Heavy metal concentrations in dry and wet atmospheric deposits in Paris district: comparison with urban runoff

In urban areas, dry and wet atmospheric deposits are more rarely sampled than atmospheric particles. Nevertheless, fallout data are needed in order to compare concentrations and fluxes with street deposits and with samples collected during rain periods at roof outlets, gullies or within the sewer system. Such comparisons represent key issues in the understanding of micropollutant transport and evolution in urban areas. Within the Paris conurbation, four sites have been studied for dry, wet and total atmospheric deposits: Chatou, a suburb west of the Paris conurbation, Cr´eteil, suburb, south-east, Fontainebleau at 48 km south-east from the centre of Paris, and ‘Le Marais’ within the centre of Paris. On each site, samples were continuously collected from 2 to 13 months. Comparison of median values of metal concentrations in various components of atmospheric fallout illustrates the influence of urban emissions: rainwater contamination with trace metals is only slightly larger in the centre of Paris than at Fontainebleau which illustrates the occurrence of medium range transport of atmospheric contamination. Focusing on an experimental urban catchment equipped with combined sewers, situated inside the ‘Le Marais’ district, within Paris, this paper compares metal concentrations of atmospheric deposits to dissolved and particulate ones in runoff from four roofs, three yards, six gullies, and at the catchment outlet. This comparison allows a better understanding of metal transport in urban areas and of the evolution of metal distribution between dissolved and particulate fractions.