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Microorganisms play an essential role in soil ecosystem functioning as they are responsible for nutrient cycling, humus formation and building of soil structure. The microbial biomass is considered to be a dynamic source and sink of nutrients, and it is the driving force behind SOM transformations. Soil microbial biomass (SMB) C and N dynamics, as well as microbial community patterns were studied under laboratory and field conditions in soils of high yield (HY) and low yield (LY) areas in an agricultural field. The turnover of C and N through the soil microbial biomass was monitored using isotopic labels (13C, 15N). Microbial diversity was estimated using culture-independent methods (16S rDNA, DGGE). The different yield performance in HY and LY areas of the agricultural field was reflected in the respective turnover times of C and N through the microbial biomass, but not in the soil microbial diversity., Abbau und Umbau organischer Substanz im Boden erfolgt zum grössten Teil durch dessen mikrobielle Populationen. Die mikrobielle Biomasse ist darüber hinaus ein dynamischer Speicher von Nährstoffen. Sie spielt eine Schlüsselrolle in der Nährstoffnachlieferung. In Labor- und Feldversuchen anhand der Markierung mit stabilen Isotopen der C und N Umsatz durch die mikrobielle Biomasse in Bodenmaterial von Hoch- und Niedrigertragsbereichen eines konventionell bewirtschafteten Ackers bestimmt, sowie die Zusammensetzung der mikrobiellen Population mit DNA fingerprints untersucht. Die unterschiedliche Ertragsstruktur der untersuchten Böden spiegelte sich in den Umsatzraten von C und N durch die mikrobielle Biomasse wieder, nicht aber in der Diversität der gesamten Population.

Die vorliegende Arbeit befaßt sich mit Struktur- und Größencharakterisierung von Huminstoffen (HS) und ihren methylierten Derivaten. Hierfür wurden die HS mit einer Kombinationsmethode (Methyliodid und Diazomethan) methyliert und die entstandenen Derivate mittels 1D- und 2D-NMR-Spektroskopie untersucht. Zur Bestimmung von Molekulargewichten, Durchmessern und Diffusionskoeffizienten der HS wurden diese mittels asymmetrischer Feld-Flussfraktionierung (AFFFF) in wässriger Lösung analysiert. Zudem fand die AFFFF erstmals Anwendung bei der Messung von methylierten HS in organischen Lösungsmitteln (Methanol, THF)., The aim of this thesis was to gain further knowledge of the molecular structure and size of Humic Substances (HS) and their methylated derivatives. The HS were methylated with methyl iodide and diazomethane. The resulting derivatives were analysed by 1D- and 2D-NMR-Spectroscopy. Asymmetric Flow-Fieldflowfractionation (AFFFF) measurements in aqueous solution were carried out to determine molecular weights, diameters and diffusion coefficients of the HS. Furthermore, AFFFF was used for the first time to examine methylated HS in organic solvents (Methanol, THF).

Huminstoffe bestehen aus einer komplexen Mischung einzelner Komponenten und besitzen daher keine definierte molekulare Struktur. Polare funktionelle Gruppen sind als relevante Konstituenten von Huminstoffen verantwortlich für das physikochemische Verhalten sowie das ökologische Wirkungsspektrum von Huminstoffen. Die NMR-Spektroskopie spielt eine herausragende Rolle für die Charakterisierung von Huminstoffen. Die Kombination aus chemischer Derivatisierung mit NMR aktiven Markern und zweidimensionaler NMR Spektroskopie ist eine neue Methode für die Identifizierung und Quantifizierung von aziden, sauerstoffhaltigen Funktionen in Huminstoffen. Mit dieser Methode können sowohl aliphatische und aromatische Carboxylgruppen als auch primäre, sekundäre und tertiäre Hydroxylgruppen unterschieden werden., Humic substances are a complex mixture with a nearly infinite number of components and for this reason, they do not possess a well defined molecular structure. Functional groups are relevant constituents of humic substances and affect their physico-chemical properties and ecological efficacy. NMR spectroscopy is a valuable tool for the characterization of humic substances. The combination of chemical derivatization with NMR active labels and two dimensional NMR spectroscopy is a new method for the identification and quantification of exchangeable protons in humic materials. It allows a detailed distinction of aliphatic and aromatic carboxylic acids as well as a differentiation of primary, secondary and tertiary alcohols in humic substances.

Microorganisms play an essential role in soil ecosystem functioning as they are responsible for nutrient cycling, humus formation and building of soil structure. The microbial biomass is considered to be a dynamic source and sink of nutrients, and it is the driving force behind SOM transformations. Soil microbial biomass (SMB) C and N dynamics, as well as microbial community patterns were studied under laboratory and field conditions in soils of high yield (HY) and low yield (LY) areas in an agricultural field. The turnover of C and N through the soil microbial biomass was monitored using isotopic labels (13C, 15N). Microbial diversity was estimated using culture-independent methods (16S rDNA, DGGE). The different yield performance in HY and LY areas of the agricultural field was reflected in the respective turnover times of C and N through the microbial biomass, but not in the soil microbial diversity., Abbau und Umbau organischer Substanz im Boden erfolgt zum grössten Teil durch dessen mikrobielle Populationen. Die mikrobielle Biomasse ist darüber hinaus ein dynamischer Speicher von Nährstoffen. Sie spielt eine Schlüsselrolle in der Nährstoffnachlieferung. In Labor- und Feldversuchen anhand der Markierung mit stabilen Isotopen der C und N Umsatz durch die mikrobielle Biomasse in Bodenmaterial von Hoch- und Niedrigertragsbereichen eines konventionell bewirtschafteten Ackers bestimmt, sowie die Zusammensetzung der mikrobiellen Population mit DNA fingerprints untersucht. Die unterschiedliche Ertragsstruktur der untersuchten Böden spiegelte sich in den Umsatzraten von C und N durch die mikrobielle Biomasse wieder, nicht aber in der Diversität der gesamten Population.

Huminstoffe bestehen aus einer komplexen Mischung einzelner Komponenten und besitzen daher keine definierte molekulare Struktur. Polare funktionelle Gruppen sind als relevante Konstituenten von Huminstoffen verantwortlich für das physikochemische Verhalten sowie das ökologische Wirkungsspektrum von Huminstoffen. Die NMR-Spektroskopie spielt eine herausragende Rolle für die Charakterisierung von Huminstoffen. Die Kombination aus chemischer Derivatisierung mit NMR aktiven Markern und zweidimensionaler NMR Spektroskopie ist eine neue Methode für die Identifizierung und Quantifizierung von aziden, sauerstoffhaltigen Funktionen in Huminstoffen. Mit dieser Methode können sowohl aliphatische und aromatische Carboxylgruppen als auch primäre, sekundäre und tertiäre Hydroxylgruppen unterschieden werden., Humic substances are a complex mixture with a nearly infinite number of components and for this reason, they do not possess a well defined molecular structure. Functional groups are relevant constituents of humic substances and affect their physico-chemical properties and ecological efficacy. NMR spectroscopy is a valuable tool for the characterization of humic substances. The combination of chemical derivatization with NMR active labels and two dimensional NMR spectroscopy is a new method for the identification and quantification of exchangeable protons in humic materials. It allows a detailed distinction of aliphatic and aromatic carboxylic acids as well as a differentiation of primary, secondary and tertiary alcohols in humic substances.

Organic matter plays a major role in the chemical and physical attributes of highly weathered soils usually found in tropical and subtropical regions. In the present work, soil organic matter (SOM) of six representative Brazilian Ferralsol profiles was examined by chemical analyses, solid state 13C and 15N nuclear magnetic resonance (NMR) spectroscopy and electron spin resonance (ESR) spectroscopy. The HF treatment, realized with the soil samples prior to the spectroscopic analysis, promoted both C and N enrichment, and no selective dissolution of specific C-compounds was identified. The recovery of C and N ranged between 47% and 66% in the A horizon and decreased pronouncedly with depth. The solubility of SOM after HF treatment, especially in deeper horizons, was related to its occurrence in organo-mineral associates. The results obtained by 13C NMR revealed that the SOM of A horizons of the Brazilian Ferralsols is characterized by a considerable amount of O-alkyl (29–38%), followed by lower proportions of alkyl (24–30%) and aromatic structures (10–14%). The organic nitrogen occurred mainly as amide, as indicated by the 15N NMR analysis. A similar pattern was exhibited by the SOM of lower horizons. The C/N ratio varied between 8 and 21 and tended to decrease with depth. The same trend was found for the semiquinone-type free radicals concentrations, determined by ESR spectroscopy. The occurrence of a SOM showing a medium decomposition degree containing structures of low chemical recalcitrance points to a stabilization of organic matter mainly through surface interactions with iron oxides and kaolinite.

The long-term soil management effects on C and N stocks of soil physical fractions are still poorly understood for South American subtropical soils. This study aimed (i) to evaluate the influence of cereal- and legume-based cropping systems and N fertilisation on C and N stocks of the sand-, silt- and clay-size fractions of a no-tilled subtropical Acrisol in southern Brazil, (ii) to compute the Carbon Management Index (CMI) for those cropping systems using physical fractionation data, and (iii) to investigate the possible existence of finite capacity of those soil physical fractions to store C and N. Soil samples of a long-term experiment were collected from the 0–2.5 and 2.5–7.5 cm layers of three no-till cropping systems [fallow bare soil, oat/maize (O/M) and pigeon pea+maize (P+M)] under two N fertilisation levels (0 and 180 kg N ha−1). However, for fallow bare soil, only the non-fertilised sub-plot was sampled. An adjacent native grassland soil was sampled as a reference. The C and N stocks of the three soil physical fractions were higher in the legume-based cropping system (P+M) than in O/M and bare soil, because of the higher residue input in the former. The P+M cropping system restored the C and N stocks in sand- and silt-size fractions to the same levels found in grassland soil. Higher C and N stocks in all physical fractions were also obtained with N fertilisation. The C and N stocks and the C:N ratio were most affected by cropping systems in the sand- and least in the clay-size fraction. Particulate organic matter was found in the silt-size fraction, showing this fraction is not only constituted by mineral-associated organic mater, as commonly believed. Taking grassland soil as reference (CMI = 100), the CMI ranged from 46, in O/M no N, to 517, in P+M with N, pointing to a better soil management in the latter. The clay-size fraction tended to show a finite capacity to store C and N (48.8 g C kg−1 and 4.9 g N kg−1 of clay), which was not verified in sand- a

This study was conducted to investigate the influence of land-use systems (grassland and cropland) and of long-term no-till cropping systems [bare soil, oat/maize (O/M), pigeon pea+maize (P+M)] on the composition of organic N forms in a subtropical Acrisol. Soil samples collected from the 0- to 2.5-cm layer in the study area (Eldorado do Sul RS, Brazil) were submitted to acid hydrolysis and cross-polarization magic angle spinning (CPMAS) 15N and 13C nuclear magnetic resonance (NMR) spectroscopies. The legume-based cropping system P+M contained the highest contents of non-hydrolysable C and N, hydrolysable C and N, amino acid N and hydrolysed unknown N. The relative proportion of non-hydrolysable N was higher in bare soil (30.0%) and decreased incrementally in other treatments based on the total C and N contents. The amino acid N corresponded to an average of 37.2% of total N, and was not affected by land use and no-till cropping systems. The non-hydrolysable residue contained lower O-alkyl and higher aromatic C concentrations, as revealed by CPMAS13C NMR spectroscopy, and higher C: N ratio than the bulk soil. No differences in the bulk soil organic matter composition could be detected among treatments, according to CPMAS 13C and 15N NMR spectra. In the non-hydrolysable fraction, grassland showed a lower concentration of aromatic and a higher concentration of alkyl C than other treatments. From CPMAS 15N NMR spectra, it could be concluded that amide N from peptide structures are the main organic N constituent. Amide structures are possibly protected through encapsulation into hydrophobic sites of organic matter and through organomineral interaction.

Detailed information about structure and composition of organic sorbents is required to understand their impact on sorption capacity and sorption kinetic of organic pollutants. Therefore, the chemical composition of organic material from 18 geosorbents was investigated by solid-state 13C nuclear-magnetic-resonance (NMR) spectroscopy. Structural parameters such as aromaticity, polarity, and alkyl-C content were related to the Freundlich sorption exponent (1/n) and the sorption coefficient equation image. The geosorbents included three natural and four combusted coals (carbonaceous material), three Histosols, five mineral soils from Germany containing inputs of technogenic carbonaceous material, derived from industrial activities, and four non-contaminated mineral soils from Germany. Equilibrium sorption was measured for five hydrophobic organic compounds and analyzed with the solubility-normalized Freundlich sorption isotherm. With increasing maturation degree, the proportion of polar constituents decreases from the natural soils to the coals. In contrast to the non-polluted mineral soils, the soils with technogenic input are characterized by high aromaticity and low polarity. A positive correlation between sorption coefficient equation image and aromaticity was found. The Freundlich exponent (1/n) is negatively correlated with the aromaticity, denoting an increase of adsorption processes with increasing aromaticity. Likewise, the contribution of partitioning decreases. This sorption mechanism predominates only if the organic matter in the samples contains a high proportion of polar compounds.

We know much about the influence of management on stocks of organic matter in subtropical soils, yet little about the influence on the chemical composition. We therefore studied by CPMAS 13C NMR spectroscopy the composition of the above-ground plant tissue, of the organic matter of the whole soil and of silt- and clay-size fractions of the topsoil and subsoil of a subtropical Acrisol under grass and arable crops. Soil samples were collected from three no-till cropping systems (bare soil; oats−maize; pigeon pea + maize), each receiving 0 and 180 kg N ha−1 year−1, in a long-term field experiment. Soil under the original native grass was also sampled. The kind of arable crops and grass affected the composition of the particulate organic matter. There were no differences in the composition of the organic matter in silt- and clay-size fractions, or of the whole soil, among the arable systems. Changes were observed between land use: the soil of the grassland had larger alkyl and smaller aromatic C contents than did the arable soil. The small size fractions contain microbial products, and we think that the compositional difference in silt- and clay-size fractions between grassland and the arable land was induced by changes in the soil's microbial community and therefore in the quality of its biochemical products. The application of N did not affect the composition of the above-ground plant tissue nor of the particulate organic matter and silt-size fractions, but it did increase the alkyl C content in the clay-size fraction. In the subsoil, the silt-size fraction of all treatments contained large contents of aromatic C. Microscopic investigation confirmed that this derived from particles of charred material. The composition of organic matter in this soil is affected by land use, but not by variations in the arable crops grown.

Iron oxides with high specific surface areas promote the stabilisation of soil organic matter. We compared solid state 13C nuclear magnetic resonance (NMR) spectra of clay fractions from A horizons before and after demineralisation with 10% hydrofluoric acid (HF) to study selective associations between Fe oxides and functional groups in soil organic matter. The samples were collected from soils under temperate forest conditions, classified as Cambisols, Leptosols, Luvisols and Phaeozem. After removal of Fe oxides by demineralisation, solid state 13C NMR spectra of clay fractions from Leptosols and Luvisols showed an increase in the relative O/N-alkyl C intensity that ranged from 3% to 20%. A variable contact time experiment with a sample from a Luvisol without HF treatment showed that protons in the vicinity of O/N-alkyl C relaxed faster than in the vicinity of other functional groups. Therefore, part of the O/N-alkyl C was invisible unless very short contact times were applied. This demonstrated that Fe oxides and O/N-alkyl C are preferentially associated in soils. The O/N-alkyl C signal loss in the untreated samples was strongly correlated with the ratio of dithionite-extractable iron oxides and the organic carbon (OC) concentration. Our study showed that OC:Fe ratios >1 do not necessarily assure that reasonable solid state 13C NMR spectra will be obtained. In fact, clay fractions with OC:Fe ratios between 2.2 and 3.8 were affected by association between Fe oxides and O/N-alkyl C and had to be treated with HF to circumvent a selective signal loss of O/N-alkyl C.

Soil organic matter is an ecosystem component with agronomic and environmental functions and is affected by soil management. The objectives of this study were to evaluate (i) soil organic C and N losses during a period of conventional cultivation (1969–1983) that followed on native grassland and (ii) the potential of four long-term (17 years) no-till cereal- and legume-based cropping systems (bare soil, oat (Avena strigosa Schreb.)/maize (Zea mays L.), lablab (Lablab purpureum L. Sweet) + maize and pigeon pea (Cajanus cajan L. Millsp.)+maize) with different N fertilisation levels (0 and 180 kg N ha−1 year−1) to increase the C and N stocks of a southern Brazilian Acrisol. Samples were taken from 0 to 107.5 cm depth, in 10 soil layers. The C content in the 0–17.5 cm layer of grassland decreased by 22% (8.6 Mg C ha−1) during the period of conventional cultivation. Meanwhile, N decreased by 14% (0.44 Mg N ha−1). Additional C and N losses occurred after the establishment of bare soil and oat/maize (no N). With N fertilisation, the C and N stocks of oat/maize were steady with time. Legume-based cropping systems (lablab + maize and pigeon pea + maize) increased C and N stocks due to the higher residue input. Although the major soil management effects were found in the 0–17.5 cm layer, up to 24% of the overall C losses and up to 63% of the gains of the whole 0–107.5 cm layer occurred below the 17.5 cm depth, reinforcing the importance of subsoil as a C source or sink. The average C sequestration rate of legume-based cropping systems (with N) was 0.83 Mg C ha−1 year−1 in the top 0–17.5 cm layer and 1.42 Mg C ha−1 year−1 in the whole 0–107.5 cm layer, indicating the remarkable potential of legume cover crops and N fertilisation under no-tillage to improve SOM stocks and thus, soil and environmental quality in humid subtropical regions.

[EN]: Relationships between soil lightness, soil organic matter (SOM) composition, content of organic C, CaCO3, and texture were studied using 42 top-soil horizons from different soil types located in southern Germany. SOM composition was determined by CPMAS 13C NMR spectroscopy, soil color was measured by diffuse-reflectance spectrophotometry and given in the CIE L*a*b* color coordination system (Commission Internationale de l'Eclairage, 1978). Multiple-regression analysis showed, that soil lightness of top-soil horizons is principally determined by OC concentration, but CaCO3 and soil texture are also major variables. Soil lightness decreased with increasing OC content. Carbonate content had an important effect on soil lightness even at low concentrations due to its lightening property. Regressions between soil lightness and organic C content were strongly linear, when the soils were differentiated according to texture and CaCO3 content. The aryl-C content was the only SOM component which correlated significantly with soil lightness (rS = –0.87). In the linear regressions carried out on the different soil groups, soil aryl-C content was a more significant predictor for soil lightness than total OC content., [GR]: Der Zusammenhang zwischen Bodenhelligkeit, Zusammensetzung der organischen Substanz und Gehalt an Corg., CaCO3 und Textur wurde in 42 Oberböden aus verschiedenen Bodentypen Süddeutschlands untersucht. Die Zusammensetzung der organischen Substanz wurde mittels CPMAS-13C-NMR-Spektroskopie bestimmt, die Bodenfarbe mittels Spektralphotometer und als Bodenhelligkeitswert im CIE L*a*b*-Farbkoordinatensystem (Commission Internationale de l'Eclairage, 1978) angegeben. Die Auswertung über multiple Regression zeigte, dass die Bodenhelligkeit hauptsächlich vom OC-Gehalt bestimmt wird; CaCO3-Gehalt und Textur erwiesen sich als weitere relevante Variablen. Die Bodenhelligkeit nimmt mit zunehmendem OC-Gehalt ab. Aufgrund seiner stark aufhellenden Wirkung hat der Carbonatgehalt auch bei niedrigen Konzentrationen einen deutlichen Einfluss auf die Bodenhelligkeit. Bei Berücksichtigung der Textur und des Carbonatgehalts ergaben sich lineare Beziehungen zwischen Bodenhelligkeit und OC-Gehalt. Der Aryl-C-Gehalt des Bodens war als einzige Humuskomponente signifikant mit der Bodenhelligkeit korreliert (rS = –0.87). Der Aryl-C-Gehalt des Bodens bestimmt die Bodenhelligkeit schärfer als der OC-Gehalt.

Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) was used to reveal the influence of iron on the detectability of condensed tannins extracted from Picea abies. Iron chloride mixed with condensed tannins suppresses the detection of tannins by MALDI-TOF MS in a dose-dependent manner. Total suppression is observed at concentrations of 250 and 500 mg FeCl3 g–1 of sample. At lower concentrations, spectrum quality is still greatly reduced, but short chain tannins are detected. At 100 mg FeCl3 g–1 of sample, iron increased the intensity of the tannin galloyl ester peaks above those of the corresponding tannin polymers. This points to an antagonistic effect of the galloyl ester moiety on iron complexation with condensed tannins and, thus, their reduced susceptibility to iron interference during MALDI-TOF MS.

129Xe nuclear magnetic resonance (NMR) spectroscopy of adsorbed xenon was applied for the characterisation of soil meso- and microporosity. Model systems (Ca-montmorillonite, quartz sand) and three soil types (Luvisol Alh, Bt and Cv horizons; Gleysol Go horizon; Podzol Bvs horizon) were studied. For Ca-montmorillonite, the average intercrystallite pore size has been evaluated. In natural soils, 129Xe resonance parameters were shown to be affected by different factors: pore heterogeneity, influence of organic functional groups, possible presence of paramagnetic compounds, occurrence of xenon exchange between inter- and intraparticle void spaces. The effect of those factors on the pattern of 129Xe NMR spectra was tested. In the three soils studied, no micropores within the mineral phase available for xenon adsorption were found. The most probable reason is that such pores are occupied by small molecules of the soil organic matter (SOM). Variable extent of accessibility of mesopores within the mineral phase of the various soils was revealed. It was highest in the Podzol. Here, xenon exchange between different adsorption zones (i.e., pores of differing size, e.g., internal and external void spaces) was slow on an NMR time scale that allowed to detect separate signals, each characterising xenon behaviour in the respective adsorption zone. The pore system of the soil organic matter was shown to be not accessible for xenon, as it is accepted for N2 and other nonpolar adsorbates. Based on analysis of the spectra, a model for the possible mutual location of organic matter and iron compounds in natural soils was suggested. According to this model, a certain part of organic matter species can form the layers above iron species, thus masking them and preventing 129Xe NMR spectra from significant low-field shifts and signal broadening.

Simplified equations are used in common approaches to describe cross polarization (CP) dynamics of solids. The CP behavior may be modulated by several nuclei interactions and physicochemical sample properties. At high magnetic fields and spinning speeds, these modulations can obscure the results. To elucidate their impact on the CP behavior of natural organic materials variable contact time (VCT) experiments were acquired with a high temporal resolution for two coal samples. The measurements were distinctly influenced by interfering fluctuations. Conventional approaches showed insufficient flexibility in terms of degrees of freedom to calculate the CP dynamics. The use of an original fundamental equation as model resulted in sufficient flexibility for such heterogeneous systems. The best results were obtained assuming a two component system. On these conditions a differentiation between amorphous and crystalline domains within the coal samples was enabled.

MALDI-TOF mass spectrometry and 13C NMR spectroscopy were applied to unveil typical characteristics of condensed tannins of leaves and needles from willow (Salix alba), spruce (Picea abies) and beech (Fagus sylvatica) of three tree species that are ubiquitous in German forests and landscapes. For further evaluation, lime (Tilia cordata) was included. The 13C NMR spectroscopy confirmed the purity of the condensed tannin fractions and the efficiency of the procedure used for their extraction. While signals representative for procyanidin units are observable in all liquid-state 13C NMR spectra, resonance lines of prodelphinidin were only detected in those obtained from the condensed tannins of spruce needles and beech leaves. Typical signals in the chemical shift region between 70 and 90 ppm demonstrated the presence of stereoisomers (catechin/epicatechin; gallocatechin/ epigallocatechin). The MALDI-TOF mass spectra of the condensed tannins show signals of polymers of up to undecamers. Supporting the observations from the NMR spectroscopy, the mass spectra of the willow and lime leaf condensed tannins were identified as polymers with mainly procyanidin units, while the polymers of the spruce needle and beech leaves exhibit varying procyanidin/prodelphinidin ratios. Post source decay (PSD) fragmentation lead to a sequential loss of monomers and allowed a detailed characterization and sequencing of individual chains. In the case of the condensed tannins of lime this technique clearly excludes a pelargonidin terminal unit followed by a prodelphinidin unit, which would result in the same molecular masses as a polymer solely built up of procyanidin units.

Alterations of the chemical structure of condensed tannins (CT) during decomposition of Norway spruce (Picea abies) needles and white willow (Salix alba) leaves were investigated by gel permeation chromatography (GPC), 13C nuclear magnetic resonance (NMR) spectroscopy, and matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS). The effect of these alterations on their protein binding capacity was determined by radial diffusion assay on an agarose plate. For these studies an incubation experiment was performed with spruce needles and willow leaves. From the fresh foliage and its decomposed materials obtained after 4-days, and 1-, 2-, 4-, and 8-weeks of incubation, CT were extracted and analyzed. Dynamics of CT alterations during decomposition of the fresh foliage were different for the two plant species, although the amount of extractable CT for both decreased soon after incubation and only slight amounts of CT were extractable after 8 weeks of incubation. The decrease was faster for the willow leaves than for the spruce needles. Solution 13C NMR revealed alterations of CT isolated from both degrading plant materials, but only to a small extent. However, considerable changes in chemical composition and chain length of the CT were detected by MALDI-TOF MS. Changes in the chemical composition of CT are expected to decrease the protein binding capacity. Applying the radial diffusion assay, this assumption was confirmed for spruce CT, but not for willow CT. This may be explained by (1) higher reactivity of prodelphinidin (PD) than procyanidin (PC), the former is contained in spruce CT but not in willow CT and (2) the slower decomposition rate of spruce needles than willow leaves. Thus, CT in spruce needles may have suffered a greater extent of chemical alteration, which formed partially altered CT with less protein binding capacity. Further, since the decomposition rate of spruce needles was slower than that of willow leaves, the pa

Organic matter in B and C horizons of mineral soils is extremely important in terms of carbon sequestration of soils because it may contain stabilized carbon compounds. The aim of this study was to examine the composition of the organic matter found in deeper soil horizons and to compare it with the surface soil horizon. The conceptual approach included the analyses of bulk soil and particle size fractions by elemental analyses and isotopic characterization. The chemical structure of the organic matter was examined by 13C CPMAS NMR spectroscopy and pyrolysis GC/MS. Additionally single plant litter compounds were analyzed. Isotopic analyses pointed to an increasing degree of organic matter stabilization with depth. The chemical composition of the organic matter of the B horizons suggest that root-derived compounds are stabilized preferentially. In the C horizons, microbial compounds seem to dominate.

The investigation of the chemical composition of soil organic matter (SOM) in Ferralsols by means of solid-state cross-polarization magic angle spinning (CPMAS) 13C nuclear magnetic resonance (NMR) spectroscopy is limited by their high iron oxide concentration and their low organic carbon content. In order to circumvent those limitations, such samples are often treated with hydrofluoric acid (HF) to remove paramagnetic material and to concentrate the amount of SOM. The main objectives of this study were to elucidate the impact of this approach on the resolution of the CPMAS 13C NMR spectra and on the chemical composition of the SOM in the A and B horizons of four Brazilian Ferralsols. Therefore, those soils were subjected to up to eight successive treatments with 10% (w/w) HF. Each of those extractions resulted in an enhancement of the C content of the samples. A relationship between mass loss caused by the treatment and texture and mineralogy was observed. However, high losses of carbon occurred during the HF treatments, particularly in the B horizons, but no consistent alterations in the distribution of carbon functional groups were determined by CPMAS 13C NMR, suggesting that preferential loss of specific carbon groups was not induced. The concentration of total and dithionite extractable Fe increased after two treatments for most of the samples. This may be best explained by the preferential dissolution of silicate leading to a selective enrichment of iron containing minerals. After four treatments, the Fe concentration declined considerably. After the second treatment, the spectral resolution improved. Considering the obtained results, it can be confirmed that the efficiency of the HF treatment is rather controlled by the number than by the duration of the extraction. We suggest that, for A horizons of Ferralsols, four repetitions of HF treatment are sufficient to yield well-defined spectra. For their B horizons, on the other hand, the CPMAS 13C NMR spectra obt

To obtain reliable estimates for the loss of polycyclic aromatic hydrocarbons (PAHs) from contaminated soils, one has to distinguish between (i) losses due to release and solute transport and (ii) losses resulting from degradation. We studied the interplay of these processes in a column experiment representing a typical soil contamination scenario: in the upper part of the column was a contaminated layer, spiked with 9-13C-labelled anthracene, and beneath it uncontaminated pristine soil. The experimental course comprised a steady-state flow phase (constant irrigation for 4 months) followed by several periods during which flow was halted. The effects of varied residence time on anthracene biodegradation and on anthracene mass transfer were investigated. We monitored labelled anthracene and its transformation products, dissolved organic carbon, electric conductivity (EC), pH, and inorganic carbonate content in the column effluent, and the CO2 evolved. Under steady-state flow, pH, dissolved organic C, and EC approached steady states after 350 pore volumes. Concentrations of anthracene in the effluent, however, increased continuously and levelled off after 800 pore volumes. This marked retardation reflects the great affinity of anthracene to soil organic matter. The response to interruptions in the flow revealed that mass is transferred without equilibrium between solid and liquid phase for both anthracene and dissolved organic C. Thus, residence time is one factor controlling the concentration of anthracene in the effluent and therefore the export of contaminant to the aquifer. In the course of the experiment several labelled anthracene degradation products appeared in the effluent. At least three of them were identified as transformation products showing a dramatic increase in mobility relative to the parent compound. A third of the overall anthracene loss from the column was due to solute transport, and biodegradation was responsible for the remaining two th

The amount and chemical structure of the aromatic carbon fraction in archaeological soil materials was investigated. Samples from several Neolithic pits and a ditch from a settlement in southern Germany were analysed together with the surrounding loamy soil. A suite of complementary methods including 13C CPMAS nuclear magnetic resonance (NMR) spectroscopy, dipolar dephasing NMR, combined fractionation/high-energy ultraviolet (UV) photo-oxidation/13C CPMAS NMR spectroscopy and analysis of benzenepolycarboxylic acids (BPCA) were used to investigate the aromatic organic matter composition of the pits. Most of the Neolithic samples gave the highest proportion of NMR spectral intensity in the aryl carbon region with a dominant peak at 130 ppm with very low, if any, signals for substituted aromatic carbons, such as in lignin or other phenols. Between 29% and 77% of soil organic carbon survived UV photo-oxidation, mostly present as aromatic structures. Dipolar dephasing NMR spectroscopy indicated a high degree of condensation for the aromatic rings while scanning electron microscopy showed that the material had a plant-like morphology. The analysis of BPCAs as specific markers provided further evidence for the presence of highly condensed aromatic structures in the organic matter of the Neolithic pits. The evidence therefore that the aromatic carbon is derived from charcoal is strong. This material either originated from soil material that has undergone vegetation fires or from other charred organic material, e.g., residues from Neolithic fire places.

[EN]: Due to high nitrogen deposition in central Europe, the C : N ratio of litter and the forest floor has narrowed in the past. This may cause changes in the chemical composition of the soil organic matter. Here we investigate the composition of organic matter in Oh and A horizons of 15 Norway spruce soils with a wide range of C : N ratios. Samples are analyzed with solid-state 13C nuclear magnetic resonance (NMR) spectroscopy, along with chemolytic analyses of lignin, polysaccharides, and amino acid-N. The data are investigated for functional relationships between C, N contents and C : N ratios by structural analysis. With increasing N content, the concentration of lignin decreases in the Oh horizons, but increases in the A horizons. A negative effect of N on lignin degradation is observed in the mineral soil, but not in the humus layer. In the A horizons non-phenolic aromatic C compounds accumulate, especially at low N values. At high N levels, N is preferentially incorporated into the amino acid fraction and only to a smaller extent into the non-hydrolyzable N fraction. High total N concentrations are associated with a higher relative contribution of organic matter of microbial origin., [GR]: Hohe Stickstoffeinträge haben in Mitteleuropa zu einer Abnahme des C : N-Verhältnisses in der Streu und der Auflage geführt. Dies führt möglicherweise zu Änderungen in der Zusammensetzung der organischen Bodensubstanz. In der vorliegenden Arbeit wurde die Zusammensetzung im Oh- und A-Horizont von 15 Böden unter Fichte untersucht, die einen weiten Bereich im C : N-Verhältnis abdecken. Die Zusammensetzung der organischen Substanz wurde mittels Festkörper-13C-NMR-Spektroskopie und chemolytischen Methoden zur Bestimmung von Lignin, Polysacchariden und Aminosäure-N untersucht. Diese Daten wurden auf funktionelle Zusammenhänge zwischen den Gehalten an C, N und dem C : N-Verhältnis mittels einer strukturellen Analyse geprüft. Mit zunehmendem N-Gehalt nehmen die Gehalte an Lignin in den Oh-Horizonten zu, in den A-Horizonten nehmen sie dagegen ab. Ein negativer Effekt des N-Gehalts auf den Ligninabbau ist also nur im Mineralboden, aber nicht im Auflagehumus nachzuweisen. Im Mineralboden reichern sich nichtphenolische aromatische Strukturen an, insbesondere bei niedrigen N-Gehalten. Bei hohen N-Gehalten wird N bevorzugt in die Aminosäurefraktion inkorporiert und nur in geringerem Ausmaß in die Fraktion des nichthydrolysierbaren Stickstoffs. Generell sind höhere N-Gehalte mit einem größeren Beitrag mikrobieller Produkte an der organischen Substanz verbunden.

In Central Europe, composting and anaerobic digestion of municipal solid waste (MSW) is used as pretreatment before landfilling to reduce landfill emissions. MSW samples were analyzed before, during, and after pretreatment to assess the stability of the organic matter. Chemolytic, nuclear magnetic resonance (NMR) spectroscopic, and respiration parameters were correlated to evaluate a substitution of the time-consuming respiration analysis by chemical parameters. 13C cross polarization magic angle spinning (CPMAS) NMR spectroscopy showed a preferential biodegradation of O-alkyl carbon (carbohydrates) and a selective accumulation of plastics during all pretreatments, confirming findings from chemolytic analyses. Principal component analysis exhibited a strong association between the respiration rate, the carbohydrate content, and the O-alkyl C content, corroborating that carbohydrates are the most important compounds of MSW with regard to the emission potential. Rank correlation (Spearman) also showed strong relationships between the respiration rate and the content of carbohydrates (r=0.75) and of O-alkyl C (r=0.72).

The archaeological site in Murr, Upper Bavaria, was settled throughout the entire Neolithic period, between 5500 and 2700 BC. Various pits and a ditch found in the area are distinct from the surrounding loamy soil because of the dark brown color of their filling materials. Although several artifacts have been discovered, at the present stage of research neither the nature of the filling material nor the function of pits and the ditch are well understood. Thus, the organic matter composition of 30 filling layers from 11 Neolithic pits found in this settlement was investigated and compared with that of a nearby Luvisol profile and two A horizons from contemporary Phaeozems. All samples were subjected to C and N analysis, soil lightness measurements, solid-state 13C CPMAS nuclear magnetic resonance (NMR) spectroscopy, and polysaccharide and lignin analysis. The organic carbon contents are higher in the Neolithic samples than in the Luvisol horizons, but they are generally lower than in the A horizons of contemporary phaeozemic soils developed from loess. The Neolithic samples have a much higher intensity in darkness than do the surrounding Luvisol horizons. The organic carbon content of the Neolithic samples correlates with the lightness value. Solid-state 13C NMR measurements revealed that this correlation is primarily because of their aromatic C content, which is considerably higher in the Neolithic samples than in the contemporary soils. Small polysaccharide amounts and no lignin-derived phenols were found in the Neolithic samples. Thus, the organic material filling the Neolithic pits is significantly different in overall chemical composition from the surrounding soil. It represents a highly altered, highly aromatic material showing no evidence of lignin degradation products and probably deriving from nonsoil origins.

Soil organic matter (SOM) comprises refractory compounds, to which a turnover time of more than 1000 years has been attributed in SOM models. The goal of this study is to characterize the chemical structure of refractory compounds of organic carbon in arable soils by means of 13C NMR spectroscopy and analysis of carbohydrates. C-depleted soils that are expected to be enriched in refractory compounds are compared with fertilized soils from long-term agroecosystem experiments. In the C-depleted soils, lower proportions of O/N-alkyl C and higher proportions of aromatic and carboxyl C compared with the fertilized counterparts are observed. Ratios of alkyl to O-alkyl C are higher in the depleted soils than in the fertilized ones. Along with the overall C-depletion, the absolute amount of all carbon species was reduced. This net decrease is highest for the O/N-alkyl C and smallest for the aromatic C. Yields of wet chemically determined carbohydrates positively correlate with the relative intensities of O-alkyl C in the NMR spectra, and confirm the net decrease of O-alkyl C compounds along with C-depletion. The refractory organic carbon pool in arable soils appears to have a lower contribution of O/N-alkyl C, and a higher proportion of recalcitrant aromatic structures compared with more labile fractions of organic carbon.

The chemical structure of soil organic matter from the eluvial (Aeh) and (illuvial) Bh horizon of a Podzol was studied in primary organo-mineral associations by 13C CPMAS NMR spectroscopy and acid hydrolysis. In Podzols, organic matter is leached from the forest floor and Aeh horizons into the Bh horizon, where it is intimately associated with the mineral phase. In the Aeh horizon the majority of the residual organic matter was present in methylene structures, contributing 42% to the organic matter associated with the clay fraction. In the Aeh horizon decreasing particle size was typically accompanied by increasing ratios alkyl C-to-O–alkyl C, suggesting increasing decomposition of polysaccharides for the residual organic matter. The illuvial Bh horizon, containing high proportions of iron- and aluminum-oxides and hydroxides, was higher in aromatic carbon, while polysaccharides were similar and methylene carbon were smaller than in the Aeh horizon. In the particle size separates proportions of polysaccharides were constant, resulting in decreasing ratios alkyl C/O–alkyl C. Proportions of hydrolyzable amino acids were larger in the Aeh horizon (52% of the total N) than in the Bh horizon (21%), both for bulk soils and size separates. Our results suggested that in Bh horizons of Podzols, aromatic structures and also presumably labile structures like polysaccharides can be stabilized by organo-mineral associations.

Solid-state nuclear magnetic resonance (NMR) spectroscopy was used to elucidate the composition of total organic carbon (TOC) in fresh and composted municipal solid waste (MSW) samples and to estimate the behavior of composted MSW after landfilling. We showed that the cross polarization magic angle spinning (CPMAS) technique provided 13C NMR spectra of MSW with representative intensity distribution, whereas O-alkyl carbon was underestimated in the single pulse excitation experiment. Fresh MSW was dominated by signals in the O-alkyl C region that are derived most probably from carbohydrates. Signals assignable to plastics could also be identified. The presence of plastics was confirmed by dipolar dephased (DD) and proton spin relaxation editing (PSRE) 13C NMR spectra. During composting, the intensity of O-alkyl C decreased, while that of signals from plastics increased. This indicates a decrease of the biodegradable fraction and of the landfill emission potential. As estimated from a PSRE subspectrum, the content of plastics in the composted MSW was 37% of TOC, which equals 26% of OM. CPMAS 15N NMR spectra revealed that peptide structures play a major role in the organic nitrogen fraction. Some of these peptides appear to resist acid hydrolysis and biodegradation.

Soil organic matter (SOM) comprises refractory compounds, to which a turnover time of more than 1000 years has been attributed in SOM models. The goal of this study is to characterize the chemical structure of refractory compounds of organic carbon in arable soils by means of 13C NMR spectroscopy and analysis of carbohydrates. C-depleted soils that are expected to be enriched in refractory compounds are compared with fertilized soils from long-term agroecosystem experiments. In the C-depleted soils, lower proportions of O/N-alkyl C and higher proportions of aromatic and carboxyl C compared with the fertilized counterparts are observed. Ratios of alkyl to O-alkyl C are higher in the depleted soils than in the fertilized ones. Along with the overall C-depletion, the absolute amount of all carbon species was reduced. This net decrease is highest for the O/N-alkyl C and smallest for the aromatic C. Yields of wet chemically determined carbohydrates positively correlate with the relative intensities of O-alkyl C in the NMR spectra, and confirm the net decrease of O-alkyl C compounds along with C-depletion. The refractory organic carbon pool in arable soils appears to have a lower contribution of O/N-alkyl C, and a higher proportion of recalcitrant aromatic structures compared with more labile fractions of organic carbon.

In the German Ruhr-area industrial coal processing emitted large amounts of carbonaceous particles for a century until 1970. Our objectives were to detect the presence of airborne carbonaceous particles and assess their impact on the chemical structure of soil organic matter in two forest soils (Podzols) with potential sources of carbonaceous particles approximately 10 to 30 km away. Contamination was not visible macroscopicaily. Organic matter was characterized in bulk soils and in particle-size separates by elemental analysis, magnetic susceptibility measurement, reflected light microscopy, and 13C solid-state nuclear magnetic resonance (NMR) spectroscopy. Organic and mineral horizons contained carbonaceous particles including char, coke, and bituminous coal from coal combustion, coking, coal processing, and steel production. In the organic horizons of both soils we observed a material high in magnetic susceptibility (max. 109 × 10−8 m3 kg−1), whereas in the mineral horizons only the Podzol with an intense intermixing moder-type humus had high magnetic susceptibly. This Aeh horizon was extremely rich in organic carbon (139.4 g organic C kg−1), concentrated in the 20 to 2000 µm size separates. In the second Podzol, like in many natural soils, C concentrations were largest in the <20 µm separates. Bloch decay 13C magic angle spinning (MAS) NMR spectroscopy revealed a highly aromatic structure of the carbonaceous particles. Airborne carbonaceous particles formed a macroscopically indistinguishable mixture with natural soil organic matter and could be present in many soils neighboring industrialized areas.

To study the effect of Hieracium pilosella L. invasion on the transformations of soil organic matter of New Zealand tussock grassland soils (Ustoebrepts), plant material and soils underneath Hieracium, the surrounding halo, and the adjacent herbfield (depleted tussock grassland) were examined for their chemical composition. An attempt was made to reveal possible changes in chemical composition of the soil organic malter induced by H. pilosella invasion. Small differences were detected by solid-state 13C nuclear magnetic resonance (NMR) spectroscopy in the composition of the plant and soil materials from these zones. Most of the differences in soil organic matter occurred due to differences in the amount and quality of plant-residue inputs. Comparable amounts of phenolic C were detected in the solid-state 13C NMR spectra of H. pilosella and herbfield vegetation, while alkaline CuO oxidation yielded considerable lower lignin oxidation products for H. pilosella. A slightly higher proportion of these compounds in H. pilosella soil revealed an accumulation and a low degradation rate of lignin compounds under H. pilosella. The HCI hydrolysis and solid-state 15N NMR spectroscopy showed similar chemical compositions of the N fractions of the three different soils. The absence of 15N NMR signal intensity assignable to aniline derivatives or aromatic heterocyclic N indicates that the condensation of phenolic compounds with N groups plays a minor role in N sequestration in these soils.

Nitrogen availability in soils plays an important role for the productivity of agricultural systems. After entering the soil, material of biogenic origin experiences decay and microbial reworking. During these processes, the labile compounds are quickly mineralized into inorganic nitrogen forms, directly available for the production of new biomass. The more stable compounds and metabolic products accumulate to form the refractory organic pool of soils (Kelly and Stevenson, 1996). Their nitrogen will be sequestered from the overall nitrogen cycle and therefore from bioproductivity over a expended time range.