PARENT SESSION
8A CICTA2001
9:00 AM to 7:00 PM, Wednesday, 09 May 2001

(W/FF235) Heavy Metals (Hg, Pb and Cd) Content in Core Sediments of three Andean Lakes in Chile.

Urrutia, Roberto¹, Yévenes, Mariela¹, Espinoza, Cristian¹, Barra, Ricardo¹, ¹

ABSTRACT- The Andean lakes are considered pristine ecosystems with low anthropogenic influence. Studies carried out in the Northern Hemisphere show a rise in trace metals in the sediments of remote lakes, caused by external contaminants sources. Heavy metals (Hg, Cd and Pb), organic matter and dating analyses were performed on sediment cores from three Chilean Andean lakes, distributed along a latitudinal gradient: lake Chungara (18^°S), lake Laja (37^°S) and lake Castor(45^° S). Short cores were collected with a Kayak corer from the deepest part of each lake. The cores were vertically extruded, sliced into 1-cm slices (subsamples), which were carefully sealed to avoid contamination. For each subsample, routine measurements of dry density (drying at 105^°C), ²¹⁰Pb and Organic Matter were performed. X-ray analysis was used to check possible physical or biological disturbances within the cores. Approximately 0.2 g of dried, crushed sediment from each core section was digested in 3 ml of 65% HNO₃ in a Parr Pump for 8 h at 120^° C. Pb and Cd were analyzed using a graphite furnace AAS with an AS-70 autosampler. Hg was analyzed by FIAS-400 system with autosampler AS-90. The baseline concentrations were : (1) Hg 0.0582 ug g-1 for lake Chungara, 0.0306 ug g^-1 for lake Laja and 0.0286 ug g^-1 for lake Castor; (2) Pb 2.95 ug g^-1 for lake Chungara, 6.65 ug g^-1 for lake Laja and 5.4 ug g^-1 for lake Castor; (3) Cd 0.0622 ug g^-1 for lake Chungara, 0.1213 ug g^-1 Laja and 0.0637 ug g^-1 for lake Castor. The results show that the concentration of trace metals increases towards the surface. The enrichment factor (EF) indicates that both in Chungara and Castor lakes the trace metals levels are higher than the established baseline. Research funded by the Research Directorate of the University of Concepcion Project N^° 99.310.31.1-3.

Key words: Chile, Trace metals, Sediments, Andean lakes