Effect of temperature on reduction of iron and production of carbon dioxide and methane in anoxic wetland rice soils |
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Authors: | H Yao R Conrad |
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Institution: | (1) Max-Planck-Institut für terrestrische Mikrobiologie, Karl-von-Frisch-Strasse, 35043 Marburg, Germany e-mail: conrad@mailer.uni-marburg.de Tel.: +49-6421-178801 Fax: +49-6421-178809, DE |
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Abstract: | Wetland rice soils from Italy (Pavia) and the Philippines (Bugallon, Luisiana, Maligaya) were incubated under anoxic conditions
at 31 different temperatures ranging from 4.7 °C to 49.5 °C. Production of CO2 was most intensive at the beginning of the incubation (0–4 days) and was predominantly coupled to the reduction of free Fe(III).
The optimum temperature for these processes was between 32 °C and 41 °C. After 9–16 days, CO2 production rates had decreased and the available Fe(III) had been completely reduced at the optimum temperatures. However,
Fe(III) was still available at temperatures below and above the optimum. Maximum CH4 production rates were observed after 4–16 days (except in soil from Maligaya) with temperature optima between 32 °C and
41 °C, similar to those for CO2 production and Fe reduction. Since ongoing Fe reduction is known to suppress CH4 production, the temperature range of optimum CH4 production was restricted to those temperatures at which Fe(III) had already been depleted. Nevertheless, the temperature
characteristics of both CO2 and CH4 production often exhibited two temperature optima at some time during the incubation, suggesting a complex pattern of adaptation
of the methanogenic microbial community to temperature. When available Fe(III) was completely depleted by anoxic pre-incubation
at 30 °C, CH4 was produced at a constant rate (steady state conditions) which increased with increasing temperature. Steady state CH4 production reached a first maximum at about 40 °C, but increased further up to at least 50 °C, suggesting the presence
of thermophilic microorganisms whose activity was apparently masked when Fe had not been completely reduced. The apparent
activation energy of CH4 production at steady state ranged between 48 kJ mol–1 and 65 kJ mol–1.
Received: 26 August 1999 |
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Keywords: | Methane Sequential reduction Thermophile Activation energy Iron reduction |
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