(455) The Effects of Sediment Resuspension on the Cycling of PAHs and PCBs in the Lower Hudson Estuary.
Adams, R.1, MacFarlane, J.2, Geyer, W.3, Gschwend, P.2, 1 Environmental Protection Agency, Washington, DC, USA2 Massachusetts Institute of Technology, Cambridge, MA, USA3 Woods Hole Oceanographic Institution, Woods Hole, MA, USA
ABSTRACT- The elevated levels of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) in the sediments of the lower Hudson Estuary coupled with the tidally-driven sediment resuspension that occurs there, provide for the transport of these hydrophobic organic contaminants to and from the overlying water column. A passive, in situ sampler was used to measure dissolved concentrations of pyrene and PCB #52 during both neap and spring tides during April and October field campaigns in order to assess the impact of increased sediment resuspension. The chemical potential in the sediments was found to be higher than that of the overlying waters for both pyrene and PCB #52. A comparison of inputs caused by sediment resuspension to other sources and sinks suggest that sediment resuspension is an important source. A one-box model was used to estimate the dissolved concentration within the estuary. This allowed for the validity of the model to be assessed and for missing sources or sinks to be examined. In April 1999 resuspended sediments appear to have served as a source of pyrene to the estuary, while during October 2000 the sediments and water were close to equilibrium suggesting a diminished source of pyrene to the overlying water. In contrast, mixing diagrams in April 1999 suggest that the resuspended sediments were serving as a sink, scavenging PCB #52. However, the sediment and water samples indicate that there was a driving force from the sediments to the water. A possible explanation for this observation may be the scavenging of PCB #52 by cleaner sediments throughout the estuary. In October 2000, as with pyrene, the sediments and water were more closely equilibrated with respect to PCB #52. These results show that sediment resuspension is important to the cycling of PAHs and PCBs in the lower Hudson Estuary.
Key words: polychorinated biphenyls, polycyclic aromatic hydrocarbons, Hudson Estuary, sediment resuspension