Karst Watershed Storm Response Of Metal Cations In An Underground River, Qingmu Guan, Chongqing

Water resources is the reliance resources of mankind survival,is the basic guarantee of human living and developing,the development and utilization of water resources is the permanent goal of humanity.Ground water resources in karst region is an important freshwater resources,and the karst region is considered to be a fragile environment as the desert margin by environment scientist.With a very low environmental capacity, once the karst region is degraded,it is too difficult to restore.The karst region has surface and subsurface structures in space medium.The water and land resources are separated which is described as the land on upstairs and the water in downstairs.Karst rock is hard to change into the soil,water is not homogeneously distributed,the connection of groundwater and surface water is consanguineous,water source is easy to leak,and the weak ecological environment is always influenced by human activity.All this make the development and utilization of groundwater resources more prominent.Qingrnu Guan karst subterranean river system is the principal water source of local people,and it is the primarily outlet in flood season.This underground river is a typical ground water in karst region which develops along structure fissures,the water level rising suddenly and dropping sharply according to the amount of rainfall,so the subterranean stream belongs to the type of pipe ground river.It is signality to study on response of hydro-geochemical behavior to rainfall in Qingrnu Guan karst subterranean river system.The thesis has investigated two rainfall events with high density to a groundwater of Qingmu Guan,Chongqing,specific conductivity,pH,temperature and metals concentration at the outlet of Jiangjia Spring were monitored,the results show that:1.The analysis of hydro-geochemical indices of JiangJia spring indicates that the hydro-geochemical contents of groundwater are mainly HCO₃^- and a few SO₄^2- in anion, and basically Ca²⁺ in cation with small quantity of Mg²⁺,and the groundwater hydro-geochemical type of JiangJia spring is HCO₃^-—Ca²⁺.2.The study of metals cation concentration changes shows that the seasonal nature change is to influence the metals cation concentration in Qingrnu Guan,the cation concentration of Ca,Mg,Sr were reducing when the groundwater flow rate increase, and raising when flow rate decrease,the cation concentration of Fe,Mn,A1,Ba were growing when the groundwater flow rate increase,and falling when the groundwater flow rate lower,and the cation concentration of K,Na were mainly effect by human activity probably.3.In Qingmu Guan area,the hydro-geochemical response of groundwater to rainfall events is very fast and dramatic,it is verified the result of tracer test.In a rain fall event,the dynamic changes of flow rate in JiangJia spring is very high,water level rising suddenly and dropping sharply according to the amount of rainfall,it indicats that Qingmu Guan karst subterranean river system is a well-developed and connected conduit system.4.Based on the data of metals cation concentration,there two types of metal cation in Qingmu Guan ground river,one type is the Ca,Mg,Sr cation,which controlled by the dilution of rain,are come from dissolved carbonate rock,the other is the A1,Fe,Mn, Ba cation,which eroded into groundwater system by the rain are mainly contained in the soil of Qingmu Guan area.So the soil erosion during the storm events can probably be a pollution,the connected conduit groundwater system is easily polluted by the external material.5.With the monitoring of two storm events,we can obtain that the metals cation are highly sensitive the amount of rainfall,especially the A1,Fe,Mn cations,the related coefficients of their concentration to flow rate are 0.88,0.93,0.86.The results could be used as indices for the hydrogeneity of the karstic aquifer.