Distribution of PAH residues in humic and mineral fractions of sediments from stormwater infiltration basins

EL MUFLEH ; BECHET ; GRASSET ; RUBAN

Type de document
ARTICLE A COMITE DE LECTURE REPERTORIE DANS BDI (ACL)
Langue
anglais
Auteur
EL MUFLEH ; BECHET ; GRASSET ; RUBAN
Résumé / Abstract
Purpose: The management of sediments from stormwater infiltration basins is nowadays a key issue for local authorities to ensure long-term performance. Speciation of pollutants is particularly required in view of reuse of these materials. If fractionation of trace metals in sediments is relatively well described, PAHs speciation was only studied using particle size distribution. Therefore this study aims at the characterization of the PAHs bearing–fractions in sediments. Materials and methods: Three sediments with various physico-chemical properties were sampled in the West and North of France to characterize the distribution of PAHs among organic and inorganic components. Respective organic and inorganic matrixes were obtained by alkaline extraction and MIBK (Methyl IsoButyl Ketone) fractionation procedure. The nature of the solid fractions was assessed through microanalyses: Infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy with X-ray spectroscopy (SEM-EDX). Bulk sediments and extracted fractions were analyzed for organic matter parameters : elemental analysis (C, N, H), total organic matter (TOM), total organic carbon (TOC), hydrocarbons (C10-C40) and PAHs. Results and discussion: The characterization of bulk sediments highlighted that they were mainly composed of single particles, originating from the geological background, and aggregates (10 to 300 µm) composed of minerals and large organic matter content. The C/N ratio and PAH ratios were shown to be helpful for the determination of the natural or anthropogenic origin of OM or to evaluate additional contribution of industrial activities. The fractionation results underlined the role of the aggregates on the distribution of PAHs. Humin fraction and bound-humic acids were mainly composed of aggregates (10 to 150 µm) and accounted for 60 to 70% of sample mass. The PAHs are mainly sequestrated in these fractions. Only up to 1% of PAHs are adsorbed on the mineral fraction. Conclusions: Both alkaline extraction and MIBK procedure demonstrated that PAH residues were readily sequestrated in humin and bound-humic acids fractions and that fulvic acids, humic acids and mineral fractions contained poor concentrations of PAHs. Microanalyses underlined the high level of aggregation of particles in sediments and their mixed inorganic and organic nature. In case of stormwater sediments, the location of PAHs in highly organic aggregates is consistent with their sources, being both oil products and debris from vehicles and road.
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