Abstract
Stormwater ponds can provide flood protection and efficiently treat stormwater using sedimentation. As the ponds also host aquatic biota and attract wildlife, there is a growing concern that the sediment bound pollutants negatively affect aquatic organisms and the surrounding ecosystem. In this study, we used three methods to assess the accumulation and the potential ecological risk of 13 different heavy metals and metalloids (e.g. trace elements) including both elements that are frequently monitored and some which are rarely monitored in sediment from 5 stormwater ponds located within catchments with predominately industrial activities. Ecological risk for organisms in the older ponds was observed for both commonly (e.g. Cd, Cu, Zn) and seldom (e.g. Ag, Sb) monitored trace elements. The 3 methods ranked the degree of contamination similarly. We show that methods usually used for sediment quality assessment in aquatic ecosystems can also be used for screening the potential risk of other trace elements in stormwater ponds and may consequently be useful in stormwater monitoring and management. Our study also highlights the importance of establishing background conditions when conducting ecological risk assessment of sediment in stormwater ponds.
Highlights
Urban stormwater runoff may cause flooding and pollution in downstream watercourses if neither the flow is reduced nor the pollutants are removed (Baekken 1994; Maltby et al 1995; Blecken et al 2012; Sharley et al 2016)
The measured concentrations of four commonly monitored (Cd, Cu, Pb and Zn) and four seldom measured (Ag, As, Ba and Sb) trace elements in stormwater ponds are presented in Figs. 2 and 3, respectively
There is an urgent need to update the list of trace elements that are routinely monitored in sediment in stormwater ponds when evaluating ecological risk, especially in ponds with catchments in areas of industrial land use
Summary
Urban stormwater runoff may cause flooding and pollution in downstream watercourses if neither the flow is reduced nor the pollutants are removed (Baekken 1994; Maltby et al 1995; Blecken et al 2012; Sharley et al 2016). Concern has been raised over the ecological risks to aquatic life in wetlands and stormwater ponds and for the surrounding wildlife caused by the accumulated sediment. A study in Minnesota by Crane (2019) found that industrial areas in Minnesota were more contaminating than residential and commercial areas, leading to statistically significant increases in zinc and some organic micropollutant content in the studied stormwater ponds. This suggests that stormwater ponds in catchments with industrial activity may accumulate high levels of trace elements which could pose a significant risk to the ecosystem
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