Urban heavy rains (UHR) during the summer were sequentially collected at Shinjuku by a newly-developed heavy rainwater collector. Geographical distributions of air pollutants just before UHR were also performed by a GIS in the 23 wards of Tokyo. The volume-weighted mean pH of UHR from 2012 to 2019 was 4.41 (n=16), which was lower than other types of rainfall. The total concentration of major inorganic ions in UHR was similar to that in normal rainfall and the sum of H⁺, NO₃^-, and SO₄^2-accounted for 62.3% of UHR. Compared to typhoon heavy rain, these acidic components in UHR showed a gradual decrease in concentration during the first stage and nearly constant later. The wet deposition fluxes of H⁺, NO₃^-, and SO₄^2- in UHR were 31, 20, and 15 times that in normal rainfall, respectively. A rader image analysis showed that UHR has three patterns, i.e. upper pattern, eastern pattern, and northwestern pattern. A highly concentrated area of PM_2.5 was formed near the formation area of UHR, but it disappeared before UHR. This suggests that air pollutants were transported and accumulated in the formation area of UHR, and rose to the upper and pattern involved in formation and development of cumulonimbus clouds.

Thermal power plant was recently built near an existing wind farm. The pollutant emitted from the thermal power plant is possibly affected by the rotating wind turbine at the wind farm, and the high concentration of the pollutant potentially reaches at the ground. However, the effect of the rotating wind turbine on the pollutant dispersion is less understood. In the present study, a large-eddy simulation was implemented to investigate the effect of the rotating wind turbine on the pollutant dispersion emitted from a point source. The arbitrary mesh interface technique was applied to represent the rotation of the wind turbine in the computational domain. The point sources were located upwind or downwind of the wind turbine. In the case of the upwind source location, the rotating wind turbine strongly affected the pollutant dispersion and increased the pollutant concentration at the ground level when the source height was equal to the wind turbine hub height. As the source height increased, the rotating wind turbine had less influence on the pollutant dispersion. In the case of the downwind sources where the velocity defect mostly vanishes, the pollutant dispersion was not strongly affected by the rotating wind turbine irrespective of the source height.

For obtaining scientific knowledge and information about the effectiveness of reducing the PM_2.5, photochemical oxidants and other pollutants due to the air pollution control measures, previous scientific reports were reviewed in this study. The reports were categorized into five groups and their scientific knowledge and information was summarized for each group. In conclusion, much useful knowledge about the quantitative analysis for mitigation effectiveness due to short/mid/long-term air pollution measures in China, Europe and the US, and the methodology and index for effectiveness estimation were obtained. It is expected that the scientific information will contribute to the air pollution control policy making in Japan.

To use Doppler LiDAR for continuous long-term observations for environmental impact assessment of thermal power plants, it is necessary to confirm two parameters: (i) the measurement accuracy of the wind direction and wind speed, and (ii) the annual missing rate. Several studies conducted on Doppler LiDAR have confirmed its measurement accuracy. However, few studies have compared the measurement accuracies of different models. In this study, we performed parallel observations using different Doppler LiDAR models, with steep terrains and large buildings nearby. The results showed that models having different specifications exhibit different measurement accuracies. In addition, after continuous long-term observation of four locations with different topographies and weather conditions, a clear regional difference was observed in the missing rate of the Doppler LiDAR. Although the missing rate depended on the models and the observation area, the missing rate satisfied the meteorological guidelines for safety analysis of nuclear power facilities (the annual missing rate should be less than 10%, and the sequential 30-day missing rate should be less than 30%), except at one site where the wiper was broken. We concluded that Doppler LiDAR is capable of providing continuous long-term observations throughout the year.

Water-soluble organic carbon (WSOC) in PM_2.5 at an urban site in Tokyo from April 2013 to March 2018 was measured by both manual and automated analytical methods and the sampling and analytical conditions were validated. The concentrations of WSOC in PM_2.5 collected under different linear velocities were within 10%. As for the extraction condition, the concentration of WSOC concentrations were not influenced by the different water-extract volumes. However, WSOC in PM_2.5 collected on the quartz fiber filters were approximately 20% higher than those on the PTFE filters, suggesting a positive artifact the same as the OC analysis. Regarding the automated analysis method by a continuous dichotomous aerosol chemical speciation analyzer (ACSA), the WSOC concentrations were measured by UV absorbance. While the concentration of WSOC obtained by the manual and automated analyses revealed a strong positive correlation, the slope and intercept of the monthly regression lines had a seasonal variation due to the seasonal variation of the chemical composition of WSOC. For the WSOC concentration of ACSA based on UV spectrophotometry, attention should be paid to the varying WSOC compositions by seasons and locations, thus it is necessary to verify the measured WSOC concentrations by another analytical method such as a filter analysis.