We have developed a system that can measure OH reactivity by laser spectroscopy. Simultaneous measurements of the OH reactivity and reactive trace species were performed in various atmospheric environments. The OH reactivities derived from a chemical composition analysis were compared with direct measurements by the pump-probe laser method. As a result of observations at many places, such as areas with active anthropogenic activities (central area in Tokyo, Yokohama), suburban areas (Hachioji, Tsukuba, Kyoto), and forest (Manitou Colorado, Arida Wakayama, Tama hills), 120 kinds of VOCs and other reactive species were determined. However, 25–50% of an unknown reactivity was ubiquitously observed. In addition to ambient air observations to search for the origin of the unknown reactivity, analysis of the gas emitted from a single plant, exhaust gas analysis of gasoline cars by a chassis dynamometer, and analysis of air in which a photochemical reaction occurred in a smog chamber were conducted. As a result, the unknown reactivities could be responsible for the nonmeasured VOCs either of plant or anthropogenic origin and secondary VOCs generated in the atmosphere.

Plants support the lives of heterotrophs such as oxygen-consuming organisms including human beings. However, the atmospheric environment of plants has been changing, and probably getting worse, due to our industrial activity. Many researchers have indicated the adverse effects of air pollutants on plants based on their many studies on the effects of SO₂, NO₂, acid deposition, such as acid rain, particulate matter, and photochemical oxidants, such as tropospheric ozone (O₃), on plants. To expand the knowledge and develop the discussion on the effects of air pollutants on plants, I have conducted experimental studies regarding the effects of fine particulate matter (PM_2.5) and O₃ on plants. In the present paper, I have summarized the results obtained from the experimental studies on the long-term effects of black carbon (BC) and ammonium sulfate (AMS) particles on plants, and those on the evaluation of O₃ effects on plants based on the cumulative stomatal O₃ uptake. Moreover, I introduced the experiments conducted in Nagasaki, Japan, where the transboundary air pollution has been frequently observed, in order to evaluate effects of the long-range transported air pollutants such as PM_2.5 and O₃ on plants.

For the environmental impact assessment of thermal power plants, it is necessary to determine the wind speed distribution inside an outdoor-type coal storage yard to predict coal dust scattering. In this study, a computational fluid dynamics (CFD) model was developed for prediction of the wind velocity distribution in the coal storage yards. This model is based on a large-eddy simulation and can accurately consider the effect of wind fences with a wide range of opening ratios. The validity of the model was confirmed by comparing it to two types of wind-tunnel experiments; one is for the wake of a quasi-two-dimensional wind fence, while the other is for the wind field inside a coal storage yard, including its buildings and coal piles. We confirmed that the CFD model can accurately reproduce both types of wind fields with a slight overestimation. In addition, we predicted the amount of coal dust deposition using the wind speeds obtained from the wind-tunnel experiment and CFD model. Although the method based on the CFD model tends to overestimate the amount of deposition compared to the wind-tunnel based method, it was shown that the distribution shape and scattering range of the coal dust were similar for both methods.

Correlations between high concentrations of ozone in ambient air and high air temperatures such as daily maxima in a target area are studied with using official monitoring data. The summer ozone data from the Tokyo metropolitan area in two periods since 2001, during which the ozone precursor (NO_x and NMHC) concentration levels were kept comparatively stable, were statistically analyzed along with temperature data from the Saitama AMeDAS (Urawa). The maximum ozone concentration, when averaged for every summer, is highly correlated the with number of days with a clear sky, rather than the air temperature. In order to focus on the contribution of the air temperature, exclusion of cloudy/rainy days from the statistics, and furthermore, extraction of sample days of similar weather and wind patterns, become required. As a result, the daily maxima of the ozone concentrations have a clear dependence on the maximum temperature only in its range above 33 deg. C, and is sharply influenced at about 37 deg. C and above, which occurs frequently in recent years. In this very high temperature range, no ozone reduction due to decreases in NMHC is observed in the examined periods.