADDED TO AMBIENT AIR IN OPEN-TOP CHAMBERS ON THE YIELD OF SELECTED CROPS'3
-xl
1
1 — >
1 — >
CO
Plant species
Soybean (plot)
(Davis)
(Davis)
0, concentration,
ppra
0.025
0.116
0.023
0.098
Exposure duration
Beginning
116 days,
(0820-1520
Beginning
116 days,
(0820-1520
23 days
Seasonal
ST)
23 days
Seasonal
ST)
after
7-hr
after
7-hr
planting for
average
planting for
average
Percent yield reduction Monitoring Calibration
from control method method
Control
48*, seed
Control
28*, seed
Chem. 1* NBKI
wt/plant
wt/plant
Reference
Heagle et
al. , 1983b
where a column entry is blank the information is the same as above.
Chem = chemiluminescence.
r>
1% NBKI = 1% neutral buffered potassium iodide.
Significant effect at p = 0.05.
-------
0.
^)
K
o
LU
§
Q
LU
LU
(A
3
Q.
I
e>
Q
LU
LU
V)
I I
WINTER WHEAT
(BLUEBOY II)
RALEIGH, 1977
(A)
1. Y = 5.908 + 3.958 ± 03 - 137.7 + 032
2. Y = 6.6 -18 + 03 R2 = .92
I
I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
I I I
WINTER WHEAT (HOLLY)
RALEIGH, 1977
1C)
1. Y = 4.533 + 19.31 ± 03 - 215.1 ± 032
2. Y = 5.7 -16 + 03 R3 = .82
3. Y = 4.9 IF03< .087
Y = 8.2 - 38 ± 03 IF 03 0.87 R'= .99
I I I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
Q.
"ft
I 4
LU
Q
LU
LU 7
w •*
i i n
WINTER WHEAT (COKER 47 27)
RALEIGH, 1977
(B)
1. Y = 5.765 - 18.79 + 03 - 20.00 + 032
2. Y = 5.8 -21+03 R2 = .98
I
I
I
0.00
0.05
0.10
0.15
0.20
03 CONCENTRATION, ppm
4
52
i
Q
LU
LU q
w J
I I I
WINTER WHEAT (OASIS)
RALEIGH, 1977
(D)
1. Y = 4.475 + 3.320 ± 03 - 93.49 ± 032
2. Y = 4.9 - 12 ± 03 R* = .88
I I I •
0.00
0.05
0.10
0.15
0.20
O3 CONCENTRATION, ppm
Figure 7-13. Effects of O3 exposures on winter wheat and field corn yields. O3 concentra-
tion is expressed as 7-hr seasonal mean, o indicates mean of plants in open top
chambers; X indicates mean of plants in ambient air, which were not used in the regres-
sion analysis. (A-D) Data are from Heagle et al., 1979c. Quadratic equations are from
Heagle and Heck, 1980. In Heagle and Heck, 1980 the data are presented as the yield per
four plants; however, in this figure the values were divided by four to express yield on a
per plant basis. All other equations are from Heck et al., 1982. Each point is the mean of
4 plots with 48 plants per plot.
7-114
-------
t-
o>
ij]
Q
LLJ
UJ
(A
260
240
220
200
180
160
CORN (COKER 16)
RALEIGH, 1976
- (E) _
1. Y = 222.91 + 331.11 ± 03 - 3511.99 ± 032
2. Y = 247.8 - 260 ±03 R2 = .65
I
I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
Figure 7-13. (continued) (E) Data are from
Heagle et al., (1979a) with a correction for
the yield at 0.07 ppm (personal communica-
tion, A.S. Heagle). The quadratic equation
(solid line, O symbol) is from Heagle and
Heck, 1980. Data point at the concentration
of 0.07 is different from the original paper;
the correction was based on information
from A.S. Heagle. The straight line equation
(dashed line, A symbol), is from Heck et al.,
1982. In developing the quadratic equation,
the data from Heagle et al, 1979a, were divid-
ed by a factor of 1.045 to adjust the moisture
content (Heagle, personal communication);
for the linear equation the unadjusted data
were used. A indicates an adjusted treat-
ment mean; y indicates the adjusted ambient
plot mean. Each point is the mean of five
plots with eight plants/plot.
7-115
-------
Statistically, the yield responses of the four cultivars are uniform (Heck et
al., 1983).
The effects of 03 on the yield of field corn have been examined in two
studies, but the results from one study have been reanalyzed three times and
have thus been published in four different forms. First presented in tabular
form with means comparison tests (Heagle et al. , 1979a) (Table 7-20), the data
for Coker 16 were subsequently analyzed using quadratic (Heagle and Heck,
1980) and linear (Heck et al., 1982) regression models (Figure 7-13e).
Reductions in seed yield (g/plant) were originally shown to be 4 percent at
0.11 ppm and 16 percent at 0.15 ppm of 0_ when compared to a 0.02 ppm control
(Table 7-20). The quadratic regression predicted a yield increase of 1 percent
at 0.06 ppm and a yield reduction of 3 percent at 0.10 ppm (Figure 7-13e). The
linear equation did not fit the data as well as the quadratic; therefore, it was
not considered. The divergent yield reduction estimates resulting from different
regression models illustrate the need to check the fit of the model to the data
before using the equations to estimate yield reductions. The Weibull equation
predicted yield reductions of 0.3 percent at 0.06 ppm of 0. and 3 percent at
0.10 ppm of 03 (Table 7-19). Heck et al. (1983) also derived Weibull equations
for two other field corn hybrids (Table 7-19). Yield reductions of 5 percent at
0.06 ppm and 23 percent at 0.10 ppm were predicted for Pioneer 3780, and 2 per-
cent at 0.06 ppm and 13 percent at 0.10 ppm of 0, for PAG 397. These yield re-
ductions were significantly greater than for Coker 16. It should be noted that
the Weibull function does not allow for a yield stimulation at low 0_ concentra-
O
tions, because the function has a maximum at zero and decreases with increasing
0- concentrations.
Four cultivars of spinach appeared to be relatively sensitive to 0.,
(Table 7-20). All cultivars exhibited significant yield reductions (35 to
44 percent) when exposed to 0.096 ppm of 0., (7-hr seasonal mean) compared to
a control of 0.024 ppm (Heagle et al., 1979b). Nonsignificant reductions of
4 to 26 percent were noted at 0.056 pprn of 0_ (Heagle et al. , 1979b). The same
data were subsequently subjected to regression analyses (Heck et al., 1982).
Yield reductions predicted from the linear regressions for America, Hybrid 7,
Viroflay, and Winter Bloomsdale, respectively were 19 percent, 18 percent, 21
percent, and 21 percent at 0.06 ppm (7-hr seasonal mean) (Figure 7-14 a-d).
Weibull equations applied to the data predicted 17 percent, 9 percent, 7 percent,
and 16 percent yield reductions, respectively, at 0.06 ppm (Table 7-19) (Heck et
al., 1983). The four cultivars were not significantly different (p = 0.05) in
their responses to 0-,.
01900/A 7-116 4/12/84
-------
ZJV
40
1
» 30
£
O)
0 20
C/3
10
0
I I I
SPINACH (AMERICA)
RALEJGH, 1976
— —
- —
'X,.
^Q*^\
(A) 0
Y = 22.7 - 106 + 03 R2 = .98
-III-
UU
40
1
1 30
o>
0 20
O
i
10
0
I I I
SPINACH (WINTER BLOOMSDALE)
RALEIGH, 1976
— —
_ _
^^
^°V.
(B) 0
Y = 23.3 - 121 +03 R2 = .996
-III-
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
0.00 0.05 0.10 0.15
O, CONCENTRATION, ppm
0.20
50
40
£ -JO
w JO
£
•+-
O)
O 20
O
X
10
T
T
T
SPINACH (HYBRID 7)
RALEIGH, 1976
(O
Y = 42.1 - 193 ±03 R2 = .93
- I I I
50
40
» 30
£
4-
D)
O 20
V)
10
T
T
T
SPINACH (VIROFLAY)
RALEIGH, 1976
(D)
Y = 46.1 - 238 ±03 R2 = .94
I I I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
Figure 7-14. Effects of O3 exposures on spinach and lettuce yields. O3 concentration is
expressed as 7-hr seasonal mean; O indicates mean of plants in open top chambers;
indicates mean of plants in ambient air, which were used in the regression analysis.
(A-D) Data are from Heagle et al., 1979b. Regression equations are from Heck et al.,
1982. Another set of straight line equations is given in Heagle and Heck, 1980. Each
point is the mean of four plots with four quadrants (two to three plants per quadrant)
per plot.
7-117
-------
O>
Q
<
UJ
X
900
800
700
600
500
400
300
200
100
I I
HEAD LETTUCE (EMPIRE)
RIVERSIDE, 1980
h-(E)
Y = 1065.7 - 5978 ±03 R2 = .94
I I I
0.00 0.05 0.10 0.15
O3 CONCENTRATION, ppm
0.20
Figure 7-14. (continued) (E) Data and equations
are from Heck et al., 1982. Each point is the
mean of four plots.
7-118
-------
The impact of (L on the yield of head lettuce was investigated by varying
the amount of ambient 0., filtered from the air to create a series of different
0, exposure levels, and the data were analyzed with a linear regression model
(Figure 7-14E) (Heck et al., 1982). The linear regression model predicted
13 percent and 42 percent yield reductions at 7-hr seasonal mean 0, concentra-
tions of 0.06 and 0.10 ppm, respectively. The Weibull model predicted similar
yield reductions--!? percent (0.06 ppm) and 48 percent (0.10 ppm), the (Table 7-20)
as the linear regression (Heck et al., 1983). At the test plots in southern
California, the ambient 0- (7-hr seasonal mean = 0.106 ppm) reduced the yield
47 percent when compared to a concentration in the charcoal-filtered chamber
(control) of 0.043 ppm. The authors cautioned that the lettuce data should not
be regarded as conclusive. Because there were high winds near the end of the
study that stressed the plants, they were harvested before they reached full
maturity. The yield response of Acala SJ-2 cotton to 0, was evaluated with the
Weibull model (Heck et al., 1983) (Table 7-19). Predicted yield reductions were
18 percent at 0.06 ppm of 0. (7-hr seasonal mean) and 34 percent at 0.10 ppm of 0,.
Turnips were among the more sensitive crops tested by NCLAN (Heck et al.,
1982). Four cultivars were tested. The absolute yields varied by three-fold
among cultivars, with the yield of Shogun and Purple Top White Globe being
especially low (Figure 7-15). The percent yield reductions due to 0_ were
remarkably uniform among cultivars. The cultivar Shogoin exhibited a linear
regression with an edible root fresh weight reduction of 35 percent (0.06 ppm)
compared to a control of 0.014 ppm. More complex plateau-linear models accounted
for significantly more of the variation than the linear models for the three
other cultivars (Just Right, Purple Top White Globe, Tokyo Cross). With 0^
thresholds of 0.038, 0.034, and 0.054 ppm respectively the predicted yield
reductions were 27 percent, 26 percent, and 14 percent at 7-hr seasonal mean
0., concentrations of 0.06 ppm. The threshold value in a plateau-linear model
is a statistical estimate of the 0, concentration that must be exceeded before
there will be a significant effect. The Weibull models predict nearly identical
loss estimates (Table 7-19) and also demonstrate homogeneity among the cultivar
responses to 0., (Heck et al. , 1983). [The turnip yield data should be used with
caution (A.S. Heagle, personal communications -- to be published). Part of the
yield loss was attributed to an acute injury episode from a low concentration of
0. after a period of dark, cool, rainy weather. These data illustrate one of
the problems with the 7-hr seasonal mean as a statistic to characterize the 0,
exposure.]
01900/A 7-119 4/12/84
-------
4tU
15
2
CD
£
£ 10
Ul
cc
u.
l-
O
O
CC 5
0
I | I
TURNIP (JUST RIGHT)
RALEIGH, 1980
__ (A) _
1. Y = 12.9-94 ±03 R2 = .86
2. Y = 10.7 IF 03 < .038
v Y = 15.5 - 127 + 03 IF 03 > .038 R2 = .96
X _p
N£
\\
\^
^^
~~ * "V, ~
V
— I I I —
zu
15
0
^
w 10
LU
CC
u.
H
o
o
5
0
I I I
TURNIP (PUR TOP WH
RALEIGH, 1980
m~
(B)
1. Y = 7.2-49 ±03 R2 = .94
2. Y = 6.0 IF 03 < .034
Y = 8.1 - 60 + 03 IF 03 » .034
JfcivLn
-O*^>
- ^^.
X CK.
w
-III
0.00 0.05 0.15 0.20 0.00 0.05 0.10 0.15
GLOBE)
^—
—
R2 = .99
—
u.2
03 CONCENTRATION, ppm O3 CONCENTRATION, ppm
20
15
^
CD
Lj
$
w 10
Ul
DC
U.
1-
o
O
cc 5
0
I I I
TURNIP (SHOGOIN)
RALEIGH, 1980
— —
— —
(C)
Y = 5.3 - 36 + 03 R2 = .89
~~G>t*>Xv
^^""""^"-^
X ^~~~rr*"Q.
-II I —
20
15
2
O
L|
§
M 10
111
CC
U.
I-
O
O
CC 5
0
1 1 1
TURNIP (TOKYO
RALEIGH, 1980
X ^
~ (D) N
1. Y = 18.1 -116 ±03 R2 = .75
2. Y = 14.8 IF 03 «. 054
Y = 27.0 - 226 ± 03 IF 03 > .054
-III
CROSS)
—
—
*™
R2 = .94
—
0.00 0.05 0.10 0.15 0.20 0.00 0.05 0.10 0.15 0.2
O, CONCENTRATION, ppm
O3 CONCENTRATION, ppm
Figure 7-15. Effects of O3 exposures on turnip yields. O3 concentration is given as 7-hr
seasonal mean, o indicates mean of plants in open top chambers; X indicates mean of
plants in ambient air, which were not used in the regression analysis. (A-D) Data and all
regression equations are from Heck et al., (1982). Each point is the mean of four plots.
7-120
-------
In most of the open-top chamber studies, the potential chamber influence
on the plant response was studied by comparing the yield of plants growing in
open air plots without chambers with the yield from plants grown in chambers
receiving nonfiltered air. No significant chamber effects were noted in any
of the soybean studies (Figure 7-12), the kidney bean study (Figure 7-12), and
the lettuce study (Figure 7-14). However, in the wheat (Figure 7-13) and
turnip studies (Figure 7-15), the plants grew significantly better in the
non-filtered chambers than ambient air plots. In 1979, peanuts yielded more
in the nonfiltered chambers than in ambient air plots, but the difference was
not significant. However, in 1980, the peanut plants yielded significantly
less in the chambers (Figure 7-12). As part of the Weibull model evaluation,
the predicted chamber effect was tested for all crops except spinach, with
much the same results (Heck et al., 1983) (Table 7-19). In the peanut study,
the relationship between the (k concentration and percent yield reduction was
similar in both 1979 and 1980, despite a chamber effect in 1980. It is not
known if the chamber effect modified the 0, exposure response relationships in
the turnip and wheat studies.
As part of an open-top chamber study, Heagle et al., (1983b) compared the
yield of soybean plants growing directly in the soil with plants growing in
pots placed in the soil. Over 2 years, virtually no differences in the percent
yield reduction due to 0~ exposure were noted. Similar comparisons were made
in studies with corn (Heagle et al., 1979a), wheat (Heagle et al., 1979c), and
spinach (Heagle et al., 1979b), and in all of them, the percent yield reductions
due to 0, were similar whether the plants were in pots or directly in the
soil. There was, however, a trend toward lesser sensitivity in pot-grown
plants. The trend of pot-grown plants being less sensitive to 0., than soil-
grown plants is to be expected, because pot-grown plants, are probably sub-
jected to more moisture stress than plants grown directly in soil. In most
field studies in which the plants were grown directly in the soil, the investi-
gators have attempted to provide sufficient water, so that water was not a
limiting factor. This observation makes the results from the following study
more relevant, in terms of typical conditions. Four cultivars of soybean
grown in pots were exposed to 0.10 ppm of 0,. in open-top chambers (Heagle and
Letchworth, 1982). Three of the cultivars (Forrest, Ransom, Davis) exhibited
significant yield reductions that were similar to those estimated from previously'
mentioned studies (Figure 7-12, Table 7-20). One cultivar (Bragg) exhibited a
slight yield increase.
01900/A 7-121 4/12/84
-------
7.4.3.2.1.2 Other field studies. Low concentrations of 0~ added to filtered
air in field chambers induced yield reductions in a variety of plant species
(Table 7-21). Alfalfa exhibited a 49 percent decrease in top dry weight when
exposed to 0.05 ppm of 0~ for 68 days (Neely et al., 1977). Extended (several
weeks) exposures to 0.10 ppm caused yield reductions in alfalfa (Neely et al.,
1977), soybean (Heagle et al. , 1974), sweet corn (Heagle et al., 1972), and
ponderosa and western white pine (Wilhour and Neely, 1977). Stem specific
gravity, an indicator of wood density and quality of several hybrid poplar
clones, was consistently less in response to 0.15 ppm of 0- 12 hr/day for 102
days, but effects on height ranged from slight stimulations in four clones to
a significant reduction in one clone (Patton, 1981).
7.4.3.2.1.3 Greenhouse and indoor chamber studies. The effects of 0_ on
plant yield may be mediated by myriad genetic, cultural, and environmental
factors (see section 5.3). The previously discussed studies have attempted to
quantify plant responses to 0, under ambient or normal environmental and
cultural conditions. Several investigations on the yield responses of plants
to 0,, have been performed under more controlled (to various degrees) conditions
(Tables 7-22, 7-23). These exposures at 0.041 to 0.40 ppm of 03 will be
discussed as they relate to the previous studies.
Ozone caused significant yield reductions in exposures lasting several
weeks (Table 7-23). At 0., concentrations of 0.05 ppm or greater, the response
varied among species. Hybrid poplar cuttings exhibited a 13-fold increase in
leaf abscission in response to 0.041 ppm for 5 months (Mooi, 1980). American
sycamore seedlings exhibited significant 9 percent height reduction (Kress et
al., 1982b), and loblolly pine seedlings showed 18 percent height reductions
(Kress and Skelly, 1982) at 0.05 ppm for 4 weeks. Several species showed no
change in yield due to the 0.05 ppm exposure; however, there was also some
yield stimulation (some significant). In the same hybrid poplar study dis-
cussed above (Mooi, 1980), there was a significant 14 percent increase in
height accompanied by a slight decrease in stem dry weight. Yellow poplar and
white ash seedlings exhibited significant 60 percent and 22 percent increases
in height and total dry weight, respectively (Kress and Skelly, 1982). In
general, slight growth stimulations are more common in hardwood tree species
than in coniferous tree species (Kress and Skelly, 1982) (Table 7-23).
Significant yield reductions were noted for many species exposed to 0.05
to 0.10 ppm of Oo for one to several weeks (Tables 7-22, 7-23). Carnations
O
had significantly fewer flowers and flower buds when grown in air containing
019SY/A 7-122 5/4/84
-------
TABLE 7-21. EFFECTS OF OZONE ADDED TO FILTERED AIR IN FIELD CHAMBERS ON THE YIELD OF SELECTED CROPS
Plant species
Alfalfa
Alfalfa
Soybean
(Dare)
Sweet corn
(Golden midget)
(White midget)
Douglas fir
Jeffrey pine
Lodgepole pine
Monterey pine
0, concentration,
ppm
0.05
0.10
0.05
0.10
0.05
0.10
0.05
0.10
0.10
0.10
0.10
0.10
Percent yield reduction Monitoring1"
Exposure duration from control method
7 hr/day, 68 days 31, top dry wt , 1st harvest; Mast
49* top dry wt , 2nd harvest
17, total protein, top, 1st harvest;
42*, total protein, top, 2nd harvest
32*, total nonstructural carbo-
hydrate (TNC), 1st harvest (top)
55*, total nonstructural car-
bohydrate (TNC), 2nd harvest
(top)
7 hr/day, 70 days 51*, top dry wt, final harvest Mast
53*, total nonstructural car-
bohydrate (TNC), final harvest
38*, total protein, final harvest
6 hr/day, 133 days 3, seed wt/plant Mast
55*, seed wt/plant
6 hr/day, 64 days 9, kernel dry wt Mast
45*, kernel dry wt
6 hr/day, 71 days 0
6 hr/day, 126 days 6, height; 15, stem dry wt Mast
2, height; 2, stem dry wt
8, height, 8, stem dry wt
0, height; 0, stem dry wt
d e
Calibration Fumigation
method facility
Known 0, FC-CT
source
1% NBKI
Known 03 FC-CT
source,
1% NBKI
2% NBKI FC-CT
2% NBKI FC-CT
Known Oj FC-CT
source,
IX NBKI
Reference
Neely et al. ,
1977
Neely et al . ,
1977
Heagle et al . ,
1974
Heagle et al . ,
1972
Wilhour and
Neely, 1977
-------
TABLE 7-21 (con't) EFFECTS OF OZONE ADDED TO FILTERED AIR IN FIELD CHAMBERS ON THE YIELD OF SELECTED CROPS
ro
0., concentration
Plant species ppm
Ponderosa pine
Shore pine
Sugar pine
Western white pine
Sitka spruce
Hybrid poplar
(252)
(279)
(346)
(W5)
(W87)
Hybrid poplar
(42)
(50)
(207)
(215)
0.10
0.10
0.10
0.10
0.10
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
0.15
, Percent yield reduction Monitoring0 Calibration Fumigation8
Exposure duration from control method method facility Reference
11, height,
2, height;
0, height;
0, height,
0, height,
12 hr/day, 102 days +16, height;
gravity
23, height;
gravity
3, height;
gravity
5, height;
gravity
+19, height;
gravity
12 hr/day, 102 days 25, height;
gravity
58*, height;
gravity
+8, height;
gravity
+17, height;
gravity
21*, stem dry wt
6, stem dry wt
0, stem dry wt
9* , stem dry wt
14, stem dry wt
12*, stem specific UV Known 03 OT Patton, 1981
source
14*, stem specific
6*, stem specific
12*, stem specific
11*, stem specific
8, stem specific UV 'Known 0 OT Patton, 1981
Source
1, stem specific
7*, stem specific
11, stem specific
''Where a column entry is blank the information is the same as above.
+ = an increase above the control
cMast = Mast meter (coulometric); UV = ultraviolet spectrometry
dNBKI = neutral buffered potassium iodide
eOT = open-top chamber; FC-CT = closed-top field chamber
*
Significant at p = 0.05
-------
TABLE 7-22 EFFECTS OF OZONE ADDED TO FILTERED AIR ON THE YIELD OF SELECTED CROPS
Plant species
Pinto bean
Sweet corn
(Golden jubilee)
,L Wheat
rvs (Arthur 71)
en
(Blueboy)
Radish
(Cherry belle)
Radish
(Cavalier)
03
concentration
ppm
0.15
0 25
0.35
0 20
0.35
0.35
0.20
0.20
0.20
0.40
0.25
Exposure duration
2 hr/day, 63 days
3 hr/day, 3 days/
wk, 8 wk
3 hr/day, 3 days/
wk, 8wk
4 hr/day, 7 days
4 hr/day, 7 days
3 hr or 6 hr
3 hr
Percent yield
reduction from control
44 , pod fresh wt
100ng, pod fresh wt
100ng, pod fresh wt
13*, ear fresh wt , 13*,
kernel dry wt;
+1300*, length of ear with
shrivelled kernals
22* kernel dry wt
30*, seed yield, 17*,
kernel wt; 8, % seed set
24, seed yield; 2, kernel wt;
22*, % seed set
6n9, root fresh wt; 6n9,
root dry wt
38ng, root fresh wt; 40ng,
root dry wt
33*, root dry wt (average
of 4 pre- or post-fumi-
Monitoring Calibration Fumigation
method method facility Reference
Mast (not given) Room Hoffman et al . ,
1973
Mast 2% NBKI GH Oshima, 1973
Mast (not given) GC Shannon and
Mulchi, 1974
Chem. Known 0, CH-CSTR Reinert and Gray,
source 1981
Mast (not given) Adedipe and
Omrod, 1974
(Cherry belle)
Beet
0.25
0.20
3 hr
0.5 hr/day, 38 days
1 hr/day, 38 days
2 hr/day, 38 days
3 hr/day, 38 days
gation temperature regimes)
37*, root dry wt (average
of 4 pre- or post-fumigation
temperature regimes)
+9, storage root dry wt
+2, storage root dry wt
40*, storage root dry wt
40*, storage root dry wt
Mast
(not given)
GC Ogata and Maas,
1973
-------
TABLE 7-22 (con't). EFFECTS OF OZONE ADDED TO FILTERED AIR ON THE YIELD OF SELECTED CROPS
Plant species
Potato
(Norland)
(Kennebec)
Pepper
(M-75)
Tomato
~~J (Walter)
ro Cotton
°"' (Acala SJ-2)
Carnation
(White sim)
Coieus
(Pastel rainbow)
Snapdragons
(Rocket mixture)
(Floral carpet formula
mixture)
°3
concentration
ppm
0.20
0.20
0.12
0.20
0.20
0.25
0.25
0.05-0.09
0.10
0.20
0.40
0.10
0.20
0.40
0.10
0.20
0.40
Exposure duration
3 hr/day, every
2 wk, 120 days
3 hr/day, every
2 wk, 140 days
3 hr/day, 3 day/
wk, 11 wk
4 hr/day, 2 day/
wk, 13 wk
6 hr/day, 2 day/
wk, 13 wk, 6 hr/
day, 2 day/wk,
18 wk
24 hr/day, 12 days
23 days
44 days
56 days
2 hr
2 hr
2 hr
2 hr
2 hr
2 hr
2 hr
2 hr
2 hr
Percent yield Monitoring Calibration
reduction from control method method
20*, tuber no.; 25*, (not given) (not given)
tuber wt; 13*, total solids
36*, tuber no. ; 42*,
tuber wt; 20*, total solids
19*, dry wt/fruit; 20, no. Mast UV
mature fruit; 50*, dry
wt/fruit; 53*, no mature fruit
6, fruit fresh wt Chem. Known 0^
source
52*, no. of bolls; 62*, UV UV
fiber dry wt; 55*, no.
of bolls; 59*, fiber dry wt
74*, no. of flower buds Mast (not given)
53*, no. of flower buds
46*, no. of flower buds
100*, no. of normal open
flowers
+3, flower no. Mast (not given)
4, flower no.
8*, flower no.
+1, flower no. Mast (not given)
10, flower no.
9, flower no.
+3, flower no. Mast (not given)
2, flower no.
4, flower no.
Fumigation
facility Reference
GC Pell et al. ,
1980
CH Bennett et al. ,
1979
GH-CSTR Shew et al. , 1982
CH Oshima et al . ,
1979
GH Feder and
Campbell, 1968
CH Adedipe et al. ,
1972a
CH
CH
-------
TABLE 7-22 (con't) EFFECTS OF OZONE ADDED TO FILTERED AIR ON THE YIELD OF SELECTED CROPS
Plant species
Begonia
(Linda)
(Scarletta)
(White Tausendschon)
— I
i — »
rv>
^ Petunia
(Canadian All Double
Mixture)
(Capri)
(Bonanza)
Coleus
(Scarlet Rainbow)
concentration
ppm Exposure duration
0
0.
0
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
10
20
40
10
20
40
10
20
40
10
20
40
10
20
40
10
20
40
10
20
40
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
hr
4,
9,
5,
+5,
+ 3,
8*
5,
10,
10,
0,
4,
7,
7,
6,
14*
+3
8,
10,
+3,
20*
28*
Percent yield Monitoring Calibration1" Fumigation
reduction from control method method facility Reference
flower
flower
flower
f 1 owe r
flower
, f 1 ower
flower
flower
flower
flower
flower
flower
flower
flower
, flower
, flower
flower
flower
flower
, flower
, flower
no
no
no.
no.
no.
no
no.
no.
no.
no.
no.
no.
no.
no.
no.
no.
no.
no.
no.
no.
no.
Mast (not given) CH
Mast - CH
Mast - CH
Mast - CH
Mast - CH
Mast - CH
Mast - CH
Begonia 0.25
(Schwabenland red)
(Whisper-0-pink) 0.25
4 hr/day, 4 times
once every 6 days
4 hr/day, 4 times
once every 6 days
39*, flower wt; (54%
foliar injury)
22*, flower wt, (25%
foliar injury)
Chem.
Chem.
(not given)
GH-CSTR
GH-CSTR
Reinert and
Nelson, 1980
-------
TABLE 7-22 (con't) EFFECTS OF OZONE ADDED TO FILTERED AIR ON THE YIELD OF SELECTED CROPS
Plant species
(Fantasy)
(Renaissance)
(Turo)
"p1 Alfalfa
(_ i (Moapa)
ro
co
Alfalfa
(Moapa)
Pasture grass
(N.Z. grasslands)
(Victorian)
(Austral ian)
Ladino clover
(Till man)
Tall fescue
(Alta)
°3
concentration
ppm
0.25
0.25
0.25
0.10
0.15
0.20
0.10
0.10
0.09
0.09
0.09
0.10
0.10
0.20
0.30
0.40
Exposure duration
4 hr/day, 4 times
once every 6 days
2 hr/day, 21 days
2 hr/day, 21 days
2 hr/day, 21 days
2 hr/day, 21 days
2 hr/day, 42 days
4 hr/day, 5 days/
wk, 5 wk
4 hr/day, 5 days
wk, 5 wk
4 hr/day, 5 days
wk, 5 wk
6 hr/day, 5 days
6 hr/day, 1 day/wk,
7 wk
6 hr/day, 1 day/wk,
7 wk
Percent yield
reduction from control
6*, flower wt; (2%
foliar injury)
55*, flower wt; (15%
foliar injury)
+10, flower wt; (8%
foliar injury)
16* , top dry wt
26*, top dry wt
39*, top dry wt
21*, top dry wt
20*, top dry wt
20*, top dry wt
14*, top dry wt
18*, top dry wt
20*, shoot dry wt; 38*.
shoot total nonstructural
carbohydrate (TNC)
10, dry wt/plant
20, dry wt/plant
significant linear
30, dry wt/plant
Monitoring Calibration""
method method
Chem.
Chem.
Chem.
Mast (not given)
Mast (not given)
Chem. (not given)
Chem. (not given)
Chem. (not given)
Chem. 2% NBKI
UV UV
Fumigation
facility Reference
GH-CSTR
GH-CSTR
GH-CSTR
CH Hoffman et al . ,
1975
CH
GC Horsman et al . ,
1980
GC
GC
GH-CH Blum et al. , 1982
GH-CSTR Flagler and
Younger, 1982a
-------
TABLE 7-22 (con't) EFFECTS OF OZONE ADDED TO FILTERED AIR ON THE YIELD OF SELECTED CROPS
°3
concentration
Plant species ppm
(Fawn) 0.10
0.20
0.30
0.40
--J (Kentucky-31) 0.10
,L 0.20
ro
10 0.30
0.40
Tall fescue 0.10
(Alta) 0.20
0.30
Exposure
6 hr/day,
7 wk
6 hr/day,
7 wk
6 hr/day,
7 wk
6 hr/day,
12 wk
6 hr/day,
12 wk
duration
1 day/wk,
1 day/wk,
1 day/wk,
1 day/wk,
1 day/wk,
Percent yield
reduction from control
regression, r = .98
9, dry wt/ plant
18, dry wt/plant
significant linear
36, dry wt/ plant
regression, r = . 99
13, dry wt/plant
27, dry wt/plant
significant linear
40, dry wt/plant
regression, r = . 98
54, dry wt/plant
+3, top dry wt
19, top dry wt
41, top dry wt
Monitoring Calibration0 Fumigation
method method facility Reference
UV UV CH-CSTR Flagler and
Younger, 1982b
+ = an increase above the control
Chem. = chemiluminescence; Hast = Mast meter (coulombmetric); UV = ultraviolet spectrometry
NBKI = neutral buffered potassium iodide
GH = greenhouse; CSTR = continuous stirred tank reactor; GH=CSTR = CSTR in greenhouse; GC = controlled environment growth chamber; CH = manufactured
chamber other than CSTR or GC; GH-CH = CH in greenhouse; Room = plant growth room.
'Significant at p = 0.05; ng = not given
-------
TABLE 7-23. EFFECTS OF OZONE ADDED TO FILTERED AIR ON THE YIELD OF SELECTED TREE CROPS.
03 concentration
Plant species ppm Exposure duration
Poplar
(Dorskamp)
(Zeeland)
American Sycamore
(16-SYC-19)
(16-SYC-23)
American Sycamore
(16-SYC-19)
-~j
i
£ (16-SYC-23)
O
Sweetgum
American Sycamore
White ash
Green ash
0.041
0.041
0.05
0.05
0.05
0.05
0.05
0.10
0.15
0.05
0.10
0.15
0.05
0.10
0.15
0.05
0.10
0.15
12 hr/day, 5
12 hr/day, 5
6 hr/day, 28
6 hr/day, 28
6 hr/day, 28
6 hr/day, 28
6 hr/day, 28
6 hr/day, 28
6 hr/day, 28
6 hr/day, 28
mo
mo
days
day
days
day
days
days
days
days
Percent yield reduction Monitoring Calibration0
from control method method
+14*, stem length; 12 stem dry wt; Chem.
+1333, no. of dropped leaves; 6, total dry wt
2, stem length; 4, stem dry wt; Chem.
+692, no. of dropped leaves; 0, total dry wt
9*, height growth Chem.
2, height growth
11, height growth Chem.
9*, height growth
+9, height growth; 10, total dry wt Chem.
29*, height growth; 26, total dry wt
45*, height growth; 42*, total dry wt
+4, height growth; 23, total dry wt Chem.
27*, height growth; 61*, total dry wt
21*, height growth; 69*, total dry wt
+12, height growth; +22*, total dry wt Chem.
9, height growth; 9, total dry wt
15, height growth; 17*, total dry wt
2, height growth; 14, total dry wt Chem.
24*, height growth, 28, total dry wt
30*, height growth; 33, total dry wt
NBKI
NBKI
1% NBKI
1% NBKI
Constant
source,
NBKI, UV
Constant
source,
NBKI, UV
Constant
source,
NBKI, UV
Constant
source,
NBKI, UV
Fumigation
facility Reference
GH-CH Mooi ,
1980
GH-CH Mooi,
1980
CH Kress et
al . , 1982b
CSTR Kress et
al . , 1982b
CSTR Kress and
Skelly,
1982
CSTR
CSTR Kress and
Skelly,
1982
CSTR Kress and
Skelly,
1982
-------
TABLE 7-23 (con't). EFFECTS OF OZONE ADDED TO FILTERED AIR ON YIELD OF SELECTED TREE CROPS
Plant species
Willow oak
Sugar maple
Yel low poplar
--j
i
i — »
*•*•> Yellow poplar
Cottonwood
White ash
White ash
Black cherry
03 concentration,
ppm Exposure duration
0.05 6 hr/day, 28 days
0.10
0.05 6 hr/day, 28 days
0.10
0.15
0.05 6 hr/day, 28 days
0.10
0.15
0.10 12 hr/day, 48 days
0.10
0.10
0.10 4 hr/day, 1 day/wk,
0.20 9 wk
0.30
0.40
0.10
0.20
0.30
0.40
Percent yield reduction
from control
1, height growth; 2, total dry wt
4, height growth; 11, total dry wt
5, height growth; 2, total dry wt
+8*, height growth; 7, total dry wt
12*, height growth; 41*, total dry wt
+60*, height growth; +41, total dry wt
+8, height growth; +5, total dry wt
12, height growth; +18, total dry wt
19 , relative growth rate
59 , relative growth rate
no significant effects
+13, total height; +7, shoot dry wt
0, total height; +5, shoot dry wt
0, total height; 11, shoot dry wt
0, total height; 14, shoot dry wt
+16, total height; +15, shoot dry wt
+5, total height; 4, shoot dry wt
+3, total height; 4, shoot dry wt
28*, total height; 15, shoot dry wt
Momtonngb Ca1lbrationc Fum1gationd
method method facility Reference
Chem. constant CSTR Kress and
source Skelly
NBKI, UV 1982
Chem. CSTR Kress and i
Skelly, 1983
Chem. CSTR
Chem. (not given) CSTR Jensen,
1981a
(not given) (not given) (not given) McClenahen,
1979
(not given) (not given) (not given) McClenahen,
1979
Hybrid poplar
(NS 207 + NE 211)
0.15 8 hr/day, 5 days/wk,
6 wk
50*, dry wt new shoots from terminal cuttings
62*, dry wt new shoots from basal cuttings
(not given) (not given)
GH-CH
Jensen and
Dochinger,
1974
-------
TABLE 7-23 (con't). EFFECTS OF OZONE ADDED TO FILTERED AIR ON YIELD CF SELECTED TREE CROPS
0
Plant species
Hybrid poplar
(207)
Yel low birch
White birch
Bigtooth aspen
^i Eastern cottonwood
i
i-1 Red maple (163 ME)
OJ
IX)
(167 NB)
(128 OH)
Loblolly pine
(4-5 x 523)
(14-5 x. 517)
Loblolly pine
Pitch pine
3 concentration, Percent yield reduction
ppm Exposure duration from control
0.20
0 20
0.25
0.25
0 25
0.25
0.25
0.05
0.05
0.05
0.10
0.15
0.05
0.10
0.15
7 5 hr/day, 5 day/wk, 5,
6 wk 8,
8 hr/day, 5 day/wk, 9,
15 wk
34,
+7,
8 hr/day, 6 wk 18,
32,
37*
6 hr/day, 28 days 6,
6 hr/day, 28 days 18*
27*
41*
6 hr/day, 28 days 4,
13*
26*
he i ght
height
height
height
height
height
height
, height
height growth
, height growth; 14, total dry wt
, height growth; 22*, total dry wt
, height growth; 28*, total dry wt
height growth; 8, total dry wt
, height growth; 19, total dry wt
, height growth, 24*, total dry wt
Monitorinqb 0 , ., . c ,- d
Calibration Fumigation
method method facility Reference
(not given) (not given) CH Jensen,
1979
MAST NBKI GH-CH Jensen and
Masters ,
1975
MAST 1* NBKI CH Dochinger
and Town-
send, 1979
Chem. 1% NBKI CH Kress et
al. , 1982a
Chem. Constant CSTR Kress and
source, Skelly,
NBKI, UV 1982
-------
TABLE 7-23 (con't). EFFECTS OF OZONE ADDED TO FILTERED AIR ON YIELD OF SELECTED TREE CROPS
Plant species
Virginia pine
i — > White spruce
CO
CO
Japanese larch
^concentration, Percent yield reduction Monitoringb Cal ibration<: Fumigationd
ppm Exposure duration from control3 method method facility Reference
0.05
0.10
0.15
0.25
0.25
6 hr/day, 28 days 5, height growth; +2, total dry wt
11, height growth; 3, total dry wt
14, height growth; 13, total dry wt
8 hr/day, 5 day/wk, 5, height Mast NBKI GH-CH Jensen and
15 wk Masters,
1975
+6, height Mast NBKI GH-CH
+ = an increase above the control
Chem. = chemiluminescence; Mast = Mast meter (coulometric); UV = ultraviolet spectrometry
NBKI = neutral buffered potassium iodide
GH = greenhouse; CSTR = continuous stirred tank reactor; CH = manufactured chamber other than CSTR or GC; GH-CH = CH in greenhouse
*Significant at p = 0.05; ng = not given.
-------
0.05 to 0.09 ppm of 03 for 24 hr/day for 12 to 56 days (Feder and Campbell,
1968). Pasture grasses produced less top growth when exposed to 0.09 ppm of
0~ for 4 hr/day for 5 weeks (Horsman et al., 1980). Exposure response equa-
tions were developed for three fescue cultivars under greenhouse conditions
(Flagler and Youngner, 1982a). Based on yield they found that the cultivar
Kentucky 31 showed the largest yield decrease with increasing 03 concentration;
based on these data it was ranked most sensitive and Fawn the least sensitive
of the three. Significant yield reductions (10 percent) were predicted for
each of the cultivars at the following 03 concentrations (ppm): 0.119 Kentucky
31), 0.10 (Alta), 0.11 (Fawn). The cultivars were exposed for 6 hours/day, 1
day/week for 7 weeks. Significant yield reductions have been noted for alfalfa,
(Hoffman et al. , 1975); clover (Blum et al., 1982), and loblolly pine, pitch
pine, sweetgum, American sycamore, and green ash (Kress and Skelly, 1982) when
exposed to 0.10 ppm of Oo for various lengths of time. However, numerous
studies reported no significant effects, and some have reported yield stimula-
tions. Significant yield stimulations in response to 0.10 ppm of 0^ for 6
hr/day for 4 weeks have been noted for sugar maple (Kress and Skelly, 1982).
Ozone concentrations of 0.10 ppm Q3 and greater for several days to weeks
generally caused yield reductions (Tables 7-21, 7-22), although some growth
stimulations were noted at higher concentrations.
7.4.3.2.1.4 Effects of Ozone on Crop Quality. Quality is a broad term which
includes many features such as chemical composition, physical appearance,
taste, and ability to withstand storage and transport. All these features
have economic importance.
Four types of experimental approaches were used to investigate the effects
of Oo or oxidants on crop quality: (1) field experiments in which the impact
O
of ambient oxidants and charcoal-filtered air were contrasted; (2) field
experiments in which ambient oxidant injury was prevented by using an antioxi-
dant chemical spray; (3) field experiments in which 03 was added to ambient or
charcoal-filtered air; and (4) laboratory experiments in which potential
effects were measured by exposing plants to 03<
The effects of ambient oxidants were studied at three different locations
(Riverside, California; Geneva, New York; and Beltsville, Maryland) to deter-
mine their impact on the quality of alfalfa, grape, and soybean (Thompson et
al., 1976b; Musselman et al., 1978; Howell and Rose, 1980). Alfalfa plants
experienced oxidant concentrations greater than 0.08 ppm between 25 and 60
019SY/A 7-134 5/4/84
-------
percent and 0.12 ppm between 5 and 50 percent of daylight hours (measured with
a Mast meter). Plants receiving ambient oxidants exhibited significant (p =
0.05 or 0.01) changes in a number of quality variables in some harvests.
Ambient oxidants decreased crude fiber, p-carotene, and vitamin C; increased
niacin; and had no effect on protein efficiency and nitrogen digestibility
ratios (Thompson et al., 1976b). Grape crops receiving ambient oxidants
suffered a 6 percent reduction in soluble solids (p = 0.05), which would
reduce the value of this fruit for wine (Musselman et al., 1978); however,
ozone concentrations were not measured at the Fredonia, NY site where grape
experiments were conducted. Soybean seed quality exhibited small but signifi-
cant (p = 0.05) changes: protein was increased 2 percent and oil was de-
creased 3.8 percent (Howell and Rose, 1980) when the plants were exposed to
ambient oxidants at 0.08 ppm or greater and at 0.12 ppm or greater for 0.3
percent of the growing season (the experimental conditions for the seed quality
study are reported in Howell et al., 1979). In addition to measuring yield in
terms of biomass, some of the NCLAN studies have examined the quality of the
2
yield. Corsoy soybeans exhibited a significant linear decrease (R = 0.81) in
percent oil content of seeds as the 0,. concentration increased. Concurrently,
there was a significant increase in percentage of protein content with increas-
ing OT concentration (Kress and Miller, 1983). Estimated changes resulting
from a seasonal 7-hr average concentration of 0.10 ppm of CL were a 5 percent
decrease in percent oil content and a 4 percent increase in percentage of
protein content.
Clarke et al. (1983) grew potatoes in ambient air plots in central New
Jersey; half the plants were treated with the antioxidant EDU to suppress 0.,
effects. In 1980, the ambient oxidant dose was 110 ppm-hours. Specific
gravity, a quality directly correlated with high quality of processed and
tablestock potatoes, was 0.4 percent lower in non-EDU-treated plants (p =
0.05). In 1978, the ambient oxidant dose was 65 ppm-hours; changes in specific
gravity were not detected. Foster et al. (1983a) found no difference in the
specific gravity or total solids of potatoes exposed to ambient oxidants in
open-top field chambers in California.
Alfalfa plants exposed to 0.10 ppm of 0., (7 hr/day for 70 days) showed an
increased protein and amino acid content per unit area, but a decrease in
total protein and amino acid due to reduced dry matter production (Neely et
al., 1977). Reductions were also noted in the p-carotene and total nonstruc-
tural carbohydrate.
019SY/A 7-135 4/19/84
-------
Small trees from several clones of hybrid poplar have exhibited decreased
stem specific gravity (a measure of wood quality which could result in reduced
wood strength or reduced pulpwood value) when exposed to 0.15 ppm 0~ of for 12
hr/day for 102 days in open-top chambers (Patton, 1981).
A number of investigators have exposed greenhouse-grown crops to con-
trolled doses of DO and subsequently measured the impact on crop composition.
These results serve more as indicators of potential impact than predictors
that effects would occur in a field environment. Results are summarized
below.
Pippen et al. (1975) exposed cabbage, carrot, corn, lettuce, strawberry,
and tomato to intermittent acute doses of 0.,. Ozone concentrations ranged
from 0.20 to 0.35 ppm for 2.5 to 6.5 hr, from 1 to 3 days per week from emer-
gence to harvests. Plants were exposed to 03 for 1.62 to 3.59 percent of the
life cycle, depending on the species. Some of the species studied exhibited
significant (p = 0.05) changes in quality in response to one or more of the 0^
regimes employed. Corn exhibited a decrease in solids, p-carotene, and carbo-
hydrates, but total nitrogen and vitamin C levels increased. The niacin
concentration increased in carrots and strawberries. Solids, fiber content,
vitamin C, and thiamine were all reduced in tomato. Cabbage exhibited signifi-
cant increases in total solids and vitamin C.
When greenhouse-grown potato plants were exposed to 0^ at a concentration
of 0.20 ppm for 3 hr once every 2 weeks throughout the growth period, tubers
exhibited a decrease in percent dry matter which is associated with a decrease
in fluffiness of tablestock potatoes (Pell et al. , 1980). Reducing sugars,
associated with undesirable darkening of potato chips, increased in tubers
harvested from plants exposed to 0.,. Glycoal kaloids, compounds which can
cause a bitter taste in potato tubers, either decreased or were unaffected by
the 03 treatment (Speroni et al., 1981).
The potential of 03 to induce a series of estrogenic isof1avonoids was
investigated in five different alfalfa cultivars (Hurwitz et al. , 1979; Skarby
and Pell, 1979; Jones and Pell, 1981). These biochemicals have been directly
correlated with breeding disturbances in both domesticated and wild animal
species. Coumestrol, daidzein, genistein, and formononetin, all with poten-
tially adverse affects on crop quality, were not detected in greenhouse-grown
alfalfa plants which received 03 concentrations of 0.20 to 0.40 ppm (392 to
784 ug/m3) for 3 hr. Ladino clover, another forage crop, exhibited reduced
total nonstructural carbohydrate and generally increased mineral content
019SY/A 7-136 4/19/84
-------
(except for sodium) when exposed to 0.10 ppm of 0-, (6 hr/day for 5 days) (Blum
et al., 1982).
The impact of 0^ and ambient oxidants on crop quality has important
implications from both health and economic perspectives. A reduction in
nutritional value of food or forage such as reduced vitamin content or precur-
sors to proteins, will be detrimental to the consumer. An adverse effect on a
crop destined for processing, such as grapes for wine or potatoes for chips,
will reduce the economic value of the crop. However, it is, at present,
difficult to completely correlate these effects with the more conventional
measures of 03 effects on foliage and yield.
7.4.3.2.1.5 Effects of Ozone on Plant Reproduction. Ozone has been shown to
affect the reproductive capacities of plants. The flowering and seed produc-
tion of soybean plants was reduced by 03 at 0.10 ppm (6 hr/day, 133 days)
(Heagle et al. , 1974). In sweet corn plants, seed production as estimated by
percentage of ear filled was reduced when the plants were grown in an environ-
ment of 0.10 ppm of 03 (6 hr/day, 64 days) (Heagle et al., 1972). Wheat
plants exposed to 0.20 ppm of 0., (4 hr/day, 7 days) at anthesis exhibited
reduced percent seed set (Shannon and Mulchi, 1974). Reduced seed production
of cotton plants exposed to 0.25 ppm 03 (6 hr/day, 2 day/week, 13 weeks) was
reported (Oshima et al. , 1979). The number of tillers in three tall fescue
cultivars increased slightly as 03 was increased from 0.10 to 0.40 ppm (6
hr/day, 1 day/wk, 7 weeks) Flagler and Younger, 1982a). These data indicate
that OT may decrease the reproductive capacity of plants. The reductions in
seed production suggest an Oo impact on fertilization processes. The observa-
tion that 03 (0.05 ppm for 5.5 hr) reduced pollen germination (40 to 50 percent)
in tobacco and petunia and pollen tube elongation in (Feder, 1968) supports
this conclusion. Ozone also reduced the germination of corn pollen 60 (0.06
ppm) and 70 percent (0.12 ppm), respectively (Mumford et al., 1972). Plants
were exposed to 03 (0.06 or 0.12 ppm for 5.5 hr/day for 60 days) and the
pollen was harvested daily as soon as it was mature and percent germination
could be determined. Because the pollen was harvested as soon as it reached
maturity, it is probable that the pollen was exposed to 03 for only a short
time period.
7.4.3.2.1.6 Relationship between foliar injury and yield loss. Because plant
growth depends on their being functional leaves to conduct the photosynthesis
required for plant growth, various studies have been conducted to determine the
019SY/A 7-137 5/4/84
-------
association between foliar injury and yield for species in which the foliage is
not part of the yield. Some investigations discussed in the 1978 criteria docu-
ment (U.S. Environmental Protection Agency, 1978) demonstrated yield loss with
little or no foliar injury (Tingey and Reinert, 1975; Tingey et al., 1971a);
others demonstrated significant foliar injury not accompanied by yield loss
(Heagle et al., 1974; Oshima et al., 1975). Many other studies can be cited
to illustrate the inconsistency of the relationship between foliar injury and
yield loss when the foliage is not the yield component. Significant yield
reductions with no foliar injury have been noted for American sycamore (Kress
et al., 1982b), loblolly and pitch pine (Kress and Skelly, 1982), carnations
(Feder and Campbell, 1968), and petunia and coleus (Adedipe et al., 1972a).
With red maple seedlings, foliar injury was directly correlated with subsequent
height reductions (Dochinger and Townsend, 1979). The relative sensitivities
of two potato cultivars were reversed when judged on yield reductions rather
than foliar injury (Pell et al., 1980). In a study comparing the effects of
long- and short-term exposures, a long-term exposure (0.15 ppm for 8 hr day, 5
days/week for 6 weeks) resulted in 75 percent foliar injury and 50% growth
reduction, whereas the short-term exposure (1.0 ppm for 2.4 or 8 hr) resulted
in 70 percent foliar injury and no growth reduction (Jensen and Dochinger,
1974).
All of the studies in Table 7-20 reported foliar injury as well as yield
responses. For field corn, foliar injury response was at lower concentrations
than the yield effects, but with increased 0^ concentration, the percent yield
reductions became greater than the percent foliar injury (Heagle et al. ,
1979a). For wheat, the increases in foliar injury were generally accompanied
by decreases in yield, but foliar injury was not a good predictor of yield
reduction. For example, at 0.06 ppm, the wheat cultivar Coker 47-27 had 5
percent foliar injury (compared to the control) and 11 percent yield reduction,
but the cultivar Holly had 6 percent foliar injury and 1 percent yield reduc-
tion (Heagle et al., 1979c). There were no obvious relationships between
foliar injury and shoot fresh or dry weight of spinach (Heagle et al. , 1979b).
In the soybean study also, relative cultivar injury did not predict relative
yield response (Heagle and Letchworth, 1982). The cultivars Bragg and Ransom
had equal amounts of foliar injury (35 percent) when exposed to 0.10 ppm of
DO, but Bragg yield increased 4 percent and Ransom yield decreased 20 percent.
019SY/A 7-138 5/4/84
-------
The lack of correlation between foliar injury and yield reduction for
many crops should not be surprising. Plants have evolved with a reserve
capacity to cope with some level of stress, for example a plant species may
develop more leaf area than that needed for maintaining yield. Therefore 0^
would not be expected to reduce plant yield unless its effects were sufficiently
great to make some process limiting for plant yield. Yield would also be
reduced if Og directly impacted the process limiting growth. Unless either of
these two conditions are achieved, the plant may display a biological (phyto-
toxic) response to 0^ but the yield would not be impaired. However, for
plants in which the foliage is the marketable portion (either for food or
ornamental use) a phytotoxic impact on the foliage may reduce the yield without
the plant weight being altered. These concepts imply that not all impacts of
03 on plants are reflected in growth or yield reductions. Also CL would not
impact plant growth or yield unless it made some process more limiting for
growth or yield than the environmental factors that currently were controlling
growth. These conditions suggest that there are combinations of 03 concentra-
tion and exposure duration that the plant can experience which will not result
in visible injury or reduced plant growth and yield. Numberous studies of
many plant responses have demonstrated combinations of concentration and time
that did not cause a significant effect.
Ozone can decrease the yield of a variety of crops. In the field, ozone
addition studies performed primarily in open-top chambers provide the closest
simulation of ambient conditions. The data show that yields of soybean,
kidney bean, peanut, winter wheat, turnip, spinach, cotton, and lettuce de-
creased with increasing 03 concentrations. Ozone concentrations (7-hr seasonal
mean) currently occurring in ambient air (0.042 to 0.056 ppm) are estimated to
cause up to 26 percent yield decrease of these crops. Of the crops studied by
NCLAN (and similar studies), cotton, spinach, turnip, peanut, lettuce, and
soybean are the most sensitive. Winter wheat and kidney bean appear to be
somewhat less sensitive. Field corn is relatively tolerant.
It is more difficult to extrapolate data from studies conducted under
more controlled conditions (greenhouse, growth chamber) to field conditions,
except when plants are normally grown under these conditions (e.g., flower
crops). However, the more controlled chamber data can serve to strengthen the
demonstration of 0, effects in the field. Concentrations of 0.05 ppm of 0,,
in extended or repeated exposures, have been shown to cause yield reductions
019SY/A 7-139 5/4/84
-------
in some species or cultivars, no effects in others, and increased yield in
others. Concentrations of 0.10 ppm and above appear to more consistently
cause yield reductions, although exceptions can be found (Tables 7-21, 7-22,
7-23).
The impact of 0- on crop quality has important implications from both
health and economic perspectives. A reduction in nutritional value of food or
forage, such as reduced vitamin content or fewer protein precursors, can be
detrimental to the consumer. An adverse effect on a crop destined for pro-
cessing (e.g., grapes for wine or potatoes for chips) will reduce the economic
value of the crop. It is, at present, difficult to completely correlate these
effects with the more conventional measures of 03 effects on foliage and
yield.
7.4.3.2.2 Biomass and yield responses from ambient exposures. Determination
of the effects of ambient air pollutants directly shows the impact of existing
air quality on plant yield in the environment. Two basic types of studies are
used to describe the effects of ambient exposures on plants. In one type,
field observations are used to develop an association between 0, exposure and
plant response (growth or yield reductions or mortality). In the other type,
the difference between plant yield in charcoal-filtered air and in ambient air
(it may contain a single major pollutant or several) is used to indicate the
impact of the pollutant; some type of exposure chamber is required for these
studies. In either case, plants are exposed to pollutant concentrations at
the frequency of occurrence found in the ambient air. When only a single
pollutant is present and/or the study is conducted at a single location, the
interpretation of the results is simplified. However, when the studies are
conducted at different locations, differences in climatic and edaphic condi-
tions, in addition to the pollutant time series that may influence the results
and complicate the interpretation, can occur.
The previous criteria document (U.S. Environmental Protection Agency,
1978) reviewed the effects of 03 in ambient air (Table 7-24). These studies
utilized charcoal filtration in greenhouses or open-top chambers or simply
correlated effects with the ambient 03 concentrations. Leaf injury (sweet
corn, tobacco, potato), yield reductions (citrus, grape, tobacco, cotton,
potato), and quality changes (grape) were documented. It was concluded that
ambient oxidants were causing decreased plant growth and yield.
More recently, studies have also been conducted to evaluate the yield of
plants grown in the presence of photochemical oxidants (ambient air) versus
019SY/A 7-140 5/4/84
-------
TABLE 7-24. EFFECTS OF OXIOANTS (OZONE) IN AMBIENT AIR ON GROWTH, YIELD, AND FOLIAR INJURY IN SELECTED PLANTS3
—i
i
Plant species
Lemon
Orange
Grape,
Zinfandel
Corn, sweet
Bean, white
Tobacco, cultivar
Bel W3
Tobacco, cultivar
Bel W3
Cotton, cultivar
Acula
Potato, 4 .
cultivars
Potato, cultivar
Haig
Oxidant concen-
tration, ppm
>0.10
>0.10
>0.25
0.20-0.35
>0.08
0.02-0.03
>0.05
Ambient
>0.05
0.15
Duration of exposure
Over growing season
148 hr/month average from
March-October, 254 hr/month
average from July-September
Often over May-September
growing season
Hourly maximum for 3 to 4 days
before injury
9 hr
6 to 8 hr
Often over growing season
Over growing season
326 to 533 hr (2 years)
3 consecutive days
Plant response
(reduction from control listed as %)
32, yield
52, yield (leaf drop and other effects)
54, yield (other reductions found)
12, yield (first year)
61, yield (second year)
(increased sugar content)
47, yield (third year)
67, injury (10 cultivars, 5 unmarketable)
18, injury (13 cultivars)
1, injury (11 cultivars)
(Bronze color, necrotic stipple, premature)
abscission)
(Minimal injury)
22 (fresh wt), top
27 (fresh wt), root
7-20, lint + seed (3 locations, 1972)
5-29, lint + seed (3 locations, 1973)
34-50, yield (2 years for 2 cultivars)
20-26, yield (1 year for 2 cultivars)
95, injury (leaf area covered)
Location of study
Cal ifornia
Cal ifornia
Cal ifornia
California
Ontario, Canada
Ohio
North Carol
California
Maryland
Delaware
ina
Table taken from National Reseach Council (1977).
Greenhouse studies.
-------
charcoal-filtered air (Table 7-25). Ozone induced significant yield reductions
in tomato (33 percent at a mean concentration of 0.035 ppm), bean (26 percent
at 0.041 ppm), soybean (average of four cultivars) (20 percent at 03 concentra-
tions > 0.05 ppm), two cultivars of sweet corn (9 percent and 28 percent at 0,
concentration > 0.08 ppm), and forbes, grasses, and sedges (31 percent at
0.052 in 1982; 20 percent at 0.051 in 1980; 15 percent at 0.035 in 1981)
(Table 7-25). The yields of bean cultivars varied from a 5 percent increase
to a 22 percent yield decrease in response to 0., concentrations above 0.06 ppm
03- Mean height of several tree species grown in air containing 0.052 ppm 0.,
was reduced 12 to 67 percent (Table 7-25).
Some of the early ambient air studies in California incorporated multiple
locations sited along an ambient 0^ gradient in a portion of the South Coast
Air Basin, where phytotoxic pollutants other than 03 occur only at extremely
low concentrations (Oshima et al., 1976; Oshima et al., 1977a). These studies
used a modified cumulative 0^ dose (sum of hourly averages above 0.10 ppm for
the exposure period, ppm-hr) as a summary exposure statistic (Table 7-26).
The dose calculation was further modified in the 1977 study by including only
these pollutant concentrations present during daylight hours. In the 1976 study,
the lowest dose was 2.64 ppm-hr, the equivalent of 0.11 ppm for 264 hr (1.26
hr/day) of the 5040-hr season. The highest dose was 55.52 ppm-hr, the equiva-
lent of 0.111 ppm for each hour of the 5040-hr season. Alfalfa yield was
reduced (10 percent) at a seasonal dose of 10.8 ppm-hr. Tomatoes were substan-
tially more sensitive than alfalfa. The tomato yield was reduced at a seasonal
dose of 4.2 ppm-hr.
Oshima (1978) designed and constructed an exposure facility (modified
®
CSTR) by using chambers enclosed by a Teflon film to minimize environmental
alterations. The exposure system used proportional charcoal filtration of
ambient air, thus retaining the ambient exposure properties at several pollu-
tant concentrations. Ozone concentrations were expressed as cumulative dose
(sum of hourly averages for the exposure period, ppm-hr) (see Section 7.2.2.1
and 7.4.3.3). Both Oshima (1978) and Foster et al. (1983b) (Table 7-26) were
able to demonstrate yield losses in pot-grown red kidney bean and Centennial
Russet potato, respectively, at low concentrations of ambient 0^. Potato
yield was reduced (10 percent) at a seasonal dose of approximately 9.7 ppm-hr
but a substantially higher dose (>51.6 ppm-hr) was required to impact the
yield of red kidney beans. Many of the ambient concentrations used in both
019SY/A 7-142 5/4/84
-------
TABLE 7-25. EFFECTS OF AMBIENT AIR IN OPEN-TOP CHAMBERS, OUTDOORS CSTR CHAMBERS, OR GREENHOUSE ON THE GROWTH AND YIELD OF SELECTED CROPS
Plant species
Tomato
(Fireball 861 VR)
Bean
(Tendergreen)
Snap Bean (3 cultivars.
Astro, BBL 274, BBL
290)
Soybean (4 cultivars:
Cutler, York, Clark,
Dare)
Forbes, grasses,
sedges
concentration,
ppm
0.035
(0.017-0.072)
0.041
(0.017-0.090)
0.042
>0.05
0.052
0.051
0.035
Exposure duration
99 day average (0600-2100)
43 day average (0600-2100)
3 mo average (0900-2000)
31% of hr between
(0800-2200) from late
June to mid-September
over three summers, 5%
of the time the concen-
tration was above 0.08 ppm
8 hr/day average (1000-
1800), April -September,
1979
1980
1981
Percent
reduction Location
from control of study
33*, fruit fresh New York
weight
26*, pod fresh wt,
24*, number of pods
1, pod weight Maryland
20*, seed wt; 10*, Maryland
wt/100 +2, % pro-
tein content, 4%
oil content
31, total above Virginia
ground biomass
§
20, total above Virginia
ground biomass
15 total above
ground biomass
Monitoring Calibration
method3 method
Mast NBKI
Mast NBKI
(not given) (not given)
Mast NBKI, known
03 source
Chem Known 03
source,
UV
Chem
Fumigation
facility Reference
OT MacLean and
Schneider,
1976
OT
OT Heggestad
and Bennett,
1981
OT Howell et
al. , 1979
Rose, 1980
OT Duchelle et
al. , 1983
Skelly et
al. , 1982
-------
TABLE 7-25 (con't) EFFECTS OF AMBIENT AIR IN OPEN-TOP CHAMBERS, OUTDOORS CSTR CHAMBERS, OR GREENHOUSE ON THE GROWTH
AND YIELD OF SELECTED CROPS
Plant species
Snap bean
(Gallatin 50)
(BBL 290)
(Astro)
(Astro)
Snap bean
(Gallatin 50)
(BBL 290)
(BBL 274)
concent rat i on ,
(ppm) Exposure duration
>0 06 Average 170 hr over 60
days exposure (1972-1974)
(6 crops)
>0.06 Average 170 hr over 60
days exposure (1972-1974)
(6 crops)
>0 06 Average 170 hr over 60
days exposure (1972-1974)
(6 crops)
>0.06 Average 160 hr over 60
days exposure (1975-1976)
(2 crops)
>0.06 Average 160 hr over 60
days exposure (1975-1976)
(2 crops)
>0.06 Average 160 hr over 60
days exposure (1975-1976)
(2 crops)
>0 06 Average 160 hr over 60
days exposure (1975-1976)
Percent
reduction
from control
+5, pod fresh
wei ght
14*, pod fresh
wei ght
3, pod fresh
weight
6, pod dry weight
+1, pod dry weight
10, pod dry weight
22*, pod dry weight
Location
of study
Maryland
Maryl and
Maryland
Mary 1 and
Maryland
Maryland
Maryland
Monitoring Calibration
method method
Mast 1% NBKI,
Chem
Mast 1% NBKI ,
Chem
Mast 1% NBKI,
Chem
Mast 1% NBKI,
Chem
Mast 1% NBKI
Chem
Mast 1% NBKI
Chem
Mast 1% NBKI
Chem
Fumi gati on
faci 1 i ty
OT
OT
OT
OT
OT
OT
OT
Reference
Heggestad et
al. , 1980
Heggestad et
al , 1980
Heggestad et
al. , 1980
Heggestad et
al , 1980
Heggestad et
al , 1980
Heggestad et
al , 1980
Heggestad et
al. , 1980
(2 crops)
-------
TABLE 7-25. (con't).
EFFECTS OF AMBIENT AIR IN OPEN-TOP CHAMBERS, OUTDOORS CSTR CHAMBERS, OR GREENHOUSE ON THE GROWTH
AND YIELD OF SELECTED CROPS
^J
1
1 — >
en
Plant species
Sweet corn
(Bonanza)
(Monarch Advance)
concentration,
ppm Exposure duration
>0.08 58% of hr (0600-2100)
between 1 July and
6 September
0.08
Percent
reduction Location Monitoring
from control of study method
9*, ear fresh wt; California Mast
10*, no. seeds/ear
28*, ear fresh wt;
42*^, no. seeds/ear
Calibration Fumigation
method facility1"
UV OT
Reference
Thompson et
al. , 1976
chem = chemi luminescence; Mast = Mast oxidant meter (coulombmetric); UV = ultraviolet spectrometry.
NBKI = neutral buffered potassium iodide; UV = ultraviolet spectrometry.
COT = open-top chamber; CSTR = continuous stirred tank reactor.
*significant at p = 0.05; ng = not given.
§28*, total above ground biomass -- 3 yr average -- NF and open plot versus CF a significant at p = 0.05
-------
TABLE 7-26. EXPOSURE-RESPONSE FUNCTIONS RELATING OZONE DOSE TO PLANT YIELD3
Dose (ppnrhr) for
predicted 10% .
Plant species Yield equation Yield reduction Reference
Alfalfa0 y = 162.4 - 1.5 x Dose 10.8 Oshima et al., 1976
(Moapa 69)
Tomato0 y = 9.742 - 0.23 x Dose 4.2 Oshima et al., 1977a
(6718VF)
Potato y = 1530 - 15.8 x Dose 9.7 Foster et al., 1977a
(Centennial Russett)
Bean0 y = 306.7 - 33.33 x log x Dose >51.6 Oshima, 1978
(Red Kidney)
aThe studies were conducted in California and plants were exposed to ambient 03.
For Alfalfa and tomato the hourly averages above 0.10 ppm were summed to compete the seasonal dose. For
potato and bean hourly average 03 concentrations for the duration of the study were summed to complete
seasonal dose.
°The original equation was based on pphm-hr but for this table the regression coefficient was converted
to ppm-hr for consistency with the data in the rest of the chapter.
-------
studies were equivalent to ambient concentrations in cleaner regions of Cali-
fornia and the eastern United States.
Another approach to estimating the effects of ambient CL has been the use
of ECU, an antioxidant (Clarke et al., 1983; Foster et al., 1983a). EDU can
protect plants from the effects of CL (see Section 7.3.2.2.2). By using this
experimental approach, plants may be grown under completely normal field
conditions without potential chamber effects. However, there is the potential
for effects of other non-oxidant-type pollutants and the possibility of a
direct EDU effect on yield. Foster et al. (1983a) determined that EDU applied
in a greenhouse in the absence of CU had no effect on yield of Centennial
Russet or White Rose potatoes. EDU-treated Centennial Russet plants exposed
to ambient air yielded 19 percent more marketable yield than plants exposed
to ambient photochemical oxidants but treated with EDU. White Rose yields
were unaffected by EDU treatment. Ambient CL concentrations were not reported
for either study.
Several studies have measured various plant effects and attempted to
describe associations between ambient CU and 0, injury symptoms or yield
responses. Oxidant-induced changes in forest ecosystems of California, Vir-
ginia, and Utah are discussed in Chapter 8. Some specific references to these
and other areas follow. Increasing Cu sensitivity of ponderosa pine has been
correlated with insect-induced mortality (Cobb and Stark, 1970). Over a
3-year period, 24 percent of 150 study trees died, of which 92 percent had
exhibited severe foliar 0^ symptoms. No trees classed as healthy or slightly
symptomatic died. In a mixed-conifer stand in the San Bernardino Mountains,
radial growth for the 30-year period 1945 to 1975 decreased an average of 34
percent, 1 percent, and 4 percent in areas with severe, moderate, and no
injury, respectively (Kickert et al., 1977). Concentrations of 0, that "com-
monly exceeded 0.10 ppm" have been associated with foliar injury and defo-
liation.
Reduced growth of O^-sensitive eastern white pine appears to be attribut-
able to reduced foliar biomass, which results from shortened needles and
premature needle loss (Mann et al., 1980). The annual radial growth was
reduced 50 percent. The reduced foliar biomass and foliar symptoms were
associated with several episodes of Cu above 0.08 ppm. White pines exhibiting
relatively severe symptoms (chlorosis, tipburn, short needles, premature de-
foliation) experienced a steady decline in average ring width (71 percent over
019SY/A 7-147 5/4/84
-------
15 years) and a loss in capacity for recovery (Mclaughlin et al., 1982). The
annual radial growth of eastern white pine trees exhibiting symptoms of 0~
stress was 28 percent less than that of trees exhibiting few or no symptoms
(Benoit et al., 1982). Field studies in the San Bernardino National Forest in
California showed that during the last 30 years, ambient (L reduced the height
growth of ponderosa pine by 25 percent, annual radial growth by 37 percent and
the total volume of wood produced by 84 percent (Miller et al., 1982).
The research presented in this section demonstrates that ambient 0^ in
many areas of this country can reduce plant yield. Although the most severe
effects appear to occur in the South Coast Air Basin of California and the
San Bernardino Mountains, areas with high ambient 03 concentrations, other
agricultural areas in the nation are impacted as well. Data presented in the
1978 criteria document (U.S. Environmental Protection Agency, 1978) suggested
that ambient (L reduced yields for orange (54 percent) grape (47 to 61 percent)
and cotton (5 to 29 percent). Also, the yield of potatoes growing in the East
were reduced 20-50 percent by ambient 0.,. More recent research indicated
similar yield reductions are still occurring throughout the country from
ambient 03 exposures. Recent open-top chamber studies have demonstrated
losses in tomato (33 percent), bean (26 percent), soybean (20 percent), snap-
bean (0 to 22 percent), sweet corn (9 percent), several tree species (12 to 67
percent), and forbes, grasses, and sedges (9 to 33 percent). Still other
chamber studies have shown yield reductions in potato (42 percent) exposed to
ambient photochemical oxidants. The use of chemical protectants such as (EDU)
has demonstrated yield losses in potatoes ranging from 2 to 31 percent.
Correlations of plant yield with ambient 0-, concentrations based on either an
Oo gradient or differential cultivar or species sensitivity have been used to
predict ambient yield losses in alfalfa (53 percent), tomato (22 percent) and
ponderosa and white pines.
7.4.3.3 Exposure-Response Relationships (Empirical Mode1s)--Empirica1 exposure
response models are mathematical functions that describe a relationship between
pollutant exposure and a biological response. These models are very useful
because the entire relationship defined between the range of exposures is
quantitatively defined. This desirable property differentiates the models
from the results of descriptive designs described in Section 5.4.3.2. In
addition, empirical models are useful as research tools because they suc-
cinctly summarize relationships in the form of an equation.
019SY/A 7-148 5/4/84
-------
Empirical response models describing plant yield losses from 0, have two
major uses that are distinctly different in theory and requirements.
1. Models are used for crop production forecasting. The unit used
in the forecasts is yield per unit land area. Because this
forecast's essentially biological errors introduced from aggre-
gative methods and the exclusion of environmental, cultural,
and edaphic variables must be dealt with if model estimates are
to be reliable.
2. Models are used to interface biological systems with economic
models. The units used as a measure of effect in an economic
model are monetary (profit and loss). These models are driven
by economic variables such as input and output substitutions,
supply, demand, and associated price fluctuations, and regional
linkages. Problems of aggregation methods and impacts of
economically important variables are considered in terms of the
economic units. Errors introduced by aggregation and exclusion
of environmental variables also affect the results obtained by
economic models.
The development of empirical models is the first and the least complex
step in their use. It is the application of these models that is most apt to
be misunderstood.
The available empirical models were developed by using various exposure
techniques ranging from ambient gradients to highly controlled laboratory
exposures; therefore they have different constraints on their application.
Additionally, until the emergence of NCLAN (National Crop Loss Assessment
Network) as a multi-site effort to develop credible crop-loss assessments, no
organized effort to standardize developmental methodology had occurred. NCLAN
represents the first organized effort to establish defensible crop-loss esti-
mates on a national scale.
Only one empirical model was discussed in the dose-response section of
the 1978 criteria document (U.S. Environmental Protection Agency, 1978). The
Heck and Tingey (1971) injury model was used to derive tabular and graphic
data predicting (L concentrations for specific amounts of foliar injury for a
number of species. Most other discussion revolved around the limiting value
concept used to relate (k concentrations from the existing data base. Many
empirical models have been developed since the 1978 air quality document was
published, and such models have expanded to the point that they are commonly
used as tools in most areas of air pollution research.
019SY/A 7-149 5/4/84
-------
There are different categories of empirical exposure-response models.
Physiological models generally are used as research tools to summarize relation-
ships and provide a quantitative means of comparing responses. Injury models
predict leaf response at various levels of exposure, and growth models define
biomass accumulation, canopy development, and growth of reproductive organs.
Yield response models focus on the economically or biologically essential por-
tion of plant growth.
7.4.3.3.1 Physiological models. This section is included to provide an
example of the uses of physiological models in basic research, which is the
primary area of their application. Physiological response models are used as
effective research tools in summarizing relationships or allowing comparisons
among species (Tingey et al. , 1976; Coyne and Bingham, 1981). The slope of
linear models offers a convenient means for comparison of plant species or
populations within a species. Physiological processes are particularly amenable
to quantification with functions. Use of these response models fulfills ob-
jectives quite different from those fulfilled by the predictive models required
for yield-loss estimates.
7.4.3.3.2 Injury models. Injury models estimate the magnitude of foliar
injury incurred from pollutant exposures or, in one case, the concentration of
pollutant from the degree of injury (Table 7-27). These models have been used
to compare air quality in different geographical areas (Goren and Donagi,
1980; Naveh and Chaim, 1978). Heck and Tingey (1971) developed a model that
would estimate the 0., concentration required to cause specific amounts of
foliar injury (Table 7-27). This model was the source of tabular and graphic
data presented in the dose-response section of the previous ozone criteria
document (Environmental Protection Agency, 1978).
A major contribution to the evolution of injury models was the model
developed by Larsen and Heck (1976). They presented a mathematical model
based on the assumption that percent leaf injury was distributed lognormally
as a function of pollutant concentration for a specific exposure duration.
This model also has been used for black cherry (Davis et al., 1981) and Hodgson
soybean (Pratt and Krupa, 1981). Both groups of investigators modified the
Larsen and Heck model slightly by using a probit transformation of the dependent
variable.
Nouchi and Aoki (1979) developed injury models for both short-term con-
trolled exposures and long-term ambient exposures with morning glory (Table
7-27). They recognized that foliar injury did not have a linear relationship
019SY/A 7-150 5/4/84
-------
TABLE 7-27. SUMMARY OF MODELS DESCRIBING THE RELATIONSHIP BETWEEN FOLIAR INJURY AND OZONE EXPOSURE
Model
Plant species
Reference
1. y = a + bx
y = injured leaves, area (%)
x = ozone index (ppb x hr)
a = -3.5 (winter), -0.38 (summer),+
-1.85 (fall)
b = 0.0037 (winter), 0.0016 (summer),
0.0015 (fall)
2. P = P (l-e~kt)
P = % injured leaves at time t
P. = equilibrium % of injured leaves
k - constant determined by least squares
^j 3. C = A0 + Atl + A2/t
1 C = ozone concentration
£n A0, A!, A2 = regression coefficients
•—' I = percent foliar injury
t = time of exposure
4. Z = -In Mghr/ln Sg - p Int/lnSg + InC/lnSg
Z = no. of standard deviations that the
percentage of injury is frojnthe
median
C = ozone concentration
t = exposure duration
Mghr = geometric mean concentration
Sg = standard geometric deviation
p = slope of the line on a logarithmic
scale.
5. Model 5
Probit (y) = 1.3 Inc + 0.49 Ind + 0.77
where
c = concentration in ul/1
d = duration in hr
y = % leaf surface injured
Tobacco Bel-W3
Winter R2 = 0.94
Summer R2 0. 98
Tobacco Bel-W3
No correlation coefficient
available
Selected species
Range of R2 = 0.85 to 0.35
Selected species
Range of R2 = 0.96 to 0.58
Soybean cv. Hodgson
R2 = 0.84
Goren and Oonagi , 1980
Naveh and Chaim, 1978
Heck and Tingey, 1971
Larsen and Heck, 1976
Pratt and Krupa, 1981
-------
en
no
TABLE 7-27 (con't). SUMMARY OF MODELS DESCRIBING THE RELATIONSHIP BETWEEN FOLIAR INJURY AND OZONE EXPOSURE
Model
Plant species
6. Model 5
PIF = 0.2174 + 2.2457 Inc + 2.1378 Int
where
c = concentration in ul/1
t = duration in hr
PIF = Probit mean proportion of injured
foliage/plant
Black cherry
R2 = 0.77
7. Short-term controlled fumigations
S = n InD + K
where ,
D = (C x t) and S is in the range
0 to 1 fa
S = plant injury degree
C = concentration in ppm
t = exposure duration in hr
m = constant
n = constant
K = constant
S = 0.278 InO + 0.999
Morning glory
R2 = 0.97
Morning glory
R2 = 0.70
872
Reference
Davis et al., 1981
Nouchi and Aoki, 1979
Nouchi and Aoki, 1979
8. Ambient conditions
S = n InD + A InD' + K'
where ,„
D = 1C m/n b
S - plant injury degree
C. = hourly average concentration at
1 the ith hour in ppm
A InD' = contribution to the injury
on the day due to the effects
of oxidant dosage up to the
previous day
A = constant
K' = constant
S = 0.278 InD. + 0.041 (InD. , + InDi-o + lnDi-3) + 1"
J J J «J
Following information relates to model 1.
aHalf the accumulating sum of average hourly 03 concentration between the first value > 40 ppb and the
last value £ 40 ppb.
Plant injury degree = (1% damaged leaf per leaf)/! area of the leaves that can be damaged to the maximum
degree.
-------
with the conventional dose statistic (concentration x time) and developed a
powered dose (dose raised to some power) for the acute exposure model. Further,
Nouchi and Aoki included a factor in the ambient model that incorporated the
time-dependent contribution of previous 0^ exposures and modified the dose
expression to account for the long-term variable exposures that characterize
ambient CL episodes. These investigators were the only group that attempted to
O
account for the effects of previous 0- exposures on foliar injury in their model.
7.4.3.3.3 Growth models. Only a few empirical growth models quantify 03~
induced alterations in biomass accumulation and assimilate partitioning.
Oshima et al. (1978; 1979) developed growth models for parsley and cotton and
later refined the cotton model (Oshima and Gallavan, 1980). Growth models are
used primarily for research purposes and are included in this report only as
an example to indicate progress in quantifying 0., growth responses.
7.4.3.3.4 Yield and loss models. Yield models are the most sought after and
most difficult models to develop. These models are necessary for estimates of
production and economic loss because they relate yield directly to pollutant
exposure. The number and quality of yield models is increasing rapidly because
of increased interest and the NCLAN program. Existing models are summarized
in Table 7-28. A more detailed discussion of actual yield responses that were
derived from many of these studies is presented in tabular and graphic form
in Section 7.4.3.2.
Oshima and his coworkers developed predictive models to estimate yield-
losses from 0- within California. Using an ambient 0~ gradient in southern
California, Oshima et al. (1976) developed both yield and yield-loss models
for a clone of Moapa 69 alfalfa (Table 7-28). Multiple-regression techniques
were used to test the relative contributions of 03 and other meteorological
variables to changes in alfalfa yield. Ozone was determined to be the greatest
contributor to yield variation, it vastly overshadowed the contributions of
the other tested variables. The 03-yield function was then transformed to a
predictive loss model using the intercept as the zero-loss reference value.
Similar techniques were used to develop an O^-loss model for fresh market
tomatoes (Table 7-28) (Oshima et al., 1977a). This model incorporated the
unique feature of transforming plant yield to economic packing container
units. Tomato fruit yield was predicted as percent loss in marketable con-
tainer units (flats or lugs) based on U.S. Department of Agriculture fruit
size categories. The inclusion of the marketing criteria sharply increased
the proportion of loss.
019SY/A 7-153 5/4/84
-------
TABLE 7-28. SUMMARY OF MODELS OF OZONE YIELD AND LOSS
Model
Crop
Reference
1. a) Total fresh wt. function
y = a + bx y = fresh wt (g/plant)
y = 162.4 - O.OlSx a = intercept
x = ozone dose
(pphm-hr > 10 pphm)
b) Loss function - transformed from la by % loss = (a - wt)/a x 100
% Loss = -1.068 x 10-4 + 9.258 x 10-3x
x = ozone dose (pphm-hr > 10 pphm)
2. a) Marketable fruit
y = [sin(-0.0076x + 84.2816)]2
y = % fruit marketable USDA minimum size
x = ozone dose (pphm-hr > 10 pphm)
b) Yield function
y = 9.742 - 0.0023X
y = container yield based on USDA fruit
size and packing configuration
x = ozone dose (pphm-hr > 10 pphm)
c) Loss function - transformed from 2b by % loss = (a - container yield)/a x 100
% Loss = 0 + 0.0232x x = ozone dose (pphm-hr > 10 pphm)
3. a) y = a + bx
b) y = a + b0x +
4. a) Linear yield function
y = b0 + bjX
y = yield (varies with crop)
x = ozone exposure in seasonal 7 hr/day
mean ozone concentrations (ppm)
a = intercept
b = slope
y = yield (varies with crop)
x = ozone exposure in seasonal 7 hr/day
mean ozone concentration (ppm)
a = intercept
b0 and bj = regression coefficients
y = crop yield (g/plant)
x = ozone exposure in seasonal 7 hr/d
b0 = intercept
bj = slope
Alfalfa cv Moapa 69
R2 = 0.68
Tomato VF 6718
R2 = 0.85
R2 = 0.62
Selected crops
R2 statistics are
not available
Selected crops
range of R2 =
0.99 to 0.65
Oshima et al., 1976
Oshima et al., 1977a
Heagle and Heck, 1980
Heck et al., 1982
-------
TABLE 7-28 (con't). SUMMARY OF MODELS OF OZONE YIELD AND LOSS
Model
Crop
Reference
b) Plateau -
y =
y =
bo
(b0
linear yield function
if x < f
range of R2 =
0.99 to 0.94
c)
Loss function
y = 100 bi (0.025
a
if x > f
y = crop yield (g/plant)
x = ozone exposure in seasonal 7 hr/day
mean concentration (ppm)
f = threshold 7 hr/day mean concentration (ppm)
b0 = intercept
bt = slope
- x)
y = % yield reduction
bl = regression coefficient from function 4a
a = predicted yield from function 4a at 0.025 ppm
7 hr/day mean ozone concentration in g/plant
x = ozone exposure in seasonal 7 hr/day mean ozone
concentration
5. Weibull function
y = a exp [- (x/o) ] + e
y = yield
a = hypothetical maximum yield at 0 ozone
x = ozone dose in seasonal 7 hr/day mean ozone concentration in
o = the ozone concentration when yield is 0.37 a
c = dimensionless shape parameter
Selected crops
parameters esti-
timated from
empirical data
Heck et al. , 1983
ppm
6. a) Tuber weight yield function
y=a+bx y = % tuber yield in g/plant
y = 1530 - 15.8D D = ozone dose in ppm-hr
b) Tuber number yield function
y = 34.3 - 0.318D y = tuber yield in number/plant
D = ozone dose in ppm-hr
c) Plant dry matter function
DM = 382 - 3.83D DM = total dry matter in g/plant
D = ozone dose in ppm-hr
Potato cv Centennial
Russet
R2 = 0.77
R2 = 0.62
R2 = 0.73
Foster et al., 1983b
-------
Heagle and Heck (1980) developed both linear and quadratic yield models
for cultivars of field corn, winter wheat, soybeans, and spinach (Table 7-28).
The models were derived from open-top chamber experiments and used a seasonal
7 hr/day mean 0~ concentration to characterize 0~ exposures. These models
were the precursors of those developed by NCLAN.
The first published yield models produced by NCLAN (Heck et al. , 1982)
were presented as either linear or plateau-linear functions (Table 7-28). The
plateau-linear function combines two linear functions; the first with a slope
of zero, depicting no response, and a second with a measurable slope. The
intersection of the two functions can estimate a threshold value. A loss
model was developed with the yield at 0.025 ppm (seasonal 7 hr/day mean 0.,
concentration) as the reference zero-loss value. Yield functions were devel-
oped from open-top chamber data obtained by the regional research laboratories
participating in the NCLAN program. Each model was developed with a standard-
ized method monitored by a quality-control program. Yield-loss models were
developed for cultivars of corn, soybean, kidney bean, head lettuce, peanut,
spinach, turnip, and wheat. Some models included in this publication were
generated from earlier experiments that involved the corn, wheat, and spinach
models of Heagle et al. (1979a, 1979b, 1979c).
Recently, Heck et al. (1983) used a 3-parameter Weibull function to model
NCLAN yield losses (Table 7-28). The Weibull function was selected because it
could be used to represent a variety of functional forms, its parameters could
be interpreted to be biologically meaningful, and it offered a method of
summarizing species responses by developing a common proportional model. The
Weibull modeling approach was subsequently used with NCLAN data previously
modeled with linear, plateau-linear, or quadratic functional forms (Heck et
al., 1983). In addition, a comparison of crop-loss estimates from the Weibull,
linear, and plateau-1inear models was completed using production estimates to
project economic surplus figures for the Corn Belt (Ohio, Indiana, Illinois,
Iowa, and Missouri). This comparison used a regional approach with relevant
units (economic surplus) but did not address the impact of other regions or
economic adjustments characteristic of more sophisticated estimates.
Foster et al. (1983b) produced yield and plant dry weight functions for
Centennial Russet, an extremely sensitive potato cultivar. These models were
developed using an ambient exposure facility composed of a series of large
Teflon® chambers with 0,, exposure controlled by proportional filtration of
ambient Q.,.
019SY/A 7-156 5/4/84
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A multi-point crop-loss technique was developed (Teng et al. as reported
in Benson et al. , 1982) and used to assess the impacts of 0«. Previously the
multi-point models had been used to predict biotic yield losses (resulting
from biotic pathogens) but the authors further refined this technique by
summing daily multi-point loss models over a season to arrive at a seasonal
loss for alfalfa (Table 7-29). When single harvest crops such as corn, wheat,
and potato were used, the authors divided the seasonal exposure into 12 time
steps and regressed final harvest on the exposure steps. However, this appli-
cation of the model was seriously flawed because only one time series of 0,
•3
exposures was used. Separating total CL exposure into several time steps
creates a model with several colinear variables. The estimated coefficients
of these variables are unstable. The alfalfa model is important because 0~
O
exposures were represented by multiple variables that indicate specific expo-
sure periods, which may more closely approximate the ambient patterns of
exposure than do the single summary statistics used by other researchers.
Three kinds of models have been used to describe yield and loss: linear,
plateau-linear, and Weibull functions. These empirical models are intended to
describe the behavior of plants in the absence of a known functional relation-
ship between 0~ concentration and yield. Each type of model has strengths and
limitations. The class of linear models, including straight line and quadratic
equations, is very flexible because it can take on a large variety of shapes
and can be used to approximate other functions and statistical methods for
computing confidence bands (Draper and Smith, 1966). Straight line models are
limited because they allow no curvature and they do not allow threshold levels
below which no yield loss occurs. Quadratic models allow curvature and gradual
changes in slope, but like straight line models, they do not allow plateau
shapes or thresholds. They can, however describe situations in which low
levels of a pollutant stimulate growth but higher levels cause yield reductions.
Two nonlinear models have been used in attempts to describe situations in
which response to 0-. has a threshold. Statistical theory for nonlinear models
is not as well developed as that for linear models; consequently, confidence
bands are not usually fit to nonlinear models. The two nonlinear models
discussed are the plateau-linear and Weibull models. The plateau-linear model
incorporates a threshold value but does not allow curvature of any increase in
yield followed by a decrease. The Weibull model can take on a plateau shape
followed by curved gradual decreases, but this model is limited, because above
zero concentration, no decrease can be preceded by an increase.
019SY/A 7-157 4/19/84
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TABLE 7-29. SUMMARY OF CROP-LOSS MODELS
Model
Loss criteria
00
General models
1. y = f (xti)...
2. Net yield reduction is
Functional models
1. Alfalfa
y = ax + bx2 + ex3
Range of R2 = 0.99 to 0.13
2. Corn
y = axt + bx2 Ix12
R2 = 0.87
y = proportion of yield reduction
x. = dose parameter at time t.
n
I ydt
i
dt = time step
n = maximum number of growing days
y = daily yield loss (fresh wt)
x = Z hourly averages for 1 day
a to c = regression coefficients
y = yield loss based on 100 kernel wt
to x12 = ozone summary statistic for
periods 1 to 12 calculated
as:
N
I [(2 hi/n)24]
i = 1
NA°
NA"
Loss = 1.0 - Biomass at site (x)
Biomass at control site
Loss = 10 - 100 kernel yield for (x)
100 kernel yield for control
N
where: N = the number of days in a period (7 days)
hi = ozone concentrations
n = number of hours for which there are
ozone concentrations
a to 1 = regression coefficients
-------
TABLE 7-29. SUMMARY OF CROP-LOSS MODELS
Model
Loss criteria
3. Wheat
y = axt + bx2...gx7
R2 = 0.95
I
I—»
en
Potato
y = axt + bx2
R2 = 0.93
cx3 + dx4
exs
y = yield loss based on 100 seed ct.
Xi to x7 = ozone summary statistics for
periods 1 to 7 calculated
as:
N
I [(i hi/n)24]
i = 1
N
where: N is the number of days in a
period (7)
hi = ozone concentrations
n = number of hours for which
there are ozone concentrations
a to g = regression coefficients
y = yield loss based on tuber wt/plant
to xs = ozone summary statistic for
periods 1 to 5 calculated
as:
N
I [U hi)]
i = 1
Loss = 1.0 - 100 seed yield for (x)
100 seed yield for carbon
filtered treatment
Loss = 1.0 - tuber wt yield for (x)
tuber wt yield for
control treatment
where
: N = the number of days in a period (14 days)
hi = hourly ozone concentrations in 1 day
a to e = regression coefficients
Source: Benson et al., 1982.
aNA = Not available.
-------
All the yield and loss models presented have some common weaknesses for
production forecasting. With the exception of Teng's model (Benson et al.,
1982), none of the models uses a statistic that characterizes the episodic
nature of ambient exposures. The multi-exposure variables used by Teng
(Benson et al., 1982) partition the seasonal exposure into discrete periods,
which account for some of the ambient fluctuations in 0., levels. However, the
temporal periods of exposure were preselected and did not correspond to natural
fluctuations. Only the alfalfa model incorporated the daily variations in
ambient exposures because of the nature of its yield.
An additional weakness common to all the yield loss models relates to
their reference loss criteria. Every model presented uses the experimental
data base to estimate its zero-loss reference value (Section 7.2.5). These
values may bear no relationship to actual zero-loss values that are in the
areas where the models are to be applied for production forecasting.
7.4.3.3.5 Interpreting exposure response models. Interpretation of exposure-
response models requires an understanding of the subjects presented in Section
7.2. The loss models presented in Tables 7-28 and 7-29 were developed by
means of a range of diverse exposure methods, exposure characterizations,
experimental designs, and reference loss criteria. Despite their enormous
differences, the models are mathematically very similar because all but the
Weibull functions used linear or multiple linear regression techniques. All
but the Weibull and quadratic models are linear functional forms, use percent
as the unit of loss, and with the exception of Teng (Table 7-29), use a single
independent variable to represent 0, exposure. These models differ because
they use several independent variables that represent periods of exposure
within a season. For simplicity, these loss models can be represented by a
general function:
Y - a + b(x) (7-2)
Y = yield loss;
a = the regression intercept;
b = regression coefficient; and
x = (L exposure representation.
The variable x represents CL exposure in the general model. The models present-
ed in Tables 7-28 and 7-29 use different statistics to represent the 03 exposure,
019SY/A 7-160 4/19/84
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and as previously stated in Section 7.2.2, these statistics can not be readily
transformed f6r comparison.
The y variable in the general model represents the dependent variable
(yield loss). All models utilize percentages as loss units but calculate the
loss percentages from different reference zero-loss values. Only a single
model (Oshima et al., 1977a) used percentages calculated from commercial
marketing criteria. All other models used biological yield parameters as the
basis for converting to percent loss. The models used are the best available,
and they serve to define the relationship between 0- exposure and yield of
specific crops. These models also serve as criteria used to develop simulation
models designed to generate the coefficients necessary to drive more sophisti-
cated crop production models described by Holt et al. (1979) or serve to focus
research into areas required for rational crop-loss assessments (Teng and
Oshima, 1982).
Use of a loss model requires 0- exposure data in the appropriate format,
good judgment to guide its application, and an appreciation of what the pre-
dicted value represents. The fresh market tomato loss model (Oshima et al.,
1977a) can be used as an example.
Loss = 0.0232 (03 dose) (7-3)
This linear model predicts the loss in marketing container yield caused by
seasonal 03 exposure expressed as cumulative 03 dose greater than 0.10 ppm.
This model was developed from ambient plots along an 03 gradient; therefore,
it is representative of plot level yields. The zero reference level is the
intercept of the yield model in Table 7-29.
This model requires information on ^the cumulative dose of 03 exposure.
Other exposure statistics, such as the seasonal 7-hr daily average used by
NCLAN, cannot be used with this model. By calculating the 03 doses for loca-
tions of interest, plot level predictions can be calculated. Using this
model's exposure statistic, the hourly averages for each hour between 0700 to
2100 that had an 0- concentration greater than 0.10 ppm were summed for the
4-month season to determine the 0., dose.
019SY/A 7-161 5/4/84
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Examples of loss calculations for three hypothetical locations are
Location Ozone dose Predicted loss
1 500 pphm-hr 11.6%
2 1000 pphm-hr 23.2%
3 1500 pphm-hr 34.8%
The predicted values can be used either to estimate losses in tomato production
or to arrive at an estimate of economic crop loss. This distinction must be
made because application of these loss estimates requires different proce-
dures.
Ideally, the model would include an applications validation test wherein
an independent data set of tomato losses at specific 0. doses would be compared
to predicted losses from the model to determine the precision of the estimates.
If the three previously calculated location estimates represent three locations
in the area of interest, the next procedure required is aggregation. The
estimates represent three plots of plants grown in different 03 exposure
conditions. To represent tomato production on a larger scale, the plot level
estimates must be aggregated to estimate field level production, the production
from all fields in the area, and the production from the region that includes
the three fields.
If an economic crop-loss assessment is required, the inputs into the
economic model of choice are the estimates or the loss function. The three
yield-loss estimates provide the basis for an economic transformation to
profit or loss estimates, depending on the factors incorporated into the
economic model. For instance, if they are inputs into the linear program,
representative farm model used by NCLAN, then grower crop substitutions,
alternate cultural practices, and other farm level options would be explored
to determine predicted economic impact. The aggregation methods would be
economically derived and would probably incorporate regional supply and demand,
market price dynamics, and regional linkages. Alternative approaches such as
econometric modeling might be selected in some instances.
Use of a yield-loss model is a process that requires adhering to the
limitations and requirements of the model, having the required data necessary
to drive the model, deciding on the specific application desired, and using
the appropriate step to aggregate estimates to the organizational level required.
019SY/A 7-162 4/19/84
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7.5 ECONOMIC ASSESSMENTS OF OZONE EFFECTS
Previous sections of this chapter discuss the potential negative effects
of 0,, on crop yields. In view of the importance of U.S. agriculture for both
domestic and world consumption of food and fiber, reductions in crop yield
caused by 0., could substantially affect human welfare. The plausibility of
this premise has resulted in numerous attempts to assess, in monetary terms,
the losses or benefits of 03 control. The resulting estimates from these
studies and their validity are discussed in this section.
7.5.1 Economic and Methodological Issues in Performing Assessments
Three procedures are used to assess crop loss caused by 0.,. The ability
to discriminate among these assessment types is important because their data
requirements, informational content, and economic validity differ. The first
method reports crop losses in physical units (reduction in crop production)
for a given geographical unit (e.g., a state or region). These aggregate
physical losses are typically estimated by extrapolating from crop dose-response
models. Examples include the recent work by Loucks and Armentano (1982) and
the "damage" model defined in Moskowitz et al. (1982). This type of assessment
is not discussed further in this section because it does not report economic
losses.
The second type of assessment translates physical losses into a dollar
value by multiplying estimated yield or production losses by an assumed constant
crop price. This procedure is commonly used for obtaining dollar estimates of
0.-induced crop losses. In this section, this approach is defined as the
traditional procedure. As an economic assessment methodology, this approach
has serious conceptual weaknesses that limit the validity of the estimates to
very restrictive cases. Given these conceptual limitations, the pecuniary
loss estimates obtained from the traditional approach should not be viewed as
estimates of the economic consequences of 0,.
The third assessment type uses theoretically justified economic methodol-
ogies; therefore, the assessment may be viewed as economic rather than pecuniary.
Such studies provide estimates of the benefits of 0~ control or the costs of
air quality degradation by accounting for producer and consumer decision-making
and associated responses. Assessments of this type usually address price
changes caused by adjustments in production and the role of producer input and
019SY/A 7-163 4/19/84
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output substitution strategies. Thus, the resulting estimates will more ac-
curately reflect the true economic costs of (L where economic decision-making
and markets are known to operate (e.g., agricultural production).
Dollar loss estimates arising from the last two assessment types are
seldom distinguished in the popular press. However, economists generally
discount the monetary estimates obtained from the traditional type of assess-
ment. Leung et al. (1978) and Crocker (1982) have critiqued this approach.
The assessments of CL-induced vegetation effects reported in the 1978
oxidant criteria document (U.S. Environmental Protection Agency, 1978) use the
simplistic traditional procedure. Examples of this procedure for obtaining
dollar estimates (as cited in the 1978 document) are reported in Table 7-30.
The advantage of such an assessment is the relative ease with which dollar
values may be obtained. This advantage must be weighed against the weak
conceptual basis and the implications this has for the validity of the loss
estimates.
TABLE 7-30. PRE-1978 ESTIMATES OF ECONOMIC LOSSES TO CROPS AND VEGETATION
ATTRIBUTABLE TO OZONE AIR POLLUTION IN THE UNITED STATES
Area
United States
Cal i fornia
Pennsylvania
New Jersey
New England
Year
1963
1963
1970
1963
1969
1970
1971
1972
1961
Estimated
loss, $103
65,000
121,400
33,700
17,500
6,300
9,600
60
950
60
1,100
Comments
First approximation for commercial
crops (SRIa)
Revised SRI report to include
ornamentals
Revised SRI report
Does not include ornamentals or
indirect costs
Revised SRI report
Pa. survey; includes indirect costs
Pa. survey; includes indirect costs
N.J. survey of a limited number
of crops, based on visible injury
N.J. survey of a limited number of
crops, based on visible injury
Mass, survey; primarily crops and
ornamental s
Source: National Research Council, 1977 (Benedict et al. , 1971.
U.S. Environmental Protection Agency, 1978).
aSRl = Stanford Research Institute.
Cited in
019SY/A
7-164
4/19/84
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More comprehensive economic assessments, as exemplified by Leung et al.
(1982), Benson et al. (1982), and Adams et al. (1982), attempt to account for
market impacts of yield reductions. These studies use various techniques, as
determined by the structure of the particular economic problem. However, each
study explicitly measures crop price adjustments caused by changes in produc-
tion (supply). This measurement provides estimates of the economic losses to
both producers and consumers, and thus can suggest possible distributional
consequences of 03- In the Benson et al. (1982) and Adams et al. (1982)
studies, results were compared with estimates obtained (from the same data)
study explicitly measures crop price adjustments caused by changes in produc-
tion (supply). This measurement provides estimates of the economic losses to
both producers and consumers, and thus can suggest possible distributional
consequences of 0~. In the Benson et al. (1982) and Adams et al. (1982)
studies, results were compared with estimates obtained (from the same data)
using the traditional procedure. The differences were moderate to large; the
traditional procedure overestimated losses from air pollution when comparing
an area with clean air to an area with ambient (L. The specific magnitude of
these differences is reported in Section 7.5.3.
The most appropriate measure of economic benefits or losses must be
defined. The economic literature suggests that concepts of economic surplus
are the appropriate measures of the effect of alternative policies on social
well-being under certain restrictive assumptions (Mishan, 1964, 1971; Willig,
1976; Just et al., 1982). Following this reasoning, most economic assessments
of policy issues measure changes in the economic surplus accruing to consumers
(consumers' surplus) and producers (producers' quasi-rents). This surplus is
generally defined as the difference between the total amount consumers would
be willing to pay (or producers would be willing to accept) and the amount
they actually pay (accept). Economic surplus also may be approximated geo-
metrically as the triangle formed by the intersection of conventional demand
and supply curves for the commodity in question. Adams et al. (1982), Leung
et al. (1982), and Adams and McCarl (1984) define economic effects in these
terms. In contrast, the traditional procedure, which ignores price effects
and, implicitly, the demand curve, at best addresses only producer effects,
with no attention paid to the fate of consumers. Thus, conceptually and
empirically, a fundamental difference exists between losses measured by the
traditional procedure and those obtained from more comprehensive economic
assessments.
019PP/A 7-165 4/19/84
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In addition to conceptual differences in methodologies, other factors
also contribute to the wide range of loss estimates in the literature. These
factors, which are primarily technical, are discussed in the following section.
7.5.2 Biological and Practical Issues in Performing Economic Assessments
In the 1978 criteria document (U.S. Environmental Protection Agency,
1978) and in Section 7.2.5 of this document, a distinction is made between
injury (defined as any identifiable and measurable response of a plant to air
pollution) and loss (defined as any measurable adverse effect on the desired
or intended use of the plant). Such a distinction is made because the evalua-
tion of the economic effects of 0, exposure require that the plant be altered
either quantitatively (yield) or qualitatively (market acceptability) so that
its value is reduced. In some cases, exposure may result in injury, such as
leaf necrosis, without affecting yield.
The need to obtain response data in terms of yield rather than injury has
been noted by most economists doing assessment research (e.g., Leung et al.,
1978; Adams and Crocker 1982a). Oshima and coworkers (Oshima, 1974, Oshima et
al., 1976; Oshima and Gallavan, 1980) have worked extensively to develop
methods for evaluating and reporting crop losses in terms of yield reduction.
Oshima1s dose-response function for alfalfa has been used as the basis for
several estimates of the dollar loss resulting from 0, exposure. The recent
work resulting from NCLAN (Heck et al., 1982a) also provides response informa-
tion that can be .easily used for economic assessments. Preliminary NCLAN
response studies are used to derive some of the loss estimates reported in
this document and serve as the primary data source for ongoing assessments.
Biological data on yield response to 03 are important inputs to economic
assessments of crop damage. As noted in Section 7.4.3.3, these data also are
the most difficult biological loss models to develop. Prior to the availa-
bility of NCLAN data, economists and other assessors who needed such informa-
tion either extrapolated data from a narrow set of existing response functions
reported in the plant science literature or estimated these relationships from
secondary data on production and air quality. The credibility of these extra-
polation or estimation procedures and their implications in terms of the
resultant economic loss estimates are ill-defined. Thus, the biological and
air quality data used in these economic assessments, along with misspecified
or overly simplified economic models, must be recognized as a potentially
critical source of uncertainty in resulting loss estimates.
019PP/A 7-166 5/4/84
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Some of the data problems mentioned above have contributed to the highly
divergent loss estimates reported for 0~ (Table 7-31). In addition to the
role that different assessment methodologies play in loss estimates, the
divergences also may be attributed to specific biological and air quality data
problems:
1. Few data or no data on O^induced crop losses for the crops
under investigation. As noted above, lack of such data has
caused assessors to (a) extrapolate from available foliar-
injury estimates to obtain questionable yield-reduction esti-
mates, (b) extrapolate from one crop response for which data
are available to crops where no data exist; and (c) extrapolate
from site and cultivar specific responses to other regions and
cultivars.
2. The use of different crops, regions, and time periods in the
analyses. Crop prices, production levels, and Og exposure vary
geographically and temporally, with resultant changes in loss
estimates.
3. The use of different background ambient levels to portray
"clean air." When used in combination with a standardized
dose-response function, the use of different background levels
provides different yield-reduction estimates and ultimately
different dollar-loss estimates.
4. The difficulty of extrapolating from controlled-chamber experi-
ments to agronomic regions with all the required assumptions
regarding soil type, precipitation regimes, oxidant exposure
patterns, solar radiation levels, and interactions among these
edaphic and climatic variables.
5. The use of different measures of dose or exposure. The recent
NCLAN experiments standardize dose as the seasonal 7-hr average
in parts per million. Other researchers use cumulative dose
(e.g., hours of exposure to concentrations exceeding 0.10 ppm)
or some other measure. The statistical link between these
various dose measures and their correspondence to actual levels
of plant exposure need to be better understood.
The impact of the above factors on dollar estimates may be seen in a
brief chronological review of loss assessments. The earliest estimates of
dollar losses were largely subjective because credible data on yield losses
were not available, and the traditional procedure for calculating dollar
losses was used. For example, figures of $3 to $4 million in California and
$18 million on the East Coast (National Research Council, 1977) were later
019PP/A 7-167 4/19/84
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TABLE 7-31. SUMMARY OF RECENT REGIONAL OZONE CONTROL BENEFITS ESTIMATES
cr>
CO
Region
Reference
Annual
benefits or
loss estimate,
$ mi 11 ion
Comments
Southern California
Adams et al., 1982
South Coast Air Leung et al., 1982
Basin (California)
Ohio River Basin
Minnesota
Page et al., 1982
Benson et al., 1982
45
93-103
(300)a
278U
(6,960)c
30.5
Corn Belt
Adams and McCarl, 1984 688
Illinois
Mjelde et al., 1984
55-200e
Losses estimated as economic surplus in 1976
dollars for 14 annual crops. Employs
mathematical programming model to compare
0.04 ppm ozone assumption with 1976 ambient
levels.
Losses estimated as economic surplus in 1975
dollars for citrus, avacados, and selected
annual crops. Employs econometric procedures
to compare "clear air case" (no oxidant
pollution) with ambient levels.
Losses estimated as producer losses for corn,
soybean, and wheat in 1976 dollars. Region
includes Illinois, Indiana, Ohio, Kentucky,
West Virginia, and Pennsylvania.
Losses estimated in 1980 dollars for corn,
alfalfa, and wheat under alternative ozone
assumptions. Uses dynamic loss
functions incorporating crop growth stage
and ozone episodes. Farm level dollar losses
obtained from econometric model of national
commodity markets national.
Uses a sectoral model of U.S. agriculture to
record economic effects of changes in yields
of corn, soybean, and wheat because of alter-
native oxidant standards. Benefits include
effects on both consumer and producer of a
federal ozone standard (0.08 ppm).
Uses cost functions to measure effect of ozone
on producers' profits. Aggregate effect over
corn, soybean, and wheat for 4 years assuming
a 25-percent reduction in ambient ozone.
Estimate of direct and indirect losses for entire state.
Estimated annual equivalent loss caused by oxidants.
Present value of losses caused by ozone for 25-year period (1976-2000).
Worst case ozone situation (ignores production effects outside Minnesota). If other regions included in
analysis, worsening of ozone increases total gross returns to Minnesota producers by $67 million because of
inelastic nature of commodity demand.
Range of economic benefits caused by a 25-percent reduction in ozone from ambient levels over a 4-vear period
(1978-1981). v
-------
raised to $500 million on the basis of increased awareness of potential pollu-
tion effects on plants and of additional sensitive species. Starting in 1969,
some states and regions developed estimates of loss caused by oxidant pollution.
Most of these surveys estimated yield reductions on the basis of foliar injury,
and they made no direct assessments of growth or yield, although subjective
estimates of damage were obtained.
The first national assessment (Benedict et al. 1971) used data from
controlled exposure of various crops and data from simulated reaction chambers
to estimate the effects of 0- and other oxidants. This Stanford Research
Institute (SRI) model estimated that the 1969 economic crop loss caused by 0.,
exposure was about $125 million. Increased crop values, better air quality
data, and more complete crop dose-response coverage have raised the dollar-loss
estimates in recent years. Results of the SRI model and other estimates
compiled before 1978 are summarized in Table 7-30; when compared with national
estimates generated from more recent analyses (Table 7-31), a general escala-
tion in dollar estimates is observed.
The relative contribution of better economic methodologies can not be
sorted out y_[s-a-yj_s better biological data. However, in a reanalysis of the
results of Adams et al. (1982), Crocker (1982) suggests that adequate economic
representation may contribute as much as accurate biological data to reliable
measure of benefits. In this particular case, estimates of the ultimate
benefits of air pollution control hinge as much on an adequate representation
of producer and consumer reactions as on the magnitude of the change in biolog-
ical yield. The implication is that an accurate portrayal of both biological
and economic responses is critical. Studies lacking in either category should
be reviewed as incomplete.
7.5.3 A Review of Economic Assessments of Ozone Effects on Agriculture
Both regional and national assessments are found in the post-1978 litera-
ture. While each type of assessment can provide useful information, the
geographical scale has implications for the validity and tractability of
alternative assessment techniques. For this reason, regional and national
studies are discussed separately. Only the third type of methodology (economic
assessment) is presented in the regional review. In the review of studies at
the national level, analyses using both traditional and economic approaches
are discussed. This approach responds to the importance that the popular
019PP/A 7-169 4/19/84
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press normally attaches to any nationwide estimate of pollution damage and the
resultant need to describe any limitations inherent in the underlying analyses.
The emphasis of the critique is on how well the assessments conform to economic
realities. However, the studies also may be lacking in their biological
basis.
7.5.3.1 Regional Loss Estimates. Most of the economic assessments of agricul-
tural losses since 1978 have focused on regional losses. This focus may be
caused by the relative abundance of data on crop response and air quality for
selected regions, as well as by the obvious importance of certain agricultural
regions (e.g., the Corn Belt and California). While estimates of regional
losses are not adequate for evaluation of the national impact of alternative
ozone levels, such studies can provide useful information on alternative
economic methodologies. Also, regional loss estimates may indicate a lower
bound on national losses if that region produces a dominant share of major
commodities (e.g., the Corn Belt for corn and soybean). Finally, regional
studies can measure the effects of CU on the regional economy. Loss or benefit
O
estimates for regional studies are presented in Table 7-31.
Several regional studies have focused on southern California because this
region has high 0, levels and an important agricultural economy. Adams et al.
O
(1982) assessed the impact of CL on 14 annual vegetable and field crops in
four agricultural subregions of central and southern California for 1976 by
using a mathematical programming model of California agriculture. The model
predicted the effects of changed (L levels on the welfare of both producers
and consumers. Ozone-induced reductions in yield were estimated for most
crops from the Larsen-Heck foliar injury models. Foliar injury was then
converted to yield loss using Millecan's "rule of thumb" (1971). A cumulative
dose exposure-response model (Oshima et al., 1976) was used to estimate yield
loss for tomatoes. These yield data, which at best are approximations, were
incorporated into the economic model. This model also included a system of
linear-demand functions used to measure price changes associated with produc-
tion changes. The model was calibrated against 1976 production data to estab-
lish the model's general accuracy. The researchers then estimated the 1976
crop production and price by assuming that the 1976 national ambient air
quality standard, 0.08 ppm, not to be exceeded more than one day per year, had
been achieved.
019PP/A 7-170 4/19/84
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As a percentage of total crop value (about $1.5 billion), the estimated
losses caused by air pollution that exceeded the federal standard were found
to be relatively small--$45.2 million (see Table 7-31). In terms of distri-
butional consequences, meeting the 1976 standard would have increased 1976
agricultural income (quasi-rents) by $35.1 million and consumers' welfare
(ordinary consumer surplus) by $10.1 million. To provide a comparison, the
authors also applied the traditional method of computing losses (multiplying
the estimated difference between actual and potential yield by market price)
and obtained a total estimated loss of $52.5 million. While the empirical
difference between the methods appears small, the traditional procedure mea-
sures only the effects on producers. Thus, if this latter figure ($52.5
million) is compared with the producer loss from the economic analysis ($35.1
million), the difference is approximately a 50 percent greater loss estimate
for the traditional approach.
Leung et al. (1982) estimated 0^ damage to nine annual and perennial
crops in the California South Coast Air Basin. These nine crops represent
about 40 percent of the value of crop production in the region. Crop yields
for 1963 through 1975 were obtained from county agricultural commissioners'
reports of yields realized by farmers. Principal component analysis (PCA), a
technique in which highly correlated variables are replaced with one or two
components that contain most of the information of the original variables, was
used to transform monthly environmental data (e.g. , 0^ concentration, tempera-
ture, relative humidity, and precipitation) into yearly indices. Then yield
was regressed on these indices using linear regression procedures. Finally,
1975 crop-yield reductions were estimated by calculating differences between
actual yields (with 1975 levels of 0.,) and yields predicted at zero-ozone
concentration.
Leung et al. (1982) calculated changes in consumer surplus and producer
surplus to approximate the welfare effects of changes in agricultural supply
caused by air pollution. Estimated 1976 losses of consumer and producer
surplus from 0, exposure were $103 million.
Finally, the estimate of crop loss was subjected to input-output analysis
(which traces the economy-wide effects of changes in a single economic variable)
to determine the indirect impact on related economic sectors in California.
Leung et al. (1982) estimated that the indirect loss of sales caused by 03
damage was $276 million in the study region and $36.6 million in the rest of
019PP/A 7-171 4/19/84
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the state. These figures translate into lost income (value added) of $117
million in the region and $14.1 million in the rest of the state. Associated
employment losses were 9525 person-years (region) and 667 person-years (state).
While the Leung et al. analysis represents an innovative attempt to over-
come some data and statistical problems that have plagued economic assessments
of pollution damage, a number of potential limitations need to be recognized.
First, by assuming a zero background 0, concentration, the anthropogenically
induced economic losses are overstated if the background or biogenic levels
exceed zero level. While the issue of what is a precise background 0., level
is not available in the literature, some researchers have suggested that the
background CL concentration should range from 0.025 to 0.035 ppm (7-hour
seasonal mean). Second, the use of PCA has not overcome the statistical
problems of extrapolation beyond the range of data for some functions as well
as the continued presence of multicollinearity. Finally, given the national
linkages involved in California agriculture, the use of a regional input-output
model for agriculture may be overstating multipliers, and hence influencing
the regional economic effects.
Losses within the Ohio River Basin (Illinois, Indiana, Ohio, Kentucky,
West Virginia, and Pennsylvania) were estimated by Page et al. (1982). The
region is a major producer of corn, soybean, and wheat; it also experiences
oxidant levels that depress crop yields. While the study examined two pollu-
tants, S02 and 0.,, the largest losses (approximately 98%) were attributed to
°3-
The yield reduction data were derived from Loucks and Armentano (1982).
Economic losses were measured at the producer level as changes in producers'
income (quasi-rents) between clean air and ambient 0., levels. The net present
value of 0.,-induced losses across the various loss scenarios for the period
O
(1976 to 2000) is approximately $6.8 billion, or an annual equivalent of $278
million. Most of these losses accrue to the states with the largest agricul-
tural production, Illinois and Indiana. The yield data used to generate these
economic estimates have problems that are similar to those noted earlier, and
they do not conform well to the subsequent experimental data generated within
the NCLAN program.
Benson et al. (1982) provide economic-loss estimates for Minnesota. The
biological basis for the study is summarized in Section 7.4.3.2. The authors
evaluate 0.,-induced crop losses for alfalfa, wheat, and corn through applica-
O
tion of dynamic loss functions that specifically account for crop development
7-172 5/4/84
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and episodic exposure. The loss functions are then evaluated at the county
level with actual or simulated 1980 CL data.
The potential yield losses for each county are aggregated to provide a
statewide crop loss. A national econometric model is then used to convert
yield (production) adjustments for each crop into dollar losses, under two
alternative supply assumptions: (1) 0,, and crop production are unchanged in
areas outside of Minnesota and (2) CL changes nationwide. In the second case,
the analysts account for supply and demand relationships for each crop as
affected by production changes in all regions. The two assumptions gave
highly divergent estimates of losses to Minnesota producers. For example, the
estimated dollar loss attributable to a worst case 0~ level obtained from the
first assumption is approximately $30.5 million in 1980 dollars. But when the
econometric model accounts for price changes resulting from production changes
in all regions, there is a $67 million gain to Minnesota producers in the
short run if 0_ levels increased (in Minnesota as well as other production
areas). This gain is caused by the rise in prices associated with reduced
supply. These results and similar observations from Adams et al. (1982) and
Leung et al. (1982) suggest the importance of using assessment methodologies
that account for regional market linkages and resultant price effects.
Mjelde et al. (1984) estimated the effects of 0., on Illinois cash grain
farms by measuring cost functions for individual farms that experience varying
levels of 0.,. In addition to measuring the direct economic consequences of 03
on farmers' incomes, this analysis demonstrated the methodological utility of
the cost function approach, under some fairly restrictive conditions.
One of the primary objectives of the study was to test whether a meaningful
link could be established between the physical loss estimates obtained under
controlled experimentation and response information inherent in observed
economic behavior (i.e., farmers' cost data). Mjelde et al. (1984) developed
profit and cost functions for Illinois grain farms. These profit functions
were estimated from a large sample of detailed cost and production data for
Illinois farms and incorporate environmental variables (i.e., 0.,, temperature,
and rainfall) as well as the traditional economic variables.
In most specifications, 0., has a negative and significant (at the 5
percent level) impact on profit. When direct production effects of 0^ are
compared with NCLAN results obtained in Illinois, the production responses
appear to be comparable. For a 25 percent increase in 03, it is estimated that
019PP/A 7-173 4/19/84
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output for the three crops would decline 3.3 percent. The same 25 percent
increase using the NCLAN data indicates an 11.7 percent and 3.7 percent
decrease in output for two cultivars of soybean. For two corn cultivars,
output would decline between 1.4 and 0.6 percent. The Dixon et al. (1983)
estimate (3.3 percent) lies between these estimates.
Mjelde et al. (1984) calculated that 0, resulted in an aggregate loss in
profits to Illinois farmers of approximately $200 million in 1980. This
result seems consistent with some previous loss estimates (Heck et al., 1983;
Page et al., 1982). The procedure applied by Mjelde et al. (1984) provides
encouraging preliminary results; however, certain caveats need to be noted.
First, the authors had abundant economic and air quality data. Similarly
detailed data probably would not exist at the national level. In addition, a
number of statistical and estimation problems occurred. Even though some of
these problems were resolved, the stability of the coefficients in several
specifications is suspect and thus reinforces some well-recognized difficulties
that result from using secondary data to statistically sort out the effect of
one environmental variable from among the many that affect yield.
A study of GO effects on Corn Belt agriculture by Adams and McCarl (1984)
uses a mathematical programming model to measure effects of alternative oxidant
standards on producers and consumers. Changes in yields for corn, soybean,
and wheat associated with NCLAN response data provide the basis for regulatory
impact analysis. The results of the analysis suggest that a reduction in
oxidants from the present Federal standard of 0.12 ppm to 0.08 ppm would
provide a net benefit of $668 million. Conversely, relaxing the standard to
0.16 ppm would result in a loss to consumers and producers of approximately
$2.0 billion. The results of this analysis are consistent with distributional
shifts that are associated with changes in supply when the demand is inelastic.
The 0.08 ppm scenario benefits consumers at the expense of producers, whereas
the 0.16 ppm assumption results in the opposite situation.
The authors also performed extensive sensitivity analyses to measure the
effect of different yield data (predicted yield changes) on the economic esti-
mates. The results of these analyses indicate that the effect of the biologi-
cal data on economic estimates varies dramatically. In cases where little or
no prior information on the effects of QS or 03 interactions on a given crop
exists and extrapolations across crops are used to approximate these effects,
the difference between these economic estimates and those economic estimates
019PP/A 7-174 4/19/84
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derived from data generated specifically for the crops in question (e.g., the
NCLAN data) is quite large. Conversely, when some data exist, such as the
NCLAN data for a given crop, and additional response data are generated for
the same crop, the effect of added precision tends to be less important. One
implication of this analysis is that the error within some early economic
estimates that were based on biological responses extrapolated from other
crops or were not cross-checked against experimental data may be quite large.
7.5.3.2 National Loss Estimates. Properly structured national analyses over-
come a fundamental limitation of regional analyses by providing a more compre-
hensive accounting of economic link between regional production (supply) and
national demand. However, national assessments require more data and therefore
are more costly. Moreover, yield loss data become more questionable as they
are extrapolated farther beyond the experiments from which they are derived.
As a result of these difficulties, fewer estimates of oxidant damages exist at
the national level than at the regional level. Several of these national
estimates use the traditional approach to quantify damages.
The principal improvements in current national assessments over those
appearing in the 1978 air quality criteria document (U.S. Environmental Protec-
tion Agency, 1978) include more complete dose-response information for an
increasing number of major commodities and more complete air quality data.
National estimates of 0^ damages are summarized in Table 7-32. As indicated,
the range of damages falls between $1.8 and $3.0 billion. However, such
relative consistency does not imply that this amount is the range of national
agricultural losses; because the analyses are based on somewhat different
crops, yield responses, and alternative assessment approaches.
The recent national estimates of oxidant damages to vegetation include an
updated version of the Benedict et al. (1971) study. This SRI study Ryan
et al. (1981) provides estimates of dollar losses to major agricultural crops
caused by oxidants and S0?. For oxidants, 16 crops with demonstrated oxidant
sensitivity serve as the empirical base. The principal differences between
Benedict et al. (1971) and the SRI effort include the use of a wider range of
dose-response functions drawn from more recent literature, updated data on
crop production from the 1974 Census of Agriculture, and updated data on air
quality and crop prices.
Using alternative response functions and county-level data on air quality
the loss in potential yield is estimated for 531 counties, around the United
019PP/A 7-175 4/19/84
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TABLE 7-32. SUMMARY OF RECENT NATIONAL DAMAGE ESTIMATES FOR OZONE
CTi
Study
Annual
loss
Crops estimates Comments
Institute (1981)
Shriner et al. (1982)
(Office of Technology
Assessment)
Adams and
Crocker (1982b)
alfalfa, and 13
other annual crops
Corn, soybean,
wheat, peanut
Corn, soybean,
cotton
measured in 1980 dollars for 531
counties.
$3.0 billion Losses estimated in 1978 dollars,
measured at producer level.
Assumes a background or clean air
oxidant level of 0.025 ppm ozone.
$2.2 billion Losses measured in 1980 dollars
using economic surplus. Loss
represents difference between
current production and production
if a background ozone level of 0.040
ppm had been achieved.
SRI = Stanford Research Institute.
Source: Ryan et al., 1981.
-------
States, not in compliance with the current 1984 national ambient air quality
standard for ozone (0.12 ppm). Yield loss is then translated to dollar loss
by multiplying the decrease in production by the 1980 crop price for each
commodity. The resulting potential benefit of implementing the secondary
standard for oxidants is $1.8 billion (in 1980 dollars). This estimate is
much higher than the previous SRI damage estimate (Table 7-31), thus, it
reflects the sensitivity of these estimates to the data assumptions and time
period employed.
A national assessment by Shriner et al. (1982) for the Office of Technology
Assessment estimated the losses accruing to ambient 0- levels for corn, soybean,
wheat, and peanut. The study employed dose-response data from recent NCLAN
experiments. It simulated county-level ambient 0- data interpolated by the
Environmental Sciences Research Laboratory, U.S. Environmental Protection
Agency, Research Triangle Park, N.C., from available SAROAD monitoring sites
(U.S. Environmental Protection Agency, 1983). Percentage reductions in crop
yield were calculated against a base (assumed background) ozone level of 0.025
ppm ambient concentration. The basis for these calculated reductions is NCLAN
and other data cited in Heck et al. (1982).
Shriner et al. converted physical reduction in county production for each
crop to dollar loss by multiplying this production by the county-level price.
For the United States, the aggregate loss (difference between value of produc-
tion at ambient levels and value of production at 0.025 ppm) was estimated to
be approximately $3 billion. Both this study and the updated SRI study have
conceptual problems concerning the structure of the economic problem and
extrapolation of biological data from relatively few sites and cultivars.
Another estimate of nationwide damages was developed by Adams and Crocker
(1982b). They used information on 03 effects as a surrogate for the effects
of acid deposition on agricultural systems. The primary aim of this approach
was to determine the sensitivity of economic loss to additional information on
dose-response relationships. However, the analysis also leads to an estimate
of 0., damage to three crops representing about 60 percent of the value of U.S.
crop output (corn for grain, soybean, and cotton). The authors noted that
their numerical example, is plausible; however, when it is measured against
the gross value of these crops, the result is highly conditional given the
uncertainties associated with the biological and air quality data used to
derive the national production effects.
019PP/A 7-177 4/19/84
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In developing their estimates, Adams and Crocker used CL dose-response
functions derived from NCLAN results (Heck et al., 1982). They directly
estimated farm-level demand and supply relationships. Demand was assumed to
be a linear function, and farm-level price depended on quantity consumed and
per capita income. Quantity supplied was assumed to be a function of prices
of the same and competing commoditites in the preceding time period. The
response data, combined with the demand and supply structure of the commodity
markets in question, were used to estimate the benefits (economic surplus) of
progressively more stringent control schemes. The estimated economic conse-
quences of the difference between ambient ozone levels associated with the
1979 national ambient air quality standard of 0.12 ppm (not to be exceeded
more than 1 day/yr) and a hypothetical standard of 0.08 ppm (assuming that all
areas of the United States just met the 0.12 ppm standard) was approximately
$2.2 billion. Specifically, by using a log-normal distribution of ozone
concentrations, the authors assumed that a 7-hr seasonal mean ozone level of
0.04 ppm was approximately equivalent to an ambient level that would just
comply with a federal standard of 0.08 ppm (second hourly maximum). This
correspondence between a seasonal 7-hr average and a second hourly maximum
(federal standard) is drawn from Heck et al. (1982a).
These estimates of benefits from decreasing ambient ozone levels are
conditional on the assumed log-normal distribution of ozone events and the
assumption that all regions would not exceed that level. The analysis assumes
that 0_ levels with each standard are uniform across all crop-production
areas. If the actual concentrations are lower in most agricultural areas,
then the benefits accruing to the meeting of national standards would be
overstated. Improved data on 0~ concentrations within growing areas, more
complete economic modeling of producer behavior, and resolution of the uncer-
tainties associated with the simple dose-response functions are needed to
reduce potential errors in the economic estimates generated from this type of
assessment.
7.5.4 An Overview of Current Loss Assessments
The ability to assess Q~ damage to agricultural crops has been enhanced
by recent improvements in dose-response measurements and air quality data. As
Section 7.2.5 of this document indicates, the plant science literature contains
dose-response functions (where response is measured in yield) for many major
agricultural commodities, primarily as a result of the NCLAN program. While
019PP/A 7-178 4/19/84
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cultivar coverage remains sparse for some crops and important edaphic-climatic
interactions are superfically addressed, these simple dose-response relation-
ships are superior to the data underlying loss estimates reported in the 1978
criteria document (U.S. Environmental Protection Agency, 1978). In addition,
air quality data for rural areas are slowly improving as monitoring expands.
Interpolative procedures, as used by Shriner et al. (1982), might fill existing
gaps in air quality data. However, much of the improved information postdates
the economic assessments found in current literature.
This review of recent agricultural assessment efforts indicates that
increased applications of techniques are consistent with economic theory.
Consequently, they produce more defensible estimates of economic benefits.
This same review, however, indicates that treatment of some economic issues is
still incomplete. These deficiencies include the need to account for input
and output substitution effects through time and across regions, the need to
measure damages to perennial crops (fruits, nuts, and timber), and the need to
account for other long-term and dynamic adjustments to chronic pollution
effects, such as interactions between insect and disease injury and 0- as well
as interactions between crop inputs (pesticides and fertilizer) and 0.,.
Researchers should also assess the link between intermediate products and
final products (e.g., the relationship between feed grains and livestock
production) and the problems of evaluating economic damages to nonmarketed
plants (e.g., as manifested through aesthetic effects on forest ecosystems).
Additional technical issues require resolution before economic assessments
can be meaningfully compared. As noted earlier, the appropriate measure of
dose is an important issue. While the current NCLAN experimental design uses
the seasonal 7-hr mean concentration, other dose measurements may better charac-
terize plant response. The use of standard dose measurements would ease compari-
sons across studies. Further, the validity of extrapolating site-specific
response data across regions is not resolved. Another important issue concerns
the definition of background (clean air) 03 levels. The air quality literature
does not present a consensus on the relative importance of biogenic, anthro-
pogenic, and stratospheric sources in rural areas.
The most recent estimates of national damage (Table 7-32) exceed those
found in the 1978 criteria document on oxidants. Two of these recent studies
employ the simple traditional approach; therefore, their increase in damage
estimates is largely caused by the increased crop coverage, somewhat greater
019PP/A 7-179 5/4/84
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recognition of effects as reported in the recent literature, different quality
assumptions, and the use of different base-dollars (i.e., 1980 dollars vs.
1970 dollars). As a percentage of total crop value, the loss estimates range
from 4 to 6 percent. This range is comparable with estimates of crop losses
from sources such as those reported in Boyer (1982) but far less than the $25
billion annual loss attributed by the U.S. Department of Agriculture (1965) to
insect and disease damage.
In conclusion, the current dollar estimates of crop damage are useful
primarily as indicators of magnitudes. A full accounting of the economic
mechanisms underlying agricultural production is required to provide definitive
estimates of the extent of agricultural losses. Ideally, such an accounting
must address both annual and perennial crops (agronomic and horticultural) and
the associated dynamic adjustments of agricultural production. The effects on
intermediate consumers (such as livestock growers and food processors) and
final consumers (both domestic and foreign) must also be addressed. The
physical and economic effects of CL on ornamentals have not been addressed.
Also, improved rural air quality data and procedures for obtaining regionally
averaged yield responses are needed. None of the literature citations in this
section meets all the criteria of an ideal bioeconomic assessment, and all
give some misrepresentation to economic importance.
7.6 MODE OF PEROXYACETYL NITRATE (PAN) ACTION ON PLANTS
The sequence of events inducing vascular plant response to PAN is essen-
tially identical to that described for 0~ (Section 7.3). PAN enters the leaf
tissue through open stomata and dissolves in the aqueous layer surrounding the
substomatal chamber (Figure 7-1). Hill (1971) reported that PAN was rela-
tively insoluble and the rate of absorption by an alfalfa canopy was approxi-
mately one-half that for 0.,. The absorption rate depends upon the plant's
ability to metabolize, translocate, or otherwise remove the active pollutant
species from the absorbing solution, as well as on the solubility of PAN.
Thus, the flux of PAN into the inner leaf tissues is influenced by many physi-
cal, biochemical, and physiological factors. The equation used to describe 03
flux (Section 7.3) also can be directly applied to describe the flux of PAN
into the leaf.
019PP/A 7-180 4/19/84
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PAN is highly unstable, and if it comes in contact with an aqueous solu-
tion, breakdown occurs rapidly (Mudd, 1975). According to Nicksic et al.
(1967) and Stephens (1967), the breakdown of PAN in aqueous solution yields
acetate, nitrite, oxygen, and water. The pathway of PAN absorption and reac-
tion within the leaf tissue is not adequately described to explain why cells
at a specific stage of physiological development are highly susceptible while
adjacent cells are relatively tolerant. The magnitude of PAN injury is influ-
enced by the stage of tissue development, succulence of the tissues, and
conditions of the macro- and microclimate. Injury is manifested in several
ways. The most evident injury is necrosis of rather specific areas of the
lower and upper leaf surfaces. This characteristic symptom expression may be
accompanied by leaf distortion, premature senescence, and defoliation (Taylor,
1969). Experimental evidence shows that yield may be suppressed in the absence
of visible injury symptoms (Thompson and Kats, 1975; Temple, 1982). PAN-type
symptoms have been reported from California, the eastern United States, Canada,
Japan, and the Netherlands (Table 7-33). The smog, photochemical smog, or
oxidant injury symptoms described by Middleton et al. (1950), Went (1955), and
by other researchers working with polluted ambient air in California preceding
about 1960 were identical to injury symptoms subsequently produced with synthe-
sized PAN (Taylor et al., 1961; Taylor, 1969). Frequently, the injury symptoms
are sufficient to significantly reduce quality of leafy vegetables and ornamen-
tal crops, but they are seldom associated with suppressed growth or yield.
The phytotoxicity of PAN and processes of injury development will be
discussed in the following sections. The discussion will be limited to PAN,
the most common member of a series of homologs that increase in phytotoxicity
with molecular weight. Many of the biochemical and physiological studies with
PAN and its homologs were conducted with concentrations that exceed those
encountered in ambient air. However, the studies were conducted to identify
responses that might be more difficult to detect at lower concentrations. For
unknown reasons, most vegetation grown in glasshouses and growth chambers is
considerably less sensitive to synthesized PAN than comparable plants grown
and exposed to PAN and the total pollutant complex found in the field (Taylor,
1969).
7.6.1 Biochemical and Physiological Responses to PAN
As with 0- (Section 7.3.1), the phytotoxic effects of PAN occur only when
a sufficient amount of the gas diffuses into susceptible regions of the leaf
019PP/A 7-181 4/19/84
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TABLE 7-33. GEOGRAPHIC OCCURRENCE OF PAN (OXIDANT) INJURY ON PLANTS
Area
Species injured
Reference
California
Washington
Missouri
Illinois
Colorado
Utah
Bean
spinach,
Romaine lettuce
Oat, petunia,
tomato, Swiss
chard, sugar
beet
Middleton and Haagen-Smit (1961)
Tingey and Hill (1967)
Baltimore, MD
Philadelphia, PA
New York City, NY
Tobacco
Garden plants
Went (1955)
The Netherlands'
Little-leaf nettle,
petunia,
annual bluegrass
Floor and Posthumus (1977)
Japan'
Various species
Spinach, French
bean, lettuce
Fukuda and Terakado (1974)
Sawada et al. (1974)
Canada
Tomato
Pearson et al. (1974)
Monitoring data for PAN in southern California, the Netherlands, and Japan
were available to corroborate the reports of PAN-type symptoms observed in
those areas.
019PP/A
7-182
5/4/84
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interior and encounters the plasmalemma or passes into the liquid phase of the
cells. Once deposited on the wet cell surface, the gas will begin to break
down and the degradation products and/or PAN molecules will move by diffusion
or bulk flow to sites of action (Mudd, 1975). The target sites may include
the cell membrane, chloroplast, cytoplasm, and various cell organelles.
7.6.1.1 Gas-Phase Movement into the Leaf. The primary entry port for PAN
into leaf tissue is through open stomata. As indicated in Section 7.3.1.1,
the influence of CL on stomatal movement has received considerable attention,
but relatively little effort has been made to determine if PAN will also
induce stomatal closure. Starkey et al. (1981) reported that a PAN-susceptible
variety of bean, exposed to 80 ppb PAN for 0.5 hr, developed drought stress
symptoms, but a tolerant variety showed no effect. This finding suggests that
PAN may have stimulated stomatal opening to allow a greater rate of transpira-
tion. Metzler and Pell (1980) found that pinto bean plants exposed to sub-
threshold levels of PAN (54 ppb for 1 hr) developed no macroscopic injury and
showed no effects on stomatal conductance. At the injury threshold (70 ppb
for 1 hr) and above, abaxial glazing developed and stomatal conductance in-
creased. Temple (1982) observed no effects on stomatal conductance at concen-
trations of 25 and 50 ppb PAN after tomato leaves were exposed for 2 hr. In
this study, 0.20 ppm 0,, in combination with the two concentrations of PAN,
did suppress stomatal conductance when tomato plants were exposed for 2 hr.
The size of stomatal pores and number of stomata per unit area of leaf
vary greatly according to plant species. Many plants have stomata in both
surfaces of the leaf, whereas others have stomata only in the lower surface.
As a general rule, stomata occur in larger numbers per leaf area near the apex
of the leaf and become less numerous toward the base of the leaf. Although
plants shown to be most susceptible to PAN are among those that have stomata
in both leaf surfaces, no correlation between susceptibility and number or
size of stomata has been demonstrated.
7.6.1.2 Biochemical and Physiological Responses. PAN is a highly specific
phytotoxic agent that attacks leaf tissue at a fairly specific stage of physio-
logical development and is most injurious to succulent, rapidly expanding
tissues of herbaceous foliage (Noble, 1955; Taylor and Maclean, 1970). Concen-
trations of 14 to 15 ppb (maximum) under field conditions have been observed
to produce PAN-type injury on susceptible crops (Taylor, 1969; Temple, 1982).
Fukuda and Terakado (1974) reported that petunia plants under field conditions
019PP/A 7-183 4/19/84
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developed silvering and bronzing on the lower leaf surface when the maximum
PAN concentrations ranged from 3.0 to 6.7 ppb. The most serious observed
damage occurred when a PAN concentration of more than 5 ppb continued for 7
hr. Because PAN is phytotoxic at very low concentrations, Mudd (1963) con-
cluded that the most likely target in plant cells must be some enzyme system.
Much of the early work with enzymes involved the use of relatively high PAN
concentrations to demonstrate reactive sites in the metabolic pathways.
Ordin (1962) observed that growth of oat coleoptile sections, which
involved cell expansion rather than initiation of new cells, was inhibited by
PAN. He found that fumigation with 1.1 ppm PAN for 6 hr resulted in 32 percent
inhibition of growth and 45 percent inhibition of glucose absorption from the
solution. Fumigations were accomplished by floating the oat coleoptiles in a
solution and bubbling PAN through the solution. There was no way to determine
how much PAN the coleoptiles actually encountered. The response suggested
that PAN interfered with metabolism of cell wall sugars. Subsequently, Ordin
and Hall (1967) found that cellulose synthetase was inhibited, and Ordin et
al. (1967) reported that the enzyme phosphoglucomutase was inhibited when
coleoptile tissue was exposed to PAN. The treatment consisted of bubbling 50
ppm PAN for 4 hr at a rate of 400 ml/min through 100 ml of solution in which
the coleoptiles were floating.
Using i_n vitro procedures, Mudd and Dugger (1963) showed that PAN oxidized
NADH and NADPH. Mudd (1966) and Mudd et al. (1966) found that enzymes with
free-SH groups were inactivated, but enzymes with no free SH groups were
resistant to PAN. The amount of PAN used in these studies was not reported.
Hanson and Stewart (1970) observed that exposure to 50 ppb PAN for 1 to 4 hr
inhibited mobilization of starch in darkness, implying that the phosphorylase
reaction was inhibited. Such a response could seriously interfere with photo-
synthate partitioning and inhibit growth and development. The reaction deserves
further investigation.
Thomson et al. (1965) showed that PAN (1000 ppb for 30 min) or its degra-
dation products caused crystallization and other disruptions in the chloroplast
stroma that were similar to the effects of dessication. These observations
suggest that PAN affected the permeability of the chloroplast membrane in much
the same way as its reaction with the plasmalemma, which allowed leakage of
cell contents.
019PP/A 7-184 4/19/84
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PAN enters leaf tissue through open stomata and is rapidly dissolved in
the aqueous covering of substomatal cells. PAN and its degradation products
are transported through the cell wall and cell membrane into the aqueous cell
contents. Permeability of the cell membrane is disrupted, thus allowing
leakage into the intercellular spaces. Similarly, permeability of the chloro-
plast membrane is disrupted, thereby inducing plasmolytic-type characteristics
to develop. PAN inactivates enzymes containing sulfhydryl groups. Visible
injury from PAN results when mesophyll cells are killed and shrink causing
dessication and death of the epidermal tissue. A degree of chlorosis is often
visible on the upper leaf surface as the chloroplasts in living cells are
destroyed.
The destruction of chloroplasts (Thomson, 1965) and disruption of biochem-
ical and physiological systems (Ordin and Hall, 1967; Ordin et al., 1967;
Mudd, 1966; Hanson and Stewart, 1970) can be expected to adversely affect
growth and yield as well as the aesthetic qualities of the vegetation. Inacti-
vation of enzymes can suppress growth, as demonstrated with oat coleoptiles,
and may interfere with photosynthate, as demonstrated by inhibition of starch
mobilization in the dark, and interfere with other metabolic processes.
7.6.2 Factors that Modify Plant Response to PAN
Plant response to PAN and many other environmental stresses is conditioned
by complex, interacting internal and external factors (U.S. Environmental
Protection Agency, 1978). External physical factors such as temperature, light
conditions, humidity, and edaphic factors can influence plant response to PAN.
Similarly, biological variables such as genetic differences, physiological
stage of tissue development, and rate of plant growth can affect plant response.
7.6.2.1 Biological Factors. Trees and other woody species are apparently
quite resistant to foliar injury from PAN (Davis, 1975; Davis, 1977; Taylor,
1969). Foliar injury has been produced only once or twice by fumigations with
extremely high concentrations of PAN (1 ppm for several hours), and injury to
these species in the field has not been reported. Variations in suscepti-
bility to PAN within herbaceous species have been observed in the field and
have been demonstrated for some crops with synthesized PAN.
Genetically controlled variation in response to PAN has been observed
under field conditions and has been verified by controlled fumigations.
Drummond (1972) exposed 28 F, varieties of petunia plants to 150 ppb PAN for
019PP/A 7-185 4/19/84
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1 hr and foupd highly significant differences in susceptibility. Feder et al.
(1969) used six varieties of petunia that are common in the Boston area to
determine the genetic variation in susceptibility to PAN injury. Exposures
were for 1 hr to concentrations of 120, 250, and 500 ppb. High concentrations
were used to ensure that all varieties developed some injury. Feder et al.
found that the types of petunia varied significantly in their response to PAN.
They concluded that a variety that was resistant to one pollutant was also
resistant to other pollutants. Studies by Hanson et al. (1976) showed that
petunia varieties that are susceptible to PAN were not necessarily susceptible
to ozone. Their studies were conducted with ambient air at Arcadia, California,
using characteristic leaf injury symptoms to determine susceptibility. Fumiga-
tions with synthesized PAN using concentrations of 86 and 120 ppb and combina-
tions of exposure periods of 1, 1.5, 2, and 2.5 hr were conducted to verify
results from the ambient air studies. The objective of the study was to deter-
mine the relative susceptibility of 49 siblings from a complete diallel cross
of seven commercial inbred lines of pink flowered petunia. DeVos et al.
(1980) used inbred parents of White Cascade, a susceptible F, hybrid, and
Coral Magic, a resistant hybrid, to study inheritance of PAN resistance.
Plants were exposed to 150 ppb PAN for 1.5 hr in controlled environment cham-
bers. Significant genetic variation was detected, but there was large genotype-
by-environment interaction. Starkey et al. (1976) exposed 10 varieties of
bean for 2 hr to 120 or 150 ppb PAN to observe the injury symptomology and
determine varietal susceptibility.
Middleton et al. (1950) first described smog injury (PAN type) and listed
endive, lettuce, romaine lettuce, and spinach as extremely susceptible, whereas
carrot and members of the cabbage and melon family were tolerant or resistant.
This general ranking of susceptibility is still acceptable for PAN. Specific
varieties of petunia, bean, Swiss chard, oats, and cos lettuce have been
selected, because of their susceptibility, for controlled fumigation studies.
Tomato was originally listed as only slightly susceptible to smog, but it is
now known that many varieties are highly susceptible.
Sensitive plants show a characteristic pattern of injury when they are
exposed to PAN. The pattern described from field observations in Los Angeles
County, California, by Noble (1955), Juhren et al. (1957), and Glater et al.
(1962) indicates that leaves of different ages show damage in different posi-
tions. A similar description of PAN injury confirms that susceptibility is
019PP/A 7-186 4/19/84
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related to specific physiological stage and foliage development (Taylor, 1969;
Taylor and Maclean, 1970; Noble, 1955; and Glater et al., 1962), but the
causal factors involved in this selective sensitivity phenomenon have not been
identified.
7.6.2.2 Physical Factors. The light-exposure regime to which plants are
subjected before, during, and after exposure to phytotoxic concentrations of
PAN will significantly affect response (Taylor et al., 1961). Brief dark
periods preceding exposure and immediately following exposure can reduce or
even prevent the development of visible symptoms of injury. Maximum injury
occurs when plants are exposed in full sunlight. Dugger et al. (1963) deter-
mined that the maximum quantum responsivity to PAN occurred in the 420 to
480 nm range. There was no evidence to indicate participation of chlorophylls
or phytochrome in the sensitization phenomenon.
Juhren et al. (1957) found that plants were most susceptible to oxidant
injury (PAN-type symptoms) when grown under 8 hr photoperiods, and injury
decreased with photoperiods of 12 to 16 hr. This observation may help to
explain why symptoms of PAN injury are most prominant in late fall, winter,
and spring in southern California. Juhren also found that the greatest oxidant
injury occurred at 25° to 20°C day/night temperatures. The oxidant injury
symptoms described by Juhren et al. (1957), Middleton and Haagen-Smit (1961),
Middleton et al. (1950), and others during the period from 1951 to 1961 were
identical with those later shown to be induced by PAN.
The effects of relative humidity, air temperature, and edaphic factors
have not been investigated extensively, but some observations have been
reported. There is no cohesive evidence relative to the significance of relative
humidity and plant susceptibility, but PAN injury to vegetation in the South
Coast Air Basin of California occurs most frequently when relative humidity is
50 percent or above (Taylor, 1974).
Field observations in southern California, where irrigation is essential
for crop production, revealed that crops growing under soil moisture deficits
developed few or no 0^ or PAN-type injury symptoms during a severe smog attack,
while adjacent, recently irrigated crops were severely injured (Taylor, 1974).
Similarly, the author observed increased tolerance of beans and tobacco to CL
and PAN when potted test plants were inadvertently allowed to wilt briefly
during the day preceding fumigation, even though the plants were watered several
hours before treatment and appeared to be normal. Oertli (1959) reported
019PP/A 7-187 4/19/84
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increased tolerance of sunflower plants to oxidant air pollutants (PAN-type
symptoms) with increasing salinity and soil moisture stress.
Very little information is available on the effects of nutrition on plant
response to PAN. The few available reports are contradictive; they suggest
that injury may be enhanced by addition of nitrogen when it is deficient but a
luxury amount may not increase injury and may even suppress it (Taylor, 1974).
7.6.2.3 Chemical Factors. The effectiveness of chemical additives applied
for pest control and specifically for the prevention of oxidant air pollutant
injury has been studied by Freebairn and Taylor (1960), Pell (1976), Pell and
Gardner (1975), and Pell and Gardner (1979). These studies were made to
determine if cultural practices could be modified to mediate the effects of
PAN and other oxidant air pollutants. None of the chemical treatments have
been sufficiently effective in preventing or reducing PAN injury to encourage
general grower use.
Phytotoxicants seldom occur alone in the atmosphere; consequently, inter-
actions may occur to enhance or suppress the development of vegetation injury.
A synergistic response from nitrogen oxides, CL, and PAN in combination could
significantly increase plant response.
7.6.2.3.1 Pollutant interactions. Although 0., was identified as a major
chemical component of the photochemical oxidant complex in the 1950's, its
importance as a phytotoxicant was not recognized before the 1960's. Descrip-
tions of injury symptoms observed in the field were identical to those subse-
quently produced by fumigations with PAN. The fumigations conducted before
1960 used reaction products of 03 and hydrocarbons in an attempt to reproduce
the PAN type injury symptoms. PAN is rarely present by itself in the photo-
chemical^ polluted atmosphere (Oshima et a!., 1974; Penkett et al., 1977).
However, PAN is almost always present when 0^ occurs; the ratio of 0., to PAN
in southern California has been reported to be about 10:1 (Taylor, 1969), and
at Calgary the ratio was reported to vary according to atmospheric conditions
(Peake and Sandhu, 1983). Conversely, PAN is about 10 times more phytotoxic
than 03 (Taylor and Maclean, 1970; Pell, 1976; Darley et al., 1963).
Interactions involving plant exposure to mixtures of PAN and 0., in pollu-
ted atmospheres probably occur, but the few published reports of controlled
PAN + 0., interaction studies with plants have shown variable and inconsistent
effects on symptom type and intensity of injury. Kohut et al. (1976) found 03
(0.18 ppm) + PAN (180 ppb) treatments for 4 hr in midday produced 0^-type
019PP/A 7-188 4/19/84
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symptoms on hybrid poplar seedlings, but the amount of injury was highly
variable. Davis (1977) found that ponderosa pine seedlings that were exposed
to an 0- (0.40 ppm) + PAN (200 ppb) combination for 4 hr developed significant-
ly less injury than those exposed to 03 alone. Kohut and Davis (1978) reported
greater-than-additive 0.,-type injury on bean leaves exposed to the CL (0.30
ppm) + PAN (50 ppb) combination for 4 hr, but PAN injury was almost completely
suppressed. In a study of the protective effects of benomyl on bean plants
exposed to 0.25 ppm 03 and 150 ppb PAN for 3 hr, Pell (1976) found that the
combination of 0, and PAN produced more injury than PAN alone.
Posthumus (1977) exposed little-leaf nettle and annual bluegrass to 0^
(0.17 ppm) and PAN (50 ppb) singly and in combination for 2 hr in either the
morning or afternoon. The combination induced more foliar injury in the
morning than in the afternoon. However, there was no clear increase or
decrease in the foliar injury in the plants exposed to the combination com-
pared to the injury from the single gases. More recent studies with little-
leaf nettle (Tonneijck, 1984) show that no interaction between 0, and PAN was
detected when both were applied at their respective injury threshold concentra-
tions. However, the pollutant combination caused less than additive injury
when the PAN concentration exceeded the injury threshold concentration.
Matsushima (1971) reported additive or less than additive injury from combina-
tions of PAN and sulfur dioxide. Nouchi et al. (1984) exposed petunia and
bean plants for 4 hr to mixtures of 03 and PAN to assess effects on visible
symptoms of injury. Ozone concentrations for the petunia study were 0, 0.10,
0.20, 0.30, and 0.40 ppm and PAN concentrations were 0, 10, 20, 30, and 40 ppb.
In the bean study, 0., concentrations were 0, 0.15, 0.20, 0.30, and 0.40 ppm,
and PAN concentrations were 0, 30, 45, 65, 85, and 100 ppb. For PAN alone,
injury symptoms appeared on petunia at 20 ppb PAN, and with bean, injury
appeared at 30 ppb PAN. The percent of foliar injury was greatest when plants
were exposed to PAN alone, and the percent injury decreased as the 03 concen-
tration increased. Temple (1982) found that the response of four varieties of
tomato plants to PAN-03 mixtures was variable. He exposed the plants to a
combination of 0, 25, and 50 ppb PAN and 0, 0.10, and 0.20 ppm 03 for 4 hr
once a week for 3 weeks.
7.6.2.3.2 Chemical sprays and nutrients. Reports in the early literature
indicated that efforts were made to find chemicals that would prevent or
reduce foliage injury induced by the photochemical oxidant air pollutants
019PP/A 7-189 4/19/84
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(Section 7.3.2.3.2). The experiments included dust or spray applications to
the foliage and applications through the soil. In most of these studies, no
differentiation was made between CL- and PAN-type symptoms.
Chemicals tested for effectiveness in controlling "oxidant" injury in-
cluded various formulations of ascorbic acid (vitamin C); several types of
carbamate fungicides; benomyl; and ethylene diurea. None of these treatments
consistently protected vegetation used in the tests to the extent that they
could be used commercially. Benomyl showed some promise as a protectant in
earlier studies, but results were variable. Pell (1976) found that use of
benomyl as a soil treatment did not protect the primary leaves of pinto bean
from PAN injury, and at some concentrations it may have stimulated injury.
The plants were exposed to 150 ppb PAN or to 150 ppb PAN and 0.25 ppm 0_ for 3
hr. In subsequent studies, Pell and Gardner (1979) found that soil drenched
with benomyl increased PAN injury on petunia plants, and the most PAN-sensitive
variety exposed to 150 ppb PAN for 1.5 hr was particularly affected.
Imbalance of available plant nutrients has been suggested as a factor
that may influence plant response to some air pollutants. No studies have
been made to investigate the importance of this factor to PAN injury. However,
general observations in the field and in controlled experiments have indicated
that PAN injury is enhanced by all physical and chemical factors that promote
optimum plant growth.
Plant response to PAN is influenced by light quality, intensity, and
timing relative to PAN exposure. However, chlorophylls and phytochrome do not
appear to participate in the sensitization process. Air temperature, photo-
period, and water potential in the foliage can influence response to PAN.
Woody perennials are much less sensitive to PAN than are the succulent
herbaceous species. Sensitivity of varieties within a plant species is gene-
tically controlled, but the genetic process through which the differential
sensitivity occurs has not been identified.
PAN may interact with other air pollutants, particularly 0.,, to enhance
phytotoxicity, but the experimental results are variable. Chemical additives
that are applied to the foliage and through the soil have provided variable
results as protectants from PAN. Some may even enhance sensitivity. Plant
nutrient balance and soil moisture conditions that are optimum for growth and
development also are usually optimum for PAN sensitivity.
019PP/A 7-190 4/19/84
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AREAS INJURED
BY PAN
*-UPPER EPIDERMIS
PALISADE LAYER
SPONGY
PARENCHYMA
,— •
^J^SSSt***-LOWER EPIDERMIS
/ STOMATA
SITE OF
INITIAL INJURY
Figure 7-16. PAN injury. Note position effect
with age of leaf. On sectioning, initial collapse
is in the region of a stomata.
Source: Brandt (1962).
7-191
-------
7.7 PAN EXPOSURE AND RESPONSE
Initial PAN-injury symptoms, which fully develop during the 24 to 72 hr
following exposure, are a glazed, bronzed, or metallic sheen on the lower
(abaxial) leaf surface. These symptoms are identical to those described on
five garden species exposed to gaseous air pollutants in the Los Angeles area,
(Middleton et a!., 1950). The oxidant or PAN symptoms were clearly distinct
from those produced by 0^, which typically caused upper surface necrotic
stipple or fleck chlorosis or bifacial necrosis on susceptible species (Temple,
1982). Transverse bands of bleached, necrotic tissue and glaze and bronze on
the lower surface (Noble, 1955) are characteristic of the PAN injury syndrome
(Taylor, 1969). Most sensitive plant species develop diffuse transverse bands
of injury in regions where the tissue is in identical stages of physiological
development (Figure 7-16). This phenomenon results in injury at the apex of
the youngest susceptible leaf and at regions nearer the base of the next
successively older three or four leaves. Exposure on successive days results
in a series of two or more injured bands separated by bands of healthy tissue,
demonstrating that the stage of high susceptibility lasts for only a relatively
short period (Noble, 1965). Some leaves, such as the two primary leaves on
bean plants, do not develop the bands; the injury may be distributed at random
or as a solid cover over the entire lower surface.
Ordin and Propst (1962) demonstrated that the auxin IAA in oat coleoptiles
was completely inactivated when 1.3 ppm PAN was passed through the solution in
which they were suspended for 3 hr. Similarly, enzyme activity was inhibited
by exposures to 1 ppm PAN for 1 hr (Ordin et al., 1971) and to 125 ppm for 6
min (Mudd, 1963). Thomson et al. (1965) found that exposure to 1 ppm PAN for
30 min damaged leaves of pinto bean, and chloroplasts were markedly altered as
the damage developed. The cell membranes were disrupted and the cell contents
clumped together in a large mass. Dugger et al. (1965) reported that PAN
14
inhibited ATP and NADPH formation and the fixation of C 09, thus inhibiting
•*£
the photosynthesis of carbohydrates. These biochemical and physiological
studies were conducted with high concentrations of PAN (1 ppm and above) which
far exceed those found in the atmosphere, but they demonstrate that reactions
essential for plant growth and development may be inhibited.
The response of plants to PAN was summarized in Chapter 11 of the criteria
document for photochemical oxidants published in 1978 (U.S. Environmental
Protection Agency, 1978). Figure 7-17 graphically presents the estimated
019PP/A 7-192 4/19/84
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0.24
a
a- 0.16
oc
z
Ul
o
O
O
1
0.08
1 I I I I 11II
LIMITING VALUES
I I I I I 1 I I
1 I I I I I
I I 1 I I I
1200
800
400
•o
>
O
o
z
o
m
>
o
z
•c
3
0.1 0.5 1 5
DURATION OF EXPOSURE, hours
Figure 7-17. Dose-response relationships and limiting values for
foliar injury to vegetation by peroxyacetylnitrate (PAN).
Source: U.S. Environmental Protection Agency (1978).
7-193
-------
limiting values for PAN injury as calculated by Jacobson (1977) and presented
by the U.S. Environmental Protection Agency (1978). Susceptible plants exposed
to doses in the region above and to the right of the data points have a low
risk for development of visible injury symptoms. Those plants exposed to
doses to the left and below the data points are at greater risk of developing
injury symptoms. This illustration was based on a limited amount of informa-
tion and the data were produced by controlled fumigation with synthesized PAN.
Plants growing and exposed under ambient field conditions may be at greater
risk than indicated by the illustration. This chapter indicates that PAN is
one member of a family of highly phytotoxic, gaseous compounds in the photo-
chemical oxidant complex. Acute responses of plants to CL and PAN result from
disruption of normal cell structure and processes. The biochemical and physio-
logical effects of PAN are less understood than those for 0.,. Plant growth
and yield response to PAN exposure was recognized in Chapter 11 of the previous
criteria document (U.S. Environmental Protection Agency, 1978), but this
response was associated with visible injury symptoms. The concept of limiting
values (i.e., those concentrations below which foliar injury and, presumably,
reduced growth and yield would not occur) was used to illustrate potentially
harmful exposures. The range of limiting values for PAN was
100 |jg/m3 (200 ppb) for 0.5 hr
500 pg/m3 (100 ppb) for 1 hr
175 ug/m3 (35 ppb) for 4 hr
Studies using little-leaf nettle showed the limiting values proposed by Jacobson
(1977) were insufficient to protect that species from PAN injury (Tonneijck,
1984). In this species the limiting values would need to be reduced 30 to 40
percent to prevent foliar injury.
Physical and biological factors involved in visible injury development
and the studies of biochemical and physiological responses produced by PAN
exposure were discussed briefly in the 1978 criteria document for oxidant air
pollutants (U.S. Environmental Protection Agency, 1978). However, primarily
because of the deficiency of supporting experimental data, the potential for
growth and yield responses to intermittent PAN exposures was not discussed.
While the deficiency of supporting data for growth and yield response to
PAN exposures, the intent in this revision of the criteria document is to
emphasize yield and growth effects with and without extensive visible symptom
019PP/A 7-194 4/19/84
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development. This section focuses on yield loss as described in Section 7,2.
Foliar injury is an important factor as a bioindicator (see Section 7.7.1) and
as a yield loss factor reported periodically in southern California during the
past 30 years.
7.7.1 Bioindicators of PAN Exposure
Foliar injury symptoms frequently seriously reduce market value and in
some instances render the product unmarketable. These symptoms also may
destroy a significant amount of photosynthetically active leaf tissue. The
injury symptom syndrome can serve as a very important indicator that damaging
PAN exposures have occurred, and the effect may be considerably greater than
the actual tissue destruction observed.
The concept of using bioindicators to assess the impact of air pollutants
and the methodology involved are presented in Section 7.4.1. The PAN injury
symptoms that are most useful in field diagnosis are the diffuse transverse
bands of injury, which may be visible only on the lower leaf surface or on
both surfaces, and the glazing, silvering, bronzing, and/or metallic sheen on
the lower leaf surface. Recognition of PAN injury in the field is not always
a simple process because a type of lower leaf surface glaze and bronze may be
produced by other factors such as cold temperatures, insects (mites), and
other air pollutants: CL, hydrochloric acid (HC1), S02, hydrofluoric acid
(HF)). In making field assessments, it is important that the observer know
the relative susceptibility of the crop and the native and ornamental species
in the area and that as many different species as possible be examined.
Noble (1965) reported on a 6-year study in southern California designed
to use plant indicators to identify injury induced by air pollutants. He used
six agricultural crops and two weed species widely distributed in the area.
The study revealed that annual blue grass (meadowgrass) was a very good indica-
tor for PAN. Posthumus (1977) found that little-leaf nettle and annual blue-
grass developed characteristic PAN-type injury symptoms when exposed to about
50 ppb PAN, and he suggested that these wild species might be accurate indica-
tors. Sawada et al. (1974) used 16 plant species in a survey for 0., and PAN
injury and observed PAN injury on 28 percent of the 138 plants used in the
study.
Field surveys in southwestern Ontario, Canada (Pearson et al., 1974)
revealed PAN-type injury symptoms on tomato crops. On the basis of these
019PP/A 7-195 4/19/84
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symptoms and the meteorological conditions that occurred during their develop-
ment, the authors concluded that the air pollutants probably originated in the
Cleveland area. Bioindicators should be used cautiously when monitoring data
are not available as verification and when observations are made on a single
plant species. Lewis and Brennan (1978) reported PAN-type injury on petunia
leaves exposed to mixtures of 03 and ${)„. Wood and Drummond (1974) suggested
that PAN-type injury may be caused by interactions of PAN and other phytotoxi-
cants or perhaps by a single pollutant such as HC1.
Field observations and diagnosis provide an important means of determining
if a PAN problem exists and they give some indication of its importance. PAN
can be measured chromatographically, but the instrument can be calibrated only
with known concentrations of PAN. The problems associated with its synthesis,
dilution, and measurement of the calibration gases has discouraged the estab-
lishment of monitors for long-term use. Plant-damaging exposures of PAN can
be verified with monitoring instrumentation in only a very few locations.
Therefore, the ability to recognize and evaluate PAN injury symptoms in the
field is very important. PAN is produced in the same photochemical process as
03, and at locations where both are monitored continuously. With very few
brief exceptions, they occur simultaneously in oxidant-polluted atmosphere.
PAN-type oxidant foliar injury has been reported in more than half of the
counties in California, in several states, and in several foreign countries.
Went (1955) reported PAN-type injury in some European and South American
cities as well as in several cities in the eastern United States. Locations
at which PAN injury was observed on vegetation in the United States are pre-
sented in Table 7-33.
Bioindicators have been used successfully to show that phytotoxic levels
of PAN have occurred. In addition to observations for the presence of a
syndrome of injury symptoms, it may be necessary to observe a plant community
that contains both susceptible and tolerant species. Researchers have cau-
tioned that injury symptoms that resemble those attributed to PAN can be
produced by other pollutants and by certain adverse environmental conditions.
7.7.2 Nonvascular Plant Response to PAN Exposure
Gross and Dugger (1969) examined the effects of PAN on algae (Chlamydomonas
reinhardtii) by measuring growth, photosynthesis, respiration, and pigment
content of the cells. PAN was bubbled through a liquid medium containing the
019PP/A 7-196 5/4/84
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algal cells, and treatment usually lasted for several minutes. The gaseous
mixture usually contained an average PAN concentration of 125 ppm in nitrogen
(Np), and treatment dose was expressed in nanomoles. Exposures ranged from 20
nanomoles to 250 nanomoles. The study results indicated that both autotrophic
and heterotrophic growth was inhibited, photosynthesis and respiration were
adversely affected, and photosynthesis was more severely affected than respira-
tion. The results also indicated that carotenoids were destroyed and that
there was destruction of both chlorophylls, although chlorophyll a was more
stable than chlorophyll b. Gross and Dugger (1969) also reported that PAN
lowered the free sulfhydryl content of the cells.
Field studies of the lichen populations in the southern California moun-
tains indicated trends in community parameters that inferred that oxidant air
pollutants had a deleterious effect on lichens (Sigal and Taylor, 1979). They
fumigated three species for 4 hr/day for 8 days with 50 ppb PAN. In one
experiment, the lichens were fumigated for only 7 days with 100 ppb PAN.
Response to PAN, evaluated as reduction in gross photosynthesis, indicated
that Parmelia sulcata was more sensitive than Hypogymnia enteromorphia, and
Collema nigrescens was not affected. Photosynthesis was inhibited in Parmelia
sulcata, probably inhibited in Hypogymnia entermospha (results were highly
variable), and appeared not to be affected in Collema m'grescens.
PAN was apparently destructive to chlorophyll and carotenoids in a species
of algae. Treatments also adversely affected photosynthesis and respiration
and suppressed growth. The difference in gross photosynthesis response to PAN
fumigations exhibited by three lichen species tended to indicate that PAN,
along with other pollutants, may be detrimental to lichen populations.
7.7.3 Losses in Vascular Plants Caused by PAN
The term loss is used in this section to mean loss in the intended use or
value of vegetation caused by PAN injury. The loss may be a reduction in
amount of marketable product or a loss resulting from aesthetic degradation.
7.7.3.1 Losses in Aesthetic Use and Foliar Yield. Various types of petunias
are used as bedding plants. This species is highly susceptible to PAN injury,
and although monetary losses have not been reported, it is obvious that they
have been heavy in the wholesale industry, retail market, and to the consumer.
Although such information is not reported in the literature, attempts have
been made to produce plants outside heavily polluted areas and transport them
019PP/A 7-197 5/4/84
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to the market. This practice was only partly successful because substantial
foliar injury usually developed after delivery to retail outlets and before
retail sale. While the petunia is one of the most susceptible species, other
ornamentals that are planted for foliage and blossoms also are affected. No
evidence indicates that the petals or other blossom parts are injured by PAN.
Several vegetable crops such as leaf lettuce, spinach, mustard greens,
table beets, endive, and romaine lettuce are grown and marketed for their
foliage. Some of these crops are grown in close proximity to metropolitan
areas and marketed as specialty crops. These species are harvested early in
the morning and are supplied, at relatively high prices, to restaurants and
specialty stores. After a heavy PAN attack, entire crops in some areas are
not marketable, and others require expensive hand work to sort and trim the
product to make them acceptable. No reliable assessment of such losses has
been made, but losses of several hundred thousand dollars per year in the Los
Angeles area have been suggested (Middleton et al., 1950).
The indirect effect of PAN on plant growth resulting from destruction of
leaf tissue has not been measured. However, destruction of a significant
amount of leaf area caused by the necrotic bands and damage to the lower
epidermis and increased defoliation of deciduous plants should be expected to
suppress growth. Earlier reports indicated that growth and yield by most
plants are not measurably affected until the loss of photosynthetic surface
exceeds 5 percent (Thomas and Hendricks, 1956). Plants that rapidly replace
foliage (e.g., grasses) might be expected to express less growth reduction
because of foliage loss than plants that retain their foliage for several
years (e.g., citrus trees) and replace the lost foliage more slowly.
Thompson and Kats (1975) reported a trend toward reduced yield of mature
navel orange fruit when branches of mature trees were enclosed and fumigated
with PAN dosages equivalent to those occurring in the Riverside, California
area. PAN treatments consisted of carbon-filtered air, ambient air, and
carbon-filtered air plus additions of PAN adjusted to simulate concentrations
monitored in the ambient air at Riverside. The continuous treatments were
administered for 9 months. Tree growth also was suppressed, presumably because
of lost photosynthetically active tissue when leaf drop was stimulated.
Middleton et al. (1950) estimated the dollar loss for 11 crops in Los
Angeles County, California during the 1949 growing season to be $479,495. The
foliar symptoms described as the cause of this loss were identical with those
019PP/A 7-198 4/19/84
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later found to be caused by PAN (Taylor et al., 1960). Though 0, was undoubted-
ly a component of the smog described in 1950, symptoms of 0- injury were not
included in the injury symptom syndrome implicated in the crop losses. Oshima
et al. (1974) did not attempt to estimate monetary loss after the severe PAN
attack. In Los Angeles and San Bernardino Counties, the crop could be marketed
after extensive trimming. Assessment of economic loss due to PAN has not been
attempted in recent years.
7.7.3.2.1. PAN addition studies. Based on PAN addition studies, Temple
(1982) concluded that the potentially phytotoxic episodes could be defined as
concentrations greater than 15 ppb for 4 hr in the morning or greater than 25
ppb for 4 hr in the afternoon. His experiments were conducted in Teflon®-
covered CSTR chambers in a greenhouse. PAN concentrations of approximately 14
ppb for 4 hr in ambient air are sufficient to produce foliar injury on suscep-
tible plants growing in the field (Taylor, 1969). However, in chamber studies,
approximately two to three times this dose is required to induce injury symptoms
(Posthumus, 1977). Because of this discrepancy between chamber and field
studies, it is inappropriate to relate responses obtained in chambers using
synthesized PAN to responses expected in the field.
Exposure of lettuce and Swiss chard to 0, 25, and 50 ppb PAN for 4 hr/day
once a week for up to 4 weeks caused no visible leaf injury and appeared to
have little, if any, effect on plant growth (Temple, 1982). PAN by itself or
in combination with 0, had no effect on stomatal conductance. Temple found
that PAN and 0- alone and in combination reduced growth of four tomato varie-
ties and altered partitioning of photosynthate between roots and shoots. He
exposed the plants to 0, 0.1, and 0.2 ppm 03 and 0, 25, and 50 ppb PAN, alone
and in all combinations, for 4 hr/day once a week for 3 weeks. No PAN-type
visible injury developed on the tomato plants, and this exposure had no effect
on expression of 03 injury. The PAN treatments had no effect on stomatal
conductance, but 0.2 ppm 0~ reduced stomatal conductance in all four varieties.
Results from two separate experiments were erratic, perhaps because the studies
were conducted at different times of the year, but the evidence that the
root/shoot ratio was altered suggests that further study is needed.
Greenhouse-grown plants (radish, lettuce, chard, oat, tomato, pinto bean,
beet, and barley) representing root, foliage, fruit and seed crops were exposed
to PAN (0, 5, 10, 20, or 40 ppb) for 4 hr/day, twice per week from germination
to maturity of the harvestable crop (Taylor et al., 1983). Significant yield
019PP/A 7-199 5/4/84
-------
reductions were observed only in lettuce (Empire) and chard; the threshold for
yield reduction appeared to be between 10 and 20 ppb. Yield was reduced
13 percent in lettuce and 23 percent in chard exposed to 40 ppb. Of all the
crops tested, only pinto bean developed a significant amount of foliar injury
and only after exposure to 40 ppb; this sensitivity persisted throughout the
developmental cycle of the crop. The results indicate that PAN at concentra-
tions below the visible injury threshold can cause significant yield reductions
in sensitive cultivars of leafy (foliage) crops.
Field observations in southern California during the past 30 years have
revealed that severe visible PAN injury seldom appears during mid-summer, even
though higher dosages and concentrations occur during the four summer months
(Temple and Taylor, 1983). Ozone dosage also is highest during this period.
To effectively assess the impact of PAN, in the presence and absence of visible
symptoms, experiments should be designed to use 0, and PAN mixtures, be conduc-
ted in as near full sunlight as possible, and be able to simulate fall and
spring environmental conditions limited to those periods.
Youngner and Nudge (1980) measured the relative susceptibility of cultivars
of 10 turf grass species to 50 ppb PAN and to 0.5 ppm 0.,. They reported a
significant variation in amounts of foliar injury and noted that warm-season
grasses were more tolerant of both 0, and PAN than were the cool-season grasses.
PAN is an important component of the oxidant air pollutant complex because
of its extreme reactivity with biological materials (Mudd, 1975). PAN reacts
strongly with sulfhydryl groups in enzymes (Mudd, 1963) and with low-molecular-
weight, sulfur-containing compounds such as amino acids (Leh and Mudd, 1974).
The occurrence of severe foliar injury symptoms on susceptible species in the
field and during controlled experiments with synthesized PAN is well documented
(Bobrov, 1955; Taylor, 1969; and Taylor and MacLean, 1970). Photosynthetic
processes are disrupted when isolated chloroplasts are exposed to high PAN
concentrations (Dugger et al., 1965).
Evidence of plant growth suppression following intermittant exposure to
PAN at concentrations comparable to those found in ambient polluted air without
visible leaf injury symptoms has been reported (Thompson and Kats, 1975; Temple,
1982).
7.7.3.3 Biomass and Yield Responses from Ambient Exposures. Substantial
yield losses caused by ambient PAN exposures occur in southern California and
on occasion in the highly productive central valley of the state. The
019PP/A 7-200 5/4/84
-------
losses are most evident in leafy vegetable (salad) crops and herbaceous orna-
mentals and is due primarily to the damaged crop not being aesthetically
acceptable on the market. Suppression of plant growth and reproduction because
of exposure to PAN alone cannot be substantiated under ambient conditions be-
cause 0- and PAN are present simultaneously, and no effective filter is available
to separate them. Consequently, all of the crop responses under ambient condi-
tions are the result of 03 and PAN mixtures.
Root crops such as radish, table beet, and sugar beet develop foliar
symptoms of PAN injury, but no substantiated evidence indicates that production
of marketable roots is affected. Similarly, barley and oats growing in the field
develop characteristic transverse necrotic bands on the foliage, but no evidence
exists that the grain crop was affected.
A trend toward reduced fruit production of navel oranges was reported
when tree limbs were exposed to synthesized PAN in a system designed to simulate
ambient conditions for a full year. This response has not been substantiated
with other crops or repeated with navel orange. The inability to separate PAN
and 03 under ambient conditions, difficulties in synthesizing large quantities
of a strongly reactive compound, and knowledge that greenhouse and fumigation
chamber environments greatly increase plant tolerance to PAN have discouraged
attempts to conduct the long-term experiments necessary for crop growth and
yield assessment.
Characteristic foliar injury consisting of necrotic transverse bands,
chlorotic bands, lower-surface glazing and bronzing, and leaf distortion occur
when sensitive plants are exposed to 14 to 15 ppb PAN under ambient field con-
ditions. Two to three times this concentration is required to cause injury
when plants are exposed in chambers. Injured crops of lettuce, spinach and
other susceptible leafy crops often become a complete loss in southern
California and parts of the San Joaquin Valley.
The injury symptom syndrome for smog or photochemical oxidants described
in the literature preceding about 1960 is identical with the injury produced
by PAN. Certainly 03 was present in the atmosphere and was responsible for
injury to vegetation, but the description of injury observed in the field
during early studies of oxidant air pollutants did not include those symptoms
attributed to CL. Early estimates of crop loss in southern California were
based on PAN-type symptoms.
019PP/A 7-201 5/4/84
-------
After PAN was identified and a technique for synthesizing it was developed,
studies were initiated to determine the susceptibility of species and to
identify the mode of action once PAN entered leaf tissue. These early studies
established that a high concentration, two to three or more times greater than
that usually measured in the atmosphere, could inhibit enzyme activity and
particularly those enzymes containing sulfhydryl groups. The studies revealed
auxin IAA activity in oat coleoptile was inhibited, and growth by cell expansion
was suppressed.
Evidence has been presented to show that PAN is absorbed in the aqueous
layer surrounding internal leaf tissues and PAN or its degradation products
are transported through the cell wall and plasmalemma where organelles are
attacked. The evidence indicates that PAN disrupts permeability of the plasm-
alemma and plastid membrane, thus allowing leakage and plasmolysis. Disruption
of organelles and inhibition of enzymes are the primary causes cf the reported
suppression of apparent photosynthesis.
Extensive studies have shown that species and varietal variation in
susceptibility to PAN is controlled genetically. The complexity of the genetic
influence has not been adequately described.
Under field conditions, injury symptoms may be produced on susceptible
species when PAN concentrations are approximately 15 ppb for 4 hr; in most
instances, 36 to 72 hr are required for the symptoms to fully develop. Suscep-
tibility is influenced by genetic, edaphic, and other environmental conditions.
Light conditions before, during, and immediately after exposure may influence
plant response to PAN. In general, environmental conditions (e.g., soil
moisture, nutrition, temperature, relative humidity, and light exposure) that
are conducive to producing optimum plant growth also increase plant suscepti-
bility.
The visible symptoms of PAN injury are glazing, silvering, and/or bronzing
on the lower surface, usually in a diffuse transverse band across the lower
surface of rapidly expanding leaves. As the PAN concentration increases,
the injury may extend through the leaf to produce chlorotic or collapsed
necrotic transverse bands of injury. The bands provide evidence that tissue
at a specific stage of development is most susceptible to injury. The bands
are located closer to the leaf base as the age of the expanding leaf increases.
Estimates of damage or crop loss have been based on the significance of
leaf injury. Ornamentals and leafy vegetables whose market value is related
019PP/A 7-202 4/19/84
-------
to appearance are often severely damaged. Individual growers may lose an
entire crop, while in other instances, extensive trimming is required to
produce a marketable product, thus reducing profits. Some studies have indi-
cated that growth and yield may be suppressed by PAN even when visible symp-
toms do not develop. However, only a few such studies have been conducted and
results have been too variable to conclusively state that yield of fruit and
seed is reduced significantly in the absence of visible symptoms.
Interactions between PAN and 0, and between PAN and SCL have been studied
by several researchers. In some instances, synergistic responses have been
reported, but variability is too great to conclusively state that such responses
usually occur. However, with PAN concentrations near and at ambient levels,
the studies indicated that PAN and 0~ do not interact or the resultant injury
is less than would be expected if the effects were additive.
7.8 SUMMARY
Plant growth and yield are the end products of a series of biochemical
and physiological processes related to uptake, assimilation, biosynthesis, and
translocation. Sunlight (photosynthetic energy) drives the assimilation
process that converts carbon dioxide into the organic compounds necessary for
plant growth and development. In addition to the compounds obtained through
photosynthesis, the plants must extract the essential mineral nutrients and
water from the soil. The various plant organs convert these raw materials
(carbon dioxide, mineral nutrients, and water) into the wide array of compounds
that are required for plant growth and yield. These biosynthetic reactions
occur in various plant organs, and their products are translocated through the
plant. A disruption or reduction in the rates of uptake, assimilation, or the
subsequent biochemical reactions can be reflected in reduced plant growth and
yield.
In general, 0., or PAN would be expected to reduce plant growth and yield
only if it directly impacted the process that was limiting plant growth or if
it caused some other processes to limit growth. An effect on plant growth and
yield would not occur unless 0_ or PAN caused some processes to limit growth
to the extent that environmental factors controlling plant growth were
ineffective.
019PP/A 7-203 4/19/84
-------
Ozone and PAN enter into the plant through its foliage, and this is the
primary site where they exert their phytotoxic effects. To penetrate into
active sites within the leaf, these gases must diffuse through small pores
(stomata), which partially control the amount of 0,. and PAN entering the leaf,
diffuse through the intercellular spaces, and dissolve in the hydrated cell
surfaces.
The photochemical oxidant air pollutants, i.e., CL and PAN, and other
gaseous air pollutants are phytotoxic only if they reach the active sites
within the leaf. If the rate of pollutant uptake is small and the plant is
able to detoxify or metabolize the pollutant (or its decomposition products)
or repair or compensate for the impact, injury will not occur. Injury and the
resulting effects on growth and yield will occur only when the uptake of CL or
PAN exceeds the rate at which the plant is able to detoxify or metabolize the
phytotoxins or repair the cellular disturbances. These physiological and
biochemical events also are reflected in the observations that plants can
tolerate specific concentrations of 0_ or PAN for specific time periods without
inducing visible injury or measurable effects on plant growth and yield.
Some of the initial responses to (k include increased membrane permeability
(both cell and organelle membranes), alterations in the activities of specific
enzymes, and changes in various metabolic pools. Altered membrane permeability
results in leakage of water and ions from the cells and disorganization of
organelles, and cells become plasmolyzed. In addition, stress ethylene produc-
tion is stimulated, and there are increases in secondary metabolites such as
phenolic compounds. The appearance of visible foliar injury has been associ-
ated with elevated concentrations of phenols.
Ozone inhibits photosynthesis and alters partitioning of photosynthate.
In various plant species, photosynthesis was significantly decreased by 0^ at
concentrations of 0.05 ppm for 4 hr, 0.1 ppm for 1 hr, or 0.2 ppm for 1 hr
(Table 7-1). Higher 03 concentrations or longer exposure durations also
reduced photosynthesis. The enzyme responsible for photosynthesis (RuBP
carboxylase) was inhibited by 0.12 ppm 03 for 2 hr in whole plants. These
reductions in photosynthesis occurred at 03 levels and exposure durations that
occur in the ambient air. An inhibition in photosynthesis decreases the
synthesis of the primary components needed for plant growth.
In addition to reducing the amount of material produced during photosynthe-
sis, 0.-, can alter the transport and allocation of the remaining photosynthetic
019PP/A 7-204 4/19/84
-------
material. For example, the root growth of radish was reduced more than the
top growth (0.05 ppm 0.,, 8 hr/day, 5 days/week for 5 weeks). In ponderosa
pine, the storage of sugars in the roots was depressed by 0^ (0.1 ppm, 6 hr/day
for 16 weeks). Rye grass plants exposed to 03 (0.09 ppm, 8 hr/day for 16
weeks) exhibited a 22 percent reduction in the root/shoot ratio. In addition
to these examples, numerous studies have confirmed the observation that 0^
impacts root growth more than foliage growth even though the foliage is the
primary site of 0, action. These effects on photosynthesis and translocation
«5
may explain the yield reductions observed in other studies. The nature of the
relationship between inhibition of photosynthesis and yield reduction is not
well understood.
Many biological, physical, and chemical factors influence plant responses
to 0-. Differential plant response to 0., is an inherited trait. Genetic
J *3
variance in 03 response appears to be complex; it involves a number of genes.
While each plant has a potential genetically determined susceptibility to 03,
the manifestation of that potential depends upon the physiological sensitivity
of the plant. Although differential 03 sensitivity has been documented for
numerous species, most studies that have developed exposure-response relation-
ships or attempted to assess the economic impacts of 03 on crop productions
have used only one or a few cultivars. Many biological, physical, and chemical
factors contribute to the determination of the plant physiology. The develop-
mental stage of the leaf and the plant influences sensitivity. Although
interspecific variation has been observed, in general, leaves approaching
maximum expansion seem to be most sensitive to 03- Study results indicate
that young plants and those approaching senescence are more sensitive to 03
than plants at intermediate ages.
In both ambient environment and chamber studies, 03 stimulates premature
senescence and leaf drop. This premature leaf drop decreases the time that a
leaf can contribute to plant growth and yield. Part of the (^-induced effects
on plant yield may result from premature senescence.
The biological environment of the plant also affects 03 response in
plants. Studies demonstrate that interaction exists between 03 and plant
pests, as reflected in plant response. Most laboratory evidence indicates
that 0 (at ambient concentrations or higher for 4 hr or more) inhibits infec-
tions by pathogens and subsequent disease development; however, increases in
disease development were noted in certain cases. These increases most often
019PP/A 7-205 4/19/84
-------
occurred with stress pathogens such as Bo_try_ti_s blight of potatoes or onions
or annosus root rot of ponderosa and Jeffrey pine. Also, 0., can modify plant-
insect relationships; this is best illustrated by studies conducted in the San
Bernardino Mountains in California. Pines impacted by CL were more susceptible
to invasion by bark beetles. Little evidence exists to indicate that 0.,
causes significant direct effects on microorganisms. Given the importance of
plant diseases and insects in agricultural and forestry production systems,
relatively small changes in the incidence and severity of plant pest problems
could add significantly to 0_-related losses in quality, quantity, or function
of agro- or natural ecosystems.
The physical environment around a plant influences its sensitivity to Ov
Studies of the influence of physical factors on plant sensitivity to Cu are
limited. For some factors, a general trend exists across species, but for
other factors, the responses vary among species. For example, light intensity
and temperature significantly influence plant sensitivity but there is no
clear trend among species. In contrast, plants became more sensitive to C>
with increasing relative humidity, while plants that are water stressed become
more tolerant to 0... When the water stress is relieved, the plants regain
their 0^ sensitivity. The influence of water stress has been confirmed in
both field and laboratory studies, but the results are limited primarily to
visible injury. The influence of relative humidity and soil moisture stress
is related to their effects on stomatal opening, which influences the amount
of 0 entering the plant. While studies reveal that plants growing with
different soil fertility regimes vary in 0-, sensitivity, it is not clear how
nutritional status for most nutrients influences plant sensitivity. Plants
that are low in calcium are highly sensitive to 0.,. As the tissue calcium
levels are increased from deficient to sufficient, the plants become more
tolerant of 0,. This response probably is related to the role of calcium in
maintaining membrane function.
Concern for the effects of pollutant mixtures on vegetation originated
with the observation that noninjurious concentrations of 0., and S0? induced
foliar injury when the pollutants were combined. Since that time, numerous
studies have been conducted to determine the effects of combinations of 0,, and
SOp on visible injury and plant growth and yield. For visible injury, the
majority of the studies showed that concentrations of 0., and S0? (0.05 to
0.20 ppm for 1 to a few hours) generally acted synergistically in causing
019PP/A 7-206 4/19/84
-------
visible injury. However, there were exceptions. Greenhouse studies showed
that the effects of mixtures of 03 and SO- on plant growth were in most cases
additive or antagonistic. Recent studies conducted in the field found that
S0? and 0- interacted to reduce plant growth. However, this effect was found
only at unusually high SCL concentrations. At more typical S0? concentrations,
the effect of CU was not influenced by SO^. Preliminary analysis of air
monitoring information for locations that co-monitored both pollutants showed
that at most sites, there were no more than 10 co-occurrences of 0^ and SCL
(concentrations of 0.05 ppm or greater of each gas), during the 5-month period
of May to September. Based on these data, the majority of the studies of the
effects of 0., and S0? on plant growth have used exposure regimes that are more
severe than those that occur in ambient air.
Some studies have investigated the effects of 0_ and N0?, but the results
are too limited to allow any general conclusions. Preliminary studies have
used mixtures of 0^, S0~, and N0?. The results of these studies indicated
that the addition of the other gases caused a greater effect than 0, alone.
Limited studies have investigated the interaction of 0~ and heavy metals. In
general, when plants are exposed to heavy metals and 0,, the heavy metals seem
to make the plant more sensitive to CL.
Commercial farming practices incorporate the use of a spectrum of pesti-
cides. Interactions between 0., and several pesticides have been documented.
The most notable example is the protective role of the systemic fungicide
benomyl with a diversity of plant species. However, the extent of the protec-
tion is such that these chemicals are not normally used to reduce 0^ injury in
the field.
Plants have been used extensively to index various characteristics of the
environments in which they grow. Ozone is an imposed environmental variable
that can be detected and sometimes quantified by observing the specific response
of sensitive plants. The occurrence of 0, has been confirmed in the United
States, the Netherlands, Great Britain, Germany, Japan, Israel, and Australia
by observing foliar injury to selected plant species and cultivars.
Biological methods for assessing the extent and intensity of 0., have a
value beyond that provided by physical measurements. Bioindicators are integra-
tors of their environment and can provide direct information on the effect a
given pollutant dose has on vegetation, subject to the joint influence of
other environmental variables.
019PP/A 7-207 4/19/84
-------
The response of nonvascular plants to 0~ has received little study, but
the available data suggest that microorganisms, mosses, and ferns are not
impacted at present ambient concentrations. Studies conducted in southern
California have shown a loss in the number of lichen species in areas experi-
encing elevated levels of photochemical oxidant air pollution.
Various summary statistics have been used to characterize the pollutant
exposure regime that plants experience. The summary statistics ranged from
the cumulative dose (ppm/hr) to means using various averaging times. These
exposurp statistics are not readily interconvertible. The currently used ex-
posure statistics do not characterize the impact of pollutant episodes at
specific, and perhaps critical periods during plant growth.
When pollutant concentrations exceed a given concentration for a specific
time period, plants will be impacted by 0,,. Various studies and lines of
evidence indicate that concentration is morp important than exposure duration
in causing an effect. Initial studies have shown that plants that experience
an episodic exposure are more impacted than plants that receive a constant
exposure at the same dose.
The yield losses discussed in Section 7.4.3 dealt with effects on the
intended use of the plant. Yield loss ranged from foliar injury (for those
plants where the foliage is the important yield component) to losses in weight,
size, or number and changes in plant quality. The previous criteria document
(U.S. Environmental Protection Agency, 1978) summarized earlier research by
presenting 0., concentrations and exposure durations that could potentially
reduce yield (Figure 7-6). That document displays a boundary of 0., concentra-
tion and exposure periods below which 0~ effects would not be expected. The
lower 0., limit for an effect was 0.05 ppm for exposure durations of 16 days (2
to 8 hr/day) or greater. At exposure durations of less than 16 days, the 0^
response threshold was increased to about 0.10 ppm at 10 days and 0.30 ppm for
6 days.
A summary of foliar injury effects is presented in Table 7-34, which
lists concentrations that can produce 5 percent or 20 percent injury to sensi-
tive, intermediate, or tolerant plants. That summary predicts effects (foliar
injury) on sensitive plants resulting from 8-hr exposures to 0.02 to 0.04 ppm
(5 percent) or 0.06 to 0.12 ppm (20 percent).
Studies have been conducted with the frequent use of open-top field
chambers to estimate the impact of 0, on plant yield for important cultivars
019PP/A 7-208 4/19/84
-------
TABLE 7-34. OZONE CONCENTRATIONS FOR SHORT-TERM
EXPOSURES THAT PRODUCE 5 OR 20 PERCENT INJURY TO VEGETATION
GROWN UNDER SENSITIVE CONDITIONS3
Ozone concentrations that may produce 5%
Exposure
time, hr Sensitive
0.5 0.35 -
(0.45 -
1.0 0.15 -
(0.20 -
2.0 0.09 -
(0.12 -
4.0 0.04 -
(0.10 -
8.0 0.02 -
(0.06 -
plants
0.50
0.60)
0.25
0.35)
0.15
0.25)
0.09
0.15)
0.04
0.12)
Intermediate plants
0.55 -
(0.65 -
0.25 -
(0.35 -
0.15 -
(0.25 -
0.10 -
(0.15 -
0.07 -
(0.15 -
0.70
0.85)
0.40
0.55)
0.25
0.35)
0.15
0.30)
0.12
0.25)
(20%) injury, ppm
Tolerant plants
>0.70 (0.85)
>0.40 (0.55)
>0.30 (0.40)
>0.25 (0.35)
>0.20 (0.30)
8Data developed from analysis of acute responses shown in Table 11-18 from
U.S. Environmental Protection Agency, 1978. The concentrations in
parenthesis represent the 20 percent injury level.
bl ppm = 1960 ug/m3.
of major crops. These studies can be grouped into two classes, depending on
the methods used for data analysis: (1) those studies that developed predictive
equations relating 03 exposures to plant response, and (2) those studies that
compared discrete treatment levels to a control. The first approach has the
advantage that the models can be used to interpolate results between treatment
levels.
To summarize the results from studies that developed exposure-response
equations, these equations were used to estimate the 03 concentrations that
caused 10 and 30 percent reductions in yield (Table 7-35). For several species
and cultivars, several models were fit to the same original data. In general,
when several models were fit to the same data, the models then tended to predict
similar concentrations. However, in cases involving corn, turnip, or winter
wheat, the linear model tended to underestimate the 03 concentrations. The
linear models were more likely to show systematic deviations from the data
than the models that allowed curvature. The similarity among the estimated
019PP/A 7-209 4/19/84
-------
TABLE 7-35. 7-HOUR SEASONAL AVERAGE 03 CONCENTRATIONS AT WHICH YIELD LOSSES OF
10 PERCENT OR 30 PERCENT ARE PREDICTED FROM EXPOSURE RESPONSE MODELS
I
ro
Plant
Grains/Seeds
Soybean
Corsoy
Cor soy
Davis
Davis
Essex
Hodgson-F
Hodgson-P
Wi 1 1 i ams
Peanut - 1979
Peanut - 1980C
Peanut - 1980
Peanut - 1980
Kidney bean
Kidney bean
Model
kg/ha = 3099.3
g/pl
seed
g/pl
g/pi
g/pi
g/pi
ant =
wt/m
ant =
ant =
ant =
ant =
g/plant =
pod
pod
pod
g/pi
seed
g/pi
wt/pl
wt/pl
wt/pl
ant =
15.6
- 15135 03
exp
= 534.5
31.1
18.7
15.2
15.5
19.4
ant =
ant =
ant =
148
wt/plant
ant =
16.5
exp
exp
exp
exp
exp
112
173
142
184
exp
= 17
exp
[-(03/0
- 3988.6
C-(03/0
L-(o3/o
[-(Q3/o
[-(Q3/o
C-(o3/o
- 563 0
- 1046
.129)1'70]
03 + 10,960 03* 03
.129)°'91]
.309)°'76]
.207)°-50]
.153)1'57]
.243)°'94]
3
03
. 3 if 03 < 0.037;
.6 - 1160 03 if 03 > 0.037
C-(o3/o.
.44-35
C-(o3/o
186)3-2°]
.51 03
.287)1'77]
Control 03
concentration
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
022
022
025
025
014
017
017
014
026
025
025
025
025
025
Yield
Percent
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
040
043
038
038
037
039
043
038
043
039
049
046
072
086
Loss
Percent
0.077
0.076
0.070
0.071
0.109
0.096
0.084
0.098
0.078
0.067
0.073
0.073
0.165
0.164
-------
TABLE 7-35. 7-HOUR SEASONAL AVERAGE 03 CONCENTRATIONS AT WHICH YIELD LOSSES OF
10 PERCENT OR 30 PERCENT ARE PREDICTED FROM EXPOSURE RESPONSE MODELS
Plant
Field corn
Model
(Coker 16)c
(Coker 16)
(Coker 16)
(PAG 397)
(Pioneer 3780)
g/plant
g/plant
g/plant
g/plant
g/plant
247.8 - 260* 03
= 222.91 + 331.11 03 - 3511.99 03* 03
= 240 exp [-(03/0.221)4'46]
= 166 exp [-(03/0.160)4'28]
= 149 exp [-(03/0. 155)3- H]
Control 03
concentration3
0.
0.
0.
0.
0.
02
02
02
15
15
Yield
1 Percent
0.113
0.132
0.133
0.095
0.075
Loss
Percent
0.300
0.175
0.126
0.111
Winter wheat
(Blueboy
(Blueboy
(Blueboy
II)C
II)
II)
(Coker 47-27)c
(Coker 47-27)
(Coker 47-27)
(Holly)c
(Holly)
(Holly)
(Holly)
g/plant
g/plant
g/plant
g/plant
g/plant
g/plant
g/plant
g/plant
g/plant
g/plant
= 6.
- 5.
= 5.
= 5.
= 5.
= 5.
= 5.
= 4.
= 4.
= 4.
= 8
6-18
908 +
88 exp
8-21
765 -
19 exp
7 - 16
533 +
95 exp
9 if x
.2 -38
Os
3.958 03
[-(03/0.
03
18.79 03
[-(03/0.
03
19.31 03
C-(03/0.
< 0.087
03 if 03
- 137.7 0|
175)3'22]
- 20.00 OS
171)2-06]
- 215.1 0§
156)4'95]
> 0.087
0.
0.
0.
0.
0.
0.
0.
0.
03
03
03
03
03
03
03
03
0.03
0.
03
0.
0.
0.
0.
0.
0.
0.
0.
0.
0.
063
0817
088
055
055
064
063
095
099
100
0.131
0.129
0.127
0.104
0.103
0.107
0.128
0.129
0.127
0.126
-------
TABLE 7-35. 7-HOUR SEASONAL AVERAGE 03 CONCENTRATIONS AT WHICH YIELD LOSSES OF
10 PERCENT OR 30 PERCENT ARE PREDICTED FROM EXPOSURE RESPONSE MODELS
Plant
(Oasis)c
(Oasis)
(Oasis)
Cotton
Root crops
Turnip
(Just Right)0
(Just Right)
(Just Right)
(Purple Top White
Globe)0
(Purple Top White
Globe)
(Purple Top White
Globe)
(Shogoin)
(Shogoin)
(Tokyo Cross)0
Model
g/plant = 4.9 - 12 03
g/plant = 4.475 + 3.320 03 - 93.49 0§
g/plant = 4.88 exp [-(03/0. 186)3'20]
g/plant = 41.5 exp [-(03/0. 197)1' 12]
edible root wt/plant = 12.9 - 94 03
edible root wt/plant = 10.7 if 03 < 0.038
= 15.5 - 127 03 if 03 > 0.038
g/plant = 10.89 exp [-(03/0. 090)3'05]
edible root wt/plant = 7.2 - 49 03
edible root wt/plant = 6.0 if 03 < 0.034
= 8.1 - 60 03 > 0.034
g/plant = 6.22 exp [-(03/0. 095)2' 51]
edible root wt/plant = 5.3 - 36 03
g/plant = 4.68 exp [-(03/0. 096)2' 12J
edible root wt/plant = 18.1 - 116 03
Control 03
concentration
0.03
0.03
0.03
0.018
0.014
0.014
0.014
0.014
0.014
0.014
0.014
0.014
0.014
Yield
Percent
0.068
0.088
0.093
0.041
0.026
0.046
0.043
0.027
0.045
0.040
0.027
0.036
0.028
Loss
Percent
0.143
0.138
0.135
0.092
0.051
0.063
0.064
0.054
0.065
0.064
0.054
0.060
0.057
-------
TABLE 7-35. 7-HOUR SEASONAL AVERAGE 03 CONCENTRATIONS AT WHICH YIELD LOSSES OF
10 PERCENT OR 30 PERCENT ARE PREDICTED FROM EXPOSURE RESPONSE MODELS
I
IX)
Plant
(Tokyo Cross)
(Tokyo Cross)
Foliage crops
Lettuce
Lettuce
Spinach
(America)
(America)
(Winter Bloomsdale)
(Winter Bloomsdale)
(Hybrid 7)
(Hybrid 7)
(Viroflay)
(Viroflay)
Model
edible root wt/plant = 14.8 if 03 < 0.054
= 27.0 - 226 03 if
g/plant = 15.25 exp [-(03/0.094)3'94]
fresh head wt/plant = 1065.7 - 5978 03
g/plant = 1245 exp [-(03/0.098)1'22]
g/plant = 22.7 -106 03
g/plant = 21.2 exp [-(03/0.142)1'65]
g/plant = 23.3 - 121 03
g/plant = 20.8 exp [-(03/0.127)2-°7]
g/plant = 42.1 - 193 03
g/plant = 36.6 exp [-(03/0. 139)2'68]
g/plant = 46.1 - 238 03
g/plant = 41.1 exp [-(03/0. 129)1'99]
The 03 concentration is expressed as the 7-hour seasonal mean.
The Hodgson data were obtained from two designs in 1981: a full
where some plants were removed before harvest.
This model did not fit the data well and tended to underestimate
Control 03
concentration0
0.014
03 > 0.054
0.014
0.043
0.043
0.024
0.024
0.024
0.024
0.024
0.024
0.024
0.024
harvest (F) and a partial
the 03 concentrations that
Yield
Percent
0.061
0.053
0.057
0.053
0.043
0.046
0.041
0.049
0.043
0.060
0.041
0.048
plot harvest
cause yield
Loss
Percent
0.074
0.072
0.084
0.075
0.081
0.082
0.075
0.080
0.082
0.095
0.075
0.080
(P)
losses.
-------
concentrations suggests that the predicted values are more influenced by the
original input data than by the model fit to the data. The relative responses
of five major crops to 03, based on the Weibull model combined data sets, are
presented in Figure 7-18.
A brief review of the yield response data summarized (Table 5-36) indicate
that significant yield reductions (10 percent) were predicted when the 7-hour
seasonal mean 0., concentration exceeded 0.04 to 0.05 ppm. Studies with fescue
cultivars predicted significant yield reductions when the plants were exposed
to 0.10 ppm 0 for 6 hours/week for 7 weeks.
To summarize the data from studies that used discrete treatments, the
lowest concentration that significantly reduced yield was determined from the
author's analysis (Table 7-36). The lowest concentration reported to cause a
significant yield reduction was frequently the lowest concentration used in
the study. Given the experimental design, it was not always possible to
estimate if significant yield reductions could have occurred at lower 0.,
O
concentrations. In general, the data indicate that 0, concentrations of 0.10
ppm for a few hours per day for several days to weeks generally induced signi-
ficant yield reductions. Although from this analysis it appears that higher
0^ concentrations were required to cause a yield reduction than the concentra-
tions estimated by the regression approaches, it should be noted that the
concentrations derived from the regression studies were based on a 10 percent
yield loss, but in the studies that used discrete treatments the 0.10 ppm
concentration frequently caused greater mean yield losses (10 to 50 percent).
The data from the previous criteria document (U.S. Environmental Protec-
tion Agency, 1978) developed limiting values which suggested that 0., concen-
trations of 0.04 to 0.06 ppm for 4 hours or more were likely to injure plant
foliage. The growth data summarized in the document indicated that plant
growth and yield can be reduced at 03 concentrations of 0.05 to 0.08 ppm for
several hours/day. These concentrations are similar to the concentrations
0.04 to 0.07 shown to reduce plant yield in field studies and ambient air
studies in this chapter.
Studies have shown that the ambient air in various parts of the United
States is sufficiently polluted that crop growth yield is being reduced. For
example, losses have been reported in tomato (33 percent at 0.035 ppm), bean
(26 percent at 0.041 ppm), soybean (20 percent at 0.05 ppm), snapbean (10 to
22 percent at 0.06 ppm), forest trees (12 to 67 percent at 0.052 ppm), and
019PP/A 7-214 4/19/84
-------
1.0
UJ
£ 0.8
v>
Ul
DC
a
UJ
> 0.6
Z
o
tc
O 0.4
OL
O
oc
Q.
0.2
0.0
I —
0.0
0.02 0.04 0.06 0.08
03 CONCENTRATION, ppm
0.10
Figure 7-18. Relative (^-induced yield reduction of selected crops
as predicted by the Weibull model (Heck et al., 1983).
7-215
-------
PRELIMINARY DRAFT
TABLE 7-36. OZONE CONCENTRATIONS AT WHICH SIGNIFICANT YIELD LOSSES HAVE BEEN NOTED
FOR A VARIETY OF PLANT SPECIES EXPOSED TO 03 UNDER VARIOUS EXPERIMENTAL CONDITIONS
Plant species
Alfalfa
Alfalfa
Pasture grass
Ladino clover
Soybean
^ Sweet corn
ro
^ Sweet corn
Wheat
Radish
Beet
Potato
Pepper
Cotton
Carnation
Coleus
Begonia
Exposure duration
Yield reduction, % of control
03 concentration
7 hr/day, 70 days
2 hr/day, 21 days
4 hr/day, 5 days/wk, 5 wk
6 hr/day, 5 days
6 hr/day, 133 days
6 hr/day, 64 days
3 hr/day, 3 days/wk, 8 wk
4 hr/day, 7 days
3 hr
2 hr/day, 38 days
3 hr/day, once every 2 wk, 120 days
3 hr/day, 3 days/wk, 11 wk
6 hr/day, 2 day/wk, 13 wk
24 hr/day, 12 days
2 hr
4 hr/day, 4 times once every
6 days over 24 days
51, top dry wt
16, top dry wt
20, top dry wt
20, shoot dry wt
55, seed wt/plant
45, seed wt/plant
13, ear fresh wt
30, seed yield
33, root dry wt
40, storage root dry wt
25, tuber wt
19, fruit dry wt
62, fiber dry wt
74, number of flower buds
20, flower no.
55, flower wt
0.10
0.10
0.09
0.10
0.10
0.10
0.20
0.20
0.25
0.20
0.20
0.12
0.25
0.05 - 0.09
0.20
0.25
-------
TABLE 7-36. OZONE CONCENTRATIONS AT WHICH SIGNIFICANT YIELD LOSSES HAVE BEEN NOTED
FOR A VARIETY OF PLANT SPECIES EXPOSED TO 03 UNDER VARIOUS EXPERIMENTAL CONDITIONS
Plant species
Exposure duration
Yield reduction, % of control 0^ concentration
Ponderosa pine
Western white
pine
Loblolly pine
Pitch pine
Poplar
Hybrid poplar
Hybrid poplar
Red maple
American
sycamore
Sweetgum
White ash
Green ash
Willow oak
Sugar maple
6 hr/day, 126 days
6 hr/day, 126 days
6 hr/day, 28 day
6 hr/day, 28 days
12 hr/day, 5 mo
12 hr/day, 102 days
8 hr/day, 5 day/wk, 6 wk
8 hr/day, 6 wk
6 hr/day, 28 days
6 hr/day, 28 days
6 hr/day, 28 days
6 hr/dat, 28 days
6 hr/day, 28 days
6 hr/day, 28 days
21, stem dry wt
9, stem dry wt
18, height growth
13, height growth
+1333, leaf abscission
58, height growth
50, shoot dry wt
37, height growth
9, height growth
29, height growth
17, total dry wt
24, height growth
19, height growth
12, height growth
0.10
0.10
0.05
0.10
0.041
0.15
0.15
0.25
0.05
0.10
0.15
0.10
0.15
0.15
-------
ground cover species (9 to 33 percent at 0.051 pp,Ti) exposed for several weeks
or several months. Studies of eastern white pine and ponderosa pine showed
that ambient 0,. reduced the annual radial growth of the trees by 30 to 70
percent. Such a reduction can have a significant impact on wood production.
Some effects on crop quality have been shown in a few of the CL addition
and ambient air studies. Ambient CL in the East (soybean, potato, grapes) and
West (sweet corn, alfalfa) have affected product quality. Ozone addition
studies reported altered crop quality at 0.10 ppm for alfalfa and clover and
at 0.20 ppm for potato, sweet corn, carrot, tomato, and cabbage. Reduced
reproductive capacities have also been suggested at 0- concentrations of 0,05
to 0.10 ppm.
Ozone has been identified as the most important air pollutant in terms of
reduced agricultural yields. In view of the importance of U.S. agriculture to
both domestic and world consumption of food and fiber, major reductions in
supply could have substantial consequences. Numerous studies have attempted
to assess dollar losses resulting from ambient 0., or the benefits of 0^ control.
The most recent estimates of ambient 0~ damage to agriculture range from $30
million to $250 million for selected regions and from approximately $2 billion
to $3 billion at the national level. These values typically exceed the esti-
mates found in the 1978 criteria document on photochemical oxidants. This
increase in damage estimates is partially caused by the increased crop coverage,
somewhat greater recognition of 0., effects as reported in the more recent
response literature, different air quality assumptions, and the use of differ-
ent base-dollars (e.g., 1980 dollars vs. 1970 dollars).
PAN is highly reactive chemically and with biological systems. It is
produced photochemically in the same reaction that produces Q^. Both compounds
coexist in the photochemical oxidant air pollutant complex. The effects of
PAN were a concern in southern California for almost 20 yr before the phyto-
toxicity of 0.-, under ambient conditions was identified.
The characteristic lower surface glazing and bronzing and transverse
necrotic or chlorotic bands on foliage associated with PAN exposure have been
reported in several states of these United States and in The Netherlands,
Japan, and Canada. Monitoring data have revealed even wider distribution of
the air pollutant.
Crops and ornamentals ,Tiarketed for their foliage have frequently been
rendered non-marketable or have suffered significant loss of value from ambient
019PP/A 7-218 4/19/84
-------
exposures. After severe PAN damage entire crops may be unmarketable, or
extensive hand work is required to remove the injured leaves before the crop
may be marketed. Losses of fruit, seed, root, and total biomass in other
types of crops have not been well evaluated, primarily because experimental
data are not available to make such an assessment. The growth, development,
and reproductive responses to PAN under ambient conditions are difficult to
determine because they cannot be separated from responses to ambient 0^-
Long-term experiments designed to measure growth and development responses are
difficult to conduct because (1) PAN is highly reactive chemically and difficult
to store; (2) generation of PAN is slow and time-consuming; (3) when PAN is
condensed in liquid form, it is highly explosive; and (4) plants grown in
greenhouses and exposed in chambers are much less responsive to PAN than are
plants growing in the field and exposed under ambient conditions.
Growth suppression of navel orange trees exposed for a year to PAN under
conditions designed to simulate ambient conditions was reported. Similarly,
three and four 4-hr exposures on successive weeks were reported to reduce
growth and disrupt photosynthate partitioning in four tomato varieties.
Studies with lettuce and Swiss chard indicated that these crops could sustain
significant yield losses of 13 percent (lettuce) and 23 percent (Swiss chard)
without visible injury symptoms. The plants were exposed to 40 ppb for
4 hour/day, twice week from germination to crop maturity.
A comparison of PAN concentrations likely to cause either visible injury
or reduced yield with the measured ambient concentrations (Chapter 6) indicates
that it is unlikely that PAN effects will occur to plants in the United States
except in some areas of California and possibly a few other localized areas.
PAN reacts with sulfhydryl (SH) groups and has been reported to inhibit
SH containing enzymes. PAN was reported to inhibit cell expansion in oat
coleoptile. High concentrations disrupted the photosynthesis process in
isolated spinach chloroplasts.
Limited studies have been conducted with mixtures of PAN and 03. When
high concentrations of both gases were used, no clear trend was observed. But
when PAN concentrations near and at ambient levels were used, the studies
indicated that PAN and Cu do not interact or that the resultant injury was
less than would be expected if the effects were additive.
No data have shown that woody species or native vegetation are injured by
ambient concentrations of PAN. However, the characteristic PAN-type injury
019PP/A 7-219 4/19/84
-------
symptoms have been observed on the foliage of several weed and grass species.
Such plants are frequently used as bioindicators to determine if injurious
doses of PAN have occurred and to generally establish when the episode occurred
and what concentrations were involved.
019PP/A 7-220 4/19/84
-------
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APPENDIX A
COLLOQUIAL AND LATIN NAMES OF PLANTS DISCUSSED IN THE CHAPTER
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APPENDIX A. COLLOQUIAL AND LATIN NAMES OF PLANTS DISCUSSED IN THE CHAPTER
Colloquial Name
Latin name
Alfalfa
Ash
Green
White
Aspen
Bigtooth
Azalea
Delaware valley white
Hinodegiri
Korean
Barley
Bean
var. - French
Green snapbean
Navy
Pinto
Red kidney
Snapbean
White
Bean
Broad
Beet
Garden
Sugar
Begonia
Begonia
Birch
White
Yellow
Cabbage
Carnation
Carrot
Medicago sativa L.
Fraxinus pennsylvam'ca Marsh.
Fraxinus americana L.
Populus arandidentata Michx.
Rhododendron mucronatum Don.
Rhododendron obtusum Planch.
Rhododendron poukhanensis Leveille
Hordeum yulgare L.
Phaseolus vulgaris L.
Vicia faba L.
Beta vulgaris L.
Begonia semperflorens Link and Otto
Begonia X hiemalis Fotsch.
Betula papyrifera Marsh.
Betula allegham'ensis Britton
Brassica oleracea capitata L.
Dianthus caryophyllus L.
Daucus carota var. sativa DC.
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APPENDIX A. (continued)
Colloquial Name
Latin name
Chard
Swiss
Cherry
Black
Chrysanthemum
Citrus
Clover
Landino
Coleus
Corn
Field
Sweet
Cotoneaster
Cotton
Cottonwood
Eastern
Elder
Black
Elm
Chinese
Endive
Fir
Douglas
Geranium
Grape
Grape
Gum
Black
Hemlock
Eastern
Beta vulgaris var. cicla L.
Prunus serotina Ehrh.
Chrysanthemum morifolium Ramat.
Citrus sp.
Trifolium repens L.
Coleus blumei Benth.
Zea mays L.
Cotoneaster divaricata Rehd.
Gossypium hirsutum L.
Populus del toides Bartr.
Sambucus nigra L.
Ulmus parvifolia Jacq.
Cichorium endiva L.
Pseudotsuga menziesii (Mirb.) Franco.
Pelargonium hortorum Bailey
Vitis vim'fera L.
Vitis labrusca L.
Nyssa sylvatica Marsh.
Tsuga canadensis (L.) Carr.
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APPENDIX A. (continued)
Colloquial Name
Latin name
Holly
American
Japanese
Larch
Japanese
Lettuce
var.-Cos (Romaine)
Linden
American
Locust
Black
Maple
Red
Sugar
Marigold
Mi 1kweed
Morning glory
Mountain laurel
Muskmelon
Mustard
Nettle (little leaf)
Oak
Black
California black
Wi1 low
Oat
Onion
Australian
Pasture grass
Australian
Grasslands
Victorian
Ilex opaca Ait.
Ilex crenata Thunb.
Larix leptolepis Gord.
Lactuca sativa L.
Tilia americana L.
Robim'a pseudoacacia L.
Acer rubrum L.
Acer saccharum L.
Tagetes erecta L.
Asclepias syriaca L.
Ipomea ni1 Roth.
Kalmia 1 atifolia L.
Cucumis melo L.
Brassica migra (J.) Koch
Urtica urens L.
Quercus velutina Lam.
Quercus kelloggii Newb.
Quercus phellos L.
Avena sativa L.
Alii urn cepa L.
Phalaris aquatica
Dactyl is glomerata L.
Lolium perenne L.
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APPENDIX A. (continued)
Colloquial Name
Latin name
Peanut
Pepper
Petunia
Pine
Austrian
Eastern white
Jeffrey
Loblolly
Lodgepole
Monterey
Pitch
Ponderosa
Scotch
Shore
Slash
Sugar
Table mountain
Virginia
Western white
Poinsettia
Poplar
Hybrid poplar
Hybrid poplar
Hybrid poplar
Potato
Privet
Amur
Radish
Snapdragon
Soybean
Spinach
Spruce
Sitka
White
Arachis hypogea L.
Capsicum annuum L.
Petunia hybrida Vilm.
Pinus nigra Arnold
Pinus strobus L,
Pinus jeffreyi Grev. and Balf.
Pinus taeda L.
Pinus contorta var. murrayana (Balf.)
Critch
Pinus radiata D. Don
Pinus rigida Mill.
Pinus ponderosa Laws.
Pinus sylvestris L.
Pinus contorta var. contorta Dougl.
ex Laud
Pinus elliotti Englem. ex Vasey
Pinus lambertiana Dougl.
Pinus pungens Lamb.
Pinus virgi niana Mill.
Pinus monticola Dougl.
Euphorbia pulcherrima Wildenow
Populus X euramericana
Populus sp.
Populus maximowiczii X trichocarpa
Populus deltoides X trichocarpa
Solanum tuberosum L.
Ligustrum amurense Carr.
Raphanus sativus L.
Antirrhinum majus L.
Glycine max (L.) Merr.
Spinacia oleracea L.
Picea sitchensis (Bong.) Carr.
Picea glauca (Moench) Voss
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APPENDIX A. (continued)
Colloquial Name
Latin name
Strawberry
Sunflower
Sweetgum
Sweet mock-orange
Sycamore
American
Tomato
Tree-of-heaven
Turfgrass
Annual bluegrass
Bermudagrass
Colonial bentgrass
Creeping bentgrass
Kentucky bluegrass
Red fescue
Red top
Ryegrass
Tall fescue
Zoysiagrass
Turnip
Viburnun
Tea viburnun
Linden viburnum
Walnut
Black
Wild strawberry
Wheat
Winter
Yellow poplar (Tulip poplar)
Yew
Fragaria chiloensij var. ananassa
Bailey
Helianthus anuus I.
Liquidambar styraciflua L.
Philadelphus coronarius L.
Platanus occidental is L.
Lycopersicon esculentum Mill.
Ailanthus altissima Swingle
Poa annua L.
Cynodon dactyl on L., Pers.
Agrostis tenuis Sibth.
Agrostis palustris Huds.
Poa pratensis L.
Festuca rubra Gaud.
Agrostis alba L.
Lolium perenne L.
Festuca arundinaceae Schreb.
Zoysia japonica Steud.
Brassica rapa L.
Viburnum setigerum Hance
Viburnum dilatatum Thunb.
Juglans nigra L.
Fragaria virginiana Duchesne
Triticum aestivum L.
Liriodendron tulipifera L.
Taxus X media Rehd.
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APPENDIX B
SPECIES THAT HAVE BEEN EXPOSED TO OZONE TO DETERMINE DIFFERENTIAL RESPONSES OF
GERMPLASM TO PHOTOCHEMICAL PRODUCTS
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APPENDIX B. SPECIES THAT HAVE BEEN EXPOSED TO OZONE TO DETERMINE
DIFFERENTIAL RESPONSES OF GERMPLASM TO PHOTOCHEMICAL PRODUCTS
Species
Alfalfa
Azalea
Bean
References
Begonia
Chrysanthemum
Cucumber
Eggplant
English holly
Forage legumes
Grape
Lettuce
Morning glory
Oat
Petunia
Pine
Poplar
Poinsettia
Potato
Howell et al., 1971
Gesalman and Davis, 1978
Butler and Tibbitts, 1979
Davis and Kress, 1974
Meiners and Heggestad, 1979
Heggestad et al., 1980
Reinert and Nelson, 1979
Adedipe, 1972
Wood and Drummond, 1974
Brennan and Leone, 1972
Ormrod et al., 1971
Rajput and Ormrod, 1976
Brennan and Leone, 1970
Brennan et al., 1969
Richards et al., 1958
Reinert et al., 1972
Nakamura and Matsunaka, 1974
Brennan et al., 1964
Feder et al., 1969
Cathey and Heggestad, 1972
Elkiey and Ormrod, 1980
Berry, 1971
Houston, 1974
Karnosky, 1977
Manning et al., 1973
Heggestad, 1973a
DeVos et al., 1982
019ZX/A
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APPENDIX B. (continued)
Species
References
Radish
Safflower
Soybean
Spinach
Sugar maple
Tobacco
Tomato
Turfgrasses
Wheat
Woody species
(general)
Re inert et al., 1972
Howell and Thomas, 1972
Tingey et al., 1972
Miller et al., 1974
Heagle and Letchworth, 1982
Manning et al., 1972
Hibben, 1969
Dean, 1963
Grosso et al., 1971
Heggestad et al., 1964
Huang et al., 1975
Clayberg, 1971
Reinert and Henderson, 1980
Brennan and Halisky, 1970
Heagle et al., 1979c
Davis and Coppolino, 1974; 1976
Davis and Wood, 1972
Hanson, 1972
Jensen, 1973
O'Connor et al., 1975
Wilhour and Neely, 1977
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8. EFFECT OF OZONE AND OTHER PHOTOCHEMICAL OXIDANTS
ON NATURAL AND AGROECOSYSTEMS
8.1 INTRODUCTION
Organisms do not live alone; each species exists as a breeding population.
These populations live together to form communities that interact with their
environment and each other to create ecosystems. Chapter 7 discusses the
response of individual species and subspecies of plants to ozone (0_) and
peroxyacetyl nitrate (PAN) exposure. The responses of terrestrial vegetation
to OT and PAN may be envisioned as a continuum ranging from the molecular, to
the organismal, to the ecosystem level. Ecosystems respond to stress in a
different manner from individuals. In this chapter, the responses of ecosys-
tems to 0,, stress will be emphasized. Ecosystems in both the western and
eastern United States have been under stress from 0~ transported from sources
many kilometers away for more than three decades. No attempts have been made
to examine an ecosystem response to PAN. Controlled fumigations with PAN, as
well as field observations, have been confined to assessing the response of a
few sensitive plant species.
8.2. ECOSYSTEMS: THE POTENTIAL FOR INDIRECT EFFECTS
8.2.1 Interwoven Structure, Boundaries, and Social Value
An ecosystem is an integrated unit of nature consisting of interacting
plants and animals in a given area (the community) whose survival depends on
the maintenance of biotic (living) and abiotic (nonliving) structures and
functions. An ecosystem does not have to be isolated, but usually has defin-
able limits within which are the integrated functions of energy flow, nutrient
cycling, and water flux (Odum, 1969; Odum, 1971a; Jordan and Medina, 1977).
The functions of energy flow and nutrient cycling among the biotic and abiotic
components form definite patterns that lead to clearly defined trophic struc-
tures (food webs) and biotic diversity.
Ecosystems may be large or small, natural or human-made, and are not
characterized by common physical dimensions or structures, but are character-
ized by the common processes of energy flow and chemical cycling (Botkin and
Keller, 1982; Odum, 1969; Odum, 1971a). In all cases they have boundaries and
may be delimited in several ways. Geographic, topographic, hydrologic, taxo-
nomic, or energy boundaries have been used. Boundaries between adjacent
019CC/A 8-1 May 1984
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ecosystems may be obvious and distinctive, as when terrestrial and aquatic
systems are juxtaposed, or they may be gradual and poorly defined, as in the
transitional zone of scattered trees and grass between a forest and open
grassland. Irrespective of the ease of boundary delimitation, there is always
some flow of energy and materials from one ecosystem to adjacent ecosystems.
All ecosystems are open and capable of responding to changes in the movement
of energy and materials from adjacent environments as well as to changes in
their own environment (Cox and Atkins, 1979).
A forest, fallen log, agricultural field, river, or lake is an ecosystem.
Terrestrial ecosystems are associations or communities of land-dwelling plant
and animal (including human) species and their environments. Of particular
interest from the standpoint of air pollution impacts are forest and agricul-
tural ecosystems. These systems not only hold obvious economic significance
for human society; they also represent the even more fundamental fact that
human life depends ultimately on such systems. Without plants fixing energy
and essential elements to form the base of the food chain, humans could not
survive. On the other hand, animals and microorganisms (consumers and decom-
posers) are essential to assure cycling of the essential elements. Thus, any
effects of atmospheric pollutants on terrestrial ecosystems or their components
deserve careful attention.
Natural and agricultural ecosystems possess the same basic functional
components, require energy flow and mineral cycling for maintenance, and are
subject to the dominating influences of climate and substrate. Natural eco-
systems vary in diversity from simple systems with few species to complex
systems with many species. Their populations also vary in genetic composition,
age, and species diversity. They are self-regulating and self-perpetuating.
Agroecosystems, on the other hand, are highly manipulated monocultures of
similar genetic and age composition and are unable to maintain themselves with-
out the addition of nutrients, energy, and human effort; opportunistic native
and imported species may invade the sites. The manipulation of monocultures is
designed to concentrate ecosystem productivity into a particular species to
maximize its yield (e.g., corn, wheat, soybeans) for the benefit of humans
(Cox and Atkins, 1979).
As cultural treatments intensify, the dollar value placed by humans on
the products of the ecosystem generally increases, and biological diversity
typically decreases. For example, wilderness forest areas and national parks
019CC/A 8-2 May 1984
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are high in biological diversity, and human management effort is low. Corn
fields, wheat fields, lawns, and city parks are low in diversity and are
highly managed (Figure 8-1). Natural forests managed as wilderness areas may
have products of little direct dollar value, but they provide critically
important (although unpriced) benefits to society, such as soil stabilization,
enhanced water quality, nutrient conservation, energy conservation, gene
preservation, and amenity and aesthetic functions (Bormann, 1976; Hutchinson
et al., 1982; National Research Council, 1980; Smith, W. H. , 1970; Westman,
1977). It is extremely important to recognize that societal benefits derived
from natural ecosystems, such as forests, are commonly obtained without invest-
ment of appreciable direct dollar expenditures or intensive management. The
benefits provided by forests are powered by solar energy. When forests are
removed, these benefits are no longer available. They must be replaced by
HIGH
vi
cc
01
LOW
WILDERNESS/ GENE
POOLS
URBAN
AREAS
CROPS AS
MONOCULTURES
IRRIGATED
CROPS AS
MONOCULTURES
LOW
•*- MANAGEMENT-
HIGH
Figure 8-1. The relationship of several managed ecosystems in terms of
degree of management and biological diversity.
Source: Smith and Hill (1975).
019CC/A
8-3
May 1984
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extensive and continuing investments of fossil f<»o]s and other natural resources
by humans if the quality of life is to be maintained. When forests are lost,
replacements for wood products must be found, erosion control works built,
reservoirs enlarged, air pollution control technology upgraded, flood control
works installed, water purification plants improved, air conditioning increased,
and new recreational facilities provided. These substitutes could produce an
enormous tax burden, a drain on the world's remaining supply of natural re-
sources, and an increased stress on the remaining natural systems. (Bormann
and Smith, 1980).
8.2.2 Ecosystem Components: Internal Structure
The living (biotic) components of ecosystems are populations of either
autotrophs (producers) or heterotrophs (consumers and decomposers). Autotrophs,
predominantly green plants, are capable of synthesizing their own food from
simple compounds by capturing the sun's energy and are, therefore, in the
first trophic level. The biomass (total organic matter) accumulation at this
trophic level is termed primary production. In a forest ecosystem, this is
the addition of new organic matter through the growth of trees, shrubs, and
herbs.
Heterotrophs (consumers and decomposers) require preformed food materials.
Consumers are organisms that feed on other organisms and constitute all trophic
levels above the first. In morphology and size, they are extremely variable,
ranging from single-celled microscopic forms to large mammals. Consumers that
rely directly on green plants for food are herbivores and are usually placed
in the second trophic level; those that ingest herbivores or each other are
carnivores. Decomposers are capable of degrading complex compounds and utili-
zing some of the decomposition products as their own food source while releasing
inorganic substances for use by other organisms. Decomposers are organisms
such as litter-feeding invertebrates, bacteria, fungi, and protozoa (Odum,
1971b; Botkin and Keller, 1982; Smith, R. L. , 1980). Autotrophs and hetero-
trophs (producers, consumers and decomposers) all live together as populations
of interacting organisms. "Genetically, individuals are members of their
local populations; ecologically, they are members of a community and an eco-
system" (Billings, 1978). The number of species in a given ecosystem is
variable. Desert ecosystems have fewer species than do forests. Most natural
ecosystems have more species than do agricultural ecosystems. The number of
species in a given ecosystem may change as the system matures.
019CC/A 8-4 5/1/84
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The living components of an ecosystem cannot function without the nonliving
(abiotic) components. All green plants require the energy of the sun (an
abiotic component) to make their own food. Other abiotic components utilized
by green plants in food formation include carbon dioxide, from the air, and
water and minerals (calcium, phosphorus, magnesium, iron), primarily from the
soil. Because virtually all other biotic components depend on green plants,
the energy and minerals used by the plants are passed through the ecosystem as
organic matter via the processes of energy flow and mineral cycling. Thus,
ecosystem components become organized into structural patterns based on feeding
steps (trophic levels). Food chains form when organisms eat and are eaten.
Chains become complex food webs when the food source is shared. For example,
a food web is formed when some animals are consumed by several predators or
when the same plants are eaten by a variety of herbivores. The unidirectional
movement of energy and the biogeochemical cycling of nutrients through the
highly structured interrelationships that have developed among the various
components unite the ecosystem into a complex, interacting system of physical,
chemical, and biological elements. Temperature, precipitation, radiation,
barometric pressure, climate, and pollution are additional abiotic factors
that influence ecosystem components and thus they influence the flow of energy
and cycling of minerals through the system as well (Odum, 1971a,b; Botkin and
Keller, 1982; Smith, R.L., 1980).
8.2.3 Response to Stress
Forests, prairies, marshes, and ponds or lakes, natural ecosystems in
existence today, are the culmination of years of gradual community development
known as succession. Adaptation, adjustment and evolution occur with time as
the biotic and abiotic components of the communities interact. Some organisms
die, and others reproduce and replace them. Energy and mineral nutrients
continually move through the food webs that have been established. In time
the communities arrive at some form of steady state and are more or less
self-maintaining as long as the abiotic factors remain constant. Through
succession, ecosystems evolve toward the most stable state possible within the
constraints of the environment (Odum, 1971a, b; Cox and Atkins, 1979; Smith,
R. L. , 1980).
Disturbances do occur. Fire, drought, windstorms, disease, and pollution
perturb the ecosystems. Ecosystems can respond to these stresses only through
019CC/A 8-5 May 1984
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the response of the populations of organisms of which they are composed (Smith,
R. L. , 1980). The individual organisms of a population sensitive to environ-
mental changes are removed. Therefore, the capacity of an ecosystem to maintain
internal stability is determined by the ability of individual organisms to
adjust their physiology or behavior to change. The capacity of organisms to
withstand change or injury from weather extremes, fires, storms, pesticides,
or polluted air follows the principle of limiting factors (Billings, 1978;
Odum, 1971; Smith, R. L. , 1980). According to this principle, for each physi-
cal factor in the environment there exists for each organism a minimum and a
maximum limit beyond which no members of a particular species can survive.
Either too much or too little of a factor such as heat, light, water, or
minerals (even though they are necessary for life) can jeopardize the survival
of an individual and in extreme cases, a species (Billings, 1978; Smith, R.
L. , 1980; Odum, 1971a). The range of tolerance of an organism may be broad
for one factor and narrow for another. The tolerance limit for each species
is determined by its genetic makeup and varies from species to species for the
same reason. The range of tolerance also varies depending on the age, stage
of growth, or growth form of an organism. Limiting factors are, therefore,
those which, when scarce or overabundant, limit the growth, reproduction,
and/or distribution of an organism (Billings, 1978; Smith, R. L. , 1980; Odum,
1971a). The success with which an organism copes with environmental change is
determined by its ability to produce reproducing offspring. The size and
success of a population depend on the collective ability of organisms to
reproduce and maintain their numbers in a particular environment. Those
organisms that are tolerant of or adapt best to stress contribute most to
future generations, because they have the greatest number of progeny in the
population (Woodwell, 1970; Odum, 1971a; Smith, R. L. , 1980; Roose et al.,
1982).
Some plant populations have the capacity to evolve resistance (tolerance)
to environmental stress. Sensitive plants in a population die or are unable
to compete with resistant plants, so do not reproduce. The resistant plants
reproduce and in time resistant populations develop. Resistance refers to the
relative ability of organisms of the same genetic composition (genotype) to
maintain normal growth and remain free from injury in a given polluted environ-
ment. Resistance is quantitative rather than qualitative, as resistance need
not be complete (Roose et al. , 1982). The rapidity with which a population
019CC/A 8-6 5/1/84
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develops resistance depends on the selection pressure, i.e., the period of
exposure to the stress.
Plants exposed continuously to heavy metals over time develop populations
resistant to the stress. Selection by both air pollutants and herbicides
tends to be episodic (Roose et al., 1982). Acute injury from air pollution
resembles that from herbicides in that selection for resistance occurs only
for short periods of time. Chronic air pollution more closely resembles soil
contaminated with heavy metals in that the plants experience the polluted
environment for a considerable portion of their lives. Resistance in either
situation depends on the resistant or tolerant genotype being present in the
plants that are growing in unpolluted air (Roose et al., 1982).
Variability in tolerance or resistance to air pollutants appears to be
common in most species of plants. The differential sensitivity of plants is
discussed in Chapter 7, in sections of the document that follow, by Roose et
al. (1982), and in numerous other publications. Annual plants are capable of
altering the genetic composition of the entire population every year. Perennial
plants adapt and express their resistance through differential growth and the
survival of the resistant genotype without sexual reproduction. Variability
in resistance of ponderosa pine (Pinus ponderosa Doug. ex. Laws) and eastern
white pine (Pinus strobus L.) is discussed in the sections that follow.
Competition increases selection for resistance under polluted conditions
and selection against resistance under less polluted conditions. Studies
using heavy metals and herbicides indicate that once the stress is removed and
plants are growing in a pollutant-free environment, the pollutant-resistant
plants tend to decline in number (Roose et al. , 1982). This evidence is
corroborated by observations of ecosystems functioning under specific natural
environments. Certain terrestrial ecosystems require a major disturbance
(e.g., fire, drought, and windstorms) to retain their characteristics (Vogel,
1980; Smith, W. H. , 1980). In the absence of disturbance, some ecosystems
appear to degrade, lose nutrients, become less productive, and have fewer
species with a smaller biomass (Woodwell, 1970; Gorham et al., 1979).
Two groups of organisms particularly critical to the maintenance of an
ecosystem are the producers, through which solar energy, carbon, and other
nutrients enter living systems, and the decomposers, through which nutrients
bound up in other organisms are released for reuse. Loss of either of these
groups results in the collapse of the entire system (Ehrlich and Mooney, 1983).
019CC/A 8-7 5/1/84
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The ecosystems that are particularly vulnerable die those in which a single
species appears to be the primary controller of energy flow and nutrient move-
ment, a redwood forest, for example. Controller species vary from ecosystem
to ecosystem, and the differential sensitivity of these species will determine
the extent to which injury occurs and how critical it is to the ecosystem.
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 possible, therefore, to predict
the basic biotic responses of an ecosystem to disturbances caused by environ-
mental stress (Woodwell, 1970; Woodwell, 1962). These responses to disturbance
are (1) removal of sensitive organisms at the species and subspecies level due
to differential kill; (2) reduction in the number of plants and animals (stand-
ing crop); (3) inhibition of growth or reduction in productivity; (4) disrup-
tion of food chains; (5) return to a previous state of development; and (6)
modification in the rates of nutrient cycling.
Not all ecosystems respond in the same way to stress. Some ecosystems
may be more sensitive to a given perturbation at one stage of development than
at another. Organisms can exist only within their range of tolerance. Some
populations of organisms, annual plants, insects, and mice, for example,
respond rapidly to environmental change. They increase in numbers under
favorable conditions and decline rapidly when conditions are unfavorable.
Populations of other organisms, such as trees and wolves, fluctuate less in
response to favorable or unfavorable conditions by showing little variation in
the rates of reproduction and death. Adaptation is the ability of an organism
to conform to its environment. Ecosystem stability ultimately is based on the
adaptability of organisms that compose it. Stability may be associated with
the ability of a system to return to an equilibrium state after a temporary
disturbance (Rolling, 1973). The less it varies from and the faster it returns
to its original state, the ' more stable the system (Smith, R. L. , 1980).
Stability also involves persistence, the ability of the populations of an
ecosystem to persist through time. Persistence involves resilience, the
ability of an ecosystem to absorb changes. Although individual populations
within a system may fluctuate greatly in response to environmental changes,
the system may be highly resilient (Holling, 1973; Smith, R. L. , 1980).
Contrasted with resilience is resistance, the ability of a system, because
of its structure, to resist changes from disturbances. Typically, the most
019CC/A 8-8 5/1/84
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resistant ecosystems have large living components, trees for example, and
store nutrients and energy in the standing biomass. Resistant systems such as
forests, once highly disturbed, are very slow in returning to their original
state (Smith, R. L. , 1980). Perturbation typically causes retrogression, a
return to an earlier and more simplified successional stage of ecosystem
development. Both diversity and structure are changed. Complex communities
become less complex (Whittaker and Woodwell, 1978; Woodwell, 1970). Too
frequent disturbance, or natural disturbance combined or supplemented with
anthropogenic disturbance (e.g., air pollution) may cause a system to change
slowly or to disappear. With moderate rates of disturbance, ecosystems may be
most productive and have the largest number of species and biomass.
8.3 RESPONSE TO OZONE
8.3.1 Effects on Plant Processes
The impact of 0^ and atmospheric pollutants on the environment has sti-
mulated the interest of the general public and scientists as well. The effects
of such disturbances on ecosystem structure and function have been the subject
of numerous publications (Curtis, 1956; Miller and McBride, 1975; Cairns,
1980; National Research Council, 1977; Research Foundation, State University
of New York, 1980; Johnson and Siccama, 1983; Mclaughlin et al., 1982). The
vegetational effects of 0~ can be viewed as a continuum that begins at the
molecular, continues through the organismal and terminates at the ecosystem
level of organization (Figure 8-2). The alteration of biochemical and physio-
logical processes are the fundamental cause of all other effects. The reaction
of 03, or its decomposition products, with cellular components may increase
membrane permeability, alter the activity of specific enzymes and change
metabolic pathways. Visible foliar injury, premature senescence, reduced
photosynthesis, plant vigor, and yield and/or growth are manifestations of
cellular injury. Death may result (Chapter 7).
The ecosystem processes of energy flow and nutrient cycling are directly
involved in plant growth and reproduction (yield) through the processes of
assimilation, nutrient uptake, biosynthesis, and translocation. During assimi-
lation, through the process of photosynthesis, carbon dioxide is converted
into organic compounds for use by the plant. Nutrients and water enter plants
through the roots. The raw materials formed during assimilation (sugars and
019CC/A 8-9 May 1984
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BIOCHEMICAL LEVEL
CELLULAR LEVEL
WHOLE PLANT LEVEL POPULATION LEVEL
CHRONIC OR ACUTE EXPOSURES
COMMUNITY LEVEL
00
I
CD
Figure 8-2. Conceptual sequence of levels showing continuum of plant responses.
Source: Adapted from Heck (1973).
-------
starches) and the nutrients and water taken up by the roots are, through
biosynthesis in the various plant organs, converted into a wide array of
compounds required for plant growth and reproduction. The products of biosyn-
thesis are translocated throughout the plant. A disruption or reduction in
the rate of assimilation, uptake, or the subsequent biochemical reactions, as
frequently occurs under 0, exposure, can be reflected in reduced plant growth
O
and reproduction (Chapter 7).
Plant response to 0- is also influenced by biological, physical, and
chemical variables. Success of a population of plants or animals in any
environment depends on its genetic diversity, the presence of particular gene
combinations and variations among individuals in the population that give a
species or taxon the capacity to adapt to environmental changes. Plants in a
given population (e.g., trees in a stand of ponderosa pine) will not respond
equally to CL exposure because of genetic diversity in the sensitivity of
individual plants and the environmental heterogeneity of the habitat. Differ-
ential plant response is an inherited trait. Plants at different ages, or
growing under different temperature, humidity, light intensity, or soil moisture
regimes will respond differently to equivalent CL exposures. The developmental
stage of both leaf and plant influences CL sensitivity. Leaves approaching
maximum expansion appear to be most sensitive. Evidence indicates that young
plants and those approaching senescence are more sensitive to 0_ exposure than
those of intermediate ages. The presence of several pollutants, chemical
sprays, biological pests, as well as soil moisture and fertility all contribute
to the magnitude of plant response (Chapter 7).
Ozone inhibits photosynthesis, decreases formation of organic compounds
needed for plant growth, and can alter the transport and allocation of the
decreased products of photosynthesis so that sugar storage and root growth are
reduced (Chapter 7). Concentrations of 0.05 ppm for 4 hr, 0.1 ppm for 1 hr,
or 0.2 ppm for 1 hr significantly decreased photosynthesis in a variety of
plant species. Higher concentrations or longer exposure durations also reduced
photosynthesis (Chapter 7, Table 7-1). Specifically, exposure of 3-year-old
ponderosa pine seedlings under controlled conditions to concentrations of
0.15, 0.30, and 0.40 ppm 9 hr/day for 30 days reduced photosynthesis by 10,
70, and 85 percent, respectively (Miller et al., 1969). The maximum photosyn-
thetic rates and stomatal conductance among three injury classes (I, slight;
II, moderate; III, severe) of ponderosa pine trees were compared in relation
019CC/A 8-11 5/1/84
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to cumulative incident 0., concentrations (Coyne and Bingham, 1981). Trees of
an approximately even-aged (18 yr) stand and growing in a similar environment
exhibited a continuum of CL-related foliar injury symptoms that ranged from
severe to slight, an indication of genetically related differential sensitivity
to CL. Differential photosynthetic and stomatal responses compared well with
the OT injury classification mentioned above. The decline in photosynthesis
and stomatal function normally associated with aging was accelerated as 0~
injury symptoms increased. Photosynthesis in all three age classes was reduced
to about 10 percent of the maximum rate observed in class I current needles by
incident exposures of approximately 800, 700, and 450 ppnrhr. When compared
with Class I, photosynthesis declined most rapidly in the sensitive (Class
III) trees. Photosynthetic rates were always higher in the trees with the
fewest injured needles. Premature senescence and abscission of needles oc-
curred soon after photosynthesis reached its lowest level. Losses in photosyn-
thetic capacity in all trees and needle ages exceeded reductions in stomatal
conductance, suggesting injury to the mesophyll, or carboxylation, or excitation
of components of the C0? diffusion pathway was greater than injury to the
stomata (Coyne and Bingham, 1981). Three sensitivity classes have also been
observed in white pine (Pinus strobus L). Yang et al. (1983) studied the
effect of 0~ exposure on photosynthesis in three clones of white pine with
differing 0, sensitivities. Under controlled conditions, the clones were
O
exposed to concentrations of 0.00, 0.10, 0.20, and 0.30 ppm 4 hr/day for 50
consecutive days. By day 10, photosynthesis in the sensitive plants exposed
to 0.30 ppm was significantly reduced. By day 20, photosynthesis in the
sensitive plants at all concentrations was reduced. At the end of 50 days, net
photosynthesis in the sensitive clone exposed to 0.10, 0.20, and 0.30 ppm was
reduced from the control by 24, 42, and 51 percent respectively. Photosynthesis
in the intermediately sensitive clone was reduced 6, 14, and 10 percent. The
insensitive clone varied from the control at the 20-, 30- and 40-day periods,
but had nearly recovered by 50 days. Decrease in the rates of photosynthesis
was closely associated with visible needle injury, premature senescence and
reduction of biomass in the sensitive clones. Reduction in biomass was asso-
ciated with the effect of 03 exposure upon the rate of photosynthesis, with
plant metabolism and with injury to the assimilatory apparatus of the plants.
In each of the studies discussed above, 03 exposure alters photosynthesis
and other physiological and biochemical processes. Diminished photosynthetic
019CC/A 8-12 May 1984
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capacity results in decreased carbohydrates for plant use in growth, storage,
reproduction, and injury repair. The trees are weakened as a result and more
susceptible to disease. Ultimately, the alteration and change of plant pro-
cesses will, if continued, be reflected in the ecosystem processes of energy
flow and nutrient cycling.
8.3.2 Effects on Species Composition and Succession
Ozone stress has been shown to affect species composition and succession
in forests and other plant communities in both the western and eastern United
States. Ozone exerts selection pressure on sensitive species by causing their
demise or by weakening them and making them less competitive. Ozone-tolerant
species may then replace them in the plant communities. Disruption of food
chains, modification of the rates of nutrient cycling, and a less stable
community can result.
Cobb and Stark (1970) concluded that if the air pollution transported
from the Los Angeles Basin to the San Bernardino Mountains continued unabated,
there would be a conversion from the well-stocked forests dominated by ponderosa
pine (Pinus ponderosa Dougl. ex. Laws) to poorly stocked stands of tree species
less susceptible to oxidants. Photochemical oxidant air pollution, chiefly 0^,
was first identified as the agent responsible for the slow decline and death
of ponderosa pine trees in southern California by Miller et a!., 1963. Miller
(1973) and the 1978 oxidant criteria document (U.S. Environmental Protection
Agency, 1978) provided a thorough discussion of this oxidant-induced forest
change. Ponderosa pine is one of five major species of the mixed-conifer
forest that covers wide areas of the western Sierra Nevada Mountains and
mountain ranges from 1000 to 2000 m (3000 to 6000 ft) elevation, including the
San Bernardino Mountains in southern California. Above 200 m, Jeffrey pine
(Pinus jeffreyi Grev and Balf) replaces ponderosa pine. Other species are
sugar pine (Pinus lambertiana Dougl.), white fir (Abies concolor Lindl.),
incense cedar (Libocedrus decurrens Torr.), and California black oak (Quercus
kelloggii Newb.). The response of these five major tree species to oxidant
air contaminants in the San Bernardino National Forest has varied. Ponderosa
pine exhibited the most severe visible foliar response to elevated levels of
ambient 03 (0.05 - 0.06 for 24 hr). A 1969 aerial survey conducted by the
U.S. Department of Agriculture, Forest Service, indicated some degree of
stress in 1.3 million ponderosa or Jeffrey pines over an area of more than 405
019CC/A 8-13 5/1/84
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2 2
km (155 mi ). Mortality of ponderosa pine has been extensive. Death has
been typically attributed to bark beetle infestation of trees weakened by air
pollution. White fir has generally suffered slight damage, but scattered
individual trees have exhibited severe symptoms. Sugar pine, incense cedar,
and black oak have exhibited only slight foliar injury from oxidant exposure.
A 233-ha (575-acre) study block was delineated in the southwest section of the
San Bernardino National Forest to conduct an intensive inventory of vegetation
by various size classes and to evaluate the health of the forest. There were
more ponderosa pines 30 cm (12 in) in diameter or larger than any other species
of comparable size in the study area. These pines were most abundant on the
more exposed ridge crest sites of the area. Mortality of ponderosa pine
ranged from 8 to 10 percent during 1968 to 1972. Clearly, the loss of a
dominant species in a forest ecosystem produces profound change in that system.
Miller (1973) concluded that a shift to a greater proportion of white fir will
probably occur in the lower two-thirds of the study area. It was judged that
incense cedar would probably remain secondary to white fir. Sugar pine was
thought to be restricted by its lesser competitive ability and by dwarf mistle-
toe (Arceuthobium) infection. The rate of compositional change was deemed to
depend on the rate of mortality of ponderosa pine, as its selective death
directly affects other conifer species. The upper one-third of the study
area, characterized as being more environmentally severe because of the addi-
tional climatic and edaphic stress, supported less vigorous growth of white
fir. Thus, following the loss of ponderosa pine in this area, sugar pine and
incense cedar may assume greater importance. Miller (1973) suggests, however,
that natural regeneration of these latter species may be restricted in the
more barren, drier sites characteristic of the upper ridge area, so that
California black oak and shrub species may become more abundant there.
Additional research on forest composition in the San Bernardino National
Forest has been reported (Miller and Elderman, 1977; Miller et al. , 1982).
Tree population dynamics were examined on 18 permanent plots, established in
1972 and 1973, and on 83 temporary plots, established in 1974, to investigate
forest development as a function of time since the most recent fire. Gene-
rally, the data continue to support the hypothesis that forest succession
toward species more tolerant of 0_, such as white fir and incense cedar,
O
occurs in the absence of fire. In the presence of fire, pine may be favored
by seedbed preparation and elimination of competing species. These recent
019CC/A 8-14 May 1984
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studies suggest that 5 forest subtypes exist. These are (1) ponderosa pine,
(2) ponderosa pine-white fir, (3) ponderosa pine - Jeffrey pine, (4) Jeffrey
pine - white fir, and (5) Jeffrey pine. Destruction of the pine forest canopy
by fire and CL leads to a dominance of self-perpetuating, fire-adapted, CL-
toTerant mixtures of shrub and oak species that have lower commercial and ame-
nity values than the former pine forest. Forest stand age and species structure
are variables that have the most relevance and direct effect on human welfare
in both recreational and commercial forests. The interplay of insects and
diseases, drought, ozone injury, and forest fires shapes stand age and species
structure (Miller et al., 1982).
From 1973 to 1978, during the period of interdisciplinary study of oxi-
dant impact on the San Bernardino National Forest, the average May through
September 24-hr 0_ concentrations ranged from a background of 0.03 to 0.04 ppm
up to a maximum of 0.1 to 0.12 ppm (Miller et al., 1982). Because this southern
Calfornia forest is used intensively for recreation and because the loss of
ponderosa pine has reduced its aesthetic qualities, the species changes in
forest composition caused by oxidants is a management concern.
In southern California, the predominant native shrub!and vegetation con-
sists of chaparral and coastal sage scrub. Chaparral occupies upper eleva-
tions of the coastal mountains and extends into the North Coast ranges, east
to central Arizona, and south to Baja California. Coastal sage scrub occupies
lower elevations of the coastal and interior sides of the coast ranges from
San Francisco to Baja California. Westman (1979) applied standard plant
ordination techniques used to determine species composition to these shrub
communities to examine the influence of air pollution. The reduced cover of
native species of coastal sage scrub documented on some sites was statisti-
cally correlated with elevated levels of atmospheric oxidants, with a mean
annual average concentration of 0.18 ppm on the 11 most polluted sites. Sites
of high ambient oxidant levels were also characterized by declining species
richness. Further, Stolte (1982) concluded that seedlings of pioneer species
in recently burned chaparral stands were vulnerable to oxidant stress.
Oxidant-induced injury to vegetation has also been observed in the eastern
United States for many years. Needle blight of eastern white pine was first
reported in the early 1900's; however, it was not until 1963 that it was shown
to be the result of acute and chronic 03 exposure until 1963 (Berry and
Ripperton, 1963). Hayes and Skelly (1977) monitored total oxidants and record-
ed associated oxidant injury on eastern white pine in three rural Virginia
019CC/A 8-15 May 1984
-------
sites between April 1975 and March 1976. Injury was associated with total
oxidant peaks of 0.08 ppm or higher. Ozone peak concentrations of 0.17 ppm
have been measured in the Blue Ridge Mountains (Skelly, 1980). Increased
injury symptoms were observed on pine trees previously categorized as sensi-
tive or intermediately sensitive following the 0,. exposures. No injury was
observed on trees categorized as insensitive. Hayes and Skelly (1977) sug-
gested that continued exposure of sensitive and intermediately sensitive white
pine to acute and chronic oxidant concentrations resulted in the trees being
placed under stress that could ultimately influence their vegetative vigor and
reproductive ability. Inability to reproduce could result in the pines being
replaced by another species. Injury to herbaceous vegetation growing in the
Virginia mountains was also observed (Duchelle et al., 1983). Ambient 0,
concentrations were shown to reduce growth and productivity of graminoid and
forb vegetation in the Shenandoah National Park. For each year of the study,
biomass production was greatest in the filtered air chambers. The total
3-year cumulative dry weight for the filtered chambers was significantly
(P <0.05) different from non-filtered and open air plots. Common milkweed
(Ascelepias syrica L. ) and common blackberry (Rubus alleghem'ensis Porter)
were the only two native species to develop visible injury. Milkweed has been
previously shown to be very sensitive to 0- (Duchelle and Skelly, 1981).
•J
Ozone episodes occurred several times each year during the period of the
study. Peak hourly concentrations ranged from 0.08 to 0.10 ppm; however, 0_
concentrations exceeding 0.06 ppm were recorded for 1218, 790, and 390 hours
during 1979, 1980, and 1981, respectively. The effects of 0., in altering the
natural vegetation of the Virginia mountains was not assessed. Lower biomass
production could result in selection for vegetation better able to cope with
the 0,. stress. As in California, 0~ is transported from distant sources. In
the Blue Ridge and Appalachian Mountains, these sources include the industrial
midwest, eastern Virginia, and the Washington, D.C. area.
McClenahen (1978) has provided quantitative data on the impact of pollu-
ted air on the various strata of a forest ecosystem. Forest vegetation was
2 2
measured in seven stands on similar sites in a 50 km (19 mi ) area of the
upper Ohio River Valley. The stands, some of which have been exposed to air
pollution for nearly 40 years, were situated along a gradient of polluted air
containing elevated concentrations of chloride, sulfur dioxide (S0?), fluoride,
and photochemical oxidants, although the latter were not monitored. Overstory,
019CC/A 8-16 5/1/84
-------
subcanopy, shrub, and herb strata were analyzed for pollution effects. In-
creasing exposure to air pollutants reduced the density of woody stands in the
overstory and herb layers, but density in other strata tended to increase
along the same gradient. A shift occurred in the species composition of
forests on the sites investigated. The relative abundance of sugar maple
(Acer saccharum Marsh.), the most abundant species in the overstory of low-
exposure stands, was greatly reduced in all strata as pollutant dose increased;
but yellow buckeye (Aesculus octandra Marsh.) increased in canopy dominance,
and spice bush (Lindera benzoin (L.) Blume) became a codominant with paw paw
(Asimina triloba (L.) Dunal) in the subcanopy of high-exposure areas. In the
herb layer, there was an increase in light-tolerant species, an indirect
effect of air pollution resulting from the reduced overstory density. Light-
tolerant species composed 68 percent of the total in areas of high pollution
compared to 34 percent in areas of low pollutant exposure. Concentrations of
0,. in the area of the study were not reported; however, results of the study
O
illustrate how pollutant mixtures typical of ambient conditions can change the
species composition of forested areas. Pollutant stress on forest communities
tends to decrease diversity and simplify structure as the vegetative layers are
stripped away from the overstory downward (Woodwell, 1970).
Treshow and Stewart (1973) conducted one of the few studies concerned
with the impact of air pollution on natural plant communities. The aim of the
study was to determine the concentration of CL necessary to injure the most
prevalent species in some of the vegetation associations in the intermountain
grassland, oak, aspen, and conifer communities. Seventy common plant species
indigenous to those communities were fumigated with 0- to establish vegeta-
tional sensitivity. Injury was generally evident at concentrations above 0.15
ppm for 2 hr. Species found to be most sensitive to 03 in the grassland and
aspen communities included some dominant species considered key to community
integrity. Bromus tectorum L. (cheatgrass), the most prevalent species in the
grassland community, was also the most sensitive. Severe injury to this intro-
duced annual resulted from a single 2-hr exposure to 0.15 ppm of 03. Cheatgrass
is a species that is widely distributed in the intermountain western United
States. Removal of this dominant species from plant communities could result
in a shift in dominance to another species. The significance of such a change
would depend on the species replacing cheatgrass. The other grasses studied
were not as sensitive to 0~, nor were the forbs (Table 8-1); however the pro-
duction of carbohydrates in visibly injured grasses was significantly reduced.
019CC/A 8-17 May 1984
-------
TABLE 8-1. INJURY THRESHOLDS FOR 2-KOUR EXPOSURES TO OZONE
Species
Injury threshold'
(ppm 03
for 2 hr)
Species
Injury threshold
(PP« 0,
for 2 nr)
oo
i
CO
Grassland-oak community species:
Trees and shrubs:
Acer grandidentatum Nutt.
Acer negundo L.
Arteresia tridentata Nutt.
Mahonia repens G. Don
Potentilla fruticosa L.
Quercus gambelii Nutt.
Toxlcodendron radlcans (L.) Kuntze
Perennial forbs:
Achillea millefollum L.
Ambrosia psilostachya DC.
Calochortus nuttallH Torr.
Cirsium arvense (L.) Scop.
Conium maculaturn L.
Hedysarum boreale Nutt.
Helianthus anuus L.
Hedocagp satova L.
Rumex crispus L.
Urtica gracilis Alt.
Vida aoericana Huhl.
Grasses:
Broiaus brizaefonrls Fish. & Mey.
Bromus tectorum L.
Poa pratensis L.
Aspen and conifer community species:
Trees and shrubs:
Abies concolor (Gord. & Glend.) Lindl.
Amelanchier alnifolla Nutt.
Perennial forbs:
AHium acuminatum Hook
Angelica pinnata S. Wats.
over 0.40 Aster engelmanni (Eat.) A. Gray
over 0.25 Carex siccata Dewey
0.40 Cichorium intybus L.
over 0.40 Cirsium arvense (L.) Scop.
0.30 Epilobium angustifolium L.
0.25 Epilobium watsoni Barbey
over 0.30 Eriogonum heraclioides Nutt.
Fragaria ovalis (Lehm.) Rydb.
Gentiana amarella L.
over 0.30 Geranium fremontil Torr.
over 0.40 Geranium richardsonii Flsch. & Traut.
over 0.40 Juncus sp.
0.40 Lathyrus lanzwertil Kell.
over 0.25 Lathyrus pauciflorus Fern.
0.15 Mertensia arizonica Greene
• over 0.30 Mimulus guttatus DC.
0.25 Mimulus moschatus Dougl.
0.25 Mitel la stenopetala Piper
0.30 Osmorhiza occidental is Torr.
over 0.40 Phacelia heterophylla Pursh
Polemonium foliosissimum A. Gray
Rudbeckia occidentalis Nutt.
0.30 Saxifraga arguta D. Don
0.15 Senecio serra Hook.
0.25 Taraxacum officinale VHggers
Thalictrum fendleri Engelm.
Veronica anagallis-aquatica L.
Vicia americana Muhl.
Viola adunca Sm.
0.25
0.20 Annual forbs:
0.25
0.25
0.15
0.30
0.25
0.40
0.30
0.30
0.30
0.30
0.15
0.40
0.15
0.25
0.25
0.25
0.30
0.25
0.40
0.30
0.25
under 0.25
0.30
0.30
under 0.30
0.15
0.25
0.25
0.25
0.25
0.30
under
under
over
under
over
over
over
under
over
over
over
over
over
Pachystima myrsinites (Pursh) Raf.
Populus tremuloides Michx.
Ribes hudsonianum Richards.
Rosa woodsil Lindl.
Sambucus melanocarpa A. Gray
Symphoricarpos vacdnloiders Rydb.
Perennial forbs:
Actaeu arguta Nutt.
Agastache urticlfolla (Benth.) Kuntze
Source: Treshow and Stewart (1973).
over 0.30 Chenopodlum fremontii Wats.
0.15 Callomia linearis Nutt.
0.30 Descurainla californlca (Gray) O.E. Schulz
over 0.30 Gall urn blfoil urn Wats.
over 0.25 Gayophytum racemosum T. & G.
0.30 Polygonum douglasii Greene
Grasses:
0.25 Agropyron canlnum (L.) Beauv.
0.20 Bromus caHnatus Hook. & Arn.
under 0.25
under 0.25
0.25
over 0.30
0.30
over 0.25
over 0.25
under 0.25
-------
In the aspen community the most dramatic example was aspen (Populus
tremuloides Michx.) itself. A single 2-hr exposure to 0.15 ppm 0, caused
severe symptoms on 30 percent of the foliage. Because white fir seedlings
require aspen shade for optimal juvenile growth, the authors suggested that
significant losses in aspen populations might restrict white fir development
and later forest succession; conversion to grasslands could occur. In a
companion study, Harward and Treshow (1975) evaluated the growth and repro-
ductive response of 14 understory species to CL. Plants were fumigated in
greenhouse chambers 3 hr/day, 5 days per week throughout their growing seasons
(roughly June to September). Exposure was to ambient air peaks of 0., ranging
from 0.05 to 0.07 ppm and to concentrations of 0.15 and 0.3 ppm for 2 hr each
day. Symptoms were observed on the most sensitive species (Chenopodium
fremontii, Descurainia pinnata, and Polygonum aviculare) after 3 to 4 weeks of
exposure to ambient air peaks of 0.,. All species were injured at 0.15 ppm and
0.30 ppm. The most resistant species were injury-free until nearly mature.
The most sensitive species produced fewer seeds. Reduction in root and top
growth also occurred. It was apparent that in a natural community exposed to
0,., the tolerant species would soon become the dominants. The authors concluded
that 0~ must be considered a significant environmental parameter that influences
the composition, diversity, and stability of natural plant communities and
"may ultimately play a major role in plant succession and dominance."
The foregoing studies indicate that the impact of 03 changes the composi-
tion and succession patterns of plant communities. The more mature stages of
ecosystems use nutrients and energy more efficiently. Mature systems are
tight; disturbances cause leakage. The leakage may be large enough under
certain circumstances to in time reduce the potential of the site to support
life (Woodwell, 1974). Changes that cause reductions in biotic structure are
destabilizing and retrogressive. The entire array of plants is changed by
disturbance from one in which large-bodied, long-lived species occur to one in
which small-bodied, short-lived, rapidly reproducing plants predominate
(Woodwell, 1974). This pattern is exemplified by the San Bernardino National
Forest, where the mixed conifer forest is being replaced by low-growing shrubs
and annual herbs. It is also occurring in the eastern United States, where
the degradation of the Appalachian forests from North Carolina to Maine is
currently taking place as the red spruce (Picea rubens Sarg.) and other large,
long-lived species are being removed by at present unknown forces (Johnson and
Siccama, 1983). Also associated with the loss of stable ecosystems is the
019CC/A 8-19 May 1984
-------
maintenance of normal water and climatic conditions, protection from wind and
erosion, and protection from noise pollution (Guderian, R., 1977).
8.3.3 Effects on Tree Growth
Plant growth and yield is the culmination of a variety of biochemical and
physiological processes (Chapter 7). Impairment of any of these processes
places stress on the plant. Response of plants to stress is mediated by
biological, physical, and chemical variables. Tree responses, unless they are
the result of a specific biotic disease or an acute pollutant exposure, are
cumulative and frequently the culmination of a number of chronic stresses.
The term decline has been used by forest pathologists to describe responses of
this type that are not the result of a single causative agent (Figure 8-3;
Manion, 1981). Forest declines involve three or more sets of factors: predis-
posing, incitants, and contributing (Figure 8-4). Predisposing factors weaken
a plant. Incitants are of short duration and may be physical or biological in
nature. They usually produce drastic injury. Contributing factors are indica-
tors of a weakened host. They appear over time (Manion, 1981).
Decline in vigor is a response commonly observed in trees sensitive to 0_
stress (Miller et al. , 1982; McLaughlin et al., 1982; Skelly, 1980). Symptoms
of chronic decline include the following sequence of events and conditions:
(1) premature senescence and loss of older needles at the end of the growing
season, (2) reduced storage capacity in the fall and resupply capacity in the
spring to support new needle growth, (3) increased reliance of new needles on
self-support during growth, (4) shorter new needles resulting in lower gross
photosynthetic productivity, (5) higher retention of current photosynthate by
foliage resulting in reduced availability of photosynthate for external usage
(including repair of chronically stressed tissues of older needles), and
(6) premature casting of older needles (McLaughlin et al., 1982).
Ozone-associated stress on the mixed coniferous forest ecosystem of the
San Bernardino Mountains of southern California decreased photosynthesis,
affected directly or indirectly translocation of carbon, mineral nutrients,
and water, and reduced trunk diameter, tree height, and seed production in
ponderosa and Jeffrey pine (Miller et al., 1982). White fir, black oak;
incense cedar, and sugar pine were less sensitive. Average 24-hr 0^ concen-
trations ranged from a background of 0.03 to 0.04 ppm to maxima of 0.10 to
0.1? ppm. Foliar injury, needle abscission, and premature senescence were
019CC/A 8-20 5/1/84
-------
DECLINE DISEASES
OF COMPLEX ORIGIN
ABIOTIC AGENTS
OF DISEASE
AIR POLLUTION
HIGH
TEMPERATURES
FREEZING
TEMPERATURES
PESTICIDES
DROUGHT
SALT
POOR SOIL
AERATION
MINERAL
DEFICIENCY
SOIL
POLLUTION
MECHANICAL
DAMAGE
FUNCTIONAL PARTS
OF A TREE
REDUCED
GROWTH
SHOOT
BLIGHT
CHLOROSIS OF
FOLIAGE
^-HEIGHT GROWTH
FOLIAGE DISEASES
BRANCHES AND STEM:
TRANSLOCATION
STRUCTURE
STORAGE
SECONDARY GROWTH
HEART ROT
CANKER GALL
ROOTLET ,
NECROSIS
BIOTIC AGENTS
OF DISEASE
FUNGI
BACTERIA
MYCOPLASMAS
RICKETTSIA
SPIROPLASMA
VIRUSES
INSECTS
MITES
NEMATODES
HIGHER PLANTS
TRANSLOCATION
STRUCTURE
STORAGE
MYCORRHIZAE (FUNGUS ROOTS):
WATER AND MINERAL
ABSORPTION
PROTECTION AGAINSTV*
ROOT PATHOGENS
Figure 8-3. Summation of abiotic and biotic agents involved in diseases of trees, given by
types of diseases and functional parts of the tree. Decline diseases are caused by a combina-
tion of biotic and abiotic agents.
Source: Manion (1981).
8-21
-------
PREDISPOSING
INCITING
CONTRIBUTING
Long-Term Factors:
Climate
Soil Moisture
Genotype of Host
Soil Nutrients
AIR POLLUTANTS
Short-Term Factors:
Insect defoliation
Frost
Drought
Salt
Mechanical Injury
AIR POLLUTANTS
Long-Term Factors:
Bark Beetles
Canker Fungi
Viruses
Root-decay Fungi
Figure 8-4. Categories of factors influencing declines.
Source: Manion (1981).
8-22
-------
noted on the affected trees. Injury to ponderosa pine occurred at concentra-
tions of 0.05 to 0.06 ppm for 24 hr. PAN has not been associated with injury
to trees.
The best documented correlation of growth variables of large trees growing
under field conditions with ambient 0., levels is the comprehensive oxidant
study conducted in the San Bernardino National Forest in California (Miller
and Elderman, 1977; Miller et al., 1982). Radial growth of ponderosa pine
during periods of low pollution (1910 to 1940) was compared to periods of high
pollution (1941 to 1971) (Table 8-2). The average annual rainfall for these
periods was 111 and 117 cm/yr (43 and 46 in/yr), respectively. It was postu-
lated that 30-year-old trees grown in the two periods would have diameters of
30.5 cm and 19.0 cm. The difference in these diameters is attributed to air
pollution during the 1941 to 1971 period. Oxidant air pollution reduced the
average annual growth in diameter of ponderosa pine by approximately 40 percent
and height by 25 percent in trees less than 30 years of age. Marketable
volume growth of trees of this age was reduced by 83 percent in zones with the
highest 0, concentrations. The San Bernardino study documented reduced seed
production of Jeffrey pine (Miller et al., 1980).
In the east, reduced growth of eastern white pine under ambient conditions
caused by 0., exposure has been documented (Benoit et al. , 1982). A study of
radial increment growth of native eastern white pines of reproducing age
evaluated the possible effects of oxidant (primarily 0.,) air pollution on
long-term growth of forest species in a region of the Blue Ridge Mountains of
Virginia extending from the northern end of Skyline Drive in Shenandoah National
Park to the southernmost end of the Blue Ridge Parkway in Virginia. White
pines in the study plots were classified as sensitive, intermediate, and
tolerant, based on a foliar rating scale that incorporated needle length,
needle retention by number of years, and the presence of typical CU symptoms
on needles. The mean ages of tolerant, intermediate, and sensitive tree
classes were 53, 52, and 56 years, respectively. Growth in mean annual incre-
ment for sensitive trees was significantly less (P = 0.01) than that of the
tolerant trees for the period 1955 to 1978 (Table 8-3). Growth for sensitive
trees was 25 percent less, and for intermediate trees, 15 percent less than
tolerant trees. Smaller mean increments in the last ten years when compared
to the previous 24-year period indicated a decline in overall growth rates in
all classes of trees. A comparison of growth during the 1974 to 1978 period
with that during 1955 to 1959 showed a decrease of 26, 37, and 51 percent for
019CC/A 8-23 May 1984
-------
TABLE 8-2. AVERAGE ANNUAL RADIAL GROWTH OF 19 PONDEROSA PINE TREES
IN TWO LEVELS OF OXIDANT AIR POLLUTANTS IN THE SAN BERNARDINO
NATIONAL FOREST, CALIFORNIA.
High
Agea
(yr)
20
21
29
22
25
35
27
28
35
22
39
35
29
33
35
35
36
36
34
Pollution (0.03-0.12 ppm)
Average radial
growth (cm)
1941-1971
0.20
0.33
0.22
0.33
0.30
0.23
0.29
0.31
0.26
0.43
0.21
0.34
0.37
0.37
0.34
0.37
0.35
0.33
0.36
Age3
(yr)
60
55
55
57
64
63
60
65
60
71
63
71
66
63
60
70
61
62
59
Low Pollution (<0.03 ppm)
Average annual
radial growth (cm)
1910-1940
0.52
0.49
0.61
0.34
0.40
0.55
0.44
0.46
0.75
0.67
0.71
0.65
0.78
0.53
0.33
0.38
0.32
0.37
0.37
Source: Miller and Elderman, 1977.
Age at 1.4 m above ground in 1971.
019CC/A
8-24
May 1984
-------
TABLE 8-3. ANNUAL MEAN RADIAL GROWTH INCREMENT (MM) BASED ON THE 24-YEAR
PERIOD (1955 to 1978)3 FOR TREE OZONE SENSITIVITY CLASSES OF
NATIVE EASTERN WHITE PINES (PINUS STROBUS L.) GROWING IN TEN PLOTS OF THREE
TREES EACH ALONG THE BLUE RIDGE MOUNTAINS IN VIRGINIA
Plot
Mean
Tolerant trees*
Intermediate trees
Sensitive trees
1
2
3
4
5
6
7
8
9
10
4.59
3.52
8.19
4.80
5.94
4.64
2.85
3.91
3.32
1.67
2.13
2.12
6.34
3.75
6.53
3.76
2.75
4.52
2.04
2.98
3.08
2.86
6.89
2.62
5.73
2.62
1.51
1.96
2.61
1.46
4.34 AL
3.69 AB
3.10 B
Source:
a
Benoit et al. (1982).
White pines rated tolerant, intermediate, or sensitive to 0- based on
foliar symptoms.
Sensitivity classes with the same letter are not significantly different at
P = 0.01 based on Duncan's multiple range test.
019CC/A
8-25
5/1/84
-------
tolerant, intermediate, and sensitive trees, respectively. The significant
reduction in radial growth of (^-sensitive white pines was associated with
cumulative stress resulting from reduced photosynthetic capacity of oxidant-
injured trees. Developing first-year needles utilize photosynthate from
needles of previous years (Benoit et al., 1982). Extensive oxidant injury to
needles, senescence, or premature abscission of needles could decrease the
amount of photosynthate available for growth. The monitoring of CL in the
study area indicates the presence of concentrations of 0.05 to 0.07 ppm on a
recurring basis, with episodic peaks frequently in excess of 0.12 ppm. Concen-
trations during the peak episodes ranged from 0.10 to 0.20 ppm.
The effects of chronic 0, stress on the growth of white pine trees has
also been reported by Mclaughlin et al. (1982), who studied the decline of
white pines in the Cumberland Plateau area of east Tennessee. A steady decline
in annual ring increment of sensitive white pines was observed during the
years 1962 to 1979 (Figure 8-5). Reductions of 70 percent in average annual
growth (Figure 8-5A) and 90 percent in average bole growth (Figure 8-5B) of
sensitive trees, compared to the growth of tolerant and intermediate trees,
were noted. Tolerant trees showed a consistently higher growth rate of 5 to
15 percent (P > F < 0.05) than intermediate trees for the 1960 to 1968 interval.
The cause of decline is attributed primarily to chronic 0_ exposure, which
frequently occurs at phytotoxic concentrations (0.08>) in the area (Table 8-4).
Though the pollutants S0? and fluoride have been measured in the area, the
premature loss of needles and occasional tip necrosis of needles of the current
year are manifestations associated with 0~, which occurs in high concentrations
during the occurrence of stable air masses. Needles of sensitive trees were
15 to 45 percent shorter than those of either of the other classes. The
decline in vigor and reduced annual growth of sensitive trees have taken place
during the past 25 years. In addition to the reduced growth above ground,
less available carbohydrate reduces the vigor of root systems and enhances
susceptibility of trees to root diseases (Mclaughlin et al., 1982). The loss
in vigor of the trees has been accompanied by reduced annual radial growth and
a loss in the capacity to respond in years when conditions are favorable for
growth. The primary cause of decline appears to be exposure to elevated
concentrations of 0., and the sequence of events and conditions that lead to
O
premature senescence and loss of older needles, lower gross photosynthetic
productivity, and reduced photosynthate availability for growth and maintenance
of trees (Mclaughlin et al., 1982).
019CC/A 8-26 5/1/84
-------
I
Q
C3
2
cc
2
<
HI
11
10
9
8
7
I I I I I I \ I T
(a)
I I I I
I
I I I I 1
I I I I I T
A TOLERANT
• INTERMEDIATE
• SENSITIVE
I I
90
80
70
60
50
40
30
20
10
0
1960 '62 '64 '66 '68 '70 '72 '74 '76 '78 '801960'62 '64 '66 '68 '70 '72 '74 '76 '78 '80
YEAR
Figure 8-5. Average annual growth of white pine trees in each of
three sensitivity classes expressed as increment in ring width (a)
and cross-sectional area (b). Data are averages of three trees in
each sensitivity class.
Source: Mclaughlin et al. (1982).
rn
DO
O
rn
>
Z
Z
c
I"
S >
(B O
Z
O
X
m
£
m
8-27
-------
TABLE 8-4. ANNUAL OCCURRENCES OF OZONE AT HOURLY CONCENTRATIONS > 0.08 PPM IN
THE KNOXVILLE, TENNESSEE AREA
Month
March
Apri 1
May
June
July
August
September
October
November
Total
Maximum level (ppm)
1976
0
0
0
35
40
75
40
0
0
190
0.130
Number of hours with
1977
0
35
89
105
110
(a)
(a)
(a)
(a)
>339
0.200
03 > 0.08 ppm
1978
0
15
28
28
33
27
34
13
12
190
0.124
1979
3
10
40
44
4
24
0
0
0
125
0.134
Source: McLaughlin et al. (1982).
Data missing.
019CC/A
8-28
5/1/84
-------
Documentation of foliar symptoms on western conifers in the southern
Sierra Nevada mountain range in central California (Williams et al., 1977;
Williams, 1980, 1983) and on eastern white pine in Indiana and Wisconsin
(Usher and Williams, 1982) may suggest growth impacts by oxidants in these
regions also.
Studies by Krause (1984) and others in West Germany associate 03 with the
dieback of fir (Abies alba Mill.) and spruce (Picea alba (L.) Karst.). Ozone
damages the cell membranes in the needles of conifers and the leaves of certain
hardwoods (beech, Fagus sylvatica L.) and leads to uncontrolled loss of nutri-
ents. Fog and/or rain, depending on ionic strength and pH, readily leach the
nutrients from the needles or leaves. Leaching is enhanced by high light
intensity and low nutrient soils. Membrane damage may occur without visible
injury.
Forest decline began in the early 1970's in West Germany. Dieback of fir
was the first indication that the Black Forest and the forests in the mountain-
ous areas of Bavaria were under stress. Acid rain was first blamed for forest
decline, but studies did not confirm this hypothesis. Injury affects spruce
and fir of virtually all ages. Ozone was first postulated as the cause of
forest decline (Krause, 1984) in 1982. Field observations and laboratory
experiments have confirmed this hypothesis. Loss of nutrients and reductions
in photosynthesis, carbohydrate production, and root growth due to OT injury
leads to a mobilization by trees of nutrient reserves from older needles and
their translocation to the sites of greatest metabolic activity. Dieback
occurs because the growing tips of tree branches do not receive the nutrients
and carbohydrates necessary for growth.
Trees are the controller organisms, those that determine structure (species
composition and trophic relationships) of forest ecosystems (Ehrlich and
Mooney, 1983). Injury to or disturbance of these species begins the retrogres-
sive successional processes that may ultimately lead to the loss of the ecosys-
tem.
Replacement or reforestation of one tree species by another is not neces-
sarily a valid solution. Substitution of Monterey pine (Pinus radiata D. Don)
for native Australian tree species resulted in reduced energy flow and a lower
rate of mineral cycling in the ecosystem and a loss of soil nutrients. Substi-
tution of a different trees species can require large energy subsidies to
produce growth, and the new species are almost totally unable to supply the
genetic pool of the forest ecosystem they replaced (Ehrlich and Mooney, 1983).
019CC/A 8-29 May 1984
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8.3.4 Effects on Food Webs
Autotrophs are organisms that manufacture their own food and are, there-
fore, in the first trophic level. They are the producers. Biomass accumulation
at this trophic level is termed primary production. In a forest ecosystem,
this is the addition of new organic matter in trees, shrubs, and herbs.
Producers, as discussed previously, are the primary sources of the energy
transferred within ecosystems. Energy from the sun is harnessed through
photosynthesis for the production of food by plants, and it is subsequently
available to consumers and decomposers (heterotrophs) along food webs. Any
mature natural community transfers 10 to 20 percent of the energy fixed by
plants to herbivores (Woodwell, 1974). Previous sections have discussed the
impact of 0, on photosynthesis. Disruption of photosynthesis and subsequent
carbon allocation for vegetative and reproductive growth can decrease the
amount of food available to other trophic levels in the food web and thus slow
the movement of energy and nutrients through an entire system. Disturbance
causes leaks and losses of nutrients from the system. The indirect effects of
0., on food web components are discussed in the following sections.
O
8.3.4.1 Heterotrophs (Consumers). Heterotrophs are organisms that feed on
other organisms and constitute all trophic levels above the first. Production
(energy storage) of heterotrophs is termed secondary production. Heterotrophs
are extremely diverse, and only a limited amount of information on their
response to pollutants is available (Newman, 1979). The influence of oxidants
on these organisms is assumed to be chiefly through the food web. At this
time, studies have not indicated a direct impact of 0., on the organisms them-
selves. However, disruption of photosynthesis, reproduction, or a structural
change among the producers within ecosystems can affect heterotrophs (consumers)
by removing their shelter and food sources.
Small vertebrates, for example, unable to migrate to relatively unpolluted
areas, may receive a direct effect from 03 exposure, as well as an indirect
effect, through alterations in food abundance from plants that provide an
important segment of their diet. In the San Bernardino Mountains of California,
a trapping program at vegetation plots differentially impacted by chronic
oxidant dose indicated that the same species were present as compared to
results from trappings made 70 years ago (Kolb and White, 1974). Population
numbers, however, appeared to be lower in comparison with other similar forest
systems. There is some evidence to suggest that the size and frequency of
acorn crops from California black oak may be smaller in areas receiving the
019CC/A 8-30 5/1/84 .
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greatest seasonal oxidant exposure (Miller et al., 1980). Reduced acorn avail-
ability could have an impact on small mammal populations.
The San Bernardino National Forest study has also provided evidence for
the impact of 0- stress on other mammals (Newman, 1980). Fruit and seeds make
up the largest part of the diet of most of the small mammals in this mixed
conifer forest. This is particularly true for the deer mouse (Peromyscus
sp.), harvest mouse (Reithrodontormys sp.), chipmunk (Eutamias sp.), ground
squirrel (Callospermophilus sp.), and western gray squirrel (Sciurus griseus
anthonyi). Alterations in availability of seeds and fruits can alter the
habitats and reproduction of these rodents (Taylor, 1973). Certain bird
species are known to prefer coniferous forests (Smith, R. L. , 1980). No
studies appear to have been made concerning changes in bird populations due to
the death of tree species. It is not clear what other specific effects oxidants
may have on ambient wildlife, nor are exposure-response levels available.
8.3.4.2 Phytophagous Insects. Invertebrate consumer populations (e.g.,
arthropods) may be subject to the influence of oxidant impact on their habitat
or host. Insects are among the most important heterotrophic groups in ecosys-
tems. The literature addressing the relationship between 0_ and insects in
temperate forests is meager and extremely disproportionate to the importance
of arthropods in forest ecosystems. Generally speaking, the killing or injury
of leaves by injured air pollution would most adversely affect insect defolia-
tors.
Bark beetles are the most damaging and economically significant insect
pests of commercially important conifers in the United States. Beetle out-
breaks in western forests are associated with several predisposing factors.
These include host weakening caused by photochemical oxidants; microbial
infection, such as root disease initiated by fungi, Heterobasidion annosum
(Fomes annosus) or Verticicladiella wagenerii (Stark and Cobb, 1969); by
insect defoliation, such as pine looper stripping of ponderosa pine (Dewey et
al., 1974); or by various climatic stresses, such as drought and windthrow
(uprooting and breakage by strong winds) (Rudinsky, 1962). Photochemical
oxidant injury of ponderosa pines results in reduced oleoresin yield, rate of
flow and exudation pressure, moisture of phloem and sapwood, and phloem thick-
ness. All of these are believed to be important in the defense of the tree
against bark beetles (Stark and Cobb, 1969).
Studies at the University of California Blodgett Research Forest indicate
that a disease-insect relationship exists between root-infecting fungi and
019CC/A 8-31 May 1984
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bark beetles. Approximately 80 percent of the ponderosa pines infested with
bark beetles had been infected by root-disease fungi prior to beetle infesta-
tion (Stark and Cobb, 1969). Verticicladiella wagenerii was the major fungus
attacking the roots. The fungus moves from tree to tree via the roots.
Skelly (1980) reported oxidant injury of eastern white pines in Virginia
increased the incidence of root disease caused by Verticicladiella procera.
Heterobasidion annosum was likewise found to have infected conifer roots prior
to beetle attack. Heterobasidion usually does not become a serious problem in
California forest until disturbances by humans, such as logging, have occurred
(Stark and Cobb, 1969).
During the summer of 1966, a survey of ponderosa pines was carried out in
the San Bernardino Mountains of California. These forests are subject to
elevated levels of atmospheric oxidants from the Los Angeles urban complex to
the west. Over 1000 trees were examined for amount of 0, injury, for infes-
tation from the western pine beetle (Dendroctonus brevicomis) and/or the mountain
pine beetle (D. monteola), and for tree mortality. Trees with the greatest
pollution injury were most commonly found to be supporting populations of one
or both bark beetle species. As the degree of oxidant injury increased, live
crown ratio decreased, and the occurrence of bark beetle infestation increased
(Stark et al. , 1968). This is perhaps the most completely documented example
of enhancement of insect damage by air pollution in North America (Miller,
1973).
Dahlsten and Rowney (1980) investigated the interaction between ponderosa
pine weakened by photochemical oxidants and the western pine beetle. It was
found that an initial attack by a smaller number of bark beetles in oxidant-
damaged trees produced approximately the same total brood as a large number in
healthier trees. Therefore, in stands with a higher proportion of injured
trees, beetles can spread through the stands faster and a given population of
bark beetles could kill more trees and propagate at a greater rate than in a
stand with a lower proportion of damaged trees.
8.3.4.3 Pathogens. By weakening the trees, 0., makes the trees of the forest
o
ecosystem more susceptible to attack by certain parasites and can thus hasten
structural changes within an ecosystem. There is some indication that 0, may
enhance the development of disease caused by pathogens that normally infect
stressed or senescent plant parts or invade nonliving woody plant tissues.
Lophodermium pinastri and Aureobasidium pullulans were the fungi more commonly
collected from eastern white pine foliage showing 0_ injury. When inoculated
O
019CC/A 8-32 May 1984
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in conjunction with tree exposure to 0.06 to 0.10 ppm 0_ for 4.5 hr, however,
no evidence of additive or interactive effects were found (Costonis and Sinclair,
1972).
Weidensaul and Darling (1979) inoculated Scots pine (Pinus sylvestris L.)
seedlings with the fungus, Scirrhia acicola 5 days before or 30 min following
fumigation for 6 hr with 0.20 ppm SO-, 0.20 ppm 0_, or both gases combined.
Significantly more brown spot lesions were formed on seedlings fumigated with
S0? alone or S0? combined with 0- than on controls, when inoculation was done
5 days before fumigation. When inoculation was done 30 min after gas expo-
sure, seedlings exposed to S0? alone had more lesions than those exposed to 0.,
alone or 03 combined with SO-, but no significant differences were noted
between fumigated seedlings and controls. The authors judged that 0,-induced
stomatal closure may have been responsible for the latter observation.
Heterobasidion annosum (syn Fomes annosus) is a basidiomycete fungus
capable of causing significant root decay in a variety of coniferous hosts
throughout temperate forests. A comprehensive examination of oxidant stress
on California forest ecosystems has included a study of the influence of 0., on
this fungus and the disease it causes in ponderosa and Jeffrey pines (Miller
and Elderman, 1977). Root inoculations were made on trees exhibiting varying
degrees of oxidant stress. Pine seedlings were also artificially inoculated
following fumigation with 0_. Because of the importance of freshly cut stump
surfaces in the spread of this fungus, trees exhibiting different levels of
susceptibility to 0- were cut, and their stumps were inoculated with H_._ annosum.
There was no correlation between the amount of disease development in roots of
field-inoculated ponderosa and Jeffrey pines and the degree of oxidant damage
of the two. Results of stump inoculation tests, however, did suggest that air
pollution injury may have increased the susceptibility of pine stumps to
colonization by H. annosum (James et al., 1980). The percentage of infection
of fumigated seedlings was also greater than that of nonfumigated seedlings.
Pollutant-plant-pest and pollutant-plant-pathogen interactions are discussed
in greater detail in section 7.3.2 of Chapter 7.
8.3.4.4 Other Microorganisms, Symbionts, and Decomposers. The dose of 0_
required for direct impact on microbial metabolism may be quite high. The
data of Hibben and Stotsky (1969) are illustrative. These investigators
examined the response of detached spores of 14 fungi to 0.1 to 1.0 ppm of 0.,
for 1, 2, and 6 hr. The large pigmented spores of Chaetomium sp., Stemphylium
sarcinaeforme, S. loti, and Alternaria sp. were not influenced by 1.0 ppm
019CC/A 8-33 5/1/84
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(1960 ug/m ) of 0,. Germination of Trichoderma viride, Aspergillus terreus,
A. niger, Penicilliuni egyptiacum, Botrytis allii, and Rhizopus stolonifera
spores were reduced by 0., exposure, but only in concentrations above 0.5 ppm
and occasionally by doses of 0.25 ppm of (L for 4 to 6 hr; lower doses stimu-
lated spore germination in some cases.
Symbiotic microbes play important roles in nutrient relations in forest
ecosystems. Trees have evolved critically important symbiotic relationships
with soil fungi and bacteria that enhance nutrient supply and uptake. This
relationship is particularly important in trees growing on nutrient-poor
soils. The feeder rootlet systems of ponderosa pines in the San Bernardino
Mountains have shown marked deterioration; this involves a decrease in the
number of mycorrhizal rootlets and their replacement by saprophytic fungi in
the small rootlets on stressed trees (Parmeter et al., 1962). Mycorrhizae are
very sensitive to the photosynthetic capacity of the host and the host capacity
to translocate carbon compounds to the roots (Hacskaylo, 1973). When seedlings
of Virginia pine (Pinus virginiana Mill.) inoculated with the mycorrhizal
fungus Thelephora terrestris and growing under a 16-hr photoperiod, were
switched to 8-hr photoperiods, the seedlings became dormant within 4 weeks.
No further infection of rootlets by the fungus occurred even though root
growth continued. Fungal sporophores were formed on the seedlings that remained
under the 16-hr photoperiod. Studies have shown that simple sugars provided
by plant roots are readily utilized by mycorrhizae and enhance infection
(Hacskaylo, 1973).
McCool et al. (1979) observed that 0^ exposure reduced mycorrhizal infec-
tion of the host plant. Both infection and chlamydospore production by the
mycorrhizal fungus Glomus fasciculatus were reduced when Troyer citrange,
a hybrid between Trifoliate and Sweet Orange [Ponicirus trifoliata (L.) Raf x
Citrus sinesis (L.) Asbeck], were exposed to CL concentrations of 0.09 ppm for
6 hr once a week for 19 weeks. In mycorrhizal plants, dry weight was reduced
42 percent, but in non-mycorrhizal plants there was only 19 percent reduction.
Exposure to 03 (0.45 ppm, 3 hr/day, 2 days/week for 19 weeks) decreased mycor-
rhizal spore production.
Ozone exposure changed cation levels in citrange leaf tissue. Possibly
this change reflected reduced cation absorption by the roots (McCool et al.,
1979). Reductions in availability of photosynthates for the fungus could
affect the degree of mycorrhizal infection.
019CC/A 8-34 May 1984
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Mycorrhizae are known to assist in protecting conifer roots from pathogens
such as Heterobasidion annosum (Krupa and Fries, 1971). Injury to the mycor-
rhizae can remove this protection. Non-mycorrhizal and mycorrhizal root
systems contain essentially the same major volatile compounds; however, studies
using Scots pine (Pinus sylvestris L.) indicate that the concentrations of
primarily monoterpenes and sesquiterpenes increase twofold to eightfold in
the roots infected by mycorrhizae. Many of the monoterpenes identified in
mycorrhizal root systems are constituents of the oleoresins commonly found in
conifers. Oleoresins play an important role in the resistance of wood to
decay fungi (Rishbeth, 1951). Volatile oleoresin components from ponderosa
pine inhibit the growth of Heterobasidion annosum and four Ceratocystis species
(Cobb et al., 1968), and are believed to aid in defense of trees from bark
beetles (Stark and Cobb, 1969).
Properly functioning mycorrhizal systems are necessary for the growth of
healthy trees. Mycorrhizae absorb nutrients from the soil and protect tree
roots from certain pathogens. Ozone, by inhibiting photosynthesis and reducing
the photosynthate available for transfer to the tree roots, disrupts the
relationship between the mycorrhizal fungus and the host tree. Bark beetles
attack the weakened trees usually after the mycorrhizal relationship has been
destroyed, and hasten their demise.
Ozone also influences bacterial symbiosis. Reduced root growth and nodula-
tion of soybeans (Glycine max (L.) Merr.) cv Dare, by the bacterium Rhizobium
japonicum occurred when plant tops were exposed to 0~. No growth reductions
occurred when the plant tops were protected from exposure to 0., (Blum and
Tingey, 1977). In an earlier study (Tingey and Blum, 1973), nodule number,
nodule weight per plant, root growth, and leghemoglobin content per plant were
all reduced by a 1-hr exposure to 0.075 ppm 0~. The reductions were associated
with reduced photosynthetic capacity and less photosynthate for translocation
to the roots. The rate of nitrogen fixation is also dependent on the rate of
photosynthesis. Symbiotic nitrogen fixation is the major biological source of
fixed nitrogen (Tingey and Blum, 1973). Ladino clover (Trifolium repens L.
cv. Tillman) was treated with filtered air, 0.3 ppm (588 fjg/m ) of 0_, or 0.6
3 *
ppm (1176 ug/m ) of 0,, for two 2-hr exposures, one week apart in controlled
environment chambers (Letchworth and Blum, 1977). Plants of various ages were
treated. Ozone reduced the growth and nodulation of test plants. The influence
of 0., varied with gas concentration and plant age. Mahoney (1982) has presented
evidence that indicates that the mycorrhizal association of loblolly pine
019CC/A 8-35 May 1984
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seedlings was not impaired by exposure to 0.07 ppm of 03 plus 0.06 ppm of S0?
for 6 hr/day for 35 days.
A comparison of lichen species found on conifers in the San Bernardino
Mountains of southern California during the years 1976 to 1979 with collections
from the early 1900's was made to determine the effects of oxidant air pollu-
tion. Fifty percent fewer lichen species were found. Marked morphological
deterioration of the common species Hypogymnia enteromorpha was documented
in areas of high oxidant concentrations (Sigal and Nash, 1983).
Generally, one third or more of the energy and carbon fixed annually in
the forests is contributed to the forest floor as litter (mostly leaves)
(Ovington, 1957). The reservoir of energy and mineral nutrients represented
by litter is a very important resource in natural ecosystems. The growth of
new green plants depends on the slow release of nutrients by decomposer organ-
isms. In agroecosystems, litter is often removed or burned. Fertilizer is
added to the soil to replace the nutrients lost. In a conifer forest, litter
production and decomposition release approximately 80 percent of the total
minerals in the biomass of the stand; the remainder is retained in the living
parts of the tree (Millar, 1974). Decomposer organisms are essential compo-
nents of ecosystems, because they release bound nutrients from litter and
provide elements essential for the continued growth and development of living
organisms by recycling them. Numerous small animals, arthropods, fungi, and
bacteria occupy the mantle on the surface layers of the soil where they degrade
dead plant and animal material and release essential elements such as calcium,
phosphorus, and magnesium to growing plants. Much of this decomposition
occurs in the forest floor; however, pine needles are infected by fungal
microflora several months before needles are shed (Stark, 1972). Although
rapid fluxes of 0_ to soil surfaces and the forest floor can occur (Smith,
1981), it is not yet clear what effect this may have on decomposer organisms
in natural environments.
Bruhn (1980) has investigated the effects of oxidants on needle microflora
population dynamics of pine in the San Bernardino National Forest. The de-
composition of litter comprised of 0,,-stressed needles was concluded to be
O
more rapid. However, the taxonomic diversity and population density of fungi
that colonized living needles and later participated in decomposition were
both reduced by 0,. injury as the normal increase with age was blocked by
O
premature needle senescence and abscission. The author concluded that this
alteration in microflora could weaken the stability of the decomposer community.
019CC/A 8-36 5/1/84
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Laurence and Weinstein (1981) have emphasized the critical importance of
examining multiple pollutant effects and the interactive effects of air pollu-
tants with pathogens and insects in determinations of growth impacts. Ecosystem
responses will always be the integration of multiple stresses acting over time
and space on diverse populations.
8.3.5 Oxidant-Induced Effects on a Western Coniferous Forest Ecosystem: The
San Bernardino Study
8.3.5.1 Introduction. The interdisciplinary study of the pine and mixed
conifer forests of the San Bernardino Mountains of southern California is the
most comprehensive and best documented report on the effects of oxidants on an
ecosystem (Miller et al., 1982). The mixed conifer forests in the San Gabriel
and San Bernardino mountain ranges east of Los Angeles have been exposed to
oxidant air pollution since the early 1950's (Miller, 1973). Extensive visible
injury and concern about possible adverse effects of chronic CL exposure on an
important ecosystem led to the inderdisciplinary study from 1973 to 1978. The
study was designed to answer two questions: (1) How do the organisms and
biological processes of the conifer forest respond to different levels of
chronic oxidant exposure; and (2) how can these responses be interpreted
within an ecosystem context (Miller et al. , 1982)?
The major physical (abiotic) components studied were water (precipita-
tion), temperature, light, mineral nutrients (soil substrate), and 0, air
pollution. Biological components included producers (an assortment of tree
species and lichens), consumers (wildlife, insects, disease organisms), and
decomposers. The decomposer populations were composed of the populations of
saprophytic fungi responsible for the decay of leaf and woody litter.
The ecosystem processes analyzed were (1) carbon flow (the movement of
carbon dioxide into the plant; its incorporation into green plant organic
matter; and then its partitioning among consumers, litter and decomposers, the
soil and return to the atmosphere); (2) the movement of water in the soil-piant-
atmosphere continuum; (3) mineral nutrient flow through the green plant litter
and soil-water compartments; and 4) the shift in diversity patterns in time
and space as represented by cha'nges in composition of tree species in stands,
age, structure, and density.
8.3.5.2 Effects Observed. In previous sections of this chapter the effects of
CL on a variety of ecosystem components have been discussed. The San Bernardino
019CC/A 8-37 May 1984
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study illustrates the response of a whole ecosystem to the stresses placed on its
components. The effects of chronic 0- stress observed were associated with
average 24-hr 0., concentrations in the San Bernardino Mountains during the months
of May through September. They ranged from a background of 0.03 to 0.04 ppm to
maxima of 0.10 to 0.12 ppm. Foliar injury of ponderosa pine, a very sensitive
species, occurred at 24-hr concentrations of 0.05 to 0.06 ppm. Other trees, in
decreasing order of sensitivity, were Jeffrey pine, white fir, black oak, in-
cense cedar, and sugar pine. Decreased photosynthetic capacity due to foliar
injury and premature leaf fall decreased radial growth and height of stem,
reduced nutrient retention, and caused the weakening of trees. Pines became
more susceptible to root rot (Heterobasidion annosum) and pine beetle
(Dendroctonus brevicomis) due to host weakening by photochemical oxidants.
Stressed trees showed a decrease in the number of mycorrhizal rootlets (Parmeter
et al., 1962). Mortality rate of the trees reached 2 to 3 percent in some years.
Injured ponderosa and Jeffrey pines older than 130 years produced significantly
fewer cones per tree than uninjured trees of the same age (Luck, 1980). Eco-
system components most directly affected by 0^ were tree species, the fungal
microflora of needles, and foliose lichens occupying tree bark. Heavy litter
accumulation occurred in stands with the most severe needle injury and defolia-
tion. Pine seed establishment was hindered by litter depth, but the growth of
oxidant-tolerant understory species was encouraged. Buildup of litter and the
presence of easily ignited foliage on smaller trees could lead to destructive
fires. Removal by fires and by 0~ of the pine forest overstory has resulted in
a shift in dominance to self-perpetuating, fire-adapted, 0.,-tolerant shrub and
oak species mixtures that provide fewer commodity and amenity values than the
former pine forest.
The most important ecosystem processes affected either directly or indi-
rectly were flows of carbon, mineral nutrients, and water. Changes in vegeta-
tion cover diversity patterns over time and space also occurred. Diminished
flow of carbon in the tree layer resulted from a decrease in the amount of
foliage conducting photosynthesis and the decreased photosynthetic capacity of
the remaining foliage. Stressed trees also retained a smaller amount of
assimilated carbon after respiration losses. The store of carbon and mineral
nutrients that accumulated in the thick needle litter layer understands of
0_-injured trees influenced nutrient availability due to losses by volatiliza-
tion during fires and in subsequent surface runoff. In the absence of the
019CC/A 8-38 May 1984
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pine-dominated forest, a cover of shrub and oak species emerges as a self-
perpetuating community of species capable of sprouting after fire, quickly
obtaining crown closure and inhibiting the natural reestablishment of pines
and other conifers. Chronic Cu stress can be seen to have had a severe effect
on this coniferous forest ecosystem.
8.4 INTERRELATED ECOSYSTEMS
8.4.1 Aquatic Ecosystems
Because evidence for assessing the influence of ambient 0- on aquatic
ecosystems is not available, it is not possible to judge accurately this
relationship.
Nevertheless, it is extremely important to consider that an adverse
impact on a forest ecosystem may in turn adversely affect adjacent aquatic
systems. A variety of linkages for energy and nutrient exchange exist.
Disruptions induced by air pollution stress on terrestrial ecosystems often
trigger dysfunctions in neighboring aquatic ecosystems, such as streams,
lakes, and reservoirs. Sediments resulting from erosion can change the physical
character of stream channels, causing changes in bottom deposits, erosion of
channel banks, obstruction of flow, and increased flooding. They can fill in
natural ponds and reservoirs. Finer sediments can reduce water quality,
affecting public and industrial water supplies and recreational areas. Tur-
bidity caused by increased erosion can also reduce the penetration of light
into natural waters. This, in turn, can reduce plant photosynthesis and lower
supplies of dissolved oxygen, leading to changes in the natural flora and
fauna (Bormann and Smith 1980). Significant forest alterations, therefore, may
have a regional impact on nutrient cycling, soil stabilization, sedimentation,
and eutrophication of adjacent or nearby aquatic systems. Interfacing areas,
such as wetlands and bogs, may be especially vulnerable to impact.
As noted in the San Bernardino study, forest biomass reduction results in
a corresponding reduction in the total inventory of nutrient elements held
within a system, and loss of the dominant vegetation destroys cycling pathways
and mechanisms of nutrient conservation. Research on the northern hardwood
forest has clearly established that retention of nutrients within a forest
ecosystem depends on constant and efficient cycling between the various compo-
nents of the intrasystem cycle and that deforestation impairs this retention
019CC/A 8-39 May 1984
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(Likens et al. , 1977). Extensive nutrient loss can pollute downstream aquatic
resources; this can result in enrichment or eutrophication of a site, with
long-term consequences for potential plant growth.
8.4.2 Agricultural Ecosystems
Agricultural ecosystems are artificial systems created by humans for
efficient food and forage productivity. Such systems generally have a single,
dominant autotrophic plant species. If this component is very sensitive to
03, its market value may be destroyed. If this occurs, efforts are made to
find a resistant cultivar (e.g., with tobacco) or to convert the site to a
crop less sensitive to 03 stress. If the plant is not severely injured by
exposure to ambient Og, it may be influenced in one of the many ways described
in Chapter 7. In such a case, the primary concern is oxidant impact on produc-
tion, growth, and yield. This topic is thoroughly treated in Chapter 7. In
structure, agroecosystems resemble primary successional stages of natural
ecosystems. Unlike natural ecosystems, their maintenance requires large
investments of human and fossil fuel energy and the addition of nutrients.
8.5 ECOSYSTEM MODELING
Systems ecology is a useful tool for addressing the complexity of the
impact of 03 on ecosystems. Forest models provide a mechanism for integrating
forest growth and development data with indicators of air pollution stress.
Shugart et al. (1980) have provided a comprehensive review of forest growth
models, including tree, stand, and gap models. Although lack of critical
information limits model completeness, these approaches have already yielded
valuable information. The importance of competition in modifying the responses
of individual species to air contamination in a forest stand has been indicated
(Shugart and West, 1977; West et al., 1980). Kickert and Gemmill (1980)
modeled 0^ effects on the San Bernardino National Forest. They concluded that
the exclusion of natural fires and exposure to 0^ pollution can induce sudden
qualitative changes in conifer forest composition.
019CC/A 8-40 May 1984
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8.6 VALUING ECOSYSTEMS
Natural ecosystems provide free public and private goods and services to
humans. The free services are provided only if the integrity of the ecosystems
is maintained. One of the greatest obstacles to the conservation, wise use,
and sound management of natural ecosystems is that humans do not recognize, or
else grossly undervalue, the functions and services provided by these systems
(Farnworth et al., 1981).
A major barrier to communication between ecologists and economists is the
ambiguity surrounding the concept and usage of the word value. Most defini-
tions contain a monetary interpretation; a few definitions characterize value
in relative terms without assignment or intrinsic worth. Definitions of value
are relativistic in that they compare one item against another or against
money (Farnworth et al., 1981). Value in each of these definitions is estab-
lished as ordinal (ranked) or cardinal (related to a standard) measure. Both
ordinal and cardinal measures are relativistic means of valuation, i.e.,
values exist only in comparison with other things, and value exists only on
the basis of human judgment or preferences. Any sense of immaterial, intrinsic,
or absolute value is not included except to the extent that these factors are
relevant to individual judgment (Farnworth et al., 1981).
To incorporate the subtle and indirect meanings associated with the
concept of value, Farnworth et al. (1981) presented a framework that integrated
economic and ecological thought to separate value into (a) market values of
private goods and (b) non-market values of public goods and services (though
admittedly, many public goods and services have many market values). Non-market
values are separated into attributable or assignable values and intangible or
non-assignable values. Value I is defined as market price and is based on the
functioning of the marketplace and on how accurately the marketplace reflects
a theoretical concept, the market model. Frequently, but not always, market
value reflects accurately society's evaluation of an item. Farnworth et al.
(1981) use tropical moist forests as an example of how a natural resource
provides market and non-market values. Conversion of tropical moist forests
has provided marketable goods that have brought increased wealth to certain
individuals and political groups, but has also resulted in the severe altera-
tion or destruction of the systems that produce the goods (Myers, 1979, 1980).
Lumber, plywood and veneer, and fiber used for paper are some of the
marketable products. In addition, forests are being converted to agriculture,
019CC/A 8-41 May 1984
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tree plantations, and pasture. Beef cattle have become a major commodity in
the tropics. Cattle-ranching produces an exportable commodity that has created
a great incentive to cut and clear forests for this alternative use. The
forest is viewed as an exploitable resource from which foreign exchange or
personal wealth can be realized. The value of the forest products in the long
term is likened to the value of the system. The integrated system also produces
other goods and services that are not included in the market price of the
commodities obtained from the forests (Farnworth et al., 1981).
In the area of common property resources the marketplace is irrelevant
even though the language of the market model is used to discuss common property
and public goods. Political mechanisms are used to assign a price or value to
Value II items because society believes that the value assigned by the market-
place mechanisms are inadequate. If an item is improperly handled by the
marketplace, the item is placed before the political process which seeks to
judge values and allocate resources more efficiently. The political process
strives through negotiations to achieve agreement. Free services and goods
provided to humans by natural ecosystems are services for which no marketplace
values exist. These services have been or can be incorporated into a political
system (Farnworth et al., 1981). Among the free services provided to humans by
forests, both temperate and tropical, are the maintenance of global air and
water quality, aesthetic and recreational benefits and genetic stocks. Type II
values are inherent in the integrated functioning of the forest. The free
services provided by the forest are reduced or eliminated when marketable
goods are extracted and the forests disrupted or destroyed (Farnworth et al.,
1981).
Values I and II, comprising market values and non-market attributable or
assignable values, respectively, are established by institutional mechanisms,
the market and the political system. Value III items, unlike those in the two
previous values, have not been incorporated into any agreement system because
the intangible or non-assignable non-market goods and services are difficult
to evaluate. These absolutely non-market values are seen as individual or
societal (public) benefits. Often they conflict with the private benefits of
natural systems. Farnworth et al. (1981) state, "At present, private market
economics cannot efficiently price these mainly ecological benefits, but
non-market valuation theory to determine these intangibles is now emerging."
019CC/A 8-42 May 1984
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Assignable values that currently are not incorporated into any valuation
system are natural life-support systems that provide free service and the
inherent value of natural systems. Examples of these are maintenance of the
global carbon balance; maintenance of atmospheric stability; habitats for
native people; intrinsic value of species, culture, and ecosystems; a natural
laboratory for the study of evolution, natural selection, and nutrient cycling
(Farnworth et al. , 1981). A majority of these attributes apply to all of the
world's forest ecosystems. At the present no agreement system exists, and thus
the total value of the system can only be approximated.
High-technology societies are coupled to the natural system only through
extensive outside subsidies of materials and energy. Natural ecosystems are
regarded as exploitable entities rather than human/nature compatible systems.
Frequently, the natural system is exploited for short-term gain. The decision
to alter irreversibly a natural resource implicitly assumes that future genera-
tions will not value the unaltered resources as highly as present generations do
the development of the resource (Farnworth et al., 1981).
Westman (1977) also points out certain corollaries that accompany the
decisions to utilize natural ecosystems for present day benefits:
(1) The human species has the exclusive right to use and manipulate
nature for its own purposes. (2) Monetary units are socially accept-
able 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 compen-
sation has been transferred.
Each of these assumptions, and others not listed, can and have been challenged.
Humans receive from natural ecosystems free public and private goods.
The free work and provision is inherent in the integrity of the system, and
its value is related to this integrity. Only if the integrity of the systems
is maintained will the natural life-support ecosystems continue to provide
free services to humans. Functional systems provide not only public goods and
services but in addition yield private goods. Only through the maintenance of
an integrated, functional system will both public and private goods (values)
be assured (Farnworth et al., 1981). Natural systems have an integrity which
019CC/A 8-43 May 1984
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is embodied in the totality of structure and functioning of the system. It is
this integrity that is valued as having inherent worth, as without it the
goods and services they provide would not be available.
Although markets for pricing environmental services usually are lacking,
analysts have developed—and are continuing to test and compare—a variety of
techniques to value such services indirectly.
8.7 SUMMARY
Temperate forest ecosystems within the United States currently are experi-
encing perturbation by (L. Decline of ponderosa and Jeffrey pine in the San
Bernardino Mountains of southern California, and of eastern white pine along
the Blue Ridge Parkway in Virginia and on the Cumberland Plateau of East
Tennessee has been attributed to 03 stress. Decline in vigor is a commonly
observed response in trees sensitive to 0~ exposure. The decline in vigor and
reduced annual growth of sensitive trees have resulted from the following
sequence of events and conditions: 1) premature senescence and the loss of
older needles at the end of the growing season, 2) reduction in storage capacity
in the fall and resupply capacity of photosynthate in spring to support new
needle growth, 3) increased reliance of new needles on self-support for growth,
4) shorter new needles resulting in lower gross photosynthetic productivity,
5) higher retention of currently formed photosynthate by needles so that the
photosynthate available for translocation, as well as repair of chronically
stressed tissues of older needles, is reduced, and 6) premature dropping of
older needles. These events and conditions, when coupled with a higher res-
piratory to photosynthetic ratio as indicated by gas exchange measurements,
lead to a reduction in photosynthesizing tissue and availability of carbohy-
drates for growth and maintenance of trees.
Ecosystems, because of their complexity, respond to stress in a manner
different from individuals. Trees are a single, highly, visible component of
these multifaceted, highly structured organizations. Their decline is an
indication that the whole system is under stress. Ecosystems respond to
perturbations through the populations of organisms that comprise the system.
There are three main levels of interaction: between the individual and its
environment, the population and its environment, and the ecosystem (the commun-
ity and its environment). These ecological systems are involved in the proces-
ses of energy transfer and nutrient cycling so that the ecosystem develops a
019CC/A 8-44 May 1984
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specific structure. Perturbation disrupts energy transfer and nutrient cycling.
The ecosystem reverts to a simpler structure when the functioning of its
components is impaired or altered.
The most thoroughly studied ecosystem is that in the San Bernardino Moun-
tains of southern California. The mixed conifer forests of the San Gabriel
and San Bernardino mountain ranges east of Los Angeles have been exposed to
oxidant air pollution since the early 1940's. From 1973-1978 an interdiscip-
linary study was made of the impact of 0~ on the pine and mixed conifer forests
in the San Bernardino Mountains. Both biotic and abiotic components were
studied. The biotic components were the producers (an assortment of tree
species and lichens), the consumers (wildlife, insects, disease organisms),
and decomposers (mainly fungi); abiotic components included water (precipita-
tion), temperature, light, mineral nutrients (soil substrate) and the air
pollutant, ozone. Changes in the ecosystem processes of energy flow (carbon),
water movement, mineral nutrient cycling and the shift in diversity patterns
were noted. Ecosystem components most directly affected by exposure to ozone
were various tree species, the fungal microflora of needles, and the foliose
lichens occupying the bark of trees. Ozone inhibits photosynthesis, decreases
the products formed in photosynthesis, and alters the transport and allocation
of these products from the leaf to other parts of the plant (Chapter 7).
Foliar injury to sensitive ponderosa and Jeffrey pine was observed when CL
concentrations ranged from 0.05 to 0.06 ppm. During the period of study,
average 24-hr 0, concentrations during the months May through September ranged
•3
from a background of 0.03 to 0.04 ppm to a maximum of 0.10 to 0.12 ppm. Less
sensitive trees in decreasing order of sensitivity were white fir, black oak,
incense cedar and sugar pine. Associated with foliar injury were a decrease
in photosynthesis, a reduction in tree growth in both height and diameter and
in seed production in ponderosa and Jeffrey pine. Reduced tree growth and
seed production is an indication that the important ecosystem processes of
energy (carbon), mineral nutrients and water flow were affected either directly
or indirectly by 0» exposure. A comparison of the radial growth of ponderosa
pine during years of low pollution (1910 to 1940) with years of high pollution
(1941 to 1971) indicate that 0~ exposure reduced the average annual radial
O
growth by approximately 40 percent, height by 25 percent, and wood volume by
84 percent in trees less than 30 years of age.
019CC/A 8-45 May 1984
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Studies made along the Blue Ridge Parkway and on the Cumberland Plateau
of east Tennessee support the view that exposure to (L reduces growth in
sensitive trees (Benoit et al., 1982). Eastern white pine of reproducing age
located in experimental plots situated along the Blue Ridge Parkway from the
Shenandoah National Park in the north to the southernmost end of the Parkway
in Virginia were studied to determine the radial increment during 1955-1978
period. Growth of trees classified as sensitive was 25 percent less, and of
trees classified as intermediate in sensitivity was 15 percent less than
tolerant trees. Mean radial increments for all trees during the last 10 years
of the study were smaller than for the previous 24 years. Comparison of
growth during 1974-1978 with radial growth during 1955-1959 indicated a decrease
in growth of 26, 37, and 51 percent for tolerant, intermediate, and sensitive
trees. During the period of the study, concentrations of 0.05 to 0.07 ppm of
0^ were recorded on a recurring basis with episodic peaks of 0.12 ppm or
higher (Benoit et al., 1982). Steady decline in annual ring increments of
sensitive white pine was also observed on the Cumberland Plateau during the
years 1962-1979. A reduction of 70 percent in average annual growth and 90
percent in average bole growth was observed in sensitive white pine when
compared to both tolerant trees and trees of intermediate sensitivity. Annual
occurrences of 0^ at hourly concentrations of 0.08 ppm or greater were associ-
ated with the growth reductions. Reduction in growth of sensitive white pine
on the Blue Ridge Parkway and on the Cumberland Plateau, as in the case of the
San Bernardino Mountains, was correlated with extensive oxidant injury to pine
needles, senescence or premature abscission of needles, decrease in photosyn-
thesis, reduction in stored photosynthate and impairment of its transfer and
allocation; weakened trees result. Weakened trees are predisposed to attack
by root rot fungi such as Heterobasidion annosum and Verticicladella wagenerii,
to defoliation by insects and to attack by the pine beetle, Dendroctonus
brevicomis. In the San Bernardino Mountains several bark beetles attacked the
weakened ponderosa pines. Weakened trees are also subject to attack by various
pathogens that infect stressed or senescent plant parts or invade nonliving
woody tissue. Mortality in the San Bernardino forest reached 2 to 3 percent
in some years.
Studies indicate that a disease-insect relationship exists between root-
infecting fungi and bark beetles. In the majority of the cases studied root
disease fungi infected ponderosa pine trees before they became infested with
019CC/A 8-46 May 1984
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bark beetles. Both Verticicladi'ella Wagnerii and Heterobasidlon annosum were
found to have entered tree roots prior to beetle attack. In eastern white
pine, oxidant injury increased the incidence of Verticicladiella precera.
Heterobasidion annosum usually becomes a serious problem in California only
after forest disturbances by humans such as logging.
The presence of mycorrhizae on the roots of conifers assists in protecting
the trees from attack by such root pathogens as Heterobasidion annosum (Krupa
and Fries, 1971). The presence of mycorrhizae on conifer roots increases the
concentrations of monoterpenes and sesquiterpenes two to eight times. Monoter-
penes are constituents of the oleoresins that are commonly found in conifers
and play an important role in the resistance of wood to decay fungi (Risbeth,
1951) and also in preventing attack by Heterobasidion annosum and four species
of Ceratocystis.
The presence of mycorrhizae, on the other hand, is greatly influenced by
the photosynthetic capacity of the host and its capacity to translocate carbohy-
drates to the roots. Seedlings of Virginia pine inoculated with the mycorrhizal
fungus Thelephora terrestris and growing under an 18-hr photoperiod became
dormant when transferred to an 8-hr photoperiod. In contrast with the seedlings
continuing to grow under the 18-hr photoperiod, no further infection of rootlets
occurred. Studies indicate that simple sugars found in the tree roots are
readily utilized by mycorrhizae and enhance infection. McCool et al. (1979)
noted that infection of Troyer citrange by Glomus fasiculatus, a mycorrhizal
fungus, was reduced when the host was exposed to CL concentrations of 0.09 ppm.
Mycorrhizae on the roots of trees are essential for the growth of healthy
trees. Inhibition of photosynthesis in conifer needles by 0^ begins a chain
reaction that ultimately disrupts the functioning of mycorrhizae on the tree
roots and leads to their being weakened and more readily attacking root rot
fungi and bark beetles.
Declines of trees are usually the result of a number of chronic stresses.
The predisposing factor in these studies was oxidant air pollution, accompanied
by reduced photosynthesis, carbohydrate, moisture flow, and soil nutrients.
Insects, bark beetle and fungus attack all contribute to the further weakening
of trees. Declining trees usually have a serious depletion of stored carbohy-
drates, reserves necessary for starting growth in the spring or in regenerating
tissues attacked by fungi or insects as well as infection by mycorrhizae.
Depletion of its stored carbohydrate reserves by excessive continuous demands
019CC/A 8-47 May 1984
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limits a tree's ability to respond to stresses. Death eventually results
after continued stress. The process usually takes a number of years for
completion, and mature trees are the ones involved.
Forest ecosystems are not the only ecosystems impacted by oxidant air
pollution. The coastal sage scrub vegetational community of California ranges
from Baja California to San Francisco. The reduced cover of native species in
this shrub community was correlated with high oxidant concentrations on the
most polluted sites. A decline in species number was also observed. In
recently burned chaparral communities in the same area, seedling pioneer
species were vulnerable to oxidant stress. Other ecosystems in which ozone
injury has been observed are the grassland, oak, aspen and conifer communities
in the Salt Lake Valley and Wasatch Mountains of Utah and the indigenous
vegetation communities of the Blue Ridge Mountains of Virginia.
In Utah, some dominant species considered keys to community integrity
were found to be sensitive. Bromus tectorum L. (cheatgrass), the most preva-
lent species in the grassland community was also the most sensitive to 0^.
Other grasses and forbs were not as sensitive; however, in those grasses with
visible injury, carbohydrate production was significantly reduced. Aspen
(Populus tremuloides Michx) was the most sensitive member of the aspen community.
In both cases single 2-hr exposures to 0.15 ppm of 0., caused severe injury.
Removal of the dominant species (cheatgrass) from plant communities could re-
sult in a shift to another species. Decline in or removal of aspen could af-
fect the growth of white fir because seedlings require the shade provided by
aspen for optimal juvenile growth. Loss of aspen populations could influence
forest succession by restricting white fir development, causing a shift from a
forest to a grassland or forb vegetation community. In a companion study con-
ducted in chambers in the greenhouse, 0, exposures of 0.15 to 0.3 ppm for 2-hr
per day reduced root- and top growth and fewer seeds were produced. A reduc-
tion in biomass production was also observed in the study conducted in the
Shenandoah National Park and the Blue Ridge Mountains of Virginia. Native
forbs, grasses and sedges in a high meadow community were exposed to monthly
hourly average 0^ concentrations ranging from 0.035 to 0.06 ppm. Peaks ranged
from 0.08 to 0.12 ppm. The studies discussed above illustrate that 03 inhibits
photosynthesis, decreases formation of organic compounds needed for plant
growth and can alter transport and allocation of the decreased products of
photosynthesis so that sugar storage and root growth are affected (Duchelle
et al., 1983).
019CC/A 8-48 May 1984
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Changes in diversity in plant communities occurring with time and space
result as those plant species sensitive to 0~ decrease in numbers and CL-tolerant
species take their place. The shift in species has been particularly obvious
in the San Bernardino Forest where shrub and oak species have emerged as
dominants after removal of ponderosa and Jeffrey pine. The breakdown in the
processes of energy flow and nutrient cycling has also had its impact on other
components of the forest ecosystem. The change in dominant producers influenced
the small mammal population by changing its habitat and upsetting its food
web. Fruits and seeds comprise the major portion of the small mammal diet.
Removal of their food source directly impacts them. Decomposition also was
affected as the species composition and density of fungi which colonize living
needles and later participate in decomposition were prevented from developing
due to the premature needle senescence and abscission.
The impact of 0^ on ecosystems depends on the response of the producer
community. Producers as well as decomposers are critical to the maintenance
of ecosystems. The solar energy and mineral nutrients necessary for the
proper functioning of ecosystems enters through the producers. Interference
of CL with the proper functioning of the process of photosynthesis results in
a perturbation felt throughout the ecosystem.
Natural and agricultural ecosystems possess the same basic functional
components. They require energy flow and mineral nutrient cycling for main-
tenance and are subject to the dominating influences of climate and substrate.
Agroecosystems, however, are highly manipulated monocultures, usually similar
in genetic composition and age. Manipulation of the monocultures is to maxi-
mize the yield of a particular species. If the species grown does not produce,
it is replaced. Cost alone would prevent the replacement of the variety of
species in a natural ecosystem. The complexity of natural ecosystems makes it
much more difficult to quantify their benefits. No one knows what all of the
benefits are and in many cases the benefits may not have dollar value. Some
of the unpriced benefits to society are soil stabilization, enhanced water
quality, climate amelioration, nutrient and energy conservation, gene preser-
vation and amenity and aesthetic function. It is extremely important to
recognize that societal benefits derived from natural ecosystems are obtained
without appreciable direct dollar expenditures or extensive management.
019CC/A 8-49 May 1984
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Ozone injury to the foliage of Pinus ponderosa. Phytopathology 53: 1072-
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Miller, P. R. ; Taylor, 0. C.; Wilhour, R. G. (1982) Oxidant air pollution
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9. OTHER WELFARE EFFECTS OF OZONE AND OTHER PHOTOCHEMICAL OXIDANTS
9.1 INTRODUCTION
Photochemical oxidants comprise various chemical species capable of
reacting with a number of nonbiological materials. The nature and amount of
damage to these materials can be approximated from oxidant concentrations
(Chapter 6) and the rate constants of individual species. Unfortunately,
there is virtually no information on the rates of reaction of photochemical
oxidants other than ozone (0.,) on specific materials. Although ozone has been
the primary photochemical oxidant studied, its prominence in the research
literature does not necessarily indicate that it is the only important oxidant
responsible for damaging materials. Under experimental conditions with certain
chemical groups, OH radicals, which are far less abundant than ozone, have rates
of reactivity much higher than those of ozone.
Nearly all research on photochemical oxidants has focused on economically
important or abundant materials that are susceptible to oxidant damage. These
include elastomers (natural rubber and certain synthetic polymers), textile
fibers and dyes, and, to a lesser extent, paints. It has been shown that
oxidants harden and embrittle elastomers, causing a loss in physical integrity
and cracking. Damage, specifically by ozone, occurs mainly on the surface of
these materials and is accelerated by mechanical stress. In the absence of
ozone, oxidation by atmospheric oxygen still occurs, but at a slower rate and
more in the bulk of the material. These effects have been known for years,
and various antioxidants and other protective measures have been formulated to
reduce the rates of attack. Oxidant exposure weakens certain textile fibers
(i.e., reduces the breaking strength and increases the rate of wear) and
changes the color of some dyes. Like elastomeric products, fibers and dyes
particularly sensitive to ozone may be partly protected with resistant coatings
or replaced with more durable formulations. Ultimately, these protective mea-
sures add to the cost of products. The effects of oxidants on paints are not
defined well, but they may be similar to some of the effects on elastomers;
damage from other gaseous pollutants, such as sulfur dioxide, tends to over-
shadow the role of ambient ozone in estimating paint damage.
0190GI/B 9-1 May 1984
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To determine the actual damage to in-use materials, exposure must be
estimated. As an example of the variables that must be taken into account,
the ozone exposure of textile fibers and dyes used for clothing depends on the
activity patterns of the wearer (i.e., time at home, at work, or outdoors),
but the exposure of the same materials used for carpets and drapes involves
only indoor air. Accordingly, a knowledge of product use and indoor/outdoor
ozone gradients is essential when evaluating estimates of materials damage.
The literature selected for review in this section includes research
previously reported in the 1978 criteria document (U.S. Environmental Protec-
tion Agency, 1978) and a limited number of references published before and
after 1978. Of the twelve recent post-1978 references in this review, eight
involve laboratory/field research, and four involve analyses that use previously
published material. Because little recent work has been reported on the
effects on nonbiological materials, reference to older studies is necessary
for unity and coherence, for determining dose-response relationships, and for
assessing economic impact. Technical areas considered in evaluating the cited
studies include the type of study and exposure methods used (field versus
laboratory; ambient conditions versus accelerated, artificial environments),
the pollutant-monitoring and analytical methods used, the design and conditions
of the experiment (e.g., inclusion of variables such as relative humidity and
temperature), the statistical methods and level of significance, and the
importance of the specific material studied. The absence of this type of
information is noted in the text, when applicable.
This assessment of the effects on nonbiological materials includes a
review of the mechanisms of damage and protection; it also presents dose-
response information from laboratory and field studies and evaluates previously
reported economic assessments.
9.2 MECHANISMS OF OZONE ATTACK AND ANTIOZONANT PROTECTION
9.2.1 Elastomers
Most elastomeric materials found in the marketplace are composed of
unsaturated, long-chain organic molecules. That is, the molecules contain
carbon-carbon double bonds. Natural rubber and synthetic polymers/copolymers
of butadiene, isoprene, and styrene account for the bulk of elastomer production
for products such as automobile tires and protective electrical coverings used
in outdoor environments (Mueller and Stickney, 1970). These types of compounds
0190GI/B 9-2 May 1984
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are susceptible to oxidation and are particularly susceptible to (k attack.
In contrast, synthetic elastomers with saturated chemical structures, such as
butyl rubber, polymers of silicones, ethylene, propylene, hypalon, and polyure_
thanes, have an inherent resistance to CL damage (Mueller and Stickney, 1970),
but higher cost and limiting physical and chemical properties have constrained
their use in outdoor environments.
The differences and similarities between simple oxidation (reaction with
oxygen) and 0- attack are described by Mueller and Stickney (1970). In the
elastomer molecule, simple oxidation is postulated to proceed through the
removal of a hydrogen atom from a carbon atom adjacent to a double bond; this
is followed by the formation of a peroxy radical and subsequent radical reac-
tions, which leads to chain scission and/or cross-linking (see Figure 9-1).
Ozone is thought to attack by adding atoms directly across the double bond,
forming a five-membered ring structure. This structure quickly rearranges
(via Criegee ozonolysis) to form a zwitterion and an aldehyde (see Figure 9-2).
Subsequent reactions of the zwitterion lead to a permanently oxidized elastomer.
Ozone damage, usually in the form of cracking, tends to be more of a
surface phenomenon than simple oxidation. It is greatly accelerated by mechan-
ical stress, which produces fresh surface area at crack boundaries. Simple
oxidation, on the other hand, is slower; it occurs more in the bulk of a
material, and it is less affected by the degree of stress.
At very high concentrations and high mechanical stress, 0~ damage can
result in a large number of surface microcracks that produce a frosted appear-
ance and mechanical weakening (Crabtree and Malm, 1956). However, because
both simple oxidation and 0~ reactions lead to chain scission and chain cross-
linking, the end result of both types of damage can be very similar in appear-
ance. At pollutant concentrations and stress levels normally encountered
outdoors (and in many indoor environments), the elastomer hardens or becomes
brittle and cracked, which results in a loss of physical integrity. The
influence of 0,, is evidenced primarily by the increased rate at which damage
accumulates and by the degree of protection provided by various antioxidants
and antiozonants.
According to Fisher (1957), work at the Rock Island Arsenal by R. F.
Shaw, Z. T. Ossefa and W. J. Tonkey in 1954 lead to the development of effec-
tive antioxidant additives to protect elastomers from 0^ degradation. Subse-
quently, antiozonants were generally incorporated into elastomeric formulations
0190GI/B 9-3 May 1984
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I RADICAL I
-C—C=C ^- C—C=C (a)
I H H • H H
H
-C — C = C— *»- —C —C = C (b)
• H H i H
0 —O.
SEVERAL
C = C ^ CHAIN SCISSION (c)
H STEPS PRODUCTS
O — O.
Figure 9-1. Postulated mechanism for damage to
elastomers by oxygen.
Source: Adapted from Mueller and Stickney (1970).
9-4
-------
o
/\
R R O 0
I o3 III
-C — C=C ^ —C—C —C (a)
H H H H H H
o
/ \
R O O R
III I +
C —C —C ^- —C —C —O —O +O = C (b)
I H H I H H
H H
Figure 9-2. Postulated mechanism for damage to
elastomers by ozone.
Source: Mueller and Stickney (1970).
9-5
-------
during mixing, and their protection was effective even when elastomers were
stretched or flexed (Fisher, 1957; Mueller and Stickney, 1970).
Several theories have been advanced to explain the mechanism of anti-
ozonant protection. As summarized by Andries and Diem (1974), these are the
scavenger theory, the protective film theory, the recombination theory, and
the self-healing film theory.
The scavenger theory suggests that the antiozonant diffuses to the sur-
face, where it reacts with the 0~ at a faster rate than with the carbon-carbon
double bonds of the rubber, thereby protecting it sacrificially. The protective
film theory also includes diffusion to the surface, but assumes that the
resulting layer is less reactive with 0., than is the rubber and thus constitutes
a protective layer. The recombination theory proposes that the antiozonant
prevents the propagation of the radical chain reactions initiated by 0., attack.
The self-healing film theory assumes that reaction products form on the surface
and resist further degradation.
The work of Razumovskii and Batashova (1970) on the mechanism of protec-
tive action by the antiozonant N-phenyl-N'-isopropyl-p-phenylenediamine (PIPP)
is most consistent with the scavenger mechanism. These investigators showed
that CL reacts preferentially with PIPP at a ratio of three CL molecules per
one PIPP molecule.
Andries et al. (1979), by using carbon-black-loaded natural rubber (NR)
compounds with and without antiozonants, attempted to distinguish between
possible mechanisms with attenuated total reflectance spectroscopy and scanning
electron microscopy. Their experiments indicated that a combination of the
scavenger and protective film mechanisms best explains antiozonant protection.
Examination of the surface of the rubber samples with antiozonant showed that
only ozonized antioxidant and not ozonized rubber was present. This layer of
ozonized antioxidant functioned as a relatively nonreactive film over the
surface, preventing the CL from reaching and reacting with the rubber below.
In addition to reactive antiozonants, paraffinic and microcrystal1ine
waxes are used to protect the elastomers in rubber products such as tires.
Typically, the wax migrates to the surface of the rubber and forms a barrier
against 0~ attack. The wax's ability to protect the rubber depends on how
well the wax migrates to the surface. This phenomenon, known as blooming,
depends on a number of factors besides the characteristics of the wax. Dimauro
et al. (1979) studied the ability of 18 waxes to protect rubber against degra-
dation due to OT- Dimauro found that no wax by itself provided an optimal
0190GI/B 9-6 May 1984
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level of protection; blending with a reactive antiozonant was required. The
paratfinic waxes protected best at lower exposure temperatures, and the micro-
crystalline waxes were more effective at higher temperatures. Wax blends,
which combine the best effects of each type of wax, offered the best protection
over a wide range of temperature. However, it was found that wax alone can be
detrimental to dynamic 0,, resistance. Wax can induce localized stresses in
the rubber that can lead to premature rubber failure under dynamic testing
conditions.
9.2.2 Textile Fibers and Dyes
Damage to textile fibers from 0- is difficult to distinguish from that
caused by oxidation by oxygen. Reduction in breaking strength and an increased
rate of wear are the types of damage most commonly observed. Cellulose-based
fibers, acrylic fibers, and nylon fibers are affected by CL, and modacrylic
and polyester fibers have been shown to be relatively unaffected by the levels
of 0, normally experienced in the ambient atmosphere (Zeronian et al., 1971).
However, as stated by Bogaty et al. (1952), for most uses of textile fibers,
the action of CL or oxygen is less important in product lifetime than physical
abrasion, biological degradation, soiling, fashion, and other factors. Accord-
ingly, the economic significance of CL damage to textile fibers is relatively
low, and the differences in the mechanisms of attack are not important.
Nevertheless, an important property of textile products is appearance or
color; 0~ reacts with a number of dyes to cause fading or changes in color.
Oxidation is the fundamental chemical reaction leading to color change in
dyed fibers exposed to CL. Compared with other oxidizing pollutants such as
nitrogen oxides, 0., often leads to a higher degree of oxidation and thus to
different types of color changes. Terms such as 0-fading and Gulf Coast
fading have been given to some of the unique color changes attributed to
reactions with CL.
Figure 9-3 illustrates the reaction of Disperse Blue #3 with CL and with
nitrogen oxides (Haylock and Rush, 1976). Although the nitrogen oxides removed
an alkylamine side chain, 0.-, attacked the quinoid portion of the molecule,
completely rupturing the ring system chromophore and oxidizing the dye to
phthalic acid, which is colorless.
The reactions between various chemical categories of dyestuffs and CL is
influenced not only by the properties of the dye but also by the chemical
019QGI/B 9-7 May 1984
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OZONE
NITROGEN
OXIDES
DISPERSE BLUE NO. 3
Figure 9-3. Reaction of anthraquinone dyes with ozone
and with nitrogen oxides.
Source: Haylock and Rush (1976).
9-8
-------
nature of the fiber to which the dye is applied and the manner in which the
dye is applied. Additional factors include the presence of protective agents;
synergistic or additive effects of temperature, air moisture, and other pollu-
tants; and even the degree of strain of the base fiber caused by folding or
creasing.
For example, in a study of 0., fading of anthraquinone dyes on nylon,
Haylock and Rush (1976, 1978) found that fiber properties such as cross-section
shape, draw ratio, and the degree of steam heat setting had significant effects
on the rate and severity of 0., damage, even for chemically identical systems.
Given this complexity and sensitivity, it is not practical to relate a specific
mechanism of damage to a broad class of damage situations. Furthermore, it
may not be necessary to do so. In most cases, some combination of dye, fibers,
and protective treatments can eliminate major problems due to CL exposure and
still provide the range of colors desired in the final products.
9.2.3 Paint
The mechanisms of paint damage due to 0., have not been defined well:
Damage is probably related to oxidation of the organic binders that hold the
pigment and form the protective seal over the surface. Damage is likely to be
similar to that of elastomers; that is, embrittlement and cracking due to
chain scission and cross-linking. However, the data available on 0~ damage to
paints come primarily from studies of surface erosion caused by gaseous pollu-
tants. Because the polymeric structure of dried paint film is significantly
different from that of an elastomer under elongation stress, direct comparisons
should be made with great caution.
9.2.4 Other Materials
Although the effects of oxidants on other materials have been examined by
several investigators, most of the limited information is qualitative and
centers on mechanisms of effects. Sanderson (1975), in a review of the effects
of photochemical smog on materials, included possible effects on plastic and
asphalt. However, because these effects were recorded in a laboratory environ-
ment at extremely high 0., levels, the indicated impacts have little direct
applicability.
Haynie and Upham (1971) reported a possible beneficial effect of photo-
chemical oxidants on the corrosion behavior of steel on the basis of field
0190GI/B 9-9 May 1984
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study data. However, laboratory studies did not show any statistically signi-
ficant effect of CL on steel corrosion.
Polyethylene, commonly used as electrical insulating material, may be
adversely affected by ambient 0~ concentrations. Laboratory studies (National
Research Council, 1977) have demonstrated by means of infrared and other
techniques that terminal double bonds in polyethylene end groups are attacked
by "ozonized" oxygen to form carboxylic acid groups and, through ruptures in
the polymer chain, to produce short-chain dicarboxylic acids.
It is also known that atomic oxygen reacts with polyethylene at room
temperature to produce a loss in weight and some morphologic changes. The
work of Trozzolo and Winslow (1968) and Kaplan and Kelleher (1970) suggests
that singlet oxygen also interacts with polyethylene to form hydroperoxides.
Laboratory studies suggest that hydroperoxides may be the dominant oxidants
that attack polyethylene or other materials in ambient air.
Despite the known interactions of oxidants with polyethylene and other
polyolefins to form intermediate peroxy radicals, there is no evidence that
the chemical reactions go far beyond the surface. It is believed that the
effects of atmospheric CL on polyethylene insulation and other polyethylene
products are negligible in comparison with the embrittlement caused by a
combination of oxygen and sunlight. The mechanisms by which this embrittlement
occurs probably involve sensitization to oxidation by absorption of ultraviolet
(UV) radiation, by residual hydroperoxy and carbonyl groups in the polymer,
and by surface deposits of aromatic sensitizers from polluted air. Deteriora-
tion of the electrical insulating properties of polyethylene by oxidation in
some environments cannot be attributed to ambient 0.
9.3 DOSE-RESPONSE DATA
Most dose-response studies are criticized for their reliance on artificial
environments (laboratory settings) that do not contain all the critical varia-
bles encountered under ambient conditions. Scientists realize the limitations
of laboratory tests; no model could simulate conditions identical to an ambient
environment. Nevertheless, many laboratory tests have represented the outdoor
environment to some extent, and the findings from these tests have been used
in conjunction with field tests to estimate the nature and amount of damage to
materials.
0190GI/B 9-10 May 1984
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9.3.1 Elastomer Cracking
Hofmann and Miller (1969) demonstrated correlations between laboratory
tests and the actual service use of passenger vehicle tires in the Los Angeles
area. Basically, three laboratory test methods were used (Table 9-1): indoor
and outdoor belt flex, indoor and outdoor wheel, and stress relaxation. They
found that the behavior of rubber exposed to 03 under laboratory conditions
correlated well with the service behavior of tires in localities where atmos-
pheric 0., concentrations were high. The relative susceptibilities of different
formulations of white sidewall rubber were generally similar, whether exposed
3
under laboratory conditions to as much as 0.5 ppm (980 ng/m ) of 0., or exposed
in the ambient air of the Los Angeles area, which had annual average 0, concen-
3
trations near 0.04 ppm (80 pg/m ) (U.S. Department of Health, Education, and
Welfare, 1970). The exact exposure times, pollutant measurement methods, and
statistical analyses were not reported.
Bradley and Haagen-Smit (1951) evaluated a natural rubber (NR) formulation
for susceptibility to 0, cracking. Strips were strained approximately 100 per-
3
cent by bending and then exposed in a small chamber to 40,000 mg/m (20,000 ppm)
of 0.,; these specimens cracked almost instantaneously and broke completely
within 1 s. When these NR formulations were exposed to lower concentrations
of 0,, different time periods were required for cracks to develop as shown in
Figure 9-4, and this action increased with increasing temperature. Humidity
and sunlight had little influence on cracking rate. According to the data in
this figure, the initiation of cracks and subsequent deepening are controlled
by the dose of 0., (concentration x time).
Meyer and Sommer (1957) exposed thin polybutadiene specimens to constant
load, ambient room air, and 0,. Specimens exposed in the summer to average 0^
O *j O
concentrations of about 0.048 ppm (94 ug/m ) broke after 150 to 250 hr. In
3
the fall, at average CL concentrations of 0.042 ppm (82 |jg/m ), specimens
failed after exposures of 400 to 500 hr. In the winter, at average 0.-, concen-
3
trations of 0.024 ppm (~47 ug/m ), failures occurred between 500 and 700 hr.
Like the Bradley and Haagen-Smit study, these data also show the strong depen-
dence of breakage on 0., dose over the average time of exposure where failure
occurred (average concentrations x time), but not in the same linear fashion.
Dose-response levels in this study are noted parenthetically for the following
concentrations: 0.048 ppm (9.6 ppm/hr); 0.042 ppm (18.9 ppm/hr); 0.024 ppm
(14.4 ppm/hr).
0190GI/B 9-11 May 1984
-------
TABLE 9-1. TIRE INDUSTRY EXPOSURE TESTS0
Test
Strain
Conditions
Reasons for Use
Belt flexing
Stress relaxation
Outdoor wheel
Indoor wheel
Tire tests on vehicles
dynamic at 4500 to 7500 flexures per
hour
dynamic or static; 25 percent ex-
tension at 90 cpm
dynamic and static; variable loads,
inflation, and speed
dynamic and static; variable loads,
inflation, and speed
dynamic and static; variable loads,
inflation, and speed
ozone chamber at 0.35 to 0.50 ppm,
or outdoors for several days
ozone cabinet at 0.25 to 0.50 ppm
for 16-hr increments
Los Angeles area, high ozone for
several weeks
large ozone chamber at 0.01 to 0.35
ppm and -20 to 100° F, for days to
weeks
extreme and typical service areas
for 1/2 to 2 years
rapid evaluation, variable conditions
for screening sidewall compounds
rapid evaluation, variable conditions
for screening sidewall compounds
quicker and cheaper than tire testing
on autos in actual service
strain most similar to actual service,
quicker and cheaper than outdoor wheel
ultimate test of product life
Adapted from Hofmann and Miller, 1964.
-------
(0
0)
70
65
60
55
50
45
40
35
30
25
20
15
10
5
I
I
50
100 150 200 250 300
OZONE CONCENTRATION,
I I I I
350 400 450
Figure 9-4. Relationship of cracking in rubber and
ozone concentration: time to first sign of cracking
at 4x magnification in natural rubber samples
stressed at 100%.
Source: Bradley and Haagen-Smit (1951).
9-13
-------
In describing a new test method for evaluating the 0., sensitivity of
O
elastomers, Edwards and Storey (1959) presented data demonstrating the 0~
resistance of two styrene-butadiene rubber (SBR) compounds (Polysar S and
Polysar Krylene). Both compounds were exposed without and with different
levels of antiozonant protection to 0.25 ± 0.05 ppm of 03 (490 ± 98 ug/m3) at
120°F (49°C) under 100 percent strain twice the original sample length. The
results are presented in Table 9-2. Without antiozonants, a linear relation-
ship is indicated between 03 dose (ppm/hr) and cracking depth. The coefficient
of determination for the linear regression for both materials was 0.98 compared
with 0.92 for the exponential fit. Note that the Polysar S compound displays
much greater resistance to the effects of 03 than does the Polysar Krylene
compound. Nevertheless, increasing the amount of antiozonants significantly
reduced the rate of cracking for both in a dose-related manner.
Haynie et al. (1976) conducted a chamber study to evaluate the effects of
various pollutants, including 0.,, on several materials. In one part of the
study, white sidewall specimens from a top-quality, steel-belted radial tire
were exposed (strained at 10 and 20 percent) for 250, 500, and 1000 hr to 03
concentrations of 160 ug/m and 1000 ug/m3. The 0, level was found to be
J
statistically significant in the rate of cracking of this rubber. However,
cracking rates are not directly proportional to 0. concentrations for these
two levels. The average results with respect to strain and 03 level are given
in Table 9-3.
Using the mean cracking rate calculated after long-term (1000 hr) exposure
to conditions representative of the primary air quality standard for 03 and
the annual average standard for nitrogen dioxide (N0?), Haynie et al. (1976)
concluded that it would take a minimum of 2.5 years for a crack to penetrate
to the cord depth. Additional time would be necessary to attack the cords.
For this particular premium tire, therefore, sidewall failure from 0^ damage
does not appear to be the cause of reduced tire life. However, the casing
might have questionable value for retreading. Tread wear, rather than sidewall
failure, probably determines the life of a typical rubber tire, and the rubber
used in tire treads is generally more resistant to 0-, than that in the side-
walls.
Veith and Evans (1980) investigated the effect of atmospheric pressure on
the cracking rate of rubber as tested in 03 chambers. It was found that a
change in barometric pressure alters the rate of cracking. Inter!aboratory
0190GI/B 9-14 May 1984
-------
TABLE 9-2. EFFECTS OF OZONE ON DIFFERENT SBR POLYMERS CONTAINING
VARIOUS ANTIOZONANT CONCENTRATIONS
Crack depth (10~3 in.),
Antiozonant length of exposure (hr)
Polymer
Polysar
("Hot
Polysar
("Col
S
" SBR)
Krylene
d" SBR)
(pph)
0.
0.
1.
2.
0.
0.
1.
2.
0
5
0
0
0
5
0
0
19
1.37
0.95
0.50
0.25
2.17
1.25
1.05
0.50
27
2.42
1.90
0.75
0.25
4.52
2.02
1.50
0.75
43
4.20
3.10
1.47
0.45
7.25
3.75
2.24
1.00
Cracking
depth rate
51 (10 "
4.
3.
1.
0.
7.
4.
2.
1.
65
52
95
78
90
50
90
18
0.
0.
0.
0.
1.
0.
0.
0.
in./hr) (um/hr)
92
69
35
13
58
85
57
24
2.34
1.75
0.89
0.33
4.01
2.16
1.45
0.61
Source: Edwards and Storey, 1959.
TABLE 9-3. CRACKING RATES OF WHITE SIDEWALL TIRE SPECIMENS
Mean cracking rate
Ozone concentration ± standard deviation
ug/m3 (ppm) Strain percent mm/yr um/hr
160 (0.08)
1000 (0.5)
10
20
10
20
11.66 ± 7.32
17.00 ± 10.45
15.38 ± 5.38
25.74 ± 8.23
1.33
1.94
1.76
2.94
Source: Haynie et al., 1976.
0190GI/B 9-15 May 1984
-------
comparisons were made among facilities at different geographic elevations and
thus significantly different atmospheric pressures. It was found that a
16-percent difference in cracking rate or in the extent of cracking at a fixed
0- concentration could occur. In an effort to correct the problem and standard-
ize the testing techniques, Veith and Evans (1980) recommended that CL content
in accelerated chamber testing be expressed in terms of 0^ partial pressure
(in Pa units) rather than simply in terms of concentrations.
Gandslandt and Svensson (1980) evaluated the stress test methodology used
to estimate the 0,, resistance of rubber compounds. This test measures the
decrease in the isoelastic force of stressed rubber exposed to 0-. The authors
suggested that materials should be prestressed in an 03-free atmosphere for at
least 72 hr before testing, because the complicating effects of the natural
relaxation of the material's isoelastic force constant decreases exponentially
with time. The effects of this natural relaxation mechanism become insignifi-
cant after 2 to 3 days of prestressing compared to the effects caused by 0.,
cracking.
Ten different mixtures of three rubber compounds, NR, SBR, and CR (a
compound not defined by the authors) were tested with the isoelastic force
method (Gandslandt and Svensson, 1980). The 03 protection afforded each
rubber formulation is summarized in Table 9-4. After a relaxation time of
70 hr in an 0.,-free atmosphere (two hours less than their prescribed criteria
for sample exposure), the samples at 50-percent elongation were exposed to 0^
3
concentrations of 0.5 ppm (980 ug/m ) at 30°C. The time to 10-percent and
20-percent relaxation of the isoelastic force in the rubber test samples was
used to gauge the 0., resistance of the formulation. Compounds GL 2073 B,
SS 203, and SS 200 C showed greatest resistance to the effects of Og, and
those formulations that were unprotected (GL 2073 D, SS 200 B, SS 202 A,
SS 203) and the formulations protected only by paraffin wax (GL 2073 G) demon-
strated the least resistance to 03 attack. The testing showed great variety
in the kinds of visible cracking effects as a result of the exposure. The
compounds with no protection often showed a large number of small cracks over
the entire surface of the material, but those compounds protected by a combina-
tion of wax and antiozonant or by wax alone sometimes showed only a single
crack, which grew rapidly. These effects are demonstrated in Figure 9-5.
Compounds SS 202 B (Figure 9-5a) and SS 200 C (Figure 9-5b), both protected
with wax and antiozonant, showed fairly good resistance when gauged by the
0190G1/B 9-16 May 1984
-------
TABLE 9-4. PROTECTION OF TESTED RUBBER MATERIALS
Protected
Rubber formulation
Unprotected
Wax
Antiozonant
GL 2073 B, C
G
D
SS 200 A, C
X
X
SS 202
SS 203
B
A
B
X
X
X
X X
Source: Gandslandt and Svensson, 1980.
10-percent and 20-percent stress relaxation tests but failed after approximately
50 hr and 58 hr of exposure, respectively. On the other hand, compounds
SS 203 and SS 200 A, both unprotected, exhibited small surface cracking and
outlasted some of the protected compounds. Moreover, protection with wax and
antiozonant may afford long-term protection, but when one crack appears, it
can grow rapidly and cut off the test piece, as shown in Figure 9-5b.
Davies (1979) reported on the effects of ozone and other environmental
factors on interply adhesion of natural and synthetic rubber compounds.
Excellent adhesion of plies is essential to the proper manufacturing of tires.
The rubber strips must make interlocking contact at the joint boundary or the
strength of the product will be inadequate. Ozone attack on synthetic poly-
isoprene and polybutadiene produces a surface layer of ozonides. With NR, the
film consists of ozonides and carbonyl groups (Andries and Diem, 1974; Andries
et al., 1979). The results of the Davies (1979) tests indicated that before
curing, the adhesion of SBR compounds is unaffected by exposure to 0, concentra-
3
tions of 0.15 ppm (294 ug/m ), but the adhesion of the NR/SBR blend decreases
by approximately 30 percent. Large reductions (on the order of 70 percent) in
adhesion between plies were noted with the NR compounds; even exposure for a
few hours at 0.05 ppm reduced adhesion considerably. The adhesion tests on
cured NR, SBR, and isoprene rubber (IR) compounds after exposure to various
0190GI/B
9-17
May 1984
-------
Ol
O
cc
O
u.
O
O
03
100
70
50
30
SBR UNPROTECTED
(SS 202 A)
SBR, WAX + ANTIOZONANT
(SS 202 B)
(a)
I
I I
I
0 10 20 30 40 50 60 70 80 90 100
RELAXATION TIME, hours
LU
O
cc
O
UJ
O
V)
100
70
50
30
20
0
(b)
NR (SS 200)
(WAX + ANTIOZONANT
C \ (DOUBLE AMOUNT
( COMPARED TO A)
•a
B, UNPROTECTED
A, WAX +
X ANTIOZONANT
0 10 20 30 40 50 60 70 80 90 100
RELAXATION TIME, hours
Figure 9-5. Relaxation of rubber compounds in O3 is af-
fected by the combination of rubber formulation and
type of O3 protection. Compounds were tested at O3
concentration, 0.5 ppm {980 /ug/m3); temperature, 30° C;
elongation, 50%. Vertical line at the end of a curve
means total failure, and vertical axis represents relaxa-
tion where FQ is the initial force; Ft is the force after
time, t.
Source: Gandslandt and Svenson, 1980.
9-18
-------
levels of 0., and humidity are summarized in Table 9-5. The adhesion of the
SBR compound is superior to that of the other two compounds, which were greatly
affected by increased RH.
TABLE 9-5. EFFECT OF OZONE AND HUMIDITY ON INTERPLY ADHESION3
Compound
NR
IR
SBR
Initial
adhesion
5
5
5
0.15 ppm 03
(294 ug/m3)
30% RH
2-3
4-5
4-5
Final adhesion
0.25 ppm 03
(490 ug/m3)
30% RH
1
2-1
3-4
0.15 ppm 03
(294 ug/m3)
60% RH
1
1
3-4
Source: Adapted from Davies, 1979.
aAdhesion is rated from 1 (bad) to 5 (excellent), based on a visual scale
standardized by the authors.
CA11 exposures were 16 hr in duration.
Davies examined antiozonants, antioxidants, and fast-blooming waxes as
means of protecting NR compounds from sunlight and 0~ attack and the subsequent
development of the films that lead to poor adhesion between plies. The results
of these evaluations are presented in Table 9-6. Of the samples exposed after
16 hr at 0,. concentrations of 0.15 ppm (294 |jg/m ), only those protected by
the fast-blooming waxes were found to resist 03 and have excellent adhesion
between plies (Table 9-6). Antiozonants and antioxidants in the NR did not
aid interply adhesion (Tables 9-6). Davies (1979) theorized that antiozonants
and antioxidants react with ozonized rubber and form a protective film against
further attack by 0.,. However, this film also apparently acts as a barrier to
proper adhesion between plies. Davies noted that after exposure to sunlight
alone, the antioxidants generally maintained good adhesions, but the waxes
gave only fair protection. He concluded that the combination of a fast-
blooming wax and an effective antioxidant or antiozonant is necessary to
protect NR from 0, attack and sunlight.
0190GI/B 9-19 May 1984
-------
TABLE 9-6. EFFECT OF ANTIOZONANTS, ANTIOXIDANTS, AND FAST-BLOOMING
WAXES ON INTERPLY ADHESION IN NATURAL RUBBER3
Antiozonantb'd
Untreated
ETMQ
6 PPD
1 PPD
77 PPD
TBMP
TMQ
Wax 1
Wax 2
Rating0
1
1
1
1
1
2
2
5
5
Source: Davies, 1979.
Ozone resistance rated from 1 (bad) to 5 (excellent), based on a visual scale
standardized by the author.
All substances were given an initial rating of 5.
Rating assigned after 16-hr exposure to 0.15 ppm (294 (jg/m3) of 03.
See appendix for explanation of abbreviations.
Wenghoefer (1974) studied the effects of 03 on adhesion and the climatic
sensitivity of tire cords dipped in resorcinal-formaldehyde latex (RFL). Cli-
matic sensitivity was described as summer sickness, a problem affecting cords
primarily during hot, humid weather. Many fibers and dip formulations were
studied to determine their sensitivity to 0.,, humidity, nitrogen dioxide
(N02), UV light, and heat. Wenghoefer exposed these materials at a constant
temperature of 100°F (37.8°C) to 0, levels that varied between 0 and 1.5 ppm
3
(2940 ug/m ) and to relative humidity (RH) levels ranging from 20 to 90 percent.
Adhesion deteriorated due to changes in surface properties of the RFL-dipped
cords as a result of exposure to 03, humidity, UV light, and heat. The adhesion
losses due to 0^ and the combined effects of 0~ and humidity were most notable
in the first 6 hr of exposure. The detrimental effects of heat, N0?, and the
synergistic interaction of NOp and humidity were much less pronounced. Table 9-7
summarizes the elastomer dose-response studies.
9.3.2 Dye Fading
Color fading of certain textile dyes has been attributed to the effects of
ambient 0^. Although NO^ was originally identified as the pollutant most
0190GI/B 9-20 May 1984
-------
TABLE 9-7 DOSE-RESPONSE STUDIES ON EFFECTS OF OZONE ON ELASTOMERS
Conditions
Laboratory/
Field
Laboratory
Controlled
field
Laboratory
Material/Product
Automotive
tires
Vulcanized
rubber
strips
Rubber tires and
various polymers
SBR:
Plysar S
Plysar Krylene
with and without
antiozonants
Measure- Environ-
Concentration, ment mental
Pollutant ppm method exposure
Ozone 0.25 to NA NA
0.5
Ambient 0.04 03 NA >1 yr
air (annual
average)
Ozone 0.02 to NA 3 to 65
0.46 min
Ambient 0.023 to NA 150 to
air 0.048 03 700 hr
Ozone 0.25 NA 19 to 51
hr
Dose,
Variables ppm-hr
Tires
under
stress
Los Angeles >350
environ-
ment;
actual
service
use
Physical "vO.02
stress to 0.03
Physical 9 to
stress 20
and
ambient
environ-
ment
120°F, 4.75
100% to
strain 12.75
Effects
Cracking of
white side
wall
Positive
correlation
between lab-
oratory and
ambient air
tests
Surface
cracking
Time of
cracking
Percent anti-
ozonant was
related to
cracking
depth rate
Comment
Purpose was to
correlate lab-
and field tests.
Exposure time,
detai led pollu-
tant measurements,
and statistical
analyses were not
reported.
Test was designed
to establish
dose/response
curves on 03-
sensitive rubber
for use as an
analytical method.
Cracking occurred
over a broad
range of values
and was related
to stress.
Demonstrated
dose/response
linear relation-
ship for ozone
on unprotected
rubber.
Reference
Hoffman
and Miller,
1969
Bradley
and Haagen-
Smit,
1951
Meyer and
Sommer ,
1957
Edwards
and
Storey,
1959
-------
TABLE 9-7 (cont'd). DOSE-RESPONSE STUDIES ON EFFECTS OF OZONE ON ELASTOMERS
Conditions
Laboratory
Laboratory
Laboratory
Laboratory
Material/Product
White
sidewal 1
tire
specimens
Ten different
NR, SBR, CR
formulations
with and without
protection
Several NR/SBR
blends with and
without pro-
tection
Tire cords
(66 nylon; Oacron
polyester; Kevlar
aramid)
Measure- Environ-
Concentration, ment mental
Pollutant ppm method exposure
Ozone 0.08 to NA 250 to
0.5 1000
hrs
Ozone 0.5 NA Up to
300 hr
Ozone 0.05 to NA ^3 to
0.15 16 hr
Ozone 0 to 1 5 NA 0 to
48 hr
Dose ,
Variables ppm-hr
10 and 20 to
20% 500
strain
30°C Up to
50
Sunlight, -^0.15-
humidity 2.4
UV light; up to
heat 72
(100°C);
RH (20-
90%); N02
Effects
Mean cracking
rates were
determined
for different
stress and
ozone levels.
Time to 10 to
20% relaxation
Interply adhe-
sion affected
at 0. 05 ppm and
above
RFL adhesion
loss occurred
primarily dur-
ing 6-hr expo-
sure to high
RH and 0.2 ppm
o,.
Comment
Detailed data
not available
to verify
author's state-
ment that 2-1/2
years of ambient
conditions were
required for ozone
cracks to penetrate
cord depth.
Both formula-
tion and pro-
tection
affected
relaxation.
Both waxes and
antiozonants
needed for pro-
tection against
sunlight plus
ozone.
Synergism between
03 and RH; RFL
deterioration
occurred at
surface.
Reference
Haynie
et al. ,
1976
Glandslandt
and
Svensson,
1980
Davies, 1979
Wenghoefer,
1974
Nitrogen
dioxide
0 to 20
NA
-------
important to color fading, the effects of ()„ were noted by Salvin and Walker
(1955) nearly three decades ago. The phenomenon was termed 0-fading. The pri-
mary products affected were permanent press garments (polyester and cotton) and
nylon carpeting. In permanent press garments, dye fading occurs primarily at
the creases and folds. The fading of nylon carpeting occurs in the presence of
high RH and depends on the dyes used. Ozone fading most affected the blue and
red disperse dyes of the anthraquinone series but not the azo series of dyes.
Salvin and Walker (1955) tested disperse dyes that were resistant to the
effects of nitrogen oxides. They exposed a series of drapery products to
confirm their resistance to the dye fading that was thought to be attributable
to N0?. Different types of dyes ranging in vulnerability to nitrogen oxides
were exposed in Pittsburgh, Pennsylvania (an urban region of high NCL concen-
trations), and Ames, Iowa (a suburban area with low N0? concentrations).
After 6 months of exposure, the investigators found that NCL-resistant dyes
had performed well in Pittsburgh but poorly in Ames, indicating the influence
of another fading agent. By using a combination of laboratory chamber studies
and outdoor exposure, Salvin and Walker (1955) demonstrated that 0- was the
pollutant responsible for the change. Blue anthraquinone dyes and certain red
anthraquinone dyes were markedly bleached after exposure to just 0.1 ppm
3
(196 ug/m ) of 0~. Azo red and yellow dyestuffs and diphenylamine yellow dyes
were shown to be resistant to fading at these concentrations, also confirming
the results of the field study. The use of known antiozonants, such as diphenyl-
ethylenediamine and diallyl phthalate, in combination with disperse blue dyes
was effective against 03 fading, thus providing additional evidence of the
effects of 0, on dyed fabrics.
To explain much of the fading of certain dyed fabrics during lightfast-
ness testing and service exposure trials, Schmitt (1960, 1962) also invoked
the concept of 03 fading. In studies to demonstrate colorfastness of certain
dyes when exposed to sunlight, Schmitt exposed 38 color specimens for 12 months
at Phoenix, Arizona, and Sarasota, Florida, and for 7 months in Chicago,
Illinois. Specimens exposed included direct dyes on cotton, acid dyes on
nylon, acid dyes on wool, disperse dyes on acetate, disperse dyes on acrilan,
disperse dyes on dyne!, acid dyes on dyne!, cationic dyes on orlon, and disperse
dyes on dacron.
0190GI/B 9-23 May 1984
-------
Each specimen was exposed to a predetermined amount of direct sunlight,
measured by a pyroheliometer, and then examined in the laboratory to measure
the amount of fading. Schmitt found that samples given equal amounts of sun
exposure tended to fade more in Florida than in Arizona. He concluded that
the higher RH was a contributory factor and that atmospheric contaminants were
the principal factor in accelerated fading. Schmitt also exposed certain dyed
fabrics in covered test frames where the effect of sunlight would be eliminated.
After 24 days of exposure in Florida, Schmitt found that even in covered
frames, fading was of the same magnitude as noted with samples exposed to
sunlight. His work also demonstrated the importance of RH in the dye-fading
mechanism by suggesting that the increased moisture content of the fibers pro-
moted and accelerated the absorption and reaction of pollutants with vulnerable
dyes.
Ajax et al. (1967) summarized the results of a study of 69 dye-fabric
combinations that were exposed outdoors in light-free cabinets at 11 sites.
These sites were Sarasota, Florida; Phoenix, Arizona; Cincinnati, Ohio; and
four urban-rural combinations: Chicago and Argonne, Illinois; Washington,
D.C. and Poolesville, Maryland; Los Angeles and Santa Paula, California; and
Tacoma and Purdy, Washington. Among those fabrics exhibiting a high degree of
fading at both urban and rural sites in the first 6 months, fading was much
greater at the urban sites than the rural sites. The samples exposed in
Phoenix, Sarasota, and Purdy showed the lowest amount of fading, which indicated
that humidity and temperature are not, by themselves, the primary factors in
fading. The highest fading rate occurred in samples exposed in Los Angeles,
Chicago, and Washington, D.C. In addition, there was a marked seasonal varia-
tion in the test results, with greater fading during the spring and summer
seasons. Generally, the results correspond with seasonal peaks in 0^ concentra-
tions. However, editorial problems between the text and tabular material tend
to confuse the authors' discussion.
Ajax and co-workers also exposed the fabrics to irradiated and nonirradi-
ated auto exhaust with and without sulfur dioxide (SCO for 9 hr/day for six
consecutive days. From the results of this chamber study, they noted that
"photochemically produced by-products of automobile exhaust are a prime cause
of fading compared to fading caused by nonirradiated auto exhaust or by clean
air with sulfur dioxide added." Although their conclusions are easily substan-
tiated in the research literature, the 0~ levels measured in their chamber are
0190GI/B 9-24 May 1984
-------
questionable. The daily 9-hr average CL concentrations (measured by neutral KI,
Mast instrument) were identical for irradiated (UV) and nonirradiated exhaust
(0.02 ppm); irradiated exhaust plus 50^ produced 0.55 ppm of (L.
Beloin (1972, 1973) investigated the effects of air pollution on various
dyed textiles by conducting field and control!ed-environment laboratory studies.
For the field study, a wide range of dyed fabric was exposed in light-tight
cabinets at the same four urban and four rural sites used in the Ajax studies.
The study was carried out over a 2-year period, in eight consecutive 3-month
seasonal exposure periods. Color change data and air pollution and weather
measurements were analyzed to identify the factors that caused fading. About
two-thirds of the fabrics studied showed appreciable fading. Most of these
fabrics faded significantly more at urban sites than at rural sites, and the
amount of fading varied among metropolitan areas and seasons. Samples exposed
in Chicago and Los Angeles demonstrated the greatest degree of fading, and those
exposed in Purdy, Washington, and Phoenix showed the least amount. The small
amount of fading evidenced by the samples exposed at extreme temperature and/or
humidity indicated that these factors by themselves have no effect on fading.
The sample also showed some seasonal variations in fading. In areas of high
oxidant concentration, maximum fading occurred primarily in summer and fall.
Fabrics exposed in Chicago, where S0? concentrations are higher in the winter,
showed greater fading during this season.
The results of the outdoor fading study were used in a multiple regression
analysis, which examined fading as a function of six independent variables (N09,
SO^, Op nitrogen oxide, temperature, and humidity). After eliminating those
fabrics that developed only trace fading and those for which the regression
was not significant, the analysis focused on 25 fabric dye samples, 23 of
which showed SOp to be a significant variable. Ozone was also a significant
contributor to fading of eight dyed fabrics and N0? to fading of seven dyed
fabrics. The dominance of SO- as a factor in fading may have been complicated
by soiling.
The laboratory study was designed to assess the effects of air pollutants,
temperature, and RH on the colorfastness of 30 samples selected from those
exposed during the field study. Fabric samples were exposed to two concentra-
3 3
tions of 03: 0.05 ppm (98 ug/m ) and 0.50 ppm (980 ug/m ). The laboratory
studies demonstrated that high 03 levels produced more significant fading in
more fabric samples than did low levels. Visible fading did occur in about
0190GI/B 9-25 May 1984
-------
one-third of the sensitive fabrics exposed to 0~ concentrations of 0.05 ppm
3
(98 |jg/m ). These levels are similar to those frequently found in metropolitan
areas. The laboratory study also demonstrated that high RH (90 percent) is a
significant factor in promoting and accelerating 0,,-induced fading.
Haynie et al. (1976) and Upham et al. (1976) reported on the degree of
fading of three different drapery fabrics exposed in a laboratory chamber to
3
combinations of high and low 0, concentration (980 and 196 |jg/m ; 0.5 and
0.1 ppm, respectively), high and low RH (90 percent and 50 percent), and high
and low concentrations of N0? and S0?. The three fabrics selected for this
study were a royal blue rayon-acetate, a red rayon-acetate, and a plum cotton
duck. The samples were exposed in the chamber for periods of 250, 500, and
1000 hr; the degree of fading was measured with a color difference meter. The
fading of the plum-colored material was statistically related to the RH and
N0~ concentration. For the red and blue fabrics, only RH appeared to be a
significant factor. The effects of concentrations of ozone on the amount of
fading of these dyes were not statistically significant, even after exposure
3
for 1000 hr to 980 ug/m (0.5 ppm), levels much higher than typical ambient
exposures.
Haylock and Rush (1976, 1978) studied the fading of anthraquinone dyes on
nylon fibers. In the first test, nylon carpet yarn dyed with Olive I and
Olive II was exposed to varying levels of temperature, RH, and O^. Material
dyed with Olive I and exposed at 70 percent RH, 40°C (104°F), and 0.2 ppm
(392 ng/m ) of 0., showed visible fading after 16 hr of exposure. At 90 percent
O
RH, similar fading occurred in less than 4 hr. Under the same RH and tempera-
ture conditions, increasing the 0, concentration from 0.2 ppm to 0.9 ppm (392
o 3
to 1760 |jg/m ) resulted in a parallel increase in fading. Samples in knitted
sleeve form demonstrated much greater susceptibility to 0., attack than samples
exposed in skein form.
Using Disperse Blue 3 and Disperse Blue 7 dyes exposed to constant condi-
tions of 40°C (104°F), 90 percent RH, and 0.2 ppm (392 ug/m3) of 03, Haylock
and Rush (1976) investigated the effect on fading of changing the fiber cross
section, the fiber draw ratio, and the method of setting the nylon fibers with
steam heat. They found that increasing the surface area of the fibers resulted
in an increased fading rate. Increasing the fiber draw ratio reduced dye
fading, and increasing the heat-setting temperature decreased resistance to
fading in disperse dyes.
0190GI/B 9-26 May 1984
-------
The necessity of high temperature and high humidity for 0,, fading to
occur in nylon was further confirmed by the additional work of Haylock and
Rush (1978). Their studies showed a good correlation between accelerated 03
fading in the laboratory and in outdoor, in-service exposure, during which
temperature and humidity extremes were common. However, control samples
exposed indoors, where temperatures and humidities were lower, did not exhibit
nearly the same magnitude of fading as the laboratory samples.
Heuvel et al. (1978) investigated the importance of the physical nature
of Nylon 6 yarns on the 0- fading behavior of a disperse blue dye. Samples of
Nylon 6 yarns dyed avocado green with a dye mixture including Disperse Blue 3
2
were exposed in a laboratory cabinet to 0.5 ppm (980 (jg/m ) of 03 at 40°C and
an RH of 85 percent. Heuvel et al. found that the microfibril diameter and
specific surface area of the fiber were the fiber characteristics most closely
related with 0^ fading, thus confirming suspicions expressed earlier by Salvin
(1969).
Nipe (1981) summarized the results of a 3-year study to establish the
relationship between in-service atmospheric contaminant fading by CL of carpets
in a home versus the American Association of Textile Chemists and Colorists
(AATCC) Standard Test Method 129, Colorfastness to Ozone in the Atmosphere
Under High Humidities. (Measurements were also taken to compare the fading
due to oxides of nitrogen.) The test carpets were made of Nylon 6 and 66 dyed
with two disperse and two acid dye formulas. Test samples from the homes of
28 participants were returned every 3 months for the 3-year period. The
exposure sites selected for this long-term study represented variations in
home heating and cooling, utilities, climate, and geographical locations. The
carpet samples were placed in areas as close as possible to the kitchen but
away from exposure to sunlight or any traffic.
Attempts were made to relate the color change for each exposure period to
outside temperature and RH, but the statistical analyses of the data showed no
correlation between outside weather conditions and in-home fading by either
contaminant. Geographical location appeared to have a significant effect on
fading. Test samples from sites in the southeast and northeast showed far
more 0~ fading than those in the west and far west. Test samples in homes
with air conditioning exhibited less fading during the summer than those
without air conditioning. In all samples, much greater fading was caused by
0., during July, August, and September than in January, February, and March.
0190GI/B 9-27 May 1984
-------
Typically, 03 levels indoors are higher during the summer, when doors and win-
dows tend to be open, thus allowing a greater exchange between inside and
outside air. The results of the study of in-service interior carpet exposures
were compared with the results of AATCC Test 129, as shown in Table 9-8. In a
sample that performs satisfactorily through 1.08 cycles of exposure in AATCC
Test 129, there is a 98-percent probability against in-service fading over a
1-year period. A sample that performs satisfactorily through only 0.6 test
cycles of fade has only a 90-percent probability of satisfactory performance
after 1 year of in-service exposure.
Kamath et al. (1982) studied the effect of atmospheric 0- dye fading on
nylon fibers. Prior studies had postulated that 0~ does not penetrate into
the fiber to destroy the dye, but instead attacks the dye at the surface of
the fiber. Dye then diffuses outward from the fiber interior because of the
concentration gradient set up as the surface dye is destroyed. Using micro-
spectrophotometry to test this postulated mechanism, Kamath et al. studied the
diffusion and destruction of C.I. Disperse Blue Dye 3 on Nylon 6 continuous
filament yarn measuring about 45 pm in diameter. With this method, they were
able to generate a dye distribution profile across the cross section of the
fiber and to determine the diffusion coefficient of a dye in the fiber. The
fibers were exposed in a controlled environment to 0- concentrations of 0.2 ppm
3
(392 pg/m ) for 2 to 120 hr at a temperature of 40°C and RH levels of 90 percent,
85 percent, and 65 percent. The results of these laboratory studies indicated
that RH has a significant positive effect on fading, that destruction of the
dye begins near the surface of the fiber in the early stages of exposure, and
that 0., penetration into the fiber may be an important mechanism in 0., fading.
As shown in Figure 9-6, the dependence of fading rates on humidity was substan-
tial. Even slight rises in humidity from 85 percent to 90 percent caused a
significant increase in the extent of fading. At 65 percent RH, the fading
rate drops dramatically. This effect was attributed to the breakage of hydro-
gen bonds in the presence of water, which leads to a more open structure with
high segmented mobility; this condition is more favorable to diffusion of 0.,
and disperse dyes.
Kamath et al. (1982) used a surface reaction model to attempt to explain
the amount of fading (dye loss) due to 0~ exposure. However, they found that
this approach could explain only a very small portion of the loss. They
concluded that the dye distribution profile across the fiber resulted from
0190GI/B 9-28 May 1984
-------
TABLE 9-8. COLORFASTNESS OF TEST SAMPLES COMPARED WITH COLORFASTNESS OF
IN-USE CARPETING
Probability of acceptable Number of test cycles Number of test cycles
colorfastness of in-use equivalent to 1 year equivalent to 5 years
carpeting of in-use service of in-use service
99
98
95
90
80
75
70
60
50
1.36
1.08
0.80
0.60
0.42
0.37
0.33
0.27
0.22
6.80
5.40
4.00
3.00
2.10
1.85
1.65
1.35
1.10
Source: Adapted from Nipe, 1981.
penetration of 03 into the fiber itself. Subsequent reaction of this 03 with
dye diffusing toward the surface of the fiber was therefore considered to be
an important mechanism in Q3 fading of anthraquinone dyes in nylon.
Salvin (1969) reported that 03 and (to a lesser extent) N02 caused dye
fading of cotton/permanent press fabrics. As summarized by Dorset (1975), 03
was found to be the major fading agent, with nitrogen oxides also capable of
causing fading, though to a lesser extent. The fading mechanism occurs as a
result of the curing operation and involves the disperse dyes on the polyester
fibers rather than the vat dyes on cotton. During curing, some disperse dyes
partially migrate to the permanent press finish, which is a combination of
reactant resin, catalysts, softeners, and nonionic wetting agents. This
migration occurs preferentially along the folds and creases, causing fading to
predominate in these areas. The disperse dyes migrate to the solubilizing
agents in the finish, a medium in which fading by air contaminants can easily
occur. Remedial measures to avoid this problem include selecting dyes more
resistant to reaction with 03 and NO,,, avoiding the use of magnesium chloride
catalyst in the permanent press process, and using different surfactants and
softeners. The use of magnesium chloride as a catalyst makes 03~sensitive
dyes more sensitive to 0^ and less fast to washing (Dorset, 1975). When the
catalyst is zinc nitrate, dyes are more washfast and resistant to 03 fading.
Thus, the amount of dye fading might not be a function only of 03 concentra-
tion but also of the number of times the garment is washed. The present use
0190G1/B ' 9-29 May 1984
-------
100
20
40 60 80
FADING TIME, hours
120
Figure 9-6. Effects of relative humidity (RH) on fading of C.I. Disperse
Blue 3 (CIDB-3) in Nylon 6 after exposure to 0.2 ppm ozone.
Source: Adapted from Kamath et al., (1982).
"V *"* O
3-oG
-------
of a zinc nitrate catalyst appears to have generally eliminated the problem of
the prefading of dyes in permanent press fabrics due to the effects of 0~. A
summary of the dye fading studies is presented in Table 9-9.
9.3.3 Fiber Damage
Sunlight, heat, alternate wetting and drying, and microorganisms are
causative factors in the weathering and deterioration of fabrics exposed
outdoors. The influence of CL at normal ambient levels is generally small by
comparison.
In a review of the effects of weather and atmospheric pollutants on
textiles, Warty (1977) outlined a number of damage mechanisms, the complexity
of the mechanisms, and their effects on manmade and natural fibers. The
damage mechanisms reviewed included those involving soiling, 0.,, sunlight,
microbial attack, humidity, and SO^- Natural fibers such as jute, flax, hemp,
sisal, and coconut, which have a multicellular structure and contain lignin,
are much more resistant to the effects of weathering than is cotton, a natural
fiber with no lignin. However, even in amounts as small as 0.2 percent,
lignin will cause yellowing or browning of the material when exposed to light.
Compounds added to increase resistance to one weathering agent may actually
accelerate the damage caused by others. For example, phenolic compounds used
as antimicrobial agents accelerate fabric degradation due to the effects of
light.
Cellulose fibers, whether natural or manmade, are very sensitive to sun-
light in the UV portion of the spectrum. Ultraviolet light causes disruption
of the chemical bonds within the fiber itself. Even in protected fabrics, a
secondary photochemical reaction can occur with certain dyes and pigments.
Bleached fabrics, which are much more resistant to microbial attack, tend to
be much more sensitive to the action of sunlight. The bleaching weakens mole-
cular linkages, making the carbon-carbon and carbon-oxygen bonds much easier
to break when exposed to sunlight.
Synthetic fibers, though highly resistant to microbial attack, are still
adversely affected by UV light. Degradation can be minimized or avoided by
use of UV-absorbing additives applied as coatings or in the manufacturing
process. Warty (1977) concluded that, because the weathering process is a
very complex interaction of several variables, it is difficult to rely on a
single test method to define performance.
0190GI/B 9-31 May 1984
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TABLE 9-9. SUMMARY OF DYE FADING STUDIES
Dye and fabric
Dose and test conditions
Effects
Reference
Disperse dyes on drapery
material
Anthraquinone dyes
Sixty-nine dye/fabric
combinations
Various dyed fabrics
CO
ro
Thirty dyed fabric samples
Drapery fabrics: royal
blue rayon-acetate, red
rayon-acetate, and plum
cotton duck
Anthraquinone dyes on
nylon fibers
Six-month field study in suburban
area
Ozone concentration of 0.1 ppm
(196 ug/m3) in the laboratory
Outdoor exposure in light-free
cabinets at 11 sites
Eight 3-month exposure periods
in the field in urban and rural
sites
Ozone levels of 0.05 ppm
(98 ug/m3) and 0.50 ppm
(980 ug/m3) in the laboratory
Ozone levels of 0.1 ppm
(196 ug/m3) and 0.5 ppm
(980 ug/m3) and RH of 50
and 90 percent for 250,
500, and 1000 hr in the
laboratory
Various levels of RH and ozone
(0.2-0.9 ppm, 392-1760 ug/m3)
in the laboratory
Fading related to ozone con-
centrations
Marked bleaching
Fading generally corres-
ponding to seasonal vari-
ations in ozone levels
Ozone a contributor to
fading of 8 of 25 samples
More fading at higher ozone
level. Fading in about one-
third of sensitive fabrics at
lower level. High RH a sig-
nificant factor
No fading at any dose
Fading varying markedly with
RH and ozone concentration
at 40°C. Surface area of
fibers also important. Find-
ings correlated with field
study results
Salvin and Walker
(1955)
Salvin and Walker
(1955)
Ajax et al. (1967)
Beloin (1972, 1973)
Beloin (1972, 1973)
Haynie et al. (1976),
Upham et al. (1976)
Haylock and Rush
(1976, 1978)
-------
TABLE 9-9. SUMMARY OF DYE FADING STUDIES (continued)
Dye and fabric
Dose and test conditions
Effects
Reference
Disperse blue dyes on
Nylon 6 yarns
Disperse and acid dye
formulas on Nylon 6 and
66 carpet samples
C.I. Disperse Blue Dye
3 on Nylon 6 yarn
Ozone level of 0.5 ppm (980 ug/
m3) at 40°C and RH of 85 per-
cent in the laboratory
Samples exposed in homes in vari-
ous locations tested every
3 months for 3 years.
Ozone concentration of 0.2 ppm
(392 pg/m3) for 2-120 hr at
40°C and RH levels of 65, 85,
and 90 percent in the labora-
tory
Microfibril diameter and spe-
cific surface area of fibers
related to ozone fading
More ozone fading of samples
in southeast and northeast
than in west and far west.
More ozone fading in summer
than in winter
Initial fading occurred near
surface of fiber. Ozone
penetration an important
mechanism in fading. Rate of
fading greatly affected by RH
Hueval et al. (1978)
Nipe (1981)
Kamath et al. (1982)
-------
Bogaty et al. (1952), as part of a program aimed at segregating some of
the elements that cause weathering, carried out experiments to study the
possible role of 0^ in the deterioration of cotton textiles. These investiga-
tors exposed samples of duck and print cloth to air containing 0.02 and 0.06 ppm
3
(39 and 118 ug/m ) of CL. Samples were exposed both dry and wet and tested
for 50 days. The wet samples were water-saturated once per week, and moisture
was added regularly so that the moisture content of the cloth was never less
than 50 percent. Similar fabric samples were exposed to similar 03 concentra-
tions with no moisture added, and another control group was similarly wetted
but exposed to clean (0~-free) air. After exposure to 03, the wetted samples
showed a loss in breaking strength of approximately 20 percent. The wet print
control cloth showed a loss in breaking strength of only half this amount.
The study showed that low levels of 0-, degrade cotton fabrics if they are
sufficiently moist. Bogaty et al. surmised that an estimated 500 to 600 days
of natural exposure might be required to reach a similar stage of degradation
due to a 50-day exposure to 0., alone. Because unprotected fabrics typically
reach a much more advanced state of decay after such long exposures to weather-
ing, Bogaty et al. concluded that the effect of 0.-, is slighter than that of
other agents. Although not noted by Bogaty et al., the 03 and increased
moisture may have caused the formation of hydrogen peroxide (hLO-), which
could account for the loss in breaking strength.
Morris (1966) also studied the effects of 0., on cotton. Samples were
3
exposed in the absence of light to 0.5 ppm (980 ug/m ) of 03 [compared to a
National Ambient Air Quality Stadard (NAAQS) of 235 ug/m3 or 0.12 ppm] for 50
days in a chamber maintained at 70°F (21°C) and 72 percent RH. No appreciable
effect on breaking strength was found. Apparently, the moisture content of
the cotton was not high enough to produce the degradation that Bogaty et al.
(1952) measured in wet cotton samples, even though the concentration of 0^ was
considerably higher.
The laboratory study of Kerr et al. (1969) examined the effects of
the periodic washing of dyed cotton fabrics exposed to 0, and the amount of
fading and degradation of moist, dyed fabrics exposed to 0^. They exposed
samples of print cloth, dyed with CI Vat Blue 29, in a chamber to a continuous
supply of purified air containing 0, concentration levels of 1 ± 0.1 ppm
o J
(1960 ± 196 ug/m ). The samples were exposed at room temperature (25°C) in
the absence of light, and a shallow container of water was kept on the chamber
0190GI/B 9-34 May 1984
-------
floor to increase the humidity. Samples were withdrawn from the chamber after
12,, 24, 36, 48, and 60 days. After an exposure period of 60 days, which
included either 20 washing or 20 soaking treatments, the change in strength of
control fabrics was not significant. By comparison, the fabrics exposed to 0.,
changed significantly; the loss in strength of the washed fabrics was 18 percent,
and that of the soaked fabrics, 9 percent. Fading was also evident in the
fabrics exposed to 0.,, but not in the control samples. Differences in the
amount of fading between the washed and soaked samples were evident, but the
reason for the differences was not. Kerr et al. concluded that washing in
hot, soapy water may have affected the properties of the dye.
In laboratory studies, Zeronian et al. (1971) simultaneously exposed
modacrylic (dynel), acrylic (orlon), Nylon 66, and polyester (dacron) fabrics
to artificial sunlight (xenon arc) and charcoal-filtered air contaminated with
0.2 ppm (392 pg/m3) of 03 at 48°C (118°F) and 39 percent RH. During exposure,
the fabric samples were sprayed with water for 18 min every 2 hr. Ozone damage
was measured by comparing these samples with fabrics exposed to the same environ-
mental conditions without 0.,. After exposure for 7 days, Zeronian et al.
found that 0~ did not affect the modacrylic and polyester fibers. The exposure
did seem to affect the acrylic and nylon fibers slightly by reducing breaking
strength. But the degree of difference in the change of fabric properties
between those exposed to light and air and those exposed to light and air con-
3
taining 0.2 ppm (392 ug/m ) of 0- was not significant.
In general, the contribution of 0, to degradation of fabrics has not been
quantified well. Bogaty et al. (1952) concluded that the effects of other fac-
tors (sunlight, heat, wetting and drying, and microorganisms) far outweighed The
effects of 03 on cotton duck and print cloth. The work by Morris (1966) and
Kerr et al. (1969) does point to the synergistic effect of moisture and 0,, as
an important ingredient in material degradation, possibly caused by the forma-
tion of a more potent oxidizing agent like H^O,,. Finally, the work of Zeronian
et al. (1971) also indicates little if any effect of 0, on synthetic fibers.
Thus, it appears that 0^ has little if any effect on textiles, fibers, and
synthetic cloth exposed outdoors. A similar view was proposed by the National
Academy of Sciences (National Research Council, 1977) in a review of the
effects of 0 and other photochemical oxidants on nonbiological materials.
0190GI/B 9-35 May 1984
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9.3.4 Paint Damage
A paint surface may suffer several types of damage that affect its useful-
ness, including cracking, peeling, erosion, and discoloration. Of these,
erosion (i.e., wearing away of the paint surface) is the type of damage most
often studied with respect to the impact of gaseous pollutants. Studies of
paint cracking and peeling have focused on the effects of moisture and have
not dealt with the possible influence of ambient pollutants.
Several damage functions for 0, -induced erosion of paint have been reported
in the literature. Such reports are based on either accelerated chamber
studies or long-term outdoor exposure studies. Unfortunately, all studies to
date have significant flaws that render their results highly questionable.
Damage to a paint surface is the cumulative effect of the conditions to which
the surface is exposed, including various combinations of temperature, moisture,
sunlight, and pollution level. No outdoor exposure study to date has been
able to match all factors exactly to separate the impact of 0_ from the other
O
factors.
In a laboratory chamber exposure study, Haynie et al. (1976) exposed
oil -based house paint, latex house paint, vinyl coil coating, and acrylic coil
coating to 0.5 and 0.05 ppm concentrations of S0?, N02, and 0~ in various
combinations. Statistically significant effects of O^-caused damage were
observed on the vinyl coil coating and the acrylic coil coating. There was a
positive interaction between 0., and RH on the vinyl coil coating and a positive
direct 0^ effect on the erosion rate of the acrylic coil coating. However,
the rate of erosion was low, and both vinyl and acrylic coil coatings were
shown to be very durable. Coatings as thin as 20 urn should last more than
20 years before requiring replacement because of the effects of 0.,. A linear
regression for the acrylic coil coating data gives:
Erosion rate = 0.159 + 0.000714 0^ (9-1)
3
m
where erosion rate is in um/yr and 03 is ug/
Although the 0^ effect on this coating was found to be statistically
significant, it has no practical significance because the erosion rate is so
3
slow; at 0.12 ppm (235 pg/m ) of 0-, the erosion rate is 0.33 um/yr. At an
3
average annual 0- level of 100 ug/m , this regression predicts that a 20-um-
thick coating would last over 80 years.
0190GI/B 9-36 May 1984
-------
In a comprehensive study by Campbell et al. (1974), panels painted with
different exterior paints (automotive refinish, latex coating, coil coating,
industrial maintenance coating, and oil-based house paint) were exposed to air
pollutants in an environmental chamber under accelerated weathering conditions.
The panels were exposed to low (0.1 ppm) and high (1.0 ppm) concentrations of
OT and S0?. After exposure, the panels were examined by measuring erosion,
gloss, surface roughness, tensile strength, attenuated total reflectance
(ATR), and the surface effects revealed by scanning electron microscopy and
infrared examination. The panels were examined after 0, 400, 700, and 1000 hr
of chamber exposure (considered as equivalent to 0, 200, 350, and 500 days,
respectively, of exposure).
The relative sensitivity of a coating to pollutant damage depended on the
particular test used to define the damage. For example, when comparing oil-
based house paint with automotive paint, the former showed the greatest ATR
change but no change in gloss, but the latter exhibited little ATR change
3
and the largest change in gloss. In general, exposures to I ppm (1960 ug/m )
of OT produced greater increases in erosion rates than did clean air. However,
concentrations of this magnitude do not represent typical ambient exposure
levels of 0,.. At the more representative level of 0.1 ppm (196 pg/m ), 0^ did
not produce statistically significant increases in erosion rates.
In conjunction with the chamber studies, field measurements were made of
the erosion of paint from test panels exposed to outdoor environments consisting
of a clean, rural atmosphere (Leeds, North Dakota); a moderately polluted
atmosphere (Valparaiso, Indiana); a heavily polluted (S02) atmosphere (Chicago,
Illinois); and a high-oxidant, moderately polluted atmosphere (Los Angeles,
California). The results of this study showed that paint erosion was much
greater in the polluted areas than in relatively clean, rural areas. The
highest erosion rates were observed for the coil coating and oil-based house
paints at the Chicago and Los Angeles exposure sites. Since meteorology and
air quality were not measured at the exposure sites, correlation of film
damage with the environmental parameters was not possible. The study does
suggest that S02 exerts an adverse effect on exterior paints with calcium
carbonate as an extender pigment. The coil coating and oil house paints
were formulated with calcium carbonate. Oxidants are likely reacting with the
organic binder of the coil coating and oil house paints. However, a mechanism
for this reaction was not developed from this exposure study.
0190GI/B 9-37 May 1984
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In an outdoor exposure test of the effects of air pollutants on material,
Mansfeld (1980) exposed latex and oil-based house paints as well as galvanized
steel, weathering steel, stressed aluminum, silver, marble, and nylon at nine
test sites in St. Louis, Missouri. In conjunction with the material exposure,
measurements of meteorological parameters, 0_, oxides of nitrogen, total
hydrocarbons, total sulfur, SCL, and hydrogen sulfide were made. The investiga-
tor used a regression model to relate the corrosion rates (i.e., rate of
change of damage) to the meteorological parameters, air quality parameters,
and length of exposure. There is some uncertainty in the results of the
analysis because the independent variables show a degree of correlation with
each other. Nevertheless, the results of several of the material pollutant
relationships are worth noting. For the latex house paint, concentrations of
atmospheric 0\ were found to contribute significantly more to the accelerated
erosion of the painted surface than the length or direction (north, south) of
the sample's exposure. The length of exposure and sulfate were the most impor-
tant factors in explaining the erosion of oil-based paint. Mansfeld suggested
that these effects indicate the different responses and behaviors of the two
types of paint.
Some of the color pigments used in commercial paints and dyes are also
used in artists' paints. Shaver et al. (1983) studied the colorfastness of
several of these pigments exposed to 0.40 ppm of 0~ for 95 days under con-
trolled temperature and humidity conditions. Several of the 1,2-dihydroxy-
anthraquinone-type pigments faded considerably, but no dose-response curves
could be determined. Furthermore, the effects on pigments combined with the
various binders used in actual applications has not been investigated. Never-
theless, because works of art have an indefinite service life compared with, for
example, the short service life for textiles, further research is needed
before estimates of the type and amount of damage to paintings and prints are
possible.
The effects of CL on paint are still being studied. The preliminary
results of Mansfeld's work indicate that there may be a statistically signifi-
cant relationship between the erosion of latex paint, RH, and 0^. However,
further studies are necessary before a cause-and-effect relationship can be
conclusively established.
0190GI/B 9-38 May 1984
-------
9.4 ECONOMICS
9.4.1 Introduction
Damage to nonbiological materials from ozone is usually expressed in terms
one or both of the following two general classes of costs to producers and con-
sumers: (1) ozone accelerated replacement and repair costs, as when the service
life and/or aesthetics of a material are impaired, and (2) increased avoidance
costs, as when certain industries (e.g., tires, plastics, paints, dyes, and
fabrics) are obligated to incur expenditures for antiozonant research and deve-
lopment, substitute processes and materials, additives and formulations, product
packaging, advertising, etc., in order to offset sales losses that would other-
wise occur.
In theory, the approach selected should depend on the observed behavior
of the producers and consumers of the materials in question, and the type of
damage to which they are reacting. In practice, the existing empirical esti-
mates of ozone damage to materials are far from reliable for the following rea-
sons:
1. In some studies, coverage is limited to one or two classes of materials,
and to restricted geographical regions.
2. Other studies are entirely too aggregative, suffering deficiencies because
of (1) broad and vague notions of materials exposure and ozone concentra-
tions; (2) little or no data on the spatial and temporal distributions of
the exposed materials; (3) unverified guesses regarding the incidence and
level of cost increases and production adjustments incurred by ozone-
affected industries; and (4) inadequate attention to economic trade-offs
among different industries and different regions, and between producers
versus consumers.
3. The engineering/economic estimates are not well related to the scientific
literature in this area, and tend to be far too simplistic to meet the
concerns of the scientist.
4. Most of the cost assessments were conducted in the early 1970s. Few recent
studies exist. Moreover, these earlier studies cite extensively from each
other and there are few independent analyses that do not merely rework old
data.
5. As a consequence of the fourth item above, many of the ozone-related costs
reported in the early 1970s for research and development, product substitu-
tion, etc., are no longer appropriate. Some of these were presumably once-
only costs that are no longer charged against current production. Because
the literature is dated, there may also be some current research and
development, substitution attempts, and so on, not at all reflected in the
studies cited in this section. In sum, the cost estimates largely reflect
technologies and ozone concentrations prevailing some 10 to 20 years ago.
0190GI/B 9-39 May 1984
-------
6. Most of the so-called economic studies of ozone damage to materials have
been conducted using an engineering approach. That approach focuses on
the classification and quantification of the various kinds of costs in-
curred by the producers and users of the ozone-sensitive materials. Eco-
nomic theory would argue, however, that this is merely the first step in
the assessment process, and that supply-demand relationships are then
needed in order to proceed with the calculation of social net benefits
(i.e., changes in producer and consumer surpluses). In practice, however,
it appears that almost all of the damage assessments conducted to date
stop short of obtaining an econometric measure of economic surplus. As
such, the studies reported in this section must be interpreted accordingly.
9.4.2 Methods of Cost Classification and Estimation
Computation of accelerated replacement is probably the most widely applied
method of estimating the costs of materials damage to air pollutants. In this
approach a materials damage function is developed to show the increase in phy-
sical damage for an increase in the dose of the pollutant. Then a cost schedule
is constructed to show how maintenance or replacement schedules are influenced
by the pollutant level. Hershaft et al. (1978) note, however, that this method
usually assumes existing inventories, and does not take into account substitutions
of materials of more (or less) resistance to pollution. As a result, this method
tends to overestimate the cost of damage from pollutant increases and to under-
estimate the net savings realized from pollutant reductions.
A second approach considers avoidance costs. This refers to practices such
as adopting alternative production processes and materials. Some industries add
antiozonants to their products, or change the chemical formulation of their out-
put. All of these measures, mitigate the impact of ozone on the service life or
aesthetics of the products in question. Moreover, these measures also require
research, development, and implementation expenditures. As such, estimation of
these costs is conceptually and empirically difficult, since the opportunity to
use different materials changes in response to the level of ozone concentration.
A number of factors complicate the use of both the replacement and the
avoidance methodologies. Data on key variables are generally missing or merely
assumed. Lessening the reliability of the final cost estimates are deficiencies
in knowledge of (1) the physical damage functions; (2) the quantities and types
of materials exposed to ozone indoors, outdoors, and in respective regions of
the country; (3) the actual expenditures incurred for increased replacement,
0190GI/B 9-40 May 1984
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maintenance, and avoidance that can be directly attributed to ozone; (4) the
threshold ozone damage levels that prompt mitigating action; and (5) the range
of substitution strategies that can be used to ameliorate degradation. On this
latter point, few attempts have been made to identify current technology prac-
tices and possibilities. The variety of rubber compounds, paint mixtures, and
fabric dyes reflects the number of proprietary formulations, and each formulation
presumably has a different response to ozone exposure.
An additional complication is that repair, replacement, and substitution
are frequently dominated by factors unrelated to ozone concentrations. This
can lead to spurious correlations if studies are accepted uncritically. For
example, tire replacement may be high in a given region of the country because
of high ozone levels associated with automotive exhaust. Alternatively, it
may be high simply because the total miles of automotive use per year are
higher in that region than in the nation as a whole.
Another illustration is the substitution of dyes. New dyes that replace
ozone-sensitive dyes may also be more colorfast and able to survive more washings
than the dyes they replace. In this case, apportionment of the costs of the new
dyes between ozone resistance and the other improved characteristics embodied
in the new formulations is an extremely arbitrary and perhaps meaningless
exercise.
9.4.3 Aggregate Cost Estimates
The important caveats identified in the preceding discussion qualify the
empirical data presented in this and following sections. Table 9-10 summarizes
reports of highly aggregated estimates of oxidant damage to all materials.
Unfortunately, there are no known recognized studies that are more recent than
those reported in the table. For purposes of gross comparison only, the figures
are expressed in 1984 currency equivalents alongside 1970 currency equivalents,
the base data for the reference studies. They do not, however, represent 1984
supply-demand relationships, production technologies, or ozone concentrations.
It must be emphasized that the costs cited in 1984 currency equivalents there-
fore cannot be considered true 1984 costs.
Salmon (1970) was among the first to attempt to estimate the annual cost
of air pollution damage to materials. His computation included the dollar
value of annual materials production, a weighted average economic life of each
0190GI/B 9-41 May 1984
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TABLE 9-10. SUMMARY OF DAMAGE COSTS TO MATERIALS BY OXIDANTS
(in millions of 1970 and 1984 dollars)
Materials costs
Study
Barrett and
Waddell (1973)
Mueller and
Stickney (1970)
Salmon (1970)
Salvin (1970)
Waddell (1974)
Yocum and
Grappone (1976)
Freeman (1979)
Elastomers/plastics
NDa
500.0 ,
(1500)°
295.2
(915)
ND
NO
ND
ND
Fabric/dye
(260)
ND
358.4
(1H1)
83.5
(259)
ND
ND
ND
All
(3878)
ND
653.6
(2026)
ND
900.0
(2790)
572.0
(1773)
505.0
(1566)
ND=No data. Investigator(s) did not develop estimates in this category.
1984 dollars are listed parenthetically next to 1970 dollars.
material included in his study, a weighted average factor for the percentage
of the material exposed to air pollution, and a factor for increased labor to
treat damaged materials. Cost was defined as the value of the material mul-
tiplied by the difference between the rate of material deterioration in a
polluted urban versus an unpolluted rural environment. All data, except for
annual production levels of materials, were assumed.
If it is assumed that ozone affected all of the fibers, plastics, and rubber
in the study by Salmon, then annual damage costs attributed to ozone would have
been $2026 million (1984$). Salmon did not consider ozone-related damage to
paint, since the dominant paint-damaging mechanisms are soiling and gaseous
sulfur dioxide. His costs refer to maintenance and replacement only, and do
not allow for materials protection, substitution, etc.
In discussing other limitations of his study, Salmon cautioned that his
estimates were of potential loss, not of actual observed loss. Despite this
0190GI/B 9-42 May 1984
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and other qualifications that lessen the usefulness of the figures derived, the
Salmon study has been cited extensively and used quantitatively in a number of
the subsequent studies cited here.
For example, the materials estimate by Barrett and Waddell (1973) is based
primarily on the work of Salmon (1970). Barrett and Waddell supplemented this
by drawing on Mueller and Stickney (1970) for damage costs on elastomers, and
on Salvin (1970) for damage costs related to dye fading. Combining some of
these numbers, Barrett and Waddell stated that materials damage costs attri-
butable to oxidants alone were $3,878 million (1984$).
Freeman (1979) reviewed earlier studies that categorized the cost of damage
to materials. Using the work of Waddell (1974) and Salvin (1970), Freeman cal-
culated that the materials damage costs attributable to oxidants and oxides of
nitrogen were $2,031 million (1984$). Of this total, roughly 46 percent was
damage to textiles and dyes (from Salvin 1970), while the remaining 54 percent
was damage to elastomers (from Mueller and Stickney, 1970). Freeman then assumed
a 20 percent reduction in oxidant levels since 1970, and went on to conclude
that the monetary benefits of controlling oxidants, oxidant precursors, and
oxides of nitrogen were between $170 and $510 million (1984$). Freeman com-
puted the savings due to oxidant controls alone as $128 to $383 million (1984$).
Waddell (1974) likewise depended primarily on existing studies to calculate
the national cost of air pollution in 1970. Waddell used Salmon (1970), Salvin
(1970), Mueller and Stickney (1970), and Spence and Haynie (1972) to derive an
estimate of $6,820 million (1984$) as the total gross annual damage for materials
losses in 1970 resulting from air pollution. The component attributable to ozone
and oxidants alone was $2,790 million (1984$), within a wide range of $1,550 to
$4,030 million (1984$).
Yocom and Grappone (1976), in work for the Electric Power Research Institute,
estimated that the cost of air pollution damage to materials was about $6,820
million (1984$) in 1970. Of this total, ozone was responsible for $1,773
million (1984$), or some 26 percent of the total.
Because of the reliance of the later studies on the questionable data and
unverified assumptions contained in the earlier ones, the results compared here
are of extremely limited usefulness for cost-benefit purposes. The empirical
estimates of materials damage at the aggregate level are typified by a paucity
of original research, primary data, and fresh insights. Rather, successive
0190GI/B 9-43 May 1984
-------
layers of estimates have been generated upon essentially the same weak foun-
dations. No recent research (e.g., post-1979) is available to improve upon
this circumstance.
9.4.4 Damage to Elastomers
The damage to rubber and other elastomers by ozone can be significant in
terms of the kinds and quantities of materials that are susceptible. For
example, damage to rubber seals, hoses, belts, cables, pharmaceutical goods,
and vehicle tires has been mentioned as economically important (Mueller and
Stickney, 1970).
If damage induced by pollutants is to be considered economically important,
however, the effective useful life of the product must be significantly affec-
ted by pollutant exposure. The life of many rubber products is determined
more by the wear and tear of normal use than by pollutant damage. For example,
the rubber in surgical gloves can be shown to be sensitive to ozone exposure.
Because these gloves are used indoors, however, and because they also are
usually discarded after one use, the outdoor ozone concentration has no in-
fluence on their useful lifetime.
Vehicle tires represent the major use of rubber that is subject to signi-
ficant economic costs from the effects of ozone (McCarthy et al., 1983). The
amount of antiozonants added to a tire formulation depends on two factors:
ozone concentrations and expected tire life. Previously, tire manufacturers
varied the amount of antiozonants regionally, depending on ozone concentrations.
Now, however, most companies produce for a national market from each plant,
and consequently formulate their compounds for worst-case conditions with an
appropriate margin for safety.
The second factor that determines the amount of antiozonants in tire for-
mulations is expected tire life. Antiozonants are added in sufficient quanti-
ties to resist ozone damage for 5 or 6 years in radial tires, and 3 or 4 years
in bias-ply and bias-belted tires.
The cost of antiozonants is about $0.80 (1984$) per passenger car tire
and about $1.66 (1984$) per truck tire. Given a yearly national production of
100 million passenger tires and 50 million truck tires, the total annual cost
of antiozonants is $163 million (1984$). If ozone should be reduced, it is
uncertain to what extent tire manufacturers would find it possible and profita-
ble to reduce the level of antiozonants.
0190GI/B 9-44 May 1984
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Mueller and Stickney (1970) contend that if ozone concentrations were re-
duced, but the amount of antiozonant per tire was not reduced, more retreadable
tire casings would be available for passenger cars. (Truck tires have a com-
paratively shorter useful economic life and ozone damage is not a significant
factor in truck tire retreading). In 1980, nearly 17 million tires were
rejected for retreading because of weatherchecking, at least some of which was
attributable to ozone. Hence, a reduction in ozone levels cold conceivably
make available a greater supply of retreadable tire casings, lowering costs in
the retread industry. As qualified previously, however, this depends on the
extent to which tire manufacturers find it economical to adjust their levels
of antiozonant.
Mueller and Stickney (1970) estimated the damage costs to elastomeric
compounds caused by air pollutants, mainly ozone, totaled $1550 million (1984$).
Their estimates are presented in Table 9-11. Protection against the effects
of ozone (i.e., avoidance costs) represents the added cost of antiozonants,
antioxidants, and special rubber blends formulated for their oxidant-resistant
and ozone-resistant properties. The second cost element is early replacement
because of shortened service life, a cost borne directly by consumers. The
heading "indeterminate" refers to the costs of protective wrappings and coatings
and research to formulate resistant compounds, and "other" includes labor
costs for repair and replacement. To the contrary, the authors note that these
two columns cannot be estimated. All of the costs presented in the table
refer to the year 1969, and have uncertain reliability and relevance in the
context of 1984.
9.4.5 Damage to Fibers and Dyes
Ozone has a significant impact on certain sensitive dyes. Barrett and
Waddell (1973) reported that the national cost of dye fading caused by ozone
was $260 million (1984$) per year. Of this amount, 30 percent was dye fading
in acetate and triacetate, 50 percent was dye fading in nylon carpets, and 20
percent was dye fading of permanent press garments. Barrett and Waddell
assumed that avoidance costs included preventive measures to minimize damage,
such as use of more expensive dyes as well as additional research and testing.
Replacement costs took account of the assumed reduced life of the dyed materials.
No research has been conducted since 1973 to verify or update these esti-
mates. A problem with them is that a proportion of fading and physical wear
0190GI/B 9-45 May 1984
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TABLE 9-11. SUMMARY OF DAMAGE COSTS TO RUBBER BY OZONE
(in millions of 1920 and 1984 dollars)3
Protection
Early replacement
Indeterminate
Other
All Factors
I
-P>
CTi
Total cost
Cost
breakdown
170(527)
Special polymer 20.6 (64)
Antiozonant 34.1(106)
Wax 5.0(16)
225.7(700)
Tires 37.0(115)
Mechanical 29.7(90)
Medical 100.0(312)
Belting 22.5(70)
Hose 36.0(112)
78(242)
^25(78)
•^500(1550)
Source: Mueller and Stickney, 1970.
a!984 dollars are given parenthetically next to 1970 dollars.
Retail costs approximately three times the costs of manufacturing.
c"Ballpark estimates" by authors for costs of research and developing, wrapping, coating.
(Authors' Table 9 notes that these factors cannot be estimated).
Labor cost in connection with early replacement." Authors note that this amount again "represents
the area in which detailed estimates cannot be made."
-------
was arbitrarily assigned to ozone rather than to other factors. As noted pre-
viously, the use of magnesium chloride as a catalyst in the permanent-press
process led to dyes that were more sensitive to ozone and also less washfast.
Thus, the rate of fading is caused not only by the interaction between the dye
and ozone, but also by the frequency of washing.
Salvin (1970) conducted a study on how ozone and the oxides of nitrogen
increase the costs of fading of dyed fabrics. Costs in the work of Salvin
included those for more resistant dyes, inhibitors, research and development,
and reduced service life. Of the total cost of dye fading, that part caused
by ozone was $259 million (1984$) per year. Salvin contacted manufacturers to
obtain costs of dyes, processes, and preventive measures. The costs of reduced
service life were based, however, on estimates rather than observations.
Salvin's study does not seem to take account of the differences between indoor
and outdoor ozone concentrations and the significance of this for textile
exposure; thus, the result must be viewed cautiously for that reason.
9.4.6 Damage to Paint
Ozone levels typically occurring in the ambient air (chapter 6) have not
been shown to cause damage to paint. Campbell et al. (1974) were unable to
demonstrate a relationship between ozone and paint damage either in a care-
fully controlled chamber study or in outside exposure tests. Haynie and Upham
(1971) showed that the only statistically significant effects of ozone on
paint were damage to vinyl and acrylic coil coatings; however, the effects of
ozone were insignificant in shortening coating lifetimes. McCarthy et al.
(1981) found that the costs associated with premature replacement of acrylic
and vinyl coil coatings were minimal and could not be attributed to pollutants
alone.
Aesthetics tend to be a decisive factor in the use of acrylic and vinyl
coatings. Although the coating retains its primary function of providing a
protective surface, changes in gloss and sheen, as well as degradation of
color, can be problems. The causative agents for these aesthetic effects are
environmental factors (primarily sunlight), as well as the qualities of the
pigment, formulation and mixing, and application. No data are available to
suggest the role of ozone (possibly in conjunction with other pollutants) in
this fading. Hence, the costs of diminished aesthetics attributable to ozone
are largely undetermined.
0190GI/B 9-47 May 1984
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9.5 SUMMARY AND CONCLUSIONS
Over two decades of research show that ozone damages certain nonbiological
materials; the amount of damage to actual in-use materials, however, is poorly
characterized. Knowledge of indoor/outdoor ozone gradients, for example, has
expanded considerably in recent years, and this type of exposure information
has not been incorporated in materials damage studies. Moreover, virtually
all materials research on photochemical oxidants has focused on ozone. Theore-
tically, a number of the less abundant oxidants may equal or surpass ozone in
reactivity with certain materials, but this possibility has not been tested
empirically. In the absence of photochemical pollution, oxidative damage to
certain materials still occurs from atmospheric oxygen, but at a much reduced
rate and through different chemical mechanisms. Generally, ozone damages
elastomers by cracking along the line of physical stress, whereas oxygen
causes internal damage to the material.
The materials most studied in ozone research are elastomers and textile
fibers and dyes. Natural rubber and synthetic polymers of butadiene, isoprene,
and styrene, used in products like automobile tires and protective outdoor
electrical coverings, account for most of the elastomer production in the
United States. The action of ozone on these compounds is well known, and
dose-response relationships have been established and corroborated by several
studies. These relationships, however, must be correlated with adequate expo-
sure information based on product use. For these and other economically
important materials, protective measures have been formulated to reduce the
rate of oxidative damage. When antioxidants and other protective measures are
incorporated in elastomer production, the dose-cracking rate is reduced consid-
erably, although the extent of reduction differs widely according to the
material and the type and amount of protective measures used.
The formation of cracks and the depth of cracking in elastomers are re-
lated to ozone dose and are influenced greatly by humidity and mechanical
stress. Dose is defined as the product of concentration and time of exposure.
The importance of ozone dose was demonstrated by Bradley and Haagen-Smit
(1951), who used a specially formulated ozone-sensitive natural rubber.
Samples exposed to ozone at a concentration of 20,000 ppm cracked almost
instantaneously, and those exposed to lower concentrations took a propor-
tionately longer time to crack. At concentrations of 0.02 to 0.46 ppm, and
0190GI/B 9-48 May 1984
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under 100-percent strain, the cracking rate was directly proportional to the
time of exposure, from 3 to 65 min. Cracking occurred at a rate of 0.02
to 0.03 ppm/hr over the entire range of concentrations.
Similar findings were reported by Edwards and Storey (1959), who exposed
two SBR elastomers to ozone at a concentration of 0.25 ppm for 19 to 51 hr
under 100-percent strain. With ozone doses of 4.75 ppm-hr to 12.75 ppm-hr, a
proportional rate in cracking depth was observed, averaging 2.34 (jm/hr for
cold SBR and 4.01 (jm/hr for hot SBR. When antiozonants were added to the com-
pounds, the reduction in cracking depth rate was proportional to the amount
added. Haynie et al. (1976) exposed samples of a tire sidewall to ozone at
concentrations of 0.08 and 0.5 ppm for 250 to 1000 hr under 10 and 20 per-
cent-strain. Under 20-percent strain, the mean cracking rate for 0.08 ppm was
1.94 (jm/hr. From these and other data, .they estimated that at the ozone stan-
dard of the time (0.08 ppm, 1-hr average), and at the annual NO standard of
/\
0.05 ppm, it would take 2.5 years for a crack to penetrate cord depth.
In addition to stress, factors affecting the cracking rate include atmos-
pheric pressure, humidity, sunlight, and other atmospheric pollutants. Veith
and Evans (1980) found a 16-percent difference in cracking rates reported from
laboratories located at various geographic elevations.
Ozone has been found to affect the adhesion of plies (rubber-layered
strips) in tire manufacturing. Exposure to ozone concentrations of 0.05 to
0.15 ppm for a few hours significantly decreased adhesion in an NR/SBR blend,
causing a 30-percent decrease at the highest ozone level. This adhesion prob-
lem worsened at higher relative humidities. When fast-blooming waxes and
antiozonants or other antioxidants were added, only the combination of protec-
tive measures allowed good adhesion and afforded protection from ozone and
sunlight attack. Wenghoefer (1974) showed that ozone (up to 0.15 ppm), espe-
cially in combination with high relative humidity (up to 90 percent), caused
greater adhesion losses than did heat and N0? with or without high relative
humidity.
The effects of ozone on dyes have been known for nearly three decades.
In 1955, Salvin and Walker exposed certain red and blue anthraquinone dyes to
a 0.1 ppm concentration of ozone and noted fading, which until that time, was
thought to be caused by N02- Subsequent work by Schmitt (1960, 1962) confirmed
the fading action of ozone and the importance of relative humidity in the ab-
sorption and reaction of ozone in vulnerable dyes. The acceleration in fading
0190GI/B 9-49 May 1984
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of certain dyes by high relative humidity was noted later by Beloin (1972,
1973) at an ozone concentration of 0.05 ppm and relative humidity of 90 percent.
Kamath et al. (1982) also found that a slight rise in relative humidity (85 to
90 percent) caused a 20-percent dye loss in nylon fibers.
Both the type of dye and the material in which it is incorporated are
important factors in a fabric's resistance to ozone. Haynie et al. (1976)
and Upham et al. (1976) found no effects from ozone concentrations of 0.1 to
0.5 ppm for 250 to 1000 hr under high and low relative humidity (90 vs. 50
percent) on royal blue rayon-acetate, red rayon-acetate, or plum cotton. On
the other hand, Haylock and Rush (1976, 1978) showed that anthraquinone dyes
on nylon fibers were sensitive to fading from ozone at a concentration of 0.2 ppm
at 70 percent relative humidity and 40°C for 16 hr. Moreover, the same degree
of fading occurred in only 4 hr at 90 percent relative humidity. At higher
concentrations, there was a parallel increase in fading. Along with Huevel
et al. (1978) and Salvin (1969), Haylock and Rush (1976, 1978) noted the
importance of surface area in relation to the degree of fading. In explaining
this relationship, Kamath et al. (1982) found that ozone penetrated into the
fiber itself and caused most of the fading through subsequent diffusion to
the surface.
Field studies by Nipe (1981) and laboratory work by Kamath et al. (1982)
showed a positive association between ozone levels and dye fading of nylon
materials at an ozone concentration of 0.2 ppm and various relative humidities.
In summary, dye fading is a complex function of ozone concentration, relative
humidity, and the presence of other gaseous pollutants. At present, the
available research is insufficient to quantify the amount of damaged material
attributable to ozone alone. Anthraquinone dyes incorporated into cotton and
nylon fibers appear to be the most sensitive to ozone damage.
The degradation of fibers from exposure to ozone is poorly characterized.
In general, most synthetic fibers like modacrylic and polyester are relatively
resistant, whereas cotton, nylon, and acrylic fibers have greater but varying
sensitivities to the gas. Ozone reduces the breaking strength of these fibers,
and the degree of reduction depends on the amount of moisture present. Under
laboratory conditions, Bogaty et al. (1952) found a 20 percent loss in breaking
strength in cotton textiles under high-moisture conditions after exposure to a
0.06 ppm concentration of ozone for 50 days; they equated these conditions to a
500-to 600-day exposure under natural conditions. Kerr et al. (1969) found a net
0190GI/B 9-50 May 1984
-------
loss of 9 percent in breaking strength of moist cotton fibers exposed to ozone
at a concentration of 1.0 ppm for 60 days. The limited research in this area
indicates that ozone in ambient air may have a minimal effect on textile fibers,
but additional research is needed to verify this conclusion.
The effects of ozone on paint are small in comparison with those of other
factors. Past studies have shown that, of various paints, only vinyl and
acrylic coil coatings are affected, and that this impact has a negligible
effect on the useful life of the material coated. Preliminary results of
current studies have indicated a statistically significant effect of ozone and
relative humidity on latex house paint, but the final results of those studies
are needed before conclusions can be drawn.
For a number of important reasons, the estimates of economic damage to
materials are far from reliable. Most of the available studies are now out-
dated in terms of the ozone concentrations, technologies, and supply-demand
relationships that prevailed when the studies were conducted. Additionally,
little was (and is) known about the physical damage functions, and cost
estimates were simplified to the point of not properly recognizing many of
the scientific complexities of the impact of ozone. Assumptions about expo-
sure to ozone generally ignored the difference between outdoor and indoor
concentrations. Also, analysts have had difficulty separating ozone damage
from other factors affecting materials maintenance and replacement schedules.
For the most part, the studies of economic cost have not marshalled factual
observations on how materials manufacturers have altered their technologies,
materials, and methods in response to ozone. Rather, the analysts have mere-
ly made bold assumptions in this regard, most of which remain unverified through
the present time.
Even more seriously, the studies followed engineering approaches that do
not conform with acceptable methodologies for measuring economic welfare.
Almost without exception, the studies reported one or more types of estimated
or assumed cost increases borne by materials producers, consumers, or both.
The recognition of cost increase is only a preliminary step, however, towards
evaluating economic gains and losses. The analysis should then use these cost
data to proceed with supply and demand estimation that will show how materials
prices and production levels are shifted. Because the available studies fail
to do this, there is a serious question as to what they indeed measure.
0190GI/B 9-51 May 1984
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Increased ozone levels increase sales for some industries even as they
decrease welfare for others. For example, manufacturers of antiozonants for
automobile tires conceivably stand to increase sales as ozone increases, while
purchasers of tires stand to pay higher prices. This is only one illustration
of a fundamental analytical deficiency in the various studies of materials damage:
the absence of a framework for identifying gainers and losers, and the respec-
tive amounts they gain and lose.
Among the various materials studies, research has narrowed the type of
materials most likely to affect the economy from increased ozone exposure.
These include elastomers and textile fibers and dyes. Among these, natural
rubber used for tires is probably the most important economically for the
following reasons: (1) significant ambient air exposure and long use life; (2)
significant unit cost; and (3) large quantities and widespread distribution.
The study by McCarthy et al. (1983) calculated the cost of antiozonants
in tires for protection against ozone along with the economic loss to the
retread industry. While limitations in this study preclude the reliable
estimation of damage costs, the figures indicate the magnitude of potential
damage from exposure to ozone in ambient air.
Research has shown that certain textile fibers and dyes and house paint
are also damaged by ozone, but the absence of reliable damage functions make
accurate economic assessments impossible. Thus, while damage to these materials
is undoubtedly occurring, the actual damage costs cannot be estimated confi-
dently.
0190GI/B 9-52 May 1984
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Haynie, F. H.; Upham, J. B. (1971) Effects of atmospheric pollutants on corro-
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APPENDIX
CHEMICAL ABBREVIATIONS USED IN THE TEXT
CBS
6PPD
IPPD
77PD
DTPD
TMQ
ETMQ
ADPA
MBI
TBMP
N-Cyclohexyl-2-benzothiazole sulphenamide
N-phenyl-N'(1,3 dimethyl butyl)-p-phenylenediamine
N-Isopropyl-N'-phenyl-p-phenylenediamine
N,N'-bis(l,4-dimethylpentyl)-p-phen>lenediamine
Di-tolyl-p-phenylenediamine
l,2-Dihydro-2,2,4-trimethylquinoline, polymerized
6-Ethoxy-2,2,4-trimethylquinoline
Acetone diphenylamine condensate
2-Mercaptobenzimidazole
4,4'-Thiobis (2-tertbutyl-5-methylphenol)
COMPOUND DETAILS
NR
NR/SBR
SBR
IR
NR, 100; HAF, 65; Oil, 3; Stearic Acid, 1; Zinc Oxide, 5;
Sulphur, 2.5; CBS, 0.6
NR, 50; SBR, 50; HAF, 50; Oil, 8; Stearic Acid, 2; Zinc Oxide,
4; Sulphur, 2.5; CBS, 1
SBR, 100; HAF, 50; Oil, 8; Stearic Acid, 2; Zinc Oxide, 4;
Sulphur, 2.5; CBS, 1.2
IR, 100; HAF, 65; Oil, 3; Stearic Acid, 1; Zinc Oxide, 5; Sulphur,
2.5; CBS, 0.6
01901LG/B
9-57
May 1984
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