Hirose K, Aoyama M, Fukasawa M, Kim C S, Komura K, Povinec P P, Sanchez-Cabeza J A
Meteorological Research Institute, Nagamine 1-1, Tsukuba, Ibaraki 305-0052, Japan.
Sci Total Environ. 2007 Aug 1;381(1-3):243-55. doi: 10.1016/j.scitotenv.2007.03.022. Epub 2007 Apr 25.
The present plutonium and 137Cs concentrations in South Pacific Ocean surface waters were determined. The water samples were collected in the South Pacific mid-latitude region (32.5 degrees S) during the BEAGLE expedition conducted in 2003-04 by JAMSTEC. 239,240Pu concentrations in surface seawater of the South Pacific were in the range of 0.5 to 4.1 mBq m(-3), whereas 137Cs concentrations ranged from 0.07 to 1.7 Bq m(-3). The observed 239,240Pu and 137Cs concentrations in the South Pacific were almost of the same level as those in the North Pacific subtropical gyre. The surface 239,240Pu in the South Pacific subtropical gyre showed larger spatial variations than 137Cs, as it may be affected by physical and biogeochemical processes. The 239,240Pu/137Cs activity ratios, which reflect biogeochemical processes in seawater, were generally smaller than that observed in global fallout, except for the most eastern station. The 239,240Pu/137Cs ratios in the South Pacific tend to be higher than that in the North Pacific. The relationships between anthropogenic radionuclides and oceanographic parameters such as salinity and nutrients were examined. The 137Cs concentrations in the western South Pacific (the Tasman Sea) and the eastern South Pacific were negatively correlated with the phosphate concentration, whereas there is no correlation between the 137Cs and nutrients concentrations in the South Pacific subtropical gyre. The mutual relationships between anthropogenic radionuclides and oceanographic parameters are important for better understanding of transport processes of anthropogenic radionuclides and their fate in the South Pacific.
测定了南太平洋表层水体中钚和铯 - 137的当前浓度。水样于2003 - 2004年日本海洋地球科学技术机构（JAMSTEC）开展的比格尔探险期间，在南太平洋中纬度地区（南纬32.5度）采集。南太平洋表层海水中钚 - 239、钚 - 240的浓度范围为0.5至4.1毫贝克勒尔每立方米，而铯 - 137的浓度范围为0.07至1.7贝克勒尔每立方米。在南太平洋观测到的钚 - 239、钚 - 240和铯 - 137浓度与北太平洋亚热带环流中的浓度几乎处于同一水平。南太平洋亚热带环流中的表层钚 - 239、钚 - 240的空间变化比铯 - 137大，因为它可能受到物理和生物地球化学过程的影响。反映海水中生物地球化学过程的钚 - 239、钚 - 240/铯 - 137活度比，除了最东部的站点外，一般小于全球沉降物中观测到的活度比。南太平洋的钚 - 239、钚 - 240/铯 - 137比值往往高于北太平洋。研究了人为放射性核素与诸如盐度和营养物质等海洋学参数之间的关系。南太平洋西部（塔斯曼海）和东部的铯 - 137浓度与磷酸盐浓度呈负相关，而在南太平洋亚热带环流中铯 - 137与营养物质浓度之间没有相关性。人为放射性核素与海洋学参数之间的相互关系对于更好地理解人为放射性核素在南太平洋的传输过程及其归宿非常重要。
