Liquid spray transport of air-plasma-generated reactive species toward plant disease management

Liquid-phase transport of plasma-generated reactive species toward large-scale plasma treatment for agricultural applications is experimentally studied. The liquid-phase reactive species in this study are generated by the contact of water solution with air-plasma effluent gas containing mainly low-solubility reactive species under elevated pressure, followed by spraying the plasma effluent gas dissolved solution into a target pathogenic conidium suspension. Low-solubility ozone in the liquid phase at the target is found to dominate the observed germination suppression effect, which also correlates with the gas-phase ozone density. The measured ozone concentration at the target is found to be ten times lower than the ozone concentration at saturation, estimated from Henry's law with the measured gas-phase ozone density. The liquid-phase ozone loss mechanism during the transport of the sprayed liquid is interpreted as volatilization and reactions with co-dissolved species. The deduced control parameters for precise ozone transport are the droplet diameter of the sprayed solution, sprayed jet flow, and co-dissolved reactant with the liquid-phase ozone such as nitrite.