Forensic Applications for 1,4-Dioxane and Solvent Stabilizers - Environmental Investigation and Remediation - page 418

• Compound-specii c isotopic analysis

• Use of impurities and solvent stabilizers as marker chemicals to distinguish two sources of

the same solvent (Morrison et al., 2006)

This chapter focuses on the potential for solvent stabilizers to persist and be detected in solvent
plumes in a manner useful for various methods of analysis that can be applied toward deconvoluting
commingled plumes of a common solvent.

9.1 LEVERAGING 1,4-DIOXANE DATA FOR PLUME ANALYSIS
AND SOURCE APPORTIONMENT
Forensic analysis of environmental data is hampered by a high degree of uncertainty regarding
many of the parameters that can be leveraged to interpret the source and timing of a release.
Uncertainty can be reduced by collecting more data from more locations, using more accurate mea-
surement techniques, and adding additional types of data to the analysis. When multiple lines of
evidence supported by a variety of data types point predominantly in the same direction, the foren-
sic scientist begins to get a warm and fuzzy feeling, and with a little bit of luck, she or he may actu-
ally attain the much sought after “Aha!” moment and reach a conclusion.
Perhaps the most important and least available feature of solvent contamination sites is the mass
and timing of the release. It is the rare exception in which both are known with certainty, for example,
when an accident such as a truck overturn, train derailment, or above-ground tank failure is docu-
mented. The potential utility of solvent stabilizers to assist in establishing the mass released and
timing (or rate and duration of the release) depends on whether the mass fraction of the stabilizer is
sufi cient to be detected in environmental samples and whether the stabilizer compounds persist in
the subsurface. The ability to reliably identify and quantify solvent stabilizers through laboratory
analysis is of course essential to their use in forensic investigations. Detailed site operations records
and i rst-hand accounts of operating practices are also very useful in reconstructing the manner in
which solvents were used at the site. Finally, the study of solvent stabilizers at a release site cannot by
itself answer source apportionment questions. The incorporation of solvent stabilizers should be
viewed as an additional tool in the forensic toolbox whose usefulness will depend on the unique cir-
cumstances of the site's history and hydrogeology. This section examines some of the factors that
may contribute to or detract from the utility of solvent stabilizers in forensic investigations.

9.1.1 E STIMATING THE M ASS OF THE R ELEASE
Methods for estimating the release mass generally utilize a combination of the site's operating
history—for example, the timeframe during which a leaking underground solvent-waste tank was
used and the portion of that timeframe that the tank is assumed to have leaked—and the interpola-
tion of subsurface data points. The site history analysis is based on a study of tank construction,
photographs, and i eld notes that can be helpful in determining the mode of failure. Common modes
of failure include

• Corrosion from an external galvanic cell in the soil

• Acidic corrosion from within the tank due to mixtures of acid wastes or solvent breakdown

to hydrochloric acid
Physical weakening of the tank due to the practice of dropping a tank dipstick used to •

measure product volume

Subsurface data points encompass soil-core and groundwater data to delineate the mass concen-
tration at different points within the source area and various interpolation routines to allow the
investigator to infer the amount of pore space in the heterogeneous media occupied by the solvent.