Evidence of microalgal isotopic fractionation through enrichment of depleted uranium

Abstract

Resulting from the nuclear fuel cycle, large amounts of depleted uranium (DU) tails are piling up, waiting for possible use or final disposal. To date, the recovery of the residual 235U isotope contained in DU has been conducted only marginally by physical processes. Relative isotope abundances are often mediated by biological processes, and the biologically driven U isotopic fractionation has been previously identified in reducing bacteria. Our results indicate that the cells of two microalgal strains (freshwater Chlamydomonas sp. (ChlGS) and marine Tetraselmis mediterranea (TmmRU)) took up DU from the exposure solutions, inducing U isotopic fractionation with a preference for the fissile 235U isotope over 238U. The n(235U)/n(238U) isotopic fractionation magnitudes (δ235) were 23.6 ± 12.5‰ and 370.4 ± 103.9‰, respectively. These results open up new perspectives on the re-enrichment of DU tailings, offering a potential biological alternative to obtain reprocessed natural-equivalent uranium. Additionally, the findings present implications for identifying biological signatures in the geologic records.

Sword of Damocles or choosing well. Population genetics sheds light into the future of the COVID-19 pandemic and SARS-CoV-2 new mutant strains

“…46 seminal papers, a great number of studies show that mutant emergence is a recurrent process that happens randomly and in a pre-selective and pre-adaptative way (i.e., mutants emerge before natural selection acts) 47,48 . This surprising process has been demonstrated: in microorganism populations, spontaneous and recuring mutant strains arise that have resistance to newly synthetised substances, even before industry developed them 49,50,59,[51][52][53][54][55][56][57][58] even if these substances are of military use and where never before present in nature 60 or are radioisotopes of nuclear industry [61][62][63][64] .…”

The `greed ́ and `nationalism ́ in vaccination against Covid-19 lead to the Tragedy of the Commons, Nash equilibrium and Giffen's goods, giving SARS-CoV-2 more opportunities to escape mutants.

“…[51][52][53] , others more recently have also proved them right. For example, in microorganism populations spontaneously and recurringly arise new mutant strains, resistant to substances of late synthesis even before industry used them 54,55,64,[56][57][58][59][60][61][62][63] or of military use never seen in nature before 65 or radioisotopes of nuclear industry [66][67][68][69] .…”

Biosorption of Uranyl Ions from Aqueous Solution by Parachlorella sp. AA1

“…Biological sorption describes the binding of heavy metals to biomolecules or sorption on the surface of cells from an aqueous solution, which subsequently prevents contaminant release [ 12 ]. Biological methods including biosorption, bioaccumulation, and bioimmobilization may provide an interesting alternative to heavy metal ion removal methods [ 4 ].…”

“…Once released, the environmental fate and transport of these radionuclides is remarkably controlled by microbial activity, as natural microbial flora have diverse mechanisms for interacting with such metallic pollutants, including reductive precipitation, solubilization, and biosorption/bioaccumulation; these processes finally determine the environmental toxicity and mobility of metallic pollutants [ 5 ]. Microalgal uptake of nuclides has received much recent attention among radioactive wastewater treatment technologies, and selection of the most effective microalgal species for uranyl ions biosorption is a major focus for the research and applications in this area [ 12 ].…”