Characterization of DNAPL Using Fluorescence Techniques

Abstract
Dense non aqueous phase liquid (DNAPL) contaminants, comprised of chlorinated aliphatic compounds, are a major source of groundwater contamination at the Savannah River Site (SRS). To successfully remediate a site contaminated by DNAPLs, it is imperative that the slowly dissolving, non-aqueous phase source be found and removed. There are few technologies that can successfully and consistently detect DNAPLs in the subsurface either directly or by inferred measurements. Because of the use of chlorinated solvents to remove petroleum-based cutting oils and lubricants at SRS (and other manufacturing sites) in degreasing operations, waste solvents may contain small amounts of the oils and lubricants. This mixture will fluoresce when excited by light of wavelengths capable of being transmitted over optical fiber. Samples of DNAPL from the A/M area of SRS were analyzed to assess the possibilities of contaminant detection by fluorescence spectroscopy. The DNAPL sample exhibited a strong, distinct fluorescent spectrum when exposed to an appropriate excitation wavelength. A cone penetrometer-based, laser induced fluorescent system may be capable of providing direct detection of DNAPLs in the subsurface based on these results.

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