Skip to main content
ARS Home » Midwest Area » St. Paul, Minnesota » Soil and Water Management Research » Research » Publications at this Location » Publication #421099
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: Quantifying microplastics in environmental waters: Mass concentrations are superior to abundance

Author
item Rice, Pamela
item Feyereisen, Gary
item Dalzell, Brent
item FRANKSON, LARA - Former ARS Employee
item Simmerman, Claire
item Schumacher, Todd
item Malone, Robert
item Williams, Mark
item King, Kevin

Submitted to: Agricultural & Environmental Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/1/2025
Publication Date: 12/1/2025
Citation: Rice, P.J., Feyereisen, G.W., Dalzell, B.J., Frankson, L.E., Simmerman, C.B., Schumacher, T.W., Malone, R.W., Williams, M.R., King, K.W. 2025. Quantifying microplastics in environmental waters: Mass concentrations are superior to abundance. Agricultural & Environmental Letters. 10(2). Article e70031. https://doi.org/10.1002/ael2.70031.
DOI: https://doi.org/10.1002/ael2.70031

Interpretive Summary: Microplastics are contaminants of global concern that are primarily studied in marine and urban environments. Understanding of microplastics in drained agricultural watersheds is lacking. We aimed to evaluate microplastics in ditch and tile drainage water through periodic sampling. Water samples were filtered to capture particulates that were digested to remove organics then stained and evaluated using fluorescence microscopy and image analysis. Further, we compared and contrasted microplastic abundance, the current reporting standard, with microplastic mass concentration, often unreported, to determine the most accurate assessment. Open-ditch drainage had greater microplastic contamination than drainpipe outlets. Agricultural drainage contained 2 to 6 orders of magnitude less mass concentrations of microplastics than sampled urban surface waters and laundry graywater. However, when evaluated by abundance the difference was not apparent. These findings improve our understanding of microplastics in agricultural watersheds and demonstrate the importance of evaluating microplastic contamination based on mass concentrations for accurate assessments.

Technical Abstract: Microplastics (plastic pieces < 5mm in size) are contaminants of global concern. They can be taken up into plants and ingestion by animals and humans. Oceans and urban environments have been the focus of microplastic research with little known about agricultural areas. Drain tiles that remove excess moisture from agricultural land are often made of plastic. We measured microplastics in agricultural drainage to understand microplastics in tile and open ditch waters. We also compared microplastics in agricultural drainage water verses urban waters. Key findings were 1) mass concentrations of microplastics were a more accurate measure of microplastic contamination than microplastic abundance or counts - the standard assessment method, and 2) agricultural drainage water had markedly less microplastics than urban waters. This information is needed to guide allocation of resources to areas of greatest importance for the prevention and cleanup of microplastic contamination.