Microplastics in rivers of Gujarat (India) until the Arabian Sea: assessment of the sources, distribution and associated environmental risk.

Abstract

Microplastics (MPs) have become a notable concern and are released into the environment through the disposal or fragmentation of large plastics. Rivers have been the major pathways for MPs present in the oceans, which significantly affects the marine environment. In the current study, water samples were collected from the upper stream and downstream of Damanganga and Tapi rivers across different sites in the state of Gujarat, India for exploration of MPs contamination. Additionally, samples were also collected from Dumas Beach to detect the presence of MPs. MPs were extracted from the samples through sieving, density separation and wet peroxide oxidation (WPO) techniques which were subsequently analyzed using μ-FTIR, optical microscope, Pyrolysis GCMS (Py-GCMS) and SEM. The concentration of MPs was also quantified from each stretch of Damanganga, Tapi rivers as well as Dumas Beach. Findings revealed that Damanganga showed a higher concentration (3.53 particles/L) of MPs as compared to others. Further, optical microscope and μ-FTIR analysis confirm the presence of MPs like Polypropylene (PP), Polystyrene (PS), Polyethylene terephthalate (PET), Polyethylene (PE) and Polymethyl Methacrylate (PMMA). Pyrolysis products of PP, PS and Polyamide (PA) were detected from Py-GCMS studies. Additionally, SEM images revealed that MPs were subjected to weathering, oxidation and atmospheric deposition over the years. The study additionally confirmed the flux of MPs in both the rivers and beach due to anthropogenic and industrial effects. Risk assessment of MPs was performed using the Pollutant Loading Index (PLI), which indicated that the overall MPs pollution in the studied sites was marginal. Nevertheless, the PLI scores revealed that Damanganga was the most prone to MP pollution among the three study sites.