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 b iological processes is discussed. Hg-0 concentrations in the Scheldt e stuary 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 w ith 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. Tra nsfer velocities across the air-sea interface were calculated using a classical shear turbulence model. Volatilization fluxes of Hg-0 were c alculated for the Scheldt estuary and the North Sea. For the Scheldt e stuary the fluxes range from 226-284 pmol . m(-2) . d(-1) in winter an d 500-701 pmol . m(-2) . d(-1) in summer and for the North Sea the flu xes range from 59-1110 pmol . m(-2) . d(-1) for an average windspeed o f 8.1 m . s(-1). These fluxes are comparable to the wet and dry deposi tional fluxes to the North Sea. Hg-0 formation rates necessary to bala nce the volatilization fluxes vary from 0.2 to 4% d(-1). (C) 1998 Else vier Science B.V.