A stack emitting 65 g/s of SO2 has an effective stack height of 150 m. The windspeed is 4 m/s at 10 m above ground and 6 m/s at the effective smokestack height. It is a cloudy summer day. Estimate the ground- level SO concentration directly downwind at a distance of 1.75 km. Note: Strong insolation refers to a clear summer day, moderate refers to a summer day with few broken clouds, slight refers to a fall afternoon or a cloudy summer day. Atmospheric Stability Classification Daytime insolation Surface wind speed (m/s) Strong 4/8 low cloud