Sorption and competition of two persistent organic pesticides onto marine sediments: Relevance to their distribution in aquatic system

Abstract

Sorption is a key process in the distribution of substances between environmental compartments in marine ecosystems. Two persistent organic pesticides, also known as toxaphene congeners, namely B8-1413 (P26) and B9-1679 (P50), are of special interest because they are not detected in sediments while relatively concentrated in marine mammals. Sorption-desorption, entrapment and competition behaviors of these pesticides onto marine sediments were studied to explain their environmental distribution. Data obtained under marine experimental conditions were fitted to sorption models to evaluate sorption coefficients and to assess the degree of B8-1413/B9-1679 entrapment of the two toxaphene congeners in sediments. Carbon normalized sorption coefficients (Koc) of both congeners were similar under in cold (2°C) marine (30 psu) conditions with high values ranging from 1.53×10(5) to 3.28×10(5) mL g(-1)indicative of a strong affinity to marine sediments However, the sorption-desorption investigations indicate that B8-1413/B9-1679 were on average 2.5 times less entrapped in sediments compared to B7-1450, a toxaphene congener known to accumulate predominantly in sediments. These results suggest that the low entrapment of B8-1413 and B9-1679 favor their availability and transfer to biological matrices.

Keywords: Aquatic ecosystem; Desorption–entrapment; P26/P50; POPs; Sorption coefficient.