The role of biogenic and anthropogenic air pollution emissions in the production of tropospheric ozone in Middle Tennessee

In order to assess the importance of biogenic hydrocarbons on ozone formation in the lower atmosphere, photochemical simulations were carried out with a set of spatially resolved anthropogenic ozone precursors and countywide biogenic hydrocarbons emissions using EPA OZIPM-4 model. County-wide biogenic hydrocarbons (BHCs) emissions were calculated using the EPA PC-BEIS program. Results from the study show that BHC emissions accounted for 45% of the total VOC emissions in the study area. The contribution from BHCs to the total ozone loading was about 9%. The ozone standard was predicted to be attained by a 50% reduction in anthropogenic hydrocarbon emissions (AHCs) or a 50% reduction in NO_x emissions or 30% reductions in both AHCs and NO_x. Neither VOC nor NO_x were found to be controlling but rather each tended to play an equal role in ozone formation. In the urban environment, BHCs in conjunction with urban NO_x emissions were found to generate significant ozone levels even when anthropogenic emissions of VOCs were eliminated.