China's Gobi Dust Aerosol Characterization, Identification, Long-distance Transmission And Its Impact On The Downstream Environment In The Region

Mineral dust, originating from desert areas around the globe, is a major constituent of airborne particles in the global atmosphere. It is estimated that 1000-3000 Tg of mineral aerosols are emitted annually into the atmosphere. Dust aerosol, generated when the surface soil in the arid region of the Asian continental landmass is lifted by wind, is the major mineral aerosol transported from the East Asia to the pacific region. China Gobi desert is one of the two major source regions for Asian dust. The long-range transport of Asian dust presents significant impacts on the air quality of the down-stream cities, as well as the oceanic primary productivity and thereby global climate system.The main results of this research are as follows:(1) It was found that the ratio of Ca/Al in the aerosol in China Gobi located in Mongolia and Inner Mongolia is only-0.5, whereas it is over 1.5 over Takliamakan. This distinct difference makes the ratio of Ca/Al be used as excellent tracer to distinguish the two major source areas of Asian dust and to distinguish the out-city sources of those loacal urban areas.(2) It was found that there is a certain degree pollution of As, S, Cd, Pb, and Zn even in such a desolate area, China Gobi desert. The enrichment factors of As,S,Cd,Pb, and Zn in PM2.5 were 69.2,42.5,98.7,21.7,18.6, indicating that the air-pollutant in aerosol over Duolun not only from loacal pollution sources but also from the long-range transport.(3) The ratios of (SO42-/3)/S at DL was also found to be lower than the dust from other source regions, indicating that China Gobi desert tends to send more insoluble S compared to other source regions which may have a distinct impact on the air quality downstreams and climate change.Another part of this research is as follows:A dust aerosol sampling network consisting of four ground sites were operated to monitor the China dust events and the median/long range dust transport from north to south China, in spring of 2007. Combined with the backward/forward air mass trajectories analysis, the main low-Ca dust source from the northern China/Mongolia and the transport pathway from the Northern/Northeastern low Ca dust source regions to Shanghai, a downstream site in the Yangtze River Basin, were identified with the Ca/Al elemental tracer analysis. The chemical characterization of dust transport was conducted with examining the variations of mass concentrations, elemental/ionic compositions of dust from site to site.