We developed a quick update method for an emission inventory with an inverse technique, and extended the Chinese anthropogenic NO_x emission in Regional Emission inventory in the ASia version 2.1 (REAS 2.1) through 2009–May 2013 with satellite observations and a chemical transport model. The satellite observations exhibited a drastic inter-annual variation in the tropospheric NO₂ vertical column densities (VCDs) over the eastern Chinese region depending on the socioeconomic conditions. The increase in the NO₂ VCD became sluggish during 2008–2009 due to pollutant controls by the 2008 Beijing Olympic game and the global depression, but revived in 2010 with a growth rate of 37.3%/year. A posteriori NO₂ VCD successfully reproduced the inter-annual variation in the observed one, and captured the observed seasonal cycle in which the seasonal peak and bottom appear in the winter and summer, respectively. The updated Chinese anthropogenic NO_x emissions during 2009–2012 were 25.7, 27.3, 28.2, 28.4 Tg/year and fell within the range of the various estimates in the literature. We estimated an annual growth rate during 2009–2012 and 2005–2012 to be 3.5%/year (0.9 Tg/year) and 5.3%/year (1.1 Tg/year), respectively.

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The concentrations of more than 100 VOC species have been measured at three sites in Tokyo to estimate the source apportionment considering chemical loss during the summer high ozone concentration period. The photochemical initial concentrations (PICs), the levels of VOCs from sources before undergoing chemical reactions, have been calculated from the reactivity of the VOCs with OH radicals and the ethylene/1,3-butadiene ratio. When the ethylene/1,3-butadiene ratio is set to 17, the PICs are 1.4 times higher than the observed concentrations indicating a 30% chemical loss of emitted VOCs in the summer daytime. The PIC values depend on the value of the ethylene/1,3-butadiene ratio. Isoprene is the most affected because of its high reactivity. The CMB analysis using PICs have yielded better results, when comparing to the VOCs emission inventories. Diesel vehicle exhaust is the greatest source in the center of Tokyo while the biogenic source of isoprene is the highest in the site close to a mountain area. Gasoline vehicle exhaust, gasoline vapor (refueling loss and diurnal breathing loss), and coating are also important sources. Ethylene, formaldehyde, aromatics and other alkenes provide high contributions as a single substance.

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We conducted wind-tunnel experiments to study the atmospheric dispersion over a two-dimensional ridge considering the plume rise process of exhaust air from a cooling tower. The stacks were located at the upstream foot or downstream foot of the ridge. Two different model surfaces, aerodynamically smooth and rough surfaces, were used in the experiments. Exhaust air from the downstream foot of the ridge was immediately trapped by the recirculation flow forming behind the ridge. Although the maximum surface concentration appeared in the vicinity of the source for this case, the amplification factor of the maximum surface concentration from the flat case was limited due to the increase in the horizontal dispersion parameters by the wake flow of the ridge. The decrease in wind speed in the wake region of the ridge also mitigated the increase in the maximum surface concentration by enhancing the initial plume rise of the exhaust air.

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The high ozone concentration in urban atmospheres including Tokyo is still one of the important environmental issues. One of the possible causes is ozone formation by unconsidered VOC. In this study, we performed chamber experiments to understand the importance of biogenic VOCs emitted from urban green flora. Isoprene and α-pinene were added to ambient air and irradiated by UV. The ozone and formaldehyde concentrations were measured to compare the ozone formation potential with the control. The ozone formation potential of isoprene was also compared to that of toluene. Considering the typical emission rates of isoprene and α-pinene, 10 and 0.7 ppbv of these VOCs were separately added to the ambient air in the chamber. Both isoprene and α-pinene showed approximately 30% higher ozone concentrations compared to the control after 6 h of UV irradiation. On the other hand, isoprene showed a 33% higher ozone concentration than toluene for a 10 ppbv addition to the ambient air after 6 h of reaction. This means that the ozone formation by biogenic VOC is important as well as that of anthropogenic VOCs, such as toluene, which is a typical anthropogenic VOC. The possibility that biogenic VOCs emitted from green areas and street trees are important for ozone formation has been suggested by this study.

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We investigated whether nitrogen (N₂) can be substituted for helium (He) as a carrier gas for thermal/optical carbon analysis. Eighteen filter samples of atmospheric and combustion source particles and two powder standard reference material samples (urban dust: SRM1649a and diesel exhaust particles: SRM1650b) put on filters were analyzed using both carrier gases then the peak abundances and shapes and the quantitated values were compared. For the filter samples, the total carbon (TC) concentrations and the elemental carbon (EC)/TC ratios using the N₂ carrier were >20% lower than those for the He carrier for two low concentration samples (<10 μgC) when the usual linear calibration curve was used. However, the TC concentrations using the N₂ carrier became consistent within 20% with those for the He carrier for all the filter samples when the quartic calibration curve was used. The EC/TC ratios using the N₂ carrier of 16 filter samples agreed within 20% of those for the He carrier. For the SRMs, the TC concentrations and the EC/TC ratios using the N₂ carrier agreed within 6% of those for the He carrier. Thus, the N₂-carrier measurements can provide results of the TC concentrations and the EC/TC ratios equivalent to those for the He carrier, although attention is required for low level samples.

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