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与分析我们获得了爱知县1991 - 2001年的大气污染物数据集和名古屋的气象数据集。我们确定了这种变化被明确定义的时期（1985-1998）。由于名古屋氧化剂浓度的时间变化与臭氧（O_3）的时间变化密切相关，因此这2 ~ 3年的氧化剂浓度变化可视为名古屋O_3的时间变化。此外，对O_3的前体NO_x和NMHC （total）也进行了收集和分析，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03数据的分析表明，表面O_3浓度受原位光化学反应和上覆自由对流层O_3输送的控制。在夏季，名古屋的O_3也会受到北太平洋O_3输送的影响。因此，我们分析了1994 - 1997年自由对流层和小笠原岛O_3浓度的变化规律。(3)名古屋地区C_2~C_<11> NMHCs的测量为了了解O_3生产过程中光化学过程的变化，需要了解NMHCs各组分的变化。利用气相色谱/FID和空气采样装置，建立了连续测量C_2-C_<11>各组分NMHC的系统，得到了C_2-C_<11>的NMHC数据。特别是春夏季NMHC/NOx比值的增加可能与生物源性NMHC（异戊二烯）排放增加有关，这一结果将有助于探讨其机理。我们还没有揭示城市空气中氧化剂2-3年变化的机制。现在，我们正在研究定义明确的时期和未定义的时期之间过程的差异，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.