MICROPLASTIC ACCUMULATION ALONG AN URBANIZED AND ELEVATIONAL GRADIENT IN THETENNESSEE RIVER WATERSHED

Understanding the transportation of microplastics through waterways is an area of growing research. Due to their small size, water is a main mode of transportation for microplastics through our environment. Although studies have shown that microplastics are abundant in our waterways, there is little research analyzing microplastic abundance across urban and elevational gradients. This study presents a quantitative analysis of microplastic counts found in urban, suburban, rural, and natural streams within the Tennessee River watershed in East Tennessee. A total of 20 samples were collected from 10 different sites in 7 different bodies of water along an elevational and urbanized gradient. According to Strahler’s stream order classification, the bodies of water range from 2 to 7 with the higher number meaning more tributary inflow. The samples were filtered and microplastic particles were examined and tabulated under a microscope. Fibers were the most common type of microplastic found and blue was the most prevalent color. Most importantly, the highest elevated and least urbanized sample site averaged only 11 microplastics while the most urbanized site averaged 78 microplastics. Sites with intermediate levels of urbanization yielded intermediate abundances of microplastic fibers. In addition, there was an increase in microplastic abundance going downstream through the watershed from higher to lower elevation and from smaller to larger streams and water bodies. These results follow the expectation that higher population densities (pollution from urbanization) will increase microplastic abundance. This effect may be amplified by the elevational effect whereby increasingly larger streams and rivers accumulate increasing amounts of microplastics from tributaries for a higher overall abundance downstream. Given that these lower elevational water bodies such as The Tennessee River are major sources for drinking water and recreation in large urban populations, this research has important implications for identifying microplastic exposure to humans.