Cold atmospheric microplasma jet-water interactions: physicochemical analysis and growth effects in flowering plants

TL;DR

This study investigates how plasma-activated water generated by a microplasma jet influences plant growth, showing significant improvements in Chrysanthemum saplings' height and soil quality, indicating potential sustainable agricultural applications.

Contribution

It introduces a novel method of producing plasma-activated water using a microplasma jet and demonstrates its positive effects on flowering plant growth, advancing sustainable agriculture techniques.

Findings

PAW increases plant height and soil fertility.

Optimal PAW conditions: 12 ml water, 40 min treatment.

PAW contains higher nitrates and ORP, promoting growth.

Abstract

Cold atmospheric pressure plasma jets (APPJs) are non-equilibrium plasmas, that are capable of producing reactive oxygen and nitrogen species (RONS) at near-room temperature. Their interaction with water leads to the formation of plasma-activated water (PAW), whose chemical activity depends on discharge conditions. In this work, a helium-air (14:1) micro-plasma jet operated in a ring-to-ring electrode configuration is used to generate PAW and study its influence on the growth of Chrysanthemum saplings. Optical emission spectroscopy (OES) confirms the presence of $N_2$ bands and He lines, with the He-air mixture providing more chemically active discharge (in terms of favoring the generation of nitrates in PAW) as compared to pure helium. The physicochemical characteristics of PAW such as pH, electrical conductivity (EC), oxidation-reduction potential (ORP), and total dissolved solids (TDS) are analyzed as a function of plasma treatment time and water volume. The optimum condition for PAW generation is found to be 12 ml of de-ionized (DI) water treated for 40 minutes, which yields the highest ORP and nitrate concentration with a reduced pH. Comparative growth experiments over two weeks show that PAW-treated Chrysanthemum saplings exhibit significantly greater height (10.2 cm) and soil fertility (2580 $\mu$S/cm) than those watered with same amount of DI water or tap water. The results highlight the potential of PAW for sustainable enhancement of growth of flowering plants.