THEORETICAL CONSIDERATIONS ON THE OXIDATION OF SOME GASEOUS HYDROCARBONS IN THE SOIL ATMOSPHERE

Abstract

The spontaneity of 16 reactions describing the oxidation of methane, ethane, propane, and ethylene by oxygen, nitrate, iron, and sulfate was calculated for different sets of activities and/or fugacities of the participating compounds. The calculations showed that none of the gaseous hydrocarbons was stable in the presence of even a very small amount of O₂ (10⁻²⁷ Pa). At pH 7, the studied hydrocarbon gases were unstable in the presence of NO₃⁻ and Fe³⁺, even at very low activities (10⁻¹⁰M) of these species. In all considered cases, it was confirmed that CO₂ was more stable than the hydrocarbons. Methane, ethane, and propane but not ethylene can be formed at pH 7 in the presence of SO₄⁻² at activities of 10⁻⁶ and 10⁻¹⁰M.