作　　者： ; ; ; ; ;

机构地区： 中国科学院地球化学研究所环境地球化学国家重点实验室

出　　处： 《地球化学》 2008年第4期404-414,共11页

摘　　要： 流域化学侵蚀及其速率与流域生态和环境之间的关系是当前地表地球化学研究的重要前沿领域,其中碳酸盐岩的硫酸风化机制及其与区域碳循环的关系则是科学家们最为关注的科学问题。因此,近年通过研究西南喀斯特流域地表水地球化学对这一科学问题进行了研究,发现西南喀斯特地区河水一般含有较多的SO24-,从化学计量学、SO42-的δ34S和溶解无机碳(DIC)的δ13C分析发现,硫循环中形成的硫酸广泛参与了流域碳酸盐矿物的溶解和流域侵蚀:西南喀斯特流域碳酸盐岩的侵蚀速率为97t/(km2·a),消耗CO2量为25t/(km2·a)。对乌江流域河水硫酸盐离子的硫同位素研究结果认为:参与流域侵蚀的硫酸主要来自煤系地层硫化物和矿床硫化物的氧化及大气酸沉降,分别对河水SO42-的贡献为50%、27%和20.5%(其余2.5%的SO42-为硫酸盐蒸发岩的溶解);硫酸风化碳酸盐岩向大气净释放CO2的总通量为8.2t/(km2·a),依此计算西南喀斯特区域向大气释放CO2的通量为4.4×1012g/a,相当于每年西南碳酸盐岩风化消耗CO2总通量的33%。将乌江流域的研究结果对我国大陆碳酸盐岩分布区域进行相应计算发现,硫酸风化碳酸盐矿物向大气释放的CO2总通量为28×1012g/a,相当于全球硅酸盐风化消耗CO2量的26%。硫酸参与流域侵蚀改变了区域碳循环,人为过程可以通过释放酸沉降、矿业活动和土地利用等形式加速流域侵蚀和影响流域元素的生物地球化学循环。 The research on relationship between catchment erosion and eco-environmental change is one of frontier sciences in the earth＇s surface geochemistry. Crustal weathering by sulfuric acid and its relationship to carbon cycling has become one of the most interesting subjects for geochemists. In recent years, we studied water geochemistry of rivers draining karstic areas in Southwest China, and recognized that the studied river waters have high content of SO4^2-, and that sulfuric acid had significantly taken part in chemical weathering of carbonate rocks as evidenced by stoichiometrie analysis, δ^13C of dissolved inorganic carbon （DIC） and δ^34S of sulfate ion of the river waters. Weathering rate of carbonate rocks in Southwest China has estimated to be 97 t/（km2 · a）, and 25 t CO2 consumption/（km2· a）. Sulfuric acid weathering carbonate rocks was originated mainly from acid rain, oxidation of sulfide minerals in coal containing strata and ore deposits. The flux of CO2 release to atmosphere is 8.2 t/ （km2 · a）, and the calculated total flux of CO2 release due to carbonate weathering by sulfuric acid in southwest China amounts to 4.4 ×10^12 g/a, which is 33% of CO2 consumption by weathering of carbonate rocks. If this rate is applied to whole land of China, carbonate weathering by sulfuric acid will release 28 ×10^12 g CO2/a, about 26% of global consumption of CO2 by silicate weathering. weathering can change carbon cycling, and should have This work shows that sulfuric acid-involved catchment been taken into consideration in modeling global carbon cycling, and further indicate that human activities in many ways can accelerate chemical erosion of river basins and modify biogeochemical cycling of substance.

关 键 词： 喀斯特 流域侵蚀 硫酸风化 碳和硫同位素

领　　域： [天文地球] [天文地球] [天文地球] [天文地球]