Abstract:
Microplastics (MPs) are emerging global pollutants of critical environmental concern due to their widespread distribution and ecological impact. Although numerous studies have focused on marine and estuarine ecosystems, riverine systems- particularly in Goa, remain underexplored. This research presents a comprehensive assessment of MP contamination in the Valvanti River, North Goa, including an evaluation of MP abundance, physical characteristics, polymer composition, ecological risks, surface degradation, and heavy metal associations. MP concentrations in surface water ranged from 1.1 to 7.5 MPs/L, with an average (plus-minus SD) of 2.91 plus-minus 1.69 MPs/L. The majority were colourless (70.49 percent) and fibrous in shape (96.9 percent). MPs within the 0.1-0.3 mm size range were most common (40.53 percent), followed by 0.3-0.85 mm (37.50 percent) and 0.85-5 mm (21.97 percent). Polymer analysis revealed polypropylene (27.86 percent), polyamide (26.10 percent), polyethylene terephthalate (25.20 percent), and polyethylene (16.59 percent) as dominant types. Risk assessments using the Pollution Load Index (PLI=1.53), Polymer Hazard Index (hazard level V), and Potential Ecological Risk Index (464.4) indicated that, despite moderate MP concentrations, the river is subject to high ecological risk. Surface analysis through SEM-EDS showed evidence of degradation and the presence of elemental contaminants, indicating potential chemical interactions that may heighten environmental threats. Given the importance of rivers as pathways for MPs to marine environments, these findings underscore the need for regular monitoring and mitigation strategies. This study provides the first detailed ecological risk assessment of MPs in the Valvanti River and offers critical insights into freshwater contamination within an underexplored riverine system of Goa.
