峨眉山玄武岩化学风化研究——以龙苍沟小流域为例

Chemical weathering of Emeishan basalt area:Implications from Longcanggou small catchment

通过对四川省雅安龙苍沟峨眉山玄武岩小流域的水化学组成研究,分析了不同物质来源对小流域溪水溶解质的贡献,并对该小流域岩石风化速率和CO2消耗速率进行了估算。结果表明,龙苍沟流域溪水呈中性,PH平均值为6.82。溪水中阳离子以Ca^2+为主,约占阳离子总量的56%;阴离子以HCO3^-为主,约占阴离子总量的45%。碳酸盐岩风化、硅酸盐岩风化、大气降水和人为活动对溪水阳离子平均贡献率分别为50.2%、38.2%、10.5%和1.1%。流域硅酸盐岩风化速率为37.54±24.94 t/km^2/yr,硅酸盐岩风化对大气C02消耗速率为5.4±3.6 mol C/km^2/yr。本文首次对我国峨眉山玄武岩省化学风化大气CO2消耗量进行估算,得到其年消耗通量为1.35±0.89×10^11 mol C/yr,约为全球玄武岩CO2年消耗通量的3.31±2.18%。

The concentrations of major ions in the Longcanggou streams were determined in order to analyze the relative contributions of chemical weathering of different sources and to estimate the chemical weathering rates of different rock types and associated atmospheric CO2 consumption rates.The streams pH are close to neutral,with an average pH of 6.82.Calcium ion accounts for 56%of total cations,and HCO3^-for 45%of the total anions.The dissolved cations are originated from carbonate weathering(50.2%),silicate weathering(38.2%),atmospheric input(10.5%),and anthropogenic pollution(1.1%).The average chemical weathering rate of silicates of the Longcanggou catchment is 37.54±24.94 t/km^2/yr,and the associated atmospheric CO2 consumption rate is 5.4±3.6 mol C/km^2/yr.For the whole Emeishan basalt area,we firstly estimated the total annual atmospheric CO2 consumption flux of the Emeishan basalt is 1.35±0.89×10^11 mol C/yr,which accounts for 3.31±2.18%of the annual CO2 consumption flux by global basalt weathering.