Influence of fossil fuel combustion and biomass burning on tropospheric ozone

The tropospheric ozone budget is quantified over remote high northern latitudes in summer using measurements made during the summer of 1990 Arctic Boundary Layer Expedition (ABLE 3B). Regional photochemical production and loss in the 0-6 km column are found to be approximately equal; hence, net photochemical production is near zero. Dispersed in situ photochemical production driven by background NO levels is the largest source term. Influx of stratospheric ozone is of secondary importance, long-range transport of pollution ozone makes a small contribution, and photochemical production of ozone within biomass wildfire plumes is relatively negligible. Biomass fires and transport of anthropogenic pollution into the region may however have a major effect on the ozone budget through enhancement of background NO{dollar}sb{lcub}x{rcub}{dollar} mixing ratios which increase dispersed photochemical production. Good agreement is obtained between observed and model-generated vertical ozone profiles. In situ photochemistry within the 0-6 km column accounts for nearly 90% of the ozone mixing ratio within the boundary layer, while above 5 km it accounts for only about 40%. The 1-D model results indicate that influx from above is necessary to account for the observed increase in ozone mixing ratios with altitude.; The influence of biomass burning plumes on tropospheric photochemistry over the south Atlantic is examined using measurements made during the TRACE-A (TRansport and Atmospheric Chemistry near the Equator - Atlantic) expedition conducted during the 1992 southern tropical dry season. We find that {dollar}Delta{dollar}CO/{dollar}Delta{dollar}CO{dollar}sb2{dollar} decreases from 0.05 to 0.02 from regions of fresh fires to remote ocean locations as a result of photochemical loss of CO and decreasing background mixing ratios of CO{dollar}sb2{dollar}. We use {dollar}Delta{dollar}O{dollar}sb3{dollar}/{dollar}Delta{dollar}CO to infer ozone production in plumes and find an increase from 0.11 to 0.95 from fresh to old plumes. We conduct a case study of a large biomass burning plume off the west coast of Africa and simulate the evolution of this plume using a photochemical lagrangian plume model. We find that NO{dollar}sb{lcub}x{rcub}{dollar} emitted in the fire is rapidly converted to PAN. The degradation of PAN helps maintain the NO{dollar}sb{lcub}x{rcub}{dollar} concentration in the plume which is converted to HNO{dollar}sb3{dollar} over the course of a week. Net ozone production in the plume is negligible, however, and is limited by the availability of NO{dollar}sb{lcub}x{rcub}{dollar}. We also examine the influence that biomass burning plumes have on regional ozone production through the use of O-dimensional photochemical modelling along night tracks. We find that old plumes contribute substantially to regional ozone production and may be important contributors to the regional enhancement in column 03. The maintenance of NO{dollar}sb{lcub}x{rcub}{dollar} concentrations through the conversion of PAN to HNO{dollar}sb3{dollar} appears to be a regional phenomenon in aged plumes. Using a simulated wet season calculation we find that gross ozone production rates in background air during the dry season are approximately four times larger than during the wet season.; Finally, a brief case study of photochemical production of O{dollar}sb3{dollar} in two extremely large ozone enhancements observed at the trade wind inversion in Brazil is conducted. We find that O{dollar}sb3{dollar} mixing ratios in excess of 200 ppbv are generated within 1-2 days of aging of biomass burning emissions and are sustained throughout a week-long simulation. It appears that biomass burning emissions are capable of producing O{dollar}sb3{dollar} concentrations observed in highly polluted urban environments. (Abstract shortened by UMI.)...