MICROPLASTICS IN A SMALL STREAM: STORM RESPONSE IN A TRIBUTARY TO THE TENNESSEE RIVER

Streams have emerged as a major source of microplastic pollution to shallow marine ecosystems. The ecological impacts are still coming into view, but most view microplastics as a significant threat to aquatic ecosystem health. The origins of microplastics in high-order streams are believed to include degradation of macroplastics, wastewater, and industrial waste. In this study, we use a hydrograph separation technique to investigate whether residential septic systems in shallow soils are a major source of microplastic particles and fibers to smaller headwater streams draining from the Cumberland Plateau. The study site, Mountain Creek, is a 1st order stream in a low-density developed residential area that has septic waste management and is equipped with a USGS stream gage. The concentration of microplastics was determined using the Nile Red dye method and classified by shape. Stream chemistry was plotted on piper diagrams to help chemically distinguish streamflow components. We plot the concentration of microplastics at different points in the stream hydrograph (rising limb, peak, falling limb) against the relative contributions of groundwater, interflow, and runoff to help determine which type of flow is transporting more microplastics. These are compared to chemical indicators of septic effluent (chloride, nitrate, fluoride) to determine whether septic systems can be considered a major source of microplastics and their dominant pathway to the stream channel.