Study on Properties and Origins of Aerosol Particles in the Antarctic Atmosphere

   The global background air pollution has been suspected to play a part in climatic change. In order to obtain a better understanding of global air pollution, especially for aerosol pollution, extensive year-round observation of atmospheric aerosols was carried out in 1978 at Syowa Station (69°00'S, 39°35'E), Antarctica.<br>   Among aerosol particles of wide size range, submicron particles are of most importance in meteorology because of the essential role they play in cloud formation and radiation processes in the atmosphere. The items of the observation were selected so as to obtain many-sided information about submicron aerosols.<br>   Main items selected were the concentration and size distribution of Aitken particles (0.002≤radius≤0.1 μm) and Mie particles (0.18≤radius≤1 μm), the volatility of Aitken particles, and the morphology of particles (0.02≤radius≤1 μm) observed by electron microscope.<br>   For the measurement of Aitken particles was used the Pollak counter which had been improved so as to make possible the year-round measurement of concentration lower than a few hundred cm^-3 within the probable error of ±3%.<br>   From the results of these observations, in conjunction with the results which had been obtained at South Pole Station and Syowa Station by other researchers, the properties of Antarctic submicron aerosols were examined systematically, on which only a few crumbs of information had been obtained so far.<br>   Main results of analysis are as follows:<br>   (1) The seasonal and latitudinal variation of concentration of Aitken particles are closely correlated to variation in the influx of solar photons.<br>   (2) Aitken particles which disappear under furnace condition up to 500°C exist in large fractions in summer but small in winter. Sulfate or organic aerosols as commonly seen in the atmosphere have such volatile properties.<br>   (3) From April to October, the seasonal variation of Mie particle concentrations closely correlated to the seasonal variation of the influx of the northern maritime air mass, and the seasonal variation of the size distribution of Mie particles is closely correlated to the seasonal variation of the distance which the maritime air mass traverses over sea ice regions from the open sea. From November through December and February through March, when there is a plentiful supply of solar photons, the seasonal variations of the concentration and size distribution give the evidence of photochemical supplement of Mie particles in the Antarctic atmosphere.<br>   (4) Particles which can be identified as sulfuric acid droplets by their morphology observed under the electron microscope appear in summer through autumn, but disappear from winter through spring.<br>   (5) The size distribution of submicron aerosols show a bimodal shape which has a trough at 10^-6 cm in radius throughout the observation period from August to December. On the basis of this fact, it can be inferred that new particles are produced at an average rate of 10^-4 cm^-3s^-1 at least in the sunlit period in the Antarctic troposphere.<br>   The present knowledge of Antarctic aerosols thus obtained can be summarized as follows:<br>---- The future omission(over 4000 character), Please see PDF file ----