First kinetic study of the atmospherically important reactions BrHg˙ + NO<sub>2</sub>and BrHg˙ + HOO

Jiao, Yuge; Dibble, Theodore S.

doi:10.1039/c6cp06276h

Cited by 53 publications

(86 citation statements)

References 85 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The reaction product of the oxidation of HgBr by NO 2 was computed to be syn-BrHgONO under atmospheric conditions. Because no experimental studies on the reaction of HgBr of NO 2 and HO 2 have been previously reported in the literature, the rate constants computed in this study are significant for future model and laboratory studies [25].…”

Section: Br-initiated Oxidation Of Hgmentioning

confidence: 99%

See 1 more Smart Citation

Recent Advances in Atmospheric Chemistry of Mercury

Ariya

2018

Atmosphere

View full text Add to dashboard Cite

Mercury is one of the most toxic metals and has global importance due to the biomagnification and bioaccumulation of organomercury via the aquatic food web. The physical and chemical transformations of various mercury species in the atmosphere strongly influence their composition, phase, transport characteristics and deposition rate to the ground. Modeling efforts to evaluate the mercury cycling in the environment require an accurate understanding of atmospheric mercury chemistry. We focus this article on recent studies (since 2015) on improving our understanding of the atmospheric chemistry of mercury. We discuss recent advances in (i) determining the dominant atmospheric oxidant of elemental mercury (Hg 0 ); (ii) understanding the oxidation reactions of Hg 0 by halogen atoms and by nitrate radical (NO 3 ); (iii) the aqueous reduction of oxidized mercury compounds (Hg II ); and (iv) the heterogeneous reactions of Hg on atmospherically-relevant surfaces. The need for future research to improve understanding of the fate and transformation of mercury in the atmosphere is also discussed.

show abstract

Section: Br-initiated Oxidation Of Hgmentioning

confidence: 99%

“…The first kinetic study of the reactions of BrHg with NO 2 and HO 2 was recently reported by Jiao and Dibble [25], using computational chemistry. Quantum calculations were performed to obtain the rate constants and product yields for the oxidation reactions of BrHg with NO 2 and HO 2 .…”

Section: Br-initiated Oxidation Of Hgmentioning

confidence: 99%

Recent Advances in Atmospheric Chemistry of Mercury

Ariya

2018

Atmosphere

View full text Add to dashboard Cite

show abstract

“…Values of k 0 (T ) and k ∞ (T ) are tabulated by Jiao and Dibble (2017) for different temperatures. At T = {220, 260, 280, 298, 320} K, k 0 NO 2 = {27.4, 13.5, 9.52, 7.10, 5.09} × 10 −29 cm 6 molecule −2 s −1 ; k ∞ NO 2 = {22.…”

Section: Chemical Mechanismmentioning

confidence: 99%

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

et al. 2017

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…This is one area that could potentially be improved in the future. Also, kinetic data for HgBr reactions were updated most recently (Jiao & Dibble, 2017). Due to the limited time frame of the funded project, it was not possible to rerun all the cases in this study.…”

Section: Discussionmentioning

confidence: 99%

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

Mao

Driscoll

et al. 2018

J Adv Model Earth Syst

View full text Add to dashboard Cite

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.

show abstract

First kinetic study of the atmospherically important reactions BrHg˙ + NO₂and BrHg˙ + HOO

Cited by 53 publications

References 85 publications

Recent Advances in Atmospheric Chemistry of Mercury

Recent Advances in Atmospheric Chemistry of Mercury

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

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

Contact Info

Product

Resources

About

First kinetic study of the atmospherically important reactions BrHg˙ + NO2and BrHg˙ + HOO

Cited by 53 publications

References 85 publications

Recent Advances in Atmospheric Chemistry of Mercury

Recent Advances in Atmospheric Chemistry of Mercury

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

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

Contact Info

Product

Resources

About

First kinetic study of the atmospherically important reactions BrHg˙ + NO₂and BrHg˙ + HOO