Citizen Science Sampling for Microplastics in Lake Tahoe, California: Preliminary Results

Microplastics are plastic particles that measure 5 mm in size and originate from industrial processes or the degradation of larger plastic items such as consumer products. In recent years, the accumulation of microplastics in the environment has been an increasing concern. Microplastics in freshwater lakes, such as Lake Tahoe, pose a potential threat to its aquatic ecosystems and populated regions. One method for studying microplastics in the environment is through citizen science, however, few studies use this approach. Engaging the public in research can help us further understand the environmental impacts microplastics have on freshwater lakes and build awareness of strategies to mitigate sources of microplastics. In this case study, we aim to engage citizen scientists in sample collection where the collection is done by volunteers from an environmental non-profit based in South Lake Tahoe, California called the League to Save Lake Tahoe (League). The goals are to (1) develop a grab sample method for citizen science studies where the sampling method reveals meaningful results and (2) determine if the collection sites are a significant source of microplastics into the lake. Citizen scientists from the League volunteered to collect water samples from stormwater drainage pipes from 9 different sites that surround Lake Tahoe to evaluate the number of microplastics flowing into the lake. The 9 sites drain directly into the lake or a tributary. The citizen scientists collected four 1 L samples from the sites, refrigerated the bottles post-collection, and returned the bottles to the Desert Research Institute (DRI) in Reno, Nevada for analysis. The analysis begins with filtering the samples onto 1000, 100, and 20-micron stainless-steel mesh filters with a vacuum filtration process. Once filtered, the samples go through processing with reagents to oxidize any organics on the filters. After processing, the samples undergo imaging using an optical microscope (Nikon SMZ1500) to identify microparticles. The microparticles are then classified using an infrared spectrometer (FTIR) as microplastics or other. Initial observations suggest that stormwater drainage pipes are a source of microplastics to Lake Tahoe, but further analysis needs to be done to address the project goals.