Photodissociation Mechanisms of Major Mercury(II) Species in the Atmospheric Chemical Cycle of Mercury. Issue 19 (23rd January 2020)

• Record Type: Journal Article
• Authors: Francés‐Monerris, Antonio; Carmona‐García, Javier; Acuña, A. Ulises; Dávalos, Juan Z.; Cuevas, Carlos A.; Kinnison, Douglas E.; Francisco, Joseph S.; Saiz‐Lopez, Alfonso; Roca‐Sanjuán, Daniel
• Is Part Of: Angewandte Chemie international edition. Volume 59:Issue 19(2020)
• Page Start: 7605
• Page End: 7610
• Publication Date: 2020-01-23
• Subjects: atmospheric chemistry -- mercury -- multiconfigurational quantum chemistry -- non-adiabatic dynamics -- photodissociation; Chemistry -- Periodicals; 540
• DOI: 10.1002/anie.201915656
• Languages: English
• ISSNs: 1433-7851

Abstract

Abstract: Mercury is a contaminant of global concern that is transported throughout the atmosphere as elemental mercury Hg 0 and its oxidized forms Hg I and Hg II . The efficient gas‐phase photolysis of Hg II and Hg I has recently been reported. However, whether the photolysis of Hg II leads to other stable Hg II species, to Hg I, or to Hg 0 and its competition with thermal reactivity remain unknown. Herein, we show that all oxidized forms of mercury rapidly revert directly and indirectly to Hg 0 by photolysis. Results are based on non‐adiabatic dynamics simulations, in which the photoproduct ratios were determined with maximum errors of 3%. We construct for the first time a complete quantitative mechanism of the photochemical and thermal conversion between atmospheric Hg II, Hg I, and Hg 0 compounds. These results reveal new fundamental chemistry that has broad implications for the global atmospheric Hg cycle. Thus, photoreduction clearly competes with thermal oxidation, with Hg 0 being the main photoproduct of Hg II photolysis in the atmosphere, which significantly increases the lifetime of this metal in the environment. Abstract : The ultimate fate of mercury in the atmosphere is elemental Hg. This result is based on non‐adiabatic dynamics simulations, which were used to construct a complete quantitative mechanism of the photochemical and thermal conversion of atmospheric Hg II, Hg I, and Hg 0 compounds.