Aircraft observations of atmospheric pollutants were made over the seas between Japan and the Asian continent in five missions since 1991. Continuous SO2 measurements were made in Nov. 1992, March 1994, Dec. 1994, and Nov. 1995. The average concentrations of SO2 were 0.93 and 0.41 ppb at altitudes of less than and greater than 2,000 m, respectively. The vertical distributions of SO2 reflected characteristics intermediate between those of the continental polluted atmosphere and the marine background atmosphere. It was also found that air masses transported from the Asian continent to Japan can be divided into 3 types: (a) China ∼ Yellow Sea ∼ Kyushu: low SO2 and high SO42-/SO2 ratio, (b) Korea ∼ western Japan: high SO2 and low SO42-/SO2 ratio, and (c) North Asia ∼ eastern Japan: low SO2 and low SO42-.
The acidity and buffering ability to precipitation acidification of atmospheric aerosols collected in Northern and Southern China and South-Kanto, Japan were measured and discussed in consideration of the local features (emission sources, soil characteristics, developing states of area, etc.) and the particle size. Generally, the acidity of water solution suspending aerosols collected in South-China was much higher than it in North-China and for the buffering ability, the inverse relation to the acidity was observed. For the size-segregated aerosols collected at several cities in China, the acidity was decreased with the increase in particle size, whereas the buffering ability was increased. These results indicated that the H+ concentrations (aerosol acidifies) and Δ Cb concentrations (aerosol buffering abilities) in aerosol-suspended water solutions varied largely, due to local site influences such as local supply of crust materials and gaseous ammonia, distance from industrial emission sources, topography, weather condition, and transportation of acidic pollutants.
Photochemical aerosol formation from cycloalkene-NOx mixtures was studied with cycloalkene initial concentration about 0.3 ppm and cycloalkene/NOx ratio about 5. Compounds studied extended from cyclopentene to cyclooctene including a few methyl derivatives. The aerosol was found to be produced mostly through the cycloalkene-O3 reaction except for the case of cyclooctene, in which the OH reaction contributed significantly. The aerosol yields from the O3 reaction were determined on the basis of the volume concentration, and they showed an increasing trend with increasing carbon number. The yields were further pursued in a cycloalkene concentration range from 0.1 to 0.01 ppm by making the O3 reaction in the dark. The yields for 0.1 ppm were found to be generally smaller than those for 0.3 ppm in accordance with our previous experiment on cyclohexene, but they stayed constant in the concentration range down to 0.01 ppm. The average carbonmass basis percent yields were much smaller than formerly believed. However they gave a consistent connection between the existing field data on cycloalkene and dicarboxylic acid concentrations.
A research work was carried out on effect of ionizing radiation on decomposition and aerosol formation from xylene and benzene contained in air to get information for the possibility to develop a new pollution control technology. Flow and batch systems were used in the experiments. Irradiation was mainly carried out by an electron accelerator. Gamma ray from Co-60 was also used to compare the effect of dose rate on decomposition reactions. The decomposition efficiencies of xylene and benzene by electron beam were about 70 % of those by gamma ray. The conversions of decomposed xylene and benzene to aerosols at 10 kGy by electron beam irradiation were 55 % and 30 %, respectively. While, those for gamma ray irradiation were 64 % and 56 %.
In order to study the roles of ions in nucleation and gas-phase chemical reactions, it is necessary to generate ions with uniform electrical mobility at a high concentration and to measure them without significant losses of ions. In the present work, we studied the performance of a newly developed ion mobility analyzer which separates ions in axial direction of gas flow. The experimental results showed that measured ions' electrical mobility distribution is not influenced by the flow rate of carrier gas and that the average mobilities of positive and negative ions are respectively 1.6 × 10-4 and 1.9 × 10-4 m2V-1s-1. Although classification characteristics of the analyzer measured by DMA-classified NaCl particles (2.5 ∼ 8 nm) was not sharp enough to obtain ions in a narrow mobility range, the ion classifier was able to distinguish ions generated in He from those in Air and N2. Further modification of the analyzer to improve classification characteristics was proposed.
Particle formation by radiolysis was observed in the neutralizer of the differential mobility analyzer (DMA) in air or N2 under presence of O3 and/or SO2. The effects of SO2 concentration, relative humidity and O3 concentration on the particle formation in the neutralizer were investigated. This particle formation may cause artifacts in aerosol size-measuring using a DMA. The particle number concentration increased with increasing of SO2 concentration and relative humidity. In low humidity condition, remarkable increase of the number concentration was observed when 0.1 ppm of O3 was added to SO2 (0.2 ppm)/N2 (H2O < 15 ppm) mixture. The mechanisms of the particle formation in the neutralizer under presence of O3 were discussed.