We discuss the issues about automobile related aerosols and the condensation dust in combustion sources. Measurements in a traffic intersection showed the long-term trend of a decreasing of PM_2.5 due to the tightening of emission controls, while the number concentration did not. The spatial distribution of the particle number was also measured around the traffic intersection. It suggested that nanoparticles had a very short life which depended on the temperature and particle size. Due to cleaner diesel exhausts, soot generation from the direct ignition gasoline vehicle, generated secondary organic aerosols (SOAs) from exhausts, and generation of transition metals from non-combustion sources may be more important in the future.

The condensation dust included semi-volatile organic material, which is a candidate of the missing source of primary OAs as well as precursors of SOA. The emission factor of the condensation dust is changeable because it depends on the temperature and concentrations of the co-generated particulate matter. To prevent this problem, the new methodology of volatility distribution was used to indicate the emission factor of the condensation dust. To improve the PM_2.5 prediction in the air quality model, development of a measurement method of the volatility distribution and the accumulation of data of various types of emission sources are needed.

PM_2.5 is fine particulate matter of less than 2.5 micrometers in diameter under ambient conditions. The health disorders, such as respiratory, lung, and cardiovascular illness to PM_2.5 pollution are serious social issues. The most abundant particulate in the PM_2.5 is water-soluble particulates such as ammonium sulfate formed secondarily in the atmosphere. We have investigated the effect of ammonium sulfate on the degranulation of the mast cell line C57 cells. As the results, ammonium sulfate (initial reaction concentration of 1 mM) significantly caused degranulation of the C57 cells. Also, ammonium sulfate at the initial reaction concentration of 1 mM significantly enhanced the C57 cells degranulation induced by a stimulant (thapsigargin). Furthermore, it has been found that the ammonium ion in the ammonium sulfate contributed to the degranulation of the C57 cells. Therefore, it is suggested that inhalation of a high concentration ammonium ions in the PM_2.5 leads to mast cell degranulation and enhanced mast cell degranulation.

A numerical model for the environmental impact assessment of geothermal power plants was developed. The model was based on the Large Eddy Simulation (LES) that accurately takes into account the effects of plume rise, surrounding buildings and geophysical features. A new grid generation program for the LES was also included in the model. We carried out wind tunnel experiments to validate our numerical model. Based on the validation results, our numerical model represented the characteristics of the surface concentration obtained by the wind tunnel experiments. We concluded that our numerical model was applicable for the environmental impact assessment of geothermal power plants as an alternative to wind tunnel experiments.

Each size collection and analysis of carbon and metal components in the PM_0.1 and PM_2.5 were performed by day and night at a suburban site in each season from 2014 to 2015. Based on the results of daily behavior, it was confirmed that the components in the PM_0.1 and PM_2.5 were influenced by the weather conditions, and daily variation of those concentrations were influenced by the local emission sources and weather conditions. The ratios of the components in the PM_0.1 and PM_2.5 indicated two different concentration patterns of the components. One received a large source contribution through the year at a constant ratio, and the other received various source contributions in each season. Therefore, the latter showed different ratios in each season. Furthermore, it was suggested that the contribution of the photochemical reaction was greater for PM_0.1 and the condensation effect was greater for PM_2.5. In the case of the particle formation of PM_0.1 which was strongly affected by the photochemical reaction, the organic components contributed to the secondary particle formation by self-condensation, especially in the summer. On the other hand, in the case of particle formation of PM_2.5, which was strongly affected by the condensation and coagulation with the decreasing temperature or mixing layer, the metal components affected the condensable particle formation and growth as nuclei particles by mixing the organic carbon components, especially in the winter.

In order to investigate the actual situation of open burning and its influence on the PM_2.5, several measurements and data analyses were carried out. The number of complaints and patrols of open burning recorded by local governments in the Saitama prefecture tended to increase in the autumn. The monthly frequency of day observed over a 35 μg/m³ daily average PM_2.5 (the short-term environmental standard) in Kazo was higher in the autumn and winter. The chemical components of four cases when the PM_2.5 was especially high were compared. The organic carbon and nitrate were higher among the major components in all cases, and the influences of the biomass burning and waste incineration were suggested. On the other hand, it was also suggested that a high PM_2.5 concentration was relevant to meteorological conditions such as a low wind speed, high relative humidity, and stable atmospheric situation. In addition, it was frequently seen that the number of hits of open burning searched in social networking services increased on the weekend, on a rainy day, and on the day before the rain, and the PM_2.5 increased around these days in some cases. These facts are possibly relevant to the situation of farmwork and open burning of riverbeds and mountains. The score defined by the conditions that the PM_2.5 could become higher was applied to the cases over the short-term environmental standard in Kazo and roughly correlated with the daily average PM_2.5.