Factors influencing natural and anthropogenic occurrences of Fluoride rich agriculture wells and related dental fluorosis: a case study in southern Fars province, Iran

The study areas is located in Fars province (Khir,Ghir, Lamerd,Lar) Factors regulating the occurrence of fluoride in groundwater were investigated using Mineral Chemistry of geological formation (EMPA) and hydro geochemical data (UV/VIS MS). The F-rich Agricultural wells are mostly distributed along the major faults, especially in the terrain of the F-rich Evaporative rocks (Gachsaran Formation). The wide range of fluoride in water result of water-rock interaction that could be the main factor for fluoride concentration as natural source. The data obtain from analysis indicate that the variation of fluoride was 0.1 to 1.88 ppm an average of 0.67ppm for southern part of Fars province such as Ghir and Karzin (Max. 1.84 ppm), Larestan (Max. 1.88 ppm), and Khir near Estahban (Max. 1.9 ppm) .There was no correlation between pH and fluoride content of water samples. Seventy percent of water samples contain fluoride less than recommended level WHO, but fluoride content of thirty percent equaled or exceeded the recommended level. The most contaminated sites located near Persian Gulf or dry lakes. Reports also show dental fluorosis prevalence up to 67% in some regions of Fars such as Larestan region. The mineral chemistry analysis results provide substantial information for the relative mineral origin of fluoride as Hydroxyl carbonate (Ca,La,Ce) (Co3) ( OH, F, Cl) and apatite Ca5 (Po4)3 (F ,Cl , OH) in calcic – dolomite and Gypsum marl in Mol member.So latest study in these parts of province suggest that fluoride concentration raise dramatically in last 20 years result of water table changing by anthropogenic sources. Leaching of fluoride from surrounding rocks, evapotranspiration, longer contact time of water and the aquifer material, as well as high pH, HCO3 and SO4 are major parameters affecting fluoride concentration in groundwater.Fars province in middle south of Iran experiencing water table dropping very quickly, as people drain aquifers for agriculture use for these decays , So aquifer depletion process one the most important factor of increasing fluoride concentration in ground water beside water-rock interaction previously known as the only factor. Know, Dental fluorosis appear again in kids and nomads that still use of F-rich water wells especially in those affect with Amelogenesis imperfect. The results of this investigation suggest a link between the high fluoride groundwater as the only available source of drinking water, and the observed endemic dental fluorosis in the regions.