In recent years, microplastics have emerged as a contaminant of particular concern due to their ubiquitous nature in the environment and their ability to act as a vector for other toxic pollutants and contaminants. In addition, while studies regarding microplastics have become more prevalent, relatively few consider their impact in urban freshwater systems. Urban stormwater runoff in particular has been identified as a major entry pathway for microplastics into the aquatic environment. Therefore, in order to better prevent the introduction of microplastics to freshwater systems, it’s necessary to better understand the mechanics governing their movement in stormwater runoff. The purpose of this study was to investigate the presence of microplastics as seen in other stormwater pollutants by comparing the flow hydrograph to the microplastic concentration pollutograph over the stormwater runoff duration. To do so, flow-paced stormwater samples were collected from Baker Creek, Knoxville, TN, to better characterize the temporal variation of microplastics in a given storm event. The combination hydrograph-pollutographs generated for the captured storm events show significantly elevated concentrations in microplastic concentrations in the rising limb of the hydrograph. Preliminary analysis of cumulative pollutant load vs. cumulative runoff volume showed that the vast majority of collected microplastics (between 80-100%) appeared in the first 40% of the event runoff volume in the initial three-events. Better characterization of microplastics in urban runoff will provide additional understanding of potential mechanisms for transport and begin to identify methods for remediation.
