Sedimentary records of organochlorine contaminants in Central Chilean Lakes

Aquatic pollution by persistent organic compounds (POCs) in the southern hemisphere continues to be an important issue. Currently, no historic records of pollution are available to evaluate the inputs of chlorinated compounds and their environmental impact. Sedimentary records have been used to define the historical trend of pollution in lakes located in remote and urban areas. Sediment cores were collected from several urban and remote lakes in central Chile using a kayac sediment corer and cut into 1 cm slices. The organochlorine compounds were isolated in a soxhlet system with n-hexane, and successively identified and quantified by gas chromatography using an Electron Capture Detector (⁶³ Ni). Principal Components Analysis (PCA) and Pearson correlation analysis were performed. The following pesticides were identified in the sediment cores: α-HCH, Lindane, Heptachlor, Aldrin, pp'-DDT, pp'-DDE and pp'-DDD. POC distributions and concentrations differed between pristine and urban lakes. In particular, pp'-DDE was present in every lake studied. Statistical analyses showed significant correlation between pp'-DDE and pp'-DDD in the urban lakes, while correlation between pp'-DDT and its metabolites were not detected. In addition, PCA showed compound clusters based on concentrations and degradation through time. Of all the study sites, Laguna Chica is the lake most polluted by POCs although concentrations are low compared to those reported for pristine areas.