Point and diffuse source analysis of heavy metals in the Elbe drainage area: Comparing heavy metal emissions with transported river loads

Abstract

Two independent methods are presented to estimate point and diffuse source contributions in emissions and riverine loads. The first method uses emission factors and areal statistics of the Elbe catchment to estimate the emissions of the diffuse and point sources. The second method relies on relationships between load–discharge and concentration–discharge, using monitoring data from several water quality stations. These statistical relationships are then used to separate point and diffuse contributions to the total riverine load, after incorporating the point waste water flow discharges. Both methods are applied to the Elbe river for the period 1992–1995 to estimate the contribution of point and diffuse sources for six heavy metals. The results of the source apportionment estimates for the Elbe river show that there are regional differences in source strength and source origin. The main inputs of metals occur in the Czech Republic nowadays, whereas for Cd the Mulde catchment contributes large amounts. The comparison of both methods shows some differences, which are caused by retention in the river system and uncertainties in emissions.