As part of a multidisciplinary evaluation of the environmental impact of waste disposal in the New York Bight, a preliminary effort was undertaken to assess the molecular geochemistry of its sedimentary organic matter (OM). For this initial phase of the study, samples were taken from two New York Bight cores collected outside the area of known dumping, to establish the environmental context for future work on sediments from within dumpsite zones. The method employed was flash pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), which is an organic microanalysis technique suitable for solid samples, in this case dried, raw sediment. The resulting pyrolyzates show a predominance of (alkyl)benzenes, (alkyl)phenols, (alkyl)pyridines, and (alkyl)pyrroles, indicating that the bulk of the OM detected is of recent, biogenic origin. The OM includes degraded proteinaceous material, polysaccharides, lipids and higher plant waxes. While the OM is nominally 'natural', this interpretation does not exclude the possibility that the environment may have been perturbed by anthropogenically-enhanced nutrient fluxes. Samples taken deeper in the cores are relatively enriched in organic nitrogen and have more pyridinic nitrogen relative to pyrrolic. Thus the relative amounts and forms of organic nitrogen appear to be affected by diagenetic processes. In addition to its ability to characterize the bulk OM, Py-GC/MS of whole, dry sediment has been shown to be a useful tool for the rapid, semi-quantitative screening for trace concentrations of PAHs in potentially contaminated samples. The PAH data indicate that, while the majority of the OM is biogenic, there is a contribution of combustion-derived material, particularly in the upper samples from both cores. Molecular ratios employing key compounds may provide insights into the nature of the depositional environment. For example, considering the five-ring PAHs, a predominance of perylene over benzofluoranthenes and benzopyrenes is characteristic of pristine (i.e., pre-industrial era) sediments, as seen in the deepest sample examined in this study (175-200 cm sediment depth).
|Number of pages||8|
|Journal||Northeastern Geology and Environmental Sciences|
|State||Published - 1 Jan 1999|