Abstract In this study, we identify and quantify processes that lead to sedimentary potassium (K) sequestration and phosphorus (P) release on the Amazon shelf. To this end, seven short sediment cores were recovered from the Amazon shelf during R/V Meteor cruise M147. All of the sediment cores investigated in this study are characterized by elevated K to aluminum (Al) ratios compared to Amazon riverine suspended matter, which indicates that seawater K+ is incorporated into the solid phase on the entire Amazon shelf. Pore water silica profiles are characterized by irregularly increasing concentrations and plateaus, thus, deviating from the asymptotic shape that is typically found in continental margin sediments. At one site, a dissolved Si plateau coincides with a K+ minimum suggesting that these solutes are incorporated into authigenic minerals, a process referred to as reverse weathering. Previous flux estimates for elements that participate in reverse weathering on the Amazon shelf were derived from pore water diffusive fluxes, reaction rates estimated from sediment incubations and solid phase extractions. In this study, we took an alternative approach, which is based on the concentration difference between shelf sediments and river suspended particles. The resulting K flux due to reverse weathering of 1.7 ∙ 1011 mol yr−1 is in agreement with previous estimates and corresponds to 13% of the global riverine dissolved K+ input. Previous studies demonstrated that Amazon riverine particulate P is partly solubilized on the Amazon shelf. However, these results are exclusively based on sediment data close to the river mouth and no distinction between terrestrial and marine sediment components was made. Here, we quantify P release from Amazon shelf sediments by comparing terrestrial P concentrations in shelf sediments with P concentrations in river suspended particles. The resulting solubilized P flux of 2.2 ∙ 1010 mol yr−1 is about five to six times higher than previous estimates and about seven times the Amazon riverine dissolved P discharge. The magnitudes of the presented fluxes imply that the alteration of riverine shelf sediments significantly affects the mean concentrations of dissolved K+ and P in the global ocean.

中文翻译：

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亚马逊陆架上沉积性钾封存和磷释放的更新估计

摘要 在这项研究中，我们确定并量化了导致亚马逊大陆架上沉积钾 (K) 封存和磷 (P) 释放的过程。为此，在 R/V 流星巡航 M147 期间从亚马逊大陆架回收了七个短沉积物核心。与亚马逊河流悬浮物相比，本研究中调查的所有沉积岩芯的特征在于 K 与铝 (Al) 的比率升高，这表明海水 K+ 已结合到整个亚马逊大陆架上的固相中。孔隙水二氧化硅剖面的特点是浓度和平台不规则增加，因此与大陆边缘沉积物中常见的渐近形状不同。在一个地点，溶解的 Si 高原与 K+ 最小值一致，表明这些溶质被纳入自生矿物中，一种称为逆风化的过程。先前对参与亚马逊陆架逆风化的元素的通量估计来自孔隙水扩散通量、从沉积物孵化和固相提取估计的反应速率。在这项研究中，我们采用了另一种方法，该方法基于陆架沉积物和河流悬浮颗粒之间的浓度差异。由于 1.7 ∙ 1011 mol yr−1 的反向风化导致的 K 通量与先前的估计一致，对应于全球河流溶解 K+ 输入的 13%。先前的研究表明，亚马逊河流中的颗粒 P 在亚马逊大陆架上部分溶解。然而，这些结果完全基于河口附近的沉积物数据，没有区分陆地和海洋沉积物成分。在这里，我们通过比较陆架沉积物中的陆地磷浓度与河流悬浮颗粒中的磷浓度来量化亚马逊陆架沉积物中磷的释放。由此产生的溶解 P 通量为 2.2 ∙ 1010 mol yr-1，比之前的估计值高出约 5 到 6 倍，是亚马逊河流溶解 P 排放量的约 7 倍。所呈现的通量的大小意味着河流陆架沉积物的改变显着影响了全球海洋中溶解的 K+ 和 P 的平均浓度。我们通过比较陆架沉积物中的陆地磷浓度与河流悬浮颗粒中的磷浓度来量化亚马逊陆架沉积物中磷的释放。由此产生的溶解 P 通量为 2.2 ∙ 1010 mol yr-1，比之前的估计值高出约 5 到 6 倍，是亚马逊河流溶解 P 排放量的约 7 倍。所呈现的通量的大小意味着河流陆架沉积物的改变显着影响了全球海洋中溶解的 K+ 和 P 的平均浓度。我们通过比较陆架沉积物中的陆地磷浓度与河流悬浮颗粒中的磷浓度来量化亚马逊陆架沉积物中磷的释放。由此产生的溶解 P 通量为 2.2 ∙ 1010 mol yr-1，比之前的估计值高出约 5 到 6 倍，是亚马逊河流溶解 P 排放量的约 7 倍。所呈现的通量的大小意味着河流陆架沉积物的改变显着影响了全球海洋中溶解的 K+ 和 P 的平均浓度。