Ingvertsen, Simon T.4; Marcussen, Helle5; Holm, Peter E.5
1 Landscape Architecture and Planning, Department of Geosciences and Natural Resource Management, Faculty of Science, Københavns Universitet2 Section for Environmental Chemistry and Physics, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet3 Department of Agriculture & Ecology, Plant and Soil Science, Department of Agriculture & Ecology, Faculty of Life Sciences, Københavns Universitet4 Department of Agriculture & Ecology, Plant and Soil Science, Department of Agriculture & Ecology, Faculty of Life Sciences, Københavns Universitet5 Section for Environmental Chemistry and Physics, Department of Plant and Environmental Sciences, Faculty of Science, Københavns Universitet
Large quantities of untreated industrial and domestic wastewater are discharged from the city of Hanoi into urban rivers. Sediment samples from three sites in the To Lich River in Hanoi were assessed with respect to the concentrations and potential mobility of cadmium (Cd), nickel (Ni) and lead (Pb). Due to very high Cd concentrations up to 700 mg kg(-1) at one site, the sediment was considered highly unsuitable for any types of land use if dredged and disposed of on land. Chemical sequential extractions of wet and anoxic sediment samples showed that Cd and Pb were largely associated with the redox-sensitive fractions and could thus be mobilised following measures such as resuspension or dredging. To assess the potential mobilisation of heavy metals from the anoxic sediment due to oxidation, the samples were exposed to different oxidants (i.e. atmospheric air and hydrogen peroxide) and afterwards submitted to a leaching test. These experiments showed that although oxidation may increase the equilibrium pore water concentrations of heavy metals in the sediments, other sediment mineral fractions seem to effectively immobilise heavy metals potentially released from the oxidisable fraction.
Environmental Monitoring and Assessment, 2013, Vol 185, Issue 11, p. 9531-9548
Wastewater; River; Sediment; Heavy metals; Sequential extractions; Hanoi