Fractionation of stable carbon isotopes during microbial propionate consumption in anoxic rice paddy soils

作者：Ralf Conrad, Peter Claus · 年份：2023 · DOI：10.5194/egusphere-2023-244 · 被引用次数：6 · 研究领域：Methane Hydrates and Related Phenomena、Microbial Community Ecology and Physiology、Anaerobic Digestion and Biogas Production

Abstract. Propionate is an important intermediate during the breakdown of organic matter in anoxic flooded paddy soils. Since there are only few experiments on carbon isotope fractionation and the magnitude of the isotopic enrichment factors (ε) involved, we measured propionate conversion to acetate, CH4 and CO2 in anoxic paddy soils. Propionate consumption was measured using samples of paddy soil from Vercelli (Italy) and the International Rice Research Institute (IRRI, the Philippines) suspended in phosphate buffer (pH 7.0), both in the absence and presence of sulfate (gypsum), and of methyl fluoride (CH3F), an inhibitor of aceticlastic methanogenesis. Under methanogenic conditions, propionate was eventually degraded to CH4 with acetate being a transient intermediate. Butyrate was also a minor intermediate. Methane was mainly produced by aceticlastic methanogenesis. Propionate consumption was inhibited by CH3F. Whereas butyrate and CH4 were 13C-depleted relative to propionate, acetate and CO2 were 13C-enriched. The isotopic enrichment factors (εprop) of propionate consumption, determined by Mariotti plots, were in a range of -8 ‰ to -3.5 ‰. Under sulfidogenic conditions, acetate was also transiently accumulated, but CH4 production was negligible. Application of CH3F hardly affected propionate degradation and acetate accumulation. The initially produced CO2 was 13C-depleted, whereas the acetate was 13C-enriched. The values of εprop were -3.5 ‰. It is concluded that degradati...