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In U.S. Pacific Northwest coho salmon (Oncorhynchus kisutch), stormwater exposure annually causes unexplained acute mortality when adult salmon migrate to urban creeks to reproduce. By investigating this phenomenon, we identified a highly toxic quinone transformation product ofN-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD), a globally ubiquitous tire rubber antioxidant. Retrospective analysis of representative roadway runoff and stormwater-affected creeks of the U.S. West Coast indicated widespread occurrence of 6PPD-quinone (<0.3 to 19 micrograms per liter) at toxic concentrations (median lethal concentration of 0.8 ± 0.16 micrograms per liter). These results reveal unanticipated risks of 6PPD antioxidants to an aquatic species and imply toxicological relevance for dissipated tire rubber residues.
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Longevity of Bioretention Depths for Preventing Acute Toxicity from Urban Stormwater Runoff
Urbanization poses increasing threats to aquatic ecosystems, including increased chemical loading. Of relatively recent concern is the potential of urban stormwater runoff to facilitate the spread of microplastics (MPs), including tire wear particles. Previous studies have demonstrated the effectiveness of bioretention treatment systems in treating runoff, thereby reducing chemical loading into surface waters and preventing acutely lethal and sublethal effects to aquatic organisms. In this study, we aimed to determine the effectiveness and longevity of bioretention soil media (BSM) at various infiltration depths, including the shallower depth currently required by the Washington Department of Ecology (18”). Experimental columns containing three different BSM depths were dosed with roadway runoff at an accelerated rate to simulate nine water years in approximately 30 calendar months. The chemical and biological effectiveness of the columns in treating runoff was assessed by analyzing influent/effluent chemistry and characterizing the health of juvenile coho salmon (Oncorhynchus kisutch). Bioretention treatment efficiently removed copper, zinc, total PAHs, and total suspended solids (> 70% removal). Influent stormwater runoff was acutely lethal to juvenile coho salmon (88, 90, 100, and 56.3% mortality in four exposures across the nine accelerated years). However, bioretention treatment was protective of coho, altogether preventing mortality for all treatment depths in three exposures and all but one depth in the last exposure, likely due to overflow when influent flow exceeded the ponding capacity of some of the columns. This study is ongoing and will continue to assess bioretention effectiveness through 10 accelerated years. Future research should consider the ability of bioretention systems to remove MPs and associated pollutants in runoff and explore the fate of MP-contaminant complexes in bioretention systems. Although contaminants themselves, MPs can also act as vectors of other contaminants of concern in aquatic ecosystems, including antibiotic resistance genes (ARGs). Contaminants co-occurring in runoff (e.g., heavy metals) can stimulate the selection or amplification of these ARGs. If left untreated, runoff carrying ARGs to surface waters could increase resistance in environmental bacteria and risks to human health.
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- Award ID(s):
- 2129531
- PAR ID:
- 10483666
- Publisher / Repository:
- ASCE EWRI
- Date Published:
- Journal Name:
- EWRI Low Impact Development Congress
- Format(s):
- Medium: X
- Location:
- Oklahoma City, OK
- Sponsoring Org:
- National Science Foundation
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