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Effect of acid rain on the soil environment: A review
J. E. Rechcigl a; D. L. Sparks a
a
Department of Plant Science, University of Delaware, Newark, Delaware
Online Publication Date: 01 July 1985
To cite this Article Rechcigl, J. E. and Sparks, D. L.(1985)'Effect of acid rain on the soil environment: A review',Communications in Soil
Science and Plant Analysis,16:7,653 — 680
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COMMUN. IN SOIL SCI. PLANT ANAL., 16(7), 653-680 (1985)
EFFECT OF ACID RAIN ON THE SOIL ENVIRONMENT: A REVIEW
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KEY WORDS: acid rain, aluminum, soil acidity
J. E. Rechcigl and D. L. Sparks 2
Department of Plant Science
University of Delaware
Newark, Delaware, 19717-1303.
ABSTRACT
This paper reviews the literature on acid rain,
with emphasis on soils and leaching of soil elements.
Several questions still exist concerning the effects of
atmospheric acid deposition on soils:
1) does acid
rain enhance mobilization of harmful heavy metals in
soils which could leach into the groundwater; 2) does
acid rain accelerate the kinetics of weathering of
primary minerals and of secondary clay minerals in
soils which would release large quantities of Al, Fe,
and Si into the groundwater making it unfit for human
consumption; and 3) do the beneficial effects of acid
deposition outweigh the negative effects or vice versa?
Literature pertaining to these questions is addressed
in this review.
653
Copyright © 1985 by Marcel Dekker, Inc.
0010-3624/85/1607-0653S3.50/O
654
RECHCIGL AND SPARKS
INTRODUCTION
Acid
rain
is
one
of
the
most
significant
environmental problems facing the world today 3 .
becoming
a
significant
obstacle
to
It is
agricultural
production as well as an impediment to the development
of our forest and water resources 3 .
It could seriously
hinder the prospects of using coal as an energy source.
According
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Environmental
to
the
estimates
Protection
Agency
of
the
(EPA),
annually discharges nearly 5.0 x 1O
10
U.
the
U.
S.
S.
kg of S0 2 and N 2 0
into the atmosphere as a result of the combustion of
large
amounts
converted
of
into
fossil
acids
which
components in rain or snow.
may
produce
serious
fuels.
These
return
gases
to
are
earth
as
The resulting "acid rain"
ecological
effects
on
the
environment 3 .
The seriousness and the widespread nature of the
problem can be shown by simply listing the components
of the ecosystem which can be affected by acid rain.
It
affects
pathogens;
soils,
alters
plants,
lake
and
and
the
river
spread
biota;
of
plant
accelerates
material corrosion and deterioration of buildings; and
finally, it affects human health 4 .
While voluminous amounts of data have appeared on
the effects of acid rain on plants and animals, few
reports on acid effects on soils have
appeared,
yet
there is increasing concern about the effect of acid
rain on soils.
The Acid Rain Phenomenon
The
first
precipitation
published
apppeared
in
reports
the
on
acid
1
5
mid-1950 s ,
and
rain
the
ACID RAIN ON SOIL ENVIRONMENT
655
problem has been well documented for Scandinavia
6
7
eastern North America ) .
4
and
The phenomenon is apparently
not limited to northern climates, as there have been
reports of acid rain in the southern and western parts
of the United States 8 ) 9 ) 1 0 .
In both Norway and Sweden, declines in rainfall pH
of 0.02-0.05 units per year have been recorded over
recent decades 1 1 ) 1 2 .
In the northwestern U. S., 4% of
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the mountain lakes had pHs below 5.0 in 1940, whereas
13
in the 1970's 51% were less than 5.0
, the average
12
decline being 0.05 units per year .
According
to
EPA,
hundreds
of
lakes
in
North
America and Scandinavia have become so acidic that they
can no longer support fish life 3 .
in
the
Adirondack
fishless
because
reproduction3.
mountains
acidic
Other
More than 90 lakes
in New
York
conditions
areas
of
State
have
the
U.
are
inhibited
S.,
such
as
3
northern Minnesota may also be vulnerable .
Data from New York State and New England indicate
acid rain is 60-70% H 2 SO 4
14
and 30-40% HN0 3
.
These
strong acids are thought to stem primarily from gaseous
man-made pollutants such as S and N 2 0 .
Acid
rain
contains
a variety
of
heavy metals,
particularly in the vicinity of metal smelters 15 .
In
lake sediments in the northeastern U. S., Ag, Au, Cr,
Ni,
Pb,
Sb,
quantities
Acid
16
and
V
have
been
may
rain
also
contains
be
transferred
a
1S
increased
from
number
including
hydrocarbons,
phthalic
alkanes,
acid
of
plant
and possibly P
land
addition, it can also carry a wide
molecules,
in
> .
nutrients such as Ca, K, S, N
These
found
a7
to
water.
.
In
range of organic
polycyclic
esters,
15
and
aromatic
fatty
acid
656
ethyl esters, as well
RECHCIGL AND SPAEKS
as a variety of commonly used
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industrial chemicals such as polychlorinated biphenyls
Sensitivity of Soils to Acid Rain
Acid rain may bring about variable effects on
soil, depending on the type and properties of the soil
involved.
The sensitivity of soil to acid rain is
determined by four key parameters 2 0 ' 2 4 : 1) the total
buffering capacity or the cation exchange capacity
(CEC) provided primarily by clay and soil organic
matter contents; 2) the base saturation of that
exchange capacity, which can be estimated by the pH of
the soil; 3) the management system imposed on the soil,
whether it is cultivated and fertilized or renewed by
flooding or other additions; and, 4) the presence or
absence of carbonates in the soil profile.
A change in soil pH is most closely linked to its
CEC. If the soil has a low CEC (<12 cmol (+)/kg), then
the acid precipitation is likely to reduce the soil and
the groundwater pH quickly 25 . However, a soil with a
high CEC (>12 cmol (+)/kg) is strongly buffered against
changes in pH or leachate composition 23 . The original
pH of the soil also has a great bearing on the
sensitivity
of
the • soil
to
acid
precipitation.
23
According to McFee , acid soils with a pH near that of
acid rain will not change in pH rapidly in response to
acid inputs. Also, soils with a low CEC have a low
reserve of plant nutrients (such as Ca, Mg, or K) and
slight losses may be significant to their productivity.
McFee 2 5 categorized soil areas into three major
classes based on their sensitivity to acidity:
ACID RAIN ON SOIL ENVIRONMENT
1)
657
Nonsensitive Areas (NS) include a) all soils
that
are
calcareous
(i.e.,
contain
free
carbonates) in the surface layer (within 0.25m
); b) all soils that are subject to frequent
flooding
(it
is
assumed
that
the
renewal
effects of fresh deposition would negate acid
precipitation effects); and, c) all soils with
an average CEC greater than 15.4 cmol ( + )/kg
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in the top 0.25m.
2)
Slightly Sensitive Areas
(SS) include areas
not in class la or lb that have average CEC in
the range of 15.4 to 6.2 cmol(+)/kg in the top
0.25m.
3)
Sensitive Areas (S) include those areas not in
class la or lb that have average CEC less than
6.2 cmol(+)/kg in the top 0.25m.
Using the above criteria, McFee constructed maps
of soil sensitive regions for the eastern U. S.,
including New York, North Carolina, West Virginia,
Pennsylvania and Indiana 23 .
In similar fashion, Klopatek et al. 2 6 prepared
computer maps of soil pH, CEC, base saturation, and
base content for the eastern U. S., using county-level
data. By overlaying these maps with computer maps of
the H ion
loading, maps
of acid-sensitive
and
insensitive soils were made. Of 1572 counties in the
eastern U. S., 117 were classified as being acidsensitive.
Sensitivity
of
Soil
Orders
of
the
U.
S.
Soil
27
Classification System To Acid Rain (after Petersen )
658
RECHCIGL AND SPARKS
Petersen 27 has classified the major soil orders as
to their sensitivity to acid rain.
This classification
is given below.
Mollisols - are soils containing a high percentage
of humus.
and
They have not been subject to much leaching
often
contain
CaCO 3 .
Their
base
saturation
percentage and buffer capacity are usually fairly high,
and thus they are not likely to be sensitive to acid
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precipitation.
Oxisols
-
are
red
soils
usually
containing
a
considerable percentage of clay which contains a large
amount of Fe and Al oxides and kaolinite, and they have
a low CEC.
soil
The humus content is also very low and the
itself
Therefore,
is
they
capacity.
highly
have
This
weathered
a
low
soil
is
pH
and
and
leached.
low
buffering
sensitive
to
acid
precipitation.
Vertisols - are black heavy clay soils having a
high
degree
of base
saturation.
The
clay
mainly of smectite which has a high CEC.
consists
Thus, these
soils most likely would not be affected by acid rain.
Histosols
-
consist
predominantly
of
matter and have a high buffering capacity.
organic
These soils
are already very acid and any additional acidity would
not change the pH very much.
Alfisols and Ultisols - have a high clay content,
and
the
percentage.
Alfisols
have
Alfisols
a
are
high
not
base
likely
saturation
to
be
very
sensitive to acidity, whereas Ultisols, with their low
base
saturation
percentage,
may
be
susceptible
to
acidity.
Inceptisols - with a high clay content, they are
rather
insensitive
to
acid
rain, whereas
the
Inceptisols are rather susceptible to acidity.
sandy
ACID RAIN ON SOIL ENVIRONMENT
Entisols - have
659
a high degree of variation, and
thus a generalization as to their sensitivity cannot be
made.
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Soil Acidification Process
While acid rain may be a major source of soil
acidity, it is not the only source. Acidification of
soils
is
a
natural
process
occurring
22 28 29
continuously > > .
There" are
several
natural
sources of soil acidity.
One such source is H 2 C 0 3 .
Water in equilibrium with the 0.03% C 0 2 in the
atmosphere may have a pH of 5.6. When this water comes
into contact with soil, the equilibrium with C 0 2 no
longer exists. This is because topsoils may have a
higher concentration of C 0 2 due to the respiration of
soil flora and fauna. The C 0 2 concentration between
air and soil will occasionally vary as much as 0.01% by
lowering the pH from 5.6 to 4.9. A pH of 5 is thus
quite common in subsurface soils where H 2 C 0 3 is the
only source of a c i d i t y 2 2 ) 2 9 .
Another source of soil acidity is nitrification.
Plant residues and humus break down naturally in soils
by heterotrophic
microflora, producing
NH 4
ions.
Nitric acid is then formed when autotrophic bacteria
oxidize NH 4 to N 0 3 . The reaction is as follows:
N H 4 + + 2 0 2 + H 2 0 — > 2 H 3 0 + + N0
According to Bache 2 2 , the theoretical amount of acid
rain produced by the nitrification of 100 kg N/ha added
660
RECHCIGL AND SPARKS
as NH 4 salt is 13 kg.
This would be equivalent to 286
kg Ca, requiring 714 kg of CaCO 3 for neutralization.
Still another source of acidity could be organic
acids formed from the decomposition of plant residues
by microbes.
These acids are particularly important in
the formation of the podzolic soils 2 2 > 3 0 .
Finally,
the air
the oxidation
may
cause F e 2 ( S 0 4 ) 3
which may produce acid SO 4
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of pyrite by exposure
22
and H 2 SO 4
to
be
to
formed
.
Acidification of soils may cause the loss of the
cations Ca, Mg, K, and Na.
on the
water
soil
22 31
.
type, pH
A decrease
These losses are dependent
and the
amount
of
in soil pH may
percolating
also cause a
reduction in CEC because the charges on the weak acid
exchange sites are pH dependent and the
undissociated at a. low pH.
22
decreases 1
23
acids become
Thus, CEC is reduced as pH
3
> * .
Degradation of primary and secondary soil minerals
may result following large inputs of mineral acids into
acid soils 2 2 .
organic
matter
sulfonation
32
acids" .
of
Where soil is extremely acidified, the
in
the
soil
carboxylated
These
may
be
benzene
altered
changed
rings
molecules
due
to
of
"humic
will
have
strengthened capacities to bind metals and will prevent
leaching into groundwater.
This area has not yet been
extensively investigated.
One of the extreme effects of acidification is the
process of podzolization.
Podzol soils are found
in
cool, humid regions of North America, Europe and Asia.
They
are
when
there
leaching.
usually
is
confined
enough
to
rainfall
sandy
to
parent
result
materials
in
severe
Podzol soils must have an acid reaction and
usually have a low content of plant nutrients as well
ACID RAIN ON SOIL ENVIRONMENT
661
as a low content of Al, Fe, and organic matter in the
surface.
This is the result of leaching.
The Al, Fe,
and organic matter are immobilized in the lower profile
of the soil.
The solubility of Al(0H) 3 is high enough
to account for a significant equilibrium concentration
of dissolved
Al at pH 3.0-3.5.
This
range of pH is
often found in the surface horizon of Podzols.
The capacity of soils to adsorb and retain anions
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increases
with
a
decreasing
pH
and
with
the
concentration of Fe- and Al-oxides and hydroxides.
The
polyvalent anions, such as P0 4 and S 0 4 , are bound by
the hydrated Fe- and Al-oxides
and hydroxides.
anion effect increases with the ratio of hlz03
This
+ Fe203
to SiO 2 in the soil 3 0 .
Effects of Acid Rain on Soil Exchange Properties
Anion
soils
adsorption is a very
in terms
of
regulating
anions other than bicarbonate.
important feature
the
leaching
rates
of
of
Bicarbonate leaching.is
regulated by soil C 0 2 pressure and solution pH.
In
general,
the
anions to soil is:
order
of
affinities
of
major
P 0 4 3 ' > S 0 4 2 ' > Cl" = N 0 3 " .
first two anions can be
adsorbed non-specifically
The
or
specifically, while the latter two can only be adsorbed
non-specifically.
Specific
adsorption
is
penetration of the anion into the coordination
of metal oxides, and nonspecific
anion retention
in the diffuse
the
sphere
adsorption refers to
double
layer next
to
oxide surfaces.
The anion adsorption capacity of a soil is related
to the content
the
soil
33
»
34
>
35
of positively
.
charged sesquioxides
Highly weathered, Al- and
in
Fe-rich
662
_
RECHCIGL AND SPARKS
soils have higher adsorption capacities than younger
Al-
and Fe-poor
adsorbed
soils.
anions
mobilization
of
to
The
a
addition of
soil
will
non-specifically
specifically
result
in
adsorbed
the
anions.
Phosphate is the most strongly adsorbed anion and will
displace specifically
adsorbed
S0 4
as
well
as
non36
specifically adsorbed anions, such as Cl and N 0 3
.
Nitrate and Cl are considered indifferent anions, since
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they do not specifically adsorb and can be completely
desorbed
by
eliminating
the
positive
charge
on
34
sesquioxide surfaces .
This problem was investigated by Wiklander 24 using
the following soils:
1.
Cambisols,
cultivated,
loamy
clay,
podzol,
(bleached)
(Fe,
Al) 2 0 3 /Si0 2 ,
2.
Humo-orthic
A2
and
B2
(rusty) horizons, and (Fe, Al) 2 0 3 /Si0 2 medium,
and
3.
Latosol from Kenya, lateritic
clay,
(Fe,
Al) 2 0 3 /Si0 2 high.
Sodium, K, Mg, and Ca combined with Cl, N 0 3 / S0 4 ,
H 2 PO 3 ,
or
salts
were
HPO 3 were
added
added
to
to the above
solutions
fertilization or higher levels.
established,
centrifugation
the
or
solution
membrane
in
soils.
amounts
The
used
in
After equilibrium was
was
separated
filtration
and
with
analyzed.
Without exception, the adsorption of N, K, Mg, and Ca
varied with the type of salt anion and increased in the
following order:
el" NO3- < S 0 4 2 - < H 2 P0 4 - < HPO 4 =
The solubility of the added salts was highest for Cl
and N 0 3 , somewhat
less for S0 4
and
least for H 2 P0 4 .
ACID RAIN ON SOIL ENVIRONMENT
Wiklander 24
thus
663
showed
that
anions
and
soil
type
directly affect the adsorption of cations on the soil.
The results were similar for single salts with Na
and NH 4 as for combined salts with Ca, Mg, K and Na.
The lateritic soil, the B horizon from the podsol and
cultivated cambisol soils behaved similarly, with the
anion effect varying quantitatively with soil type.
Removal of hydrated oxides in the Latosol before
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the salt addition strongly reduced the differences in
retention of Ca, Mg, K, Na between the H 2 PO 4 , S0 4 and
N0 3 systems caused by decreased adsorption of H 2 PO 4 and
SO4 .
It was found that the capacity of a soil to bind
cations in exchangeable
form depends not only on the
soil properties but also on the anion of the salt used
for saturation.
The increased retention and reduced
salt
cations
processes
by
of
adsorbed
great
leaching of
polyvalent
significance
in
anions
soil
are
formation,
geochemical circulation of nutrients, fertilization in
agronomic
and
horticultural
systems
and
also
in
pollution of soils and waters.
The mobility
of
S0 4
in
soils
is
an
important
consideration in studying the possible effects of acid
rain on nutrient mobilization from the soil.
to
experiments
conducted
by
Johnson
According
Cole 3 7 ,
and
it
cannot be assumed that inputs of H 2 SO 4 will result in
equivalent
soil.
a
outputs
of
cation-S04
solutions
To test this, Johnson and Cole
gravelly
significant
Everett
increases
soil.
37
Results
in leaching
from
the
added H 2 SO 4 to
showed
occurred
in
that
the A
horizons, but no increase was noted in the B horizons.
Through soil analysis, it was found that all applied
S0 4 was retained' in the soil profile.
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664
RECHCIGL AND SPARKS
In another study, Johnson et a l . 3 8
compared
atmospheric H 2 SO 4 inputs and leaching in a tropical and
temperate forest soil.
In both cases, H was mostly
removed in the forest canopy.
The tropical forest
appeared to be accumulating S 0 4 , whereas the temperate
forest was near steady state with respect to S.
In
both soils, the lower horizon adsorbed more S0 4 than
did the upper horizon. The tropical soil had a high
capacity permanently to retain S0 4 which was probably
related to its high sesguioxide content, rendering it
very resistant to leaching by atmospheric H 2 S0, inputs.
Many researchers have noted higher soil S0 4 to be
found in subsoil horizons than in surface horizons
36, 39-42_ Hesse 3 9 suggested that there was a S0 4 cycle
operating somewhat independently of the biological S
cycle in an East African forest. He suggests that the
S0 4 leached from foliage or from input in precipitation
can leach past the organic soil horizons and adsorb to
sesguioxide surfaces in lower horizons. It may be that
surface organic matter blocks S0 4 adsorption sites to
some extent. This would explain why more S0 4 is found
in the subsoil than in surface horizons of .many soils.
The relationship between S0 4 adsorption and soil
sesguioxide content has been demonstrated by several
other investigators 3 8 » 4 2 > 4 5 .
Soils that adsorb S0 4
tend to maintain an eguilibrium between S0 4 in solution
and that sorbed into soil surface as shown below.
SO 4 2 " (solution),, > S 0 1 2 ~
The Freudlich and Langmuir
(sorbed)
adsorption isotherms have
been used to describe this eguilibrium 38 i 41 >
46
.
ACID RAIN ON SOIL ENVIRONMENT
Johnson
study
to
665
Henderson4 7
and
determine
whether
adsorption
in
a
Sesquioxide
rich
subsurface
reservoir
of
undertook
mixed
NaH 2 PO 4
S
a
laboratory
accumulates
deciduous
soils
solution
by
forest
which had
were
found
SO 4
soil.
a large
to
have
adsorbed SO 4 -S at a level of 2700 kg/ha but would not
permanently
adsorb
more.
The
surface
soils
had
no
detectable adsorbed SO 4 but had a substantial reserve
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of H20-soluble-S04-S (110 kg/ha).
This high proportion
of H 2 O soluble solution SO4 appeared to have played an
important
role
headwater
streams.
surface
in determining
It
was
SO 4
also
concentrations
found
that
in
these
soils were capable of adsorbing more
SO4
in
forms not extractable with water or PO 4 solution.
Tyler 48
studied
the
leachability
of
some
metal
ions (Mn, Zn, Cd, Ni, V, Cr, Pb) in two purely organic
spruce soils:
one control soil and one similar soil
heavily polluted with Cu and Zn from a brass foundry in
southern Sweden.
4.2, 3.2
Artificial rain water acidified to pH
and 2.8 was
leachability
of
used in the
heavy
precipitation was
metals
experiments.
through
the
found to vary greatly
different elements.
The leaching
The
action
of
between the
rate of Ni
in the
control soil (similar to that of Mn) was considerably
high.
In
the
polluted
soil,
only
V
and
Zn
released more rapidly with the pH 4.2 acid rain.
4.2
the
10%
residence
time
estimated
from
were
At pH
Tyler's
experimental data varied from 3-yr (Mn) to 70 to 90-yr
(Pb) in the control soil and from 2-yr (V) to 200-yr
(Pb) in the polluted
soil.
Residence time for most
elements in this study (except V and Cr) decreased with
pH of the precipitation"16.
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666
RECHCIGL AND SPARKS
Reuss 4 6 came up with a simulation model that
provides
a quantitative
system
using
established
relationships from soil chemistry to predict the most
likely effect of rainfall acidity on the leaching of
cations from noncalcareous soils. The model utilizes:
the relationships between lime potential (pH-Jjp Ca) and
base saturation described by Clark and Hill 4 9 and by
Turner and Clark 50 ; the equilibrium between C0 2 partial
pressure and H and HC0 3 in solutions; the apparent
solubility product of Al(0H) 3 ; the equilibrium of
cations and anions in solution; the Langmuir isotherm
description of S0 4
adsorption; and mass balance
considerations to predict the distribution of ions
between the solution and sorbed or exchangeable phases.
The ionic composition of leachates in response to
rainfall composition can thus be computed. The model
predicts almost exact chemical equivalence between
basic cations removed in the leachate and strong acid
anions entering the system in the rainfall if pH-ijp Ca
is above 3.0, at which point the base saturation will
generally not exceed 20%.
Soils with a significant capacity to adsorb S0 4
tend to dampen the effect of H 2 SO 4 induced leaching of
basic cations. The leaching of bases will respond more
slowly to acid inputs than on non-S0 4 adsorbing soils,
but will reach a similar equilibrium rate of leaching
as the S0 4 adsorption capacity reaches equilibrium with
the rainfall S0 4 .
Atmospheric
inputs
of
H 2 SO 4
and
HN0 3
to
noncalcareous higher
elevation watersheds
in the
Adirondack
regions
lead
to
comparatively
higher
concentrations of dissolved Al in the surface horizon
and in the groundwater. This appears to result from
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ACID RAIN ON SOIL ENVIRONMENT
667
increased soil Al leaching.
Aluminum leaching is
enhanced in well drained acid soils where there are
significant inputs of organic acids from litter decay
and canopy leaching.
In the presence of organic
ligands, the solubility of Al can be greatly enhanced
by the formation of soluble organic-Al complexes.
Aluminum and Fe are transported from upper to lower
soil horizons by means of such soluble organometallic
complexes. Such increased Al concentrations can lead
to fish mortality. There may be indirect effects on P
availability through increased inorganic precipitation
of A1PO.,.
Accelerated Al leaching may also have
implications for soil forming processes, the health of
plant
communities,
and
alterations
in
the
clay
minerology of the soil 5 1 . On the positive side, Al has
been found to neutralize strong acids from acid
precipitation 52 .
,
Wiklander 21 has demonstrated that neutral salts in
the precipitation reduce the acidification of soils by
acid precipitation. The magnitude of the salt effect
depends on the relative bonding energy of H 3 0 and of
Ca, Mg, Na, K,
NH 4
in the
soil as well
as
concentrations of H 3 0 and the above cations in the
precipitation.
The salt effect may be considerable in very acid
soils.
It decreases with rising pH to become very
small or negligible in neutral soils, chiefly due to
the increasing bonding energy of H 3 0 in this direction.
The adverse effect of acid precipitation, therefore, is
likely to be less in very acid soils such as podzols
than in slightly acid and neutral soils with low
buffering capacity against pH change.
668
RECHCIGL AND SPARKS
Effect of Acid Rain on Soil Microorgani sms
In the past, enormous
literature
accumulated
in
soil microbiology on various changes which are brought
about by the acidification of
the use of fertilizers.
soils, associated with
Similar
stresses induced by
acid precipitation have renewed interest in this area.
The subject has been recently reviewed by Alexander 53 .
The
studies
in
microbiological
processes
are
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usually performed in a laboratory setting which makes
it difficult to directly extrapolate
the findings to
the field.
There are six major microbial groups residing in
the
soil
fungi,
ecosystem,
algae,
i.e.,
protozoa
bacteria,
and
actinomycetes,
viruses.
The
various
species have been found in widely dissimilar soils, and
only
a
few
possess
a
distinct
biogeographical
characteristic.
Microorganisms are involved in at least four key
processes
affecting the
soil
and plant productivity.
First, they are essential for plant growth by affecting
certain essential nutrients which would
unavailable.
otherwise be
A case in point is N, P and S, which are
normally found in combination with organic materials, a
form
of
which
Microorganisms
is
unavailable
convert
the
to
higher
organic
forms
plants.
to
the
inorganic state which is a vital step in maintaining
plant growth.
Microorganisms also play a key role in affecting
the characteristic soil structure.
This is, in part,
due to the formation of humus and, in part, to the
binding of soil particles as aggregates.
The
microfiora
also
perform
a crucial
role
by
preventing the excessive accumulation of organic matter
ACID RAIN ON SOIL ENVIRONMENT
with
the
likely
669
build-up
of
high
concentrations
of
toxic chemicals.
Finally,
microflora
are
involved
in
the
maintenance of environmental quality, particularly as
it affects the soil ecosystem.
Modernized society has
introduced into soil a variety of toxic substances, be
they
synthetic
chemicals or natural waste materials.
The
degradations
of
these
materials
is
entirely
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dependent on microbial action.
It should be borne
transformations
population.
in
The
soil
in mind that most microbial
may
elimination
involve
more
of
one
any
than
one
population
therefore does not necessarily have to be detrimental,
since unaffected populations(s) may continue to carry
out the chemical reactions in question.
An example of
this is the conversion of organic N to inorganic forms.
However, there are a few processes which are known
to be carried out only by a single microbial species.
In a situation like that, elimination of the particular
population would be detrimental.
This is especially
true about the nitrification process which converts NH 4
to N 0 3 , and the nodulation of
bacteria
are
quite
legumes
specific,
for which the
depending
on
the
leguminous host.
As
it
autotrophic
sensitive
to
turns
out,
nitrifying
acidity.
of
the
various
microflora,
are
particularly
bacteria
Their
activity
falls
rapidly
with decreasing pH and is undetectable below pH 4.5
Limited nitrification that is observed
may
be
the
result
of
the
action
of
in acid
54
.
soils
heterotrophic
organisms.
Soil acidification can also be expected to cause a
general
reduction
in
population
of
bacteria
and
670
RECHCIGL AND SPARKS
actinomycetes
fungi.
and
an
The increase
decreased
increase
in
the
abundance
of
in fungi has been attributed to
competition
from
other
heterotrophic
organisms at low p H 5 4 .
Acidity is generally linked with decreased rates
of
humus
decomposition,
while
liming
will
conversion of the humic compounds to CO 2 .
promote
However, in
some instances, depending on the soil and the nature of
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the
organic
materials,
rapid
degradation
can
be
observed even at moderate or extreme acidities, such as
pH 1.8
55
.
Increasing
acidity can
also profoundly
biological N fixation rates.
the essential
fixing
prelude
system
to
involving
decrease
The nodulation, which is
the
development
legumes
and
of
the In-
Rhizobium,
especially sensitive to acid conditions.
is
In the case
of clover, nodulation is frequently absent at pH 5.2 or
below 5 6 .
The reduced numbers of root-nodule bacteria
were also reported below pH 5.0
exists
at
present
on
the
S7
.
effect
of
No
information
acidity
fixation in the roots of non-leguminous plants.
case of free-living N fixers, a majority
sensitive
resistant
to
58
low
pH,
although
a
few
on
N
In the
seem to be
may
be
quite
.
Conversion of soil organic N to NH 4 , in contrast
with nitrification, apparently does not show a marked
pH sensitivity
elevated NH«
54
.
In fact, the acid soils may show
levels in contrast to non-acid
soils in
which NO 3 is the dominant form of N.
Denitrification, which converts NO 3 to N 2 and N 2 O,
is also adversely affected by low pH.
The number of
bacteria which carry out this reaction was shown to be
inversely correlated with acidity
59
.
ACID RAIN ON SOIL ENVIRONMENT
The
decomposition
important
part
ecosystems.
of
Many
671
of
organic
nutrient
nutrients
matter
cycling
taken up
is
in
by
an
natural
plants
are
returned to the soil through litter fall.
The
matter
effect
of
artificial
decomposition
involved,
has
been
rain
process
studied
and
by
using the ecosystem approach.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
litter
were
different
isolated
H
ion
and
on
on
the
the
organic
organisms
Abrahamsen
al.60,
et
Fungi from decomposing
their
growth
concentrations.
measured
Soil
animals
at
were
extracted from soil samples taken from laboratory and
field experiments, with applications of simulated acid
rain and lime.
In coniferous
forests
located
on
acid
podzolic
soils, the abundance of many soil invertebrate animals
were found to increase under the more acidic conditions
induced
by
the
animals were
simulated
observed present
reduced by liming.
species
of
soil
animals
in
availability
available
to
animals
species
rain,
whereas
when soil
a
few
acidity was
The increased population of certain
increase
fungal
acid
may
of
due
to
have
been
fungus
the
outcompeting
food
more
more
due
to
an
reserves
acid-tolerant
acid-sensitive
bacteria for available food.
Decomposition
decomposition
of
studies
plant
showed
remains
influenced by acidification.
that
was
the
only
initial
slightly
However, decomposition of
raw humus material was pH dependent, and decreased with
increased acidity.
It should be noted that the effects
observed were produced with much higher concentrations
of H ions than normally found in precipitation, and as
a consequence, cannot be applied directly to the acid
rain problem.
Long-term
studies with more
realistic
672
RECHCIGL AND SPARKS
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inputs of H are necessary to assess acid rain effects
under natural conditions.
A case study of forest litter decomposition near
the Ni smelter at Sudbury, Ontario was recently
reported 51 .
A series of field plots of various
distance
from the
smelter were used to examine
potential effects of heavy metal and S0 4 burdens.
Decreasing inputs and accumulations of Cu, Ni, Fe and S
were shown in organic soil horizons and vegetation
along a 60 km SSE transect away from the smelter.
There was; however, no effect on the pH of the
precipitation or on the distance of the soil litter
horizons from the smelter. Rates of litter-fall were
determined to be unchanged as a function of distance
from the smelter, but the litter standing crop was
increased close to the source, implying an effect on
litter decomposition. Lower rates of decomposition of
leaves in litter bags occurred at contaminated sites,
together with low rates of soil metabolic activity.
These included soil C 0 2 flux and acid phosphatase
acitivity.
Lower populations of soil microfungi and
microarthropods
also
occurred.
In
a
laboratory
experiment involving the addition of Cu and/or Ni to a
litter
homogenate,
a
depression
of
litter
mineralization and C 0 2 flux was shown to occur at metal
concentrations
similar
to
those
observed
at
contaminated sites in the field. Whereas the observed
vegetation toxicity near the smelter was
likely
primarily an effect of S0 2 and of heavy metals in
soils, and the effects on litter decomposition were
primarily due to heavy metals, specifically Cu and Ni.
Overall, the negative effects attributable to acid
precipitation near the smelter appeared to be small,
ACID RAIN ON SOIL ENVIRONMENT
673
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relative to the effects of S0 2 and heavy metal residue
in soils.
As was mentioned above, several nutrients in the
soil are bound in organic form and thus unavailable to
the plants. In the case of P, 15-85% is organic. An
inhibition in the mineralization process would have
serious repercussions
on the
plant productivity.
62
According to Halstead et a l . , there may be in fact a
decrease in the microbial conversion of organic to
inorganic forms of P in more acid environments;
however, the data are too limited to make definite
conclusions.
There is also some evidence for slower
conversion of organic S compounds in humus to products
that can be assimilated by plants under comparable
conditions 63 .
SUMMARY
Acid rain is a phenomenon of modern times. The
first published reports on acid rain appeared in the
mid-1950's. Since that time it has'become widespread occurring in all parts of the United States. While its
effects on aquatic systems are fairly well documented,
its effects on soils are still not fully understood.
In this review we have discussed the sensitivity
of soils to acid rain.
Acid rain may bring about
variable effects on soils, depending on the type and
properties of the soil involved.
These parameters
include:
the total buffering capacity or the total
cation exchange capacity, the base saturation of the
exchange complex, the management system imposed on the
soil, viz., whether it is cultivated, fertilized, or
renewed by flooding or other additions, and the
674
RECHCIGL AND SPARKS
presence or absence of carbonates in the soil profile.
Other topics discussed in our review include the soil
acidification process, the effects of acid rain on soil
exchange properties, and the effects of acid rain on
soil microorganisms.
Several
questions
still
exist
concerning
the
effects of atmospheric acid deposition on the chemistry
of soils:
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1)
does acid rain enhance mobilization of harmful
heavy metals in soils which would leach into
the groundwater;
2)
does
acid
weathering
minerals
(kaolins,
rain
accelerate
of
and
primary
of
the
(feldspar,
secondary
smectities,
and
kinetics
clay
of
mica)
minerals
vermiculites)
in
soils which would release large quantities of
Al, Fe, and Si into the groundwater making it
unfit for human consumption; and
3)
do the beneficial effects of acid deposition
outweigh the negative effects, or vice versa?
These questions must be answered through basic research
since the stability of soils is an important, and often
unappreciated attribute of ecosystem continuity.
REFERENCES
1.
Contribution No. 174 of the Department of Plant Science, University of Delaware, Newark, DE 19717-1303.
2.
Former Graduate Research Assistant and Associate Professor of Soil Chemistry, respectively. The address
of the senior author is Dept. of Agronomy, VPI and SU,
Blacksburg, VA 24061.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
ACID RAIN ON SOIL ENVIRONMENT
675
3.
EPA. 1983. The acidic deposition phenomenon and its
effects: Critical assessment review papers. Washington, DC, N. S. Environmental Protection Agency, May,
1983. EPA-600/8-83-016B.
4.
Oden, S. 1976. The acidity problem - an outline of
concepts pp. 1-36. In:Proceedings of the First International Symposium on Acid Precipitation and the Forest Ecosystem. Dochinger, L. S. and T. A. Seliga,
(eds.). USDA Forest Service General Technical Report
NE-23, Upper Darby, Penna. Forest Service, U. S.
Dept. of Agriculture.
5.
Barett, E., and C. Brodin. 1955. The Acidity of
Scandinavian precipitation. Tellus 7:251-257.
6.
Cogbill, C. V., and G. E. Likens. 1974. Acid precipitation in the Northeastern U. S. Water Resources
Research 10(6):1133-1137.
7.
Cogbill, C. V. 1976. The history and character of
acid precipitation in Eastern North America, pp.
363-380. In: Proceedings of the First International
Symposium on Acid Precipitation and the Forest Ecosystems. Dochinger, L. S. and T. A. Seliga (eds.).
USDA Forest Service General Technical Report NE-23,
Upper Darby, Penna. Forest Service, U. S. Dept. of
Agriculture.
8.
Brezonik, P. L, E. S. Edgerton, and C. D. Hendry.
1980. Acid precipitation and sulfate deposition in
Florida. Science 208:1027-1029.
9.
Haines, B. 1980. Acid precipitation in Southeastern
United States: a brief review. Georgia J. Sci.
37:185-191.
10. Lewis, W. M., Jr., .and M. C. Grant. 1980. Acid precipitation in the western United States. Science
207:176-177.
11. Gjessing, E. T., A. Henriksen, M. Johannessen, and R.
F. Wright. 1976. Effects of acid precipitation on
freshwater chemistry (SNSF Project FR6/76 Part 3 ) .
Research Report, Oslo, Norway.
12. Wright, R. F., and E. T. Gjessing. 1976. Acid precipitation: changes in the chemical composition of
lakes. Ambio 5:219-223.
676
RECHCIGL AND SPARKS
13. Schofield, C. L. 1976. Effects of acid precipitation
on fish. Ambio 5:228-230.
14. Glass, N. R. 1979. The Federal Government Program.
In: Acid Rain. Gunnerson, C. G., and B. E. Willard,
eds. American Society of Civil Engineers, New York.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
15. Gorham, E. 1976. Acid precipitation and its influence upon aquatic ecosystems - an overview. Water,
Air and Soil Pollut. 6:457-481.
16. Galloway, J. N. 1977. Air pollution: Impact on
aquatic systems, pp. 211-215. In: New Directions in
Century Three: Strategies for Land Use. Proc. Soil
Conserv. Soc. Amer., SCSA, Aukgry, Iowa.
17. Galloway, J. N. , and G. E. Likens. 1977. Atmospheric
enhancement of metal deposition in Adirondack Lake
sediments. Research Technical Completion Report,
Project A-067-NY, Office of Water Research and Technology, U. S. Dept. of Interior, Washington, D. C.
18. Gorham, E. 1958. The influence and importance of
daily weather conditions in the supply of chloride,
sulfate and other ions to fresh waters from atmospheric precipitation. Phil. Trans. Royal Soc. London B. pp. 241-247.
19. Gorham, E., and W. W. McFee. 1980. Effects of acid
deposition upon outputs from terrestrial to aquatic
ecosystems, pp. 465-480. In:
Effects of Precipitation on Terrestrial Ecosystems. Hutchinson, T. C ,
and M. Havas (eds. ). Plenum Press: New York.
20. Wiklander, L. 1973. The acidification of soil by
acid precipitation. Grundforbattring 26:155-164.
21. Wiklander, L. 1975. The role of neutral salts in ion
exchange between precipitation and soil. Geoderma
14:93-105.
22. Bache, B. W. 1980. The Acidification of Soils, pp.
183-202. In: Effects of Acid Precipitation on Terrestrial Ecosystems. Hutchinson, T. C., and M. Havas
(eds.). Plenum Press: New York.
23. McFee, W. W. 1980. Sensitivity of soil regions to
long-term acid precipitation. pp. 495-506. In:
Atmospheric Sulfur Deposition. Shriner, D. S., C. R.
ACID RAIN ON SOIL ENVIRONMENT
Richmond, and S. E. Lindberg (eds.)ence: Michigan.
677
Ann Arbor Sci-
24. Wiklander, L. 1980. Interaction between cations and
anions influencing adsorption and leaching. pp.
239-254. In: Effects of Acid Precipitation on Terrestrial Ecosystems. Hutchinson, T. C. and M. Havas
(eds.). Plenum Press: New York.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
25. McFee, W. W. 1983. Sensitivity ratings of soils to
acid deposition: A review. Env. and Exp. Botany
23(2) :203-210.
26. Klopatek, J. M. , W. F. Harris, and R. J. Olson. 1980.
A regional ecological assessment approach to atmospheric deposition: effects on soil systems, pp.
539-553. In: Atmospheric Sulfur Deposition. Shriner, D. S., C. R. Richmond, and S. E. Lindberg (eds.)
Ann Arbor Science: Michigan.
27. Petersen, L. 1980. Sensitivity of different soils to
acid precipitation. pp. 573-577. In: Effects of
Acid Precipitation on Terrestrial Ecosystems. Hutchinson, T. C. , and M. Havas (eds.). Plenum Press: New
York.
28. Reuss, J. O. 1977. Chemical and biological relationships relevant to the effect of acid rainfall on the
soil-plant
system.
Water,
Air,
Soil
Pollut.
7:461-478.
29. Ulrich, B. 1980. Production and consumption of
hydrogen ions in the ecosphere. pp. 255-282. In:
Effects of Acid Precipitation on Terrestrial Ecosystems. Hutchinson, T. C., and M. Havas (eds.). Plenum
Press: New York.
30. Petersen, L. 1980. Podzolization: mechanism and
possible effects of acid precipitation, pp. 223-238.
In: Effects of Acid Precipitation on Terrestrial
Ecosystems. Hutchinson, T. C., and M. Havas (eds.).
Plenum Press: New York.
31. McFee, W. W. , and J. M. Kelly. 1977. Air pollution:
impact on soils, pp. 203-207. In: New Directions in
Century Three: Strategies for Land Use. Proceedings
of the Soil Conservation Society of America, Ankemy,
Iowa.
678
RECHCIGL AND SPARKS
32. Hutchinson, T. C., and L. M. Whitby. 1977. The
effects of acid rainfall and heavy metal particulates
on a boreal forest ecosystem near the Sudbury smelting region of Canada. Water, Air and Soil Pollut.
7:421.
33. Harward, M. E., and H. M. Reisenauer. 1966. Movement
and reactions of inorganic soil sulfur. Soil Sci.
101:326-335.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
34. Hingston, F. J., R. J. Atkinson, A. M. Posner, and J.
P. Quirk. 1967. Specific adsorption of anions.
Nature 215:1459-1461.
35. Mekaru, T., and G. Nehara. 1972. Anion adsorption in
ferruginons tropical soils. Soil Sci. Soc. Am. Proc.
36:296-300.
36. Johnson, D. W., and D. W. Cole. 1977. Anion mobility
in soils: relevance to nutrient transport from terrestrial to aquatic ecosystems. U. S. Environmental
Protection Agency, EPA 600/3-77-068, June, 1977.
37. Johnson, D. W. , and D. W. Cole. 1977. Sulfate mobility in an outwash soil in western Washington. Water,
Air, Soil Pollut. 7:489-495.
38. Johnson, D. W., D. W. Cole, and S. P. Gessel. 1979.
Acid precipitation and soil sulfate adsorption properties in a tropical and in a temperate forest soil.
Biotropica 11:38-42.
39. Hesse, P. R. 1957. Sulfur and nitrogen changes in
forest soils of East Africa. Plant Soil 9:86-96.
40. Neller, J. R. 1959. Extractable sulfate-sulfur in
soils of Florida in relation to the amount of clay in
the profile. Soil Sci. Soc. Am. Proc. 23:346-358.
41. Hasan, S. M., R. L. Fox, and C. C. Boyd. 1970. Solubility and availability of sorbed sulfate in Hawaiian
soils. Soil Sci. Soc. Am. Proc. 34:897-901.
42. Williams, C. H., and A. Steinbergs. 1962. The evaluation of plant available sulphur in soils. Plant Soil
17:279-294.
43. Chao, T. T., M.E. Harward, and S. C. Fang. 1964. Iron
or aluminum coatings in relation to sulfate adsorp-
ACID RAIN ON SOIL ENVIRONMENT
679
tion characteristics of soils. Soil Sci. Soc. Amer.
Proc. 28:632-635.
44. Bornemisza, E., and R. Llanos. 1967. Sulfate movement adsorption and desorption in three Costa Rican
soils. Soil Sci. Soc. Amer. Proc. 31: 356-360.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
45. Gebhardt, H. , and N. T. Coleman. 1974. Anion adsorption by allophanic tropical soils. Sulfate adsorption. Soil Sci. Soc. Amer. Proc. 38:259-262.
46. Reuss, J. O. 1980. Simulation of soil nutrient losses resulting from rainfall acidity. Ecological Modelling 11:15-38.
47. Johnson, D. W., and G. S. Henderson. 1979. Sulfate
adsorption and sulfur fractions in a highly weathered
soil under a mixed deciduous forest. Soil Sci.
128:34-40.
48. Tyler, G. 1978. Leaching rates of heavy metal ions
in forest soil. Water, Air, Soil Pollut. 9:137-148.
49. Clark, J. S., and R. G. Hill. 1964. The pH percent
base saturation relationships of soils. Soil Sci.
Soc. Amer. Proc. 28:490-492.
50. Turner, R. C., and J. S. Clark. 1964. Lime potential
and degree of base saturation of soils. Soil Sci.
99:194-199.
51. Cronan, C. S., and C. L. Schofield. 1979. Aluminum
leaching response to acid precipitation: Effects on
high elevation water sheds in the Northeast. Science
204:304-306.
52. Johnson, N. M. 1979. Acid rain: neutralization
within the Hubbard Brook Ecosystem and regional
implications. Science 204:497-499.
53. Alexander, M. 1980. Effects of acidity on microorganisms and microbial processes in soil. pp.
363-374. In: Effects of Acid Precipitation on Terrestrial Ecosystems. T. C. Hutchinson and M. Havas
(eds.). Plenum Press: New York.
54. Dancer, W. S., L. A. Petersen, and G. Chesters. 1973.
Ammonification and nitrification of N as influenced
by soil pH and previous N treatments. Soil Sci. Soc.
Am. Proc. 37:67-69.
680
RECHCIGL AND SPARKS
55. Abrahamsen, G. , R. Horntvedt, and B. Tveite. 1977.
Impacts of acid precipitation on coniferous forest
ecosystems. Water, Air, Soil Pollut. 8:57-73.
56. Dilz, K., and E. G. Mulder. 1962. The effect of soil
pH, stable manure and fertilizer nitrogen on the
growth of red clover and of red clover associations
with perennial ryegrass. Neth. J. Agr. Sci. 10:1-22.
Downloaded By: [University of Delaware] At: 18:09 10 July 2009
57. Rice, W. A., D. C. Penney, and M. Nybor. 1977.
Effects of soil acidity on rhizobia numbers, nodulation and nitrogen fixation by alfalfa and red clover.
Can. J. Soil Sci. 57:197-203.
58. Dennison, R., B. Caldwell, B. Bormann, L. Eldred, C.
Swanberg, and S. Anderson. 1977. The effect of acid
rain on nitrogen fixation in Western Washington coniferous forests. Water, Air, Soil Pollut. 8:21-34.
59. Valera, C. L., and M. Alexander. 1961. Nutrition and
physiology of denitrifying bacteria. Plant Soil
15:268-280.
60. Abrahamsen, G., J. Hovland, and S. Hagvar. 1980.
Effects of artificial acid rain and liming on soil
organisms and the decomposition of organic matter,
pp. 341-362. In: Effects of Acid Precipitation on
Terrestrial Ecosystems. T. C. Hutchinson and M.
Havas (eds.). Plenum Press: New York.
61. Freedman, B. , and T. C. Hutchinson. 1980. Smelter
pollution near Sudbury, Ontario, Canada and effects
on forest litter decomposition, pp. 395-434. In:
Effects of Acid Precipitation on Terrestrial Ecosystems. T. C. Hutchinson and M. Havas (eds.). Plenum
Press: New York.
62. Halstead, R. L., J. M. Lapensee, and K. C. Ivanson.
1963. Mineralization of soil organic phosphorus with
particular reference to the effect of lime. Can. J.
Soil Sci. 43:97-106.
63. Nelson,
F.
E.
1964.
The effect of pH on
acetate-soluble sulfur content of a Mayhew soil in
Mississippi before and after incubation. Soil Sci.
Soc. Amer. Proc. 28:290.