Measuring mine dust contamination of snow in northern Sweden using optical remote sensing

Mineral dust is produced as a by-product when mining for metals such as iron and rare-earth elements. Around mines in the Arctic and Subarctic, this dust is transported by wind and deposited on the snow surface, contaminating the seasonal snowpack. The presence of mine dust darkens the snow surface, resulting in a lower snowpack albedo. Due to their lowered albedo, seasonal snowpacks that contain mine dust experience accelerated melting. Nordic countries, including Sweden, are showing an increasing interest in the expansion of mining activities due to increasing demand for metals to use in technology and a desire to produce raw materials within Europe. The Kirunavaara mine in the Swedish Arctic is Europe’s largest iron mine, and is an accordingly large source of mineral dust, which spreads around the adjacent town of Kiruna and the surrounding areas.One possible approach to quantify mine dust contamination of the seasonal snowpack is using optical remote sensing. The change in spectral reflectance of the contaminated snow surface is used to infer optical properties and the concentration of mine dust in the surface snow. Spectral indices and radiative transfer modelling are applied to the spectral reflectance data to retrieve dust concentrations. We have measured dust concentrations in snow around Kiruna during spring 2025, and measured reflectance of the affected snow surfaces. Snow darkening in Kiruna occurs predominantly in the area located downwind from the mine where dust concentrations in snow are highest. Dust loadings in surface snow around Kiruna reach over 2000ppm, with associated snow broadband albedo values as low as 0.3 in the most heavily contaminated areas. There is a clear relationship between broadband albedo and mine dust concentrations in the surface snow. However, the spectral signatures of the contaminated snow surface show that iron mine dust darkens the snow relatively evenly across all wavelengths of visible light. Combined with the high dust loading, this even darkening effect means that previously established spectral indices for minerals dust in snow are not applicable in the case of iron dust contamination, and an approach tailored specifically to this type of dust is required.