MERCURY SPECIATION IN SURFACE WATERS OF THE NORTH-SEA

Mercury speciation was determined in samples of surface waters of the North Sea. Seventeen stations were visited including coastal waters of f the Thames, Humber, Scheldt, Rhine, Ems, Weser and Elbe estuaries, M ercury concentrations measured in the present study are significantly lower than previous estimates for the North Sea, but they are similar to concentrations recently determined in other coastal environments. C oncentrations of total dissolved mercury ranged from 0.9 to 4.8 pM wit h 0.4 to 1.8 pM as dissolved reactive mercury, representing on average about 30% of the total dissolved mercury. Particulate mercury constit uted between 13 and 82% of the total mercury (dissolved and particulat e) depending on the distribution of suspended particulate matter, with the highest proportions found near the coasts in the southern North S ea. The mercury content of the seawater particles varied between 116 a nd 484 ng . g(-1) with 6% on average as particulate monomethylmercury. A longitudinal profile was completed in the outer estuary of the Elbe river; mercury concentrations reached 16.4 pM for dissolved mercury a nd 595 pM for particulate mercury in the low salinity region, indicati ng that the Elbe estuary is contaminated with mercury. This is similar to the contamination measured recently in the Scheldt estuary. The ne t input of mercury from the Elbe river to the North Sea was estimated at 0.43 kmol . a(-1) for dissolved mercury and 4.24 kmol . a(-1) for p articulate mercury. The mercury concentrations measured in the Elbe es tuary are used to estimate the total mercury input from freshwaters to the North Sea, It is comparable to direct atmospheric inputs to the N orth Sea.