Identifying Microplastic Accumulation Hotspots in Sediment Associated with Stream Outflows into Lakes and Estuaries

Abstract:

Microplastics are one of the most common anthropogenic marine debris found in our waterways. Over time, the sediment at the bottom of aquatic environments becomes the sink for the denser of these particles. By analyzing sediment from lake and estuary systems in the Hudson River Valley, this study aimed to find a correlation between sediment type, water dynamics at stream to slackwater transitions, and resulting microplastic accumulation hotspots. Sediment was collected along a transect of sampling sites starting from the stream mouth and extending into open water in the middle of the lake or estuary system. A density separation and wet peroxide oxidation was performed on the sediment sample from each site. The microplastics from each site were weighed to find the heaviest concentration. The highest concentration sample (2.06 mg/L) was found 150 m away from the stream mouth and was associated with an environment of clay sediment deposition. Another finding of this study suggests higher microplastic concentrations in areas covered by the invasive species water chestnuts (Trapa natans) and eurasian watermilfoil (Myriophyllum spicatum). Both findings and the rest of the collected data conclude that the hotspot zones of highest microplastic concentration occur in association with finer sediment (silt/clay) deposition and are often > 100 m out into open water from the stream mouth.