Semiquantitative GC/MS analysis of thermochemolysis products of soil humic acids with various degrees of humification

Ikeya, Kosuke; Yamamoto, Shuichi; Watanabe, Akira

doi:10.1016/j.orggeochem.2003.12.004

Cited by 52 publications

(40 citation statements)

References 39 publications

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“…However, it is usually evaluated through indirect measurements that reflect the structural changes which occur during the humification process. Several techniques have been used to characterize the progress of humification, including measurement of the E 4 /E 6 ratio, defined as the ratio of optical absorbance at 465 and 665 nm in aqueous solution, which indicates the structural condensation (Chen et al, 1977;Stevenson, 1994); aromatic C, determined by CPMAS 13 C Nuclear Magnetic Resonance (NMR; Ikeya et al, 2004); area of total emission fluorescence of ultraviolet-visible light spectroscopy Milori et al, 2002); and C/H, C/O, and C/N ratios, defined as the atomic ratio between elements (carbon, hydrogen, oxygen, and nitrogen; Stevenson, 1994;Rosa et al, 2001). A more specific molecular spectroscopic technique to estimate to the degree of humification in soil organic matter is the concentration of stable free radicals (semiquinone-type obtainable by electron paramagnetic resonance (EPR)) (Riffaldi and Schnitzer, 1972;Schnitzer and Levesque, 1979;Martin-Neto et al, 1998;Bayer et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Multimethod study of the degree of humification of humic substances extracted from different tropical soil profiles in Brazil's Amazonian region

et al. 2005

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Section: Introductionmentioning

confidence: 99%

Multimethod study of the degree of humification of humic substances extracted from different tropical soil profiles in Brazil's Amazonian region

et al. 2005

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“…humification) is primarily a microbially mediated process (Zech et al 1997). The humification process is generally accompanied by changes in the amount and chemical structure of humic substances (Ikeya et al 2004). Therefore, the factors that control microbial activity, such as temperature, pH, and C/N ratio, determine doi: 10.17221/21/2015-SWR the quantity and quality of humic substances formed in soil.…”

mentioning

confidence: 99%

Moisture effect on soil humus characteristics in a laboratory incubation experiment

Li¹,

Gao²,

Zhang³

et al. 2016

Soil & Water Res.

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Li C., Gao S., Zhang J., Zhao L., Wang L. (2016): Moisture effect on soil humus characteristics in a laboratory incubation experiment. Soil & Water Res., 11: 37-43.A 180-day laboratory incubation experiment (30°C) was conducted to investigate the quantitative and qualitative characteristics of humic fractions in a Mollisol at different moisture conditions. The soil moisture contents were 30, 60, and 250% field water-holding capacity (WHC), which represented the low, middle, and high moisture levels, respectively. The results showed that the carbon contents of the total soil and corresponding humic fractions generally decreased with increasing soil moisture. A significant difference was observed between the 250% WHC and the two other moisture levels. By contrast, the carbon content of the water soluble fraction significantly increased with increasing soil moisture levels. The solid-state 13 C nuclear magnetic resonance (NMR) spectra showed that the alkyl C/O-alkyl C, aliphatic C/aromatic C, and hydrophobic C/hydrophilic C ratios were in the order of 250% WHC > 30% WHC ≈ 60% WHC, 30% WHC ≈ 60% WHC > 250% WHC and 250% WHC > 60% WHC ≈ 30% WHC for humic acid, and 250% WHC > 30% WHC ≈ 60% WHC, 60% WHC ≈ 250 % WHC > 30% WHC and 30% WHC ≈ 250% WHC > 60% WHC for humin, respectively. These results indicated that a high moisture level was unfavourable for the carbon accumulation of the total soil and humic fractions, whereas it was favourable for the accumulation of water soluble carbon. Although soil moisture levels had a distinct effect on the chemical composition of humic acid and humin, the decomposition degree of the two humic substances components, as indicated by the alkyl C/O-alkyl C ratio, were both higher at a high moisture level than at a low moisture level. Therefore, the lower soil organic carbon content at a high moisture level than at a low moisture level can be ascribed to the higher water soluble carbon content and larger decomposition degree of humic acid and humin in the former. Our results are important for understanding the behaviour and mechanisms of humic substances at specific soil moisture conditions.

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“…The 13 C NMR spectra of HA indicated the increase of hydrophobicity (sum of aromatic and alkyl C) with increasing soil C stability (Piccolo, 2001;Ikeya et al, 2004;Spaccini et al, 2006;Xiaoli et al, 2007;Conte et al, 2007;Canellas et al, 2008). This hydrophobicity in HA as a result of increased stability had previously been shown in association with the quinone moieties Perez et al, 2004;Canellas et al, 2007Canellas et al, , 2008 of HA.…”

Section: Introductionmentioning

confidence: 70%

Redox index of soil carbon stability

Baldotto

Canela²,

Canellas

et al. 2010

Rev. Bras. Ciênc. Solo

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SUMMARYAs an alternative to the relatively complex and expensive spectroscopic methods, the redox properties of humic acids, determined by potentiometric titrations, have been used to evaluate the stability of soil organic C. The objective of the present study was to establish a Redox Index of C Stability (RICS) and to correlate it with some properties of the humic acids extracted from different modal soils in Brazil (distinct weathering stages or management) to facilitate system comparison. The RICS was efficient for soil comparison and variations were comparable to those of the chemical and spectroscopic methods used for humic acid characterization. The values of soil pH, point of zero salt effect, sum of bases, exchangeable Ca content, weathering index, as well as the humic acid O/C ratio, quinone and semiquinone free radical contents, aromatic C and fluorescence intensity were closely related with the RICS. The RICS was higher in less weathered soils, with more active clays and higher fertility. The RICS values of soils under long-term sugarcane management were ranked in decreasing order: unburned, burned with vinasse, burned without vinasse.Index terms: soil chemistry, soil organic matter, humic substances, oxidation capacity.(1) Part of the doctoral and post doctoral works from the first author developed at the State University of the North Fluminense "Darcy Ribeiro" -UENF.

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Semiquantitative GC/MS analysis of thermochemolysis products of soil humic acids with various degrees of humification

Cited by 52 publications

References 39 publications

Multimethod study of the degree of humification of humic substances extracted from different tropical soil profiles in Brazil's Amazonian region

Multimethod study of the degree of humification of humic substances extracted from different tropical soil profiles in Brazil's Amazonian region

Moisture effect on soil humus characteristics in a laboratory incubation experiment

Redox index of soil carbon stability

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