TITLE PAGEABSTRACTACKNOWLEDGEMENTSEXECUTIVE SUMMARYTABLE OF CONTENTSLIST OF TABLESLIST OF FIGURESI. INTRODUCTIONA. BackgroundB. Available Chamber Data BaseC. Objectives and Scope of this StudyII. ANALYSIS OF ALTERNATIVE LIGHT SOURCESA. Specification of RequirementsB. Alternative Light SourcesC. Assessments of Light Intensity, Uniformity, and Cost ConsiderationsD. Acquisition and Initial Testing of Xenon Arc Lights.III. EXPERIMENTAL METHODSA. ChambersB. Experimental ProceduresC. Analytical MethodsD. Light Source CharacterizationE. Other Characterization DataIV. MODEL SIMULATION METHODSA. Chemical MechanismB. Derivation of Photolysis RatesC. Chamber Effects Model and ParametersD Representation of Other Run ConditionsV. RESULTS AND DISCUSSIONA. Summary of New ExperimentsB. Xenon Arc Light Evaluation ResultsC. Outdoor Chamber Light Model Evaluation ResultsD. Evaluation of Chamber Radical Source AssignmentsE. Effect of Light Source and Chamber on Mechanism Evaluation ResultsVI. CONCLUSIONSVII. REFERENCESENVIRONMENTAL CHAMBER STUDIES OF ATMOSPHERICREACTIVITIES OF VOLATILE ORGANIC COMPOUNDS.EFFECTS OF VARYING CHAMBER AND LIGHT SOURCEFinal Report toNational Renewable Energy Laboratory, Contact XZ-2-12075Coordinating Research Council, Inc., Project M-9California Air Resources Board, Contract A032-0692South Coast Air Quality Management District, Contract C91323byWilliam P. L. Carter,Dongmin Luo, Irina L. Malkina, and John A. PierceMarch 26, 1995Statewide Air Pollution Research Center, andCollege of Engineering, Center for Environmental Research and TechnologyUniversity of California, Riverside, CA 9252195:AP:034FPREFACEThis report describes work carried out at the University of Californiaunder funding from the National Renewable Energy Laboratory (NREL) throughContract no. XZ-2-12075, the California Air Resources Board (CARB) throughcontract number A032-0962, the Coordinating Research Council, Inc. (CRC) throughproject number ME-9, and the California South Coast Air Quality ManagementDistrict (SCAQMD) through contract no. C91323. NREL funded the construction andevaluation of the xenon arc light source. CARB, CRC and NREL funded most of theexperimental work, and the SCAQMD funded the building where the experiments wereconductedThe opinions and conclusions in this document are entirely those of theauthors. Mention of trade names and commercial products does not constituteendorsement or recommendation for use.iiABSTRACTAn experimental and modeling study was conducted to assess how chemicalmechanism evaluations using environmental chamber data are affected by the lightsource and other chamber characteristics. Xenon arc light lights appear to givethe best artificial representation of sunlight currently available, andexperiments were conducted in a new Teflon chamber constructed using such a lightsource. Experiments were also conducted in an Outdoor Teflon Chamber using newprocedures to improve the light characterization, and in Teflon chambers usingblacklights. These results, and results of previous runs other chambers, werecompared with model predictions using an updated detailed chemical mechanism.The magnitude of the chamber radical source assumed when modeling the previousruns were found to be too high; this has implications in previous mechanismevaluations. Temperature dependencies of chamber effects can explain temperaturedependencies in chamber experiments when T≥~300°K, but not at temperatures belowthat. The model performance had no consistent dependence on light source forexperiments not containing aromatics, but the model tended to underpredict O3inthe new xenon arc and blacklight chamber runs. This is despite the fact thatsuch biases are not seen in modeling runs in the older xenon arc chamber or inpreliminary modeling of University of North Carolina outdoor chamber runs. Thereasons for this are not clear, and additional studies are planned as part of ourongoing program.iiiACKNOWLEDGEMENTSThe authors wish to acknowledge and thank Mr Bart Croes of the CARB, Mr.Tim Belian of the CRC, Dr. Alan Lloyd of the SCAQMD, Mr. Brent Bailey of NREL,and the members of the CRC/APRAC reactivity committee for their support of thisproject and their patience with the delays in completing this report. We alsogratefully acknowledge Dr. Joseph Norbeck, Director of the University ofCalifornia, Riverside’s College of Engineering Center for Environmental Researchand Technology (CE-CERT) for providing significant salary support and equipmentused in this project.Mr. Robert Walters made major contributions to the specification, design,and construction of the xenon arc light source, and assisted in improvements tothe pure air and temperature control system used in this project. Mr. Ken Sazakidid most of the work in developing and adapting the Jeffires light model for usein calculating photolysis rates for the outdoor chamber, and assisted in otherways in the light characterization efforts. Dr. Harvey Jeffries of theUniversity of North Carolina provided very important and helpful assistance toMr. Sazaki in developing the model, and provided the Teflon characterization dataand model needed to adapt the light model to our chamber. Valuable assistancein constructing the chamber facility and conducting the experiments for thisprogram was provided by Mr William D. Long. Mr Kurt Bumiller assisted inconducting some of the xenon arc light characterization experiments. Mr. DennisFitz assisted in the preparation of this report. Assistance in conducting theexperimental runs was provided by Ms. Kathalena M. Smihula and Mr. Armando D.Avallone.ivEXECUTIVE SUMMARYBackgroundPhotochemical oxidant models are essential tools for assessing effects ofemissions changes on ground-level ozone formation. Such models are needed forpredicting the ozone impacts of increased alternative fuel use. The gas-phasephotochemical mechanism is an important component of these models because ozoneis not emitted directly, but is formed from the gas-phase photochemical reactionsof the emitted volatile organic compounds (VOCs) and oxides of nitrogen (NOx)inair. The chemistry of ground level ozone formation is complex; hundreds of typesof VOCs being emitted into the atmosphere, and most of their atmosphericreactions are not completely understood. Because of this, no chemical model canbe relied upon to give even approximately accurate predictions unless it has beenevaluated by comparing its predictions with experimental data.The primary means for