Seasonal variation of boron isotopic compositions in river water within the Qinghai Lake watershed and its controlling factors  

作　　者：Yitong QIN Zhangdong JIN Maoyong HE Longfei GOU Jun XIAO 

机构地区：[1]Institute of Global Environmental Change,School of Human Settlements and Civil Engineering,Xi’an Jiaotong University,Xi’an 710049,China [2]State Key Laboratory of Loess and Quaternary Geology,Institute of Earth Environment,Chinese Academy of Sciences,Xi’an 710061,China [3]Department of Geography,Chang’an University,Xi’an 710054,China

出　　处：《Science China Earth Sciences》2025年第3期811-823,共13页中国科学(地球科学英文版)

基　　金：supported by the National Natural Science Foundation of China (Grant Nos. 42221003 & 42103055);the Natural Science Basic Research Program of Shaanxi (Grant No. 2023JC-QN-0276);the Basic Research Fund Project of Central Universities (Grant No. 300102353202)。

摘　　要：Riverine boron(B) and its isotopic compositions(δ^(11)B) are commonly used to trace silicate weathering within watersheds, but its sources and isotopic fractionation mechanisms remain contentious. In this study, we collected the seasonal river waters of the Buha River, the largest inlet river of Qinghai Lake, which is sensitive to climate change, and analyzed its seasonal variations of the major ions, B concentrations, and δ^(11)B, to explore its sources and controlling factors. The results indicate that B in the Buha River predominantly originates from weathering of silicate rocks, with significantly seasonal variations in the geochemical behaviour of B isotopes. In the rainy seasons, the riverine B isotopic fractionation is primarily controlled by weathering of silicate rocks under the influence of hydrological conditions, where clay minerals preferentially absorb10B, leading to the enrichment of heavier B isotopes in river waters. In contrast, in the dry seasons, the B of river waters may mainly come from the recharge of groundwater(whose δ^(11)B with a notable p H dependence);owing to prolonged retention of fluids, the steady state of δ^(11)B is reached by the isotopic equilibrium through adsorption of clay minerals. This study highlights that the seasonal variations in riverine δ^(11)B in semi-arid regions are jointly governed by silicate weathering, hydrological conditions, and water-rock interactions, with water p H and rainfall as key regulators. Consequently, riverine δ^(11)B in the rainy seasons under semi-arid climatic conditions can effectively trace hydrologically-controlled silicate weathering processes within the watershed.

关 键 词：Boron isotopes Silicate weathering Seasonal variation Water-rock interactions Qinghai Lake watershed 

分 类 号：P59[天文地球—地球化学]