MEASUREMENTS OF REACTIVE NITROGEN AND OZONE TO 5-KM ALTITUDE IN JUNE 1990 OVER THE SOUTHEASTERN UNITED-STATES

Aircraft flights made in June 1990 substantiate the expected variabili ty of ozone and reactive nitrogen constituents in the lower atmosphere over Mississippi and Alabama due to the variety and proximity of sour ces and the photochemical production and loss of ozone. Urban, biomass burn, electrical power plant, and paper mill plumes are examples of s ources encountered during these flights and some of their characterist ics are described. For example, in the urban plume from Mobile, Alabam a, an upper limit to the ozone production efficiency was 6-7 parts per billion by volume (ppbv) of O-3 per ppbv of NO, oxidized. Emissions f rom several biomass fires had lower efficiencies of 2-4 ppbv ppbv(-1), but the average rate of production of ozone was as high as 58 ppbv hr (-1) for one fire where the plume was isolated from mixing to the surf ace. Close encounters with paper mill and power plant plumes showed ch emical consumption of O-3, while far-field encounters with power plant plumes showed enhanced O-3 due to photochemical production. Observati ons made in early morning, below a nocturnal inversion provide indirec t evidence of significant nighttime oxidation of freshly emitted NO, t o reservoir constituents. Although statistics for the region covered b y these flights clearly depend on precisely where the aircraft flew, t he mean and median temporal and vertical behaviors of constituent mixi ng ratios are summarized.