Fig. 2: Numerical simulation on the distributions of abundance and δ13C of short alkanes from hydrogen biodegradation of long alkyl chains.
From: Methane from microbial hydrogenolysis of sediment organic matter before the Great Oxidation Event
a Reaction scheme showing that the number of carbon and hydrogen atoms contributed by the alkyl chain and H2 to the gaseous alkanes depends on C–C cleavage positions. Brown, blue, and red represent cases of 1, 2, and 3 capping hydrogen atoms donated by H2, respectively. b Numerical simulation on the abundances of gaseous alkanes relative to CH4. c Numerical simulation on δ13C of gaseous alkanes relative to δ13CnC4H10. Legend of b and c: black lines—Kidd Creek gas (samples with both δ13C and gas content data)4,5; blue, red, and gradient colours in between—modelled results (Eqs. 4–7) with conversion (fraction of CH4-contained 12C atoms in all 12C atoms) labelled in panel b. KIE parameters (identical for hydrogenolyses on kerogen side chains and on alkanes): primary 13C KIE of 13k/12k = 1.0015 (inverse KIE); secondary 13C KIE of 13k/12k = 0.9978 (normal KIE).
