Effect of Humidity on Air Discharge and Reactive Nitrogen Oxides (RONS) in the DC Negative Corona of Needle-Plate Electrode

In this study, a chemical reaction system of air plasma containing water molecules is established to explore the effects of air humidity on air discharge and reactive nitrogen oxides (RONS) in the DC negative corona of a needle-plate electrode. The system comprises 22 species and 49 chemical reactions. Simulation results reveal that increased air humidity reduces the current amplitude and significantly raises the current pulse frequency. Above the lower polar plate, the densities of the three RONS (O3, H2O2, and NO) exhibit approximately uniform distribution, with air humidity increases causing slight decreases in their densities. For instance, the ozone density decreases from <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.95 \times 10^{\wedge} 10 \mathrm{m}^{-3}$</tex> at 40 % humidity to <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1.85 \times 10^{\wedge} 10 \mathrm{m}^{-3}$</tex> at 80 % humidity. This study offers theoretical support for seed treatment using corona discharge plasma, contributing to more efficient energy use and environmental protection. Future work will focus on investigating the combined effects of humidity and other environmental factors on the discharge process and RONS generation, as well as exploring the specific mechanisms of how RONS promote seed germination and growth.