Reply to comment by Chin‐Chang Hung et al. on “How accurate are 234Th measurements in seawater based on the MnO2‐impregnated cartridge technique?”
Reply to comment by Chin‐Chang Hung et al. on “How accurate are 234Th measurements in seawater based on the MnO2‐impregnated cartridge technique?”
复制标题
DOI：
10.1029/2007gc001837
复制
发表时间：
2008-02
期刊：
影响因子：
3.7
通讯作者：
P. Cai;M. Dai;Dongwei Lv;Weifang Chen
中科院分区：
文献类型：
--
作者：
P. Cai;M. Dai;Dongwei Lv;Weifang Chen
[1]我们不同意Hung等人[2008]的小体积MnO 2共沉淀法和MnO 2柱法的比较是充分的。这是因为至少有一些小体积Th数据用于比较依赖于早期协议的小体积方法，不包括恢复校正。因此，结果可能存在偏倚。来自中国南海的新数据证实了我们早先的结论，即筒式方法大大高估了Th的提取效率。因此，我们重申，小体积Th方法，包括恢复校正是有利的墨盒技术，并建议更准确地量化Th活动，用于限制出口的颗粒有机碳在上层海洋。[2]Hung等人[2008年]的评论认为，Cai等人[2006年a]采用的分析程序并不典型，以前应用的MnO2筒法发现，该方法与深水中的U具有良好的一致性，与小体积样品中测量的Th一致。他们试图表明，这两种方法在正确应用时，在误差范围内产生可比较的结果。我们重申，Cai等人[2006 a]采用的分析方法更可取，并提供了额外的实验数据。此外，我们指出，Hung等人[2008]的小体积MnO2共沉淀法与MnO2筒法的比较是不够的。这是因为作者引用的小体积Th数据中至少有一些是基于该方法的早期协议，该协议不包括恢复校正，因此可能存在偏差（见下文）。因此，G地球化学地球物理地球系统
[1] We disagree that the comparison of the smallvolume MnO2 coprecipitation method and the MnO2 cartridge method of Hung et al. [2008] is adequate. This is because at least some of the small-volume Th data used for their comparison relied on an early protocol of the smallvolume method that did not include a recovery correction. Thus results are potentially biased. New data from the South China Sea confirm our earlier conclusion that the extraction efficiency for Th is substantially overestimated by the cartridge method. We therefore restate that the small-volume Thmethod that includes a recovery correction is advantageous over the cartridge technique and is recommended to more accurately quantify Th activities used to constrain the export of particulate organic carbon in the upper ocean. [2] The comment by Hung et al. [2008] argued that the analytical procedures applied by Cai et al. [2006a] are not typical of other workers and that previous applications of the MnO2 cartridge method have found it to give good agreement with U in deep water and to agree with Th measured on small volume samples. They attempted to suggest that the two methods yield comparable results, within errors, when properly applied. We restate that the analytical procedures adopted by Cai et al. [2006a] is preferable by providing additional experimental data. Furthermore, we point out that the comparison of the small-volume MnO2 coprecipitation method with the MnO2 cartridge method of Hung et al. [2008] is inadequate. This is because at least some of the small-volume Th data cited by the authors were based on an early protocol of the method that did not include a recovery correction and thus could be biased (see below). Therefore the G Geochemistry Geophysics Geosystems