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ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #414613
Research Project: Developing and Evaluating Strategies to Protect and Conserve Water and Environmental Resources While Maintaining Productivity in Agronomic Systems

Location: Soil and Water Management Research

Title: A comparative analysis of microplastic inflow in atmospheric deposition and stream outflow in a small cold-water agricultural watershed

Author
item SIMMERMAN, CLAIRE - University Of Minnesota
item Baker, John
item Rice, Pamela

Submitted to: American Chemical Society Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/22/2024
Publication Date: 8/18/2024
Citation: Simmerman, C.B., Baker, J.M., Rice, P.J. 2024. A comparative analysis of microplastic inflow in atmospheric deposition and stream outflow in a small cold-water agricultural watershed. American Chemical Society, August 18-22, 2024, Denver, Colorado.

Interpretive Summary:

Technical Abstract: Currently the majority of microplastic research is focused on quantifying snapshot concentrations in different environmental settings. Scant information exists on quantifying fluxes of microplastic pieces (< 5 mm) entering and leaving compartments over a range of temporal and spatial scales. This study monitored microplastic loads in wet and dry atmospheric deposition, as well as stream outflow, for approximately three years in a predominantly agricultural watershed. Significant differences in microplastic load were observed, indicating substantially more microplastics are leaving the watershed via stream outflow compared to that entering the watershed from the atmosphere, by an order of magnitude. Hydrologic analysis and baseflow separation of the stream outflow load of microplastics revealed significantly greater loads of microplastics under baseflow conditions compared to stormflow conditions. Cumulative loads in wet deposition and dry deposition were relatively equal over the entire sampling period, demonstrating that microplastic contributions were similar from precipitation and dust deposition, though there was seasonal variation. Evaluation of wet deposition across seasons revealed significantly greater concentrations of microplastics in snow versus rain. The large difference between microplastics leaving the watershed in streamflow and microplastics entering the watershed from the atmosphere indicates substantial in situ sources of microplastics, perhaps a surprising result for a completely rural watershed. Speciation of sampled plastic is a necessary next step to determine the primary source(s) of plastic pollution.