1、Designation: D7663 11Standard Practice forActive Soil Gas Sampling in the Vadose Zone for VaporIntrusion Evaluations1This standard is issued under the fixed designation D7663; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the yea
2、r 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 techniquesfor actively collecting soil gas samples from the vadose zoneb
3、eneath or near dwellings and other buildings.1.2 ObjectivesObjectives guiding the development of thispractice are: (1) to synthesize and put in writing good com-mercial and customary practice for soil gas sampling, (2) toprovide an industry standard for soil gas sampling performed insupport of vapor
4、 intrusion evaluations that is practical andreasonable.1.3 This practice allows a variety of techniques to be usedfor collecting soil gas samples because different techniquesmay offer certain advantages for specific applications. Threetechniques are presented: sampling at discrete depths, samplingov
5、er a small screened interval, and sampling using permanentvapor monitoring wells.1.4 Some of the recommendations require knowledge ofpressure differential and tracer gas concentration measure-ments.1.5 The values stated in SI units are to be regarded asstandard. Other units are shown for information
6、 only.1.6 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 those of this practice.1.7 This standar
7、d does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.1.8 This practice offers a set
8、of instructions for performingone or more specific operations. This document cannot replaceeducation or experience and should be used in conjunction withprofessional judgment. Not all aspects of this practice may beapplicable in all circumstances. This ASTM practice is notintended to represent or re
9、place the standard of care by whichthe adequacy of a given professional service must be judged,nor should this document be applied without consideration ofa projects many unique aspects. The word “Standard” in thetitle means only that the document has been approved throughthe ASTM consensus process.
10、2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD854 Test Methods for Specific Gravity of Soil Solids byWater PycnometerD1356 Terminology Relating to Sampling and Analysis ofAtmospheresD1946 Practice for Analysis of Reformed Gas by GasChromatogr
11、aphyD2216 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)D3404 Guide for Measuring Matric Potential in VadoseZone Using TensiometersD4696 Guide for P
12、ore-Liquid Sampling from the VadoseZoneD4700 Guide for Soil Sampling from the Vadose ZoneD5088 Practice for Decontamination of Field EquipmentUsed at Waste SitesD5092 Practice for Design and Installation of Ground WaterMonitoring WellsD5314 Guide for Soil Gas Monitoring in the Vadose ZoneD5466 Test
13、Method for Determination of Volatile OrganicChemicals in Atmospheres (Canister Sampling Methodol-ogy)D5504 Test Method for Determination of Sulfur Com-pounds in Natural Gas and Gaseous Fuels by Gas Chro-matography and ChemiluminescenceD6196 Practice for Selection of Sorbents, Sampling, andThermal De
14、sorption Analysis Procedures for Volatile Or-ganic Compounds in Air1This practice is under the jurisdiction of ASTM Committee D18 on Soil andRock and is the direct responsibility of Subcommittee D18.21 on Ground Water andVadose Zone Investigations.Current edition approved April 15, 2011. Published M
15、ay 2011. DOI: 10.1520/D7663-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.1Copyright ASTM International,
16、 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.D6725 Practice for Direct Push Installation of PrepackedScreen Monitoring Wells in Unconsolidated AquifersE741 Test Method for Determining Air Change in a SingleZone by Means of a Tracer Gas DilutionE2024 Test Metho
17、ds for Atmospheric Leaks Using a Ther-mal Conductivity Leak DetectorF1815 Test Methods for Saturated Hydraulic Conductivity,Water Retention, Porosity, and Bulk Density of AthleticField Rootzones3. Terminology3.1 This section provides definitions and descriptions ofterms used in or related to this pr
18、actice. A list of acronyms anda list of symbols also are included. The terms are an integralpart of this practice and are critical to an understanding of thepractice and its use.3.2 Definitions of Terms Specific to This Standard:3.2.1 active sampling, na means of collecting a gas-phasesubstance that
19、 employs a mechanical device such as a pump orvacuum assisted critical orifice to draw air into or through asampling device.3.2.2 adsorption, na physical process in which moleculesor gas, of dissolved substances, or of liquids adhere in anextremely thin layer to the surfaces of solid bodies with whi
20、chthey are in contact.3.2.3 ambient air, nany unconfined portion of the atmo-sphere; open air.3.2.4 attenuation factor (a), nratio of indoor air concen-tration to soil-gas concentration for a given compound.3.2.5 background level, nthe concentration of a substancethat is typically found in ambient a
21、ir (for example, due toindustrial or automobile emissions), indoor air (for example,from building materials or indoor activities) or the naturalgeology of an area.3.2.6 blank sample, na sample that is intended to containnone of the analytes of interest and which is subjected to theusual analytical o
22、r measurement process to establish a zerobaseline or background value. Blank samples are namedaccording to their type and use (for example, field blank, tripblank, equipment blank, reagent blank).3.2.7 contaminant, nsubstances not normally found in anenvironment at the observed concentration.3.2.8 d
23、ead volume, nthe total air-filled internal volume ofthe sampling system.3.2.9 duplicate samples, ntwo samples taken from andrepresentative of the same population and carried through allsteps of the sampling and analytical procedures in an identicalmanner.3.2.10 effective porosity, nthe ratio of the
24、volume of thevoids of a soil or rock mass that can be drained by gravity tothe total volume of the mass.3.2.11 equipment blank, na sample of the gas which isused to purge the sampling equipment between uses. Samplingequipment blanks are used to check the cleanliness of samplingdevices and the thorou
25、ghness of the cleaning procedure.3.2.12 field blank, nunused media carried to the samplingsite, exposed to sampling conditions (for example, connectedto the sampling lines) and returned to the laboratory and treatedas an environmental sample. Field blanks are used to check foranalytical artifacts or
26、 background contaminants or both intro-duced by sampling and analytical procedures.3.2.13 fracture, na break in the mechanical continuity ofa body of rock or soil caused by stress exceeding the strengthof the rock or soil. Includes joints and faults.3.2.14 free product, nliquid phase contaminants re
27、leasedinto the environment.3.2.15 ground water, nthe part of the subsurface waterthat is in the saturated zone.3.2.16 liquid phase, ncontaminant residing as a liquid invadose zone pore space, often referred to as “free product.”3.2.17 moisture content, nthe amount of water lost from asoil upon dryin
28、g to a constant weight, expressed as the weightper unit weight of dry soil or as the volume of water per unitbulk volume of the soil.3.2.18 passive sampling, na means of collecting an air-borne substance that depends on gaseous diffusion, gravity, orother unassisted means to bring the sample to the
29、collectionsurface of sorbent.3.2.19 partitioning, nthe act or process of distributing achemical among different phases or compartments.3.2.20 perched aquifer, na lens of saturated soil above themain water table that forms on top of an isolated geologic layerof low permeability.3.2.21 permeability, n
30、the capacity of a rock or othermaterial to conduct liquid or gas. It is measured as theproportionality constant, k, between flow velocity, v, andhydraulic gradient, I; v = kI.3.2.22 preferential pathway, na migration route forchemicals of concern that has less constraint on gas transportthan the sur
31、rounding soil. Preferential pathways may be natural(for example, vertically fractured bedrock where the fracturesare interconnected) or man-made (for example, utility conduits,sewers, dry wells).3.2.23 porosity, nthe volume fraction of a rock or uncon-solidated sediment not occupied by solid materia
32、l but usuallyoccupied by liquids, vapor, or air, or combinations thereof.Porosity is the void volume of soil divided by the total volumeof soil.3.2.24 purge volume, nthe amount of air removed fromthe sampling system prior to the start of sample collection. Thisis usually referred to in number of dea
33、d volumes.3.2.25 reagent blank, nsample of one or more reagentsused in a given analysis.3.2.26 saturated zone, nthe zone in which all of the voidsin the rock or soil are filled with water at a pressure that isgreater than atmospheric. The water table is the top of thesaturated zone in an unconfined
34、aquifer.3.2.27 semi-volatile organic compound (SVOC), norganiccompounds with boiling points typically in the range 240-260to 380-400 C with polar compounds in the higher range.3.2.28 soil gas, nvadose zone atmosphere. Soil gas is theair existing in void spaces in the soil between the groundwatertabl
35、e and the ground surface.3.2.29 soil moisture, nthe water contained in the porespaces in the vadose zone.D7663 1123.2.30 sorbent sampling, nthe collection of an air samplevia removal of chemicals from a gas by passing the gas throughor allowing it to come in contact with a sorptive medium. Thechemic
36、als are subsequently desorbed for analysis.3.2.31 sub-slab vapor sampling, nthe collection of vaporfrom the zone just beneath the lowest floor slab of a building.3.2.32 tracer, na material that can be easily identified anddetermined even at very low concentrations and that may beadded to other subst
37、ances to enable their movements to befollowed or their presence to be detected.3.2.33 tracer gas, na gas used with a detection device todetermine the rate of air interchange within a space, or betweenspaces.3.2.34 trip blank, nclean, unused sampling media that iscarried to the sampling site and tran
38、sported to the laboratoryfor analysis without having been exposed to sampling proce-dures.3.2.35 vadose zone, nhydrogeological region extendingfrom the soil surface to the top of the principal water table.Perched ground water may exist within this zone.3.2.36 vapor intrusion, nthe migration of a vol
39、atilechemical(s) from subsurface soil or water into an overlying ornearby building.3.2.37 volatile organic compound (VOC), norganic com-pounds with boiling points typically ranging from a lower limitbetween 50 C and 100 C, and an upper limit between 240 Cand 260 C, where the upper limits represent m
40、ostly polarcompounds.3.2.38 water table, nthe top of the saturated zone in anunconfined aquifer.3.3 Acronyms and Abbreviations3.3.1 BLSBelow Land Surface (also known as belowground surface bgs)3.3.2 HDPEHigh density polyethylene tubing3.3.3 ODOuter Diameter3.3.4 PEEKPolyetheretherketone3.3.5 PTFEPol
41、ytetrafluoroethylene3.3.6 ppbvpart-per-billion on a volume basis3.3.7 PRTpost-run tubing3.3.8 QCQuality Control3.3.9 SVOCSemi-Volatile Organic Compound3.3.10 TOToxic Organic3.3.11 USEPAUnited States Environmental ProtectionAgency3.3.12 VOCVolatile Organic Compound3.4 Symbols3.4.1 Variables (typical
42、units)3.4.1.1 C = concentration (ppbv, g/m3,%)3.4.1.2 CDL= detection limit concentration (g/m3)3.4.1.3 d = diameter (cm)3.4.1.4 L = length (cm)3.4.1.5 M = mass (g)3.4.1.6 n = number of data points3.4.1.7 Q = flow rate (cm3/min)3.4.1.8 t = time (min)3.4.1.9 V = volume (cm3)3.4.1.10 XMW= molecular wei
43、ght of compound X (g/mol)3.4.1.11 a = attenuation coefficient or factor (dimension-less)3.4.1.12 DP = change in pressure (Pa)3.4.1.13 t = residence time (min)3.5 Superscripts3.5.1 = mean value3.6 Subscripts3.6.1 i = pertaining to compound, time, or location i4. Summary of Practice4.1 This practice d
44、escribes the active collection of soil gassamples from soil pore spaces in the vadose zone or in fillmaterial directly under building slabs to determine the concen-tration of volatile organic compounds (VOCs). Three tech-niques are presented: (1) sampling at discrete depths, (2)sampling over a small
45、 screened interval, or (3) sampling usingpermanent vapor monitoring wells with one or more screenedintervals. For sampling at a given depth, options include (i) ashort stainless steel probe installed in a small diameter holedrilled through building slab, (ii) disposable drive tips andpost-run tubing
46、 (PRT), or (iii) installation of sampling pointsusing tubing placed into a borehole and sealed in place withclay or other packing material. Several different combinationsof equipment and materials can be used to actively collect soilgas samples, and this practice is intended to allow all methodsthat
47、 typically result in representative and reproducible samples.Other techniques for assessing soil vapor concentrations exist(for example, passive sampling), but are outside the scope ofthis practice. The design of soil gas sampling programs (forexample, the number and location of samples necessary to
48、characterize a site) also is outside the scope of this practice.Table 1 summarizes the key design aspects for the mostcommon techniques. Examples of various installation ap-proaches are shown in Fig. 1.4.2 Choice of TechniqueIn choosing a technique forcollecting and measuring soil gas concentrations
49、, the usershould consider the study objectives, site geology, chemicals ofinterest, target concentrations, type of building and its con-struction, potential for preferential pathways to be present,potential for long-term or repeat sampling, the comparativecapabilities of the techniques, and the complexity of theequipment and procedures.5. Significance and Use5.1 Soil-gas sampling results can be dependent on numerousfactors both within and outside the control of the samplingpersonnel. Key variables are identified and bri
