| Oxidized halide species (X* = X·, · X2−, X2 and HOX, where X = Br, Cl, or I) in seawater, sea-salt particles, and snowpack play important roles in the chemistry of the marine boundary layer. While aqueous halogen radicals such as Br· and ·Br 2− likely play an important part in the formation of reactive halogens such as Br2, relatively little is known about the kinetics of halide radical chemistry in environmental samples. In part this is because there are few instruments or techniques that can be used to characterize aqueous oxidized halogens. To better understand this chemistry, we have developed a new chemical probe technique that can detect and quantify aqueous oxidized bromine and chlorine species (Br*(aq) and Cl*(aq)). This technique is based on the reactions of short-lived X*(aq) species with allyl alcohol (CH2=CHCHOH) to form stable 3-halo-1,2-propanediols that are analyzed by gas chromatography with electron capture detection. Using this technique in conjunction with competition kinetics allows determination of steady-state concentrations of the aqueous oxidized halogens. In some cases the technique can also be used to determine rates of formation and lifetimes of X* in aqueous solutions. In developing this method, we identified several reactions that were previously not well understood or not yet identified that could have important implications for aqueous halide radical chemistry and halogen chemistry in the marine boundary layer. In addition, the findings of this work suggest that hydroxyl radical plays a far more important role in aqueous halide chemistry in seawater and sea-salt particles than previously thought. |
