Deciphering the source contribution of microplastics in the glaciers of the North-Western Himalayas

Microplastics (MPs) and nanoplastics (NPs) have been largely studied in marine environments, but there lies a significant gap in assessing their occurrence and impacts in glacier environments. This study investigates the occurrence and pollution risks of MPs and NPs in glaciers, suspended air, and dry deposition across the northwestern Himalayas. MPs concentration ranged from 1000 particles m^-3 in Kolahai glacier to 151000 particles m^-3 in Thajwas glacier. In suspended air, MPs occurred at 5 particles m^-3, while dry deposition samples showed a concentration ranging from 1 to 13 particles m^-2 d^-1. Dynamic light scattering (DLS) confirmed the presence of NPs in all glaciers, with sizes varying between 31 and 689 nm in Thajwas glacier and 360-953 nm in Harmukh glacier. HYSPLIT modelling revealed that air masses reaching Himalayan glaciers predominantly originate from global sources (75 %). The pollution load index (PLI) ranged from 3.9 (hazard category I) to 40 (hazard category IV), indicating moderate to excessive pollution of glaciers. While as polymer hazard index (PHI) ranged from 10 (hazard category II) to 1987 (hazard category V), indicating medium to extreme danger due to presence of polyvinyl chloride (PVC) and polyacrylonitrile (PAN). The presence of MPs and NPs accelerate glacier melting due to their light absorbing properties highlighting need for further studies.