United States Environmental Protection Agency Atmospheric Sciences Research Laboratory Research Triangle Park NC 27711 Research and Development EPA/600/S3-85/029 June 1985 &EPA Project Summary Outdoor Smog Chamber Experiments to Test Photochemical Models: Phase II H. E. Jeffries, K. G. Sexton, R. M. Kamens, and M. S. Holleman The smog chamber facility of the University of North Carolina at Chapel Hill (UNC) was used in a study to provide experimental data for developing and testing kinetic mechanisms of photo- chemical smog formation. The smog chamber, located outdoors in rural North Carolina, is an A-frame structure supporting Teflon film. Because the chamber is partitioned into two sec- tions, each with a volume of 156 m3, two experiments can be conducted simultaneously. The dual chamber is operated under natural conditions of solar radiation, temperature, and rela- tive humidity. In this study, 128 dual-experiments were performed using NO« and various hydrocarbons and hydrocarbon mix- tures. The experiments performed dur- ing this three-year project have been added to the existing UNC database for model validation testing, bringing the total number of dual-experiments to 346. This report presents an organizational scheme for these 346 experiments. Six attributes of each experiment were used for classification. These are class of experiment, experimental conditions, quality, processing status, project that produced the data, and membership in a run series. Run series, a collection of experiments performed in a certain manner or addressing a particular ques- tion, formed a major organizational basis. Forty series were used, including seven types of side-by-side series, four types of chemical issues series, and five types of characterization series. All dual experiments, or runs, were classified into one of the side-by-side series. Each run could also appear in up to two addi- tional series. The report also discusses three ex- amples of selecting runs to test mecha- nisms. The examples are: runs to test an explicit toluene chemistry mechanism; runs to test mechanisms under dynamic operating conditions; and runs to test EKMA-type mechanisms for air quality modeling. Recommendations for how best to take advantage of the side-by- side nature of the UNC runs in testing mechanisms are given throughout the discussion. This Project Summary was developed by EPA's Atmospheric Sciences Re- search Laboratory, Research Triangle Park, NC, to announce key findings of the research project that is fully docu- mented in a separate report of the same title (see Project Report ordering infor- mation at back). Introduction Photochemical kinetics reaction mod- els are central components in EPA's method for computing control require- ments for organic emissions needed to meet the National Air Quality Standard for ozone. State and local control officials are expected to use these models to esti- mate control requirements. However, dif- ferent kinetic models apply different methods, often resulting in different des- criptions of the same situation. Smog ------- cha mber data must be used to test photo- chemical mechanisms to determine the adequacy of the chemical representation. Presently, mechanism testing has not used a large enough range of test data encompassing the range of conditions likely to occur in an urban control situa- tion. This is because, in part, an organized database containing the range of condi- tions needed was not available before now. This report uses a hierarchy of chemi- cal species, based on the number of hydrocarbon and oxides of nitrogen (HC/NOx) systems in which the species occur, to determine the type of smog chamber experiments needed for ideal mechanism validation. This species hier- archy included a hierarchy of operating conditions. These four sets of conditions, which include large dilution and continu- ous injection, are ordered to proceed from the standard smog chamber type experi- ment to conditions that simulate the urban environment. All experiments took place under natural sunlight and ambient temperature. An example of this hier- archy of experimental conditions is shown in Figure 1, in which a similar photochem- ical system was performed under four dif- ferent physical conditions. Two of these experiments also show the unique side- to-side nature of the UNC chambers. Three other projects using the UNC Outdoor Smog Chamber have contributed data for model testing. The types of data provided by these projects are described' briefly in this report, and the project iden- tifications are used in the classification scheme. Purpose The purpose of this research project was to: (1) measure react ant and product concentrations as functions of time in selected photochemical smog systems; (2) process these data into a form readily distributable to model developers and testers; and (3) provide auxiliary informa- tion needed to create mathematical model descriptions of the systems. The 128 dual-experiments, when added to the other experiments in the database, en- compass a range of complexity from single HC species in totally static situa- tions to complex urban mixtures in fully dynamic conditions. As a whole, the data set is well suited to develop and test models of chemical transformations in polluted atmospheres. Organizing Principles The 346 runs were classified by "keys" to allow easy selection. Six kinds of attributes were used to organize the runs in the data set. The C/ass of a run was either a characterization run that ad- dressed unique aspects of the UNC chamber or organic/NOx runs to test mechanism design. Further, either of these types could be one-day or multi-day runs. Experimental Conditions were based on four major types of run condi- tions. These conditions were: dilution , (large or normal),,injection (initial or con- tinuousK and type of HC system used, i.e., single HC species or mixture, and, if a mixture, whether the composition was constant or varying over time. Initial Con- ditions included the exact NOX and HC concentrations that occurred on both sides, as well as the identity of the HC for up to three HC species. For runs that had more than three species, HC mixture names were used. The Quality of a run was rated on a scale of 0 to 9. The major determining factors for quality were the weather conditions and the number and performance of the analytical instru- ments. The Processing Status of a run indicated the availability of validated data on tape or in other forms such as plots. All runs were included in the database, but not all have yet been completely pro- cessed to the final validated form. The Project Name identified the runs by the project that produced the experiment. Data Set The report describes how the runs were distributed across the organization keys set forth. The majority of the experi- ments were one day, normal dilution, initial injection runs performed between June and October. The experiments were summarized by HC type. All the species and named mixtures used are listed. The grading of experiments is explained: important factors are sunlight, initial conditions, analytical support, chamber conditions, and need/usefulness. Most runs were graded at 7 or 8. All experiments in the data base are listed two ways: sorted by series and by species. The seven types of series lists are characterization, matched conditions, relative reactivity between sides, carbon substitution, carbon addition, delta con- centration of HC or NOx, and static-to- dynamic transition experiments. The five species lists are: formaldehyde, acetal- dehyde, ethylene, propylene (other than matched propylene) and toluene. These lists include all experiments in which the species appeared, alone or in mixtures, on either side of the chamber. Within each series and species list, the runs are grouped by HC type beginning with the simplest type that appears in the series Within the HC type, the runs are in chro- nological order. Guidance for the useful- ness of a specific run for the purpose ol model testing is also given in terms ol general ranking categories. Selecting Runs and Obtaining Data Using three examples, the report illus- trates how experiments from the UNC Smog Chamber Database might be se- lected to test mechanisms. General rec- ommendations and assumptions are de- fined to guide modelers in general selec- tion. The examples discussed involved the testing of an explicit toluene reaction mechanism, a mechanism under dynamic conditions, and an EKMA-type mecha- nism for urban conditions. The data set described in this report is neither complete nor static. New projects are adding to this data set, and the exist- ing runs are under constant review and analysis. The possibility for, and the means of, future revisions are explained. This data set has been supplied to modelers for analysis under EPA Contract Nos. 68-02-3738 and 68-02-4104. The purpose of this report is to describe the data set and to provide guidance so others in the scientific community can use it. Fully processed runs and the experimen- tal conditions database are available on an ANSI formatted magnetic tape. Copies of the tape and other supporting informa- tion are available through the authors. ------- No Dilution Large Dilution •2 .5 1 Q | n o i o 1 n O pi i o ; .u 0.8 0.6 0.4 0.2 0.0 ,'\'\'\'\'\'\'\'\'\'\'\'\'\'. June 27. 1983 - _ _ _ _ '- o3 -. L X" : 7 NO NOi / ~ ^x^^~/^~^^ PAN , i , \ -\ i \ , \ -fr^L' • \ t i ' ' i i . i i 6 8 10 12 14 16 18 I.U 0.8 0.6 0.4 0.2 0.0 Hours, EOT 1.0 0.8 0.6 0.4 0.2 nn _' 1 ' I ' I ' 1 ' 1 ' \ ' l ' I ' ] ' 1 ' \ ' \ ' \ ' . - June 14, 1983 ~ _ _ • ~ °3 : I / ] / — NOZ / ~^-~7^—-—-^^ PAN 1.0 0.8 0.6 0.4 0.2 nn | n o i i S 6 cO O 0 S S 6 o i 5 m o i o ^ I.U 0.8 0.6 0.4 0.2 0.0 _'i'{'\'\'\'\'\'\'\'\'\'\'\'. July 29, 1983 - - — - - ~ NO ^3 "- ': 1 \ t 1 r**\ • I-JW I t r"l" ' 1 1 1 1 1 I . ! - J . 6 8 10 12 14 16 18 / .L/ 0.8 0.6 0.4 0.2 0.0 Hours. EOT 1.0 0.8 0.6 0.4 0.2 nn k ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' I ' . 7 June 27. 1983 ~ — _ " - — _ " 03 ^ff^- ---i**:?^^^^ .- 1.0 0.8 0.6 0.4 0.2 0.0 $_ n 0 i 1 S | o o o' % 8 10 12 14 16 18 Hours, EOT 10 12 14 16 18 Hours, EOT Figure 1. Outdoor smog chamber runs as examples of hierarchial experimental conditions. The NOi concentration was <=*0.25 ppm, HC concentration =2.6 ppmC of propylene/n-butane/toluene mixture. Large dilution means that 20% of initial mass is left after 10 hours of dilution fequivalent to mixing height rise from 250 m to 1250 m). H. E, Jeffries. K. G. Sexton. R. M. Kamens. and M. S. Holleman are with the University of North Carolina. Chapel Hill. NC 27514. Marcia C. Dodge is the EPA Project Officer (see below). The complete report, entitled "Outdoor Smog Chamber Experiments to Test Photochemical Models: Phase II," (Order No. PB 85-191 542/A S; Cost: $ 19.00, subject to change) will be available only from: National Technical Information Service 5285 Port Royal Road Springfield, VA 22161 Telephone: 703-487-4650 The EPA Project Officer can be contacted at: Atmospheric Sciences Research Laboratory U.S. Environmental Protection Agency Research Triangle Park, NC 27711 •t, U.S. GOVERNMENT PRINTING OFFICE: 1985-559-016/27079 ------- United States Environmental Protection Agency Center for Environmental Research Information Cincinnati OH 45268 Official Business Penalty for Private Use $300 OCOC329 PS U S ENVIR PROTECTION AGENCY REGION 5 LIBRARY 230 S DEARBCRN STPEET CMCftGO It 60604 ------- |