File:Distribución de metales pesados en sedimentos superficiales del Orinoco Medio, Venezuela.pdf

Total concentrations and chemical forms of metals in superficial sediments of the Middle Orinoco were determined with acetic acid solution 25% (v/v)/HNO3: HCl: HClO4 (3:2:1) solution, atomic absorption spectrometry with air acetylene flame and cold vapor technique. Total values ranged from 8871 to 116759 μgFeg-1, 102.45 a 469.44 μgMn g-1; 0.93 to 17.64 μgCu g-1; 4.46 to 17.48 μgNi g-1; 2.46 to 9.61 μgCo g-1; 42.56 to 181.45 μgZn g-1; 1.29 to 8.76 μgCr g-1; 0.03 to 0.74 μgCd g-1 and 0.001 to 7.88 μgPb g-1. The metals were found to be strongly associated with the residual fraction minerals, more resistant iron oxihidroxides, metallic sulfides, and organic matter. The values ranged from 7.50-99.29% Fe; 7.75-66.34% Mn; 22.55-98.89% Zn; 22.85- 91.36% Ni; 4.20-85.03% Cu; 16.76-85.48% Co; 12.56-95.49 Cr; 7.50-99.29% Pb; 2.03-85.48% Cd). The values of metals adsorbed in the surface of particles, associated with carbonates and the reactive manganese oxihidróxidos varied from 0.04-1.97% Fe; 4.15-71.59% Mn; 0.86-3.83% Zn; 0-12.10% Ni; 1.05-14.97% Cu; 6.40-33.06% Co; 1.03-5.08% Cr; 0-1.78% Pb; 0-22.97% Cd. The total concentration of Cu, Ni, Zn and Pb in some stations like the Cabruta and Caicara of Orinoco cities are superiors to the reported for non contaminated sediments.