542F04008
Deployment of Passive Vapor-Diffusion
Samplers for Detecting Volatile Organic
Compounds in Ground-Water Discharge
Areas
Through the Measurement and Monitoring Technologies for the 21 st Century (21M2) initiative,
EPA's Office of Solid Waste and Emergency Response (OSWER) is identifying and supporting
deployment of promising measurement and monitoring technologies by matching existing and
emerging technologies with OSWER program and client needs in the fields of waste management
and site cleanup. OSWER has identified a number of "needs areas" as the focus of 21 M2. These
needs reflect evolving requirements across all waste programs. A recent list and description of
needs is available at the 21 M2 Internet site at http://www.ciuin.org/programs/21 m2/needs.cfm.
Background
This fact sheet introduces the Guidance on the Use
of Passive-Vapor-Diffusion (PVD) Samplers to
Detect Volatile Organic Compounds in Ground-
Water-Discharge Areas, and Example Applications
in New England (USGS WRI02-4186). EPA
Region 1 and the headquarters 21M2 program
funded the U.S. Geological Survey's field work
that produced this guidance for personnel who
design characterization studies and install PVD
samplers.
PVD samplers are typically constructed using a
standard, uncapped 40-ml volatile organic analysis
vial that is placed inside a section of low-density
polyethylene (LDP) tubing (permeable to many
volatile organics but impermeable to water) and
heat sealed at both ends. The bagged vial is placed
into a second section of LDP tubing that prevents
sediment from contacting the first bag. Standard,
scalable, commercial polyethylene sandwich bag-
gies also may be used. The vial and bags are
attached to a survey or flag that enables them to be
located and retrieved. The PVD samplers are
buried at preselected depths and allowed to equili-
brate with the surrounding water for 14 days or
longer depending on site conditions. Volatile
organic compounds (VOCs) partition into the PVD
samplers from the water at a ratio related to their
Henry's Constant. After equilibration, the bags are
retrieved and the vials capped. The vial contents
can be analyzed with an on-site gas chromato-
graph (GC) or at an off-site laboratory.
Project Objectives
• Provide advantages, limitations, and other
background information on the use of PVD
samplers to individuals considering the
samplers as a reconnaissance tool in their site
characterization plans;
• Provide a "how to" guide on the construction
and deployment of PVD samplers;
• Describe a PVD sampler demonstration at the
Nyanza Superfund Site; and
• Evaluate the usefulness of PVD samplers that
have been deployed at nine Superfund sites in
Region 1.
Project Results
Advantages and Limitations of Using PVD
Samplers. A few of the advantages discussed in
the guidance include the following:
• The areal extent of the contaminant discharge
in surface water can be estimated;
• Discharge heterogeneity can be identified;
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Office of Superfund Remediation
and Technology Innovation
EPA/542/F-04/008
• The samplers are inexpensive and generally
easy to deploy and recover; and
• Analysis can be conducted in the field if
desired.
Some of the limitations include the following:
• Samplers are only appropriate for certain
volatile organics and require a GC for analysis;
• Deployment in deep water is problematic;
• Equilibration times can be long, and concen-
trations represent an integration over time; and
* PVD samplers provide only qualitative
information on concentrations of chemicals in
ground water.
"How To" Guidance. Some of the topics discus-
sed extensively in the guidance are assembly of
samplers, deployment techniques, recovery of
samplers, analysis of vapor samples, quality
assurance/quality control, and factors that could
affect deployment and data interpretation.
Deployment at the Nyanza Superfund Site. The
ground water at this former manufacturing facility
is contaminated primarily with chlorinated
benzenes and aliphatics. Underlaying the site are
glacial lake deposits and till over a fractured
crystalline bedrock. The glacial lake deposits range
in grain size from silt to coarse sand and gravel.
PVD samplers were deployed in the sediment of
three downgradient surface water bodies. Due to
variations in river/pond stages and temperature,
equilibration times for the samplers were estimated
to exceed three weeks in some of the sediment.
The chemical results from the PVD samplers
agreed with the results obtained from ground-water
monitoring wells and the seepage meter. The PVD
sampler results did not compare well with those
obtained from sediment samples primarily because
the PVD samplers had lower detection limits than
the sediment sample method. The investigators
concluded that the PVD method is an excellent
screening tool for mapping contaminated ground-
water discharge areas.
Evaluation of PVD Sampler Deployment
Results at Nine Region 1 Superfund Sites. Nine
case studies where PVD samplers were used
highlight the versatility of the samplers and their
successful deployment in a variety of hydrogeo-
logic settings.
Recommendation for Further Studies. The
authors recommend further studies to determine
whether PVD samplers can be used to evaluate
chemical transformations at the ground-water/
surface water interface and how VOC concentra-
tions change as hydrologic conditions change.
Project Information
For more information on this study, contact Dick
Willey, U.S. EPA Region 1, 617-918-1266,
willev.dickfg.epa.gov
View the guidance at:
http://ma.water.usgs.gov/publications/wrir/wriQ241
86/Reporthtm or
http://clu-
in.org/programs/21m2/proiects/wri024186.pdf
Additional Information
More information can be found at the following
locations:
• 21M2 program.
http://cluin.ors/prosrams/21m2/or
• Dan Powell, U.S. EPA, 703-603-7196,
powell.dan@epa.gov
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