Microbial Activity and 13C/12C Ratio as Evidence of N-Hexadecane and N-Hexadecanoic Acid Biodegradation in Agricultural and Forest Soils |
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| Authors: | Anatoly Zyakun Seth Nii-Annang Gabriele Franke Thomas Fischer Franz Buegger Oliver Dilly |
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| Institution: | 1. Skryabin Institute of Biochemistry and Physiology of Microorganisms , Russian Academy of Sciences , Pushchino , Russia;2. Pushchino State University , Pushchino , Russia;3. Chair of Soil Protection and Recultivation , Brandenburg University of Technology , Cottbus , Germany;4. Central Analytical Laboratory , Brandenburg University of Technology , Cottbus , Germany;5. Institute for Soil Ecology , Helmholtz Center Munich German Research Center for Environmental Health , Neuherberg , Germany;6. Chair of Soil Protection and Recultivation , Brandenburg University of Technology , Cottbus , Germany;7. School of Integrated Climate System Sciences , University of Hamburg , Hamburg , Germany |
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| Abstract: | The dynamics of microbial degradation of exogenous contaminants, n-hexadecane and its primary microbial oxidized metabolite, n-hexadecanoic (palmitic) acid, was studied for topsoils, under agricultural management and beech forest on the basis the changes in O2 uptake, CO2 evolution and its associated carbon isotopic signature, the respiratory quotient (RQ) and the priming effect (PE) of substrates. Soil microbial communities in agricultural soil responded to the n-hexadecane addition more rapidly compared to those of forest soil, with lag-periods of about 23 ± 10 and 68 ± 13 hours, respectively. Insignificant difference in the lag-period duration was detected for agricultural (tlag = 30 ± 13 h) and forest (tlag = 30 ± 14 h) soils treated with n-hexadecanoic (palmitic) acid. These results demonstrate that the soil microbiota has different metabolic activities for using n-hexadecane as a reductive hydrocarbon and n-hexadecanoic acid as a partly oxidized hydrocarbon. The corresponding δ13C of respired CO2 after the addition of the hydrocarbon contaminants to soils indicates a shift in microbial activity towards the consumption of exogenous substrates with a more complete degradation of n-hexadecane in the agricultural soil, for which some initial contents of hydrocarbons are inherent. It is supposed that the observed deviation of RQ from theoretically calculated value under microbial substrate mineralization is determined by difference in the time (Δti) of registration of CO2 production and O2 consumption. Positive priming effect (PE) of n-hexadecane and negative PE of n-hexadecanoic (palmitic) acid were detected in agricultural and forest soils. It is suggested that positive PE of n-hexadecane is conditioned by the induction of microbial enzymes that perform hydroxylation/oxygenation of stable SOM compounds mineralized by soil microbiota to CO2. The microbial metabolism coupled with oxidative decarboxylation of n-hexadecanoic acid is considered as one of the most probable causes of the revealed negative PE value. |
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| Keywords: | microbial activity O2 consumption and CO2 evolution respiratory quotient hydrocarbon contamination respired CO2-C isotopic signature priming effect |
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