DETERMINATION OF METALS IN SEDIMENTS OF SINAMAICA LAGOON, VENEZUELA BY ATOMIC-ABSORPTION SPECTROMETRY

Sediment points in Sinamaica Lagoon (Venezuela) was divided into seven sectors, taking into account different water mixtures, waste-water di scharges, macrophytes growth zones, etc., and each was sampled ten tim es during 2 years. A coal mine on the Guasare River (flowing into Sina maica Lagoon), has led to increasing pollution in the lagoon, with hig h concentrations of metals such as mercury and vanadium. Sodium, potas sium, calcium, magnesium, vanadium and mercury were determined in each of the sampling sectors. The sediments were mineralized by introducin g 0.1 g of lyophilized sediment into a Parr-type bomb together with 3 ml of concentrated nitric acid and 5 ml of doubly de-ionized water. Th e bomb was placed in a pre-heated oven (110 degrees C) and kept at tha t temperature for 4 h. Na and K were measured by emission spectrometry (at 589 and 766.5 nm, respectively), Ca and Mg atomic absorption spec trometry vanadium by atomic absorption spectrometry at 318.4 nm (dinit rogen oxide-acetylene flame) and Mercury by cold vapour atomic absorpt ion spectrometry at 253.8 nm with sodium tetrahydroborate as reductant . The method was checked with NIST standard reference materials and wi th another mineralization method (cold mineralization). The results sh owed high concentrations of vanadium and mercury.