关键词: 南洞岩溶水系统;水化学特征;氢氧同位素;蒸发作用;岩石风化;

Abstract: As a typical super-large underground river basin in southwest China, Nandong karst water system is selected as the research area.In view of water shortage in karst areas, aiming at rational exploitation and sustainable utilization of water resources, water samples were collected and field tests were conducted at 16 observation points in the study area at May and December 2015.The hydrochemical characteristics and their causes were analyzed by using the methods of descriptive statistics analysis, Piper diagram, Gibbs diagram.The results showed that the pH value of the water body in the study area ranged from 6.19 to 7.66,and the average value was 7.25,which was neutral and slightly alkaline.The average TDS was 329.24 mg/L,a low-salinity water body.Due to the control of carbonate strata in karst areas, the chemical type of groundwater in the study area was mainly HCO3-Ca type, while the surface water was mainly HCO3-Ca type and HCO3·SO4-Ca·Mg type.The controlling hydrogeochemistry process of major ions in this area was mainly rock weathering and leaching.The analysis of hydrogen and oxygen isotopes showed that the initial recharge source of surface water and groundwater in the study area was mainly atmospheric precipitation, while the hydrogen and oxygen isotopes of surface water were heavier due to strong evaporation.

Key words: Nandong karst water system; hydrochemical characteristics; hydrogen and oxygen isotopes; evaporation; rock weathering;