Experimental study of domestic waste material using magnetic resonance measurements
Résumé
In this paper, we present results of a laboratory and in situ study of a domestic waste landfill using magnetic resonance measurements. For our study, we used a laboratory Earth's field nuclear magnetic resonance (NMR) instrument developed at LTHE and a large-scale commercial magnetic resonance sounding (MRS) system NUMISLITE from IRIS Instruments. We show that NMR could be a tool for investigating different processes in water-saturated waste samples. Our results show that domestic waste material contains ferromagnetic or paramagnetic particles that perturb the homogeneity of the geomagnetic field at a microscopic scale and render an NMR signal short. Consequently, only the spin echo technique can be applied for measuring. At a macroscopic scale, waste and different buried objects may also perturb the natural geomagnetic field. While investigating the landfill, we observed that magnetic anomalies (±2500 nT) are localized around some cells. This is probably linked to the presence of a higher percentage of metallic objects within the waste disposal. Our first appraisal of the possibility of investigating water-saturated waste in a laboratory using an Earth's field NMR instrument shows that, with existing instruments, waste samples can be studied when the dry density of waste is less than approximately 450 kg/m3. Because the relaxation times of magnetic resonance signals in landfill may be short (T2 < 100 ms and T2*<10 ms), existing large-scale MRS instrumentation is not adapted to the investigation of domestic waste landfills.