Nanoscale chemical imaging of organo-mineral fractions of an andosol (La Martinique, France)

Miss Floriane JAMOTEAU1, Mr Nithavong CAM1, Mr Clément LEVARD1, Mr Thierry WOIGNIER2,3, Mr Romain SOULAS4,5, Mrs Isabelle BASILE-DOELSCH1

1Aix Marseille Univ, CNRS, IRD, INRA, Coll France, CEREGE, Aix-en-Provence,  France, 2Institut Méditerranéen de Biodiversité et d’Ecologie, Campus Agro Environnemental Caraïbes, Le Lamentin, France, 3Univ Avignon, CNRS, IRD, IMBE, Marseille, France, 4Univ. Grenoble Alpes, F-38000, Grenoble, France, 5CEA, LITEN,  17 Rue des Martyrs, F-38054, Grenoble, France

Organo-mineral associations are a main process driving organic matter (OM) stabilization in soils, but mechanisms of their dynamics are still not fully known. Basile-Doelsch et al. suggested that mineral alteration generating amorphous phases on minerals’s surfaces was a driver of OM stabilization. Coprecipitation synthesis led to a new model of organo-mineral associations at nanoscale, combining nanosized Co-precipitates of inorganic oLIgomers with organiCs molecules (nanoCLICs, Tamrat et al.). In the present study, we investigated nanoCLICs in soils using TEM (FEI Tecnai Osiris 200kV) coupled with 4 EDX detectors and EELS to semi-quantify C, N and major elements. We analyzed an andosol (15-20 cm) from La Martinique (French West Indies). OM-short-range-order and mineral associations were collected in the supernatant after sonication and a 48h-decantation. Areas analyzed ranged from 5 µm to 300 nm with pixel resolutions from 500 to 3 nm. Amorphous mineral phases were dominant. Fe, Si, Al and O were the main component and were homogeneous at nanoscale. Even down to 50 nm they were systematically associated to C and N. Proportions varied about 60% of Si, 30% of Al and 10% of Fe. No imogolites or allophanes were observed, mineral phases must be less polymerized (Levard et al.). Images acquired are similar to those obtained by coprecipitation on synthetic samples (Cam et al.). The nanoCLICs model (Tamrat et al.) seems to be valid in andosols. By focusing on a mg-vermiculite surrounded by amorphous material, chemical profiles showed an increasing C content from the center of the vermiculite to the amorphous material (over 150 nm). Although the amorphous phase may be bonded on mineral surface by sample preparation, these first results suggest a continuous alteration of minerals resulting in an amorphous phase progressively associated to OM molecules, as proposed by Basile-Doelsch et al.


Biography:

Dr I. Basile-Doelsch. MSc in Geology (ENSG, Nancy, France), PhD in Geochemistry for paleoclimatic reconstructions (Vostok ice core, Antarctica), Habilitation à Diriger des Recherches in geochemistry of soils and weathering systems in the critical zone. She is specialized in organomineral interactions in soils. She has been an Aix-Marseille University lecturer since 1998 (France), and a junior member of the prestigious “Institut Universitaire de France” from 2011 to April 2015. As of May 2015, she became a Director of Research at the French INRA institute(CEREGE). She recently spent one year as a visiting scientist in Jeff’s Baldock group at CSIRO Adelaide.

Strategies to improve the prediction of organic carbon in bulk soil and fractions from a target region using an existing national mid-IR library

Dr Clever Briedis1, Dr Jeff Baldock2, Dr João Carlos  de Moraes Sá3, Dr Débora Marcondes Bastos Pereira Milori1

1Brazilian Agricultural Research Corporation, São Carlos, Brazil, 2CSIRO Agriculture and Food, Glen Osmond, Australia, 3State University of Ponta Grossa, Ponta Grossa, Brazil

Currently, the measurement of organic carbon concentration in soil is completed using techniques that can be expensive, slow or generate toxic residue. Mid-infrared spectroscopy (MIR), when combined with chemometric analyses, can provide a fast and clean approach but proper model calibration is required for achieving reliable predictions of OC concentration. This study aimed to evaluate different strategies to calibrate the application of MIR to predicting OC concentration in the soil in order to improve the accuracy and cost-effectiveness values predicted for bulk soils and fractions of target samples. For this purpose, we used regional soils from Brazil (target samples – BRreL) and an existing Australian national library (AUnaL). In total, nine different model calibration strategies were tested for OC prediction in the target samples. Partial least square regression (PLSR) using only BRreL for calibration provided the highest accuracy for OC prediction in bulk soils and fractions. When only the AUnaL was used for PLSR calibration, the accuracy decreased, and OC predictions were acceptable for bulk soils but not for soil fractions. Alternative algorithms (e.g., cubist and spectrum-based learning – SBL) applied on the AUnaL, in general, did not improve OC predictions. The most promising results were found when the calibration of the model was performed by adding 20 BRreL samples in with the AUnaL samples. Through this spiking technique, regardless of the algorithm used (e.g., PLSR, cubist or SBL), the OC predictions were improved, making it very accurate for both bulk soils and fractions. In addition, this technique was more cost-effective since only a small number of samples from the target location had to be analysed in the laboratory to derive the analytical data required for model calibration. This makes the MIR technique a valuable resource for accurate, fast and cheap predictions of OC in bulk soils and fractions.


Biography:

Jeff Baldock is a research scientist working with CSIRO studying the cycling of organic carbon in a range of natural environments.

Introducing analytical results database (ARDB): Intuitive database management, data visualisation and quality control

Dr Kyle William Robert Taylor1, Mr Mike Seed1, Mr Michael Sudnik1, Dr. Lutz Lange1

1Elementar UK Ltd, Stockport, United Kingdom

Analytical Results Database (ArDB) is an intuitive software tool developed by Elementar UK, created to extend the envelope of analytical data analysis beyond simple data processing. ArDB simplifies management and visualisation of data, a particularly critical issue when generating large quantities of data associated with high-resolution and/or high-throughput analysis.

ArDB allows users to construct, maintain and manage their databases of any analytical results, including (but not limited to) results from stable isotope, elemental, and total organic carbon analysis instrumentation. Data can be visualized with 2D & 3D charts and maps, reducing the need to export data to external statistical or GIS software programs. Statistical analyses such as linear discriminant analysis (LDA) and principle component analysis (PCA) are available, e.g. to generate predictive models against which unknown samples can be tested. Compatibility with R ensures further extended statistical analysis is also possible.

Recently, ArDB has been expanded to offer comprehensive quality control (QC) statistics which allows the software to also be used to monitor instrument performance over short and long-time scales. Performance of both internal QC (e.g. instrument tuning, stability, linearity) as well as external QC (analysis of certified reference materials, laboratory standards) are recorded, centralised and monitored so the base performance can be continuously evaluated for multiple instruments across multiple laboratories. Individual QC criteria can be set at an administrator level so that basic operators cannot make unauthorised alterations, ensuring a secure controlled data management environment.

ArDB performs QC statistics calculations using the Shewart Tests, which can be enabled or disabled, allowing consistent testing of all data sets. By being able to scrutinise QC results alongside sample data, the analyst can ensure that only qualified data is accepted for population of databases, and ultimately that data used for the ongoing research themes they are pursuing is demonstrably robust and reliable.


Biography:

Dr. Lutz Lange
– Studied Chemistry in Frankfurt and Heidelberg University
o Diploma Thesis in Environmental Geosciences
– Dissertation (PhD) at Max-Planck-Institute for Chemistry in Mainz (Germany) and Utrecht University (the Netherlands)
o Atmospheric Sciences: Exchange processes between the lowermost stratosphere and the upper troposphere.
– Post Doc at Max Planck Institute for Chemistry in Mainz
– 2005: Produktmanager at Elementar (Elemental Analysis and IRMS)
– 2011 Director for R&D and innovation management
– 2017: Director Global Sales and Marketing
– August 2019: move to Elementar Australia

22-years long-term fertilizations increase soil organic carbon and alter its chemical composition in three wheat/maize cropping sites across central to south China

Professor Minggang Xu1,2, Ms Yating He2,3, Ms Wenju Zhang2, Mr Xueyun Yang4, Ms Shaomin Huang5, Mr Xinhua He6

1Institute of South Asia Tropical Crops, Chinese Academy of Tropical Agricultural Sciences, Zhanjiang, China, 2Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Haidian, China, 3Research Institute of Forestry Policy and Information, Chinese Academy of Forestry, Haidian, China, 4State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A & F University, Yangling, China, 5Institute of Plant Nutrition, Resources and Environment, Henan Academy of Agricultural Sciences, Zhengzhou, China, 6College of Resources & Environment, Southwest Univ/Univ of Western Australia, Beibei, China

As a quantifiable component of soil organic matter, soil organic carbon (SOC) is at the core of soil fertility and the C sequestration in SOC is a pathway to mitigate climate change by reducing atmospheric CO2. Studies have shown that fertilization strategies can alter SOC sequestrations and stocks, but information about fertilization effects on SOC chemical composition is limited. Using the solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy, we examined changes in the SOC chemical composition of three soils (0–20 cm depth) from an annual maize/wheat double-cropping system across central to south China. These soils had been subjected to 22-years (1990–2012) long-term fertilization. Compared with unfertilized control, SOC stocks were significantly increased under chemical nitrogen, phosphorus and potassium fertilization (NPK), NPK plus straw (wheat straw, NPKS), and NPK plus manure (varied horse, pig and cattle manure, NPKM). The O-alkyl C (labile C), not the alkyl C (persistent C), was consistently increased across the three fertilized treatments. Additionally, all fertilized treatments decreased the ratio of alkyl-C/O-alkyl-C (SOC decomposition index) or aliphatic-C/aromatic-C (SOC complexity index), indicating that the SOC decomposition was delayed, or SOC was converted into a more complicated structure. The soil C of NMR-determined functional groups (alkyl C, O-alkyl C, aromatic C, and carbonyl C) was positively correlated with the cumulative C input (P < 0.05). The conversion rate of functional groups was highest in O-alkyl C, indicating a largest contribution to the increase of SOC accumulation. Soil pH, C/N ratio and clay were the major factors affecting the functional-group conversion rates, whereas annual precipitation, temperature, and accumulated temperature (>10 °C) played little roles. In conclusion, these results can be applied to the improvement of agricultural soil C sequestration or restoration capacity through changing SOC chemical structure under long-term fertilizer managements.


Biography:

Xinhua He is currently a Professor and Director of Centre of Excellence for Soil Biology at Southwest University, Chongqing China (2015-). He has held a PhD in Plant Ecophysiology from University of Queensland, Australia since 2002, and then worked as a Postdoctoral Fellow at UC Davis and University of Tokyo, Senior Research Scientist at USDA and University of Western Australia.

During the past 20 years, Xinhua has focused on carbon/nitrogen movement in agricultural and natural ecosystems, roles of soil beneficial microbes in plant ecophysiology and soil structural stability and health, nano-minerals complexation in the preservation of soil organic matter under contrasting fertilizations. Xinhua is currently exploring emerging technologies including stable isotopes of 13C and 15N, Pyrosequencing, Electron Microscopy, Nano-scale Secondary Ion Mass Spectrometry (nano-SIMS), and Synchrotron Radiation Facility, etc., to address above-mentioned topics in a variety of plant-microbial-soil systems under global environmental change scenarios.

Currently Xinhua has >200 publications including 3 books, 26 book chapters and >170 papers in a variety of journal including Agri Ecosyst Environ, Biol Fert Soils, Biogeosciences, Glob Biogeochem Cy, Nature Commu, Nature Geosci, New Phytologist, Plant Soil, SBB, Trends Ecol & Evol, Trends Plant Sci, Tree Physiol, etc. (see https://www.researchgate.net/profile/Xinhua_He3). At present Xinhua has presented >100 talks at various universities and international conferences and his research has been viewed by 70,000 times by >4,000 readers from the Mendeley data base. Xinhua has been servicing as a Section Editor for Plant and Soil (2015) and an Associate Editor Soil Research (2019) and a regular peer reviewer for >100 journals and funding bodies (ARC, GRDC, BBSRC sLOLA, NSF, NSFC, USDA and NOW) around the world.

Characterization of soil humic acid reacting with calcium ion and its application

Dr Baohua Xiao1, Haimin Tang1,2, Peiwen Xiao1,2

1State Key Laboratory of Environmental Geochemistry, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China, 2University of Chinese Academy of Sciences, Beijing, China

Soil humic acid (SHA) practically defined as soluble in basic solution and insoluble in acidic solution is an important component of soil organic matter (SOM). SHA was considered as the main reagent for maintaining sound physical structures of soil and providing nutrients to living plants. SHA had drawn tons of attention, but the chemical properties of SHA, even its existing, remain controversial since of the large inconsistence of characteristics data between literature studies. Here we reported a study on reactions of calcium ion with SHA samples and the online spectroscopic characteristics of SHA during the reactions. This study has two major purposes: first, to understand the overall reaction of Ca2+ and SHA in soil and to dig out underlying mechanisms; second, to illustrate the inactivation effects of Ca2+ to SHA samples, which could be qualitatively described by spectroscopic information. To achieve these purposes, three bulk SHA samples were carefully extracted from three layers of a profile of limestone soil using the recommend extraction method of IHSS, one bulk SHA from the top layer was further divided into 5 sub-fractions according to their apparent molecular weights using a tangential flow filtration system, and a continuous on-line measurement system, including automatic potentiometric titrator, UV-visible spectrometer and three-dimensional excitation and emission matrix fluorescence (3D-EEM), was set up. The idea is to allow Ca2+ reacts with SHA gradually in the apparatus of automatic potentiometric titrator and so that the optical spectroscopic signals of SHA can be monitored continuously. The preliminary results showed that the overall reaction of Ca2+ and SHA is a combined process of complexation and adsorption, the reaction with Ca2+ can modify the spatial configuration and molecular size of SHA which may be reflected by changes in the spectroscopic signals of SHA.


Biography:

Baohua Xiao is a professor researcher in the State Key Laboratory of Environmental Geochemistry at the Institute of Geochemistry, Chinese Academy of Sciences, Guiyuang China. He received his Ph.D. in Earth and Environmental Science from Drexel University (2004), M.Sc. in Geochemistry from Institute of Geochemistry, Chinese Academy of Sciences (1996), and B.Sc. in Geochemistry from University of Science and Technology of China (1993). He did postdoctoral study in Department of Environmental Science of Rutgers University (2004-2008). His research interests lie in characterization of natural organic matters and understanding interactions between metals and soil organic matters.

New insights into how organic N is depolymerised

A/Prof. Charles Warren1

1University Of Sydney, University Of Sydney, Australia

Despite nitrogen (N) commonly limiting productivity, most soils contain a large pool of N in high molecular weight organic forms.  High molecular weight forms of organic N are in general not directly available for uptake by microbes or plants, and only become available after they have been depolymerised by extracellular enzymes.

Surprisingly little is known about how high molecular weight organic N is depolymerized. A particular challenge is in determining the products that are produced when high molecular weight organic N is depolymerized. Depolymerisation of organic N is often equated with production of the terminal monomers, primarily amino acids.  For example, many assays of enzyme activity focus solely on reactions that produce amino acids.  Studies to date have not determined the chemical profile of products produced by depolymerisation of organic N, and thus we do not know if amino acids are the main products of depolymerisation.

Determining how high molecular weight organic N is depolymerized has proved challenging for two reasons. First, because the products of depolymerisation are rapidly taken up by microbes; and second, because it has proven difficult to identify and quantify complex mixtures of hydrophilic organic N compounds.

This presentation will describe development of mass spectrometry methods to characterize the products of organic N depolymerisation.  We show that while amino acids are produced by depolymerisation they are not the dominant products.  The main depolymerisation products of native organic matter and added proteins are instead peptides. The same peptides that are produced in large quantities by depolymerisation are at vanishingly low concentrations in intact soil, which is consistent with the idea that peptides are preferred N sources for soil microbes.


Biography:

Charlie Warren is an Assoc Prof in the School of Life & Environmental Sciences at The University of Sydney. Charlie’s research career began as an honours student examining photosynthesis at low temperatures. After a decade examining the ecophysiology of photosynthesis, his research began heading belowground: first to examine uptake of organic N, then to examine root exudates and plant-soil interactions. Nowadays much of Charlie’s research focusses on nutrient cycling, in particular the development of novel analytical methods to solve intractable problems.

Plant residues and fungal growth as drivers for microaggregate formation in the detritusphere

Dr Alix Vidal1, PD Dr. Markus Steffens2, Dr. Derek M. Rogge3, Dr. Gerrit Angst4, Dr. Carmen Hoeschen1, PD Dr. Carsten W. Mueller1

1TU München, Lehrstuhl für Bodenkunde, Freising, Germany, 2Research Institute of Organic Agriculture, Department of Soil Sciences, Frick, Switzerland, 3Deutsche Forschungsanstalt für Luft- und Raumfahrt, Applied spectroscopy group, Wessling, Germany, 4Institute of Soil Biology & SoWa Research Infrastructure, Biology Centre of the Czech Academy of Sciences , České Budějovic, Czech Republic

Plant residues, i.e., the detritusphere, represents a hotspot for soil structure formation. The direct vicinity of labile plant residues, microorganisms and soil minerals demonstrate the perfect microenvironment for soil aggregate formation driven by microbial products as gluing agents. However, there is a lack of experimental approaches exploring this theory in intact soil samples, considering the spatial heterogeneity of soil microstructures. We aimed at depicting the sources and vectors of organic carbon during the simultaneous formation of SOM and soil structure. To exclude possible bias in differentiating between new and inherited SOM, we used an artificial soil mixture (quartz sand, illite and goethite) free of SOM, as well as spruce needles as particulate OM. Small containers filled with the artificial soil were placed in an organic layer to allow natural microbial colonization. We studied the soil structure and OM gradient formation using spectromicroscopic imaging. We used nanoscale secondary ion mass spectroscopy with subsequent digital image processing to explore the spatial distribution of mineral (¹⁶O-, ²⁷Al¹⁶O-, ⁵⁶Fe¹⁶O-) and organic (¹²C, ¹²C¹⁴N-, ³²S-) compounds on 69 measurements. At the start of the incubation, we depicted OM free mineral surfaces in the vicinity of the needle, demonstrating the feasibility to follow subsequent OM distribution without the need of isotopic labelling. Already after 14 days, fresh OM was associated with the mineral domains surrounding the needles. After 42 days, we could demonstrate that the needles were massively infested with saprotrophic fungi, which extended into the mineral matrix of the artificial soil acting as vectors for litter derived C and N into the bulk soil. There was also an increase of the OM at greater distance to the needle and in association with mineral particles. We demonstrate the formation of micro-aggregates in the direct vicinity of plant residues as driven by microbial activity.


Biography:

Dr. Alix Vidal, born 1989 in Epernay, France

7 ISI-papers with 43 citations, h-index is 4

Professional and academic career

->since 2016 – Research Assistant (Akademischer Ratin auf Zeit), Chair of soil science, Technical University of Munich

->Sep. 2016 – Dr. in Soil science, University Pierre et Marie Curie (UPMC), France

->2013 – 2016 – Doctoral candidate at UMR Metis, UPMC, France

->2013 – Dipl. Agricultural engineering, Ecole Supérieure d´Agriculture d´Angers, France

->2013 – Dipl. Agricultural engineering, Escola Superior de Agricultura « Luiz de Queiroz », São Paulo, Brazil

->2007-2013 – Study of agricultural engineering, France/Brazil

Research areas

->Soil biogeochemistry

->Biotic factors (litter type and earthworms) controlling soil organic matter decomposition

->Interactions between plant, soil and microorganisms in the rhizosphere

->Influence of organic amendments on soil characteristics

->Use of carbon stable isotope (13C) to trace carbon flows in soils

->Combination of classical quantitative (EA-IRMS, GC-MS, NMR spectroscopy) and spectromicroscopic (NanoSIMS) and imaging techniques (TEM, SEM)

Field testing labile soil organic carbon using potassium permanganate in tropical soils

Dr Wipawan Thaymuang1, Miss Aunthicha  Phommuangkhuk1, Miss Sirisuda   Bootpetch1

1Department Of Soil Science, Faculty of Agriculture at Kamphaeng Saen, Kasetsart University, Kamphaeng Saen, Thailand

Permanganate (KMnO4) was used to test for oxidizable organic carbon (POXC) as labile soil organic carbon. Soil samples were collected from five different soil types based on clay mineral types; kaolinite, kaolinite+iron oxides, smectite, siliceous, and mix. Active soil organic matter was estimated visually in a range consisting of 6 levels (0.5%, 1%, 1.5%, 2%, 2.5% and >3%) of KMnO4 to evaluate the quantity of active soil organic matter using the visual solution color of deep purple color (<0.05%OM) to a lighter KMnO4 solution color (>3%OM) based on comparison with the RHS color chart. Then, the color chart was modified based on the percentage of organic carbon compared with Walkley and Black method (the routine method). The results showed that the POXC color chart was strongly correlated with the percentage of organic carbon based on the routine method in all clay mineral types. Where the red color of a clay soil had been interfered by iron oxides added as flocculants or had been allowed to stand for a longer period (10-20 min), the solution became clear. However, about 75% of all samples, potassium permanganate was able to evaluate the quantity of labile soil organic matter in same-colored shades of soil samples with different organic carbon based on the routine method. The relationships to potassium permanganate oxidized organic carbon occurred in clay mineral types and amount of organic carbon. These results suggest that this method can be used as a labile organic matter test kit that is quick and inexpensive to evaluate active soil organic carbon content in the field for use in nitrogen fertilizer recommendations.

Key words: Labile Soil Organic Carbon Test Kit, Potassium Permanganate, Tropical Soils


Biography:

I received B.A. and M.S. in Agriculture (soil science) in 1997 and 2001 respectively, and Ph.D. in Soil Science in 2013 from Kasetsart University that focus on the stabilization of soil organic matter by iron oxides in highly weathered Tropical Soils.

I have worked for Department of Soil Science, Kasetsart University, since 2001.

My research focus on interaction between clay mineralogy and organic matter, labile and stabilization of soil organic matter in Tropical Soils, including soil fertility and plant nutrient management for crop production such as rice, corn, and sugarcane.

Utilizing rapid spectral techniques to assess impacts of agriculture on soil function in pacific soils

Dr Uta Stockmann1, Dr Mark Farrell2, Mr Thomas Carter2, Mrs Seija Tuomi1, Mr Shaun Krawitz3, Ms Brigitte Small3, Dr Ben Macdonald1

1CSIRO Agriculture and Food, Black Mountain, Canberra, Australia, 2CSIRO Agriculture and Food, Waite Campus, Urrbrae, Australia, 3School of Earth, Atmosphere and Environment, Monash University, Melbourne, Australia

Intensive agricultural production systems have had a dramatic impact on the status of pacific island soils, and have changed their soil physical, chemical and biological function. Their ability to deliver crucial ecosystem services, including soil organic carbon storage, soil nutrient delivery and soil water holding capacity has been affected. The state of the soil is a key factor in farm value on pacific islands and therefore warrants monitoring to ensure the sustainability of the soil resource for future generations. However, traditional soil laboratory techniques are expensive to use for soil monitoring purposes and also hard to access at times, because of remoteness of the islands and limited laboratory capacity. Soil spectroscopic techniques offer cost-effective and rapid analyses, and hand-held, field-portable devices have the potential to be used for instantaneous soil analysis results. Spectral techniques operating in the X-ray, vis-NIR and MIR part of the electromagnetic spectrum offer the ability to predict a range of soil properties of agronomic importance including soil organic matter, pH, soil texture and macro-, micro and trace-nutrients. Here, we conducted a study to assess the suitability of soil spectral techniques to quantify aspects of soil fertility for allophanic soils of several agricultural plots on Tongatapu island, Tonga. Locations were chosen to also allow for comparison of the impact of management practices on the soil’s status. This work will contribute to building a soil spectral library for pacific island soils, to make possible the use of spectral devices to gain valuable soil information.

 

Evaluation of soil organic matter stability by Rock-Eval pyrolysis – Influence of organic content and texture on measured parameters

Mr Pierre Gatel1, Dr Katell Quenea1, Mrs Sylvie Derenne1, Mr Manuel Nicolas2, Mrs  violaine Lamoureux Var3, Mrs Isabelle Kowalewski3

1Sorbonne University, Paris, France, 2ONF, Fontainebleau, France, 3IFPEN, Rueil malmaison, France

Rock-Eval pyrolysis is a powerful technique developed for the rapid characterization of sedimentary organic matter (OM), based on its thermal reactivity. Originally designed for the study of petroleum rocks, Rock-Eval is increasingly used for soil OM characterization and more recently to assess its stability. The thermal reactivity of OM evaluated by Rock-Eval analysis could be influenced by its chemical composition, but also by interaction with minerals. It is thus necessary to take into account the soil characteristics to establish the potential of the Rock-Eval analysis to diagnose the thermal stability of soil OM in relation to their level of biodegradability and therefore their biological sensitivity. To this end, we have selected surface soil samples from the French national network for the long term monitoring of forest ecosystems. The selection comprises on the one hand, soil samples with similar amount of organic carbon content but with contrasting texture (sandy vs clayey), and on the other hand, samples exhibiting similar texture but differing in TOC content. Due to the higher level of chemical functions in soil OM with respect to sedimentary OM, the Rock-Eval parameters must be optimized. The effect of different heating rates and starting temperatures in Rock-Eval analysis on the commonly measured parameters (total organic carbon, hydrogen index and oxygen index) was first evaluated. Taken together, these analyses aimed at evaluating the influence of i) OM content, ii) texture and iii) forest litter chemical composition on Rock-Eval measured parameters and at providing a reliable protocol for soil OM analysis. Finally, in parallel to Rock-Eval pyrolysis, the released effluents have been directly characterized by GC /MS in an attempt to relate the Rock-Eval parameters to the molecular composition of the pyrolysed soil OM.


Biography:

Quenea is assistant professor in geochemistry in Sorbonne University. She is a specialist in chemical characterisation of soil organic matter. She focused her research on the processes implied in organic matter stabilisation, and on the role of macrofauna on this stabilisation.

SOIL ORGANIC MATTER

7th International Symposium
Soil Organic Matter

6 – 11 October 2019

Hilton Adelaide

Adelaide, South Australia

Australia

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