Distribution of PAHs and trace metals in urban stormwater sediments: combination of density fractionation, mineralogy and microanalysis

Abstract

Sediment management from stormwater infiltration basins represents a real environmental and economic issue for stakeholders due to the pollution load and important tonnages of these by-products. To reduce the sediment volumes to treat, organic and metal micropollutant-bearing phases should be identified. A combination of density fractionation procedure and microanalysis techniques was used to evaluate the distribution of polycyclic aromatic hydrocarbons (PAHs) and trace metals (Cd, Cr, Cu, Ni, Pb, and Zn) within variable density fractions for three urban stormwater basin sediments. The results confirm that PAHs are found in the lightest fractions (d < 1.9, 1.9 < d < 2.3 g cm(-3)) whereas trace metals are equally distributed within the light, intermediary, and highest fractions (d < 1.9, 1.9 < d < 2.3, 2.3 < d < 2.6, and d > 2.8 g cm(-3)) and are mostly in the 2.3 < d < 2.6 g cm(-3) fraction. The characterization of the five fractions by global analyses and microanalysis techniques (XRD and MEB-EDX) allowed us to identify pollutant-bearing phases. PAHs are bound to the organic matter (OM) and trace metals to OM, clays, carbonates and dense particles. Moreover, the microanalysis study underlines that OM is the main constituent responsible for the aggregation, particularly for microaggregation. In terms of sediment management, it was shown that density fractionation is not suitable for trace metals but could be adapted to separate PAH-enriched phases.

Energy Dispersive X-ray (EDX) microanalysis: A powerful tool in biomedical research and diagnosis

“…Cd, Cr, Cu, Ni, Pb, and Zn) for three urban storms water basin sediments. 30 The sensibility of microanalysis allows the authors to identify pollutantbearing phases in their samples. Their results confirm that PAHs are found in the lightest fractions (d < 1.9, 1.9 < d < 2.3 g cm −3 ) whereas trace metals are equally distributed within the light, intermediary, and highest fractions (d < 1.9, 1.9 < d < 2.3, 2.3 < d < 2.6, and d > 2.8 g cm −3 ) and are mostly in the 2.3 < d < 2.6 g cm −3 fraction.…”

“…Their results confirm that PAHs are found in the lightest fractions (d < 1.9, 1.9 < d < 2.3 g cm −3 ) whereas trace metals are equally distributed within the light, intermediary, and highest fractions (d < 1.9, 1.9 < d < 2.3, 2.3 < d < 2.6, and d > 2.8 g cm −3 ) and are mostly in the 2.3 < d < 2.6 g cm −3 fraction. 30 …”

Relationship between Polycyclic Aromatic Hydrocarbons in Sediments and Invertebrates of Natural and Artificial Stormwater Retention Ponds

“…Some investigations indicate that 11%-17% of the PAH content in the road runoff was dissolved, and the rest was particle-bound [48], and therefore after sedimentation would end up in the SWRP sediments. Of the particle-bound fraction, El-Mufleh et al [49] found that roughly half of the PAH was associated with particles lighter than 1.9 g•cm −3 , a density that contributed the main part of the organic matter in the investigated samples. A screening study of sediments from 70 Danish SWRPs found that 83% of the samples had total PAH concentrations below 4 mg•(kg•DM) −1 , and hence were to be treated as unpolluted soil with respect to this contaminant [39].…”

Sediments from stormwater drainage system as sorbents of organic and inorganic pollutants

“…In polluted aquatic sediments, elevated concentrations of cadmium, chromium, copper, nickel, zinc or lead are found most often. Their presence in the aquatic environment may result both from natural processes occurring in the atmosphere, which provides a dispersed source of pollutants, and from anthropogenic processes (transportation, industries, mining, municipal and industrial sewage, and also agriculture) which constitute point emission sources [7][8][9]. Polycyclic aromatic hydrocarbons are on the list of the most dangerous substances, which was compiled by the American Environmental Protection Agency (EPA).…”