Characterization and risk assessment of microplastic contamination in a tropical man-made Lake and adjacent water using multi-approach analysis

Microplastic (MP) pollution in lacustrine environments remains largely overlooked in the South Asian region, despite its widespread presence and adverse effects. Hence, this pioneering study investigated the contamination levels and multi-approach ecological risks of MPs in water and sediment samples collected from ten key stations across Kaptai Lake, the largest artificial lake in South Asia. MPs abundance ranged from 650 to 2450 items/m³ in water and 135-607.5 items/kg in sediment. Significant spatial variation in MP concentrations (p < 0.05) was observed along the lake. Their variation was influenced by polymer properties, local hydro-geography, and point pollution sources. The majority of identified MPs were fibers measuring less than 0.5 mm in size, with transparent MPs being the most prevalent in both water (39.5 %) and sediment (46.2 %). FTIR analysis identified six polymer types including PE, PET, PP, PS, EVA, and PU. The detected polymers reflect diverse pollution sources e.g., primarily packaging materials, synthetic textiles, and fishing gear, originating from anthropogenic activities surrounding the lake. Evaluation through contamination indices, namely the contamination factor (CF) and pollution load index (PLI), revealed a moderate level of plastic contamination. However, high PHI values (>1000) observed at several locations indicate severe contamination, categorized under Hazard Level IV, indicating significant environmental risks. The PERI analysis showed considerable variability in risk levels across the lake, with certain areas classified as "extreme Danger" (>1200), highlighting severe ecological threats from MP contamination. Multivariate analyses (CA and PCA) revealed that human activities are likely the primary sources of MPs in the lake. These findings reveal pronounced spatial variations in MPs contamination and ecological risk across Kaptai Lake, underscoring the need for improved waste management and awareness initiatives around industrial, residential, and tourism-influenced zones.