Analysis Of Hydrogeochemistry And Hydrogen And Oxygen Isotopes Of Surface Water And Groundwater In Jinfo Mt

Water is a valuable resource to the survival of humans, and, groundwater is an important part of water resources occupying 98.5% of the available water resources. Groundwater which occurs in karst pores is karst water. Karst area occupies 15% of the total global land area, at least 1 billion people live in karst area or take karst water as the main source of water supply. As the increase of human activities, the karst water pollution and waste of water resources is becoming increasingly prominent in environmental problem, rational utilization and conservation of groundwater resources has become increasingly important. Under these circumstances people need to find out the temporal and spatial changes of groundwater water cycle pattern.This paper selected a typical karst region of Chongqing, Jinfo Mt as the study area, on the basis of the regional natural geographical and hydrogeological conditions, analyzed the variation of hydrogeochemical characteristics and spatial distribution of stable isotopes of surface water and groundwater, and, further explored the recharge and cycle pattern of groundwater and surface water in this area.. The results are as follows:Hydrogeochemical characteristics of surface water and groundwater is HCO3-Ca and Ca(Mg)-HCO3, reflecting the widespread distribution of limestone and dolomite in study area. The hydrogeochemical characteristics of surface water and groundwater in Jinfo Mt indicate that the water in study area is controlled by the natural process of rock weathering. The ion constitution of surface water and groundwater also show a high degree of consistency. The pH value of groundwater shows weak alkaline, and the ratio between total hardness and total alkalinity in the outside of Jinfo Mt natural reserve is higher than that inside, which indicates that the dissolution process of soluble rocks is affected by the other acid substances, especially in some individual samples. The ratio between total hardness and total alkalinity is higher than that in 1970s both inside and outside of the Jinfo Mt natural reserve, moreover this condition of outside is more obvious. The contents of Ca2+,Mg2+are controlled by the geological background, for example, the Ca2+ content is higher in limestone formation and higher Mg2+ dolomite formation,. In a word, geological background is the major factor affecting the content of cation in Jinfo Mt underground water, in addition, human activities are also included. The anion contents of groundwater in Jinfo Mt changes at different degree than that in 1970s, and, the major factor is human activities.The hydrogen and oxygen isotopic composition of water in Jinfo Mt lie in the vicinity of the Chongqing Meteoric Water Line and Global Meteoric Water Line, locates in the upper left, indicate that the surface water and groundwater in Jinfo Mt is recharged by meteoric waters and snow melt. Along the direction of surface runoff, the electro conductivity of the water increases and isotopic composition rich in heavy isotopes. Lixiviation and the cation exchange is chief geochemistry action that results in the electro conductivity of groundwater higher than surface water.A conception model of water cycling in Jinfo Mt was established based on the hydrogeochemistry and stable isotopes data:At 1267-2133m high altitude Jinfo Mt district, meteoric water infiltrates into the water circulatory system of Jinfo MT as rain and snow. When the process that rainfall infiltrates downward the ground and recharges underground water is influenced by evaporation effect, the stable isotopes composition of groundwater that recharged by meteoric water became rich in heavy isotopes. Part of the groundwater is exposed to the earth surface with shallow cycles and becomes cold spring during the process of groundwater migration. The other part of groundwater continues to infiltrate and goes through deep cycles and becomes underground thermal water which is lack of heavy isotopes, then underground thermal water migrates upward and mixes with cold groundwater, eventually forms thermal spring in the outcrop. Part of underground water being infiltrated from high mountain region and being exposed on the earth’s surface at the foot of the mountain through long distance migration shows big difference from underground water that recharged by local meteoric water in the composition of hydrogen and oxygen isotope.