|
(46-37) Does air-water exchange control PCB and PAH concentrations in estuarine phytoplankton. Eisenreich, Steven*,1,2, Yan, Shu2, Dachs, Jordi3, Reinfelder, John2, Fan, C.-W2, 1 Inland and Marine Waters Unit, Ispra, Italy2 Department of Environmental Sciences, New Brunswick, USA3 Department of Environmental Chemistry, Barcelona, Spain ABSTRACT- Diffusive air-water exchange and phytoplankton uptake of semivolatile organics (SOCs) are both important processes in fate and transport of SOCs in aquatic ecosystems. A dynamic model that couples air-water exchange and phytoplankton uptake of SOCs has been developed. Simultaneous measurements of PCBs in the air, water, and phytoplankton in Lower Hudson River Estuary (LHRE, NY, USA) were made in 6 cruises from December 1999 through April 2001. The over-water gaseous PCB concentrations ranged from 300 to 3200 pg/m3 with highest concentrations occurring under warm air temperatures and when winds were from westerly and notherly quadrants. Relatively constant seasonal concentrations of dissolved and particulate water phase (phytoplankton) PCBs were observed, ranging from 700 to 1600 pg/L, and 250 to 670 ng/g, respectively. Instantaneous net air-water exchange fluxes were calculated using a modifyed two layer model. Net fluxes of total PCBs exhibited net volatilization for all sampling seasons with and average of 290 ng/m2d demonstrating that the LHRE is a net source of PCBs to the ambient atmosphere. Intensive seasonal field measurements were used to validate the air-water-phytoplankton model in the LHRE site for several representative PCB congeners. For the lower chlorinated congeners, volatilization fluxes exceed absorption fluxes due to large surface water PCB inputs. Thus the atmosphere does not play an important role in contributing the bioaccumulation of low Cl-PCBs in phytoplankton in this system. For the higher chlorinated congeners that exhibit net absorption fluxes, the gas phase supports the PCB concentrations in phytoplankton. The dynamic model for air-water-phytoplankton exchange predicts the observed PCB concentrations within a factor of two. Key words: PCBs, PAHs, air-water-phytoplankton exchange, estuarine waters |
