FLUORIDE LEVELS AND THE POSSIBLE ENRICHMENT PROCESS IN SHALLOW GROUNDWATER IN HEZE CITY, SHANDONG PROVINCE, CHINA

Groundwater from 24 monitoring wells was sampled to reveal fluoride levels and the possible enrichment process in Heze City, Shandong Province, China. The groundwater has fluoride levels of 0.32-4.26 mg/L (a mean of 1.7 mg/L). 45.8% of samples and 70.8% of samples have fluoride levels exceeding the WHO standard of 1.5 mg/L and China's limit of 1.0 mg/L respectively. The groundwater fluoride levels are positively correlated with pH, HCO3 - and negatively with Ca2+ levels. The groundwater with F>1.0 mg/L is oversaturated with respect to CaF2 and MgF2 minerals, while that with F