Abstract Number: 677 Working Group: Bioaerosols: Characterization and Environmental Impact
Abstract The Japanese cedar is widely distributed over Japan and emits large amount of pollen into the atmosphere. The cedar pollen is causing the pollinosis that is most common in Japan. The bioaerosols (bacteria, pollen, spores, etc.) have been shown to have significant impacts both on human health and on climate. However, ice nucleation activity of pollen has been investigated only by a few experiments. The purpose of this study is to investigate the climate impact of the cedar pollen, a species characteristically found in Japan. In order to probe the vertical distribution of the pollen grains as well as their derivative substances in atmosphere, samples were collected at altitudes of 10m, 500m, 1000m and 2500m, over Noto peninsula onboard a helicopter in spring 2013. In addition to the pollen grains themselves, the distributions of the allergens specific to Japanese cedar (namely, Cry j1 and Cry j2) were also investigated as the proxies for the pollen derived substances. These derivatives were measured in order to test the suspected release of allergens from the pollen grains for example following rainfall. In one case, we detected Cry j2 even at altitudes as high as 2500m, with maximum concentration found at 1000m. In addition, the ice nucleation activity of the pollen was investigated in the laboratory by cooling the grain suspension in pure water. We chose Arizona Test Dust (ATD) as reference ice nuclei. The result showed that numbers of ice nuclei per mg of the pollen (or its extracts) were lower than that of ATD. Thus, it was suggested that Japanese cedar could potentially inject significant amount of pollen and related derivatives into the altitudes relevant for aerosol-cloud interactions. At the same time however, their impact on ice cloud formation could be considered modest as compared mineral dust aerosol.