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ACCENT is a Network of Excellence funded by EC, FP6, PRIORITY 1.1.6.3 Global Change and Ecosystems

European Laboratory Data Compilations and Mechanisms

Data Compilations

IUPAC Subcommittee for Gas Kinetic Data Evaluation

The IUPAC Gas Kinetic Data Evaluation database is a compilation of evaluated kinetic and photochemical data. Gas-phase reactions, heterogeneous reactions and photolysis reactions are covered. Datasheets are given for individual reactions, which summarise the available literature and give recommendations for the preferred value. A summary table is also available to provide a quick reference for the complete range of evaluated data.

The tabulated parameters and rate expressions are described in supplementary information, available from the home page, which allows users with limited knowledge of chemical kinetics, to understand the data tables.

It should be noted that the IUPAC database is not currently searchable but users can work around this by using the 'find' option of Acrobat Reader on the PDF summary table.

The IUPAC database is updated every few months: the user can be notified of changes by registering to an email list. The database is hosted by the Centre for Atmospheric Science at the University of Cambridge.

OVOC Database

A new chemical kinetics database on gas-phase reactions of oxygenated VOCs has been put online by the Laboratoire de Combustion et Systemes Reactifs, LCSR-CNRS, Orleans, in Spring 2006. Data is available for reactions of saturated, unsaturated, aromatic and nitrogen-containing oxygenates with OH, NO₃, O₃, Cl and Br.

ACCENT has had some participation in this website development, by providing the means by which Panel members could come together for planning and evaluation meetings.

UV-VIS Database

A database of UV-vis spectra has been compiled by Hannelore Keller-Rudek and Geert Moortgat at MPI-Mainz. ACCENT has assisted with the cost of putting the database on-line and a provisional version may now be found from www.atmosphere.mpg.de/spectral-atlas-mainz. The database contains approximately 4000 data files for nearly 600 species of atmospheric interest. Individual data sets are given and plots to compare spectra from different authors may be displayed. References to the original work are given and, where relevant, comments are provided.

The database does not contain quantum yields.

Henry's Law Coefficients

A compilation of Henry's Law coefficients has been made available by Rolf Sander and is hosted on the Internet by MPI, Mainz. The compilation, which may be downloaded as a PDF file, is fully referenced. As it is the work of an individual, it is presented to the community on a good-will basis. The author invites individuals to recommend updates.

Mechanisms

The Master Chemical Mechanism

The Master Chemical Mechanism (MCM) is a near-explicit chemical mechanism describing the degradation of volatile organic compounds (VOCs) in the troposphere. It is possible to extract parts of the mechanism by selecting primary VOCs and their initial degradation products. The extracted information can be viewed as a list of reactions (reactants, products and rate coefficients) or used directly for numerical modelling (either using a FORTRAN numerical integrator or using FACSIMILE, which is commercially available). It is also possible to download model input files, which enable the user to run the complete MCM, with or without a 5-day trajectory model, provided that the user has access to FACSIMILE. The MCM, which was originally developed to investigate the production of ozone in the troposphere, also aims to provide a research tool for investigating other areas where detailed chemistry is required, e.g. the generation of intermediates.

In order to improve the usability of the MCM contextual information has recently been added. Each reaction is being linked to a web page which refers to the associated section in the appropriate protocol paper. This documents either the source of the physico-chemical parameters or their method of calculation. The protocol web pages are linked to a central citations database, which contains a list of references. A future aim is to put more detailed source information online.

The MCM web-site is hosted by the University of Leeds. It is periodically updated to include new physico-chemical data and mechanisms. The user can be notified of changes or report errors by registering their email to the online mailing list. A number of contacts are provided to help potential MCM users with queries.

The Chemical Aqueous Phase radical Mechanism (CAPRAM )

The Chemical Aqueous Phase Radical Mechanism is a detailed and extended chemical mechanism describing tropospheric aqueous phase chemistry. The mechanism has been coupled to gas phase mechanisms e.g. RADM2 (Stockwell et al., 1990). Different versions of the model have been tuned for different uses e.g. it has been used:

as a 1D cloud model,
with fewer reactions (183) for use with larger scale models
with additional reaction schemes (e.g. halogen chemistry, additional organic chemistry)

It is possible to download information on two different versions of CAPRAM (2.3 and 2.4). Special modules focusing on halogen chemistry and aromatic chemistry are also available. The data, which the mechanisms are based on, are tabulated and provided, together with comments and references to the source material. Input files for numerical simulation are available as text files or (for version 2.4) directly for use with some versions of FACSIMILE (which is commercially available). The website is hosted by IfT, Leipzig.

Aerosol Inorganics Model (AIM)

AIM is an equilibrium thermodynamic model currently available via the Internet for three different systems: ( H⁺ - SO4^2- - NO3^- - Cl^- - Br^- - H2O) , (H⁺ - NH4⁺ - SO4^2- - NO3^- - H2O), (H⁺ - NH4⁺ - Na⁺ - SO4^2- - NO3^- - Cl^- - H2O). The different species that the models contain and the temperatures for which the models are valid are explained in the online documentation. The model can be run directly from your web browser. A tutorial is provided, which not only helps you to learn how to use the model but it is also useful as a teaching aid for those new to the research area.

As part of the ACCENT project, the data, on which the AIM models are based, has been put on line. Please follow the link to the AIM model and click on 'thermodynamic data'.