赤水河流域岩石化学风化及其对大气CO_2的消耗

Chemical Weathering and CO_2 Consumption of Chishuihe River Basin,Guizhou Province

岩石风化碳汇是全球碳汇的重要组成部分,通过对赤水河流域水体主要离子组成进行测定,分析赤水河流域河水水化学特征及其岩石风化过程对大气CO_2的消耗。结果表明:赤水河流域离子组成以Ca^(2+),Mg^(2+),HCO_3^-和SO_4^(2-)为主,河水总溶解性固体(TDS)含量均值为317.88 mg/L,高于全球流域均值(65 mg/L)。元素比值分析表明赤水河流域离子组成主要受岩石风化控制,其中碳酸盐岩风化为主导控制因素,碳酸盐岩、硅酸盐岩对河水溶质贡献率分别为70.77%和5.03%。人类活动和大气降水对流域河水溶质的贡献很小。流域岩石化学风化速率为126.716 t/(km^2·a),高于黄河、长江、乌江及世界河流均值。流域岩石化学风化对大气CO_2的消耗量为10.96×10~9mol/a,岩石风化对大气CO_2消耗速率为5.79×10~5mol/(km^2·a),与长江流域接近,高于黄河流域。

Carbon sink produced during rock weathering is critical to global carbon cycles. In this work, we an- alyzed the major ion chemistry of the Chishuihe River Basin, and the major ion composition of the Chishuihe River system and the principal component analysis was applied for estimating the weathering rate and atmospheric CO2 consumption via the rock chemical weathering. The results demonstrated that the chemical composition of the river was dominated by Ca2＋, Mg2＋, HCO3 and SO42-. The average concentration（317.88 mg/L） of the total dissolved solids within the Chishuihe River was higher than the average value （65 mg/L） of world rivers. The Gibbs graph combining major ion element ratio analysis indicated that the catchment major ion composition mainly originated from rock weathering, primarily from carbonate weathering, sparsely from silicate weathering. Carbonate and silicate weathering contributed 70.77% and 5.03% separately to the dissolved loads. The anthropogenic and precipitation impact was limited. According to calculation based on principal component and the ion composition characteristics, the chemical weathering rate was 126.716 t/（km2 a）, significantly higher than that of the Yellow River and Yan- gtze River, and also higher than the average rate of the global major rivers. The CO： consumption flux based on annual average runoff was 10.96× 109 mol/a, and the CO2 mol/（km2 a）. consumption rate by chemical weathering was 5.79x 105