USING ENVIRONMENTAL FORENSICS TO DISTINGUISH LEGACY AND ONGOING CONTAMINATION IN URBAN WATERWAYS
In urban sediments contaminant hydrocarbons most often coexist with complex mixtures of biologically-derived organic compounds, which may in turn be signatures of other types of environmental stress. As indicators of a particularly vexing problem, sewage-derived steroids, fatty acids, and surfactants are incorporated into sediments from discharges of inadequately treated urban waste or via combined sewer overflows (CSOs) after heavy rainstorms. Water bodies enriched in nutrients from treatment plant discharges or fertilizer runoff may suffer seasonal algal blooms, which in turn leave their own molecular signatures in bottom sediments.
Molecular characterization of sediments by pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) permits the recognition of all the above-mentioned types of organic pollutants in a single analysis. This can include contaminants not yet recognized by government regulators and overlooked by conventional analytical methods. The method also permits the assessment of the degree to which the "natural" organic matter co-occurring in the sediment is predominantly aquatic or terrestrial in origin.