| Abstract
| - Rapid depletions of atmospheric mercury (Hg0) and ozone coinciding with high halogen concentrations haverecently been observed in several high-Arctic and sub-Arctic regions. The lack of kinetic data on the halogen-initiated reactions of elemental mercury precluded the drawing of any conclusions on the chemistry of thesemercury depletion events. We carried out extensive kinetic and product studies on the reactions of gaseousHg0 with molecular and atomic halogens (X/X2 where X = Cl, Br) at atmospheric pressure (750 ± 1 Torr)and room temperature (298 ± 1 K) in air and N2. Kinetics of the reactions with X/X2 was studied usingrelative and absolute techniques by cold vapor atomic absorption spectroscopy (CVAAS) and gaschromatography with mass spectroscopic detection (GC-MS). The measured rate constants for reactions ofHg0 with Cl2, Cl, Br2, and Br were (2.6 ± 0.2) × 10-18, (1.0 ± 0.2) × 10-11, <(0.9 ± 0.2) × 10-16, and(3.2 ± 0.3) × 10-12 cm3 molecule-1 s-1, respectively. The reaction products were analyzed in the gas phase,from the suspended aerosols, and from the wall of the reactor using MS, GC-MS, and inductively coupledplasma mass spectrometry (ICP-MS). The major products identified were HgCl2 and HgBr2 adsorbed on thewall. Suspended aerosols, collected on the micron filters, contributed to less than 0.5% of the reaction productsunder our experimental conditions. The importance of halogen reactions of mercury in the formation ofparticulate matter, which tends to be bioaccumulative, is discussed herein.
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