Dorau, Kristof, Uteau, Daniel ORCID: 0000-0003-1499-4344, Hoevels, Maren Pia, Peth, Stephan ORCID: 0000-0001-9799-212X and Mansfeldt, Tim (2022). Soil aeration and redox potential as function of pore connectivity unravelled by X-ray microtomography imaging. Eur. J. Soil Sci., 73 (1). HOBOKEN: WILEY. ISSN 1365-2389

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Platinum (Pt)-tipped electrodes are frequently employed to measure the soil redox potential (E-H). Thereby, the timely transition from reducing towards oxidising soil conditions is one of the most important biogeochemical changes that can occur in soil. This condition is mainly linked to the air-filled pore volume (epsilon) and pore geometries. However, even when the Pt electrodes are located in close vicinity to each other, E-H readings behave non-uniformly, presumably due to the millimetre scaled heterogeneity of pore spaces controlling oxygen (O-2) availability and transport. In this study, we examined the epsilon distribution and pore connectivity in the close vicinity of a Pt electrode during an artificial evaporation experiment using an undisturbed soil sample (Ah-horizon, Calcaric Gleysol). We combined physio-chemical methods with non-destructive X-ray computed microtomography (mu CT) and 3D-image analysis. mu CT scans were conducted at three-time points, that is, reducing conditions with E-H < -100 mV (CT-1), the transition from reducing towards oxidising conditions with an E-H increase > 5 mV h(-1) (CT-2), and oxidising conditions with E-H > 300 mV (CT-3). We observed that the shift from reducing towards oxidising conditions took place at an air-filled porosity (epsilon(CT)) of similar to 0.03 cm(3) cm(-3), which matches very with gravimetrically calculated data obtained by tensiometry of epsilon similar to 0.05 cm(3) cm(-3). Besides the relation of E-H and epsilon, image analysis revealed that a connected epsilon(CT) (epsilon(CT_conn)) of similar to 0.02 cm(3) cm(-3) is needed to enable enhanced O-2 diffusion from the soil surface towards the Pt surface and facilitate a straightforward E-H response. We conclude that epsilon(CT_conn) is a critical parameter to assess aeration processes in temporarily water-saturated soils to characterise a switch in redox conditions. Highlights Usually, soil redox dynamics are related to the air-filled porosity (epsilon(CT)) but here its connected portion (epsilon(CT_conn)) was found more relevant. 3D X-ray computed microtomography imaging close to a redox electrode enabled us to understand the soil aeration process. Connected epsilon(CT) (epsilon(CT_conn)) of similar to 0.02 cm(3) cm(-3) facilitated oxidising soil conditions. epsilon(CT_conn) is a critical parameter to assess the aeration process in temporarily water-saturated soils.

Item Type: Journal Article
CreatorsEmailORCIDORCID Put Code
URN: urn:nbn:de:hbz:38-580585
DOI: 10.1111/ejss.13165
Journal or Publication Title: Eur. J. Soil Sci.
Volume: 73
Number: 1
Date: 2022
Publisher: WILEY
Place of Publication: HOBOKEN
ISSN: 1365-2389
Language: English
Faculty: Unspecified
Divisions: Unspecified
Subjects: no entry
Uncontrolled Keywords:
Soil ScienceMultiple languages


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