| 地质与生态环境影响下的地表水化学以及碳同位素地球化学特征 ——以贵州境内珠江水系为例 | |
| 其他题名 | Characteristics of Geohydrochemistry and Carbon Isotope Geochemistry of the Surface Water under the Influence of Geology and Ecological Environment —— A Case Study of Pearl River Drainage Area in Guizhou Province |
| 薛紫晨 | |
| 学位类型 | 硕士 |
| 导师 | 刘丛强、郎贇超 |
| 2007 | |
| 学位授予单位 | 中国科学院大学 |
| 学位授予地点 | 中国科学院地球化学研究所 |
| 关键词 | 水化学 同位素地球化学 碳同位素 珠江水系 喀斯特 |
| 摘要 | 河流是连接海洋和陆地生态系统的重要途径，也是全球碳循环研究的重要环节。因此，河水的水文地球化学研究是获得有关流域侵蚀、风化以及元素在大陆-河流- 海洋系统中外生循环过程等的重要途径。由于碳酸盐岩风化作用的产物在很大程度上控制着地表水系的地球化学组成, 因此对碳酸盐岩地区河流的水文地球化学特征的研究, 对于了解碳酸盐岩地区的侵蚀、风化强度以及河流地球化学组成变化的多种控制因素有很大的意义。
单就珠江水系而言，目前该方面的研究范围较窄，主要集中于珠江流域水文气候监测、水体有机污染物的迁移转化以及珠江三角洲与河口水体的同位素示踪研究等几个方面，而对于典型气候、地质地貌区域内的各支流的系统的水文地球化学研究少之又少。事实上，对于珠江水系的干流西江而言，流域内由于喀斯特地貌广泛发育，具有极强的地理特异性，因而各支流在不同地质地貌特征、土壤、
气候、植被等条件下的水文地球化学的系统研究以及同位素示踪流域侵蚀状况等方面的研究，不仅对于更好地了解中国西南地区典型喀斯特岩溶区域内土壤、岩石的化学风化、水土流失、水文地球化学特征以及环境污染等方面具有极其重要的意义，同时也对全球碳循环的系统研究有着极其重要的研究价值。
本研究在导师刘丛强研究员主持的国家重大基础规划“973”计划项目“西南喀斯特山地石漠化与适应性生态系统调控”课题的支持下开展完成，选择贵州境内珠江水系干流西江及其支流（红水河流域），以及一级支流柳江源头都柳江及其支流为研究对象，分别通过对流域内，变质碎屑岩以及海相碳酸盐岩两大岩性区域内不同植被覆盖状况下各地表水体中水文地球化学特征以及碳同位素地球化学特征分析，得出以下结论：
1、流域岩性特征是控制流域内各地表水体水文地球化学特征以及流域风化侵蚀程度的重要影响因素。与此同时，研究区内由于人为活动造成的水体污染对于地表水体离子组成特征的变化，也有一定的影响。
2、研究区珠江流域内的地表水体来源主要为大气降水和地下水。研究区内的受西南季风影响下的频繁的降雨过程，是研究区地表水体的主要补给源。研究区内大气降水大多透过表层土壤，进入深部土壤含水层后，或以地表径流的形式冲刷土壤岩石表层后汇入流域内地表河流；或参与地下水体循环，最终以地下水补给地表河流。研究区内 NNE 方向褶皱断裂构造极其发育，地表河网与地下河网相互连接，转换频繁。
3、研究区内地表水体的离子组成特征以及物理化学性质，主要受流域内土壤岩石化学风化过程的控制。不同岩性特征区域内，地表水体的离子组成特征以及水化学参数有着显著的差异。
4、通过对贵州境内珠江水系 75 个地表水体中三种不同形态碳 DIC、DOC、POC 及其部分稳定碳同位素的分析测试，发现研究区内地表水体中的 DIC 主要来源于研究区内土壤 CO2 对不同流域内土壤、岩石矿物的化学风化过程。一般而言，植被覆盖状况较好的区域，土壤 CO2 较为丰富，化学风化作用较为强烈；碳酸盐
岩比硅酸盐类易于风化，并且不同岩性区域化学风化过程可以使得地表水体具有不同的离子组成特征与水化学特性。
5、研究区各流域地表水体中的有机碳主要与流域内植被状况相关。地表水体中 DOC 浓度在一定程度上反映了流域内的植被状况，而 TSS 以及 POC 则反映了流域内土壤有机质的情况。研究区地表水体中 DOC、POC 含量变化情况，是探讨喀斯特地区碳的源汇关系及循环模式的重要依据。
6、河流悬浮物中的 POC 主要来源于土壤有机质和陆地植物，是研究流域侵蚀问题的重要指标。研究区内变质碎屑岩以及海相碳酸盐岩区域内各地表水体均表现出 δ13CPOC 与 TOC/TN 之间的负相关关系，且地表水体中颗粒有机物具有较低的 TOC/TN，表明研究区内各地表水体中 POC 很可能来源于深层土壤。水动力越强，流域侵蚀越强烈，因而 TSS 中 TOC/TN 越低。
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| 其他摘要 | River is the most essential way to connect the ocean with the terrestrial environments. The research on river is the crucial aspect of the global carbon cycling research.
Therefore, the geohydrochemistry research of river is the vital method to trace the drainage erosion, weathering and element cycling among the terrestrial system, river and ocean. The main cations and anions from the carbonate weathering dominate the construction of the ions in the surface river. Hence, it plays a pivotal role in researching on the geohydrochemical character of the surface river in the carbonate drainage area for understanding the controlling factors of the erosion, weathering intensity, geochemical construction of river.
The research of the geohydrochemical character in Pearl River is limited and only concentrates on the monitoring of the climate change in pearl drainage area, migration of the organic pollutant in the river and isotope tracing in the Pearl River delta and estuarine river. However, there is nearly no systematical research on a large multitude of branch rivers of Pearl river, especially in the typical climatic and geological area. In fact, it is very essential to research on the geohydrochemical character and drainage erosion with the isotopic tracing method in the small branch rivers in Xijiang drainage area systematically, which is the main branch of Pearl River, owing to the geographic particularity such as morphological characteristics, soil, climate and vegetation. This research has a great contribution both to the geochemical characters of the chemical weathering and erosion of the rock and soil and environmental pollution in the typical Karst region, SW China, and to the systematical research on the global cycling of carbon.
This research was supported by the 973 National Programme on Key Basic Research Project- Stone Desertification and Ecological System Regulation in typical Karst drainage basin, SW China. This thesis analyzed the geohydrochemical character and carbon isotope geochemical character of the surface water in the different types of vegetation both in metamorphic clasolite area and marine face carbonate rocks area in Xijiang drainage area, Guizhou province and addressed some main conclusions as
follows:
1. The lithologic features in the Xijiang drainage area were the crucial controlling factors of the geohydrochemical character of the surface water and the weathering erosion intensity. The pollution in the rivers from the human activities had some effects on the ion construction of the surface water as well.
2. The main resources of the surface water in the research area were rainwater and groundwater. Rainfall was more frequent in this period of time affected by Southwest
Monsoon. Most of rainwater passed through the surface soil, and enter the aquifer of deep water. Then the rainwater might enter the open river as the direct surface runoff or took part in the cycling of groundwater. The surface water net and groundwater net were interconnected because of the frequent faulted structure in NNE direction; hence, the conversion between surface water and groundwater was very frequent.
3. The ion compositions and the physical and chemical properties of the surface water in this research area were controlled by the chemical weathering process of soil and
rocks. The lithologic feather of bedrocks in different drainage area led to the big difference in ion concentration and geohydrochemical features of surface water.
4. It was found that DIC in the surface water of this research area derived from the chemical weathering of silicate and carbonate by soil CO2, based on the
concentrations and carbon isotope analysis of DIC, DOC and POC in 75 surface water samples of Pearl River in Guizhou province. Generally speaking, the richer of the soil
CO2 in the research area with better vegetational cover, the more intensive of the chemical weathering. The chemical weathering was easier to occur in carbonate than in silicate and the product of chemical weathering could change the ion compositions and the characters of surface water.
5. The organic carbon in the surface water was related to the type of vegetation in the drainage area. The concentration of DOC in surface water could reflect the types of vegetation and the rate of vegetational cover. The concentration of TSS and POC could illustrate the situation of organic matters in the soil of drainage area. The
concentration of DOC and POC in surface water could help to distinguish the source and sink of carbon in Karst drainage area and to set up the carbon cycling model.
6. POC from the suspended matters in surface water, derived from soil organic matters and terraneous vegetation, was the crucial proxy of drainage erosion. The
value of δ13CPOC had the inverse correlation with the ratio of TOC/TN in the surface water of research area; hence，POC in the surface water was probably coming from
the deep soil in drainage area. The lower ratio of TOC/TN was with the stronger hydropower and more intensive drainage erosion.
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| 页数 | 100 |
| 语种 | 中文 |
| 文献类型 | 学位论文 |
| 条目标识符 | http://ir.gyig.ac.cn/handle/42920512-1/10793 |
| 专题 | 研究生 |
| 推荐引用方式 GB/T 7714 | 薛紫晨. 地质与生态环境影响下的地表水化学以及碳同位素地球化学特征 ——以贵州境内珠江水系为例[D]. 中国科学院地球化学研究所. 中国科学院大学,2007. |
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