【作者】 林明珠；

【导师】 袁道先；

【作者基本信息】 西南大学 ， 自然地理学， 2012， 博士

【摘要】 表层岩溶带处于大气圈、生物圈、岩石圈、水圈四大圈层的交汇地带,是岩溶动力系统四大圈层间有关水资源和能量转换重要的前沿阵地。其中的表层岩溶水是我国西南岩溶山区居民生产和生活的重要水源。同时表层岩溶系统也因碳酸盐岩-水-C02-生物圈四相的动态平衡而产生特殊的碳循环,成为大气CO2汇的重要组成部分。但随着土地利用/土地覆被的变化,石漠化加剧,对环境变化反应敏感的表层岩溶生态系统正发生显著的变化,这不仅包括表层岩溶水资源的变化也包括表层岩溶碳汇效应的变化。因此土地利用/土地覆被变化引起的表层岩溶水资源变化和岩溶碳汇效应都需要进行有效的评估,以为岩溶山区人们的生产生活提供保障,也为全球碳循环研究提供一定的科学依据。本文以此为题,选取了重庆市南川区3个不同土地覆被下的表层岩溶水对其水文地球化学特征及碳汇效应进行研究。3个泉水分别为灌草丛地的柏树湾泉、耕地的兰花沟泉和石漠化地的后沟泉。通过研究得出以下初步结论：(1)对不同土地覆被下表层岩溶泉水化学性质进行研究,结果发现：不同土地覆被下表层岩溶泉水水温受气温变化影响表现明显的季节变化,但变化幅度不一。各泉水pH都表现为雨季低、旱季高,后沟泉水pH值略高于另外两个泉水。随着土地覆被的转变,基岩裸露率增加,植被覆盖率降低,下伏泉水中的HC03-浓度及HC03-和Ca2+的比例都逐渐减少。三个泉水的电导率和N03-、SO42-、C1-、Na+浓度都是后沟泉水>兰花沟泉水>柏树湾泉水,这和基岩裸露率有很好的正相关,和植被覆盖状况呈负相关。这些发现说明,电导率、N03-、SO42-、C1-、Na+、HC03-等泉水水化学指标可以作为不同土地利用方式和植被覆盖变化的重要指标。对不同土地覆被下表层岩溶泉水进行的水质综合评价结果显示,三个泉水的水质综合指数P都小于1,泉水水质均达到生活饮用水Ⅰ级标准,但柏树湾泉水水质优于兰花沟泉水,兰花沟泉水水质好于后沟泉水。(2)通过对不同土地覆被下表层岩溶带上覆土壤水水文地球化学特征进行研究,结果发现：受降雨、地表植被及土壤物理性质等的影响,不同月份不同土地覆被下表层岩溶带上覆土壤水获取量不同,同一种土地覆被下不同层次士壤水的获取量也不同。柏树湾土壤水的获取量最多,兰花沟次之,后沟最少。在富钙偏碱的岩溶土壤环境中,Ca2+是土壤水中主要的阳离子。受溶蚀强度和土壤淋失作用影响,柏树湾和后沟土壤水Ca2+和SO42-含量随土层加深而递增,而兰花沟受施肥影响,C2+和SO42-含量出现相反的现象。不同土地覆被下土壤水Na+和Mg2+变化规律不同。随着土层的加深,三个泉域土壤水N03-、K+、全Fe、A13+和Ba2+都逐渐减少。土壤水的N03-、SO42-和P043-平均含量从大到小依次为：后沟>兰花沟>柏树湾。通过土壤水中的各种地球化学元素和下伏表层岩溶泉水的相同元素相关分析得出,表层岩溶泉水水文地球化学元素受到土壤水一定的影响,但是由于不同土地覆被土壤物质来源不同以及各种元素的形态和运动形式不同,所以不同土地覆被土壤水的水文地球化学元素和泉水中相应元素的相关性存在差异。(3)对不同土地覆被下表层岩溶泉水文地球化学特征昼夜动态变化进行观测,结果发现：在降雨条件下,主要有三个效应控制着表层岩溶泉水的水化学动态,一是活塞效应；二是稀释效应；三是水-岩-气效应,但是对于不同土地覆被下表层岩溶泉水,其控制效应不同。通过对兰花沟泉和后沟泉水降雨条件下短时间尺度水文地球化学特征的研究,进一步论证了土地利用及地表植被覆盖在提高表层岩溶泉水流量上的重要作用。同时,良好的植被覆盖和较厚的土层有利于碳酸盐岩溶蚀的进行,也有利于水土保持。降雨条件下,兰花沟泉水离子来源主要为碳酸盐岩溶蚀和雨水对士壤的淋溶,而后沟泉水离子来源主要为雨水对土壤的淋溶和水士流失作用。(4)对不同土地覆被下表层岩溶泉水碳汇效应进行研究,结果发现：泉水溶解无机碳(DIC)含量和其碳稳定同位素组成(δ13CDIC)表现出明显的季节变化,雨季泉水具有低DIC含量和低δ13CDIC值,旱季则相反。但是不同士地覆被下泉水具有不同的DIC含量和δ13CDIC值,总体上,随着土地向耕地的转变和石漠化的发展,泉水的参13CDIC越重。柏树湾和兰花沟泉水的DIC和δ13CDIC值成正相关关系,而后沟泉水两者成负相关关系。对泉水水化学指标和δ13CDIC值之间相关关系分析得出,碳酸溶蚀碳酸盐岩是泉水DIC的主要来源,硫酸和硝酸也参与了碳酸盐岩的溶蚀,对泉水DIC有一定的贡献。但不同土地覆被下泉水受到的影响因素不同,各泉水硝酸和硫酸参与碳酸盐岩的溶蚀比例不同,柏树湾泉、兰花沟泉和后沟泉硝酸和硫酸溶蚀碳酸盐岩的比例范围分别为：2%-7%、9%31%和10%～46%。另外,不同土地覆被下表层岩溶泉水中HCO3-来自土壤CO2的比例体现了碳酸盐岩溶解的HCO3-输出中并非是50%的士壤(大气)CO2消耗及50%的碳酸盐岩的溶解。灌草丛地的柏树湾泉水中HC03-来自土壤CO2的比例为53%,而有农业活动的兰花沟和后沟泉水,其泉水中HC03-来自士壤CO2的比例分别为45%和40%,可见随着农业耕作面积的增大及泉域肥料输入量的增加,泉水HCO3-来自土壤CO2的比例逐渐下降。植被的恢复有利于增强岩溶碳汇,而耕地和石漠化则会减少岩溶碳汇量。柏树湾泉、兰花沟泉和后沟泉水对大气CO2沉降的年贡献分别为：2303Kg/a、1284Kg/a和176Kg/a。更多还原

【Abstract】 The epikarst zone is in the convergence zone of atmosphere, lithosphere, biosphere and hydrosphere. And it is the important forward position about the water resources and energy conversion of karst dynamic system. The epikarst water which is in the epikarst zone is the importance water resources for production and living to the people in southwest karst mountains area. At the same time, because the carbonate rock-water-CO2-biology four-phase is dynamic balance, the epikarst system have a special carbon cycle, and as an important part of the atmospheric CO2sinking. But with the change of the land cover and the development of karst rocky desertification, the epikarst ecosystem which is sentitive to the change of the environment is changing. This includes not only the change of the epikarst water resources but also the change of the epikarst carbon sinking effect. Therefore, the change of epikarst water resources and karst carbon sinking effect which caused by land use and land cover change are needed to assess effectively.This not only can provide the security for the people’s production and life in karst mountainous area, but also can provide a scientific basis for the global carbon cycle research.The author chose this as the topic of the dissertation. Three sites which had different land cover in Nanchuan city of Chongqing were selected for this research. They are:Boshuwan spring with shrud-grass land cover, Lanhuagou spring with agriculture land cover and Hougou spring with rocky desertification land cover. In the study, the hydrological geochemistry characteristics and carbon sinking effect of these there sites were researched. The following conclusions are obtained through this research.The chemical properties of epikarst springs under different land cover were studied. The results showed that water temperature, pH, EC and major ions in springs all exhibited obvious variations. The water temperature which affected by the air temperature had obvious seasonal variation. But the seasonal variation extent of epikarst springs was different. The pH of springs showed lower in the rainy season and higher in the dry season. And the pH of Hougou spring is slightly higher than the other two springs. Under the order of land cover from shrud-grass land, agricultural land to rocky desertification land, pH, EC and the contents of NO3-、SO42-、Cl-、Na+were significantly enhanced, while the content of HCO3-and the percentage of HCO3-+Ca+were markly decreased. With the changed of land cover and reduced of vegetation coverage, the purification and water conservation of soil decreased. At the same time, the contents of the major ions in epikaist springs were significantly enhanced. Therefore, all these indicate that the karst hydrochemical parameters, e.g., electronic conductivity, NO3-, SO42-, Cl-, Na+, HCO3-, can serve as indicators of different land use patterns and land cover change. And during the processes of protecting water resource and water environment, it has important significance to considering the change of land cover.The hydrological geochemistry of soil water in epikarst zone which had different land cover were studied. The results showed that: due to rainfall, vegetation and different soil physical properties and so on, the soil water quantity under different land cover was different. And the soil water quantity in different depth was also different. In the lime-stone soil environment that was rich in calcium, Ca2+was the major cation ion in soil water. By the effect of erosion intensity and soil leaching, the Ca2+and SO42-contents of soil water in Boshuwan and Hougou was increased with the increased of soil depth. But by the effect of fertilization, the the Ca2+and SO42-contents of soil water in Lanhuagou appeared opposite phenomenon. The Na+and Mg2+contents of soil water changed differently under different land cover. With the increase of soil depth, the contents of NO3-, K+, Total Fe, Al3+and Ba2+all reduced gradually. Under the order from Boshuwan spring, Lanhuagou spring to Hougou spring, the average contents of NO3-, SO42-and PO43-in soil water were significantly enhanced. According the correlation analysis between hydrological geochemistry of soil water and spring water, it showed that the hydrogeochemical elements of epikarst springs were affected by infiltration of soil water. But because of the different material sources in soil and the different morphology and motility of elements, the correlation between hydrogeochemical elements of soil water and epikarst spring was different.The diurnal variations of hydrological geochemistry characteristics of epikarst spring under different land cover were observed. The result showed the chemical dynamics of epikarst spring water were controlled by there main effects under rainfall condition. There were piston effect, dilution effect and water-rock-gas effect. But for the epikarst springs under different land cover, the effect which controled it was different.Through the research on the short time scale of hydrological and geochemical characteristics in Lanhuagou spring and Hougou spring, it further discussed the important role of land use and vegetation cover in improving the epikarst spring flow. At the same time, good vegetation and thick soil layer were benefit for the carbonate dissolution and the soil and water conservation. Under the condition of rainfall, for Lanhuagou spring, the carbonate rock dissolution and rainfall on soil leaching were the main sources of the water ions. While for Hougou spring, the rainfall on soil leaching and the erosion effect were the main sources of the water ions.The DIC concentrations and the δ13CDIC values showed seasonal variations, with lower DIC concentrations and δ13CDIC values in wet season. However, due to the different land cover of the spring catchments, the DIC concentrations and δ13CDIC values in springs were different. The relationship between DIC and δ13CDIC values showed positive in Boshuwan and Lanhuagou spring, while showed negative in Hougou springs.Through the correlation analysis between hydrochemistry and δ13CDIC values of springs, the dissolution of carbonate rock by carbonate is the major source of DIC in springs. Sulfuric acid and nitric acid also took park in the dissolution of carbonate rock. But the springs under different land cover affected by different factors. So the ratios of nitric and sulfuric acid in carbonate rock dissolution was different. The ratios of nitrate and sulfate in carbonate rock dissolution in Boshuwan spring, Lanhuagou spring and Hougou spring ranged from2%to7%,9%to13%,10%to46%, respectively. In addition, the HCO3-of springs from the soil was not like that the karst carbonate dissolved HCO3-in springs involved50%of soils or atmospheric CO2consumption and50%of the carbonate rock dissolution. In Boshuwan spring, the HCO3-of spring had53%from the soil CO2. While in the Lanhuagou and Hougou spring, the HCO3-of spring had45%and40%from the soil CO2respectively. So, as the increase of farming area and fertilizer input in the spring catchments, the ratios of the water HCO3-from the soil CO2decreased gradually. Vegetation restoration is conductive to enhancing the karst carbon sinking, while the cultivated land and rocky desertification will reduce the carbon sequestration.The annual atmospheric CO2deposition of Boshuwan,Lanhuagou and Hougou spring were2303Kg/a,1284Kg/aand176Kg/a, respectively.更多还原