A study on the hydrogeochemical mechanisms controlling groundwater fluoride enrichment in Jaipur: a semi-arid terrain in India

ABSTRACT

The main objective of this research paper was to find out the major governing factors controlling fluoride enrichment in groundwater resources in the Jaipur region of India. Chemical analysis of collected water samples revealed that 36% of the collected groundwater samples exhibit fluoride concentration of more than 1.5 mg/L as per BIS, 10,500 and WHO, 2017. An attempt has been made to discuss occurrence of fluoride alongside its spatial distribution in the study area with respect to geology and groundwater flow direction. Chloroalkaline indices, Gibb’s plot, Piper diagram and various inter-ionic bivariant plots have been applied to recognize hydrochemical processes and dissolution trends resulting in high concentration of fluoride in groundwater. There exist five water types in the study area: Ca-HCO₃, Na-HCO₃, Na-Cl, Ca-Mg-Cl and Ca-Na-HCO₃. Due to ion association of excess Cl⁻ emanating from wastewater, Na-HCO₃ type water finally gets changed as Na-Cl type in aquifer. In the study area, 82% of water samples enriched in F⁻ concentration (>1 ppm) pertain to Na-Cl type. Geochemical modelling confirms that reduced Ca²⁺ ion activity due to oversaturation of calcite with respect to fluorite might have triggered the favourable condition for dissolution of fluoride bearing minerals leading to fluoride enrichment in groundwater. To further assess the extent of natural and anthropogenic processes, the data was subjected to multivariate statistical analysis by performing correlation analysis, principal component analysis and hierarchical cluster analysis.

KEYWORDS:

• Geochemical modelling
• Chloroalkaline indices
• hierarchical cluster analysis
• fluoride enrichment

Acknowledgments

The authors express sincere thanks to CGWB management for the facilities extended towards the publication of this paper. The ideology addressed in this paper, solely belongs to the authors only and not necessarily of their organizations.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data availability statement

Derived data supporting the findings of this study are available from the corresponding author on request. [email protected]