Probing the sensitivity of gaseous Br2 production from the oxidation of aqueous bromide-containing aerosols and atmospheric implications

Abstract

This paper presents a global sensitivity and uncertainty analysis of the bromine chemistry included in the Model of Aqueous, Gaseous and Interfacial Chemistry (MAGIC) in dark and photolytic conditions. Uncertainty ranges are established for input parameters (e.g. chemical rate constants, Henry's law constants, etc.) and are used in conjunction with Latin hypercube sampling and multiple linear regression to conduct a sensitivity analysis that determines the correlation between each input parameter and model output. The contribution of each input parameter to the uncertainty in the model output is calculated by combining results of the sensitivity analysis with input parameters' uncertainty ranges. Model runs are compared using the predicted concentrations of molecular bromine since Br2(g) has been shown in previous studies to be generated via an interface reaction between O3(g) and Br(surface)- during dark conditions [Hunt et al., 2004]. Formation of molecular bromine from the reaction of ozone with deliquesced NaBr aerosol: evidence for interface chemistry. Journal of Physical Chemistry A 108, 11559-11572]. This study also examines the influence of an interface reaction between OH(g) and Br(surface)- in the production of Br2(g) under photolytic conditions where OH(g) is present in significant concentrations. Results indicate that the interface reaction between O3(g) and Br(surface)- is significant and is most responsible for the uncertainty in MAGICs ability to calculate precisely Br2(g) under dark conditions. However, under photolytic conditions the majority of Br2(g) is produced from a complex mechanism involving gas-phase chemistry, aqueous-phase chemistry, and mass transport. © 2009 Elsevier Ltd. All rights reserved.