File:DISTRIBUCIÓN Y COMPORTAMIENTO DE LOS METALES TRAZA CD, CU, NI Y ZN ENSEDIMENTOS SUPERFICIALES DEL SECTOR ORIENTAL DEL GOLFO DE CARIACO, VENEZUELA..pdf

In October 2002 we assessed the mobility and bioavailability baseline levels of four heavy metals – Cd, Cu, Ni,and Zn – by analyzing their spatial distribution and geochemical fractioning in surface sediments of the eastern region of theGulf of Cariaco, heavily affected by industrial and urban development. Metal recovery yielded mg/g-concentrations greaterthan those permitted for non-contaminated sediments, the Cd, Cu, Ni, and Zn content in exchangeable fraction (F1) being0.73, beyond detection levels, 0.12, and 0.46, respectively; in carbonate-bound fraction (F2): 0.46, 0.03, 0.60, and 8.08,respectively; in reducible fraction (F3): 0.47, 0.28, 5.94, and 28.27, respectively; in oxidizable fraction (F4): 0.02, 4.99, 7.18,and 8.61, respectively; and in residual fraction (F5): 0.08, 3.59, 0.84, and 8.53, respectively. Geochemical speciation yieldeda metal accumulation following the sequence: organic matter > Fe and Mn oxihydroxides > residual > carbonates > exchangeable.Sequential analysis revealed exchangeable fraction associated with Cd, suggestive of anthropogenic origin. Mean values ofsands, silts, clays, and total organic matter were 54.21, 39.14, 6.65, 11.22, and 19.33 %, respectively, which render thesediments as sandy-silty, with a higher content of organic matter as a consequence of the biological productivity in surfacewaters. All parameters show a trend to accumulate towards the center of the eastern region of the Gulf of Cariaco.