United States
Environmental Protection
Agency
Environmental Monitoring
Systems Laboratory
Las Vegas NV 89193-3478
Research and Development
EPA/600/S8-87/020 Jan. 1988
Project Summary
Analytical Methods Manual for the
Direct/Delayed Response Project
Soil Survey
K. A. Cappo, L. J. Blume, G. A. Raab, J. K. Bartz, and J. L. Engels
The U.S. Environmental Protection
Agency, in conjunction with the National
Acid Precipitation Assessment Program,
has designed and implemented a re-
search program to predict the long-
term response of watersheds and
surface waters in the United States to
acidic deposition. On the basis of this
research, each watershed system
studied will be classified according to
the time scale in which it will reach an
acidic steady state, assuming current
levels of acidic deposition.
The U.S. Environmental Protection
Agency requires that data collection
activities be based on a program which
ensures that the resulting data are of
known quality and are suitable for the
purpose for which they are intended. In
addition, it is necessary that the data
obtained be consistent and comparable
throughout the survey. For these rea-
sons, the same detailed analytical
methodology must be available to and
must be used by all analysts participat-
ing in the study.
The manual specifies the analytical
methods and internal quality control
used to process and analyze samples
for the Direct/Delayed Response Pro-
ject Soil Survey. This document was
submitted in partial fulfillment of con-
tract number 68-03-3249 by Lockheed
Engineering and Management Services
Company, Inc. under sponsorship of
the U.S. Environmental Protection
Agency. Work on this document
spanned a period from February 1985
to March 1987.
This Project Summary was developed
by ERA'S Environmental Monitoring
Systems Laboratory, Las Vegas, NV, to
announce key findings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The U.S. Environmental Protection
Agency (EPA), in conjunction with the
National Acid Precipitation Assessment
Program (NAPAP), has designed and
implemented a research program to pre-
dict the long-term response of watersheds
and surface waters in the United States
to acidic deposition. On the basis of this
research, each watershed system studied
will be classified according to the time
scale in which it will reach an acidic
steady state, assuming current levels of
acidic deposition.
As an element of NAPAP, the National
Surface Water Survey (NSWS) was initi-
ated to evaluate the water chemistry of
lakes and streams, to determine the status
of fisheries and other biotic resources,
and to select regionally representative
surface waters for a long-term monitoring
program that will study future changes in
aquatic resources. Subsequently, the
Direct/Delayed Response Project (DDRP)
was designed as the soil study comple-
ment to NSWS. DDRP, like NSWS,
focuses on areas of the United States
that have been identified as potentially
sensitive to surface-water acidification.
Specific goals of the DDRP soil survey
are (1) to define physical, chemical, and
mineralogical characteristics of the soils
and to define other watershed charact-
eristics across these regions, (2) to assess
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the buffering capacity of the soil."
Two saturating solutions are used:
buffered ammonium acetate
(NH4OAc) solution to measure total
CEC and neutral ammonium chloride
(NH4CI) solution to measure effective
CEC. Analysis is by titration or by
flow injection analysis.
• Exchangeable Basic Cations — The
exchangeable basic cations, CA2+,
Mg2+, 1C, and Na+ extracted during
the CEC determinations, are deter-
mined by atomic absorption (AA) or
by inductively coupled plasma (ICP).
Measurement of the level of ex-
changeable basic cations indicates
the base saturation of the soil.
• Exchangeable Acidity — Exchange-
able acidity is a measure of the
exchangeable cations that are not
part of the base saturation. Two
methods of analysis are used. One
employs a buffered BaCI2-TEA ex-
traction; the other, a neutral 1.0 N
KCI extraction. The BaCI2-TEA
method is a back-titration method
which indicates total exchangeable
acidity. The KCI method is a direct
titration method which estimates ef-
fective exchangeable acidity. KCI-
extractable Al is determined by AA
or by ICP. {
Chemical Parameters
• Lime and Aluminum Potential —
Lime potential is used in place of
base saturation as an input for cer-
tain models. Lime potential is defined
as [pH-1 /2 pCa]. Another character-
istic important to watershed model-
ing is the relationship of pH to
solution AI3+ levels. This is defined
as aluminum potential (KA) which is
equal to [3pH-pAI]. This method in-
volves extracting soil wjth 0.002 M
CaCI2 and determining Ca2+ and AI3+
in the extract. The cations, Na+, K+
and Mg2+, and exchangeable Fe3+
are also determined in this extract
for comparison to cation concentra-
tions in other extracts.
• Extractable Iron and Aluminum —
Iron and aluminum oxides are highly
correlated to sulfate adsorption and
are important in standard soil char-
acterization. Extractable Fe and Al
are determined by AA or by ICP in
three different extracts. Each extract
yields an estimate of a specific Al or
Fe fraction. The three fractions of
extractable iron and aluminum in-
clude those extracted by: sodium
pyrophosphate which estimates I
organic Fe and Al, ammonium oxalate
the variability of these characteristics,
and (3) to determine which of these
characteristics are most strongly related
to surface-water chemistry. Additional
DDRP goals are (4) to estimate the relative
importance of key watershed processes
in controlling surface-water chemistry
across the regions of concern, and (5) to
classify the sample of watersheds as
direct response, delayed response, or
capacity protected (to the degree that is
scientifically defensible) and to extrapolate
the results from the sample of watershed
to the regions of concern.
The three classes of watersheds are
defined as follows:
• Direct response systems — Water-
sheds in which surface waters are
presently acidic (i.e., alkalinity < O
^ieq/L) or will become acidic within
3 to 4 mean water residence times
(i.e., within 10 years). A mean water
residence time is the average time
period required to replenish totally
the water contained in a lake.
• Delayed response systems — Water-
sheds in which surface waters will
become acidic in the time frame of a
few mean residence times to several
decades (i.e., 10 to 100 years).
• Capacity Protected Systems —
Watersheds in which surface waters
will not become acidic for centuries
to millennia.
The proposed methods of data analysis
fall into three levels of complexity: (1)
system description, (2) single-factor
response time estimates, and (3) dynamic
systems modeling. Each level of analysis
involves decision criteria that are used to
classify watersheds as direct response,
delayed response, or capacity protected.
After the representative watersheds are
classified, the results will be extrapolated
to classify the response time of each
watershed in a given region. This manual
defines the physical, chemical, and
mineralogical procedures used to analyze
the soils from these watersheds.
Procedures
The manual describes the analytical
methods and quality assurance/quality
control procedures utilized during the col-
lection, preparation, and analysis of soil
samples. Included are sections on sample
handling and shipping, labware cleanli-
ness standards, calibration procedures,
and quality control samples
The detailed procedures for physical
and chemical parameters are described
in 17 separate sections of the manual,
according to the analysis being conducted.
Each section addresses the following:
• Scope and Application
• Summary of Method
• Interferences
• Safety
• Apparatus and Equipment
• Reagents and Consumable Materials
• Sample Collection, Preservation,
and Storage
• Calibration and Standardization
• Quality Control
• Procedure
• Calculations
• Precision and Accuracy
• References
The physical, chemical, and mineralogi-
cal procedures presented in the manual
are briefly summarized below:
Physical Parameters
• Moisture Content — A standard soil
testing method is used to determine
soil moisture content on a dray
weight basis. Air-dry soil is weighed,
dried in an oven, then reweighed.
The moisture content is then used to
place all measurements on an over-
dry basis.
• Particle Size — Soil textural analysis
is routinely determined for soil
characterization and classification
purposes. Rock fragments greater
than 20 mm are determined by field
sieving and weighing. Rock frag-
ments 2 to 20 mm are determined at
the preparation laboratory, and soil
particles less than 2 mm are deter-
mined at the analytical laboratory by
the standard sieve/pipet method.
• Specific Surface — A gravimetric
method that employs saturation with
ethylene glycol monoethyl ether
(EGME) is used to measure specific
surface. Specific surface is highly
correlated to cation exchange capac-
ity, sulfate adsorption, analyte ad-
sorption/desorption, and the type of
clay minerals.
Physical/Chemical
Parameters
• pH — pH is an indication of free
hydrogen ion activity. pH measure-
ments are determined in three soil
suspensions: deionized water, 0.01
M CaCI2, and 0.002 M CaCI2.
• Cation Exchange Capacity — Cation
exchange capacity (CEC) is a standard
soil characterization parameter. CEC
indicates the ability of a soil to adsorb
cations, especially the exchangeable
basic cations, Ca2+, Mg2+, K+, and
Na+. CEC is highly correlated with
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which measures organic Fe and Al
plus sequioxides, and citrate-dithio-
nite which indicates nonsilicate Fe
and Al. Analysis is performed by AA
or by ICP.
• Extractable Sulfate and Nitrate —
The amount of extractable sulfate
and nitrate indicates the sulfate and
nitrate saturation of the anion ex-
change sites. Sulfate is determined
in two different extracts: deionized
water and 500 mg P/L sodium
phosphate. Nitrate is determined only
in the deionized water extract.
Analysis is by ion chromatography.
• Sulfate Adsorption Isotherms — The
ability of soil to adsorb sulfate is
related to soil buffering capacity.
Isotherms are developed by placing
soil samples in six magnesium sul-
fate solutions of different concentra-
tions: 0, 2, 4, 8,16, and 32 mg S/L
Subsequently the amount of sulfate
remaining in solution after contact
with the soil is determined. Sub-
traction yields the amount of sulfate
adsorbed by the soil. These isotherms
represent the maximum sulfate
adsorption capacity of the soil under
laboratory conditions.
• Total Carbon and Total Nitrogen —
These two parameters are closely
related to soil organic matter type
and quantity. The method of analysis
is rapid oxidation followed by thermal
conductivity detection using an
automated CHN analyzer.
• Inorganic Carbon — Inorganic carbon
is quantified because of the inherent
ability of carbonates to buffer acidic
input. In soils with a water pH
greater than or equal to 6.0, car-
bonates are determined by coulo-
metric detection of evolved CO2 after
decomposition with a strong acid.
• Total Sulfur — Total sulfur is mea-
sured to inventory existing sulfur
levels in order to monitor future
input of anthropogenic sulfur. An
automated method involving sample
combustion followed by infrared
detection or titration of evolved
sulfur dioxide is specified.
Mlneraloglcal Parameters
• Semiquantitative X-Ray Diffraction
— The mineral content is quantified
by X-rating the samples selected for
mineralogical study. To determine
the mineral content, the samples
are X-rayed and are compared
against mineral standards for
quantification. Physical separations
of the <0.002-mm fraction and the
2-mm to 0.002-mm fractions are
required.
• X-ray Fluorescence — This method
gives the general chemistry of the
bulk sample and of the clay fraction.
The samples are pulverized, pressed
into pellets, and analyzed. These data
combined with data from X-ray dif-
fraction identify the distribution of
the elements.
• Scanning Electron Microscopy/
Energy Dispersive XRF— With these
two methods, topographic features
are examined, and local chemistry
of discrete particles is analyzed.
These results give information con-
cerning type and degree of mineral
weathering.
Conclusion
The Analytical Methods Manual will be
of interest to those involved in environ-
mental research and analysis. The
methods are innovative in their u«|jzation
of state-of-the-art instrumentation and
procedures, including the Centurion
mechanical extractor, coulometric tech-
niques, and quantitative clay mineralogy.
The application of QA/QC criteria is more
extensive than in other soils investiga-
tions of this magnitude.
This manual is a key document in a
series of reports concerning various facets
of the DDRP soil survey. Other recom-
mended DDRP documents include the
following:
• Direct/Delayed Response Project:
Quality Assurance Plan for Soil
Sampling, Preparation, and Analysis
by Bartz, Drouse, Papp, Cappo, Raab,
Blume, Stapanian, Garner, and
Coffey(1987).
• Direct/Delayed Response Project:
Field Operations and Quality Assur-
ance Report for Soil Sampling and
Preparation in the Northeastern
United States, Volume I: Sampling
(in preparation).
• Direct/Delayed Response Project:
Field Operations and Quality Assur-
ance Report for Soil Sampling and
Preparation in the Southern Blue
Ridge Province of the United States,
Volume II: Preparation (in pre-
paration).
• Direct/Delayed Response Project:
Quality Assurance Report for Physical
and Chemical Analyses of Soils from
the Northeastern United States (in
preparation).
• Direct/Delayed Response Project:
Quality Assurance Report for Miner-
alogy of Soils from the Northeastern
United States (in preparation).
• Direct/Delayed Response Project:
Field Operations and Quality Assur-
ance Report for Soil Sampling and
Preparation in the Southern Blue
Ridge Province of the United States,
Volume I: Sampling (in preparation).
• Direct/Delayed Response Project:
Field Operations and Quality Assur-
ance Report for Soil Sampling and
Preparation in the Southern Blue
Ridge Province of the United States,
Volume II: Preparation (in pre-
paration).
• Direct/Delayed Response Project:
Quality Assurance Report for Physical
and Chemical Analyses of Soils from
the Southern Blue Ridge Province of
the United States (in preparation).
• Direct/Delayed Response Project:
Quality Assurance Report for Miner-
alogy of Soils from the Southern
Blue Ridge Province of the United
States (in preparation).
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The EPA author, L. J. Blume (a/so the EPA Project Officer, see below) is with
Environmental Monitoring Systems Laboratory, Las Vegas, NV 89193-3478;
and K. A. Cappo, G. A. Raab, J. K. Bartz, and J. L. Engels are with Lockheed
Engineering and Management Services Company, Inc., Las Vegas, NV 89119.
The complete report, entitled "Analytical Methods Manual for the Direct/
Delayed Response Project Soil Survey," (Order No. PB 87-227 468/AS; Cost:
$30.95, 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 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
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