INSTITUTO ARGENTINO DE NIVOLOGIA, GLACIOLOGIA Y CIENCIAS AMBIENTALES
Unidad Ejecutora - UE
capítulos de libros
Fluoride content in central and southeast Argentinean groundwaters
GOMEZ, MARÍA LAURA; QUIRÓZ LONDOÑO, MAURICIO
Fluoride: Properties, Applications and Environmental Management
Nova Science Publishers, Inc.
Lugar: Hauppauge, New York; Año: 2010; p. 1 - 12
Naturally occurring fluoride in groundwater is an important aspect in the central and southeast sector of Argentine. Former investigations have demonstrated that volcanic glass dissolution disseminated in the loess-like sediments is the main source of fluoride in the Argentine pampas. Nevertheless groundwater fluoride distribution is erratic and the controlling factors of it are not well known. Rural and urban activities in these zones rely exclusively on the exploitation of groundwater and in many cases it is the only source of drinking water. For these reasons, fluoride content in groundwater is a sanitary problem which needs special attention since several fluorosis cases have been detected in Córdoba Province. The aim of this study is to analyze the geochemical conditions associated with the presence of fluoride (F) in the phreatic aquifer in three areas in the central and southeast sectors of the Argentine Chacopampean plain. Two study areas are located in the south of Córdoba province, involving 1,040 km2. Aquifers in these zones are mainly composed of silty sand sediments of aeolian origin, typically loess-like sediments of Holocene, and are situated near igneous-metamorphic basement rocks of the Paleozoic. The other study area is located in the north west of the inter-mountainous plain at Buenos Aires province, involving more that 2,760 km2. It extends between two low hills ranges of Precambrian metamorphic rocks and sedimentary Paleozoic rocks, and it is filled by a thick sequence of Cenozoic sediments, mainly silts and silty-clayed, with sand layers intercalated. High concentrations of F (0 - 18 mg.l-1) in groundwater were detected in the three study areas. More than 80 % of domestic wells exceed the drinking water limit of Argentine Law (1.3 mg.l-1). Hydrogeochemical data indicates a high relationship between sodium bicarbonate waters and the highest pH values. There was a high correlation between F- and As(Total), and F- and Na+/Ca+2 ratio. Saturation indexes indicate that dissolution are the main processes that control F contents. Fluorite saturation index showed that fluorite saturation is reached just in few samples. In some areas F- distribution appears to be mainly controlled by a general salinity increase and the proximity of Paleozoic rocks containing minerals with F- contents. Sediment compositions and hydrogeochemical conditions are the main factors in determining the F concentration. The composition and texture of loess, low permeability and hydraulic gradients, mineralogical composition of the basement rocks together with sodium bicarbonate watertypes are proper conditions for fluoride mobilization in groundwater in central and east sectors of Argentina.