Nonthermal plasma reactors, which enable electrical discharges to be generated in various gases and both liquid and gaseous water, have attracted considerable attention as an alternative method for producing ammonia and fixing nitrogen. In this work, we investigated the basic performance of multihollow surface dielectric barrier discharge (MSDBD) to generate plasma in synthetic air and nitrogen-containing admixtures of water aerosols. The MSDBD in combination with the aerosol stream represents a rather complex geometry for generating the discharge; the plasma is significantly affected by the physicochemical properties of water aerosols on the one hand, on the other hand, this system facilitates the solvation of gaseous plasma products in water and the production of plasma-activated nitrogen-rich water (PAW). The plasma interaction with the water aerosols was studied using optical emission spectroscopy and a scanning mobility particle sizer to provide information about the size and distribution of the water particles entering and exiting the plasma reactor. The gas exiting the plasma reactor was analyzed using Fourier-transform infrared spectroscopy, and the PAW collected in an ice-cooled vessel was analyzed for nitrates (NO₂ ⁻), nitrites (NO₃ ⁻), and ammonia (NH₃). MSDBD shows promise as a catalyst- and H₂-free method for fixing nitrogen in water. Additionally, given the low energy consumption (<5 W) of MSDBD and the straightforward construction of the plasma unit, the suggested approach for PAW production offers a viable route for advancing a decentralized sustainable economy.

Surface DBD (SDBD) discharge maintained in moist air in the immediate vicinity of the water surface is an effective source of reactive species for the production of plasma-activated water (PAW). In this work, we investigated the water activation process for two different DBD energization methods; i.e. using periodic HV pulses with nanosecond risetimes and amplitude-modulated HV AC. We combined UV–vis–NIR ICCD spectroscopy with electrical characteristics to determine the basic characteristics of SDBD microfilaments. Formation of N₂O₅/NO₂/N₂O/H₂O₂/NO₂ ⁻/NO₃ ⁻ species was followed and the production yields of species generated in PAW (H₂O₂/NO₂ ⁻/NO₃ ⁻) were determined in a flow-through reactor under well-defined and stable discharge conditions. Both energization methods reached comparable energy efficiencies of nitrogen fixation in the range of 1–6 g kWh⁻¹ with minimal concentrations of H₂O₂ (10 s μM). However, the AC-powered SDBD produced mainly NO₃ ⁻ with minimal NO₂ ⁻ (1/10 of NO₃ ⁻), while in the case of pulsed SDBD the better-balanced NO₂ ⁻/NO₃ ⁻ ratio was achieved.

The plasma filaments propagating along the air–water interface offer a useful approach to enhance the transport of reactive species from plasma into the liquid medium. In this work, we investigated the novel streamer-spark discharge geometry, where both electrodes are submerged in water, inside a continuous flow-through reactor as a source of plasma-activated water (PAW) that can be used as a nitrogen-enriched water fertilizer and/or antimicrobial agent. We have inspected the efficiency of nitrogen fixation by varying the external parameters such as airflow and discharge repetition rate at fixed water flow through the reactor. The concentrations of generated NO_x species exhibit linear dependence on input power in both gaseous and dissolved forms, with the production rate of NO_x ⁻ reaching as high as 48.5 μmol min⁻¹ with standard energy efficiencies of around 16 mmol MJ⁻¹. Biocidal efficiency was tested on three selected fungal species (Botrytis cinerea, Penicillium italicum, Aspergillus carbonarius), which are usually more resilient than bacteria. The best efficacy in conidia germination inhibition has been achieved for Penicillium italicum (nearly 40%). The results presented also indicate that the energy efficiency of NO₃ ⁻ synthesis is tied to the characteristics/parameters of individual streamer-spark discharge events, while the total NO₃ ⁻ concentration and production throughput are determined by the overall discharge power.

Plasma-assisted treatment is a potentially interesting technology for advanced seed processing. In this work, we address the issue of defining and quantifying the plasma dose during the exposure of seeds to microdischarges formed in a barrier discharge configuration fed with synthetic air at atmospheric pressure. Using advanced imaging and other optoelectrical diagnostics, we identify suitable conditions for the formation of microdischarges developing exclusively between the powered electrode and the seed coat, which allows for the relatively accurate quantification of the plasma dose for an individual barley seed. In addition to determining the microdischarge energy/power consumed to treat a single seed during controlled exposure, we also provide an estimate of the electric field and gas temperature, which are key parameters that can affect seed viability. In this way, each individually exposed seed can be linked to the exact exposure time, total number, energy, and temperature of the microdischarges that came into contact with it. This is fundamentally different from conventional “averaging” approaches based on the simultaneous exposure of many seeds, which makes it virtually impossible to correlate the responses of individual seeds with the corresponding individual plasma dose. Finally, we propose a minimal treatment protocol that could allow for the more direct interpretation of the results of subsequent biological tests to reveal seed responses to specific plasma–chemical stimuli during germination and seedling growth.

Cold atmospheric plasma (CAP) is an emerging, chemical-free technology with significant potential to enhance crop performance. This study investigates the impact of direct plasma treatment on barley (Hordeum vulgare) seeds...