Release of heavy metals after spiking and leaching from different sediment fractions

Measurement of availability and mobility of heavy metals in river sediments is required in order to understand the behavior of these metals and to prevent potential toxic hazards. Leaching column experiments were conducted for four sediment samples to determine the degree of mobility and the distribution of Zn, Cd, Ni, Cu, and Pb because of an application of spiked heavy metals in sediments. Sequential extraction results showed that in spiked sediments the major proportion of Zn, Ni and Cu were associated with residual fraction and major fractions of Cd was associated with exchangeable and mineral fractions and major fraction of Pb was associated with residual and mineral fractions. In sediment (1) distill water mobilized more Cd, Zn and Ni than Cu and Pb. In sediment (3) and (4) distill water mobilized more Pb and Cu than Cd, Zn and Ni. Therefore, Cu and Pb were least affected by the pore water pH volatility. The release of Pb and Cu were considerable from organic matter fraction in sediment (4). Based on relative percent in exchangeable fraction, the order of solubility was Cd > Ni = Zn > Pb > Cu for spiked sediments before and after leaching indicating possible mobility of Cd, Ni, and Zn. Among sediment properties the pH in pore water influences the behavior of heavy metals in sediments. Spiking and leaching approach is conducive for evaluating of heavy metals toxicity and mobility tests.