Fluoride-bearing groundwater in Gummanampadu Sub-basin, Guntur District, Andhra Pradesh, India
2013
Subba Rao, N. | Subrahmanyam, A. | Babu Rao, G.
The functional factors responsible for fluoride (F⁻)-bearing groundwater used for drinking as well as for cooking in the area of Gummanampadu Sub-basin, Guntur District, Andhra Pradesh, India are discussed. The study area is a part of an Archean Gneissic Complex, consisting of banded-biotite-hornblende-gneisses, over which the Proterozoic Cumbhum quartzites, shales, phyllites, and dolomitic limestones occur. The chemistry of groundwater is dominated by carbonates (HCO₃⁻and CO₃²⁻) at a higher pH. This results in a higher total alkalinity over total hardness, causing an excess alkalinity. Sodium ion is dominated among the cations (Ca²⁺, Mg²⁺, and K⁺). The concentration of F⁻(2.1–3.7 mg/L) is higher than that of desirable national limit (1.2 mg/L) prescribed for drinking purpose. A significant positive correlation exists between F⁻and pH as well as that between F⁻and HCO₃⁻ + CO₃²⁻. This indicates that the alkaline condition is the prime conducive factor for dissolving F⁻-bearing minerals more effectively leading to a higher concentration of F⁻in the groundwater. Furthermore, a positive chloro-alkaline index reflects the ion exchange, and an oversaturation with respect to CaCO₃indicates the evaporation. In addition, a negative relation between the well depth and F⁻shows the effect of solubility and/or leaching of salts in different depth levels. These factors regulate the concentration of F⁻in the groundwater. On the other hand, a positive correlation of F⁻with SO₄²⁻as well as with K⁺shows the human land use activities (namely, use of chemical fertilizers, disposal of domestic wastes, etc.), which add F⁻to the groundwater. A significant number of the residents of the study area suffer from the health disorders related to fluorosis, which is a consequence of higher concentration of F⁻in the drinking water. Thus, this study emphasizes the need for supply of safe drinking water, nutritional diet, rainwater-harvesting structures, and public education to realize “health for all” motto of World Health Organization.
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