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Ingrid Kogelknabner - One of the best experts on this subject based on the ideXlab platform.

  • the effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

  • the effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

Cristiano Nunes Gonçalves - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of soil organic matter of different Brazilian Ferralsols under native vegetation as a function of soil depth
    Geoderma, 2004
    Co-Authors: Deborah Pinheiro Dick, Ingrid Kögel-knabner, Cristiano Nunes Gonçalves, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Marcelo Luiz Simões, Ladislau Martin-neto
    Abstract:

    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 13 C and 15 N 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 13 C 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 15 N 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 effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

  • the effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

Deborah Pinheiro Dick - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of soil organic matter of different Brazilian Ferralsols under native vegetation as a function of soil depth
    Geoderma, 2004
    Co-Authors: Deborah Pinheiro Dick, Ingrid Kögel-knabner, Cristiano Nunes Gonçalves, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Marcelo Luiz Simões, Ladislau Martin-neto
    Abstract:

    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 13 C and 15 N 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 13 C 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 15 N 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 effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

  • the effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

Heike Knicker - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of soil organic matter of different Brazilian Ferralsols under native vegetation as a function of soil depth
    Geoderma, 2004
    Co-Authors: Deborah Pinheiro Dick, Ingrid Kögel-knabner, Cristiano Nunes Gonçalves, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Marcelo Luiz Simões, Ladislau Martin-neto
    Abstract:

    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 13 C and 15 N 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 13 C 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 15 N 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 effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

  • the effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

Ricardo Simão Diniz Dalmolin - One of the best experts on this subject based on the ideXlab platform.

  • Characteristics of soil organic matter of different Brazilian Ferralsols under native vegetation as a function of soil depth
    Geoderma, 2004
    Co-Authors: Deborah Pinheiro Dick, Ingrid Kögel-knabner, Cristiano Nunes Gonçalves, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Marcelo Luiz Simões, Ladislau Martin-neto
    Abstract:

    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 13 C and 15 N 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 13 C 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 15 N 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 effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.

  • the effect of 10 hf treatment on the resolution of cpmas 13c nmr spectra and on the quality of organic matter in Ferralsols
    Geoderma, 2003
    Co-Authors: Cristiano Nunes Gonçalves, Deborah Pinheiro Dick, Ricardo Simão Diniz Dalmolin, Heike Knicker, Egon Klamt, Ingrid Kogelknabner
    Abstract:

    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 obtained after four HF extractions were of poor quality, indicating that for these soils at least eight HF treatments have to be performed to acquire reasonable spectra.