Speciation of Zn, Pb and Cd in overbank sediments contaminated by mining and smelting: the Geul river (E-Belgium and S-Netherlands), a case study

摘要

The floodplain of the Geul river (E-Belgium and S- Netherlands) has been severely contaminated with Zn, Pb and Cd due to Pb-Zn mining and smelting activities in the region mainly during the 19th century. The extent of the contamination was assessed by the investigation of eight vertical overbank sediment profiles on different locations in the river catchment. The highest concentrations found were 7% Zn, 5900 mg/kg Pb and 37 mg/kg Cd. The vertical distribution patterns of the heavy metals in the overbank sediment profiles can be related with the regional mining history. The speciation of Zn, Pb and Cd was assessed by leaching tests. Single extractions with CaCl2 (0. 01 M) and EDTA (0. 05 M) were applied to estimate the "actual" and "potential" mobilization of the heaw metals. pHstat leaching tests were performed to investigate the acid neutralizing capacity and the potential mobilization of heavy metals upon acidification. The geochemical research showed that the contamination represents a threat for the environment.