ESTIMATING PRODUCT YIELDS OF CARBON-CONTAINING PRODUCTS FROM THE ATMOSPHERIC PHOTOOXIDATION OF AMBIENT AIR ALKENES

The yields of products have been calculated for the reactions of hydroxyl radicals and ozone with 19 of the two-through-six carbon anthropogenic alkenes. Based on their rate of reaction, mechanisms of reactions and the ambient air distribution for these alkenes their seasonal ambient air yields have been estimated. Aldehydes predominate as products irrespective of season, with smaller yields of several ketones. Other minor products include carboxylic acids, carbon monoxide, carbon dioxide, and alkenes. About a two-fold increase is estimated in the yields of 'hot' biradicals and their products from summer to winter. One sensitivity analysis was made by recomputing yields at a different OH radical to O3 concentration than assumed most likely in the calculations discussed above. In addition, the sensitivity of product yields to an estimated range of seasonally averaged sunset-to-sunrise NO3 radical concentrations was calculated. The effects of free radical reactions are discussed, but these are believed to make a relatively minor contribution within the NO(x)-rich atmospheres that contain anthropogenic alkenes. The uncertainties in product yields associated with the range of NO3 radical concentrations assumed present is relatively small for aldehydes, as is the decrease in yield of the one carbon 'hot' biradical. Larger uncertainties occur for ketones. Significant decreases in yields occur for larger 'hot' biradicals, especially the branched-chain 'hot' radicals in the presence of NO3 radicals.