Anomalous Plutonium Isotopic Ratios in Sediments of Lake Qinghai from the Qinghai-Tibetan Plateau, China
Anomalous Plutonium Isotopic Ratios in Sediments of Lake Qinghai from the Qinghai-Tibetan Plateau, China
复制标题
青藏高原青海湖沉积物中钚同位素比异常
DOI：
10.1021/es202315c
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发表时间：
2011-11-01
影响因子：
11.4
通讯作者：
Wan, Guojiang
中科院分区：
文献类型：
--
作者：
Wu, Fengchang;Zheng, Jian;Wan, Guojiang
测定了青藏高原青海湖3个沉积物柱样的（239+240）Pu和（137）Cs活度及（240）Pu/（239）Pu同位素比值的垂直剖面，并与其它3个湖泊的沉积物进行了比较（博斯腾湖，苏干湖和双塔湖），唯一现存的最接近罗布泊地区，中国西北部的核武器试验场。青海湖（239+240）Pu活度的平均存量为47.7 ± 18.7 MBq km（-2），与全球沉降物的平均值相当，而（137）Cs活度的平均存量为1112.0 ± 78.0 MBq km（-2），略低于全球沉降物的平均值。在3-6.5厘米深的沉积层中发现了异常低的（240）Pu/（239）Pu同位素比值（0.038-0.125），表明1950- 60年代在湖流域的原子城进行的早期核武器研究活动中输入了微量Pu。模型计算表明，钚输入约占总钚库存的5-16%。在深层沉积物层中观察到的低240 Pu/239 Pu比值为湖泊和周围地区的现代沉积物测年提供了新的时间标志。研究结果对进一步认识全球和区域核活动在环境中的来源、记录和环境影响具有重要意义，为进一步研究青海湖流域水体富营养化过程和气候变化、重建有机污染物和重金属污染历史提供了重要的年代学信息。
The vertical profiles of (239+240)Pu and (137)Cs activities and (240)Pu/(239)Pu isotopic ratios are determined for three sediment cores of Lake Qinghai from the Qinghai-Tibetan Plateau, China, and compared with those in sediments of another three lakes (Lakes Bosten, Sugan, and Shuangta), the only existing ones closest to Lop Nor area, China's nuclear weapons test site in the northwestern part of the country. The mean inventory of 47.7 +/- 18.7 MBq km(-2) for (239+240)Pu activity in Lake Qinghai is comparable to the average value of global fallout expected at the same latitude, yet the mean inventory of 1112.0 +/- 78.0 MBq km(-2) for (137)Cs is slightly lower than that of global fallout. Anomalously low (240)Pu/(239)Pu isotopic ratios (0.038-0.125) were found in the 3-6.5 cm deep sediment layers, indicating the trace Pu input from early nuclear weapons research activities at Atomic City in the lake's watershed during the 1950-60s. Model calculation indicated that the Pu input accounted for approximately 5-16% of the total Pu inventory. The observation of low 240Pu/239Pu ratio in the deep sediment layer provided a new time marker for recent sediment dating in the lake and around the area. The results are of great significance to the further understanding of sources, records, and environmental impacts of global and regional nuclear activities in the environment and provide important chronological information for further studies on the water eutrophication process and climatic change, and reconstruction of pollution history of organic contaminants and heavy metals in the watershed of Lake Qinghai.