Journal ArticleDOI
The photochemistry of a remote marine stratiform cloud
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In this article, coupled gas and aqueous-phase photochemistry of a stratiform cloud in a remote region of the marine atmosphere is investigated with a time-dependent box model.Abstract:
The coupled gas- and aqueous-phase photochemistry of a stratiform cloud in a remote region of the marine atmosphere is investigated with a time-dependent box model. Both scavenging of ambient acidic aerosols and gases as well as aqueous-phase chemical reactions within droplets are found to be important sources of acidity to cloud water and can lead to pH levels in cloud water in the remote marine atmosphere well below 5.6. The major sources of acidity via aqueous-phase chemical reactions are the generation of sulfuric acid from dissolved SO2 and the generation of formic acid from dissolved formaldehyde. In both cases, aqueous-phase free radicals can play a significant role either directly by oxidizing dissolved SO2 and HCHO or indirectly by producing the aqueous-phase oxidant H2O2. The rate of SO2 conversion to sulfuric acid is sensitive to a variety of parameters including the accommodation or sticking coefficient for SO2, H2O2, HO2, and OH, the liquid water content, and the ambient levels of SO2, HNO3, and other acidic or basic gases. Because high levels of SO2 tend to deplete cloud water of H2O3, the possibility exists that the pH of precipitation in polluted regions will respond nonlinearly to reduced SO2 emissions.read more
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Compilation of Henry's law constants (version 4.0) for water as solvent
TL;DR: According to Henry's law, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution as discussed by the authors, and a compilation of 17 350 values of Henry's Law constants for 4632 species, collected from 689 references is available at http://wwwhenrys-law.org
Book
Fundamentals of atmospheric modeling
TL;DR: In this paper, the authors propose numerical solutions to partial differential equations and finite-differencing the equations of atmospheric dynamics, including boundary-layer and surface processes, and Radiative energy transfer.
Journal ArticleDOI
Mass-independent fractionation of sulfur isotopes in Archean sediments: strong evidence for an anoxic Archean atmosphere.
TL;DR: It is concluded that the atmospheric O2 concentration must have been < 10(-5) PAL prior to 2.3 Ga, which would have meant that all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediments, so any signature of MIF would have been lost.
Journal ArticleDOI
Photodissociation in the atmosphere: 1. Actinic flux and the effects of ground reflections and clouds
TL;DR: In this paper, it was shown that photodissociation rate coefficients inside clouds, and particularly inside cloud droplets, can frequently exceed the clear-sky values, in contrast to current usage in cloud chemistry models, due to the ∼2 cos θ factor incurred in the actinic flux when the solar beam is scattered and diffused into nearly isotropic light.
Journal ArticleDOI
Carboxylic acids in the troposphere, occurrence, sources, and sinks: A review
A. Chebbi,P. Carlier +1 more
TL;DR: In this paper, a synthesis of low molecular weight carboxylic acids in tropospheric aqueous and gaseous phases and in aerosol particles for different environments is presented.
References
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Thermal decomposition of peroxyacetylnitrate in the presence of nitric oxide
Richard A. Cox,Michael J. Roffey +1 more
TL;DR: In this paper, the thermal reactions occurring in mixtures containing peroxyacetyl nitrate and nitric oxide at part-per-million concentrations in synthetic air were investigated, and the results can be explained by a mechanism involving the following reactions: CH/sub 3/COO/sub 2/NO/sub2/
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Sulfate enrichment in marine aerosols owing to biogenic gaseous sulfur compounds
TL;DR: In this paper, the sulfate excess concentrations are found to be proportional to those of marine SO2, and sulfate enrichment could be consequently explained by the oxidation of marine sulfate, which is consistent with the distribution of SO4−/Na+ ratios on different size particles collected with a high volume cascade impactor.
Journal ArticleDOI
Cloud water chemistry and the production of sulfates in clouds
Dean A. Hegg,Peter V. Hobbs +1 more
TL;DR: In this article, the pH and ionic content of water collected in clouds over western Washington and the Los Angeles Basin was analyzed and evidence for sulfate production in some of the clouds was presented.
Journal ArticleDOI
Kinetics and mechanism of the oxidation of S(IV) by ozone in aqueous solution with particular reference to SO2 conversion in nonurban tropospheric clouds
TL;DR: In this article, a laboratory study of the kinetics of the S(IV)-O3 reaction in aqueous solution, including measurements of the effects of UV radiation, dissolved transition metals, and an antioxidant (hydroquinone) on the rate.
Journal ArticleDOI
Marine aerosol at southern mid‐latitudes
J. L. Gras,G. P. Ayers +1 more
TL;DR: In this paper, the results of an investigation of aerosol particles at Cape Grim (41°S, 145°E) for the period February 1978 to May 1980 are presented.