This became evident in the mid-1940s in Los Angeles and its effects caused eye irritation,plant damage and visibility degradation .
In Los Angeles and Southern California the topography of the region,intensely sunny days which favorise photochemical processes,and the high density of automobiles which are the most important source of pollutants make the photochemical smog to be a serious problem.
In this project we want to analyse a reaction mechanism for photochemical smog, emphasizing the relation between the concentration of NOx and organic reactants in atmosphere and the evolution of the tropospheric ozone. Our model is presented in the table below,together with the constant rate for each reaction,and even if only 12 reactions involving 16 species are considered, many important features of the tropospheric ozone characteristics can be recovered from it.
Table 1:
This can be done using the KPP symbolic preprocessor,by fixing an initial concentration for the organic reactants (RH and RCHO) and the other species (as CO2,H2O,O2,...) and varing the NOx concentrations.
A complete description of the KPP preprocessor can be found here
The ozone concentration depends on the initial NOx concentration linearly or not? Decreasing NOx concentrations implies always a reduction of the ozone concentrations?
Detailes can be found here
(1) NO2 + hv --> O+NO
(2) O + O2 + M -->O3 + M
In a "clean" atmosphere,a steady state for the ozone concentration is quickly achieved and the effect of the reactions (1) and (2) is balanced by the reaction between O3 and NO to regenerate NO2 :
(3) O3 +NO --> NO2 +O2
As results from Table 1 above,in the presence of organic reactants and the OH radical,the oxidation process and ozone formation are completely changed.
Here we want to study the temporal dynamics of RH,RCHO,NO,NO2 and O3 for three sets of initial concentrations (all in ppm),as presented in Table 2 below:
Table 2:
Plot the evolution of the concentration for each substance in each case and interpret the results.
Detailes can be found here
The chemical features of ozone formation in the photochemical smog system can be studied by plotting isoplets of maximum concentrations achieved over a fixed period of time of irradiation.
Consider the plane of the initial NOx concentration [NOx]=[NO2]+[NO] and the initial reactive concentration,expressed in units of parts-per-million of carbon.
Use the KPP and MATLAB to generate various constant level curves for maximum concentration of ozone and interpret the results. In order to get smooth curves,a fine grid should be considered on each axis. each point on each curve represents a separate experiment using the Kinetic mechanism.
Detailes can be found here
a) Assume that in region A the measurements indicate a concentration of the initial NOx of 0.1 ppm and a concentration of initial reactive organic of 2 ppmC. What action should be taken to reduce the ozone levels to 0.12 ppm in an efficient way?
b) Assume that in region B the measurements indicate a concentration of the initial NOx of 0.5 ppm and a concentration of initial reactive organic of 1.75 ppmC. What action should be taken to reduce the ozone levels below 0.3 ppm in an efficient way?
Detailes can be found here
The chemistry of sulfur dioxide and the presence of more organic reactants should be considered. A complex model involving 88 species and 178 reactions was considered. The evolution of the ozone,NO and NO2 concentrations over a period of 5 days are shown here
Explain the results obtained.
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