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Freeze-Induced Reactions: Formation of Iodine−Bromine Interhalogen Species from Aqueous Halide Ion Solutions

“…On the basis of the above results, it would appear that the conversion of diiodobromide to dibromoiodide ions in solution occurs as a result of the enhanced oxidation of iodide by nitrous acid when the mixtures are frozen. Enhanced product formation arising from freezing dilute solutions of reactants has become a well-documented phenomenon. − ,, The acceleration of reaction rates arising from freeze concentration has been theoretically treated by Takenaka et al The authors showed that during freezing, reaction rates are accelerated relative to those in solution by a factor of [ C fp /( C T,0 + px)] n −1 . Here, C fp and C T,0 are the total concentrations of solutes in the micropockets and bulk unfrozen solution, respectively, px is the molar change that occurs during the reaction, and n is the overall reaction order.…”

“…As observed in the case where X = Cl − , it was shown that the freezing process itself can lead to unexpected chemical behavior . Previous reports in the literature have shown that a variety of reactions are in fact accelerated as a result of the freezing process. − In particular, a number of atmospherically relevant autoxidation reactions, such as those involving nitrite, iodide, sulfide, or sulfite ions, are known to be promoted when dilute solutions are frozen. − ,− Indeed, an acceleration of reaction rates up to 10 5 times above those at room temperature have been reported in the literature . When a solution of dilute electrolytes is frozen, it is known that some species are incorporated more readily into the ice than others, the so-called Workman−Reynolds effect. , The concentrations of electrolytes in the liquid phase may increase dramatically as liquid water is removed to the growing solid phase and, as the freezing front advances, the remaining liquid becomes trapped between grain boundaries, leading to the formation of unfrozen, liquid-phase “micropockets”.…”

Natural Denitrification in Drying Process of Dew

“…In fog and cloud droplets, high concentrations of nitrite and ammonium have also been observed (23)(24)(25)(26). These droplets also experience drying in nature.…”

“…In the drying process of dew containing high concentration of ammonium and nitrite at relatively high pH, it is clarified that the natural denitrification can occur via a chemical process. In fog and cloud droplets, high concentrations of nitrite and ammonium have also been observed ( − ). These droplets also experience drying in nature.…”

PM1.0-Nitrite Heterogeneous Formation Demonstrated via a Modified Versatile Aerosol Concentration Enrichment System Coupled with Ion Chromatography

“…Another challenge is related to the chemical instability of particulate NO 2 – (i.e., it is easily oxidized and decomposed). NO 2 – is easily oxidized during sampling by dissolved oxidants such as oxygen, hydrogen peroxide, and ozone. − The methods to remove these strong oxidizers were compared, and the results showed that purging N 2 was the most effective method . In previous studies, vitamin C was also added to scavenge reactive oxygen and nitrogen species; − however, vitamin C is acidic in aqueous solution (the pH of 0.5% vitamin C is approximately 3, and the higher the concentration, the lower is the pH), which will cause NO 2 – transformation (pH < 3), such as the conversion to HONO .…”