A smelter emits SO2 at a rate of 10,000 kg/day. The stack is 200 m tall and the plume rise is 100 m. The windspeed is 2 m/s at a height of 10 m and it is an overcast day. Estimate the ground-level SO2 concentration in units of µg/m3. a. 6000 m directly downwind b. 6000 m downwind and 300 m off the centerline