Microplastic Concentration in the Truckee River, United States

Microplastics (MPs) are an emerging contaminant that is found throughout the environment. In this study we sought to quantify and characterize MPs along the Truckee River, located in the western United States. The Truckee River begins in the Sierra Nevada, flows to Lake Tahoe, a lake known for its clarity and pristine water quality and continues to Pyramid Lake. The Truckee River basin is utilized for its drinking water and all-season recreation throughout the watershed. Additionally, the Truckee River system is an important aquatic habitat for endangered and endemic species. For these reasons, assessing the MPs present in this system is essential for determining risks to human and aquatic health.Samples were taken along the Truckee River starting downstream of Lake Tahoe’s outlet sampling above and below major areas of land use change: urban population centers, wastewater treatment facilities, confluences, and agricultural areas at a total of 6 sampling sites in the fall of 2022 and 8 sampling sites during the spring of 2023. Two seasons were analyzed to capture the low flow (fall) and high flow (spring) discharge periods along the Truckee River. MP results were compared to a variety of spatial data to understand the concentration of MPs in the Truckee River, potential sources of MPs to the river from land use, and whether MP concentrations vary with seasonal flow changes. We show that MP concentrations vary with discharge and number of stormwater drainages. We also show the plastic types reflect commonly used single-use plastics.