Heterogeneous Interconversion Reactions of BrNO₂, ClNO₂, Br₂, and Cl₂

Abstract

The heterogeneous reactions leading to formation and loss of BrNO2 on salt solutions as a model substrate for atmospheric sea salt aerosol are investigated. Further to the reaction of ClNO2 with bromide solutions, the reaction of Br2 with nitrite solution was found to be a convenient method for the synthesis of BrNO2. We measured the temperature-dependent lifetime of BrNO2 in a quartz cell and obtained the activation energy E A = 89 ± 9 kJ/mol for the unimolecular decay at atmospheric pressure. The reactive uptake of BrNO2 and ClNO2 on water and aqueous solutions was determined using a wetted-wall flow tube technique. We observed the reactions Br2 + NO2 - ↔ BrNO2 + Br-, Cl2 + NO2 - → ClNO2 + Cl-, and the net reaction ClNO2 + Br- ↔ BrNO2 + Cl-. BrNO2 and ClNO2 both react with NO2 - to release NO2 into the gas phase. Observed concentration profiles in the gas phase and in solution can be described qualitatively by a numerical model of the diffusion and reaction processes in the experimental setup.

Measurements and modelling of I<sub>2</sub>, IO, OIO, BrO and NO<sub>3</sub> in the mid-latitude marine boundary layer

“…Nevertheless, one potentially interesting detail is that I 2 was observed at low mixing ratios (∼10-20 ppt) at night in westerly winds, irrespective of the state of the tide. This may indicate that I 2 is also produced over the open ocean, as originally proposed by Garland and Curtis (1981). Of course, other possible explanations are the re-circulation of air-masses that originated at the coast during low tide, or perhaps that moderate I 2 emissions still occur at higher states of the tide.…”

“…Release of ICl was only observed after depletion of Br − (Holmes et al, 2001). The corresponding Henry's law constants (mol l −1 atm −1 ) for the different species are: (Frenzel et al, 1998), k H (ICl)=110 and k H (IBr)=24 (Wagman et al, 1982).…”

Evaluated kinetic and photochemical data for atmospheric chemistry: Volume VI – heterogeneous reactions with liquid substrates

“…, where k = k ter [H + ][Cl − ] and the ionic concentrations are in M. The termolecular rate constant, k ter , was taken from Vogt et al (1996), the solubility and diffusion coefficient for HOBr were taken from Frenzel et al (1998). This expression predicts uptake coefficients that are close to the accommodation coefficient for pH < 7 when applied to fresh sea-salt with [Cl − ] ≈ 5.3 M. This is in accord with the large lower limit to the uptake coefficient measured by Abbatt and Waschewski, but is higher than the uptake coefficients (factor 20) determined by .…”

Inland Concentrations of Cl2 and ClNO2 in Southeast Texas Suggest Chlorine Chemistry Significantly Contributes to Atmospheric Reactivity

“…Observations [24,37,[45][46][47], modeling work [39][40][41][42] and laboratory studies [36][37][38][48][49][50][51][52] in the recent past have identified heterogeneous ClNO2 formation as a major route for the production of reactive gas phase chlorine. The mechanism of ClNO2 production is initiated by the reactive uptake of N2O5 on chloride-containing aerosol particles, as seen in Reaction (R5).…”