PAH fluctuations in rivers in the Paris region (France): Impact of floods and rainy events

PAHs produced by motor vehicle combustion were determined in the dusts from the substructures of a parisian car park. The high levels of benzo(ghi)perylene (bgp) and pyrene (pyr) expressed as ratios to fluoranthene (flu), were 1.73 and 1.23, respectively, which was typical of these exhausts. From these findings, bgp and pyr may be used as tracers for estimating the contamination fluctuations and transfer processes in rain waters and river waters, in a highly industrialized and urbanized area. During flood events, the pollution related to atmospheric scavenging alone was negligible as compared to that due to urban surface leaching, contrary to steady period events. During that last period, when the river contamination was low, about 40 ng L-1, and when mean bulk precipitation concentrations were about 350 ng L-1, minor precipitations might contribute less than 2% to river contamination, whereas heavy showers might induce a quite important pollution flush: PAH concentrations were twice higher and 26% of the inputs came from rain and 74% from runoff in the river Seine.