A 300-MW power plant has a 150-m effective stack (H). Ambient temperature is 20C; windspeed is directly measured at the effective stack height (H) at 5 m/s; and the atmosphere is stable, Class E (with a lapse rate of 5C/km). If the plant emits 300 g/s of SO2 (yuk!), (a) estimate the concentration at ground level at a distance of 20 km directly downwind and 1 km off (perpendicular) the downwind axis. (b) Besides lowering the emission rate, how could this value (concentration at ground level) be changed considering the same weather/stability conditions?