Fate of Heavy Metals and Nutrients at the Catchment.

Rain gardens are an element of green infrastructure, promoting human health and well-being. They have also emerged as an effective strategy to treat stormwater runoff in urban areas by encouraging infiltration and the capture of pollutants such as heavy metals and nutrients. The establishment of a rain garden on UK's campus (named the CATchment) is an initiative to educate the UK community about stormwater control measures as part of its Municipal Separate Storm Sewer Systems Permit. In this study, water quality was followed by measuring heavy metal and anion concentrations since 2015 from separate sections of the CATchment (inlet, bank, basin) coupled with data loggers which were installed to record daily redox potential in the bank and basin. Dissolved copper was identified at the inlet with an average concentration of 2.74 ng/ml whereas zinc averaged 1.59 ng/ml over the entire time period. In general, chloride was the most abundant anion at the inlet followed by sulfate. As stormwater enters the basin, it becomes reduced as shown by the negative redox potentials, loss of nitrate and sulfate, and appearance of high levels of dissolved iron(II). There was a concurrent decrease in both dissolved copper and zinc at the basin and bank when compared with the inlet, possibly indicating the rain garden serves as a sink for heavy metals. Even though we did not measure sulfide in the pore water, it is possible that the decreasing solubility of the metals is due to metal-sulfide precipitation.