PCBs and HCHs in a salt-marsh sediment record from South-Central Chile: use of tsunami signatures and 137 Cs fallout as temporal markers Ricardo Barra a, * , Marco Cisternas b , Claudia Suarez a , Alberto Araneda a , Osvaldo Pi ~ nones c , Peter Popp d a Aquatic Systems Research Unit, EULA-Chile Center, Environmental Sciences Center, University of Concepci on, Barrio Universitario S/N, P.O. Box 160-C, Concepci on, Chile b Faculty of Agronomy, Catholic University of Valparaiso, Chile c Environmental Radiation Laboratory, Chilean Agency of Nuclear Energy, La Reina, Chile d Department of Analytical Chemistry, UFZ Center for Environmental Research, Leipzig-Halle, Germany Received 2 July 2003; received in revised form 12 December 2003; accepted 18 December 2003 Abstract This paper documents the occurrence of polychlorinated biphenyl (PCB) and hexachlorocyclohexane (HCH) deposition inferred from a sedimentary record exposed in a salt-marsh trench in South-Central Chile. Sediments were carefully collected every 1 cm from the trench wall. The samples were analyzed for PCBs, HCHs, 137 Cs, organic carbon and grain size. The 137 Cs fallout and the sedimentary signature left by the 1960 Chilean tsunami were used as temporal markers to estimate the stratigraphic chronology and the sedimentation rates. PCBs were quantified by gas chroma- tography with electron capture detection (GC–ECD), and positive samples were confirmed by gas chromatography and mass spectrometry detection (GC–MS). Based on these results, PCBs and HCHs deposition over the last 40 years was estimated. No PCBs were detected below the tsunami signature. Total concentrations ranged from undetectable (ND) to 32 ng/g d.w. for PCBs and from undetectable (ND) to 1.29 ng/g d.w. for HCHs. The highest PCB concentrations were found in the upper 7 cm of the core. Even though PCBs were banned in 1982 as electrical fluids in Chile, total estimated PCB fluxes have increased approximately 20 times during the last 40 years: from undetectable values to 102.6 ng/cm 2 /year, reflecting that PCBs are still in use and being released into the environment. Ó 2004 Elsevier Ltd. All rights reserved. Keywords: Chile; Sediments; Temporal trend; HCH; POPs; PCBs 1. Introduction Even though the general environmental levels of Persistent Organic Pollutants have lower recorded val- ues in the southern than the northern hemisphere, the behavior of chlorinated compounds is not well under- stood due to an inadequate characterization of sources and environmental levels (Barra et al., 2002). Considering that both PCBs and chlorinated pesti- cides have been widely used at global level and that pollution monitoring in developing countries is still lacking, retrospective-time trend techniques can be con- venient tools for evaluating the environmental levels of pollutants through the reconstruction of historical levels of these persistent pollutants. Historical patterns of organochlorine depositions in sediments have several applications. They provide * Corresponding author. Tel.: +56-41-203-293; fax: +56-41- 207-076. E-mail address: ricbarra@udec.cl (R. Barra). 0045-6535/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved. doi:10.1016/j.chemosphere.2003.12.006 Chemosphere 55 (2004) 965–972 www.elsevier.com/locate/chemosphere