Use este identificador para citar ou linkar para este item: http://repositorio.inpa.gov.br/handle/123/5991
Título: Reduction of mercury(II) by tropical river humic substances (Rio Negro) - A possible process of the mercury cycle in Brazil
Autor(es): Júlio Cesar Rocha
Ézio Sargentini Junior
Luiz Fabrício Zara
André Henrique Rosa
Ademir dos Santos
Peter Burba
Assunto: aquatic humic substance
Rio Negro
Mercury reduction
ISSN: 0039-9140
Revista: Talanta (Oxford)
Volume: 53
Resumo: The evolution of elemental Hg from its environmental compounds has already been supposed to be an important process within the global mercury cycle. The present study characterizes the abiotic reduction of Hg(II) ions by typical river humic substances (HS) conventionally pre-isolated by the adsorbent XAD 8 from the “Rio Negro” near Manaus, Brazil. For the investigation of this reduction process a special reaction and Hg(0) trapping unit combined with cold-vapor atomic absorption spectrometry (CVAAS) was developed. Preconcentration of traces of mercury(II), if required, was obtained by a home-made FIA system using microcolumns filled with the Hg(II)-selective collector CheliteS® (Serva Company). The effect of environmentally relevant parameters such as the pH value, the Hg(II)/HS ratio and the HS concentration on the Hg(II) reduction process was studied as a function of the time. The Hg(0) production was highest at pH 8.0 and in the case of decreasing HS amounts (0.5 mg) when about 65% of initially 1.0 μg Hg(II) was reduced within 50 h. Moreover, the reduction efficiency of HS towards Hg(II) strongly depended on the HS concentration but hardly on the Hg(II)/HS ratio. The reduction kinetics followed a relatively slow two-step first-order mechanism with formal rate constants of about 0.1 and 0.02 h−1, respectively. Based on these findings the possible relevance of the abiotic evolution of mercury in humic-rich aquatic environments is considered.
URI: http://repositorio.inpa.gov.br/handle/123/5991
ISSN: 0039-9140
DOI: http://dx.doi.org/10.1016/S0039-9140(00)00532-4
Local de publicação: Estados Unidos
Aparece nas coleções:Coordenação de Dinâmica Ambiental (CDAM)

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