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.
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