Investigating the drivers of microbial H2 uptake: a summary of measured fluxes from a range of soil types and locations

The widescale global use of Hydrogen (H₂) fuel may result in increasing concentrations of atmospheric H₂ gas as a result of diffuse operational leakage. While H₂ is not a direct greenhouse gas (GHG), it does exhibit secondary GHG effects and influences several important atmospheric chemistry reactions which could have cascading environmental effects. The dominant process of H₂ removal from the atmosphere is uptake by soils; however, this removal mechanism is poorly understood and the fate and impact of increased H₂ emissions on the soil sink remain highly uncertain. In order to better understand future impacts of increased H₂ concentrations we need to understand current uptake rate of a range of different soils. Models require more information and data to improve the simulation of microbial processes in soils that dominate the global sink of atmospheric H₂. Over the past year, we have carried out H₂ flux measurements from a number of soils, both in the field (grasslands, arable, forests and peatland soils in the UK) as well as under controlled laboratory conditions, by completing several controlled incubation experiments with soil from the UK and abroad. These studies have provided important information regarding the impact that soil moisture, soil pH, temperature and other soil properties have on H₂ fluxes in soils. Our studies highlight that both physical (e.g. soil aeration) and microbial (e.g. pH and temperature) parameters strongly influence the microbial uptake of H₂ in soil types, with large differences in fluxes observed between different soil types under relatively similar environmental conditions.