【作者】 蒲俊兵；

【导师】 袁道先；

【作者基本信息】 西南大学 ， 自然地理学， 2011， 博士

【摘要】 我国南方岩溶区3066条地下河水资源是我国重要的战略资源,是区域可持续发展的重要支撑。然而,由于岩溶环境本身的脆弱性,以及人类活动的影响,岩溶地下河正面临水质退化,水源枯竭等多方面的威胁。重庆地区是我国西南岩溶地区的重要组成部分,岩溶分布面积约3.0万km2,主要分布在东北部和东南部。2006年夏和2010年春重庆都遭遇了百年不遇的特大干旱灾害。在抗旱救灾的紧急关头,对岩溶地区丰富的地下水资源作为应急水源的需求显得非常迫切。因此了解重庆地区的地下河发育、分布及水文地球化学特征,对于重庆地区岩溶水资源的开发、利用与保护显得非常重要。岩溶地下河的发育、分布受到区域岩性、构造、地貌等条件的综合控制。国内这方面的研究多关注于我国南方其它岩溶地区,如贵州、云南、广西等地,而关于重庆地区地下河的发育、分布及其控制机制缺少深入研究。地下河的水文地球化学特征受到地质、环境条件的综合影响,具有明显的空间特征。研究地下河水文地球化学特征的区域演化及与地质、环境的耦合关系,对于地下河水资源的开发利用与保护具有重要意义。根据历史资料分析和野外调查得出重庆地区分布有岩溶地下河380条,总长度约2155公里,多年平均流量151.5m3/s,水资源量47.77亿m3/a,岩溶区地下河发育密度为116.64m/km2,多年平均径流模数为6.56L/s.km2。重庆市岩溶地下河长度以中、短型为主,长度小于5km的占50%；流量以中、小流量为主,流量小于200L/s的地下河占总量的58.9%。研究发现重庆地区岩溶地下河发育、分布主要受区域线状构造的控制,地下河主要分布在川东褶皱带,川东南陷褶带和大巴山弧形断褶带等三个主要的构造带内。在渝东北大巴山弧形断褶带地区由于受到北西向构造的控制,地下河管道主要呈NW-SE展布；而在渝东南川东南陷褶带地区由于受到北东、北北东构造的控制,地下河管道主要呈NE-SW展布。在主城、渝东川东褶皱带地区由于地下河多位于背斜核部的碳酸盐岩中,因此地下河管道主要沿背斜展布方向(主要为北东向)成纵向分布。根据重庆地区地下河的构造控制因素和岩溶水的运动特征,系统地将重庆地区地下河分为汇流型、分流型和平行流型三种类型。汇流型地下河多分布向斜地区和宽缓背斜地区以及垄脊槽谷地区。分流型地下河多分布于背斜地区和一些向斜台原地区。平行流型地下河多分于可溶岩与非可溶岩相间分布的紧密褶皱地区。通过对70条典型地下河水文地球化学特征的研究,揭示了重庆岩溶地区分布的地下河水化学特征从渝东北、渝东南“两翼”地区向主城地区水质变差,水化学类型变复杂的区域演化规律。渝东南、渝东北地区主要受自然条件控制,水质较好,水化学类型主要是Ca-HCO3型、Ca+Mg-HCO3型；由于人类活动引入大量外来离子,主城周边、渝东地区水化学类型复杂,出现了Ca+Na- HCO3+SO4型,Ca- SO4+HCO3型,Ca+Mg-SO4+HCO3等多种类型。渝东南的万盛—南川—綦江三角形地区,由于工矿企业林立,人类活动频繁,出现了Ca+Na-SO4型、Ca+Na-SO4+HCO3型、Ca-SO4+HCO3型的复杂的水化学类型,水质较差,形成地下河水化学分布“黑三角”地区。利用多种同位素结合技术研究重庆岩溶地下河水文地球化学特征的区域演化规律及溶质来源。通过δ18O、δD值分析揭示重庆市地下河水主要起源于大气降水。受雨季降水云团运动规律(环流效应)和区域地形的影响,雨季δ18O、δD值表现出渝东北地区<主城周边<渝东地区<渝东南地区的明显区域分布规律(“<”表示偏负于),旱季由于地下河水在含水层中运动较慢,δ18O、δD值的区域性规律不明显。由于地下河水体具有较快的运动速度,水体水-岩相互作用程度相对于孔隙含水层,裂隙含水层较低,因此岩溶含水层中d-excess值的水文地质学意义并不十分明显。而通过δ180,δD值与高程的关系,建立了二者之间的二元回归模型,揭示了重庆岩溶地下河水旱季δ18O值随高度的变化率为-0.34‰/100m,雨季为-0.31‰/100m；旱季δD值随高度的变化率为-2.3‰/100m,雨季为-2.9‰/100m,可据此反推重庆地区降水的高程效应,这对于区域水循环研究具有重要意义。根据δ13C同位素质量平衡方法,计算得到重庆地下河旱季碳酸盐岩溶蚀对DIC贡献为45.1%～79.7%,雨季平均为17.2%～82.1%。计算结果表明,碳酸盐岩溶解参与岩溶地下水DIC的形成并不一定是岩溶作用方程中所计算的50%,而是有一定的变化范围,因此在计算岩溶作用碳汇时建议通过δ13C值计算碳酸盐岩溶蚀占DIC的比例后再进一步推算岩溶作用形成的碳汇通过87Sr/86Sr同位素分析发现地下河水中的Sr主要来自于碳酸盐岩溶蚀。但一部分地下河显著的受到人类活动Sr输入的影响,它们主要分布在渝东地区的三叠系地层中。渝东南地区寒武系地层中发育的地下河也受到了一定的人类活动的影响。通过634S-SO42-同位素分析发现地下河中SO42-具有多重来源,也有明显的区域差异。具有蒸发岩硫来源的地下河多发育在三叠系地层中。具有硫化物氧化硫来源的地下河多发育在二叠系地层中。雨水和人类活动排放废水对地下河硫输入也有贡献。渝东地区和主城周边地区发育的地下河多具有人类活动的硫来源。分布在渝东南和渝东北海拔较高人类活动影响较小的地区的地下河,其SO42-具有大气降水硫来源特征。综上所述,重庆地区地下河的发育、分布的控制机制主要是区域线状构造,地下河水质存在从渝东北、渝东南地区向主城地区变差的区域演化规律,利用多种同位素技术研究了地下河的同位素水文地球化学特征的区域演化规律,探索了地下河的溶质来源,能够为重庆地区岩溶地下河的合理开发利用与保护提供技术支撑。更多还原

【Abstract】 Karst groundwater is an important strategic resources and life-support system for sustainable development in China. The storage type of karst groundwater in south China is mainly separate subterranean stream system. According to the latest geology survey, there are 3066 subterranean streams (SS) in south China, which are the important water resources for local people. However, karst aquifer in this region is facing some threats such as the water quality deterioration, water sources exhaustion due to the fragility of karst environment and the disturbance of human activities. The karst areas in Chongqing distribute mainly in the northeast and southeast with the area about 3.0×104km2 is an important area of the southwest karst China. Chongqing have suffered serious and rare drought in the summer 2006 and the spring 2010. The demand for the rich groundwater as an emergency water supply in karst areas was very urgent for the fighting against drought. Therefore, researching on the formation, distribution and hydrogeochemistry of subterranean streams in Chongqing is very important for exploitation, utilization and protection of karst groundwater resources of Chongqing.The formation and distribution of SS is combined controlled by the carbonate rock, structure and relief in karst areas. In south China including Guizhou, Yunnan. Guangxi, many researchers have focused on the controlling factors of formation and distribution of SS. But the same researches are seldom in Chongqing. Hydrogeochemistry of SS is combined influenced by the geological and environmental characters and it has significance spatial variation features. It is very important for the utilization and protection of SS to study on the regionality of SS’s hydrogeochemistry and its coupling relationships with the geology and environmental features.Based on the historical references analysis and field surveys, we researched the formation and distribution of SS of Chongqing and sectioned their types in this dissertation. There are approximately 380 subterranean streams with a total length of about 2155km, the multi-annual mean discharge about 151.5m3/s, and the water resources about 47.77×108m3/a in Chongqing. The mean coefficient of development density of subterranean streams is 116.64m/Km2, and the multi-annual mean coefficient of runoff modulus of subterranean streams is 6.56L/s·Km2. Most of the length of SS is short and medium length, and the numbers of SS of which the length is less than 5km account for about 50% of the total SS numbers. Most of the discharge of SS is medium and small discharge, and the numbers of SS of which the discharge is less than 200L/s account for 58.9% of the total discharges. Overall, the SS exists mostly in the southeast and northeast of Chongqing. Its distribution is consistent with the area of carbonate rock in Chongqing.In this dissertation, a new founding is that the formation and distribution of SS is controlled by the lineament structure in Chongqing. As a whole, the SS distributes mostly in the Eastern Sichuan fold belt, Southeastern Sichuan fall-fold belt and Daba Mt. arc-shaped fault-fold belt of Chongqing. The bearing of trend of SS in Daba Mt. arc-shaped fault-fold belt in northeastern Chongqing is NW-SE direction because of the control of the NW trend lineament structure. Due to the influence of the NE and NNW trend lineament structure, the bearing of trend of SS in Southeastern Sichuan fall-fold belt in southeastern Chongqing is NE-SW direction. The SS mainly locates in the core part of a series of anticlines in Eastern Sichuan fold belt in the main districts of Chongqing city and central area of Chongqing municipality, which is the carbonate rock area, and its trends is along the anticline extension direction (NE direction). According to the structure features and groundwater movement features of SS, it is divided into the following three types:afflux-flow type, distributary-flow type and parallel conduit-flow type. The afflux-flow type SS largely distributes in the syncline areas, wide-spaced shallow-dip anticline areas and ridge-trough valley areas. The distributary-flow type SS mainly locates in the anticline areas and syncline chapada areas, and the parallel conduit-flow type SS in the appressed fold areas which is the areas of soluble rock alternating with non-soluble rock.By analyzing the hydrogeochemistry of 70 typical SSs in Chongqing, this study reveals that the water quality is deteriorating and the hydrochemistry type is complicating from the northeastern Chongqing and southeastern Chongqing to the main districts of Chongqing city. The water quality of subterranean streams existed in the main districts of Chongqing city and central area of Chongqing municipality is poorer than that existed in the southeast and northeast Chongqing municipality. In the northeastern and southeastern Chongqing, the solutes of SS mainly originated from the dissolution of carbonate rock by water-rock interaction, which lead to the fact that most groundwater chemistry of SS were typical Ca-HCO3 type or Ca+Mg-HCO3 type. However, some of subterranean karst streams have been changed into the type of Ca+Na-SO4, Ca+Na-HCO3+SO4, Na+Ca-Cl+HCO3 or Ca-SO4+HCO3 in the main districts of Chongqing city and central area of Chongqing municipality due to the strong impact of human activities. The water quality of SSs, which is mainly Ca+Na-SO4, Ca+Na-SO4+HCO3 or Ca-SO4+HCO3 type, is worse in the triangle areas of Wansheng district-Nanchuan district-Qijiang county, where is called the "black triangle" area, of hydrogeochemistry.Multi isotopes were used to study the solute origin and regionality of hydrogeochemistry of SSs, Chongqing. All of the SS water origin from the modern precipitation because theirδ18 O andδD plot along the line of GMWL or LMWL, which shows that the evaporation of groundwater does not occur or is not strong. Under the control of movement of rain cloud cluster from south to north (atmospheric circulation effect) and the regional relief, the regionality ofδ18O and 8D for SS in Chongiqng is shown in the following way: the northeastern Chongqing< the main districts of Chongqing city< the central area of Chongqing municipality< the southeastern Chongqing (the symbol "<" means "more minus"). In dry season, the regionality ofδ18O and 8D for SS is not clear due to the slower movement velocity in karst aquifer. The hydrogeological implication of d-excess value is not clear for karst aquifers because the movement velocity of groundwater in it is faster than pervious aquifers and fissure aquifers with the lower degree of water-rock interaction. Considering the relations between the altitude and the mean value forδ18O or 8D of subterranean streams within 100m altitude differences, we established the second order polynomial of karst groundwater betweenδ18O orδD and altitude. According to the equations, theδ18O-elevation gradient of karst groundwater in Chongqing is -0.34‰/100m in dry season and-0.31‰/100m in wet season, as well as the 8D-elevation gradient is-2.3‰/100m in dry season and-2.9‰/100m in wet season. In most test sites, theδ13C values of SS in wet season is more minus than in dry season, except in main districts of Chongqing city, which shows the concentrations of biogenic CO2 in groundwater may be more in wet season. Based on theδ13C isotope mass balance equation, we calculated the amounts of DIC which came from the carbonate rock dissolution. The calculated results show that 45.1%-79.7% of the DIC in the dry season and 17.2%-82.1% in the wet season is from dissolution of carbonate rocks in karst groundwater. The range of calculated results also shows that the DIC proportion of karst groundwater originated from the carbonate rock dissolution is not necessarily the 50% according to the molar ration of karst chemical reaction equation, but has a range of changes at some extend. As a result, this dissertation suggests that we should count first the rate of carbonate rock dissolution in groundwater DIC using theδ13C when we calculate the carbon sink of karst processes, and then calculate further the karst carbon sink.According to the results of 87Sr/86Sr, the Sr element in test sites mainly origin from the carbonate rock dissolution. Also, Sr element may come from the silicate rock weathering in some test sites. By analyzing the relationship of the 87Sr/86Sr and [K++Na+]/Sr2+, some SSs are greatly impacted by human activities, which exist mainly in the Triassic limestone aquifer in southeast Chongqing. Some subterranean streams are also affected by human activities in Cambrian karst aquifer in Southeast Chongqing. Based on the analysis ofδ34S values, this research found that the SO42- in SS has multiple sources and has obvious regional differences. The sources of SO42- include the source of gypsum solution, oxidation of sulfide minerals, atmospheric acid deposits and human activities by the relation of 87Sr/86Sr vs.δ34S. With the source of the evaporating SO42-, the SSs mainly develop in the Triassic karst aquifer. With the source of the oxidation of sulfide minerals, the SO42- mainly develops in the Permian karst aquifer. The S in rainwater and sewage also contributed to the SO42 of SSs. The SO42- originated mainly from the human activities in the main districts of Chongqing city and in east Chongqing. The SO42- of SSs originated mainly from the atmospheric acid deposits in the areas of higher altitude and smaller disturbance of human activities in southeast and north east Chongqing. Overall, the multiple sources of S clearly contribute to the existence of the SO42- in some SSs, so that those SSs tend to lie in the combined influenced area of multiple S sources.Generally, the controlling factor of formation and distribution of SS is the regional lineament structure in Chongqing. The water quality of SS is deteriorating and the hydrochemistry type is complicating from the northeastern Chongqing and southeastern Chongqing to the main districts of Chongqing city. The regionality of isotope hydrogeochemistry and the solutes origin were revealed using the multi- isotope coupling technology. The research productions of this dissertation will provide science and technology supports for the rational exploitation and protection of subterranean streams in Chongqing municipality.更多还原