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Abstract:
The interaction between secondary organic aerosols (SOAs) and reactive bromine species (e.g. BrO, Br-2, HOBr) coexisting in the environment is not well understood and not included in current chemistry models. The present study quantifies the quenching of bromine release from an artificial salt aerosol caused by SOAs from ozonolysis of three precursors (-pinene, catechol or guaiacol) in a Teflon smog chamber and incorporates it into a chemical box model. The model simulations perform very well for a blank experiment without SOA precursor, capturing BrO formation, as detected by differential optical absorption spectrometry. A first-order BrO loss rate of 0.001s(-1) on the surface of SOA represents the overall effective Br-x (total inorganic bromine) loss included in the model. Generally, the model agrees with the maximum BrO mixing ratio in time and magnitude, with some disagreements in the exact shape. Formation of reactive OClO was observed in the presence of organics but could not be reproduced by the model. According to current knowledge, most inorganic chlorine would be in the form of HCl in the presence of organics, as predicted by the model. In order to reproduce the net effects of the presence of SOA, the effective uptake coefficients of reactive bromine on the SOA surface are estimated to be 0.01, 0.01 and 0.004 for -pinene, catechol and guaiacol respectively. The uptake coefficient can now be incorporated into box models and even global models, where sinks for bromine species are thought to be inadequately represented.
