Fotoprodução de peroxidos de hidrogenio em aguas naturais sob a ação da luz solar

AUTOR(ES)
DATA DE PUBLICAÇÃO

1994

RESUMO

The photoproduction of hydrogen peroxide was investigated under simulated and natural conditions. Solutions containing a well characterised sediment and a commercial humic acid were used as sources of particulate matter and dissolved organic matter, respectively. In a 30 mg.L sediment suspension 0.31 mmol.L of H2O2 were generated after 5 h irradiation and 1.55 mmol.L were produced in a 5.0 mg.L humic acid solution, during the same time. Total organic carbon measurements showed a non-destructive photooxidation process related to the dissolved organic matter. Photoproduction of H2O2 was algo investigated using 0.5, 1.0 and 2.0 mmol.L of Fe(III), Cu(II) and Cd(Il) in a 5.0 mg.L solution of humic acid. A decrease in the H2O2 concentration was observed with increase in the concentrations of Fe(III) and Cu(II). Solutions containing Cd(II) ions showed a different behaviour as increased H2O2 levels were observed with the increase in metal concentration. The use of ASV showed a 8% and a 29% increase in the concentration of "free" Cd(II) and Cu(II), respectively, after 5 h photolysis. Iron speciation studies showed the generation of Fe(Il) during the irradiation. Photoproduction of Fe(Il) was also observed when a sea water sample from ltanhaém, SP was spiked with 1.0 mmol.L of Fe(III) and catalase, showing a Fenton-dependent type reaction in this medium. Primary production and H2O2 photoproduction were evaluated "in situ", in experiments conducted in Cananéia and Ubatuba, two different trophic environments. Hydrogen peroxide and primary production levels were always higher in the estuarine waters of Cananéia. Toxicity tests using natural populations from both regions showed that the coastal Ubatuba phytoplancton community was less resistant to hydrogen peroxide. A portable photometer, battery operated, was specially constructed to carry out "in situ" determinations of H2O2.

ASSUNTO(S)

metais - oxidação agentes oxidantes fotoquimica

ACESSO AO ARTIGO

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