Higher concentrations of microplastics in runoff from biosolid-amended croplands than manure-amended croplands

Land-applied municipal biosolids, produced from municipal wastewater treatment sludge, contribute to microplastics (MPs) contamination in agroecosystems. While impacts of biosolids on MP concentrations in agricultural soil have been examined, the potential for MP transport from biosolid-amended croplands has not been quantified. In this study, manure and biosolids were applied to field plots, runoff was collected following natural precipitation events, and the potential for bacterial biofilm growth on different MP morphologies was investigated. Higher concentrations of MPs were detected in runoff from biosolid-amended plots compared with manure-amended and control plots. Fibers and fragments were the most frequently detected morphologies in runoff, likely due to decreased surface roughness. The potential contribution of biosolids to MP contamination of U.S. surface waters was quantified, among the first estimates of nonpoint source MP contamination from agricultural production areas.