18:15 〜 19:30
[AAS22-P19] 大気中 PANs・有機硝酸エステル連続測定装置の開発および能登半島珠洲における観測
キーワード：ペルオキシアシル硝酸(PANs), 有機硝酸エステル, 反応性総窒素酸化物, キャビティ減衰位相シフト分光法
Peroxyacyl nitrates (PANs) and alkyl nitrates (ANs) are generated in the atmosphere by oxidation of NOx in the presence of solar ultraviolet. They have a comparatively long lifetime, and are important as transboundary air pollutants. On the other hand, PANs and ANs act as the reservoirs of NOx. In order to clarify transboundary pollution of nitrogen oxides, comprehensive measurements of total odd nitrogen species (NOy), including PANs and ANs, are required. In this research, a continuous measurement system of total PANs and ANs has been developed by a thermal dissociation / cavity attenuated phase shift spectroscopy (TD/CAPS) method.
This instrument consists of heated quartz tubes to decompose PANs and ANs into NO2, and a CAPS-NO2 analyzer. This system has three intake lines; NO2, PANs and ANs lines. The NO2 line equip of a quartz tube without heating. The PANs and ANs line equip quartz tubes heated at 433 K and 633 K, respectively for thermally decomposing them into NO2. Concentrations of NO2, NO2 + PANs and NO2 + PANs + ANs can be obtained from the NO2, PANs and ANs lines, respectively. These concentrations are sequentially measured by switching solenoid valves and then NO2, PANs and ANs concentrations are obtained. Since a part of HNO3 is pyrolyzed in the ANs line, annular denuder coated with NaCl to remove HNO3 is set before the heated quartz tube in the ANs line. The decomposition efficiencies of PANs and ANs were calibrated to be 100 and 95%, respectively, for all kinds of PANs and ANs examined.
Continuous field observations of PANs and ANs have been being performed at NOTOGRO (Noto ground-based Research observatory) supersite in Suzu, the Noto Peninsula, since November 2012. Continuous measurements of NOx, NOy, T.NO3 (the sum of gaseous nitric acid and particulate nitrate) O3, and CO have also been being conducted. NOy concentrations were in agreement with the sum of observed NOy components (= NOx + T.NO3 + PANs + ANs) regardless of seasons. NOx fractions were the highest in NOy constituents. Fractions of T.NO3 in January and February were lower than those in other months. This reflects that wet deposition of T.NO3 would be accelerated in winter due to snowfall. On the other hand, PANs fractions in spring and summer were smaller than those in winter. This suggests that temperature increasing promotes decomposition of PANs.
This instrument consists of heated quartz tubes to decompose PANs and ANs into NO2, and a CAPS-NO2 analyzer. This system has three intake lines; NO2, PANs and ANs lines. The NO2 line equip of a quartz tube without heating. The PANs and ANs line equip quartz tubes heated at 433 K and 633 K, respectively for thermally decomposing them into NO2. Concentrations of NO2, NO2 + PANs and NO2 + PANs + ANs can be obtained from the NO2, PANs and ANs lines, respectively. These concentrations are sequentially measured by switching solenoid valves and then NO2, PANs and ANs concentrations are obtained. Since a part of HNO3 is pyrolyzed in the ANs line, annular denuder coated with NaCl to remove HNO3 is set before the heated quartz tube in the ANs line. The decomposition efficiencies of PANs and ANs were calibrated to be 100 and 95%, respectively, for all kinds of PANs and ANs examined.
Continuous field observations of PANs and ANs have been being performed at NOTOGRO (Noto ground-based Research observatory) supersite in Suzu, the Noto Peninsula, since November 2012. Continuous measurements of NOx, NOy, T.NO3 (the sum of gaseous nitric acid and particulate nitrate) O3, and CO have also been being conducted. NOy concentrations were in agreement with the sum of observed NOy components (= NOx + T.NO3 + PANs + ANs) regardless of seasons. NOx fractions were the highest in NOy constituents. Fractions of T.NO3 in January and February were lower than those in other months. This reflects that wet deposition of T.NO3 would be accelerated in winter due to snowfall. On the other hand, PANs fractions in spring and summer were smaller than those in winter. This suggests that temperature increasing promotes decomposition of PANs.