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Fungi-assisted uranium uptake by plants: considerations of soil biogeochemistry and its mechanistic implications

Dunlap, Katherine (2021) Fungi-assisted uranium uptake by plants: considerations of soil biogeochemistry and its mechanistic implications. Masters thesis, Northern Arizona University.

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Hundreds of abandoned uranium mines pepper the landscape of the Navajo Nation, which exposes residents to radiogenic and chemotoxic hazards.1,2 Uranium soil contamination also impacts regions of China, Canada, and Europe. Typical uranium remediation techniques (e.g., soil removal, plant uptake) are undesirable because they increase erosion, release uranium-containing dust, or potentially lead to the unintentional consumption of uranium by livestock such as mutton and local fauna.3, 4 A method that could reduce this exposure is phytostabilization, which has the primary goal of quelling contaminant transport by using plants to take up uranium but keeps uranium predominantly in the plant roots where livestock would be less likely to consume the plant. New discoveries associated with this method prompt new questions about underlying mechanisms. One discovery is that root symbiotic arbuscular mycorrhizal fungi (AMF) can increase the uptake and isolation of uranium in the roots of sunflowers.5 Studies have demonstrated this phenomenon, but researchers have yet to pinpoint the underlying mechanism or mechanisms.3, 6, 7, 8, 9 A missing element of study may be the mineralogy of the plant growing medium, which can influence the bioavailability of uranium and other metals.10 We hypothesize that AMF are able to increase the uptake of uranium in the roots of plants because they can access a phase of uranium that is chemically held to clay minerals that plants cannot acquire alone. To test this hypothesis, we conducted sunflower growth experiments using kaolinite and native soils, continuously exposing the plants to uranium of varying concentration for eight weeks. The plants were processed and analyzed via ICP-MS to determine the concentrations of uranium in the roots and shoots. Statistical analysis using ANOVA was performed where appropriate to determine the significance of the treatments. In the kaolinite growth experiment, the only groups with statistically significant differences in uranium concentrations were the roots of the +AMF +Clay 10 ppb uranium treatment, which had a higher uranium concentration, and the +AMF -Clay 10 ppb uranium treatment, which had a lower uranium concentration. In the soil growth experiment, there were no statistically significant differences in mean uranium concentrations between any groups. These results indicate that soil uranium host phase likely impacts the ways in which uranium is taken up by sunflowers.

Item Type: Thesis (Masters)
Publisher’s Statement: © Copyright is held by the author. Digital access to this material is made possible by the Cline Library, Northern Arizona University. Further transmission, reproduction or presentation of protected items is prohibited except with permission of the author.
Keywords: Uranium; Soils; Phytostabilization; Arbuscular mycorrhizal fungi; Navajo Indian Reservation
Subjects: Q Science > QK Botany
NAU Depositing Author Academic Status: Student
Department/Unit: Graduate College > Theses and Dissertations
College of the Environment, Forestry, and Natural Sciences > Biological Sciences
Date Deposited: 07 Feb 2022 17:29
Last Modified: 07 Feb 2022 17:29
URI: https://openknowledge.nau.edu/id/eprint/5671

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