Influence of humic acids on voltage generation in plant bioelectrochemical system

The paper examines the possibility of increasing the electrogenic properties of the root environment through the use of potential electron carriers – humic acids (HA). Using the example of the Typhoon variety lettuce, it was determined that increasing the concentration of HA in the root environment by 2 times made it possible to increase the voltage by 7–16% from the control variant, depending on the place of their introduction. The best result – more stable and higher generation of potential difference already from the early periods of the growing season, was characteristic of the variant with additional addition of HA to the area of the upper electrode – the average voltage value for it was 418 $\pm$ 29 mV and the specific power was 0.2 mW/m$^2$. A number of physicochemical indicators of near-electrode areas in plant bioelectrochemical systems have been studied: electrical conductivity, pH, HA concentration at the end of the growing season. The potential electroactivity of microorganisms in the root environment of lettuce was revealed. It has been shown that the ability of HA to play the role of a redox mediator in a bioelectrochemical system largely depends on the location of their concentration.