TOTAL MERCURY, METHYL MERCURY AND SULFIDE LEVELS IN BRITISH ESTUARINE SEDIMENTS .3.

Results from large scale studies of British estuaries (South West Rivers, Clyde, Mersey) for mercury, methyl methyl, sulphide and Eh levels are presented. The importance of sulphide concentrations in sediments as a controlling factor for methyl mercury levels is demonstrated for these locations. The data showing methyl mercury concentrations for most of the locations discussed has not been available previously. As was found previously for the River Carron, Scotland, above a sulphide concentration of about 3. 0 mg g** minus 1 in River Clyde sediments, methyl mercury levels present decline as sulphide further increases. Below 3. 0 mg g** minus 1 (sulphide), methyl mercury levels increase as sulphide concentrations increase.