The photochemistry of acetone in the upper troposphere: A source of odd‐hydrogen radicals
The photochemistry of acetone in the upper troposphere: A source of odd‐hydrogen radicals
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对流层上层丙酮的光化学：奇数氢自由基的来源
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发表时间：
1997
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通讯作者：
D. Fahey
中科院分区：
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作者：
S. Mckeen;T. Gierczak;J. B. Burkholder;P. Wennberg;T. Hanisco;E. Keim;R. Gao;S. Liu;A. Ravishankara;D. Fahey
本文总结了对流层上层压力和温度特征的 290-320 nm 波长范围内丙酮光解离量子产率的测量结果。计算将这些实验室数据与 NASA 和 NOAA 赞助的大气传输平流层示踪剂 (STRAT) 现场活动中获得的痕量气体浓度相结合，其中在 1995/1996 年秋冬期间在夏威夷和加利福尼亚州西部收集了 OH、HO2、奇数氮和其他化合物的测量结果。对流层顶下方 2 至 5 公里层内的 OH 和 HO2 浓度比仅从 O3、CH4 和 H2O 化学中预期的值高约 50%。尽管在 STRAT 期间没有测量丙酮，但丙酮是根据之前现场研究的 CO 测量和丙酮-CO 相关性推断出来的。这些推断的丙酮水平是奇数氢自由基的重要来源，可以解释对流层上层的大部分差异。对于较低海拔，推断的丙酮对 HOx (HO+HO2) 的贡献可以忽略不计，但会影响 NOy 分配。丙酮产生的 HOx 的主要部分是通过 CH2O 形成，无论来源如何，HOx 差异也可以通过 20 至 50 pptv 范围内的 CH2O 水平来解释。
This paper summarizes measured photodissociation quantum yields for acetone in the 290‐320 nm wavelength region for pressures and temperatures characteristic of the upper troposphere. Calculations combine this laboratory data with trace gas concentrations obtained during the NASA and NOAA sponsored Stratospheric Tracers of Atmospheric Transport (STRAT) field campaign, in which measurements of OH, HO2, odd‐nitrogen, and other compounds were collected over Hawaii, and west of California during fall and winter of 1995/1996. OH and HO2 concentrations within 2 to 5 km layers just below the tropopause are ∼50% larger than expected from O3, CH4, and H2O chemistry alone. Although not measured during STRAT, acetone is inferred from CO measurements and acetone‐CO correlations from a previous field study. These inferred acetone levels are a significant source of odd‐hydrogen radicals that can explain a large part of the discrepancy in the upper troposphere. For lower altitudes, the inferred acetone makes a negligible contribution to HOx (HO+HO2), but influences NOy partitioning. A major fraction of HOx production by acetone is through CH2O formation, and the HOx discrepancy can also be explained by CH2O levels in the 20 to 50 pptv range, regardless of the source.