Project at a Glance

Title: SOA formation: chamber study and model development

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

Contractor: UC Riverside

Contract Number: 08-326

Research Program Area: Atmospheric Processes

Topic Areas: Chemistry & Reactivity


An experimental and mechanism development study was carried out to enhance the recently developed SAPRC-11 gas phase aromatic mechanism so it can predict secondary organic aerosol (SOA) formation from the atmospheric reactions of aromatics. This phase of the project covered dry conditions and 300K. A total of 158 dual reactor chamber experiments were carried out using the UCR-EPA environmental chamber, and their results were combined with previous data from this chamber to provide a database of 315 separate reactor irradiations for mechanism evaluation. A total of 14 representative aromatic hydrocarbons and 7 representative phenolic compounds were studied with varying reactant and NOx levels and in some cases with different light sources and other added reactants. Methods were developed and evaluated to represent gas-particle partitioning, nucleation, and chamber effects when modeling the experiments. Alternative mechanisms were examined and SOA yield and gas-particle partitioning parameters were optimized to simulate the available chamber data. The model simulated most of the data without large biases but with larger run-to-run variability in model performance than observed in ozone mechanism evaluations, and potential evaluation problems were observed for some compounds. It is concluded that this new mechanism reflects the current state of the science. Recommendations are given for the next phase of SOA mechanism development and other needed research.

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

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