我国北方小流域硫酸参与碳酸盐矿物化学风化过程研究

硫酸参与碳酸盐岩的风化机制及与区域碳循环的关系是全球气候变化研究的重要课题.选择我国北方小流域(沁河)为研究对象,结合水化学及溶解性无机碳碳同位素组成,通过化学计算法,分析了河水溶解性组分的来源及混入比例,验证了硫酸参与区域碳酸盐的风化过程.结果表明:河水阳离子以Ca2+和Mg2+为主,阴离子以HCO-3和SO2-4为主;沁河流域碳酸盐岩风化、大气输入及蒸发盐溶解对河水阳离子贡献较大,平均比例分别为48.5%、35.3%和14.1%,硅酸盐风化和人为输入贡献比例较小,平均比例分别为1.7%和0.6%;沁河流域碳酸盐类、硅酸盐类及蒸发盐类风化速率分别为8.41、0.07和2.43 t·km-2·a-1,碳酸盐和硅酸盐矿物风化CO2消耗量分别为1.43×105mol·km-2·a-1和0.03×105mol·km-2·a-1;沁河流域硫酸参与碳酸盐风化产生的CO2净释放量为0.63×105mol·km-2·a-1,小于我国南方喀斯特地区CO2净释放量,可能与不同的气候条件及硫化物赋存条件和含量等有关.

Chemical weathering of carbonate rocks by sulfuric acid on small basin in North China

The role of sulfuric acid in the chemical weathering of carbonate rock and its influences on the regional carbon cycling have been recognized as important issues for global climate change. One small drainage basin in North China named Qin River was selected in this study. The contributions from potential sources to the dissolved component were calculated based on chemical compositions of river water. Carbon isotopes of dissolved inorganic carbon were also used to verify the chemical weathering by sulfuric acid. The results demonstrated that Calcium and Magnesium were the dominant cations, and biocarbonate and sulfate were the dominant anions in the river water; Dissolved cations of river water were mainly controlled by carbonate weathering, atmospheric inputs, and evaporate dissolution with mean values of 48.5%, 35.3%, and 14.1%, respectively, while minor controlled by silicate weathering and human inputs which accounted for 1.7% and 0.6%, respectively; The chemical weathering rates of carbonate, silicate and evaporates in Qin River basin were estimated to be approximately 8.41, 0.07 and 2.43 t·km^-2·a^-1, respectively, and CO₂ consumption rates for carbonate and silicate were 1.43×10⁵ mol·km^-2·a^-1 and 0.03×10⁵ mol·km^-2·a^-1, respectively; and CO₂ released from carbonate chemical weathering by sulfuric acid was estimated to be 0.60×10⁵ mol·km^-2·a^-1 lower than the results obtained in karst regions in South China. South China probably due to different climate and occurrence and content of sulfide.