ماهى نسبة الفلور في المياه الجوفية ؟
Fluoride naturally occurring in water can be above, at, or below recommended levels. Rivers and lakes generally contain fluoride levels less than 0.5 mg/L, but groundwater, particularly in volcanic or mountainous areas, can contain as much as 50 mg/L. Higher concentrations of fluorine are found in alkaline volcanic, hydrothermal, sedimentary, and other rocks derived from highly evolved magmas and hydrothermal solutions, and this fluorine dissolves into nearby water as fluoride. In most drinking waters, over 95% of total fluoride is the F<sup>−</sup> ion, with the magnesium–fluoride complex (MgF<sup>+</sup>) being the next most common. Because fluoride levels in water are usually controlled by the solubility of fluorite (CaF), high natural fluoride levels are associated with calcium-deficient, alkaline, and soft waters. Defluoridation is needed when the naturally occurring fluoride level exceeds recommended limits. It can be accomplished by percolating water through granular beds of activated alumina, bone meal, bone char, or tricalcium phosphate; by coagulation with alum; or by precipitation with lime.
50 mg/L