Presentation on theme: "EVALUATED KINETIC AND PHOTOCHEMICAL DATA FOR ATMOSPHERIC CHEMISTRY Roger Atkinson Air Pollution Research Center University of California Riverside, CA."— Presentation transcript:
EVALUATED KINETIC AND PHOTOCHEMICAL DATA FOR ATMOSPHERIC CHEMISTRY Roger Atkinson Air Pollution Research Center University of California Riverside, CA
Available Data IUPAC kinetic and photochemical evaluations, at: Kinetic and mechanistic reviews and evaluations: (a) OH/NO 3 /O 3 reactions (Atkinson). (b) CRC funded (Calvert et al.).
IUPAC data evaluation Initiated in 1977 by CODATA, superceded by IUPAC in Published “complete” evaluation in the Journal of Physical and Chemical Reference Data in 1980, with updates and extensions in 1982, 1984, 1989, 1992 and Published further updates and extensions of portions in 1997, 1999 and 2000.
Since 2000, additional updates to portions of the database have appeared on the world wide web. The content consists of: Introduction summarizing the format for bimolecular and association/dissociation reactions. Summary Table listing recommended values of k(298 K) and temperature- dependent parameters.
Individual data sheets for gas-phase reactions and photochemical reactions, each as a pdf file. Currently there are 525 data sheets available on the web, comprising: Inorganic reactions of O x, HO x, NO x and SO x species. Reactions of C 2 organosulfur compounds. Reactions of inorganic halogen species, plus reactions of CH 3 I and CF 3 I.
Reactions of C 3 organics, plus reactions involved in n-butane and isoprene photooxidations. Reactions of F, Cl and Br atoms and ClO, BrO and IO with selected organic and organosulfur compounds. An additional 270+ data sheets on halogen-containing organics and their degradation intermediates are currently being updated/prepared and these will be posted on the web.
IUPAC current/future activities In addition to current update of most halogen reactions, the panel is publishing sections of the web-based material in Atmospheric Chemistry and Physics. The first section on O x, HO x, NO x and SO x reactions has appeared, and the organic reactions are being prepared for submission.
IUPAC evaluation By late 2004, data sheets for 800 (or more) gas-phase reactions and photolysis reactions will be available via the web, and 50% of these will have appeared in Atmos. Chem. Phys., which is freely available via the web. Currently 8 committee members, from: UK (2), Germany (2), USA (2), Switzerland (1) and Australia (1).
Issues Funding. Presently available solely for travel and subsistence at the yearly meeting. Sheer number of reactions - only the simplest organic compounds (mainly C 3 ) are presently included, and any extension to larger compounds would rapidly add a substantial number of additional reactions/data sheets ( 21 for addition of n- butane).
Other review/evaluations on atmospheric gas-phase reactions
CRC funded reviews Panels chaired by Jack Calvert, plus 6 other members. Atmospheric chemistry of alkenes (2000). Atmospheric chemistry of aromatic hydrocarbons (2002). Published by Oxford University Press. Access? Time-scale of publication?
Organic Reactions (Atkinson) OH radical reactions, in JPCRD in 1989 with updates in 1994 and (alkanes and alkenes) O 3 reactions, in Chem. Rev. in 1984 with updates (in JPCRD) in 1994 and (alkenes) NO 3 reactions, in JPCRD in 1991 with updates in 1994 and (alkanes and alkenes) 1997.
Organic Reactions (Atkinson) Complete re-evaluation of OH + alkane rate constants, published in 2003 in Atmos. Chem. Phys., which is freely available on the web. List all rate constants measured, together with reported temperature-dependent parameters for absolute studies.
OH + n-Butane
Personal comment “Relatively easy” to evaluate rate constants for which only absolute rate data are available. Relative rate data need re-evaluation before use, and evaluation of a series of rate constants for which most of the data are available from relative rate studies may require one or more iterations.
As a very rough guess, rate constants for about 700 OH + organic reactions, about 200 O 3 + organic reactions, and about 200 NO 3 + organic reactions have been measured. IUPAC and NASA deal with only a small fraction of these, and then mostly with the halogenated organics (e.g., HFCs, HCFCs and flourinated ethers).