Tateda Yutaka, Iwao Kenji
Environmental Science Research Laboratory, Central Research Institute of Electric Power Industry, 1646, Abiko, Chiba 270-1194, Japan.
J Environ Radioact. 2008 Jan;99(1):98-108. doi: 10.1016/j.jenvrad.2007.07.005. Epub 2007 Sep 7.
Bulk atmospheric deposition fluxes of (210)Po and (210)Pb were measured at three coastal regions of Japan, the Pacific Ocean coastal area of the Japanese mainland (Odawa Bay), the Chinese continental side of Japanese coastal area (Tsuyazaki), and an isolated island near Okinawa (Akajima). Wet and dry fallout collectors were continuously deployed from September 1997 through August 1998 for periods of 3 to 31 days depending on the frequency of precipitation events. Annual (210)Pb deposition fluxes at Odawa Bay (35 degrees N 139 degrees E), Tsuyazaki (33 degrees N 130 degrees E) and Akajima (26 degrees N 127 degrees E) were 73.3+/-8.0, 197+/-35 and 78.5+/-8.0 Bqm(-2)y(-1), respectively. Higher (210)Pb deposition was observed at the Chinese continental side of Japanese coast than at the Pacific Ocean coastal site. The high (210)Pb atmospheric flux at the Chinese continental side coast was thought to be attributable to (222)Rn-rich air-mass transport from the Chinese continent during the winter monsoon. In contrast, the annual (210)Po deposition fluxes at the three study sites were 13.0+/-2.3 (Odawa Bay), 21.9+/-4.4 (Tsuyazaki) and 58.4+/-7.7 (Akajima)Bqm(-2)y(-1), respectively, indicating unusual high (210)Po deposition at Akajima during winter. Anomalous unsupported (210)Po input was observed during summer 1997, suggesting unknown source of (210)Po at this area.
在日本的三个沿海地区测量了钋 - 210（²¹⁰Po）和铅 - 210（²¹⁰Pb）的大气沉降通量，分别是日本本土的太平洋沿岸地区（小田湾）、日本沿海地区的中国大陆一侧（津屋崎）以及冲绳附近的一个孤岛（赤岛）。从1997年9月至1998年8月持续部署了干湿沉降收集器，根据降水事件的频率，部署时间为3至31天。小田湾（北纬35度，东经139度）、津屋崎（北纬33度，东经130度）和赤岛（北纬26度，东经127度）的年²¹⁰Pb沉降通量分别为73.3±8.0、197±35和78.5±8.0 Bq m⁻² y⁻¹。在日本海岸的中国大陆一侧观测到的²¹⁰Pb沉降高于太平洋沿岸地区。认为在中国大陆一侧海岸²¹⁰Pb大气通量高是由于冬季风期间来自中国大陆富含氡 - 222（²²²Rn）的气团传输。相比之下，三个研究地点的年²¹⁰Po沉降通量分别为13.0±2.3（小田湾）、21.9±4.4（津屋崎）和58.4±7.7（赤岛）Bq m⁻² y⁻¹，表明冬季赤岛的²¹⁰Po沉降异常高。在1997年夏季观测到异常的非支持性²¹⁰Po输入，表明该地区存在未知的²¹⁰Po来源。
