Project at a Glance

Title: Development of the SAPRC-07 chemical mechanism and updated ozone reactivity scales.

Principal Investigator / Author(s): Carter, William P. L

Contractor: UC Riverside

Contract Number: 03-318

Research Program Area: Atmospheric Processes

Topic Areas: Chemistry & Reactivity, Modeling


A completely updated version of the SAPRC-99 chemical mechanism, designated SAPRC-07, has been developed and is documented in this report. This includes a complete update of the rate constants and reactions based on current data and evaluations, reformulated and less parameterized aromatics mechanisms, a representation of chlorine chemistry, a reformulated method to represent peroxy reactions that is more appropriate for modeling secondary organic aerosol formation, and improved representations for many types of VOCs. This mechanism was evaluated against the result of ~2400 environmental chamber experiments carried out in 11 different environmental chambers, including experiments to test mechanisms for over 120 types of VOCs. The performance of the mechanism in simulating the chamber data was comparable to SAPRC-99, with generally satisfactory results for most types of VOCs but some increases in biases in simulations of some mixture experiments. The mechanism was used to derive an update to the MIR and other ozone reactivity scales for almost 1100 types of VOCs.

The average changes in relative MIR values was about 10%, with > 90% of the VOCs having changes less than 30%, but with larger changes for some types of VOCs, including halogenated compounds. Recommendations are given for future mechanism development research. The mechanism documentation includes some large tabulations that are being provided only in electronic form. Links to downloading these tabulations are available at

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

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