Project at a Glance

Title: Development of an updated base case ambient VOC mixture for assessing atmospheric reactivity. Revised

Principal Investigator / Author(s): Sullivan, David W.

Contractor: University of Texas

Contract Number: 08-327

Research Program Area: Climate Change, Atmospheric Processes

Topic Areas: Chemistry & Reactivity, Modeling, Science, Toxic Air Contaminants


Volatile organic compounds (VOC) – also referred to as reactive organic gas (ROG) mixtures – are important precursors of ozone (O3) and particulate matter (PM) pollution, and many VOC species are themselves considered as air toxics. Accurate information about VOC composition in the air is needed both to assess possible effects of pollution and to develop plans to improve air quality. One specific regulatory approach is to take the data describing the typical mixture of VOCs in an urban area and then to simulate the atmospheric chemistry and physics using specialized computer programs. Much of the data in use currently to do air pollution modeling comes from studies from late 1980s to early 1990s. In this project, data for the Los Angeles area from 2006 – 2009 plus select older data have been used to construct new “base case” ROG mixtures to characterize the air for modern air modeling software tools. Among the changes observed in the base case ROG mixture from earlier periods to more recent years is that in general, fractions of paraffins, carbonyls and biogenic hydrocarbons are higher, while anthropogenic olefins tend to be lower in updated ROG mixture profiles. This combination of changes leaves the typical ROG mixture less reactive than in the past, which predicts generally lower ozone concentrations. Maximum incremental reactivity calculates slightly higher with the new profile, particularly for alkanes, oxygenated VOCs and aromatics.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

Stay involved, sign up with CARB's Research Email Distribution List