| 贵州喀斯特地区河流的地球化学研究 | |
韩贵琳
| |
| 2000 | |
| Degree Grantor | 中国科学院地球化学研究所 |
| Place of Conferral | 中国科学院地球化学研究所 |
| Degree Name | 博士 |
| Degree Discipline | 环境地球化学 |
| Keyword | 喀斯特 河流 主量元素 微量元素 Sr同位素 |
| Abstract | 河水的地球化学研究可以获得有关流域盆地化学风化、气候、上地壳的平均化学和同位素组成以及化学元素在大陆－河流－海洋系统中外生循环过程的重要信息。作为岩溶环境分异强烈的贵州碳酸盐岩区，其地表岩石土壤的风化侵蚀过程，必然具有很大的特殊性，也必然对地表环境系统产生重要的影响。构成该地区生态环境脆弱性和地球化学敏感性的一个重要特性。本论文通过对喀期特地区河流中河水的主量元素、微量元素及其锶同位素组成和分布特征的研究，得出如下主要结论和几点新认识。（1）贵州喀斯特地区河流水化学及地球化学特征主要受控于亚热带湿润气候条件下碳酸盐岩的溶解过程，以高Ca、Mg和高碱度区别亚洲和其它地区河流，其主量元素含量的沿程变化是由流域的岩石和土壤的化学成分、矿物组成及流域的物理、化学风化作用决定的。（2）碳酸盐的溶解－沉淀平衡是制约贵州喀斯特地区河流水化学的重要因素，高Ca、Mg和高碱度导致贵州喀斯特地区河流河水具有沉积性特征，河水相对于CaCO_3处于过饱和状态。（3）贵州喀斯特地区河流大多数河水样品的Sr同位素组成均落在显生宙海水的变化范围内。贵州喀斯特地区河流的Sr同位素组成主要受自然风化过程的影响，河水中Sr的浓度及其同位素组成主要来源于两个端员即具有高的Sr浓度、低的~(86)Sr/~(87)Sr比值的碳酸盐岩端员的风化和具有低的Sr浓度、高的~(86)Sr/~(87)Sr比值的硅酸盐岩端员的风化的混合。Sr同位素组成与元素比值（如Na/Ca、Mg/Ca等）的变化同时辨别出以白云岩为主和以石灰岩为主的溶解端员，贵州喀斯特地区河流的化学组成主要受石灰岩风化作用的控制。（4）通过对贵州喀斯特地区河流河水的主量元素、特别是阴离子（SO~(2-)_4、NO~-_3）和微量元素的含量及其控制因素的研究，表明贵州喀斯特地区河流受污染的程度远低于许多发达国家的河流。贵州乌江水系河流受工业污染的程度高于沅江水系的河流，而沅江水系河流受农业污染的程度高于乌江水系的河流，这与乌江流域的工业比沅江流域的工业发达相一致。（5）对贵州喀斯特地区河流中的一些重金属元素分布的初步研究表明，碳酸盐岩地区河流的高碱度使得河水中重金属离子的停留时产不长，其自然净化能力可能比硅酸盐岩地区的河流高。 |
| Other Abstract | Geochemical study of river water allows us to develop important imformation on the chemical weathering of catchment, climate change and the chemical and isotopic compositions of upper continental crust(UCC) on a basin-wide scale and reveals the exegetic cycles of elements in the continent-river-ocean system. The weathering and erosion processes in Guizhou carbonate regions with strong karst environment fractionation have remarkable characteristics and great influence on the crust environmental system inevitably. So ecological environmental weakness and geochemical sensitivity are an outstanding feature in Guizhou karst regions. Through studying the major elements, trace elements and strontium isotopes of river water in Guizhou karst regions, some conclusions are drawn as follows: (1) The water chemistry and geochemistry of river water in Guizhou karst regions seem to be largely influenced by dissolution of carbonates under the subtropical climate conditions. Its hydrogeochemical characteristics with high Ca, Mg contents and high alkalinity are different from those in Asia and other areas. The compositions of major elements are controlled by those of rock/soil, mineral weathering, physical and chemical weathering in the drainage areas. (2) The water in Guizhou karst regions shows saturation relative to CaCO_3 and the dissolution-precipitation balance in the CaCO_3-H_2O-CO_2 system becomes a factor controlling for hydrochemical process. (3) The strontium isotopic compositions of river water in Guizhou karst regions fall within the Phanerozoic seawater area. The strontium isotopic compositions of rivers are controlled by natural weathering reaction. The strontium concentrations and isotopic compositions of river water are largely defined by mixing of strontium derived from the weathering of two endmembers. One endmember is mainly carbonate which is relatively easily eroded and has higher strontium contents and lower ~(87)Sr/~(86)Sr rations.The other endmember is silicate rock which is more resistant to weathering and has lower strontium contents and higher ~(87)Sr/~(86)Sr ratios. The source identification by isotopic and chemical ratios suggests the dissolution of limestone and dolomite for these rivers, so weathering of limestone controls the chemical compositions of river water in Guizhou karst regions. (4) Studies on the concentrations of major elements, especially anions and trace elements in Guizhou karst rivers and their controlling factors demonstrate that the rivers in Guizhou karst regions are less polluted than those in the advanced countries. Rivers in the Yuanjiang River drainage are less polluted by industrial activities than those in the Wujiang River drainage. However, the Yuanjinag River is polluted heavily by agricultural activities. This is consistent with the fact that the developing level of industry in the Wujiang River drainage is higher than that in the Yuanjiang River drainage. (5) A study of some heavy metals of river water in Guizhou karst regions showed that the time of some heavy metals retained in water is very short under high alkinity condition. So the natural purification capacity of rivers in carbonates areas is higher than that in silicate rock areas. |
| Pages | 51 |
| Language | 中文 |
| Document Type | 学位论文 |
| Identifier | http://ir.gyig.ac.cn/handle/352002/3546 |
| Collection | 研究生_研究生_学位论文 环境地球化学国家重点实验室 |
| Recommended Citation GB/T 7714 | 韩贵琳. 贵州喀斯特地区河流的地球化学研究[D]. 中国科学院地球化学研究所. 中国科学院地球化学研究所,2000. |
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