Modelling of runoff behaviour of particle-bound polycyclic aromatic hydrocarbons (PAHs) from roads and roofs.

Road and roof dust was collected and samples of runoff were taken at an urban storm sewer system in a residential area in Japan. Suspended solids (SS) in the runoff samples were classified into two fractions: fine (smaller than 45 microm) and coarse (larger than 45 microm). Runoff monitoring and chemical analysis data were also used to validate a runoff model for particle-bound polycyclic aromatic hydrocarbons (PAHs) that was originally developed to explain the behaviour of SS in the same area. The model, in which roads and roofs were considered separately as impervious surfaces, expressed the SS and particle-bound PAHs runoff behaviour for fine and coarse particles very well, except during and after heavy rainfalls (more than 10mm/h). However, the model could not explain the PAH profiles of runoff particles; the profiles of 12 PAH compounds tracked in this study were almost constant and more similar to those of road dust than roof dust throughout the event. An improved model is developed which explains the runoff behaviour by considering two types of road dust with different mobility.