First report on chlorinated pesticide deposition in a sediment core from asmall lake in central Chile

sThis paper presents a first report on chlorinated pesticide deposition ana lyzed through sedimentary records in a small mesotrophic lake (Chica de San Pedro) in central Chile. The sediment core was sliced and dated using Pb-2 10, Cs-137 and pollen analyses. Organochlorine pesticides were analyzed by gas chromatography with electron capture detection (GC-ECD). From these res ults, pesticide deposition over the last 50 years was estimated. No pestici des were detected below the 1940 slice of the core. Concentrations were in the range 0.640-1.4 ng/g d.w. for total DDTs, 0.046-0.362 ng/g d.w. for lin dane and 0.015-0.310 ng/g d.w. for alpha -hexachlorohexane. Highest concent rations of pp'DDT were found in 1993-1996 and higher concentrations of pp-D DE and ppi-DDD were found in the seventies (1972-1978). Total organic carbo n (TOC) normalized data were used for statistical analysis. Although signif icant correlation was observed between concentrations of DDE and DDD, no co rrelation was found for DDT, suggesting that it had a different source. Fac torial analysis grouped DDE together with DDD, while DDT was grouped togeth er with gamma- and alpha -HCH. Total DDT fluxes were highest during the 197 0s, while those for HCHs have been increasing in the 1990s. In Chile, organ ochlorine compounds were banned in 1985, and the historical deposition patt erns seem to indicate that such measures have been effective. On the other hand, results point out a relatively new occurrence of pp'-DDT in the water shed, but the source remains unknown. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.