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Evidence for 13‐carbon enrichment in oxalic acid via iron catalyzed photolysis in aqueous phase
Author(s) -
Pavuluri Chandra Mouli,
Kawamura Kimitaka
Publication year - 2012
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2011gl050398
Subject(s) - oxalic acid , photodissociation , aqueous solution , chemistry , fractionation , catalysis , carbon fibers , isotopes of carbon , kinetic isotope effect , radical , photochemistry , irradiation , isotope fractionation , inorganic chemistry , environmental chemistry , total organic carbon , materials science , organic chemistry , deuterium , physics , quantum mechanics , composite number , nuclear physics , composite material
To investigate the effect of photochemical aging on the stable carbon isotopic ratio ( δ 13 C) of oxalic acid (OxA), a dominant organic species in atmospheric aerosols, we conducted a laboratory photolysis of OxA under H 2 O 2 ‐Fe 3+ (Fe 2+ )‐UV system in aqueous phase and measured δ 13 C of remaining OxA. Our results showed that a significant photolysis of OxA occurred with OH radical but the isotopic fractionation of OxA was insignificant. In contrast, in the presence of Fe 3+ (Fe 2+ ), we found a significant enrichment of 13 C in remaining OxA. We also found that kinetic isotope effect (KIE) of OxA largely depends on photochemical age (irradiation time) and concentration ratios of OxA to iron; 3.20 ± 0.49‰ (2.18 ± 1.18‰) and 21.62 ± 5.41‰ in 90 min and 180 min irradiation, in which OxA and Fe 3+ (Fe 2+ ) ratios were 50:1 and 200:1, respectively. The enrichment of 13 C in remaining OxA was more significant during the photolysis catalyzed by Fe 3+ (7‰) than by Fe 2+ (3‰) in 90 min irradiation when OxA and iron ratios are the same (50:1). This study provides a laboratory evidence for the isotopic enrichment of 13 C in OxA with photochemical aging. This approach is useful for better interpretation of atmospheric isotopic measurements in terms of the extent of atmospheric processing of aerosols.