Radiocarbon Content in Urban Atmospheric Aerosols
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We attempted to elucidate seasonal variations in fossil-fuel-derived carbon (FC) and biomass-derived carbon (BC) in urban atmospheric aerosols. We undertook continuous measurements of the composition of fine particle (PM2.1) in central Tokyo, including the 14C/12C ratio. The percent modern carbon (pMC) contained in all samples averaged 43, and the highest was 54 in late December and the lowest was 31 in early August. From the observed carbonaceous component concentrations and the pMC we could calculate the content ratio of FC and BC in PM2.1 and investigate their seasonal variations. Although there was almost no seasonal variation in the ratio of FC, the ratio of BC was observed to rise in early winter. This indicates that FC is influenced by the emission sources without seasonal variations (such as automobiles driven in urban areas). Furthermore, there is significant correlation between BC and organic carbon (OC), and even for urban areas, it is considered that the contribution of biomass carbon to OC in PM2.1 is high.
KeywordsBiomass carbon Fossil carbon Organic carbon Elemental carbon
We received valuable advice concerning analysis of radiocarbon from Dr. Minoru Yoneda of the National Institute for Environmental Studies. We take the opportunity to thank him here. This study in part was supported by the Japan Science and Technology Agency through its Cooperative System for Supporting Priority Research, and Global Environmental Research Fund (Code No. C-061) from Ministry of Environmental of Japan.
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