Monitoring of wastewater percolation in unsaturated sandy soil using geoelectrical measurements at Gabal el Asfar farm,northeast Cairo,Egypt |
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Authors: | Khaled M Said Gemail |
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Institution: | (1) Present address: Department of Geology, Faculty of Science, Zagazig University, Zagazig, Egypt;(2) Geological Sciences Department, Saskatchewan University, 114 Science place, Saskatoon, SK, S7N 2E5, Canada |
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Abstract: | The use of wastewater for irrigation in sandy soil increases the pollution risk of the soil and may infiltrate to the shallow
groundwater aquifer. In such environment, some important parameters need to be obtained for monitoring the wastewater in the
unsaturated zone over the aquifer. These parameters include clay content, heterogeneities of the upper soils, depth to the
aquifer and the variations of groundwater quality. In the present work, the efficiency of DC resistivity method in forms of
1-D and 2-D measurements was studied for wastewater monitoring in the Gabal el Asfar farm, northeast of Cairo, Egypt. Forty-one
Schlumberger soundings (VES) were performed then followed by three pole-dipole 2-D profiles along some considered regions
within the area. The resistivity measurements were integrated with the boreholes, hydrogeological and hydrochemical (surface
and groundwater samples) information to draw a clear picture for the subsurface conditions. The obtained results were presented
as cross sections and 3-D visualization to trace the clay intercalations within the unsaturated zone. In addition, a vulnerability
map was created using the obtained results from 1-D Schlumberger survey and confirmed with the 2-D resistivity profiling.
The obtained results have shown that the 2-D resistivity imaging technique is a powerful tool for mapping the small-scale
variability within the unsaturated zone and the wastewater infiltration. However, limitations of resistivity techniques were
observed in the area with limited resistivity contrast such as thin clay layers with brackish water background. Under that
condition, the measured pattern of resistivity distributions depends on the applied electrode array, electrode spacing and
using the available geological information during the inversion process. |
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Keywords: | |
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