Sources and behavior of pollutants in several catchments in the Western Harz Mountains, F.R.G

Abstract

The "Case Study Harz Mountains" investigates the effects of airborne pollutants (heavy metals and acidifying chemicals) on the catchment of a drinking water reservoir. The path of heavy metals into the lake sediments can be traced back to the well waters via inflowing stream sediments with similarly high heavy metal contents. In heavily polluted areas, groundwater with a pH from 3.6 to 5.2 has the following typical contents (μg1-1) Al (1000), Cd (2), Co (3), Cr (0.3), Cu (3) Fe (250), Mn (500), Ni (12), Pb (25), and Zn (100). These concentrations are comparable to those of acidic percolation water below the root zone of exposed forest ecosystems. Wells with pH > 5.5 do not have such elevated concentrations of metals. Water acidification has already caused heavy metal mobilization within the brooks. An acidification front creeps down towards the lake, the intermediate repository for the heavy metals and other pollutants. Compared with the local bedrock, the lake sediments have high concentrations of heavy metals. With continuing water acidification and a decrease in pH of the lake water from 6.5 to 5, a sharp increase in heavy metal, Al, Fe, and Mn concentrations in the water column is to be expected. Sequential extraction (ammonium acetate, ammonium oxalate, H2O2) of metals from the lake sediments shows that the majority of the trace metals are in ion-exchangeable from.