Observation of filterable bromine variabilities during Arctic troposphericozone depletion events in high (1hour) time resolution

The halogen ions Br and Cl- together with NO3-, SO4(=), MSA(-) (methane sul fonate), Na+ and NH4+ were analysed by ion chromatography in extracts of mo re than 800 aerosol cellulose filter samples taken at Ny (A) over circle le sund, Svarbard (79 degrees N, 12 degrees E) in spring 1996 (March 27 - May 16) within the European Union project ARCTOC (Arctic Tropospheric Ozone Che mistry). Anticorrelated variations between f-Br (filterable bromine, i.e. w ater soluble bromine species that can be collected by aerosol filters) and ozone within the arctic troposphere were evaluated at a resolution of 1 or 2 hours for periods with depleted ozone and 4 hours at normal ozone. A mean f-Br concentration of 11 ng m(-3) (0.14 nmol m(-3)) was observed for the w hole campaign, while maximum concentrations of 80 ng m(-3) (1 nmol m(-3)) w ere detected during two total O-3-depletion events (O-3 drop to mixing rati os below the detection limit of < 2 ppb). Anticorrelation between f-Br and O-3 was also seen during minor O-3-depletion episodes (sudden drop in O-3 b y at feast 10 ppb, but O-3 Still exceeding the detection limit) and even fo r ozone variations near its background level (40-50 ppb). A time lag of abo ut 10 hours between the change of ozone and of f-Br concentrations could on ly be found during a total ozone depletion event, when f-Br reached its max imum values several hours after ozone was totally destroyed. Bromine oxide (BrO) concentrations, measured by DOAS (Differential Optical Absorption Spe ctroscopy), and f-Br showed a coincident variability during almost the enti re campaign (except in the case of total O-3-loss). Frequently enhanced ant hropogenic nitrate and sulphate concentrations were observed during O-3-dep letion periods. At O-3 concentrations < 10 ppb sulphate and nitrate exceed their typical mean level by 54% and 77%, respectively. This may indicate a possible connection between acidity and halogen release.