Consider the airshed over a city with 100,000m on each side and a mixing depth of 1,200m.

a. Assuming clean air blows into the airshed at an average speed of 4m/s and PM2.5 is emitted within the airshed at a rate of 20kg/s, estimate the steady- state concentration of PM2.5 in the airshed. Assume PM2.5 is conservative (Ignore removal due to settling). Include a diagram/drawing of the model.

(Hint: set this up just like our box models from unit 1 using the conservation of

mass principles).

b. Recalculate 4a assuming there is an inversion layer that starts at 200m

reducing the mixing depth to 250m.