Project at a Glance
Project Status: complete
Title: Environmental chamber studies of atmospheric reactivities of volatile organic compounds. Effects of varying chamber and light source
Principal Investigator / Author(s): Carter, William P. L.
Contractor: Statewide Air Pollution Research Center, UC Riverside
Contract Number: A032-069
Research Program Area: Atmospheric Processes
An experimental and modeling study was conducted to assess how chemical mechanism evaluations using environmental chamber data are affected by the light source and other chamber characteristics. Xenon arc light lights appear to give the best artificial representation of sunlight currently available, and experiments were conducted in a new Teflon chamber constructed using such a light source. Experiments were also conducted in an Outdoor Teflon Chamber using new procedures to improve the light characterization, and in Teflon chambers using blacklights. These results, and results of previous runs other chambers, were compared with model predictions using an updated detailed chemical mechanism. The magnitude of the chamber radical source assumed when modeling the previous runs were found to be too high; this has implications in previous mechanism evaluations. Temperature dependencies of chamber effects can explain temperature dependecies in chamber experiments when TĽ ~3000K, but not at temperatures below that. The model performance had no consistent dependence on light source for experiments not containing aromatics, but the model tended to underpredict O3 in the new xenon arc and blacklight chamber runs. This is despite the fact that such biases are not seen in modeling runs in the older xenon arc chamber or in preliminary modeling of University of North Carolina outdoor chamber runs. The reasons for this are not clear and additional studies are planned as part of our ongoing program.
For questions regarding research reports, contact: Heather Choi at (916) 322-3893
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