中文摘要：

为研究城市化作用下的岩溶区地下水水质演变状况,基于2008-2012年对老龙洞地下河的pH值、电导率、水温、K^＋、Na^＋、Ca^2＋、Mg^2＋、HCO3^-、Cl~-、NO3^-、SO4^2-、PO4^3-等水物理化学指标的连续监测,分析了老龙洞地下河流域水质的演变趋势,并对2011年8月的单场降雨条件下地下河水质的动态变化进行主成分分析（PCA）。结果表明,在城市化过程中,地下河水Na^＋、Cl~-、PO4^3-、Ca^2＋、Mg^2＋、HCO3^-等离子浓度受人类活动影响而明显上升,NO3^-、SO4~（2-）浓度则因为城市化效应增强和农业活动强度的降低而下降。老龙洞地下河水补给来源复杂,其中碳酸盐岩地质背景、人类活动及水土流失对地下河水质变化起着决定作用。城市化水平的提高、区域环境的变化,使得老龙洞地下河的水质也处于不断变化中,从硝酸盐、硫酸盐的年际变化看,地下河水质已有较大改善。

英文摘要：

The underground river is in Nanshan district of Chongqing City where the karst groundwater is well-developed.There are karst depressions,sinkholes,underground rivers and exposed springs,which has the features of sensitivity and vulnerability of typical karst groundwater systems.Due to urbanization and human activities,groundwater in this area has been seriously polluted in recent years.In this paper,an underground river conduit in the karst area is taken as an example.Through analyzing the evolution of the underground,water quality deterioration and pollution sources of the groundwater,the main controlling factors of groundwater pollution in the study area are discussed,in order to protect the groundwater and provide a scientific basis for groundwater governance in this area.From 2008 to 2012,the outlet of Laolongdong underground river was chosen as a water quality minoring locality where pH value,conductivity,water temperature,potassium,sodium,calcium,magnesium,bicarbonate,chloride,nitrate,sulfate and phosphate were measured on monthly basis.The principal component analysis（PCA）was used to analyze the variation of water quality during the rainfall event in August 2011.Results indicated that in the process of urbanization,the ion concentrations of sodium,chloride,phosphate,calcium,magnesium,bicarbonate increased because of human activities.Meanwhile,the ion concentrations of nitrate,sulfate decreased due to the urbanization effect and agricultural activities.Moreover,water-rock interaction,human activities,and soil erosion played a crucial role in the hydrochemistry compositions and variation of the groundwater.Among them,dump of domestic sewage and solid wastes and the excessive uses of pesticide/fertilizers in urban residential areas are the main sources of pollutants such as potassium,sodium,chloride,sulfate,nitrate,phosphate,iron,manganese and aluminum in underground rivers.The water quality in this region varies because of the improvement of the urbanization levels and regional environment change.From th