A first-order geochemical budget for suspended sediment discharge to the Bay of Bengal from the Ganges-Brahmaputra river system
A first-order geochemical budget for suspended sediment discharge to the Bay of Bengal from the Ganges-Brahmaputra river system
复制标题
恒河-雅鲁藏布江水系向孟加拉湾排放悬浮沉积物的一阶地球化学预算
DOI：
10.1016/j.scitotenv.2020.138667
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发表时间：
2020
影响因子：
9.8
通讯作者：
Ronay, Elli R.
中科院分区：
文献类型：
--
作者：
Dietrich, Matthew;Best, Kelsea B.;Raff, Jessica L.;Ronay, Elli R.
恒河-雅鲁藏布江-梅格纳河 (G-B) 河流系统每年输送 >1 × 109 吨沉积物，估计每年有 0.7 × 109 吨沉积物到达孟加拉湾 (BoB)。这种排放代表了沉积物和相关元素进入全球海洋的主要输入，但到达 BoB 的沉积物元素质量的量化尚未得到充分探索。已发布的地球化学和悬浮沉积物数据用于计算向 BoB 提供现代沉积物地球化学元素的一阶预算。河流剖面的大量沉积物元素浓度是根据恒河和布拉马普特拉河中的悬浮沉积物和元素测量值计算的。应用蒙特卡罗分析来解释每条河流的可变沉积物和地球化学贡献。结果表明，平均而言，G-B 系统贡献了全球河流从沉积物到海洋的固相元素排放量的约 5%。 G-B 沉积物输送了超过全球 10% 的 Hf 和 Zr 元素供应。对于其他物质，如砷和铜，G-B 的贡献小于 5%。结果还表明，与 UCC 元素浓度相比，到达 BoB 的沉积物相对富集 Hf、Zr、Th、REE、Sn 和 Bi，而主要贫乏 Na 和 Sr。尽管受到数据可用性和必要的简化假设的限制，这项研究仍然为向 BoB 提供现代固相元素排放提供了合理的一阶预算。这项工作的见解对于理解 G-B 河流系统在全球元素循环中的作用具有重要意义，并为根据该地区发生的快速环境变化为未来沉积物元素排放提供比较基础。
The Ganges-Brahmaputra-Meghna (G-B) river system transports >1 × 109t/yr of sediment, with an estimated 0.7 × 109t/yr reaching the Bay of Bengal (BoB). This discharge represents a major input of sediment and associated elements to the global ocean, but quantification of the sediment-element mass reaching the BoB has yet to be fully explored. Published geochemical and suspended sediment data are used to calculate a first-order budget for the modern sediment supply of geochemical elements to the BoB. River profile bulk sediment-element concentrations are calculated based on suspended sediment and element measurements taken in the Ganges and Brahmaputra rivers. A Monte Carlo analysis is applied to account for variable sediment and geochemical contributions from each river. Results show that on average, the G-B system contributes ~5% of the global riverine discharge of solid-phase elements from sediment to the oceans. G-B sediments transport >10% of the global element supply of Hf and Zr. For others, like As and Cu, contributions from the G-B are <5%. Results also show that sediment reaching the BoB is relatively enriched in Hf, Zr, Th, REEs, Sn, and Bi, and majorly depleted in Na and Sr compared to UCC elemental concentrations. While limited by data availability and necessary simplifying assumptions, this study nevertheless provides a reasonable first-order budget for the modern discharge of solid-phase elements to the BoB. Insights from this work are significant for understanding the role of the G-B river system in global elemental cycling, and for providing a basis of comparison for future sediment-element discharge in light of rapid environmental change taking place in the region.