Plastic debris in water systems has long been a source of concern, and recently an international effort has been made to address the unique problems presented by the small pieces of plastic suspended in water , >1.6µg. Quantifying these microplastics contributes to a clearer picture of marine and freshwater pollution. Initial efforts to quantify mircoplastics have concentrated on marine environments. This study attempts to investigate the origin of microplastics found in Puget Sound by sampling Lake Washington and surrounding watershed.
This study utilizes the sampling and processing protocol developed by researchers at University of Washington, Tacoma.
Multiple water samples were collected from basins and waterways that populate Lake Washington for the purpose of quantifying the presence of microplastics. The sites sampled include the Cedar River Basin, Sammamish River Basin, Ship Canal Bridge, North Coast of Mercer Island and the Coast of Kirkland, one of Lake Washington’s busiest leisure areas. Two methods were used for the collection of samples. For the in-flows from the basins a line was drawn across the surface of the water with a drift net attachment and a flow meter to track the rate of the water entering Lake Washington. For samples gathered in the middle of the lake, a drift net was set aft of our small sailing vessel by a pole and rope. The drift net remained in the epilimnion of the Lake which is 12m deep (Washington.gov). We trolled at no less than .5 knots and no greater than 5 knots. The samples were then brought to a lab for processing. Processed samples were examined under a microscope and plastic pieces <>
Processed samples were found to have less than 1mg of non organic debris per (unit volume) of water flow. The presence of these microplastics is most likely due to urban waste run-off and further study is warranted.
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