Universität zu Köln

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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Abstract

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
Creators:	Creators Email ORCID ORCID Put Code Dorau, Kristof UNSPECIFIED UNSPECIFIED UNSPECIFIED Uteau, Daniel UNSPECIFIED orcid.org/0000-0003-1499-4344 UNSPECIFIED Hoevels, Maren Pia UNSPECIFIED UNSPECIFIED UNSPECIFIED Peth, Stephan UNSPECIFIED orcid.org/0000-0001-9799-212X UNSPECIFIED Mansfeldt, Tim UNSPECIFIED UNSPECIFIED UNSPECIFIED
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:	Keywords Language AIR-FILLED POROSITY; WATER Multiple languages Soil Science Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/58058