Characterization and sources of aerosol particles over the southeastern Tibetan Plateau during the Southeast Asia biomass-burning season

The Tibetan Plateau is one of the highest regions in the world, exerting profound influence on the large-scale atmospheric circulation of Asia and the global climate. Here we report ambient concentrations of black carbon (BC), aerosol mass (PM2.5 and PM10) and associated carbonaceous species and water-soluble inorganic ions from a remote mountain site in the southeastern part of the Tibetan Plateau during spring, in order to characterize the major sources contributing to the ambient aerosol in the background atmosphere of Southeast Asia. Significant build-up of aerosol and BC concentrations was observed during a dry period, accompanied by the occurrence of fires and transport of pollution from the nearby regions of Southeast Asia and the northern part of the Indian Peninsula. The concentrations of BC, PM2.5 and PM10 mass reached maximum hourly values of 1470 ng m-3, 107 and 117 mu g m-3, respectively. Organic carbon (OC), elemental carbon (EC) and sulfate were the predominant aerosol components. OC showed strong correlations with EC (R2 = 0.93 for PM2.5 and 0.74 for PM10) and non-sea-salt potassium, especially in fine aerosol (R2 = 0.95). In addition, the relative change rates of K+ against OC reached characteristically high values, highlighting the important contributions of biomass-burning smoke.