Air Toxic Emissions Distribution and Performance Analysis of the CMAQ Air Toxic Model - A Case Study of Houston Area, Texas

Air quality models have been used in the past to predict the ambient air toxic concentration but CMAQ air toxics model, used in this thesis, is the first air quality model, which accounts the toxic chemical reactions in the ambient atmosphere. The main objective of this thesis was to analyze the distribution of air toxics emission in the Houston region, Texas using an emission processing tool and to determine the performance of the advanced air toxics model (CMAQ) used. Each year large amount of air toxics are emitted in the state of Texas, particularly in the Houston region. A study on the hourly distribution of major toxics species emitted in the region would help the emission reduction policy makers to focus on the counties and areas within the counties which emit large amount of toxics in the region. The Texas toxic inventory and the national emissions were processed using an EPA developed emission processing tool and the output from the tool was used to analyze the distribution of toxic emissions in the region. The latest air toxic model developed by the EPA is exclusively developed for air toxic species. The model has a detailed mechanism for chemical speciation in the atmosphere and has the ability to process most of major air toxic species. The output from the processing tool was also used to study the performance of this latest third generation air toxics model. The model was used to predict the concentration of major air toxics species for the year 2000 and the predicted concentration was compared with the monitored values in the region. A detailed analysis on the performance of the model was made and a conclusion on the effectiveness of the model was drawn.