Heavy metals and organic micropollutants in floodplains of the river Waal, a distributary of the river Rhine, 1958-1981.

During periods of high water discharge, dyke-protected floodplains of the river Rhine in the Netherlands become inundated and suspended matter from the river settles out. In the last 30 years, floodplain top layers have been sampled several times just after deposition; samples were dried and stored in a specimen bank. The samples were used to assess the development of sediment contamination with heavy metals and organic micropollutants during the past decades. Heavy metals studied include Zn, Cu, Cr, Pb, Cd, Ni, Hg and As. Different groups of chemically persistent organic micropollutants were studied: polycyclic aromatic hydrocarbons, polychlorobiphenyls, hexachlorobenzene, DDT and DDT-metabolites. The levels of most contaminants decreased substantially between 1958 and 1981. The variation among the different floodplain locations is due to differences in hydrodynamic characteristics of the location. A comparison was made between the concentrations found and the levels considered acceptable if the floodplain area is used for cattle grazing; a comparison was also made with estimated natural background levels and with reference values defined by the Dutch government. (Abstract retrieved from CAB Abstracts by CABI’s permission)