Optimization of pinhole plasma jet for reactive nitrogen species generation in Plasma-Activated water and its application in microgreen cultivation

Abstract

PAW is considered a novel replacement of nitrogen fertilizers for sustainable agriculture. The process optimization for a pinhole plasma jet system (i.e., air flow rate and discharge time) to produce PAW with high reactive nitrogen species content and its application in microgreen production was investigated using response surface methodology. According to optimal conditions (i.e., an air flow rate of 5.0 L/min and a discharge time of 240 min), the highest NO₃^– (668.16 mg/L) and NO₂^– (60.59 mg/L) were obtained. Broccoli and radish microgreens treated with optimized PAW show higher growth attributes, such as germination percentage and fresh weight, compared to the control treatment. Additionally, the total protein content of both microgreens was significantly increased under optimal PAW, whereas no significant effects were exhibited in total phenolic compounds and antioxidant capacity. The stability of properties of the optimized PAW over 30 days of storage was determined, which is critical for preserving its effectiveness. This study confirms the ability of pinhole plasma jet technology to produce PAW with improved RNS components, as well as the efficacy of PAW in microgreen growing, taking a step towards its broader use in sustainable agriculture.