GAW Report No. 205 - IGAC Project

CHAPTER 3 - ASIAFigure 34 - NOX emission rates over the East Asia (left) and Kansai area (right). Numbers indicate six prefectures in theKansai area (1, Osaka; 2, Hyogo; 3, Kyoto; 4, Shiga; 5, Nara; 6, Wakayama).Red points in the right panel show the locations of monitoring stations in the AEROS networkEmissions sources and regulationsIn the entire Kansai area, motor vehicles accounted for 75%, 50%, 42%, 15%, and 5% ofemissions of CO, PM 2.5 , NO X , VOCs, and SO 2 , respectively, in 2000 [Table 14, Kannari et al., 2007].Large point sources were the largest contributors to SO 2 emissions (~46%) and other transportsector sources (mostly ships) were the second largest contributors (37%). Stationary evaporativesources were the largest contributors to VOCs emissions (~48%) and biogenic sources were thesecond largest (35%).Table 14 - Source contributions to NOX, SO2, PM2.5, VOC, and CO emissions (Gg/year) over the Kansai area in 2000estimated in the EAGrid inventory (Kannari et al., 2007)NOX SO2 PM2.5 VOC COLarge point sources 85 24% 42 46% 4.0 21% 2.9 1% 148 19%Other point sources 16 5% 11 11% 1.2 6% 1.6 0% 19 2%Motor vehicles 149 42% 4.2 5% 9.7 50% 79 15% 598 75%Off-road vehicles 24 7% 0.5 0% 0.8 4% 3.0 1% 26 3%Other transport 78 22% 34 37% 3.8 20% 3.7 1% 8.9 1%Stationary evaporativesources248 48%Biogenic 179 35%Total 352 92 20 517 800Trends of ozone and its precursorsWakamatsu et al. [1996] reported that maximum hourly oxidant concentrations in the OsakaBay area showed a decreasing trend during 1978–1990 (Figure 35). By contrast, increasing trendswere observed in the inland Kyoto and Nara areas. The locations where daily maximum oxidantconcentrations were observed tended to move further away from the emission area of the OsakaBay area to the Kansai area. Concentrations of non-methane hydrocarbons (NMHCs) greatlydecreased during the 1970s and 1980s, whereas NO X concentrations did not show any significanttrend. As a result, ratios of the NMHCs concentration to the NO X concentration decreased. Thedecrease of NMHCs indicates a decrease in photochemical reactivity, which leads to a decrease inthe photochemical reaction rate. By contrast, the increase in the NO X /NMHCs ratio caused anincrease in the O 3 formation potential. Higher concentrations of O 3 are usually observed near theshore in the morning, and as the sea-breeze penetrates inland, the high O 3 concentration area also105