The NAAQs for particulate matter less than 10 microns (PM10) are an annual average concentration of 50 mg/m3 and a daily maximum of 150 mg/m3. For the region surrounding the city of Middleburgh, the typical background concentration of PM10 is 30mg/m3. The city has dimensions of 75 km x 75 km and an atmosphere mixing height of 900 m in the region.
(a) Estimate the steady state PM10 concentration assuming a PM10 deposition velocity of 0.12 cm/s, prevailing wind velocity of 2.5 m/s, and a constant emission flux of PM10 0.82 mg/m2-s.
(b) For a few days each year meteorological conditions drop the mixing height to 250m and wind speed to 0.8 m/s. Assuming the emission rate remains constant and unchanged during this period, estimate how long it will take before the daily maximum NAAQS for PM10 is exceeded.