2. An air pollution source emits a nonreactive pollutant at a rate of 500 g/s from a stack height of

125 m during a clear night. The plume rise is 75 m. The wind speed is 4 m/s as measured by

an anemometer at 10 m height. Use Briggs urban dispersion coefficients and rough terrain.

(a) Estimate ground level concentrations in µg/m³ at a distance 4000 m downwind of the

source and 50 m orthogonal to the plume centerline (i.e., x = 4000 m, y = 50 m). Assume

the dispersion is unbounded at both the ground and above. For this part of the problem,

perform the calculations by hand (to practice for an exam scenario).

(b) Set up in Excel or another spreadhseet program to compute the ground level concentrations

in µg/m³ for the same scenario as part (a) at downwind distances x of [100, 200, 300, ......

10000] m from the source. When setting up the spreadsheet, you should have columns for

x, Oy, G, and C(x.y.z).

(c) Compute the ground level concentrations in µg/m³ at x from 100 to 10000 m, assuming

the pollutant is perfectly reflected from the ground and unbounded from above.

(d) Compute the ground level concentrations in µg/m³ at x from 100 to 10000 m, assuming a

fumigation scenario with an inversion height z; of 400 m.

(e) Plot all scenarios (b, c, d) on the same graph. Explain the differences between the three

concentrations based on the physical description of the model. Discuss which scenario

would be the most hazardous.