Analysis of arsenic pollution in groundwater aquifers by X-ray fluorescence

The serious contamination of groundwater in the southeastern plain of the province of Córdoba (Argentina), a phenomenon mentioned in the literature for over 80 years, has given rise to this initial hydrologic study covering an area over 250 km2. This study analyzes a rural area near a little town called La Francia, and is motivated by the existence of an important pollution with arsenic in the first-aquifer groundwater of the region. This phenomenon has been mentioned for a long time and evidenced by the high incidence of diseases associated with this element in the local population. By means of the X-ray fluorescence (XRF) technique, and using an energy-dispersive spectrometer, 50 samples of groundwater of the rural zone of La Francia from about 100 m deep (second aquifer), were analyzed. The samples were excited with a 3 kW X-ray tube and measured using a reflecting geometry with 45° of incident and take-off directions. Preconcentration techniques for the preparation of the samples were employed in order to obtain an adequate signal-to-noise ratio. The As concentration in water was obtained using calibration curves and the internal standard method for quantification. A high percentage of the analyzed samples showed concentrations lesser than or equal to 0.05 mg l−1. This value corresponds to the maximum pollutant level for humans. The maximum measured value reaches 3 mg l−1 in samples collected in perforations of first-aquifer wells and in some second-aquifer isolated wells.