Abundance, distribution and composition of microplastics in sediment and fish species from an Urban River of Bangladesh

Microplastics (MPs) are a growing concern due to its ubiquitous presence and exceptional stability. We examined the abundance, dispersion, and attributes of MPs in the sediment and fish species of the Turag River in Bangladesh, which separated the industrial city Gazipur from the Mega-city Dhaka. Collected samples were digested and the chemical structure was identified using ATR-FTIR spectroscopy. The concentration of MPs in the sediment ranged from 10 to 35 particles kg-1, with a mean abundance of 19.2 ± 2.44 particles kg-1and MPs of the fragment type account for 34 % of all. The majority of MPs were discovered in the 3-5 mm size range. MPs concentrations in freshwater fish gut from the Turag River ranged from 0.63 ± 0.18 to 7.0 ± 1.1 microplastics individual-1. Fiber was found to be the most commonly ingested MPs type (43 %), followed by fragments (41 %), film (12 %), and foam (4 %). The most common type of MPs was transparent (34 %) followed by red (28 %), white (20 %), green (9 %) and black (8 %). The results showed that demersal (1.87 ± 0.39 items individual-1) and benthopelagic (1.5 ± 0.26 items individual-1) fish species had more MPs than pelagic fish (0.63 ± 0.18 items individual-1) species. Polypropylene (PP) was found to be the most dominant polymer type in the sediment sample, and PS (39 %) in the fish sample. Polyethylene (PE) was discovered to be 30 % and PP 25 % in sediment and fish samples, respectively. Other commonly detected polymer types include polyamide (PA), polystyrene (PS), cellulose acetate (CA), and polyethylene terephthalate (PET). In different sampling sites along the Turag River, the pollution load index (PLI) of MPs contamination was found to be in the risk level category I. The PLI values reflected the city's anthropogenic influence. The findings of the study could be used to establish a baseline for MPs pollution in Bangladesh's vast freshwater ecosystem.