Filter measurement results from the Airborne Antarctic Ozone Experiment

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Abstract
During the Airborne Antarctic Ozone Experiment (AAOE), filter samples were obtained for the determination of the total nitrate, sulfate, acidic chloride and acidic fluoride content along the flight path of the NASA ER‐2. On three flights of the 12‐flight series, filters were flown that allowed the separate but simultaneous collection of these species in the aerosol and vapor phase. The ratio of particulate sulfate observed outside the chemically perturbed region (CPR) of the vortex to that inside the CPR was 2.6. The total nitrate levels observed inside the CPR were less than those outside the CPR with one exception. The total nitrate levels observed inside the CPR decreased at a rate of 0.06 parts per billion by volume (ppbv) nitrate d−1 over the 36‐day period of the measurements. Nitrate was observed in the particulate phase on two flights and was correlated with the coldest temperatures observed on the flights. Vapor phase nitrate within the CPR was measured on two flights and it ranged from 1.3 to 2.8 ppbv. Chloride and fluoride were not observed in the particulate phase at concentrations above the detection limits for those determinations. Total acidic fluoride was observed to be larger inside the CPR than outside in contrast to the other measured species. Ratios of total acidic chloride to total acidic fluoride observed at flight altitude exhibit values near 1, rather than the accepted mid‐latitude value of 4–5, suggesting a loss of chloride from the reservoir species HCl and ClONO2. The existence of larger amounts of total acidic fluoride inside the CPR compared to outside the CPR, coupled with the observation of less sulfate inside than outside suggests that the air inside the CPR had descended from a higher altitude.