ASTM D4696-92(2008)
(Guide)Standard Guide for Pore-Liquid Sampling from the Vadose Zone (Withdrawn 2017)
Standard Guide for Pore-Liquid Sampling from the Vadose Zone (Withdrawn 2017)
SIGNIFICANCE AND USE
Sampling from the vadose zone may be an important component of some groundwater monitoring strategies. It can provide information regarding contaminant transport and attenuation in the vadose zone. This information can be used for mitigating potential problems prior to degradation of a groundwater resource (1).
The choice of appropriate sampling devices for a particular location is dependent on various criteria. Specific guidelines for designing vadose zone monitoring programs have 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 and Palmer (11), U.S. EPA (12), Ball (13), and Wilson (14). In general, it is prudent to combine various unsaturated and free drainage samplers into a program, so that the different flow regimes may be monitored.
This guide does not attempt to present details of installation and use of the equipment discussed. However, an effort has been made to present those references in which the specific techniques may be found.
SCOPE
1.1 This guide covers the equipment and procedures used for sampling pore-liquid from the vadose zone (unsaturated zone). The guide is limited to in situ techniques and does not include soil core collection and extraction methods for obtaining samples.
1.2 The term “pore-liquid” is applicable to any liquid from aqueous pore-liquid to oil. However, all of the samplers described in this guide were designed, and are used to sample aqueous pore-liquids only. The abilities of these samplers to collect other pore-liquids may be quite different than those described.
1.3 Some of the samplers described in this guide are not currently commercially available. These samplers are presented because they may have been available in the past, and may be encountered at sites with established vadose zone monitoring programs. In addition, some of these designs are particularly suited to specific situations. If needed, these samplers could be fabricated.
1.4 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 guide offers an organized collection of information or a series of options and does not recommend a specific course of action. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide 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 of this document means only that the document has been approved through the ASTM consensus process.
WITHDRAWN RATIONALE
This guide covers the equipment and procedures used for sampling pore-liquid from the vadose zone (unsaturated zone). The guide is limited to in situ techniques and does not include soil core collection and extraction methods for obtaining samples.
Formerly under the jurisdiction of Committee D18 on Soil and Rock, this guide was withdrawn in January 2017 in accordance with section 10.6.3 of the Regulations Governing ASTM Technical Committees, which requires that standards shall be updated by the end of the eighth year since the last approval date.
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D4696 − 92 (Reapproved 2008)
Standard Guide for
Pore-Liquid Sampling from the Vadose Zone
This standard is issued under the fixed designation D4696; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope unique aspects. The word “Standard” in the title of this
document means only that the document has been approved
1.1 This guide covers the equipment and procedures used
through the ASTM consensus process.
for sampling pore-liquid from the vadose zone (unsaturated
zone). The guide is limited to in situ techniques and does not
2. Referenced Documents
include soil core collection and extraction methods for obtain-
2.1 ASTM Standards:
ing samples.
D653Terminology Relating to Soil, Rock, and Contained
1.2 The term “pore-liquid” is applicable to any liquid from
Fluids
aqueous pore-liquid to oil. However, all of the samplers
described in this guide were designed, and are used to sample
3. Terminology
aqueous pore-liquids only. The abilities of these samplers to
3.1 Definitions—Where reasonable, precise terms and
collect other pore-liquids may be quite different than those
names have been used within this guide. However, certain
described.
termsandnameswithvaryingdefinitionsareubiquitouswithin
1.3 Some of the samplers described in this guide are not
the literature and industry of vadose zone monitoring. For
currently commercially available. These samplers are pre-
purposes of recognition, these terms and names have been
sented because they may have been available in the past, and
included in the guide with their most common usage. In these
may be encountered at sites with established vadose zone
instances, the common definitions have been included in
monitoring programs. In addition, some of these designs are
Appendix X1. Examples of such terms are soil, lysimeter,
particularly suited to specific situations. If needed, these
vacuum and pore-liquid tension.
samplers could be fabricated.
3.2 Definitions of Terms Specific to This Standard:
1.4 The values stated in SI units are to be regarded as
3.2.1 Appendix X1 is a compilation of those terms used in
standard. No other units of measurement are included in this
this guide. More comprehensive compilations, that were used
standard.
as sources for Appendix X1, are (in decreasing order of their
1.5 This standard does not purport to address all of the usage):
3.2.1.1 Terminology D653,
safety concerns, if any, associated with its use. It is the
3.2.1.2 Compilation of ASTM Terminology,
responsibility of the user of this standard to establish appro-
3.2.1.3 Glossary of Soil Science Terms,SoilScienceSociety
priate safety and health practices and determine the applica-
of America, and,
bility of regulatory limitations prior to use.
3.2.1.4 Webster’s New Collegiate Dictionary,
1.6 This guide offers an organized collection of information
or a series of options and does not recommend a specific
4. Summary of Guide
course of action. This document cannot replace education or
experienceandshouldbeusedinconjunctionwithprofessional
4.1 Poresinthevadosezonecanbesaturatedorunsaturated.
judgment. Not all aspects of this guide may be applicable in all Somesamplersaredesignedtoextractliquidsfromunsaturated
circumstances. This ASTM standard is not intended to repre-
pores; others are designed to obtain samples from saturated
sent or replace the standard of care by which the adequacy of
a given professional service must be judged, nor should this
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
document be applied without consideration of a project’s many
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.
1 3
ThisguideisunderthejurisdictionofASTMCommitteeD18onSoilandRock Compilation of ASTM Terminology, Sixth edition, ASTM, 1916 Race Street,
and is the direct responsibility of Subcommittee D18.21 on Groundwater and Philadelphia,PA19103,1986.(Currently, ASTM Dictionary of Engineering Science
Vadose Zone Investigations. & Technology, 10th edition, ASTM International, 2005.)
Current edition approved Sept. 15, 2008. Published October 2008. Originally Glossary of Soil Science Terms, Soil Science Society of America, 1987.
approved in 1992. Last previous edition approved in 2000 as D4696–92 (2000). Webster’s New Collegiate Dictionary,Fifthedition,1977.(Currently Merriam-
DOI: 10.1520/D4696-92R08. Webster’s Collegiate Dictionary , Eleventh edition, 2006.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D4696 − 92 (2008)
pores (for example, perched groundwater) or saturated mac- 6.1.1 Required sampling depths,
ropores (for example, fissures, cracks, and burrows). This 6.1.2 Required sample volumes,
guide addresses these categories. The sampler types discussed
6.1.3 Soil characteristics,
are: 6.1.4 Chemistry and biology of the liquids to be sampled,
4.1.1 Suction samplers (unsaturated sampling), (see Section
6.1.5 Moisture flow regimes,
7),
6.1.6 Required durability of the samplers,
4.1.2 Free drainage samplers (saturated sampling), (see
6.1.7 Required reliability of the samplers,
Section 8),
6.1.8 Climate,
4.1.3 Perched groundwater samplers (saturated sampling),
6.1.9 Installation requirements of the samplers,
(see Section 9), and
6.1.10 Operational requirements of the samplers,
4.1.4 Experimental absorption samplers (unsaturated
6.1.11 Commercial availability, and
sampling), (see Section 10).
6.1.12 Costs.
4.2 Most samplers designed for sampling liquid from un-
6.2 Some of these criteria are discussed in this guide.
saturated pores may also be used to sample from saturated
However, the ability to balance many of these factors against
pores. This is useful in areas where the water table fluctuates,
one another can only be obtained through field experience.
so that both saturated and unsaturated conditions occur at
differenttimes.However,samplersdesignedforsamplingfrom
7. Suction Samplers
saturated pores cannot be used in unsaturated conditions. This
7.1 Table 1 presents the various types of suction samplers.
is because the liquid in unsaturated pores is held at less than
The range of operating depths is the major criterion by which
atmospheric pressures (see Richard’s outflow principle,in
suctionsamplersaredifferentiated.Accordingly,thecategories
Appendix X1).
of suction samplers are as follows:
4.3 The discussion of each sampler is divided into specific
7.1.1 Vacuum Lysimeters—These samplers are theoretically
topics that include:
operational at depths less than about 7.5 m. The practical
4.3.1 Operating principles,
operational depth is 6 m under ideal conditions.
4.3.2 Description,
7.1.2 Pressure-Vacuum Lysimeters—These samplers are op-
4.3.3 Installation,
erational at depths less than about 15 m.
4.3.4 Operation, and
7.1.3 High Pressure-Vacuum Lysimeters— (Also known as
4.3.5 Limitations.
pressure-vacuum lysimeters with transfer vessels.) These sam-
plers are normally operational down to about 46 m, although
5. Significance and Use
installations as deep as 91 m have been reported (15).
5.1 Sampling from the vadose zone may be an important
7.1.4 Suction Lysimeters With Low Bubbling Pressures
component of some groundwater monitoring strategies. It can
(Samplers With PTFE Porous Sections)—These samplers are
provide information regarding contaminant transport and at-
available in numerous designs that can be used to maximum
tenuation in the vadose zone.This information can be used for
depths varying from about 7.5 to 46 m.
mitigatingpotentialproblemspriortodegradationofaground-
NOTE 1—The samplers of 7.1.1, 7.1.2, 7.1.3, and 7.1.4 are referred to
water resource (1).
collectively as suction lysimeters. Within this standard, lysimeter is
5.2 The choice of appropriate sampling devices for a par-
defined as a device used to collect percolating water for analyses (16).
ticular location is dependent on various criteria. Specific
7.1.5 Filter Tip Samplers—These samplers theoretically
guidelines for designing vadose zone monitoring programs
have no maximum sampling depth.
have been discussed by Morrison (1), Wilson (2), Wilson (3),
7.1.6 Experimental Suction Samplers— The samplers have
Everett (4), Wilson (5), Everett, et al (6), Wilson (7), Everett,
limited field applications at the present time. They include
et al (8), Everett, et al (9), Robbins, et al (10), Merry and
cellulose-acetate hollow-fiber samplers, membrane filter
Palmer (11), U.S. EPA (12), Ball (13), and Wilson (14).In
samplers, and vacuum plate samplers. They are generally
general, it is prudent to combine various unsaturated and free
limited to depths less than about 7.5 m.
drainage samplers into a program, so that the different flow
7.2 Operating Principles:
regimes may be monitored.
7.2.1 General:
5.3 This guide does not attempt to present details of
7.2.1.1 Suction lysimeters consist of a hollow, porous sec-
installation and use of the equipment discussed. However, an
tion attached to a sample vessel or a body tube. Samples are
effort has been made to present those references in which the
obtained by applying suction to the sampler and collecting
specific techniques may be found.
pore-liquidinthebodytube.Samplesareretrievedbyavariety
6. Criteria for Selecting Pore-Liquid Samplers
of methods.
7.2.1.2 Unsaturated portions of the vadose zone consist of
6.1 Decisions on the types of samplers to use in a monitor-
interconnecting soil particles, interconnecting air spaces, and
ing program should be based on consideration of a variety of
interconnecting liquid films. Liquid films in the soil provide
criteria that include the following:
hydraulic contact between the saturated porous section of the
samplerandthesoil(seeFig.1).Whensuctiongreaterthanthe
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof
this standard. soil pore-liquid tension is applied to the sampler, a pressure
D4696 − 92 (2008)
TABLE 1 Suction Sampler Summary
A
Porous Section Air Entry Operational Suction Maximum Operation
Maximum Pore
Sampler Type
Material Size (µm) Value (cbar) Range (cbar) Depth (m)
A
Vacuum lysimeters Ceramic 1.2 to 3.0 (1) >100 <60 to 80 <7.5
A
PTFE 15 to 30 (2) 10 to 21 <10 to 21 <7.5
B
Stainless steel NA 49 to 5 49 to 5 <7.5
A
Pressure-vacuum lysimeters Ceramic 1.2 to 3.0 (1) >100 <60 to 80 <15
A
15 to 30 (2)
PTFE 10 to 21 <10 to 21 <15
A
High pressure-vacuum lysimeters Ceramic 1.2 to 3.0 (1) >100 <60 to 80 <91
A
15 to 30 (2)
PTFE 10 to 21 <10 to 21 <91
B B B
Filter tip samplers Polyethylene NA NA NA None
2to3(1) >100 <60 to 80
Ceramic <7.5
B B B
NA NA NA
Stainless steel none
Cellulose-acetate hollow-fiber samplers Cellulose <2.8 >100 <60 to 80 <7.5
Acetate
Non cellulosic
Polymer <2.8 >100 <60 to 80 <7.5
Membrane filter samplers Cellulose <2.8 >100 <60 to 80 <7.5
Acetate
B B
PTFE 2to5 NA NA <7.5
B B B
Vacuum plate samplers Alundum NA NA NA <7.5
Ceramic 1.2 to 3.0 >100 60 to 80 <7.5
B B
Fritted glass 4 to 5.5 NA NA <7.5
B
Stainless steel NA 49 to 5 49 to 5 <7.5
A
Pore size determined by bubbling pressure (1) or mercury intrusion (2).
B
NA = Not available.
maximum pore sizes are larger, and only a very limited range
of sampling suction can be applied before meniscuses break
down and sampling ends (see 7.6.1.3). Therefore, samplers
made with PTFE porous segments may be used only for
sampling soils 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. The
bubbling pressure is measured by saturating the porous
segment, immersing it in water, and pressurizing the inside of
the porous segment with air. The pressure at which air starts
bubbling through the porous segment into the surrounding
water is the bubbling pressure. The magnitude of the bubbling
pressureisequaltothemagnitudeofthemaximumsuctionthat
can be applied to the sampler before air entry occurs (air entry
value). Because the bubbling pressure is a direct measure of
how 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-
FIG. 1 Porous Section/Soil Interactions crease. Also, the soil hydraulic conductivity decreases expo-
nentially. These result in lower flow rates into the sampler.At
pore-liquid tensions above about 60 (for coarse grained soils)
potential gradient towards the sampler is created. If the
to 80 cbar (for fine grained soils), the flow rates are effectively
meniscuses of the liquid in the porous segment are able to
zero and samples cannot be collected.
withstand the applied suction (depending on the maximum
7.2.2 Suction Lysimeters:
pore sizes and hydrophobicity/hydrophilicity), liquid moves
7.2.2.1 Vacuum lysimeters directly transfer samples to the
into the sampler. The ability of the meniscuses to withstand a
surfaceviaasuctionline.Becausethemaximumsuctionliftof
suction decreases with increasing pore size and also with
water is about 7.5 m, these samplers cannot be operated below
increasing hydrophobicity of the porous segment (see 7.6). If
this depth. In reality, suction lifts of 6 m should be considered
the maximum pore sizes are too large and hydrophobicity too
a practical maximum depth.
great, the meniscuses are not able to withstand the applied
7.2.2.2 Samples may be retrieved using the same technique
suction.Asaresult,theybreakdown,hydrauliccontactislost,
as for vacuum lysimeters or, for deeper applications, the
and only air enters the sampler. As described in 7.6, ceramic
sample is retrieved by pressurizing the sampler with one line;
porous segments are hydrophilic and the maximum pore sizes
this pushes the sample up to the surface in a second line.
are small enough to allow meniscuses to withstand the entire
range of sampling suctions. Presently available polytetrafluo- 7.2.2.3 High pressure-vacuum lysimeters operate in the
roethylene (PTFE) porous segments are hydrophobic, the same manner as pressure-vacuum lysimeters. However, they
D4696 − 92 (2008)
include an inbuilt check transfer vessel or a chamber between
thesamplerandthesurface.Thispreventssamplelossthrough
theporoussectionduringpressurization,andpreventspossible
cup damage due to overpressurization.
7.2.2.4 Suction lysimeters with low bubbling pressures are
availab
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