Mixture of Kosa (Asian dust) and bioaerosols detected in the atmosphere over the Kosa particles source regions with balloon-borne measurements: possibility of long-range transport

Long-range transport of atmospheric microbiota with Asian dust (Kosa) particles is of great concern in Northeast Asia in view of the health effect of Kosa particles on human being, disturbance of ecosystems caused through invasion of new microbe, contribution of microorganisms to biogeochemical cycle on global/regional scales, and others. Information on atmospheric microbes over the desert areas has been desired for a long time. Detection of atmospheric microbiota on the desert regions, on the base of balloon-borne measurements, has been made at Dunhuang, China (40 degrees 00' N, 94 degrees 30' E; east end of Taklamakan desert) in the summer of 2007. The measurements showed that microbiota mixed internally with Kosa particles were frequently floating from the ground to about 2-km heights (above sea level), and possible long-range transport of atmospheric microbiota with dust particles taking local circulations is strongly suggested, causing active mixing of atmospheric dust over the Taklamakan desert from the ground to the free troposphere where westerly jet dominates (Iwasaka et al. in J Geophys Res 108:8652, 2003a, J Geophys Res 108:8644, b). The concentration of the mixed particles of Kosa and microbiota having a size larger than about 1 mu m in diameter is estimated to be about 1 particle/cm(3) at those heights on the basis of measurements of particle concentration with an optical particle counter and analysis of particles having fluorescence light due to dye of DAPI (4'6-diamidino-2 phenylindole) with an epifluorescence microscope. The mixing situation of microbiota and Kosa particles is the important factor controlling atmospheric lifetime of floating microbiota, since the mixing state certainly can protect microbiota from stressful environments [dryness, solar ultraviolet (UV) radiation, low temperature] in the atmosphere, and therefore, it is useful to discuss the data of the first description of microbiota in the atmosphere on the Taklamakan desert.