Transport and sedimentation of pollutants in a river reach: A chemical mass balance approach

Abstract

The River Höje in the south of Sweden is a typical receiving water for urban and rural runoff. Mass balance calculations over a 17‐month period indicate that pollutants are retained in the sediments of the investigated 5‐km‐long reach of the stream (90 tons of biochemical oxygen demand (BOD7), 850 tons of chloride, 2.1 tons of copper, 3.2 tons of zinc, and 1.0 ton of lead). Other pollutants such as suspended solids and phosphorus appear to be both retained and washed‐out, depending on loading rates and local stream conditions. The retained pollutants represent a substantial part of the total mass transport through the stream (14–47%). Almost half of the transported zinc is retained within the stream sediment. Subsequently, the deposited pollutants represent a potential pollution source. Analyses of sediment samples verify that the upper sediments contain high concentrations of heavy metals.