Hydrology and Biogeochemistry of an Urban Mitigation Wetland

Abstract

The hydrology and biogeochemistry of the urban mitigation wetland located at the Olentangy River Wetland Research Park (ORWRP) in Columbus, Ohio was studied during the summer months of 2015. The freshwater resource is susceptible to nutrient contamination due to industrial and agricultural runoff. These nutrients in high enough concentrations can pose a health hazard and also have been linked to the hypoxia of the Gulf of Mexico. Wetlands have been created along rivers throughout the Mississippi watershed to reduce and trap these pollutants. Excess floodwater flows into the wetlands, where the floodwater undergoes biogeochemical transformations and then is reintroduced back into the river. The water in the wetland at the ORWRP was tested from June 11th, 2015 to July 16th, 2015 for anion concentrations (nitrate, sulfate, chlorine), dissolved organic carbon concentrations, the amount of dissolved oxygen present in the water column, and pH. The wetland was effective at reducing the concentration of nitrate that was introduced into it after three flooding events. Sulfate did not undergo any biogeochemical transformations during the study, but evidence suggests that the wetland may act as a sulfate sink. Chloride also did not undergo any biogeochemical transformations, but showed evidence of the hydrological connection between the Olentangy River and the wetland. The water from the Olentangy River had low dissolved organic carbon concentrations, high dissolved oxygen concentrations, and also more acidic pH. After each of the three flooding events, the water in the wetland concentrations of dissolved organic carbon decreased, the concentrations of dissolved oxygen increased, and the water in the wetland became more acidic. The urban mitigation wetland located at the ORWRP is effective at mitigating the amount of contaminants that are introduced into it by floodwater from the Olentangy River and the wetland ecosystem is healthy and thrives based off its concentrations of dissolved organic carbon, dissolved oxygen, and its pH.