Urban Stormwater: An Overlooked Pathway of Extensive Mixed Contaminants to Surface and Groundwaters in the United States

Abstract

Increasing global reliance on stormwater control measures to reduce discharge to surface water, increase groundwater recharge, and minimize contaminant delivery to receiving water-bodies necessitates improved understanding of stormwater—contaminant profiles. A multiagency study of organic and inorganic chemicals in urban stormwater from 50 runoff events at 21 sites across the United States demonstrated that stormwater transports substantial mixtures of polycyclic aromatic hydrocarbons, bioactive contaminants (pesticides and pharmaceuticals), and other organic chemicals known or suspected to pose environmental health concern. Numerous organic-chemical detections per site (median number of chemicals detected = 73), individual concentrations exceeding 10 000 ng/L, and cumulative concentrations up to 263 000 ng/L suggested concern for potential environmental effects during runoff events. Organic concentrations, loads, and yields were positively correlated with impervious surfaces and highly developed urban catchments. Episodic storm-event organic concentrations and loads were comparable to and often exceeded those of daily wastewater plant discharges. Inorganic chemical concentrations were generally dilute in concentration and did not exceed chronic aquatic life criteria. Methylmercury was measured in 90% of samples with concentrations that ranged from 0.05 to 1.0 ng/L.

Biochar-augmented biofilters to improve pollutant removal from stormwater – can they improve receiving water quality?

“…While rarely regulated, pyrethroid pesticides as well as fipronil are increasingly detected in urban stormwater and subsequently urban waterways. 22,105,[113][114][115] Results show that installation of infiltrating biochar-augmented biofilters could reduce loads of bifenthrin, a common pyrethroid, by 93%; the same conventional biofilters provide 78% bifenthrin load reduction. This result was even more exaggerated for fipronil, which is more hydrophilic and thus even more poorly removed by conventional biofilters (reduction of 93% with biochar compared to 55% for conventional).…”

“…18,19 Additionally, trace organic contaminants (TOrCs), such as plasticizers and pesticides, are present in stormwater, contributing to toxic levels found in surface waters. [20][21][22] While much is unknown about TOrCs in stormwater, work has begun to identify the differences in concentrations across land uses 23 and the hydrologic controls over export from watersheds. 24 Collectively, contaminated stormwater currently threatens or impairs 2.6 × 10 8 km (49 330 miles) of river, 3100 km 2 (759 483 acres) of lakes, and 43 000 km 2 (10 6 acres) of estuaries in the US.…”

Is the Hyporheic Zone Relevant beyond the Scientific Community?

“…Furthermore, urban drainage, combined sewer overflow [146], or leaking water from sewer systems [147], onsite wastewater treatment systems [148], and landfills [149] reach the aquatic environment without undergoing human-induced purification processes. This means that a significant amount of TrOCs are discharged into rivers and streams [150]. In cities with partially closed water cycles or with water supply wells downstream of TrOC sources, TrOCs might end up in drinking water supply systems [151].…”

Hydrophilic trace organic contaminants in urban stormwater: occurrence, toxicological relevance, and the need to enhance green stormwater infrastructure

“…Recently, urban stormwater runoff has received increased attention as an important but often overlooked input pathway of hyphil-TrOCs to receiving water bodies. 12,[30][31][32] In the face of global water scarcity, urban stormwater is increasingly valued as a currently underused freshwater resource. [33][34][35] The capture, treatment, and recharge of stormwater runoff can augment urban water supplies and diversify urban water supply portfolios.…”