Microplastic Composition in Soils Reflects Anthropogenic Inputs Across Contrasting Land Uses

Microplastic contamination of soils is influenced by both land use and anthropogenic inputs, yet the extent to which polymer composition reflects potential sources remains poorly understood. In this study, microplastics were quantified in soils under contrasting land uses within a representative continental catchment using a mass-based pyrolysis–GC-MS approach. Potential input materials, including sewage sludges and composts, were also analyzed to assess possible source signatures. Microplastics were detected in all soil samples, with concentrations ranging from 2 to 99.5 mg kg⁻¹. Clear differences were observed among land-use categories, with urban soils exhibiting the highest contamination levels and greatest variability, whereas cropland, grassland and forest soils displayed lower but heterogeneous concentrations. Polymer composition was dominated by PE, PP and PVC, indicating that a limited number of polymers account for most of the microplastic mass in soils. Principal component analysis revealed a clear separation between soils and input materials, reflecting distinct polymer signatures. Among the investigated inputs, the compost derived from wastewater-treatment residues exhibited particularly high PE concentrations, whereas sewage sludges were characterized by elevated PVC and N66 contents. These results suggest that soil microplastic composition reflects both land use and anthropogenic inputs, although local environmental conditions contribute substantially to the observed variability.