INVESTIGADORES
GOMEZ Maria Laura
congresos y reuniones científicas
Título:
Behaviour of arsenic in groundwater in a loessical aquifer. Córdoba, Argentine
Autor/es:
GOMEZ, MARÍA LAURA; BLARASIN, MONICA; MARTÍNEZ, DANIEL EMILIO
Lugar:
México
Reunión:
Congreso; Natural Arsenic in groundwater of Latin America; 2006
Institución organizadora:
Bundschuc et al.
Resumen:
In the South of Córdoba province a lot of
people, in rural and even in urban areas, are
drinking non apt water (with high tenor of
As, F, nitrates, and others), because they do
not know the aptitude for human
consumption and the consequences on
health. Groundwater from Coronel Moldes
city and surrounding rural areas, presents
problems with arsenic contamination. The
objective of the investigation was to
establish the geochemical conditions
associated with the presence of As in the
unconfined aquifer, which is used for all the
human activities. The sediments that
constitute the unconfined aquifer involve
aeolian silts and very fine sands (loess). The
loess deposits also contain abundant
secondary carbonate in the form of discrete
layers, concretions and disseminated grains.
The geochemical composition of
groundwater varies between sodiumbicarbonate
to sodium-chloride, resulting in
3% of the samples being brackish and the
remaining 97% fresh. The typical pHs are
near neutral to alkaline (7.3-8.8). High levels
of fluoride were also detected (up to 12
mg/l) which show a strong correlation with
As concentrations (R2= 0.84). Nitrate
concentrations reach up to 200 mg/l,
demonstrating the oxidizing aquifer
conditions. The concentrations of As in the
aquifer vary from 0 to 250 ug/l, with the
higher concentrations of As (>200 mg/l)
corresponding to the sodium-bicarbonate
waters and the highest pHs. A good
correlation between F- and Na/Ca was found.
A clear spatial pattern of As have not been
found and correlations with sampling depth,
flow direction, total dissolved solids and
with the unsaturated thickness were not
found, this could be due to local scale
lithological heterogeneities. It is assumed,
therefore, that the texture and composition of
the loess, low permeabilities and hydraulic
gradients, and geochemical groundwater
characteristics are conditions that favor the
mobilization of As and F- in the studied
aquifer, although the highest values are
associated with a sodium-bicarbonate
chemistry with higher pHs. The results were
very useful for the determination of new
potential areas to be explored for
groundwater abstraction.2= 0.84). Nitrate
concentrations reach up to 200 mg/l,
demonstrating the oxidizing aquifer
conditions. The concentrations of As in the
aquifer vary from 0 to 250 ug/l, with the
higher concentrations of As (>200 mg/l)
corresponding to the sodium-bicarbonate
waters and the highest pHs. A good
correlation between F- and Na/Ca was found.
A clear spatial pattern of As have not been
found and correlations with sampling depth,
flow direction, total dissolved solids and
with the unsaturated thickness were not
found, this could be due to local scale
lithological heterogeneities. It is assumed,
therefore, that the texture and composition of
the loess, low permeabilities and hydraulic
gradients, and geochemical groundwater
characteristics are conditions that favor the
mobilization of As and F- in the studied
aquifer, although the highest values are
associated with a sodium-bicarbonate
chemistry with higher pHs. The results were
very useful for the determination of new
potential areas to be explored for
groundwater abstraction.- and Na/Ca was found.
A clear spatial pattern of As have not been
found and correlations with sampling depth,
flow direction, total dissolved solids and
with the unsaturated thickness were not
found, this could be due to local scale
lithological heterogeneities. It is assumed,
therefore, that the texture and composition of
the loess, low permeabilities and hydraulic
gradients, and geochemical groundwater
characteristics are conditions that favor the
mobilization of As and F- in the studied
aquifer, although the highest values are
associated with a sodium-bicarbonate
chemistry with higher pHs. The results were
very useful for the determination of new
potential areas to be explored for
groundwater abstraction.- in the studied
aquifer, although the highest values are
associated with a sodium-bicarbonate
chemistry with higher pHs. The results were
very useful for the determination of new
potential areas to be explored for
groundwater abstraction.