Tillämpbarheten av en helikopterburen transient elektormagnetisk metod för att avgränsa deponier. En fallstudie av torpadeponin

Abstract

A comprehensive national compilation of closed landfills in Sweden is missing. The total amount of landfill sites is estimated to be several thousands. The geographical extension of these landfills is often unknown, and they can affect their environment even if they have been closed for many years. This study investigates the possibility to use airborne transient electromagnetic surveys to delineate landfills. To test its applicability as a delineation method for landfills, traditional ground-based geophysical investigations were carried out at Torpa landfill in Trollhättan municipality. Resistivity and induced polarization were measured to enable the comparison to airborne transient electromagnetics, laboratory analyses and archive studies. This study considered the resolution of the airborne survey to be too low to delineate the Torpa landfill, because of the size of the landfill and the stratigraphy of the soil in the area. However, a plume of leachate water from the landfill can be seen with the airborne survey, but since the resistivity of the water overlaps the resistivity of the surrounding clay, is it hard to distinguish them from each other. Furthermore, analyses of the leachate water show that the concentrations of metals and contaminates are generally low. To see a landfill with airborne transient electromagnetics, a larger landfill is required, or a landfill where both the deposited waste and leachate water shows a large contrast in resistivity from its surroundings. Further alternatives are to decrease the size of the measuring instrument to enable registration of small structures.