Modelling of Road Runoff Pollution Load and Sources in the City of Goteborg, Sweden

A modified version of the substance flow model SEWSYS, adapted for modelling road runoff, is presented. The modified SEWSYS model has been used for the simulations of road runoff pollution load and sources in 34 different catchments that cover the city of Goteborg, Sweden. Roads and streets that account for at least 80% of the total traffic load in the city were included in the study and in total 770 ha of road area were modelled. Modelled substances are copper, zinc, lead, cadmium, phosphorus, nitrogen, PAH and suspended solids. The results show that road runoff is an important source of heavy metals, and for zinc and lead it is an equally important source as the regional WWTP. Roads that in this study account for only 20% of the total road area contribute up to 40 % of the total pollutant load. This implies that measures for decreasing the pollutant load should primarily be done on roads with high traffic loads. The origin of the different pollutants is also presented and it is shown that 90% of the total copper load originates from brake wear and 70% of the zinc load comes from tyre wear.