2014 Volume 49 Issue 6 Pages 242-251
High concentrations of PM2.5 were observed in the Kanto area from November 2–6, 2011. The PM2.5 concentrations were compared from all over Japan, and high concentrations were only observed in the Kanto area. Therefore, this episode was mainly caused not by long-range transport or trans-boundary pollution, but by local pollution. The atmosphere was generally stagnant during this period, and the atmospheric stability was stable on November 3–4 due to the formation of an inversion layer, and was neutral on November 5–6. These conditions were one of the reasons for this episode. NO3- and OC were dominantly high among the observed chemical species in the PM2.5. NO3- was particularly high on November 5–6 probably due to remarkable HNO3 production from NO under a very high humidity condition during the nighttime. NO was also irregularly high on November 3–4, which possibly implies the influence of the combustion of agricultural residues (biomass burning). The chemical species indicators of biomass burning such as K+, char-EC, and levoglucosan were also high. Thus it was suggested that the influence of biomass burning on the PM2.5 was predominant during this period. However, the influence of fossil fuel burning was observed in the southern part of the Kanto area based on the SO42- and V. Although the PM2.5 concentration is measured by methods decreasing the water content, it was estimated that the water content affected the high concentration of the observed PM2.5 during this period in comparison to the reconstructed PM2.5 concentration from the main chemical species.
