A street deposit sampling method for metal and hydrocarbon contamination assessment

Urban surface contamination, by atmospheric deposits as well as human activ ities, is a major concern for urban pollution management. Besides coarse st reet deposits which are clearly perceived and easily removed, suspended sol id (SS) surface loads and contamination by heavy metals and hydrocarbons ar e rarely assessed although they could be of major importance with regards t o combined or separate server overflow (CSO and SSO) impacts. Both dry and wet vacuum sampling procedures have been first compared, in the laboratory, using dry and sieved clay or street deposits. Then the wet Vacuum sampling procedure has been refined, coupling the injection of water and the hand-b rushing of the surface prior to its vacuum cleaning, and evaluated on a car parking area close to the University. Finally this procedure has been asse ssed in Bearn Street within the 'Le Marais' district in Paris centre, and 3 4 samples have been analysed for metal and eight for aromatic hydrocarbon c ontamination. Heavy metal concentrations (0.1-1.7 g kg(-1) dry wt. Cu, 0.9- 6.1 g kg(-1) dry wt. Pb and 1.5-4.6 g kg(-1) dry wt. Zn) within street depo sit samples collected in Paris centre, indicate a high contamination, espec ially for copper and zinc, as compared to reported data. Total polyaromatic hydrocarbons (PAHs) are in the 3-11 mg kg(-1) dry wt, range, thus approxim ately 10 times less contaminated than dry atmospheric deposits. This paper presents data obtained and discusses the difficulties encountered when samp ling street deposits in busy areas of a city like Paris. The water jet stre et cleaning procedure used by Paris city workers was tested for its efficie ncy, by comparison of surface loads before and after the cleaning procedure . Although solids cleaning efficiency is highly variable (20-65%) and somew hat higher for particles larger than 100 mu m, particulate metal cleaning e fficiency is even more variable (0-75%) and particulate PAHs appear not to be significantly removed. (C) 1999 Elsevier Science B.V. All rights reserve d.