Leachability of heavy metals from contaminated sediments of the To Lich and Kim Nguu river systems in Hanoi, Vietnam

Abstract

We have assessed the leaching of heavy metals from the contaminated sediments of the To-Lich and Kim Nguu river systems in Hanoi, Vietnam We used different solutions such as distilled water (pH 5.5), nitric acid (HNO₃), acetic acid (CH₃COOH) and Ethylene diamine tetra acetic acid (EDTA) in a batch leaching test. The average concentrations of heavy metals leached were: (1) using H₂O: 63.4% of Cd, 10.6% of Cr, 5.3% of Cu, 33.6% of Ni, 1.6% of Pb and 6.2% of Zn; (2) using HNO₃: 67.2% of Cd, 10.6% of Cr, 5.0% of Cu, 34.1% of Ni, 1.3% of Pb and 5.5% of Zn; (3) using CH₃COOH: 65.0% of Cd, 12.7% of Cr, 5.1% Cu, 45.2% of Ni, 1.2% of Pb and 5.4% of Zn; and (4) using EDTA: 70.5% of Cd, 15.6% of Cr, 17.0% of Cu, 59.5% of Ni, 7.2% of Pb and 33.0% of Zn. The EDTA had high heavy metal leachability compared to water, acetic acid, and nitric acid. The average potential leachability decreased in the following order: Cd > Ni > Cr > Cu = Zn > Pb. The leachability exhibited a tendency to decrease with increasing organic matter for heavy metals other than Cr and Zn.