The impact of adsorption-desorption reactions on the chemistry of Himalayan rivers and the quantification of silicate weathering rates

被引:1
|
作者
Knight, Alasdair C. G. [1 ]
Stevenson, Emily I. [1 ]
Bridgestock, Luke [2 ]
Baronas, J. Jotautas [3 ]
Knapp, William J. [1 ]
Adhikari, Basanta Raj [4 ]
Andermann, Christoff [5 ,6 ]
Tipper, Edward T. [1 ]
机构
[1] Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ, Cambs, England
[2] Univ St Andrews, Sch Earth & Environm Sci, St Andrews KY16 9AJ, Fife, Scotland
[3] Univ Durham, Dept Earth Sci, Durham DH1 3LE, Durham, England
[4] Tribhuvan Univ, Dept Civil Engn, Kathmandu 44613, Bagmati, Nepal
[5] Univ Rennes, Geosci Rennes, CNRS, UMR 6118, F-35042 Rennes, Brittany, France
[6] GFZ German Res Ctr Geosci, Helmholtz Ctr Potsdam, Sect Geomorphol 4 6, D-14473 Brandenburg, Germany
关键词
Adsorption-desorption reactions; Silicate weathering; River chemistry; ATMOSPHERIC CO2 CONSUMPTION; CATION-EXCHANGE CAPACITY; CLAY-MINERALS; ION-EXCHANGE; SUSPENDED SEDIMENT; CLIMATIC CONTROLS; EROSION RATES; AMAZON; BASIN; CARBONATE;
D O I
10.1016/j.epsl.2024.118814
中图分类号
P3 [地球物理学]; P59 [地球化学];
学科分类号
0708 ; 070902 ;
摘要
Common environmental adsorbents (clay minerals, metal -oxides, metal-oxyhydroxides and organic matter) can significantly impact the chemistry of aqueous fluids via adsorption-desorption reactions. The dissolved chemistry of rivers have routinely been used to quantify silicate mineral dissolution rates, which is a key process for removing carbon dioxide (CO 2 ) from the atmosphere over geological timescales. The sensitivity of silicate weathering rates to climate is disproportionately weighted towards regions with high erosion rates. This study quantifies the impact of adsorption -desorption reactions on the chemistry of three large Himalayan rivers over a period of two years, utilising both the adsorbed and dissolved phases. The concentration of riverine adsorbed cations are found to vary principally as a function of the concentration and cation exchange capacity (CEC) of the suspended sediment. Over the study period, the adsorbed phase is responsible for transporting -70% of the mobile (adsorbed and dissolved) barium and -10% of the mobile calcium and strontium. The relative partitioning of cations between the adsorbed and dissolved phases follows a systematic order in both the monsoon and the dry -season (preferentially adsorbed: Ba > Sr & Ca > Mg & K > Na). Excess mobile sodium (Na * =Na-Cl) to silicon (Si) riverine ratios are found to vary systematically during an annual hydrological cycle due to the mixing of low temperature and geothermal waters. The desorption of sodium from uplifted marine sediments is one key process that may increase the Na*/Si ratios. Accounting for the desorption of sodium reduces silicate weathering rate estimates by up to 83% in the catchments. This study highlights that surficial weathering processes alone are unable to explain the chemistry of the rivers studied due to the influence of hydrothermal reactions, which may play an important role in limiting the efficiency of silicate weathering and hence modulating atmospheric CO 2 concentrations over geological time.
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页数:15
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