Analysis and characterization of microplastics in river water and sediments of the Doon Valley foothills in the Himalayan region

ABSTRACT Schematic representation showing sources, pathways, and impacts of microplastics in river systems. Microplastic (MP) contamination in freshwater ecosystems has emerged as a significant global concern, yet region-specific assessments remain limited. This study investigates the occurrence, distribution, and characteristics of MPs in river water and sediments from five major rivers of the Doon Valley (Sahastradhara, Song, Bindal, Asan, and Tons). A total of six water and 10 sediment samples were collected and processed using oxidative digestion and density separation, followed by microscopic observation and Fourier-transform infrared (FTIR) spectroscopy. MPs were detected in all rivers, with concentrations exhibiting notable variability across sites. Morphological classification revealed fibers and pellets as the most abundant forms, with minimum–maximum ranges spanning from 3 to 26 particles across categories. Particle sizes varied from 68.15 μm to 1.28 mm in water and from 71.02 to 633.41 μm in sediments, indicating a predominance of fine particles capable of bioavailability and trophic transfer. FTIR analysis confirmed polyethylene as the dominant polymer, followed by polyethylene terephthalate and polypropylene, suggesting contributions from both domestic and industrial sources. The findings underscore the widespread distribution of MPs in Doon Valley rivers, highlighting their potential ecological and human health implications. This work provides a baseline for regional monitoring and emphasizes the urgent need for sustainability.