SPATIAL AND TEMPORAL DISTRIBUTION, FLUXES, AND BUDGETS OF ORGANOCHLORINATED COMPOUNDS IN NORTHWEST MEDITERRANEAN SEDIMENTS

A total of 30 NW Mediterranean surficial sediment samples collected in the prodeltas of the Rhone and Ebro Rivers, continental shelf, slope, and deep basin were analyzed for 12 individual polychlorinated biphenyl (PCB) congeners, chlorinated diphenylethane pesticides (2,4'- and 4,4'-DDT and their metabolites), and hexachlorobenzene (HCB). The spatial distribution of the PCB congeners and their concentrations illustrate the relative contribution to the pollution burden in the NW Mediterranean basin of river inputs, urban sewage disposal, and atmospheric deposition, the latter particularly relevant in the deep basin. Estimates of annual fluxes of these compounds in the NW Mediterranean sediments were from 0.5 to 1580 mu g/m(2) for PCBs (in Clophen A60 equivalents), from 0.3 to 2060 mu g/m(2) for DDTs (DDT + DDE + DDD), and from 0.02 to 170 mu g/m(2) for HCB. These results account for an accumulation rate in the whole area of 2705 kg/year for PCBs, 2030 kg/year for DDTs, and 205 kg/year for HCB. However, the major accumulation of organochlorinated compounds was found to occur in the prodelta areas with an apparent decrease in the Rhone area during the last 15 years, but not in the Ebro, probably reflecting the earlier banning of the usage of these compounds in that region.