Hydroclimatic Drivers of Soil Microplastic Pollution in Landfills: Insights from an Urban City of Bangladesh

Landfills are emerging sources of microplastics (MPs), yet the hydroclimatic controls that accelerate MP release and subsequent terrestrial contamination remain poorly characterized in developing urban settings in Bangladesh. This study investigates the characteristics of MPs and the hydroclimatic factors governing their leaching from two active landfills in Rangpur City, Bangladesh. Soil samples were collected from 24 sites across the Nasinabad and Rangpur–Dinajpur Highway landfills, and MP data were integrated with hydrological and meteorological observations to evaluate hydroclimatic influences. MPs were detected in both landfills, with mean abundances of 164.5 ± 30.48 pieces kg−1 and 84.0 ± 16.39 pieces kg−1 in Nasinabad and Rangpur–Dinajpur Highway sites, respectively. Fourier transform infrared (FTIR) analysis identified polyethylene (PE), polypropylene (PP), and cellulose as the dominant polymers. Increased MP loads in Nasinabad indicate greater refuse dumping at this location. The ecological risk assessment showed low contamination, as indicated by the pollution load index (PLI) and contamination factor (CF), with the combined-polymer risk also being considered low by the Nemerow integrated pollution index (NIPI). The seasonal patterns, characterized by lower levels of MP contamination during the dry season compared to the monsoon period, and their association with rainfall and temperature, point to an implication of acceleration toward vertical translocation from the soil surface to subsurface layers. Overall, remediation pathways are proposed to reduce MP burdens in landfill soils from a developing-country perspective.