Decoupling peroxyacetyl nitrate from ozone in Chinese outflows observed at Gosan Climate Observatory

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Han, Jihyun ; Lee, Meehye ; Lee, Gangwoong ; Emmons, Louisa K. (2017)

We measured peroxyacetyl nitrate (PAN) and other reactive species such as O<sub>3</sub>, NO<sub>2</sub>, CO, and SO<sub>2</sub> with aerosols including PM<sub>10</sub> and PM<sub>2.5</sub> organic carbon (OC) and elemental carbon (EC) at Gosan Climate Observatory in Korea (33.17°&thinsp;N, E126.10°&thinsp;E) during October 10 to November 6, 2010. PAN was determined through fast gas chromatography with luminol chemiluminescence detection at 425&thinsp;nm every 2&thinsp;min. The PAN mixing ratios ranged from 0.1 (detection limit) to 2.4&thinsp;ppbv with a mean of 0.6&thinsp;ppbv. For all measurements, PAN was unusually better correlated with PM10 (Pearson correlation coefficient, ?&thinsp;=&thinsp;0.75) than with O<sub>3</sub> (?&thinsp;=&thinsp;0.67). In particular, the O<sub>3</sub> level was highly elevated with SO<sub>2</sub> at midnight, along with a typical midday peak when air was transported rapidly from the Beijing areas. The PAN enhancement was most noticeable during the occurrence of haze under stagnant conditions. In Chinese outflows slowly transported over the Yellow Sea, PAN gradually increased up to 2.4&thinsp;ppbv at night, in excellent correlation with a concentration increase of PM<sub>2.5</sub> OC and EC, PM<sub>1.0</sub> K<sup>+</sup>, and PM<sub>10</sub> mass. The high K<sup>+</sup> and OC&thinsp;/&thinsp;EC ratio indicated that the air mass was impacted by biomass combustion. This study highlights PAN decoupling with O<sub>3</sub> in Chinese outflows and suggests PAN as a potential indicator of overall aerosol formation in aged air masses impacted by biomass burning.
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