Pollutant dispersal in groundwater and sediments of gaining and losing river reaches affected by metal mining

The presented work couples groundwater and sediment chemistry in the metal mining-polluted Przemsza River valley in southern Poland to reveal regularities in pollutant distribution and to relate them to sedimentary processes and surface water/groundwater exchange. Ten piezometers were installed in transects across the low-gradient, meandering losing river reach and in the incised, channelised gaining reach. At each sampling site, cores of sediments were sampled for heavy metals and groundwater samples were collected over a year, for standard physicochemical analysis as well as Zn, Pb, Cd, Mg and Fe. In the losing river reach, the magnitude of pollution of groundwater in the levee zone was similar to that in the river, and declined in the backswamp. In the levee zone of the incised reach, minimum groundwater pollution adjacent to the highly polluted river was related to gaining relatively clean groundwater. In the losing reach, the dispersal of heavy metals in the levee zone is controlled mainly by overbank accumulation of polluted sediments. Post-depositional changes of metal concentrations in profiles of the losing reach indicate the important role of groundwater in metal dispersal. In the gaining river reach, the redistribution of metals in the profiles was not ascertained due to a much lower groundwater table.