Size Fractionation of Heavy Metals in Highway Runoff Waters
Highway runoff waters may contain pollutants that have accumulated on the carriageway. Numerous field surveys have demonstrated that heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) are common pollutants in highway runoff waters that degrade the quality of natural w
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Introduction Highway runoff waters may contain pollutants that have accumulated on the carriageway. Numerous field surveys have demonstrated that heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) are common pollutants in highway runoff waters that degrade the quality of natural water bodies [1–6]. These hazardous pollutants have been found to be attached to particles, especially finer particles than 100 mm, usually quantified by dissolved, suspended and settleable solids measurements [7]. Clay minerals, very fine silts, metallic oxy-hydroxides and organic matter were identified as main components of the composite particulate matter [8, 9]. The knowledge of partitioning of trace metals between the different solids fractions is crucial for stormwater management. The pollutant size distribution determines the efficiency of runoff water treatment by settling in detention basins. Moreover, the toxicity and bioavailability metal characteristics also depend on the speciation of pollutants that could be discharged into natural water bodies. Partitioning of pollutants is also challenging nowadays due to issues of colloid-mediated transfer of heavy metals, as it was already shown for roadside soils impacted by runoff waters [10]. In the case of stormwater treatment in detention-infiltration basins, previous studies have demonstrated that the settling of particles contributes to the formation of contaminated sediments [11, 12]. Even if earlier field data assess that groundwater is seldom contaminated [13, 14], recent studies have pointed out potential
B. Béchet, B. Durin, and M. Legret Laboratoire Central des Ponts et Chaussées, Division Eau et Environnement, Route de Bouaye, BP 4129, 44341, Bouguenais cedex, France DDE 69/SERDD/MPE, 33 rue Moncey, 69421, Lyon CEDEX 03, France P. Le Cloirec Ecole de Chimie de Rennes (ENSCR), Campus de Beaulieu, Avenue du Général Leclerc, 35700, Rennes, France S. Rauch et al. (eds.), Highway and Urban Environment, Alliance for Global Sustainability Bookseries 17, DOI 10.1007/978-90-481-3043-6_26, © Springer Science+Business Media B.V. 2010
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downward colloid-transport of heavy metals [15, 16]. Seasonal and temporal variations in runoff quality, such as spreading of de-icing salts may have an important impact on the colloidal matter in the runoff waters and in the sediment (aggregation, adsorption/desorption of pollutants). Several studies highlight the partitioning of trace metals in runoff waters between particulate and dissolved-bound fractions, the “dissolved” fraction being operationally defined by filtration through a 0.45-mm pore size membrane [7, 17]. But, only few studies have begun recently to investigate the colloidal fractions of metals in runoff waters (nanometer to micrometer size range) [9, 18]. A peri-urban experimental site was chosen to sample highway runoff waters. The objective was to study the distribution of selected trace metals (Cd, Cr, Cu, Ni, Pb, Zn) among dissolved, colloidal and particulate fractions, in relation to potential constituents of colloidal
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