ASTM D5314-92e1
(Guide)Standard Guide for Soil Gas Monitoring in the Vadose Zone
Standard Guide for Soil Gas Monitoring in the Vadose Zone
SCOPE
1.1 This guide covers information pertaining to a broad spectrum of practices and applications of soil atmosphere sampling, including sample recovery and handling, sample analysis, data interpretation, and data reporting. This guide can increase the awareness of soil gas monitoring practitioners concerning important aspects of the behavior of the soil-water-gas-contaminant system in which this monitoring is performed, as well as inform them of the variety of available techniques of each aspect of the practice. Appropriate applications of soil gas monitoring are identified, as are the purposes of the various applications. Emphasis is placed on soil gas contaminant determinations in certain application examples.
1.2 This guide suggests a variety of approaches useful to successfully monitor vadose zone contaminants with instructions that offer direction to those who generate and use soil gas data.
1.3 This guide does not recommend a standard practice to follow in all cases nor does it recommend definite courses of action. The success of any one soil gas monitoring methodology is strongly dependent upon the environment in which it is applied.
1.4 Concerns of practitioner liability or protection from or release from such liability, or both, are not addressed by this guide.
1.5 This guide is organized into the following sections and subsections that address specific segments of the practice of monitoring soil gas:Section4Summary of Practice4.1Basic principles, including partitioning theory, migration and emplacement processes, and contaminant degradation4.7Summary Procedure5Significance and Use6Approach and Procedure6.1Sampling Methodology6.5Sample Handling and Transport6.6Analysis of Soil Gas Samples6.7Data Interpretation7Reporting
1.6 This guide does not purport to set standard levels of acceptable risk. Use of this guide for purposes of risk assessment is wholly the responsibility of the user
1.7 The values stated in either inch-pound or SI units are to be regarded separately as the standard. The values given in parentheses are for information only.
1.8 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
1.9 This guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many unique aspects. The word "Standard" in the title of this document means only that the document has been approved through the ASTM consensus process.
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e1
Designation: D 5314 – 92
Standard Guide for
Soil Gas Monitoring in the Vadose Zone
This standard is issued under the fixed designation D 5314; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Paragraph 1.9 was added editorially October 1998.
1. Scope acceptable risk. Use of this guide for purposes of risk assess-
ment is wholly the responsibility of the user.
1.1 This guide covers information pertaining to a broad
1.7 The values stated in either inch-pound or SI units are to
spectrum of practices and applications of soil atmosphere
be regarded separately as the standard. The values given in
sampling, including sample recovery and handling, sample
parentheses are for information only.
analysis, data interpretation, and data reporting. This guide can
1.8 This standard does not purport to address all of the
increase the awareness of soil gas monitoring practitioners
safety problems, if any, associated with its use. It is the
concerning important aspects of the behavior of the soil-water-
responsibility of the user of this standard to establish appro-
gas-contaminant system in which this monitoring is performed,
priate safety and health practices and determine the applica-
as well as inform them of the variety of available techniques of
bility of regulatory limitations prior to use.
each aspect of the practice. Appropriate applications of soil gas
1.9 This guide offers an organized collection of information
monitoring are identified, as are the purposes of the various
or a series of options and does not recommend a specific
applications. Emphasis is placed on soil gas contaminant
course of action. This document cannot replace education or
determinations in certain application examples.
experience and should be used in conjunction with professional
1.2 This guide suggests a variety of approaches useful to
judgment. Not all aspects of this guide may be applicable in all
successfully monitor vadose zone contaminants with instruc-
circumstances. This ASTM standard is not intended to repre-
tions that offer direction to those who generate and use soil gas
sent or replace the standard of care by which the adequacy of
data.
a given professional service must be judged, nor should this
1.3 This guide does not recommend a standard practice to
document be applied without consideration of a project’s many
follow in all cases nor does it recommend definite courses of
unique aspects. The word “Standard” in the title of this
action. The success of any one soil gas monitoring methodol-
document means only that the document has been approved
ogy is strongly dependent upon the environment in which it is
through the ASTM consensus process.
applied.
1.4 Concerns of practitioner liability or protection from or
2. Referenced Documents
release from such liability, or both, are not addressed by this
2.1 ASTM Standards:
guide.
D 653 Terminology Relating to Soil, Rock, and Contained
1.5 This guide is organized into the following sections and
Fluids
subsections that address specific segments of the practice of
D 1356 Terminology Relating to Atmospheric Sampling
monitoring soil gas:
and Analysis
Section
D 1357 Practice for Planning the Sampling of the Ambient
4 Summary of Practice
4.1 Basic principles, including partitioning theory, migration and em-
Atmosphere
placement processes, and contaminant degradation
D 1452 Practice for Soil Investigation and Sampling by
4.7 Summary Procedure
Auger Borings
5 Significance and Use
6 Approach and Procedure
D 1605 Practices for Sampling Atmospheres for Analysis of
6.1 Sampling Methodology
Gases and Vapors
6.5 Sample Handling and Transport
D 1914 Practice for Conversion Units and Factors Relating
6.6 Analysis of Soil Gas Samples
6.7 Data Interpretation
to Atmospheric Analysis
7 Reporting
D 2652 Terminology Relating to Activated Carbon
1.6 This guide does not purport to set standard levels of
D 2820 Test Method for C Through C Hydrocarbons in
1 5
the Atmosphere by Gas Chromatography
This guide is under the jurisdiction of ASTM Committee D-18 on Soil and
Rock and is the direct responsibility of Subcommittee D18.21 on Ground Water and Annual Book of ASTM Standards, Vol 04.08.
Vadose Zone Investigations. Annual Book of ASTM Standards, Vol 11.03.
Current edition approved Nov. 15, 1992. Published January 1993. Annual Book of ASTM Standards, Vol 15.01.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
D 5314
D 3249 Practice for General Ambient Air Analyzer Proce- is effective to free and open gaseous flow and exchange, such
dures porosity generally being macroporosity.
D 3416 Test Method for Total Hydrocarbons, Methane, and 3.1.6 liquid phase—contaminant residing as a liquid in
Carbon Monoxide (Gas Chromatographic Method) in the vadose zone pore space, often referred to as “free product.”
Atmosphere 3.1.7 macroporosity—large intergranular porosity with
D 3584 Practice for Indexing Papers and Reports on Soil large pore throats, including soil cracks, moldic porosity,
and Rock for Engineering Purposes animal burrows and other significant void space.
D 3614 Guide for Laboratories Engaged in Sampling and 3.1.8 microporosity—intragranular porosity and micro-
Analysis of Atmospheres and Emissions scopic intergranular porosity with submicroscopic pore throats.
D 3670 Guide for Determination of Precision and Bias of 3.1.9 occluded vapor phase—condition of contaminant resi-
Methods of Committee D-22 dence in which volatilized contaminants occur in porosity that
D 3686 Practice for Sampling Atmospheres to Collect Or- is ineffective to free and open gaseous flow and exchange, such
ganic Compound Vapors (Activated Charcoal Tube Ad- porosity generally being microporosity; frequently termed
sorption Method) dead-end pore space.
D 3687 Practice for Analysis of Organic Compound Vapors 3.1.10 partitioning—the act of movement of contaminants
Collected by the Activated Charcoal Tube Adsorption from one soil residence phase to another.
Method 3.1.11 soil gas—vadose zone atmosphere.
D 4220 Practices for Preserving and Transporting Soil 3.1.12 solute phase—a condition of contaminant residence
Samples in which contaminants are dissolved in ground water in either
D 4490 Practice for Measuring the Concentration of Toxic the saturated or the vadose zone.
Gases or Vapors Using Detector Tubes 3.1.13 sorbed phase—a condition of contaminant residence
D 4597 Practice for Sampling Workplace Atmospheres to in which contaminants are adsorbed onto the surface of soil
Collect Organic Gases or Vapors with Activated Charcoal particles or absorbed by soil organic matter.
Diffusional Samplers 3.1.14 vadose zone—the hydrogeological region extending
D 4696 Guide for Pore-Liquid Sampling from the Vadose from the soil surface to the top of the principal water table.
Zone
4. Summary of Guide
D 4700 Guide for Soil Core Sampling from the Vadose
4.1 Soil gas monitoring in the vadose zone is a method used
Zone
to directly measure characteristics of the soil atmosphere that
D 5088 Practice for the Decontamination of Field Equip-
are frequently utilized as an indirect indicator of processes
ment Used at Non Radioactive Waste Sites
occurring in and below a sampling horizon. Soil gas monitor-
E 177 Practice for Use of the Terms Precision and Bias in
ing is used as a method to suggest the presence, composition,
ASTM Test Methods
and origin of contaminants in and below the vadose zone.
E 260 Practice for Packed Column Gas Chromatography
Among other applications, this method is also employed in the
E 355 Practice for Gas Chromatogaphy Terms and Relation-
exploration for natural resources, including petroleum, natural
ships
gas and precious metals. Soil gas monitoring is a valuable
E 594 Practice for Testing Flame Ionization Detectors Used
screening method for detection of volatile organic contami-
in Gas Chromatography
nants, the most abundant analytical group of ground-water
E 697 Practice for Use of Electron-Capture Detectors in
contaminant compounds (1).
Gas Chromatography
4.2 Basic Theoretical Principles—The processes indicated
3. Terminology
by the soil gas monitoring method are partitioning, migration,
emplacement and degradation. Partitioning represents a group
3.1 Definitions of Terms Specific to This Standard:
of processes that control contaminant movement from one
3.1.1 capillary fringe—the basal region of the vadose zone
physical phase to another, these phases being liquid, free vapor
comprising sediments that are saturated, or nearly saturated,
near the water table, gradually decreasing in water content with (that is, through-flowing air (2)), occluded vapor (that is,
locally accessible air and trapped air (2)), solute and sorbed.
increasing elevation above the water table. Also see Terminol-
ogy D 653. Migration refers to contaminant movement over distance with
any vertical, horizontal or temporal component. Emplacement
3.1.2 contaminant—substances not normally found in an
environment at the observed concentration. refers to establishment of contaminant residence in any phase
within any residence opportunity. Degradation is the process
3.1.3 emplacement—the establishment of contaminant resi-
dence in the vadose zone in a particular phase. whereby contaminants are attenuated by oxidation or reduction
in the vadose zone, either through biogenic or abiogenic
3.1.4 free product—liquid phase contaminants released into
processes. Soil gas monitoring measures the result of the
the environment.
interaction of these processes in a dynamic equilibrium.
3.1.5 free vapor phase—a condition of contaminant resi-
Measurement of these processes in static equilibrium is unre-
dence in which volatilized contaminants occur in porosity that
alistic.
Annual Book of ASTM Standards, Vol 04.09.
6 8
Annual Book of ASTM Standards, Vol 14.02. The boldface numbers given in parentheses refer to a list of references at the
Annual Book of ASTM Standards, Vol 14.01. end of the text.
D 5314
4.3 The following subsections provide detailed information the contaminant(s) in the soil atmosphere.
on partitioning, migration, emplacement and degradation. Sub- 4.3.2.2 The effects of temperature upon dissolution equilib-
section 4.4 provides a summary procedure for soil gas sam- rium are generally insignificant for aliphatic hydrocarbons
pling. Users of this guide who do not wish to study details of between 15 and 50°C (4), the temperature range from which
partitioning, migration, emplacement and degradation at this most soil gas samples are recovered. However, temperature
time may skip to 4.4. effects upon dissolution equilibrium can be significant for other
common families of contaminant compounds within similar
4.3.1 Partitioning is the initial step by which contaminants
begin to move away from their source. Partitioning occurs in temperature ranges (5). These effects must be considered when
planning or interpreting the results of a soil gas survey.
water saturated and unsaturated environments. This group of
processes is complex and difficult to quantify when considered 4.3.2.3 Dissolution equilibrium is altered by changes in
water salinity. Modest decreases in the solubility of contami-
in the vadose zone due to the unique makeup of the vadose
matrix, i.e. air-filled porosity (microporous and macroporous), nants in water are to be expected with increases in salinity of
pore water, free product, solid-phase soil organic matter, clay the solution.
and discrete inorganic soil particles. Important individual 4.3.2.4 The rate of dissolution is strongly dependent upon
processes of partitioning are dissolution, volatilization, air- the partitioning coefficient of the particular contaminant of
water partitioning, soil-water partitioning and soil-air partition- interest and the amount of mixing of the liquid phase and water
ing (3). (3). For example, partitioning of a particular contaminant into
4.3.2 Dissolution is the process whereby volatile contami- ground water is accelerated by frequent water level fluctuations
within a contaminated capillary fringe. The downstream im-
nants move between the liquid phase (free product) and the
plications for subsequent partitioning of the contaminant from
solute phase (dissolved in water). At equilibrium, the product
the solute to the vapor phase for eventual soil gas recovery are
of the mole fraction of a particular compound in the liquid
obvious.
phase and the activity coefficient of that compound in the liquid
4.3.3 Volatilization is the process during which volatile
phase is equal to the product of the mole fraction of that
contaminants move between the liquid phase (free product) or
compound in the solute phase and the activity coefficient of
solute phase and a vapor phase, either the free vapor phase or
that compound in the solute phase. This process is more clearly
the occluded vapor phase or both. Contaminant mixtures can
described by the following expression:
contain compounds with a considerable range of vapor pres-
L L W W
X G 5 X G (1)
I I I I
sures that can contribute contaminants to the soil atmosphere
by volatilization. This atmosphere will exhibit a composition
where:
L
similar to that of the parent contaminant but lacking in those
X 5 the mole fraction of compound ( I) in the liquid (L)
I
constituents with the lowest vapor pressures. The likelihood of
phase (free product),
W
X 5 the mole fraction of compound (I) in the solute ( W) the presence of a particular contaminant introduced into the
I
phase (dissolved in water), soil atmosphere by volatilization can be estimated by consid-
L
G 5 the activity coefficient of compound ( I) in the liquid ering the partial pressure of that contaminant in a vapor phase.
I
(L) phase (free product), and
This partial pressure is equal to the product of the mole fraction
W
G 5 the activity coefficient of compound (I) in the solute
concentration of the subject component in the liquid contami-
I
(W) phase (dissolved in water).
nant solution, the activity coefficient of the subject component
Dissolution equilibrium is therefore influenced by concen-
and the vapor pressure of the pure component. This concept is
tration of the subject compound in both the free product
more clearly expressed as follows:
contaminant mixture and water. The most common practical
o
P 5 X G P (3)
I I
application of expression (Eq 1) in soil gas monitoring is in
hydrocarbon detection. Simplification of (Eq 1) is
...
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