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Particle surfaces of mineral aerosols are important reaction sites in the atmosphere. Previous studies suggested that calcite in aerosols, which are emitted during dust periods, neutralizes sulfuric acid. In this study, depth-dependent X-ray absorption fine structure spectroscopy for individual particles was employed to determine calcium (Ca) species at particle surface and in the bulk of individual particles, using an X-ray microbeam measured in the conversion electron yield and fluorescence yield modes, which is a powerful method to understand chemical processes at aerosol surfaces.