Hydrogen consumption and carbon monoxide production in soils with different properties

Soils are the dominant sink in the global budget of atmospheric H2, and can be an important local source of atmospheric CO. In order to understand which soil characteristics affect the rates of H2 consumption and CO production, we measured these activities in 16 different soils at 30% and 60% of their maximum water holding capacity (whc). The soils were obtained from forests, meadows and agricultural fields in Germany and exhibited different characteristics with respect to texture, pH, total C, substrate-induced respiration (SIR), respiration, total and inorganic N, N mineralization, nitrification, N2O production and NO turnover. The H2 consumption rate constants were generally lower at 60% than at 30% whc, whereas the CO production rates were not influenced by the whc. Spearman correlation analysis showed that H2 consumption correlated significantly (r>0.5, P<0.05) at both water contents only with SIR and potential nitrification. The correlation with these variables that are largely dominated by soil microorganisms is consistent with our understanding that atmospheric H2 is oxidized by soil hydrogenases. Multiple regression analysis and factor analysis gave similar results. Production of CO, on the other hand, was significantly correlated to soil total C, respiration, total N and NH4/+. The correlation with these variables that are largely dominated by a soil's chemical composition is consistent with our understanding that CO is produced by chemical oxidation of soil organic C. CO production was also influenced by soil usage, with rates increasing in the order: arable<meadow<forest. H2 consumption was not influenced by soil usage.