United States
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis OR 97330
EPA 600 3-80-014
ary 1980
Research and Development
&EPA
Effects of Sulfuric
Acid Rain on Two
Model Hardwood
Forests
-------
RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal spe-
cies, and materials. Problems are assessed for their long- and short-term influ-
ences. Investigations include formation, transport, and pathway studies to deter-
mine the fate of pollutants and their effects. This work provides the technical basis
for setting standards to minimize undesirable changes in living organisms in the
aquatic, terrestrial, and atmospheric environments.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
-------
EPA-600/3-80-014
January 1980
EFFECTS OF SULFURIC ACID RAIN ON TWO MODEL HARDWOOD FORESTS:
THROUGHFALL, LITTER LEACHATE, AND SOIL SOLUTION
by
Jeffrey J. Lee
Terrestrial Division
Con/all is Environmental Research Laboratory
Con/all is, OR 97330
and
David E. Weber
Energy Effects Division
Office of Research and Development
U.S. Environmental Protection Agency
Washington, D.C. 20460
CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
CORVALLIS, OR 97330
-------
DISCLAIMER
This report has been reviewed by the Con/all is Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved for publica-
tion. Mention of trade names or commercial products does not constitute
endorsement or recommendation for use.
-------
FOREWORD
Effective regulatory and enforcement actions by the Environmental Protec-
tion Agency would be virtually impossible without sound scientific data on
pollutants and their impact on environmental stability and human health.
Responsibility for building this data base has been assigned to EPA's Office
of Research and Development and its lb major field installations, one of which
is the Corvallis Environmental Research Laboratory.
The primary mission of the Corvallis Laboratory is research on the
effects of environmental pollutants on terrestrial, freshwater, and marine
ecosystems; the behavior, effects and control of pollutants in lakes and
streams; and the development of predictive models on the movement of pollu-
tants in the biosphere.
This report describes the effects of simulated sulfuric acid rain on
experimental model hardwood forests, and compares the results to the predic-
tions of a computer simulation model. This work was undertaken as part of a
research program at CERL to determine the effects of acid rain on forest
ecosystems.
Thomas A. Murphy, Director
Corvallis Environmental Research Laboratory
m
-------
ABSTRACT
Simulated sulfuric acid rain was applied to model forests containing
either sugar maple (Acer saccharum) or red alder (Alnus rubra). One set of
four plots (two alder and two maple) received a control rain consisting of a
stock solution equilibrated with atmospheric C02 to approximately pH 5.6. For
three sets of four plots, sufficient H2S04 was added to the stock solution to
lower the pH to 3.0, 3.5, or 4.0. Nozzles were used to apply simulated acid
rain at the rate of 2.8 mm/hr (maple) or 3.7 mm/hr (alder) for three hours per
day, three days per week, throughout the year. Water samples were collected
above and below the canopy, below the litter layer, and from 20-cm and 1-m
depths below the surface of the soil.
While throughfall chemistry was not very different from rain chemistry,
the litter leachate (the actual input to the soil) had consistently higher
concentrations of calcium and magnesium, and higher pH, than the acid rain.
For the first six months, sulfate absorption by the soil prevented any
apparent differences in sulfate, calcium, or magnesium concentrations among
plots receiving either acid or control treatments. Sulfate concentrations on
plots receiving the most acid rain (pH 3.0) then became increasingly higher
than on the other plots until, after three years, they were approximately
equal to sulfate concentrations in the rain. Soil solutions corresponding to
the pH 3.5 and pH 4.0 treatments responded similarly starting one year and two
years, respectively, after initiation of exposure to acid rain. Increased
calcium and magnesium concentrations and lowered pH in 20-cm soil solution
occurred simultaneously with increased sulfate concentrations. At a depth of
one meter, no acid rain related effects were evident even after 3.5 years
exposure to pH 3.0 sulfuric acid rain.
Comparisons of the data with the predictions of a computer simulation
model indicated that soil properties obtained under laboratory conditions can
oe used with established relationships to predict cation concentrations in
soil solutions associated with increased anion concentrations from acid rain.
However, sulfate concentrations in the 20-cm soil solution increased consider-
ably faster than predicted by using laboratdry values in a Langmuir represen-
tation of sulfate absorption.
This report covers a period from June, 1976 through August, 1979.
IV
-------
CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables vii
1. Introduction 1
2. Conclusions 3
3. Recommendations 4
4. Experimental Procedures 5
5. Results 8
6. Discussion 27
References 35
-------
FIGURES
Number
1. pH of Throughfall vs. pH of Rain 9
2. Sulfate Concentration in Throughfall vs. Sulfate Concentration in
Rain 10
3. Magnesium Concentration vs. Sulfate Concentration in Throughfall. . . 11
4. Calcium Concentration vs. Sulfate Concentration in Throughfall. ... 12
5. pH of Litter Leachate vs. pH of Rain 13
6. Sulfate Concentration of Litter Leachate vs. Sulfate Concentration
of Rain 14
7. Magnesium Concentration vs. Sulfate Concentration of Litter Leachate 15
8. Calcium Concentration vs. Sulfate Concentration of Litter Leachate. . 16
9. Sulfate Concentration of 20-cm Soil Solution vs. Time 18
10. Magnesium Concentration of 20-cm Soil Solution vs. Time 19
11. Calcium Concentration of 20-cm Soil Solution vs. Time 20
12. pH of 20-cm Soil Solution vs. Time 21
13. Magnesium Concentration vs. Sulfate Concentration of 20-cm Soil
Solution 22
14. Calcium Concentration vs. Sulfate Concentration of 20-cm Soil
Solution 23
15. pH vs. Sulfate Concentration of 20-cm Soil Solution 24
16. Calcium Concentration vs. Magnesium Concentration of 20-cm Soil
Solution 25
17. pH of 1-m Soil Solution vs. Time 26
18. Simulated Time Series of Sulfate Concentration of 20-cm Soil
Solution in Maple Plots 32
VI
-------
FIGURES (cont.)
Number Page
19. Simulated Relationship of Calcium Concentration vs. Sulfate
Concentration of 20-cm Soil Solution 33
TABLES
Number
1. Chemical Analyses of Soil Used in Lysimeter Studies 6
2. Chemical Content of Precipitation and Throughfall in a Sugar Maple
Stand 28
3. Parameters Used in LEACH Soil Solution Simulation Model 30
4. Results of LEACH Simulation 33
vn
-------
SECTION 1
INTRODUCTION
Rainfall over large portions of Europe and North America has become
increasingly acidic during the past thirty years.1-7 The increased acidity of
precipitation is primarily due to higher concentrations of sulfuric and nitric
acids derived from the air pollutants sulfur dioxide (S02) and oxides of
nitrogen (NO ). Although precipitation may be acidified by a local emission
source, transport over hundreds and even thousands of kilometers is common.
Acid precipitation thus tends to be regional and chronic.1'5'6'7 With the
increased use of fossil fuels, precipitation will probably continue to become
more acidic. Currently, all states east of the Mississippi River regularly
receive precipitation which is more acidic than the expected value of pH 5.6
for carbonic acid rain.3'5'6 In the northeastern United States, pH 4.2 is
typical of winter precipitation; for summer rains, pH 3.5 is typical.6 Acid
precipitation is not limited to the east, but also occurs in the western
(j 5 8 »9 > 10
The impact of acid precipitation on agricultural and forest ecosystems is
not understood. The potential effects of chronic, long term, exposure of
forest soils to acid precipitation have been identified as a major concern
since, compared to agricultural soils, forest soils are relatively unman-
aged.11>12'13 Increased anion loading of forest soils can^ theoretically,
cause increased concentrations of cations, both bases and H , in soil solu-
tions, and, eventually, lead to acidification of soils.7'14-17 Leaching of
bases and acidification of soils by acid rain have been observed,2'18-21 as
has increased mineral weathering.22-25 Increased soil acidity was thought to
be a possible cause of decreased forest productivity in Sweden.26'27
Before reaching the forest soil, precipitation percolates through the
forest canopy and litter layer. Throughfall from canopies of deciduous
trees2'28-38 and leachates from hardwood litter layers39 tend to have higher
pH values, higher Ca and Mg concentrations, and lower volumes than incident
acid precipitation. Any study of the effects of acid precipitation on forest
soils must consider the differences in quality and quantity between precipita-
tion and the actual input to the soil, the litter leachate. Similarly, any
study of biological processes in forest litter or soil must consider the
chemical environment as determined by the litter leachate or soil solution.
At EPA's Con/all is Environmental Research Laboratory in Oregon, we have
studied the effects of simulated sulfuric acid rain on nutrient cycling in two
types of model hardwood forest ecosystems.40 As part of this study, rainwater
has been regularly collected above and below the canopy, below the litter
layer, and at two depths in the soil during a period of more than three years.
In this paper, we report on the chemical changes in acid rain as it percolates
-------
though the ecosystem. The concentrations of divalent cations (Ca plus
Mg , equivalent basis) and S04 in the soil solution 20 cm below the surface
are compared with the predictions of a computer simulation model, LEACH.17'41
-------
SECTION 2
CONCLUSIONS
A well developed hardwood canopy and litter layer can significantly raise
the pH and increase concentrations of bases in rainwater. This will result in
a decreased tendency for acid rain to acidify forest soils.
Increased anion concentrations in soil solutions will cause increased
concentrations of cations, generally including both bases and hydrogen ions.
However, sulfuric acid rain might not cause significantly higher sulfate
concentrations in soil solutions until the ability of the soil to absorb
sulfate is exhausted. The response of soil solutions to nitric acid rain
would be more rapid.
Soil properties identified under laboratory conditions can be used with
established relationships to predict cation concentrations in soil solutions
associated with increased sulfate concentrations. However, using laboratory
values in a Langmuir representation of sulfate absorption does not accurately
simulate the time series of sulfate concentrations in these solutions.
-------
SECTION 3
RECOMMENDATIONS
The effects of acid precipitation on forest soils can only be adequately
studied in an ecosystem context. Specifically, the following must be con-
sidered:
1. Changes in rain chemistry caused by passage through canopy and
litter layer.
2. Effects of altered soil solution chemistry on uptake of chemicals by
plants.
3. Effects on other soil biological processes such as decomposition,
nitrogen fixation, nitrification, sulfur oxidation/reduction, etc.
4. Effects on weathering of minerals.
5. Role of sulfate absorption by the soil in controlling the chemistry
of the soil solution.
-------
SECTION 4
EXPERIMENTAL PROCEDURES
Each of 18 lysimeter plots consisted ofal.5mxl.5mxl.2m water-
tight enclosure constructed of fiberglass covered plywood and filled to a
depth of 1.1 m with a forest soil. The soil (Bohannon series of the fine-
loamy, mixed, mesic family of Typic Halpumbrepts) was obtained from the
Si us!aw National Forest, Oregon, and formerly had supported a red alder-
Douglas-fir community. The horizons were reconstituted with respect to
litter, topsoil, and subsoil layers. Each layer was mixed to minimize inter-
plot differences. Soil properties are summarized in Table 1.
In 1975, 36 tree seedlings were planted in each system. Sugar maple
(Acer saccharum) was planted in 9 of the plots, and red alder (Alnus rubra) in
the other 9 plots. The model ecosystems also contained herbs and ferns
brought in with the forest soil. Insects and tree frogs were observed on all
plots. Each plot initially received litter obtained from natural tree stands
of the corresponding species. Subsequently, leaf fall was collected from each
plot and placed on the soil.
Each plot received simulated acid rain at one of four acidities, and each
treatment was replicated. All plots received a stock solution approximating
npn-acidic rain containing 11 ueq/1 Ca ,12 ueq/1 NH4 , 5 ueq/1 Na _, 2 ueq/1
K , 5 ueq/1 Mg ,11 ueq/1 S04" , 12 ueq/1 N03", and 12 ueq/1 Cl . These
concentrations were based on a seven year average from Hubbard Brook, New
Hampshire,42 after elimination of estimated sulfuric and nitric acid compo-
nents. One set of four plots (two alder and two maple) served as controls,
receiving only the stock solution equilibrated with atmospheric C02 to approx-
imately pH 5.6. For three sets of four plots, sufficient H2S04 was added to
the stock solution to lower the pH to 4.0, 3.5, or 3.0. One plot on each end
of the row of plots received only deionized water, and served as a buffer
plot. Nozzles were used to apply simulated acid rain to the plots at the rate
of 2.8 mm/hr (maple) or 3.7 mm/hr (alder) for 3 hours per day 3 days per week,
throughout the year. Annual rain amounts (131 cm for maple and 173 cm for
alder) approximated those of areas in which these species usually grow.
Application of simulated acid rain began the last week of June, 1976. Rain
was interrupted from December 6, 1977 to February 16, 1978 (32 rain events)
clue to winter damage to equipment. Severe freezing temperatures prevented
nine rain applications during the winter of 1978-1979.
The plots were -located under a transparent (90% transmittance) roof open
on the ends and sides. Shade cloths were positioned over the plots during
simulated rain events. The plots were thus subjected to ambient temperature,
relative humidity, and light intensity except during simulated rain events.
The facility is located on. the Schmidt Research Farm of Oregon State Univer-
sity, near Corvallis, Oregon.
5
-------
TABLE 1. CHEMICAL ANALYSES OF SOIL USED IN LYSIMETER STUDIES
Level
1
2
3
4
5
Original
Depth
cm
0-20
20-40
40-50
50-60
60-110
Salts
mmhos
cm
0.22
0.28
0.20
0.13
0.10
Organic
Matter
%
11.1
8.1
8.1
3.9
2.0
Total -N
%
0.30
0.24
0.26
0.15
0.08
N03-N
15.4
24.1
16.9
11.1
4.1
Zn S04-S
mg/kg
0.25 7.8
0.14 7.4
0.09 12.0
0.09 20.4
P
10
7
5
4
3
K Ca
204 1.0
254 2.2
218 0.9
138 0.6
114 0.6
Mg
0.43
0.93
0.40
0.40
0.74
Na
1/100 g
0.07
0.17
0.12
0.10
0.11
Cation
Exchange
Capacity
31.5
33.0
37.7
30.7
30.6
-------
Polypropylene beakers and funnels (Nalgene) were used to sample rain and
throughfall bi-weekly for chemical analysis. Ceramic candles (Soil Moisture
Equipment Corp.) were joined to form 1.3 m tubes; seven such tubes were placed
parallel to each other 10 cm above the bottom of each plot (100 cm below the
soil surface) and connected to a five-gallon glass carboy (Kimble) above the
soil. Two 30 cm ceramic candles were placed 23 cm below the soil surface
(Level 2 in Table 1) and connected to a 500 ml polypropylene filtering flask
(Nalgene); after the soil settled, these were approximately 20 cm below the
surface. Porous ceramic disks (Coors) were cemented to polypropylene funnels
(Nalgene). These were placed so that the ceramic disks were slightly above the
soil surface in the litter layer, and the funnels were connected to 500 ml
polypropylene filtering flasks (Nalgene). In all cases, tubing and fittings
were polypropylene and stoppers were Vikem (Belart). Litter leachate and
20-cm soil solution were sampled bi-weekly for chemical analysis by applying
vacuum to the filtering flasks. To prevent soil saturation, vacuum was ap-
plied to the ceramic at 100 cm depth whenever water could be drawn from the
soil; this solution was sampled fjj>r chemical analysis every four weeks. Water
samples were analyzed for pH, Ca , Mg , S04 , and N03 .
-------
SECTION 5
RESULTS
Changes in chemical content of water after percolation through various
layers are summarized in Figures 1 through 17. Throughout this set of fig-
ures, the same set of symbols is used to indicate the four rain pH treatments.
On several figures, a diagonal line indicates points at which concentrations
at two locations within a plot (e.g. rain and throughfall) would be equal.
There are 150 to 160 points for each rain treatment on each figure, for an
approximate total of 600 points per figure. In many cases, results from the
control plots fell over an extremely narrow range. Thus, what appears as a
single plus (+) in the lower left of the figures frequently represents many
independent measurements.
THROUGHFALL
Figure 1 shows pH and Figure 2 sulfate concentration of throughfall
versus pH of rain. For both pH and sulfate, results fell close to the line of
equality for both alder (la, 2a) and maple (lb, 2b).
Figure 3 shows magnesium concentration and Figure 4 calcium concentration
versus sulfate concentration in throughfall. Little if any tendency towards
increased leaching of either cation with increased sulfate concentration is
evident for alder (3a, 4a) or maple (3b, 4b).
LITTER LEACHATE
The pH of water that had percolated through the litter is plotted against
the pH of the incident rainwater in Figure 5. For all sulfuric acid treat-
ments, the pH of the litter leachate was considerably higher than the pH of
the incident rain, indicating partial neutralization of the acid by the
litter. This effect was stronger for alder litter (5a) than for maple litter
(5b), to the point that no difference in the pH of the litter leachate was
apparent between alder plots receiving either pH 4.0 or control rain. For
plots receiving control rain, the pH of the litter leachate typically was
somewhat less than the pH of the rain for alder and somewhat higher for maple.
The concentrations of sulfate in litter leachate and in rain are compared
in Figure 6. For both alder (6a) and maple (6b) the concentration was gener-
ally greater in the litter leachate than in the corresponding acid rain. This
tendency was most pronounced for maple, especially for the pH 3.0 rain treat-
ment.
8
-------
7.0
X = 3.0
+ = 5.7
7.0
7.0 r
= 5.7
3.0
6.0
7.0
4.0 5.0
PH
RAIN
Figure 1. pH of throughfall vs. pH of rain. Symbols refer to nominal pH of
rain treatment. Diagonal line represents points at which rain and
throughfall pH values would be equal.
-------
A.
B.
X = 3.0
ALDER
= 3.5 0
+• = 5.7
Id**!
8.0 r
1.0 2.0
3.0 4.0 5.0
SUi_FATt MG/L
RAIN
6.0 7.0
10*41
8.0
1.0 2.0
6.0 7.0
8.0
Figure 2.
3.0 4.0 5.0
SULFATE MG/L
RAIN
Sulfate concentration in throughfall vs. sulfate concentration in
rain. Symbols refer to nominal pH of rain treatment. Diagonal line
represents points at which rain and throughfall sulfate
concentrations would be equal.
10
-------
A.
2.5
X = 3.0
ALDER
3.5 0 = 4.0
= 5.7
B.
2-0
THROUGH FAL
MAGNESIUM MG
!_i M
In ° ^
x
O
. + GO - x x
O x
-H- O XX
+0 - - xxx
n-f <2> ~ xx xxxxx
- -H-Q83D ~ -- xxx
d&f RS) _r_fi*Lfi*-jvQ XX X XX 3XX X X X
SSffiF) r-r^r- - XX X X XSIOBKXW jSO <38D
^SfiKcSx'XN
tpoft^» ^
1 —
•»*• xxx
XX
**• X XX
" * •" •«• X X XX
«•*»'• XX XXX X
•**•" X X XXXXXXX
*<«' • ' ' x xx xoooocxxxx x
1 1 1 | , , ,
1-Q
2.0
B.O
7.0
8.0
Figure 3.
3.0 4.0 5.0
SULFATE MG/L
THROUGH FALL
Magnesium concentration vs. sulfate concentration in throughfall
Symbols refer to nominal pH value of rain treatment.
11
-------
A.
B.
7.0
6.0
5.0
X = 3.0
ALDER
3.5 0 = 4.0
+• = 5.7
-------
A.
X = 3.0
= 3.5 0 = 4.0 + = 5.7
B.
7.0
Figure 5.
pH of litter leachate vs. pH of rain. Symbols refer to nominal pH
value of rain treatment. Diagonal line represents points at which
pH values of rain and litter leachate would be equal.
13
-------
A.
B.
ALDER
3.5 0 = 4.0
= 5.7
1.2
1.0 2.0
X = 3.0
3.0 4.0 5.0
SULFATE MG/L
RAIN
MAPLE
- = 3.5 0 =
6-0
7.0
B-0
Ul
1.0
2.0
7.0
8-0
Figure 6.
3.0 4-0 5-0
SULFATE MG/L
RAIN
Sulfate concentration of litter leachate vs. sulfate concentration
of rain. Symbols refer to nominal pH value of rain treatment.
Diagonal line represents points at which sulfate concentrations of
rain and litter leachate would be equal.
14
-------
The variation of magnesium with sulfate in litter leachate is shown in
Figure 7; Figure 8 shows this variation for calcium. Although the data points
shown in Figures 7 and 8 were scattered, there was an apparent tendency
towards increased leaching of calcium from the maple litter layer with
increased sulfate concentrations (Figure 8b).
TWENTY-CENTIMETER SOIL SOLUTION
Figures 9 through 12 show the time series of sulfate, magnesium, calcium,
and pH in solution 20 cm below the soil surface. Week one, the last week in
June, 1976, was the first week in which the plots received acid rain. During
week zero, all plots received control rain.
For the first six months, there were no apparent differences in sulfate
(9b), magnesium (lOb), or calcium (lib) concentrations in 20-cm soil solutions
from maple plots receiving acid rain or control treatments. At that time,
sulfate concentrations for plots receiving the most acid rain (pH 3.0) became
increasingly higher than for the other plots. After three years, sulfate
concentrations in the 20-cm soil solution became approximately equal to the
concentrations in the rain. Solutions corresponding to the pH 3.5 and pH 4.0
treatments responded similarly starting one year and two years, respectively,
after the initiation of simulated acid rain exposures. Magnesium (lOb) and
calcium (lib) concentrations generally followed the sulfate trend. Figures
13b and 14b show the relation between sulfate concentrations and the concen-
trations of magnesium and calcium; the curves are "eyeball fits" to the data.
Magnesium and calcium concentrations followed similar trends (16b).
Dry soil conditions prevented extraction of 20-cm soil solution samples
from the alder plots during the early part of the experiment. For the period
for which samples were taken, the patterns for alder (Figures 9a, lOa, lla,
13a, 14a, 16a) were similar to those for maple. There was, however, greater
scatter of the data points, and, especially for magnesium (lOa), an indication
of seasonal trends.
The pH of the 20-cm soil solution followed a trend towards lower values
for both alder (12a) and maple (12b) plots for all treatments. The lower pH
values were often associated with with higher sulfate concentrations (15a,
15b).
ONE-METER SOLUTION
The pH values of soil solutions at a depth of one meter did not vary
greatly during 3.5 years (Figure 17). For all plots, sulfate concentrations
were generally below the sensitivity of the analytical method (3 mg/1).
15
-------
A.
B.
1.0
.B
S-J
01
-B
1.0 r
.B
X = 3.0
ALDER
3.5 0 = 4.0
= 5.7
.2
.6 .8
MG/L
LITTER LE«=ICHATE.
1.0
X = 3.0
MAPLE
0 = 4.0 1- = 5.7
1.2
.6 .8
5ULFATE MG/U
LITTER LErtCHATE
1.0 1.2
Figure 7. Magnesium concentration vs. sulfate concentration of litter
leachate. Symbols refer to nominal pH value of rain treatment.
16
-------
A.
B.
X = 3.0
ALDER
= 3.5 0 4.0
= 5. 7
l.G
1.4
1.2
UJ
I s 1-°
LlTTtR LE.AC
CALCIUM M<
i> cn a
.1
\
O
x
'+ x
0 x x
-*
-
+ 0 ^ X xx x
-1 8 ° J** "x x XX X XX>jf* * X
P.
,
.2 .4 .6
SULPATE
LITTER LE<
MAPLE
X = 3.0 *. = 3.5
1.6 r1 **:
1.4 -
1.2 -
x
Ul XX.,
I- x
f^l.O - x >
0° + x * >
a r^
UJ s x X x>
2|^^+xX 6X
W^.
+
n 1 1 1 1
1
.8 1.0 1.2
MG/L
0 = 4.0 •<- = 5.7
x
x
^^ 5t ^ ^
<*xxxxxx xv
SXX,M X X
^x H X
* xxX
x x
'x^xXx
xXx
X
.2
.4 .G .8
SULFATE MG/L
LITTER LEACHATE
1.0
1.2
Figure 8.
Calcium concentration vs. sulfate concentration of litter leachate.
Symbols refer to nominal pH value of rain treatment.
17
-------
A.
B.
X = 3.0
ALDER
SOIL SOLN 2CCM
* = 3.5 0 = 4.0
= 5.7
B.O
7.0
6.0
| 5.0
U.O
tn 3.0
2.0
1.0
i
0
50
X = 3.0
100
UJEEK (NUMBER
MAPLE
SOIL SOLN 20CM
- = 3.5 0 = 4.0
150
= 5.7
8.0
7.0
6.0
UJ
H4.0
_
in 3.0
2.0
10**1
X
x
X
x
-------
A.
1.0
X = 3.0
<=)LDER
SOIL SOLN 20CM
^ = 3.5 0 =
= 5.7
.8 -
B.
o
2 .6
•s.
1— 1
in
z
C£> .4
Z
X XX
X X
>« x
^ x>~ x
w
•H- x<$)x x
x -ff H,
*x * o**
(Sx >^x&x
X
5C<
x« x
ac-»< x
T x x
Xx
x^ 5A
X ?S V1 V^
x< xx
x *
.2
xxV
-------
A.
X = 3.0
2.5
2.0 •
ol.5
2
ID
i—i
O
-------
A.
B.
7.0
6.0
5.0
X = 3.0
ALDER
SOIL SOLN 20CM
^ = 3.5 0 =
+ = 5.7
I
a
4.0
3.0
2.0
O
7.0
6.0
5.0
50 100 150
UJEEK (NUMBER
MAPLE
SOIL SOLN 20CM
X = 3.0 ^ = 3.5 0 = 4.0 + = 5.7
a.
4.0
3.0
2.0
50
100
WEEK NUMBER
150
200
200
Figure 12. pH of 20-cm soil solution vs. time since beginning of treatment.
Symbols refer to nominal pH value of rain treatment.
21
-------
1.0
.8
CM 2" .6
uJ
o
-------
X = 3.0
ALDER
3.5 0
= 4.0 +• = 5.7
0
2.5 r
2.0
1.5
10**1
tn 1-1
o
w
-------
A.
B.
7.0
6.0
O
° 5.0
O
01
4.0
3.0
2.0
o
7.0 r
6.0 -
5.0
f=J 4.0
3.0
2.0
X = 3.0
ALOER
= 3.5 0 = 4.0
o
= 5.7
o
0 1.0 2.0
_i 1_
3.0 4.0 5.0
5ULFATE MG/L
SOIL SOLN 20CM
X = 3.0
MAPLE
.* = 3.5 0 = 4.0 + = 5.7
xxx
x x
* x
_l U
ao**i
6.0 7.0 B-0
_i 1 1 1
1.0 2.0 3.0 4.0 5.0 6.0 7.0 B.O
SULFATE MG/L
SOIL SOLN 20CM
Figure 15. pH vs. sulfate concentration of 20-cm soil solution.
refer to nominal pH value of rain treatment.
Symbols
24
-------
X = 3.0
ALDER
= 3.5 0
= 4.0 + = 5.7
10*»1
2.0
O _i
eg ol.5
in I-H
o
i=l Cl.O
O O
en
.2
.4 .6
MAGNESIUM MG/L
SOIL SOLN 20CM
.8
1.0
X = 3.0
MAPLE
= 3.5 0 = 4.0
= 5.7
2.5
2.0
2
O _l
o ^
csio 1.5
s:
_) 2
0 Z>
tn i-.
o
_J _!
ss1-0
.5
0
x
x
X
X
X
X X
X X
X X x XX
x* x x Xx * X
x x
X
^ x x a* x^ xx x* x
* *~ * •^yfe'jt x x
v^^^t^fz XX X
*^K^ ^ _ | 10**1Q
0 .2 .4 .B .8 1.0
MAGNESIUM MG/L
SOIL SOLN 20CM
Figure 16. Calcium concentration vs. magnesium concentration of 20-cm soil
solution. Symbols refer to nominal( pH value of rain treatment.
25
-------
A.
B.
7.0
6.0
X = 3.0
5.0
Q.
4.0
3.0
2.0
ALDER
SOIL SOLN 1 M
- = 3.5 0 = 4.0
= 5.7
O
O
x± A * -t-
+ , + •*•
¥?** ±* x _
x i~ +K
O
O
7.0
6.0
50 100 150
WEEK NUMBER
MAPLE
SOIL SOLN 1 M
X = 3.0 v. A = 3.5 0 = 4.0 + = 5.7
200
5.0
a.
4.0
3.0
2.0
O
Ox
06
50
100
WEEK NUMBER
150
200
Figure 17. pH of 1-m soil solution vs. time since beginning of treatment.
Symbols refer to nominal pH value of rain treatment.
26
-------
SECTION 6
DISCUSSION
Eaton et a^.35 determined throughfall chemistry in a^sugar^maple stand
receiving ambient acid rain (pH 4.1). Their results for Ca , Mg , and S04 ,
summarized in Table 2, indicated that partial neutralization oc££irred+Hjn the
canopy, and that throughfall was considerably enriched in Ca , Mg , and
S04 , compared to incident precipitation. These effects were more pronounced
for trees with 40-65 cm dbh (diameter breast height) than for trees with 15-25
cm dbh. Our results for small maple trees (less than 5 cm dbh) exposed to
simulated sulfuric acid rain at pH 4.0 were similar to theirs; however, we did
not observed increases in sulfate concentration caused by passage of rainwater
through the canopy.
When Fairfax and Lepp39 exposed maple (Acer pseudoplatanus) leaf litter
to simulated sulfuric acid rain at pH 4.0, the resultant leachate had a pH of
5.2. Calcium concentration in this leachate was 13 times that in leachate
from litter exposed to deionized water (pH 6.8); similar results were obtained
for the other hardwood litters they tested. We also found significant neu-
tralization of sulfuric acid by litter (Figure 5), and that, for maple litter,
higher calcium concentrations (Figure 8b) were associated with the more acidic
treatments. Thus, when acid rain falls on a hardwood forest with a well
developed canopy and litter layer, the actual input to the soil will probably
be considerably less acid than the incident precipitation. Also, precipita-
tion which is more acid will cause more rapid leaching of cations into the
soil. These effects could, for at least a few years, tend to offset any
leaching of cations from the soil.
Cronan et aJL43 observed average sulfate concentrations of 8 mg/1 in soil
solutions beneath a coniferous forest in New England; they attributed 76% of
cation leaching from the soil to the presence of sulfate anion. For solutions
obtained from beneath a hardwood forest subject to acid rain, Koterba et al.44
observed an average sulfate concentrations of 5 mg/1. In both cases, the
soils had been exposed to sulfuric acid rain for approximately 30 years, and
to non-acidic sulfate rain for considerably longer. The ability of the soil
to absorb sulfate probably has been exhausted in that area. While soil solu-
tions in areas which have only recently begun to receive sulfuric acid rain
might not show an immediate response to increased sulfate loadings, the re-
sponse to nitric acid rain would be more rapid.16'17'45
The soil used in our experiment was a strong sulfate absorber.16 Figure
9b demonstrates a breakthrough phenomenon as the sulfate absorption capacity
of the soil was approached. As expected from the theoretical work of
Wiklander,14'15 Johnson and Cole,16 and Reu^s,17 increased anion concentra-
tions caused increased concentrations of Ca and Mg and lowered pH in the
27
-------
TABLE 2. CHEMICAL CONTENT OF PRECIPITATION AND THROUGHFALL IN A SUGAR MAPLE
STAND
« ++
M3-
Mg
S04
PH
Precipitation
0.16 mg/1
0.03
2.7
4.1
Small
1.13
0.37
16.4
4.6
Throughfall
Trees* Large Trees*
mg/1 1.58 mg/1
0.40
25.2
4.9
* 15-24 cm dbh.
** 40-65 cm dbh.
Adapted from Eaton et al.
35
28
-------
soil solutions (Figures 13-15). These changes were not necessarily due to
changes in the base saturation of the soil, but were probably the result of
increased ionic strength of the soil solution. The increased scatter of data
on cation concentrations for alder plots was probably due to variable N03
concentrations associated with symbiotic nitrogen fixation, a characteristic
of the genus Alnus. Although the "sulfate front" presumably has moved down-
wards into the soil, it has not reached a depth of 1 m; no effects attribut-
able to acid rain were observed in solutions extracted from this depth.
To better compare the data with theoretical predictions, the expected
response of soil solution chemistry to acid rain was simulated using the LEACH
computer model.17'41 Given the temporal pattern of chemical content and
amount of rain, this model uses established soil chemistry rejatioijijhips £o
predict the time series of soil solution concentrations of H , Ca , Al3 ,
SO , Cl , and HC03 in non-calcareous, acid soils. In this model, calcium
may be considered to be a proxy for other cations, and chloride a proxy for
other anions. The model uses the Langmuir equation for the relationship
between absorbed sulfate, S , and sulfate in solution, S ,
3. S
SMAX • S
Sa = SKLR + S '
where S is in moles/kg soil and S is in moles/1. SMAX and SKLR are con-
stants Determined from laboratory data.
While evapotranspiration effects are considered, the model does not take
into account the weathering of minerals by acids, uptake of nutrients by
plants, or microbial alteration of chemical species.
Soil parameters used for these simulations are listed in Table 3a. Soil
solution data obtained shortly after the start of the experiment were used to
estimate the initial value of the non-sulfate anion content of the soil and to
translate the lime potential (LP) vs. base saturation (BS) curve for non-
montmorillonitic soils17 to pass through the point LP = 3.15, BS = 0.10. All
other soil parameters were those obtained from results of laboratory analyses,
including those listed under "Level 2" of Table 1. Evapotranspiration rates
(Table 3b) were adjusted so that predicted values of soil water content were
consistent with the rates at which water was extracted from the plots.
The chemical composition of the simulated "rains" (Table 3d) approximated
those values observed for the litter leachate. The volume of rain (Table 3c)
was set equal to the amount of throughfall for each month, and was somewhat
less than the amount of rain applied to the experimental plots.
The simulated time series of sulfate concentrations in the maple plots is
shown in Figure 18. Observed sulfate concentrations (Figure 9b) increased
considerably faster than predicted by the model. For example, for the pH 3.0
treatment the model predicts that a concentration of 40 mg/1 would be reached
only after 10 years; this concentration was actually reached in approximately
2 years. Thus, either the Langmuir parameters obtained under laboratory
conditions were not relevant to field conditions, or the Langmuir formulation
may not be an appropriate representation of sulfate absorption by this soil.
29
-------
TABLE 3. PARAMETERS USED IN LEACH SOIL SOLUTION SIMULATION MODEL
3A. Soil Parameters
Thickness
Bulk Density
Field Capacity
Wilting Point
Cation Exchange Capacity
Total Calcium*
Total Sulfate
Total Chloride**
Partial Pressure C02
Sulfate Absorption: (see text)
SMAX
SKLR
* Represents all bases.
** Represents all anions except sulfate.
20.3 cm
0.84 kg/1
0.382 1 H20/l soil
0.193 1 H20/l soil
56.2 equiv/m2
3.350 moles/m2
0.042 moles/m2
0.004 moles/m2
0.001 atmosphere
0.811 x 10-2 moles/kg soil
0.800 x 10-3 moles/1
3B. Daily Evapotranspiration (mm H20)
July Aug Sept Oct Nov Dec Jan Feb Mar Apr May June
Alder 0.49 0.43 0.29 0.08 0.05 0.04 0.04 0.07 0.09 0.28 0.31 0.41
Maple 0.44 0.38 0.22 0.06 0.04 0.03 0.03 0.05 0.08 0.16 0.23 0.36
3C.
Alder
Maple
Rainfall Rate (cm/rain event)
July Aug Sept
0.7 0.6 0.7
0.5 0.6 0.6
Oct Nov
0.8 0.9
0.7 0.9
Dec Jan Feb
1.1 1.0 1.0
1.0 0.9 0.8
Mar Apr May
1.0 1.0 0.9
0.8 0.7 0.6
June
0.8
0.5
3D.
Chemical Composition
Nominal
pH
5.6
4.0
3.5
3.0
of Rain
Solution
pH
(5.6)
4.4
3.8
3.1
„++..++
Ca +Mg
10-5
1.75
4.76
9.64
12.03
S04"~
moles/1
0.55
5.55
32.17
50.60
3E. Chloride + Nitrate Content of Rain (10-5 moles/1)
July Aug Sept Oct Nov Dec Jan Feb Mar Apr May June
Alder 19.1 2.99 10.1 15.5 19.1 22.6 28.0 29.8 31.6 31.6 29.8 28.0
Maple 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20 1.20
30
-------
The simulated relationship between sulfate concentration and calcium
concentration for the maple plots is shown in Figure 19a. Four points ob-
tained by summing calcium and magnesium concentrations from the curves in
Figures 13b and 14b are also shown. The predicted and observed relationships
are quite similar.
An attempt was made to simulate the effects of nitrogen fixation in the
alder plots by introducing a seasonal variation in the anionic content (repre-
sented by Cl ) of the simulated rain (Table 3e). This induced a seasonal
variation in anionic concentration of the simulated soil solution similar to
that observed in extracts from the alder plots, but with higher average
anionic content. This caused the predicted concentrations of Ca and Mg to be
higher than the observed concentrations (Figure 19b). The variability of
simulated anion concentrations caused the results to be more scattered for
alder (Figure 19b) than for maple (Figure 19a); this same tendency was ob-
served in the data (Figures 13a and 14a vs. Figures 13b and 14b).
The simulation results demonstrate that established relationships can be
used to predict the response of cations in soil solutions to increased loading
of anions due to acid rain. In particular, the LEACH model is an adequate
representation of those relationships. Future efforts need to focus on simu-
lating sulfate concentrations more closely. Mineral weathering and plant
uptake of nutrients also need to be considered.
According to the LEACH simulations, the changes in soil solution chem-
istry (increased calcium and magnesium concentrations, lowered pH) were almost
entirely due to increases in total anion concentration rather than to changes
in base saturation. An example is the simulation summarized in Table 4.
While the predicted pH of the soil solution dropped from 5.3 to 4.9, base
saturation was virtually unchanged. The change in pH was associated with the
change in sulfate concentration. The dependence of the pH of a solution in
equilibrium with soil on the ionic strength of the equilibrating solution is
well known to those routinely performing soil analyses. These results empha-
size the need to distinguish between acidification of soil solution, on the
one hand, and acidification of soil as measured by decreases in base
saturation.14>15>17
31
-------
CO
PO
1976 ' 1977 ' 1978 ' 1979 ' I960 ' 1981 ' 1982 ' 1983 ' 1984 ' 1985 ' 1986
Figure 18. Simulated Time Series of 20-cm soil solution in maple plots. Results were produced bv LEACH
computer simulation model.
-------
A.
B.
CO
10
70
60
^ 50
o>
0
E
to 40
O
+o 30
o
20
10
°c
o
Alder
o
~ 0 ~"
o
o
o o
e
00
° 0
o A
o Oo
o
_ 0 ° 0 _
r ° *
o°6«f ° 0»°»0«
0^
o o 0
o
o
A
o
o
8
-------
TABLE 4. RESULTS OF LEACH SIMULATION
PH
H+
Ca2+
A13+
S0|~
cr
HC03~
Base Saturation
Starting Value
5.3
5 ueq/1
102 ueq/1
0 ueq/1
48 ueq/1
55 ueq/1
3 ueq/1
12%
Ending Value
4.9
12 ueq/1
750 ueq/1
1 ueq/1
726 ueq/1
34 ueq/1
1 ueq/1
12%
All values except base saturation refer to the soil solution at 20 cm.
Simulation used values in Table 3 for maple plots, and was for 10 years.
34
-------
REFERENCES
1. Bolin, B. , L. Granat, L. Ingelstam, M. Johannesson, E. Mattsson, S. Oden,
H. Rodhe and C. 0. Tamm. 1971. Air pollution across national bound-
aries. The impact of sulfur in air and precipitation. Sweden's case
study for the United Nations Conference on the Human Environment. P. A.
Norstedt and Sons, Stockholm, Sweden. 97 pp.
2. Braekke, F. H. 1976. Impact of acid precipitation on forest and fresh-
water ecosystems in Norway. Research Report FR6/76. SNSF Project, As,
Norway. Ill pp.
3. Cogbill, C. V. and G. E. Likens. 1974. Acid precipitation in north-
eastern United States. Water Resources Research 10:1133-1137.
4. Gambell, A. W. and D. W. Fisher. 1966. Chemical composition of rain-
fall, eastern North Carolina and southeastern Virginia. U.S. Geological
Survey Water Supply Paper 1535-K. 41 pp.
5. Likens, G. E. and F. H. Bormann. 1974. Acid Rain: a serious regional
environmental problem. Sci. 184:1176-1179.
6. Likens, G. E., R. E. Wright, J. N. Galloway and R. J. Butler. 1979.
Acid rain. Sci. Am. 241:42-51.
7. Forest Service. 1976. Proceedings of the First International Symposium
on Acid Precipitation and the Forest Ecosystem. USDA Forest Service
General Technical Report NE-23, Northeastern Forest Experiment Station,
Upper Darby, PA. 1974 pp.
8. Larson, T. V., R. J. Charlson, E. J. Knudson, G. D. Christian and H.
Harrison. 1975. The influence of a sulfur dioxide point source on the
rain chemistry of a single storm in the Puget Sound region. Water, Air
and Soil Pollut. 4:319-328.
9. Liljestrand, H. M. and J. J. Morgan. 1978. Chemical composition of acid
precipitation in Pasadena, Calif. Environ. Sci. Techno!. J2:1271-1273.
10. McColl, J. G. and D. S. Bush. 1978. Precipitation and throughfall
chemistry in the San Francisco Bay area. J. Environ. Qual. 7:352-357.
11. Forest Service. - 1976. Workshop report on acid precipitation and the
forest ecosystem. USDA Forest Service General Technical Report NE-26.
35
-------
12. Galloway, J. N. , E. B. Cowling, E. Gorham and W. W. McFee. 1978. A
national program for assessing the problem of atmospheric deposition
(acid rain). A report to the Council on Environmental Quality. Natural
Resource Ecology Laboratory, Colorado State University, Ft. Collins.
13. Electric Power Research Institute (EPRI). 1979. Ecological effects of
acid precipitation. Report of workshop held at Gatehouse-of-Fleet,
Galloway, U.K., September 4-7, 1978. EPRI SOA77-403.
14. Wiklander, L. 1973. The acidification of soil by acid precipitation.
Grundforbattring 26:155-164.
15. Wiklander, L. 1975. The role of neutral salts in the ion exchange
between acid precipitation and soil. Geoderma 14:93-105.
16. Johnson, D. W. and D. W. Cole. 1977. Anion mobility in soils: rele-
vance to nutrient transport from terrestrial to aquatic ecosystems.
USEPA, Con/all is Environmental Research Laboratory, EPA-600/3-77-068,
Corvallis, OR. 27 pp.
17. Reuss, J. 1978. Simulation of nutrient loss from soils due to rainfall
acidity. U.S. EPA, Corvallis Environmental Research Laboratory, EPA-600/
3-78-053, Con/all is, OR. 44 pp.
18. Crowther, C. and A. G. Ruston. 1911. The nature, distribution and
effects upon vegetation of atmospheric impurities in and near an indus-
trial town. J. of Agric. Sci. 4:25-55.
19. Overrein, L. N. 1972. Sulfur pollution patterns observed; leaching of
calcium in forest soil determined. Ambio. 2:145-147.
20. Nyborg, M. and McMinnon, Allen and Associates, Ltd. 1973. Atmospheric
sulfur dioxide: effects on the pH and sulfur content of rain and snow:
addition of sulfur to surface waters, soil, and crops; and acidification
of soils. In: D. Hocking and R. Reiter, eds., Proceedings of a workshop
on sulfur gas research in Alberta. Information Report NOR-X-72. North-
ern Forest Research Centre, Edmonton, Canada.
21. Cronan, C. S. 1979. Effects of acid precipitation on soil leaching
processes in high elevation forests of the northeastern U.S. In: H. H.
Izard and J. S. Jacobson, eds., Scientific papers from the public meeting
on acid precipitation, Lake Placid, NY. May 4-5, 1978. New York State
Assembly, Albany.
22. Carroll, D. 1962. Rainwater as a chemical agent of geologic processes—
a review. U.S. Geological Survey Water Supply Paper 1535-G. 18 pp.
23. Johnson, N. M. , R. C. Reynolds and G. E. Likens. 1972. Atmospheric
sulfur: its effect on the chemical weathering of New England. Sci.
177:514-516.
36
-------
24. Norton, S. A. 1976. Changes in chemical processes in soils caused by
acid precipitation. In: Proceedings of the first international sympos-
ium on acid precipitation and the forest ecosystem. USDA Forest Service
General Technical Report NE-23.
25. Turk, J. T. and N. E. Peters. 1979. Acid rain weathering of a metasedi-
mentary rock basin, Herkimer County, New York. In: H. H. Izard and J.
S. Jacobson, eds., Scientific papers from the public meeting on acid
precipitation, Lake Placid, NY. May 4-5, 1978. New York State Assembly,
Albany.
26. Jonsson, B. and R. Sundberg. 1972. Has the acidification by atmospheric
pollution caused a growth reduction in Swedish forests. Research Note
No. 20. Department of Forest Yield Research, Royal College of Forestry,
Stockholm, Sweden. 49 pp.
27. Jonsson, B. and R. Sundberg. 1976. Soil acidification by atmospheric
pollution and forest growth. In: Proceedings of the First international
symposium on acid precipitation and the forest ecosystem. USDA Forest
Service General Technical Report NE-23.
28. Tamm, C. 0. 1953. Growth, yield and nutrition in carpets of a forest
moss (Hylocomium splendens). Medd. Stat. Skogsforskn. Inst. 43:1-140.
29. Madgwick, H. A. I. and J. D. Ovington. 1959. The chemical composition
of precipitation in adjacent forest and open plots. Forestry 32:14-22.
30. Voigt, G. K. 1959. Distribution of rainfall under forest stands.
Forest Sci. 6:2-10.
31. Voigt, G. K. 1960. Alteration of the composition of rainwater by trees.
Amer. Midi. Nat. 63:321-326.
32. Carlisle, A., A. H. F. Brown and E. J. White. 1966. The organic matter
and nutrient elements in precipitation beneath a Sessile Oak (Quercus
petraea) canopy. J. Ecology 54:87-98.
33. Nihlgard, B. 1970. Precipitation, its chemical composition and effect
on soil water in a beech and a spruce forest in south Sweden. Oikos
21:208-217.
34. Henderson, G. W. , W. F. Harris, D. E. Todd and T. Grizzard. 1972.
Quantity and chemistry of throughfall as influenced by forest-type and
season. J. Ecology 65:365-374.
35. Eaton, J. S. , G. E. Likens and F. H. Bormann. 1973. Throughfall and
stemflow chemistry in a northern hardwood forest. J. Ecology 61:495-508.
36. Wood, T. and F. -H. Bormann. 1975. Increases in foliar leaching caused
by acidification of an artificial mist. Ambio. 4:169-171.
37
-------
37. Wood, T. and F. H. Bormann. 1976. Short-term effects of an artificial
acid rain upon the growth and nutrient relations of Pinus strobus L. In:
Proceedings of the first international symposium on acid precipitation
and the forest ecosystem. USDA Forest Service General Technical Report
NE-23.
38. Mayer, R. and B. Ulrich. 1976. Acidity of precipitation as influenced
by the filtering of atmospheric sulfur and nitrogen compounds—its role
in the element balance and effect on soil. In: Proceedings of the first
international symposium on acid precipitation and the forest ecosystem.
USDA Forest Service General Technical Report NE-23.
39. Fairfax, J. A. W. and N. W. Lepp. 1976. The effect of simulated acid
precipitation on cation losses from a range of tree litters. In: L.
Karenlampi, ed., Proceedings of the Kuopio Meeting on plant damages
caused by air pollution, August 16-18, 1976, University of Kuopio,
Finland.
40. Lee, J. and D. E. Weber. 1976. A study of the effects of acid rain on
model forest ecosystems. In: Proceedings of the annual meeting of the
Air Pollution Control Assoc. Portland, OR., June 1976. 17 pp.
41. Hart, J. W. 1978. User manual for the LEACH acid rain simulation model.
USEPA, Corvallis Environmental Research Laboratory, Con/all is, OR.
CERL-046.
42. Likens, G. E. and F. H-. Bormann. 1972. Nutrient cycling in ecosystems.
In: Ecosystem Structure and Function, p. 25-47. Proc. 31st Annual
Biology Colloquim, Oregon State University Press, Corvallis, OR.
43. Cronan, C. S. , W. A. Reiners, R. C. Reynolds and G. E. Lang. 1978.
Forest floor leaching: contributions from mineral, organic, and carbonic
acids in New Hampshire subalpine forests. Sci. 200:304-311.
44. Koterba, M. T. , J. W. Hornbeck and R. S. Pierce. 1979. Effects of
sludge applications on soil water solutions and vegetation in a northern
hardwood stand. J. Environ. Qual. 8:72-78.
45. Johnson, D. W. and D. W. Cole. 1976. Sulfate mobility in an outwash
soil in western Washington. In: Proceedings of the first international
symposium on acid precipitation and the forest ecosystem. USDA Forest
Service General Technical Report NE-23.
38
-------
TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
1. REPORT NO.
EPA-600/3-80-014
3. RECIPIENT'S ACCESSION NO.
4. TITLE AND SUBTITLE
Effects of Sulfuric Acid Rain on Two Model Hardwood
Forests: Throughfall, Litter Leachate, and Soil
Solution
5. REPORT DATE
January 1980 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Jeffrey J. Lee and David E. Weber
8. PERFORMING ORGANIZATION REPORT NO.
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Environmental Research Laboratory
U.S. Environmental Protection Agency
200 S.W. 35th Street
Corvallis, OR 97330
10. PROGRAM ELEMENT NO.
11. CONTRACT/GRANT NO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory
U.S. Environmental Protection Agency
200 S.W. 35th Street
Corvallis, OR 97330
13. TYPE OF REPORT AND PERIOD COVERED
Final, 1975-1979
14. SPONSORING AGENCY CODE
EPA/600/02
15. SUPPLEMENTARY NOTES
16. ABSTRACT
Simulated sulfuric acid rain (pH 3.0, 3.5, 4.5, and 5.6) was applied to model forests
containing either sugar maple (Acer saccharum) or red alder (Alnus rubra). Water
samples were collected above and below the canopy, below the litter, and from 20 cm
and 1 m below the surface of the soil. While throughfall chemistry was not very
different from rain chemistry, the litter leachate (the actual input to the soil) had
consistently higher concentrations of calcium and magnesium, and higher pH than the
acid rain. For the first 6 months, sulfate absorbtion by the soil prevented any
apparent differences in sulfate, calcium, or magnesium concentrations in the 20-cm
soil solution among plots receiving acid or control rain treatments. Sulfate concen-
trations on plots receiving the most acid rain (pH 3.0) then became increasingly
higher than on the other plots until after 3 years, they were approximately equal to
sulfate concentrations in the rain. Twenty-cm soil solutions corresponding to the pH
3.5 and 4.0 treatments responded similarly starting respectively 1 year and 2 years
after initiation of exposure to acid rain. Increased calcium and magnesium concen-
trations and lowered pH in 20-cm soil solution occurred simultaneously with increased
sulfate concentrations. No acid rain related effects were evident in the 1-m soil
solution even after 3.5 years exposure to pH 3.0 sulfuric acid rain. Cation responses
to increased anion concentrations followed those predicted by a computer simulation
model. However, sulfate concentrations in 20-cm soil solutions increased considerably
17.
aster than predicted by a
absorbtion.
DESCRIPTORS
b.lDENTIFIERS/OPEN ENDED TERMS C. COSATI Field/Group
Rainfall, pollution, sulfuric acid,
sulfates, ecology, forest trees, soil
chemistry, and computerized simulation
Acid rain, bioyeochemica!
cycles, sugar maple, red
alder, and sulfate ab-
sorbtion
06/F
07/B
18. DISTRIBUTION STATEMENT
Release to public
19. SECURITY CLASS (ThisReport)
Unclassified
21. NO. OF PAGES
20. SECURITY CLASS (This page I
Unclassified
22. PRICE
EPA Form 2220-1 (Rev. 4-77)
39
------- |