Temperature resolved alteration of soil organic matter composition during laboratory heating as revealed by C and N XANES spectroscopy and Py-FIMS

Kiersch, Kristian; Kruse, Jens; Regier, T. Z.; Leinweber, Peter

doi:10.1016/j.tca.2012.02.034

Cited by 33 publications

(18 citation statements)

References 53 publications

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“…Knicker et al [140] Wildfire induced loss of thermolabile compounds and thermal cracking of long-chain SOM components. The combination of XANES and Py-FIMS to investigate changes in OM structure with increasing heating temperature (from 100°C to 700°C) confirmed the distinction of alteration occurring at temperatures lower and higher than 400°C [143]. A similar pattern of degradation was reported upon pyrolysis of pine forest soils which underwent fire of different intensity [144].…”

Section: Analytical Pyrolysis As a Tool To Evaluate Fire Impactsupporting

confidence: 66%

Analytical pyrolysis as a tool to probe soil organic matter

Derenne

Quénéa

2015

Journal of Analytical and Applied Pyrolysis

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The environmental importance of soil organic matter (SOM) in the ecosystems and in the C biogeochemical cycle is well established. Indeed, it represents the main terrestrial carbon pool and due to its vulnerability, it plays a key role in the global carbon cycle. However, as SOM is mainly composed of products resulting from microbial and physicochemical transformations of vegetal, microbial and animal biomass, it results in a heterogeneous mixture. This complexity, along with organo-mineral interactions, makes challenging the characterization of SOM composition at the molecular scale. Nevertheless, its precise characterization is essential to determine its fate in the environment and eventually to provide recommendations on sustainable practices. Among the available techniques to analyse SOM, thermal degradations appear as especially efficient as they are less selective than some chemical ones, leading to a larger view of the SOM chemical structure. Analytical pyrolysis was thus used in a wide range of soil science fields including studies on pedogenesis and anthropic effects. It allows to characterize SOM at the molecular level, including identification of biomarkers, and to compare different soils and/or different horizons in a given soil profile under various impacts (land use, evolution, …). The review of recent developments in data acquisition and/or processing leads us to provide guidelines to select the most appropriate method and to avoid possible pitfalls. Examples will illustrate the wide range of soil science applications and show the potential and limitations of this approach.

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Section: Analytical Pyrolysis As a Tool To Evaluate Fire Impactsupporting

confidence: 66%

Analytical pyrolysis as a tool to probe soil organic matter

Derenne

Quénéa

2015

Journal of Analytical and Applied Pyrolysis

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“…Still, the N local coordination can be partly inferred based on the energy of absorption features 42, 45, 46 : imine, nitrile and pyridinic N will generate absorption features below 400 eV, while absorption features above 400 eV will indicate the presence of amide, nitro and pyrrolic N. Fresh G . violaceus and E .…”

Section: Resultsmentioning

confidence: 99%

Organic molecular heterogeneities can withstand diagenesis

Alleon

Bernard

Guillou

et al. 2017

Sci Rep

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Reconstructing the original biogeochemistry of organic fossils requires quantifying the extent of the chemical transformations that they underwent during burial-induced maturation processes. Here, we performed laboratory experiments on chemically different organic materials in order to simulate the thermal maturation processes that occur during diagenesis. Starting organic materials were microorganisms and organic aerosols. Scanning transmission X-ray microscopy (STXM) was used to collect X-ray absorption near edge spectroscopy (XANES) data of the organic residues. Results indicate that even after having been submitted to 250 °C and 250 bars for 100 days, the molecular signatures of microorganisms and aerosols remain different in terms of nitrogen-to-carbon atomic ratio and carbon and nitrogen speciation. These observations suggest that burial-induced thermal degradation processes may not completely obliterate the chemical and molecular signatures of organic molecules. In other words, the present study suggests that organic molecular heterogeneities can withstand diagenesis and be recognized in the fossil record.The fossil record contains crucial information about the evolution of Life on Earth 1, 2 . Molecular investigations regarding ancient Life are yet limited by the poor quality of the 'biogeochemical' signals preserved in the fossil record: in addition to biodegradation, burial-induced alteration processes (i.e. thermal maturation) inevitably modify the original biochemical signatures of fossilized organic molecules 1, 3 . With increasing temperature, weaker organic bonds are thermally broken and significant deoxygenation and dehydrogenation reactions occur 1, 4 . Thermal degradation eventually promotes increasing structural reorganization and may ultimately lead to the formation of pure graphite 5,6 .It has long been recognized that biomacromolecules exhibit conspicuous differences in decay in natural environments 7,8 . For instance, cell-wall biopolymers that protect some algae, cysts, spores and pollen grains are intrinsically more resistant than polysaccharides, proteins and nucleic acids 9-11 . In some contexts, taxon-specific chemosystematic data can even be preserved in the fossil record 12,13 . Still, the general perception in paleobiology remains that thermal maturation processes lead to a converging composition of organic materials from different origins, thereby limiting the use of chemical composition for discriminating between possibly different fossilized taxa 14 .Taking advantage of advanced spectroscopic tools (including synchrotron-based techniques), a number of studies have demonstrated that organic molecules may undergo only partial degradation during diagenesis in natural settings [15][16][17][18][19][20][21][22][23][24] . In parallel, laboratory experiments have helped evaluating the influence of key factors such as the pressure-temperature conditions, the redox conditions, the presence or absence of a fluid or of certain mineral phases on the degradation of organics 22,[25][26][27][28...

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“…During the pyrolysis, no relevant amounts of benzonitrile and naphthalene were formed ( e.g. , Kiersch et al, 2012a). The total ion intensity (TII) of each compound class was normalized by the summed TII measured for all compound classes to obtain relative values (% TII).…”

Section: Methodsmentioning

confidence: 99%

Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis‐Field Ionization Mass Spectrometry^#

Leue

Eckhardt

Ellerbrock

et al. 2015

J. Plant Nutr. Soil Sci.

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In the clay‐illuvial horizons (Bt) of Luvisols, surfaces of biopores and aggregates can be enriched in clay and organic matter (OM), relative to the bulk of the soil matrix. The OM composition of these coatings determines their bio‐physico‐chemical properties and is relevant for transport and transformation processes but is largely unknown at the molecular scale. The objective of this study was to improve the interpretation of spectra from Fourier transform infrared spectroscopy in diffuse reflectance mode (DRIFT) by using thermograms and released ion intensities obtained with pyrolysis‐field ionization mass spectrometry (Py‐FIMS) for a more detailed analysis of the mm‐scale spatial distribution of OM components at intact structural surfaces. Samples were separated from earthworm burrow walls, crack coatings, uncoated cracks, root channels, and pinhole fillings of the Bt‐horizons of Luvisols. The information from Py‐FI mass spectra enabled the assignment of OM functional groups also from spectral regions of overlapping DRIFT signal intensities to specific OM compound classes. In particular, bands from C=O and C=C bonds in the infrared range of wave numbers between 1,641 and 1,605 cm−1 were related to heterocyclic N‐compounds, benzonitrile, and naphthalene. The OM at earthworm burrow walls was composed of chemically labile aliphatic C‐rich and rather stable lignin and alkylaromatic compounds whereas the OM of thick crack coatings and pinholes was dominated by heterocyclic N and nitriles and high‐molecular compounds, likely originating from combustion residues. In combination with Py‐FIMS, DRIFT applications to intact samples seem promising for generating a more detailed mm‐scale spatial distribution of OM‐related sorption and wettability properties of crack and biopore surfaces that may serve as preferential flow paths in structured soils.

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Temperature resolved alteration of soil organic matter composition during laboratory heating as revealed by C and N XANES spectroscopy and Py-FIMS

Cited by 33 publications

References 53 publications

Analytical pyrolysis as a tool to probe soil organic matter

Analytical pyrolysis as a tool to probe soil organic matter

Organic molecular heterogeneities can withstand diagenesis

Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis‐Field Ionization Mass Spectrometry^#

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Temperature resolved alteration of soil organic matter composition during laboratory heating as revealed by C and N XANES spectroscopy and Py-FIMS

Cited by 33 publications

References 53 publications

Analytical pyrolysis as a tool to probe soil organic matter

Analytical pyrolysis as a tool to probe soil organic matter

Organic molecular heterogeneities can withstand diagenesis

Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis‐Field Ionization Mass Spectrometry#

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Analyzing organic matter composition at intact biopore and crack surfaces by combining DRIFT spectroscopy and Pyrolysis‐Field Ionization Mass Spectrometry^#