7-21 Investigating Different Methodologies for the Separation of Microplastic Pollution in the Soil Sediment of Southwest Virginia Caves

Session: Undergraduate Research, Part I (Posters)

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Abstract:

Plastics are one of the most utilized resources that humans have integrated into everyday life for their cost-effectiveness, durability, and easy production. Due to their overproduction and limited recycling methods, millions of tons of plastics are discarded into various environments, where they break down into microplastics and impact water quality, soil quality, and expose chemical pollutants. While the impacts of these microplastics are known, research on the separation of these plastics from their host environments is limited, especially for karst environments. Microplastics are transported and deposited into caves through various processes, including animal traffic, atmospheric deposition, infiltration, and human activities. This research tests the effectiveness of using manual extraction, density separation, and centrifugation for separating microplastics from cave sediments in three different caves in Southwest Virginia. For each cave, sediment samples were collected at the entrance, in the back, and in a water pool. The manual extraction method consisted of sieving sediments with three different mesh sizes (1mm, 500 µm, and 300 µm), spreading the sediment on a petri dish under a microscope, and manually counting the number of microplastics collected. The density separation method used an overflow protocol to separate low-density microplastics using a salt solution. The sediments were mixed with the salt solution, set to separate, gently overflowed, and the overflowed mixture was vacuum filtered with filter paper. The microplastics caught on the filter paper were then counted, and the sediment that sank was examined to test effectiveness. The centrifugation method was started by filling the centrifuge tubes with 20g of sediment and ~40mL of DI water. The tubes were spun in the machine until the mixture was fully separated. The top portion of water was then filtered and counted, while the remaining sediment was examined to test effectiveness. For each method, a UV black light was used to detect remaining microplastics. The manual extraction method extracted the most microplastics at an average of 123 per 10g. The centrifugation method extracted 51% of the microplastics, while the density separation method extracted 48%. Of the microplastics found, 97% were fibers with the most being at each entrance. These results support future research in stopping the spread of microplastics and promotes new methods for their separation from cave sediments.

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