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Satellite-model global long-term mean (2004–2008) PM2.5 composition. PM2.5 composition is represented as dry mass. Abbreviations are Secondary Inorganic Aerosol (SIA; the sum of SO42–, NO3– ,and NH4+), Organic Mass (OM), and Black Carbon (BC). Gray denotes water. Values from in situ observations are overlaid as colored circles. SI Table S1 contains the detailed comparison statistics.
