Aqueous-phase chemistry

Hancock, R.D., Bartolotti, L.J. and Kaltsoyannis, N. (2006) Density Functional Theory-Based Prediction of Some Aqueous-Phase Chemistry of Superheavy Element 111. Roentgenium (I) Is the Softest Metal Ion. Inorganic Chemistry, 45, 10780-10785. 

Fotovat A., Naidu R., Sumner M.E. Water Soil ratio influences aqueous phase chemistry of indigenous copper and zinc in soils. Aust J Soil Res 1997 35 687-710. 

In addition to gas-phase chemistry, aqueous-phase chemistry discussed in Chapter 8.C.3 taking place in clouds can also be important in remote regions. For example, modeling studies by Lelieveld and Crutzen (1990) suggest that clouds may decrease the net production of 03 by uptake of H02, dissociation to H+ + 02, and reaction of 03 with 02 in cloud droplets. 

Again, the chemistry is analogous to the OH-initiated oxidation of chloride and bromide in solution. The subsequent aqueous-phase chemistry for the halogens is summarized in the following chapter. 

HNO-, and HONO separately in Chapter 7. As a result, we shall deal in this chapter primarily with H2S04 and organic acids. In addition, since much of the chemistry occurs in the aqueous phase, with oxidation of dissolved S02 initiated by a variety of free radical species, we shall also discuss the associated aqueous-phase chemistry of HOx, carbonate/bicarbonate, and the halogens. 

The aqueous-phase and gas-phase chemistries of HO, are sufficiently closely coupled that the chemistry shown in Tables 8.11 and 8.12 can affect gas-phase concentrations as well. For example, including the aqueous-phase chemistry in models of tropospheric ozone formation alters predicted 03 concentrations, although whether the perturbation is significant is subject to some controversy (e.g., see Lelieveld and Crutzen, 1990 Jonson and Isaksen, 1993 Walcek et al., 1997 Liang and Jacob, 1997). 

Excellent summaries of aqueous-phase chemistry are found in Huie (1995) and Zellner and Herrmann (1995). 

TABLE 8.14 Aqueous-Phase Chemistry Involving S(IV) and Reactive Chlorine and Bromine Ions... 

Gurciullo, C. S., and S. N. Pandis, Effect of Composition Variations in Cloud Droplet Populations on Aqueous-Phase Chemistry, J. Geophys. Res., 102, 9375-9385 (1997). 

Schwartz, S. E., Gas- and Aqueous-Phase Chemistry of H02 in Liquid Water Clouds, J. Geophys. Res., 89, 11589-11598 (1984b). 

It is safe to conclude that there is no equilibrium aqueous phase chemistry of Tl2+. 

A simple calculation of the lifetime of MSA in cloud water can be made using model estimates of the free radical chemistry of cloud droplets. The OH concentration in cloud water is a complex function of both the gas and aqueous phase chemistry and the dynamics of gas/liquid exchange. A recent model (21) estimated cloudwater OH concentration as 2-6 x 10 M for droplets of 5 -30/im radius. Using the rate constant measured here (4.7 x 107 M 1 s 1), this yields a lifetime of 1.2 3.5 hours. Considering that the lifetime of a nonraining cloud is on the order of a few minutes to an hour, some fraction of the MSA present could react with OH, presumably being converted to sulfate. While such a process may lower the concentratron of MSA in the droplet, it would only have a minor effect on the cloudwater sulfate levels because of the typically low MSA non-sea-saIt sulfate ratio in the aerosol entering the cloud. 

The significance of this work is its identification of SC water as a medium which supports and enhances aqueous phase chemistry ordinarily observed at much lower temperatures. Fundamental studies of the reaction chemistry of biopolymer related model compounds described in this paper offer insights into the details of reaction mechanisms, and facilitate the choice of reaction conditions which enhance the yields of valuable products. Chemical reaction engineering in supercritical solvents, based on the ability to choose between heterolytic and homolytic reaction mechanisms with foreknowledge of results, holds much promise as a new means to improve our utilization of the vast biopolymer resource. 

Hoffmann, M. R., and Calvert, J. G., Chemical Transformation Modules for Eulerian Acid Deposition Models. Volume II The Aqueous-Phase Chemistry. National Center for Atmospheric Research, Boulder, Colo., 1985. 

Background non-methane hydrocarbon levels are generally less than 20 ppbC. A typical sample (Table I) indicates that the major components are ethane, propane and acetylene. Because only picomolar amounts of these hydrocarbons would exist in the cloud water, the effects of these background levels on aqueous-phase chemistry are expected to be negligible. The effect of the organic acids is not expected to be significant unless sources of OH exist. Formaldehyde is known to inhibit aqueous SO2 oxidation, but its concentration here is insignificant compared to the concentrations of SO2 intentionally... 

Over the past 25 years, a number of significant theoretical and algorithmic advances have been proposed towards incorporating solvent effects into quantum chemical computations. These methodologies were presented in Section 1.4. Interested readers looking for further computational details are referred to the monographs by Cramer and Jensen and comprehensive reviews by Tomasi, ° Cramer and Truhlar, and Mennucci. " This chapter presents representative case studies of aqueous-phase chemistry analyzed using quantum mechanical computations. 

Caltech unified GCM (Global) GISS GCM IF Harvard tropospheric Os-NO -hydrocarbon chemistry (305-346 reactions, 110-225 species) bulk aqueous-phase chemistry of S(IV) (5 equilibria and 3 kinetic reactions) prognostic aerosol/ cloud treatments with prescribed size distribution Global chemistry-aerosol interactions aerosol direct radiative forcing the role of heterogeneous chemistry impact of future climate change on O3 and aerosols Liao et al. (2003), Liao and Seinfeld (2005)... 

Processes needed aerosol thermodynamics/d3mamics, aqueous-phase chemistry, gaseous precursor emissions, primary aerosol emissions, and water uptake... 

Betterton, E.A. (1992) Henry s law constants of soluble and moderately soluble organic gases Effects of aqueous phase chemistry. Adv. Environ. Sci. Technol. 24, 1-50. 

After polymerization processes, one of the most important aqueous phase reactions to be performed on an industrial scale is the Rhone-Poulenc hydro-formylation process that utilizes a water soluble rhodium phosphine catalyst. This process will be discussed in more detail in Chapter 10. The success of this process has led to many exciting results in metal catalysed aqueous phase chemistry. Additionally, amazing advances have been made where reactions that are typically considered unsuited to the presence of moisture, e.g. Grignard-type chemistry, can be performed in water. 

The pH of sea salt aerosol is an important property as many important aqueous phase reactions are pH dependent. For example, oxidation of S(IV) (SO2 + HSOs + SO ) by O3 is only important for pH of more than 6. Sea salt aerosol is buffered with HC03. Uptake of acids from the gas phase leads to acidification of the particles. According to the indirect sea salt aerosol pH determinations by Keene and Savoie (1998, 1999), the pH values for moderately polluted conditions at Bermuda were in the mid-3s to mid-4s. The equilibrium model calculations of Fridlind and Jacobson (2000) estimated marine aerosol pH values of 2-5 for remote conditions during ACE-1. Using a one-dimensional model of the MBL which includes gas phase and aqueous phase chemistry of sulfate and sea salt aerosol particles, von Glasow and Sander (2001) predicted that under the chosen initial conditions the pH of sea salt aerosol decreases from 6 near... 

During ultrasonic irradiation of aqueous solutions, OH radicals are produced from dissociation of water vapor upon collapse of cavitation bubbles. A fraction of these radicals that are initially formed in the gas phase diffuse into solution. Cavitation is a dynamic phenomenon, and the number and location of bursting bubbles at any time cannot be predicted a priori. Nevertheless, the time scale for bubble collapse and rebound is orders of magnitude smaller than the time scale for the macroscopic effects of sonication on chemicals (2) (i.e., nanoseconds to microseconds versus minutes to hours). Therefore, a simplified approach for modeling the liquid-phase chemistry resulting from sonication of a well-mixed solution is to view the OH input into the aqueous phase as continuous and uniform. The implicit assumption in this approach is that the kinetics of the aqueous-phase chemistry are not controlled by diffusion limitations of the substrates reacting with OH. 

In this review the emphasis will be placed on results obtained by direct and fast detection techniques for phenoxyl radicals, mainly in aqueous solutions. Results for other solvents, however, will be included if they appear relevant to the aqueous phase chemistry of phenoxyl or if they are of general interest. 

Ooi, K. et al., Lithium-ion insertion/extraction reaction with X-MnO, in the aqueous phase, Chemistry Lett., 989, 1988. 

The widely held view that reactions of relatively low rate constants may be safely neglected in the modelling of aqueous phase chemistry should be verified. As shown for the cross-activation of S(IV) and nitrate, the neglected reactions may accelerate, possibly by orders of magnitude, due to an increase of the concentration of inorganic components in desiccating aerosols. 

The chemistry that occurs in cloud and fog droplets in the atmosphere has been shown, in the last decade or so, to be highly complex. Most atmospheric species are soluble to some extent, and the liquid-phase reactions that are possible lead to a diverse spectrum of products. The aspect of atmospheric aqueous-phase chemistry that has received the most attention is that involving dissolved S02. Sulfur dioxide is not particularly soluble in pure water, but the presence of other dissolved species such as H202 or 03 displaces the dissolution equilibrium for S02, effectively... 

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