Road runoff carries a mixture of contaminants that threatens the quality of natural water bodies and the health of aquatic organisms. The use of sedimentation ponds is a nature-based solution for the treatment of road runoff. This study assessed the concentration of polycyclic aromatic hydrocarbons (PAHs) and their alkylated homologues in sediment from seven highway sedimentation ponds and three natural urban ponds. In addition, the study explored the bioaccumulation of PAHs in dragonfly nymphs (Anisoptera). Finally, biota-sediment accumulation factors (BSAFs) were estimated. The results revealed a significant difference in the concentrations of 16 priority PAHs in sediment, with overall higher levels in sedimentation ponds (2,911 µg/kg on average) compared to natural urban ponds (606 µg/kg on average). PAH levels increased substantially once alkylated homologues were considered, with alkylated comprising between 42 and 87% of the total PAH in sediment samples. these results demonstrate the importance of alkylated forms in the environmental assessment of PAHs. The bioaccumulation assessment indicates that dragonfly nymphs bioaccumulate PAHs to a certain degree. It is not clear, however, whether they metabolize PAHs. BSAF results ranged from approx. 0.006 to 10 and indicate that BSAFs can be a powerful tool to determine the functionality of sedimentation ponds. During traffic-related activities, a complex mixture of inorganic and organic contaminants is released into the environment. Some of these contaminants remain in the air or settle on the ground, being eventually washed off by rain 1,2. Road runoff and tunnel wash water, enriched with contaminants, can eventually reach natural water bodies, threatening the water quality, and the health of all organisms dependent directly or indirectly on these systems. Among many traffic-related contaminants, polycyclic aromatic hydrocarbons (PAHs) are probably the most studied group of organic contaminants. Tire and asphalt wear, and incomplete combustion of fuel are the main sources of PAHs from traffic 3. PAHs are found in complex mixtures, with those of pyrogenic origin (from incomplete combustion) being mainly parent PAHs (without alkyl groups, heteroatoms or hydroxides), whereas those of petrogenic origin (from petroleum derivate) are associated with high levels of alkylated forms 4. Several PAHs and their metabolites are known to be potentially carcinogenic and mutagenic 5-7 , and some exhibit photo-induced toxicity 8,9. Consequently, several PAHs have been added to the list of substances of concern in environmental risk assessment and monitoring. A list of 16 parent PAHs issued by the U.S. Environmental Protection Agency (EPA) in the 1970s, and referred in this study as PAH-16, is often used as a standard set of PAHs for environmental analysis 10. A more recent study has, however, recommended a list of 40 PAHs when
Polycyclic aromatic compounds (PACs) and metals are important contaminants in road runoff. Vital mitigation measures against aquatic contamination from road runoff include the use of sedimentation ponds. However, it has been demonstrated that ecosystems in sedimentation ponds might be affected by road runoff. Sediments from six natural ponds and 27 sedimentation ponds were investigated to determine the environmental risk of contaminants. The amount of traffic on the respective roads associated with the sedimentation ponds was correlated with the environmental concentrations. Quantification included seven metals, the 16 US Environmental Protection Agency polycyclic aromatic hydrocarbons, alkylated PACs, dibenzothiophene, benzo[e]pyrene, and perylene. The environmental risk was assessed according to the European Union Water Framework Directive guidelines. Sedimentation ponds had a higher level of contaminants than natural ponds, and environmental risks were dominated by the concentration of PACs. Alkylated PACs contributed to the environmental risk posed by PACs and should be included in future monitoring. Only Cu and Zn were measured at concentrations above the environmental quality standards (EQSs), while 13 PACs exceeded the EQS. Sediment concentrations of Cu, Zn, and most PACs correlated significantly with the amount of traffic. The sources of PACs were determined by source apportionment ratios between PACs. Alkylation and pyrogenic indices showed that sources in natural ponds were of mostly pyrogenic origin, whereas in sedimentation ponds they were predominantly petrogenic. Asphalt was the probable main source of PACs. A hierarchical clustering technique was used to investigate both the environmental risks and the pattern of PACs in the ponds and revealed that a few sedimentation ponds were not protecting the environment as intended because the upper sediment layers had not been regularly dredged. Environ Toxicol Chem 2022;41:1838–1850. © 2022 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.
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