Column 1 Discovery of the OH Radical Chain Reaction

The chain reaction mechanism with OH radical as a carrier, which is now accepted as the most fundamental reaction process in tropospheric chemistry, was proposed at the beginning of 1970s. The proposals were made in two research communities independently. One is out of the scientists who were interested in the mechanism of formation and dissipation of CO and HCHO in the natural atmosphere. In 1971 Levy (1971) presented the OH chain reaction scheme shown in Fig. 7.1 in Science for the purpose of explaining the formation of HCHO in the clean atmosphere. The chain reaction mechanism initiated by the reaction of OH and methane CH4, 

This mechanism is equivalent to the chain reaction for CH4 proposed by Levy, and was proposed independently. This reaction mechanism was originally presented in 1969 in the bulletin of Pennsylvania University (Heicklen et al. 1969). However, it was never published as a peer-reviewed journal paper, and followed the unhappy history that it is not referred in most of the present textbooks on atmospheric chemistry. 

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