CMAQ and dispersion modeling of 1,3-butadiene for the Houston-Galveston Area

1,3-Butadiene is considered one of the important air toxics, and is classified by USEPA as a known human carcinogen. Apart from this direct impact on human health 1,3 butadiene is a highly reactive volatile organic compound and known to be involved in photochemical processes leading to ozone formation. Currently, studies are underway to characterize total human exposures to 1,3-butadiene in the Houston metropolitan area using individual- and population-based exposure modeling and also to determine contributions of industrial emissions to population exposures to 1,3-butadiene in this area. Here we present modeling results for ambient levels of 1,3-butadiene for an episodic period during Summer 2006. Ambient levels were estimated for the Second Texas Air Quality Study (TexAQS-II) in the Houston-Galveston area in Summer 2006 through the Community Multiscale Air Quality model (CMAQ) including the SAPRC99-extended mechanism (Czader et al., 2008), which contains explicit chemical reactions involving 1,3-butadiene. Ambient levels were also estimated using simpler dispersion modeling using AERMOD. The results are compared to observations of 1,3-buatdiene based on the auto-GC network available in this area. The ambient level estimates are studying for identifying relative contributions of different type of emissions to overall ambient levels.