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* old and bolonia study programme


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Uranium isotope fractionation during adsorption, (co) precipitation, and biotic reduction
Douglas R. Evans, Bastian R. Georg, Wei Wang, Breda Novotnik, Duc Huy Dang, 2016, original scientific article

Abstract: Uranium contamination of surface environments is a problem associated with both U-ore extraction/processing and situations in which groundwater comes into contact with geological formations high in uranium. Apart from the environmental concerns about U contamination, its accumulation and isotope composition have been used in marine sediments as a paleoproxy of the Earth’s oxygenation history. Understanding U isotope geochemistry is then essential either to develop sustainable remediation procedures as well as for use in paleotracer applications. We report on parameters controlling U immobilization and U isotope fractionation by adsorption onto Mn/Fe oxides, precipitation with phosphate, and biotic reduction. The light U isotope (235U) is preferentially adsorbed on Mn/Fe oxides in an oxic system. When adsorbed onto Mn/Fe oxides, dissolved organic carbon and carbonate are the most efficient ligands limiting U binding resulting in slight differences in U isotope composition (δ238U = 0.22 ± 0.06‰) compared to the DOC/DIC-free configuration (δ238U = 0.39 ± 0.04‰). Uranium precipitation with phosphate does not induce isotope fractionation. In contrast, during U biotic reduction, the heavy U isotope (238U) is accumulated in reduced species (δ238U up to −1‰). The different trends of U isotope fractionation in oxic and anoxic environments makes its isotope composition a useful tracer for both environmental and paleogeochemical applications.
Found in: ključnih besedah
Keywords: Uranium, fractionation, biotic, abiotic, oxides
Published: 04.10.2019; Views: 490; Downloads: 0
.pdf Fulltext (4,30 MB)

Under fungal attack on a metalliferous soil: ROS or not ROS? Insights from Silene paradoxa L. growing under copper stress
Cosimo Taiti, Elisabetta Giorni, Ilaria Colzi, Sara Pignattelli, Nadia Bazihizina, Antonella Buccianti, Simone Luti, Luigia Pazzagli, Stefano Mancuso, Cristina Gonnelli, 2016, original scientific article

Abstract: We investigated how the adaptation to metalliferous environments can influence the plant response to biotic stress. In a metallicolous and a non-metallicolous population of Silene paradoxa the induction of oxidative stress and the production of callose and volatiles were evaluated in the presence of copper and of the PAMP fungal protein cerato-platanin, separately and in combination. Our results showed incompatibility between the ordinary ROS-mediated response to fungal attack and the acquired mechanisms of preventing oxidative stress in the tolerant population. A similar situation was also demonstrated by the sensitive population growing in the presence of copper but, in this case, with a lack of certain responses, such as callose production. In addition, in terms of the joint behaviour of emitted volatiles, multivariate statistics showed that not only did the populations respond differently to the presence of copper or biotic stress, but also that the biotic and abiotic stresses interacted in different ways in the two populations. Our results demonstrated that the same incompatibility of hyperaccumulators in ROS-mediated biotic stress signals also seemed to be exhibited by the excluder metallophyte, but without the advantage of being able to rely on the elemental defence for plant protection from natural enemies.
Found in: ključnih besedah
Summary of found: ...environments can influence the plant response to biotic stress. In a metallicolous and a non-metallicolous...
Keywords: Biotic interactions Callose Heavy metals Oxidative stress VOCs
Published: 20.04.2020; Views: 243; Downloads: 0
.pdf Fulltext (6,63 MB)

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