Tansport processes controlling uranium uptake by plants
| dc.contributor.advisor | Kirk, Guy | |
| dc.contributor.advisor | Otten, Wilfred | |
| dc.contributor.author | Darmovzalova, Jana | |
| dc.date.accessioned | 2023-10-12T12:05:48Z | |
| dc.date.available | 2023-10-12T12:05:48Z | |
| dc.date.issued | 2018-11 | |
| dc.description.abstract | The mechanisms of uranium (U) uptake by plants growing in contaminated soils are poorly understood, constraining the development of mitigation measures and models of U fate and behaviour. Uptake involves a complex interaction between diffusion and reaction processes in the rhizosphere, and root-induced changes in the soil affecting these processes. This thesis is concerned with developing better understanding of these processes, as represented in predictive mathematical models. Most past research on U transport and reaction in soils has been in shaken suspensions or flow-through systems, in which the rate-limiting processes are artificially altered. This thesis develops a novel experimental approach in which diffusion and reaction are measured simultaneously in soil with stationary pore water, better representing the rhizosphere. Concentration- distance profiles of U were measured between two half-cells of soil, one of which initially contained U and the other not, giving rates of desorption in the source and adsorption in the sink cell. The effects of typical root-induced changes in soil pH and CO₂ pressure were measured. Two models were compared: (a) an analytical solution of the appropriate diffusion equation with a constant diffusion coefficient, and (b) a numerical solution allowing for time- and concentration-dependent diffusion. The model parameters were measured or otherwise estimated independent of the concentration-distance profiles. The simple analytical solution correctly accounted for the effects of pH and CO₂ pressure on U diffusion, but under-predicted the diffusive flux. The numerical model correctly predicted the flux and concentration-distance profiles, including a discontinuity at the source-sink boundary due to differences in the kinetics of desorption and adsorption. The results show the importance of correctly allowing for the effects of pH, CO₂ pressure and sorption kinetics in modelling U uptake by plant roots. The model should be further corroborated in mesocosm, half-cell and field experiments, and by verifying U speciation. | en_UK |
| dc.description.coursename | PhD in Environment and Agrifood | en_UK |
| dc.identifier.uri | https://dspace.lib.cranfield.ac.uk/handle/1826/20361 | |
| dc.language.iso | en | en_UK |
| dc.publisher | Cranfield University | en_UK |
| dc.publisher.department | SWEE | en_UK |
| dc.rights | © Cranfield University, 2018. All rights reserved. No part of this publication may be reproduced without the written permission of the copyright holder. | en_UK |
| dc.subject | Diffusion | en_UK |
| dc.subject | uranium | en_UK |
| dc.subject | soil modellling | en_UK |
| dc.subject | radionuclide uptake | en_UK |
| dc.subject | rhizosphere processes | en_UK |
| dc.subject | reaction processes | en_UK |
| dc.title | Tansport processes controlling uranium uptake by plants | en_UK |
| dc.type | Thesis or dissertation | en_UK |
| dc.type.qualificationlevel | Doctoral | en_UK |
| dc.type.qualificationname | PhD | en_UK |