Latitudinal variation in the multiphase chemical processing of inorganic halogens and related species over the eastern North and South Atlantic Oceans

摘要: Abstract. Volatile inorganic and size-resolved particulate Cl- Br-species were measured in near-surface air over a broad range of conditions within four distinct regimes (European – EURO, North African N-AFR, the Intertropical Convergence Zone ITCZ, South Atlantic S-ATL) along latitudinal gradient from 51° N to 18° S through eastern Ocean. Median dry-deposition fluxes sea salt, oxidized N, non-sea-salt varied by factors 25, 17, 9, respectively, among regimes. Sea-salt production was primary source for Cl Br. Acidification dechlorination salt primarily HNO3 sustained HCl mixing ratios ranging medians 82 (ITCZ) 682 (EURO) pmol mol−1. aerosol pHs inferred phase partitioning with super-μm size fractions ranged ~3.0 EURO ~4.5 ITCZ. Because SO2 solubility this pH low, S(IV) oxidation hypohalous acids unimportant under most conditions. Simulations detailed multiphase box model indicated that BrCl photolysis ClO + NO major sources atomic all Simulated midday concentrations atoms 2.1×104 7.8×104 cm−3 ITCZ N-AFR regimes, respectively. Measured Br− (median enrichment factor = 0.25) greater volatile Br less than simulated values, suggesting halogen activation mechanism overestimated Br-radical processing. Reaction an important sink modeled O3 (5% 46% N-AFR). Formation nitrates accelerated NOx (NO NO2) via hydrolysis reactions involving aerosol. Relative simulations no halogens, lower coupled direct halogens yielded steady state OH (20% 54%) (22% 62%) OH:HO2 (3% 32%)