Sorption and competition of two persistent organic pesticides onto marine sediments: Relevance to their distribution in aquatic system Youssouf Djibril Soubaneh a,b,⇑ , Jean-Pierre Gagné b , Michel Lebeuf c , Vladimir Nikiforov d , Bruno Gouteux e , Awaleh Mohamed Osman f a Département de biologie, chimie et géographie, Université du Québec à Rimouski, 300, Allée des Ursulines, Rimouski, QC G5L 3A1, Canada b Institut des sciences de la mer de Rimouski, Université du Québec à Rimouski, 310, Allée des Ursulines, Rimouski, QC G5L 3A1, Canada c Department of Fisheries and Oceans, Maurice Lamontagne Institute, P.O. Box 1000, 850 Route de la Mer, Mont-Joli, QC G5H 3Z4, Canada d Saint-Petersburg Scientific Research Centre for Ecological Safety, Russian Academy of Sciences Korpusnaya, 18, St. Petersburg 197110, Russia e Aquatic Ecosystem Protection Research Division, Environment Canada, Burlington, ON L7R 4A6, Canada f Laboratoire de Chimie, Institut des Sciences de la Terre, Centre d’Etude et de Recherche de Djibouti (CERD), Route de l’aéroport, B.P. 486, Djibouti highlights  The B8-1413 (P26) and B9-1679 (P50) sorption–desorption coefficients were reported.  High sorption and low entrapment in the sediments were observed.  Results enhance understanding of the absence of these compounds in sediments.  Results suggest a more availability of these congeners in the aquatic system. graphical abstract article info Article history: Received 30 October 2014 Received in revised form 12 February 2015 Accepted 14 February 2015 Handling Editor: Caroline Gaus Keywords: POPs P26/P50 Sorption coefficient Desorption–entrapment Aquatic ecosystem abstract Sorption is a key process in the distribution of substances between environmental compartments in mar- ine 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 relative- ly concentrated in marine mammals. Sorption–desorption, entrapment and competition behaviors of the- se 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 coef- ficients and to assess the degree of B8-1413/B9-1679 entrapment of the two toxaphene congeners in sedi- ments. Carbon normalized sorption coefficients (K oc ) 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. Ó 2015 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.chemosphere.2015.02.039 0045-6535/Ó 2015 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Département de biologie, chimie et géographie, Université du Québec à Rimouski, 300, Allée des Ursulines, Rimouski, QC G5L 3A1, Canada. Tel.: +1 418 7231986x1123; fax: +1 418 724 1849. E-mail address: Youssoufdjibril_Soubaneh@uqar.ca (Y.D. Soubaneh). Chemosphere 131 (2015) 48–54 Contents lists available at ScienceDirect Chemosphere journal homepage: www.elsevier.com/locate/chemosphere