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  • absorption  (2)
  • acid rain  (2)
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  • 1
    Digitale Medien
    Digitale Medien
    On the scavenging of SO2 by cloud and rain drops: IV. A wind tunnel and theoretical study of the absorption of SO2 in the ppb(v) range by water drops in the presence of H2O2 (1991)
    Springer
    Journal of atmospheric chemistry 12 (1991), S. 1-17 
    Details
    ISSN: 1573-0662
    Schlagwort(e): Scavenging ; acid rain ; mass transfer ; washout ; sulfur dioxide ; gas absorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract An experimental study involving the Mainz vertical wind tunnel is described where the rate of SO2 removed from the air by freely suspended water drops was measured for SO2 concentrations in the gas phase ranging between 50 and 500 ppb, and for various H2O2 concentrations in the liquid phase. In a first set of experiments, the pH inside the SO2 absorbing drops was monitored by means of colour pH indicators added to the drops. In a second set of experiments, the amount of SO2 scavenged by the drops was determined as sulfate by an ionchromatograph after the drops had been removed from the vertical air stream of the wind tunnel after various times of exposure to SO2. The results of our experimental study were compared with the theoretical gas diffusion model of Walcek and Pruppacher which was reformulated for the case of SO2 concentrations in the ppbv(v) range for which the main resistance to diffusion lies in the gas phase surrounding the drop. Excellent agreement between experiment and theory was obtained. Encouraged by this agreement, the theory was used to investigate the rate of sulfate production inside a drop as a function of pH. The sulfate production rate, which includes transport and oxidation, was compared with the production rate based on bulk equilibrium, as cited in the literature.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00053932
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    On the scavenging of SO2 by large and small rain drops: V. A wind tunnel and theoretical study of the desorption of SO2 from water drops containing S(IV) (1993)
    Springer
    Journal of atmospheric chemistry 16 (1993), S. 201-218 
    Details
    ISSN: 1573-0662
    Schlagwort(e): Scavenging ; acid rain ; mass transfer ; sulfur dioxide ; gas desorption
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract An experimental and theoretical study has been carried out to investigate the rate of desorption of SO2 from water drops falling at terminal velocity in air. The experiments were carried out in the Mainz vertical wind tunnel in which water drops of various sizes containing S(IV) in various concentrations were freely suspended in the vertical airstream of the tunnel. The results of these experiments were compared with the predictions of three theoretical models, and with the experiments of Walceket al. This comparison shows that the predictions of the diffusion model of Kronig and Brink in the formulation given by Walcek and Pruppacher agree well with the experimental results for all relevant large and small rain-drop sizes, and for all considered concentrations of S(IV) inside the drops. In contrast, the predictions of the diffusion model which assumes complete internal mixing inside a drop agrees with the experimental results only if the concentration of S(IV) inside the drop is less than that equivalent of an equilibrium SO2 concentration of 15 ppbv. At larger concentrations, the theoretical predictions of the model for complete internal mixing progressively deviate from the experimental results. It is further shown that Barrie's double film model can be used to interpret the resistance to diffusion inside a drop in terms of a diffusion boundary layer inside the drop which increases in thickness with decreasing concentration of S(IV). Applying our results to the desorption of SO2 from small and large rain drops falling below an assumed cloud base, shows that for typical contents of S(IV) inside the drops substantial amounts of SO2 will desorb from these drops unless H2O2 is present in the surrounding air.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00696896
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    On the scavenging of gaseous nitrogen compounds by large and small rain drops I. A wind tunnel and theoretical study of the uptake and desorption of NH3 in the presence of CO2 (1995)
    Springer
    Journal of atmospheric chemistry 21 (1995), S. 293-307 
    Details
    ISSN: 1573-0662
    Schlagwort(e): Gas scavenging ; ammonia ; absorption ; desorption ; convective diffusion models ; CO2-hydration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract An experimental study has been carried out in the Mainz vertical wind tunnel to determine the rate at which NH3 in the presence of CO2 is absorbed by freely suspended water drops. The experimental uptake rates were found to be in good agreement with the rates predicted by the Kronig-Brink convective diffusion model and, for gas concentrations in the ppbv range also by the model in which it is assumed that the absorbed gas is well mixed inside the drop (henceforth called well mixed model). The same conclusion was shown to apply also to the desorption of NH3 from a drop previously exposed to NH3. The latter result is in contrast to the desorption of SO2 which must be described by a model which accounts for the diffusion of the species inside the drop. Comparison of our experimental results with theory show further that the uptake of NH3 in presence of CO2 is significantly overestimated if the slow reaction CO2(aq)+H2O⇌HCO 3 − +H+ is neglected in the theoretical computation.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00696760
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    On the scavenging of gaseous nitrogen compounds by large and small rain drops: II. Wind tunnel and theoretical studies of the simultaneous uptake of NH3, SO2 and CO2 by water drops (1996)
    Springer
    Journal of atmospheric chemistry 24 (1996), S. 271-284 
    Details
    ISSN: 1573-0662
    Schlagwort(e): gas scavenging ; absorption ; sulfur dioxide ; ammonia ; plume washout ; CO2-hydration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Geologie und Paläontologie
    Notizen: Abstract An experimental investigation of the simultaneous absorption of NH3 and SO2 from the ambient atmosphere by freely falling water drops has been carried out in the Mainz vertical wind tunnel. The experimental results were found to be in good agreement with the results derived from computations with the Kronig-Brink convective diffusion model and also with a model which assumes a drop to be well mixed at all times. Encouraged by this agreement, these computation schemes for the uptake of gas by single drops where incorporated in a pollution washout model with realistic SO2, NH3 and CO2 gas profiles. This model allows an entire raindrop size distribution to fall through a gas layer. The results of this ‘plume-model’ show that the SO2 uptake is strongly dependent on the NH3 concentration in the atmosphere and on the rainrate. We also find that the small drops contribute more towards the washout of these gases. In the case of simultaneous presence of NH3 and SO2, desorption of these gases is negligible.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00210286
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
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