Abstract

Sediment cores from four Chilean lakes along the Andes Chain (Chungará, Laja, Castor and Venus) were analysed in order to investigate PCB concentrations and distributions in sediment samples. Sediment cores were analysed for PCBs using gas chromatography (GC-ECD/MS) and radioisotopically dated using 210Pb. Organic carbon content (OC) and 210Pb fluxes were also measured. Results showed that sediment PCB concentrations (ng g-1 d.w.) at Lake Chungará (1.2 ± 1) in northern Chile, Laja (5 ± 4) in central, and in Lake Castor (3.5 ± 4) in southern Chile (the eastern side of the Andes Mountain) were lower than sediments collected from Lake Venus (64 ± 30) located in southern Chile (the western side) which contained 15-fold higher concentrations of PCBs. The percentage (%) of organic carbon was variable and showed a high range of values in the sediment fluctuating from 2% (Lake Laja) to 22% (Lake Chungará). Analysis of 210Pb fluxes, presented a decrease trend following Lake Laja > Castor > Chungará with a positive correlation with rainfall at each site. Sedimentation rates in Lake Castor (1846 g m-2 yr-1) were higher than at Chungará (748 g m-2 yr-1) and Lake Laja (508 g m-2 yr-1). Focusing factor (FF) is used as a tool to elucidate PCB input in the aquatic ecosystem. FF were lower (<1) for the shallower lakes (Lakes Chungará and Castor). This study provides background levels of PCBs at remote lakes in Chile. Differences in geographical characteristics (orographic effect) might play an important role in the arrival of PCBs, particularly into the southern lakes. PCB fluxes indicated deposition of PCBs in recent sediments is higher than in previous years with peaks of PCB between 1991 and 1998. The continuing increase of PCB inputs in remote Chilean lakes, could be associated with long range atmospheric transport (LRAT). © 2006 Elsevier Ltd. All rights reserved.