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Abstract Submission Form

Desert Remedial Action Technologies

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<Aycock.Mary@epa.gov>

**Title:** HOW'D THAT GET IN THERE? A Practical Approach to Determining
Sources of Unexpected Contaminants OR Why Geochemical Characterization
is Key to Remedial Investigations

**Name of First Author:** Tiffany Downey, Ph.D.

**Email of Author:** tiffany.downey@geotransinc.com **Author Phone
Number:** 602-682-3392

**Organization to Which Author(s) belong:** GeoTrans, Inc.

**Conference Theme Considered Appropriate for Contents of
Presentation:** Dissolved phase VOCs

**Other Authors (name and e-mail):** Jasenka Zbozinek,
jzbozinek@geotransinc.com

**Author Biography:**

**Dr. Downey** obtained her doctorate in Chemistry from the University
of California, Davis. Dr. Downey has 10 years of in-depth environmental
chemistry background, including extensive experience with numerous
laboratory techniques and equipment, geochemical modeling software,
field techniques, sample collection, data analysis and document
research. She has worked with Lawrence Livermore National Laboratory
(LLNL), U.S. Department of Energy, the Delaware Department of Natural
Resources and Environmental Controls, Arizona Department of Water
Resources (ADWR), and the Arizona Department of Environmental Quality
(ADEQ). Dr. Downey's primary interests are geochemical speciation, risk
assessment, and nanotechnology.

**Dr. Zbozinek** obtained her doctorate from the California Institute of
Technology in Environmental Engineering Science and is the Arizona
Operations Manager for GeoTrans, Inc. Dr. Zbozinek has over 28 years
experience in technical reviews and directing, managing, and performing
projects, ranging from contamination assessment, development of remedial
investigations, remediation feasibility studies, development of early
response actions and remediation plans, and remediation oversight and
site closures, to regulatory interpretations and negotiations, and legal
support/expert witness testimony. The contaminants investigated included
chlorinated and other solvents, heavy metals, pesticides, cyanides,
PCBs, dioxins, dibenzofurans, petroleum hydrocarbons, and polynuclear
aromatic hydrocarbons. Dr. Zbozinek's experience includes over 15 NPL
and proposed NPL sites, over 30 State Superfund/WQARF sites.

**Text of the Abstract:**

So you thought you had a well-behaved, run-of-the-mill volatile organic
compound (VOC) plume, meandering predictably and spawning degradation
products just as it should with no other chemistry to consider? When
chlorinated solvents, petroleum hydrocarbons, and inorganic salts
co-mingle to form a toxic concoction, unconventional geochemical
analyses can decipher the source of your plume's "mystery guests." This
presentation uses a cyanide and tetrachloroethylene (PCE)-contaminated
confidential field site that has co-mingled with a hydrocarbon plume
emanating from a neighboring site in Arizona to elucidate the source of
unusual degradation daughter products as well as the importance of a
full geochemical characterization of the impacted aquifer. Number range
CHAPTER

Under standard reductive conditions, PCE is dechlorinated to form
trichloroethylene (TCE). The second dechlorination step forms the three
isomers of dichloroethylene (DCE); cis-DCE (95%), trans-DCE (\~5%), and
1,1-DCE (\<1%). Therefore, the presence of high relative concentrations
of 1,1-DCE and the lack of cis-DCE in an area of the plume triggered the
need for further investigation of the 1,1-DCE source(s). There are
several possible 1,1-DCE formation pathways that depend on the original
solvent released, as well as the biochemical and geochemical
characteristics of the aquifer. The three primary pathways are the
abiotic degradation of PCE in the presence of high sulfide
concentrations, microbial biodegradation of PCE in the presence of
petroleum hydrocarbons, and the dominant abiotic degradation of
1,1,1-TCA. Our site-specific data is reviewed to determine potential
1,1-DCE source(s) and to present practical groundwater analyses to
establish the source(s) of 1,1-DCE.

This presentation will elaborate on the practical geochemical analyses
required to differentiate the sources of the various daughter products,
including the ramifications of these analyses on the choice of remedial
technologies employed at the site.