Changes in optical properties caused by UV-irradiation of aquatic humic substances from the Amazon River Basin: seasonal variability evaluation

Autor(es)

Rodríguez-Zuniga, Ursula Fabiola ^[1] ; Milori, Débora Marcondes Bastos Pereira ; Silva, Wilson Tadeu Lopes da ^[3] ; Martin-Neto, Ladislau ^[4] ; Oliveira, Luciana Camargo ^[5] ; Rocha, Julio Cesar ^[6]

Afiliação do(s) autor(es)

^[1] Brasil. Ministério da Agricultura, Pecuária e Abastecimento. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) - Brasil

^[3] Brasil. Ministério da Agricultura, Pecuária e Abastecimento. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) - Brasil

^[4] Brasil. Ministério da Agricultura, Pecuária e Abastecimento. Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) - Brasil

^[5] Universidade Estadual Paulista (UNESP). Campus de Araraquara. Instituto de Química - Brasil

^[6] Universidade Estadual Paulista (UNESP). Campus de Araraquara. Instituto de Química - Brasil

• Tipo de documento: Artigo Científico
• Fonte: Environmental Science & Technology; v. 42, n. 6, p. 1948-1953, 2008.
• Área do conhecimento: Ciências Agrárias - Agronomia
• Assunto(s): Substâncias húmicas Análise espectroscópica Fotoluminescência Meio ambiente Bacia amazônica

Resumo

Aquatic humic substances (AHS) isolated from two characteristic seasons of the Negro river, winter and summer corresponding to floody and dry periods, were structurally characterized by 13C nuclear magnetic ressonance. Subsequently, AHS aqueous solutions were irradiated with a polychromatic lamp (290-475 nm) and monitored by its total organic carbon (TOC) content, ultraviolet-visible (UV-vis) absorbance, fluorescence, and Fourier transformed infrared spectroscopy (FTIR). As a result, a photobleaching up to 80% after irradiation of 48 h was observed. Conformational rearrangements and formation of low molecular complexity structures were formed during the irradiation, as deduced from the pH decrement and the fluorescence shifting to lower wavelengths. Additionally a significant mineralization with the formation of CO2, CO, and inorganic carbon compounds was registered, as assumed by TOC losses of up to 70%. The differences in photodegradation between samples expressed by photobleaching efficiency were enhanced in the summer sample and related to its elevated aromatic content. Aromatic structures are assumed to have high autosensitization capacity effects mediated by the free radical generation from quinone and phenolic moieties. (AU)

• Processo FAPESP: 99/09133-4 - Estudos espectroscópicos da complexação de íons metálicos com a matéria orgânica e constituintes húmicos de solos sob diferentes manejos
• Beneficiário: Martha González Pérez
• Modalidade de apoio: Bolsas no Brasil - Doutorado
• Processo FAPESP: 98/14270-8 - Centro de Ciências Ópticas e Fotônica
• Beneficiário: Vanderlei Salvador Bagnato
• Modalidade de apoio: Auxílio à Pesquisa - Centros de Pesquisa, Inovação e Difusão - CEPIDs