Japan Geoscience Union Meeting 2018

Presentation information

[EJ] Oral

A (Atmospheric and Hydrospheric Sciences) » A-AS Atmospheric Sciences, Meteorology & Atmospheric Environment

[A-AS06] Atmospheric Chemistry

Thu. May 24, 2018 9:00 AM - 10:30 AM A05 (Tokyo Bay Makuhari Hall)

convener:Yoko Iwamoto(Graduate School of Biosphere Science, Hiroshima University), Tomoki Nakayama(Graduate School of Fisheries and Environmental Sciences, Nagasaki University), Sakae Toyoda(東京工業大学物質理工学院, 共同), Nawo Eguchi(Kyushu University), Chairperson:Ikeda Kohei(National Institute for Environmental Studies )

9:30 AM - 9:45 AM

[AAS06-08] Seasonal variation of wet deposition fluxes of black carbon in East Asia: long-term measurements

*Tatsuhiro Mori1, Kazuhiko Miura1, Sho Ohata2, Nobuhiro Moteki2, Makoto Koike2, Yutaka Kondo3, Kazunori Nakagome4, Masanori Yoshikawa5, Aya Iwasaki6 (1.Tokyo University of Science, 2.Graduate School of Science, The University of Tokyo, 3.National Institute of Polar Research, 4.Nagano Environmental Conservation Research Institute, 5.Fukui Prefectural Institute of Public Health, 6.Okinawa Prefectural Institute of Health and Environment)

Keywords:Black carbon, Wet deposition, Field observation, East Asia

Quantitative understanding of wet removal process of black carbon (BC) is important because it controls temporal and spatial distribution of BC in atmosphere. Majority of BC-containing particles in a planetary boundary layer are mainly active as cloud condensation nuclei and removed by precipitation. To understand the wet removal process of BC, it is essential to measure BC mass concentration in air (MBC) and in rainwater (CBC) for a long-term period, simultaneously. In this study, a simultaneous measurement of MBC and CBC was made at Cape Hedo in Okinawa prefecture during 2010-2016, at Cape Echizen in Fukui prefecture during 2012-2016, and at Happo in Nagano prefecture during 2012-2016. Seasonal variations of both mass concentrations and the wet deposition fluxes (FBC) of BC were presented.

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.