Surface ozone at four remote Island sites and the preliminary assessment of the exceedances of its critical level in Japan

Pakpong Pochanart, Hajime Akimoto, Yoshikatzu Kinjo, Hiroshi Tanimoto

Atmospheric Environment, 36 (26), 4235-4250, 2002.


Analysis of the recent surface ozone data at four remote Islands (Okinawa, Oki, Rishiri, and Ogasawara) in Japan indicated that the East Asian large-scale anthropogenic emissions significantly influence the boundary layer ozone characteristics in Japan. Due to these regional-scale emissions, an enhancement of ozone concentration associated with continental outflow occurs mostly during fall, winter, and spring. The O3 concentrations in this regional polluted continental outflow among sites are as high as 41-46 ppb in winter and 54-61 ppb in spring. Meanwhile, the marine air masses from the Pacific Ocean bring as low as 13-14 ppb of O3 at Okinawa and Ogasawara in summer but show higher O3 concentration, 24-27 ppb, at Oki and Rishiri due to the sub-regional scale pollution mainly from Japan mainland. The preliminary analysis of the exceedances of the ozone critical level using the AOT40 and SUM06 standard exposure indices indicated that the damage from high levels of O3 exposures to forests and crop yield reduction in Japan may still not be severe at the present years since the plants growing season in Japan is during the low O3 period in summer.