Characterization of the reactivities of volatile organic compounds using amaster chemical mechanism

A comprehensive description of the ozone-forming potentials of 101 organic compounds has been constructed under North American urban "averaged conditi ons" using a detailed master chemical mechanism and a simple air parcel tra jectory model. This chemical mechanism describes the reactions of 3603 chem ical species taking part in more than 10,500 chemical reactions. An index v alue has been calculated for each organic compound, which describes the inc rement in ozone concentrations found downwind of an urban area following th e emission of a fixed increment in the mass emission of each organic compou nd. These indices, termed photochemical ozone creation potentials (POCPs), have been expressed on a scale relative to ethylene (ethene) = 100, and a r eactivity scale has been generated for alkanes, alkenes, and oxygenated and halogenated organic compounds. A high degree of correlation (R-2 = 0.9) wa s found between these POCP values and the most widely accepted urban reacti vity scale. While the reactivities of most of the 86 organic compounds comp ared fell within a consistent range, significant discrepancies were found f or only 5 compounds. Single-day or multiday conditions appear to be importa nt in establishing quantitative reactivity scales for the less reactive org anic compounds.