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Master Thesis

In situ measurements of pH and O2 by planar optodes: improvements and adaptations for soil and rhizosphere applications

Abstract : Soil is a highly heterogeneous system in which complex biogeochemical interactions occur at fine scale affecting ecosystem functioning at larger scale. Knowledge of spatio-temporal dynamics of soils processes is still scarce as access and continuous monitoring is challenging. Planar optodes are an emerging technology allowing the imaging of pH and oxygen dynamics in a non-invasive way and at sub-mm scale. It is based on the reversible interaction between protons or oxygen with a sensitive fluorescent probe and combined with a dedicated imaging set-up. The objective of this work was to develop and adapt oxygen and pH optodes (pH range of 5.5–7.5 and 6.5-9.5) for monitoring soil chemical processes as well as soil-root interactions. In addition, we focused on determining the effect of soil experimental conditions on optode measurements, including background heterogeneity, soil water content and experiment duration. Results revealed the need to test and overcome effects of background heterogeneity when working with transparent optodes, Moreover, depending on experimental condition, optode signals were occasionally found to be affected by biogeochemical processes, highlighting the necessity to assess optode performance after its application to soil. Improved optodes were applied in two case studies: the imaging of (1) oxygen dynamics in the rhizosphere of flooded rice and of (2) pH changes around metallic tungsten sources in non-water saturated soil.
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Master Thesis
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Submitted on : Wednesday, July 8, 2020 - 4:18:37 PM
Last modification on : Friday, August 5, 2022 - 2:54:00 PM


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  • HAL Id : dumas-02893946, version 1



Gabrielle Daudin. In situ measurements of pH and O2 by planar optodes: improvements and adaptations for soil and rhizosphere applications. Inorganic chemistry. 2018. ⟨dumas-02893946⟩



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