Microplastics build-up in soils - spatial distribution patterns across different land uses and associated health risks

Microplastic (MP) pollution in soil is an emerging environmental concern due to the extensive use and persistence of plastics, which degrade soil quality and pose potential risks to human health through accidental ingestion; however, the extent and implications of MP in soil environments remain poorly understood. This study assessed the extent, composition, distribution patterns, and potential hazards of MP across major ten Land Use types in five districts of Punjab, Pakistan to support environmental sustainability and policy design. Microplastics were extracted from soil samples by treating organic matter with 30% H₂O₂ in the presence of FeSO₄ as a catalyst, followed by density separation with saturated NaCl solution. The supernatant was filtered through 0.45 μm cellulose nitrate membranes to isolate MP. Visual classification was performed under a stereomicroscope, and polymer types were identified using FT-IR spectroscopy based on spectral library matching. The MP concentrations in soil significantly varied across cities and Land Use types, ranging from 18 to 1872 MP/kg. Greenhouse soils showed the highest contamination (1867 ± 32 MP/kg), followed by residential (751 ± 19) and industrial soils (693 ± 18) and Fish farm (18 ± 2) showed lowest values. Microplastic characterization revealed the dominance of fibrous and film shaped MP, particularly in agricultural and residential soils, with larger size MP particles 1–5 mm linked to fragmentation of agricultural mulching films and wastewater inputs. The FTIR spectra identified nine polymers, with HDPE and polypropylene as the most abundant, sourced primarily from mulching films, while Nylon and ABS were associated with textile effluents. Igeo values indicated severe contamination in Greenhouse > Residential > Landfill > Industrial > Roadside > Sewage irrigated > Mulching> Cropland > Fish farm, with Rawalpindi and Lahore most contaminated and Bahawalpur least. Principal Component Analysis (PCA) linked industrial and roadside soils to large durable fragments, agricultural soils to films and fibers, with urban density and climatic conditions. MP particles were found in all soils, even areas with minimal direct plastic use contained MP particles, emphasizing the role of atmospheric deposition and hydrological transport in shaping spatial heterogeneity. Microplastic particles adsorb pollutants, and may leach into groundwater, posing ecological and human health risks. These findings underscore the urgent need for robust policies, improved plastic waste management, and expanded research across diverse Land Use systems and environmental contexts.