混合岩溶流域碳酸盐岩溶蚀速率与岩溶碳汇——以漓江流域上游为例

Carbonate dissolution rate and karst carbon sink in mixed carbonate and silicate terrain:Take the upper reaches of the Lijiang river basin as an example

碳酸盐岩矿物的化学风化速率要显著高于硅酸盐岩矿物,碳酸盐岩和硅酸盐岩混合流域中碳酸盐岩矿物风化对河流水化学的贡献占主导。为研究混合岩溶流域碳酸盐岩风化及岩溶碳汇特征,在漓江流域上游大溶江、小溶江、灵渠3个混合岩溶流域选取了24个点放置标准溶蚀试片并测试对应的土壤理化性质。基于雨季和全年试片溶蚀量和土壤理化特征,分析试片溶蚀量的主控因素及季节差异,定量评估大溶江、小溶江和灵渠流域岩溶碳汇强度。结果表明:空中试片溶蚀量主要受控于降雨,植被会部分遮挡降雨,使试片溶蚀量显著下降,而地表和土下碳酸盐岩溶蚀受降雨和水文过程共同控制;雨季碳酸盐岩溶蚀更快,空中试片溶蚀量主要受控于降雨,而地表和土下试片主要受控于土壤水分的变化;基于溶蚀试片法,大溶江、小溶江和灵渠流域岩溶碳汇强度分别为0.75、0.30和2.92 tC·km^(-2)·yr^(-1)。

The chemical weathering of carbonates is faster than silicates,and the contribution of carbonate mineral weathering to river water chemistry is dominant in the mixed carbonate and silicate terrain.In order to study the characteristics of carbonate weathering and karst carbon sink in the mixed carbonate and silicate terrain,24 standard dissolution samples were placed at the Darongjiang river,the Xiaorongjiang river and Lingqu basins in the upper reaches of the Lijiang river basin and the physical and chemical properties of the corresponding soil were tested.Based on the dissolution amounts and soil physical and chemical characteristics during the rainy season and the whole year,the main controlling factors and seasonal differences of the dissolution amounts are analyzed,and the intensities of karst carbon sink in Darongjiang river,Xiaorongjiang river and Lingqu basins are quantitatively evaluated.The results show that the dissolution amounts of aerial samples are mainly controlled by rainfall.While the dissolution amounts decreased significantly when the vegetation partly blocks the rainfall,the surface and subsoil dissolution amounts are controlled by both rainfall and hydrological processes.The dissolution rate is bigger in rainy season,and the aerial samples are mainly controlled by rainfall,while the surface and subsoil samples are mainly controlled by soil moisture changes.Based on the dissolution of carbonate tablet,the karst carbon sink intensities in the the Darongjiang river,the Xiaorongjiang river and Lingqu basins are respectively 0.75,0.30 and 2.92 tC·km^(-2)·yr^(-1).