Distribution Patterns and Ecological Risks of Microplastics at Major Waste Disposal Environments in Dhaka, Bangladesh

Microplastics (MPs), recently identified as emerging contaminants in environmental and biological systems, currently lack a comprehensive ecological risk assessment in waste disposal environments. This study investigates the presence, abundance, and distribution patterns of MPs in agricultural soils and surface water near the largest waste disposal area in Dhaka, Bangladesh, mainly focusing on assessing ecological risks and identifying potential hazards. MPs were characterized using ATR-FTIR spectroscopy, stereomicroscopy, and SEM–EDX analysis. The agricultural soils were categorized into 5–2 mm, 2–1 mm, and 1–0.5 mm size fractions, concentrating on MPs less than 5 mm in surface waters. The mean abundance of MPs in surface soils was 2800 ± 696.42, 2320 ± 622.09, and 2040 ± 313.05 particles/kg, while in subsurface soil they were 2680 ± 576.19, 2200 ± 570.09, and 1760 ± 443.72 particles/kg for respective size fractions, and 376 ± 57.29 particles/liter in surface water. MPs were significantly correlated with soil moisture, pH, electrical conductivity, organic matter, nitrogen, and phosphorus. The predominant polymers were polyethylene, polypropylene, and polystyrene, mainly in fiber and film forms. The ecological risk evaluation indicated a high risk for surface soil and a medium-to-high risk for subsurface soil of agricultural land and surface water. Plastic mulch, solid waste, surface water irrigation, and organic compost were probably the potential sources of MPs, and their entrance into farmland and adjacent environments should be strictly limited. This study would provide the baseline reference for the current situation on agricultural fields and surface water near waste dumping sites, as well as emphasize the need for strong environmental regulations and effective mitigation techniques to address microplastic pollution.