Geological respiration of a mountain belt revealed by the trace element rhenium
Geological respiration of a mountain belt revealed by the trace element rhenium
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DOI：
10.1016/j.epsl.2014.06.021
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发表时间：
2014-10-01
影响因子：
5.3
通讯作者：
Birck, Jean-Louis
中科院分区：
文献类型：
--
作者：
Hilton, Robert G.;Gaillardet, Jerome;Birck, Jean-Louis
在沉积岩风化过程中，岩源性有机碳（OCpetro）的氧化是大气中二氧化碳（CO2）的主要来源。这种地质呼吸被认为是由物理侵蚀增强的，这表明山带可以释放大量的二氧化碳来抵消由侵蚀、河流转移和海洋从陆地生物圈中埋藏有机碳所实现的二氧化碳固存。然而，山区油气氧化速率尚未量化。在这里，我们使用铼（Re）作为代理来跟踪台湾山区河流集水区的OCpetro氧化，在那里现有的物理侵蚀速率测量允许评估OCpetro氧化的控制。Re与岩石中的OCpetro密切相关，在化学风化过程中氧化形成可溶性氧化离子（ReO4-），有助于河流的溶解负荷。台湾变质沉积岩土壤在风化过程中，Re的损失与OCpetro的损失是耦合的，这证实了其他地区沉积岩土壤剖面的观测结果。在台湾河流中，溶解Re通量随流域平均产沙量的增加而增加，表明物理侵蚀速率是OCpetro氧化的主要控制因素。根据我们目前对风化过程中Re迁移率的理解，溶解Re通量可以用来量化OCpetro氧化速率和相关CO2转移的上限。由OCpetro氧化产生的估计的该山带的二氧化碳释放量并不能否定由近海生物圈OC埋藏产生的二氧化碳固存量。这些发现与喜马拉雅地区的OC转移估计进行了比较，在喜马拉雅地区，OCpetro在山带的氧化仍然不受限制。综上所述，这些案例表明，热带地区的造山活动可以产生碳的净汇，从而封存大气中的二氧化碳。Crown Copyright (C) 2014由Elsevier B.V.出版。这是一篇基于CC by许可（http://creativecommons.org/licenses/by/3.0/）的开放获取文章。
Oxidation of rock-derived, petrogenic, organic carbon (OCpetro) during weathering of sedimentary rocks is a major source of carbon dioxide (CO2) to the atmosphere. This geological respiration is thought to be enhanced by physical erosion, suggesting that mountain belts could release large amounts of CO2 to counter the CO2 sequestration achieved by the erosion, riverine transfer and oceanic burial of organic carbon from the terrestrial biosphere. However, OCpetro oxidation rates in mountain belts have not been quantified. Here we use rhenium (Re) as a proxy to track OCpetro oxidation in mountain river catchments of Taiwan, where existing measurements of physical erosion rate allow the controls on OCpetro oxidation to be assessed. Re has been shown to be closely associated with OCpetro in rocks and following oxidation during chemical weathering forms a soluble oxyanion (ReO4-) which contributes to the dissolved load of rivers. Soils on meta-sedimentary rocks in Taiwan show that Re loss is coupled to OCpetro loss during weathering, confirming previous observations from soil profiles on sedimentary rocks elsewhere. In Taiwan rivers, dissolved Re flux increases with the catchment-average sediment yield, suggesting that physical erosion rate is a major control on OCpetro oxidation. Based on our current understanding of Re mobility during weathering, the dissolved Re flux can be used to quantify an upper bound on the OCpetro oxidation rate and the associated CO2 transfer. The estimated CO2 release from this mountain belt by OCpetro oxidation does not negate estimates of CO2 sequestration by burial of biospheric OC offshore. The findings are compared to OC transfers estimated for the Himalaya, where OCpetro oxidation in the mountain belt remains unconstrained. Together, these cases suggest that mountain building in the tropics can result in a net sink of OC which sequesters atmospheric CO2. Crown Copyright (C) 2014 Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/3.0/).