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

Land-applied municipal biosolids, produced from municipal wastewater treatment sludge, contributes to microplastics contamination in agroecosystems. The impacts of biosolids on microplastic concentrations in agricultural soil have been previously investigated, however, the potential for microplastics transport from biosolid-amended croplands has not been previously quantified. In this study, manure and biosolids were applied to field plots, runoff was collected following natural precipitation events and the potential of bacterial biofilm to grow on different microplastic morphologies was investigated. Higher concentrations of microplastics were detected in runoff from plots with land-applied biosolid in comparison with manure-amended and control plots. Fibers and fragments were the most frequently detected plastic morphologies in runoff, correlated with their decreased surface roughness. The potential of biosolids to contribute to microplastic contamination to U.S. surface waters was quantified which is among the first to quantify the potential for nonpoint source microplastic contamination of surface waters adjacent to agricultural production areas. Application of biosolids derived from municipal wastewater treatment sludge to agricultural croplands in Nebraska, US elevated microplastic concentrations in runoff water, and could contribute to microplastic contamination of surface waters, suggests a field study in summer 2020.