Speciation and leaching of trace metal contaminants from e-waste contaminated soils

Primitive electrical and electronic waste (e-waste) recycling activities have caused serious environmental problems. However, little is known about the speciation and leaching behaviors of metal contaminants at e-waste contaminated sites. This study investigated trace metal speciation/mobilization from e-waste polluted soil through column leaching experiments involving irrigation with rainwater for almost 2.5 years. Over the experimental period, Cu and Zn levels in the porewater were 0.14 +/- 0.08 mg/L, and 0.16 +/- 0.08 nng/L, respectively, increasing to 0.33 +/- 0.16 mg/L, and 0.69 +/- 0.28 mg/L with plant growth. The amounts of Cu, Zn, and Pb released in surface soil (0-2 cm) contributed 43.8%, 22.5%, and 13.8%, respectively, to the original levels. The released Cu and Zn were primarily caused by the mobilization of the carbonate species of metals, including Cu(OH)(2), CuCO3, and Zn-5(CO3)(2)(OH)(6), and amorphous Fe/Mn oxides associated fractions characterized by sequential extraction coupling with X-ray absorption spectroscopy. During the experiments, trace metals were not detected in the effluent, and the re-sequestration of trace metals was mainly attributed to the adsorption on the abundant Fe/Mn oxides in the sub-layer soil. This study quantitatively elucidated the molecular speciation of Cu and Zn in e-waste contaminated soil during the column leaching process. (C) 2017 Elsevier B.V. All rights reserved.