Gusyev M A, Morgenstern U, Nishihara T, Hayashi T, Akata N, Ichiyanagi K, Sugimoto A, Hasegawa A, Stewart M K
International Centre for Water Hazard and Risk Management (ICHARM)/National Graduate Institute for Policy Studies (GRIPS), Public Works Research Institute (PWRI), Tsukuba 305-8516, Japan.
GNS Science, Lower Hutt 5010, New Zealand.
Sci Total Environ. 2019 Apr 1;659:1307-1321. doi: 10.1016/j.scitotenv.2018.12.342. Epub 2018 Dec 26.
Tritium dating requires a good understanding of the tritium and water inputs into hydrologic systems, including their main trends due to latitudinal, seasonal and altitudinal effects. Although tritium reached ambient levels at the end of the 20th century, tritium released from nuclear facilities and bomb tests since then has the potential to confound use of tritium for age dating. We therefore collected precipitation and snowpack samples for tritium analysis to confirm that tritium levels in Japanese precipitation had not exceeded ambient levels following the North Korean nuclear tests in January 6th 2016 and September 3rd 2017. As the result, the highest tritium concentration was 5.52(±0.27)TU at samples collected from January 8 to 11th at one Honshu and four Hokkaido locations and samples collected at six Honshu locations had 8.01(±1.5)TU from September 6 to 19th 2017. Confirming ambient tritium concentrations after both events we investigated the latitude tritium effect at selected coastal stations in Asia, indicating a break of latitude trend around Tokyo area, and established the latitude scaling factors to the north and south of the Tokyo area data. The seasonal trend was investigated during the winter-spring 2016 in precipitation samples confirming the higher spring tritium compared with winter continental tritium values. The altitude effect on tritium and stable (O and H) isotopes was observed in Hokkaido snowpack, which had tritium concentrations ranging between 4.08 and 5.93 TU during March-April, and demonstrated two trends for western and central Hokkaido mountain ranges. Using established latitude and altitude scaling factors with the long-term continuous time-series of monthly Tokyo area tritium we estimated the annual weighted tritium at 110 meteorological stations in Japan with monthly precipitation demonstrating the applicability of this approach for future tritium-tracer studies across Asia.
氚测年需要深入了解氚和水进入水文系统的情况，包括受纬度、季节和海拔影响的主要趋势。尽管氚在20世纪末达到了环境水平，但自那时以来，核设施和核试验释放的氚有可能混淆氚用于年代测定的用途。因此，我们采集了降水和积雪样本进行氚分析，以确认在2016年1月6日和2017年9月3日朝鲜进行核试验后，日本降水中的氚水平未超过环境水平。结果显示，在本州岛的一个地点和北海道的四个地点，1月8日至11日采集的样本中氚的最高浓度为5.52（±0.27）TU，2017年9月6日至19日在本州岛六个地点采集的样本中氚浓度为8.01（±1.5）TU。在这两次事件之后，为确认环境氚浓度，我们研究了亚洲部分沿海站点的纬度氚效应，结果表明东京地区附近纬度趋势出现中断，并确定了东京地区南北两侧数据的纬度比例因子。我们在2016年冬春季节对降水样本的季节性趋势进行了研究，结果证实春季氚含量高于冬季大陆地区的氚值。在北海道积雪中观察到了海拔对氚和稳定（氧和氢）同位素的影响，3月至4月期间氚浓度在4.08至5.93 TU之间，并显示出北海道西部和中部山脉的两种趋势。利用已确定的纬度和海拔比例因子以及东京地区氚的长期连续月度时间序列，我们估算了日本110个气象站的年度加权氚值，这些气象站有月度降水量数据，证明了该方法在未来亚洲氚示踪研究中的适用性。
