DOI: 10.1016/j.atmosenv.2017.06.006
Scopus记录号: 2-s2.0-85020894252
论文题名: Light absorption and the photoformation of hydroxyl radical and singlet oxygen in fog waters
作者: Kaur R ; , Anastasio C
刊名: Atmospheric Environment
ISSN: 0168-2563
EISSN: 1573-515X
出版年: 2017
卷: 164 起始页码: 387
结束页码: 397
语种: 英语
英文关键词: Aqueous secondary organic aerosol
; Atmospheric aqueous photochemistry
; Photooxidants
Scopus关键词: Aromatic compounds
; Aromatic hydrocarbons
; Atmospheric chemistry
; Carbon
; Chemical compounds
; Chemical reactions
; Dissolution
; Drops
; Electromagnetic wave absorption
; Fog
; Light absorption
; Organic carbon
; Organic compounds
; Polycyclic aromatic hydrocarbons
; Rate constants
; Transport properties
; Chemical transformations
; Dissolved organic carbon
; Dissolved organic compounds
; Mass absorption coefficient
; Photooxidants
; Secondary organic aerosols
; Singlet molecular oxygen
; Steady state concentration
; Molecular oxygen
; dissolved organic matter
; glyoxal
; glyoxylic acid
; guaiacol
; hydroxyl radical
; nitrate
; nitrite
; organic carbon
; organic compound
; oxygen
; polycyclic aromatic hydrocarbon
; singlet oxygen
; syringol
; water
; absorption
; aerosol
; aqueous solution
; dissolved organic matter
; fog
; hydroxyl radical
; organic compound
; PAH
; phenol
; photochemistry
; photooxidation
; Article
; California
; concentration at steady-state
; electron
; fog
; light absorption
; oxidation
; priority journal
; sunlight
; winter
Scopus学科分类: Environmental Science: Water Science and Technology
; Earth and Planetary Sciences: Earth-Surface Processes
; Environmental Science: Environmental Chemistry
英文摘要: The atmospheric aqueous-phase is a rich medium for chemical transformations of organic compounds, in part via photooxidants generated within the drops. Here we measure light absorption, photoformation rates and steady-state concentrations of two photooxidants – hydroxyl radical (•OH) and singlet molecular oxygen (1O2*) – in 8 illuminated fog waters from Davis, California and Baton Rouge, Louisiana. Mass absorption coefficients for dissolved organic compounds (MACDOC) in the samples are large, with typical values of 10,000–15,000 cm2 g-C−1 at 300 nm, and absorption extends to wavelengths as long as 450–600 nm. While nitrite and nitrate together account for an average of only 1% of light absorption, they account for an average of 70% of •OH photoproduction. Mean •OH photoproduction rates in fogs at the two locations are very similar, with an overall mean of 1.2 (±0.7) μM h−1 under Davis winter sunlight. The mean (±1σ) lifetime of •OH is 1.6 (±0.6) μs, likely controlled by dissolved organic compounds. Including calculated gas-to-drop partitioning of •OH, the average aqueous concentration of •OH is approximately 2 × 10−15 M (midday during Davis winter), with aqueous reactions providing approximately one-third of the hydroxyl radical source. At this concentration, calculated lifetimes of aqueous organics are on the order of 10 h for compounds with •OH rate constants of 1 × 1010 M−1 s−1 or higher (e.g., substituted phenols such as syringol (6.4 h) and guaiacol (8.4 h)), and on the order of 100 h for compounds with rate constants near 1 × 109 M−1 s−1 (e.g., isoprene oxidation products such as glyoxal (152 h), glyoxylic acid (58 h), and pyruvic acid (239 h)). Steady-state concentrations of 1O2* are approximately 100 times higher than those of •OH, in the range of (0.1–3.0) × 10−13 M. Since 1O2* is a more selective oxidant than •OH, it will only react appreciably with electron-rich species such as dimethyl furan (lifetime of 2.0 h) and substituted polycyclic aromatic hydrocarbons (e.g., 9,10-dimethylbenz[a]anthracene with a lifetime of 0.7 h). Comparing our current Davis samples with Davis fogs collected in the late 1990s shows a decrease in dissolved organic carbon content, similar mass absorption coefficients, lower •OH concentrations, but very similar 1O2* concentrations. © 2017 Elsevier Ltd Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/82557
Appears in Collections: 气候变化事实与影响
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作者单位: Department of Land, Air and Water Resources, University of California-Davis, One Shields Avenue, Davis, CA, United States; Agricultural and Environmental Chemistry Graduate Group, University of California-Davis, One Shields Avenue, Davis, CA, United States
Recommended Citation:
Kaur R,, Anastasio C. Light absorption and the photoformation of hydroxyl radical and singlet oxygen in fog waters[J]. Atmospheric Environment,2017-01-01,164