Chandra Mouli Pavuluri
& Kimitaka Kawamura
【Abstract】To investigate the applicability of compound
specific stable carbon isotope ratios (δ13C) of organics in
assessment of their photochemical aging in the atmosphere, batch UV irradiation
experiments were conducted on two ambient (anthropogenic and biogenic) aerosol
samples in aqueous phase for 0.5–120?h. The irradiated samples were analyzed for δ13C
of diacids, glyoxylic acid (ωC2)
and glyoxal. δ13C
of diacids and related compounds became larger with irradiation time (i.e.,
aging), except for few cases. In general, δ13C of C2C4diacids
showed an increasing trend with decreasing chain length. Based on δ13C
of diacids and related compounds and their relations to their concentrations,
we found that C2 and C3 are enriched with 13C
during the photochemical decomposition and production from their higher
homologues and oxoacids. Photochemical breakdown of higher (≥C3)
to lower diacids is also important in the enrichment of 13C in C3-C9 diacids whereas their production from primary precursors causes depletion of 13C.
In case of ωC2 and glyoxal, their photochemical production and
further oxidation to highly oxygenated compounds both cause the enrichment of 13C.
This study reveals that δ13C of diacids and related compounds can be
used as a proxy to trace the aging of organic aerosols during long-range
atmospheric transport.
【More Information】http://www.nature.com/articles/srep36467
