TY - JOUR
T1 - An examination of the oxidation of elemental mercury in the presence of halide surfaces
AU - Sheu, Guey Rong
AU - Mason, Robert P.
PY - 2004/6
Y1 - 2004/6
N2 - Recent field investigations in polar regions, and over the ocean, have suggested that elemental mercury (Hg0) can be photochemically oxidized in the presence of reactive halogen species that are formed in the presence of salt particles, typically through a reactive catalytic cycle involving ozone destruction. Furthermore, these studies have suggested that the Hg0 oxidation reaction involves the reaction with reactive bromine species such as Br, BrO, and Br2. To investigate these reactions in more detail, we performed experiments using a quartz reactive chamber so that the oxidation of Hg0, and the formation of ionic Hg products, could be examined in detail under different reaction scenarios, but at realistic levels of Hg. To examine if the reactions were enhanced by the presence of deliquescent salt surfaces, as has been postulated to be the case for the formation of reactive halogens, one surface of the cell was coated with either NaCl or NaBr for some experiments. In addition to laboratory experiments with a Xenon lamp, outdoor experiments under natural light were also conducted. The results of these studies showed that oxidation of Hg0 did not occur in the dark, except in the presence of a deliquescent NaBr salt surface. The rate of oxidation was slow in the absence of salt surfaces, and in the absence of low wavelength light (<324 nm). In the presence of NaCl surfaces, oxidation rates were at least two orders of magnitude faster, but the rate was further increased in the presence of NaBr, by a further factor of 25. With outdoor light, while the rates of oxidation were lower, the results were similar overall. The results are discussed in terms of the reactions occurring and the mechanisms of Hg0 oxidation. Finally, the implications of these reactions to the overall global Hg cycle are discussed.
AB - Recent field investigations in polar regions, and over the ocean, have suggested that elemental mercury (Hg0) can be photochemically oxidized in the presence of reactive halogen species that are formed in the presence of salt particles, typically through a reactive catalytic cycle involving ozone destruction. Furthermore, these studies have suggested that the Hg0 oxidation reaction involves the reaction with reactive bromine species such as Br, BrO, and Br2. To investigate these reactions in more detail, we performed experiments using a quartz reactive chamber so that the oxidation of Hg0, and the formation of ionic Hg products, could be examined in detail under different reaction scenarios, but at realistic levels of Hg. To examine if the reactions were enhanced by the presence of deliquescent salt surfaces, as has been postulated to be the case for the formation of reactive halogens, one surface of the cell was coated with either NaCl or NaBr for some experiments. In addition to laboratory experiments with a Xenon lamp, outdoor experiments under natural light were also conducted. The results of these studies showed that oxidation of Hg0 did not occur in the dark, except in the presence of a deliquescent NaBr salt surface. The rate of oxidation was slow in the absence of salt surfaces, and in the absence of low wavelength light (<324 nm). In the presence of NaCl surfaces, oxidation rates were at least two orders of magnitude faster, but the rate was further increased in the presence of NaBr, by a further factor of 25. With outdoor light, while the rates of oxidation were lower, the results were similar overall. The results are discussed in terms of the reactions occurring and the mechanisms of Hg0 oxidation. Finally, the implications of these reactions to the overall global Hg cycle are discussed.
KW - Elemental mercury
KW - Oxidation
KW - Reactive gaseous mercury
KW - Reactive halogens
UR - http://www.scopus.com/inward/record.url?scp=4344652900&partnerID=8YFLogxK
U2 - 10.1023/B:JOCH.0000036842.37053.e6
DO - 10.1023/B:JOCH.0000036842.37053.e6
M3 - 期刊論文
AN - SCOPUS:4344652900
SN - 0167-7764
VL - 48
SP - 107
EP - 130
JO - Journal of Atmospheric Chemistry
JF - Journal of Atmospheric Chemistry
IS - 2
ER -