Transport of polycyclic aromatic hydrocarbons through a partly urbanized river basin

The PAH-pollutant loads resulting from storm runoff to a receiving stream are associated with high concentrations of suspended sediments. This is explained by the sorption coefficients and isotherms on street dust, suspended solids, bedload and other sorbents. Pollutographs for a stream with storm runoff mainly from storm water overflows from a combined sewered medium sized town show strong ‘first-flush’ phenomena. Rainfall and bedload contribute only to a lesser extent to the overall transport which stems from street dust washoff. High correlation between total PAH load and maximum flow, but no relation between total PAH load and the number of days since the previous storm, indicates a ‘low washoff case’ under ‘transport limited’ conditions. 3.4-Benzopyrene load was modeled by a pollutant washoff function analoguous to that of the EPA storm water model.