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 discharges, macrophytes growth zones, etc., and each was sampled ten times during 2 years. A coal mine on the Guasare River (flowing into Sinamaica Lagoon), has led to increasing pollution in the lagoon, with high concentrations of metals such as mercury and vanadium. Sodium, potassium, calcium, magnesium, vanadium and mercury were determined in each of the sampling sectors. The sediments were mineralized by introducing 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. The bomb was placed in a pre-heated oven (110 °C) and kept at that temperature for 4 h. Na and K were measured by emission spectrometry (at 589 and 766.5 nm, respectively), Ca and Mg atomic absorption spectrometry vanadium by atomic absorption spectrometry at 318.4 nm (dinitrogen oxide–acetylene flame) and Mercury by cold vapour atomic absorption spectrometry at 253.8 nm with sodium tetrahydroborate as reductant. The method was checked with NIST standard reference materials and with another mineralization method (cold mineralization). The results showed high concentrations of vanadium and mercury.