[en] The atmospheric concentrations of CCl₃F, CO, SO₂, sulfates, and several trace elements were measured in a Lagrangian mode upwind, in and downwind of St. Louis during the afternoons of several days in July and August of 1973, 1974 and 1975, to determine the emission rates of these pollutants, the rates at which deposition and dilution due to atmospheric mixing caused the concentrations to decrease downwind of St. Louis, and the rate of conversion of SO₂ to sulfates. Beyond 10 to 20 miles downwind of St. Louis, dilution due to atmospheric mixing decreased the concentrations 6.6 +- 2.27% hr^-1 (2sigma) in 1973 and 4.5 +- 1.3% hr^-1 in 1975. The concentrations of anthropogenic particulates such as lead, bromine and zinc decreased 13.3 +- 3.5% hr^-1 in 1973 and 10.0 +- 2.4% hr^-1 in 1975 as a result of deposition and mixing. The deposition velocity for these elements was calculated to be 2.2 +- 1.4 cm sec^-1 in 1973 and 1.8 +- 0.7 cm sec^-1 in 1975. Beyond 40 to 50 miles downwind of St. Louis, mixing, deposition and conversion to sulfates caused the SO₂ concentrations to decrease 25 +- 10% hr^-1 in 1973 and 22.8 +- 5.5% hr^-1 in 1975. This decrease was due primarily to deposition and the SO₂ deposition velocity and was calculated to be 3.8 +- 1.7 cm sec^-1 in 1973 and 6.2 +- 1.3 cm sec^-1 in 1975. The rate of conversion of SO₂ to sulfates was calculated to be 3.3 +- 1.7% hr^-1 in 1973 and 3.7 +- 1.2% hr^-1 in 1975