Chemical characterization of soil organic matter fractions by analytical pyrolysis-gas chromatography-mass spectrometry

Abstract

SUMMARYCurie-point pyrolysis-gas chromatography-mass spectrometry has been used to chem ically characterize fulvic acid, humic acid, hymatomelanic acid and polysaccharide fractions of a representative soil. A detailed study of all the pyrolysis products was made. By comparing the results of this study with previous pyrolysis data for lignins, degraded lignins. polysaccharides, proteins, etc., we have been able to obtain more detailed information aboul the chemical composition of the pyrolysis products from different soil organic matter fractions. It is shown that fulvic acid fractions consist mainly of polysaccharide and/or carbohydrates and polyphenols, that humic acid and humin fractions are complex mixtures of several biopolymers such as polysaccharides, partially degraded lignins, peptides and lipids and that the hymatomelanic acid fraction represents mainly lipid materials.

Feasibility of Soil Dust Source Apportionment by the Pyrolysis-Gas Chromatography/Mass Spectrometry Method

“…In contrast, Py at 740°C yielded five times more resolved Table 2 shows the 178 compounds found by Py in the PO sample and which were reported previously in studies conducted with larger samples of bulk soil. 41,45 The number of organic species obtained by Py-GC/MS is much larger than the two carbon fractions obtained by current thermal/optical reflectance anaysis. 12…”

“…26,33,46 The identified compounds in Table 2 agree well with previous studies. Some of the listed compounds were not reported by either Saiz-Jimenez and De Leeuw 45 or by Hempfling and Schulten, 41 and standards were available for two of these. Both compounds were present at Ͻ1 ng/mg concentration in some of the soil samples in the present study.…”

Características estruturais de ácidos húmicos isolados de solos com adição de resíduos orgânicos de origem urbana: composição elementar, análise de RMN 13C e Pi-CG/EM

“…Mass spectra (1scan/s) were recorded under electron impact at 70 eV condition. The assignment of compounds released from the pyrolysis was based on a search of a mass spectral library (Nist) and by comparison with other published collections of Pyrolysis-CG/MS data of similar samples (Saiz-Jimenez & Leeuw, 1986;1987;Lu et al, 2000). The structural attribution for mass spectra fragmentation is not unequivocal but is consistent with the Pyrolysis-GC/MS data state of art (Davies et al, 2001).…”

Caracterização das substâncias húmicas extraídas do solo do manguezal de Pai Matos (Cananéia, SP, BR) e de marismas da Espanha (Galícia e Valência)

“…Ultimamente, a pirólise associada à cromatografia gasosa/espectrometria de massas (Pi-CG/EM) também tem sido muito utilizada no estudo tanto da MOS quanto de suas SHs (SAIZ-JIMENEZ; DE LEEUW, 1986;SCHNITZER, 1997;LEINWBER;SCHULTEN, 1999), pois permite seu maior detalhamento químico, permitindo distinguir por exemplo, a contribuição de compostos derivados diretamente das plantas e de microorganismos (ALCÂNTARA et al, 2004;BUURMAN et al, 2006;PETERSE;MARTINS, 2007;, complementando assim, as informações obtidas pelas demais técnicas químicas e espectroscópicas citadas anteriormente (STEVENSON, 1994).…”

“…A formação da MOS depende do arranjo de uma grande quantidade de variáveis, incluindo a composição dos resíduos das plantas (OADES, 1988;NIEROP; RALPH;HATFIELD, 1991;PLAGE;SCHNITZER, 1991;SAIZ-JIMENEZ;DE LEEUW, 1986), sendo de ocorrência comum na MOS e em solos orgânicos como as turfas (BUURMAN et al, 2006;KAAL et al, 2007a). Já os alquilbenzenos (A2-6), têm sido associados tanto a processos de aromatização durante a pirólise na presença de enxofre (SAIZ-JIMENEZ, 1992) quanto a queimadas (KAAL et al, 2007b), enquanto o catecol (A7) tem sido atribuído a taninos (GALLETI;REEVES, 1992 Desta forma, se os compostos nitrogenados são os primeiros a se adsorverem às argilas, eles não deveriam aparecer em extratos da MOS, pois as frações fortemente adsorvidas aos minerais de argila são difíceis de extrair.…”