The Euro-RADM mechanism: a gas-phase chemical mechanism for European air quality studies

Abstract

In this report we present the Euro-RADM gas-phase chemical mechanism which was developed to model European atmospheric chemistry. It is based upon the Regional Acid Deposition Model Mechanism, version 2. Organic compounds typically measured at the Schauinsland field state were implemented into the RADM2 modelusing the review of Carter (1990). The primary chemistry ofthe measured VOCs and the yields of the secondary products were added to the RADM2 mechanism using the Carter review. The secondary chemistry of RADM2 remained unchanged except that the chemistry of the peroxy radical reactions was modified to account for the new product yields and the chemistry of PAN was updated to be consistent with recent laboratory measurements. The Euro-RADM mechanism is a much more complete parameterization of organic chemical species found at European field stations. A completely explicit approach would require the addition of an extremely large number of species to the mechanism. An explicit approach would not be practical because many of the required reactions and species have not been measured in laboratory experiments and the explicit mechanism would be too expensive and difficult to implement in a current 3-d transport/transformation model. The Euro-RADM mechanism was developed according to the principle that a mechanism should be no more detailed than justified by both laboratory and field measurement data. Laboratory and field measurement data are used to develop atmospheric chemical mechanisms. All mechanisms are in constant need of correction and improvements due to new scientific data. A priority for future development is to incorporate the most recent LACTOZ results into the Euro-RADM model. Recent LACTOZ results on the production of peroxides from the reactions of ozone and NO$_{3}$ with alkenes needs to be included in revised versions of the Euro-RADM mechanism. Aromatic oxidation reactions present an especially difficult problem because the secondary reactions of aromatics are poorly understood. Additional experimental data will be required before a completely reliable parameterization of aromatic chemistry can be incorporated into atmospheric chemistry mechanisms