Abundance, distribution and characterization of microplastics in Tropical River Estuary, South East Coast of India

Rivers play pivotal role in transporting plastic litter into the ocean. The present study aimed to estimate microplastics (MPs) in Palar River (PR), that receives waste inputs of agricultural, industries, fishing, and domestic origin. Water and sediment samples were collected during low tide, at seven locations from inner check dam to mouth region. Highest concentration of MPs in water are observed at PR-6 (28.01 × 10⁴ particles.km⁻²) and the lowest was recorded at PR-4 (2.6 × 10⁴ particles.km⁻²). In sediment, highest count was detected at PR-1 (8.8 × 10² ± 226 particles.kg⁻¹ d.w) and the lowest was recorded in PR-6 (2.5 × 10² ± 14 particles.kg⁻¹d.w). MPs distribution in water is more in the outer mouth (PR-6) in comparison to inner region (PR-4). Fibres were dominating morphotype of MPs, comprised of 79.4% in water and 89.8% in sediment samples. According to size classification, the majority of particles (41.02% in water and 56.1% in sediment) were in the size range of 1 μm to 1000 μm. Characterization of MPs through Attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy revealed that High Density Polyethylene (HDPE) is the dominant polymer indicating the use of plastic fishing nets and ropes along with the outfall from nearby industries may be the main contributor to the microplastic pollution in the river.