Distribution of organic pollutants in coastal sediments of Cádiz Bay (SW Spain)

Abstract

Concentrations of surfactants and persistent organic pollutants have been determined in coastal marine sediments (Cádiz Bay, SW Spain) from two areas affected by different contamination sources and levels: a tidal channel (Sancti Petri Channel) subjected to the discharge of untreated urban effluents, and an estuarine zone (Guadalete River) subjected to the occasional discharge of effluents from agriculture and from an urban and industrial wastewater treatment plant. Linear alkylbenzene sulfonates (LAS), nonylphenol polyethoxylates (NPEOs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorinated pesticides were determined by an analytical procedure based on the use of an accelerated solvent extraction unit, a preconcentration and cleaning stage using solid phase extraction, and later quantification by LC/MS and GC/MS. In general, the highest concentrations were found in surface sediments near the untreated urban effluent, with levels above 80 mg kg^–1 for LAS, 200 µg kg^–1 for PAHs, and 10 and 50 µg kg^–1 for PCBs and DDT, respectively. Also observed was a decrease in the concentrations of the compounds with the depth of the sediment, with the exception of PAHs and PCBs, which show a maximum at 25–30 cm. In the area subjected to agricultural and wastewater treatment plant effluents, high levels of NPEOs (122 mg kg^–1) and DDT (63 mg kg^–1) were recorded as a result of their industrial and agricultural uses, respectively.