FLUORIDE CONTAMINATION THREAT IN THE GROUNDWATER OF ASSAM, INDIA: A CASE STUDY IN THE HIGH CONCENTRATION ZONE OF NAGAON

Abstract

This  work focuses on  the  chemistry  of  groundwater in the district of Nagaon, Assam, India, which is a high concentration zone for fluoride; with  areas  of  particular  interest  being  the  major  ion  chemistry, and identification  of  contamination levels with reference to fluoride. Fluoride  concentration  well  above  the  WHO guideline  value  was  found in several locations of the  district with a range of values between  0.14  and  3.65 mg/L. About 60% of the samples studied had F^- content higher than the recommended maximum permissible level of 1.5 mg/L, while about 10% samples had it below the recommended level of 0.6 mg/L. The chemical characteristic of the groundwater study shows that the cationic chemistry is dominated by Ca²⁺ and Na⁺ while anionic chemistry is primarily dominated by Cl^- ; the geological formation of the area is the basic cause of high fluoride content in its groundwater.