Sulfate and Carboxylate Suppress the Formation ofClNO 2 at Atmospheric Interfaces

We report measurements of the nitryl chloride (ClNO2) branching fraction following reactive uptake of N2O5 to mixed organic and inorganic solutions representative of atmospheric interfaces. For sodium chloride containing solutions, mixed with either sodium sulfate (Na2SO4) or sodium acetate (NaAc), the ClNO2 branching fraction (ΦClNO2) is suppressed relative to a sodium chloride only solution. In the case of the sulfate-chloride solution, ΦClNO2 is reduced from 0.85 ± 0.03 (0.5 M NaCl) to 0.32 ± 0.14 upon the addition of 2.0 M Na2SO4. In the case of the acetate-chloride solution, ΦClNO2 is reduced to 0.18 ± 0.03 upon the addition of 0.5 M NaAc. In contrast, no statistically significant suppression in ΦClNO2 was observed for the addition of sodium perchlorate up to 3.0 M, implying that an increase in ionic strength of the solution does not necessitate a reduction in ΦClNO2. We suggest that the reduction in ΦClNO2 may result from a direct reaction between SO42– (and Ac–) with NO2+ (or NO2+NO3–) which compet...