Regional Air Quality Model Application of the Aqueous-Phase Photo Reduction of Atmospheric Oxidized Mercury by Dicarboxylic Acids

Bash, Jesse O.; Carlton, Annmarie G.; Hutzell, William T.; Bullock, O. Russell

doi:10.3390/atmos5010001

Cited by 23 publications

(23 citation statements)

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“… Note . The reaction kinetics follow the recommendations of Holloway et al (), Bieser et al (), Bash et al (), and Horowitz et al (). GOM = gaseous oxidized mercury; PBM = particulate bound mercury.…”

Section: Discussionmentioning

confidence: 91%

“…The model configuration and model uncertainty of CMAQ-Hg have been discussed in detail previously Lin et al, 2010Lin et al, , 2007Lin et al, , 2006Pongprueksa et al, 2008). Briefly, CMAQ v5.1 is based on the CMAQ (Byun, 1999) and modified by Bullock and Brehme (2002), and Gbor et al (2006), Bash (2010), and Bash et al (2014) include Hg chemistry, deposition fluxes of GOM and PBM, and the bidirectional flux exchange of GEM between the air and natural surfaces. The current atmospheric Hg chemistry in CMAQ v5.1 is implemented in the cb05tump_ae6_aq mechanism.…”

Section: Domain and Model Descriptionmentioning

confidence: 99%

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Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

et al. 2018

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Mainland China is the largest emission region of anthropogenic mercury (Hg) in the world. There have been concerns regarding the emission outflow and chemical transport budget of Hg in the region. Earlier assessments of Hg chemical transport were based on relatively outdated emission data. Recent estimates for anthropogenic (Wu et al., 2016, https://doi.org/10.1021/acs.est.6b04308) and natural Hg emissions (X. Wang, Lin, et al., 2016, https://doi.org/10.5194/acp-16-11125-2016) show substantial differences from earlier emission inventories. In this study, we applied the updated Hg emission estimates to reassess the regional transport budget using Community Multiscale Air Quality‐Hg v5.1. Our results show that the variation of simulated concentration, deposition, and associated emission outflow of Hg are primarily influenced by the spatial‐temporal variation of Hg emissions, monsoon shifts, and particulate matter pollution in China. Total Hg deposition in Mainland China is estimated to be 422 Mg/year, and approximately two thirds of the deposition is contributed by domestic emissions. The net Hg transport budget from Mainland China is 511 Mg/year, contributing to 10% of Hg deposition in other regions of the world. This reassessment points to a ~25% reduction in total annual outflow compared to the previous estimate by Lin et al. (2010, https://doi.org/10.5194/acp-10-1853-2010). Such reduction is mainly caused by changes in Hg emission quantity, speciation, and spatial/temporal distributions. More modeling studies focusing on reducing uncertainties of emission inventories and Hg atmospheric chemistry are needed for continuous assessment of Hg emission outflow in this emission‐intensive region.

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Section: Discussionmentioning

confidence: 91%

Section: Domain and Model Descriptionmentioning

confidence: 99%

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

et al. 2018

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“…Laboratory experiments have shown that photoreduction of Hg 2+ can occur in the aqueous phase by dissolved organic acids [96,97]. This reduction mechanism was incorporated in the Community Multiscale Air Quality (CMAQ) Hg model by Bash et al [6], who showed that this process improved model representation of wet deposition in the USA. Some models use a mechanism that involves reduction via HO 2 ; however, this mechanism is thought to be unlikely under most atmospheric conditions [98].…”

Section: Atmospheric Chemistrymentioning

confidence: 99%

“…Atmospheric models have been used extensively for assessing speciation, transport, and deposition of various atmospheric Hg species at both regional [5][6][7][8][9][10][11][12][13][14][15][16][17] and global scales [18][19][20][21][22][23][24][25]. Atmospheric models are increasingly being This article is part of the Topical Collection on Air Pollution * Noelle E. Selin selin@mit.edu Sae Yun Kwon saeyunk@mit.edu used to interpret global trends in atmospheric Hg concentrations [26,27] and to project future changes in Hg emissions and deposition under various policy and technology scenarios [28, 29••, 30].…”

Section: Introductionmentioning

confidence: 99%

Uncertainties in Atmospheric Mercury Modeling for Policy Evaluation

Kwon

Selin

2016

Curr Pollution Rep

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Mercury (Hg) contamination is an issue of a growing environmental and public health concern. Atmospheric chemistry transport models for Hg are a critical tool for understanding the sources, processes, and fate of Hg. Uncertainties in multiple aspects of atmospheric Hg models, however, limit their application for policy evaluation and for monitoring global trends in atmospheric Hg concentrations. This review aims to identify uncertainties in atmospheric Hg modeling that are relevant in the context of policy and for informing decision-making. We focus on specific requirements of the Minamata Convention on Mercury, a global treaty signed in 2013 to protect human health and the environment from Hg, to demonstrate how existing uncertainties in atmospheric Hg modeling can influence our ability to evaluate source-receptor relationships. Modeling studies of source attribution suggest that major uncertainties in atmospheric Hg modeling arise from anthropogenic emissions, biogeochemical cycling, and atmospheric chemistry. Uncertainties in these aspects of modeling are expected to increase under the Convention, with regulation of anthropogenic emissions, changes in atmospheric conditions, and legacy and natural Hg source contribution to the global biogeochemical cycle. These uncertainties can interact with one another and with the current Hg species measurement capability and pose challenges to effectively monitoring trends in atmospheric Hg. Developing additional means to attribute simulated atmospheric Hg trends and improve source-receptor relationships in atmospheric Hg models would improve our ability to evaluate the Convention's effectiveness.

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“…Photoreduction of Hg II bound to dissolved organic carbon (DOC) and other organic matter has been widely reported in aquatic environments (Amyot et al, 1994;Xiao et al, 1995;O'Driscoll et al, 2006;Whalin and Mason, 2006) and could also possibly take place in organic aerosols (OA). Bash et al (2014) found that including incloud aqueous photoreduction via organic acids based on the mechanism proposed by Si and Ariya (2008) improved the simulation of Hg wet deposition in their regional air quality model. Observed photochemically driven shifts in the abundance of naturally occurring Hg isotopes in the atmosphere and precipitation support the occurrence of aqueous-phase photoreduction involving Hg II -organic complexes (Gratz et al, 2010;Sonke, 2011;Sonke et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

et al. 2017

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Abstract. Mercury (Hg) is emitted to the atmosphere mainly as volatile elemental Hg 0 . Oxidation to water-soluble Hg II plays a major role in Hg deposition to ecosystems. Here, we implement a new mechanism for atmospheric Hg 0 / Hg II redox chemistry in the GEOS-Chem global model and examine the implications for the global atmospheric Hg budget and deposition patterns. Our simulation includes a new coupling of GEOS-Chem to an ocean general circulation model (MITgcm), enabling a global 3-D representation of atmosphereocean Hg 0 / Hg II cycling. We find that atomic bromine (Br) of marine organobromine origin is the main atmospheric Hg 0 oxidant and that second-stage HgBr oxidation is mainly by the NO 2 and HO 2 radicals. The resulting chemical lifetime of tropospheric Hg 0 against oxidation is 2.7 months, shorter than in previous models. Fast Hg II atmospheric reduction must occur in order to match the ∼ 6-month lifetime of Hg against deposition implied by the observed atmospheric variability of total gaseous mercury (TGM ≡ Hg 0 + Hg II (g)). We implement this reduction in GEOS-Chem as photolysis of aqueous-phase Hg II -organic complexes in aerosols and clouds, resulting in a TGM lifetime of 5.2 months against deposition and matching both mean observed TGM and its variability. Model sensitivity analysis shows that the interhemispheric gradient of TGM, previously used to infer a longer Hg lifetime against deposition, is misleading because Southern Hemisphere Hg mainly originates from oceanic emissions rather than transport from the Northern Hemisphere.The model reproduces the observed seasonal TGM variation at northern midlatitudes (maximum in February, minimum in September) driven by chemistry and oceanic evasion, but it does not reproduce the lack of seasonality observed at southern hemispheric marine sites. Aircraft observations in the lowermost stratosphere show a strong TGM-ozone relationship indicative of fast Hg 0 oxidation, but we show that this relationship provides only a weak test of Hg chemistry because it is also influenced by mixing. The model reproduces observed Hg wet deposition fluxes over North America, Europe, and China with little bias (0-30 %). It reproduces qualitatively the observed maximum in US deposition around the Gulf of Mexico, reflecting a combination of deep convection and availability of NO 2 and HO 2 radicals for second-stage HgBr oxidation. However, the magnitude of this maximum is underestimated. The relatively low observed Hg wet deposition over rural China is attributed to fast Hg II reduction in the presence of high organic aerosol concentrations. We find that 80 % of Hg II deposition is to the global oceans, reflecting the marine origin of Br and low concentrations of organic aerosols for Hg II reduction. Most of that deposition takes place to the tropical oceans due to the availability of HO 2 and NO 2 for second-stage HgBr oxidation.

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Regional Air Quality Model Application of the Aqueous-Phase Photo Reduction of Atmospheric Oxidized Mercury by Dicarboxylic Acids

Cited by 23 publications

References 58 publications

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

Assessment of Regional Mercury Deposition and Emission Outflow in Mainland China

Uncertainties in Atmospheric Mercury Modeling for Policy Evaluation

A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget

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