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Volume 18, issue 11 | Copyright

Special issue: Anthropogenic dust and its climate impact

Atmos. Chem. Phys., 18, 8155-8171, 2018
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 08 Jun 2018

Research article | 08 Jun 2018

Long-range-transported bioaerosols captured in snow cover on Mount Tateyama, Japan: impacts of Asian-dust events on airborne bacterial dynamics relating to ice-nucleation activities

Teruya Maki1, Shogo Furumoto1, Yuya Asahi1, Kevin C. Lee2, Koichi Watanabe3, Kazuma Aoki4, Masataka Murakami5, Takuya Tajiri5, Hiroshi Hasegawa1, Asami Mashio1, and Yasunobu Iwasaka6 Teruya Maki et al.
  • 1College of Science and Engineering, Kanazawa University, Kakuma, Kanazawa, Ishikawa, 920-1192, Japan
  • 2School of Science, Auckland University of Technology, Private Bag 92006, Auckland 1142, New Zealand
  • 3Department of Environmental and Civil Engineering, Faculty of Engineering, Toyama Prefectural University, 5180 Kurokawa, Imizu, Toyama 939-0398, Japan
  • 4Department of Earth Sciences, Faculty of Science, University of Toyama 3190 Gofuku, Toyama 930-8555, Japan
  • 5Cloud Physics Section, Forecast Research Department, Meteorological Research Institute, Nagamine 1-1, Tsukuba, Ibaraki 305-0052, Japan
  • 6Community Research Service Group, University of Shiga Prefecture, 2500 Yasakamachi, Hikoneshi, Shiga, 522-8533, Japan

Abstract. The westerly wind travelling at high altitudes over eastern Asia transports aerosols from the Asian deserts and urban areas to downwind areas such as Japan. These long-range-transported aerosols include not only mineral particles but also microbial particles (bioaerosols), that impact the ice-cloud formation processes as ice nuclei. However, the detailed relations of airborne bacterial dynamics to ice nucleation in high-elevation aerosols have not been investigated. Here, we used the aerosol particles captured in the snow cover at altitudes of 2450m on Mt Tateyama to investigate sequential changes in the ice-nucleation activities and bacterial communities in aerosols and elucidate the relationships between the two processes. After stratification of the snow layers formed on the walls of a snow pit on Mt Tateyama, snow samples, including aerosol particles, were collected from 70 layers at the lower (winter accumulation) and upper (spring accumulation) parts of the snow wall. The aerosols recorded in the lower parts mainly came from Siberia (Russia), northern Asia and the Sea of Japan, whereas those in the upper parts showed an increase in Asian dust particles originating from the desert regions and industrial coasts of Asia. The snow samples exhibited high levels of ice nucleation corresponding to the increase in Asian dust particles. Amplicon sequencing analysis using 16S rRNA genes revealed that the bacterial communities in the snow samples predominately included plant associated and marine bacteria (phyla Proteobacteria) during winter, whereas during spring, when dust events arrived frequently, the majority were terrestrial bacteria of phyla Actinobacteria and Firmicutes. The relative abundances of Firmicutes (Bacilli) showed a significant positive relationship with the ice nucleation in snow samples. Presumably, Asian dust events change the airborne bacterial communities over Mt Tateyama and carry terrestrial bacterial populations, which possibly induce ice-nucleation activities, thereby indirectly impacting climate change.

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Atmospheric bacteria are thought to act as ice nuclei influencing the cloud formation. We used the aerosols captured in the snow cover on alpine mountain to investigate the sequential changes of ice-nucleation activities and bacterial communities at high elevation. The snow-cover samples exhibited high ice nucleation corresponding to the increase in natural and anthropogenic dust particles. Terrestrial bacteria (Bacilli) recorded in snow cover increased in relation to ice-nucleation activities.
Atmospheric bacteria are thought to act as ice nuclei influencing the cloud formation. We used...