FLUORIDES IN THE PHREATIC AQUIFER OF THE LOESS PLAIN, CORDOBA PROVINCE, ARGENTINA

BLARASIN M., ; CABRERA A., ; HILDMAN F., ,; MATTEODA E., ; BÉCHER F. ; GIULIANO J. ; L. MALDONADO

Journal of Environmental Hydrology

The electronic Journal International Association for Environmental

Año: 2011 vol. 19 p. 1 - 10

1058-3912

The natural occurrence of excessive quantities of dissolved fluorides in water has affected people?s health for centuries. The aim of this paper is to assess fluoride contents and the geochemical environment that determines their presence and distribution in the unconfined aquifer in Malena town and its surrounding rural area (Córdoba, Argentina). The area presents two hydrogeologic environments: one composed by loess sediments and another where fluvial and aeolian sediments are interstratified. The F- levels range between 1.53 mg/ L and 8.75 mg/L, the lowest contents being related to paleochannels. The statistical multivariate analysis (cluster and principal components) showed two groups: one is composed of the majority of main ions, with a high correlation nucleus formed by electrical conductivity and Na+, which explains water mineralization. The other group is composed by F--As-pHHCO 3-, which validates the affinity of these two trace elements to high pH, alkaline solutions. The negative high correlation (R -0.82) found between F- and Ca 2+ corroborates that in groundwater with low levels of Ca2+, high concentrations of F- in solution are stable. The results show the geomorphological and lithological control over the dissolved F- levels. The highest levels of F- are related to: textural characteristics of the aquifer in the Aeolian environment (very fine sands-silts) that generate slow groundwater flow; the mineralogy (volcanic glass, amphibole, pyroxene, apatite, all possible fluorine sources); and the bicarbonate sodium groundwater type and high pH of the solution (>7.80). Numerous cases of dental fluorosis were found in children, youngsters, and adults from the study region.