Measurements of lower carbonyls in Rome ambient air

Ambient levels and diurnal profiles of lower carbonyls were measured in Rome during selected days of summer 1994 and winter 1995. The most abundant carbonyls were formaldehyde (up to 27 ppb) followed by ethanal (< 17 ppb) and acetone (< 9 ppb). Gas-phase concentrations of other seven carbonyls were in the 0–3 ppb range. The results were discussed with respect to direct emissions and photochemical production. Using carbonyl/CO concentration ratios mobil source emissions of carbonyls were estimated for the urban area. The secondary production of C1–C3 aldehydes from reactions of alkenes with O3 and OH radicals during the early morning hours of summer days was also calculated. The daytime pattern of carbonyls was found to be similar to that of toluene in wintertime and close to that of ozone in summer periods conductive to photochemical pollution episodes.