###### Abstract  
A gliding arc discharge (GAD) plasma device has been developed and tested. Possible applications areas for GAD plasma could be microalgae suspension treatments and the creation of plasma-activated water. To understand its behavior, the influence of the input power on the electrical characteristics of the generated GAD plasma was investigated using an oscilloscope. The waveforms of the voltage and current of GAD plasma are presented. The duration of the discharge time and the evolution of the arc during discharge were determined and investigated. It was revealed that the increase in the output voltage prolonged the duration of the arc discharge. The composition of the air plasma was investigated using a flame-emission spectrometer and acousto-optic emission spectrometer. It was revealed that the main species in the emission spectra of the GAD air plasma were N\({}_{2}\), N\({}^{+}\), N\({}^{+}\), NO, and O species. Furthermore, the increase in the input power enhanced the ionization degree of the air plasma and increased the intensities of the emission lines associated with N\({}_{2}\)+, NO, and O species. An increase in the conductivity of the BG-11 medium was observed. Physicochemical analyses of the plasma-activated BG-11 medium indicated an increase in the concentration of nitrite and nitrate ions and hydrogen peroxide with an enhancement of the voltage. g 2024 1 20  
fuel and waste treatment [12; 13; 14; 15; 16], and it could be also used for bacterial inactivation and food decontamination [10; 17; 18; 19; 20], the creation of plasma-activated water [5; 8; 21], and surface treatments and modifications [22; 23; 24; 25; 26]. Gliding arc discharge characteristics such as current and voltage values, the arc column length, discharge duration, density, and type of species produced in the plasma are strongly affected by the geometry and configuration of the electrodes, the experimental parameters, and the type of gas used for the plasma's generation [13; 16; 18; 20]. It should be noted that for the application of GAD plasma in the creation of plasma-activated water and the treatment of seeds, plants, or microalgae, the elemental composition of the plasma and the type of species produced play a crucial role [3; 8; 19; 20; 21]. The authors of previous studies observed that plasma-irradiated liquids had higher conductivity values [4; 6; 8; 21]. Meanwhile, the main ions and radicals which are produced in water or various liquids after plasma treatment are nitrate, nitrite, nitrogen dioxide, and hydrogen peroxide [4; 6; 8]. Therefore, the pH values, conductivities, and amount of the various species in these liquids depended not only on the type of liquids, but also on the type of gases used, plasma treatment times, the type of discharge, etc. [4; 6; 8; 21]. Optical emission spectroscopy (OES) is a widely used technique to determine the main species in various atmospheric plasmas [4; 6; 21; 27; 28; 29; 30; 31; 32; 33; 34; 35]. Air, oxygen, nitrogen, and oxygen-nitrogen gas mixtures are widely used for plasma formation in order to create reactive oxygen and nitrogen species, which are considered to be the main agents inducing structural, chemical, or biological changes in the plasma treatment of water and seeds [4; 6; 8; 19; 20; 21; 27; 28; 31]. The intensity of the emission lines is related to the density of the species produced in the plasma. The variation of the process parameters (applied voltages, frequency, used gas flow rate, type of gas, etc.) has a strong influence on the composition and densities of the species produced in the plasma [6; 19; 22; 27; 28; 29; 35]. It was determined that the typical emission spectra of air plasma produced by a gliding arc discharge had spectral lines related to the excited states of NO, OH, NH, N\({}_{2}\), N\({}_{2}\)+, and O species [19; 20; 21; 26]. The variation of the discharge power and air flow rate allows us to increase or reduce the density of the dominant species in an air plasma [20; 35]. [PERSON] et al.