Is the HO4−Anion a Key Species in the Aqueous-Phase Decomposition of Ozone?

2012 ◽  
Vol 18 (42) ◽  
pp. 13435-13445 ◽  
Author(s):  
Josep M. Anglada ◽  
Miquel Torrent-Sucarrat ◽  
Manuel F. Ruiz-Lopez ◽  
Marilia Martins-Costa
Keyword(s):  
Aqueous Phase ◽  
Phase Decomposition ◽  
Key Species

scholarly journals Temperature Dependence of Aqueous-Phase Decomposition of α-Hydroxyalkyl-Hydroperoxides

2020 ◽  
Vol 124 (49) ◽  
pp. 10288-10295
Author(s):  
Mingxi Hu ◽  
Kunpeng Chen ◽  
Junting Qiu ◽  
Ying-Hsuan Lin ◽  
Kenichi Tonokura ◽  
...  
Keyword(s):  
Temperature Dependence ◽  
Aqueous Phase ◽  
Phase Decomposition

scholarly journals Air-snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS – Part 1: In-snow bromine activation and its impact on ozone

2013 ◽  
Vol 13 (8) ◽  
pp. 20341-20418 ◽  
Author(s):  
K. Toyota ◽  
J. C. McConnell ◽  
R. M. Staebler ◽  
A. P. Dastoor
Keyword(s):  
Boundary Layer ◽  
Aqueous Phase ◽  
Ambient Air ◽  
Atmospheric Mercury ◽  
Chemical Mechanism ◽  
The Arctic ◽  
Radical Chemistry ◽  
Ozone Loss ◽  
Key Species ◽  
Reactive Trace Gases

Abstract. To provide a theoretical framework towards better understanding of ozone depletion events (ODEs) and atmospheric mercury depletion events (AMDEs) in the polar boundary layer, we have developed a one-dimensional model that simulates multiphase chemistry and transport of trace constituents from porous snowpack and through the atmospheric boundary layer (ABL) as a unified system. In this paper, we describe a general configuration of the model and the results of simulations related to reactive bromine release from the snowpack and ODEs during the Arctic spring. The model employs a chemical mechanism adapted from the one previously used for the simulation of multiphase halogen chemistry involving deliquesced sea-salt aerosols in the marine boundary layer. A common set of aqueous-phase reactions describe chemistry both in the liquid-like (or brine) layer on the grain surface of the snowpack and in "haze" aerosols mainly composed of sulfate in the atmosphere. The process of highly soluble/reactive trace gases, whether entering the snowpack from the atmosphere or formed via gas-phase chemistry in the snowpack interstitial air (SIA), is simulated by the uptake on brine-covered snow grains and subsequent reactions in the aqueous phase while being traveled vertically within the SIA. A "bromine explosion", by which, in a conventional definition, HOBr formed in the ambient air is deposited and then converted heterogeneously to Br2, is a dominant process of reactive bromine formation in the top 1 mm (or less) layer of the snowpack. Deeper in the snowpack, HOBr formed within the SIA leads to an in-snow bromine explosion, but a significant fraction of Br2 is also produced via aqueous radical chemistry in the brine on the surface of the snow grains. These top- and deeper-layer productions of Br2 both contribute to the Br2 release into the atmosphere, but the deeper-layer production is found to be more important for the net outflux of reactive bromine. Although ozone is removed via bromine chemistry, it is also among the key species that control both the conventional and in-snow bromine explosions. On the other hand, aqueous-phase radical chemistry initiated by photolytic OH formation in the liquid-like layer is also a significant contributor to the in-snow source of Br2 and can operate without ozone, whereas the delivery of Br2 to the atmosphere becomes much smaller after ozone is depleted. Catalytic ozone loss via bromine radicals occurs more rapidly in the SIA than in the ambient air, giving rise to apparent dry deposition velocities for ozone from the air to the snow on the order of 10−3 cm s-1 under sunlight. Overall, however, the depletion of ozone in the system is caused predominantly by ozone loss in the ambient air. Increasing depth of the turbulent ABL under windy conditions will delay the build-up of reactive bromine and the resultant loss of ozone, while leading to the higher column amount of BrO in the atmosphere. If moderately saline and acidic snowpack is as prevalent as assumed in our model runs on sea ice during the spring, the shallow, stable ABL under calm weather conditions may undergo persistent ODEs without substantial contributions from blowing/drifting snow and wind-pumping mechanisms, whereas the column densities of BrO in the ABL will likely remain too low during the course of such events to be detected unambiguously by satellite nadir measurements.

scholarly journals Air–snowpack exchange of bromine, ozone and mercury in the springtime Arctic simulated by the 1-D model PHANTAS – Part 1: In-snow bromine activation and its impact on ozone

2014 ◽  
Vol 14 (8) ◽  
pp. 4101-4133 ◽  
Author(s):  
K. Toyota ◽  
J. C. McConnell ◽  
R. M. Staebler ◽  
A. P. Dastoor
Keyword(s):  
Boundary Layer ◽  
Mass Transfer ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Ambient Air ◽  
Atmospheric Mercury ◽  
The Arctic ◽  
Radical Chemistry ◽  
Ozone Loss ◽  
Key Species

Abstract. To provide a theoretical framework towards a better understanding of ozone depletion events (ODEs) and atmospheric mercury depletion events (AMDEs) in the polar boundary layer, we have developed a one-dimensional model that simulates multiphase chemistry and transport of trace constituents from porous snowpack and through the atmospheric boundary layer (ABL) as a unified system. This paper constitutes Part 1 of the study, describing a general configuration of the model and the results of simulations related to reactive bromine release from the snowpack and ODEs during the Arctic spring. A common set of aqueous-phase reactions describes chemistry both within the liquid-like layer (LLL) on the grain surface of the snowpack and within deliquesced "haze" aerosols mainly composed of sulfate in the atmosphere. Gas-phase reactions are also represented by the same mechanism in the atmosphere and in the snowpack interstitial air (SIA). Consequently, the model attains the capacity of simulating interactions between chemistry and mass transfer that become particularly intricate near the interface between the atmosphere and the snowpack. In the SIA, reactive uptake on LLL-coated snow grains and vertical mass transfer act simultaneously on gaseous HOBr, a fraction of which enters from the atmosphere while another fraction is formed via gas-phase chemistry in the SIA itself. A "bromine explosion", by which HOBr formed in the ambient air is deposited and then converted heterogeneously to Br2, is found to be a dominant process of reactive bromine formation in the top 1 mm layer of the snowpack. Deeper in the snowpack, HOBr formed within the SIA leads to an in-snow bromine explosion, but a significant fraction of Br2 is also produced via aqueous radical chemistry in the LLL on the surface of the snow grains. These top- and deeper-layer productions of Br2 both contribute to the release of Br2 to the atmosphere, but the deeper-layer production is found to be more important for the net outflux of reactive bromine. Although ozone is removed via bromine chemistry, it is also among the key species that control both the conventional and in-snow bromine explosions. On the other hand, aqueous-phase radical chemistry initiated by photolytic OH formation in the LLL is also a significant contributor to the in-snow source of Br2 and can operate without ozone, whereas the delivery of Br2 to the atmosphere becomes much smaller after ozone is depleted. Catalytic ozone loss via bromine radical chemistry occurs more rapidly in the SIA than in the ambient air, giving rise to apparent dry deposition velocities for ozone from the air to the snow on the order of 10−3 cm s−1 during daytime. Overall, however, the depletion of ozone in the system is caused predominantly by ozone loss in the ambient air. Increasing depth of the turbulent ABL under windy conditions will delay the buildup of reactive bromine and the resultant loss of ozone, while leading to the higher column amount of BrO in the atmosphere. During the Arctic spring, if moderately saline and acidic snowpack is as prevalent as assumed in our model runs on sea ice, the shallow, stable ABL under calm weather conditions may undergo persistent ODEs without substantial contributions from blowing/drifting snow and wind-pumping mechanisms, whereas the column densities of BrO in the ABL will likely remain too low in the course of such events to be detected unambiguously by satellite nadir measurements.

Aqueous-Phase Decomposition of Isoprene Hydroxy Hydroperoxide and Hydroxyl Radical Formation by Fenton-like Reactions with Iron Ions

2020 ◽  
Vol 124 (25) ◽  
pp. 5230-5236 ◽  
Author(s):  
Ting Fang ◽  
Pascale S. J. Lakey ◽  
Jean C. Rivera-Rios ◽  
Frank N. Keutsch ◽  
Manabu Shiraiwa
Keyword(s):  
Hydroxyl Radical ◽  
Aqueous Phase ◽  
Radical Formation ◽  
Iron Ions ◽  
Phase Decomposition

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Transmission Electron Microscopic Observations of Al3Li and Al3Ti Precipitation in A Rapidly Solidified Al-3Li-0.2Ti ALLOY

1980 ◽  
Vol 38 ◽  
pp. 336-337
Author(s):  
J. E. O’Neal ◽  
K. K. Sankaran ◽  
S. M. L. Sastry
Keyword(s):  
Rapid Solidification ◽  
Metallic Substrate ◽  
Deformation Characteristics ◽  
Phase Decomposition ◽  
Electron Microscopic ◽  
Transmission Electron ◽  
Supersaturated Solid Solutions ◽  
Transmission Electron Microscopic ◽  
Rapidly Solidified ◽  
Microstructural Homogeneity

Rapid solidification of a molten, multicomponent alloy against a metallic substrate promotes greater microstructural homogeneity and greater solid solubility of alloying elements than can be achieved by slower-cooling casting methods. The supersaturated solid solutions produced by rapid solidification can be subsequently annealed to precipitate, by controlled phase decomposition, uniform 10-100 nm precipitates or dispersoids. TEM studies were made of the precipitation of metastable Al3Li(δ’) and equilibrium AL3H phases and the deformation characteristics of a rapidly solidified Al-3Li-0.2Ti alloy.

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