Microplastic pollution in surface waters of urban watersheds in Central Texas, USA : a comparison above and below treated wastewater effluents.

Microplastics are polymer-based particles ranging in size from 50 µm to 5 mm. The behavior of microplastics within freshwater systems remains understudied. The purposes of this study are to assess microplastic levels in spring-fed and runoff-fed freshwater systems in small, urban watersheds above and below local point-source wastewater effluents, to investigate patterns in microplastic spatial distribution and to evaluate the influence that seasonality and land use may have on microplastic frequency and form. A total of 779 surface water samples of 800-mL were collected across five study locales and analyzed via visual inspection. In total, 1,198 microplastics were found, inclusive of fibers (95.0%) and fragments (5.0%). Approximately 57% of all samples were contaminated with microplastics, on average, ranging from 33.3%-80% per study locale. Overall, significant differences between sample site and sampling interval suggest that seasonality and land use influence microplastic frequency within a system, while spatial locale influences particle color and form.