The photochemistry of a remote marine stratiform cloud
TL;DR: 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.
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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
Abstract: Many atmospheric chemicals occur in the gas phase as well as in liquid cloud droplets and aerosol particles Therefore, it is necessary to understand the distribution between the phases 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 Henry's law constants of trace gases of potential importance in environmental chemistry have been collected and converted into a uniform format The compilation contains 17 350 values of Henry's law constants for 4632 species, collected from 689 references It is also available at http://wwwhenrys-laworg
1,935 citations
Cites background or methods from "The photochemistry of a remote mari..."
...T − 1 T )) mol(2) m6 Pa 63) Chameides and Stelson (1992) give a value of H ′ = 7....
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...to Jacob (1986) and Chameides (1984) as the source but this value cannot be found there....
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...to Jacob (1986) and Chameides (1984) as the source but this value cannot be found there. 64) The value is from Table 1 of the paper. However, J. Geophys. Res. forgot to print the tables and I received them directly from the author. 65) Fickert (1998) extracted a value from wetted-wall flow tube experiments. However, it was later discovered that under the experimental conditions no evaluation of H is possible (J. Crowley, pers. comm., 1999). 66) Value at T = 275 K. 67) Value at T = 290 K. 68) Calculated using data from Wagman et al. (1982) and the aqueous-phase equilibrium Cl2 + Br2 2 BrCl from Wang et al....
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...to Jacob (1986) and Chameides (1984) as the source but this value cannot be found there. 64) The value is from Table 1 of the paper. However, J. Geophys. Res. forgot to print the tables and I received them directly from the author. 65) Fickert (1998) extracted a value from wetted-wall flow tube experiments. However, it was later discovered that under the experimental conditions no evaluation of H is possible (J. Crowley, pers. comm., 1999). 66) Value at T = 275 K. 67) Value at T = 290 K. 68) Calculated using data from Wagman et al. (1982) and the aqueous-phase equilibrium Cl2 + Br2 2 BrCl from Wang et al. (1994). 69) Thompson and Zafiriou (1983) quote a paper as the source that gives only the solubility but not the Henry’s law constant....
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...to Jacob (1986) and Chameides (1984) as the source but this value cannot be found there. 64) The value is from Table 1 of the paper. However, J. Geophys. Res. forgot to print the tables and I received them directly from the author. 65) Fickert (1998) extracted a value from wetted-wall flow tube experiments....
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Book•
28 Sep 1998TL;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.
Abstract: Preface Acknowledgements 1. Introduction 2. Atmospheric structure, composition and thermodynamics 3. The continuity and thermodynamic energy equations 4. The momentum equation in Cartesian and spherical coordinates 5. Vertical-coordinate conversions 6. Numerical solutions to partial differential equations 7. Finite-differencing the equations of atmospheric dynamics 8. Boundary-layer and surface processes 9. Radiative energy transfer 10. Gas-phase species, chemical reactions and reaction rates 11. Urban, free-tropospheric and stratospheric chemistry 12. Methods of solving chemical ordinary differential equations 13. Particle components, size distributions and size structures 14. Aerosol emission and nucleation 15. Coagulation 16. Condensation, evaporation, deposition and sublimation 17. Chemical equilibrium and dissolution processes 18. Cloud thermodynamics and dynamics 19. Irreversible aqueous chemistry 20. Sedimentation, dry deposition and air-sea exchange 21. Model design, application and testing Appendix A. Conversions and constants Appendix B. Tables References Index.
863 citations
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.
Abstract: Mass-independent fractionation (MIF) of sulfur isotopes has been reported in sediments of Archean and Early Proterozoic Age (>2.3 Ga) but not in younger rocks. The only fractionation mechanism that is consistent with the data on all four sulfur isotopes involves atmospheric photochemical reactions such as SO2 photolysis. We have used a one-dimensional photochemical model to investigate how the isotopic fractionation produced during SO2 photolysis would have been transferred to other gaseous and particulate sulfur-bearing species in both low-O2 and high-O2 atmospheres. We show that in atmospheres with O2 concentrations <10-5 times the present atmospheric level (PAL), sulfur would have been removed from the atmosphere in a variety of different oxidation states, each of which would have had its own distinct isotopic signature. By contrast, in atmospheres with O2 concentrations ≥10-5 PAL, all sulfur-bearing species would have passed through the oceanic sulfate reservoir before being incorporated into sediment...
853 citations
Cites background from "The photochemistry of a remote mari..."
...The relevant equilibrium constants were taken from Chameides (1984)....
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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.
Abstract: The actinic flux must be distinguished from other radiometric quantities such as the irradiance. This distinction shows that (1) a fraction of the recent atmospheric chemistry literature contains improperly calculated rates of photodissociation, and (2) 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. Both of these findings are traceable to the ∼2 cos θ factor incurred in the actinic flux (but not in the irradiance) when the solar beam is scattered and diffused into nearly isotropic light.
764 citations
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.
696 citations
References
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Book•
01 Jan 1973TL;DR: CRC handbook of chemistry and physics, CRC Handbook of Chemistry and Physics, CRC handbook as discussed by the authors, CRC Handbook for Chemistry and Physiology, CRC Handbook for Physics,
Abstract: CRC handbook of chemistry and physics , CRC handbook of chemistry and physics , کتابخانه مرکزی دانشگاه علوم پزشکی تهران
52,268 citations
Book•
01 Sep 1971
4,078 citations
15 Aug 1992
TL;DR: As part of a series of evaluated sets, rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation are provided in this article, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena.
Abstract: As part of a series of evaluated sets, rate constants and photochemical cross sections compiled by the NASA Panel for Data Evaluation are provided. The primary application of the data is in the modeling of stratospheric processes, with particular emphasis on the ozone layer and its possible perturbation by anthropogenic and natural phenomena. Copies of this evaluation are available from the Jet Propulsion Laboratory.
3,218 citations
TL;DR: A model for the photochemistry of the global troposphere constrained by observed concentrations of H2O, O3, CO, CH4, NO, NO2, and HNO3 is presented in this paper.
Abstract: A model for the photochemistry of the global troposphere constrained by observed concentrations of H2O, O3, CO, CH4, NO, NO2, and HNO3 is presented. Data for NO and NO2 are insufficient to define the global distribution of these gases but are nonetheless useful in limiting several of the more uncertain parameters of the model. Concentrations of OH, HO2, H2O2, NO, NO2, NO3, N2O5, HNO2, HO2NO2, CH3O2, CH3OOH, CH2O, and CH3CCl3 are calculated as functions of altitude, latitude, and season. Results imply that the source for nitrogen oxides in the remote troposphere is geographically dispersed and surprisingly small, less than 107 tons N yr−1. Global sources for CO and CH4 are 1.5 × 109 tons C yr−1 and 4.5 × 108 tons C yr−1, respectively. Carbon monoxide is derived from combustion of fossil fuel (15%) and oxidation of atmospheric CH4 (25%), with the balance from burning of vegetation and oxidation of biospheric hydrocarbons. Production of CO in the northern hemisphere exceeds that in the southern hemisphere by about a factor of 2. Industrial and agricultural activities provide approximately half the global source of CO. Oxidation of CO and CH4 provides sources of tropospheric O3 similar in magnitude to loss by in situ photochemistry. Observations of CH3CCl3 could offer an important check of the tropospheric model and results shown here suggest that computed concentrations of OH should be reliable within a factor of 2. A more definitive test requires better definition of release rates for CH3CCl3 and improved measurements for its distribution in the atmosphere.
1,762 citations
Book•
01 Jan 1952
TL;DR: The Selected Values of Chemical Thermodynamic Properties as mentioned in this paper, published by the National Bureau of Standards (NBS) in 1952, is a seminal work in the field of thermodynamics.
Abstract: The theoretical framework of thermodynamics was well established by the time NBS was founded, and certain important applications, such as improving the efficiency of steam engines, had been demonstrated. However, the broad application of thermodynamics to the design and control of industrial processes had to await the accumulation and organization of a large amount of experimental data, as well as theoretical contributions from quantum mechanics and statistical mechanics. The appearance of Selected Values of Chemical Thermodynamic Properties [1] in 1952 marked a significant milestone in this process. This book represented the culmination of 20 years of work by Frederick D. Rossini and coworkers in evaluating and systematizing the data that had appeared in the world literature on thermochemistry. It tabulated accurate values of the thermodynamic properties of all inorganic and simple organic compounds that had been investigated in a format that allowed prediction of the outcome of many thousands of chemical reactions. Such calculations, which indicate whether a reaction will take place and, if so, the extent of reaction and amount of heat released or absorbed, are immensely important in research and engineering. Selected Values, which was often referred to simply as “Circular 500” after its NBS publication designation, presented recommended values of the enthalpy (heat) of formation, Gibbs energy of formation, entropy, and heat capacity of individual chemical compounds in different physical states (solid, liquid, gas, or aqueous solution). All values were reduced to standard state conditions, defined by parameters such as temperature (25 C) and pressure (one standard atmosphere). Since the laws of thermodynamics require that the change in properties such as energy and entropy cannot depend on the path followed in going from an initial to a final state—otherwise one could build a perpetual motion machine—the net change in thermodynamic properties in a chemical reaction can be calculated by addition and subtraction of the standard state values for the substances taking part in the reaction. This allows a simple prediction of whether the reaction will occur at all and, if it does, whether it will go to completion. In intermediate situations, one can obtain a quantitative measure of the extent of reaction from the equilibrium constant, which is easily calculated from the tabulated standard state values. Finally, most chemical changes involve either an absorption or release of heat, and the amount of this heat may be calculated from the same data. Thus Selected Values provided an extremely powerful tool for predicting the course of chemical reactions, a goal of chemists since the earliest days of the science. The book itself was 822 pages in length and covered about 5000 chemical species. It was divided into two parts, the first dealing with the thermodynamic properties in a particular physical state and the second with the change in properties in transitions between states (such as melting and vaporization). All data were internally consistent, in the sense that all physical and thermodynamic relations existing between different properties for the same substance, or the same property for different substances, were satisfied by the tabulated values. The table layout in Circular 500 became the norm for thermodynamic tabulations throughout the world. Fig. 1. Frederick D. Rossini.
1,460 citations