Temporal analysis of soil bioremediation by electrical resistivity
Diesel oil, geophysical method, experimental analysis.
The soil is the oldest and also the most used material in civil construction. Brazil and the other countries, that had a rapid process of urbanization development, face challenges about the "soils health". Different pollutants contaminate the soil, especially oil hydrocarbons. Geophysical methods are an alternative for the detection of contamination plumes, especially electroresistivity. Thus, we aimed to evaluate the relation between the soil resistivity and four factors: contaminant concentration, soil granulometry, water concentration in soil and the time of contaminant presence in the soil. Controlled laboratory experiments were performed in a cylindrical experimental apparatus of PVC and soils in different combinations of factors: i) water concentration (30%, 40% and 50%); ii) different granulometries (<2mm to 0.06mm and <0.06mm) and diesel oil concentrations (0%, 5% and 10%), were stored in hermetically sealed containers for seven months. Two types of variance analysis were used: factorial and paired. Results indicated that the four factors and the interaction between them significantly explain the biodegradation process, indirectly measured by resistivity. This process does not stabilize at seven months and its speed depends on the configuration of the granulometry factors, water and diesel concentration. In most of the scenarios with diesel, there was a drop in the resistivity in the second, third and fourth months, which may indicate the biodegradation beginning of diesel oil. Finally, the method developed in the present research, to evaluate the biodegradation through the soil resistivity, proved to be efficient in the detection of contaminated soil patterns and can be used in future studies of different soils contamination by different contaminants.