A platform for research: civil engineering, architecture and urbanism
A platform for research: civil engineering, architecture and urbanism
Reactive scavenging of pollutants by rain: a modeling approach
Abstract An Eulerian model for rain scavenging of pollutants (Kumar, 1985) has been extended to take into account the processes of absorption of multiple pollutant species and chemical reactions within the raindrops. Model simulations have been performed to compare the rates of S(IV) oxidation by O3 and H2O2. A comparison of these two oxidation paths indicates that for raindrops, oxidation by O3 can be the dominating path at pH values near or above 4.7. However, oxidation by H2O2 will dominate at lower pH values. Oxidation of S(IV) catalyzed by Fe(III) and Mn(II) is potentially a very important path but there are many uncertainties regarding the magnitude and the pH dependence of the reaction rates as well as the presence of catalytic synergism between Fe(III) and Mn(II). At lower temperatures, solubilities of SO2, O3 and H2O2 increase while the rate constants for oxidation reactions decrease. Model simulations indicate that, all other conditions remaining the same, [SO4 −2] in raindrops would increase at lower temperatures but [NO3 −], which is produced solely as a result of HNO3 absorption, would not change. The lower [SO4 −2] in winter rains is thus, most likely, a result of the limited availability of oxidants. As a result of model simulations, it was also found that formaldehyde (HCHO) does not bind any appreciable amount of S(IV) in raindrops and that the [SO4 −2] and [S(IV)] in raindrops are not affected by the presence of HCHO in the atmosphere.
Reactive scavenging of pollutants by rain: a modeling approach
Abstract An Eulerian model for rain scavenging of pollutants (Kumar, 1985) has been extended to take into account the processes of absorption of multiple pollutant species and chemical reactions within the raindrops. Model simulations have been performed to compare the rates of S(IV) oxidation by O3 and H2O2. A comparison of these two oxidation paths indicates that for raindrops, oxidation by O3 can be the dominating path at pH values near or above 4.7. However, oxidation by H2O2 will dominate at lower pH values. Oxidation of S(IV) catalyzed by Fe(III) and Mn(II) is potentially a very important path but there are many uncertainties regarding the magnitude and the pH dependence of the reaction rates as well as the presence of catalytic synergism between Fe(III) and Mn(II). At lower temperatures, solubilities of SO2, O3 and H2O2 increase while the rate constants for oxidation reactions decrease. Model simulations indicate that, all other conditions remaining the same, [SO4 −2] in raindrops would increase at lower temperatures but [NO3 −], which is produced solely as a result of HNO3 absorption, would not change. The lower [SO4 −2] in winter rains is thus, most likely, a result of the limited availability of oxidants. As a result of model simulations, it was also found that formaldehyde (HCHO) does not bind any appreciable amount of S(IV) in raindrops and that the [SO4 −2] and [S(IV)] in raindrops are not affected by the presence of HCHO in the atmosphere.
Reactive scavenging of pollutants by rain: a modeling approach
Kumar, Sudarshan (author)
Atmospheric Environment ; 20 ; 1015-1024
1985-09-26
10 pages
Article (Journal)
Electronic Resource
English
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