9:30 AM - 9:45 AM
[AAS06-08] Seasonal variation of wet deposition fluxes of black carbon in East Asia: long-term measurements
Keywords:Black carbon, Wet deposition, Field observation, East Asia
MBC was measured by a Continuous Soot Monitoring System (COSMOS). Rainwater samples were collected on a daily basis by using an automated wet-only sampler and CBC was measured by consisting of a pneumatic nebulizer (Marin-5) and a single-particle soot photometer (SP2). The monthly averaged MBC and CBC at Cape Hedo showed a marked seasonal variation, which was highest in spring (0.25±0.11 μg m-3 and 66.1±70.0 μg L-1, respectively) and lowest in summer (0.06±0.03 μg m-3 and 5.2±4.2 μg L-1, respectively). The high MBC and CBC in spring were associated with transport of air masses from the Asian continent by northwesterly winds. At Cape Echizen and Happo, both monthly averaged MBC also showed a distinct seasonal variation, which was highest in spring (0.31±0.05 μg m-3 and 0.17±0.08 μg m-3, respectively). On the other hand, both monthly averaged CBC were highest in winter (19.6±14.1 μg L-1 and 14.4±10.8 μg L-1, respectively). The high CBC in winter were not always associated with MBC in a planetary boundary layer. FBC, estimated as the product of CBC and precipitation, also showed a distinct seasonal variation. The monthly FBC at Cape Hedo was highest in spring (11.8 mg m-2 month-1) and about 80% of annual FBC occurred in this season on average. Monthly FBC at Cape Echizen and Happo were highest in winter (4.08 mg m-2 month-1 and 2.05 mg m-2 month-1, respectively) and about 40-50% of annual FBC occurred in this season on average. These FBC observed in this study were very useful data to varify FBC calculated by climate models.