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Fluoride in Groundwater, Its Variation with Seasons and Relationship with Other Water Quality Parameters in Rangareddy District of Telangana, India

Fluorine, which occurs naturally as fluoride in the earth’s crust in small amounts, is essential to humans and animals and is known to stimulate plant growth when present in small concentrations. However, higher concentrations of fluoride in drinking water cause dental and skeletal fluorosis in animals and humans and when present in high concentrations in groundwater used for irrigation, it accumulates in the plants and the soil and causes undesirable effects. A study was carried out during kharif, 2015 and rabi season of 2015-16 in Talakondapalle Mandal of Rangareddy District, Telangana state, India, to measure and map the distribution of fluoride in groundwater in borewells used for irrigation, to observe seasonal variation in fluoride content and to examine the relationship of fluoride with other water quality parameters such as pH, EC, Cl-1, CO3-, HCO3-, SO4-2, Ca+2, Mg+2, Na+, K+, RSC and SAR. Fluoride in groundwater ranged between 0.72 to 4.50 ppm with a mean of 2.84 ppm and standard deviation of 1.30 ppm in kharif season and from 1.32 to 4.92 ppm with a mean of 3.29 ppm and standard deviation of 0.24 ppm in rabi season. Except for two borewells in kharif, fluoride concentration was higher than the permissible limit of 1 ppm. Groundwater fluoride map of the study area was generated using kriging technique. Fluoride concentration was higher in all the borewells in rabi over kharif with mean fluoride concentration being 15.8% higher in rabi season. Fluoride concentration was significantly positively correlated with pH, HCO3-, Na+, SAR and RSC of ground water and significantly negatively correlated with Ca+2.