# Water Modification by Cold Plasma Jet with Respect to Physical and Chemical Properties
## Appendix A
Through this simple modification to the configurations, the spatiotemporal characteristics of the discharge were significantly affected which, in turn, affected the composition of the generated plasma activated water. Colorimetric testing of the plasma activated water generated from each system revealed that only one configuration was able to generate plasma activated water with a high concentration of H\({}_{2}\)O\({}_{2}\). Using time-, space-, and wavelength-resolved imaging of excited plasma species [OH, N\({}_{2}\)(SPS), N\({}_{2}^{+}\)(FNS), and atomic O], the differences in plasma activated water composition were linked to the differences observed in the discharge dynamics between the two configurations. [PERSON] and [PERSON] [58] studied the effect of process parameters, viz., air flow rate, water stirrer speed, and the temperature of water during plasma-water interaction on the reactivity and electrical conductivity of plasma activated water using a three-way full factorial design of experiments. They also attempted to optimize these process parameters. At optimum values of these parameters, they studied how the physicochemical properties of the plasma activated water vary by changing the volume of water and discharge power. Furthermore, they studied the physicochemical properties of the plasma-activated solution and how the electrical conductivity and pH of virgin solutions affect these properties. The obtained results showed that the flow rate of air, plasma treatment time with water, volume of water, and plasma discharge power, play a significant role in controlling the reactivity and electrical conductivity of plasma activated water. Moreover, the pH and electrical conductivity of virgin solution do not have a significant (\(p<0.05\)) impact on the reactivity of plasma activated solution. This investigation also showed the effect of the aging time on the reactive oxygen-nitrogen species and the physicochemical properties of plasma activated water. The observed changes in physicochemical properties, and NO\({}_{3}^{-}\) ion and H\({}_{2}\)O\({}_{2}\) concentrations in the plasma activated water were less than 10%. However, NO\({}_{2}^{-}\) ions and dissolved O\({}_{3}\) concentration in the plasma activated water decreased significantly over time. [PERSON] et al. [69] mentioned that there are three major multi-electron reactions in nature: nitrogen fixation by bacteria, water oxidation in photosynthesis, and oxygen reduction during respiration, whereas they found that a cold atmospheric pressure He-plasma jet can oxidize N\({}_{2}\) to HNO\({}_{3}\) and HNO\({}_{2}\) at low temperature and atmospheric pressure at the plasma-air-water interface. Redox reactions induced by cold plasma occurred not only at the plasma-air and plasma-water interfaces, but also in the volume of the aqueous phase. Analysis of the images which displayed the presence of pH indicators in the aqueous phase showed that redox reactions and acid formation occur at the plasma-air-water interface and the products of electrochemical reactions slowly diffuse into the bulk of the aqueous solution. Acidification of an aqueous solution during the plasma treatment was correlated with an increase in HNO\({}_{x}\) concentration in the aqueous phase. HNO\({}_{2}\) was found to be unstable and could be oxidized to HNO\({}_{3}\) by plasma generated H\({}_{2}\)O\({}_{2}\) or ozone. It was suggested that the plasma induced production of HNO\({}_{x}\) at the plasma-water interface at room temperature and atmospheric pressure can be used in the industry for nitrogen fixation and production of nitrogen compounds, replacing the expensive old technology processes. [PERSON] et al. [70] worked towards the control of the plasma activated water chemical composition. To achieve this aim, a UV spectrophotometric method (190-255 nm) was implemented to simultaneously detect the nitrate and nitrite ions in plasma activated water by a gliding arc discharge reactor at atmospheric pressure.