Land-use influence on soil microplastic pollution in Thailand: Implications for sustainable land management

Microplastic (MPs) pollution in soil has been increasingly reported worldwide; however, data from Thailand remain very scarce, and the issue is largely unexplored. This study addresses that critical knowledge gap by investigating the abundance and characteristics of soil MPs across diverse land use types in Thailand. Topsoil samples were collected from 31 sites representing seven land-use categories: paddy fields, roadside areas, urban parks, forest, university area, sugarcane fields, and cassava fields. MPs concentrations ranged from 83 to 12,100 items/kg of soil, with an average of 3,303 ± 3,749 items/kg. Land use type significantly influenced MPs abundance, with roadside soils showing the highest levels, averaging 7,467 ± 4,020 items/kg, as confirmed by FTIR analysis, and 187.68 mg/g, as determined by pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS). Conversely, cassava fields exhibited the lowest MPs abundance, with 100 ± 45 items/kg and 9.88 mg/kg. Spatial variability in MPs characteristics, including polymer type, shape, size, and color, also closely followed land use patterns. Particles smaller than 0.5 mm were the most dominant size class, while blue and transparent MPs were the most frequently observed colors. Among all soil samples, polyethylene (PE) was the most prevalent polymer (35%), followed by polystyrene (PS) at 32%, as identified by FTIR. Our findings reveal the widespread presence of soil MPs across natural and artificial ecosystems, from urban centers to rural landscapes in Thailand, underscoring the urgent need for improved plastic waste management and greater attention to this emerging environmental threat.