Comparison of two calorimetric methods to determine the loss of organic matter in Galician soils (NW Spain) due to forest wildfires

Salgado, Juan José; Mato, M. M.; Vázquez-Galiñanes, Alejandro; Paz-Andrade, M. J.; Carballas, T.

doi:10.1016/s0040-6031(03)00400-3

Cited by 30 publications

(13 citation statements)

References 15 publications

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“…36 The endothermic peaks found in the 287 to 297 and 499 to 513 o C temperature ranges are attributed to the presence of gibbsite and kaolinite, in agreement with other data in the 290 to 350 and 520 to 530 o C ranges. The presence of quartz is described in the 575 o C region 10,37 and, in this investigation, it was found from 540 to 575 o C as weak peaks, shown at 575 o C for RQ2, 555 and 540 o C for RL and CL soils, respectively. Based on these results, it is possible that the first peak, referring to the gibbsite form, is superimposed on the goethite one.…”

Section: Resultssupporting

confidence: 51%

Thermal analysis of brazilian tropical soils originating from different sources

Critter¹,

Airoldi²

2006

J. Braz. Chem. Soc.

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As amostras de solos tropicais brasileiros foram analisadas pelas técnicas térmicas termogravimetria (TG) e calorimetria exploratória diferencial (DSC) em atmosferas de ar sintético ou argônio. Nesse processo foi investigado o solo eutrudox Ródico com vegetação de floresta, queimado ou não em plantação de cana de açúcar, e aquele de fase arenosa com vegetação de cerrado. A partir da fração orgânica do solo, foram extraídos ácidos húmicos que se decompõem similarmente ao produto comercial, de acordo com as etapas: i) água adsorvida, desidratação, descarboxilação e perda de moléculas orgânicas, ii) decomposição da fração termolábil, iii) matéria orgânica macromolecular e iv) resíduos acima de 950 o C. As curvas de DSC deram correspondentes picos de perda de água perto de 100 o C e exotérmicos em temperatura maior que 300 o C, atribuídos à combustão de fração de matéria orgânica termolábil. As curvas TG dos solos são mais complexas que os ácidos húmicos, devido aos componentes inorgânicos, caracterizando os estágios: i) desidratação, ii) matéria orgânica termolábil, iii) domínio orgânico macromolecular, e iv) resíduos de óxidos. Essas decomposições correspondem a três picos endotérmicos em DSC e um exotérmico mostrado em atmosfera de ar sintético, atribuído à combustão da fração orgânica macromolecular na região de 300 o C. As curvas de DSC dos solos provenientes de plantação de cana de açúcar mostraram picos endotérmicos mais intensos do que aqueles de solo de floresta. Os resultados térmicos demonstram a influência do material orgânico, que é altamente influenciado pelo componente mineral com alto teor de resíduo, pelo uso na atividade da terra e também pelos processos de queimadas.Brazilian tropical Latosol soil samples were thermally analyzed associating thermogravimetric (TG) and differential scanning calorimetric (DSC) techniques under synthetic air or argon atmospheres. Rhodic eutrudox soils with forest vegetation, from unburnt and burnt cane plantations and that of a sandy phase having cerrado vegetation were investigated. From the organic soil fraction humic acids were extracted that decompose similarly to the commercial product, following the steps: i) adsorbed water, dehydrations, decarboxylations and release of organic molecules, ii) thermolabile decomposition fraction, iii) macromolecular organic matter and iv) residues. The DSC curves gave the corresponding peak for water release near 100 o C and exothermic peaks at temperatures higher than 300 o C, attributed to the combustion of thermolabile organic matter. The TG curves for all soil samples are more complex than those of the humic acids due to the inorganic components, being characterized by stages i) dehydration process, ii) thermolabile organic matter, iii) macromolecular organic domain and iv) oxide residues. These steps of decomposition correspond to three endothermic DSC peaks and one exothermic peak clearly shown under a synthetic air atmosphere, being attributed to the combustion of the macromolecular organic fraction near 300 o C. The DSC c...

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Section: Resultssupporting

confidence: 51%

Thermal analysis of brazilian tropical soils originating from different sources

Critter¹,

Airoldi²

2006

J. Braz. Chem. Soc.

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“…The first, endothermic, peak is due to loss of the water as pointed out Grisi et al (1998) and Gibbs et al (2000). But the most interesting transformations in soil occur in the temperature interval from 229°C to 579°C, corresponding to SOM combustion, which is pointed out by one exothermic peak also observed by Mitchell and Birnie (1970) and Giovannini et al (1990) using DTA andSalgado et al (2004) using DSC. So Plante et al (2005) also found in a DSC thermogram two exothermic peaks: a sharp one just below 300°C and a second, broader peak at approximately 350°C.…”

Section: Differential Thermal Analysismentioning

confidence: 69%

Changes in a Humic Cambisol heated (100–500 °C) under laboratory conditions: The significance of heating time

2007

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The influence of the temperature and its duration, that are among the most important components to determine the fire effects on soil properties, were studied in the 0-5 cm layer of a Humic Cambisol developed over siliceous conglomerates and under a shrub of Erica australis. Soil was sandy loam with 8.5 g 100 g − 1 of organic matter, pH of 4.7 and available P about 0.16 mg kg − 1 . The water stability index (WSI) was 64.9, which was considered good. Differential thermal analysis (DTA) showed the presence of two peaks, one endothermic until 177°C and other exothermic between 229°C and 579°C. Samples were heated at 100°C, 200°C and 500°C during 5, 15, 30 and 60 min after reaching the selected temperature. To avoid a temperature gradient in the profile a sample layer of 2 cm depth was used. Soil heating to 100°C at the four heating times and to 200°C for 5 min did not produce significant changes in pH, organic matter, total N, C/N ratio, available P, extractable cations and WSI. Soils heated to 200°C for 15, 30 and 60 min and 500°C for 5 min, showed a significant increase in available P (from 0.9 to a maximum of 17.6 mg kg −1 ) and divalent cations (Ca 2+ from 4.4 to 46.3 and Mg 2+ from 1.5 to 8.7 mg kg − 1 ). For soils heated to 500°C for 15, 30 and 60 min, a clear increase in soluble Na + content (from 0.5 to 1.8 mg kg −1 ) and pH (from 5.5 to 8.1), in addition to a significant decrease in organic matter (from 8.7% to 2.4%) was detected. As a consequence an important decrease in WSI was found (from 64.9% to 54.3%).

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“…Given the importance of knowing the behavior of different types of soil when affected by fire, a significant number of scientific studies have been made by analyzing, in field or laboratory, these structural changes (Certini 2005;González-Pelayo et al 2006;Arcenegui et al 2010;Salgado et al 2004;Carrington 2010;Esque et al 2010;Santin et al 2008;Ferreira et al 2008;Notario del Pino et al 2007). …”

Section: Characterization Of Soils Subjected To Thermal Shockmentioning

confidence: 99%