Research Projects

The reactivity of carbon monoxide and 30 individual organic compounds was assessed using a 3-D photochemical air quality model with online sensitivity analysis based on the direct decoupled method (DDM-3D). Reactivity was assessed using an extended version of the SAPRC99 chemical mechanism in the South Coast Air Basin and in Central California (including San Francisco Bay Area, Sacramento, and the San Joaquin Valley). Reactivity scales developed using 3-D modeling resulted in similar rankings to those developed by Carter using a box model. Relative measures varied less than absolute measures of reactivity as a function of location. Different measures of reactivity including MIR, MOIR, population exposure, and 1-hour vs. 8-hour average ozone all gave similar results. Isoprene and a-pinene in the South Coast Air Basin were found to be less reactive than previous calculations have suggested, because of a different spatial distribution vs. anthropogenic emissions. Alkenes and carbonyls were found to vary in their relative reactivity as a function of location, due to special features of their atmospheric chemistry. Uncertainties in relative reactivity of individual VOC were dominated by uncertainties in the rate parameters of their primary oxidation reactions.