Modeling formaldehyde sources in the Houston-Galveston area during the Texas Air Quality Study 2006

Ambient formaldehyde concentrations can reach very high levels in Houston, in particular near the highly industrialized Houston Ship Channel (HSC) area. At various occasions enhanced levels of HCHO were observed during summer 2006. Formaldehyde can be formed from the chemical formation and/or directly emitted from mobile and industrial sources or barge operations in the HSC area. The relative contribution of formaldehyde sources to its ambient mixing ratios is not apparent for the Houston conditions. This work investigates sources of formaldehyde during the Second Texas Air Quality Study (TexAQS) in summer 2006 by means of utilizing the Community Multiscale Air Quality (CMAQ) model and its integrated processes and reactions analyzes. While photochemical formation from abundant anthropogenic olefins dominates observed formaldehyde levels during daytime, direct emissions from industrial sources are significant contributors during nighttime. However, on several nights chemical reactions of olefins also add significantly to formaldehyde formation.