since there is not a net or significative microbial discrimination of 13Cduring microbial degradation and microbial synthesis the 13C abundance ofSOM reflect the composition of the plant species cultivatedby adding to soil an organic material with different 13C content it istherefore possible to label the new entering SOC and differentiate betweenold and new organic material, thereby following both processes of OCaccumulation and mineralizationplant speciesplant species S13C BPos813C A-oXSAoldSOCnew SOC8A<8X<SB0timeThe amount of recent SOC is calculated as percentage(8X - SA)% SOC× TOC(%)recent(8B - SA)
by adding to soil an organic material with different 13C content it is therefore possible to label the new entering SOC and differentiate between old and new organic material, thereby following both processes of OC accumulation and mineralization since there is not a net or significative microbial discrimination of 13C during microbial degradation and microbial synthesis the 13C abundance of SOM reflect the composition of the plant species cultivated plant species plant species δ13C A SOC content (%) 100 0 δA The amount of recent SOC is calculated as percentage % SOC recent = ( δX– δA) ( δB – – δA) × TOC(%) old SOC old SOC δ X new SOC new SOC time plant species plant species δ13C B δA < δX X < δ B
in long term field experiment the shift between old and recent SOM is obtainedby “natural labelling"' replacing the previous cultivated plant species withanother crop with different e.g. wheat (C, plant) replaced with corn (C4plant)in short term laboratory incubation experiment, synthesized labelledorganic compound, with a significant different 8, are likely used inorder to have a rapid shift between old and recent SOMlabelledorganiccompoundsSB8B-8A >100%0100(%) oXSAnewSOColdSOC8A<8X<8B0timedays/weeks
C3plantδA C4plant δB δA old SOC old SOC δX new SOC new SOC time T O C c o n t e n t (% ) 100 0 δA < δX< δB in long term field experiment the shift between old and recent SOM is obtained by “natural labelling” replacing the previous cultivated plant species with another crop with different δ e.g. wheat (C3 plant) replaced with corn (C4 plant) months/years δB – δA = 10-15‰ labelled organic compounds labelled organic compounds δB δB – δA > 100 A > 100‰ days/weeks in short term laboratory incubation experiment, synthesized labelled organic compound, with a significant different δ, are likely used in order to have a rapid shift between old and recent SOM
"Organic carbon sequestration through protection by humic substancesObjectiveStudy the effect of humified organic matter on the mineralizationof labile organic compound in soila short chain alcohol (2 decanol) was labelled with 13C isotope andused for soil incubation to study the OC mineralizationthe 13C labelled alcohol was added to soil either alone or inmixture with two humic acids extracted from lignite and fromrecycled organicbiomassthe mineralization of labelled alcohol was followed for 6 monthsin all soil treatments either in bulk soils and in soil-size fractions.determining also the final incorporation of labelled compounds insoil humic substances
“Organic carbon sequestration through protection by humic substances Objective Objective Study the effect of humified organic matter on the mineralization of labile organic compound in soil a short chain alcohol (2 decanol) was labelled with 13C isotope and used for soil incubation to study the OC mineralization the 13C labelled alcohol was added to soil either alone or in mixture with two humic acids extracted from lignite and from recycled organic biomass the mineralization of labelled alcohol was followed for 6 months in all soil treatments either in bulk soils and in soil-size fractions, determining also the final incorporation of labelled compounds in soil humic substances
13C-labelling of 2-decanol13C labelled 2-decanol was synthesized in our laboratory by aGrignard reaction between nonanoic aldehyde and a 13C-labelled methyliodide with a yield of 76.3% as reported in thefollowing scheme:ether13CH,Mgl13CH,I + MgC, aldehydeOMgCether→CH,-(CH2)-C_13CH3CHs-(CH2)-° + 13CH,MglHHOHOMglH,.O+CH3-(CH2)-C-13CHCH3-(CH2)-C-13CH3HH13C labelled 2-decanol = 13C2-dec
13C-labelling of 2-decanol 13C labelled 2-decanol was synthesized in our laboratory by a Grignard reaction between nonanoic aldehyde and a 13Clabelled methyliodide with a yield of 76.3% as reported in the following scheme: 13CH3I + Mg I + Mg ether 13CH3 3MgI ether 13CH3MgI CH3 3 -(CH2 )7 - C - 13CH 3 OMgI H CH3 -(CH2 )7 - C - 13CH 3 OMgI H H3 O + CH3 3 -(CH2 2 )7 7 -C + H O C9aldehyde aldehyde CH3 -(CH2 )7 - C - 13CH 3 OH H 13C labelled labelled 2 -decanol decanol = 13 C 2 -dec
Computer simulation of 2-decanol NMR spectra/8102370501060402030OH1CH,-CH,-CH,-CH,-CH,-CH,-CH,-CH,-CH-13CH,95384210761910NMR spectra of 13C2-decanol8X3250704020601030
CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH2-CH-13CH3 70 60 50 40 30 20 10 70 60 50 40 30 20 10 7 6 5 4 3 2 1 OH 10 9 8 10 10 2 2 9 9 1 1 4 4 3 3 8 8 Computer Computer simulation simulation of 2-decanol decanol NMR spectra spectra NMR spectra spectra of 13C2-decanol decanol