Neutralization of Acidic Sulfur Species by Calcite in Mineral Aerosols Collected in China and Japan Studied by Ca K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy

Neutralization of Acidic Sulfur Species by Calcite in Mineral Aerosols Collected in China and Japan Studied by Ca K-Edge X-Ray Absorption Near-Edge Structure Spectroscopy X-ray absorption near-edge structure studies at the calcium K-edge have been used to show that acidic sulfur species in the atmosphere (e.g., H2SO4), mainly released by human activities, can be neutralized by the calcite present in mineral aerosols produced in the arid areas of western China. In the neutralization process, gypsum is secondarily formed from the calcite in the aerosol. These processes are suggested since the gypsum fraction of the total Ca content increases with increasing transportation distance of the “Kosa” aerosol particles. In addition, use of the surface sensitive conversion electron yield method showed that gypsum is preferentially present at the surface of the particles.