DETERMINACIóN DE LOS NIVELES BASALES DE METALES TRAZA EN SEDIMENTOS DE TRES LAGOS ANDINOS DE CHILE: LAGOS CHUNGARá, LAJA Y CASTOR

the increase in trace metals concentrations (mercury, lead, cadmium, copper, chromium and zinc) in sediment cores from three andean lakes, located along a latitudinal gradient were determined (chungará, laja and castor lakes). samples were obtained in the deepest part of each lake, using a gravity corer model kayac. the sediment cores were vertically extruded at 1 cm intervals. trace metals analysis were performed through atomic absorption spectrophotometry (aas) with hydride generation technique for mercury flame atomic absorption (faa) for copper, chromium and zinc and graphite furnace for lead and cadmium. at the chungará lake the highest concentrations corresponding to hg and cd ranged from 0.038 -34; 0.12 μg/g and 0.048 - 0.210 μg/g, respectively. the highest concentrations at the laja lake corresponding to pb and cu, ranging from 6.7 - 14μg/g and 30 - 55 μg/g, respectively. at the castor lake only high concentrations of zn were detected reaching values of about 700 μg/g. results shown that only the chungará lake register an increase hg, pb and cd levels in the uppermost sections, showing enrichments factors about two times higher than the deepest sections. the laja lake shown a general trend of lower levels of most trace elements analyzed with the exception of zn showing higher levels in the uppermost section of the core. finally, the castor lake showed a increase of pb and cd levels upward the core, but the other metals didn？t show a clear trend. the increase in trace elements content of the chungará lake sediments is attributed to both local and regional pollution factors and are very similar to enrichments found in highland lakes in the northern hemisphere.