Low-intensity radiolysis study of free-radical reactions in cloudwater: H sub 2 O sub 2 production and destruction. [Gamma radiation]

• Published in: Environmental science & technology Vol. 25:4
• Main Authors: Weinstein-Lloyd, J., Schwartz, S.E.
• Format: Journal Article
• Language: English
• Published: United States 01.04.1991
• Subjects: 400600 - Radiation Chemistry; 540120 - Environment, Atmospheric- Chemicals Monitoring & Transport- (1990-); ABSORPTION SPECTROSCOPY; AQUEOUS SOLUTIONS; ATMOSPHERIC CHEMISTRY; CHALCOGENIDES; CHEMICAL ANALYSIS; CHEMICAL RADIATION EFFECTS; CHEMICAL REACTION KINETICS; CHEMICAL REACTIONS; CHEMISTRY; CHROMATOGRAPHY; CLOUDS; DATA; DECOMPOSITION; DISPERSIONS; EARTH ATMOSPHERE; ELECTROMAGNETIC RADIATION; ELEMENTS; ENVIRONMENTAL SCIENCES; EXPERIMENTAL DATA; G VALUE; GAMMA RADIATION; HYDROGEN COMPOUNDS; HYDROGEN PEROXIDE; HYDROXYL RADICALS; INFORMATION; IONIZING RADIATIONS; KINETICS; LIQUID COLUMN CHROMATOGRAPHY; MATHEMATICAL MODELS; METALS; MIXTURES; NUMERICAL DATA; OXIDATION; OXIDES; OXYGEN COMPOUNDS; PEROXIDES; QUANTITATIVE CHEMICAL ANALYSIS; RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY; RADIATION EFFECTS; RADIATIONS; RADICALS; RADIOLYSIS; REACTION KINETICS; REDUCTION; SEPARATION PROCESSES; SOLUTIONS; SPECTROSCOPY; SULFUR COMPOUNDS; SULFUR DIOXIDE; SULFUR OXIDES; SUPEROXIDE RADICALS; SYNTHESIS; TRANSITION ELEMENTS; TROPOSPHERE; WATER
• ISSN: 0013-936X; 1520-5851
• DOI: 10.1021/es00016a027

Reactions in cloudwater can be important pathways for chemical transformation of atmospheric trace gases. One such reaction is the oxidation of dissolved sulfur dioxide by hydrogen peroxide. H{sub 2}O{sub 2} is formed by the disproportionation of hydroperoxyl and superoxide radicals, O{sub 2}({minus}I). The authors report measurements of the rate of H{sub 2}O{sub 2} production from O{sub 2}({minus}I) radicals generated by low-intensity cobalt-60 radiolysis of synthetic cloudwater solutions and actual precipitation samples. The authors results, employing O{sub 2}({minus}I) production rates comparable to those expected upon transfer of HO{sub 2} from interstitial cloud air to cloudwater, confirm model predictions that H{sub 2}O{sub 2} production if frequently the major fate of O{sub 2}({minus}I) radicals. However, there is evidence of significant reaction between S(IV) and O{sub 2}({minus}I), with a rate coefficient of (3 {plus minus} 2) {times} 10{sup 4} at pH 4.96. In addition, the presence of 1 {mu}M dissolved iron decreases the H{sub 2}O{sub 2} yield, principally because of destruction of H{sub 2}O{sub 2} by Fe(II).