Metals and polycyclic aromatic hydrocarbons (PAHs) in stormwater sediments: particle distribution and catchment area emission factors (CAEFs)

Paper in proceeding, 2010

Emissions from traffic and construction materials contaminate stormwater with both metals and organic pollutants, and techniques for efficient removal of contaminants are reguested. The purpose of this study was to determine the particle distribution of some selected metals and polycyclic aromatic hydrocarbons (PAHs) in a stormwater sedimentation facility, and to caiculate the emitted amounts of these contaminants in the studied catchment area. Chemical analysis and determination of physical parameters were performed on sediments sampled at a stormwater treatment facility consisting of seven sedimentation chambers connected in series. The facility is located in central Gothenburg, Sweden, and receives runoff from the E6 and E20 motorway, with a daily traffic bad of approximately 86 000 vehicies. The concentrations of the PAHs and metals showed a trend with sediment concentrations increasing from the first to the last chamber. The pollutant concentrations were weil correlated with the particle size distribution, dry densities, water and organic content of the sediments. in two or more of the chambers, the concentrations of Cd, Pb, Cu, Zn, Ni, Cr and carcinogenic PAHs were higher than the given guideline vaiues for contaminated soil. The relative composition of the PAHs in sediment, with a dominance of pyrene, phenanthrene, fluoranthene and chrysene, indicates that rubber tyres, diesel exhaust and road asphalt could be important sources of PAH pollution. The calculated catchment area emission factors (CAEFs) showed, in Wyear ha, the following order: petroleum hydrocarbons Cio - C4o (15 000) > Zn (3200) > Ni (~3000) > Cu (1500) > Sb (930) > Cr (820) > V (640)> Pb (260) > Co (120) > As (87) > Sn (25)> Mo (43) > ~16-EPA PAH (13) > Cresols (3.4) > Cd (1.3)> Hg (0.43). The results show that large parts of the finest sediment particle fractions, with high concentrations of the contaminants, are released with outiet water from the sedimentation facility. The treatment facility could be more efficient if a filter was installed after the sedimentation steps, before discharge of water to the nearby stream.