On the importance of the decay of 234Th in determining size‐fractionated C/234Th ratio on marine particles
On the importance of the decay of 234Th in determining size‐fractionated C/234Th ratio on marine particles
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DOI：
10.1029/2006gl027792
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发表时间：
2006-12
影响因子：
5.2
通讯作者：
P. Cai;M. Dai;Weifang Chen;T. Tang;K. Zhou
中科院分区：
文献类型：
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作者：
P. Cai;M. Dai;Weifang Chen;T. Tang;K. Zhou
准确测定下沉颗粒上的 POC/234Th 比率对于应用 234Th 作为上层海洋颗粒有机碳（POC）输出的代理至关重要。先前的研究表明，POC/234Th 比率可能变化多达两个数量级，但这种变化的机制仍然知之甚少。在本研究中，对从南海某站海拔 500 m 处收集的样品检查了三个粒径级别的 POC/234Th 和 POC/228Th 比率。我们的结果表明，给定深度处 POC/234Th 比率随颗粒尺寸的变化主要是由 234Th 的简单衰变驱动的。事实上，POC/234Th 比率与颗粒尺寸的各种趋势可以通过颗粒聚集过程中 234Th 衰变和 POC 相对于 Th 优先再矿化的组合来解释。我们还观察到 234Th/228Th 比率随粒径减小的趋势。这一趋势与布朗泵浦模型的预期结果一致。
Accurate determination of the POC/234Th ratio on sinking particles is essential for the application of 234Th as a proxy for the export of particulate organic carbon (POC) from the upper ocean. Previous studies have shown that POC/234Th ratios may vary by as much as two orders of magnitude, but the mechanism for this variability remains poorly understood. In this study, POC/234Th and POC/228Th ratios in three particle size classes were examined for samples collected from the upper 500 m at a station in the South China Sea. Our results indicate that changes in the POC/234Th ratio with particle size at a given depth are mostly driven by simple decay of 234Th. In fact, various trends in the POC/234Th ratio versus particle size are explained by a combination of 234Th decay and the preferential remineralization of POC relative to Th during particle aggregation. We also observed a trend of decreasing 234Th/228Th ratios with particle size. This trend is consistent with results expected from a Brownian‐pumping model.