Long-term characterization of carbonaceous aerosol in Uji, Japan

Measurements of carbonaceous aerosols in eastern Asia are still scarce, and existing data are in most cases short-termed and limited to only a few places. Concentrations of organic carbon, elemental carbon (EC), and total aerosol (PM-10) were measured continuously in Uji (Kyoto prefecture), Japan in the period of June 1998 to November 1999. Carbonaceous material was measured by an Ambient Carbon Particulate Monitor (R&P, Series 5400), PM-10 was observed with a β-gauge system, and all data are available on a 1 h basis. Since the carbon monitor underestimates fine particle concentrations, we correct EC concentrations using measured EC size distributions. Additional measurements of EC size-distributions at two urban locations (Uji and Nagoya) and a site on the Pacific coast of Japan (Shirahama) were performed during spring 2000. The near-continuous long-term data and measured size-distributions allow a discussion of the background EC concentration in Japan. Our measurements show that EC contributes on average 25% of the PM-10 concentration and the annual average EC/TC ratio is about 70% at Uji. This shows that the Japanese aerosol has a high fraction of EC, which can have serious implications for climate, the hydrological cycle and human health.