Elemental mercury concentrations and formation rates in the Scheldt estuary and the North Sea

Concentrations of Hg-0 in surface waters and atmosphere of the Scheldt estuary and the North Sea are presented and their relationship with biological processes is discussed. Hg-0 concentrations in the Scheldt estuary range from 0.1 to 0.38 pmol . l(-1) in the winter and from 0.24 to 0.65 pmol . l(-1) in the summer and show a positive relationship with phytoplankton pigments. In the North Sea Hg-0 concentrations range from 0.06 to 0.8 pmol . l(-1) and are higher in coastal stations. Transfer velocities across the air-sea interface were calculated using a classical shear turbulence model. Volatilization fluxes of Hg-0 were calculated for the Scheldt estuary and the North Sea. For the Scheldt estuary the fluxes range from 226-284 pmol . m(-2) . d(-1) in winter and 500-701 pmol . m(-2) . d(-1) in summer and for the North Sea the fluxes range from 59-1110 pmol . m(-2) . d(-1) for an average windspeed of 8.1 m . s(-1). These fluxes are comparable to the wet and dry depositional fluxes to the North Sea. Hg-0 formation rates necessary to balance the volatilization fluxes vary from 0.2 to 4% d(-1). (C) 1998 Elsevier Science B.V.