- The OSU-Benton County Green Stormwater Infrastructure Research (OGSIR) Facility was created to test various methods of stormwater treatment. At this facility, runoff from the Benton County Development Department property is captured and pumped into a bioswale. This bioswale is comprised of layers of rock, gravel, sand, and soil, and is split into three treatment cells. One of the cells was designed as a no-stormwater control, and the other two cells contain plants and are designed to remove pollutants in the stormwater. However, effective removal of dissolved contaminants in the bioswales has been degrading over time. Higher concentrations of compounds such as zinc, copper, and orthophosphate have been found in effluent streams than were present in the influent streams. Therefore, the purpose of this research project is to characterize the composition of nutrients and other soil indicators in each cell to determine if contaminant release is due to the initial soil matrix in the facility (a mix of native soil and compost), or the desorption of captured contaminants from the soil. Further, concentrations in the control cell were compared to the two active cells to determine if the presence of plants impacts nutrient concentrations in the soil. Concentrations of nitrogen species in both active cells were found to be much lower than in the control cell, which suggests that the presence of plants in the active cells was removing nutrients from the soil. Soil parameters such as pH, total organic carbon, and particle size distribution were also evaluated, as well as quantification of antibiotic-resistant bacteria.
Key Words: bioswale, stormwater, soil, nutrients, antibiotic resistant bacteria