Pyrolysis‐Gas Chromatography/Mass Spectrometry Characterization of Humic Acids in Coastal Spodosols from Southeastern Brazil

Abstract

This study on humic acids (HAs) of podzol horizons from the southeastern region of Brazil investigated the accumulation and degradation of soil organic matter (SOM) in warm-climate podzols. Humic acids from sandy coastal Spodosols (Histic Alaquod and Arenic Alorthod) from Cardoso Island in Sao Paulo State were characterized by pyrolysis in combination with gas chromatography and mass spectrometry (Py-GC/MS). The soils developed on quartzitic, sandy, nutrient-poor parent materials under restinga forest in a coastal area. The Py-CC/MS results show that the chemical composition of HAs in B horizons in one out of three profiles was influenced by both dissolved organic C (DOC) and C from in situ decaying roots. Carbon derived from DOC dominated in the deepest part of the B horizons. In the Arenic Alorthod (H9) profile, SOM from the B horizon seemed to be largely derived from roots. The DOC-derived SOM was characterized by large contributions of phenol, methylphenols, and degraded polysaccharide products, while root contributions were mainly characterized by lignin products. Aliphatics were most abundant in A horizons (E and EB horizons were not analyzed). Both DOC-derived and lignin-derived SOM showed distinct degradation patterns. The Py-GC/MS results corroborate those obtained by ^^C variable amplitude cross polarization magic angle spinning nuclear magnetic resonance spectroscopy and Fourier-transform infrared spectroscopy. Molecular chemistry showed that podzol B horizons are variable in composition, and local influences, such as drainage and vertical or lateral water transport, and SOM decomposition play an important role in podzolization processes in warm climates.Abbreviations: DOC, dissolved organic carbon; FTIR, Eourier-transform infrared; HA, humic acid; OM, organic matter; Py-CC/MS, pyrolysis in combination with gas chromatography and mass spectrometry; SOM, soil organic matter; VACP/MAS NMR, variable amplitude cross polarization and magic angle spinning nuclear magnetic resonance.T he podzolization process in temperate regions has been investigated for a long time (Petersen, 1976;Chesworth and Macias-Vasquez, 1985;van Breemen and Buurman, 2002; Buutman et al., 2005). Although Spodosols of tropical and temperate climates are identified by the same set of tules, their genèses are different, and this aspect has hardly been investigated. Podzols, ot Spodosols, in general, ate characterized by a typical horizon sequence: an organic surface O horizon followed by a mineral A horizon, a weathered albic eluvial E horizon, and a dark brownish-reddish illuvial B horizon (Bh, Bhs, ot Bs), which is characterized by an accumulation of Al, Fe, ot both with varying amounts of otganic mattet (Wilcken et al., 1997; Soil Survey Staff, 1999;van Breemen and Buurman, 2002).

Molecular Fingerprints of Soil Organic Matter in a Typical Freshwater Wetland in Northeast China

“…Multiple regression analysis allows for the recognition of correlations between variables and the detection of structures in the data set. It is a primary method for reducing the number of variables (González-Pérez et al, 2012). Prior to statistical analysis, tests for normality of the raw were performed.…”

“…Relative distributions (RF, %) of products were estimated using the peak areas of total ion current (TIC) pyrograms. Pyrolytic compounds were grouped according to the method of González-Pérez et al (2012), which was based on probable origin and chemical similarity, into alkyl (including n-alkanes (C ‫׃‬ 0) and n-alkenes (C ‫׃‬ 1) and other alkyls), aliphatics (Al), aromatics (Ar), lignin (Lg), nitrogen containing compounds (Nc), polycyclic aromatic hydrocarbons (PAHs), phenols (Phs), polysaccharides (Ps), and sulfur containing compounds (Sc).…”

“…Pyrolysis gas-chromatography/mass-spectrometry (Py-GC/MS) is widely used to research the chemical composition of soil organic matter because it provides detailed information at the molecular level (Belgacem, 2000;Nebbioso and Piccolo, 2013). It is a powerful tool for exploring unknown complex mixtures of materials (González-Pérez et al, 2012;Schellekens et al, 2017). Pyrolysis of soil organic matter generates a wide range of products with diverse chemical properties that can be related to their biochemical origin.…”

Soil morphological and chemical properties in homegardens on sandy beach ridges along the east coast of Peninsular Malaysia

“…These soils are classified mostly as Entisols or Spodosols in the USDA classification system (Soil Survey Staff 2014). Because of their intrinsic infertility due to sandy texture, these soils are usually regarded as unsuitable for agricultural use and therefore left under forest or grassland vegetation (Thompson et al 1996;Sommer et al 2001;Perez et al 2011).…”

Variações das estruturas das comunidades de bactérias e fungos em Espodossolos sob diferentes regimes de drenagem

“…Para as amostras de solo das manchas e regiões adjacentes foram feitas apenas a determinação de Al 3+ , K c v s C s v q quantidade de solo amostrado, o que impossibilitou a análise química completa. Para avaliar a relação entre a estrutura da comunidade microbiana encontrada nas diferentes amostras e as propriedades físico-químicas do solo, foi utilizada análise de correlação de Spearman, devido a não homogeneidade da variância dos dados físico-químicos e por esses não serem transformados.4.2.4 Análise da matéria orgânica do solo por pir lise acoplada cro atogra ia gasosa e espectrometria de massa (Pi-CG/EM)As amostras coletadas também foram processadas para extração da matéria orgânica do solo e pirólise associada à cromatografia gasosa/espectrometria de massas (Pi-CG/EM) (SCHULTEN;SCHNITZER, 1997;LEINWEBER;SCHULTEN, 1999;GONZÁLEZ-PÉREZ et al, 2012;LOPES, 2013). A caracterização molecular da MO do solo é parte do projeto de doutorado de Josiane Millani Lopes e os resultados foram usados para identificar os fatores que determinam a estruturação das comunidades de bactérias nos diferentes perfis e regimes de drenagem dos Espodossolos estudados.…”