Publications (2)4.68 Total impact
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Article: THE RELATIONSHIP BETWEEN OXIDATION‐REDUCTION POTENTIALS AND OXYGEN‐DIFFUSION LEVELS IN SOME WATERLOGGED ORGANIC SOILS
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ABSTRACT: In valley and blanket-bog peat, oxygen-diffusion rates and corresponding oxidation-reduction potentials have been measured, and the relationship between them expressed graphically.Oxygen-diffusion rates were obtained ‘polarographically’, and the Pt cathode also served as the redox indicator-electrode.Plateau-shifts towards more positive potentials made it necessary to use the reduced voltage setting of −0.48 v for oxygen determinations. These plateaushifts correlate with a lowering of the oxygen content, and an increase in acidity, or, perhaps, with the type of buffer systems found in peat.The ratio redox potential/oxygen diffusion is not constant. At very low oxygen values there is a relatively large increase in redox potential per unit of oxygen, but, as oxygen approaches 2 × 10−8 g O2cm−2min−1, the ratio becomes much lower, while variations become more obvious.rH values calculated according to Jeffery (1961), show that, in peat of high iron content at pH 6, the first traces of oxygen correspond to an rH 1.10–1.20 (E6, 50–120; reduced and oxidized iron probably present), while above 2 × 10−8 g O2 cm−2min−1 the rH is greater than 1.20 and oxidized iron probably predominates. Thus oxidized soil, as defined by Jeffery, may be maintained at very low oxygen levels.It is suggested that oxygen diffusing from plant roots into these peats will oxidize reduced soil products, and thereby protect the plant.European Journal of Soil Science 07/2006; 18(1):27 - 34. · 2.34 Impact Factor -
Article: A POLAROGRAPHIC TECHNIQUE FOR THE MEASUREMENT OF DISSOLVED SULPHIDE IN WATERLOGGED SOILS
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ABSTRACT: The polarographic oxidation of sulphide at the dropping mercury electrode reported by Revenda (1934), forms the basis of this technique for the assay of dissolved sulphide in soil solutions.Soil solution is expressed from cores removed from the soil in a Hiller-type borer, and transferred to tubes containing pyrogallol and NaOH. A current-voltage curve for each sample is then obtained using the dropping mercury electrode in conjunction with a saturated calomel electrode. The current in the plateau region of a curve is proportional to the sulphide concentration, and after volume and temperature corrections, the sulphide concentration in a sample can be read from a previously prepared calibration curve.The possibility of sulphide loss from the samples before analysis has been found to be slight.Details of construction, and calibration of the dropping mercury electrode using standard Na2S solutions, are included in the description of the technique and apparatus. The inclusion of such minor modifications as (a) the insertion of a condenser across the microammeter terminals to dampen the large current oscillations produced by the dropping mercury electrode, and (b) the inclusion of a switch to allow reversal of polarity at the microammeter, enabled a circuit of the type currently used for soil oxygen diffusion measurements to be used also for sulphide estimation.European Journal of Soil Science 07/2006; 18(2):282 - 288. · 2.34 Impact Factor
