M5 PM Marine Environmental Chemistry of Organic Pollutants
Monday, 14 November 2005: 1:50 PM - 5:30 PM in 321-323

(SMI-1117-699181) Seasonality in the concentrations and partitioning of PCBs in Baltic Sea surface waters.

Smith, K.¹, Czub, G.², McLachlan, M.², ¹ Institut für Ostseeforschung, Warnemünde., Germany² Laboratory for Analytical Environmental Chemistry, Department of Applied Environmental Science, Stockholm University, Stockholm., Sweden

ABSTRACT- In the marine environment the partitioning of PCBs between the dissolved and suspended matter phases in the water column plays a fundamental role in determining PCB fate e.g. air-water exchange or food-chain uptake. It was hypothesized that this partitioning could vary seasonally, particularly in temperate latitudes where biological, chemical, and physical conditions in the marine environment show a pronounced seasonality. Surface water samples from the western Baltic Sea were sampled regularly over an 18 month period between February 2003 and July 2004. The concentrations of seven PCB congeners were determined in the dissolved and suspended particulate matter (SPM) phases. A negative linear relationship was found between K_POC (i.e. the ratio between the particulate organic carbon (POC) normalized PCB concentration in SPM (pg/kg POC) and the dissolved concentration (pg/L)) and temperature. The decrease in the water temperature between summer and winter of 20°C resulted in approximately a factor of 5 increase in K_POC. POC normalized PCB concentrations in SPM were higher in winter than in summer by a factor of around 10. This was a reflection of the higher K_POC in winter and also somewhat greater PCB concentrations in the dissolved phase. The results demonstrate a clear seasonality in contaminant partitioning in the marine environment that should be accounted for when interpreting field data or modeling contaminant fate. Further research is needed to clarify whether the seasonality observed in the PCB levels associated with POC in the water column is also representative for those organisms occurring at the lower trophic levels such as phytoplankton and zooplankton, or whether the high concentrations in winter are largely associated with detritus.

Key words: PCB, Seawater, Partitioning, Seasonality