Kinetics Fractionation of Heavy Metals Release From Clayey Sediments Using Leaching Column

The kinetics of release of heavy metal ions zinc, lead, nickel, copper and cadmium from the depth of 0 to 10 cm of downstream river sediment located in Hamedan Province, polluted with nitrate salt of these metals, were studied using the leaching column method. The rate of desorption of heavy metals from polluted sediments was initially rapid and, then, gradually declined over time; the behavior of Pb was different and it was released in a gradual and continuous manner. In general, the release of heavy metals from clayey sediments polluted by an inorganic source conformed to a two-site model of first order kinetics; however, the release of Zn, Cd and Pb from sediment (1) and Pb from sediment (2) could also be adequately accounted for by a single-site model. The average coefficients of determination and RMSE for metals in the first order kinetics were 0.905 and 0.054 for a single-site model and for a two-site model were 0.986 and 0.046, respectively. Considering the total heavy metal content of sediments, the cumulative quantity of leached metals was low, indicating a high retention capacity of the sediments for heavy metals. This statement can be elucidated by the low values of the apparent coefficient of desorption in the first order kinetics model.