United States
                Environmental Protection
                Agency
Environmental Monitoring
Systems Laboratory
Las Vegas, NV 89193-3478
                Research and Development
EPA/600/S4-90/023  Oct. 1991
EPA       Project Summary
                Handbook  of  Methods for Acid
                Deposition  Studies,  Laboratory
                Analyses for Soil  Chemistry
                L. J. Blume, B. A. Schumacher, P. W. Shaffer, L. A. Cappo, M. L. Papp,
                R. D. Van Remortel, D. S. Coffey, M. G. Johnson, and D. J. Chaloud
                 This handbook describes methods
                used to process and analyze soil
                samples. It Is Intended as a guidance
                document for groups Involved In acid
                deposition monitoring activities similar
                to those implemented by the U.S. Envi-
                ronmental Protection Agency's Aquatic
                Effects Research Program, a part of the
                National Acid Precipitation Assessment
                Program.  Much of the methodology
                presented in this handbook Is based on
                existing soil survey protocols; however,
                most of the methods were modified to
                meet the particular needs of the Direct/
                Delayed Response Project. These modi-
                fications Include  specifications for
                sample size, quality assurance and qual-
                ity control samples, soil-to-solution ra-
                tios, extraction times, extraction appara-
                tus, and holding times. The handbook
                also delineates methods that were used
                to make the following laboratory deter-
                minations: rock fragments, bulk density,
                pH, organic  matter, air-dry moisture,
                partical size analysis, cation exchange
                capacity, exchangeable cations in am-
                monium acetate, exchangeable cations
                In calclumchloride for lime and aluminum
                potential, exchangeable acidity, ex-
                tractable Iron, aluminum, silicon, and
                sulfate,  sulfate adsorption  Isotherms,
                and total carbon, nitrogen, and sulfur.
                 This Project Summary was developed
                by the EPA's Environmental Monitoring
                Systems Laboratory, Las Vegas, NV, to
                announce key findings of the handbook
                that Is fully documented In a separate
                handbook of the same title (see Hand-
                book ordering Information at back).
Introduction
  Concern about the effects of acidic depo-
sition on the Nation's surface water re-
sources led the U.S. Environmental Pro-
tection Agency (EPA) to initiate research in
the field in the late 1970s. Early research,
focusing on a diversity of potential effects,
provided insight into those research areas
which were considered central to key policy
questions. Recognizing the  need for an
integrated, stepwise approach to resolve
the issues, EPA implemented the Aquatic
Effects Research Program (AERP) in 1983
with its present structure, focus, and ap-
proach. The AERP is a major component of
the National Acid Precipitation Assessment
Program's (NAPAP) Aquatic Effects Re-
search Task Group 6, a cooperative effort of
nine federal agencies tasked with address-
ing important policy and assessment
questions relating to the acidic deposition
phenomenon and its effects.
  The Direct/Delayed Response Project
(DDRP) is one of the major component
projects within  the AERP.  Its principal
mandate is to make regional projections of
future effects of sulfur deposition on long-
term surface water chemistry based on the
best available data and  most widely ac-
cepted hypothesis of the acidification pro-
cess (Church et al., 1989). Specific objec-
tives of the DDRP are:
•  To describe the regional variability of soil
  and watershed characteristics.
•  To determine which soil and watershed
  characteristics are most strongly related
  to surface water chemistry.
•  To estimate the relative importance of key
  watershed processes in moderating re-
  gional effects of acidic deposition.

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• To classify a sample of watersheds with
  regard to their response characteristics
  to inputs of acidic deposition and to ex-
  trapolate the results from this sample of
  watersheds to the DDRP study regions.

Scope of Handbook
  The Handbook of Methods for Acid Depo-
sition Studies, Laboratory Analyses for Soil
Chemistry describes methods used to pro-
cess and analyze soil samples.  These
procedures are based on methods  used
during the three soil surveys comprising the
DDRP. Most of the methods were based
originally on methodologies  employed  by
the U.S. Department of Agriculture/Soil Con-
servation Service (USDA/SCS), including
methods described in the National Soils
Handbook (USDA/SCS, 1983), Soil Survey
Manual (USDA/SCS, 1951; supplement
1962),  Field Study Program Elements to
Assess the Sensitivity of Soils toAcidDepo-
sition Induced Alterations in Forest Produc-
tivity (Fernandez,  1983),  Procedures  for
Collecting  Soil Samples and Methods of
Analysis for  Soil Surveys  (USDA/SCS,
1972),  Methods of Soil Analysis, Part 1
(Klute,  1986) and Part2(Pageetal., 1982).
Soil Taxonomy (USDA/SCS, 1975), Keys to
Soil  Taxonomy (USDA/SCS, 1988), and
Soil Survey Laboratory Methods and Pro-
cedures for Collecting Soil Samples (USDA/
SCS, 1984). These original methodologies
were modified to meet the particular needs
of the DDRP. Modifications included speci-
fications for sample  sizes, quality assur-
ance and quality control  samples, soil-to-
solution ratios, extraction times, extraction
apparatus, holding times, standard internal
quality control procedures, and standard or
automated equipment.
  The  handbook also delineates methods
for making the following laboratory analyses:
• Rock fragment determination.
• Bulk density determination.
• Field moist pH determination.
• Organic matter determination.
• Air-dry moisture determination.
• Particle size analysis.
• pH determination.
• Cation exchange capacity.
• Exchangeable cations in ammonium ac-
  etate.
• Exchangeable cations in calcium chloride
  for lime and aluminum potential.
• Exchangeable acidity.
• Extractable iron, aluminum, and silicon.
• Extractable sulfate.
• Sulfate adsorption isotherms.
• Total carbon and nitrogen.
• Total sulfur.

Methods Described in
Handbook

Sample Processing and Rock
Fragment Determination
  The procedures presented here are spe-
cific to bulk sample preparation methods
employed in the DDRP. Alternatives tothese
procedures are available in the published
literature (e.g., USDA/SCS, 1972).
  Sample processing includes sample dry-
ing, disaggregation, sieving, homogeniza-
tion,  and subsampling.  Each of  these is
performed as sample processing steps in
the preparation laboratory. Homogenization
and subsampling are completed at the ana-
lytical laboratory. The objective of these
procedures is to produce homogeneous
subsamples  for subsequent analyses of
physical and chemical parameter. Also in-
cluded in this section is the procedure used
for determination of percent rockfragments.

Bulk Density Determination
  In the DDRP surveys, the clod method is
the primary method for determining bulk
density. Where possible, three replicate clod
samples are extracted from each horizon.
The average bulk density of the replicates is
assumed to be the bulk  density of that
particular horizon. Analysis of the clods is
based on the method described in the USDA/
SCS (11984), Kern and Lee (1989), and Kern
et al. (in preparation).
  Two alternate methods are also presented
for soil horizons that fail to yield satisfactory
clods. One method is volume replacement
(VR), a method similar to one described by
Flint  and Childs  (1984), which utilizes  a
known volume of small foam beads packed
into a cylinder to replace a selected volume
of soil excavated from  a given  horizon.
Subtracting the initial from the final volume
yields the estimated volume of sample col-
lected. The other method is a volume filling
(VF)  method that is used if the clod or VR
methods do not produce representative
samples. The volume of this type of sample
is based on the absolute height of a 250-mL
beaker, which is a constant 300 cm3. The
known volume samples are processed in a
manner similar to the method described in
Blake (1965).

Field-Moist pH Determination
  This method is applicable to the determi-
nation of pH in soil samples. For the DDRP,
field-moist pH is determined in the prepara-
tion laboratory using an Orion Model 611 pH
meter and an Orion Ross combination pH
electrode. The method  has  been written
assuming that the Orbn meter and elec-
trode are used (Orion, 1983); however, it
can be modified for use with other instru-
mentation.

Organic Matter Determination
  Loss-on-ignition (LOI) isthe method used
to determine an approximation of percent
organic matter of soil samples.  Because
organic samples are oxidized at high tem-
peratures, percent organic matter can be
calculated on a weight-loss basis. From the
percent organic matter, the percent organic
carbon can be estimated. In the DDRP, LOI
was used to classify samples as mineral or
organic for subsequent analysis purposes.
Oven-dried soil  samples  are ashed in a
muffle furnace to remove organic material.
The difference  in pre- and post-ashing
weights is used to calculate percent organic
content. A modified version of the method
described in MacDonald (1977) is used.

Air-Dry Moisture Content
  Air-dry moisture determination is done
both at the preparation laboratory and at the
analytical  laboratory.  In the preparation
laboratory, the process is used to ensure
that each sample is at  an acceptable
moisture level for further processing. In the
analytical laboratory, the air-dry moisture is
determined on all samples to  convert all
results to an oven-dry basis, and if specified
in, a procedure, to calculate the weight of
sample equivalent to agiven weight of oven-
dry soil (Brady, 1974).
  A subsample of the air-dried  bulk soi
sample is weighed, oven-dried for approxi-
mately 24 hours, and reweighed. The inrtia
and final  weights are used to calculate a
percent weight loss.

Particle Size Analysis
  Particle size analysis is determined on
the less than 2-mm  fraction from minera
horizons only. The sieve/pipet/gravimetrk
method described in (USDA/SCS 1984) is
used. Organic matter is removed from the
sample by digestion with hydrogen perox-
ide. The sand fractions are separated from
the silt and clay fractions by wet sieving
The silt and clay fractions are suspended in
water; aliquots taken from the suspension
under specified conditions are dried anc
then weighed. The sandf ractions are sieved
and each fraction is weighed. The resulting
gravimetric data allow calculation of the
percentage of each particle size class.

pH Determination
  The following procedure was developec
to standardize the measurement of pH ir
soils. The method has been written assum
ing that the Orion Model 611 pH meter anc
an Orion Ross combination pH electrode

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are used (Orion, 1983); however, it can be
modified for use with other instrumentation.
The applicable pH range for soil solutions is
3.0 to 11.0.
  Two suspensions of each soil sample are
prepared, one in deionized (Dl) water and
one in 0.01 M calcium chloride (CaCI2) pH.
The pH of each suspension is measured
with a pH meter and a combination elec-
trode. This method is modified from USDA/
80S (1984). The Dl water pH is generally
higher than the 0.01 M CaCI2 pH.

Cation Exchange Capacity
  Two saturating  solutions are  used for
cation exchange capacity (CEC) determi-
nation. Ammonium acetate (1.0 N NH4OAc)
buffered at pH 7.0  yields a CEC which is
close to the total cation exchange capacity
for a specific soil. This saturating solution is
commonly used for soil  comparisons.  In
acid soils, this estimate  results in a high
CEC value because of adsorption of NH4*
ions to the pH-dependent exchange sites
that exist above the soil's natural  pH level.
The overestimation will not occur when an
unbuffered  saturating solution of ammo-
nium chloride (1.0 N NH4CI) is used. The
NH Cl CEC has  been termed "effective"
CEC (i.e., that which occurs at field pH and
is of greater importance because it is a more
realistic estimate of CECthan the total CEC
by NH4OAc). The two saturating solutions
are retained for the exchangeable cation
determinations. This method has  been
written assuming use of a mechanical ex-
tractor.
  The soil sample  is saturated with NH4*
from a solution of NH OAc or NH4CI. Ex-
cess NH4* is  removed  by ethanol rinses.
The NH/ is displaced by Na* and is ana-
lyzed by one of three methods: automated
distillation-trtration,  manual distillation-au-
tomated titration, or ammonium displace-
ment-flow injection analysis. The entire
procedure is repeated with a fresh aliquot
sample and a solution of NH4CI as the NH4*
source. These methods are based  on
Doxsee (1985), Rhoades (1982), and USDA/
SCS(1984).

Exchangeable  Cations In
Ammonium Acetate
  The exchangeable cations (Ca2*, Mg2*, K*,
and Na*) in the soil can be used to estimate
the ability of a soil to buffer acidic deposi-
tion. Ammonium chloride  and buffered am-
monium acetate are used to extract ex-
changeable base cations at pH values near
the soil  pH and at the buffered pH of 7.0,
respectively. Base saturation is defined as
the sum of exchangeable base cations di-
vided by the cation exchange capacity (CEC)
and is expressed as a percentage.
  Previously prepared extracts from the
CEC procedure are analyzed for calcium,
magnesium, potassium, and sodium. Once
the concentration of each cation in the soil
extract is determined, the cation concen-
tration  in the original soil sample may be
calculated. Atomic absorption spectroscopy
can be used to measure calcium, magne-
sium, potassium, and sodium. Inductively
coupled plasma spectroscopy can be used
to measure cadmium,  magnesium,  and
sodium. Emission spectroscopy can be used
to measure potassium and sodium.

Exchangeable Cations In
Ammonium Chloride
  The exchangeable cations (Ca2*, Mg2*, K*,
Na* and Al3*) obtained in unbuffered 1.0 N
NH4CI representthe effective exchange that
occurs at field pH. Values of the exchange-
able cations determined by this procedure
are theoretically equal to those determined
by the buffered NH4OAc  exchange.  The
concentrations  (meq/100 g) of the ex-
changeable cations plus acidity should ap-
proximate  the  CEC.
  Base saturation  is given as the total
amount of exchangeable base cations di-
vided by the CEC. Exchangeable acidity is
a measure of the amount of exchangeable
acidic cations on the soil cation exchange
complex,
  Previously prepared extracts from the
CEC procedure are analyzed for aluminum,
calcium, magnesium, potassium, and so-
dium. Once the concentration of each cat-
ion in the soil  extract  is determined, the
cation  concentrations in the  original soil
sample can be measured by using atomic
absorption  spectroscopy,  inductively
coupled plasma spectroscopy, or emission
spectroscopy.

Exchangeable Cations In CaCI2
for Lime and Aluminum
Potential
  Lime and aluminum potential are related
to the concentrations of calcium (Ca2*) and
aluminum (Al3*), respectively, that are ex-
tracted from a soil sample by dilute calcium
chloride (CaCL,) solution. Lime potential is
defined as pH -1/2 pCa. The  p-function is
defined as the negative logarithm (base 10)
of the molar concentration of that species,
or: pX = -log [X]. The advantage of using the
p-function is that concentration information
is available in terms of small positive num-
bers. Aluminum potential, K is defined as:
KA = 3pH - pAL.
  The pH value determined in this method
should be between the two pH values deter-
mined  for each soil sample. Extractable
Mg2*, K*, and Na* are also determined for
comparison to amounts determined in the
CEC extracts. Fe3* and Al3* are determined
for comparison to amounts obtained by the
extractable iron and aluminum procedures.
  The procedure involves extraction of soil
with  0.002 M  CaCI2. The soil-to-solution
ratio is1:2 for  mineral soils and 1:10 for
organic soils. The pH is determined using a
pH meter and a combination electrode.

Exchangeable Acidity
  The method most frequently used to de-
termine exchangeable acidity  involves
treatment of the soil sample with a barium
chloride triethanolamine (BaCL-TEA) solu-
tion buffered to pH 8.2 followed by titration
of the  extracted  solution.  This method
measures total potential acidity (Thomas,
1982).
  Exchangeable acidic ions are extracted
from a soil sample using a mechanical ex-
tractor  with a BaCI2-TEA extracting solu-
tion. The excess reagent in the extract is
back-titrated with  HCI. Results are ex-
pressed  as milliequivalents  (meq) ex-
changeable acidity per 100 g soil.

Extractable Iron, Aluminum,
and Silicon
  Iron and aluminum are extracted from soil
by sodium pyrophosphate, citrate-dithionite,
and acid-oxalate solutions. According to the
Johnson and Todd (1983) iron and aluminum
speciation scheme, the pyrophosphate ex-
tract contains organically bound iron and
aluminum; the citrate-dithionite extract
contains non-silicate Fe3* and Al3*, and the
acid-oxalate extract contains organic and
amorphous oxides of Fe3* and Al3*.  The
exchangeable Al3* from the unbuffered
NH^CI extract is more indicative of readily
available Al3*  under field conditions.  The
Fe3* and Al3* values from  the pyrophos-
phate,  acid-oxalate, and citrate-dithionite
extracts relate directly to the sulfate adsorp-
tion capacity and have  been used as an
indication of this property (Fernandez, 1983).
Silicon  is extracted with the acid oxalate.
  Each of three portions of a soil sample is
treated with a  different solution to extract
iron and  aluminum. The three  extracting
solutions are 0.1 M sodium pyrophosphate,
a sodium citrate-sodium dithionite solution,
and an oxalic ammonium oxalate solution.
After extraction,  the  three  solutions are
analyzed for iron, aluminum, and silicon by
inductively coupled plasma spectroscopy.

Extractable Sulfate
  The  ability  of soils to  adsorb sulfate
(SO42-) is one  of the  principal factors af-
fecting the rate  and extent of  soil  and
watershed response to  acidic deposition.
Quantification of existing pools of adsorbed
sulfate on a soil, concurrent with measure-

-------
ments of sulfate adsorption capacity of that
soil, provide useful information for under-
standing the status and for predicting the
future response of the soil to acidic deposi-
tion.
  This method requires  the extraction of
two aliquots of a soil  sample. Deionized
water is the extracting matrix for  readily
available sulfate. The extracting matrix for
sulfate that is more difficult to  dislocate is
0.016 M sodium phosphate (containing 500
mg P/L). Afterthe extractions arecompleted,
the analytes are determined by ion chro-
matography.

Sulfate Adsorption Isotherms
  The most direct and  effective way to
determine sulfate-adsorption capacity uti-
lizes sulfate adsorption isotherms. In this
method, sulfate adsorption isotherms are
developed  by  measuring the  amount of
sulfate remaining in solution after contact
with asoil sample. These sulfate adsorption
isotherms  allow comparisons to be made
between horizons or between pedons.
  Six aliquots of the same soil sample are
shaken with solution containing 0,2,4,8,16,
and 32 mg sulfur per liter, respectively. The
mixtures are centrifuged and filtered, and
the resulting filtrate is analyzed for sulfate
by ion chromatography. The difference be-
tween the original  concentrations of the
sulfur solutions and the final concentrations
after this  procedure  indicates the sulfur
uptake or release by the soil.

Total Carbon and Nitrogen
  Quantification of carbon and nitrogen pro-
vides information about  the amount and
nature of organic material in the soil. Char-
acterization of organic C and N also pro-
vides insight about the potential for uptake
or release of nitrogen and/or sulfur by the
soil organic matter due to microbial activity.
Analyses of total carbon and nitrogen were
conducted using automated elemental
analyzers.
  After sample processing and analysis for
moisture content, a soil sample is oxidized
at temperatures greater than 1,000°C with
catalysts as specified by the instrument
manufacturer. The evolved gases (CO2 and
N2) are determined by thermal conductivity
or infrared spectroscopy.

Total Sulfur
  The determination of total sulfur is useful
for characterizing relationships between
inputs of sulfur from acidic deposition and
soil sulfur pools. In this method, total sulfur
in soil samples is determined by an auto-
mated sulfur analyzer by combustion of the
sample at approximately 1,370°C. This pro-
cedure is based on the operating instruc-
tions for a LEGO SC-132 sulfur analyzer
(LEGO Corporation, 1983), adapted to per-
mit analysis of very low levels of total S (as
low as 10 mg/L) in soils.
  The sample is placed in a ceramic cru-
cible  with combustion  accelerators and
heated to a maximum of 1,370°C in a re-
sistance furnace. The combustion of  the
sample liberates SO2 which  is determined
by an infrared detector. A microprocessor
calculates results by combining the outputs
of the infrared detector and system ambient
sensors with preprogrammed calibration,
linearization, and mass compensation fac-
tors. This method is based on research by
David etal. (1989).

References
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Brady, N. C. (ed.). 1947.  The Nature and
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Church, M. R., K. W. Thornton, P. W. Shaffer,
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David, M. B., M. J. Mitchell, D. Aldcorn, and
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Doxsee, K. 1985. Cation Exchange Capac-
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Fernandez, I. 1983.  Field Study Program
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Flint, A.  L. and S. Childs.  1984. Develop-
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Johnson, D. W. and  D.  E. Todd.  1983.
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                                                                           l.S. GOVERNMENT PRINTING OFFICE: 19ğl - 548-0 28/400*5

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 L J. Blume, B. A. Schumacher, P. W. Shaffer, L A. Cappo, M. L Papp, R. D. Van
   Remortel, D. S. Coffey, M. G. Johnson, and D. J. Chalaud are with Lockheed
   Engineering & Sciences Company, Las Vegas, NV 89119.
 D. T. Heggem is the EPA Project Office (see below).
 The complete report, entitled "Handbook of Methods for Acid Deposition Studies,
   Laboratory Analyses for Soil Chemistry," (Order No. PB91-218 016/AS; Cost:
   $39.00, subject to change)  will be available only from:
         National Technical Information Service
         5285 Port Royal Road
         Springfield, VA 22161
         Telephone: 703-487-4650
 The EPA Project Officer can be contacted at:
         Environmental Monitoring Systems Laboratory
         U.S. Environmental Protection Agency
         Las Vegas, NV 89193-3478
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati, OH 45268
BULK RATE
POSTAGE & FEES PAID
EPA PERMIT NO. G-35
  Official Business
  Penalty for Private Use $300
  EPA/600/S4-90/023

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