Alterations in electrical resistivity of sandy soil in controlled experiment by infiltration of stillage

Abstract

The sugar and alcohol sector represents one of the most profitable economic activities in Brazil, being ethanol one of the main products. Among the residues related to the production of ethanol, it is highlighted the stillage, a liquid substance generated in the approximate proportion of 13 liters for each liter of ethanol produced. This paper presents the results of a stillage infiltration experiment, in various proportions, through trenches in sandy soil, with the aim to evaluate possible alterations in electrical properties in the geological materials, in individual experiments, with 60L, 300L and 900L of effluent. The initial proportion was defined based on a standard stipulated by the Environmental Agency of the State of São Paulo, which considers the cation exchange capacity of the soil, while the other quantities were defined from ratios of 4 and 15 times higher than those defined by legislation. The experiment was monitored by means of electrical resistivity measurements by indirect means through the geophysical method of Electroresistivity. The data indicate the absence of alterations in electrical properties in the soil below the point of infiltration in the experiment for 60L of stillage. The data for infiltrations with 300L and 900L revealed a zone of low resistivity below the infiltration point, basically limited to the 1m layer of sandy soil and with tendency for lateral flow supported by the soil/rock interface. The results demonstrate that the infiltration of inorganic solutions, in a proportion inferior to the cation exchange capacity of the soil, does not perceptibly alter its electrical properties in studies using the geophysical method of Electro resistivity, whereas proportions that exceed natural absorption capacity are characterized by the geoelectric signature of low resistivity.