Discharge model for piled soil media under negative DC voltage

Corona discharge plasma is a promising technology for soil remediation, butt the underlying discharge mechanisms within complex piled soil media remain poorly understood. This study establishes a physical model for corona discharge in piled soil particles under negative DC voltage using a pin-plate electrode configuration. First, the charging behaviour of individual soil particles is analysed to reveal the local electric field distortion induced by mutual particle interactions. Subsequently, by integrating Townsend discharge theory with species transport equations, a theoretical criterion for corona inception and discharge range in inter-particle micro-gaps is derived. To validate the model, experiments were conducted to capture discharge images and measure key parameters across varying voltages and bulk densities. Results demonstrate that the model accurately predicts the discharge characteristics, with the calculated corona inception voltage aligning well with experimental observations. This work transitions soil remediation research from empirical optimization to mechanism-based design, providing a theoretical foundation for the engineering scale-up of plasma-based soil treatment systems.