engleski

Distribution and behaviour of methylmercury in sediments of the Seine estuary (France)

The environmental factors governing the distribution and behaviour of total and methylmercury within the Seine estuary have been assessed through the use of sediment cores. Box-cores taken at the coastal, estuarine and riverine locations in the period from 1994 to 1997 were analysed for bulk sediment and pore-water total and methylmercury concentrations, as well as a number of other chemical variables. The level of total mercury in sediment (300 - 1000 ng/g) showed neither significant temporal or spatial variations, nor characteristic changes with sediment depth. Contrary, the distribution of methylmercury was distinct from that of its inorganic counterpart since it displayed seasonal and spatial variability. Maximal methylmercury concentrations (up to 6 ng/g) and percentages (up to 2%) were obtained at estuarine locations with peak loadings just below the sediment surface and a decreasing trend towards the deeper layers. Total and methylmercury were not correlated, but the temporal and spatial behaviour of methylmercury appeared to reflect variations in salinity, redox potential, availability of the mercury ion and the sulphate reduction rate. Low reactive mercury, but very high total mercury concentrations were measured in the pore-waters (10 - 400 ng/l) with maxima at or just below the sediment/water interface. In spite of a high portion of organically complexed dissolved mercury, methylmercury in pore-waters was mainly below the detection limit of the method used (< 2 ng/l). From mercury speciation in the solid phase and the dependence of its dissolved fraction on iron and manganese in pore-water, source and distribution of mercury in pore-waters are discussed.

nije evidentirano

nije evidentirano