Seasonal variations of fluoride content in groundwater from wells drilled in bedrock

Abstract

The aim of the present study was to investigate seasonal variations in the concentration of fluoride in water samples from bedrock groundwater in the county of Hordaland. Water samples from 42 deep wells were obtained once a month for a period of one year (1995), Samples were analysed for fluoride and pH. Some seasonal variation in fluoride concentration was found in all the sampled wells. As compared to Low-fluoride wells, high-fluoride wells shoved significantly higher seasonal variations in fluoride content. The statistical assessment revealed an asymptoic significant difference between the fluoride content in groundwater from the different bedrock types.There was also an asymptotic significant difference in the seasonal variation of the fluoride content of water in the different bedrock groups. A negative correlation was found between variation in the fluoride content and the age of the well. The fluoride concentration in the groundwater typically declined after periods of heavy rain, with an apparent delay of up to 3 months.