乌江源区阳长流域化学侵蚀作用的碳汇效应

河流溶解无机碳(DIC)的输出反映了流域化学侵蚀消耗大气CO2的碳汇强度,其碳汇效应是全球大气"遗漏汇"的主要组成之一,是全球碳循环研究的重要内容。对乌江源区喀斯特广泛发育的三岔河流域阳长水文站断面的水文与水化学过程进行1个水文年的观测,其总溶解物质(TDS)的年输出通量达到2.68×1011 g,其化学侵蚀模数为1.02×108 g/(km2.a),流域断面的DIC年输出量为1.88×109 mol,其流域DIC的输出模数达到7.12×105 mol/(km2.a)。按碳酸盐岩的溶蚀作用对河水中DIC的贡献率为98%计算,约消耗大气二氧化碳9.56×108 mol,流域碳汇模数达到3.63×105 mol/(km2.a),其中雨季6-11月的碳汇约占92%,其碳汇强度约为非喀斯特流域的2～10倍。

The Atmospherical CO2 Consumption in the Chemical Weathering Processes of the Yangchang Hydrological Stations Basin in Wujiang River Source Drainage Basins Area

The flux of the riverine dissolved inorganic carbon(DIC) in a drainage basin implied the atmospherical CO2 consumption rate in the chemical weathering processes,which was a key element of the missing sink of the atmospheric carbon playing an important role for understanding the law on the global carbon cycle.A riverine hydro-chemical investigation was carried out during a hydrologic year in the water channel of the Yangchang hydrological stations in Wujiang river source drainage basins area in which the cover layer was mainly carbonate as well as Karst landforms were developed widely.The annual fluxes on the total dissolved solids was amount to 2.68×1011 g with 1.02×108 g/(km2·a) in chemical weathering modulus,and the annual fluxes of the DIC was 1.88×109 mol with 7.12×105 mol/(km2·a) in DIC weathering modulus.According to the carbonate weathering contribution rate amounting to 98% of the riverine DIC,the annual fluxes of the atmospherical CO2 consumption of the Yangchang drainage basin mounted to 9.56×108 mol with 3.63×105 mol/(km2·a) in modulus,about 92% of which was discharged during the rainy season from June to November in the surveying year.The annual flux in modulus of the atmospherical CO2 consumption of the Yangchang drainage basin was about 2~10 times as much as those of the no-karstic granitic drainage basins.