Dissolved silicon isotope dynamics in large river estuaries
Dissolved silicon isotope dynamics in large river estuaries
复制标题
大河口溶解硅同位素动态
DOI：
10.1016/j.gca.2020.01.028
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发表时间：
2020
影响因子：
5
通讯作者：
Martin Frank
中科院分区：
文献类型：
--
作者：
Zhouling Zhang;Zhimian Cao;Patricia Grasse;Minhan Dai;Lei Gao;Henning Kuhnert;Martha Gledhill;Cristiano M. Chiessi;Kristin Doering;Martin Frank
河口系统对于河流向海洋输入硅（Si）至关重要，这是沿海地区硅藻生产力的限制因素。本研究提供了在世界三大河流亚马逊河 (ARE)、长江 (YRE) 和珍珠河 (PRE) 河口获得的表面溶解硅同位素组成 (δ30SiSi(OH)4) 的现场数据集，这些河流覆盖了不同的气候带。虽然 δ30SiSi(OH)4 在 YRE 和 PRE 中表现保守，支持水团混合的主导控制，但在 ARE 中观察到由于硅藻利用 Si(OH)4 而显着增加了 δ30SiSi(OH)4 特征，并反映了 Si 同位素富集因子 30ε 为 -1.0±0.4‰（瑞利模型）或 -1.6±0.4‰（稳态模型）。此外，通过与之前的工作进行比较，观察到 YRE 中硅同位素行为的季节性变化，很可能是由于水停留时间、温度和光照水平的变化造成的。根据ARE获得的30ε值，我们估计由于河口的Si滞留，进入海洋的全球平均δ30SiSi(OH)4比河流高0.2-0.3‰。为了更好地限制大河口在海洋硅循环中的作用，需要考虑河口混合过程中河流硅同位素组成的系统改变，以及单个河口硅同位素动态的季节性。
Estuarine systems are of key importance for the riverine input of silicon (Si) to the ocean, which is a limiting factor of diatom productivity in coastal areas. This study presents a field dataset of surface dissolved Si isotopic compositions (δ30SiSi(OH)4) obtained in the estuaries of three of the world’s largest rivers, the Amazon (ARE), Yangtze (YRE), and Pearl (PRE), which cover different climate zones. While δ30SiSi(OH)4behaved conservatively in the YRE and PRE supporting a dominant control by water mass mixing, significantly increased δ30SiSi(OH)4signatures due to diatom utilization of Si(OH)4were observed in the ARE and reflected a Si isotopic enrichment factor30ε of −1.0 ± 0.4‰ (Rayleigh model) or −1.6 ± 0.4‰ (steady state model). In addition, seasonal variability of Si isotope behavior in the YRE was observed by comparison to previous work and most likely resulted from changes in water residence time, temperature, and light level. Based on the30ε value obtained for the ARE, we estimate that the global average δ30SiSi(OH)4entering the ocean is 0.2–0.3‰ higher than that of the rivers due to Si retention in estuaries. This systematic modification of riverine Si isotopic compositions during estuarine mixing, as well as the seasonality of Si isotope dynamics in single estuaries, needs to be taken into account for better constraining the role of large river estuaries in the oceanic Si cycle.