The Study On The Difference Of Hydrochemical Characteristics Between Adjacent Drip Points In The Same Fractured Zone In Kunming Old Yellow Dragon Cave

Because of the complicated geological environment in karst area,it is difficult to use groundwater resources.If groundwater resources are polluted,it is difficult to control them.Therefore,the study of karst aquifers is a difficult and challenging problem in scientific field.In the study of karst area,the drip water of the cave roof has always been a hot spot at home and abroad.It is the result of the comprehensive effect of three phase inside the gas zone,and its hydrogeochemical and infiltration process can directly or indirectly reflect the water storage and movement characteristics of the surface karst zone.In this paper,three adjacent dripping points on a fractured zone of Old Yellow Dragon Cave are used as the research object.A large number of first-hand data were obtained by monitoring three drip points for a long time:The small field meteorological station is used to monitor the precipitation and temperature in the area.The data recorder has continuously observed the flow,temperature and electrical conductivity of the drip point.The hydrochemical parameters of water samples about anion,cation,DIC,pH and hardness of water samples were measured in the laboratory.We studied the hydrochemical process of the response of drip water to precipitation.At the same time,the dynamic changes of the chemical parameters of the drip water in a hydrological year are also studied,and discussed the influence of the internal structure of the karst layer on the hydrochemical and hydrochemical process of the drip water.These studies has certain theoretical and practical significance in understanding the function of storage and storage of aquifer zone and the vulnerability of aquifer in karst area.The main results are as follows:?1?In the study of the characteristics of drop water response to precipitation,we see that the average monthly flow rate of S14 drip point is smaller than that of S1 in a hydrological year,and its the flow rate varies greatly and the seasonal characteristics are significant.It can be deduced that the water storage space of S14 drip point is limited,so its the storage capacity ability is weak and the flow dynamic change range is great in the dry and wet season.Meanwhile S1 dripping water is relatively high in karstification and has a stronger storage capacity in karst aquifer system.?2?the time series analysis about discharge of S1 and S14 drip point responsing to precipitation,the maximum correlation coefficient of S1 and S14 is 0.593 and 0.388,and the maximum correlation coefficient of S1 number appears earlier than that of S14drip point,indicating that S1 number drop point is more sensitive to precipitation and the precipitation reaches S1 drop point time is shorter;In the autocorrelation analysis of the drop of water drop point of S1 and S14,The autocorrelation function of the S14 drip point is fluctuating in the later period,which indicates that the duality of the recharge from the karst aquifers is more prominent.The main reason is that the old water from the small pore water from the karst aquifer start to influence,so old wate in the amount of S14 water dripping is more significant than new water.?3?The experiment selected the representative precipitation events in the rainy and dry seasons to study the response of the drip points to the precipitation.?1?the base flow of the S1 drip point is largeand still be on the rise;The flow rate of S12 dripping point showed a slow downward trend;the base flow rate of S14 drop point was very small,The flow rate drops rapidly after reaching the peak value.Therefore,the water delivery capacity of the three drop points is S1>S12>S14.?2?The flow depression of S14 drip point is divided into two stages,the duration of which are short and the attenuation coefficients of the two stages are 0.09463 and 0.08107 respectively,indicating that the S14 drip point is mainly small pores in the karst interior space,and there is no large fissure.?3?The physicochemical parameters of three dripping drops were compared in the single precipitation in the dry season,the results show that the conductivity of S1 drip point is greater than that of S12 drop point,and the conductivity of S14 drip point is the smallest,so we can say that electrical conductivity is high in the transport path with high water transport capacity,and EC is low in poor water conveyance capacity.The response of electrical conductivity to precipitation is earlier than discharge indicating that conductivity has a good indication for precipitation.?4?The value of Ca²⁺/HCO₃^-in the dripping water is around 5 fluctuations.the ratio of Ca²⁺to HCO₃^-in the three drip points is less than 0.5 before the rainy season,because the water rock interaction time is long,the dissolution of calcite has reached saturation state,andprecipitation carries CO₂ in the soil into the karst aquifer,which makes the amount of HCO₃^-increase.In the rainy season the value of Ca²⁺and HCO₃^-is fluctuating in 0.5 show the hydrodynamic process is complex in this period.The concentration of calcium ion in water is controlled by precipitation and precipitation intensity.After the rainy season the ratio of Ca²⁺to HCO₃^-is larger than 0.5,which is mainly due to the decrease of precipitation and then coming from soil CO₂concentration in water fall.?5?In a hydrologic year,the PH and DIC of three dripping points have obvious characteristics between dry and wet season.the dry season of pH is high,but the rainy season is low.It is limited by the water transport capacity,so the pH change range of the S14 drip point is obviously smaller than that of S1 and S12.The DIC has a high content in the rainy season and low content in the dry season,The drip points of S1 and S12 have periodic variations of a small time scale with a time scale of 14 weeks,but S14dosen't,which indicates that the DIC concentration in dripping is controlled by precipitation and is particularly evident at drip points with strong water conveyance capacity.?6?EC in the drip water was correlated with the dominant ions HCO₃^-and Ca²⁺?S14 has a good linear relationship between EC and Ca²⁺or HCO₃^-.The drip points of S1and S12 are weakly correlated or even uncorrelated.So it can be inferred that S14dripping water ions mainly come from rock dissolution,while S1 and S12 drip water ions mainly come from soil leaching.?7?After dropping from the roof of the cave,the pressure state of the drip water changes,and the CO₂ is easy to degassing.Therefore,the saturation index of the three drip points is above 0.3 during the observation period,and the deposition phenomenon is easy to occur.