A review of geomagnetic noise sources and denoising methods for landfill sites

Landfills are the primary means of centralized solid waste disposal, and it is also the place where the environmental impact of solid wastes on groundwater is concentrated. The leakage of HDPE membrane of the impermeable layer is the main way to lead to groundwater pollution. It is of great significance to carry out the rapid detection and accurate positioning of the leakage of the impermeable layer. The traditional electrical leakage method is difficult to detect the damage of the lower liner of the double-layer or multilayer liner system. The improved electromagnetic method based on the traditional electrical method shows the potential of detecting the lower liner. However, it is urgent to solve the problem of electromagnetic noise interference in the complex service and human environment of the landfill site and the earth's magnetic field environment. The in-depth analysis of the magnetic detection principle and signal characteristics, as well as the overview of the background magnetic noise types, sources, characteristics and electromagnetic noise denoising methods, was thus performed. It is concluded that under specific conditions, the closer the loophole is, the stronger its magnetic field signal is; the landfill noise is mainly derived from the geomagnetic and humanities magnetic fields, and different noises have different characteristics and require different processing; the denoising process is first pre-processed to exclude interference, followed by the selection of appropriate filtering or measurement method to remove noise in the detection.