| Karst groundwater is an important drinking water source for residents in karst mountainous areas.Due to its special dual structure,groundwater is vulnerable to pollution.In this paper,the construction of Duba highway as an example,a total of 13 sampling points.Six sampling points were located in Jiangnanxiangiang spring-group,and seven sampling points were located in Fulongquan Basin.Physical and chemical parameters and isotopic data of water in the study area were obtained.Descriptive statistical analysis,hydrochemical analysis and isotope analysis were used to explore the hydrochemical characteristics and influencing factors of Jiang-nan-xiang Spring-Group and Fulongquan Basin in Jiangnan.The source of groundwater material was analyzed,and the water quality during construction was evaluated,which provided the basis for groundwater environmental protection in the study area.The results show that:pH,TDS and Ec in the study area met the national drinking water health standards.Ca2+and HCO3-are dominant cations and anion,respectively.The hydrochemical type is mainly HCO3--Ca2+type,the chemical composition of groundwater is mainly affected by the dissolution of carbonate minerals,ion composition is mainly controlled by water-rock interaction.The hydrodynamic conditions in the study area are good and the leaching effect is strong.Isotope composition characteristics in the study area show that groundwater recharge comes from atmospheric precipitation,and the composition ofδD andδ18O at each water point is close.The water bodies along the Dubba highway may have similar sources or similar changes,and the water samples of the Jiang-nan-xiang Spring-Group have a strong evaporation effect in the runoff process.Theδ15N-NO3-value of non-karst surface water in dry season is greater than 5‰,indicating that it may be polluted by nitrate.The main sources of nitrate are atmospheric nitrogen deposition,agricultural production activities,and production and living wastewater discharge.The seasonal variation of DIC content andδ13C value was small,and theδ13C value was negative in the wet season than in the dry season.Discharge of tunnel construction wastewater into groundwater circulation during highway construction,and the change of water quality and quantity caused by excavation and landfill activities.The monitoring of Poguan Spring during the Duba highway construction showed that the water temperature,pH value,DO,Ec,and TDS of Poguan Spring changed greatly in the rainy season,and the changes of various indicators in the dry season tended to be stable.The dust generated during the construction process may have an impact on Poguan Spring.Road barriers should be built before the construction to prevent emergencies that may have a negative impact on the Poguan Spring-water body.During the construction of Fulong tunnel,the water body of Fulong Spring becomes turbid,the water quantity decreases,and the water quality is not greatly affected.The results of water quality comprehensive evaluation show that,the water quality of the study area is in good condition during the construction of the highway,and accords with the drinking water standard.Karst spring water is severely affected by agricultural production activities.The discharge of untreated domestic wastewater and farmland water is the main way to cause water pollution in karst area. |
