Ra Ximhai (Sep 2012)
Design and implementation of equipment for monitoring the salinity in the subsoil
Abstract
Geochemical exploration equipments to explore the contaminants and structures geological in the subsoil come from abroad are expensive and sometimes parts for replacement are not available in the market. So it is necessary design apparatus that meet cover these needs. To the monitoring of variations in salinity there is semi-automatic equipment, but it always has difficult to manage. However, is not equipment for the indirect study of salinity in the subsoil. In this work was design equipment for measurement the apparent resistivity in the subsoil, at same time allow know the salinity, as well as the detection of any pollutant in groundwater. For make it, was selected a design of earthing systems, with electronic hardware which were jointed for apply to subsoil a direct current (DC) through an array dipole-dipole and vertical electric sounding, with brass and stainless steel electrodes. In the earthing systems the electrodes were collocated in the equidistant line between the detectors of potential and current. A geometric factor (K), that depend on theelectrodes distance and direct current (I) injected in the electrodes A and B, was used for measure the potential difference between the electrodes M and N; after was calculate the resistivity point to point for obtain a subsoil tomography geoelectrical. The equipment was calibrated with minimum error (rms < 2%) whit respect to curves obtained in similar commercial equipment. On this situation, in this work was modernized and automated an equipment to determine thesalinity of the subsoil. The instrument was tasted in the micro basin Texcoco, State of Mexico, to define the environment geometry formed by alluvial or lake sediments from igneous rocks (andesites, rhyolites and tuffs vitreous or “tepetates”) which by its mineralogical composition allowed to the lateral resistivity be associate with free components trace from the aquifer: Cd, Cu, Cr, Co, Ni, Pb or Zn and others. This method constitutes an advance in studies of environmental impact, especially for the monitoring of sites where the subsoil are in process of recovery.
