Theoretical investigation of the bromine-catalyzed oxidation of methane in the Earth's atmosphere
Abstract
The primary purpose of the present study has been to assess the atmospheric significance of methane (CH4) in terms of its reactivity toward bromine-containing species. Methane is an important greenhouse gas that exists in abundance in the Earth's atmosphere. Its presence affects the temperature structure and climate system of the Earth. Methane's primary impact on the environment arises from its contribution to global warming of the Earth, and is a cause of concern. The chemical reactions of methane in the atmosphere not only affect its lifetime, but also the concentrations of other greenhouse gases such as ozone in the troposphere and water vapor in the stratosphere. Methane reacts readily with hydroxyl (OH) radicals present in the atmosphere. The oxidation of methane is then catalyzed by bromine (Br) atoms and bromine monoxide (BrO) radicals. Br atoms are formed due to the photolysis of molecular bromine and bromine-containing compounds released from the Earth's surface from natural and anthropogenic sources, and BrO radicals are formed due to ozone destruction by bromine atoms. The overall bromine-catalyzed oxidation cycle of methane proceeds through a series of steps involving the formation and absorption of various species. The oxidation of methane finally results in the formation of carbon monoxide (CO), together with water (H2O) and oxygen (O2) molecules. For each molecule of methane, three molecules of ozone are destroyed, and, thus, the oxidation process is detrimental to the presence of the ozone layer in the upper atmosphere. From the results obtained in this study, it is proposed that the possible new inorganic bromine reservoirs could be HOOOBr, HOOBrO, CH3OOOBr, and CH3OOBrO. The proposition of such reservoirs forms a basis from which future sinks of bromine atoms in the stratosphere can be identified.
Degree
Ph.D.
Advisors
Francisco, Purdue University.
Subject Area
Chemistry
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