Astudy on the establishment of environmental standard of photochemical oxidants for protecting plants

本研究调查了光化学氧化剂的主要成分臭氧（O3）对日本近郊作物生长和产量的影响，并评价了保护植物的环境标准。日本关东郊区种植的作物对O_3的生长和产量敏感性差异较大。根据O_3对作物产量影响的实验研究结果，认为评价O_3对作物产量影响最合适的O_3参数为AOT30 （O_3超过30 ppb阈值的累积剂量）。我们建议将AOT30的1.5 ppm h（9:00-16:00）作为保护日本郊区农作物产量的O_3临界水平。在东京都和埼玉县的大部分地区，7 - 9月O_3的AOT30在1.5 ppm h以上。结果表明，在O_3浓度和剂量较高的东京都西部地区和埼玉县北部地区，O_3对5种作物（小松、青根菜、芜菁、花菊和洋葱）的诱导减产率为11-35%。因此，为了保护植物，应尽快建立光化学氧化剂的环境标准。

In the present study, we investigated the effects of ozone (O3), a major component of photochemical oxidants, on growth and yield of crops cultivating in the suburban areas of Japan and evaluated environmental standard for protecting plants. There was great difference in the sensitivity of growth and yield in O_3 among the crops cultivating in the suburban areas of Kanto-district of Japan. Based on the results of experimental study on the effects of O_3 on yield of crops, the most suitable O_3 parameter for evaluating the effects of O_3 on the yield of crops was considered to be AOT30 (accumulated dose over a threshold of 30 ppb of O_3). We propose 1.5 ppm h of AOT30 (9:00-16:00) as critical level of O_3 for protecting the yield of crops cultivating in the suburban areas of Japan. In most areas of Tokyo Metropolis and Saitama Prefecture, AOT30 of O_3 is above 1.5 ppm h from July to September. We evaluated O_3-induced yield reduction of 5 crops (komatsuna, quing-geng-cai, turnip, garland chrysanthemum and welsh onion) from July to September As a result, the O_3-induced reduction rate of the 5 crops was estimated to be 11-35% in the western part of Tokyo Metropolis and northern part of Saitama Prefecture where the concentration and dose of O_3 are relatively high. Therefore, we should establish environmental standard of photochemical oxidants for protecting plants as soon as possible.