Iron Variability Reveals the Interface Effects of Aerosol‐Pollutant Interactions on the Glacier Surface of Tibetan Plateau

Abstract

AbstractIron (Fe) as a limiting nutrient has profound impacts on ecosystems and the global biogeochemical cycle. Field observations were made at the atmosphere—snowpack interface in various glaciers of the Tibetan Plateau. The formand chemical properties of the Fe detected were investigated in laboratory using TEM‐EDX measurements, to obtain insights in the content and sources of Fe in aerosol pollutants in glaciers, as well as micro‐structure changes and their environmental effects, as well as interface transformation dynamics. We find that Fe occurs in forms of aggregated and single particulates with diameter d < 5 μm. The Fe particulates collected from different locations show clear spatial heterogeneity, with fly ash and soot constituting the major components of anthropogenic Fe. The concentration of Fe aggregates with pollutants (e.g., sulfate and nitrate) is dominant in regions close to the areas of human activity. Moreover, in the remote areas of the interior plateau, an increased concentration of mineral Fe particles is found in the aggregates. These observations are crucial to elucidate the evolution processes of pollutant‐Fe mixing, from generation or emission through anthropogenic activities to accumulation in remote areas and modification of Fe occurrence form during transportation. Our results also show that, during interface deposition, soluble Fe particle concentration increased by 13.8% on average, as Fe solutes with sulfate‐coating enhances of the dissolution of Fe in fly ash‐soot and minerals—a process that produces large quantities of ultrafine Fe particle under reductive dissolution in snowpack. Overall, these changes significantly contribute to enhancing the bioavailable iron content in the study areas affecting thereby the glacier ecosystem.