Abstract
In order to understand the source apportionment of carbonaceous aerosols using a receptor model, we examined the source contribution of fine particles. The observation was done in the summer of 2007 at Maebashi and Kisai. Samples were collected every 6 hours (during the daytime) and 12 hours (during the nighttime), and the following chemical components were analyzed: carbonaceous compounds, ionic components, inorganic elements and radiocarbon content. The Chemical Mass Balance (CMB) method was applied to these data to estimate the source contribution into 10 sources. The carbonaceous compounds were apportioned into the 10 sources using these results, and elemental carbon (EC) was almost entirely diesel-exhaust derived. On the other hand, there was limited primary particle contribution in the organic carbon (OC), and it was estimated as either unknown or secondary particles. The EC and OC were divided into fossil-fuel-derived carbon and biogenic-derived carbon based on the value of the pMC (percent modern carbon) of individual sources derived from the literature. For the secondary organic carbon (SOC), it was found that although the ratio of the fossil-fuel-derived carbon to the biogenic-derived carbon was around 1:2 during the daytime, the fossil-fuel-derived carbon transported from metropolitan area decreased and the ratio dropped to 1:10 during the nighttime, and the observed pMC of total carbon (=EC+OC) increased. As the biogenic-derived-carbon accounted for 70 % of the SOC during the daytime, it was shown that biogenic-derived-carbon provided the major contributions to the SOC.
