Seasonal variations in the groundwater fluoride of Swarna river basin in southern India: A GIS-based study

Objectives: The study aimed (1) to assess fluoride concentration of groundwater along the Swarna river basin in Udupi District; (2) to investigate variations in fluoride concentration with respect to rainfall status in Udupi district; and (3) to develop a spatial distribution map for the groundwater fluoride concentration in Udupi district. Materials and Methods: Water samples were procured from 30 different sampling points across three time zones in a year: pre-monsoon, monsoon, and post-monsoon. The samples thus collected were analyzed for fluoride ion concentration using fluoride ion selective electrodes (Orion™). Mean determination readings at each time zone were calculated. Repeated-measures analysis of variance was done to analyze whether there was a difference in the concentration of fluoride over different time zones. Results: The mean (SD) pre-monsoon concentration was 0.25 (± 0.07) ppm, whereas the mean monsoon and post-monsoon concentrations were 0.26 (± 0.09) and 0.57 (± 0.23) ppm, respectively. There was a significant increase in post-monsoon fluoride levels when compared with the pre-monsoon and monsoon levels. Conclusion: The groundwater fluoride concentration in the Swarna river basin was found acceptable for human consumption at all the sampled sites and across all time zones. As the fluoride concentration was found to be lower than the recommended values for dental caries prevention at most of the sampling sites, use of topical fluorides needs to be encouraged.