清水江流域岩石风化特征及其碳汇效应

岩石风化产生的碳汇是全球碳循环的重要组成部分,文中对清水江流域主要离子组成进行分析测定,通过主成分分析、化学物质平衡法和扣除法估算流域岩石风化速率及对大气CO_2的消耗量.结果表明,流域河水溶质主要来源于碳酸盐岩和硅酸盐岩风化,并以碳酸盐岩风化为主.碳酸盐、硅酸盐、大气CO_2对河水溶质的贡献率分别为58.28%、17.38%、17.74%.流域岩石化学风化速率为109.97 t·(km~2·a)~(-1),与乌江接近,高于全球流域均值.流域岩石风化对大气CO_2的消耗通量为7.25×10~5mol·(km~2·a)~(-1),岩石风化对大气CO_2的消耗量为12.45×10~9mol·a~(-1),其中,碳酸盐岩风化消耗量占63.13%,为7.86×10~9mol·a~(-1),硅酸盐岩风化消耗量占36.87%,为4.59×10~9mol·a~(-1).SO_4~(2-)、F~-、NO_3~-的相关分析及空间分布特征表明,人为活动对清水江流域河水溶质的影响不容忽视,其贡献率为4.87%.

Rock Weathering Characteristics and the Atmospheric Carbon Sink in the Chemical Weathering Processes of Qingshuijiang River Basin

Carbon sink produced during rock weathering is critical to global carbon cycles. In this work, the major ion chemistry and ion sources of Qingshuijiang River Basin were investigated. The principal component analysis, mass balance approach and deduction method were applied for estimating the weathering rate and atmospheric CO₂ consumption via the chemical weathering of rocks. The results demonstrated that the chemical weathering of carbonate and silicate rocks within the drainage basin was the main source of the dissolved chemical substances in the Qingshuijiang River Basin, prior to carbonate rock weathering. Some 58.28% of the total dissolved chemical substances were derived from the chemical weathering of carbonate rock, 17.38% from the dissolution of silicate rock, and 17.74% from atmospheric CO₂ contribution rates. The chemical weathering rate of this catchment was estimated to be 109.97t·(km²·a)^-1, which was comparable to Wujiang River Basin, but higher than the average of global rivers. Furthermore, the atmospheric CO₂ consumption rate was estimated to be 7.25×10⁵ mol·(km²·a)^-1. The CO₂ flux consumed by the rock chemical processes within this catchment was 12.45×10⁹ mol·a^-1, of which about 63.13%(7.86×10⁹ mol·a^-1) was resulted from carbonate weathering and 36.87%(4.59×10⁹ mol·a^-1) from silicate weathering. The CO₂ consumed by rock chemical weathering in the Qingshuijiang River reduced the atmospheric CO₂ level and constituted a significant part of the global carbon budget. Correlation and spatial distribution analysis of SO₄^2-, F^-, NO₃^- showed that anthropogenic activities contributed remarkably to dissolved solutes and associated CO₂ consumption worldwide, and anthropogenic inputs probably contributed some 4.87% to the dissolved solutes in the Qingshuijiang River.