1、Designation: D4696 18Standard 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. A number in pare
2、ntheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This guide covers the equipment and procedures usedfor sampling pore-liquid from the vadose zone (unsaturatedzone). The guide is limited to in situ
3、techniques and does notinclude soil core collection and extraction methods for obtain-ing samples.1.2 The term “pore-liquid” is applicable for liquids fromaqueous pore-liquid to oil. However, the samplers described inthis guide were designed, and are used to sample aqueouspore-liquids only. The abil
4、ities of these samplers to collectother pore-liquids may be quite different than those described.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 be encountered at sites wi
5、th 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 included in thisstandard.1.
6、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, health, and environmental practices and deter-mine the applicability of regulatory limitations prior to use.1
7、.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 applicable in all
8、circumstances. 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 thisdocu
9、ment means only that the document has been approvedthrough the ASTM consensus process.1.7 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, G
10、uides and Recom-mendations issued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2D653 Terminology Relating to Soil, Rock, and ContainedFluidsD3740 Practice for Minimum Requirements for AgenciesEngaged in Testing and/or Inspection
11、 of Soil and Rock asUsed in Engineering Design and Construction3. Terminology3.1 Definitions3.1.1 For common definitions of terms in this standard, referto Terminology D653.3.2 Definitions of Terms Specific to This Standard:3.2.1 air entry value, nin vadose zone, the applied suctionat which water me
12、nisci of the porous segment of a suctionsampler break down, and air enters.3.2.2 bubbling pressure, nin vadose zone, the applied airpressure at which water menisci of the porous segment of asuction sampler break down, and air exits.3.2.3 cascading water, nin groundwater, perched ground-water that en
13、ters a well casing via cracks or uncoveredperforations, trickling, or pouring down the inside of thecasing.3.2.4 hydrophobicity, nin vadose zone, the property thatdefines a material as being water repellent. Water exhibits anobtuse contact angle with hydrophobic materials.1This guide is under the ju
14、risdiction ofASTM Committee D18 on Soil and Rockand is the direct responsibility of Subcommittee D18.21 on Groundwater andVadose Zone Investigations.Current edition approved Nov. 15, 2018. Published November 2018. Originallyapproved in 1992. Last previous edition approved in 2008 as D4696 92(2008),w
15、hich was withdrawn January 2017 and reinstated in November 2018. DOI:10.1520/D4696-18.2For 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
16、 page onthe ASTM website.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principle
17、s on standardization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.13.2.5 matric potential, nin vadose zone, the energy neededto extract water from
18、 a soil against the capillary and adsorptiveforces of the soil matrix.3.2.6 pore-liquid, nin vadose zone, liquid that occupies anopen space between solid soil particles. Within this guide,pore-liquid is limited to aqueous pore-liquid; that includeswater and its solutes.3.2.7 pore-liquid tensionsee s
19、oil-water pressure.3.2.8 soil-water pressure, nin vadose zone, the pressureon the water in a soil-water system, as measured by apiezometer for a saturated soil, or by a tensiometer for anunsaturated soil.3.2.9 tensiometer, nin vadose zone, a device for measur-ing soil-water matric potential (or tens
20、ion or suction) of waterin soil in situ; a porous, permeable ceramic cup connectedthrough a water filled tube to a pressure measuring device.3.2.10 tremie, nin groundwater, the method wherebymaterials are emplaced in the bottom of a borehole with a smalldiameter pipe.3.3 Terminology from D653:3.3.1
21、The following terms are found in D653 and arepresented here as a convenience to users.3.3.1.1 cation exchange capacity, CEC, nin soils,isapHdependent measure of the negative electrical charge present onthe surfaces of soil minerals, particularly clay minerals, and onsoil organic materials, especiall
22、y humic compounds, capable ofdynamically adsorbing positively charged ions (cations) andpolar compounds.3.3.1.1.1 DiscussionThe units for CEC are typically inmilliequivalents per 100 grams of oven-dry soil (meq/100 g).The SI units for CEC are centimoles of charge per kilogram ofoven-dry soil (cmolc/
23、kg).3.3.1.2 exchange capacitythe capacity to exchange ionsas measured by the quantity of exchangeable ions in a soil orrock.3.3.1.2.1 DiscussionExchange capacity is only significantin materials having high specific surface area, such as clayminerals.3.3.1.3 hydraulic gradient, i D, nin hydraulics, t
24、hechange in total head (head loss, h) per unit distance (L) in thedirection of fluid flow, in which i = h/L.3.3.1.3.1 DiscussionIn most cases, the application of hy-draulic gradient applies to flowing water in a saturated testspecimen or aquifer consisting of soil or rock, or both. Theliterature typ
25、ically does not use h/L to indicate head loss;however, there is a need to emphasize that head loss is a change(delta), , in total head.3.3.1.4 vadose zone, nin geohydrology/hydrogeology, thehydrogeological region extending from the soil surface to thetop of the water (groundwater) table.3.3.1.4.1 Di
26、scussionThe capillary fringe is included inthis zone. Overall movement of water is vertical in the vadosezone. There can be more than one vadose zone in special cases,such as when there is perched groundwater. The vadose zone iscommonly referred to as the “unsaturated zone” or “zone ofaeration.” The
27、se alternate names are inadequate as they do nottake into account locally saturated regions, such as perchedgroundwater.4. Summary of Guide4.1 Pores in the vadose zone can be saturated or unsaturated.Some samplers are designed to extract liquids from unsaturatedpores; others are designed to obtain s
28、amples from saturatedpores (for example, perched groundwater) or saturated mac-ropores (for example, fissures, cracks, and burrows). Thisguide addresses these categories. The sampler types discussedare:4.1.1 Suction samplers (unsaturated sampling), (see Section7),4.1.2 Free drainage samplers (satura
29、ted sampling), (seeSection 8),4.1.3 Perched groundwater samplers (saturated sampling),(see Section 9), and4.1.4 Experimental absorption samplers (unsaturatedsampling), (see Section 10).4.2 Most samplers designed for sampling liquid from un-saturated pores may also be used to sample from saturatedpor
30、es. This is useful in areas where the water table fluctuates,so that both saturated and unsaturated conditions occur atdifferent 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
31、 thanatmospheric pressures. According to Richards Outflow Prin-ciple that states that pore-liquid will not generally flow into anair-filled cavity (at atmospheric pressure) in unsaturated soil.4.3 The discussion of each sampler is divided into specifictopics that include:4.3.1 Operating principles,4
32、.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 contaminant transport and at-tenuation in the vadose zone. Th
33、is information can be used formitigating potential problems prior to degradation of a ground-water resource (1).35.2 The choice of appropriate sampling devices for a par-ticular location is dependent on various criteria. Specificguidelines for designing vadose zone monitoring programshave been discu
34、ssed 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 prudent to combine various unsaturated and free3The boldf
35、ace numbers in parentheses refer to the list of references at the end ofthis standard.D4696 182drainage 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
36、has been made to present those references in which thespecific techniques may be found.NOTE 1The quality of the result produced by this standard isdependent on the competence of the personnel performing it and thesuitability of the equipment and facility used. Agencies that meet thecriteria of Pract
37、ice D3740 are generally considered capable of competentand objective testing/sampling/observation/ and the like. Users of thisstandard are cautioned that compliance with Practice D3740 does not itselfguarantee reliable results. Reliable results depend on many factors; D3740provides a means of evalua
38、ting some of those factors.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 Needed sampling depths,6.1.2 Needed sample volumes,6.1.3 Soil char
39、acteristics,6.1.4 Chemistry and biology of the liquids to be sampled,6.1.5 Moisture flow regimes,6.1.6 Durability of the samplers,6.1.7 Reliability of the samplers,6.1.8 Climate,6.1.9 Installation requirements of the samplers,6.1.10 Operational requirements of the samplers,6.1.11 Commercial availabi
40、lity, 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 samplers.The range of operating dep
41、ths 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 under ideal conditions.7.1.2
42、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, althoughinstallations as deep as 91 m have been r
43、eported (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 2The samplers of 7.1.1, 7.1.2, 7.1.3, and 7.1.4 are referred tocollectively as su
44、ction 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 SamplersThe samplers havelimited field applications at the presen
45、t 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-tion attached to a sample vesse
46、l 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 air spaces, andinterconnecting l
47、iquid films. Liquid films in the soil provideTABLE 1 Suction Sampler 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 100NAB10
48、0 60 to 80 7.5Fritted glass 4 to 5.5 NABNAB7.5Stainless steel NAB49 to 5 49 to 5 7.5APore size determined by bubbling pressure (1) or mercury intrusion (2).BNA = Not available.D4696 183hydraulic contact between the saturated porous section of thesampler and the soil (see Fig. 1). When suction greate
49、r than thesoil pore-liquid tension is applied to the sampler, a pressurepotential 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 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 m
