Global S&T Development Trend Analysis Platform of Resources and Environment
DOI | 10.5194/acp-17-6353-2017 |
A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget | |
Horowitz, Hannah M.1; Jacob, Daniel J.1,2; Zhang, Yanxu2; Dibble, Theodore S.3; Slemr, Franz4; Amos, Helen M.2; Schmidt, Johan A.2,5; Corbitt, Elizabeth S.1; Marais, Eloise A.2; Sunderland, Elsie M.2,6 | |
2017-05-29 | |
发表期刊 | ATMOSPHERIC CHEMISTRY AND PHYSICS |
ISSN | 1680-7316 |
EISSN | 1680-7324 |
出版年 | 2017 |
卷号 | 17期号:10 |
文章类型 | Article |
语种 | 英语 |
国家 | USA; Germany; Denmark |
英文摘要 | 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 atmosphere-ocean Hg-0 / HgII 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 NO2 and HO2 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 similar to 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 NO2 and HO2 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 HgII reduction. Most of that deposition takes place to the tropical oceans due to the availability of HO2 and NO2 for second-stage HgBr oxidation. |
领域 | 地球科学 |
收录类别 | SCI-E |
WOS记录号 | WOS:000402393600001 |
WOS关键词 | MARINE BOUNDARY-LAYER ; FIRED POWER-PLANT ; AIR-SEA EXCHANGE ; DEPENDENT RATE COEFFICIENTS ; CARIBIC PASSENGER AIRCRAFT ; LASER-INDUCED FLUORESCENCE ; DISSOLVED GASEOUS MERCURY ; LOWER STRATOSPHERIC AGE ; ELEMENTAL MERCURY ; OXIDIZED MERCURY |
WOS类目 | Environmental Sciences ; Meteorology & Atmospheric Sciences |
WOS研究方向 | Environmental Sciences & Ecology ; Meteorology & Atmospheric Sciences |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/21733 |
专题 | 地球科学 |
作者单位 | 1.Harvard Univ, Dept Earth & Planetary Sci, 20 Oxford St, Cambridge, MA 02138 USA; 2.Harvard Univ, Harvard John A Paulson Sch Engn & Appl Sci, Cambridge, MA 02138 USA; 3.State Univ New York Environm Sci & Forestry, Chem Dept, Syracuse, NY USA; 4.Max Planck Inst Chem MPI C, Dept Atmospher Chem, Mainz, Germany; 5.Univ Copenhagen, Dept Chem, Univ Parken 5, DK-2100 Copenhagen O, Denmark; 6.Harvard Univ, TH Chan Sch Publ Hlth, Dept Environm Hlth, Boston, MA 02115 USA |
推荐引用方式 GB/T 7714 | Horowitz, Hannah M.,Jacob, Daniel J.,Zhang, Yanxu,et al. A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget[J]. ATMOSPHERIC CHEMISTRY AND PHYSICS,2017,17(10). |
APA | Horowitz, Hannah M..,Jacob, Daniel J..,Zhang, Yanxu.,Dibble, Theodore S..,Slemr, Franz.,...&Sunderland, Elsie M..(2017).A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget.ATMOSPHERIC CHEMISTRY AND PHYSICS,17(10). |
MLA | Horowitz, Hannah M.,et al."A new mechanism for atmospheric mercury redox chemistry: implications for the global mercury budget".ATMOSPHERIC CHEMISTRY AND PHYSICS 17.10(2017). |
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