1、Designation: D4696 92 (Reapproved 2008)Standard Guide forPore-Liquid Sampling from the Vadose Zone1This standard is issued under the fixed designation D4696; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision
2、. 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 This guide covers the equipment and procedures usedfor sampling pore-liquid from the vadose zone (unsaturatedzone). The guide is li
3、mited to in situ techniques and does notinclude soil core collection and extraction methods for obtain-ing samples.1.2 The term “pore-liquid” is applicable to any liquid fromaqueous pore-liquid to oil. However, all of the samplersdescribed in this guide were designed, and are used to sampleaqueous p
4、ore-liquids only. The abilities of these samplers tocollect other pore-liquids may be quite different than thosedescribed.1.3 Some of the samplers described in this guide are notcurrently commercially available. These samplers are pre-sented because they may have been available in the past, andmay b
5、e encountered at sites with established vadose zonemonitoring programs. In addition, some of these designs areparticularly suited to specific situations. If needed, thesesamplers could be fabricated.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are in
6、cluded 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 standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior
7、 to use.1.6 This guide offers an organized collection of informationor a series of options and does not recommend a specificcourse of action. This document cannot replace education orexperience and should be used in conjunction with professionaljudgment. Not all aspects of this guide may be applicab
8、le in allcircumstances. This ASTM standard is not intended to repre-sent or replace the standard of care by which the adequacy ofa given professional service must be judged, nor should thisdocument be applied without consideration of a projects manyunique aspects. The word “Standard” in the title of
9、 thisdocument means only that the document has been approvedthrough the ASTM consensus process.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluids3. Terminology3.1 DefinitionsWhere reasonable, precise terms andnames have been used within this guide
10、. However, certainterms and names with varying definitions are ubiquitous withinthe literature and industry of vadose zone monitoring. Forpurposes of recognition, these terms and names have beenincluded in the guide with their most common usage. In theseinstances, the common definitions have been in
11、cluded inAppendix X1. Examples of such terms are soil, lysimeter,vacuum and pore-liquid tension.3.2 Definitions of Terms Specific to This Standard:3.2.1 Appendix X1 is a compilation of those terms used inthis guide. More comprehensive compilations, that were usedas sources for Appendix X1, are (in d
12、ecreasing order of theirusage):3.2.1.1 Terminology D653,3.2.1.2 Compilation of ASTM Terminology,33.2.1.3 Glossary of Soil Science Terms, Soil Science Societyof America,4and,3.2.1.4 Websters New Collegiate Dictionary,54. Summary of Guide4.1 Pores in the vadose zone can be saturated or unsaturated.Som
13、e samplers are designed to extract liquids from unsaturatedpores; others are designed to obtain samples from saturated1This guide is under the jurisdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Curren
14、t edition approved Sept. 15, 2008. Published October 2008. Originallyapproved in 1992. Last previous edition approved in 2000 as D4696 92 (2000).DOI: 10.1520/D4696-92R08.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annu
15、al Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Compilation of ASTM Terminology, Sixth edition, ASTM, 1916 Race Street,Philadelphia, PA19103, 1986. (Currently, ASTM Dictionary of Engineering Science& Technology, 10th edition, ASTM Interna
16、tional, 2005.)4Glossary of Soil Science Terms, Soil Science Society of America, 1987.5Websters New Collegiate Dictionary, Fifth edition, 1977. (Currently Merriam-Websters Collegiate Dictionary , Eleventh edition, 2006.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocke
17、n, PA 19428-2959. United StatesNOTICE: This standard has either been superseded and replaced by a new version or withdrawn.Contact ASTM International (www.astm.org) for the latest information1pores (for example, perched groundwater) or saturated mac-ropores (for example, fissures, cracks, and burrow
18、s). Thisguide addresses these categories. The sampler types discussedare:4.1.1 Suction samplers (unsaturated sampling), (see Section7),4.1.2 Free drainage samplers (saturated sampling), (seeSection 8),4.1.3 Perched groundwater samplers (saturated sampling),(see Section 9), and4.1.4 Experimental abso
19、rption samplers (unsaturatedsampling), (see Section 10).4.2 Most samplers designed for sampling liquid from un-saturated pores may also be used to sample from saturatedpores. This is useful in areas where the water table fluctuates,so that both saturated and unsaturated conditions occur atdifferent
20、times. However, samplers designed for sampling fromsaturated pores cannot be used in unsaturated conditions. Thisis because the liquid in unsaturated pores is held at less thanatmospheric pressures (see Richards outflow principle,inAppendix X1).4.3 The discussion of each sampler is divided into spec
21、ifictopics that include:4.3.1 Operating principles,4.3.2 Description,4.3.3 Installation,4.3.4 Operation, and4.3.5 Limitations.5. Significance and Use5.1 Sampling from the vadose zone may be an importantcomponent of some groundwater monitoring strategies. It canprovide information regarding contamina
22、nt transport and at-tenuation in the vadose zone. This information can be used formitigating potential problems prior to degradation of a ground-water resource (1).65.2 The choice of appropriate sampling devices for a par-ticular location is dependent on various criteria. Specificguidelines for desi
23、gning vadose zone monitoring programshave been discussed by Morrison (1), Wilson (2), Wilson (3),Everett (4), Wilson (5), Everett, et al (6), Wilson (7), Everett,et al (8), Everett, et al (9), Robbins, et al (10), Merry andPalmer (11), U.S. EPA (12), Ball (13), and Wilson (14).Ingeneral, it is prude
24、nt to combine various unsaturated and freedrainage samplers into a program, so that the different flowregimes may be monitored.5.3 This guide does not attempt to present details ofinstallation and use of the equipment discussed. However, aneffort has been made to present those references in which th
25、especific techniques may be found.6. Criteria for Selecting Pore-Liquid Samplers6.1 Decisions on the types of samplers to use in a monitor-ing program should be based on consideration of a variety ofcriteria that include the following:6.1.1 Required sampling depths,6.1.2 Required sample volumes,6.1.
26、3 Soil characteristics,6.1.4 Chemistry and biology of the liquids to be sampled,6.1.5 Moisture flow regimes,6.1.6 Required durability of the samplers,6.1.7 Required reliability of the samplers,6.1.8 Climate,6.1.9 Installation requirements of the samplers,6.1.10 Operational requirements of the sample
27、rs,6.1.11 Commercial availability, and6.1.12 Costs.6.2 Some of these criteria are discussed in this guide.However, the ability to balance many of these factors againstone another can only be obtained through field experience.7. Suction Samplers7.1 Table 1 presents the various types of suction sample
28、rs.The range of operating depths is the major criterion by whichsuction samplers are differentiated.Accordingly, the categoriesof suction samplers are as follows:7.1.1 Vacuum LysimetersThese samplers are theoreticallyoperational at depths less than about 7.5 m. The practicaloperational depth is 6 m
29、under ideal conditions.7.1.2 Pressure-Vacuum LysimetersThese samplers are op-erational at depths less than about 15 m.7.1.3 High Pressure-Vacuum Lysimeters (Also known aspressure-vacuum lysimeters with transfer vessels.) These sam-plers are normally operational down to about 46 m, althoughinstallati
30、ons as deep as 91 m have been reported (15).7.1.4 Suction Lysimeters With Low Bubbling Pressures(Samplers With PTFE Porous Sections)These samplers areavailable in numerous designs that can be used to maximumdepths varying from about 7.5 to 46 m.NOTE 1The samplers of 7.1.1, 7.1.2, 7.1.3, and 7.1.4 ar
31、e referred tocollectively as suction lysimeters. Within this standard, lysimeter isdefined as a device used to collect percolating water for analyses (16).7.1.5 Filter Tip SamplersThese samplers theoreticallyhave no maximum sampling depth.7.1.6 Experimental Suction Samplers The samplers havelimited
32、field applications at the present time. They includecellulose-acetate hollow-fiber samplers, membrane filtersamplers, and vacuum plate samplers. They are generallylimited to depths less than about 7.5 m.7.2 Operating Principles:7.2.1 General:7.2.1.1 Suction lysimeters consist of a hollow, porous sec
33、-tion attached to a sample vessel or a body tube. Samples areobtained by applying suction to the sampler and collectingpore-liquid in the body tube. Samples are retrieved by a varietyof methods.7.2.1.2 Unsaturated portions of the vadose zone consist ofinterconnecting soil particles, interconnecting
34、air spaces, andinterconnecting liquid films. Liquid films in the soil providehydraulic contact between the saturated porous section of thesampler and the soil (see Fig. 1). When suction greater than thesoil pore-liquid tension is applied to the sampler, a pressure6The boldface numbers in parentheses
35、 refer to the list of references at the end ofthis standard.D4696 92 (2008)2potential gradient towards the sampler is created. If themeniscuses of the liquid in the porous segment are able towithstand the applied suction (depending on the maximumpore sizes and hydrophobicity/hydrophilicity), liquid
36、movesinto the sampler. The ability of the meniscuses to withstand asuction decreases with increasing pore size and also withincreasing hydrophobicity of the porous segment (see 7.6). Ifthe maximum pore sizes are too large and hydrophobicity toogreat, the meniscuses are not able to withstand the appl
37、iedsuction.As a result, they break down, hydraulic contact is lost,and only air enters the sampler. As described in 7.6, ceramicporous segments are hydrophilic and the maximum pore sizesare small enough to allow meniscuses to withstand the entirerange of sampling suctions. Presently available polyte
38、trafluo-roethylene (PTFE) porous segments are hydrophobic, themaximum pore sizes are larger, and only a very limited rangeof sampling suction can be applied before meniscuses breakdown and sampling ends (see 7.6.1.3). Therefore, samplersmade with PTFE porous segments may be used only forsampling soi
39、ls with low pore-liquid tensions (12, 17).7.2.1.3 The ability of a sampler to withstand applied suc-tions can be directly measured by its bubbling pressure. Thebubbling pressure is measured by saturating the poroussegment, immersing it in water, and pressurizing the inside ofthe porous segment with
40、air. The pressure at which air startsbubbling through the porous segment into the surroundingwater is the bubbling pressure. The magnitude of the bubblingpressure is equal to the magnitude of the maximum suction thatcan be applied to the sampler before air entry occurs (air entryvalue). Because the
41、bubbling pressure is a direct measure ofhow a sampler will perform, it is more useful than measure-ment of pore size distributions.7.2.1.4 As soil pore-liquid tensions increase (low pore-liquid contents), pressure gradients towards the sampler de-crease. Also, the soil hydraulic conductivity decreas
42、es expo-nentially. These result in lower flow rates into the sampler. Atpore-liquid tensions above about 60 (for coarse grained soils)to 80 cbar (for fine grained soils), the flow rates are effectivelyzero and samples cannot be collected.7.2.2 Suction Lysimeters:7.2.2.1 Vacuum lysimeters directly tr
43、ansfer samples to thesurface via a suction line. Because the maximum suction lift ofwater is about 7.5 m, these samplers cannot be operated belowthis depth. In reality, suction lifts of 6 m should be considereda practical maximum depth.7.2.2.2 Samples may be retrieved using the same techniqueas for
44、vacuum lysimeters or, for deeper applications, thesample is retrieved by pressurizing the sampler with one line;this pushes the sample up to the surface in a second line.7.2.2.3 High pressure-vacuum lysimeters operate in thesame manner as pressure-vacuum lysimeters. However, theyTABLE 1 Suction Samp
45、ler SummarySampler TypePorous SectionMaterialMaximumAPoreSize (m)Air EntryValue (cbar)Operational SuctionRange (cbar)Maximum OperationDepth (m)Vacuum lysimeters Ceramic 1.2 to 3.0 (1)A100 10010 to 2110010 to 21100NABNAB100 100 100NAB100 60 to 80 7.5Fritted glass 4 to 5.5 NABNAB7.5Stainless steel NAB
46、49 to 5 49 to 5 7.5APore size determined by bubbling pressure (1) or mercury intrusion (2).BNA = Not available.FIG. 1 Porous Section/Soil InteractionsD4696 92 (2008)3include an inbuilt check transfer vessel or a chamber betweenthe sampler and the surface. This prevents sample loss throughthe porous
47、section during pressurization, and prevents possiblecup damage due to overpressurization.7.2.2.4 Suction lysimeters with low bubbling pressures areavailable in each of the three previous designs. The onlydifference between these samplers and the three previousdesigns is that these porous sections ar
48、e made with PTFE. Thelow bubbling pressure (and hence large pore size orhydrophobicity, or both) of PTFE constrains these samplers tosoils that are nearly saturated (see 7.2.1.2 and 7.6.1.3).7.2.3 Filter Tip SamplersSamples are collected from afilter tip sampler by lowering an evacuated sample vial
49、downan access tube to a permanently emplaced porous tip. The vialis connected to the porous tip and sample flows through theporous section and into the vial. Once full, the vial is retrieved.7.2.4 Experimental Suction Samplers Experimental suc-tion samplers generally operate on the same principle asvacuum lysimeters with different combinations of porousmaterials to enhance hydraulic contact. The samplers aregenerally fragile and difficult to install. As with vacuumlysimeters, they are generally limited to depths of less thanabout 7.5 m.7.3 Descri
