Chemical weathering processes in the Chinese Loess Plateau  

作　　者：Ningpan Chai Zhiqi Zhao Xiaoke Li Jun Xiao Zhangdong Jin 

机构地区：[1]School of Earth Science and Resources,Chang’an University,Xi’an 710054,China [2]State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710061,China [3]Xi’an Institute for Innovative Earth Environment Research,Xi’an 710061,China

出　　处：《Geoscience Frontiers》2024年第5期197-209,共13页地学前缘（英文版）

基　　金：supported by the Western Light-Key Laboratory Cooperative Research Cross-Team Project of Chinese Academy of Sciences(xbzg-zdsys-202309);the Strategic Priority Research Program of Chinese Academy of Sciences(XDB40020502);the Shaanxi Science Fund for Distinguished Young Scholars(2020JC-030).

摘　　要：Covered by erodible loess and affected by significant seasonal climate variations,chemical weathering in the Chinese Loess Plateau(abbreviated as CLP)has important effects on the hydrochemistry of the Yellow River and the global carbon cycle.However,chemical weathering processes in the CLP are still unclear.Based on 296 river water samples in the CLP in the different seasons,hydrochemistry,weathering processes,and their controlling factors were revealed.River waters in the CLP exhibited slightly alkalinity(pH=8.4±0.5)with much high total dissolved solids(TDS)values(691±813 mg/L).The water types of river water in the CLP were primarily SO_(4)^(2-)-Cl^(-)-Na^(+),HCO_(3)^(-)-Ca^(2+)-Mg^(2+),and SO_(4)^(2-)-Cl^(-)-Ca^(2+)-Mg^(2+).According to the forward model,evaporite dissolution has the largest contribution(55.1%±0.2%)to riverine solutes in the CLP,then followed by carbonate weathering(35.6%±0.2%)and silicate weathering(6.5%±0.1%).For spatio-temporal variations,the contribution of evaporite dissolution in the CLP decreased from northwest to southeast with higher proportion in the dry season,carbonate weathering increased from northwest to southeast with a higher proportion in the wet season,and silicate weathering showed minor spatio-temporal variations.Ca^(2+)and Mg^(2+)were affected by carbonate precipitation and/or incongruent calcite dissolution,and about 50%of samples exhibited cation exchange reactions.The physical erosion rate in the CLP,which was 372±293 t·km^(-2)·yr^(-1),varied greatly and was greater than those of other worldwide rivers.Chemical weathering rates in the CLP showed an increasing trend southward.During the wet season,high runoff led to the release of evaporite and carbonate from loess,while the interfacial reaction kinetic limited the increase of the silicate weathering rates.The CO_(2)consumption budget by carbonate weathering(6.1×10^(10)mol/yr)and silicate weathering(1.6×10^(10)mol/yr)in the CLP accounted for 0.29%and 0.08%of the global carbon cycle,respectively.Meanwhile,the we

关 键 词：Chemical weathering Chinese Loess Plateau Spatio-temporal variations CO_(2)budget Physical erosion 

分 类 号：P59[天文地球—地球化学]