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Title: Photochemical Oxidation of Dissolved Elemental Mercury by Carbonate Radicals in Water

In this study, photochemical oxidation of dissolved elemental mercury, Hg(0), affects mercury chemical speciation and its transfer at the water-air interface in the aquatic environment. The mechanisms and factors that control Hg(0) photooxidation, however, are not completely understood, especially concerning the role of dissolved organic matter (DOM) and carbonate (CO32-) in natural freshwaters. Here, we evaluate Hg(0) photooxidation rates affected by reactive ionic species (e.g., DOM, CO32-, and NO3) and free radicals in creek water and a phosphate buffer solution (pH 8) under simulated solar irradiation. The Hg(0) photooxidation rate (k = 1.44 h-1) is much higher in the presence of both CO32- and NO3- than in the presence of CO32-, NO3-, or DOM alone (k = 0.1–0.17 h-1). Using scavengers and enhancers for singlet oxygen (1O2) and hydroxyl (HO) radicals, as well as electron paramagnetic resonance spectroscopy, we found that carbonate radicals (CO3•-) primarily drive Hg(0) photooxidation. The addition of DOM to the solution of CO32- and NO3- decreased the oxidation rate by half. This study identifies an unrecognized pathway of Hg(0) photooxidation by CO3•- radicals and the inhibitory effect of DOM, which could be important in assessing Hg transformation and the fate of Hg in water containing carbonatemore » such as hard water and seawater.« less
Authors:
 [1] ;  [2] ;  [3] ;  [3]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Zhejiang Univ. of Technology, Hangzhou (China)
  2. Zhejiang Univ. of Technology, Hangzhou (China)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1185776
Grant/Contract Number:
AC05-00OR22725; SC0007042
Type:
Accepted Manuscript
Journal Name:
Environmental Science & Technology Letters
Additional Journal Information:
Journal Volume: 1; Journal Issue: 12; Journal ID: ISSN 2328-8930
Publisher:
American Chemical Society (ACS)
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Michigan, Ann Arbor, MI (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; mercury; photo-oxidation; reduction; carbonate radical; 54 ENVIRONMENTAL SCIENCES