A multiphase chemical box model of Arctic halogen chemistry has been developed using a PC-based modeling program developed by Environment Canada called the Chemical Reactions Modeling System(CREAMS). The multiphase model contains 125 gas phase reactions, 19 photolysis reactions, and 16 aqueous reactions occurring in suspended aerosol particles and the quasi-liquid component of snow. The model simulates mass transfer of species between the gas phase and particles, and between the gas phase and the snowpack. Model simulations were conducted for the Arctic for the period April 16 to April 24 at 245 K within a 400 m boundary layer. The complete model simulates halogen-catalyzed ozone depletion within 5 days from the start of the model run, via known gas and heterogeneous phase activation mechanisms. A critically important model reaction is BrO + HCHO –> HOBr + CHO, which has a substantial impact on gas phase HOBr, and subsequent condensed phase chemistry. When coupled with a necessary snowpack efflux of aldehydes, required to maintain the aldehyde concentrations at observed levels, the new BrO chemistry has a significant impact on the concentrations of gas phase bromine species, particle bromide, and chlorine atoms, through chemistry occurring in the snowpack. We also find that O-3 depletion cannot be simulated without the presence of heterogeneous halogen chemistry occurring in the snowpack and that the rate of O-3 depletion is limited by the mass transfer rate of HOBr to the snowpack.
Correlations between 35 different organic and inorganic species or tracers in the aerosols of Hong Kong were derived based on the GC−MS organic results from our 1993−1994 study and Hong Kong Environmental Protection Department inorganic data. Source apportionment is essential in fingerprinting of air pollutants for cross-boundary studies. It is also important in the development of emissions inventory data, control strategies, and legislature. Traditionally, emission sources are identified from either the inorganic or organic tracers in the aerosols, but not both. Each of these techniques yields much source information; however, each by itself provides only a partial picture due to the complicated nature of ambient aerosols. Since many of the organic and inorganic species in aerosols are from the same source, correlations between the two are to be expected. In this study, such correlations were indeed found. For example, benzo[b,k]fluoranthene, the most abundant PAH (polycyclic aromatic hydrocarbon) in all the PAHs detected in Hong Kong, exhibited good correlation with Pb, Zn, As, nss SO42- (nonseasalt sulfate), total PAHs, and benzo[a]pyrene. This paper further demonstrates that a combination of the two techniques could be an improved method for source apportionment than using either method alone.