text: Biological soil uptake is the dominant sink of atmospheric H. Both aerobic and anaerobic microbial metabolisms consume H by oxidizing it in order to reduce other compounds during respiration. Aerobic H oxidation is known as the Knallgas reaction.
  Anaerobic H oxidation often occurs during interspecies hydrogen transfer in which H produced during fermentation is transferred to another organism, which uses the H to reduce CO to CH or acetate,  to HS, or Fe to Fe. Interspecies hydrogen transfer keeps H concentrations very low in most environments because fermentation becomes less thermodynamically favorable as the partial pressure of H increases.