Hydrodynamic Fate and High-Hazard Source Apportionment of Microplastics in Freshwater Bodies of Semi-Arid Rajasthan, India

Abstract

Microplastics (MPs) have garnered substantial attention as emerging pollutants in recent years; however, their occurrence, characteristics and specific impact factors within semi-arid regions remain poorly understood. This study assesses the degree of MPs pollution in dams and freshwater lakes in Rajasthan, India namely, Mansagar Lake (MS), Nevta Dam (ND), Anasagar Lake (AL), and Bisalpur Dam (BD). A multi-metric approach utilizing Fourier Transform Infrared spectroscopy (FTIR) and risk indices like Pollution Load Index (PLI), Polymer Hazard Index (PHI), and Polymer Ecological Risk Index (PERI) were employed to quantify MPs concentrations and assess their ecological impact. Evaluation through risk indices revealed pronounced spatial variations: BD was categorized under Low Risk (Category I), while MS and AL exhibited Medium-High Risk (Category II) profiles. Notably, ND emerged as a critical hotspot, falling into the High Risk (Category III) with the highest PLI > 1, PHI (2500), and PERI (> 120000) values, indicating severe ecological threats from concentrated anthropogenic inputs. Principal Component Analysis (PCA) successfully differentiated these sites into unique fingerprints, explaining 75.35% of the total variance and demonstrating that pollution profiles are dictated by localized activities, such as film dominated signatures in protected sites versus fibre and fragment in urban lakes. The results suggest that MPs pollution in semi-arid regions is primarily driven by localized anthropogenic sources, where the ecological risk depends more on specific polymer hazard levels and unique cultural-industrial pathways than on total particle abundance. Consequently, these findings provide a critical framework for achieving Sustainable Development Goals (SDG) 6 (Clean water and sanitation) and SDG 12 (Responsible consumption and production) in water-stressed landscapes.