Theoretical investigation of mercury reactions with halogen species in the Arctic troposphere

Mercury is one of the most toxic elements present in the geosphere, present in many chemical and physical forms. Nearly uniform mixing ratios are observed within a hemisphere, the concentration being higher in the northern than in the Southern Hemisphere. Lack of kinetic data regarding mercury reactions prevents an explanation of the behaviour and deposition pathways of mercury from the atmosphere. Theoretical calculations have been carried out using DFT theory to investigate the thermodynamics and kinetics of the reactions of Hg0 with Cl, Br, ClO, and BrO radicals and with Cl 2 and Br2. The results from these calculations were used to evaluate the kinetic rate constants at 298.15 K and 238.15 K for the reactions involving gaseous mercury. In this paper, the results of this study are presented and relevance to the chemistry of the Arctic is discussed