A capacidade de complexação de substâncias húmicas extraídas de amostras de turfa coletadas na região do Rio Mogi em Ribeirão Preto, SP, Brasil, foi determinada utilizando Al(III), Pb(II), Cr(VI) e Cd(II). A seguinte ordem de afinidade foi observada: Cr(VI)< Cd(II)
A new procedure was developed for the in situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory to evaluate the influence of complexation time, mass of exchanger, pH, metal ions (Cu, Cd, Fe, Mn, and Ni), and concentration of organic matter on the relative lability of metal species. It was found that the pH and kinetics strongly influence the process of metal complexation by the DM-Cell-PAB system. At all pH levels, Cd, Mn, and Ni showed lower complexation with Cell-PAB resin than Cu and Fe metals. Note that relative lability of metals complexed to aquatic humic substances (AHS) in the presence of Cell-PAB resin showed the following order: Cu approximately or = Fe>>Ni>Mn=Cd. The results presented here also indicate that increasing the AHS concentration decreases the lability of metal species by shifting the equilibrium to AHS-metal complexes. Our results indicate that the system under study offers an interesting alternative that can be applied to in situ experiments for differentiation of labile and inert metal species in aquatic systems.
Recebido em 21/11/05; aceito em 11/4/06; publicado na web em 30/8/06LABILITY STUDY OF Cu(II), Cd(II), Mn(II) AND Ni(II) COMPLEXED BY AQUATIC HUMIC SUBSTANCES USING ORGANOMODIFIED CELLULOSE MEMBRANES. In this work commercial filters papers were organomodified with tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (3-APTS), aiming at the development of a new analytical procedure for in-situ speciation of labile and inert metal species in aquatic systems. Parameters that exert influence on the metal lability such as pH, chelating time, concentration and characteristics of the organic matter were studied in the laboratory using tests for metal recuperation. The results showed slower kinetics for Cu ion than for Ni, Mn and Cd in the absence of aquatic humic substances (AHS). The relative lability observed for complexed metals in aquatic humic substances using organomodified filter papers was Cu>>Cd>Ni>Mn. The pH values, structural characteristics and concentration of AHS exert strong influence on the lability of the metals. The results obtained showed that the utilization of organomodified filter papers can be an interesting and promising alternative for in situ characterization of metal lability in aquatic systems.Keywords: water; aquatic humic substances; metal. INTRODUÇÃOCerca de 20% da matéria orgânica natural (MON) nos ecossistemas naturais consiste de compostos orgânicos com estruturas químicas definidas, tais como carboidratos, aminoácidos e hidrocarbonetos. Os 80% restantes correspondem à matéria orgâni-ca detrítica, pertencentes a um grupo de estrutura química indefinida, com tempo de residência mais longo no ambiente e relativamente resistente à degradação, denominada matéria orgânica refratária (MOR) 1 . Os principais constituintes da MOR globalmente distribuídos nos sistemas aquáticos e terrestres são definidos operacionalmente por substâncias húmicas (SH). Estas são formadas por processos microbiológicos, pela decomposição de resíduos de plantas e animais, sendo constituídas por uma grande variedade de sub-estruturas alifáticas e aromáticas 2 .Devido as suas propriedades físico-químicas polieletrolíticas, as SH exercem grande influência no comportamento de metais em ambientes aquáticos 3-5 . Nestes, íons metálicos e substâncias húmicas aquáticas (SHA) apresentam variadas ligações e os metais podem se distribuir em complexas trocas entre solução e fase sólida. Transporte, complexação, (bio-)disponibilidade e ação de metais no ambiente dependem também da estabilidade do complexo SHA-Metal. A estabilidade das espécies SHA-Metal é determinada por uma série de fatores, incluindo o número de átomos que formam a ligação com o metal, a natureza e a concentração do íon metálico, concentração/característica das SHA, pH, tempo de complexação etc. 2,6,7 .Desta forma, informações associadas à labilidade de metais, às transformações e à estabilidade de complexos SHA-Metal são importantes para o entendimento de processos biogeoquímicos que ocorrem no ambiente. Com esta finalidade, várias metodologias/proc...
O objetivo deste trabalho foi comparar a complexação de substâncias húmicas (SH) e α-aminoacidos (metionina, metionina sulfoxido e cloridrato de cisteína) por elementos traço de interesse biológico (Al, Cu, Pb, Mn, Zn, Cd e Ni). Sistema de ultrafiltração tangencial foi utilizado para diferenciação entre os complexos SH-metal e α-aminoácidos-metal. As determinações de metal foram feitas utilizando ICP-OES. Os resultados mostraram que as SH podem ser consideradas agentes complexantes seletivos com alta capacidade de complexação a Al, Cu e Pb, podendo ser clinicamente importante. The aim of the present work was to carry out experimental comparison between humic substances (HS) and representative α-amino acids (methionine, methionine sulfoxide and cysteine hydrochloride) in relation to the complexation of biologically active trace elements (Al, Cu, Pb, Mn, Zn, Cd and Ni). A mobile time-controlled tangential-flow UF technique was applied to differentiate between HSmetal and α-aminoacids-metal complexes. Metal determinations were conventionally carried out using a ICP-OES. The results showed that HS may be considered as a selective complexing agents with higher metal bonding capability in relation to Al, Cu and Pb, the fact that may be clinically important.
Mangrove ecosystems develop in coastal areas and possess intrinsic characteristics being considered in Brazil environmental preservation areas, however, anthropogenic impacts associated with property speculation and petroleum activities are altering the landscape of these ecosystems. This study aimed to perform organic and inorganic geochemical characterization (pH, organic matter content (MO), elemental analysis, determination of metals -Al, Na, K, Fe, Cd, Cr, Cu, Ni and Pb) in mangrove sediments of the São Francisco Estuary, Sergipe. Mineralogical characteristics defined the sediments as high acidity (pH <4.9), consisting of little decomposed organic matter and low humification. Measurements of elemental analysis with C/N ratio > 10% and MO greater than 15% are related to the proximity of the sampling stations to urban and industrial centers, intrinsic characteristics of native vegetation and different contributions from biomass. The Cd, Cu and Ni metals in sediments showed some upper bounds when compared to the legislation Threshold Effect Level (TEL) e Probable Effect Level (PEL) of Canadian Sediment Quality Guidelines for the Protection of Aquatic Life and Conselho Nacional do Meio Ambiente (CONAMA), being linked to anthropogenic activity in the region and alerting for toxicological reasons.Keywords: Mangrove ecosystems; San Francisco Estuary; Sediments; Metals. ResumoEcossistemas de manguezais se desenvolvem em regiões litorâneas e possuem características intrínsecas, sendo no Brasil considerados áreas de preservação ambiental, porém, impactos antropogênicos associados a especulação imobiliária e atividades petrolíferas estão alterando o cenário desses ecossistemas. O presente trabalho objetivou realizar a caracterização geoquímica orgânica e inorgânica (pH em água, teor de matéria orgânica (MO), análise elementar, determinação de metais -Al, Na, K, Fe, Cd, Cr, Cu, Ni e Pb) de sedimentos de manguezais do Estuário São Francisco, Sergipe. Características mineralógicas definiram os sedimentos como de acidez elevada (pH < 4,9), constituídos de matéria orgânica pouco decomposta e de baixa humificação. As medidas de análise elementar com razão C/N > 10 e % MO superiores a 15 % estão relacionados à proximidade das estações de coleta a centros urbanos e industriais, características intrínsecas da vegetação nativa e diferentes aportes de biomassa. Os metais Cd, Cu e Ni, em alguns sedimentos, se mostraram acima dos limites referenciados por Threshold Effect Level (TEL) e Probable Effect Level (PEL) do Canadian Sediment Quality Guidelines for the Protection of Aquatic Life e do Conselho Nacional do Meio Ambiente (CONAMA), estando associados à atividades antropogênica na região e alertando para fins toxicológicos.
This work involved the development and application of a new analytical procedure for in-situ characterization of the lability of metal species in aquatic systems by using a system equipped with a diffusion membrane and cellulose organomodified with p-aminobenzoic acid groups (DM-Cell-PAB). To this end, the DM-Cell-PAB system was prepared by adding cellulose organomodified with p-aminobenzoic acid groups (Cell-PAB) to pre-purified cellulose bags. After the DM-Cell-PAB system was sealed, it was examined in the laboratory. The in-situ application involved immersing the DM-Cell-PAB system in two different rivers, enabling us to study the relative lability of metal species (Cu, Cd, Fe, Mn, and Ni) as a function of time and quantity of exchanger. The procedure is simple and opens up a new perspective for understanding environmental phenomena relating to the complexation, transport, stability, and lability of metal species in aquatic systems rich in organic matter.
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