In addition to geological, geochemical, and geophysical aspects, also, microbial aspects have to be taken into account when considering the final storage of high-level radioactive waste in a deep geological repository. Rock salt is a potential host rock formation for such a repository. One indigenous microorganism, that is, common in rock salt, is the halophilic archaeon Halobacterium noricense DSM15987ᵀ, which was used in our study to investigate its interactions with the trivalent actinide curium and its inactive analogue europium as a function of time and concentration. Time-resolved laser-induced fluorescence spectroscopy was applied to characterize formed species in the micromolar europium concentration range. An extended evaluation of the data with parallel factor analysis revealed the association of Eu(III) to a phosphate compound released by the cells (F₂/F₁ ratio, 2.50) and a solid phosphate species (F₂/F₁ ratio, 1.80). The association with an aqueous phosphate species and a solid phosphate species was proven with site-selective TRLFS. Experiments with Cm(III) in the nanomolar concentration range showed a time- and pCH₊-dependent species distribution. These species were characterized by red-shifted emission maxima, 600–602 nm, in comparison to the free Cm(III) aqueous ion, 593.8 nm. After 24 h, 40% of the luminescence intensity was measured on the cells corresponding to 0.18 μg Cm(III)/gDBM. Our results demonstrate that Halobacterium noricense DSM15987ᵀ interacts with Eu(III) by the formation of phosphate species, whereas for Cm(III), a complexation with carboxylic functional groups was also observed.

Nuclear power reactors are operating in 31 countries around the world. Along with reactor operations, activities like mining, fuel fabrication, fuel reprocessing and military operations are the major contributors to the nuclear waste. The presence of a large number of fission products along with multiple oxidation state long-lived radionuclides such as neptunium (²³⁷Np), plutonium (²³⁹Pu), americium (²⁴¹/²⁴³Am) and curium (²⁴⁵Cm) make the waste streams a potential radiological threat to the environment. Commonly high concentrations of cesium (¹³⁷Cs) and strontium (⁹⁰Sr) are found in a nuclear waste. These radionuclides are capable enough to produce potential health threat due to their long half-lives and effortless translocation into the human body. Besides the radionuclides, heavy metal contamination is also a serious issue. Heavy metals occur naturally in the earth crust and in low concentration, are also essential for the metabolism of living beings. Bioaccumulation of these heavy metals causes hazardous effects. These pollutants enter the human body directly via contaminated drinking water or through the food chain. This issue has drawn the attention of scientists throughout the world to device eco-friendly treatments to remediate the soil and water resources. Various physical and chemical treatments are being applied to clean the waste, but these techniques are quite expensive, complicated and comprise various side effects. One of the promising techniques, which has been pursued vigorously to overcome these demerits, is phytoremediation. The process is very effective, eco-friendly, easy and affordable. This technique utilizes the plants and its associated microbes to decontaminate the low and moderately contaminated sites efficiently. Many plant species are successfully used for remediation of contaminated soil and water systems. Remediation of these systems turns into a serious problem due to various anthropogenic activities that have significantly raised the amount of heavy metals and radionuclides in it. Also, these activities are continuously increasing the area of the contaminated sites. In this context, an attempt has been made to review different modes of the phytoremediation and various terrestrial and aquatic plants which are being used to remediate the heavy metals and radionuclide-contaminated soil and aquatic systems. Natural and synthetic enhancers, those hasten the process of metal adsorption/absorption by plants, are also discussed. The article includes 216 references.