The maximum eight-hour average concentration of carbon monoxide (CO) in an urban area is measured to be 17 ppm. The NAAQS is 9 ppmv (equivalent to 10.3 mg/m^3 estimated at P = 1 atm and T=298.25°K). Automobile emissions are believed to be the only major source of CO; it is assumed there is no background contribution for other sources. Assume also that CO can be modeled as chemically non-reactive over the period of interest. Answer the following questions:
a. If the average wind speed is 3 m/s and the urban area has the dimension of 95 x 95 km with a mixing height of 500 m, what is the steady state emission rate (mg/m^2-s) of CO by the automobiles that would lead to the measured city air concentration of CO of 17 ppm?
b. How much of a reduction in the automobile emission rate would be required to achieve the maximum eight-hour average NAAQS for CO at steady state 9 ppmv ( (10.3 mg/m^3)?