Air Plasma Generation with an Electrically Conductive Liquid Column Jet*

For the plasma agricultural application, a liquid jet spray through an air plasma has been developed. An electrically conductive water solution jet with KNO$_{\mathrm{3}}$ is injected into a discharge domain and utilized as the grounded electrode to generate the plasma. This realizes significant power loading to the gas-liquid interface plasma and the plasma exposed liquid column jet collapses into droplets. Liquid phase reactive oxygen and nitrogen species (RONS$_{\mathrm{aq}})$ and the gas phase RONS$_{\mathrm{gas}}$ are experimentally characterized by reagent test kits and FTIR, respectively. The experimental characterization on the OH$_{\mathrm{aq}}$ production indicates that most of OH$_{\mathrm{aq}}$ can be generated near the liquid surface. The gas-liquid interface reactions can be significantly modulated by the liquid flow rate, inferred from the measured gas phase RONS$_{\mathrm{gas}}$ composition. Conidium suspension liquid droplets are sprayed by the plasma exposed solution to evaluate the antibacterial effect of the plasma exposed solution. The generated NO$_{\mathrm{2gas}}$ density founds to be well related to the conidium germination suppression effect under a similar OH$_{\mathrm{aq}}$ generation. Therefore, the gas-liquid interface reactions generating RONS are considered to play an important role on suppressing the conidium germination.