Microplastics in the Tennessee River: Are Small Streams a Major Source?

Freshwater streams transport more than 2 million tons of microplastic particles and fibers to the ocean each year. In the Tennessee River, mechanical and chemical breakdown of plastic waste, industry, and wastewater effluent are often cited as the most common source of microplastics in freshwater. Sources in more rural areas may include atmospheric deposition, fibers shed from clothing or other fabrics used in recreational activities, and residential septic effluent. In this study, we investigated the importance of these sources by quantifying and classifying the microplastics load in headwater streams draining from the following land use/type: undeveloped (control), low-density developed with residential septic, and low-density developed with sewer. The latter of these included sample sites above and below a popular recreational swimming hole. Samples collected over 3 months were filtered onto 0.2 µm black polycarbonate filters. The Nile Red dye method was used to quantify microplastics in each sample and classify them as particulate or fiber. The results of our study show that effluent from residential septic tanks and recreational activities contribute large quantities of microplastics to headwater streams in Eastern Tennessee and may be overlooked as a major source of microplastics pollution to the Tennessee River.