Dorau, K. und Luster, J. und Mansfeldt, T.
(2017)
Soil aeration - The relationship between redox potential and air-filled pores.
In: Jahrestagung der DBG 2017: Horizonte des Bodens, 02.-07.09.2017, Göttingen.
Kurzfassung
Soil water contents are variable with impact on oxygen diffusion rates and redox potentials (EH). When water saturated soils become aerated, a switch from reducing to oxidizing conditions occurs. However, only limited information are available at which air-filled pore volume (ε) this dramatic shift happens. Therefore, undisturbed soil cores were taken by steel cylinders from the topsoils of a Fluvisol and a Gleysol that differed in soil structure and clay content. After submergence in the laboratory, the samples were sealed by a glass dome to exclude oxygen and to achieve strongly reducing conditions
(EH < -100 mV). We aerated the sample on demand by removal of glass plugs in the dome and consecutively measured EH by platinum-(Pt) tipped electrodes and ε by pressure head readings on hourly basis. We propose to use the terms: i) εPt reaction, to indicate the air-filled pore volume at which a response of the Pt-tipped electrode due to contact with oxygen occurs (i.e., EH increase > 5 mV h-1), and ii) εPt aeration, to indicate when oxidizing soil conditions are present (i.e., EH > 300 mV at pH 7). These characteristic εPt reaction values were at 0.036±0.013 cm3 cm–3 for the Fluvisol and at 0.048±0.017 cm3 cm–3 for the Gleysol whereas εPt aeration values were at 0.047±0.005 and at 0.085±0.002 cm3 cm–3, respectively. This study provided important information to determine the aeration status of a soil when, e.g., ε is known but EH measurements are absent.
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