Contaminant accumulation in stormwater retention and detention pond sediments: Implications for maintenance and ecological health

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Stormwater retention/detention pond maintenance schedules are based on either pond age or sediment accumulation, not contaminant levels of sediments. We examined the effect of stormwater pond characteristics on sediment contaminant concentrations and resulting ecological risk. We sampled the inlet, middle, and outlet of stormwater pond sediments up to 30 cm depth at five locations in Rhode Island three times between June 2014 and June 2015 for polycyclic aromatic hydrocarbons (PAHs) and heavy metals (Pb, Zn, and Cr). The ponds were selected based on stormwater runoff origin and land uses (industrial, urban, highway). Sediment PAH concentrations ranged from 0.9-195.8 mg/kg. Heavy metal concentrations were nondetect to 864.5 mg/kg for Zn, nondetect to 502.9 mg/kg for Pb, and 5.4-320.0 mg/kg for Cr. Ponds in urban areas had the highest concentrations of contaminants, and ponds with a sediment forebay exhibited a decreasing concentration gradient of contaminants across the pond. Ecological risk assessments indicated that benthic organisms are likely to experience adverse effects due to contaminant exposure in all ponds. Here, we found that elevated contaminant concentrations were influenced by factors such as impervious cover fraction, age, and ecological risk assessments. We posit that these factors should be considered when drafting maintenance schedules instead of relying on regular time intervals since installation.

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ACS Symposium Series