Hydrogeochemistry of the fluoride in groundwater in the Dali area of the Guanzhong Basin

In order to study hydrogeochemistry of the fluoride in groundwater in the Dali area of the Guanzhong basin,239 groundwater samples and 35 soil samples were analyzed.The influence of water type and compositions on fluoride in groundwater was examined by using the Piper diagram and Durov diagram,combining with the box diagram.The results show that in the alkalescence environment,saleratus type water is the main factor of promoting fluoride richment and building up fluoride transfer from wall rock to groundwater.Calcium(magnesium) sulphate type water counterworks fluoride to enrich.Sodium,chloride,bicarbonate and pH have active function to enrich the fluoride in the groundwater,but calcium contents is negative correlative to fluoride content.The Migration coefficient is in a positive relation with bicarbonate and pH and in a negative relation with other main chemiscal ions.Groundwater circulation condition is the motive of the fluoride enrichment and transfer.Using the Phreeqci software to analyze saturated index and calcium and fluorine ion activity,we found that fluorite and calcite control water chemical compositions which have some relations with fluoride in groundwater.