Microplastics pollution in the Brahmaputra River and the Indus River of the Indian Himalaya

Rivers act as temporary sinks of microplastics and a key medium allowing microplastics to enter the ocean. In this study, microplastics pollution in river shore sediment of the Indian Himalaya, including the Brahmaputra River and the Indus River was discussed. Sampling campaigns were performed in years 2018 and 2019. Sample pretreatment was performed using Na₂WO₄·2H₂O for density separation and H₂O₂ for oxidation of organic material. Microplastics analysis was performed by using FTIR microscope. The smaller size of microplastics 20–150 μm were more abundant (531–3485 MP/kg in the Brahmaputra River and 525–1752 MP/kg in the Indus River) than microplastics in size range between 150 μm and 5 mm (20–240 MP/kg in the Brahmaputra River and 60–340 MP/kg in the Indus River). Microplastics were found in sediments of all sampling sites. Fragmented, secondary microplastics were dominant in the river shore sediment of the Indian Himalaya. This study contributes towards filling research gap of microplastics in India's freshwater source and highlights the importance of in-depth complete studies of microplastics in the rivers that act as pathways and sinks for microplastics.