Nitrate anion (NO3ˉ) is ubiquitous in the environment and its photochemistry produces nitrous acid (HONO), a major source of tropospheric hydroxyl radical (OH). Enhanced HONO(g) emissions have been observed from NO3ˉ(aq) photolysis in field studies, although the underlying reasons for this enhancement are debated. Here, we show that the enhancement is induced by changes in secondary nitrate anion photochemistry due to dissolved aliphatic organic matter (DAOM). Increased yields of superoxide radical (O2ˉ) and HONO were observed when NO3ˉ solutions (pH 6) were photolyzed in the presence of DAOM surrogates of varying solubility.An additional experiment titrated with additional DAOM showed a further increase in O2ˉ(aq) and HONO(g) simultaneously with decreased yields of gaseous nitric oxide (NO) and nitrogen dioxide (NO2). To our knowledge, this is the first time that superoxide was directly observed as an intermediate in nitrate photolysis experiments, produced through DOAM oxidation by OH(aq).Herein, we suggest that enhanced HONO(g) emissions from NO3ˉ(aq) photolysis result from the reaction of O2ˉ(aq) with NO2(aq) and NO(aq) to respectively form peroxynitrate (OONO2ˉ) and peroxynitrite (OONOˉ), which are precursors to nitrite (NO2ˉ). Overall, this points to an important role of O2ˉ in aqueous aerosol chemistry, which is currently under-appreciated.

This work reports a combined experimental and computational study of the activation of an otherwise catalytically inactive cobalt complex, [Co(TIM)-Br 2 ] + , for aqueous nitrite reduction. The presence of phosphate buffer leads to efficient electrocatalysis, with rapid reduction to ammonium occurring close to the thermodynamic potential and with high Faradaic efficiency. At neutral pH, increasing buffer concentrations increase catalytic current while simultaneously decreasing overpotential, although high concentrations have an inhibitory effect. Controlled potential electrolysis and rotating ring-disk electrode experiments indicate that ammonium is directly produced from nitrite by [Co(TIM)Br 2 ] + , along with hydroxylamine. Mechanistic investigations implicate a vital role for the phosphate buffer, specifically as a proton shuttle, although high buffer concentrations inhibit catalysis. These results indicate a role for buffer in the design of electrocatalysts for nitrogen oxide conversion. Article pubs.acs.org/IC

Halogen atoms are important atmospheric oxidants that have unidentified daytime sources from photochemical halide oxidation in sea salt aerosols. Here, we show that the photolysis of nitrate in aqueous chloride solutions generates nitryl chloride (ClNO2) in addition to Cl2 and HOCl. Experimental and modeling evidence suggests that O­(3P) formed in the minor photolysis channel from nitrate oxidizes chloride to Cl2 and HOCl, which reacts with nitrite to form ClNO2. This chemistry is different than currently accepted mechanisms involving chloride oxidation by OH and could shift our understanding of daytime halogen cycling in the lower atmosphere.

The first rare-earth (RE) thiosulfate complexes, RE­(S2O3)6 9–, have been crystallized via room-temperature reactions and structurally characterized through single-crystal X-ray diffraction. The incorporation of KCl was essential to their successful crystallization. Then through the use of both solvent-layering and heating techniques, these complexes can undergo structural changes through breaking the thiosulfate S–S bond and forming the sulfite anion (SO3 2–). Using the former approach, two novel lanthanide mixed thiosulfate–sulfite compounds were synthesized; moreover, through the addition of low-temperature heating time, a new structure with a higher proportion of sulfite to thiosulfate was produced. These syntheses and techniques open the door to a new family of unexplored complexes containing hard lanthanide cations and soft thiosulfate anions. The 23 compounds discussed herein show how simple changes to the synthetic process illuminate manipulatable redox reactions able to produce unique rare-earth thiosulfate materials.