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Unified modeling of contrasting basin-scale dissolved Al distributions using dissolution kinetics of diatom aggregates: Implication for upwelling intensity as a primary factor to control opal burial rate
Marine Chemistry ( IF 3 ) Pub Date : 2021-07-20 , DOI: 10.1016/j.marchem.2021.104009
Tasuku Akagi 1 , Hirotaka Nishino 1
Affiliation  

Distribution of dissolved aluminum is strongly coupled with dissolution of diatom frustules, since opal is the main scavenger of dissolved oceanic Al. Given Al has a much shorter residence time compared with silicic acid, vertical processes affecting Al must be much more important. It may therefore be possible to understand dissolution behavior of diatom frustules indirectly via Al distribution.

In this paper, we explore the features that dissolution kinetics of diatom frustule aggregates would provide with respect to vertical profiles of silicic acid, opal and dissolved Al. This dissolution kinetics has merits to understand 1) the elemental composition of siliceous fraction of settling particles and 2) limited occurrence of opal deposition. The dissolution kinetics of diatom frustule aggregates describes dissolution as a function of aggregate size, which depends on diatom productivity. To heighten our understanding, a unidimensional model has been developed incorporating the dissolution kinetics. This model reproduces basin-scale Al vertical profiles in the Atlantic and Pacific Oceans and Arctic and Mediterranean Seas with the identical parameter of Al absorption by opal as well as maximum Si concentration and minimum Al concentration at increasing depths with increasing Si concentrations.

The distribution of opal predicted by this model may be useful and may explain discrepancies between the observed and previously-modeled depth profiles for dissolved Al. This model predicts the effective dissolution/burial of frustules during periods of smaller/greater production. Because upwelling triggers the production of diatoms, we propose that increase in upwelling intensity may be most important parameters to reduce the oceanic silicic acid inventory.



中文翻译:

使用硅藻聚集体的溶解动力学对对比盆地尺度溶解铝分布进行统一建模:上涌强度作为控制蛋白石埋藏速率的主要因素的含义

溶解铝的分布与硅藻壳的溶解密切相关,因为蛋白石是溶解的海洋铝的主要清除剂。鉴于与硅酸相比,铝的停留时间要短得多,因此影响铝的垂直过程必须更加重要。因此,可以通过铝分布间接了解硅藻壳的溶解行为。

在本文中,我们探讨了硅藻壳聚集体的溶解动力学在硅酸、蛋白石和溶解铝的垂直分布方面的特征。这种溶解动力学有利于理解 1) 沉降颗粒的硅质部分的元素组成和 2) 蛋白石沉积的发生有限。硅藻壳聚集体的溶解动力学将溶解描述为聚集体尺寸的函数,这取决于硅藻生产力。为了加深我们的理解,已经开发了一个包含溶出动力学的一维模型。

该模型预测的蛋白石分布可能是有用的,并且可以解释观察到的和先前模拟的溶解铝深度剖面之间的差异。该模型预测在较小/较大生产期间硅藻壳的有效溶解/埋藏。由于上升流触发了硅藻的产生,我们提出上升流强度的增加可能是减少海洋硅酸库存的最重要参数。

更新日期:2021-07-28
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