ASTM D7758-11(2016)
(Practice)Standard Practice for Passive Soil Gas Sampling in the Vadose Zone for Source Identification, Spatial Variability Assessment, Monitoring, and Vapor Intrusion Evaluations
Standard Practice for Passive Soil Gas Sampling in the Vadose Zone for Source Identification, Spatial Variability Assessment, Monitoring, and Vapor Intrusion Evaluations
SIGNIFICANCE AND USE
5.1 Passive soil gas samplers are a minimally invasive, easy-to-use technique in the field for identifying VOCs and SVOCs in the vadose zone. Similar to active soil gas and other field screening techniques, the simplicity and low cost of passive samplers enables them to be applied in large numbers, facilitating detailed mapping of contamination across a site, for the purpose of identifying source areas and release locations, focusing subsequent soil and groundwater sampling locations, focusing remediation plans, identifying vapor intrusion pathways, tracking groundwater plumes, and monitoring remediation progress. Data generated from passive soil gas sampling are semi-quantitative and are dependent on numerous factors both within and outside the control of the sampling personnel. Key variables are identified and briefly discussed in the following sections.
Note 1: Additional non-mandatory information on these factors or variables are covered in the applicable standards referenced in Section 2, and the footnotes and Bibliography presented herewith.
5.2 Application—The techniques described in this practice are suitable for sampling soil gas with sorbent samplers in a wide variety of geological settings for subsequent analysis for VOCs and SVOCs. The techniques also may prove useful for species other than VOCs and SVOCs, such as elemental mercury, with specialized sorbent media and analysis.
5.2.1 Source Identification and Spatial Variability Assessment—Passive soil gas sampling can be an effective method to identify contaminant source areas in the vadose zone and delineate the extent of contamination. By collecting samples in a grid with fewer data gaps, the method allows for an increase in data density and, therefore, provides a high-resolution depiction of the nature and extent of contamination across the survey area. By comparing the results, as qualitative or quantitative, from one location to another, the relative distribution and spatial variability of t...
SCOPE
1.1 Purpose—This practice covers standardized techniques for passively collecting soil gas samples from the vadose zone and is to be used in conjunction with Guide D5314.
1.2 Objectives—Objectives guiding the development of this practice are: (1) to synthesize and put in writing good commercial and customary practice for conducting passive soil gas sampling, (2) to ensure that the process for collecting and analyzing passive soil gas samples is practical and reasonable, and (3) to provide standard guidance for passive soil gas sampling performed in support of source identification, spatial variability/extent determinations, site assessment, site monitoring, and vapor intrusion investigations.
1.3 This practice does not address requirements of any federal, state, or local regulations or guidance or both with respect to soil gas sampling. Users are cautioned that federal, state, and local guidance may impose specific requirements that differ from those of this practice.
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, 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.
1.6 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice 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 “...
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Designation:D7758 −11 (Reapproved 2016)
Standard Practice for
Passive Soil Gas Sampling in the Vadose Zone for Source
Identification, Spatial Variability Assessment, Monitoring,
and Vapor Intrusion Evaluations
This standard is issued under the fixed designation D7758; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope nor should this document be applied without consideration of
a project’s many unique aspects. The word “Standard” in the
1.1 Purpose—This practice covers standardized techniques
title means only that the document has been approved through
for passively collecting soil gas samples from the vadose zone
the ASTM consensus process.
and is to be used in conjunction with Guide D5314.
1.2 Objectives—Objectives guiding the development of this
2. Referenced Documents
practice are: (1) to synthesize and put in writing good com-
2.1 ASTM Standards:
mercial and customary practice for conducting passive soil gas
D653 Terminology Relating to Soil, Rock, and Contained
sampling, (2) to ensure that the process for collecting and
Fluids
analyzing passive soil gas samples is practical and reasonable,
D1356 Terminology Relating to Sampling and Analysis of
and (3) to provide standard guidance for passive soil gas
Atmospheres
sampling performed in support of source identification, spatial
D2216 Test Methods for Laboratory Determination of Water
variability/extent determinations, site assessment, site
(Moisture) Content of Soil and Rock by Mass
monitoring, and vapor intrusion investigations.
D2487 Practice for Classification of Soils for Engineering
1.3 This practice does not address requirements of any
Purposes (Unified Soil Classification System)
federal, state, or local regulations or guidance or both with
D3740 Practice for Minimum Requirements for Agencies
respect to soil gas sampling. Users are cautioned that federal,
Engaged in Testing and/or Inspection of Soil and Rock as
state, and local guidance may impose specific requirements
Used in Engineering Design and Construction
that differ from those of this practice.
D4597 Practice for Sampling Workplace Atmospheres to
1.4 Units—The values stated in SI units are to be regarded Collect Gases or Vapors with Solid Sorbent Diffusive
Samplers
as standard. No other units of measurement are included in this
standard. D5088 Practice for Decontamination of Field Equipment
Used at Waste Sites
1.5 This standard does not purport to address all of the
D5314 Guide for Soil Gas Monitoring in the Vadose Zone
safety concerns, if any, associated with its use. It is the
(Withdrawn 2015)
responsibility of the user of this standard to establish appro-
D5792 Practice for Generation of Environmental Data Re-
priate safety and health practices and determine the applica-
lated to Waste Management Activities: Development of
bility of regulatory limitations prior to use.
Data Quality Objectives
1.6 This practice offers a set of instructions for performing
D6196 Practice for Choosing Sorbents, Sampling Param-
one or more specific operations. This document cannot replace
eters and Thermal Desorption Analytical Conditions for
education or experience and should be used in conjunction
Monitoring Volatile Organic Chemicals in Air
with professional judgment. Not all aspects of this practice may
D6311 Guide for Generation of Environmental Data Related
be applicable in all circumstances. This ASTM standard is not
to Waste ManagementActivities: Selection and Optimiza-
intended to represent or replace the standard of care by which
tion of Sampling Design
the adequacy of a given professional service must be judged,
1 2
This practice is under the jurisdiction of ASTM Committee D18 on Soil and For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Rock and is the direct responsibility of Subcommittee D18.21 on Groundwater and contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Vadose Zone Investigations. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Oct. 1, 2016. Published October 2016. Originally the ASTM website.
approved in 2011. Last previous edition approved in 2011 as D7758–11. DOI: The last approved version of this historical standard is referenced on
10.1520/D7758-11R16. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7758−11 (2016)
E2600 Guide for Vapor Encroachment Screening on Prop- 3.1.12 groundwater, n—part of the subsurface water that is
erty Involved in Real Estate Transactions in the saturated zone.
2.2 U.S. EPA Methods 3.1.13 method blank, n—quality control check to measure
Method 8260C Volatile Organic Compounds by Gas
laboratory contamination during sample analysis.
Chromatography/Mass Spectrometry (GC/MS)
3.1.14 moisture content, n—the moisture present in a
Method 8270C Semivolatile Organic Compounds by Gas
material, as determined by definite prescribed methods, ex-
Chromatography/Mass Spectrometry
pressed as a percentage of the mass of the sample on either of
Method TO-17 Determination of Volatile Organic Com-
the following bases: (1) original mass ; (2) moisture-free (oven
pounds in Ambient Air Using Active Sampling Onto
dried) mass (see Test Method D2216).
Sorbent Tubes
3.1.15 passive sampling, v—meansofcollectingagas-phase
substance that uses sorbent materials in a sampling device
3. Terminology
exposed for a finite duration in the medium being sampled.
3.1 Definitions of Terms Specific to This Standard:
3.1.16 preparation blank, n—quality control check to define
3.1.1 This section provides definitions and descriptions of
theefficiencyofconditioningabatchofsorbentsamplersatthe
terms used in or related to this practice.Alist of acronyms and
laboratory for sample collection (also referred to as manufac-
a list of symbols are also included. The terms are an integral
turing blanks).
part of this practice and are critical to an understanding of the
practice and its use. Also see Terminology D653 and D1356. 3.1.17 porosity, n—volume fraction of rock or soil not
3.1.2 absorption, n—the penetration of one substance into occupied by solid material but usually occupied by liquids,
the inner structure of another. vapor, or air, or combinations thereof.
3.1.17.1 Discussion—Porosity is the void volume of soil or
3.1.3 active sampling, v—means of collecting a gas-phase
rockorbothdividedbythetotalvolumeofsoilorrockorboth.
substance that uses a mechanical device such as a pump or
vacuum-assisted critical orifice to draw air into or through a
3.1.18 sampling rate, n—the ratio of mass of a given
sampling device.
compound collected by a diffusive sampler per unit time of
exposure to the concentration of that compound in the atmo-
3.1.4 adsorption, n—adherence of the atoms, ions, or mol-
sphere being sampled.The sampling rate is sometimes referred
ecules of a gas or liquid to the surface of another substance
to as the uptake rate.
(chemisorption).
3.1.19 saturated zone, n—zone in which all of the voids in
3.1.5 ambient air, n—any unconfined portion of the atmo-
the rock or soil are filled with water at a pressure that is greater
sphere; open air.
than atmospheric.
3.1.6 background level, n—concentrationofasubstancethat
3.1.19.1 Discussion—The water table is the top of the
is typically found in ambient air (for example, as a result of
saturated zone in an unconfined aquifer.
industrial or automobile emissions), indoor air (for example,
from building materials or indoor activities), or the natural
3.1.20 soil gas, n—vadose zone atmosphere; soil gas is the
geology of an area.
air existing in void spaces in the soil between the groundwater
table and the ground surface.
3.1.7 blank sample, n—clean sample or a sample of matrix
processed to measure artifacts in the measurement process.
3.1.21 soil moisture, n—water contained in the pore spaces
3.1.7.1 Discussion—Blank samples are named according to
in the vadose zone.
their type and use (for example, method blank, trip blank, field
3.1.22 sorbent, n—a solid or liquid medium in or upon
blank, and preparation or manufacturing blank).
which materials are collected by adsorption, absorption, or
3.1.8 contaminant, n—substances not normally found in an
chemisorption.
environment at the observed concentration.
3.1.23 sorbent sampling, v—the collection of chemicals
3.1.9 desorption, n—the process of freeing from a sorbed
fromanairoremissionsamplebyallowingtheairoremissions
state.
to contact a sorbent.
3.1.10 duplicate samples, n—two samples taken from and
3.1.24 sorption, n—a process by which one material (the
representative of the same population that are carried through
sorbent) takes up and retains another material (the sorbate) by
all steps of the sampling and analytical procedures in an
the processes of adsorption or absorption.
identical manner.
3.1.25 source, n—area(s) at a site where releases have
3.1.11 field blank, n—cleansamplingmediathatiscarriedto
occurredthatareemanatingvaporsfromeitherthevadosezone
the sampling site, exposed to ambient air during field sampling
or groundwater.
procedures, and transported to the laboratory for analysis (also
3.1.25.1 Discussion—There may be multiple sources at a
referred to as an ambient air control sample).
siteandtheareaoverwhichanyonesourceisdefinedissubject
to interpretation from multiple data sets.
3.1.26 spatial variability, n—relationship of organic com-
Available from United States Environmental Protection Agency (EPA), Ariel
pound mass from one location to many others at a site as a
Rios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20004, http://
www.epa.gov. function of distance.
D7758−11 (2016)
3.1.27 starvation effect, n—when the analyte uptake rate of typesandcombinationsofsorbentmaterialscanbeusedtotrap
apassivesorbentsamplerisgreaterthanthereplenishmentrate VOCs and SVOCs in soil gas, this practice is intended to
of the analyte around the sampler, which results in a low bias achieve representative and reproducible samples of known
measurement. quality. The design of PSG surveys (for example, sampler
design, sample spacing, the sampler exposure period, and
3.1.28 trip blank, n—clean, unused sampling media that is
analytical methods) is within the scope of this practice. These
carried to the sampling site and transported to the laboratory
guidelines are not intended to restrict the sampler design or its
for analysis without having been exposed to field sampling
application in regards to spacing, sampler distribution, or time
procedures.
of exposure; however, these guidelines are meant to provide a
3.1.29 vadose zone, n—hydrogeological region extending
general idea of common practice at the time this standard was
from the soil surface to the top of the principal water table.
prepared.
3.1.29.1 Discussion—Perched groundwater may exist
within this zone.
5. Significance and Use
3.1.30 vapor intrusion, n—migration of a volatile chemi-
5.1 Passive soil gas samplers are a minimally invasive,
cal(s)fromsubsurfacesoilorwaterintoanoverlyingornearby
easy-to-use technique in the field for identifying VOCs and
building.
SVOCs in the vadose zone. Similar to active soil gas and other
3.1.31 water table, n—top of the saturated zone in an field screening techniques, the simplicity and low cost of
unconfined aquifer. passive samplers enables them to be applied in large numbers,
facilitatingdetailedmappingofcontaminationacrossasite,for
3.2 Acronyms:
the purpose of identifying source areas and release locations,
3.2.1 BLS—Below land surface (also know as below ground
focusing subsequent soil and groundwater sampling locations,
surface (bgs))
focusing remediation plans, identifying vapor intrusion
3.2.2 COC—Compound of concern
pathways, tracking groundwater plumes, and monitoring reme-
3.2.3 EPA—Environmental Protection Agency
diation progress. Data generated from passive soil gas sam-
pling are semi-quantitative and are dependent on numerous
3.2.4 ID—Identification
factors both within and outside the control of the sampling
3.2.5 MDL—Method detection limit
personnel. Key variables are identified and briefly discussed in
3.2.6 QA/QC—Quality assurance and quality control
the following sections.
3.2.7 PSG—Passive soil gas NOTE 1—Additional non-mandatory information on these factors or
variables are covered in the applicable standards referenced in Section 2,
3.2.8 SVOC—Semivolatile organic compound
and the footnotes and Bibliography presented herewith.
3.2.9 TD-GC/MS—Thermal desorption-gas chromato-
5.2 Application—The techniques described in this practice
graphy/mass spectrometry
are suitable for sampling soil gas with sorbent samplers in a
3.2.10 U.S.—United States
wide variety of geological settings for subsequent analysis for
VOCs and SVOCs. The techniques also may prove useful for
3.2.11 VOC—Volatile organic compound
species other than VOCs and SVOCs, such as elemental
3.3 Symbols:
mercury, with specialized sorbent media and analysis.
3.3.1 cm—centimeter
5.2.1 Source Identification and Spatial Variability
3.3.2 m—meter
Assessment—Passive soil gas sampling can be an effective
3.3.3 mm—millimeter methodtoidentifycontaminantsourceareasinthevadosezone
and delineate the extent of contamination. By collecting
3.3.4 min—minute
samples in a grid with fewer data gaps, the method allows for
-9
3.3.5 ng—mass in nanograms or 10 g
an increase in data density and, therefore, provides a high-
3.3.6 s—seconds
resolution depiction of the nature and extent of contamination
-6
3.3.7 µg—mass in micrograms or 10 g across the survey area. By comparing the results, as qualitative
or quantitative, from one location to another, the relative
4. Summary of Practice
distribution and spatial variability of the contaminants in the
4.1 This practice describes the passive collection and sub- subsurface can be determined, thereby improving the concep-
sequent analysis of soil gas samples, using sorbent samplers to tual site model. Areas of the site reporting non-detects can be
trapVOCs and SVOCs in soil vapor by placing samplers in the removed from further investigation, while subsequent sam-
subsurface for a period of time at multiple locations across a pling and remediation can be focused in areas determined from
site. Placement of the sampler can be in open soils (i.e., not the PSG survey to be impacted.
covered by a surface such as asphalt or concrete), or advanced 5.2.2 Monitoring—Passive soil gas samplers are used to
through slab surfaces (e.g., parking
...
This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7758 − 11 D7758 − 11 (Reapproved 2016)
Standard Practice for
Passive Soil Gas Sampling in the Vadose Zone for Source
Identification, Spatial Variability Assessment, Monitoring,
and Vapor Intrusion Evaluations
This standard is issued under the fixed designation D7758; 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 (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 Purpose—This practice covers standardized techniques for passively collecting soil gas samples from the vadose zone and
is to be used in conjunction with Guide D5314.
1.2 Objectives—Objectives guiding the development of this practice are: (1) to synthesize and put in writing good commercial
and customary practice for conducting passive soil gas sampling, (2) to ensure that the process for collecting and analyzing passive
soil gas samples is practical and reasonable, and (3) to provide standard guidance for passive soil gas sampling performed in
support of source identification, spatial variability/extent determinations, site assessment, site monitoring, and vapor intrusion
investigations.
1.3 This practice does not address requirements of any federal, state, or local regulations or guidance or both with respect to
soil gas sampling. Users are cautioned that federal, state, and local guidance may impose specific requirements that differ from
those of this practice.
1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
1.5 This standard does not purport to address all of the safety concerns, 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.
1.6 This practice offers a set of instructions for performing one or more specific operations. This document cannot replace
education or experience and should be used in conjunction with professional judgment. Not all aspects of this practice 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 means only that the document has been approved through the ASTM
consensus process.
2. Referenced Documents
2.1 ASTM Standards:
D653 Terminology Relating to Soil, Rock, and Contained Fluids
D1356 Terminology Relating to Sampling and Analysis of Atmospheres
D2216 Test Methods for Laboratory Determination of Water (Moisture) Content of Soil and Rock by Mass
D2487 Practice for Classification of Soils for Engineering Purposes (Unified Soil Classification System)
D3740 Practice for Minimum Requirements for Agencies Engaged in Testing and/or Inspection of Soil and Rock as Used in
Engineering Design and Construction
D4597 Practice for Sampling Workplace Atmospheres to Collect Gases or Vapors with Solid Sorbent Diffusive Samplers
D5088 Practice for Decontamination of Field Equipment Used at Waste Sites
This practice is under the jurisdiction of ASTM Committee D18 on Soil and Rock and is the direct responsibility of Subcommittee D18.21 on Groundwater and Vadose
Zone Investigations.
Current edition approved Dec. 1, 2011Oct. 1, 2016. Published January 2012October 2016. Originally approved in 2011. Last previous edition approved in 2011 as
D7758–11. DOI: 10.1520/D7758-11.10.1520/D7758-11R16.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7758 − 11 (2016)
D5314 Guide for Soil Gas Monitoring in the Vadose Zone (Withdrawn 2015)
D5792 Practice for Generation of Environmental Data Related to Waste Management Activities: Development of Data Quality
Objectives
D6196 Practice for Choosing Sorbents, Sampling Parameters and Thermal Desorption Analytical Conditions for Monitoring
Volatile Organic Chemicals in Air
D6311 Guide for Generation of Environmental Data Related to Waste Management Activities: Selection and Optimization of
Sampling Design
E2600 Guide for Vapor Encroachment Screening on Property Involved in Real Estate Transactions
2.2 U.S. EPA Methods
Method 8260C Volatile Organic Compounds by Gas Chromatography/Mass Spectrometry (GC/MS)
Method 8270C Semivolatile Organic Compounds by Gas Chromatography/Mass Spectrometry
Method TO-17 Determination of Volatile Organic Compounds in Ambient Air Using Active Sampling Onto Sorbent Tubes
3. Terminology
3.1 Definitions of Terms Specific to This Standard:
3.1.1 This section provides definitions and descriptions of terms used in or related to this practice. A list of acronyms and a list
of symbols are also included. The terms are an integral part of this practice and are critical to an understanding of the practice and
its use. Also see Terminology D653 and D1356.
3.1.2 absorption, n—the penetration of one substance into the inner structure of another.
3.1.3 active sampling, v—means of collecting a gas-phase substance that uses a mechanical device such as a pump or
vacuum-assisted critical orifice to draw air into or through a sampling device.
3.1.4 adsorption, n—adherence of the atoms, ions, or molecules of a gas or liquid to the surface of another substance
(chemisorption).
3.1.5 ambient air, n—any unconfined portion of the atmosphere; open air.
3.1.6 background level, n—concentration of a substance that is typically found in ambient air (for example, as a result of
industrial or automobile emissions), indoor air (for example, from building materials or indoor activities), or the natural geology
of an area.
3.1.7 blank sample, n—clean sample or a sample of matrix processed to measure artifacts in the measurement process.
The last approved version of this historical standard is referenced on www.astm.org.
Available from United States Environmental Protection Agency (EPA), Ariel Rios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20004, http://www.epa.gov.
3.1.7.1 Discussion—
Blank samples are named according to their type and use (for example, method blank, trip blank, field blank, and preparation or
manufacturing blank).
3.1.8 contaminant, n—substances not normally found in an environment at the observed concentration.
3.1.9 desorption, n—the process of freeing from a sorbed state.
3.1.10 duplicate samples, n—two samples taken from and representative of the same population that are carried through all steps
of the sampling and analytical procedures in an identical manner.
3.1.11 field blank, n—clean sampling media that is carried to the sampling site, exposed to ambient air during field sampling
procedures, and transported to the laboratory for analysis (also referred to as an ambient air control sample).
3.1.12 groundwater, n—part of the subsurface water that is in the saturated zone.
3.1.13 method blank, n—quality control check to measure laboratory contamination during sample analysis.
3.1.14 moisture content, n—the moisture present in a material, as determined by definite prescribed methods, expressed as a
percentage of the mass of the sample on either of the following bases: (1) original mass ; (2) moisture-free (oven dried) mass (see
Test Method D2216).
3.1.15 passive sampling, v—means of collecting a gas-phase substance that uses sorbent materials in a sampling device exposed
for a finite duration in the medium being sampled.
3.1.16 preparation blank, n—quality control check to define the efficiency of conditioning a batch of sorbent samplers at the
laboratory for sample collection (also referred to as manufacturing blanks).
3.1.17 porosity, n—volume fraction of rock or soil not occupied by solid material but usually occupied by liquids, vapor, or air,
or combinations thereof.
D7758 − 11 (2016)
3.1.17.1 Discussion—
Porosity is the void volume of soil or rock or both divided by the total volume of soil or rock or both.
3.1.18 sampling rate, n—the ratio of mass of a given compound collected by a diffusive sampler per unit time of exposure to
the concentration of that compound in the atmosphere being sampled. The sampling rate is sometimes referred to as the uptake
rate.
3.1.19 saturated zone, n—zone in which all of the voids in the rock or soil are filled with water at a pressure that is greater than
atmospheric.
3.1.19.1 Discussion—
The water table is the top of the saturated zone in an unconfined aquifer.
3.1.20 soil gas, n—vadose zone atmosphere; soil gas is the air existing in void spaces in the soil between the groundwater table
and the ground surface.
3.1.21 soil moisture, n—water contained in the pore spaces in the vadose zone.
3.1.22 sorbent, n—a solid or liquid medium in or upon which materials are collected by adsorption, absorption, or
chemisorption.
3.1.23 sorbent sampling, v—the collection of chemicals from an air or emission sample by allowing the air or emissions to
contact a sorbent.
3.1.24 sorption, n—a process by which one material (the sorbent) takes up and retains another material (the sorbate) by the
processes of adsorption or absorption.
3.1.25 source, n—area(s) at a site where releases have occurred that are emanating vapors from either the vadose zone or
groundwater.
3.1.25.1 Discussion—
There may be multiple sources at a site and the area over which any one source is defined is subject to interpretation from multiple
data sets.
3.1.26 spatial variability, n—relationship of organic compound mass from one location to many others at a site as a function
of distance.
3.1.27 starvation effect, n—when the analyte uptake rate of a passive sorbent sampler is greater than the replenishment rate of
the analyte around the sampler, which results in a low bias measurement.
3.1.28 trip blank, n—clean, unused sampling media that is carried to the sampling site and transported to the laboratory for
analysis without having been exposed to field sampling procedures.
3.1.29 vadose zone, n—hydrogeological region extending from the soil surface to the top of the principal water table.
3.1.29.1 Discussion—
Perched groundwater may exist within this zone.
3.1.30 vapor intrusion, n—migration of a volatile chemical(s) from subsurface soil or water into an overlying or nearby
building.
3.1.31 water table, n—top of the saturated zone in an unconfined aquifer.
3.2 Acronyms:
3.2.1 BLS—Below land surface (also know as below ground surface (bgs))
3.2.2 COC—Compound of concern
3.2.3 EPA—Environmental Protection Agency
3.2.4 ID—Identification
3.2.5 MDL—Method detection limit
3.2.6 QA/QC—Quality assurance and quality control
3.2.7 PSG—Passive soil gas
3.2.8 SVOC—Semivolatile organic compound
D7758 − 11 (2016)
3.2.9 TD-GC/MS—Thermal desorption-gas chromato-
graphy/mass spectrometry
3.2.10 U.S.—United States
3.2.11 VOC—Volatile organic compound
3.3 Symbols:
3.3.1 cm—centimeter
3.3.2 m—meter
3.3.3 mm—millimeter
3.3.4 min—minute
-9
3.3.5 ng—mass in nanograms or 10 g
3.3.6 s—seconds
-6
3.3.7 μg—mass in micrograms or 10 g
4. Summary of Practice
4.1 This practice describes the passive collection and subsequent analysis of soil gas samples, using sorbent samplers to trap
VOCs and SVOCs in soil vapor by placing samplers in the subsurface for a period of time at multiple locations across a site.
Placement of the sampler can be in open soils (i.e., not covered by a surface such as asphalt or concrete), or advanced through slab
surfaces (e.g., parking lots, streets, sidewalks, building slabs, and basement floors) to allow for subslab soil gas sampling. This
practice provides standard guidance for passive soil gas (PSG) sampling and analysis performed in support of, but not limited to,
site assessment, site monitoring, and vapor intrusion investigations. While several different types and combinations of sorbent
materials can be used to trap VOCs and SVOCs in soil gas, this practice is intended to achieve representative and reproducible
samples of known quality. The design of PSG surveys (for example, sampler design, sample spacing, the sampler exposure period,
and analytical methods) is within the scope of this practice. These guidelines are not intended to restrict the sampler design or its
application in regards to spacing, sampler distribution, or time of exposure; however, these guidelines are meant to provide a
general idea of common practice at the time this standard was prepared.
5. Significance and Use
5.1 Passive soil gas samplers are a minimally invasive, easy-to-use technique in the field for identifying VOCs and SVOCs in
the vadose zone. Similar to active soil gas and other field screening techniques, the simplicity and low cost of passive samplers
enables them to be applied in large numbers, facilitating detailed mapping of contamination across a site, for the purpose of
identifying source areas and release locations, focusing subsequent soil and groundwater sampling locations, focusing remediation
plans, identifying vapor intrusion pathways, tracking groundwater plumes, and monitoring remediation progress. Data generated
from passive soil gas sampling are semi-quantitative and are dependent on numerous factors both within and outside the control
of the sampling personnel. Key variables are identified and briefly discussed in the following sections.
NOTE 1—Additional non-mandatory information on these factors or variables are covered in the applicable standards referenced in Section 2, and the
footnotes and Bibliography presented herewith.
5.2 Application—The techniques described in this practice are suitable for sampling soil gas with sorbent samplers in a wide
variety of geological settings for subsequent analysis for VOCs and SVOCs. The techniques also may prove useful for species
other than VOCs and SVOCs, such as elemental mercury, with specialized sorbent media and analysis.
5.2.1 Source Identification and Spatial Variability Assessment—Passive soil gas sampling can be an e
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