title: Characterization of typical aquatic humic substances in areas of sugarcane cultivation in Brazil using tetramethylammonium hydroxide thermochemolysis.
abstract: Aquatic humic substances (AHSs) differ from one environment to another depending on land use and occupation. In addition, the effects of planting sugarcane on AHSs are not well known. Thus, the aim of this study was to characterize AHSs extracted from a river in a typical region of sugarcane cultivation during dry and rainy seasons. The main characteristics of the AHSs were obtained using Fourier transformation infrared (FTIR) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and off-line pyrolysis coupled with gas chromatography and mass spectrometry (off-line tetramethylammonium hydroxide (TMAH)-GC-MS-thermochemolysis). The FTIR and NMR results were used to infer that no distinctions occurred between the sampling periods. The samples were composed of aromatic groups that were potentially associated with the presence of residual vegetable materials (lignin). The results of the off-line TMAH-GC-MS-thermochemolysis indicated that the structures of the AHSs had uniform compositions that were rich in fatty acid methyl esters (FAMEs), polysaccharide derivatives, aliphatic biopolymers derived from plants, long hydrocarbon chains, branched alkyl groups and methylene carbons. Thus, the results showed that the AHSs obtained from the sugarcane cultivation area during the crop period mainly consisted of resistant aliphatic hydrocarbons, which are derivatives of lignin and FAMEs in compounds rich in humic acid. Therefore, we concluded that sugarcane cultivation produces changes in AHSs because greater amounts of lignin derivatives were observed during the dry season, corresponding to sugarcane cultivation.
authors.affiliation: Departamento de Química e Ciências Ambientais, Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista "Júlio de Mesquita Filho", R. Cristóvão Colombo 2265, 15054-000 São José do Rio Preto, SP, Brazil.
authors.forename: A M
authors.initials: AM
authors.lastname: Tadini
authors.affiliation: Departamento de Química e Ciências Ambientais, Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista "Júlio de Mesquita Filho", R. Cristóvão Colombo 2265, 15054-000 São José do Rio Preto, SP, Brazil.
authors.forename: I C
authors.initials: IC
authors.lastname: Constantino
authors.affiliation: Dipartimento Scienze del Suolo, della Pianta, e dell'Ambiente, Università di Napoli Federico II, Via Università 100, 80055 Portici, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Nuzzo
authors.affiliation: Dipartimento Scienze del Suolo, della Pianta, e dell'Ambiente, Università di Napoli Federico II, Via Università 100, 80055 Portici, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Spaccini
authors.affiliation: Dipartimento Scienze del Suolo, della Pianta, e dell'Ambiente, Università di Napoli Federico II, Via Università 100, 80055 Portici, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Piccolo
authors.affiliation: Departamento de Química e Ciências Ambientais, Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista "Júlio de Mesquita Filho", R. Cristóvão Colombo 2265, 15054-000 São José do Rio Preto, SP, Brazil.
authors.forename: A B
authors.initials: AB
authors.lastname: Moreira
authors.affiliation: Departamento de Química e Ciências Ambientais, Instituto de Biociências, Letras e Ciências Exatas, Universidade Estadual Paulista "Júlio de Mesquita Filho", R. Cristóvão Colombo 2265, 15054-000 São José do Rio Preto, SP, Brazil. Electronic address: bisinoti@ibilce.unesp.br.
authors.forename: M C
authors.initials: MC
authors.lastname: Bisinoti
mesh_terms: D000383:Agriculture; D001938:Brazil; D004784:Environmental Monitoring; D008401:Gas Chromatography-Mass Spectrometry; D006812:Humic Substances / Q000032:analysis*; D009682:Magnetic Resonance Spectroscopy; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D031786:Saccharum; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
chemical_list: D006812:Humic Substances; D000644:Quaternary Ammonium Compounds; D014874:Water Pollutants, Chemical; C027917:tetramethylammonium
keywords: Aquatic humic substances; Infrared; NMR; Off-line TMAH-GC–MS; Sugarcane