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Distribution of organochlorine compounds in superficial sediments from the Gulf of Lion, northwestern Mediterranean Sea

August 14, 2013

Superficial sediments from Cap de Creus to the Rhone Delta, in the Gulf of Lion, Northwestern Mediterranean Sea, including the mid-shelf mud belt and the continental slope were collected between 2005 and 2008 to assess the levels, main sources and distribution patterns of organochlorine pollutants. Discharges from the Rhone River are the main source for all these compounds in the whole area. The spatial distribution of organochlorine pollutants is also related to their physicochemical properties and to sediment grain size and composition. The concentrations of polychlorobiphenyls (PCBs), dichlorodiphenyltrichloroethane (DDT) and its metabolites (DDD and DDE), chlorobenzenes (CBzs) – pentachlorobenzene (PeCB) and hexachlorobenzene (HCB)- decrease westwards along the mid-shelf mud belt. In contrast, hexachlorocyclohexane isomers (HCHs), namely lindane (γ-HCH), present another concentration pattern suggesting a different transport mode. The major concentrations of organochlorine compounds are observed off the Rhone River mouth, in the prodelta, where PCBs, DDTs and CBzs concentrations reach 38, 29 and 8.3 ng·g-1, respectively. These average concentrations in the mid continental shelf are between two and ten times lower than those found in a study performed about 20 years ago. Nevertheless, PCBs and DDTs still exceed the NOAA’s Sediment Quality Guideline value for effect range low in almost all sites. In contrast, concentrations in the continental slope do not show any significant decrease, which may evidence that background concentrations associated to diffuse pollution have not decreased in the deep continental margin after banning of most of these compounds.

Salvadó J A, Grimalt J O, López J F, Durrieu de Madron X, Pasqual C, Canals M, in press., Distribution of organochlorine compounds in superficial sediments from the Gulf of Lion, northwestern Mediterranean Sea, Progress in Oceanography, 2013, doi:10.1016/j.pocean.2013.07.014. Article.

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