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

Journal Article · · Environmental Science & Technology Letters (Online)
DOI:https://doi.org/10.1021/ez500322f· OSTI ID:1185776
 [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)
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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 in natural freshwaters containing dissolved organic matter (DOM) and carbonate. Here, we evaluate Hg(0) photooxidation rates affected by various reactive ionic species [e.g., DOM, CO32-, NO3-] and free radicals in a creek water and a phosphate buffer solution (pH=8) under simulated solar irradiation. We report a high Hg(0) photooxidation rate (k = 1.44 h-1) in the presence of both HCO32- and NO3-, whereas HCO32-, NO3-, or DOM alone increased the oxidation rate slightly (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 identify that carbonate radicals (CO3 ∙-) primarily drive the Hg(0) photooxidation, whereas addition of DOM resulted in a 2-fold decrease in Hg(0) oxidation. 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 fate in water containing carbonate such as hard water and seawater.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC)
DOE Contract Number:
AC05-00OR22725
OSTI ID:
1185776
Journal Information:
Environmental Science & Technology Letters (Online), Vol. 1, Issue 12; ISSN 2328-8930
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English

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Cited By (1)

Quantification of Trace Mercury in Water: Solving the Problem of Adsorption, Sample Preservation, and Cross‐Contamination journal November 2019

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Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
mercury
photo-oxidation
reduction
carbonate radical