Spaceborne spectroscopy links dust source composition to atmospheric acidity and nitrate

Mineral dust influences atmospheric chemistry, air quality, and climate, yet its impacts remain uncertain due to limited knowledge of its mineral composition. Here we use novel spaceborne imaging spectroscopy of arid surfaces from NASA’s Earth Surface Mineral Dust Source Investigation (EMIT), together with a global chemistry model constrained by satellite-inverted dust emissions, to quantify how variability in the dust calcite fraction alters aerosol chemistry and optical properties. EMIT-derived, source-resolved calcite distributions substantially improve agreement with airborne observations and reveal large regional contrasts in dust alkalinity. These variations modulate the formation of secondary inorganic aerosols and shift aerosol acidity over a span of -4 to +3 pH units, which profoundly affects the solubility of iron and other trace metals that impact ecosystems upon deposition. The spatial pattern of calcite further controls the intensity and frequency of extreme nitrate formation events, particularly where mineral dust interacts with anthropogenic pollution in East Asia and the Middle East. Resulting changes in single scattering albedo are small and remain secondary to the much larger radiative contrasts arising from variability in iron-oxide absorption. These findings identify dust alkalinity as a dominant, previously underconstrained driver of atmospheric acidity and heterogeneous chemistry, highlighting the need to represent real-world mineral heterogeneity in global models of air quality and climate.