Enhancing La(III) biosorption and biomineralization with Micromonospora saelicesensis: Involvement of phosphorus and formation of monazite nano-minerals.

The release of rare earth elements (REEs) from mining wastes and their applications has significant environmental implications, necessitating the development of effective prevention and reclamation strategies. The mobility of REEs in groundwater due to microorganisms has garnered considerable attention. In this study, a La(III) resistant actinobacterium, Micromonospora saelicesensis KLBMP 9669, was isolated from REE enrichment soil in GuiZhou, China, and evaluated for its ability to adsorb and biomineralize La(III). The findings demonstrated that M. saelicesensis KLBMP 9669 immobilized La(III) through the physical and chemical interactions, with immobilization being influenced by the initial La(III) concentration, biomass, and pH. The adsorption kinetics followed a pseudo-second-order rate model, and the adsorption isotherm conformed to the Langmuir model. La(III) adsorption capacity of this strain was 90 mg/g, and removal rate was 94 %. Scanning electron microscope (SEM) coupled with energy dispersive X-ray spectrometer (EDS) analysis revealed the coexistence of La(III) with C, N, O, and P. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) investigations further indicated that carboxyl, amino, carbonyl, and phosphate groups on the mycelial surface may participate in lanthanum adsorption. Transmission electron microscopy (TEM) revealed that La(III) accumulation throughout the M. saelicesensis KLBMP 9669, with some granular deposits on the mycelial surface. Selected area electron diffraction (SAED) confirmed the presence of LaPO4 crystals on the M. saelicesensis KLBMP 9669 biomass after a prolonged period of La(III) accumulation. This post-sorption nano-crystallization on the M. saelicesensis KLBMP 9669 mycelial surface is expected to play a crucial role in limiting the bioimmobilization of REEs in geological repositories.

Episodes of fissure formation in the Alps: connecting quartz fluid inclusion, fissure monazite age, and fissure orientation data.

Fluid assisted Alpine fissure-vein and cleft formation starts at prograde, peak or retrograde metamorphic conditions of 450-550 °C and 0.3-0.6 GPa and below, commonly at conditions of ductile to brittle rock deformation. Early-formed fissures become overprinted by subsequent deformation, locally leading to a reorientation. Deformation that follows fissure formation initiates a cycle of dissolution, dissolution/reprecipitation or new growth of fissure minerals enclosing fluid inclusions. Although fissures in upper greenschist and amphibolite facies rocks predominantly form under retrograde metamorphic conditions, this work confirms that the carbon dioxide fluid zone correlates with regions of highest grade Alpine metamorphism, suggesting carbon dioxide production by prograde devolatilization reactions and rock-buffering of the fissure-filling fluid. For this reason, fluid composition zones systematically change in metamorphosed and exhumed nappe stacks from diagenetic to amphibolite facies metamorphic rocks from saline fluids dominated by higher hydrocarbons, methane, water and carbon dioxide. Open fissures are in most cases oriented roughly perpendicular to the foliation and lineation of the host rock. The type of fluid constrains the habit of the very frequently crystallizing quartz crystals. Open fissures also form in association with more localized strike-slip faults and are oriented perpendicular to the faults. The combination of fissure orientation, fissure quartz fluid inclusion and fissure monazite-(Ce) (hereafter monazite) Th-Pb ages shows that fissure formation occurred episodically (1) during the Cretaceous (eo-Alpine) deformation cycle in association with exhumation of the Austroalpine Koralpe-Saualpe region (~ 90 Ma) and subsequent extensional movements in association with the formation of the Gosau basins (~ 90-70 Ma), (2) during rapid exhumation of high-pressure overprinted Briançonnais and Piemontais units (36-30 Ma), (3) during unroofing of the Tauern and Lepontine metamorphic domes, during emplacement and reverse faulting of the external Massifs (25-12 Ma; except Argentera) and due to local dextral strike-slip faulting in association with the opening of the Ligurian sea, and (4) during the development of a young, widespread network of ductile to brittle strike-slip faults (12-5 Ma). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s00015-021-00391-9.

Gross alpha activity in urban sediments as an important indicator of urban environmental processes on the example of three Russian cities.

The protection of the urban environment from radioactive wastes (including technologically enhanced natural radionuclides) and potentially harmful elements have recently become very critical. Thus, the present study aimed to assess the radioactive levels in low-volume samples of dust and fine sand fractions of the urban surface deposited sediments (USDS) collected in three Russian cities. The detection was conducted via CR-39 and LR-115 type II solid-state nuclear track detectors (SSNTDs) have been used to detect gross alpha activity concentrations. A statistically significant difference was observed between the average gross alpha activity concentrations in the dust fraction and the fine sand fraction in each city. The obtained results also illustrate the gross alpha activity concentration in the dust fraction is higher than in the fine sand fraction. This is consistent with the results of the chemical and mineralogical analysis. The dust fraction size has a higher gross alpha activity concentration than the fine sand fraction due to the natural partitioning of the main minerals constituting USDS with trace uranium and thorium content (feldspar, plagioclase, amphibole and others) and negligible uranium and thorium content (quartz). In some cases, USDS radioactivity is associated with monazite and zircon. A good correlation (0.58) was found between the gross alpha activity concentration and the effective content of uranium and thorium. Finally, an assessment of the gross alpha activity concentrations in the USDS size fractions was considered an essential indicator of environmental processes that are significant in terms of their impact on human health.

Assessment of a naturally occurring high background radiation area with elevated levels of thorium along coastal Odisha, India using radiometric methods.

The present study evaluates the enrichment and distribution of radioelements along the eastern coast of India. India possesses the second largest reserve of thorium bearing monazite in the world, in terms of heavy minerals present primarily along its long coastline. Radioelement estimation of about 30 km long beach area along the eastern coast of India is reported and implications discussed. A total number of 822 data points were studied using a portable Geiger Muller counter, to estimate the variation of dose rates, due to the ambient radionuclides along two different trends. One was parallel (northeast-southwest) and the second one perpendicular to the coastline. Pre-selected samples from in-situ radiometric surveys on the heavy mineral placers were studied further, for quantitative estimation of the abundance of radioactive elements primarily uranium and thorium, using a High Purity Germanium detector. Radioelement concentration assessment of core samples (depth ~2 m), were studied from two different beaches. Radiological parameters like radium equivalent, annual effective doserate and absorbed dose rate has been calculated based on the 238U, 232Th and 40K concentrations. Heavy mineral placers along the shoreline indicate a very high thorium (avg - 2990.22 Bq kg-1) which is due to the extensive distribution indicative of monazite. The coastal area also exhibits relatively low uranium (avg - 319.1 Bq kg-1). Based on its high thorium concentration, the area can be considered as a high natural background radiation area. Based on the concentrations of uranium and thorium, the weathering conditions and depositional environment prevalent along the beach areas have been discussed.

Geochemical behavior of uranium and thorium in sand and sandy soil samples from a natural high background radiation area of the Odisha coast, India.

Owing to their natural radioactivity, uranium (U) and thorium (Th) play significant roles in environmental sciences for monitoring radiation dose and in geological sciences for understanding sedimentary processes. The Odisha coastal area, in eastern India, is a well-known high background radiation area that is rich in monazites and rutile. This area was selected to study geochemical characteristics of U and Th in sand and sandy soil samples. The concentrations of U and Th were measured using inductively coupled plasma mass spectrometry (ICP-MS). The median, geometric mean, and standard deviation for U were determined to be 6, 4.5, and 2.5 µg/g and for Th were 186, 123.3, and 3.1 µg/g, respectively. Major element concentrations were evaluated using X-ray fluorescence spectroscopy to get the mineralogical composition and state of chemical weathering. The ratios of Th/U and Th/K varied from 4 to 37 and from 13 to 1058, respectively. These results clearly indicate that the samples from the coastal region were formed in an oxidizing and intense chemical weathering terrestrial environment with an enrichment of radiogenic heavy minerals (monazites and zircon) and clay mineral association. Since the majority of the samples have undergone moderate to intense weathering in the oxidizing environment, U is leached from the soil and sand matrix. Eventually, Th resides in the matrix and becomes a major source for radiation exposure in the environment. The high ratios of Th/U, along with the strong positive correlation between Th and P2O5, evidence the enrichment of the Th-bearing radioactive mineral, monazite, in these samples.

Grey monazite (rare earths) mining in centre of Spain: Characterization and pre-operational radiological evaluation.

A radiological evaluation associated to the future mining of grey monazite nodules enriched in light rare-earths, from a modest superficial deposit located in the centre of Spain, has been performed at pre-operational level, and the main results are shown in this paper. Although the monazite nodules in the deposit are clearly enriched in radionuclides from the uranium and thorium series with activity concentrations higher than 1 Bq/g, the size of these nodules (in the 0.5 mm-2 mm grain size interval), its refractory behaviour that prevents the leaching or dissemination of natural radionuclides to waters or other ecosystem compartments and consequently the impact in the food chain, and its presence quite diluted in the deposit at concentrations of 2.5-3 kg/m3, conducted to conclude that pre-operationally the area to be mined for the extraction of the monazite is generating a negligible radiological impact in the public and the nearby environment. Additionally, the extraction of the raw material and the restoration of the area after mining (i.e. the mining activities which will be done in-situ, in the mining area) will be exempted of any radiological regulation attending to the European Union legislation being expected that will not generate a radiological impact.

Baseline evaluation for natural radioactivity level and radiological hazardous parameters associated with processing of high grade monazite.

Egyptian monazite is a promising resource and investment attractive for production of valuable metals of industrial or nuclear interest such as rare earth elements (REEs), thorium (Th) and uranium (U). The study was focused to establish a baseline framework in viewpoint of radiation protection for the workers in production of REEs from high-grade monazite treated by sodium hydroxide (NaOH) solutions. Radiological hazard indices (cancer, gonadal and other risks) were evaluated, due to emissions (α-, ß- and γ-radiations) of radium-isotopes (228Ra, 226Ra, 223Ra) and lead (210Pb). The values of the estimated radiological hazard indices were higher than the permissible safe limits, worldwide average and varied with those reported in other countries. It was found that more than 70% of radioactivity and radiological hazardous indices resulted from emissions of 228Ra, while the rest was attributed to 226Ra, 223Ra and 210Pb. Therefore, processing of the Egyptian monazite can cause a significant radiological impact on workers through external exposure from γ-radiations and/or internal exposure through inhalation or ingestion airborne contaminated by the radionuclides. Thus, the results recommended that protection rules could be considered to prevent the radiation hazards associated with the production of the REEs from the high grade monazite attacked by caustic method.