Evaluation of CMAQ Coupled With a State-of-the-Art Mercury Chemical Mechanism (CMAQ-newHg-Br)

Zhuyun Ye, Huiting Mao, Charles T Driscoll, Yan Wang, Yanxu Zhang, Lyatt Jaeglé

Research output: Contribution to journalArticle

7 Citations (Scopus)

Abstract

Most regional three-dimensional chemical transport models neglect gaseous elemental mercury (GEM) oxidation by bromine (Br) radicals and Br chemistry. In this study, the Community Multiscale Air Quality model with its default mercury module (CMAQ-Hg) was modified by implementing a state-of-the-art algorithm depicting Hg reactions coupled with Br chemistry (CMAQ-newHg-Br). Using CMAQ-newHg-Br with initial and boundary concentrations (ICs and BCs) from global model output, we conducted simulations for the northeastern United States over March–November 2010. Simulated GEM mixing ratios were predominantly influenced by BCs and hence reflected significant seasonal variation that was captured in the global model output as opposed to a lack of seasonal variation using CMAQ-Hg's default constant BCs. Observed seasonal percentage changes (i.e., seasonal amplitude [=maximum – minimum] in percentage of the seasonal average) of gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) were 76% and 39%, respectively. CMAQ-newHg-Br significantly improved the simulated seasonal changes in GOM and PBM to 43% and 23%, respectively, from 18% and 16% using CMAQ-Hg. CMAQ-newHg-Br reproduced observed Hg wet deposition with a remarkably low fractional bias (FB; 0.4%) as opposed to a −56% to 19% FB for CMAQ-Hg simulations. Simulated Hg dry deposition using CMAQ-newHg-Br excluding the GEM + OH reaction agreed well with studies using inferential methods and litterfall/throughfall measurements, and the discrepancy varied over 13%–42%. This study demonstrated the promising capability of CMAQ-newHg-Br to reproduce observed concentrations and seasonal variations of GEM, GOM and PBM, and Hg wet and dry deposition fluxes.

Original languageEnglish (US)
Pages (from-to)668-690
Number of pages23
JournalJournal of Advances in Modeling Earth Systems
Volume10
Issue number3
DOIs
StatePublished - Mar 1 2018

Fingerprint

Bromine
bromine
Mercury
seasonal variation
wet deposition
dry deposition
mercury
state of the art
chemical
evaluation
throughfall
litterfall
Air quality
mixing ratio
simulation
air quality

Keywords

  • atmospheric Hg modeling
  • Br chemistry
  • CMAQ-Hg
  • Hg wet and dry deposition

ASJC Scopus subject areas

  • Global and Planetary Change
  • Environmental Chemistry
  • Earth and Planetary Sciences(all)

Cite this

Evaluation of CMAQ Coupled With a State-of-the-Art Mercury Chemical Mechanism (CMAQ-newHg-Br). / Ye, Zhuyun; Mao, Huiting; Driscoll, Charles T; Wang, Yan; Zhang, Yanxu; Jaeglé, Lyatt.

In: Journal of Advances in Modeling Earth Systems, Vol. 10, No. 3, 01.03.2018, p. 668-690.

Research output: Contribution to journalArticle

Ye, Zhuyun ; Mao, Huiting ; Driscoll, Charles T ; Wang, Yan ; Zhang, Yanxu ; Jaeglé, Lyatt. / Evaluation of CMAQ Coupled With a State-of-the-Art Mercury Chemical Mechanism (CMAQ-newHg-Br). In: Journal of Advances in Modeling Earth Systems. 2018 ; Vol. 10, No. 3. pp. 668-690.
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AU - Jaeglé, Lyatt

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AB - Most regional three-dimensional chemical transport models neglect gaseous elemental mercury (GEM) oxidation by bromine (Br) radicals and Br chemistry. In this study, the Community Multiscale Air Quality model with its default mercury module (CMAQ-Hg) was modified by implementing a state-of-the-art algorithm depicting Hg reactions coupled with Br chemistry (CMAQ-newHg-Br). Using CMAQ-newHg-Br with initial and boundary concentrations (ICs and BCs) from global model output, we conducted simulations for the northeastern United States over March–November 2010. Simulated GEM mixing ratios were predominantly influenced by BCs and hence reflected significant seasonal variation that was captured in the global model output as opposed to a lack of seasonal variation using CMAQ-Hg's default constant BCs. Observed seasonal percentage changes (i.e., seasonal amplitude [=maximum – minimum] in percentage of the seasonal average) of gaseous oxidized mercury (GOM) and particulate bound mercury (PBM) were 76% and 39%, respectively. CMAQ-newHg-Br significantly improved the simulated seasonal changes in GOM and PBM to 43% and 23%, respectively, from 18% and 16% using CMAQ-Hg. CMAQ-newHg-Br reproduced observed Hg wet deposition with a remarkably low fractional bias (FB; 0.4%) as opposed to a −56% to 19% FB for CMAQ-Hg simulations. Simulated Hg dry deposition using CMAQ-newHg-Br excluding the GEM + OH reaction agreed well with studies using inferential methods and litterfall/throughfall measurements, and the discrepancy varied over 13%–42%. This study demonstrated the promising capability of CMAQ-newHg-Br to reproduce observed concentrations and seasonal variations of GEM, GOM and PBM, and Hg wet and dry deposition fluxes.

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