Impact of land use land cover on microplastic accumulation in high-altitude freshwater lakes of the central Himalayas

This study investigated the spatial distribution and occurrence of MPs in the surface water (n = 24) of three lakes (Nainital, Garudtal and Bhimtal) in the Kumaun region of the Central Himalaya, alongside the influence of land use and land cover (LULC) at the catchment scale. The selected lakes represent both pristine and urbanised environments. MPs were detected in all analysed samples, including those from the isolated and presumed pristine Garudtal Lake. The mean abundance of MPs (≥ 90 µm) was higher for the Nainital Lake with 813 ± 346 items m^-3 (mean ± SD, n = 8), followed by Bhimtal Lake with 413 ± 274 items m^-3(mean ± SD, n = 8) and Garudtal Lake with 175 ± 108 items m^-3 (mean ± SD, n = 8). Fibre shaped particles are the dominant (84%) type, followed by fragments (12%). Particle characterisation using micro-Fourier transform infrared spectroscopy (µ-FTIR) indicated a prevalence of polyester-based materials (31%), followed by polypropylene (15%), rayon (8%) and polyethylene (6%). Most MPs were in the size range of 1000-5000 µm (53%). The rest of the particles were mainly in the size range of 300-999 µm (38%) and 100-299 µm (10%). Particles were mainly blue and pink in colour with 31% and 23% respectively. The inter relationship between the lakes with respect to the MPs characters were assessed through the multivariate statistical techniques were utilized. The quality of the water was assessed using the Pollution Load Index (PLI) and the Polymer Hazard Index (PHI). Higher PHI values (> 1000) were found to be due to the polyester present. PLI findings show that there is less MPs contamination in the water of Kumaun lakes. The abundance of MPs identified at each location was positively correlated with watershed pollution and development levels suggesting direct local inputs from anthropogenic activities such as waste management, transportation, and fishing activities.