Abstract
It has been proposed that the sensitivity regimes of ozone concentrations to precursor emissions can be estimated by measurements of the parameters called photochemical indicators, i.e., the concentration ratios of several secondary formed species, for each location. In the present study, we first evaluated whether these parameters were also applicable for the Kanto area, Japan, using the simulation results from a companion paper. This evaluation indicated that the ozone / total nitrate concentration ratio was applicable with the derived threshold values of 8.6 (or below) and 9.0 (or above) for discerning the VOC-sensitive and NOx-sensitive regimes, respectively. Hence, we measured the total nitrate concentrations and derived the ozone / total nitrate concentration ratios at five sites in Tokyo and Saitama prefecture on several days with a clear sky and high air temperature in the summer, during which warning-level ozone was easily formed, and then evaluated the sensitivity regimes at these locations. The results showed that the sensitivity regimes were NOx-sensitive at all the measurement sites except for two sites within the urban center. These results, based on the measurements of the ozone / total nitrate concentration ratio, were almost consistent with the simulation results from the companion paper, obtained using BVOC emission estimates which were derived by considering recent emission measurements for Japanese native plant species.
