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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2017-39
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
15 Feb 2017
Review status
This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). The revised manuscript was not accepted.
Measurement-based modeling of daytime and nighttime oxidation of atmospheric mercury
Maor Gabay1, Mordechai Peleg2, Erick Fredj3, and Eran Tas1 1The Department of Soil and Water Sciences, The Robert H. Smith Faculty of Agriculture, Food and Environment, Hebrew University of Jerusalem, Rehovot, Israel
2Institute of Earth Sciences, Edmud Safra Campus, Givat Ram, The Hebrew University of Jerusalem, Jerusalem 91904, Israel
3Department of Computer Science, Jerusalem College of Technology, Jerusalem 91160, Israel
Abstract. Accurate characterization of gaseous elemental mercury (GEM) chemical oxidation pathways and their kinetics is critically important for assessing the transfer of atmospheric mercury to bioaquatic systems. Recent comprehensive field measurements have suggested that the nitrate radical (NO3) plays a role in efficient nighttime oxidation of GEM, and that the role of the hydroxyl radical (OH) as a GEM oxidant has been underestimated. We used the CAABA/MECCA chemical box model and additional kinetic calculations to analyze these measurement results, in order to investigate the nighttime and daytime oxidation of GEM. We assumed a second-order reaction for the NO3 induced nighttime oxidation of GEM. Our analysis demonstrated that nighttime oxidation of GEM has to be included in the model to account for the measured variations in nighttime reactive gaseous mercury (RGM) concentration. A lower limit and best-fit rate constant for GEM nighttime oxidation are provided. To the best of our knowledge, this is the first time that a rate for nighttime oxidation of GEM has been determined based on field measurements. Our analysis further indicates that OH has a much more important role in GEM oxidation than commonly considered. A lower-limit rate constant for the OH–RGM reaction is provided.

Citation: Gabay, M., Peleg, M., Fredj, E., and Tas, E.: Measurement-based modeling of daytime and nighttime oxidation of atmospheric mercury, Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2017-39, 2017.
Maor Gabay et al.
Interactive discussionStatus: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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RC1: 'Review of acp-2017-39', Anonymous Referee #1, 14 Mar 2017 Printer-friendly Version 
AC1: 'response to comments by referee #1', Eran Tas, 02 Apr 2017 Printer-friendly Version Supplement 
 
RC2: 'Review comments', Anonymous Referee #3, 16 May 2017 Printer-friendly Version 
AC2: 'response to comments by referee #3', Eran Tas, 29 Jun 2017 Printer-friendly Version Supplement 
Maor Gabay et al.
Maor Gabay et al.

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Short summary
Accurate characterization of atmospheric mercury oxidation pathways and their kinetics is critically important for assessing the transfer of atmospheric mercury to bioaquatic systems, where it can be further converted into the highly toxic biocumulative, methyl mercury. We show that nighttime oxidation of atmospheric mercury and daytime oxidation by hydroxyl radical are both more important than has been previously reported. These findings should eventually affect mercury deposition assessment.
Accurate characterization of atmospheric mercury oxidation pathways and their kinetics is...
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