| This thesis addresses the issue of how to control photochemical air pollution: specifically, whether emissions of nitrogen oxides (NO;Comparable predictions of responses of ambient pollutant concentrations to emissions reductions were given by Lagrangian and Eulerian model formulations. Different chemical mechanisms also gave similar results. Averaged over a wide range of initial conditions, four different mechanisms predicted ozone concentrations to within a standard deviation of seven percent, relative to the mean of their predictions. However, larger differences were found in predictions of other key species. Local sensitivity analysis indicates that the major discrepancies among the four mechanisms involve reactions of aromatics and alkenes.;Uncertainties in photochemical air quality models preclude total confidence in their predictions, so it is important to establish what constitutes an "acceptable" model. A case study of factors that have influenced the evolution of models used to estimate ROG control requirements indicates that the U.S. Environmental Protection Agency (EPA) has most often modified models in response to concerns of state or local officials, especially that models not be biased toward over control. Barriers to upgrading models include limited resources and time, uncertainty about whether suggested modifications would noticeably improve model accuracy, and concerns that more refined models would be used to deliberately underestimate control requirements.;The results call into question the adequacy of control strategies that rely on ROG emissions reductions. Modeling results indicate that reductions in NO... |
