Kinetic isotope effects of 12CH3D  + OH and 13CH3D  + OH from 278 to 313 K

doi:10.5194/acp-16-4439-2016

GSTDTAP > 地球科学

DOI	10.5194/acp-16-4439-2016
	Kinetic isotope effects of ¹²CH₃D  + OH and ¹³CH₃D  + OH from 278 to 313 K
	L. M. T. Joelsson, J. A. Schmidt, E. J. K. Nilsson, T. Blunier, D. W. T. Griffith, S. Ono, and M. S. Johnson
	2016-04-11
发表期刊	Atmospheric Chemistry and Physics
出版年	2016
英文摘要	Methane is the second most important long-lived greenhouse gas and plays a central role in the chemistry of the Earth's atmosphere. Nonetheless there are significant uncertainties in its source budget. Analysis of the isotopic composition of atmospheric methane, including the doubly substituted species ¹³CH₃D, offers new insight into the methane budget as the sources and sinks have distinct isotopic signatures. The most important sink of atmospheric methane is oxidation by OH in the troposphere, which accounts for around 84 % of all methane removal. Here we present experimentally derived methane + OH kinetic isotope effects and their temperature dependence over the range of 278 to 313 K for CH₃D and ¹³CH₃D; the latter is reported here for the first time. We find k_CH₄/k_CH₃D = 1.31 ± 0.01 and k_CH₄/k_¹³CH₃D = 1.34 ± 0.03 at room temperature, implying that the methane + OH kinetic isotope effect is multiplicative such that (k_CH₄/k_¹³CH₄)(k_CH₄/k_CH₃D) = k_CH₄/k_¹³CH₃D, within the experimental uncertainty, given the literature value of k_CH₄/k_¹³CH₄ = 1.0039 ± 0.0002. In addition, the kinetic isotope effects were characterized using transition state theory with tunneling corrections. Good agreement between the experimental, quantum chemical, and available literature values was obtained. Based on the results we conclude that the OH reaction (the main sink of methane) at steady state can produce an atmospheric clumped isotope signal (Δ(¹³CH₃D) = ln([CH₄][¹³CH₃D]/[¹³CH₄][CH₃D])) of 0.02 ± 0.02. This implies that the bulk tropospheric Δ(¹³CH₃D) reflects the source signal with relatively small adjustment due to the sink signal (i.e., mainly OH oxidation).
领域	地球科学
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文献类型	期刊论文
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/287939
专题	地球科学
推荐引用方式 GB/T 7714	L. M. T. Joelsson, J. A. Schmidt, E. J. K. Nilsson, T. Blunier, D. W. T. Griffith, S. Ono, and M. S. Johnson. Kinetic isotope effects of ¹²CH₃D  + OH and ¹³CH₃D  + OH from 278 to 313 K[J]. Atmospheric Chemistry and Physics,2016.
APA	L. M. T. Joelsson, J. A. Schmidt, E. J. K. Nilsson, T. Blunier, D. W. T. Griffith, S. Ono, and M. S. Johnson.(2016).Kinetic isotope effects of ¹²CH₃D  + OH and ¹³CH₃D  + OH from 278 to 313 K.Atmospheric Chemistry and Physics.
MLA	L. M. T. Joelsson, J. A. Schmidt, E. J. K. Nilsson, T. Blunier, D. W. T. Griffith, S. Ono, and M. S. Johnson."Kinetic isotope effects of ¹²CH₃D  + OH and ¹³CH₃D  + OH from 278 to 313 K".Atmospheric Chemistry and Physics (2016).