Consumption of hydrogen in a shallow aquifer. Rapid consumption of hydrogen injected into a shallow aquifer by ecophysiologically different microbes

The envisaged future hydrogen economy requires a hydrogen gas grid as well as large deep underground stores. However, the consequences of an unintended spread of hydrogen through leaky pipes, wells, or subterranean gas migrations on groundwater resources and their ecosystems are poorly understood. Therefore, we emulated a short-term leakage incident by injecting gaseous hydrogen into a shallow aquifer at the TestUM test site and monitored the subsequent biogeochemical processes in the groundwater system. At elevated hydrogen concentrations, an increase in acetate concentrations and a decrease in microbial alpha diversity with a concomitant increase in microbial beta diversity were observed. Additionally, particularly aerobic, but also anaerobic, hydrogen oxidation is indicated by temporal higher abundances of taxa known for being capable of the respective hydrogen consumption processes. After hydrogen concentrations diminished below detection limit, alpha and beta diversity approached to baseline values. In summary, the emulated hydrogen leakage resulted in a temporally limited change of the groundwater microbiome and associated geochemical conditions due to intermediate growth of hydrogen consumers. The results confirm the general assumption that hydrogen, being an excellent energy source for microorganisms, is quickly microbiologically consumed in the environment after a certain leakage.