1,721,403 research outputs found
Structure defines function - NMR as a tool to improve our understanding of how does carbonized organic matter work
No full textComunicación Oral presentada en el 13º Encontro Brasileiro de Substâncias Húmicas e Matéria Orgânica Natural (XIII EBSH-MO). October, 28th to 31st, 2019, Alagoas (Brazil)Application of carbonized organic matter (COM) is often suggested as a strategy for improving soil fertility or restoring C to depleted soils by concomitantly sequestering significant amounts of CO2. With the increase of research related to COM, it became evident that depending on the feedstock and the production condition, these products can greatly vary in their chemical compositions and physical properties. Thus, COM application is not a ¿one-size fit-all paradigm¿ (Spokas et al., 2012), but instead requires careful consideration of the properties associated with each particular COM and how those properties might remedy a specific soil/substrate deficiency. In order to provide some more certainty and consistency with respect to the quality of COM, certificates (i.e. IBI or EBC) were developed to provide guidelines which chemical and physical properties are required for a material to be defined as biochar or bio-organic mineral. In line with most literature reports about COM characterization, the analyzed parameters are limited to basic descriptive data such as elemental composition, content of pollutants, pH, water holding capacity (WHC) or nutrient contents (Spokas et al., 2012). Only during the last years, increased efforts were conducted toward a better chemical characterization, since basic parameters cannot adequately describe the impact of the variability in surface chemical functional groups or core-structures on the interactions of elements and COM. They also fail to explain why different feedstocks result in pyrolysis products with great variation in porosity, adsorption behavior or biochemical resistance.
Indeed, COM represents an ill-defined continuum of organic forms. Its atomic C/N ratio can vary from 100 in pyrolyzed wood (de la Rosa et al., 2014). Commonly, the chemical structure of COM is assumed to be a polycondensed graphite-like aromatic network, but in COM with atomic H/C values > 0.5 at least every second C must be protonated. Application of special NMR techniques (Knicker et al., 2005) showed that in barbeque charcoal and charred peat the aromatic C occurs in small clusters with an average size of at most six aromatic rings. It is assumed that bigger clusters are formed increasing temperature. However, new NMR relaxation measurements cannot confirm this. In order to bring some light onto the chemical changes occurring during pyrolysis, established and advanced solid-state NMR spectroscopy was applied to chars produced from model structures such as cellulose, lignin, chitin, casein, as well as peat, nutshells, and greens of dried tomato plants.Peer reviewe
Black carbon, pyrogenic carbon
No full textBlack carbon or pyrogenic carbon (PyC) represents a ubiquitous entity of soil organic matter (SOM). Presently, it is best described as a continuum of thermally altered biomolecules. The degree of their alteration depends on heat severity, heating conditions (oxic, pyrolysis), and the nature of the feedstock. Comparably, a paradigm shift occurred with respect to the biochemical recalcitrance of PyC taking into consideration that the latter depends not only on the degree of charring of the respective PyC but also relies on soil conditions. There is a clear effect on PyC properties (increasing pH, darkness, hydrophobicity, and plant nutrient contents), which can survive on a long-term scale. Thus, fire and biochar amendment may play an important role in pedogenetic processes. © 2023 Elsevier Ltd. All rights reserved.111 referencias.Peer reviewe
Correction to: Biochar and Metallic Nanoparticle Additives in Agricultural Residues Composting Modulate the Mineralization Patterns of End-Products When Added to Tropical Soils
No full textThe following Funding information was missing from the article as originally published:
This research was funded by ANID (National Research and Development Agency of Chile) through FONDECYT Initiation N°11201107 and Regular 1201375 projects. M. Panettieri acknowledges the funding received from Comunidad de Madrid (Spain) through the “Atracción de Talento” grant (Ref: 2019T1/AMB14503) and Fundación General CSIC by the support through LINCGLOBAL (LINCG24018). The authors thank to UOH, IRNAS-CSIC, UFRO, and ICA-CSIC for their valuable support.
The original article has been corrected.Peer reviewe
Sulfur K-edge XANES spectroscopy reveals differences in sulfur speciation of bulk soils, humic acid, fulvic acid, and particle size separates
No full text14 pages, 5 figures, 6 tables, 45 references.X-ray absorption near edge structure (XANES) spectra at the sulfur (S) K-edge (E=2472 eV) were compared for bulk soil material, humic and fulvic acid fractions, and different particle size separates from Ah horizons of two arable Luvisols, from an O and a Bs horizon of a Podzol under Norway spruce forest, and from an H horizon of a Histosol (peat bog). In the bulk soil samples, the contribution of reduced organic S (organic mono- and disulfides) to total sulfur increased from 27% to 52%, and the contribution of ester sulfate and SO42−-S decreased from 39% to 14% of total S in the following order: arable Luvisols Ah—forested Podzol O—Histosol H. This sequence reflects the increasing organic carbon content and the decreasing O2 availability in that order. Neither sulfonate nor inorganic sulfide was detected in any of the bulk soil samples. For all samples except the Podzol Bs, the XANES spectra of the bulk soils differed considerably from the spectra of the humic and acid fractions of the respective soils, with the latter containing less reduced S (16–44% of total S) and more oxidized S (sulfone S: 19–35%; ester sulfate S: 14–38% of total S). Also the S speciation of most particle size fractions extracted from the Ah horizon of the Viehhausen Luvisol and the Bs horizon of the Podzol was different from that of the bulk soil. For both soils, the contribution of oxidized S species to total S increased and the contribution of sulfoxides and organic mono- and disulfides decreased with decreasing particle size. Thus, sulfur K-edge XANES spectra of alkaline soil extracts, including humic and fulvic acids or of particle size separates are not representative for the S speciation of the original soil sample they are derived from. The differences can be attributed to (i) artificial changes of the sulfur speciation during alkaline extraction (conversion of reduced S into oxidized S, loss of SO42− during purification of the extracts by dialysis) or particle size separation (carry-over of water-soluble S, such as SO42−), but also to (ii) preferential enrichment of oxidized S in hydrophilic water-soluble soil organic matter (ester sulfate) and in the clay fraction of soils (ester sulfate, adsorbed SO42−).Peer reviewe
Preface—special issue in memory of Frank J. Stevenson
Full text linkNatural organic matter (NOM) comprises a complex mixture of thousands of organic compounds found in water, soils, and sediments that was naturally formed from residues of plants, microorganisms, and animal matter at various stages of the decaying process. It is ubiquitous and plays an important role for the functioning of ecosystems. In soils it appears as soil organic matter (SOM) and in surface water mostly as dissolved (DOM) or particulate organic matter (POM). However, it occurs also in fossil and recent sediments as well as in composts, sewage sludge, or organic waste. Its chemical composition and physical properties can vary largely and depend on the quality of the substrate, the environmental conditions in which it was formed and the time and intensity of its humification. According to the International Humic Substance Society (IHSS), humification describes the chemical and biochemical processes included in the degradation and transformation of plant and microbial residues into the so called humic substances (HS) (IHSS 2017). NOM is involved in many processes in soils and natural waters, e.g., weathering, plant nutrition, pH buffering, major and trace metal mobility and toxicity, bioavailability, transport of organic chemicals and inorganic compounds, formation of disinfection by-products during water treatment, and heterotrophic production in black-water ecosystems. Bearing this in mind, a better understanding of the character and function of NOM and HS are of broad interest and have received attention from scientists in a wide variety of discipline. Frank J. Stevenson (1922–2015) was one of the scientists who dedicated their professional life to increase our understanding of the properties and functions of NOM. He can be certainly considered as a pioneer of NOM and HS research by exploring innovative approaches to the study of both bulk SOM and humus chemistry. For more than thirty years, he was among the most influential in pushing forward the frontiers and guiding the directions in these research areas, which encouraged the IHSS to dedicate this Special Issue to his memory
Supplementary data for: High-pH and anoxic conditions during soil organic matter extraction increases its electron-exchange capacity and ability to stimulate microbial Fe(III) reduction by electron shuttling
No full textSoil organic matter (SOM), including humic substances (HS), is redox-active, can be microbially reduced, and transfers electrons in an abiotic reaction to Fe(III) minerals thus serving as electron shuttle. The standard procedure to extract HS from soil and separate it into humic acids (HA) and fulvic acids (FA) involves alkaline and acidic solutions potentially leading to unwanted changes in SOM chemical and redox properties. To determine the effects of extraction conditions on the redox and electron shuttling properties of SOM extracts, we prepared HS and SOM extracts from a forest soil applying either a combination of 1 M NaOH and 6 M HCl, or water (pH 7). Both chemical extractions (NaOH/HCl) and water extractions were done in separate setups under either oxic or anoxic conditions. Furthermore, we applied to a subsample of the water-extracted-SOM the NaOH/HCl treatment. We found that soil extraction with NaOH lead to ca. 100 times more extracted C and the extracted HS had 2-3 times higher electron exchange capacities (EEC) than SOM extracted by water. For water-extracted SOM, anoxic extraction conditions lead to about 7 times more extracted C and 1.5 times higher EEC than under oxic extraction conditions. This difference was probably due to the occurrence of microbial reduction and dissolution of Fe(III) minerals in the soil during the water extraction at neutral pH and the concomitant release of Fe(III) mineral-bound organic matter. NaOH/HCl treatment of the water-extracted SOM lead to 2 times higher EEC values in the HA isolated from the SOM compared to the water-extracted SOM itself, suggesting the chemical treatment with NaOH and HCl caused changes of redox-active functional groups of the extracted organic compounds. Higher EEC of extracts in turn resulted in a higher stimulation of microbial Fe(III) mineral reduction by electron shuttling, i.e. faster initial Fe(III) reduction rates, and in most cases also in higher reduction extents. Our findings suggest that SOM extracted with water at neutral pH should be used to better reflect environmental SOM redox processes in lab experiments and that potential artefacts of the chemical extraction method and anoxic extraction condition need to be considered when evaluating and comparing abiotic and microbial SOM redox processes
Use of biochar as soil amendment; agronomic and environmental application
No full textTutores: Knicker, Heike; Murillo Carpio, José Manuel y Rosa Arranz, José M. de laPeer Reviewe
Biodegradability of Disposable Surgical Face Masks Littered into Soil Systems during the COVID 19 Pandemic—A First Approach Using Microcosms
No full textThe COVID-19 pandemic caused massive use and improper disposal of surgical polypropylene (PP)-based face masks. For a first evaluation of the respective environmental consequences, we performed a 6-month microcosm experiment at 25 °C to determine the microbial degradability of 10 × 10 mm cuts of single mask layers and of a complete mask mixed with topsoil (Cambisol). By analyzing the CO2 production, we identified a fast pool with a mean residence time (MRTfast) of 3 to 7 days, corresponding to approximately 4 to 5% of the total mask carbon. Solid-state nuclear magnetic resonance (NMR) spectroscopy of the degraded masks suggests a cut-off of PP units or oligomers as a main degradation mechanism. The slow carbon pool of the center mask revealed an MRTslow of 7 years and those of the remaining mask material MRTslows between 19 and 28 years, which is three to five times longer than those of soil organic matter (SOM) of the pure soil. Since the masks were not pretreated, and decomposed in the dark without UV radiation, our data support our hypothesis that in soils, microbes must exist that can decompose PP, although their nature still has to be revealed in future attempts
Solid-state 2-D double cross polarization magic angle spinning 15N 13C NMR spectroscopy on degraded algal residues
No full text4 pages, 2 figures, 8 references.Solid-state 2-D 15N 13C NMR spectroscopy was applied for the first time to reveal the chemical nature of nitrogen in degraded algae. Cross peaks indicating coupling between 13C and 15N were detected only for carboxyl/amide-C and N-substituted-alkyl-C. Cross peaks correlating 15N intensity to sp2-C and supporting the presence of heteroaromatic-N were not observed. The Bloch decay 15N NMR spectrum demonstrated that the lack of pyridine-type-N and/or imine-N signals in the CPMAS 15N NMR spectrum is not caused by inefficient magnetization transfer. The results give further evidence that amide-N in peptide-like structures comprises the major form of nitrogen in degraded algal residues.The author thanks the German Federal Ministery of Education and Science (BMBF) for financial support.Peer reviewe
Biochar and Metallic Nanoparticle Additives in Agricultural Residues Composting Modulate the Mineralization Patterns of End-Products When Added to Tropical Soils
No full text11 February 2025A Correction to this paper has been published: https://doi.org/10.1007/s42729-025-02316-zThis study evaluated the effects of biochar and metallic oxide nanoparticles (iron oxide and halloysite nanoclays) used as compost additives on the decomposition and mean residence time (MRT) of soil organic matter (SOM) in tropical grassland soils. The objective was to explore their impact on decomposition rates and the chemical structure of compost-derived SOM to optimize carbon storage and organic fertilization strategies. Organic residues that included cow manure and wheat straw, with a C3 signature, were initially composted adding biochar, metallic oxides, and their combination as additives. The end products (stabilized compost) were applied to tropical soil naturally enriched in 13C due to theC4 vegetation in an incubation experiment, where basal respiration, compost, and SOM decomposition were analyzed, and the mean residence time (MRT) was estimated. Additionally, the preservation of different carbon pools and functional groups during the mineralization of SOM and compost organic matter was assessed and modeled, using a combination of δ13C stable isotope and 13C NMR spectroscopy. The results showed that additives such as biochar and halloysite nanoparticles reduced the decomposition rate of compost, increasing its MRT from 4.5 to 7.6 and 5.4 years, respectively. This could be driven by organo-mineral interactions of organic matter (OM) with metallic nanoparticles, and biochar adsorption of the soluble compost-derived OM. However, the combination of biochar and metallic nanoparticles showed no synergistic effect for compost-derived-OM preservation, but a probable mineralization of biochar-derived C. These findings suggest that additives significantly modulate organic matter decomposition and structural rearrangement, extending its MRT in the studied soil. These additives can be crucial in improving soil carbon storage, presenting a promising avenue for long-term organic fertilization and soil management practices.This research was funded by ANID (National Research and Development Agency of Chile) through FONDECYT Initiation N°11201107 and Regular 1201375 projects. M. Panettieri acknowledges the funding received from Comunidad de Madrid (Spain) through the “Atracción de Talento” grant (Ref:2019T1/AMB14503) and Fundación General CSIC by the support through LINCGLOBAL (LINCG24018). The authors thank to UOH, IRNAS-CSIC, UFRO, and ICA-CSIC for their valuable support.Peer reviewe
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