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Assessment of microplastic contamination and associated risks in agricultural soils: a case study along the National Highway-66, Goa, India
Summary
Researchers surveyed microplastic contamination in paddy field soils along a major highway in Goa, India, finding concentrations of 250–423 MP/kg dominated by fiber-shaped polypropylene and polycarbonate particles with extensive surface weathering and adsorbed heavy metals — and showed through hazard index analysis that abundance alone is a poor predictor of ecological risk.
Agricultural soils near major transportation corridors increasingly act as repositories for anthropogenic debris, yet the dynamics of this contamination in tropical paddy fields remain under-researched. This study investigates the abundance, morpho-chemical characteristics, and calculated ecological risks of microplastics in paddy field soils along National Highway 66 in Goa, India. Using Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS), and standardized hazard indices, microplastic contamination was found to be ubiquitous, with concentrations ranging from 250 to 423 MP/kg (mean: 336.7 ± 55.47 MP/kg). Population density and proximity to urban centers were key drivers of accumulation, with low-lying paddy regions functioning as depositional sinks for pollutants transported via runoff. Morphological analysis revealed a predominance of fibers (63%) and fine-sized particles (0.1-0.063 mm), indicating high potential for soil mobility. Polypropylene (51.85%) and polycarbonate (17.59%) were the dominant polymers identified. Notably, while the study area is traffic-influenced, tire-wear particles were not detected within the analytical range of the Raman technique employed, with the profile instead reflecting agricultural and consumer-related inputs. SEM analysis highlighted extensive surface weathering, while elemental profiling confirmed the adsorption of heavy metals (Pb, Cu, Fe), establishing these particles as active vectors for contaminants. Ecological risk assessments using the Polymer Hazard Index (PHI), Pollution Load Index (PLI), and Potential Ecological Risk Index (PERI) demonstrated a disconnect between abundance and hazard. These findings suggest that mitigation must prioritize hazard-weighted assessment over simple abundance monitoring to protect agricultural soil health.