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Hybrid method development for isolating microplastics from marine sediments
Citation:
Langknecht, T., M. Cashman, K. Ho, AND R. Burgess. Hybrid method development for isolating microplastics from marine sediments. UMass Boston School for the Environment Earth Day Symposium, online, April 22, 2020.
Impact/Purpose:
Microplastics are a contaminant of emerging concern in marine environments. Estimating microplastic abundance in sediments is crucial to understanding their impacts on the marine ecosystems; however, the current isolation methods vary greatly, making meaningful comparisons of environmental relevance difficult. Therefore, methods development for isolation of microplastics from marine sediments is critical. The intended audience of this research includes state, local, and federal agencies interested in conducting microplastic research, as well as academic and private research institutions.
Description:
Microplastics (1-1000 µm) are a contaminant of emerging concern in marine environments. Studies suggest marine microplastics settle into sediments due to weathering, biofouling, ingestion, and other biotic and abiotic processes. Quantification and identification of microplastics in sediments is crucial to understanding their impacts on the marine benthos; however, the current published isolation methods vary greatly, thereby making meaningful comparisons of environmental relevance difficult. A previous methods comparison indicated that method, sediment matrix, and microplastic properties greatly influenced microplastic recoveries from sediments. Based on the findings of that comparison, a hybrid method was developed to isolate plastics of various sizes and densities from a diversity of sediment types. The hybrid method requires separating a wet sediment sample (100g) into two size classes, followed by sodium bromide solution density separations. After each density separation, the supernatant is filtered over a 20 µm polycarbonate filter, which is then oxidized, as needed, using hydrogen peroxide. The hybrid method was tested on two sediment types (i.e., sand and silt) using five common plastic polymers and achieved mean recovery rates ranging from 45-100%. The hybrid method showed an increase in recovery for a variety of microplastics from marine sediments as compared to the previous methods. This hybrid method continues to be refined to next optimize results for spectral analysis of plastic particles for polymer identification.
