Oxidation in natural waters

Mill, T., Hendry, D.G., Richardson, H. (1980) Free radical oxidants in natural waters. Science 207, 886-887. 

Hohl, H., L. Sigg, and W. Stumm (1980), "Characterization of Surface Chemical Properties of Oxides in Natural Waters The Role of Specific Adsorption Determining the Specific Charge," in M. C. Kavanaugh and J. O. Leckie, Eds., Particulates in Water, Advances in Chemistry Series, ACS 189, 1-31. 

Sulzberger, B., D. Suter, C. Siffert, S. Banwart, and W. Stumm (1989), "Dissolution of Fe(III)(hydr)-oxides in Natural Waters Laboratory Assessment on the Kinetics Controlled by Surface Coordination", Marine Chemistry 28, 127-144. 

The rates of Mn(II) oxidation in natural waters, although slow, are typically orders of magnitude faster than the rate of oxidation of Mn(II) in solution (8,12). It has been suggested that the enhanced rate of Mn(II) oxidation in natural waters is due either to bacterial oxidation (13-16) or to the "catalytic" effects of surfaces such as metal oxides (8, 17-19). The existing evidence suggests that in certain environments bacterial mediation of the reaction is important (13-15). But in many cases the relative importance of bacterial and abiotic "catalysis" in natural waters has not been clearly defined. 

This paper discusses the oxidation of Mn(II) in the presence of lepidocrocite, y-FeOOH. This solid was chosen because earlier work (18, 26) had shown that it significantly enhanced the rate of Mn(II) oxidation. The influence of Ca2+, Mg2+, Cl", SO,2-, phosphate, silicate, salicylate, and phthalate on the kinetics of this reaction is also considered. These ions are either important constituents in natural waters or simple models for naturally occurring organics. To try to identify the factors that influence the rate of Mn(II) oxidation in natural waters the surface equilibrium and kinetic models developed using the laboratory results have been used to predict the... 

Mn(II) Oxidation in Natural Waters Implications of Experimental Studiei... 

Waite, T.D. and Morel, F.M.M., 1989b. Photoreductive dissolution of colloidal iron oxides in natural waters. Environ. Sci. Technol., 18 860-868. 

The variety of mechanisms possible for reductive mineral dissolution processes that are mediated by organic ligands is discussed by J. G. Hering and W. Stumm, op. cit.,26 A. T. Stone and J. J. Morgan, op. cit.,28 andB. Sulzberger, D. Suter, C. Siffert, S. Banwart, and W. Stumm, Dissolution of Fe(III) (hydr)oxides in natural waters Laboratory assessment on the kinetics controlled by surface coordination, Mar. Chem. 28 127 (1989). The examples considered in this section are illustrative only. 

Andreae described a method for the sequential determination of arsenate, arsenite, mino-, di- and trimethylarsine, MMAA and DMAA and trimethylarsine oxide in natural waters with detection limits of several ngl. The arsines are volatilized from the sample by... 

Andreae described a method for the sequential determination of arsenate, arsenite, mono-, di- and trimethyl arsine, MMAA, DMAA and trimethylarsine oxide in natural waters with detection limits of several ng/1. The arsines are volatilized from the sample by gas stripping the other species are then selectively reduced to the corresponding arsines and volatilized. The arsines are collected in a cold trap cooled with liquid nitrogen. They are then separated by slow warming of the trap or by gas chromatography, and measured with atomic absorption, electron capture and/or flame ionization detectors. He found that these four arsenic species all occurred in natural water samples. 

Example 12. L Estimation of Steady-State Concentrations of a Photoreactant in a Natural Water We follow the theoretical treatment by Haag and Hoigne (1985) (photosensitized oxidation in natural waters via OH radicals.) The scheme is given by reactions ia and ib ... 

Despite the fact that OH is a very reactive radical toward many organic pollutants, its low steady-state concentration makes it a nondominant oxidant in natural waters. As Schwarzenbach et al. (1993) point out, the second-order rate constant for reaction with OH (see Figure 11.10c) is on the order of 6 x 10 M s . Multiplying this rate constant with [OH ]ss = 10 gives a first-... 

Haag, W. R., and Hoign6, J. (1985) Photo-sensitized Oxidation in Natural Water via OH Radicals, Chemosphere 14(11/12), 1659-1671. 

Trichloroacetate rapidly reacts with the solvated electrons produced by laser flash photolysis of natural organic matter isolated from the Suwannee River, and thus quenches the absorption of the electrons at 720 nm. The ibsorption is also quenched by the addition of other good electron acceptors, including oxygen, protons, or nitrous oxide. In natural waters, halocarbon concentrations are typically very low, and the dominant scavenger of solvated electrons is oxygen. 

W.R. Haag, J. Hoigne (1985). Photo-sensitized oxidation in natural water via OH radicals. Chemosphere, 14, 1659-1671. 

Waite, T. D., and F, M. M. Morel (1984), Photoreductive Dissolution of Colloidal Iron Oxides in Natural Waters, Environ. Sci. Technol. 18, 860-868. 

An extensive survey of the thermodynamic and kinetic properties of manganese in natural aqueous systems has been presented by Morgan (3). From a thermodynamic standpoint, Mn(II) is unstable with respect to oxidation in natural waters. The kinetics of the oxidation reactions are sufficiently slow so that Mn(II) can exist as a metastable species in natural waters. The solubility of Mn(II) in most natural systems probably is limited by the solubility of MnC03. Soluble complexes such as MnHCCV make varying contributions to the total soluble Mn(II) species in natural waters. Some of the equilibria which are relevant to this study are listed in Table I. 

Characterization of Surface Chemical Properties of Oxides in Natural Waters... 

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