Microplastics distribution in water and sediment from river Uhl, Himachal Pradesh, India

Abstract

Microplastic (MP) pollution in freshwater ecosystems is a growing environmental concern, particularly in the fragile Himalayan River systems. This study investigated the occurrence, abundance, and characteristics of MPs in water and sediment samples collected from the River Uhl, originating from the Thamsar Glacier in the Dhauladhar range, Himachal Pradesh, India. Sampling was conducted at three sites representing varying degrees of anthropogenic influence and analysed through microscopic examination and Fourier-Transform Infrared (FT-IR) spectroscopy analysis. From each site, n=3 water samples (1 L each) and sediment samples (1 kg each) were collected. MP concentrations were expressed as particles L−1 for water and particles Kg−1 (dry weight) for sediment. MP abundance showed clear spatial variability, with lower concentrations at the relatively pristine site (50–100 particles L−1 or Kg−1) and comparatively higher levels at downstream sites (100–500 particles L−1 or Kg−1). Fragmented MP was the dominant morphotype in both water (83.16%) and sediment (87.61%), followed by fibres and films. Colour analysis revealed a predominance of colourless and blue particles in both matrices. FT-IR spectroscopy confirmed the presence of common polymer types and revealed site-specific spectral variations, indicating differences in polymer composition and degradation states influenced by local environmental conditions. The detection of MP even at sites with limited human activity underscores its widespread distribution and potential for transport. These findings underscore the need for continuous monitoring and targeted management strategies to mitigate MP pollution and protect freshwater ecosystems in the Himalayan region.