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Abstract.

A constructed wetland south of the Michigan State University campus has been monitored to document its effectiveness at reducing nitrogen, phosphorus, and carbon loads. The wetland is adjacent to an 8.7-hectare parking lot and was designed to receive that runoff, which is detained in a settling pond before entering the wetland. Other small parking lots discharge runoff directly into the wetland via a culvert. Wetland influent and effluent water samples were collected after eight rain events, and concentrations of nitrate, total phosphorus, and chemical oxygen demand (COD) were measured. Effluent nutrient concentrations were greater than the influent, necessitating a closer examination of the wetland. A flow balance was completed to discover there were three inputs and a single outlet pipe. Each input was delineated to determine its drainage area and land use type, which allowed for discharge calculations at each point. Samples were collected from each input and the output for five storm events, and the concentrations and discharges were combined to generate a nutrient loading. Overall, the wetland appeared to be generating nutrients as opposed to removing. Potential reasons were: input water relatively void of nutrients, particularly nitrogen and carbon; vegetation and organismal overgrowth; or sampling error. Although the wetland does not remove nutrients as expected, it still maintains its value for flood attenuation. The University should should maintain its stormwater management practices and invest in prescribed burns of invasive species, as well as conduct future monitoring on the wetland‘s water storage capacity and removal of metals, oil, and grease from stormwater.