Microplastic Contamination at the Agriculture–Freshwater Interface: Sources, Spatial Distribution, and Potential Transport Pathways in Bahraich District, Uttar Pradesh, India

Microplastic pollution at the agriculture–freshwater interface is an emerging concern in the Indo-Gangetic Plain, but district-level evidence remains limited for the middle and lower Ghaghra basin. This study synthesises secondary government datasets and peer-reviewed evidence to assess the probable sources, spatial distribution, and transport pathways of microplastics in Bahraich district, Uttar Pradesh, India. In the absence of district-specific primary sampling, a proxy-based risk framework was developed using land use, hydrological connectivity, canal irrigation, settlement patterns, floodplain exposure, and evidence from comparable Indian agro-ecosystems. The synthesis identifies plasticulture inputs, river-sourced irrigation water, unmanaged rural solid waste, riverine and floodplain exchange, wastewater and sewage inputs, and atmospheric deposition as probable sources. Four indicative spatial risk zones are distinguished: riparian and floodplain areas with the highest relative risk, peri-urban areas with moderate-to-high risk, canal-command agricultural areas with moderate risk, and Terai forest-fringe and rain-fed upland areas with lower relative risk. Five interacting pathways are identified, including surface runoff, canal–field–drain exchange, vertical leaching, flood-pulse exchange, and terminal crop and food-chain uptake. The possible co-occurrence of microplastic vulnerability and documented arsenic contamination in the shallow alluvial aquifer represents an important water-quality concern. Because microplastic concentrations have not been measured in Bahraich, the proposed zonation is intended to guide field validation, baseline monitoring, and integrated waste and water-resource management rather than to represent a definitive contamination map.