Measurement of 224Ra:228Th disequilibrium in coastal sediments using a delayed coincidence counter
Measurement of 224Ra:228Th disequilibrium in coastal sediments using a delayed coincidence counter
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使用延迟符合计数器测量沿海沉积物中的 224Ra:228Th 不平衡
DOI：
10.1016/j.marchem.2012.05.004
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发表时间：
2012-07-20
期刊：
影响因子：
3
通讯作者：
Dai, Minhan
中科院分区：
文献类型：
--
作者：
Cai, Pinghe;Shi, Xiangming;Dai, Minhan
我们描述了一种基于延迟符合计数系统（RaDeCC系统）测量沿海沉积物中Ra-224和Th-228活性的方法。将ml - q水加入到大块沉积物中形成浆液。间隙水中的Ra-224被二氧化锰悬浮液共沉淀。MnO2悬浮液和吸收了Ra-224和Th-228的沉积物被过滤到一个142毫米0.7 μ m（公称孔径）的GFF过滤器上。过滤器放置在指定的沉积物样品的样品支架上，并在RaDeCC系统中计数。Ra-224和Th-228活性是在样品采集后6-12小时和8-10天内进行的两次测量中计算出来的。RaDeCC系统使用U-232-Th-228标准，使用标准加法法进行校准。基于该方法测定Ra-224和Th-228的重现性和总体准确度分别为+/- 5%和+/- 5-7%。我们将这种方法应用于沿海沉积物，观察到Ra-224相对于Th-228在上部3-4厘米处的显著缺陷。(c) 2012 Elsevier B.V.版权所有
We describe a method for measuring Ra-224 and Th-228 activities in coastal sediments based on a delayed-coincidence counting system (the RaDeCC system). Milli-Q water is added to bulk sediment to form a slurry. Ra-224 in interstitial water is co-precipitated by MnO2 suspension. The MnO2 suspension and the sediment with absorbed Ra-224 and Th-228 are filtered onto a 142-mm 0.7 mu m (nominal pore size) GFF filter. The filter is placed onto a sample holder specified for sediment samples and counted in a RaDeCC system. Ra-224 and Th-228 activities are calculated from two measurements that are conducted within 6-12 h and in 8-10 days after sample collection. The RaDeCC system is calibrated with a U-232-Th-228 standard using the method of standard addition. The reproducibility and the overall accuracy of Ra-224 and Th-228 measurements based on this method are estimated to be +/- 5% and +/- 5-7%, respectively. We have applied this method to a coastal sediment and observed a significant deficit of Ra-224 with respect to Th-228 in the upper 3-4 cm. (c) 2012 Elsevier B.V. All rights reserved.