Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds

[摘要] Kinetic and mechanistic data relevant to the tropospheric degradation of volatile organiccompounds (VOC), and the production of secondary pollutants, have previously been used todefine a protocol which underpinned the construction of a near-explicit Master ChemicalMechanism. In this paper, an update to the previous protocol is presented, which has been usedto define degradation schemes for 107 non-aromatic VOC as part of version 3 of the MasterChemical Mechanism (MCM v3). The treatment of 18 aromatic VOC is described in acompanion paper. The protocol is divided into a series of subsections describing initiationreactions, the reactions of the radical intermediates and the further degradation of first andsubsequent generation products. Emphasis is placed on updating the previous information, andoutlining the methodology which is specifically applicable to VOC not considered previously(e.g. a- andb-pinene). The present protocol aims to take into consideration work available inthe open literature up to the beginning of 2001, and some other studies known by the authorswhich were under review at the time. Application of MCM v3 in appropriate box modelsindicates that the representation of isoprene degradation provides a good description of thespeciated distribution of oxygenated organic products observed in reported field studies whereisoprene was the dominant emitted hydrocarbon, and that the a-pinene degradation chemistryprovides a good description of the time dependence of key gas phase species ina-pinene/NO_Xphoto-oxidation experiments carried out in the European Photoreactor (EUPHORE).Photochemical Ozone Creation Potentials (POCP) have been calculated for the 106 non-aromaticnon-methane VOC in MCM v3 for idealised conditions appropriate to north-westEurope, using a photochemical trajectory model. The POCP values provide a measure of therelative ozone forming abilities of the VOC. Where applicable, the values are compared withthose calculated with previous versions of the MCM.

[学科分类] 大气科学