Electrical resistivity methods to characterize the moisture content in Brazilian sanitary landfill

The moisture content of the municipal solid waste (MSW) is a physical characteristic that plays a fundamental role in the stability and settlement of landfills. However, this physical index is difficult to monitor within the mass of landfilled MSW because it undergoes great variation due, mainly, to the heterogeneity and biodegradation of the waste. Brazilian MSW generally has a large amount of organic matter, that when biodegraded, generates a considerable volume of gases and fluids, aggravated by climatic conditions, such as high rainfall and temperatures. Hence, the importance of obtaining and evaluating the distribution of moisture content in the MSW mass over time. Currently, the electrical resistivity properties have been presented as an interesting approach to obtain the moisture content in landfills indirectly. This study aimed to apply geoelectrical methods as a tool to obtain and evaluate the moisture content distribution in an experimental cell of a sanitary landfill using Archie's law, which correlates the volumetric moisture content and electrical resistivity. Moisture content values were obtained in laboratory tests with MSW samples collected in two vertical holes and electrical resistivity measurements by means of vertical electrical sounding. The moisture content and the resistivity values of the samples were used to calculate the parameters a and m of Archie's law. This allowed to convert the resistivity tomography to moisture content tomography. The good correlation achieved between the moisture content calculated by Archie's law and that obtained from samples indicates that the use of electrical resistivity methods is useful to assess and monitor quantitatively the moisture content in landfills using Archie's law.