Plasma discharge characteristics and reactive species evolution in dielectric barrier discharge soil reactors

Soil particles are used as medium spheres in a fixed packed bed to perform numerical simulation calculations of the plasma discharge process in soil particle gaps. In a dielectric barrier discharge (DBD) reactor using helium as the discharge gas, the effects of soil particle arrangement, discharge spacing, and soil particle dielectric constant on the electric field strength and electron density in the interstitial spaces between particles were investigated. The results showed that under uniform particle arrangement, the electric field distributed more uniformly in the interstitial spaces, but under non-uniform arrangement, the discharge effect was more pronounced. Increasing the distance between discharge electrodes weakens the polarization effect between soil particles, making discharge more difficult to occur. Soil particles with high dielectric constants enhance local electric fields, and differences in dielectric constant values affect the generation and propagation of plasma. In a DBD reactor using air as the discharge gas, the temporal evolution of plasma substance concentrations during discharge was investigated, and the types and quantities of active particles entering the soil region were determined. The results indicate that the concentration of excited-state active particles, as intermediate products, rapidly decays during the discharge process. The primary active particles entering the soil domain and participating in reactions are long-lived active particles such as O₃. The tripartite reaction is the main pathway for O₃ generation. The reaction rates of the main gas-phase reactions involving O₃ were analyzed, along with the production and consumption pathways of key gas-phase particles involved in ozone synthesis.