Distribution and formation factors of high fluoride deep groundwater in typical area of north Anhui Province

The fluorine of the deep groundwater in the typical area of north Anhui Province was selected as the object of interest in this work. On the basis of data collection, hydrogeological survey and sample analysis, the data of 81 deep groundwater samples and 71 shallow groundwater samples were determined.Fluorine distributions, fluorine sources, and factors that influence the fluorine formation of the deep groundwater were analyzed via descriptive statistics, correlation analysis, ion ratio coefficient and Piper graphic method.The results demonstrate that the fluorine of the deep groundwater in this area was characterized by low concentration in the edge area, high concentration in the middle area, and weak alkaline in high fluoride water. Based on hydrochemical type characteristics, the area of interest was divided into three systems: Bozhou, Fuyang and Mengcheng systems. Among the three systems, the water type of most samples in Bozhou system and Fuyang system were Cl—Na and HCO3—Na, respectively.However, the Mengcheng system was complex, and included more water types such as Cl—Na, HCO3·SO4·Cl—Na, HCO3—Ca·Mg and HCO3—Na·Mg·Ca. Fluorine minerals dissolution was the main source of fluorine in deep groundwater.Weak alkaline water, dissolution/precipitation and cationic alternate adsorption were major factors that influence the fluorine formation of deep groundwater in typical area of north Anhui Province.