INVESTIGADORES
GOMEZ Maria Laura
capítulos de libros
Título:
Fluoride content in central and southeast Argentinean groundwaters
Autor/es:
GOMEZ, MARÍA LAURA; QUIRÓZ LONDOÑO, MAURICIO
Libro:
Fluoride: Properties, Applications and Environmental Management
Editorial:
Nova Science Publishers, Inc.
Referencias:
Lugar: Hauppauge, New York; Año: 2010; p. 1 - 12
Resumen:
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.