Urban stormwater runoff carries many pollutants including heavy metals and nutrients. Many existing stormwater wetlands function primarily as retention ponds, rather than provide ecosystem services including flood prevention and water quality improvement. We aim to evaluate the effectiveness of a Kent State University wetland that will be re-constructed as part of the Summit Street Improvement Project. We predict that the existing wetland offers little water quality improvement due to its current design, in which most stormwater bypasses the wetland.
To determine the wetland’s influence on water quality, we compared samples and discharge rates collected during storm events by automatic water samplers (ISCO, Teledyne) upstream and downstream of the wetland. When the outflow, which drains KSU’s stormwater into the city of Kent’s drainage system, is overwhelmed, water back-floods the wetland. We measured a suite of water chemistry parameters, including chloride (Cl-), nitrate (NO3-), sulfate (SO42-), and phosphate (PO43-) concentrations to indicate road salt and fertilizer pollution.
To date, we have sampled four storm events total; one captured in the outflow. Across all samples, stormwater was high in Cl- (average=272.8 ppm, n=53) and SO42- (average=56.25 ppm, n=53). In the same storm, outflow Cl- (average=514.5 ppm, n=12) was higher than inflow Cl- concentrations (average=108.7 ppm, n=41). This trend followed for NO3- and SO42-. Preliminary data suggest that inflow and outflow concentrations differ substantially. Outflows contain higher concentrations of pollutants than inflows, likely reflecting chemical changes occurring within the storm drain system, rather than biogeochemical functions of the stormwater wetland.