MEASUREMENTS OF ATMOSPHERIC POLLUTANTS IN ST-LOUIS AREA

The concentrations of trace gases and particles were measured in the plume from metropolitan St. Louis, Missouri, USA, at 80 and 120 km from the urban center. The concentrations of SO2, NO2, NO, NH3, H2S, aldehydes, CO, total hydrocarbons and CFCl3 [fluorocarbon-11] were determined. The concentrations of many of these gases were significantly higher in the plume than outside the plume at these distances. Measurements were made near the ground and from an aircraft. The width of the plume was usually 20-30.degree., less than expected. By comparing the concentrations measured at 80 km from the city with those measured at 120 km from the city, and using the decrease of conservative trace gases to account for loss through physical process, we have arrived at preliminary estimates of the decay rates were made for a few trace gases. The evidence is most compelling for SO2. At about 100 km from the city, the overall half-life of SO2 is 2-8 h.