[A-AS22_1AM1] 大気化学

[AAS22-11] 能登半島珠洲における有機硝酸エステル類の連続観測

*定永 靖宗¹、高治 諒¹、石山 絢菜¹、松木 篤²、佐藤 啓市³、長田 和雄⁴、坂東 博¹ (1.大阪府立大学、2.金沢大学、3.アジア大気汚染研究センター、4.名古屋大学)

キーワード：有機硝酸エステル, 反応性総窒素酸化物, 長距離輸送

Peroxyacyl nitrates (PANs) and alkyl nitrates (ANs) act as one of the reservoirs of nitrogen oxides (NO_x) in the atmosphere. Since their lifetime is longer than that of NO_x, they can be transported over a long-distance and would be important as transboundary pollutants. In this research, continuous measurement system of total PANs and ANs in the troposphere has been developed by using a thermal dissociation / cavity attenuated phase shift spectroscopy (TD/CAPS) method. Both PANs and ANs are thermally decomposed to produce NO₂ and then NO₂ is measured by CAPS method. This system can observe PANs and ANs with high time resolution while this system cannot separate constituents of PANs and ANs. Total PANs and ANs can be measured separately by setting up decomposition lines at different temperatures.Continuous field observations of PANs and ANs concentrations have been being carried out at NOTOGRO (NOTO Ground-based Research Observatory) supersite in Suzu, Noto Peninsula, since November 2012. NO_x, NO_y, total inorganic nitrate (T.NO₃), O₃ and CO concentrations have also been being observed at NOTOGRO.NOy concentrations were in agreement with the sum of observed NO_y components (= NO_x + T.NO₃ + PANs + ANs) regardless of seasons. NO_x fractions were the highest in NO_y constituents. T.NO₃ fractions were small in winter and increased in spring. Opposite tendencies were observed for PANs fractions. These reflect that wet deposition of T.NO₃ is promoted in winter and temperature increasing accelerates decomposition of PANs.Seasonal variations of both PANs and ANs concentrations showed spring maximum and summer minimum. From winter to spring, both PANs and ANs concentrations from Korea-China air mass origin were higher than those from the other air mass origins. On the other hand, both PANs and ANs concentrations were independent of air mass origins from spring to summer. These indicate that PANs and ANs concentrations in winter and spring are governed by long-range transport and local photochemical productions of PANs and ANs are relatively important from spring to summer. In addition, PANs and ANs diurnal variations being high and low in the daytime and nighttime, respectively, in spring and summer also imply the local photochemical productions of PANs and ANs.