Organochlorine Pesticide Residues in Sediment Cores of Sunderban Wetland, Northeastern Part of Bay of Bengal, India, and Their Ecotoxicological Significance S. K. Sarkar Æ A. Binelli Æ C. Riva Æ M. Parolini Æ M. Chatterjee Æ A. K. Bhattacharya Æ B. D. Bhattacharya Æ K. K. Satpathy Received: 18 September 2007 / Accepted: 3 January 2008 / Published online: 29 January 2008 Ó Springer Science+Business Media, LLC 2008 Abstract This paper presents the first comprehensive report of the organochlorine pesticide residues (OCs) such as hexachlorocyclohexane isomers (HCHs), dichlorodi- phenyltrichloroethane and its six metabolites (DDTs), and hexachlorobenzene (HCB) in core sediments ( \ 63-lm particle size) from the Indian Sunderban wetland. The pooled mean values of the mass fraction of RHCHs, HCB, and RDDTs in the sediments were 0.05–12, 0.05–1.4, and 0.05–11.5 ng g -1 dry weight, respectively. The vertical distribution of pesticides reveals an erratic pattern. The concentration of four isomers of HCHs reveals a hetero- genic distribution where c-HCH (lindane) and b-HCH shared the dominant part. The mass fraction of HCB did not show any sharp spatial variation. The prevailing sequence of DDT metabolites indicates an active degra- dation of the parent compound in the sediments and/or inputs of already degraded pp’DDT to the region. Peak concentrations of HCH isomers and DDT metabolites have the potential to induce ecotoxicological impact as per the sediment quality guidelines. Organochlorine pesticides (OCs) such as hexachlorocy- clohexane (HCH), dichlorodiphenyltrichloroethane (DDT), and hexachlorobenzene (HCB) are ubiquitous, persistent, toxic, and bioaccumulative in nature. These organic com- pounds are of anthropogenic origin and resist photolytic, chemical, and biological degradation. Being semivolatile, they used to move long distances in the atmosphere, resulting in widespread distribution across the earth, including ‘‘remote areas’’ such as the polar regions (Allen- Gil et al. 1997). A major fraction of the OCs released worldwide to the global environment is known to originate from Asian regions (Iwata et al. 1994a). The relatively high hydrophobicity of OCs leads to their accumulation in organisms and adsorption on particles. The lipophilic nature, hydrophobicity, and low chemical and biological degradation rates of organochlorine pesticides have led to their accumulation in biological tissues and subsequent biomagnification in organisms progressing up the food chain (Borga et al. 2001). High concentrations of organochlorines have been reported in birds and marine mammals (Aguilar et al. 2002; Senthil Kumar et al. 2001). Most of these OCs have been classified recently as endo- crine disruptors that are able to interrupt physiological balance as they behave like environmental hormones (Senthil Kumar et al. 2005). These ecotoxicological con- cerns for OCs in organisms have occurred (Fry and Toone 1981; Kelee et al. 1995; Podreka et al. 1998; Vallack et al. 1998), which disrupt reproductive cycles of humans and wildlife (Colborn Smolen 1996). The concentrations of OCs in surface sediments pro- vide information on recent contamination, whereas concentrations of OCs in sediment cores may provide information on contamination over decades. Several studies have reported that contamination of OCs in the sediments from Asian coastal areas (Takeoka et al. 1991; S. K. Sarkar Á M. Chatterjee (&) Á A. K. Bhattacharya Á B. D. Bhattacharya Department of Marine Science, University of Calcutta, 35 Ballygunge Circular Road, Calcutta 700019, India e-mail: maussim@gmail.com A. Binelli Á C. Riva Á M. Parolini Department of Biology, University of Milan, Via Celoria 26, 20133 Milan, Italy K. K. Satpathy Indira Gandhi Center for Atomic Research, Environmental and Industrial Safety Section, Safety Group, Kalpakkam 603102, Tamil Nadu, India 123 Arch Environ Contam Toxicol (2008) 55:358–371 DOI 10.1007/s00244-008-9133-6