流域岩石风化是重要的碳源/汇过程,也是全球碳循环中的重要环节.外源酸参与流域岩石风化,影响碳元素的地球化学循环和流域碳源/汇效应.漾弓江属长江上游金沙江水系,流域岩石风化过程和碳汇效应尚不清楚.在 2023年旱季和雨季分别采集了漾弓江的干流和主要支流的水样品(地表水点 9个、地下水点 6个),对主要离子浓度进行检测,并利用水化学平衡法和Galy估算模型分析该流域的岩风化类型,估算了碳酸与硫酸共同作用下的岩石风化CO2 消耗量.结果表明:(1)漾弓江流域水系离子成分主要源于硅酸盐岩和碳酸盐岩风化,水化学类型为HCO3-Ca型或HCO3-Ca·Mg型.(2)硫酸和碳酸共同参与了漾弓江流域的岩石风化过程.在不考虑硫酸作用时,漾弓江流域岩石风化的大气CO2 消耗量为 38.35 t CO2·km-2·a-1,而当考虑了硫酸参与时,岩石风化碳汇量降至25.54 t CO2·km-2·a-1,扣除约 33%,大大提高了计算精度.(3)漾弓江流域岩石风化的大气CO2 消耗量为 4.27×104 t CO2·a-1,是一个碳汇过程.硫酸参与流域岩石的风化改变了区域碳循环,这是全球碳循环模型不可忽略重要环节.
Rock weathering and carbon sink effects under exogenous acid action:A case study of the Yanggong river
Rock weathering in the river basin is not only an essential carbon source and sink mechanism,but also an important link in the global carbon cycle.Rivers are indispensable components of water bodies,and the hydrochemistry of rivers is a representation of the degree to which weathering and denudation occur at the surface of the river basin.Therefore,it is possible for us to collect information on rock weathering in the river basin by conducting an analysis of the chemical compositions of rivers.In turn,the analytical results can be used for the estimation of weathering rates and the amount of carbon dioxide that is consumed by the Earth's atmosphere.The presence of exogenous acids in the process of rock weathering in the river basin has an impact on the geochemical cycling of carbon as well as the carbon source/sink effect.The chemical weathering rate of carbonatite is accelerated by sulfuric acid,but the weathering does not consume atmospheric carbon dioxide.As a result,the effect of sulfuric acid on carbonatite weathering should be taken into consideration when the amount of atmospheric carbon dioxide that is consumed by rock weathering in the basin is calculated.The Yanggong river is a part of the Jinsha river system located in the upper reaches of the Yangtze river.The process of rock weathering and the influence of carbon sinks in the Yanggong river basin are not yet fully understood.As a result of climate warming,the considerable increase in water output from the high-altitude area of this basin has accelerated the water cycle there.This will undoubtedly exert a strong influence on rock weathering rates and geochemical cycling processes that occur within the Yanggong river basin.In addition,a large number of coal layers are distributed in this basin,so the sulfuric acid produced by sulfide oxidation or the dissolution of carbonate rocks by sulfuric acid caused by human activities would also alter rock weathering rates in this basin.For this reason,it is necessary for us to do more research in order to quantify the effect of exogenous acids on rock weathering as well as on the carbon source and sink in the Yanggong river basin.In this study,water samples from main streams and major tributaries of the Yanggong river were collected during the dry and rainy seasons of 2023.The major concentrations of anion and cation,metasilicic acid,and total dissolved solids(TDS)in these water samples were examined.Additionally,different types of rock weathering in the Yanggong river basin were analyzed by the water chemical equilibrium method and the Galy estimation model.Finally,the amount of carbon dioxide that was consumed by rock weathering under the combined effect of carbonic acid and sulfuric acid was estimated.The findings indicated that the ionic compositions of the water system in the Yanggong river basin were mostly derived from the weathering of silicate and carbonate rocks,and the hydrochemical types were either the HCO3-Ca type or the HCO3-Ca·Mg type.Sulfuric acid and carbonic acid worked together to contribute to the process of rock weathering in this basin.The atmospheric CO2 consumption of rock weathering in this basin was 38.35 t CO2·km-2·a-1 when sulfuric acid was not taken into consideration.However,when sulfuric acid participation was taken into consideration,the carbon sink of rock weathering was reduced to 25.54 t CO2·km-2·a-1,with a reduction of approximate 33%,which significantly improved the accuracy of the calculation.The atmospheric CO2 flux consumed by carbonatite weathering contributed 95.5%of the total,which indicated dominance of the atmospheric CO2 flux consumed by carbonatite weathering in the Yanggong river basin.The quantity of atmospheric CO2 consumed by rock weathering in the Yanggong river basin is 4.27×104 t CO2·a-1,suggesting a process of carbon sink.That sulfuric acid participated in the process of rock weathering in the river basin changed the regional carbon cycle is a significant link that cannot be overlooked in the model of the global carbon cycle.Meanwhile,in studies on the carbon source/sink effect of rock weathering in the river basin,it was essential for us to consider the regional geological background,particularly the types of minerals rich in sulfides.
rock weatheringcarbon sink effectsulfuric acidcarbonic acid
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