Activation of Aqueous Solutions Using a Multi-Spark Ring Discharge with Gas Injection in the Discharge Gap

The paper presents the results of studies of the formation of reactive oxygen and nitrogen species in Milli-Q® deionized water (electrical conductivity of ≤0.1 µS/cm) under the influence of a multi-spark pulse discharge with gas injection into the interelectrode space. The discharge is a set of microplasma formations in a multiphase medium, for which the specific energy input is estimated. The influence of injected gases (argon, air) on the formation of a plasma discharge in the interelectrode space and long-lived chemical compounds: hydrogen peroxide, nitrite ions and nitrate ions is analyzed. The variation of the exposure duration to water from 2 to 10 min leads to a change in its chemical composition and electrical conductivity properties, but has virtually no effect on the characteristics and duration of the breakdown stage of the discharge. At the same time, changes in the concentrations of hydrogen peroxide, nitrite ions and nitrate ions are recorded within 1 h after the termination of the plasma exposure. Sputtering of stainless steel electrodes is detected, which is about 1 mg/min and leads in some cases to the formation of an insoluble precipitate. The data obtained allow the optimization of the effect of plasma-activated liquid on plants and planting material.