Servizio Comunitario di Informazione in materia di Ricerca e Sviluppo - CORDIS

Modelling and impact studies

The global model TM3 is already able to simulate the O3/HxOy/NOx and C1-C5 chemistry (182 gas phase chemical reactions). This chemistry has been extended by a highly-reduced chemical scheme suitable for incorporation in global models containing 45 additional gas phase chemical reactions (11 compounds (Decane, Acetone, MEK, MIBK, Toluene, Xylene, Benzene, Methanol, Ethanol, Ethyl acetate and 2-butoxy ethanol) and 19 reactions for the solvents in use and 10 compounds (Dipropylene glycol monoethylether (DPM), Octadecyl vinyl ether (ODVE), Dodecyl vinyl ether (DDVE), Diethyleneglycol monovinyl ether (MVE-2), Cyclohexanedimethanol divinyl ether (CHDVE), Diethyleneglycol divinyl ether (DVE-2), Triethyleneglycol divinyl ether (DVE-3), 2,4 pentadione, 2,5 hexadione) and 26 reactions for the new solvents). This reduced chemical mechanisms considers oxidation of the solvents from all three major oxidants (ozone, hydroxyl radical and nitrate radical). It has been produced by the mechanism generation program CHEMATA and was built at the top of the base chemistry described by Poisson et al (2000). This version of TM3 model developed for the MOST project contains a total of 281 chemical reactions involving 133 species.

The highly reduced gas phase chemistry scheme obtained by CHEMATA for solvent degradation has been evaluated by comparison with the explicit degradation scheme of the Master Chemical Mechanism by performing box model simulations using the FACSIMILE software. For the base case scenario the percentage difference in the average ozone concentration that is calculated by the two mechanisms after five days of simulation, remains below 3% for all solvents considered.

Two different criteria have been used in order to rank the individual VOCs according to their capability to generate ozone. The first one is the maximum ozone concentration during the five days of the model run. This value is generally obtained in the late afternoon of the last day of the simulation. The second one corresponds to the O3 production efficiency of the organic species (AO3/AHC) and represents the quantity of ozone produced during the five days of the simulation as a result of the degradation of the corresponding quantity of the hydrocarbon reacted.

Global emissions: For realistic scenarios it is necessary to have good estimates for the origin and the chemical composition of the solvents in use. For the global model this information for the current solvent-use emission inventories is based on the EMEP/CORINAIR Emission Inventory Guidebook (http://reports.eea.eu.int/ technical_report_2001_3/en/group06.pdf) which provides information on the relative contribution of the human activities (9 main categories) to solvent emissions in W. Europe as well as the major constituents emitted per activity (chemical speciation of emissions - 8 major chemical groups with several individuals per group) and on the emission inventory EDGAR which is available for the years 1990 and 1995 on the TNO / RIVM web site (ftp://info.rivm.nl/pub/lae/EDGARV20/ DATA/details/NMV/) on a 1ox1o resolution. Future emission inventories by changes in the amounts emitted and in the chemical speciation of the emissions require knowledge of the properties of the new compounds with regard to the specific usage they are planned. To detour this problem we have performed a number of sensitivity studies that allow the evaluation of potential maximum gain we could have from solvent replacement.

Global model components: The TM3 model modified to be able to simulate emissions and fate of solvents in the troposphere. For this, in addition to the implementation of emissions and the gas phase chemistry that has been developed in the frame of the project, the aerosol module of Tsigaridis and Kanakidou (2003) has been incorporated in the model. Dry and wet deposition processes for the solvents in use are also taken into account in TM3.

The potential maximum benefit for air quality from changes in solvent use emissions has been investigated with the global model by comparing the base case simulation (BC) considering all solvents in use (represented in the global model by the 11 chosen compounds that are mentioned earlier) with a simulation without any solvent emissions (NS). Note that the solvent in use emissions constitute about 7% of the total VOC emissions of the BC scenario.

Informazioni correlate

Reported by

UNIVERSITY OF CRETE
Leoforos Knosou, Ampelokipi
71409 IRAKLION
Greece
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