Measurement of 224Ra:228Th disequilibrium in coastal sediments using a delayed coincidence counter

被引：41

作者：

Cai, Pinghe ^{[1
]}

Shi, Xiangming ^{[1
]}

Moore, Willard S. ^{[2
]}

Dai, Minhan ^{[1
]}

机构：

[1] Xiamen Univ, State Key Lab Marine Environm Sci, Xiamen 361005, Peoples R China

[2] Univ S Carolina, Dept Earth & Ocean Sci, Columbia, SC 29208 USA

来源：

MARINE CHEMISTRY | 2012年 / 138卷

基金：

中国国家自然科学基金;

关键词：

Ra-224:Th-228 disequilibrium; Coastal sediments; RaDeCC system; GEOTRACES; SUBMARINE GROUNDWATER DISCHARGE; RADIUM ISOTOPES; RA-224; TRANSPORT; RN-222; ESTUARY; TRACER; MARINE;

D O I：

10.1016/j.marchem.2012.05.004

中图分类号：

O6 [化学];

学科分类号：

0703 ;

摘要：

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.

引用

页码：1 / 6

页数：6

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