Characteristics Of Carbonaceous Aerosols AndTheir Relationship With Emission Sources

Due to enforcing vehicle emission reduction requirements in Japan, particulate matter (PM) concentration, especially the elemental carbon (EC) concentration in roadside atmosphere, significantly decreased during the last decade. However, in spite of vehicle emission reductions, recent EC concentrations in the overall ambient air did not show a clear decrease. To achieve the PM2.5 environmental standard, measurements based on emission source contribution was desired. However, source apportionment of carbonaceous aerosol was ambiguous because chemical components are complicated, and the components change through photochemical reaction. The goal of this study was to determine source apportionment for carbonaceous aerosols. Examination of PM2.5 was performed in south Kanto including Tokyo in the summer of 2008 and the winter of 2009. Emissions from the industrial area around Tokyo Bay and the agricultural northern area showed PM transport and accumulation due to a seasonal prevailing wind. The characteristics of carbonaceous aerosol were obtained using carbon profile analysis and carbon isotope analysis. Soot-EC was found as a substance with fossil fuel origin which did not contain biomass combustion matter. Since soot-EC is stable, there was no Air Pollution XXI 195 www.witpress.com, ISSN 1743-3541 (on-line) WIT Transactions on Ecology and The Environment, Vol 174, © 2013 WIT Press doi:10.2495/AIR130171 observed difference by site and a uniform concentration was observed in winter. It became apparent from the carbon isotope analysis using C that carbon from biomass origin comprised 29% of the total carbon in the summer, and 48% of the total carbon in winter. This was found at all sites, even at Kudan in central Tokyo. The biomass contribution measured for this study did not show a significant difference from the 2004 measured results. It is not understood why the influence of the diesel exhaust purification on the carbon aerosol of the fossil fuel origin was not observed. Fossil fuel origin carbon was understood to consist of EC as the main component. However, the contribution of organic carbon (OC) increased. Subsequently, the effect of diesel exhaust purification is difficult to determine.