- 著者
- Syuichi Itahashi Junichi Kurokawa Toshimasa Ohara Itsushi Uno Shin-ichi Fujita
- 出版者
- Meteorological Society of Japan
- 雑誌
- SOLA (ISSN:13496476)
- 巻号頁・発行日
- vol.17, pp.184-190, 2021 (Released:2021-10-14)
- 参考文献数
- 44
- 被引用文献数
- 1
Precipitation chemistry was observed at the remote background site at Ryori, Ofunato in northeastern Japan, from 1976 to 2011 as the part of World Meteorological Organization-Global Atmospheric Watch (WMO-GAW). During this period, anthropogenic emissions in East Asia varied widely, which affected the precipitation chemistry. The precipitation amount also affects the wet deposition amount. Thus, to eliminate the effect of the precipitation amount, we used the ratio of nitrate (NO3−) to non-sea-salt sulfate (nss-SO42−) concentration in precipitation on an equivalent basis (Ratio). The historical trend of NO3− and nss-SO42− concentrations in precipitation was not clear; however, Ratio showed a strong increase in the 1990s, a sudden drop in 2001, and an increase again after 2007. Based on the analysis of the historical emission dataset, the increases in Ratio during the 1990s and after 2007 were attributed to anthropogenic emission changes in Japan and China. The drop in Ratio in 2001 was explained by the massive SO2 release from Miyakejima volcano from mid-August 2000, rather than by anthropogenic emissions. The 36-year historical record analysis of precipitation chemistry at Ryori detected both anthropogenic and natural emission changes and indicated the transition from local to transboundary air pollution in Japan.
- 著者
- Haruo Tsuruta Yasuji Oura Mitsuru Ebihara Yuichi Moriguchi Toshimasa Ohara Teruyuki Nakajima
- 出版者
- GEOCHEMICAL SOCIETY OF JAPAN
- 雑誌
- GEOCHEMICAL JOURNAL (ISSN:00167002)
- 巻号頁・発行日
- vol.52, no.2, pp.103-121, 2018-03-30 (Released:2018-04-19)
- 参考文献数
- 35
- 被引用文献数
- 42
Using an hourly-resolution time series of the Fukushima radionuclides collected on used filter-tapes installed in suspended particulate matter (SPM) monitors, we measured the hourly radiocesium values at the SPM monitoring sites of Futaba and Naraha located within 20 km of the Fukushima Daiichi Nuclear Power Plant (FD1NPP) during March 12–25, 2011. The time-series of the 137Cs concentrations at the sites were analyzed and compared with radiation dose rates at the many monitoring posts/points of Fukushima Prefecture and the Tokyo Electric Power Company. At Futaba, nine plumes of high 137Cs concentrations were found on March 12–13, 15–16, 18–20, and 24–25, 2011, when southeasterly winds prevailed. On March 12, the first peak of the 137Cs concentrations was detected at Futaba at 9:00 Japanese Standard Time (JST) due to the first release from reactor Unit 1 (U1) in the early morning. Furthermore, the highest 137Cs concentration, i.e., 13,600 Bq m–3 was observed at 15:00 JST after a vent operation at U1, just before the hydrogen explosion of U1 at 15:36 JST. On the afternoon of March 15, plumes from the FD1NPP were observed at Futaba due to a constant southeasterly wind and were then transported to downwind, resulting in the formation of a highly deposited zone of radionuclides spanning more than 30 km from near the FD1NPP to the northwest. In contrast, seven plumes of high 137Cs concentrations were found at Naraha on March 15–16, 18, 20–21, 2011, when northerly winds prevailed. On March 15, a plume caused by the first release from Unit 2 was observed at Naraha at 1:00 JST, and the highest concentration, i.e., 8,300 Bq m–3, was observed at 3:00 JST, and then were transported southward to the Kantou area. The activity ratios of 134Cs/137Cs in the plumes were divided into two groups. The plumes at Futaba on March 12–13, which had ratios of 0.92–0.94, are identified to be released from U1, compared to its ratio of 0.94, as derived from the inventory data. All other plumes with the ratios of 1.02–1.04 at Futaba and Naraha during March 15–21 have not been determined to be released from U2 and/or Unit 3.