Seasonal Variation and Source Analysis of Carbonaceous Aerosol at Urban Site in Nagoya Using Radiocarbon

Abstract

Abstract To evaluate seasonal variations and sources of the carbonaceous components in aerosols emitted from biomass burning and vegetation in urban site, we measured organic carbon, elemental carbon, radiocarbon (¹⁴C) in total carbon (TC), and levoglucosan concentrations in total suspended particulate matter collected in Nagoya. Higher ¹⁴C concentrations were observed during spring (56.4 pMC) and summer–early fall (57.4 pMC) than during late fall–winter (47.1 pMC). In particular, ¹⁴C concentration in April was influenced by pollens, and it showed the highest ¹⁴C value (about 70 pMC) in our observations. Levoglucosan concentrations had clear seasonal variations: the contents from late fall–winter were higher than those in other seasons, similar to other reports in Japan. Moreover, levoglucosan had a good correlation with non-fossil carbon in total carbon (TC_nf) calculated by ¹⁴C concentration, from early fall–winter. Furthermore, TC_nf was roughly divided into two origins: biomass burning (TC_bb) and biogenic carbon except for biomass burning (TC_bio). The contributions of TC_bb to TC_nf and TC in late fall–winter were found to be the highest. Meanwhile, TC_bio was higher than TC_bb in all seasons, and the main sources of TC_bio were considered to vary by seasons: pollens in spring and biogenic secondary organic aerosols in summer.