Major atmospheric particulate matter sources for glaciers in Coquimbo Region, Chile.

Tapado Glacier is a subtropical mountain glacier in the Coquimbo region of Chile that has been continuously retreating during the last 60 years due to diminishing precipitation rates and rising temperatures and likely due to a currently unknown influence from atmospheric pollutant deposition. Climatic and meteorological impacts on this, and other, Andean glacier have been previously studied; however, cryosphere changes driven by aerosols are still largely unknown. To contribute to the understanding of the origin of aerosols and their dispersion, this study aims to identify natural and anthropogenic sources of air pollution deposited on the Tapado Glacier (4500-5536 m a.s.l.) and their transport by using a receptor model (positive matrix factorization) together with the concentration of major ions as proxies of air pollution deposited on this glacier. This model's outcomes were complemented with daily wind backward trajectories computed for a whole year using the HYSPLYT meteorological model. Four sources were identified as the main contributors to major soluble ions in the Tapado surface snow. These sources are natural Aeolian dust (38%) from the Atacama Desert (including mining sites), natural weathered sulphates (27%), anthropogenic nitrates (25%), and coastal aerosols (10%). Coastal nitrate emissions and coastal aerosols are both sources with an important anthropogenic component, coming from La Serena and Coquimbo's coastal cities. The crustal components and sulphate profiles are similar to detritus dispersed from the glacier after wind erosion. Although the glacier is located over 4000 m above sea level, anthropogenic pollutants reached this location. However, their contributions were smaller compared to natural contaminants. Our findings can likely be extended to the nearest glaciers in Northern Chile, which have similar potential contaminant sources from cities, ports, and thriving mining activity. However, these findings may not be suitable for southern Chilean glaciers, which are closer to bigger cities and to smoke from residential heating prevalent in winter months and wildfires during the summer.