Carbon monoxide, ozone, and hydrocarbons in the Baltimore metropolitan area

Tropospheric ozone is one of the worst air pollution problems faced by the Baltimore area. Aircraft measurements of trace gases and meteorological variables showed that downwind ozone (O;The hydrocarbon analysis for the years 1993 (at Essex) and 1995 (at Lake Clifton) suggested that alkanes were the most abundant species by mass during summer and fall. In contrast, reactivity calculations showed alkenes and aromatic compounds as the most significant species in producing tropospheric ozone. The natural hydrocarbon isoprene was the most important (by reactivity) of all measured hydrocarbon species. Its concentration increased with increasing ambient temperature during ozone episodes in 1993. Ozone episodes in 1995, however, showed a decrease in isoprene mixing ratios at highest ambient temperatures due to drought and increased ventilation.;The suitability of the target transformation factor analysis (TTFA) technique for apportioning major hydrocarbon emission sources is evaluated. Overall, the summer of 1993 showed gasoline vapor and petrochemical emissions as the most important hydrocarbon emissions by mass. In 1995, tailpipe and refinery emissions were the most prominent by mass. Source apportionment by reactivity showed that biogenic and tailpipe emissions were the most significant sources at both receptor sites, together accounting for 75% of the total reactivity of the measured hydrocarbons.