A kinetic study of the gas-phase reaction between the hydroxyl radical and atomic mercury

The atom is the dominating species of mercury in the atmosphere. Its oxidation processes are of great interest since it is mainly oxidised mercury that undergoes deposition and thereby spreads into the ecosystems and becomes bioaccumulated. The kinetics of the gas-phase reaction between atomic mercury and hydroxyl radical has been determined at room temperature and atmospheric pressure of air by relative rate technique. OH radicals were produced by photolysis employing methyl nitrite. By using cyclohexane as the reference compound, the rate coefficient obtained was k(Hg0+•OH)=(8.7±2.8)×10−14 cm3 s−1 leading to natural lifetimes of mercury at global mean conditions of 4–7 month due to this reaction.