Seasonal variability of a conditional stability constant and the characterization of sedimentary humic substances from typical agricultural and urban areas

Autor(es)

Pantano, Glaucia ^[1] ; Tadini, Amanda Maria ^[1] ; Bisinoti, Marcia Cristina ^[1] ; Moreira, Altair Benedito ^[1]

Afiliação do(s) autor(es)

^[1] State Univ Sao Paulo Julio De Mesquita Filho, Inst Biosci Languages & Exact Sci, Dept Chem & Environm Sci, BR-15054000 Sao Jose Do Rio Preto, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: Journal of Soils and Sediments; v. 14, n. 2, p. 385-393, FEB 2014.
• Citações Web of Science: 1

Resumo

Brazil is the largest producer of sugarcane in the world. This extensive production of sugarcane has changed the use and form of Brazilian soil, causing changes in the structural characteristics of humic substances (HS). In this context, the main objective of this study was to evaluate the effect of seasonality on a conditional stability constant (Kc) of the complexes HS-Cu (II) and HS-Cr (III) from the HS of urban and agricultural regions, with an emphasis on sugarcane culture. The study was conducted in the northwestern region of the state of So Paulo, which is the leading producer of sugar and ethanol in the country and is the region with the lowest percentage of riparian vegetation (3 %). Sediments were sampled during the rainy and dry seasons at four locations: (1) a typical agricultural area, (2) an urban area, (3) a sugarcane cultivation area, (4) and an area that receives the entire pollutant load from the hydrographic basin. The HS were extracted and characterized using conventional techniques. The Kc of the HS with copper (Cu) and chromium (Cr) ions was determined by fluorescence suppression employing the Stern-Volmer model. Kc values were higher in the rainy seasons for HS-Cu (II) and HS-Cr (III). The highest value of Kc for the HS with Cu (1.23) and Cr (5.2 x 10(-1)) ions was found during the rainy season in the area receiving the pollutant load from the basin and in the typical area of sugarcane cultivation, respectively. All of the FTIR spectra showed characteristic bands of HS, and the values of the E-4/E-6 ratio confirmed the presence of more aromatic groups. An elemental analysis and molecular fluorescence spectra in the emission mode confirmed that the HS from the agricultural area and sugarcane culture area mostly exhibited characteristics of humic acids and that the HS from the urban area and the area receiving the pollutant load from the basin had a mixture of humic and fulvic acids. We can conclude that HS-metal complexes from the area that received the entire load of pollutants from the watershed and the typical area of sugarcane culture showed the highest stability among the study areas. The Kc values found in the basin were lower than those previously obtained by several studies that were performed in other locations. The HS obtained in rainy season had more aromatic groups in the HS structure, and the HS from the sugarcane area presented more characteristics of humic acids. (AU)

• Processo FAPESP: 05/51242-8 - Emprego de indicadores de qualidade de água e outras ferramentas de gestão ambiental para avaliar o efeito das atividades antrópicas sobre os rios Preto, Turvo e Grande na região de São José do Rio Preto
• Beneficiário: Márcia Cristina Bisinoti
• Modalidade de apoio: Auxílio à Pesquisa - Jovens Pesquisadores
• Processo FAPESP: 10/13879-2 - Interação entre substâncias húmicas e íons cromo e proposta de um indicador de matéria orgânica lábil
• Beneficiário: Amanda Maria Tadini
• Modalidade de apoio: Bolsas no Brasil - Mestrado
• Processo FAPESP: 12/23066-4 - O papel das substâncias húmicas aquáticas na disponibilidade de metais tóxicos e proposta de um indicador para labilidade de matéria orgânica em ambientes aquáticos
• Beneficiário: Márcia Cristina Bisinoti
• Modalidade de apoio: Auxílio à Pesquisa - Regular