Microplastic distribution in the surface water and sediment of the Ergene River

Rivers are major transport pathways for microplastics to reach the oceans. Although gained much attention over the last few years, there is still a relatively lack of knowledge on microplastics in rivers. This study aims to investigate (i) spatiotemporal distribution of microplastics in an industrially polluted river, (ii) the relationship of microplastic abundance with river's morphological and hydrodynamic characteristics (iii) the potential sources of microplastics inferred from the particle characteristics including shape, size, color and type. To achieve these aims, water and sediment samples were collected from six sites upstream of the Ergene River in May 2019 and Sep 2020. According to the results, surface water had an average concentration of 4.65 ± 2.06 and 6.90 ± 5.16 items L^-1 (mean ± standard deviation, n = 12), respectively for the May 2019 and September 2020 periods, whereas 97.90 ± 71.72 and 277.76 ± 207.21 items kg^-1 (n = 18) were observed for the sediment compartment, respectively. Microplastic levels in water correlated positively with stream depth but negatively with channel width. Fibers were the dominating shape both in water (88%) and sediment (70%) and majority of the particles were black (49% in water and 39% in sediment) and blue (25% in water and 18% in sediment). According to Raman spectroscopic analysis, polyethylene terephthalate (PET, 28%) and polyamide (PA, 27%) were dominating polymers in water, while polystyrene (PS, 56%) were dominant in sediment. Compared to many other rivers, the Ergene River had excessive levels of microplastics. The research indicated that textile industries and effluents from organized industrial zones were the foremost contributor of microplastics in the river.