FIG. 2.

Kinetics of H₂ utilization in the soil microcosm experiments. All readings taken from the second experiment with the GES soil (A) and the second experiment with the QRS soil (C) are shown. The four readings shown in panels A and C are as follows: ○, artificial air enriched with 500 ppm H₂ at the inlet to the microcosm; •, the H₂-enriched gas mixture sampled from the outlet of the soil microcosm; ▵, the artificial air mixture at the inlet to the microcosm; and ▴, the artificial air mixture sampled from the outlet of the soil microcosm. Also shown are the H₂ measurements from the outlet of the soil microcosms treated with the H₂-enriched gas mixture from the four experiments using the GES soil (B) and the three experiments using QRS soil (D). The experiment numbers shown in panels B and D are as follows: ⋄, 1; •, 2 (the same as displayed in panels A and C); □, 3; and ▿, 4.