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Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions.

Quin P, Joseph S, Husson O, Donne S, Mitchell D, Munroe P, Phelan D, Cowie A, Van Zwieten L - Sci Rep (2015)

Bottom Line: X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces.With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents.Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

View Article: PubMed Central - PubMed

Affiliation: University of New England, Armidale, NSW 2351, Australia.

ABSTRACT
Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C)--0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS)--in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

No MeSH data available.


Related in: MedlinePlus

(a) STEM HAADF image of biochar with organomineral layer; (b) Fe-L2,3 EELS spectra (background stripped) were obtained from the points marked in (a). The EELS 1 spectrum is characteristic of haematite (Fe III). The spectrum from EELS 2 (red line) shows a pronounced low energy shoulder, suggesting a mixed (II–III) valence state. Note: peak maxima aligned at 709 eV for comparison.
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f5: (a) STEM HAADF image of biochar with organomineral layer; (b) Fe-L2,3 EELS spectra (background stripped) were obtained from the points marked in (a). The EELS 1 spectrum is characteristic of haematite (Fe III). The spectrum from EELS 2 (red line) shows a pronounced low energy shoulder, suggesting a mixed (II–III) valence state. Note: peak maxima aligned at 709 eV for comparison.

Mentions: Scanning transmission electron microscope (STEM) images and x-ray mapping reveal a nanostructure that is highly heterogeneous. Figure 4 shows a high angle annular dark field (HAADF) STEM image of a section of the biochar particle that has interacted with the soil organic and mineral matter. The associated EDS spectra (Fig. 4) demonstrate the considerable organic content of the mineral phases (see also Supplementary Figure S3). Electron energy loss spectrometry (EELS) of the regions showed strong Fe signals but of varying oxidation state (Fig. 5) with some of the Fe/O phases having an oxidation state of 3 + (haematite) and others a mixed oxidation state of 2+/3+ (possibly magnetite). Transmission electron microscopy (TEM) imaging with selected area electron diffraction indicated that these nanophases could be a mixture of haematite, magnetite and possibly goethite (see Supplementary Figure S4). Figure 6 is an analysis of another interface between a biochar region and a region that has a number of nanophase minerals. On the biochar boundary there are nanophase particles rich in Si/O (probably SiO2) and also Fe/O phases that have a mixed (II-III) Fe oxidation state (probably magnetite). In the organomineral phase adjacent to the biochar there are various Al/Si/Ca/Fe/C/S/O nanophase minerals.


Lowering N2O emissions from soils using eucalypt biochar: the importance of redox reactions.

Quin P, Joseph S, Husson O, Donne S, Mitchell D, Munroe P, Phelan D, Cowie A, Van Zwieten L - Sci Rep (2015)

(a) STEM HAADF image of biochar with organomineral layer; (b) Fe-L2,3 EELS spectra (background stripped) were obtained from the points marked in (a). The EELS 1 spectrum is characteristic of haematite (Fe III). The spectrum from EELS 2 (red line) shows a pronounced low energy shoulder, suggesting a mixed (II–III) valence state. Note: peak maxima aligned at 709 eV for comparison.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663753&req=5

f5: (a) STEM HAADF image of biochar with organomineral layer; (b) Fe-L2,3 EELS spectra (background stripped) were obtained from the points marked in (a). The EELS 1 spectrum is characteristic of haematite (Fe III). The spectrum from EELS 2 (red line) shows a pronounced low energy shoulder, suggesting a mixed (II–III) valence state. Note: peak maxima aligned at 709 eV for comparison.
Mentions: Scanning transmission electron microscope (STEM) images and x-ray mapping reveal a nanostructure that is highly heterogeneous. Figure 4 shows a high angle annular dark field (HAADF) STEM image of a section of the biochar particle that has interacted with the soil organic and mineral matter. The associated EDS spectra (Fig. 4) demonstrate the considerable organic content of the mineral phases (see also Supplementary Figure S3). Electron energy loss spectrometry (EELS) of the regions showed strong Fe signals but of varying oxidation state (Fig. 5) with some of the Fe/O phases having an oxidation state of 3 + (haematite) and others a mixed oxidation state of 2+/3+ (possibly magnetite). Transmission electron microscopy (TEM) imaging with selected area electron diffraction indicated that these nanophases could be a mixture of haematite, magnetite and possibly goethite (see Supplementary Figure S4). Figure 6 is an analysis of another interface between a biochar region and a region that has a number of nanophase minerals. On the biochar boundary there are nanophase particles rich in Si/O (probably SiO2) and also Fe/O phases that have a mixed (II-III) Fe oxidation state (probably magnetite). In the organomineral phase adjacent to the biochar there are various Al/Si/Ca/Fe/C/S/O nanophase minerals.

Bottom Line: X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces.With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents.Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

View Article: PubMed Central - PubMed

Affiliation: University of New England, Armidale, NSW 2351, Australia.

ABSTRACT
Agricultural soils are the primary anthropogenic source of atmospheric nitrous oxide (N2O), contributing to global warming and depletion of stratospheric ozone. Biochar addition has shown potential to lower soil N2O emission, with the mechanisms remaining unclear. We incubated eucalypt biochar (550 °C)--0, 1 and 5% (w/w) in Ferralsol at 3 water regimes (12, 39 and 54% WFPS)--in a soil column, following gamma irradiation. After N2O was injected at the base of the soil column, in the 0% biochar control 100% of expected injected N2O was released into headspace, declining to 67% in the 5% amendment. In a 100% biochar column at 6% WFPS, only 16% of the expected N2O was observed. X-ray photoelectron spectroscopy identified changes in surface functional groups suggesting interactions between N2O and the biochar surfaces. We have shown increases in -O-C = N /pyridine pyrrole/NH3, suggesting reactions between N2O and the carbon (C) matrix upon exposure to N2O. With increasing rates of biochar application, higher pH adjusted redox potentials were observed at the lower water contents. Evidence suggests that biochar has taken part in redox reactions reducing N2O to dinitrogen (N2), in addition to adsorption of N2O.

No MeSH data available.


Related in: MedlinePlus