Mass budgets and contribution of individual sources and sinks to the abundance of gamma-HCH, alpha-HCH and PCB 153 in the North Sea

Mass budgets of hexachlorocyclohexanes (alpha-HCH and gamma-HCH) and a polychlorinated biphenyl (PCB 153) for 1995--2001 were calculated based on model simulations and observations for the North Sea as a whole and the German Bight, a coastal shallow subregion. For the North Sea the air-sea fluxes of the three pollutants were net depositional and dominated by local sources (gamma-HCH and PCB 153) or atmospheric deposition (alpha-HCH). The air-sea fluxes were net volatilizational in the German Bight. Unlike HCH, PCB 153 does not show a downward trend in the North Sea marine environment during the study period. Due to its physicochemical properties it is expected to readily enter the food chains. Model results suggest that during studied period, the North Sea was a sink for PCB 153 and a source of HCHs for the outer world.