Radiocarbon-Based
Source Apportionment of Carbonaceous
Aerosols at a Regional
Background Site on Hainan Island, South China
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Abstract
To assign fossil
and nonfossil contributions to carbonaceous particles,
radiocarbon (<sup>14</sup>C) measurements were performed on organic
carbon (OC), elemental carbon (EC), and water-insoluble OC (WINSOC)
of aerosol samples from a regional background site in South China
under different seasonal conditions. The average contributions of
fossil sources to EC, OC and WINSOC were 38 ± 11%, 19 ±
10%, and 17 ± 10%, respectively, indicating generally a dominance
of nonfossil emissions. A higher contribution from fossil sources
to EC (∼51%) and OC (∼30%) was observed for air-masses
transported from Southeast China in fall, associated with large fossil-fuel
combustion and vehicle emissions in highly urbanized regions of China.
In contrast, an increase of the nonfossil contribution by 5–10%
was observed during the periods with enhanced open biomass-burning
activities in Southeast Asia or Southeast China. A modified EC tracer
method was used to estimate the secondary organic carbon from fossil
emissions by determining <sup>14</sup>C-derived fossil WINSOC and
fossil EC. This approach indicates a dominating secondary component
(70 ± 7%) of fossil OC. Furthermore, contributions of biogenic
and biomass-burning emissions to contemporary OC were estimated to
be 56 ± 16% and 44 ± 14%, respectively