Journal of Atmospheric Chemistry 42: 281–286, 2002. © 2002 Kluwer Academic Publishers. Printed in the Netherlands.

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A Database for Volatile Organic Compounds K. MANNSCHRECK 1
, K. BÄCHMANN 2, I. BARNES 3, K. H. BECKER 3, TH. HEIL 1, R. KURTENBACH 3, M. MEMMESHEIMER 4, V. MOHNEN 5, A. OBERMEIER 6, D. POPPE 1, R. STEINBRECHER 5, TH. SCHMITZ 1, A. VOLZ-THOMAS 1 and F. ZABEL 7 1 Institut für Chemie und Dynamik der Geosphäre II, Forschungszentrum Jülich, 52425 Jülich,

Germany 2 Institut für Anorganische Chemie, Technische Universität Darmstadt, Petersenstr. 18, 64287 Darmstadt, Germany 3 Institut für Physikalische Chemie, Bergische Universität Wuppertal, Gauss Str. 20, 42097 Wuppertal, Germany 4 Institut für Geophysik und Meteorologie, Universität zu Köln, Aachener Str. 201–209, 50931 Köln, Germany 5 Fraunhofer Institut für Atmosphärische Umweltforschung, Kreuzeckbahnstr. 19, 82467 Garmisch-Partenkirchen, Germany 6 Lehrstuhl für Technische Thermodynamik und Transportprozesse, Universität Bayreuth, Universitätsstr. 30, 95440 Bayreuth, Germany 7 Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany (Received: 1 November 2000; 21 March 2001) Abstract. The database for volatile organic compounds (VOC data base) was created with the aim of providing an overview of tropospheric hydrocarbon measurements. The data base contains 202 substances, for which atmospheric and useful kinetic data such as rate coefficients, photolysis frequencies, mixing ratios, emission data and ozone formation potentials are compiled from available literature. The database file can be downloaded without charge from http://www.physchem.uniwuppertal.de/PC-WWW_Site/VOC-Database/index.html. Registered users will be informed about the appearance of updates. Key words: data base, tropospheric chemistry, volatile organic compounds, ambient air measurements, emissions, kinetic data.

1. Introduction The large amount of experimental data created in the field of atmospheric research makes it difficult for scientists to effectively use them for their own studies. A compilation of information and data relevant for a specific area of research is a useful tool which can be realised by means of a database. In this paper a database is presented which contains information concerning the abundance and chemistry of volatile organic compounds (VOCs) in the troposphere. The aim of the database
Present address: Deutscher Wetterdienst, Meteorologisches Observatorium Hohenpeissenberg,

Albin-Schwaiger Weg 10, 82382 Hohenpeissenberg, Germany.

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is to provide a basis for laboratory investigations, simulation experiments, field studies and model calculations. Integration in the database was considered for VOCs from anthropogenic sources such as combustion (e.g., vehicle exhaust, industry) and evaporation (solvent emissions) processes which attribute to photooxidant formation. In addition main components of biogenic emissions were considered. For the included compounds various parameters (e.g., kinetic data, ozone forming potential) are given. These values are taken from recent publications. References are included to provide information about the origin and reliability of the data. With respect to ambient air measurements the database focuses on field campaigns performed in Germany. However, in order to study differences between conditions in Germany and other countries some measurements from elsewhere in Europe, Canada and United States are included. In the latter cases only data sets from recent years were considered which include a representative amount of measured VOC rather than only e.g., Benzene, Toluene and Xylenes. In the case of data concerning anthropogenic emissions entries were restricted to identifying emission types. Emission factors are only given for biogenic emissions. 2. Database Structure The VOC database is compiled under the software package Microsoft
Access 97 (version 8.0). Figure 1 gives an overview of the thematic areas contained in the database. The data pertaining to the individual areas are listed in the form of tables linked to each other. In the following these thematic areas are briefly explained. The database is built around a table named SUBSTANCES (table headings are given in italics) which contains 199 different VOCs, CO, NOx and O3 . The table allocates each substance to an index (Substance IDentifier) and contains for each substance chemical information, i.e., IUPAC name, trivial name, chemical formula, molar mass, number of C atoms, compound class, the rate coefficients for reactions with OH, O3 and NO3 , as well as photolysis frequencies. Heterogeneous reactions and reactions with halogen atoms are not included because they are not important in the continental planetary boundary layer except possibly in coastal areas. Table SUBSTANCES also contains information on anthropogenic and biogenic emissions, as well as the ozone formation potentials of individual compounds. 2.1. RATE COEFFICIENTS AND PHOTOLYSIS FREQUENCIES The rate coefficients (in units of cm3 · molecules−1 · s−1 ) are taken from recent publications. They are specified as a function of temperature and additionally for a temperature of 293 K. The photolysis frequencies (in units of · s−1 ) are calculated for clear sky local noon in summer at 50◦ N and ground level. An additional column (Optical Properties Flag) indicates if photolysis is a relevant process under tropospheric conditions. For calculation of the photolysis frequencies for other conditions, absorption cross-sections and quantum yields for several VOCs are

A DATABASE FOR VOLATILE ORGANIC COMPOUNDS

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Figure 1. Organisation chart of the database.

listed in separate tables as function of wavelength in the spectral region relevant for the troposphere. These tables are not part of the database but are contained in the directory ‘spectra’ available together with the database. It is planned to include in the future also the most important stable degradation products of each compound for the different oxidation processes considered.

2.2. OZONE FORMING POTENTIALS The Photochemical Ozone Creation Potential (POCP; Derwent et al., 1996) and the Maximum Incremental Reactivity (MIR; Carter, 1994) of VOCs as derived from model calculations are included in the database. They quantify the reactivity of a VOC mixture by calculating the ozone forming potential for the individual VOC taking other degradation processes into account. MIR is defined as the maximum change in ozone concentration caused by adding a single VOC-burden to a particular base scenario. POCP is also based on a model investigation of the ozone production when adding a single VOC to a mixture, the path of the air mass over Europe being simulated with the aid of a trajectory model. The POCP value is a relative value and relates to the ozone forming potential of ethene (100%). The corresponding references are also part of the database.

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2.3. EMISSION DATA Emission data are compiled separately for anthropogenic and biogenic sources. As mentioned above the information about anthropogenic emissions is confined to emission types. They are subdivided into road traffic (V), mineral oil refineries (R) and solvents and other processes (L). An allocation to the emission type is only provided for those components for which data are available for the calculation of emissions. For example, the use of aliphatic and aromatic hydrocarbons as solvents can only rarely be quantitatively allocated to particular compounds because technical mixtures of undefined or changing composition are frequently employed. For the biogenic emissions, only plant species growing in Europe are considered. Apart from the plant species and the ecosystem, the associated emission factors and the algorithms used are listed. The quoted emission factor represents the emission rate at 30 ◦ C leaf temperature and a photon flux density of 1000 µmol m−2 s−1 of photosynthetically active radiation (in case of temperatureand light-dependent emissions) or at 30 ◦ C (temperature-dependent emission) and is specified in units of [µg · g−1 · dw · h−1 ] (dw = dry weight). Several recent algorithms for parameterization of the emissions are entered in the database. The ISOS algorithm is based on the isoprene algorithm originally developed by Guenther (1997). In order to include the seasonality of the emission factor of isoprene for Quercus robur, the most important isoprene emitting plant in Europe, an additional term was added in the ISOS algorithm. It was derived from a nonlinear regression analysis based on the enzymatic activity of the isoprene synthase (Schnitzler et al., 1997). The MTG algorithm describes the monoterpene emissions of plants as a function of temperature. MTG∗ means that the MTG algorithm is recommended. However, by using the emission algorithm proposed by Schuh et al. (1997) taking into account a light and temperature effect, the monoterpene emission of Helianthus annuus may be described in a better way. The relevant literature sources are specified in the database. 2.4. ATMOSPHERIC MEASUREMENTS The data sets from field experiments are compiled in separate tables named CAMPAIGNS and MEASURED VALUES. They are either taken from the literature or have been made available by the respective investigators. Included are both longterm data sets extending over a period of several years and data sets from shorter measurement campaigns. Data are available from 70 campaigns. CAMPAIGNS contains for each data set information about time period, GC techniques, sampling systems and number of measurements, as well as a characterisation which classifies the data set in terms of scenarios types (Table SCENARIOS). 254 scenarios for measurements in Germany and 17 scenarios for measurements outside Germany are provided. For the description of these scenarios, six different scenario types have been defined which can also serve as a selection criterion: urban, suburban, rural, maritime, free troposphere continental and free troposphere maritime. ‘Ur-

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Table I. Number of data sets for the different scenario types Scenario type

Germany

Outside Germany

Urban Suburban Rural Maritime Free troposphere continental Free troposphere maritime

130 40 53 – 28 –

8 2 2 4 – 1

Table II. Compilation of the amount of data and parameters available for the individual substance classes (–: not applicable) Substanceclasses

#a

#b

k(OH)

k(O3 )

k(NO3 )

Jc

MIRfactor

POCPvalues

Anthr. emiss.type

Biog. emiss.type

Alkanes Alkenes Alkynes Alcohols Aromatics Carbonyl compounds Esters Ethers Oxigenated aromatics Terpenes Others

61 37 2 8 35

1958 496 167 – 1517

61 36 2 6 32

– 26 2 1 32

57 34 2 6 14

– – – – –

48 29 2 5 27

24 12 1 4 14

8 13 2 – 16

1 4 – 3 1

19 6 3

14 – –

16 6 3

8 1 –

13 4 3

11 –

8 – 2

6 – 1

4 – –

4 1 –

6 15 10

– – 318

5 15 6

3 14 3

5 15 6

– – 2

5 – –

1 2 3

1 4 –

– 15 2

a Number of compounds. b Number of measured values. c Number of photolysis frequencies.

ban’ relates to measurements directly performed in cities. Examples of suburban measurements are motorway and tunnel measurements, flight measurements above cities or measurements at the outskirts of cities. ‘Rural’ means that there are no emission sources near the measuring location. Table I contains an overview of the number of scenarios for each scenario type. The index L-ID refers to the original literature where the data set is described. The references are compiled in a separate table LITERATURE. As far as indicated in the original literature, more precise explanations concerning the measurement conditions, e.g., ‘flight measurement at 0.3 to 2 km altitude, residential area near a chemical plant (at 200 m distance) and a busy road (e.g., 100 m to the east with 35,000 vehicles per day)’ are given in the table SCENARIOS.

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The Table MEASURED VALUES contains the measured hydrocarbon mixing ratios (always in units of ppbV) from each campaign. This table is interlinked with the tables CAMPAIGNS, SCENARIOS and SUBSTANCES. The amount of measured data and parameters available for the different substance classes is compiled in Table II. 3. Location of the VOC Data Base The VOC data base and a help file containing guidelines on the structure and usage can be downloaded from http://www.physchem.uni-wuppertal.de/ PC-WWW_Site/VOC-Database/index.html. References Carter, W. P. L., 1994: Development of ozone reactivity scales for volatile organic compounds, J. Air Waste Manage. Assoc. 44, 881–899. Derwent R. G., Jenkin, M. E., and Saunders, S. M., 1996: Photochemical ozone creation potentials for a large number of reactive hydrocarbons under European conditions, Atmos. Environ. 30, 181–199. Guenther, A., 1997: Seasonal and spatial variations in the natural volatile organic compound emissions, Ecological Applications 7(1), 34–45. Schnitzler, J. P., Lehning, A., and Steinbrecher, R., 1997: Seasonal pattern of isoprene synthase activity in Quercus robur leaves and its impact on modeling isoprene emission rates, Botanica Acta 110, 240–243. Schuh, G., Heiden, A. C., Hoffmann, Th., Kahl, J., Rockel, P., Rudolph, J., and Wildt, J., 1997: Emissions of volatile organic compounds from sunflower and beech: Dependence on temperature and light intensity, J. Atmos. Chem. 27, 191–318.