United States
Environmental Protection
Agency
Office of
Research and
Development
Office of Solid
Waste and
Emergency
Response
EPA/540/R-97/501
November 1996
&EPA Federal Facilities Forum Issue
FIELD SAMPLING AND SELECTING ON-SITE
ANALYTICAL METHODS FOR EXPLOSIVES
IN SOIL
A. B. Crockett1, H. D. Craig2, T. F. Jenkins3, and W. E. Sisk4
The Federal Facilities Forum is a group of
U.S. Environmental Protection Agency
(EPA) scientists and engineers, representing
EPA regional offices, committed to the
identification and resolution of issues affect-
ing the characterization and remediation of
federal facility Superfund and Resource
Conservation and Recovery Act (RCRA) sites.
Current forum members are identified in the
text. The forum members identified a need to
provide Remedial Project Managers (RPMs)
and other federal, state, and private personnel
working on hazardous waste sites with a
technical issue paper that identifies screening
procedures for characterizing soils contaminated
with explosive and propellant compounds.
Forum members Scott Marquess and Paul
Leonard provided technical guidance and
direction in the development of this Issue paper
and other Forum members provided comments.
This paper was prepared by A. B. Crockett,
H. D. Craig, T. F. Jenkins, and W. E. Sisk.
Support for this project was provided by the
EPA National Exposure Research Labora-
tory's Characterization Research Division
with the assistance of the Superfund Project's
Technology Support Center for Monitoring
and Site Characterization. For further
information, contact Ken Brown, Technology
Support Center Director, at (702) 798-2270,
Alan B. Crockett at (208) 526-1574, or Harry
Craig at (503) 326-3689.
It is imperative that any persons working
on sites believed to be contaminated with
explosive residues thoroughly familiarize
themselves with the physical and toxic
properties of the materials potentially
present and to take all measures as may be
prudent and/or prescribed by law to protect
life, health, and property. This publication
is not intended to include discussions of the
safety issues associated with sites contam-
inated with explosive residues. Examples of
safety issues to be considered include but are
not limited to: explosion hazards, toxicity of
secondary explosives, and/or personal
protective equipment. Information pertaining
to these concerns can be found in Roberts and
Hartley (1992) and Yinon (1990). Specifically,
this paper is not intended to serve as a guide
for sampling and analysis of unexploded
ordnance, bulk high explosives, or where
secondary explosives concentrations in soil
exceed 100,000 mg/kg (10%). These
conditions present a potential detonation
hazard, and as such, safety procedures and
safety precautions should be identified
before initiating site characterization activ-
ities in these environments. Finally, this
paper does not address primary explosives or
initiating compounds, such as lead azide, lead
styphnate, or mercury fulminate, which are
extremely unstable and present a substantial
safety risk at any concentration.
1 Idaho National Engineering and Environmental Laboratory, Lockheed Martin Idaho Technologies Company
2 U.S. Environmental Protection Agency, Region 10
3 U.S. Army Cold Regions Research and Engineering Laboratory
4 U.S. Army Environmental Center
Technology Support Center for
Monitoring and Site Characterization,
National Exposure Research Laboratory
Characterization Research Division
Las Vegas, NV 89193-3478
Technology Innovation Office
Office of Solid Waste and Emergency Response,
U.S. EPA, Washington, B.C.
Walter W. Kovalick, Jr., Ph.D., Director
&
'•w Printed on Recycled Paper
381asb96
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PURPOSE AND SCOPE
The purpose of this issue paper is to provide
guidance to Remedial Project Managers regarding
field sampling and on-site analytical methods for
detecting and quantifying secondary explosive com-
pounds in soils (Table 1). The paper also includes
a brief discussion of EPA Method 8330 (EPA
1995a), the reference analytical method for the
determination of 14 explosives and co-contaminants
in soil.
This issue paper is divided into the following
major sections: (1) background, (2) an overview
of sampling and analysis for explosives in soil,
(3) data quality objectives, (4) unique sampling
design considerations for explosives, (5) a
summary of on-site analytical methods, and (6) a
summary of the EPA reference analytical method.
While some sections may be used independently,
joint use of the field sampling and on-site
analytical methods sections is recommended to
develop a sampling and analytical approach that
achieves project objectives.
Many of the explosives listed in Table 1 are not
specific target compounds of screening methods, yet
they may be detected by one or more screening
methods because of their similar chemical structure.
Also listed are the explosive and propellant
compounds targeted by high performance liquid
chromatography (HPLC) methods including EPA
SW-846 Method 8330, the standard method
required by EPA regions for laboratory confirm-
ation.
BACKGROUND
Evaluating sites potentially contaminated with
explosives is necessary to carry out EPA, U.S.
Department of Defense, and U.S. Department of
Energy policies on site characterization and
remediation under the Superfund, RCRA,
Installation Restoration, Base Closure, and Formerly
Used Defense Site environmental programs.
Facilities that may be contaminated with explosives
include, for example, active and former
manufacturing plants, ordnance works, Army
ammunition plants, Naval ordnance plants, Army
depots, Naval ammunition depots, Army and Naval
proving grounds, burning grounds, artillery impact
ranges, explosive ordnance disposal sites, bombing
ranges, firing ranges, and ordnance test and
evaluation facilities.
Historical disposal practices from manufacturing,
spills, ordnance demilitarization, lagoon disposal of
explosives-contaminated wastewater, and open burn/
open detonation (OB/OD) of explosive sludges, waste
explosives, excess propellants, and unexploded
ordnance often result in soils contamination. Common
munitions fillers and their associated secondary explosives
include Amatol (ammonium nitrate/TNT), Baratol (barium
nitrate/TNT) Cyclonite or Hexogen (RDX), Cyclotols
(RDX/TNT), Composition A-3 (RDX), Composition B
(TNT/RDX), Composition C-4 (RDX), Explosive D or
Yellow D (AP/PA), Octogen (HMX), Octols (HMX/TNT),
Pentolite (PETN/TNT), Picratol (AP/TNT), tritonal (TNT),
tetrytols (tetryl/TNT), and Torpex (RDX/TNT).
Propellant compounds include DNTs and single base
(NC), double base (NC/NG), and triple base
(NC/NG/NQ) smokeless powders. In addition, NC is
frequently spiked with other compounds (e.g., TNT,
DNT, DNB) to increase its explosive properties. AP/PA
is used primarily in Naval munitions such as mines,
depth charges, and medium to large caliber projectiles.
Tetryl is used primarily as a boosting charge, and PETN
is used in detonation cord.
A number of munitions facilities have high levels of
soil and groundwater contamination, although on-site
waste disposal was discontinued 20 to 50 years ago.
Under ambient environmental conditions, explosives are
highly persistent in soils and groundwater, exhibiting a
resistance to naturally occurring volatilization, biodeg-
radation, and hydrolysis. Where biodegradation of TNT
occurs, 2-AmDNT and 4-AmDNT are the most
commonly identified transformation products. Photo-
chemical decomposition of TNT to TNB occurs in the
presence of sunlight and water, with TNB being
generally resistant to further photodegradation. TNB is
subject to biotransformation to 3,5-dinitroaniline, which
has been recommended as an additional target analyte in
EPA Method 8330. Picrate is a hydrolysis trans-
formation product of tetryl, and is expected in
environmental samples contaminated with tetryl. Site
investigations indicate that TNT is the least mobile of
the explosives and most frequently occurring soil
contamination problem. RDX and HMX are the most
mobile explosives and present the largest groundwater
contamination problem. TNB, DNTs, and tetryl are of
intermediate mobility and frequently occur as
co-contaminants in soil and groundwater. Metals are
co-contaminants at facilities where munitions
compounds were handled, particularly at OB/OD sites.
Field analytical procedures for metals, such as x-ray
fluorescence, may be useful in screening soils for metals in
conjunction with explosives at munitions sites.
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Table 1. Analytical Methods for Commonly Occurring Explosives, Propellants, and
Impurities/Degradation Products.
Acronym
TNT
TNB
DNB
2,4-DNT
2,6-DNT
Tetryl
2AmDNT
4AmDNT
NT
NB
Nitramines
RDX
HMX
NQ
Compound Name
2,4,6-trinitrotoluene
1 ,3 ,5 -trinitrobenzene
1 ,3 -dinitrobenzene
2,4-dinitrotoluene
2,6-dinitrotoluene
Methyl-2,4,6-trinitrophenylnitramine
2-amino-4,6-dinitrotoluene
4-amino-2,6-dinitrotoluene
Nitrotoluene (3 isomers)
Nitrobenzene
Hexahydro- 1 ,3,5-trinitro- 1 ,3,5-triazine
Octahydro-l,3,5,7-tetranitro-l,3,5,7-tetrazocine
Nitroguanidine
Nitrate Esters
NC
NG
PETN
Nitrocellulose
Nitroglycerin
Pentaerythritol tetranitrate
Field
Method
Cs
Cp,Ip
Cs,Is
Cs
Cp, Cs
Cs,Is
Cs
Is
Cs
Cp,Ip
Cs
Cs
Cs
Cs
Cs
Cs
Laboratory
Method
N
N
N
N
N
N
N
N
N
N
N
N
N
N
G
*L
*P
*P
Ammonium Picrate/Picric Acid
AP/PA Ammonium 2,4,6-trinitrophenoxide/2,4,6-trinitrophenol Cp, Is A
Cp = Colorimetric field method, primary target analyte(s).
Cs = Colorimetric field method, secondary target analyte(s).
Ip = Immunoassay field method, primary target analyte(s).
Is = Immunoassay field method, secondary target analyte(s).
N = EPA SW-846, Nitroaromatics and Nitramines by HPLC, Method 8330 (EPA 1995a).
P = PETN and NG (Walsh unpublished CRREL method).
G = Nitroguanidine (Walsh 1989).
L = Nitrocellulose (Walsh unpublished CRREL method).
A = Ammonium Picrate/Picric Acid (Thorne and Jenkins 1995a).
*The performance of a number of field methods have not been assessed utilizing "approved" laboratory
methods. It is recommended that verification of the performance of any analytical method be an integral
part of a sampling/analysis projects quality assurance program.
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The frequency of occurrence of specific explosives
in soils was assessed by Walsh et al. (1993), who
compiled analytical data on soils collected from 44
Army ammunition plants, arsenals, and depots, and two
explosive ordnance disposal sites. Of the 1,155 samples
analyzed by EPA Method 8330, atotal of 319 samples
(28%) contained detectable levels of explosives. The
frequency of occurrence and the maximum
concentrations detected are shown in Table 2. TNT was
the most commonly occurring compound in
contaminated samples and was detected in 66% of the
contaminated samples and in 80% of the samples if the
two explosive ordnance disposal sites are excluded.
Overall, either TNT or RDX or both were detected in
72% of the samples containing explosive residues, and
94% if the ordnance sites are excluded. Thus, by
screening for TNT and RDX at ammunition plants,
arsenals, and depots, 94% of the contaminated areas
could be identified (80% if only TNT was determined).
This demonstrates the feasibility of screening for one or
two compounds or classes of compounds to identify the
initial extent of contamination at munitions sites. The
two ordnance sites were predominantly contaminated
with DNTs, probably from improper detonation of
waste propellant. The table also shows that NB and
NTs were not detected in these samples; however, NTs
are found in waste produced from the manufacture of
DNT.
OVERVIEW OF SAMPLING AND ANALYSIS
FOR EXPLOSIVES IN SOIL
The environmental characteristics of munitions
compounds in soil indicate that they are extremely
heterogenous in spatial distribution. Concentrations
range from nondetectable levels (< 0.5 ppm) to percent
levels (> 10,000 ppm) for samples collected within
several feet of each other. In addition, the waste
disposal practices at these sites, such as OB/OD,
exacerbate the problem and may result in conditions
ranging from no soil contamination up to solid
"chunks" of bulk secondary explosives, such as TNT or
RDX. Secondary explosives concentrations above 10%
(> 100,000 ppm) in soil are also of concern from a
potential reactivity standpoint and may affect sample
and materials handling processes during remediation.
An explosives hazard safety analysis is needed for
materials handling equipment to prevent initiating
forces that could propagate a detonation throughout the
soil mass.
Reliance on laboratory analyses only for site
characterization may result in a large percentage of the
samples (up to 80% depending upon the site)
Table 2. Occurrence of Analytes Detected in Soil
Contaminated with Explosives.
% Sample
with Maximum Level
Compound Analyte (/•*§/§)
Present
Nitroaromatics
TNT
TNB
DNB
2,4-DNT
2,6-DNT
2-AmDNT
4-AmDNT
Tetryl
Nitramines
RDX
HMX
66
34
17
45
7
17
7
9
27
12
102,000
1790
61
318
4.5
373
11
1260
13,900
5700
TNT and/or RDX
72
Derived from Walsh et al. (1993).
with nondetectable levels. The remaining samples may
indicate concentrations within a range of four orders of
magnitude. Analyzing a small number of samples at an
off-site laboratory may result in inadequate site
characterization for estimating soil quantities for
remediation and may miss potentially reactive material.
Laboratory analytical costs vary depending on the
turnaround time required. Typical costs for EPA
Method 8330 analysis range from $250 to $350 per
sample for 30-day turnaround, $500 to $600 for 7-day
turnaround, and approximately $1,000 per sample for
3-day turnaround, if it is available.
Because of the extremely heterogeneous distrib-
ution of explosives in soils, on-site analytical
methods are a valuable, cost-effective tool to assess
the nature and extent of contamination. Because
costs per sample are lower, more samples can be
analyzed and the availability of near-real-time results
permit redesign of the sampling scheme while in the
field. On-site screening also facilitates more effective
use of off-site laboratories using more robust
analytical methods. Even if only on-site methods are
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used to determine the presence or absence of
contamination (i.e., all positive samples are sent
off-site for laboratory analysis), analytical costs can be
reduced considerably. Because on-site methods provide
near-real-time feedback, the results of screening can be
used to focus additional sampling on areas of known
contamination, thus possibly saving additional
mobilization and sampling efforts. This approach has
been successfully used for a Superfund remedial
investigation of an OB/OD site (Craig et al. 1993).
During site remediation, such as Superfund remedial
actions, data are needed on a near-real-time basis to
assess the progress of cleanup. On-site methods can be
used during remediation to guide excavation and
materials handling activities and to evaluate the need
for treatment on incremental quantities of soil (EPA
1992b). Final attainment of soil cleanup levels should
be determined by an approved laboratory method, such
as EPA Method 8330. This approach was effectively
used at a Superfund remedial action for an explosives
washout lagoon (Oresik et al. 1994; Markos et al.
1995).
DATA QUALITY OBJECTIVES
The EPA Data Quality Objectives process is
designed to facilitate the planning of environmental
data collection activities by specifying the intended
use of the data (what decision is to be made), the
decision criteria (action level), and the tolerable error
rates (EPA 1994; ASTM 1996). Integrated use of
on-site and laboratory methods for explosives in soil
facilitate achieving such objectives as determining
the horizontal and vertical extent of contamination,
obtaining data to conduct a risk assessment,
identifying candidate wastes for treatability studies,
identifying the volume of soil to be remediated,
determining whether soil presents a potential
detonation hazard (reactive according to RCRA
regulations), and determining whether remediation
activities have met the cleanup criteria.
Environmental data such as rates of occurrence,
average concentrations, and coefficients of variation
are typically highly variable for contaminants
associated with explosive sites. These differences are
a function of fate and transport properties,
occurrence in different media, and interactions with
other chemicals, in addition to use and disposal
practices. Information on frequency of occurrence
and coefficient of variation determines the number of
samples required to adequately characterize exposure
pathways and is essential in designing sampling
plans. Low frequencies of occurrence and high
coefficients of variation, such as with explosives,
mean that more samples will be required to
characterize the exposure pathways of interest.
Sampling variability typically contributes much more
to total error than analytical variability (EPA 1990,
1992a). Under these conditions, the major effort
should be to reduce sampling variability by taking
more samples using less expensive methods (EPA
1992a).
EPA's Guidance for Data Useability in Risk
Assessment (EPA 1992a) indicates that on-site
methods can produce legally defensible data if
appropriate method quality control is available and
if documentation is adequate. Field analyses can be
used to decrease cost and turnaround time as long as
supplemental data are available from an analytical
method capable of quantifying multiple explosive
analytes (e.g., Method 8330) (EPA 1992a).
Significant quality assurance oversight of field
analysis is recommended to enable the data to be
widely used. The accuracy (correctness of the
concentration value and a combination of both
systematic error [bias] and random error [precision])
of on-site measurements may not be as high in the
field as in fixed laboratories, but the quicker
turnaround and the possibility of analyzing a larger
number of samples more than compensates for this
factor. Remedial project managers, in consultation
with chemists and quality assurance personnel,
should set accuracy levels for each method and
proficiency standards for the on-site analyst.
On-site methods may be useful for analysis of
waste treatment residues, such as incineration ash,
compost, and bioslurry reactor sludges. However,
on-site methods should be evaluated against
laboratory methods on a site and matrix-specific
basis because of the possibility of matrix
interference. Treatability studies are used to evaluate
the potential of different treatment technologies to
degrade target and intermediate compounds and to
evaluate whether cleanup levels may be achieved for
site remediation. Treatability study waste for
explosives-contaminated soils should be of higher
than average concentration to evaluate the effects of
heterogeneous concentrations and for potential
toxicity effects for processes such as bioremediation.
During remediation of soils contaminated
with explosives, monitoring the rate of
degradation and determining when treatment
criteria have been met are necessary so that
residues below cleanup levels can be disposed
of and additional soil treated. Soils
contaminated with explosives are currently
being treated by incineration, composting, and
-------
solidification/stabilization (Noland et al. 1984;
Turkeltaub et al. 1989; EPA 1993; Craig and
Sisk 1994; Miller and Anderson 1995; Channell
et al. 1996). Other biological treatment systems
that have been evaluated for treating
explosives-contaminated soils include anaerobic
bioslurry, aerobic bioslurry, white rot fungus,
and land farming (Craig et al. 1995; Sundquist
etal. 1995).
UNIQUE SAMPLING DESIGN
CONSIDERATIONS FOR EXPLOSIVES
Heterogeneity Problems and Solutions
The heterogeneous distribution of explosives
in soil is often alluded to but seldom quantified.
The problem is probably considerably greater
for explosive residues in soil than most other
organic waste. From available Superfund site data,
the median coefficient of variation (CV) (standard
deviation divided by the mean) for volatile s,
extractables, pesticides/polychlorinated biphenyls
(PCBs), and tentatively identified compounds in
soils ranges from 0.21 to 54% for individual
contaminants (EPA 1992b). Data from 10 munitions
sites show the median CV for TNT was 284%, and
the TNT CV ranged from 127% to 335% for
individual sites. Comparable data for RDX are
median CV of 137% with a range of 129% to 203%,
and the median CVs for 2,4-DNT and AP/PA were
414% and 184% respectively. If the natural
variability of the chemicals of potential concern is
large (e.g., CV > 30%), the major planning effort
should be to collect more environmental samples
(EPA 1992b).
Jenkins et al. (1996a, 1996b) recently conducted
a study to quantify the short range sampling
variability and analytical error of soils contaminated
with explosives. Nine locations, three at each of
three different facilities, were sampled. At each
location, seven core samples were collected from a
circle with a radius of 61 cm: one from the center
and six equally spaced around the circumference.
The individual samples and a composite sample of
the seven samples were analyzed in duplicate,
on-site, using the EnSys RIS£ colorimetric soil test
kit for TNT (on-site method) and later by Method
8330 at an off-site laboratory. Results showed
extreme variation in concentration in five of the nine
locations, with the remaining four locations showing
more modest variability. For sites with modest
variability, only a small fraction of the total error was
because of analytical error, i.e., field sampling error
dominated total error. For the locations showing
extreme short-range heterogeneity, sampling error
overwhelmed analytical error. Contaminant
distributions were very site specific, dependant on a
number of variables such as waste disposal history,
the physical and chemical properties of the specific
explosive, and the soil type. The conclusion was that
to improve the quality of site characterization data,
the major effort should be placed on the use of
higher sampling densities and composite sampling
strategies to reduce sampling error.
There are several practical approaches to reducing
overall error during characterization of soils
contaminated with explosives, including increasing
the number of samples or sampling density,
collecting composite samples, using a stratified
sampling design, and reducing within sample
heterogeneity. Because explosives have very low
volatility, loss of analytes during field preparation of
composite samples is not a major concern.
Increasing the Number of Samples - One simple
way to improve spatial resolution during
characterization is by collecting more samples using
a finer sampling grid such as a 5-m grid spacing
instead of a 10-m spacing. Though desirable, this
approach has been rejected in the past because of the
higher sampling and analytical laboratory costs.
When inexpensive on-site analytical methods are
used, this approach becomes feasible. The slightly
lower accuracy associated with on-site methods is
more than compensated for by the greater number of
samples that can be analyzed and the resultant
reduction in total error.
Collection of Composite Samples - The
collection of composite samples is another very
effective means of reducing sampling error. Samples
are always taken to make inferences to a larger
volume of material, and a set of composite samples
from a heterogeneous population provides a more
precise estimate of the mean than a comparable
number of discrete samples. This occurs because
compositing is a "physical process of averaging"
(adequate mixing and subsampling of the composite
sample are essential to most compositing strategies).
Averages of samples have greater precision than the
individual samples. Decisions based on a set of
composite samples will, for practical purposes,
always provide greater statistical confidence than for
a comparable set of individual samples. In the study
discussed above by Jenkins et al. (1996a, 1996b), the
composite samples were much more representative of
each plot than the individual samples that made up
the composites. Using a composite sampling
strategy, usually allows the total number of samples
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analyzed to be reduced which reduces costs while
improving characterization. Compositing should be
used only when analytical costs are significant. An
American Society for Testing and Materials (ASTM)
guide was developed on composite sampling and
field subsampling (Gagner and Crockett, 1996),
(ASTM, 1997).
Stratified Sampling Designs - Stratified sampling
may also be effective in reducing field and
subsampling errors. Using historical data and site
knowledge or results from preliminary on-site
methods, it may be possible to identify areas in
which contaminant concentrations are expected to be
moderately heterogeneous (pond bottom) or
extremely heterogeneous (open detonation sites).
Different compositing and sampling strategies may
be used to characterize different areas that may result
in a more efficient characterization.
Another means of stratification is based on particle
size. Because explosive residues often exist in a wide
range of particle sizes (crystals to chunks), it is
possible to sieve samples into various size fractions
that may reduce heterogeneity. If large chunks of
explosive are present, it may be practical to
coarse-sieve a relatively large sample (many
kilograms), medium-sieve a portion of those fines,
and subsample the fines from medium screening as
well. This would yield three samples of different
particle size and presumes that heterogeneity
increases with coarseness. Each fraction would be
analyzed separately but not necessarily by the same
method (visual screening of the coarser fractions for
chunks of explosive may be possible) and then could
be summed to yield the concentration on a weight or
area basis. In addition, aqueous disposal of explosive
wastewaters such as washout lagoons or spill sites
often results in preferential sorption to fine-grained
materials, such as fines or clays, particularly for
nitroaromatics.
Reducing Within Sample Heterogeneity - The
heterogeneity of explosives in soils is frequently
observed during the use of on-site analytical methods
in which duplicate subsamples are analyzed and
differ by more than an order of magnitude. Grant et
al. (1993) conducted a holding time study using
field-contaminated soils that were air-dried, ground
with a mortar and pestle, sieved, subsampled in
triplicate, and analyzed using Method 8330. Even
with such sample preparation, the results failed to
yield satisfactory precision [the relative standard
deviations (RSDs) often exceeded 25% compared
with RSDs below 3% at two other sites].
Subsampling in the field is much more challenging
because complete sample processing is not feasible.
However, most screening procedures specify
relatively small samples, typically a few grams.
To reduce within-sample heterogeneity, two
methods can be employed: either homogenization
and extraction or analysis of a larger sample. Unless
directed otherwise, an analyst should assume that
information representative of the entire contents of
the sample container is desired. Therefore, the
subsample extracted or directly analyzed should be
representative of the container. The smaller the
volume of that subsample removed for analysis and
extraction, the more homogeneous the entire samples
should be before subsampling (e.g., a representative
0.5-g subsample is more difficult to obtain than a
20-g subsample from a 250-g sample). Collecting
representative 2-g subsamples from 300 g of soil is
difficult and can require considerable sample
processing such as drying, grinding, and riffle
splitting. Even in the laboratory, as discussed above,
obtaining representative subsamples is difficult. An
ASTM guide is being developed to help in this
regard (Gagner and Crockett 1996). While
sample-mixing procedures such as sieving to
disaggregate particles, mixing in plastic bags, etc.,
can and should be used to prepare a sample,
extracting a larger sample is perhaps the easiest
method of improving representativeness. For this
reason, 20 g of soil is extracted for the Cold Regions
Research and Engineering Laboratory (CRREL)
method, and the same approach may easily be used
to improve results with most of the on-site methods
shown in Table 3. The major disadvantage of
extracting the larger sample is the larger volume of
waste solvent and solvent-contaminated soil that
needs disposal.
The effectiveness of proper mixing in the field is
illustrated in the recent report by Jenkins et al.
(1996a, 1996b). Duplicate laboratory analyses of the
same samples, including drying, grinding, mixing,
and careful subsampling resulted in an RSD of 11%.
Because this field-mixing procedure was so effective
in homogenizing the sample, the sampling and
subsampling procedure is presented here (Jenkins et
al. 1996a). Soil cores (0 to 15 cm in length and 5.6
cm in diameter) were collected into plastic resealable
bags, and vegetation was removed. The sample of
dry soil, a mixture of sand and gravel, was placed
into 23-cm aluminum pie pans, the soil was broken
up using gloved hands, and large rocks were
7
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Table 3. Comparative Data for Selecting On-Site Analytical Methods for Explosives in Soil".
Method/
Kit
CRREL
EnSys RIS^S)
USAGE
D TECH™
Idetek Quantix™
EnviroGard™
Ohmicron RaPID Assay®
Criteria
Method Type
Analytes and EPA
Method No.
Colorimetric
TNT, RDX, 2,4-DNT,
Ammonium Picrate /Picric
Acid
Colorimetric
TNT: Method 85 15 draft
RDX: Method 8510
proposed
Colorimetric
TNT
Immunoassay - ELISA
TNT: Method 4050 draft
RDX: Method 4051 draft
Immunoassay - ELISA
Antigen- Antibody
TNT
Immunoassay - ELISA
TNT: Plate kit
TNT: Soil (tube) kit
Immunoassay - ELISA
Magnetic particle/tube
kit
TNT: Method 4050
proposed
Detection Range and
Range Factor
TNT: 1 to 22 mg/kg (22 X)
RDX: 1 to 20 mg/kg (20 X)
2,4-DNT: 2 to 20 mg/kg (10X)
AP/PA: 1.3 to 69 mg/kg (53 X)
TNT: 1 to 30 mg/kg (30 X)
RDX: 1 to 30 mg/kg (30 X)
6 to 100 mg/kg (17 X)
TNT: 0.5 to 5.0 mg/kg (10 X)
RDX: 0.5 to 6.0 mg/kg (12 X)
TNT: 0.25 to 100 mg/kg (400 X)
Plate kit: 1 to 100 mg/kg (100 X)
Tube kit: 0.2 to 15 mg/kg (75 X)
TNT: 0.07 to 5 mg/kg (71 X)
Type of Results
TNT, RDX: Quantitative
2,4-DNT: Semiquantitative
AP/PA: Quantitative
Quantitative
Quantitative
Semiquantitative
(concentration range)
Quantitative
Plate: Quantitative
Tube: Semiquantitative
(concentration range)
Quantitative
Samples per Batch
TNT: Batch or single
RDX: 6 to 7/batch or single
2,4-DNT & AP/PA: Single
or batched
Single
Single or batched
4 (single or batch)
20 to 40 (batch only)
Plate: batch of 8
Tube: batch of 14
5 to 5 1 (batch only)
Soil
Sample
Size
20 g
10 g
6g
3mL
(~4.5g)
-4.2 g
2g
10 g
Sample
Preparation
& Extraction
3 min shaking in 100
mL acetone; settling;
filtration.
Dry < 10% moisture
(optional); 3 min
shaking in 50 mL
acetone; 5 min settling
filtration.
1 min shaking in 35 m
methanol; settling;
filtration as needed.
3 min shaking in 6. 5
mL acetone; settle 1
to 10 min.
3 min shaking in 21
mL acetone; settle
several minutes.
Air dry soil, 2 min
shaking in 8 mL
acetone; filter.
1 min shaking in 20
mL methanol; settle
5 min; filter
Analysis Time -
Production Rate
(one person)
30 minute extract 6/samples;
TNT: 5 minutes/sample;
RDX: 30 minutes/6 RDX samples;
25 samples/day for TNT + RDX
DNT: 30 minutes/6 samples
AP/PA: 15 minutes/sample
TNT: 30 to 35 minutes/10 samples i
lab; estimated 40 to 45 minutes in
field.
RDX: 60 minutes/6 samples.
Optional drying time not included.
^10 to 20 samples/day depending on
soil characteristics
30 minutes for 1 to 4 samples for
TNT or RDX.
2.5 to 3.5 hours for 20 to 40 samples
Idetek estimates - 2 hours for up to '
TNT samples.
Plate: 90 minutes for 8 samples
Tube: 30 minutes for 14 samples
Drying time not included.
1 hour for 20 extractions; 45 minute
for analysis (51 samples)
"Expanded and modified from EPA 1995b
-------
Table 3. Comparative Data for Selecting On-Site Analytical Methods for Explosives in Soil "(continued).
Criteria
Method/
Kit
Interferences and Cross-reactivities > 1% based on IC50 (see text)
Recommended QA/QC
Storage Conditions and
Shelf Life of Kit or
Reagents
Skill Level
CRREL
TNT = TNT + TNB + DNB + DNTs + tetryl;
- detection limits (ppm); TNB 0.5; DNB < 0.5; 2,4-DNT 0.5; 2,6-DNT 2.1; tetryl 0.9
RDX = RDX + HMX + PETN+ NQ + NC + NG
- detection limits (ppm); HMX 2.4; PETN 1; NQ 10; NC 42; NG 9
Soil moisture > 10%, and humics interfere with TNT and RDX; nitrate and nitrite interfere with RDX.
2,4-DNT = 2,4-DNT + 2,6-DNT + TNT + TNB + tetryl; high copper, moisture and humics interfere.
AP/PA = relatively free of humic and nitroaromatic interferences.
Blank and calibration standards
analyzed daily before and after
sample analyses. Blank and spiked
soil run daily.
Store at room temperature.
Medium
EnSys RIS^S
TNT = TNT + TNB + DNB + DNTs + tetryl;
- detection limits (ppm); TNB 0.5; DNB < 0.5; 2,4-DNT 0.5; 2,6-DNT 2.1; tetryl 0.9
RDX = RDX + HMX + PETN + NQ + NC + NG
- detection limits (ppm); HMX 2.4; PETN 1; NQ 10; NC 42; NG 9
Soil moisture > 10%, and humics interfere with TNT and RDX; nitrate and nitrite interfere with RDX.
Method and soil blanks and a
control sample daily, one
duplicate/20 samples.
Some positive field results (1:10)
should be confirmed.
Store at room temperature.
Shelf life:
TNT = 2 to 24 months at 27°C
RDX = 2 to 12 months at 27 °C
TNT: Low
RDX: Medium
USAGE
TNB interferes by raising minimum detection limit.
Blank soil sample, and calibration
standard prepared from clean site
soil.
Store at room temperature
Medium
D TECH™
Cross reactivity:
TNT: tetryl =35%; TNB = 23%; 2AmDNT=ll%; 2,4-DNT = 4%;
AP/PA unknown but —100% at lower limit of detection
RDX: HMX = 3%
Samples testing positive should be
confirmed using standard methods.
Store at room temperature or
refrigerate; do not freeze or exceed
37°C for prolonged period. Shelf
life 9 months at room temperature
Low
Idetek Quantix1
1 Cross reactivity:
TNB = 47%; tetryl = 6.5%; 2,4-DNT = 2%; 4AmDNT = 2%
Duplicate extractions
1 in 10 replicate
2 sample wells/extract
Refrigerate 2 to 8°C, do not freeze or
exceed 37 °C. Shelf life 9 to 12
months. Avoid direct light.
Medium-high, initial
training recommended
EnviroGard11
Cross reactivity:
Plate: 4-AmDNT = 41%; 2,6-DNT =41%; TNB = 7%; 2,4-DNT = 2%
Tube: 2,6-DNT = 20%; 4AmDNT=17%; TNB = 3%; 2,4-DNT = 2%
Plate: Samples run in duplicate.
Store 4 to 8° C; do not freeze or
exceed 37°C. Do not expose
substrate to direct sunlight.
Shelf life: Plate 3 to 14 months.
Tube 3 to 6 months.
Plate: Medium-high
Tube: Medium
Ohmicron RaPII) Cross reactivity:
Assay® TNB = 65%; 2,4-Dinitroaniline = 6%; tetryl = 5%; 2,4-DNT = 4%; 2AmDNT = 3%;
DNB = 2%
Duplicate standard curves; positive
control sample supplied. Positive
results requiring action may need
confirmation by another method.
Refrigerate reagents 2 to 8°C.
Do not freeze.
Shelf life 3 to 12 months.
Medium-high, initial
training recommended
"Expanded and modified from EPA 1995b
-------
Table 3. Comparative Data for Selecting On-Site Analytical Methods for Explosives in Soil "(continued).
Methot
Kit
CRREL
EnSys RlS^d
USAGE
D TECH™
Idetek
Quantix™
Enviro-
Gard™
Ohmicron
RaPID Assa
Criteria
/ Training
Availability
Free video for TNT and
RDX, see text for addre
None available for 2,4-
DNT, AP/PA.
) Training available.
Applicable video on
CRREL method availab
address in text.
None available.
2 to 4 hours free on-site
training.
1 day free on-site
training.
Free training available.
4 hours free on-site
'(training.
Costs
(not including labor)
$15/sample plus $1,500 for
>sHach spectrometer.
$2 I/sample for TNT,
$25/sample for RDX plus
e$160/day or $430/wkfor lab
station. Lab station cost =
$1,950
$4/sample or $5/sample if
filtered plus $1,500 for
Hach spectrometer
$30/sample for TNT or RDX
plus $300 for DTECHTOR
(optional)
$2 I/sample for TNT plus
$5,880 for lab station or
$500/month rental.
Plate: $17/sample plus $4129
for equip. & small supplies.
Tube: $20/sample plus $2409
for equip. & small supplies.
$13 to $20/sample plus $5,500
for equip, (purchase) or $800
for first month, $400 each
additional month (rental).
Comparisons to Method 8330
References
Brouillard et al. 1993; EPA 1993, 1995a
(Method 85 15), 1995b;
Jenkins 1990; Jenkins and Walsh 1992;
Markos et al. 1995; Lang et al. 1990;
Walsh and Jenkins 1991;
Jenkins et al. 1996a; Jenkins and Walsh
1991, 1992; Thorne and Jenkins 1995a
EPA 1995a (Method 8515); EPA 1995b;
IT 1995; Jenkins etal. 1996a, 1996b;
Markos et al. 1995; Myers et al. 1994.
IT 1995; Medary 1992
EPA 1995a (Methods 4050 and 4051);
EPA 1995b; Haas and Simmons 1995;
Markos et al. 1995; Myers et al. 1994;
Teaney and Hudak 1994
EPA 1995b; Haas and Simmons 1995;
Markos et al. 1995
Haas and Simmons 1995
EPA 1995b; Haas and Simmons 1995;
Markos et al. 1995; Rubio et al. 1996
Other
Reference
Jenkins
et al. 1995;
Thorne and
Jenkins
1995b
Teaney et al.
1993.
Calif. EPA
1996a and
1996b
Calif. EPA
1996c
Calif. EPA
1996d
Developer
s Information
Dr. Thomas F. Jenkins
CRREL
72 Lyme Road
Hanover, NH 03755- 1290
(603) 646-4385
Strategic Diagnostics, Inc.
375 Pheasant Run
Newtown, PA 18940
(800) 544-8881
Dr. Richard Medary
U.S. Army Corps of Eng.
60 IE. 12th Street
Kansas City, MO 64106
(816)426-7882
Strategic Diagnostics, Inc.
375 Pheasant Run
Newtown, PA 18940
(800) 544-8881
Idetek, Inc.
1245 Reamwood Ave.
Sunnyvale, CA 94089
(800)433-8351
Strategic Diagnostics, Inc.
375 Pheasant Run
Newtown, PA 18940
(800) 544-8881
Strategic Diagnostics, Inc.
375 Pheasant Run
Newtown, PA 18940
(800) 544-8881
Additional Considerations
Large work area (2 large desks); requires the most setup time;
possible TNB interference, no electricity or refrigeration
required; deionized water required; must assemble materials;
glassware must be rinsed between analyses; larger volume of
acetone waste, color indicative of compounds.
Large work area (desk size) power supply required to charge
Hach spectrometer; possible TNB interference; color indication
of other compounds; requires acetone and deionized water;
cuvettes must be rinsed between analyses. Nitrate and nitrate
interferences with RDX kit can be corrected using alumin-a-
cartridges from EnSys.
Large work area (2 large desks); requires the most setup time;
possible TNB interference; no electricity or refrigeration
required; must assemble materials; glassware must be rinsed
between analyses.
Small working area; few setup requirements; no electricity or
refrigeration required; temperature dependent development
time (effect can be reduced by changing DTECHTOR setting);
significant amount of packing; relatively narrow range; no
check on test; easy to transport or carry; kits can be
customized. Out-or range reruns require use of another kit.
Large work area (desk); requires setup time, electricity,
refrigeration and deionized water; requires careful washing of
microwells; replicate run for each sample, average of the two
is the result; less temperature dependent. Out of range reruns
require use of another kit.
Large work area (desk size); requires setup time, refrigeration
and power; acetone not supplied. Out-of-range reruns require
use of another kit.
Large work area (desk); requires setup time, electricity and
refrigeration; less temperature dependent; low detection limit;
all reagents supplied; reagents and kit need refrigeration.
Out-of-range reruns require use of another kit.
"Expanded and modified from EPA 1995b
-------
removed (sieving may work well too). A second pie
pan was used to cover the sample, which was then
shaken and swirled vigorously to disperse and
homogenize the soil. The sample was then coned
and quartered, and 5 g subsamples were removed
from each quarter and composited to form the 20-g
sample for analysis. Splits of the same sample were
obtained by remixing the soil and repeating the
coning and quartering.
Wilson (1992) studied sample preparation
procedures for homogenizing compost prior to
analysis for explosives. Wilson (1992) method
involves macerating air-dried compost using a No.
4 Wiley mill followed by sample splitting using a
Jones-type riffle splitter. The improved method
decreased the RSD from more than 200% to 3% for
TNT analyses.
Sample Holding Times and Preservation
Procedures
The EPA-specified holding time for nitroaromatic
compounds in soil is 7 days until extraction and
extracts must be analyzed within the following 40
days (EPA 1995a). The specified sample pre-
servation procedure is cooling to 4°C. This criterion
was based on professional judgment rather than
experimental data.
Two significant holding time studies have been
conducted on explosives (Maskarinec et al. 1991;
Grant et al. 1993, 1995). Based on spiking clean
soils with explosives in acetonitrile, Maskarinec
recommended the following holding times and
conditions: TNT—immediate freezing and 233 days
at -20 °C; DNT—107 days at 4°C; RDX—107 days
at 4°C; and HMX—52 days at 4°C. Grant spiked
soils with explosives dissolved in water to eliminate
any acetonitrile effects and also used a
field-contaminated soil. The results on spiked soils
showed that RDX and HMX are stable for at least 8
weeks when refrigerated (2°C) or frozen (-15 °C)
but that significant degradation of TNT and TNB
degradation can occur within 2 hours without
preservation. Freezing provides adequate
preservation of spiked 2,4-DNT for 8 weeks or
longer. The results on field-contaminated soils did
not show the rapid degradation of TNT and TNB
that was observed in the spiked soils, and
refrigeration appeared satisfactory. Presumably, the
explosives still present in the field soil after many
years of exposure are less biologically available than
in the spiked soils.
Another study (Bauer et al. 1990) has shown that
explosives in spiked, air-dried soils are stable for a
62-day period under refrigeration. Data from the
Grant et al. (1993) study indicate that air drying of
field-contaminated soils may not result in
significant losses of explosive contaminants.
Explosives in air-dried soils are stable at room
temperature if they are kept in the dark.
Acetonitrile extracts of soil samples are expected
to be stable for at least 6 months under refrigeration.
Acetone extracts also are thought to be stable if the
extracts are stored in the dark under refrigeration
(acetone enhances photodegradation of explosives).
Explosion Hazards and Shipping Limitations
The Department of Defense Explosive Safety
Board approved the two-test protocol (Zero Gap and
Deflagration to Detonation Transition tests) in
March 1988 for determining the explosive reactivity
of explosive-contaminated soil. Tests on TNT and
RDX in sands with varied water content showed that
soils with 12% or more explosive are susceptible to
initiation by flame, and soils containing more than
15% explosives are subject to initiation by shock
(EPA 1993). Explosives exist as particles in soil
ranging in size from crystals to chunks, which can
detonate if initiated. However, if the concentration
of explosives is less than 12%, the reaction will not
propagate. The water content of the soil has minimal
effects on reactivity. The test results apply to total
weight percent of secondary explosives such as
TNT, RDX, HMX, DNT, TNB, and DNB. The tests
do not apply to primary or initiating explosives such
as lead azide, lead styphnate, and mercury
fulminate. As a conservative limit, the EPA Regions
and the U.S. Army Environmental Center consider
soils containing more than 10% secondary
explosives, on a dry weight basis, to be susceptible
to initiation and propagation (EPA 1993). If
chemical analyses indicate that a sample is below
10% explosives by dry weight, that sample is
considered to be nonreactive. In most cases, this
eliminates the requirement to conduct the expensive
two-test reactivity protocol.
In sampling to determine whether an explosion
hazard exists, a biased sampling approach must be
adopted (Sisk 1992). Soils suspected of having high
concentrations of explosives should be
grab-sampled and analyzed to determine whether
the level of explosives exceeds 10%. Samples to be
shipped for off-site analysis must be subsampled
11
-------
and analyzed on-site. Explosive residues are usually concentrated in the top 5 to 10 cm of soil; therefore,
deep samples must not be collected, blended, and
analyzed to determine reactivity. Vertical
compositing of surficial soils with high levels of
explosives with deeper, relatively clean material
provides a false indication of reactivity. Soils
containing explosive residues over the 10% level
can, using proper precautions, be blended with
cleaner material to reduce the reactivity hazard and
permit shipment to an off-site laboratory. The
dilution factor must be provided with the sample. If
analytical results indicate that explosives are present
at a concentration of 10% or greater, the samples
must be shipped to an explosives-capable laboratory
for analysis. The samples must be packaged and
shipped in accordance with applicable Department of
Transportation and EPA regulations for reactive
hazardous waste and Class A explosives (AEC 1994).
In addition to the above information, the Army
Environmental Center requires certain minimum
safety precautions, as summarized below, for field
sampling work at sites with unknown or greater than
10% by weight of secondary explosives contam-
ination (AEC 1994). An extensive records search
and historical documentation review must be
conducted regarding the contaminated area to
identify the specific explosives present, determine
how the area became contaminated, estimate the
extent of contamination, and determine the period of
use. Personnel responsible for taking, packaging,
shipping, and analyzing samples must be
knowledgeable and experienced in working with
explosives. Soil samples must be taken using
nonsparking tools, and wetting the sampling area
with water may be necessary. If plastic equipment is
used, it must be conductive and grounded. Sample
containers must be chemically compatible with the
specific explosive, and screw tops are prohibited.
Samples are to be field screened for explosives if
possible. Sufficient soil samples must be collected
to characterize the site in a three-dimensional basis
in terms of percent secondary explosives
contamination with particular attention paid to
identifying hot spots, chunks of explosives, layers of
explosives, discolorations of the soil, etc.
In screening samples for reactivity, it should be
remembered that most screening procedures test for
only one analyte or class of analyte. Without other
supporting knowledge, concluding that a soil is not
reactive based upon just one analysis could be
dangerous. For assessing reactivity when multiple
compounds are present at high levels, the CRREL
12
-------
and EnSys RIS£ colorimetric methods for TNT and
RDX are more appropriate than immunoassay test
kits because colorimetric tests detect a broader
range of explosive analytes. Some conservatism in
evaluating potential reactivity using colorimetric
methods is appropriate. For example, Jenkins et al.
(1996c) recommended using a limit of 7%
explosives for conservatively estimating the lower
limit of potential reactivity. High levels of
explosives in soils may result in a low bias for
on-site methods because of low extraction
efficiencies. Colorimetric tests of chemical
composition are used only to estimate potential
reactivity. There are no on-site methods available to
actually determine explosive reactivity. Explosive
reactivity is a determination made from validated
laboratory analyses.
PROCEDURES FOR STATISTICALLY
COMPARING ON-SITE AND REFERENCE
ANALYTICAL METHODS
When on-site methods are used, their performance
needs to be evaluated and this is commonly done by
analyzing splits of some soil samples by both the
on-site method and a reference method (commonly
Method 8330). The performance of the on-site
method is then statistically compared to the
reference method using a variety of methods,
depending upon the objective and the characteristics
of the data. In most cases, measures of precision and
bias are determined. Precision refers to the
agreement among a set of replicate measurements
and is commonly reported as the RSD (standard
deviation divided by the mean and expressed as a
percent), the coefficient of variation (standard
deviation divided by the mean), or the relative
percent difference. Bias refers to systematic
deviation from the true value.
The following discussion of statistical methods
applies to comparisons of analytical results based on
paired sample data, e.g., soil samples are analyzed
by both an on-site method and a reference method,
or soil extracts are analyzed by two different on-site
methods. Care must be taken in interpreting the
result. For example, if subsamples of a jar of soil
(splits) are analyzed by an on-site and reference
method, the differences detected may be caused by
subsampling error (sample was not homogeneous
and the splits actually contained different
concentrations of explosives), extraction efficiency
(shaking with acetone versus ultrasonication with
acetonitrile) rather than the analytical methods
which may also produce different results. However,
if a group of acetone extracts are analyzed by two
different on-site methods, the subsampling and ex-
traction errors are minimized and any significant
differences should be from the analytical methods.
Precision and Bias Tests for Measurements of
Relatively Homogenous Material - When multiple
splits of well-homogenized soil samples are
analyzed using different analytical methods,
statistical procedures described in Grubbs (1973),
Blackwood and Bradley (1991), and Christensen
and Blackwood (1993) may be used compare the
precision and bias of the methods. Grubbs (1973)
describes a statistical approach appropriate for
comparing the precision of two methods that takes
into account the high correlation between the
measurements from each method. An advantage of
Grubbs' approach is that it provides unbiased
estimates of each method's precision by partitioning
the variance of the measurement results into its
component parts (e.g., variance caused by
subsampling and by the analytical method).
Blackwood and Bradley (1991) extend Grubbs'
approach to a simultaneous test for equal precision
and bias of two methods. Christensen and
Blackwood (1993) provide similar tests for
evaluating more than two methods.
For comparisons involving bias alone, t-tests or
analysis of variance may be performed. For
comparing two methods, paired t-tests are
appropriate for assessing relative bias (assuming
normality of the data, otherwise data
transformations to achieve normality must be
applied, or nonparametric tests used). A paired t-test
can be used to test whether the concentration as
determined by an on-site method is significantly
different from Method 8330 or any other reference
method. For comparing multiple methods, a
randomized complete block analysis of variance can
be used, where the methods are the treatments and
each set of split samples constitutes a block.
These tests are best applied when the
concentrations of explosives are all of
approximately the same magnitude. As the
variability in the sample concentration increases, the
capability of these tests for detecting differences in
precision or bias decreases. The variability in the
13
-------
true quantities in the samples is of concern, and high
variability in sample results caused by poor
precision rather than variability in the true
concentration is well handled by these methods.
Precision and Bias Tests for Measurements
over Large Value Ranges - When the
concentrations of explosives cover a large range of
values, regression methods for assessing precision
and accuracy become appropriate. Regression
analysis is useful because it allows characterization
of nonconstant precision and bias effects and
because the analysis used to obtain prediction
intervals for new measurements (e.g., the results of
an on-site method can be used to predict the
concentration if the samples were analyzed by a
reference method).
In a regression analysis, the less precise on-site
method is generally treated as the dependent
variable and the more precise reference analytical
method (e.g., SW-846 Method 8330) as the
independent variable. To the extent that the
relationship is linear and the slope differs from a
value of 1.0, there is an indication of a constant
relative bias in the on-site method (i.e., the two
methods differ by a fixed percentage). Bias should
be expected if on-site methods based on wet-weight
contaminant levels are compared to laboratory
methods based on the dry weight of soil samples.
Similarly, an intercept value significantly different
from zero indicates a constant absolute bias (i.e., the
two methods differ by a fixed absolute quantity).
There, may of course be both fixed and relative bias
components present.
When uncertainty is associated with the
concentration of an explosive as measured by the
reference method, standard least squares regression
analysis can produce misleading results. Standard
least squares regression assumes that the
independent variable values are known exactly as in
standard reference material. When the on-site
method results contain appreciable error compared
to the reference method, regression and variability
estimates are biased. This is known as an
errors-in-variables problem.
Because of the errors-in-variables problem, the
slope coefficient in the regression of the on-site data
on the reference data will generally be biased low.
Hence a standard regression test to determine
whether the slope is significantly different from 1
can reject the null hypothesis even when there is in
fact no difference in the true bias of the two
methods. A similar argument applies to tests of the
intercept value being equal to zero.
To perform a proper errors-in-variables regression
requires consideration of the measurement errors in
both variables. The appropriate methods are
outlined in Mandel (1984). These methods require
estimating the ratio of the random error variance for
the on-site method to that of the reference analytical
method. With split sample data, suitable estimates
of these ratios may generally be obtained by using
variance estimates from Grubbs' test or the related
tests mentioned above.
If the variance ratio is not constant over the range
under study, more complicated models than those
analyzed in Mandel (1984) must be employed.
Alternatively, transformations of the data might
stabilize the variance ratio. Note that it is the
variance ratio, not the individual variances, that
must remain constant. The ratio of variances for two
methods with nonconstant absolute variances but
constant relative variances will still have a constant
variance ratio.
Two other caveats about the use of regression
techniques also are appropriate. First, standard
regression methods produce bias regression
parameters estimation and may produce misleading
uncertainty intervals. Similarly, the interpretation
of R-squared values also is affected. Second, per-
forming regressions on data sets in which samples
with concentrations below the detection limit (for
one or both methods) have been eliminated may also
result in biased regression estimates, no matter
which regression analysis method is used.
Comparison to Regulatory Thresholds, Action
Limits, etc. - When the purpose of sampling is to
make a decision based on comparison of results to a
specific value such as an action level for cleanup,
on-site and reference analytical method results may
be compared simply on the basis of how well the
two methods agree regarding the decision. The
appropriate statistical tests are based on the
binomial distribution and include tests of equality of
proportions and chi-square tests comparing the
sensitivity and specificity (or false positive and false
negative rates) of the on-site method relative to the
14
-------
reference analytical method. Note that any measure
of consistency between the two methods is affected
by how close the true values in the samples are to
the action level. The closer the true values are to the
action level, the less the two methods will agree,
even if they are of equal accuracy. For example, if
the action level is 30 //g/g and most samples have
levels of above 1000 //g/g, the agreement between
the on-site method and reference should be very
good. If, however, the concentration in most
samples is 5 to 100 //g/g , the two methods will be
much more likely to disagree. This must be kept in
mind when interpreting results, especially when
comparing across different studies that may have
collected samples at considerably different analyte
levels.
SUMMARY OF ON-SITE ANALYTICAL
METHODS FOR EXPLOSIVES IN SOIL
There is considerable interest in field methods for
rapidly and economically determining the presence
and concentration of secondary explosives in soil.
Such procedures allow much greater flexibility in
mapping the extent of contamination, redesigning a
sampling plan based on near-real-time data,
accruing more detailed characterization for a fixed
cost, and guiding continuous remedial efforts.
Ideally, screening methods provide high-quality data
on a near-real-time basis at low cost and of
sufficient quality to meet all intended uses including
risk assessments and final site clearances without
the need for more rigorous procedures. While the
currently available screening procedures may not be
ideal (not capable of providing compound specific
concentrations of multiple compounds simul-
taneously), they have proved to be very valuable
during the characterization and remediation of
numerous sites. Currently, available field methods
that have been evaluated against standard analytical
methods and demonstrated in the field include
colorimetric and immunoassay methods (Table 4).
Each method has relative advantages and
disadvantages, so that one method may not be
optimal for all applications. To assist in the
selection of one or more screening methods for
various users needs, Table 3 (modified and
expanded from EPA 1995b) provides information
on on-site test kits for detecting explosives in soil.
Selection criteria are discussed in the following
sections.
Table 4. Available On-Site Analytical Methods
for Explosives in Soil.
Analyte(s)
A. Nitroaromatics
l.TNT
2. TNB
3. DNT
4. Tetryl
B. Nitramines
l.RDX
2. HMX
3. NQ
C. Nitrate Esters
l.NC
2. NG
3. PETN
D. AP/PA
Type Test
Colorimetric
Colorimetric
Colorimetric
Immunoassay
Colorimetric
Immunoassay
Colorimetric
Colorimetric
Colorimetric
Colorimetric
Immunoassay
Colorimetric
Colorimetric
Colorimetric
Colorimetric
Colorimetric
Colorimetric
Colorimetric
Developer/Test Kit
CRREL1, Ensys RIS%>
CRREL, Ensys RIS^®
USAGE2
D TECH™
Idetek Quantix™
Ohmicron RaPID Assay®
EnviroGard™
CRREL, EnSys RIS^D
Ohmicron RaPID Assay®
CRREL, EnSys RIS^D
CRREL
CRREL, EnSys RIS^D
CRREL, EnSys RIS^D
D TECH™
CRREL, EnSsy RIS^D
CRREL
CRREL
CRREL
CRREL
CRREL
CRREL
'U.S. Army Cold Regions Research and Engineering Laboratory.
2U.S. Army Corps of Engineers, Kansas City District.
The two types of currently available on-site
methods, colorimetric and immunoassay, are
fundamentally quite different. Both methods start
with extracting a 2- to 20-g soil sample with 6.5 to
100 mL acetone or methanol for a period of 1 to 3
minutes followed by settling and possibly filtration.
The basic procedure in the CRREL and EnSys RIS£
colorimetric methods for TNT is to add a strong
base (KOH) to the acetone extract, which produces
the red-colored Janowsky anion. Absorbance is then
measured at 540 nanometers (nm) using a
spectrophotometer. The TNT concentration is
calculated by comparing results to a control sample.
The RDX test involves a couple of more steps.
The various immunoassay methods differ
considerably in their steps with the D TECH method
for TNT being the simplest. In the D TECH kit,
antibodies specific for TNT and closely related
compounds are linked to solid particles. The TNT
molecules in the soil extract are captured by the
solid particles and collected on the membrane of a
15
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cup assembly. A color-developing solution is added
to the cup assembly and the presence (or absence) of
TNT is determined by comparing the solution in the
assembly cup to a color card or by using the simple
field test meter. The color is inversely proportional
to the concentration of TNT.
Method Type, Analytes, and EPA Method
Number
The first criteria column in Table 3 lists the type
of soil screening method, the analytes it detects, and
the EPA SW-846 draft or proposed method number.
A commercially available colorimetric kit, EnSys
RIS£, is used to determine TNT and RDX in soil.
EnSys RIS£ is the commercial version of the CRPvEL
method for TNT and RDX. In addition to the
CRREL method the U.S. Army Corps of Engineers
(USAGE) developed a colorimetric method for
TNT. The EnSys RIS£ and CRREL colorimetric
methods can also be used to determine
nitroaromatics (TNB, DNB, DNTs, tetryl),
nitramines (HMX, and NQ), nitrate esters (NC, NG,
and PETN), and AP/PA.
Two companies, Idetek Inc. and Strategic
Diagnostics Inc. manufacture commercial enzyme
linked immunosorbent assay (ELISA) kits to detect
TNT in soil. Idetek, Inc. produces the Quantix kit
(both a plate and tube method are available), and
Strategic Diagnostics, Inc., offers D TECH, Enviro-
Gard, and Ohmicron RaPID Assay. D TECH kits are
also available for RDX. Other explosives
compounds can sometimes be detected using
immunoassay kits because their cross reactivity (see
Interferences and Cross Reactivity section). The
EnviroGard TNT immunoassay kit was formerly
produced by Millipore Corp.
Detection Limits and Range
The lower detection limits of most methods are
near or below 1 part per million (ppm). The
detection range of a test kit can be important, and a
broad range is generally more desirable. The
importance of the range depends on the range of
concentrations expected in samples, the ability to
estimate the approximate concentration from the
sample extract, the amount of effort required to
dilute and rerun a sample and the sampling and
analytical objective. Some test kits have a range
factor (upper limit of range + lower limit) of just
one order of magnitude (10X), while other methods
span two or more orders of magnitude (100 to
400X). Because explosives concentrations in soil
may range five orders of magnitude (100,OOOX),
reanalyzing many out-of-range samples may be
necessary. The D TECH immunoassay methods
require an additional test kit to run each sample
dilution. Other immunoassay methods can run
dilutions in the same analytical run, but one must
prepare the dilutions without knowing whether they
are needed. The CRREL, USAGE, and EnSys RIS£
colorimetric procedures for RDX provide sufficient
reagent to allow running several dilutions at no
additional cost. For the EnSys RIS£ TNT kit, the
color developed can simply be diluted and reread in
the spectrophotometer. The procedures that the test
methods use for samples requiring dilution should
be evaluated as part of the site-specific data quality
objectives.
The detection range of a kit becomes much less
relevant when the objective is to determine whether
a soil is above or below a single action limit; the
same dilution can be used for all samples. In some
cases, changing the range of a kit may be desirable
to facilitate decision-making. If a method has a
range 1 to 10 ppm and the contamination level of
concern is 30 ppm, diluting all samples (using
acetone or methanol or as directed by the
instructions) by a factor of five would change the
test kit range to 5 to 50 ppm and permit decisions to
be made without additional dilutions.
Cleanup levels for explosives in soil vary
considerably depending upon the site conditions,
compound present and their relative concentration,
threats to groundwater, results of risk assessments,
remedial technology, etc. (EPA 1993). Based on a
review of data from many sites, Craig et al. (1995)
suggested preliminary remediation goals of 30 ppm
for TNT, 50 ppm for RDX, and 5 ppm for 2,4-DNT
and 2,6-DNT.
Type of Results
The type of results provided by the various
screening methods are quantitative or
semiquantitative. The CRREL (TNT, RDX, and
AP/PA), EnSys RIS£, USAGE, Idetek Quantix,
Ohmicron RaPID Assay, and EnviroGard (Plate)
kits are quantitative methods, providing a numerical
value. The CRREL 2,4-DNT method is considered
16
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semiquantitative and provides a somewhat less
accurate numerical value. The D TECH and
EnviroGard (Tube) test kits are semiquantitative
(concentration range), and indicate that the level of
an analyte is within one of several ranges. For
example, the D TECH TNT soil kit, without
dilution, indicates a concentration within one of the
following ranges: < 0.5, 0.5 to 1.5, 1.5 to 2.5, 2.5 to
4.5, 4.5 to 6.0, and > 6.0 ppm.
Samples per Batch
Several of the available test kits are designed to
run batches of samples or single samples or both.
Using a test kit designed for analyzing a large batch
to analyze one or two samples may not be very
cost-effective or efficient. In most cases, samples
may easily be batched for extraction and processed
simultaneously.
Sample Size
The size of the soil sample extracted contributes
to the representativeness of a sample. Explosive
residues in soil are quite heterogeneously distributed
(Jenkins et al. 1996a, 1996b), and as the subsample
size actually extracted decreases, heterogeneity
increases. While sample preparation procedures
such as drying, mixing, sieving, and splitting can
reduce within sample heterogeneity, such
procedures can be time-consuming. Based on work
by Jenkins et al. (1996b), field compositing and
homogenization greatly improve sample
representativeness. The commercial test kits use 2 to
10 g of soil, while the CRREL methods extract 20 g
of soil to improve the representativeness of the
results. For some test kits, it is possible to extract a
larger sample using solvent and glassware not
provided in the kit, and then using the required
volume of extract for the analytical steps. The
smaller the sample size, the more important is the
mixing of the sample before subsampling.
Sample Preparation and Extraction
Soil extractions procedures for most of the
screening methods are similar, shaking 2 to 20 g of
soil in 6.5 to 100 mL of solvent (acetone or
methanol) for 1 to 3 minutes. This may be followed
by settling or filtration or both. One test kit
(EnviroGard) specifies air drying and for the EnSys
RIS£ colorimetric test kits, drying to less than 10%
moisture is optional. For the CRREL methods,
samples must contain 2 to 3% water by weight,
therefore, water must be added to the extract for
very dry soils or incomplete color development will
occur, resulting in a false negative.
The solvent extraction times of 1 to 3 minutes
used in on-site methods result in incomplete
extraction of explosives compared with the 18-hour
ultrasonic bath extraction step used in EPA Method
8330. The percent of explosives extracted is
sample-specific but is generally higher for high
concentration samples, higher for sandy soils, lower
for clayey soils, and lower if 1-minute extractions
are used relative to 3-minute extractions. For most
soils, a 3-minute extraction time is adequate; ratios
of 3-minute versus 18-hour extractions of TNT and
RDX using acetone or methanol range from 66 to
109% as reported by Jenkins et al. (1996c). Jenkins
recommends at least a 3-minute solvent extraction
procedure for explosives. When pinpointing
concentrations, a short kinetic study should be
conducted of the specific soils encountered at a site
(Jenkins et al. 1996c). The kinetic study would
involve analyzing an aliquot of extract after 3
minutes of shaking, and again after 10, 30, and 60
minutes of standing followed by another 3 minutes
of shaking. If the concentration of explosives in-
creased significantly with the longer extraction time,
a longer extraction period is needed. Jenkins et al.
(1996a) found that 30-minute extraction times
worked well for clay soils at the Volunteer Army
Ammunition Plant, Chattanooga, Tennessee. Where
multiple analytes are of interest in each sample, a
common extract may be used for both the
colorimetric and immunoassay test methods.
Analysis Time
The analysis time or throughput for the
colorimetric and immunoassay procedures ranges
from 3 to 11 minutes per sample for batch runs. The
EnviroGard kits specify air drying of samples
(which would add considerable time), and drying is
optional with the EnSys RIS£ colorimetric kits.
Cragin et al. (1985) investigated various procedures
for drying soils contaminated with explosives
including air, oven, desiccator, and microwave
drying. Air and desiccator drying appear to result in
only minor losses of explosives. Oven drying of
highly contaminated soil (15% TNT) at 105°C for
an unspecified period resulted in a 25% loss of
17
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TNT; however, oven drying of less-contaminated
samples, for only 1 hour, resulted in little loss of
TNT and 30 minutes of drying was estimated to be
sufficient for analytical purposes. Microwave drying
was not recommended because of spotty heating and
drying. In addition, microwave drying should not be
used because it may present a safety hazard and
such drying degrades thermally unstable explosives
in the soil. The effective production rate depends on
the number of reruns required because a sample is
out of the detection range.
Interferences and Cross-Reactivity
One of the major differences among the field
methods is interference for colorimetric methods
and cross-reactivity for immunoassay methods. The
colorimetric methods for TNT and RDX are broadly
class sensitive; that is, they are able to detect the
presence of the target analyte but also respond to
many other similar compounds (nitroaromatics and
nitramines/nitrate esters, respectively). For
colorimetric methods, interference is defined as the
positive response of the method to secondary target
analytes or co-contaminants similar to the primary
target analyte. Immunoassay methods are relatively
specific for the primary target analytes that they are
designed to detect. For immunoassay methods,
cross-reactivity is defined as the positive response
of the method to secondary target analytes or
co-contaminants similar to the primary target
analyte. The cross-reactive secondary target analytes
for TNT are mainly other nitroaromatics. The
cross-reactivity to these compounds varies
considerably among the four TNT immunoassay test
kits. The immunoassay test kit for RDX is quite
specific with only 3% cross-reactivity for HMX.
Depending upon the sampling objectives, broad
sensitivity or specificity can be an advantage or
disadvantage. If the objective is to determine
whether any explosive residues are present in soil,
broad sensitivity is an advantage. For the CRREL
and the EnSys RIS£ colorimetric methods for TNT,
the color development of the extracts can give the
operator an indication of what type of compounds
are present in soil, for example, TNT and TNB turn
red, DNB turns purple, 2,4-DNT turns blue,
2,6-DNT turns pink and tetryl turns orange. For the
CRREL method and the EnSys RIS£RDX kit, RDX
turns pink as well as HMX, nitroglycerine, PETN,
and nitrocellulose. An orange color indicates that
both TNT and RDX are present. Another advantage
of the broad response of some colorimetric methods
is they may be used to detect compounds other than
the primary target analyte. For example, the
colorimetric RDX methods may be used to screen
for HMX when RDX levels are relatively low, and
for NQ, NC, NG, and PETN in the absence of RDX
and HMX. The USAGE colorimetric procedure is
more specific to TNT than the CRREL and EnSys
RIS£ colorimetric methods, but has not been as
thoroughly evaluated. If a secondary target analyte
is present at only low concentrations in a sample,
the effect on the analytical result is minimal. If the
objective is to determine the concentration of TNT
or RDX when relatively high levels of other
nitroaromatics and nitramines are present,
immunoassay or the USAGE methods may be
appropriate.
Extremes of temperature, pH and soil water con-
tent can interfere with on-site analytical methods.
According to the California Military Environmental
Coordination Committee, the following physical
conditions are generally not recommended for both
colorimetric and immunoassay methods,
temperatures outside the 4 to 32° C range, pH levels
less then 3 or greater than 11, and water content
greater than 30% (CMECC 1996). Specific product
literature should be consulted for more information.
Colorimetric Methods - For TNT methods, the
primary target analyte is TNT, and the secondary
target analytes are other nitroaromatics such as
TNB, DNB, 2,4-DNT, 2,6-DNT, and tetryl. For
RDX methods, the primary target analyte is RDX,
and the secondary target analytes are nitramines
(HMX and NQ), and nitrate esters (NC, NG, and
PETN). If the primary target analyte is the only
compound present in soil, the colorimetric methods
measure the concentration of that compound. If
multiple analytes are present in soil, the field
methods measure the primary target analyte plus the
secondary target analytes, nitroaromatics for the
TNT test kit, and nitramines plus nitrate esters for
the RDX test kits. In addition, the response of
colorimetric methods to the secondary target
analytes is equivalent to that of the primary target
analyte, and remain constant throughout the
concentration range of the methods, although the
observed colors may be different.
18
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If multiple analytes are present in soil,
colorimetric field results can be compared directly
with EPA Method 8330 results. For example, if a
soil sample (as analyzed by Method 8330) contains
100 ppm each of TNT, TNB, RDX, HMX, and
tetryl, the CRREL and the EnSys RIS£colorimetric
methods for TNT would measure -300 ppm (100
TNT + 100 TNB + 100 tetryl), and the RDX test kit
would measure -200 ppm (100 RDX + 100 HMX).
If the sample did not contain tetryl, the TNT test kit
would measure -200 ppm (100 TNT + 100 TNB),
and the RDX test kit would still measure -200 ppm
(100 RDX + 100 HMX).
Immunoassay Methods - For TNT kits, the
primary target analyte is TNT, and the secondary
target analytes are nitroaromatics TNB, DNTs,
Am-DNTs, and tetryl. For RDX kit, the primary
target analyte is RDX, and there is but little
cross-reactivity with HMX (3%). If the primary
target analyte is the only compound present in soil,
the immunoassay methods measure the
concentration of that compound.
If multiple analytes are present in soil, the
immunoassay kits measure the primary target
analyte plus some percentage of the cross-reactive
secondary target analytes. The response of
immunoassay kits to the secondary target analytes is
not equivalent to that of the primary target analyte.
Additionally the response does not remain constant
throughout the concentration range of the kits. In
addition, different immunoassay kits have different
cross-reactivities to secondary target analytes based
on the antibodies used to develop each method.
Cross-reactivities for immunoassay kits are usually
reported at the 50% response level (IC50), typically
the midpoint of the concentration range of the kits.
Table 5 shows the reported cross-reactivities at 1C 50
for the immunoassay kits. A complete
cross-reactivity curve for the entire concentration
range should be obtained from the manufacturers for
the immunoassay kits being considered. Where
multiple analytes exist in soil samples,
immunoassay results may not directly compare with
EPA Method 8330 results. For example, an
immunoassay kit may have cross-reactivities of 23%
for TNB and 35% for tetryl for the TNT test kit, and
3% HMX cross-reactivity for the RDX test kit. The
following simple example illustrates cross-reactivity
but in practice, it is not practical to calculate
contaminant concentrations in this manner because
of synergistic effects and because cross-reactivity is
nonlinear. Using the same sample as the
colorimetric example above, if a soil sample (as
analyzed by Method 8330) contains 100 ppm each
Table 5. On-Site Analytical Methods for Explosives in Soil, Percent Interference" or Cross-Reactivity*1
Test Method
Nitroaromatics
TNT TNB DNB 2,4-DNT 2,6-DNT 2AmDNT 4AmDNT
Nitramines
Other
Tetryl RDX HMX PETN
TNT
CRREL
EnSys RIS5®
USAGE
DTECH
Idetek Quantix
EnviroGard: plate
tube
Ohmicron RaPID
Assay
RDX
CRREL
EnSys RIS%>
DTECH
100
100
100
100
100
100
100
100
NC
NC
<1
100
100
23
47
7
3
65
NC
NC
<1
100
100
NC
1
2
NC
NC
<1
100
100
NC
4
2
2
2
4
NC
NC
<1
100 NC
100 NC
11
0.5
41 <1
20 1
<1 3
NC NC
NC NC
<1 <1
NC 100 NC NC
NC 100 NC NC
<1 35 <1 <1
2 6.5 <1 <1
41 <1 <1 <1
17 0.3
1 5 <1 <1
NC NC 100 100 100
NC NC 100 100 100
<1 <1 100 3 <1
"Interference for colorimetric methods.
b Cross-reactivity for immunoassay methods at 50% response (IC5Q).
Blank cell = no data.
19
-------
NC = No color development.
of TNT, TNB, RDX, HMX, and tetryl, the TNT field
immunoassay kit would measure -158 ppm (100 TNT
+ 23 TNB + 35 tetryl), and the RDX field method
would measure -103 ppm (100 RDX + 3 HMX). If the
same sample did not contain tetryl, the TNT test kit
would measure -123 ppm (100 TNT + 23 TNB), and
the RDX test kit would still measure -103 ppm.
Matrix Interferences - Both colorimetric and
immunoassay methods may be subject to positive
matrix interference from humic substances in soils,
which results in yellow extracts. For colorimetric
methods, interference may be significant for samples
containing less than 10 ppm of the target analyte.
Through careful visual analysis prior to colorimetric
analysis, these interferences can be observed. Many of
the immunoassay methods use a reverse coloration
process, and humic matrix interference results in less
color development, hence on-site method results are
biased high as compared to laboratory results. Nitrate
and nitrite, common plant nutrients in soil, are potential
interferents with the CRREL and EnSys RIS£
colorimetric procedures for RDX. An extra processing
step may be used to remove these interferents in soils
that are rich in organic matter or that may have been
recently fertilized.
The performance of field explosives analytical
methods on other solid-phase environmental treatment
matrices such as incineration ash, biotreatment residues
such as compost or sludges from slurry phase
bioreactors, cement-based solidification or stabilization
material, or granular activated carbon from
groundwater treatment systems have not been
extensively evaluated and will most likely be subject to
matrix interferences or low extraction efficiencies. The
performance of field methods on these matrices should
be evaluated against laboratory methods on a
site-specific basis.
Recommended Quality Assurance/Quality
Control
The recommended quality assurance/quality
control (QA/QC) procedures vary considerably with
the screening procedure. Some test methods do not
specify QA/QC procedures and leave to the
investigator the determination of the numbers of
blanks, duplicates, replicates, and standards that are
run. During field application of these methods, it is
common to send at least 10 to 20% of the positive
samples to an off-site laboratory for analysis by EPA
Method 8330, and a smaller fraction of the nondetect
samples also may be verified. In some cases, field
methods are used to identify samples containing
explosive residues. Samples containing explosives
are sent for on-site analysis. In any case, the QC
samples recommended by the method developer
should be used.
While ensuring that field methods perform as
intended is essential, requiring laboratory type QC
requirements may be inappropriate for on-site
analytical methods. Because site characterization
efforts may be cost constrained, excess QC samples
reduce the number of field samples that can be
analyzed. Since sampling error (variability) is
typically much greater than analytical error (Jenkins
et al. 1996a, 1996b), especially for explosive
residues, overall error is more effectively reduced by
increasing the number of field as opposed to the
number of QC samples. Good sample preparation
procedures and correlation of the field methods with
the laboratory HPLC method over the concentration
range of interest should be the primary performance
criteria. Documentation of procedures and results
must be emphasized.
During the initial evaluation of on-site and
off-site analytical methods, it may be desirable to
analyze a variety of QC samples to determine
sources of error. The methods can then be modified
to minimize error as efficiently as practical. This
may involve collection and analysis of composite
versus grab samples, duplicates, replicates, splits of
samples, splits of extracts, etc. For more complete
information on the types and uses of various QC
20
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samples, see A Rational for the Assessment of Errors
in the Sampling of Soils (EPA 1990).
should be noted that the per-sample costs do not
include labor hours.
Storage Conditions and Shelf Life
Storage conditions and shelf life of immunoassay
kits are more critical than colorimetric methods. The
reagents for some immunoassay kits should be
refrigerated but not frozen or exposed to high
temperatures. Their shelf life can vary from 3
months to more than 1 year. Colorimetric reagents
can be stored at room temperature. The EnSys RIS£
colorimetric kits have shelf lives of at least 2 months
and up to 1 or 2 years. Before ordering test kits, it is
important to know when they will be used to ensure
that they will be used before the expiration date.
Skill Level
The skill level necessary or required to run these
tests varies from low to moderate, requiring a few
hours to a day of training. The manufacturers of the
kits generally provide on-site training. A free
training video tape on the CRREL TNT and RDX
procedures (which also is useful for the EnSys RIS £
colorimetric kits) is available by submitting a written
request to Commander U.S. Army Environmental
Center, Attn: SFIM-AEC-ETT/Martin H. Stutz,
Aberdeen Proving Ground, MD 21010. Training
video tapes are also available from some kit
suppliers.
Cost
As shown in Table 3, routine sample costs vary
by method. The per-sample cost is affected by
consumable items and instrument costs to run the
method. In figuring costs per sample, it is important
to include the costs of reruns for out-of-range
analyses. With the EnSys RIS£ colorimetric TNT kit,
the color-developed extract may be simply diluted
and reread with the spectrometer. With all other
methods, the original soil extract needs to be
reanalyzed, which in the case of immunoassay
procedures requires the use of another kit.
Colorimetric methods typically have sufficient extra
reagents to rerun samples with no increase in cost. It
Comparisons to Laboratory Method, SW-846
Method 8330
The objectives of the study or investigation, the
site-specific contaminants of concern, the concen-
tration ranges encountered or expected, and their
relative concentration ratios affects the selection of
a particular on-site method. The accuracy of an on-
site method is another selection criteria but care must
be used in interpreting accuracy results from com-
parisons between reference analytical methods and
on-site methods.
Colorimetric methods actually measure groups of
compounds (i.e., nitroaromatics or nitramines) and
immunoassay methods are more compound specific.
Therefore the reported accuracy of a method may
depend on the mix of explosives in the soil and the
reference method data used for the comparison (i.e.,
data on specific compounds, or total nitroaromatics
or nitramines).
The precision and bias of the screening methods
are most appropriately assessed by comparison to
established laboratory methods such as EPA Method
8330. Methods of comparison that have been used
include relative percent difference (RPD), linear
regression, correlation, coefficient of determination
(R2), percent false positive and false negative results,
analysis of variance, and paired t-tests. It should also
be remembered that the contribution of analytical
error is generally quite small compared to total error
(field error is the major contributor).
Three studies have been conducted comparing
the performance of two or more on-site methods with
Method 8330. The procedures used in the studies for
making the comparisons are given here and a
summary of the results of each study follows. EPA
(1995b) calculated RPDs (the difference between the
field and reference method concentration divided by
the mean value and expressed as a percent),
established a comparison criterion of ± 50% for
RPDs, and determined the frequency with which
various methods met that criteria within various
sample concentration ranges. EPA (1995b) also
calculated regression lines and the R2. Haas and
21
-------
Simmons (1995) compared on-site methods using
the percentage of false positives and false negatives
for determining whether samples were above or
below two proposed remediation criteria for TNT in
soil, 48 and 64 mg/kg. They also plotted regression
data and reported calculated R2 values. Myers et al.
(1994) calculated regression lines with 99%
confidence intervals.
While no study has compared all the field
methods under the same conditions, the three studies
evaluated multiple methods under slightly different
field conditions (EPA 1995b; Haas and Simmons
1995, Myers et al. 1994). Summary data from these
studies are provided in Table 6. The table includes
the intercept and slope of regression lines for TNT
and RDX data for two concentration ranges, from the
detection limit to 100 mg/kg and from 100 to 1000
mg/kg. Also included are the correlation coefficient
(r) and the mean RPD (absolute value of RPDs). The
ideal regression line would have a slope of 1 and go
through the origin (intercept of 0). The correlation
coefficient shows the degree of association between
the on-site method and Method 8330 and can range
between -1 and +1. For a perfect positive correlation
r = 1. The mean RPD closest to 0 shows the greatest
agreement with the reference laboratory method. The
RPDs presented are for TNT or RDX. The accuracy
of colorimetric methods should improve when
compared to total nitroaromatics or nitramines
because the methods detect numerous related
explosives. As the level of nitroaromatics other than
TNT increases, the accuracy of the CRREL and
EnSys RIS£ methods should appear to decrease. But
when compared to total nitroaromatics, the accuracy
should increase. Thus, to attempt to identify the
preferred screening method, it is important to
determine specifically what analytical information is
desired from a screening procedure and the relative
concentration of the explosives at a site. Readers
should consult the original studies for more details;
however, some summary conclusions from the three
cited studies follow.
The EPA (1995b) study compared the CRREL,
EnSys RIS£, D TECH, Idetek Quantix, and
Ohmicron RaPID Assay methods for TNT. The study
concluded that "no single method significantly
out-performed other methods" and accuracies for all
the on-site methods were comparable. CRREL,
EnSys RIS£, and Ohmicron were more accurate in
the greater-than-30-mg/kg TNT ranges, and D TECH
was more accurate in the less-than-30-mg/kg range.
The same study compared the CRREL, EnSys RIS£,
and D TECH methods for RDX in soil and
concluded that they were slightly less accurate than
the corresponding TNT methods.
Table 6. Comparison of On-Site Analytical Methods for TNT and RDX to EPA Method 8330.
MDL < TNT < 100 mg/kg
Method
Regression Regression Correlation Mean RPD Number
Intercept Slope Coefficient (r) (absol. value) Samples
Reference
CRREL
EnSys RIS^®
DTECH
Idetek Quantix
Ohmicron RaPID Assay
D TECH3
one outlier deleted3
EnviroGard plate3
EnviroGard tube3
Idetek Quantix3
Ohmicron RaPID Assay3
10
19
2.9
13
16
-17
3.7
13
6.3
36
18
0.84
0.81
0.79
0.62
1.2
6.7
2.4
1.3
0.99
2.1
1.8
0.74**
0.45**
0.76**
0.46**
0.51**
0.81**
0.91**
0.79**
0.90**
0.39*
0.83**
72
90
63
84
97
110
122
95
131
127
86
123
103
124
115
37
36
36
21
37
37
EPA1995b
EPA1995b
EPA1995b
EPA1995b
EPA1995b
Haas & Simmons
Haas & Simmons
Haas & Simmons
Haas & Simmons
Haas & Simmons
1995
1995
1995
1995
1995
22
-------
EnSys RIS£a
D TECHa
CRREL
EnSys RIS^D
DTECH
Idetek Quantix
Ohmicron RaPID Assay
CRREL
EnSys RIS^®
DTECH
D TECH3
EnSys RIS^D
DTECH
3.8
5.4
-25
50
-250
210
680
-1.2
6.4
2.7
-0.35
-9.9
21
0.72
0.94
100 <
1.4
1.1
2.2
0.09
0.50
MDL
0.56
0.57
0.20
0.77
100 <
0.68
0.15
0.91**
0.30
TNT < 1000 mg/kg
0.67**
0.59**
0.59*
0.30
0.12
< RDX < 100 mg/kg
0.89**
0.50**
0.49**
0.95**
RDX < 1000 mg/kg
0.50**
0.49*
56
88
33
57
60
65
51
74
61
103
66
83
127
12
10/11
15
21
17
22
16
64
114
94
27
32
25
Myersetal. 1994
Myersetal. 1994
EPA1995b
EPA1995b
EPA1995b
EPA1995b
EPA1995b
EPA1995b
EPA1995b
EPA1995b
Haas & Simmons 1995
EPA1995b
EPA1995b
a Statistics calculated from cited reference.
* Statistically significant at the 95% probability level.
** Statistically significant at the 99% probability level.
23
-------
Haas and Simmons (1995) evaluated
immunoassay kits for TNT (D TECH, EnviroGard
Tube and Plate, Idetek Quantix, and Ohmicron
RaPID Assay). They concluded that for
semiquantitative screening, all kits have the potential
to accurately screen soil samples for contamination
at risk-based levels (EPA 1993). The study found
that compared with HPLC analysis below 1 ppm
several of the assays had significant bias.
Measurements near the detection limit "are often
problematic" and above 1 ppm, the correlation
between the immunoassay kits and HPLC was
"generally good."
Myers et al. (1994) evaluated and compared the
EnSys RIS£ and D TECH methods for TNT in soil
versus EPA Method 8330. The study found that
"EnSys demonstrated a good one-to-one linear
correlation with RP-HPLC that can be attributed to
the procedure for extraction, i.e., a large sample size
of dried homogenized soil." For the D TECH kit,
comparison was more difficult because of the
concentration range type data and because
"one-to-one linear correlation with RP-HPLC was
poorer." Both methods were susceptible to
interferences: "Although both methods showed
strong tendencies to cross react with other
nitroaromatics, sometimes resulting in false
positives, in a sampling of 99 soils, neither method
produced a false negative." The study concluded that
the EnSys RIS£ kit was well suited for analyses
requiring good quantitative agreement with the
standard laboratory method and that the D TECH kit
was "better suited for quick, on-site screening in
situations where all samples above a certain range
will be sent forward to a laboratory for confirmation
by the standard method."
Additional Considerations
Other important factors in the selection of an
on-site method are the size and type of working area
required, the temperature of the working area, the
need for electricity and refrigeration, the amount of
waste produced, the need to transport solvents, the
degree of portability, etc. Immunoassay methods are
more sensitive than colorimetric methods to freezing
and elevated temperatures, and the ambient
temperature affects the speed at which color
development takes place on some immunoassay
methods. Most tests are best run out of the weather,
in a van, field trailer, or nearby building.
Emerging Methods and Other Literature
Reviewed
Several other screening procedures exist that have
not been included in Table 3 because of the limited
information available on published methods or
commercial availability.
The Naval Research Laboratory Center for
Bio/Molecular Science and Engineering has
conducted developmental research on an antibody-
based continuous-flow immunosensor for TNT and
RDX and a fiber optic biosensor for TNT in water
(Whelan et al. 1993; Shriver-Lake et al. 1995). Both
methods have been evaluated as quantitative
methods for explosives in groundwater at two sites
(Craig et al. 1996). These methods reportedly
tolerate a certain percentage of acetone, and are
currently being evaluated for quantifying soil
extracts containing explosives. Research of and
instrument development for these methods are
continuing.
The U.S. Army has been sponsoring the
development of a cone penetrometer capable of
detecting explosives in situ in soil, at levels
determined to be 0.5 ppm in laboratory tests (Adams
et al. 1995). Field tests have been conducted in
which a probe is hydraulically pushed to depth by a
20-ton truck, samples are pyrolized in situ, and a
sensor selective to nitrogen oxide is used to detect
explosives. Research on this method is continuing.
A very simple spot test (colorimetric) kit can be
assembled to detect elevated levels of TNT and RDX
(>100 ppm) on filter paper swipes of surfaces and
soil. Samples can be analyzed in 1 to 2 minutes at
very low cost using the highly portable kit. This
nonquantitative test kit was developed at Los
Alamos National Laboratory and has been used to
screen soil to ensure that explosive contamination
does not exceed the 10% levels prior to shipping to
an analytical laboratory for analysis (Baits 1991;
Haywood et al. 1995; McRea et al. 1995).
A semiquantitative method for identifying explosives
using thermal desorption followed by ion mobility
spectroscopy has been developed for security applications
(Rodacy and Leslie 1992). The ion mobile spectroscopy
method has been tested on small quantities of soil samples
and is currently being evaluated for soil extracts
(Atkinson, Crockett and Jenkins 1997). Research on this
method is continuing.
24
-------
The use of a mobile laboratory screening method
for detecting high explosives has been described
(Swanson et al. 1996). Ten-gram soil samples are
extracted with 10 mL of acetone by shaking for 1
hour, and the extract is filtered. Analysis is by high
performance liquid chromatography using a
photo-array detector, which takes about 15 minutes
per sample and quantifies TNT, HMX, RDX, TNB,
tetryl, 1,3-DNB, 2-AmDNT + 4-AmDNT, 2,4-DNT
+ 2,6-DNT, and all three NTs at detection limits of
about 1 ppm.
A thermal desorption/Fourier transform infrared
spectroscopy screening technique was under
investigation by Argonne National Laboratory for
the U.S. Army Environmental Center. The estimated
detection limit was about 80 ppm without further
modifications to the procedure (Clapper-Gowdy et
al. 1992; Clapper et al. 1995), and no further
research is being conducted.
Fast determination (100 samples/10 h/person) of
explosives in soil (TNT, DNT, and NT) using
thermal desorption followed by gas
chromatography/mass spectrometry analysis has
been reported. While no technical report on
screening explosives in soil is available, the
approach has been described in the literature for use
with other contaminants (McDonald et al. 1994;
Abraham, Liu, and Robbat 1993).
Work is under way within CRREL to investigate
the use of a simple thin-layer chromatographic
method for use as a confirmation test following
colorimetric-based procedures. This method can be
applied to extracts that test positive for TNT or RDX
to discriminate among the several analytes that may
be present. Work is also under way using x-ray
fluorescence for screening for metals containing
primary explosives.
SUMMARY OF THE EPA REFERENCE
METHOD FOR EXPLOSIVE COMPOUNDS,
METHOD 8330
Properties of Secondary Explosives
TNT and RDX have been the two secondary
explosives used to the greatest extent by the U.S.
military over the past 70 years. With their manufac-
turing impurities and environmental transformation
products, the two compounds account for a large part
of the explosives contamination at active and former
U.S. military installations. While all of these explosive
compounds can all be classified as semivolatile organic
chemicals, their physical and chemical properties require
different analytical approaches than normally used for
other semivolatiles.
Table 7 presents some of the important physical
and chemical properties for TNT and RDX, and
some of their commonly encountered manufacturing
impurities and environmental transformation
products. The unique properties that differentiate
these chemicals from other semivolatiles such as
PCBs and polynuclear aromatic hydrocarbons
(PNAs) are their thermal lability and polarity. Many
of these compounds thermally degrade or explode at
temperatures below 300°C. Thus, methods based on
gas chromatography are not recommended for
routine use. In addition, log Kow values range from
0.06 to 2.01 compared with values of 4 to 5 for PCBs
and PNAs, indicating that these compounds are quite
polar and that normal nonpolar extraction solvents
used for other semivolatile organics may not elute
successfully. For most routine analyses,
environmental soil samples are extracted with polar
solvents. The sample extracts are analyzed using
reversed-phase high performance liquid
chromatography (RP-HPLC), often using SW-846
Method 8330 (EPA 1995a).
Soil Extraction
Extraction of TNT and RDX from soils has been
studied in terms of process kinetics and recovery
using methanol and acetonitrile with several
extraction techniques including Soxhlet, shaking,
and ultrasonication (Jenkins and Grant 1987).
Acetone, while an excellent solvent for these
compounds, was not included in this study because
extracts were to be analyzed using RP-HPLC-UV,
and acetone absorbs in the ultraviolet region used for
detection of the contaminants of interest.
Overall, methanol and acetonitrile were found to
be equally good for extraction of TNT, but
acetonitrile was clearly superior for RDX.
Equilibration of the soil with solvent using
ultrasonication or a Soxhlet extractor appears to
provide equivalent results; however, a subsequent
25
-------
Table 7. Physical and Chemical Properties of Predominant Nitroaromatics and Nitramines.
Compound
TNT
TNB
2,4-DNT
Tetryl
RDX
HMX
Molecular
Weight
227
213
182
287
222
296
Melting Pt.
(°C)
80.1 -81.6
122.5
69.5 -70.5
129.5
204.1
286
Boiling Pt.
(°C)
240 (explodes)
315
300
(decomposes)
(decomposes)
(decomposes)
(decomposes)
Water
Solubility
(mg/L at 20°)
130
385
270
80
42
5 at 25°
Vapor
Pressure
(torr at 20°)
l.lxlO-6
2.2xlO-4
1.4xlO-4
5.7xlO-9
4.1xlO-9
3.3xlO-14
log Kow
1.86
1.18
2.01
1.65
0.86
0.061
investigation indicated that tetryl, another secondary
explosive often determined in conjunction with TNT
and RDX, is unstable at the temperatures required
for Soxhlet extraction (Jenkins and Walsh 1994).
That, combined with the ability to extract many
samples simultaneously using the sonic bath
approach, makes ultrasonication the
preferred technique.
Results of extraction studies indicate that even
when acetonitrile is used with ultrasonic extraction,
the extraction is kinetically slow for weathered
field-contaminated soils (Jenkins and Grant 1987;
Jenkins et al. 1989). For that reason, SW-846
Method 8330 (EPA 1995a) requires acetonitrile
extraction in an ultrasonic bath for 18 hours.
RP-HPLC Determination
Generally, detection of the analyte within the proper
retention time window on two columns with different
retention orders is required for confirmation of the
presence of these explosives. Method 8330 specifies
primary analysis on an LC-18 (octadecylsilane) column
with confirmation on a cyanopropylsilane (LC-CN)
column (Jenkins et al. 1989).
Walsh, Chalk, and Merritt (1973) were the first to
report on the use of RP-HPLC for the analysis of
nitroaromatics in munitions waste. Most subsequent
HPLC methods for these compounds rely on ultraviolet
detection because of its sensitivity and ruggedness.
Initially, determination was specified at 254 nm
because of the availability of fixed wavelength
detectors based on the mercury vapor lamps and a
significant absorbance of all target analytes at this
wavelength. Current instruments are generally
equipped with either variable wavelength detectors or
diode array detectors, and wavelengths of maximum
absorption can be selected to optimize detection.
However, 254 nm is still often used because of the low
incidence of interference at this wavelength.
Method Specifications and Validation
Based on the research described above, SW-846
Method 8330 (EPA 1995a) specifies the following:
1. Soil samples are air-dried and ground in a mortar
and pestle for homogenization.
2. A 2-g subsample is placed in an amber vial, 10
mL of acetonitrile is added, and the vial is placed
in a temperature-controlled ultrasonic bath for 18
hours.
3. The vial is removed from the bath and the soil is
allowed to settle, a 5-mL aliquot is removed and
diluted with 5 mL of aqueous CaCl2to assist in
flocculation, and the diluted extract is filtered
through a 0.45-//m membrane.
4. A 100-//L portion is injected into an HPLC
equipped with a primary analytical column
(LC-18) and is eluted with methanol/water (1:1)
at 1.5 mL/min; retention times for the 14 target
analytes range from 2.44 to 14.23 minutes.
5. If target analytes are detected, their presence is
confirmed on a confirmation column (LC-CN).
6. The estimated quantitation limits in soil for most
analytes is about 0.25 mg/kg, with RDX and
HMX being somewhat higher at 1.0 and 2.2,
respectively. No limits are provided for the
Am-DNTs.
26
-------
This procedure was subjected to a ruggedness test
(Jenkins et al. 1989) and a full-scale collaborative
test (Bauer, Koza, and Jenkins 1990) was conducted
under the auspices of the Association of Official
Analytical Chemists (AOAC). In addition to
acceptance by the EPA Office of Solid Waste as
SW-846 Method 8330 (EPA 1995a), this procedure
also has been adopted as Standard Method 991.09 by
the AOAC (AOAC 1990) and as ASTM Method
D5143-90 (ASTM 1990). In addition, the procedure
has been used successfully by a large number of
commercial laboratories for several years.
SUMMARY
A large number of defense-related sites are
contaminated with elevated levels of secondary
explosives. Levels of contamination range from barely
detectable to levels over 10% that need special handling
because of the detonation potential. Characterization of
explosives-contaminated sites is particularly difficult
because of the very heterogeneous distribution of
contamination in the environment and within samples.
To improve site characterization, several options exist
including collecting more samples, providing on-site
analytical data to help direct the investigation, sample
compositing, improving homogenization of samples, and
extracting larger samples. On-site analytical methods are
essential to more economical and improved
characterization. What they lack in precision and
accuracy when used to simultaneously identify specific
multiple compounds, the on-site methods more than
make up for in the increased number of samples that can
be analyzed. While verification using a standard
analytical method such as EPA Method 8330 should be
part of any quality assurance program, reducing the
number of samples analyzed by more expensive
methodology can result in significantly reduced costs.
Often 70 to 90% of the soil samples analyzed during an
explosives site investigation do not contain detectable
levels of contamination.
Two basic types of on-site analytical methods are
in wide use for explosives in soil: colorimetric and
immunoassay. Colorimetric methods generally detect
broad classes of compounds such as nitroaromatics
or nitramines, while immunoassay methods are more
compound specific. Because TNT or RDX is usually
present in explosive-contaminated soils, the use of
procedures designed to detect only these or similar
compounds can be very effective.
Selection of an on-site analytical method involves
evaluation of many factors including the specific
objectives of the study, compounds of interest and
other explosives present at the site, the number of
samples to be run, the sample analysis rate,
interferences or cross reactivity of the method, the
skill required, analytical costs per sample, and the
need for and availability of support facilities or
services or both. Another factor that may be
considered is the precision and accuracy of the
on-site analytical method, but it should be
remembered that analytical error is generally small
compared to field error and that the precision and
accuracy of a method is dependent on the site
(compounds present and relative concentration) and
the specific objectives (the question being asked).
Modifications to on-site methods may be able to
improve method performance. In most cases, a larger
soil sample can be extracted to improve the
representativeness of the analytical sample. Also,
with heavy soils or soils with high organic matter
content, conducting a short-term kinetic study may
be useful to determine whether a 3-minute extraction
period is adequate. The shaking and extraction phase
of all on-site methods should last at least 3 minutes.
In all cases, a portion of the on-site analytical results
should be confirmed by using a standard laboratory
method. With appropriate use, on-site analytical
methods are a valuable tool for characterization of
soils at hazardous waste sites and monitoring soil
remediation operations.
27
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FEDERAL FACILITY FORUM MEMBERS
Region 1
U.S. EPA
JFK Federal Building
Boston, MA 02203
Meghan Cassidy
(617)573-5785
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290 Broadway
New York, NY 10007-1866
Bill Roach
(212)264-8775
Region 3
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341 Chestnut Bldg.
Philadelphia, PA 19107
Paul Leonard
(215)566-3350
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(404) 562-3555
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(404) 562-3555
Region 5
U S EPA
77 W. Jackson Blvd.
Chicago, IL 60604
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(312)886-5907
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(312)886-1482
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(312)886-6146
Region 6
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1445 Ross Avenue
Dallas, TX 75202
Nancy Morlock
(214)665-6650
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(214)665-6754
Region 7
U.S. EPA
726 Minnesota Avenue
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(913)551-7131
Region 8
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999 18th Street
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(303)312-6760
Region 9
U.S. EPA
75 Hawthorne Street
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94105-3901
Glenn Kistner
(415)744-2252
Sheryl Lauth
(415)744-2410
Region 10
U.S. EPA
1200 Sixth Avenue
Seattle, WA 98101
Harry Craig
(503) 326-3689
Kathy Stryker
(206)553-1171
Headquarters
U.S. EPA/OSWER
401 M Street, SW
Washington, DC 20460
Allison Abernathy
(202)260-9925
NOTICE
The U.S. Environmental Protection Agency
(EPA), through its Office of Research and
Development (ORD), funded and prepared this
Issue Paper. It has been peer reviewed by the EPA
and approved for publication. Mention of trade
names or commercial products does not constitute
endorsement or recommendation by EPA for use.
ACKNOWLEDGMENT
Work partly performed under the auspices of
the U.S. Department of Energy, Office Contract
No. DE-AC07-94ID13223, through Interagency
Agreement No. DW89937192-01-2 with the U.S.
Environmental Protection Agency. The EPA
wishes to thank the U.S. Army Environmental
Center and CRREL for assisting in the preparation
of this document.
28
-------
REFERENCES
Abraham, B.M., T. Liu, and A. Robbat, Jr.
1993. Data comparison study between field and
laboratory detection of polychlorinated biphenyls
and polycyclic aromatic hydrocarbons at Superfund
sites. Hazardous Waste & Hazardous Materials
10:461-473.
Adams, J.W., E.R. Cespedes, S.S. Cooper,
W.M. Davis, W.J. Buttner, and W.C. Vickers.
1995. Development and testing of cone
penetrometer sensor probe for in situ detection of
explosive contaminants. In: Field Screening
Methods for Hazardous Wastes and Toxic
Chemicals, VIP-47, Air & Waste Management
Association, Pittsburgh, Pennsylvania, 1:491-501.
AEC. 1994. Standard Comments for Health
and Safety Document Review, Memorandum for
Record, SFIM-AEC-TSS, July 18, 1994, U.S.
Army Environmental Center, Aberdeen Proving
Ground, Maryland, 9 pp.
AOAC. 1990. Munitions Residues in Soil,
Liquid Chromatographic Method, Official First
Action, September 1990, Method 991.09, Second
Supplement to the 15th Edition of Official
Methods of Analysis, Association of Official
Analytical Chemists, pp. 78-80.
ASTM. 1990. Standard Test Method for
Analysis of Nitroaromatic and Nitramine Explosive
in Soil by High Performance Liquid
Chromatography, D 5143, American Society for
Testing and Materials, West Conshohocken,
Pennsylvania.
ASTM. 1996. Standard Practice for Generation
of Environmental Data Related to Waste
Management Activities: Development of Data
Quality Objectives, D 5792, American Society for
Testing and Materials, Conshohocken,
Pennsylvania.
ASTM. 1997. Standard Guide for Composite
Sampling and Field Subsampling for
Environmental Waste Management Activities,
D 6051, American Society for Testing and
Materials, West Conshohocken, Pennsylvania.
Atkinson, D.A., A.B. Crockett, and T.F.
Jenkins. 1997. On-site analysis of soils
contaminated with explosives using ion mobility
spectrometry. In: Field Analytical Methods for
Hazardous Wastes and Toxic Chemicals,
Proceedings of the Fifth International Symposium,
EPA/A&WMA.
Bauer, C.F., S.M. Koza, and T.F. Jenkins.
1990. Collaborative test results for a liquid
chromatographic method for the determination of
explosive residues in soil. J. Assoc. of Official
Anal. Chem. 73:541-552.
Baytos, J.F. 1991. Field Spot-Test Kit for
Explosives, Los Alamos National Laboratory, Los
Alamos, New Mexico, LA-12071-MS, 6 pp.
Blackwood, L.G., and E. L. Bradley. 1991. An
omnibus test for comparing two measuring devices.
J.Qual. Tech. 23(1): 12-16.
Brouillard, L., E.R. Young, and R. Cerar.
1993. Application of modified field screening
methods to evaluate select metals and 2,4,6-TNT
concentrations in surface soils at the Cornhusker
Army Ammunition Plant, Grand Island, Nebraska.
In: Field Screening Methods for Hazardous Wastes
and Toxic Chemicals, Proceedings of the 1993
U.S. EPA/A&WMA International Symposium,
pp.783-792.
California EPA. 1996a. D TECH™ TNT kit
evaluation report. Technology Certification
Program, available from Office of Pollution
Prevention and Technology Development, 400 P
Street, Sacramento, CA 95814.
California EPA. 1996b. D TECH™ RDX kit
evaluation report. Technology Certification
Program, available from Office of Pollution
Prevention and Technology Development, 400 P
Street, Sacramento, CA 95814.
California EPA. 1996c. EnviroGard™ 2,4,6-
trinitrotoluene (TNT) in soil test kit evaluation
report. Technology Certification Program,
available from Office of Pollution Prevention and
Technology Development, 400 P Street,
Sacramento, CA 95814.
California EPA. 1996d. Ohmicron TNT RaPID
Assay® evaluation report. Technology
Certification Program, available from Office of
Pollution Prevention and Technology
Development, 400 P Street, Sacramento, CA
95814.
29
-------
Channell, M., J. Wakeman, and H. Craig.
1996. Solidification/stabilization of metals and
explosives in soil. In: Proceedings of the Great
Plains Rocky Mountain Hazardous Substance
Research Center (HSRC)AVaste Management
Education and Research Consortium (WERC) Joint
Conference on the Environment, Albuquerque,
New Mexico, May 21-23, 1996.
Christensen, R., and L.G. Blackwood. 1993.
Tests for precision and accuracy of multiple
measuring devices. Technometrics 35(4):411-420.
Clapper, M., J. Dermirgian, and G. Robitaille.
1995. A quantitative method using FT-IRto detect
explosives and selected semivolatiles in soil
samples. Spectroscopy 10(7):45-49.
Clapper-Gowdy, M., J. Dermirgian, K. Lang,
and G. Robitaille. 1992. A Quantitative Method to
Detect Explosives and Selected Semivolatiles in
Soil Samples by Fourier Transform Infrared
Spectroscopy, ANL/CP-76749, Argonne National
Laboratory, 17 pp.
CMECC. 1996. Field Analytical Measurement
Technologies, Applications, and Selection,
California Military Environmental Coordination
Committee, State of California Water Resources
Control Board, call (916) 227-4368 for copies.
Craig, H.D., A. Markos, H. Lewis, and C.
Thompson. 1993. Remedial Investigation of Site D
at Naval Submarine Base, Bangor, Washington. In:
Proceedings of the 1993 Federal Environmental
Restoration Conference, Washington, D.C.,
Hazardous Material Control Resources Institute,
May 25-27, 1993.
Craig, H., and W. Sisk. 1994. The composting
alternative to incineration of explosives
contaminated soils. In: Tech Trends, U.S.
Environmental Protection Agency, EPA 542-N-
94-008, U.S. Environmental Protection Agency,
Office of Solid Waste and Emergency Response,
Washington, D.C.
Craig, H.D., W.E. Sisk, M.D. Nelson, and
W.H. Dana. 1995. Bioremediation of explosives
contaminated soil: a status review. Tenth Annual
Conference on Hazardous Waste Research, Great
Plains Rocky Mountain Hazardous Substance
Research Center, Manhattan, Kansas, May 23-24,
1995.
Craig, H., G. Ferguson, A. Markos, A.
Kusterbeck, L. Shriver-Lake, T. Jenkins, and P.
Thorne. 1996a. Field Demonstration of On-Site
Analytical Methods for TNT and RDX in
Groundwater, In: Proceedings of the Great Plains
Rocky Mountain Hazardous Substance Research
Center (HSRC)AVaste Management Education and
Research Center (WERC) Joint Conference on the
Environment, Albuquerque, New Mexico, May
21-23, 1996.
Cragin, J.H., D.C. Leggett, B.T. Foley, and
P.W. Schumacher. 1985. TNT, RDX, and HMX
Explosives in Soils and Sediments, Special Report
85-15, U.S. Army Corps of Engineers, Cold
Regions Research and Engineering Laboratory.
EPA. 1990. A Rational for the Assessment of
Errors in the Sampling of Soils,
EPA/600/4-90/013, U.S. Environmental Protection
Agency, Environmental Monitoring Systems
Laboratory, Las Vegas, Nevada.
EPA. 1992a. Guidance for Data Useability in
Risk Assessment (Part A). Final Report, OSWER
Directive 9285.7-09A, U.S. Environmental
Protection Agency, Office of Emergency and
Remedial Response, Washington, D.C., 290 pp.
EPA. 1992b. Statistical Methods for
Evaluating the Attainment of Cleanup Standards,
Volume 3, Reference-Based Standards for Soils
and Solid Media, EPA 230-R-94-004, U.S.
Environmental Protection Agency, Office of Policy
Planning and Evaluation, Washington, D.C.
EPA. 1993. Handbook: Approaches for the
Remediation of Federal Facility Sites
Contaminated with Explosive or Radioactive
Wastes, EPA/625/R-93/013, U.S. Environmental
Protection Agency, Office of Research and
Development, Washington, D.C., 116 pp.
EPA. 1994. Guidance for the Data Quality
Objectives Process, EPA QA/G-4, Quality
Assurance Management Staff, U.S. Environmental
Protection Agency, Washington, D.C., 68 pp.
EPA. 1995a. Method 8330, Nitroaromatics and
Nitramines by High Performance Liquid Chrom-
atography (HPLC), In: Test Method for Evaluating
Solid Waste, Physical/Chemical Methods, Office
of Solid Waste and Emergency Response, U.S.
Environmental Protection Agency, Washington
D.C., SW-846, Revision 0, September 1994.
30
-------
EPA. 1995b. Field Screening Technologies
Umatilla Explosive Washout Lagoon Soils. U.S.
Environmental Protection Agency, Region 10,
Seattle, Washington (unpublished draft report).
Gagner, S., and A. Crockett. 1996.
Compositing and Subsampling of Media Related to
Waste Management Activities, In: Proceeding
Twelfth Annual Waste Testing & Quality
Assurance Symposium, July 23-26, 1996,
American Chemical Society and U.S.
Environmental Protection Agency, pp. 22-29.
Grant, C.L., T.F. Jenkins, and S.M. Golden.
1993. Experimental Assessment of Analytical
Holding Times for Nitroaromatic and Nitramine
Explosives in Soil, Special Report 93-11, U.S.
Army Corps of Engineers, 18 pp.
Grant, C.L., T.F. Jenkins, K.F. Myers, and E.F.
McCormick. 1995. Holding-time estimates for soils
containing explosives residues: comparison of
fortification vs. field contamination. Environ. Tox.
andChem. 14(11):1865-1874.
Grubbs, F.E. 1973. Errors of measurement,
precision, accuracy and the statistical comparison
of measuring instruments. Technometrics
15:53-66.
Haas, R.A., and B.P Simmons. 1995.
Measurement of Trinitrotoluene (TNT) and
Hexahydro-l,3,5-Trinitro-l,3,5-Triazine (RDX) in
Soil by Enzyme Immunoassay and High Per-
formance Liquid Chromatography (EPA Method
8330), California Environmental Protection
Agency, Department of Toxic Substances Control,
Hazardous Materials Laboratory, 20 pp.
Haywood, W., D. McRae, J. Powell, and B.W.
Harris. 1995. An Assessment of High-Energy
Explosives and Metal Contamination in Soil at
TA-67(12), L-Site and TA-14, Q-Site,
LA-12752-MS, Los Alamos National Laboratory,
18pp.
IT. 1995. Final Predesign Investigations Report
Former Weldon Spring Ordnance Work, Project
No. 312455, IT Corporation, Kansas City, Kansas.
Jenkins, T.F. and C.L. Grant. 1987.
Comparison of extraction techniques for munitions
residues in soil. Anal. Chem. 59:1326-1331.
Jenkins, T.F., M.E. Walsh, P.W. Schumacher,
P.H. Miyares, C.F. Bauer, and C.L. Grant. 1989.
Liquid chromatographic method for the
determination of extractable nitroaromatic and
nitramine residues in soil. J. Assoc. of Official
Anal Chem. 72:890-899.
Jenkins, T.F., 1990. Development of a
Simplified Field Screening Method for the
Determination of TNT in Soil, Special Report
90-38, U.S. Army Corps of Engineers, Cold
Regions Research and Engineering Laboratory.
Jenkins, T.F., and M.E. Walsh. 1991. Field
Screening Method for 2,4-Dinitrotoluene in Soil,
Special Report 91-17, U.S. Army Corps of
Engineers, Cold Regions Research and
Engineering Laboratory, 11 pp.
Jenkins, T.F., and M.E. Walsh. 1992.
Development of field screening methods for TNT,
2,4-DNT and RDX in soil. Talanta 39(4):419-428.
Jenkins, T.F., and M.E. Walsh. 1994.
Instability of tetryl to Soxhlet extraction. J.
Chromatography 662:178-184.
Jenkins, T.F., M.E. Walsh, P.W. Schumacher,
and P.G. Thorne. 1995. Development of colori-
metric field screening methods for munitions
compounds in soil. In: Environmental Monitoring
and Hazardous Waste Site Remediation, SPIE
2504:324-333.
Jenkins, T.F., C.L. Grant, G.S. Brar, P.G.
Thorne, and T.A. Ranney. 1996a. Assessment of
Sampling Error Associated with Collection and
Analysis of Soil Samples at Explosive Con-
taminated Sites, Special Report 96-15, U.S. Army
Corps of Engineers, Cold Regions Research and
Engineering Laboratory.
Jenkins, T.F., C.L. Grant, G.S. Brar, P.G.
Thorne, P.W. Schumacher, and T.A. Ranney.
1996b. Sample representativeness: the missing
element in explosives site characterization. In:
Proceedings of the American Defense Preparedness
Association's 22nd Environmental Symposium and
Exhibition, March 18-21, 1996, Orlando, Florida.
Jenkins, T.F., P.W. Schumacher, J.G. Mason,
and P.G. Thorne. 1996c. On-Site Analysis for High
31
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Concentrations of Explosives in Soil: Extraction
Kinetics and Dilution Procedures, Special Report
96-10, U.S. Army Corps of Engineers, Cold Re-
gions Research and Engineering Laboratory, 12 pp.
Lang, K.T., T.F. Jenkins, and M.E. Walsh.
1990. Field detection kits for TNT and RDX in
soil. In: Proceedings of Superfund 90, Military
Activities, pp. 889-895.
Mandel, J. 1984. Fitting straight lines when
both variables are subject to error, Journal of
Environmental Quality, 16:1-14.
Markos, A.G., H. Craig, and G. Ferguson.
1995. Comparison of field screening technologies
implemented during phase I remediation of
explosive washout lagoon soils. In: 1995 Federal
Environmental Restoration Conference IV
Proceedings, Hazardous Material Control
Resources Institute, Atlanta, Georgia.
Maskarinec, M.P., C.K. Bayne, L.H. Johnson,
S.K. Holladay, R.A. Jenkins, and B.A. Tomkins.
1991. Stability of Explosives in Environmental
Water and Soil Samples, ORNL/TM-11770, Oak
Ridge National Laboratory, Oak Ridge, Tennessee,
98pp.
McDonald, W.C., M.D. Erickson, B.M.
Abraham, and A. Robbat, Jr. 1994. Developments
and application of field mass spectrometers. Env.
Sci. and Tech. 28:336A-343A.
McRea, D., W. Haywood, J. Powell, and B.
Harris. 1995. High Explosive Spot Test Analyses
of Samples from Operable Unit (OU) 1111,
LA-12753-MS, Los Alamos National Laboratory,
New Mexico, 23 pp.
Medary, R.T. 1992. Inexpensive, rapid field
screening test for 2,4,6-trinitrotoluene in soil.
Anal. Chim. Acta 258:341-346.
Miller, J.R. and R.G. Anderson. 1995. RCRA
trial burn tests, Tooele Army Depot deactivation
furnace, 9-31 August 1993. In: Proceedings 1995
Annual Air and Waste Management Association
Meeting in San Antonio, Air & Waste Management
Association, Pittsburgh, Pennsylvania.
Myers, K.F., E.F. McCormick, A.B. Strong,
P.G. Thorne, and T.F. Jenkins. 1994. Comparison
of Commercial Colorimetric and Enzyme
Immunoassay Field Screening Methods for TNT in
Soil, Technical Report IRRP-94-4, U.S. Army
Corps of Engineers, Waterways Experiment
Station, Vicksburg, Mississippi, 28 pp.
Noland, J.W., J.R. Marks and P.J. Marks.
1984. Task 2. Incineration Test of Explosives
Contaminated Soils at Savanna Army Depot
Activity, Savanna, IL, DRXTH-TE-CR-84277.
Prepared for U.S. Army Environmental Center,
Aberdeen Proving Ground, Maryland.
Oresik, W.L.S., M.T. Often, and M.D. Nelson.
1994. Minimizing soil remediation volume through
specification of excavation and materials handling
procedures. In: 1994 Federal Environmental
Restoration II & Waste Minimization II Conference
and Exhibition Proceedings, Volume I, Hazardous
Material Control Resources Institute, April 27-29,
1994, pp.703-712.
Roberts, W.C. and W.R. Hartley. 1992.
Drinking Water Health Advisory: Munitions.
Lewis Publishers, Boca Raton, Florida.
Rodacy, P. and P. Leslie. 1992. Ion Mobility
Spectroscopy as a Means of Detecting Explosives
in Soil Samples, Sand-92-1522C, Sandia National
Laboratories, Albuquerque, New Mexico, 7 pp.
Rubio, F.R., T.S. Lawruk, A.M. Gueco, D.P.
Herzog, and J.R. Fleeker. 1996. Determination of
TNT in soil and water by a magnetic particle-based
enzyme immunoassay system. Proceedings of 11th
Annual Waste Testing and Quality Assurance
Symposium, American Chemical Society, July
23-28, 1995.
Shriver-Lake, L.C., K.A. Breslin, P.T. Charles,
D.W. Conrad, J.P. Golden, and F.S. Ligler. 1995.
Detection of TNT in water using an evanescent
wave fiber-optic biosensor. Anal. Chem.,
67(14):2431-2435.
Sisk, W. 1992. Reactivity testing and handling
explosive-contaminated soil, explosives and
munitions. In: 1992 Federal Environmental
Restoration Conference Proceedings, Hazardous
Material Control Resources Institute, Vienna, pp.
91-92.
Sundquist, J.A., S. SisodiaandG. Olsen. 1995.
Comparative treatability studies of three biological
treatment technologies for explosives-contaminated
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soils. In: 21st Annual Environmental Symposium
and Exhibition Proceedings, American Defense
Preparedness Association, Arlington, Virginia.
Swanson, A., H.E. Canavan, L.A. Kelly, and
J.B. Roberts. 1996. Comparison of mobile
laboratory screening methods for high explosive
with EPA SW-846 Method 8330. Proceedings of
Fourth International Conference On-Site Analysis,
January 21-24, 1996.
Teaney, G., J. Melby, and J. Stave. 1993. A
novel field analytical method for TNT. Proceedings
of the American Association of Analytical
Chemists.
Teaney, G.B., and R.T. Hudak. 1994.
Development of an enzyme immunoassay based
field screening system for the detection of RDX in
soil and water. Proceedings of 87th Annual
Meeting and Exhibition, Air & Waste Management
Association, Cincinnati, Ohio, 94-RP143.05, 15
pp.
Thorne, P.O. and T.F. Jenkins. 1995a.
Development of a Field Method for Ammonium
Picrate/Picric Acid in Soil and Water, Special
Report 95-20, U.S. Army Cold Regions Research
and Engineering Laboratory, Hanover, New
Hampshire, 22 pp.
Thorne, P.O. and T.F. Jenkins. 1995b. Field
screening method for picric acid/ammonium
picrate in soil and water. In: Field Screening
Methods for Hazardous Wastes and Toxic
Chemicals, VIP-47, Air & Waste Management
Association, Pittsburgh, Pennsylvania, 2:942-947.
Turkeltaub, R.B. et al. 1989. Onsite
incineration of explosives contaminated soil. In:
Proceedings of the U.S. EPA's Forum on
Remediation of Superfund Sites where Explosives
are Present, San Antonio, Texas, U.S. EPA Office
of Research and Development, Risk Reduction
Engineering Laboratory, Cincinnati, Ohio,
Contract No. 68-03-3413.
Walsh, J.T., R.C. Chalk, and C. Merritt. 1973.
Application of liquid chromatography to pollution
abatement studies of munitions wastewater. Anal.
Chem. 45:1215-1220.
Walsh, M.E. 1989. Analytical Methods for
Determining Nitroguanidine in Soil and Water,
Special Report 89-35, U.S. Army Corps of
Engineers, Cold Regions Research and
Engineering Laboratory.
Walsh, M.E., and T.F. Jenkins. 1991.
Development of a Field Screening Method for
RDX in Soil, Special Report 91-7, U.S. Army
Corps of Engineers, Cold Regions Research and
Engineering Laboratory.
Walsh, M.E., T.F. Jenkins, P.S. Schnitker,
J.W. Elwell, and M.H. Stutz. 1993. Evaluation of
SW-846 Method 8330 for Characterization of Sites
Contaminated with Residues of High Explosives,
Special Report 93-5, U.S. Army Corps of
Engineers, Cold Regions Research and
Engineering Laboratory, 17 pp.
Whelan, J.P., A.W. Kusterbeck, G.A.
Wemhoff, R. Bredehorst, and F.S. Ligler. 1993.
Continuous-flow immunosensor for detection of
explosives. Anal. Chem. 65:3561-3565.
Wilson, S.A. 1992. Preparation and Analysis of
Soil Compost Material for Inorganic and Explosive
Constituents, ADA2630069XSP, U.S. Geological
Survey, Denver, Colorado, 41 pp.
Yinon, J. 1990. Toxicity and Metabolism of
Explosives. CRC Press, Boca Raton, Florida.
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