Substâncias húmicas aquáticas: caracterização e interação com íons crômio e proposta de um indicador de matéria orgânica lábil
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Data
2013-05-10
Autores
Tadini, Amanda Maria [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Este trabalho teve como principal objetivo avaliar a capacidade de complexação (CC) das Substâncias Húmicas Aquáticas (SHA) extraídas do rio Preto com a espécie de crômio trivalente e hexavalente e avaliar o emprego da cinética de consumo de peróxido de hidrogênio como um indicador da labilidade e/ou recalcitrância da Matéria Orgânica Natural (MON). Para isto, amostras de água superficial do rio Preto foram coletadas no período de seca e de chuva, seguidas da extração de SHA empregando o método sugerido pela Sociedade Internacional de Substâncias Húmicas (IHSS). As SHA foram fracionadas em diferentes tamanhos moleculares (<10, 10-30, 30-50, 50-100 e >100 kDa) e caracterizadas pela a Espectrofotometria UV/Vis, Espectrofotometria na região do Infravermelho, Espectroscopia de Fluorescência Molecular, Espectroscopia de Ressonância Magnética Nuclear e a Pirólise off-line com o Hidróxido de Tetrametilamônio empregando a Cromatografia Gasosa acoplada ao Espectrômetro de Massa. Os estudos de capacidade de complexação com as espécies de crômio trivalente e hexavalente foram realizados empregando o Sistema de Ultrafiltração com Fluxo Tangencial (SUFT) e as espécies de Crômio hexavalente e trivalente foram quantificadas empregando-se as técnicas de Espectrofotometria da difenilcarbazida e de Espectrometria de Absorção Atômica com Atomização por Forno de Grafite, respectivamente. Os resultados das capacidades de complexação mostraram que as SHA e suas frações apresentaram baixa capacidade de complexação com as espécies de crômio trivalente e hexavalente o qual variaram em função da sazonalidade, quando comparado a outros trabalhos descritos na literatura, e as maiores CC para as espécies de crômio trivalente e hexavalente foram observados para as frações <10, 10 – 30 kDa, >100 e 30 – 50 kDa para...
This work aimed to evaluate the complexation capacity (CC) of humic substances (AHS) extracted from the Preto river with the species trivalent and hexavalent chromium and evaluate the use of the kinetic consumption of hydrogen peroxide as an indicator of lability and / or recalcitrance of Natural Organic Matter (NOM). For this, surface water samples were collected from the Preto river in two distinct periods: the dry season and the rainy season, followed by extraction AHS employing the method suggested by the International Humic Substances Society (IHSS). The AHS were fractionated into different molecular sizes (<10, 10-30, 30-50, 50-100 and >100 kDa) and characterized using UV/Vis spectrophotometry, Fourier Transform Infrared, Molecular Fluorescence Spectroscopy, Nuclear Magnetic Resonance Spectroscopy and Off-line TMAH-Thermochemolysis-GC-MS. The complexing capacity for AHS with the species of hexavalent and trivalent chromium was determined using a Tangential Flow Ultrafiltration System (TFUS) and levels of hexavalent and total chromium were determined using diphenylcarbazide Spectrophotometry method and Graphite Furnace Atomic Absorption Spectrometry, respectively. The results of the complexing capacity showed that the AHS and its fractions showed low complexing species with trivalent chromium and hexavalent which vary due to seasonality when compared to other works in the literature, and the greatest CC for species trivalent and hexavalent chromium were observed for fractions <10, 10-30 kDa, > 100 and 30-50 kDa for both periods, which may be associated with increased presence of aromatic groups in its structure as these same fractions were that showed greater degree of aromaticity. Already characterization results showed that the AHS Preto river for both sampling periods (dry and rainy)... (Complete abstract click electronic access below)
This work aimed to evaluate the complexation capacity (CC) of humic substances (AHS) extracted from the Preto river with the species trivalent and hexavalent chromium and evaluate the use of the kinetic consumption of hydrogen peroxide as an indicator of lability and / or recalcitrance of Natural Organic Matter (NOM). For this, surface water samples were collected from the Preto river in two distinct periods: the dry season and the rainy season, followed by extraction AHS employing the method suggested by the International Humic Substances Society (IHSS). The AHS were fractionated into different molecular sizes (<10, 10-30, 30-50, 50-100 and >100 kDa) and characterized using UV/Vis spectrophotometry, Fourier Transform Infrared, Molecular Fluorescence Spectroscopy, Nuclear Magnetic Resonance Spectroscopy and Off-line TMAH-Thermochemolysis-GC-MS. The complexing capacity for AHS with the species of hexavalent and trivalent chromium was determined using a Tangential Flow Ultrafiltration System (TFUS) and levels of hexavalent and total chromium were determined using diphenylcarbazide Spectrophotometry method and Graphite Furnace Atomic Absorption Spectrometry, respectively. The results of the complexing capacity showed that the AHS and its fractions showed low complexing species with trivalent chromium and hexavalent which vary due to seasonality when compared to other works in the literature, and the greatest CC for species trivalent and hexavalent chromium were observed for fractions <10, 10-30 kDa, > 100 and 30-50 kDa for both periods, which may be associated with increased presence of aromatic groups in its structure as these same fractions were that showed greater degree of aromaticity. Already characterization results showed that the AHS Preto river for both sampling periods (dry and rainy)... (Complete abstract click electronic access below)
Descrição
Palavras-chave
Química ambiental, Substâncias húmicas, Ácido húmico, Pirolise, Cromo, Rios - São José do Rio Preto (SP), Agua - Analise, Environmental chemistry
Como citar
TADINI, Amanda Maria. Substâncias húmicas aquáticas: caracterização e interação com íons crômio e proposta de um indicador de matéria orgânica lábil. 2013. 128 f. Dissertação (mestrado) - Universidade Estadual Paulista Julio de Mesquita Filho, Instituto de Biociências, Letras e Ciências Exatas, 2013.