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Kinetics of redox cycling of iron coupled with fulvic acid (1993)

Deng, Yiwei ; Stumm, Werner

Springer

Aquatic sciences 55 (1993), S. 103-111

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ISSN: 1420-9055

Keywords: iron(III) (hydr)oxide ; fulvic acid ; iron redox cycling ; dissolution ; surface reactivity ; kinetics

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The kinetics of conversion of iron(III) (hydr)oxides to ferrous iron mediated by fulvic acid have been investigated in order to improve the understanding of the redox cycling of iron at the oxic-anoxic boundary in natural waters. Under the conditions similar to natural waters, fulvic acid is able to reduce the iron(III) (hydr)oxide. The kinetics of the reaction depend on the reactivity of iron(III) (hydr)oxides and the reducing power of the fulvic acid. The rate of reaction is 60 nm/h obtained under following conditions: total concentration of Fe(III) 1.0 × 10−4 M, pH 7.5, fulvic acid 5 mg/L. The rate is considered as a net result of reduction and oxidation in the 〉 FeIII-OH/Fe(II) “wheel” coupled with fulvic acid. In a real natural water system, reductants other than fulvic acid may be of importance. The results obtained in the laboratory, however, provide evidence that the Fe(OH)3(s)/Fe(II) redox couple is able to act as an electron-transfer mediator for the oxidation of natural organic substances, such as fulvic acid by molecular oxygen either in the absence of microorganisms or as a supplement to microbial activity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00877439

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From Environmental Analytical Chemistry to Ecotoxicology - A Plea for More Concepts and Less Monitoring and Testing (1983)

Stumm, Werner ; Schwarzenbach, René ; Sigg, Laura

Weinheim : Wiley-Blackwell

Angewandte Chemie International Edition in English 22 (1983), S. 380-389

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ISSN: 0570-0833

Keywords: Environmental chemistry ; Toxicology ; Ecotoxicology ; Analytical methods ; Chemistry of the future ; Chemistry ; General Chemistry

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology

Notes: The development of cultural and technical civilization has been marked with increasing interference in hydrogeochemical cycles and the production of a growing number of chemicals; this is accompanied by a growing concern on the potential adverse effects of chemicals on biological systems. Assessment of the potential toxicological and ecological effects of pollutants is of central importance. We are of the opinion that this cannot be accomplished by merely evaluating the harmfulness of a substance on the basis of toxicity tests with individual organisms and by monitoring analytically the environment for pollutants. We would like to encourage chemists to participate in the solution of ecotoxicological problems: chemodynamical concepts permit the estimation-on the basis of physical-chemical generalizations and with the help of compound-specific data-of the fate, the distribution, the potential for bioaccumulation in the food chain, and the approximate residence time of pollutants (and thus the attainable residual concentrations) in the environment and therefore to predict the relative risk of different pollutants.

Additional Material: 11 Ill.