Geochemical sources, hydrogeochemical behaviour of fluoride release and its health risk assessment in some fluorosis endemic areas of the Brahmaputra valley of Assam, India

• Published in: Applied geochemistry 2021-04, Vol.127, p.104911, Article 104911
• Main Authors: Gogoi, Rashmi Rekha, Khanikar, Latu, Gogoi, Jahnobi, Neog, Nikita, Deka, Dhruba Jyoti, Sarma, Kali Prasad
• Format: Article
• Language: English
• Subjects: Dissolution experiment; Fluoride; Health risk assessment; Hydrogeochemistry; Petrography; Saturation index
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2021.104911

High fluoride (F−) concentration was detected in groundwater samples collected from three districts of the Brahmaputra valley of Assam, Nagaon, Kamrup Metropolitan (M) and West Karbi Anglong. The maximum F− value of 9 mgL−1 was found in southern Nagaon. About 38% of the total groundwater samples exceeded the WHO permissible limit of 1.5 mgL−1. Petrographic analyses revealed that micaceous minerals such as biotite and muscovite are the dominant contributors of F− in Nagaon and West Karbi Anglong; in Kamrup (M), it is biotite. The alkaline groundwater played a significant role in governing the dissolution and mobilization of F− from its sources. Silicate weathering was more prominent in Nagaon and West Karbi Anglong, while carbonate weathering was dominant in samples collected from Kamrup (M). Both cationic (Ca2+/Na+) and anionic (F−/OH−) exchange processes occurred extensively across the studied hydrogeochemical regime. PHREEQC simulations revealed that fluorite and calcite undersaturation govern the F− values in groundwater. This finding is well supported by the results of the dissolution experiment of rock samples, where powered samples (