Transport and Retention of Cadmium, Copper, and Lead in Soils: Miscible Displacement Experiments
Master of Science (MS)
Plant, Enviromental and Soil Sciences
Heavy metal contamination is a major concern for soil and water quality. To quantify their potential hazard, it is crucial to understand their mobility and retention in soils. The source of the problem is anthropogenic activities such as mining, smelting, usage of sewage sludge and fertilizers. The objective of this study was to quantify Cd, Cu and Pb transport and retention in three soils having different properties, and evaluate their competitive influence on the mobility of individual heavy metal. The second objective was to quantify Cd, Cu and Pb retention kinetics in the different soils. This study also investigates the extent and distribution of retained Cd, Cu and Pb with depth in soil columns. In the study, batch experiments were carried out for different range of concentrations in time. The results indicated that retention of Cd, Cu and Pb in Windsor, Mahan and Webster soil is nonlinear. Lead exhibited highest retention among all three metals. Moreover, all three metals exhibited highest affinity in Webster soil, which has a higher clay content (mostly smectite), organic material and cation exchange capacity. Sorption of all metals was also observed to be kinetic when retention time increased from one day to seven days. Miscible displacement experiments in saturated soil columns were also carried out in two ways. In the first type, consecutive pulses of Cd, Cu and Pb were sequentially introduced to each soil column followed by an extended period of leaching with the background solution (KNO3, 0.005M). In the second type, two consecutive pulses of mixed solution (Cd, Cu and Pb), each followed by leaching with the background solution, were introduced to soil columns. Results indicate that Cd was the most mobile with the highest recovery the effluent solution, whereas Pb was the least mobile with the lowest recovery among all elements and soils. It was also observed that Pb resulted in enhanced mobility of both Cd and Cu . Efforts to describe results from the column experiments based on a multirection and transport model (MRTM) showed varied degrees of success. Although the models accounts for several sorption mechanisms including nonlinear equilibrium, kinetics, and irreversible reactions, the model was not successful in predicting the competitive behavior of heavy metals in the soil columns.
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Akrami, Nazanin, "Transport and Retention of Cadmium, Copper, and Lead in Soils: Miscible Displacement Experiments" (2014). LSU Master's Theses. 3698.