An Environmental Geochemical Study Of Connecticut Marsh Sediments

Core material from Spartina-dominated Housatonic and Connecticut River estuarine sites (ranging from low to high marsh) were investigated in order to test the hypothesis that organic and inorganic pollutants preferentially accumulate in the low marsh environment. Radiometric data indicate that the low marsh setting experienced sedimentation rates an order of magnitude greater than that of the mid to high marsh. The low marsh sediments from the Housatonic tend to have significantly higher concentrations of trace metals (e.g., Cu and Zn, likely contributed by brass mills formerly active upstream). Petrographic examination of the samples under reflected white and blue light reveals fly ash, coke, char and coal particles. Molecular organic analysis by pyrolysis-gas chromatography/mass spectrometry demonstrates that the sediments enriched in anthropogenic trace metals and carbonaceous particles are also enriched in polycyclic aromatic hydrocarbons (PAHs) such as pyrene, chrysene and benzopyrenes, most likely combustion-derived. Long chain alkylamides are also unusually abundant in the pyrolyzates of these impacted sediments. These compounds are likely derived from bacterial organic matter in the sediments and we suggest that their presence could signal organic (i.e., sewage) contamination. These observations are reinforced by multivariate analysis of the combined organic/inorganic data set. The sediment cores serve in effect as archives documenting industrial pollution and environmental change in the estuaries over the last two centuries. The low marsh environments studied apparently provide a significant sink for pollutants when compared to mid and high marsh environments