Occurrence, characterization, and source delineation of microplastics in the coastal waters and shelf sediments of the central east coast of India, Bay of Bengal

The present study investigates the abundance, distribution, and characterization (shape, size, colour, chemical composition) of microplastics (MPs) in surface water and sediment from the shelf region of the central east coast of India. The surface water and sediment samples were collected at varying depths (12.8–63 m) from 21 locations covering ∼1200 km. The mean abundance of MPs in surface water and sediments were 5.3 × 10⁴ particles. km⁻², 209 ± 99 particles. kg⁻¹ of dry weight, respectively. Stereomicroscopy, Raman spectroscopy, and micro Fourier Transform Infra-red Spectroscopy (FTIR) were employed for the quantification and characterization of the polymers. Polyolefin (polyethylene and polypropylene) were the dominant polymers in both surface water and sediments indicating their source primarily land based. Surface water and sediment MPs were mostly blue coloured. Fibre (77%) and fragment (38%) were the dominant morphotypes in surface water and sediments, respectively. Surface characteristics studies using Scanning Electron Microscope (SEM) highlight the breakdown progress of the particles; Small MPs (<1 mm) account for >50% of the whole and dominant in the offshore region (10 km). The results reveal that the primary sources of MPs are most likely to be originating from riverine fluxes and fishing-based activities.