1、Designation: D7758 11Standard Practice forPassive Soil Gas Sampling in the Vadose Zone for SourceIdentification, Spatial Variability Assessment, Monitoring,and Vapor Intrusion Evaluations1This standard is issued under the fixed designation D7758; the number immediately following the designation indi
2、cates the year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 PurposeThis practice covers standardized t
3、echniquesfor passively collecting soil gas samples from the vadose zoneand is to be used in conjunction with Guide D5314.1.2 ObjectivesObjectives guiding the development of thispractice are: (1) to synthesize and put in writing good com-mercial and customary practice for conducting passive soil gass
4、ampling, (2) to ensure that the process for collecting andanalyzing passive soil gas samples is practical and reasonable,and (3) to provide standard guidance for passive soil gassampling performed in support of source identification, spatialvariability/extent determinations, site assessment, site mo
5、nitor-ing, and vapor intrusion investigations.1.3 This practice does not address requirements of anyfederal, state, or local regulations or guidance or both withrespect to soil gas sampling. Users are cautioned that federal,state, and local guidance may impose specific requirementsthat differ from t
6、hose of this practice.1.4 UnitsThe values stated in SI units are to be regardedas standard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this
7、 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.6 This practice offers a set of instructions for performingone or more specific operations. This document cannot replaceeducation or experience and should be used
8、 in conjunctionwith professional judgment. Not all aspects of this practice maybe applicable in all circumstances. This ASTM standard is notintended to represent or replace the standard of care by whichthe adequacy of a given professional service must be judged,nor should this document be applied wi
9、thout consideration ofa projects many unique aspects. The word “Standard” in thetitle means only that the document has been approved throughthe ASTM consensus process.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD1356 Terminology Relating to
10、Sampling and Analysis ofAtmospheresD2216 Test Methods for Laboratory Determination of Wa-ter (Moisture) Content of Soil and Rock by MassD2487 Practice for Classification of Soils for EngineeringPurposes (Unified Soil Classification System)D3740 Practice for Minimum Requirements for AgenciesEngaged i
11、n Testing and/or Inspection of Soil and Rock asUsed in Engineering Design and ConstructionD4597 Practice for Sampling Workplace Atmospheres toCollect Gases or Vapors with Solid Sorbent DiffusiveSamplersD5088 Practice for Decontamination of Field EquipmentUsed at Waste SitesD5314 Guide for Soil Gas M
12、onitoring in the Vadose ZoneD5792 Practice for Generation of Environmental Data Re-lated to Waste Management Activities: Development ofData Quality ObjectivesD6196 Practice for Selection of Sorbents, Sampling, andThermal Desorption Analysis Procedures for Volatile Or-ganic Compounds in AirD6311 Guid
13、e for Generation of Environmental Data Re-lated to Waste Management Activities: Selection andOptimization of Sampling DesignE2600 Guide for Vapor Encroachment Screening on Prop-erty Involved in Real Estate Transactions2.2 U.S. EPA Methods31This practice is under the jurisdiction of ASTM Committee D1
14、8 on Soil andRock and is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Current edition approved Dec. 1, 2011. Published January 2012. DOI: 10.1520/D7758-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Se
15、rvice at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Available from United States Environmental Protection Agency (EPA), ArielRios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20004, http:/www.epa.gov.1Co
16、pyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Method 8260C Volatile Organic Compounds by GasChromatography/Mass Spectrometry (GC/MS)Method 8270C Semivolatile Organic Compounds by GasChromatography/Mass SpectrometryMethod TO-17 Determi
17、nation of Volatile Organic Com-pounds in Ambient Air Using Active Sampling OntoSorbent Tubes3. Terminology3.1 Definitions of Terms Specific to This Standard:3.1.1 This section provides definitions and descriptions ofterms used in or related to this practice. A list of acronyms anda list of symbols a
18、re also included. The terms are an integralpart of this practice and are critical to an understanding of thepractice and its use. Also see Terminology D653 and D1356.3.1.2 absorption, nthe penetration of one substance intothe inner structure of another.3.1.3 active sampling, vmeans of collecting a g
19、as-phasesubstance that uses a mechanical device such as a pump orvacuum-assisted critical orifice to draw air into or through asampling device.3.1.4 adsorption, nadherence of the atoms, ions, or mol-ecules of a gas or liquid to the surface of another substance(chemisorption).3.1.5 ambient air, nany
20、unconfined portion of the atmo-sphere; open air.3.1.6 background level, nconcentration of a substancethat is typically found in ambient air (for example, as a resultof industrial or automobile emissions), indoor air (for example,from building materials or indoor activities), or the naturalgeology of
21、 an area.3.1.7 blank sample, nclean sample or a sample of matrixprocessed to measure artifacts in the measurement process.3.1.7.1 DiscussionBlank samples are named according totheir type and use (for example, method blank, trip blank, fieldblank, and preparation or manufacturing blank).3.1.8 contami
22、nant, nsubstances not normally found in anenvironment at the observed concentration.3.1.9 desorption, nthe process of freeing from a sorbedstate.3.1.10 duplicate samples, ntwo samples taken from andrepresentative of the same population that are carried throughall steps of the sampling and analytical
23、 procedures in anidentical manner.3.1.11 field blank, nclean sampling media that is carriedto the sampling site, exposed to ambient air during fieldsampling procedures, and transported to the laboratory foranalysis (also referred to as an ambient air control sample).3.1.12 groundwater, npart of the
24、subsurface water that isin the saturated zone.3.1.13 method blank, nquality control check to measurelaboratory contamination during sample analysis.3.1.14 moisture content, nthe moisture present in a mate-rial, as determined by definite prescribed methods, expressedas a percentage of the mass of the
25、 sample on either of thefollowing bases: (1) original mass; (2) moisture-free (ovendried) mass (see Test Method D2216).3.1.15 passive sampling, vmeans of collecting a gas-phase substance that uses sorbent materials in a samplingdevice exposed for a finite duration in the medium beingsampled.3.1.16 p
26、reparation blank, nquality control check to definethe efficiency of conditioning a batch of sorbent samplers at thelaboratory for sample collection (also referred to as manufac-turing blanks).3.1.17 porosity, nvolume fraction of rock or soil notoccupied by solid material but usually occupied by liqu
27、ids,vapor, or air, or combinations thereof.3.1.17.1 DiscussionPorosity is the void volume of soil orrock or both divided by the total volume of soil or rock or both.3.1.18 sampling rate, nthe ratio of mass of a givencompound collected by a diffusive sampler per unit time ofexposure to the concentrat
28、ion of that compound in the atmo-sphere being sampled. The sampling rate is sometimes referredto as the uptake rate.3.1.19 saturated zone, nzone in which all of the voids inthe rock or soil are filled with water at a pressure that is greaterthan atmospheric.3.1.19.1 DiscussionThe water table is the
29、top of thesaturated zone in an unconfined aquifer.3.1.20 soil gas, nvadose zone atmosphere; soil gas is theair existing in void spaces in the soil between the groundwatertable and the ground surface.3.1.21 soil moisture, nwater contained in the pore spacesin the vadose zone.3.1.22 sorbent, na solid
30、or liquid medium in or uponwhich materials are collected by adsorption, absorption, orchemisorption.3.1.23 sorbent sampling, vthe collection of chemicalsfrom an air or emission sample by allowing the air or emissionsto contact a sorbent.3.1.24 sorption, na process by which one material (thesorbent)
31、takes up and retains another material (the sorbate) bythe processes of adsorption or absorption.3.1.25 source, narea(s) at a site where releases haveoccurred that are emanating vapors from either the vadose zoneor groundwater.3.1.25.1 DiscussionThere may be multiple sources at asite and the area ove
32、r which any one source is defined is subjectto interpretation from multiple data sets.3.1.26 spatial variability, nrelationship of organic com-pound mass from one location to many others at a site as afunction of distance.3.1.27 starvation effect, nwhen the analyte uptake rate ofa passive sorbent sa
33、mpler is greater than the replenishment rateof the analyte around the sampler, which results in a low biasmeasurement.3.1.28 trip blank, nclean, unused sampling media that iscarried to the sampling site and transported to the laboratoryfor analysis without having been exposed to field samplingproced
34、ures.3.1.29 vadose zone, nhydrogeological region extendingfrom the soil surface to the top of the principal water table.3.1.29.1 DiscussionPerched groundwater may existwithin this zone.D7758 1123.1.30 vapor intrusion, nmigration of a volatile chemi-cal(s) from subsurface soil or water into an overly
35、ing or nearbybuilding.3.1.31 water table, ntop of the saturated zone in anunconfined aquifer.3.2 Acronyms:3.2.1 BLSBelow land surface (also know as below groundsurface (bgs)3.2.2 COCCompound of concern3.2.3 EPAEnvironmental Protection Agency3.2.4 IDIdentification3.2.5 MDLMethod detection limit3.2.6
36、QA/QCQuality assurance and quality control3.2.7 PSGPassive soil gas3.2.8 SVOCSemivolatile organic compound3.2.9 TD-GC/MSThermal desorption-gas chromato-graphy/mass spectrometry3.2.10 U.S.United States3.2.11 VOCVolatile organic compound3.3 Symbols:3.3.1 cmcentimeter3.3.2 mmeter3.3.3 mmmillimeter3.3.4
37、 minminute3.3.5 ngmass in nanograms or 10-9g3.3.6 sseconds3.3.7 gmass in micrograms or 10-6g4. Summary of Practice4.1 This practice describes the passive collection and sub-sequent analysis of soil gas samples, using sorbent samplers totrap VOCs and SVOCs in soil vapor by placing samplers in thesubs
38、urface for a period of time at multiple locations across asite. Placement of the sampler can be in open soils (i.e., notcovered by a surface such as asphalt or concrete), or advancedthrough slab surfaces (e.g., parking lots, streets, sidewalks,building slabs, and basement floors) to allow for subsla
39、b soilgas sampling. This practice provides standard guidance forpassive soil gas (PSG) sampling and analysis performed insupport of, but not limited to, site assessment, site monitoring,and vapor intrusion investigations. While several differenttypes and combinations of sorbent materials can be used
40、 to trapVOCs and SVOCs in soil gas, this practice is intended toachieve representative and reproducible samples of knownquality. The design of PSG surveys (for example, samplerdesign, sample spacing, the sampler exposure period, andanalytical methods) is within the scope of this practice. Theseguide
41、lines are not intended to restrict the sampler design or itsapplication in regards to spacing, sampler distribution, or timeof exposure; however, these guidelines are meant to provide ageneral idea of common practice at the time this standard wasprepared.5. Significance and Use5.1 Passive soil gas s
42、amplers are a minimally invasive,easy-to-use technique in the field for identifying VOCs andSVOCs in the vadose zone. Similar to active soil gas and otherfield screening techniques, the simplicity and low cost ofpassive samplers enables them to be applied in large numbers,facilitating detailed mappi
43、ng of contamination across a site, forthe purpose of identifying source areas and release locations,focusing subsequent soil and groundwater sampling locations,focusing remediation plans, identifying vapor intrusion path-ways, tracking groundwater plumes, and monitoring remedia-tion progress. Data g
44、enerated from passive soil gas samplingare semi-quantitative and are dependent on numerous factorsboth within and outside the control of the sampling personnel.Key variables are identified and briefly discussed in thefollowing sections.NOTE 1Additional non-mandatory information on these factors orva
45、riables are covered in the applicable standards referenced in Section 2,and the footnotes and Bibliography presented herewith.5.2 ApplicationThe techniques described in this practiceare suitable for sampling soil gas with sorbent samplers in awide variety of geological settings for subsequent analys
46、is forVOCs and SVOCs. The techniques also may prove useful forspecies other than VOCs and SVOCs, such as elementalmercury, with specialized sorbent media and analysis.5.2.1 Source Identification and Spatial VariabilityAssessmentPassive soil gas sampling can be an effectivemethod to identify contamin
47、ant source areas in the vadose zoneand delineate the extent of contamination. By collectingsamples in a grid with fewer data gaps, the method allows foran increase in data density and, therefore, provides a high-resolution depiction of the nature and extent of contaminationacross the survey area. By
48、 comparing the results, as qualitativeor quantitative, from one location to another, the relativedistribution and spatial variability of the contaminants in thesubsurface can be determined, thereby improving the concep-tual site model. Areas of the site reporting non-detects can beremoved from furth
49、er investigation, while subsequent sam-pling and remediation can be focused in areas determined fromthe PSG survey to be impacted.5.2.2 MonitoringPassive soil gas samplers are used tomonitor changes in site conditions (e.g., new releases on-site,an increase in contaminant concentrations in groundwater fromonsite or off-site sources, and effectiveness of remedial systemperformance) as reflected by the changes in soil gas results atfixed locations over time. An initial set of data is collected toestablish a baseline and sub
