Contaminants in Narragansett Bay sediments

Three interrelated studies using sediment samples collected at 41 stations in 1997–98 and sediment trap samples collected from 14 stations in 2000 are presented. The concentration of LABs, PAHs, TPHs, PCBs, DDTs, and chlordanes in the surface sediments (top 2 cm) were highest in the urban rivers at the head of the bay and decreased down the East and West Passages. Overall, the data indicate that sediment PAHs, PCBs and DDTs may have a significant impact on the benthos of Narragansett Bay. The ratio of PAH to TPH, as well as the alkyl homolog distribution for PAHs, indicates that petrogenic sources increase down bay relative to pyrogenic inputs.; BZTs had the highest values in Pawtuxet Cove, close to their point source in the Pawtuxet River, and decreased up and down the Providence River from this site and were present at all station in this study.; PCA analysis of PAHs showed the Seekonk and Providence river samples fell in fairly narrow ranges and were distinctly separate even though the Seekonk River flows into the Providence River. Three of the four Providence River samples fell within the range of the West Passage samples, suggesting a strong riverine influence on the PAH assemblages in the Bay proper. PCA run on the PCB data separated the Taunton River samples from all the rest of the stations suggesting a different composition and hence a different source of PCBs to that river. Congener ratios derived from PCA were useful in distinguishing stations that had sources different from the rest of the bay locations.; Sediment trap data for LABs, PAHs and PCBs show decreasing concentrations down bay. The I/E ratio ranged from 0.50 to 3.3, with the higher more degraded samples further up bay. This suggests that the Providence River is not the major source of LABs to the lower bay, but local sources, such as marinas, are more important in theses areas. The concentration of PAHs and PCBs in the traps agreed well with the sediment values at corresponding stations.