Study on the mechanisms of the 2〜3 year variation in the increasing trend of oxidant in the urban air

(1)大气污染物和气象要素数据集的收集和分析我们获得了爱知县1991 - 2001年的大气污染物数据集以及名古屋的气象数据集。我们确定了这一变化明确的时期（1985-1998年）。由于名古屋氧化剂浓度的时间变化与臭氧（O_3）浓度的时间变化密切相关，因此氧化剂浓度的2-3年变化可以看作是名古屋O_3浓度的变化。此外，还对O_3的前体物NO_x和NMHC（总）进行了采集和分析，发现它们的变化趋势相似。(2)对日本上空自由对流层和北太平洋西部海洋边界层O_3资料的分析表明，上覆自由对流层中O_3的原位光化学反应和输送控制着O_3浓度。夏季，北太平洋O_3的输送也会影响名古屋的O_3。因此，我们分析了1994年至1997年期间自由对流层和小笠原岛O_3浓度的行为。(3)名古屋地区C_2~C_ NMHCs的测定<11>为了了解O_3产生过程中光化学过程的变化，需要了解NMHCs各组分的变化。采用GC/FID和空气采样装置，研制了非甲烷总烃各组分（C_2-C_3）的连续测定系统<11>，获得了C_2-C_3的非甲烷总烃数据<11>。特别是春、夏季NMHC/NOx比值的增加可以用生物源NMHC（异戊二烯）排放的增加来解释，这一结果有助于探讨其机制，但尚未揭示城市空气中氧化剂2-3年变化的机制。现在，我们正在研究明确定义的时期和未定义的时期之间的过程差异，以揭示控制这种变化的因素。

(1) Collection and analyses of datasets for atmospheric pollutants and meteorological elementsWe obtained the atmospheric pollutants datasets of Aichi prefecture from 1991 to 2001 as well as the meteorological datasets at Nagoya. We identified the period when this variation was well defined (1985-1998). Since temporal variation in the oxidant concentration in Nagoya was closely related with that in ozone (O_3), this 2-3 year variation in oxidant can be regarded as that in O_3 in Nagoya. In addition, the precursors of O_3 such as NO_x and NMHC (total) were also collected and analyzed to find the similar variations in their trends.(2) Analyses of 03 dataset in the free troposphere over Japan and in the marine boundary layer over the western North PacificSurface O_3 concentration is controlled by in-situ photochemical reactions and transport of the O_3 in the overlying free troposphere. In summer, O_3 in Nagoya can be also affected by the transport of O_3 from the North Pacific. Therefore we analyzed the behaviors in the O_3 concentrations in the free troposphere and at the Ogasawara Island between 1994 and 1997.(3) Measurements of C_2~C_<11> NMHCs in NagoyaTo understand the variation in the photochemical processes in O_3 production, it is required to variation in the individual component of NMHCs. We developed the continuous measurement system of each NMHC component (C_2-C_<11>) with GC/FID and air sampling device, and obtained the NMHC data fro C_2-C_<11>. In particular, the ratio of NMHC/NOx increased in spring and summer could be explained by an increase emission of biogenic NMHC (isoprene), and this result will be helpful to investigate the mechanism.We have not yet revealed the mechanisms of 2-3 year variation in oxidant in urban air. Now we are investigating the differences in the processes between the well-defined periods and the not defined periods to reveal the factors controlling this variation.