PAHs In Sediments Research Articles

Behaviour of some PAH, PCB and organochlorine pesticides in an estuary, a comparison — Exe, Devon

The spatial variations in three groups of organic micropollutants: PCB, PAH and organochlorine pesticides in an estuarine environment, were interpreted by principal component and cluster analysis. The regional pattern of PAH and PCB concentration in sediments and in the water column within the Exe estuary is characterized by an increase of concentrations from river water into the mixing zone, and a decrease from there to the sea. Further, the concentrations decrease from the tidal channel towards the tidal flats. This is explained by sedimentation of PAH and PCB adsorbed on suspended sediments entering the estuary from the river. The settling PAH and PCB and the resuspended ones are carried back by the lower compensation current, thus causing a zone of high PAH and PCB concentrations within the turbidity maximum of the main channel. However, local inputs other than that from the river result in the case of the PCB in a somewhat more irregular pattern, superposed on that of a single source with hydrodynamic distribution as it is the case with the PAH. The pesticides α-BHC,γ-BHC and HCB show a distribution pattern which is dominated by a multiple input of these compounds via brooklets draining intensively used agricultural land.

Projected Consequences of Dumping Sewage Sludge at a Deep Ocean Site near New York Bight

Projections are made of the distribution of and biological response to New York/New Jersey sewage sludges if they are slowly discharged from barges at a deepwater location in annual volumes of 7 × 106 m3. We have used available information on sludge composition, dispersion of barge-dumped wastes, flow through the dumpsite, sewage sludge settling under quiescent conditions, rates of horizontal dispersion in the deep sea, chemical composition of open ocean water, ambient mass fluxes to the seafloor, sediment characteristics, bioturbation rates, and biological responses to sludge and its components. Within a 20-m surface mixed layer between the dumpsite and the Gulf Stream a chemical signal of dumping may be evident in iron, lead, zinc, chromium, and PCB concentrations. Water column contamination would appear to be less than necessary to affect planktonic organisms or fish. Seafloor contamination would be due primarily to sludge particles falling at 10−2 cm∙s−1 or faster. Allowing for bioturbation, the major sediment contaminants, PCB s and PAHs, could reach concentrations at the sediment surface of 0.2 and 0.3 μg∙g−1, respectively, after 100 yr. Concentrations of that order in shallow ocean benthic systems are not obviously related to altered benthic life. The strength of these projections would be increased with better understanding in many areas, especially on the effect of natural and barge-induced turbulence on particle flocculation and on rates of horizontal dispersion in the deep ocean. If sludge is dumped, the water column should be studied for chemical evidence of sludge and response of open ocean plankton. Arrays of sediment traps could be deployed to quantify the rate and areal extent of the settling sludge flux.