Environ Monit Assess (2011) 176:637–645 DOI 10.1007/s10661-010-1609-y High-fluoride groundwater N. Subba Rao Received: 10 March 2010 / Accepted: 9 July 2010 / Published online: 30 July 2010 © Springer Science+Business Media B.V. 2010 Abstract Fluoride (F − ) is essential for normal bone growth, but its higher concentration in the drinking water poses great health problems and fluorosis is common in many parts of India. The present paper deals with the aim of establishment of facts of the chemical characteristics respon- sible for the higher concentration of F − in the groundwater, after understanding the chemical behavior of F − in relation to pH, total alkalinity (TA), total hardness (TH), carbonate hardness (CH), non-carbonate hardness (NCH), and ex- cess alkalinity (EA) in the groundwater observed from the known areas of endemic fluorosis zones of Andhra Pradesh that have abundant sources of F − -bearing minerals of the Precambrians. The chemical data of the groundwater shows that the pH increases with increase F − ; the concentration of TH is more than the concentration of TA at low F − groundwater, the resulting water is rep- resented by NCH; the TH has less concentration compared to TA at high F − groundwater, caus- ing the water that is characterized by EA; and the water of both low and high concentrations of F − has CH. As a result, the F − has a positive N. Subba Rao (B ) Department of Geology, Andhra University, Visakhapatnam 530 003, India e-mail: srnandipati@rediffmail.com relation with pH and TA, and a negative rela- tion with TH. The operating mechanism derived from these observations is that the F − is released from the source into the groundwater by geo- chemical reactions and that the groundwater in its flowpath is subjected to evapotranspiration due to the influence of dry climate, which accelerates a precipitation of CaCO 3 and a reduction of TH, and thereby a dissolution of F − . Furthermore, the EA in the water activates the alkalinity in the areas of alkaline soils, leading to enrichment of F − . Therefore, the alkaline condition, with high pH and EA, and low TH, is a more conducive environment for the higher concentration of F − in the groundwater. Keywords Groundwater · Alkaline environment · Fluoride · Precambrian terrain Introduction India has two acute health problems due to the influence of higher concentrations of fluoride (F − ) and arsenic (As) in the drinking water. The health problems, arising as a result of F − -contamination, are far more widespread than those of As- contamination in India (Muralidharan et al. 2002). The ever-increasing demand for groundwater cou- pled with lack of assessment of its quality for