Bibliography

@article{ATENCIO2024130631,

title = {Investigating the enigma of an irregular groundwater age pattern in a confined, presumed “fossil” complex aquifer through mixing cell flow modeling},

author = {Betzabe Atencio and Roi Ram and Avihu Burg and Reika Yokochi and Yoseph Yechieli and Roland Purtschert and Zheng-Tian Lu and Wei Jiang and Zeev Ronen and Eilon M. Adar},

url = {https://www.sciencedirect.com/science/article/pii/S0022169424000258},

doi = {https://doi.org/10.1016/j.jhydrol.2024.130631},

issn = {0022-1694},

year  = {2024},

date = {2024-01-01},

journal = {Journal of Hydrology},

volume = {630},

pages = {130631},

abstract = {Significant fluctuations in the groundwater (GW) age along the eastern flow path of the Nubian Sandstone Aquifer's (NSA), as derived from Krypton-81 groundwater dating, have suggested that this aquifer, located in Israel's Negev Desert and previously presumed to be a fossil, is not entirely isolated but mixes with younger and even recent water. The intermittent rejuvenation and drastic increases in the GW age across short distances most likely imply hydraulic connectivity with the surrounding aquifers, which contribute both younger and more ancient water to the NSA. The current study aims at modeling the GW flow system to locate and quantify its water sources despite the aquifer's hydrogeological complexity and the scarcity of hydrological data. We implemented the Mixing Cell Modeling (MCM) approach, understanding that the alternating rejuvenations and increases in the GW age downstream of the NSA's eastern flow trajectory reflect the mixing of the NSA's groundwater with young and old GW bodies, respectively. Thus, prompted by the 81Kr water age distribution, yet independent of the Kr radioisotope data, a multi-tracer mixing cell flow model was adopted based on a set of balance equations of water, dissolved minerals, and stable environmental isotopes. The findings indicate that (1) there is a small, yet substantial, intrusion of old brackish GW from a deep-seated, highly pressurized aquifer into the NSA in the northeastern Negev; (2) the rejuvenation of GW in the NSA is due to significant mixing with water from nearby overlying carbonate and chert aquifers, and (3) the NSA is substantially replenished through the Nubian Sandstone (NS) outcrops along the Negev Desert anticlines. Most GW intrusions into the NSA occur near the intersections of the eastern flow path with some of the Negev's major faults and synclines, such as the Paran and Ramon Fault zones and the Zin Syncline. In light of the relatively young GW age at the end of the NSA's western flow path in the northern Negev, and based on the similarities in the hydrogeological structures in the Negev and northern Sinai Deserts, we propose that similar mixing processes with GW from the overlying carbonate aquifers and direct GW recharge through the NS outcrops also occur in the northern Sinai Peninsula. The approach presented in this study might apply to examining recharge processes and hydraulic connectivity in other aquifers that were formerly classified as “fossil,” such as the immense NSA found in the Arabian (Jordan & Saudi Arabia) and the Western (Egypt) Deserts.},

keywords = {Complex aquifer, Kr-81 groundwater age, Mixing Cell Modeling, Nubian Sandstone Aquifer},

pubstate = {published},

tppubtype = {article}

}

@article{AGUILARCANTO2024128392,

title = {Model discovery of compartmental models with Graph-Supported Neural Networks},

author = {Fernando Javier Aguilar-Canto and Carlos Brito-Loeza and Hiram Calvo},

url = {https://www.sciencedirect.com/science/article/pii/S0096300323005611},

doi = {https://doi.org/10.1016/j.amc.2023.128392},

issn = {0096-3003},

year  = {2024},

date = {2024-01-01},

urldate = {2024-01-01},

journal = {Applied Mathematics and Computation},

volume = {464},

pages = {128392},

abstract = {In this proposal, our objective is to create a neural network for the discovery of models using compartmental models as systems of Ordinary Differential Equations (ODEs), employing Graph-Supported Neural Networks (GSNN). We design the GSNN as a graph of transition functions of the structure of the model to ensure that the three properties of the ODE solution are satisfied: additivity to one, positivity, and boundness. Rather than directly estimating the solution, these neural networks approximate the transition functions. We present theoretical evidence substantiating that our GSNN maintains these properties, along with approximation outcomes from both simulated and real-world data. These outcomes demonstrate that our GSNN outperforms the non-graph-supported approach for these issues, with instances where it even surpasses full model-based solutions and Recurrent Neural Networks. Furthermore, an evolutionary algorithm successfully generated a consistent model using the data, offering a comprehensive framework for neural network-based model discovery in these scenarios.},

keywords = {Compartmental models, Graph-Supported Neural Networks, Model discovery, Neural Network approximation, Ordinary Differential Equations},

pubstate = {published},

tppubtype = {article}

}

@article{hall_sandstone-hosted_2023,

title = {Sandstone-hosted uranium deposits of the Colorado Plateau, USA},

author = {S. M. Hall and B. S. Van Gosen and R. A. Zielinski},

url = {https://www.sciencedirect.com/science/article/pii/S0169136823000689},

doi = {https://doi.org/10.1016/j.oregeorev.2023.105353},

issn = {0169-1368},

year  = {2023},

date = {2023-01-01},

journal = {Ore Geology Reviews},

volume = {155},

pages = {105353},

abstract = {More than 4,000 sandstone-hosted uranium occurrences host over 1.2 billion pounds of mined and in situ U3O8 throughout the Colorado Plateau. Most of the resources are in two distinct mineral systems with deposits hosted in the Triassic Chinle and Jurassic Morrison Formations. In the Chinle mineral system, base metal sulfides typically accompany mineralization. The Morrison mineral system is characterized by V/U ratios up to 20. The uranium source was likely volcanic ash preserved as bentonitic mudstones in the Brushy Basin Member of the Morrison Formation, and lithic volcanic clasts, ash shards, and bentonitic clay in the lower part of the Chinle Formation. Vanadium originated from two possible sources: iron–titanium oxides that are extensively altered in bleached rock near deposits or from similar minerals in variably bleached red beds interbedded with and beneath the Morrison. In Chinle-hosted deposits, in addition to volcanic ash, a contributing source of both vanadium and uranium is proposed here for the first time to be underlying red beds in the Moenkopi and Cutler Formations that have undergone a cycle of reddening-bleaching-reoxidation. Transport in both systems was likely in groundwater through the more permeable sandstones and conglomerate units. The association of uranium minerals with carbonate and more rarely apatite, suggests that transport of uranium was as a carbonate or phosphate complex. The first comprehensive examination of paleoclimate, paleotopography, and subsurface structure of aquifers coupled with analysis of the geochronology of deposits suggests that that there were distinct pulses of uranium mineralization/redistribution during the period from about 259 Ma to 12 Ma when oxidized mineralizing fluids were intermittently rejuvenated in the Plateau in response to changes in tectonic regime and climate. Multiple lines of evidence indicate that deposits formed at ambient temperatures of about 25 °C to no greater than about 140 °C. In both systems, deposits formed where groundwater flow slowed and was subject to evaporative concentration. Stagnant conditions allowed for prolonged interaction of U- and V-enriched groundwater with ferrous iron-bearing reductants, such as illite and iron–titanium oxides, and more rarely organic material such as plant debris. Paragenetically late in the sequence, reducing fluids introduced additional organic matter to some deposits. Reducing fluids and introduced organic matter (now amorphous and altered by radiolysis) may originate from regional petroleum systems where peak oil and gas generation was from ∼ 82 to ∼ 5 Ma. Our novel analysis indicates that these reducing fluids bleached rock and protected affected deposits from remobilization during exposure and weathering that followed uplift of the Plateau (∼80 to 40 Ma).},

keywords = {Colorado, Plateau, Uranium, Vanadium},

pubstate = {published},

tppubtype = {article}

}

@article{smedley_uranium_2023,

title = {Uranium in natural waters and the environment: Distribution, speciation and impact},

author = {P. L. Smedley and D. G. Kinniburgh},

url = {https://www.sciencedirect.com/science/article/pii/S0883292722003389},

doi = {https://doi.org/10.1016/j.apgeochem.2022.105534},

issn = {0883-2927},

year  = {2023},

date = {2023-01-01},

journal = {Applied Geochemistry},

volume = {148},

pages = {105534},

abstract = {The concentrations of U in natural waters are usually low, being typically less than 4 μg/L in river water, around 3.3 μg/L in open seawater, and usually less than 5 μg/L in groundwater. Higher concentrations can occur in both surface water and groundwater and the range spans some six orders of magnitude, with extremes in the mg/L range. However, such extremes in surface water are rare and linked to localized mineralization or evaporation in alkaline lakes. High concentrations in groundwater, substantially above the WHO provisional guideline value for U in drinking water of 30 μg/L, are associated most strongly with (i) granitic and felsic volcanic aquifers, (ii) continental sandstone aquifers especially in alluvial plains and (iii) areas of U mineralization. High-U groundwater provinces are more common in arid and semi-arid terrains where evaporation is an additional factor involved in concentrating U and other solutes. Examples of granitic and felsic volcanic terrains with documented high U concentrations include several parts of peninsular India, eastern USA, Canada, South Korea, southern Finland, Norway, Switzerland and Burundi. Examples of continental sandstone aquifers include the alluvial plains of the Indo-Gangetic Basin of India and Pakistan, the Central Valley, High Plains, Carson Desert, Española Basin and Edwards-Trinity aquifers of the USA, Datong Basin, China, parts of Iraq and the loess of the Chaco-Pampean Plain, Argentina. Many of these plains host eroded deposits of granitic and felsic volcanic precursors which likely act as primary sources of U. Numerous examples exist of groundwater impacted by U mineralization, often accompanied by mining, including locations in USA, Australia, Brazil, Canada, Portugal, China, Egypt and Germany. These may host high to extreme concentrations of U but are typically of localized extent. The overarching mechanisms of U mobilization in water are now well-established and depend broadly on redox conditions, pH and solute chemistry, which are shaped by the geological conditions outlined above. Uranium is recognized to be mobile in its oxic, U(VI) state, at neutral to alkaline pH (7–9) and is aided by the formation of stable U–CO3(±Ca, Mg) complexes. In such oxic and alkaline conditions, U commonly covaries with other similarly controlled anions and oxyanions such as F, As, V and Mo. Uranium is also mobile at acidic pH (2–4), principally as the uranyl cation UO22+. Mobility in U mineralized areas may therefore occur in neutral to alkaline conditions or in conditions with acid drainage, depending on the local occurrence and capacity for pH buffering by carbonate minerals. In groundwater, mobilization has also been observed in mildly (Mn-) reducing conditions. Uranium is immobile in more strongly (Fe-, SO4-) reducing conditions as it is reduced to U(IV) and is either precipitated as a crystalline or ‘non-crystalline’ form of UO2 or is sorbed to mineral surfaces. A more detailed understanding of U chemistry in the natural environment is challenging because of the large number of complexes formed, the strong binding to oxides and humic substances and their interactions, including ternary oxide-humic-U interactions. Improved quantification of these interactions will require updating of the commonly-used speciation software and databases to include the most recent developments in surface complexation models. Also, given their important role in maintaining low U concentrations in many natural waters, the nature and solubility of the amorphous or non-crystalline forms of UO2 that result from microbial reduction of U(VI) need improved quantification. Even where high-U groundwater exists, percentage exceedances of the WHO guideline value are variable and often small. More rigorous testing programmes to establish usable sources are therefore warranted in such vulnerable aquifers. As drinking-water regulation for U is a relatively recent introduction in many countries (e.g. the European Union), testing is not yet routine or established and data are still relatively limited. Acquisition of more data will establish whether analogous aquifers elsewhere in the world have similar patterns of aqueous U distribution. In the high-U groundwater regions that have been recognized so far, the general absence of evidence for clinical health symptoms is a positive finding and tempers the scale of public health concern, though it also highlights a need for continued investigation.},

keywords = {Drinking water, Mine water, NORM, Radionuclide, Redox, U isotopes, Uranium, Uranyl},

pubstate = {published},

tppubtype = {article}

}

@article{petisco-ferrero_radiological_2023,

title = {Radiological environmental monitoring of groundwater around NPP: A proposal for its assessment},

author = {S. Petisco-Ferrero and R. Idoeta and S. Rozas and C. Olondo and M. Herranz},

url = {https://www.sciencedirect.com/science/article/pii/S2405844023066781},

doi = {https://doi.org/10.1016/j.heliyon.2023.e19470},

issn = {2405-8440},

year  = {2023},

date = {2023-01-01},

journal = {Heliyon},

volume = {9},

number = {9},

pages = {e19470},

abstract = {Whether a nuclear installation has radiological impact and, in that case, its extension, are the questions behind any environmental analysis of the installation along its operational life. This analysis is based on the detailed establishment of the radiological background of the area. Accordingly, the dismantling and decommissioning process (D&D) of a nuclear power plant starts with a radiological monitoring plan, which includes the radiological characterization of the area and of its surroundings. At the completion of the D&D, unrestricted use for the site will be permitted strictly in accordance with results of the radiological survey within the limits established by the local authorities. Groundwater quality is typically included in any radiological analysis since, among other reasons, a significant part of it is highly likely to end up being extracted for domestic use and hence, human consumption. While there is no regulation containing maximum activity concentration or radionuclide guidance values for water that may be destined for uses other than public consumption, if groundwater is considered a “part” of the land, dose criteria for site release can be applied. Therefore, together with the guidance levels to be established for the different radionuclides expected in the groundwater, the detection limits to be employed when performing routine radio analytical characterization procedures in the laboratory should also be provided. In this paper, we first propose a relation of the potential radionuclides to be analyzed in groundwater, together with their detection limits to be achieved when the determinations are performed in a laboratory, and subsequently, we discuss the most suitable analytical methodologies and resources that would be necessary to undertake radiological characterization plans from a practical point of view.},

keywords = {Detection limit, Nuclear power plant dismantling and decommissioning, Radiological environmental monitoring, Radionuclides in groundwater},

pubstate = {published},

tppubtype = {article}

}

@article{alexander_impact_2023,

title = {Impact of mine closure on groundwater resource: Experience from Westrand Basin-South Africa},

author = {A. C. Alexander and J. M. Ndambuki},

url = {https://www.sciencedirect.com/science/article/pii/S1474706523000761},

doi = {https://doi.org/10.1016/j.pce.2023.103432},

issn = {1474-7065},

year  = {2023},

date = {2023-01-01},

journal = {Physics and Chemistry of the Earth, Parts A/B/C},

volume = {131},

pages = {103432},

abstract = {The mining sector is at the edge of expanding to cater for natural resources that are much needed for technological development and manufacturing. Mushrooming of mines will consequently increase the number of mines closure. Moreover, mines closure have adverse impact on the environment at large and specifically on water resources. This study analyses historical groundwater quality parameters in mine intensive basin of Westrand Basin (WRB) to understand the status of groundwater quality in relation to mining activities and mine closure. Geographic information system (GIS) was used to map the spatio-temporal variation of groundwater quality in the basin and groundwater quality index (GQI) to evaluate its status. The coefficient of variation (CV) was applied to understand the stability of groundwater quality after the mine closure. Results indicated unstable and altered trend with increasing levels of acidity and salts concentration around the mines vicinity following the mine closure. The resultant maps indicated a significant deterioration of groundwater quality around the WRB with concentrations decreasing downstream. Obtained average GQI for the study period of 1996–2015 suggested a moderate groundwater quality at a range of GQI = 64–73. The CV indicated varying water quality at CV > 30% suggesting presence of source of contamination. Observed groundwater quality trends in Westrand basin suggested that mines closure present potential threat on groundwater quality and thus, a need for a robust mine closure plan and implementation.},

keywords = {Acid mine drainage, Groundwater quality, Mine closure, Spatio-temporal variation, Westrand Basin},

pubstate = {published},

tppubtype = {article}

}

@article{jroundi_evidence_2023,

title = {Evidence of microbial activity in a uranium roll-front deposit: Unlocking their potential role as bioenhancers of the ore genesis},

author = {Fadwa Jroundi and Cristina Povedano-Priego and María Pinel-Cabello and Michael Descostes and Pierre Grizard and Bayaarma Purevsan and Mohamed L. Merroun},

url = {https://www.sciencedirect.com/science/article/pii/S0048969722077397},

doi = {https://doi.org/10.1016/j.scitotenv.2022.160636},

issn = {0048-9697},

year  = {2023},

date = {2023-01-01},

journal = {Science of The Total Environment},

volume = {861},

pages = {160636},

abstract = {Uranium (U) roll-front deposits constitute a valuable source for an economical extraction by in situ recovery (ISR) mining. Such technology may induce changes in the subsurface microbiota, raising questions about the way their activities could build a functional ecosystem in such extreme environments (i.e.: oligotrophy and high SO4 concentration and salinity). Additionally, more information is needed to dissipate the doubts about the microbial role in the genesis of such U orebodies. A U roll-front deposit hosted in an aquifer driven system (in Zoovch Ovoo, Mongolia), intended for mining by acid ISR, was previously explored and showed to be governed by a complex bacterial diversity, linked to the redox zonation and the geochemical conditions. Here for the first time, transcriptional activities of microorganisms living in such U ore deposits are determined and their metabolic capabilities allocated in the three redox-inherited compartments, naturally defined by the roll-front system. Several genes encoding for crucial metabolic pathways demonstrated a strong biological role controlling the subsurface cycling of many elements including nitrate, sulfate, metals and radionuclides (e.g.: uranium), through oxidation-reduction reactions. Interestingly, the discovered transcriptional behaviour gives important insights into the good microbial adaptation to the geochemical conditions and their active contribution to the stabilization of the U ore deposits. Overall, evidences on the importance of these microbial metabolic activities in the aquifer system are discussed that may clarify the doubts on the microbial role in the genesis of low-temperature U roll-front deposits, along the Zoovch Ovoo mine.},

keywords = {ISR, Metatranscriptomes, Microbial metabolisms, Ore genesis, Roll-front deposit, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{lawrinenko_long-term_2023,

title = {Long-term performance evaluation of zero-valent iron amended permeable reactive barriers for groundwater remediation – A mechanistic approach},

author = {Michael Lawrinenko and Sudarshan Kurwadkar and Richard T. Wilkin},

url = {https://www.sciencedirect.com/science/article/pii/S1674987122001475},

doi = {https://doi.org/10.1016/j.gsf.2022.101494},

issn = {1674-9871},

year  = {2023},

date = {2023-01-01},

journal = {Geoscience Frontiers},

volume = {14},

number = {2},

pages = {101494},

abstract = {Permeable reactive barriers (PRBs) are used for groundwater remediation at contaminated sites worldwide. This technology has been efficient at appropriate sites for treating organic and inorganic contaminants using zero-valent iron (ZVI) as a reductant and as a reactive material. Continued development of the technology over the years suggests that a robust understanding of PRB performance and the mechanisms involved is still lacking. Conflicting information in the scientific literature downplays the critical role of ZVI corrosion in the remediation of various organic and inorganic pollutants. Additionally, there is a lack of information on how different mechanisms act in tandem to affect ZVI-groundwater systems through time. In this review paper, we describe the underlying mechanisms of PRB performance and remove isolated misconceptions. We discuss the primary mechanisms of ZVI transformation and aging in PRBs and the role of iron corrosion products. We review numerous sites to reinforce our understanding of the interactions between groundwater contaminants and ZVI and the authigenic minerals that form within PRBs. Our findings show that ZVI corrosion products and mineral precipitates play critical roles in the long-term performance of PRBs by influencing the reactivity of ZVI. Pore occlusion by mineral precipitates occurs at the influent side of PRBs and is enhanced by dissolved oxygen and groundwater rich in dissolved solids and high alkalinity, which negatively impacts hydraulic conductivity, allowing contaminants to potentially bypass the treatment zone. Further development of site characterization tools and models is needed to support effective PRB designs for groundwater remediation.},

keywords = {Geochemistry, Iron, Permeable reactive barrier, Plating reactions, Reduction potential, Surface passivation},

pubstate = {published},

tppubtype = {article}

}

@article{veerasamy_234u238u_2023,

title = {234U/238U disequilibrium and 235U/238U ratios measured using MC-ICP-MS in natural high background radiation area soils to understand the fate of uranium},

author = {Nimelan Veerasamy and Sharayu Kasar and Rajamanickam Murugan and Kazumasa Inoue and Thennaarassan Natarajan and Rakesh Chand Ramola and Masahiro Fukushi and Sarata Kumar Sahoo},

url = {https://www.sciencedirect.com/science/article/pii/S0045653523004848},

doi = {https://doi.org/10.1016/j.chemosphere.2023.138217},

issn = {0045-6535},

year  = {2023},

date = {2023-01-01},

journal = {Chemosphere},

volume = {323},

pages = {138217},

abstract = {The Chhatrapur-Gopalpur coastal area in Odisha, India is a well-known natural high background radiation (HBRA) area due to the abundance of monazite (a thorium bearing radioactive mineral) in beach sands and soils. Recent studies on Chhatrapur-Gopalpur HBRA groundwater have reported high concentrations of uranium and its decay products. Therefore, the soils of the Chhatrapur-Gopalpur HBRA are reasonably suspected as the sources of these high uranium concentrations in groundwater. In this report, first the uranium concentrations in soil samples were measured using inductively coupled plasma mass spectrometry (ICP-MS) and they were found to range from 0.61 ± 0.01 to 38.59 ± 0.16 mg kg−１. Next, the 234U/238U and 235U/238U isotope ratios were measured to establish a baseline for the first time in Chhatrapur-Gopalpur HBRA soil. Multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was used for measurement of these isotope ratios. The 235U/238U ratio was observed to be the normal terrestrial value. The 234U/238U activity ratio, was calculated to understand the secular equilibrium between 234U and 238U in soil and it varied from 0.959 to 1.070. To understand the dynamics of uranium in HBRA soil, physico-chemical characteristics of soil were correlated with uranium isotope ratios and this correlation of 234U/238U activity ratio indicated the leaching of 234U from Odisha HBRA soil.},

keywords = {HBRA, MC-ICP-MS, Monazites, U/U, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{liu_study_2023,

title = {Study of natural attenuation after acid in situ leaching of uranium mines using isotope fractionation and geochemical data},

author = {Zhenzhong Liu and Chunguang Li and Kaixuan Tan and Yongmei Li and Wanyu Tan and Xiqi Li and Chong Zhang and Shuo Meng and Longcheng Liu},

url = {https://www.sciencedirect.com/science/article/pii/S0048969722081360},

doi = {https://doi.org/10.1016/j.scitotenv.2022.161033},

issn = {0048-9697},

year  = {2023},

date = {2023-01-01},

journal = {Science of The Total Environment},

volume = {865},

pages = {161033},

abstract = {Acid in situ leaching (AISL) is a subsurface mining approach suitable for low-grade ores which does not generate tailings, and has been adopted widely in uranium mining. However, this technique causes an extremely high concentration of contaminants at post-mining sites and in the surroundings soon after the mining ceases. As a potential AISL remediation strategy, natural attenuation has not been studied in detail. To address this problem, groundwater collected from 26 wells located within, adjacent, upgradient, and downgradient of a post-mining site were chosen to analyze the fate of U(VI), SO42−, δ34S, and δ238U, to reveal the main mechanisms governing the migration and attenuation of the dominant contaminants and the spatio-temporal evolutions of contaminants in the confined aquifer of the post-mining site. The δ238U values vary from −0.07 ‰ to 0.09 ‰ in the post-mining site and from −1.43 ‰ to 0.03 ‰ around the post-mining site. The δ34S values were found to vary from 3.3 ‰ to 6.2 ‰ in the post-mining site and from 6.0 ‰ to 11.0 ‰ around the post-mining site. Detailed analysis suggests that there are large differences between the range of isotopic composition variation and the range of pollutants concentration distribution, and the estimated Rayleigh isotope fractionation factor is 0.9994–0.9997 for uranium and 1.0032–1.0061 for sulfur. The isotope ratio of uranium and sulfur can be used to deduce the migration history of the contaminants and the irreversibility of the natural attenuation process in the anoxic confined aquifer. Combining the isotopic fractionation data for U and S with the concentrations of uranium and sulfate improved the accuracy of understanding of reducing conditions along the flow path. The study also indicated that as long as the geological conditions are favorable for redox reactions, natural attenuation could be used as a cost-effective remediation scheme.},

keywords = {Acid in situ leaching, Geochemical and isotopic tracing, Groundwater contamination, Natural attenuation, Uranium post-mining},

pubstate = {published},

tppubtype = {article}

}

@article{holmes_can_2023,

title = {Can diatoms be used as a biomonitoring tool for surface and groundwater? Towards a baseline for Karoo water},

author = {M. Holmes and E. E. Campbell and M. de Wit and J. C. Taylor},

url = {https://www.sciencedirect.com/science/article/pii/S0254629923004647},

doi = {https://doi.org/10.1016/j.sajb.2023.08.013},

issn = {0254-6299},

year  = {2023},

date = {2023-01-01},

journal = {South African Journal of Botany},

volume = {161},

pages = {211–221},

abstract = {The environmental risks from shale gas extraction through the unconventional method of ‘fracking’ are considerable and impact on water supplies below and above ground. Since 2010 the recovery of natural shale gas through fracking has been proposed in parts of the fragile semi-arid ecosystems that make up the Karoo biome in South Africa. These unique ecosystems are heavily reliant on underground water, intermittent and ephemeral springs, which are at great risk of contamination by fracking processes. Diatoms are present in all water bodies and reflect aspects of the environment in which they are located. As the possibility of fracking has not been removed, the aim of the project was to determine if diatoms could be used for rapid biomonitoring of underground and surface waters in the Karoo. Over a period of 24 months, water samples and diatom species were collected simultaneously from 65 sites. A total of 388 diatom taxa were identified from 290 samples with seasonal and substrate variation affecting species composition but not the environmental information. Species diversity information, on the other hand, often varied significantly between substrates within a single sample. Analysis using CCA established that the diatom composition was affected by lithium, oxidized nitrogen, electrical conductivity, and sulphate levels in the sampled water. We conclude that changes in diatom community composition in the Karoo do reflect the water chemistry and could be useful as bioindicators.},

keywords = {Bioindicator, Diatom, Hydraulic fracturing, Karoo, Water quality},

pubstate = {published},

tppubtype = {article}

}

@article{hofmann_multi-tracer_2023,

title = {Multi-tracer approach to constrain groundwater flow and geochemical baseline assessments for CO2 sequestration in deep sedimentary basins},

author = {Harald Hofmann and Julie K. Pearce and Phil Hayes and Sue D. Golding and Nick Hall and Kim A. Baublys and Matthias Raiber and Axel Suckow},

url = {https://www.sciencedirect.com/science/article/pii/S0166516223002562},

doi = {https://doi.org/10.1016/j.coal.2023.104438},

issn = {0166-5162},

year  = {2023},

date = {2023-01-01},

journal = {International Journal of Coal Geology},

pages = {104438},

abstract = {Geological storage of gases will be necessary in the push to net zero and the energy transition to reduce carbon emissions to atmosphere. These include CO2 geological storage in suitable sandstone reservoirs. Understanding groundwater flow, connectivity and hydrogeochemical processes in aquifer and storage systems is vital to prevent risk and protect important water resources, such as the Great Artesian Basin. Here, we provide a ‘tool-box’ of geochemical assessment methods to provide information on flow patterns through the basin's aquifers (changes in chemistry along flow path), stagnant versus flowing conditions (cosmogenic isotopes and noble gases), inter-aquifer connectivity and seal properties (major ions, Sr and stable isotopes), water quality (major ions and metals) and general assessments on residence times of groundwater (cosmogenic isotopes and noble gases). This information can be used with reservoir and groundwater models to inform on possible changes in the above-mentioned processes and serve as input parameters for CO2 injection impact modelling. We demonstrate the use and interpretation on an example of a potential CO2 storage geological sequestration site in the Surat Basin, part of the Great Artesian Basin, and the aquifers that overly the reservoir. The stable water isotopes are depleted compared to average rainfall and most likely indicate greater contributions from monsoonal rain events from the northern monsoonal troughs, where amount and rainout effects lead to the depletion rather than colder recharge climates. This is supported by the modern recharge temperatures from noble gases. Inter-aquifer mixing between the Precipice Sandstone reservoir and the Hutton Sandstone aquifer seems unlikely as the Sr isotope ratios are distinctly different suggesting that the Evergreen Formation is a seal in the locations sampled. Mixing, however, occurs on the edges of the basin, especially in the south-east and east where the Surat Basin transitions into the Clarence-Moreton Basin. Groundwater flow appears to be to the south in the Precipice Sandstone, with a component of flow east to the Clarence-Morton Basin. The cosmogenic isotopes and noble gases strongly indicate very long residence times of groundwater in the central south Precipice Sandstone around a proposed storage site. 14C values below analytical uncertainty, R36Cl ratios at secular equilibrium as well as high He concentrations and high 40Ar/36Ar ratios support the argument that groundwater flow in this area is extremely slow or groundwater is stagnant. The results of this study reflect the geological and hydrogeological complexities of sedimentary basins and that baseline studies, such as this one, are paramount for management strategies.},

keywords = {CO geological storage, Great Artesian Basin, Groundwater chemistry, Isotopic tracer, Surat Basin},

pubstate = {published},

tppubtype = {article}

}

@article{uddin_assessment_2023,

title = {Assessment of hydrogeochemistry in groundwater using water quality index model and indices approaches},

author = {Md Galal Uddin and Mir Talas Mahammad Diganta and Abdul Majed Sajib and Md Abu Hasan and Md Moniruzzaman and Azizur Rahman and Agnieszka I. Olbert and Md Moniruzzaman},

url = {https://www.sciencedirect.com/science/article/pii/S2405844023068767},

doi = {https://doi.org/10.1016/j.heliyon.2023.e19668},

issn = {2405-8440},

year  = {2023},

date = {2023-01-01},

journal = {Heliyon},

volume = {9},

number = {9},

pages = {e19668},

abstract = {Groundwater resources around the world required periodic monitoring in order to ensure the safe and sustainable utilization for humans by keeping the good status of water quality. However, this could be a daunting task for developing countries due to the insufficient data in spatiotemporal resolution. Therefore, this research work aimed to assess groundwater quality in terms of drinking and irrigation purposes at the adjacent part of the Rooppur Nuclear Power Plant (RNPP) in Bangladesh. For the purposes of achieving the aim of this study, nine groundwater samples were collected seasonally (dry and wet season) and seventeen hydro-geochemical indicators were analyzed, including Temperature (Temp.), pH, electrical conductivity (EC), total dissolved solids (TDS), total alkalinity (TA), total hardness (TH), total organic carbon (TOC), bicarbonate (HCO3−), chloride (Cl−), phosphate (PO43−), sulfate (SO42−), nitrite (NO2−), nitrate (NO3−), sodium (Na+), potassium (K+), calcium (Ca2+) and magnesium (Mg2+). The present study utilized the Canadian Council of Ministers of the Environment water quality index (CCME-WQI) model to assess water quality for drinking purposes. In addition, nine indices including EC, TDS, TH, sodium adsorption ratio (SAR), percent sodium (Na%), permeability index (PI), Kelley's ratio (KR), magnesium hazard ratio (MHR), soluble sodium percentage (SSP), and Residual sodium carbonate (RSC) were used in this research for assessing the water quality for irrigation purposes. The computed mean CCME-WQI score found higher during the dry season (ranges 48 to 74) than the wet season (ranges 40 to 65). Moreover, CCME-WQI model ranked groundwater quality between the “poor” and “marginal” categories during the wet season implying unsuitable water for human consumption. Like CCME-WQI model, majority of the irrigation index also demonstrated suitable water for crop cultivation during dry season. The findings of this research indicate that it requires additional care to improve the monitoring programme for protecting groundwater quality in the RNPP area. Insightful information from this study might be useful as baseline for national strategic planners in order to protect groundwater resources during the any emergencies associated with RNPP.},

keywords = {CCME index, Groundwater quality, Hydrogeochemistry, Irrigation indices, Nuclear power plant, Water quality index},

pubstate = {published},

tppubtype = {article}

}

@article{boumaiza_nitrate_2023,

title = {Nitrate sources and transformation processes in groundwater of a coastal area experiencing various environmental stressors},

author = {Lamine Boumaiza and Safouan Ben Ammar and Romain Chesnaux and Randy L. Stotler and Bernhard Mayer and Frédéric Huneau and Karen H. Johannesson and Jana Levison and Kay Knöller and Christine Stumpp},

url = {https://www.sciencedirect.com/science/article/pii/S0301479723015918},

doi = {https://doi.org/10.1016/j.jenvman.2023.118803},

issn = {0301-4797},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Environmental Management},

volume = {345},

pages = {118803},

abstract = {In coastal salinized groundwater systems, contamination from various nitrate (NO3) inputs combined with complex hydrogeochemical processes make it difficult to distinguish NO3 sources and identify potential NO3 transformtation processes. Effective field-based NO3 studies in coastal areas are needed to improve the understanding of NO3 contamination dynamics in groundwater of such complex coastal systems. This study focuses on a typical Mediterranean coastal agricultural area, located in Tunisia, experiencing substantial NO3 contamination from multiple anthropogenic sources. Here, multiple isotopic tracers (δ18OH2O, δ2HH2O, δ15NNO3, δ18ONO3, and δ11B) combined with a Bayesian isotope MixSIAR model are used (i) to identify the major NO3 sources and their contributions, and (ii) to describe the potential NO3 transformation processes. The measured NO3 concentrations in groundwater are above the natural baseline threshold, suggesting anthropogenic influence. The measured isotopic composition of NO3 indicates that manure, soil organic matter, and sewage are the potential sources of NO3, while δ11B values constrain the NO3 contamination to manure; a finding that is supported by the results of MixSIAR model revealing that manure-derived NO3 dominates over other likely sources. Nitrate derived from manure in the study area is attributed to organic fertilizers used to promote crop growth, and livestock that deposit manure directly on the ground surface. Evidence for ongoing denitrification in groundwaters of the study area is supported by an enrichment in both 15N and 18O in the remaining NO3, although isotopic mass balances between the measured and the theoretical δ18ONO3 values also suggest the occurrence of nitrification. The simultaneous occurrence of these biogeochemical processes with heterogeneous distribution across the study area reflect the complexity of interactions within the investigated coastal aquifer. The multiple isotopic tracer approach used here can identify the effect of multiple NO3 anthropogenic activities in coastal environments, which is fundamental for sustainable groundwater resources management.},

keywords = {Aquifer, Denitrification, MixSIAR, Nitrate, Nitrification, Stable isotopes},

pubstate = {published},

tppubtype = {article}

}

@article{lima_establishing_2023,

title = {Establishing a water baseline for the unconventional gas industry: A multiple environmental isotopes assessment (18O, 2H, 3H, 13C, and 14C) of surface and groundwater in the São Francisco Basin, Brazil},

author = {Gustavo Filemon Costa Lima and Carlos Alberto de Carvalho Filho and Vinícius Gonçalves Ferreira and Jussara da Silva Diniz Lima and Eduardo Duarte Marques and Paulo Sérgio Pelógia Minardi and Ilza Dalmázio and Rubens Martins Moreira},

url = {https://www.sciencedirect.com/science/article/pii/S0883292723002639},

doi = {https://doi.org/10.1016/j.apgeochem.2023.105818},

issn = {0883-2927},

year  = {2023},

date = {2023-01-01},

journal = {Applied Geochemistry},

volume = {159},

pages = {105818},

abstract = {Unconventional hydrocarbon production has become the target of an intensive environmental debate due to the risks it poses to water resources. Fracking, while enabling the extraction of oil and gas from ultra-low permeability reservoirs, also possesses the risk of polluting water systems through failures from hydraulic fracturing and its associated procedures. The need to foster national industrial development with a transitional energy matrix has led Brazil to discuss the environmental suitability before producing its large unconventional reserves. Many studies have highlighted the need for a robust environmental characterization before the development of the unconventional industry. In this sense, multiple environmental isotopes may work as a proxy for identifying water contamination right from the early stages. Environmental isotopes may also be applied to enhance the understanding of the natural geochemical processes intrinsic to a given area. This study presents an environmental isotopes baseline for the groundwater and riverine water systems within the São Francisco Basin, a proven tight gas reservoir in Brazil, in a pre-operational context. δ18O, δ2H, 3H, δ13C, and Δ14C were evaluated in three different seasons in groundwater and surface water samples, along with other auxiliary parameters such as physical-chemical parameters (in situ), major ions, and d-excess. The δ2H and δ18O in surface water shows an upstream → downstream enrichment trend, with some variations suggesting baseflow interactions in the surface water systems. An evaporation line for the study area was defined as δ2H = 4.6903 δ18O + 10.362. δ13C indicates a mutual dissolution of silicates and carbonates in the groundwater system and suggests a group of samples highly related to the recharge areas. Groundwater dating denotes the Serra da Saudade Formation as a modern fractured aquifer with a strong recharge capacity. These findings support stakeholders in environmental monitoring and management of the unconventional gas industry.},

keywords = {Fracking, Groundwater dating, Indaiá river, Isotopes assessment, Shale gas, Unconventional hydrocarbons},

pubstate = {published},

tppubtype = {article}

}

@article{kurmanseiit_streamline-based_2023,

title = {Streamline-based reactive transport modeling of uranium mining during in-situ leaching: Advantages and drawbacks},

author = {Maksat B. Kurmanseiit and Madina S. Tungatarova and Jean-Jacques Royer and Daniar Y. Aizhulov and Nurlan M. Shayakhmetov and Aidarkhan Kaltayev},

url = {https://www.sciencedirect.com/science/article/pii/S0304386X23000890},

doi = {https://doi.org/10.1016/j.hydromet.2023.106107},

issn = {0304-386X},

year  = {2023},

date = {2023-01-01},

journal = {Hydrometallurgy},

volume = {220},

pages = {106107},

abstract = {Reactive transport modeling is known to be computationally intensive when applied to 3D problems. Transforming sequential computing on the computer processor units (CPU) into parallelized computation on the high-performance parallel graphic processor units (GPU) is a classical approach to increasing computational performance. Another complementary approach is to decompose a complex 3D modeling problem into a set of simpler 1D problems using streamline approaches which can be easily parallelized, therefore reducing computation time. This paper investigates solutions to the equations governing dissolution and transport using streamlines coupled with a parallelization approach. In addition, an analytical solution to the dissolution and transfer equations of uranium describing the In-Situ Leaching (ISL) mining recovery is found using an approximation series to the 2nd order. The analytical solution is compared to the 1D numerical resolution along the streamlines and to the 3D simulation results superimposed on the streamline. Both approaches give similar results with a relative error of <2 % (2%). The proposed methodology is then applied to a case study in which the classical 3D resolution is compared to the newly suggested streamline solution, demonstrating that the streamline approach increases computational performances by a factor ranging from hundred to thousand depending on the complexity of the grid-block model.},

keywords = {3D modeling, In-situ leaching, Reactive transport model, Streamlines, Uranium recovery},

pubstate = {published},

tppubtype = {article}

}

@article{liu_geochemical_2023,

title = {Geochemical and S isotopic studies of pollutant evolution in groundwater after acid in situ leaching in a uranium mine area in Xinjiang},

author = {Zhenzhong Liu and Kaixuan Tan and Chunguang Li and Yongmei Li and Chong Zhang and Jing Song and Longcheng Liu},

url = {https://www.sciencedirect.com/science/article/pii/S1738573322005769},

doi = {https://doi.org/10.1016/j.net.2022.12.009},

issn = {1738-5733},

year  = {2023},

date = {2023-01-01},

journal = {Nuclear Engineering and Technology},

volume = {55},

number = {4},

pages = {1476–1484},

abstract = {Laboratory experiments and point monitoring of reservoir sediments have proven that stable sulfate reduction (SSR) can lower the concentrations of toxic metals and sulfate in acidic groundwater for a long time. Here, we hypothesize that SSR occurred during in situ leaching after uranium mining, which can impact the fate of acid groundwater in an entire region. To test this, we applied a sulfur isotope fractionation method to analyze the mechanism for natural attenuation of contaminated groundwater produced by acid in situ leaching of uranium (Xinjiang, China). The results showed that δ34S increased over time after the cessation of uranium mining, and natural attenuation caused considerable, area-scale immobilization of sulfur corresponding to retention levels of 5.3%–48.3% while simultaneously decreasing the concentration of uranium. Isotopic evidence for SSR in the area, together with evidence for changes of pollutant concentrations, suggest that area-scale SSR is most likely also important at other acid mining sites for uranium, where retention of acid groundwater may be strengthened through natural attenuation. To recapitulate, the sulfur isotope fractionation method constitutes a relatively accurate tool for quantification of spatiotemporal trends for groundwater during migration and transformation resulting from acid in situ leaching of uranium in northern China.},

keywords = {Acid in situ leaching of uranium, Pollution evolution, Sulfate elimination, Sulfur isotopes analysis},

pubstate = {published},

tppubtype = {article}

}

@article{wang_reformability_2023,

title = {Reformability evaluation of blasting-enhanced permeability in in situ leaching mining of low-permeability sandstone-type uranium deposits},

author = {Wei Wang and Xuanyu Liang and Qinghe Niu and Qizhi Wang and Jinyi Zhuo and Xuebin Su and Genmao Zhou and Lixin Zhao and Wei Yuan and Jiangfang Chang and Yongxiang Zheng and Jienan Pan and Zhenzhi Wang and Zhongmin Ji},

url = {https://www.sciencedirect.com/science/article/pii/S1738573323001432},

doi = {https://doi.org/10.1016/j.net.2023.03.034},

issn = {1738-5733},

year  = {2023},

date = {2023-01-01},

journal = {Nuclear Engineering and Technology},

volume = {55},

number = {8},

pages = {2773–2784},

abstract = {It is essential to evaluate the blasting-enhanced permeability (BEP) feasibility of a low-permeability sandstone-type uranium deposit. In this work, the mineral composition, reservoir physical properties and rock mechanical properties of samples from sandstone-type uranium deposits were first measured. Then, the reformability evaluation method was established by the analytic hierarchy process-entropy weight method (AHP-EWM) and the fuzzy mathematics method. Finally, evaluation results were verified by the split Hopkinson Pressure Bar (SHPB) experiment and permeability test. Results show that medium sandstone, argillaceous sandstone and siltstone exhibit excellent reformability, followed by coarse sandstone and fine sandstone, while the reformability of sandy mudstone is poor and is not able to accept BEP reservoir stimulation. The permeability improvement and the distribution of damage fractures before and after the SHPB experiment confirm the correctness of evaluation results. This research provides a reformability evaluation method for the BEP of the low-permeability sandstone-type uranium deposit, which contributes to the selection of the appropriate regional and stratigraphic horizon of the BEP and the enhanced ISL of the low-permeability sandstone-type uranium deposit.},

keywords = {Analytic hierarchy process-entropy method, Fuzzy mathematics method, Mechanical property, Mineral composition, Pore structure, Split Hopkinson pressure bar},

pubstate = {published},

tppubtype = {article}

}

@article{zhao_permeability_2023,

title = {Permeability evolution mechanism and the optimum permeability determination of uranium leaching from low-permeability sandstone treated with low-frequency vibration},

author = {Yong Zhao and Xiqi Li and Lin Lei and Ling Chen and Zhiping Luo},

url = {https://www.sciencedirect.com/science/article/pii/S167477552300063X},

doi = {https://doi.org/10.1016/j.jrmge.2022.12.031},

issn = {1674-7755},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Rock Mechanics and Geotechnical Engineering},

volume = {15},

number = {10},

pages = {2597–2610},

abstract = {Low-frequency vibrations can effectively improve natural sandstone permeability, and higher vibration frequency is associated with larger permeability. However, the optimum permeability and permeability evolution mechanism for uranium leaching and the relationship between permeability and the change of chemical reactive rate affecting uranium leaching have not been determined. To solve the above problems, in this study, identical homogeneous sandstone samples were selected to simulate low-permeability sandstone; a permeability evolution model considering the combined action of vibration stress, pore water pressure, water flow impact force, and chemical erosion was established; and vibration leaching experiments were performed to test the model accuracy. Both the permeability and chemical reactions were found to simultaneously restrict U6+ leaching, and the vibration treatment increased the permeability, causing the U6+ leaching reaction to no longer be diffusion-constrained but to be primarily controlled by the reaction rate. Changes of the model calculation parameters were further analyzed to determine the permeability evolution mechanism under the influence of vibration and chemical erosion, to prove the correctness of the mechanism according to the experimental results, and to develop a new method for determining the optimum permeability in uranium leaching. The uranium leaching was found to primarily follow a process consisting of (1) a permeability control stage, (2) achieving the optimum permeability, (3) a chemical reactive rate control stage, and (4) a channel flow stage. The resolution of these problems is of great significance for facilitating the application and promotion of low-frequency vibration in the CO2 + O2 leaching process.},

keywords = {Chemical reactive rate, Low-frequency vibration, Low-permeability sandstone, Optimum permeability, Permeability evolution mechanism, Uranium migration},

pubstate = {published},

tppubtype = {article}

}

@article{xie_leaching_2023,

title = {Leaching behaviour and mechanism of U, 226Ra and 210Pb from uranium tailings at different pH conditions},

author = {Tian Xie and Bing Lian and Chao Chen and Tianwei Qian and Xiaxiong Liu and Zhaorong Shang and Ting Li and Ruiqing Wang and Zhaoming Wang and Aiming Zhang and Jun Zhu},

url = {https://www.sciencedirect.com/science/article/pii/S0265931X23001935},

doi = {https://doi.org/10.1016/j.jenvrad.2023.107300},

issn = {0265-931X},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Environmental Radioactivity},

volume = {270},

pages = {107300},

abstract = {A large number of radionuclides remain in uranium tailings, and U, 226Ra and 210Pb leach out with water chemistry, causing potential radioactive contamination to the surrounding environment. In this paper, uranium tailings from a uranium tailings pond in southern China were collected at different depths by means of borehole sampling, mixed and homogenised, and analysed for mineral and chemical composition, microscopic morphology, U, 226Ra and 210Pb fugacity, static leaching and dynamic leaching of U, 226Ra and 210Pb in uranium tailings at different pH conditions. The variation of U, 226Ra and 210Pb concentrations in the leachate under different pH conditions with time was obtained, and the leaching mechanism was analysed. The results showed that the uranium tailings were dominated by quartz, plagioclase and other minerals, of which SiO2 and Al2O3 accounted for 65.45% and 13.32% respectively, and U, 226Ra and 210Pb were mainly present in the residue form. The results of the static leaching experiments show that pH mainly influences the leaching of U, 226Ra and 210Pb by changing their chemical forms and the particle properties of the tailings, and that the lower the pH the more favourable the leaching. The results of dynamic leaching experiments during the experimental cycle showed that the leaching concentration and cumulative release of U, 226Ra and 210Pb in the leach solution were greater at lower pH conditions than at higher pH conditions, and the leaching of U, 226Ra and 210Pb at different pH conditions was mainly from the water-soluble and exchangeable states. The present research results are of great significance for the environmental risk management and control of radioactive contamination in existing uranium tailings ponds, and are conducive to ensuring the long-term safety, stability and sustainability of uranium mining sites.},

keywords = {Leaching experiments, Pb, Ra, U, Uranium tailings},

pubstate = {published},

tppubtype = {article}

}

@article{shayakhmetov_enhancing_2023,

title = {Enhancing uranium in-situ leaching efficiency through the well reverse technique: A study of the effects of reversal time on production efficiency and cost},

author = {N. M. Shayakhmetov and K. A. Alibayeva and A. Kaltayev and I. Panfilov},

url = {https://www.sciencedirect.com/science/article/pii/S0304386X23000683},

doi = {https://doi.org/10.1016/j.hydromet.2023.106086},

issn = {0304-386X},

year  = {2023},

date = {2023-01-01},

journal = {Hydrometallurgy},

volume = {219},

pages = {106086},

abstract = {In this study, the application of the Well Reversal Technique (WRT) and the impact of reversal time on the efficiency of uranium mining via In-Situ Leaching (ISL) were investigated. A prevalent issue in ISL mineral extraction is the formation of stagnant zones caused by limited access of the lixiviant, which leads to increased operating expenditures. The WRT, which involves altering the function of some wells from injection to production or vice versa, is a potential solution to this problem. The efficiency of WRT is heavily dependent on the well pattern and reversal time. Two commonly used well patterns in ISL are the 9-spot (row arrangement) and 7-spot (hexagonal arrangement). The objective of this study was to determine the optimal reversal time for a 9-spot well pattern through mathematical modeling of hydrodynamic and physico-chemical processes and subsequent economic assessment. A mathematical model of uranium extraction processes was developed using the principles of mass conservation, Darcy's, and mass action laws. The results obtained for a 9-spot well pattern without reversal, with two reversal options, and a 7-spot scheme were analyzed comparatively. The 7-spot scheme without reversal was found to be the most effective of the options examined. The application of WRT on a 9-spot well pattern allows to enhance production efficiency to a level comparable to that of a 7-spot well pattern. Additionally, the effect of reversal time on recovery was studied based on two well reversal options. The results from calculation revealed that the optimal scenario was when the well reversal is conducted immediately after the time point at which the average concentration of the pregnant solution in the production wells reaches its peak value. The overall efficiency of WRT application was determined through economic calculations of capital (CAPEX) and operating (OPEX) expenditures. Based on economic calculations, it was determined that the utilization of WRT results in a 3–18% increase in mineral production efficiency for a 9-point scheme, depending on the chosen reversal method.},

keywords = {Economic evaluation, Hydrodynamic enhancement of mineral production, In-situ leaching, Mineral recovery, Optimal reversal time, Well reversing technique},

pubstate = {published},

tppubtype = {article}

}

@article{qiu_what_2023,

title = {What chemical reaction dominates the CO2 and O2 in-situ uranium leaching? Insights from a three-dimensional multicomponent reactive transport model at the field scale},

author = {Wenjie Qiu and Yun Yang and Jian Song and Weimin Que and Zhengbang Liu and Haicheng Weng and Jianfeng Wu and Jichun Wu},

url = {https://www.sciencedirect.com/science/article/pii/S0883292722003262},

doi = {https://doi.org/10.1016/j.apgeochem.2022.105522},

issn = {0883-2927},

year  = {2023},

date = {2023-01-01},

journal = {Applied Geochemistry},

volume = {148},

pages = {105522},

abstract = {The complex behavior of uranium in recovery is mostly driven by water-rock interactions following lixiviant injection into ore-bearing aquifers. Significant challenges exist in exploring the geochemical processes responsible for uranium release and mobilization. Herein this study provides an illustration of a ten-year field scale CO2 and O2 in-situ leaching (ISL) process at a typical sandstone-hosted uranium deposit in northern China. We also conducte a three-dimensional (3-D) multicomponent reactive transport model to assess the effects of potential chemical reactions on uranium recovery, in particular, to focus on the role of sulfide mineral pyrite (FeS2). Numerical simulations are performed considering three potential ISL reaction pathways to determine the relative contributions to uranium release, and the results indicate that bicarbonate promotes the oxidative dissolution of uranium-bearing minerals and further accelerates the uranium leaching in a neutral geochemical system. Moreover, the presence of FeS2 exerts a strong competitive role in the uranium-bearing mineral dissolution by increasing oxygen consumption, favoring the formation of iron oxyhydroxide, and therefore causing an associated decrease in uranium recovery rates. The simulation model demonstrates that dissolution of carbonate neutralizes acidic water generated from pyrite oxidation and aqueous CO2 dissociation. In addition, the cation concentrations (i.e., Ca and Mg) are increasing in the pregnant solutions, showing that the recycling of lixiviants and kinetic dissolution of carbonate generates a larger number of dissolved Ca and Mg and inevitably triggers the secondary dolomite mineral precipitation. The findings improve our fundamental understanding of the geochemical processes in a long-term uranium ISL system and provide important environmental implications for the optimal design of uranium recovery, remediation, and risk exposure assessment.},

keywords = {Carbonate minerals, In-situ leaching (ISL) of uranium, Pyrite oxidation, Reactive transport modeling (RTM)},

pubstate = {published},

tppubtype = {article}

}

@article{wang_machine_2023,

title = {Machine learning–based optimal design of the in-situ leaching process parameter (ISLPP) for the acid in-situ leaching of uranium},

author = {Bing Wang and Yue Luo and Jia-zhong Qian and Jin-hui Liu and Xun Li and Yan-hong Zhang and Qian-qian Chen and Li-yao Li and Da-ye Liang and Jian Huang},

url = {https://www.sciencedirect.com/science/article/pii/S0022169423011769},

doi = {https://doi.org/10.1016/j.jhydrol.2023.130234},

issn = {0022-1694},

year  = {2023},

date = {2023-01-01},

journal = {Journal of Hydrology},

volume = {626},

pages = {130234},

abstract = {The migration process of leached uranium in the in-situ leaching of uranium is considered a typical reactive transport problem. During this process, the lixiviant concentration and injection rate are important in-situ leaching process parameters (ISLPP) to efficiently recover uranium. However, several uncertain factors affect the outcomes of the ISLPP design. In addition, the repeated use of the reactive transport model (RTM) for investigating the acid in-situ leaching of uranium with the application of the Monte Carlo method leads to a substantial computational load. For this reason, a machine learning (ML)–based surrogate model was developed with the backpropagation neural network (BPNN) method to replace the RTM under the condition of uncertain parameters. Moreover, the simulated annealing optimisation model for ISLPP was created based on the proposed surrogate model. The optimal ISLPP was achieved that generated maximum profits from uranium recovery under different lixiviant prices, uranium prices and exploitation times. The optimal design framework of ISLPP based on the proposed ML algorithm was then applied in the Bayan-Uul sandstone-type uranium deposit in Inner Mongolia, China. From our analysis, it was demonstrated that the ML-based surrogate model exhibited great fitness with the RTM. The optimal results of the ISLPP indicated that the lixiviant concentration and injection rate could be adjusted based on the fluctuations in lixiviant price, uranium price and exploitation time. If the prices of sulphuric acid were high, a specific concentration of hydrogen peroxide could be injected into the injection well to promote the oxidation and dissolution of the uranium ore to increase the income from the uranium recovery. The optimisation model can also use the ISLPP scheme to boost the revenues from different lixiviant prices, uranium prices and exploitation times under the uncertainty of porosity, illustrating the applicability of the ML-based optimal design method of ISLPP in ISL mining. A general framework for developing surrogate models, as well as for conducting uncertainty analyses for a wide range of groundwater models was proposed here yielding valuable insights.},

keywords = {In-situ leaching, Injection rate design, Lixiviant concentration design, machine learning, Simulation-optimisation, Uncertainty},

pubstate = {published},

tppubtype = {article}

}

@article{zeng_seepage_2023,

title = {Seepage characteristics of the leaching solution during in situ leaching of uranium},

author = {Sheng Zeng and Jiayin Song and Bing Sun and Fulin Wang and Wenhao Ye and Yuan Shen and Hao Li},

url = {https://www.sciencedirect.com/science/article/pii/S1738573322004892},

doi = {https://doi.org/10.1016/j.net.2022.10.008},

issn = {1738-5733},

year  = {2023},

date = {2023-01-01},

journal = {Nuclear Engineering and Technology},

volume = {55},

number = {2},

pages = {566–574},

abstract = {Investigating the seepage characteristics of the leaching solution in the ore-bearing layer during the in situ leaching process can be useful for designing the process parameters for the uranium mining well. We prepared leaching solutions of four different viscosities and conducted experiments using a self-developed multifunctional uranium ore seepage test device. The effects of different viscosities of leaching solutions on the seepage characteristics of uranium-bearing sandstones were examined using seepage mechanics, physicochemical seepage theory, and dissolution erosion mechanism. Results indicated that while the seepage characteristics of various viscosities of leaching solutions were the same in rock samples with similar internal pore architectures, there were regular differences between the saturated and the unsaturated stages. In addition, the time required for the specimen to reach saturation varied with the viscosity of the leaching solution. The higher the viscosity of the solution, the slower the seepage flow from the unsaturated stage to the saturated stage. Furthermore, during the saturation stage, the seepage pressure of a leaching solution with a high viscosity was greater than that of a leaching solution with a low viscosity. However, the permeability coefficient of the high viscosity leaching solution was less than that of a low viscosity leaching solution.},

keywords = {In situ leaching, Leaching solution viscosity, Seepage characteristics, Seepage pressure, Uranium-bearing sandstone},

pubstate = {published},

tppubtype = {article}

}

@article{wang2022a,

title = {Ion migration in in-situ leaching (ISL) of uranium: Field trial and reactive transport modelling},

author = {Bing Wang and Yue Luo and Jin-hui Liu and Xun Li and Zhi-hong Zheng and Qian-qian Chen and Li-yao Li and Hui Wu and Qi-ren Fan},

url = {https://linkinghub.elsevier.com/retrieve/pii/S0022169422012045},

doi = {10.1016/j.jhydrol.2022.128634},

issn = {00221694},

year  = {2022},

date = {2022-12-01},

urldate = {2024-07-02},

journal = {Journal of Hydrology},

volume = {615},

pages = {128634},

abstract = {Acid in-situ leaching (ISL) can be used as a mining technique for in situ uranium recover from underground. Acids and oxidants as lixiviants were continuously injected into a sandstone-type uranium deposit in Bayan-Uul (China). It was conducted to facilitate the dissolution of uranium minerals to generate uranyl ions, which could then be extracted for the recovery of uranium resources by the pumping cycle. A reactive transport model based on PHAST was developed to investigate the dynamic reactive migration process of uranium. The simulated re­ sults well reproduce the fluid dynamic evolution in the injecting and pumping units, as well as the dynamic release of uranium. The simulated leaching area indicates that the uranium ore leaching area was much larger than the acidification area. In addition, the pollution plume of uranium and acid water was larger than that of the leaching area, which can be used as a reference for uranium mining schemes. Furthermore, the parameter sensitivity analysis indicates the volume fraction of uranium ore and the reaction rate were the main factors affecting uranium leaching efficiency. Without considering the blockage of pores by precipitation, the Fe2+ in the reinjection fluid had a significant negative influence on uranium leaching.},

keywords = {},

pubstate = {published},

tppubtype = {article}

}

@article{rooyen_using_2022,

title = {Using tritium and radiocarbon activities to constrain regional modern and fossil groundwater mixing in Southern Africa},

author = {J. D. van Rooyen and A. W. Watson and J. A. Miller},

url = {https://www.sciencedirect.com/science/article/pii/S0022169422011404},

doi = {https://doi.org/10.1016/j.jhydrol.2022.128570},

issn = {0022-1694},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Hydrology},

volume = {614},

pages = {128570},

abstract = {This study combines historical records of 14C and 3H in the atmosphere and soil with renewal rate and groundwater lumped parameter models to predict the abundance of 14C and 3H in groundwater over time. 624 groundwater samples from numerous studies, over four decades (1978–2019), in South Africa, Namibia, Botswana and Mozambique were collated to compare with predicted groundwater activities of 14C and 3H within the South African Development Community (SADC) region. Spatial datasets of carbonate bearing lithology, C3/C4 vegetation, summer/winter rainfall and coastal proximity were used to apply corrections to 14C and 3H data. Corrected values of 14C and 3H were compared with the theoretical abundance of these tracers, derived from the lumped parameter models, to estimate the general mean residence times and presence of groundwater mixing between modern recharge and older groundwaters. This study found that corrected values produced varying mean residence times derived from 14C ages (∼500–28500 years) and a wide range of potentially mixed waters within each aquifer system (0–100 % of tested wells) across the study area. The largest proportions of mixed groundwater, as well as the youngest mean residence times, were found in alluvial and primary fractured rock aquifers (e.g., western coast of South Africa and southern Mozambique). The smallest proportions of mixed groundwater were predicted in deep confined clay-rich aquifers as well as layered coal bearing carbonate sequences (e.g., Orapa, Malwewe and Serowe, Botswana). Insights into the proportions of mixed groundwater and mean residence times can help assess hydrological resilience on a regional scale. Such information is pertinent in promoting socio-economic development and increased water/food security in the SADC region. By understanding the resilience of groundwater resources, robust and informed strategies for water equality and GDP growth in the SADC region can be envisioned and implemented.},

keywords = {Radiocarbon, Residence time, SADC, Tritium},

pubstate = {published},

tppubtype = {article}

}

@article{chen_risk_2022,

title = {Risk assessment management and emergency plan for uranium tailings pond},

author = {Yifan Chen and Yang Hong and Danxia Huang and Xingwang Dai and Min Zhang and Yong Liu and Zhenghua Xu},

url = {https://www.sciencedirect.com/science/article/pii/S1687850722081882},

doi = {https://doi.org/10.1016/j.jrras.2022.06.005},

issn = {1687-8507},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Radiation Research and Applied Sciences},

volume = {15},

number = {3},

pages = {83–90},

abstract = {The safety of uranium tailings pond is closely related to social stability and economic development, so it is necessary to improve the emergency management of uranium tailings pond to ensure its safety by adjusting the emergency plan. The Interpretive Structural Model (ISM) is used to analyze the structural relationship between the main risk factors leading to the occurrence of emergencies. The results show that attention should be paid to the risk factors originating from humans and infrastructures, and effective management measures should be adopted in the process of emergency management, for example, people build tighter employee access system, clarify the responsibilities of employees at all levels, and improve monitoring and organizational means. According to the results of ISM analysis, a structural risk control system can be constructed, and a defensive barrier that can effectively block the risk coupling transmission can be designed to prevent the risk from being transformed into an event. For other risks, system resilience management should be strengthened to respond to risks. The process is set as emergency response and accident response. Different management objects use different management methods to make emergency management work efficiently.},

keywords = {Emergency management, Interpreted structural model (ISM), Resilience, Risk coupling, Uranium tailings pond},

pubstate = {published},

tppubtype = {article}

}

@article{prusty_adsorptive_2022,

title = {Adsorptive sequestration of noxious uranium (VI) from water resources: A comprehensive review},

author = {Sourav Prusty and Prathap Somu and Jitendra Kumar Sahoo and Debasish Panda and Sunil Kumar Sahoo and Shraban Kumar Sahoo and Yong Rok Lee and T. Jarin and L. Syam Sundar and Koppula Srinivas Rao},

url = {https://www.sciencedirect.com/science/article/pii/S0045653522027710},

doi = {https://doi.org/10.1016/j.chemosphere.2022.136278},

issn = {0045-6535},

year  = {2022},

date = {2022-01-01},

journal = {Chemosphere},

volume = {308},

pages = {136278},

abstract = {Groundwater is usually utilized as a drinking water asset everywhere. Therefore, groundwater defilement by poisonous radioactive metals such as uranium (VI) is a major concern due to the increase in nuclear power plants as well as their by-products which are released into the watercourses. Waste Uranium (VI) can be regarded as a by-product of the enrichment method used to produce atomic energy, and the hazard associated with this is due to the uranium radioactivity causing toxicity. To manage these confronts, there are so many techniques that have been introduced but among those adsorptions is recognized as a straightforward, successful, and monetary innovation, which has gotten major interest nowadays, despite specific drawbacks regarding operational as well as functional applications. This review summarizes the various adsorbents such as Bio-adsorbent/green materials, metal oxide-based adsorbent, polymer based adsorbent, graphene oxide based adsorbent, and magnetic nanomaterials and discuss their synthesis methods. Furthermore, this paper emphasis on adsorption process by various adsorbents or modified forms under different physicochemical conditions. In addition to this adsorption mechanism of uranium (VI) onto different adsorbent is studied in this article. Finally, from the literature reviewed conclusion have been drawn and also proposed few future research suggestions.},

keywords = {Adsorbents, Adsorption, Techniques, Uranium, Wastewater},

pubstate = {published},

tppubtype = {article}

}

@article{paradis_elucidating_2022,

title = {Elucidating mobilization mechanisms of uranium during recharge of river water to contaminated groundwater},

author = {Charles J. Paradis and Kendyl N. Hoss and Cullen E. Meurer and Jiyan L. Hatami and Martin A. Dangelmayr and Aaron D. Tigar and Raymond H. Johnson},

url = {https://www.sciencedirect.com/science/article/pii/S0169772222001243},

doi = {https://doi.org/10.1016/j.jconhyd.2022.104076},

issn = {0169-7722},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Contaminant Hydrology},

volume = {251},

pages = {104076},

abstract = {The recharge of stream water below the baseflow water table can mobilize groundwater contaminants, particularly redox-sensitive and sorptive metals such as uranium. However, in-situ tracer experiments that simulate the recharge of stream water to uranium-contaminated groundwater are lacking, thus limiting the understanding of the potential mechanisms that control the mobility of uranium at the field scale. In this study, a field tracer test was conducted by injecting 100 gal (379 l) of oxic river water into a nearby suboxic and uranium-contaminated aquifer. The traced river water was monitored for 18 days in the single injection well and in the twelve surrounding observation wells. Mobilization of uranium from the solid to the aqueous phase was not observed during the tracer test despite its pre-test presence being confirmed on the aquifer sediments from lab-based acid leaching. However, strong evidence of oxidative immobilization of iron and manganese was observed during the tracer test and suggested that immobile uranium was likely in its oxidized state as U(VI) on the aquifer sediments; these observations ruled out oxidation of U(IV) to U(VI) as a potential mobilization mechanism. Therefore, desorption of U(VI) appeared to be the predominant potential mobilization mechanism, yet it was clearly not solely dependent on concentration as evident when considering that uranium-poor river water (<0.015 mg/L) was recharged to uranium-rich groundwater (≈1 mg/L). It was possible that uranium desorption was limited by the relatively higher pH and lower alkalinity of the river water as compared to the groundwater; both factors favor immobilization. However, it was likely that the immobile uranium was associated with a mineral phase, as opposed to a sorbed phase, thus desorption may not have been possible. The results of this field tracer study successfully ruled out two common mobilization mechanisms of uranium: (1) oxidative dissolution and (2) concentration-dependent desorption and ruled in the importance of advection, dispersion, and the mineral phase of uranium.},

keywords = {Desorption, Dissolution, Groundwater, Surface water, Tracer, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{ren_mineralogical_2022,

title = {Mineralogical and geochemical evidence for biogenic uranium mineralization in northern Songliao Basin, NE China},

author = {Yisu Ren and Xiaoyong Yang and Xiaowen Hu and Jialin Wei and Chao Tang},

url = {https://www.sciencedirect.com/science/article/pii/S0169136821005825},

doi = {https://doi.org/10.1016/j.oregeorev.2021.104556},

issn = {0169-1368},

year  = {2022},

date = {2022-01-01},

journal = {Ore Geology Reviews},

volume = {141},

pages = {104556},

abstract = {The sandstone-hosted uranium mineralization areas in the Sanzhao Sag of the northern Songliao Basin have been newly identified. The target stratum is the Upper Cretaceous Sifangtai Formation and the uranium mineralization mainly occurs in the bottom of Sifangtai Formation, corresponding to channel sand bodies in meandering river system, characterized by medium to fine-grained sandstone. This study proposes the uranium metallogenic model through petrographic observation, whole rock geochemistry, mineralogical study of uranium occurrence form (SEM), organic matter rock–eval pyrolysis analysis (REP) and in-situ sulfur isotope determination of different generations of pyrite by LA-MC-ICP-MS. Compared with the sandstones collected in barren reduction and oxidization zones, the mineralized sandstones show obvious increase in the contents of TOC, total sulfur, Y and U. Petrographic observations indicate that organic matters are mainly inherited from land plants. REP data display that the organic matter (OM) disseminated in the sandstone has very low hydrogen index (HI) from around 0 to 21 mg HC/g TOC and varied oxygen index (OI) from 44 to 115 mg CO2/g TOC, corresponding to Type Ⅳ kerogen (degraded kerogen). There are two types of coffinite with different grain size, micro-particles (μm-sized) and large aggregates (generally up to 100 μm) respectively. The coffinite micro spherules exhibit short rod-like or worm-like morphology occurring in clay matrix and cell cavities in degradofusinite or around subidiomorphic-idiomorphic pyrite. The coarse-grained coffinite contains other mineral facies (e.g. pyrite, quartz) and some of large coffinite aggregates display thrombolite-type microbial structures. The irregular pyrite relict particles in coarse-grained colloidal coffinite have light sulfur isotope compositions characterized by δ34S values from –39.96‰ to –49.89‰. The δ34S values of colloidal pyrite in replacement of OM or of the sub-idiomorphic FeS2 cement filling in the cavities of OM range from –52.77‰ to –13.88‰. Some of sub-idiomorphic pyrite cement and idiomorphic crystal have the heavier signature from – 27.06‰ to + 14.23‰. The light sulfur isotope signature suggests that the sulfur originates from bacterial sulfate reduction (BSR). The OM replacement by pyrite and the highest OI values recorded by REP in uranium mineralized samples are lines of evidence of biodegradation. Bacteria use the organic matter as food source and produce isotopically light reduced sulfur species. Oxygenated uranium-bearing waters infiltrated through the denudated windows at Daqing placanticline into the porous reduced sandstones deposited in the Sanzhao Sag. Uranium was indirectly reduced by BSR-derived iron disulfides or directly reduced by sulfate-reducing bacteria.},

keywords = {Bacterial sulfate reduction, In-situ S isotope of pyrite, Northern Songliao basin, sandstone-type uranium deposit, Sifangtai Formation},

pubstate = {published},

tppubtype = {article}

}

@article{kumar_assessment_2022,

title = {Assessment of U and As in groundwater of India: A meta-analysis},

author = {Vinod Kumar and Raj Setia and Shevita Pandita and Sumit Singh and Tarik Mitran},

url = {https://www.sciencedirect.com/science/article/pii/S0045653522016927},

doi = {https://doi.org/10.1016/j.chemosphere.2022.135199},

issn = {0045-6535},

year  = {2022},

date = {2022-01-01},

journal = {Chemosphere},

volume = {303},

pages = {135199},

abstract = {More than 2.5 billion people depend upon groundwater worldwide for drinking, and giving quality water has become one of the great apprehensions of human culture. The contamination of Uranium (U) and Arsenic (As) in the groundwater of India is gaining global attention. The current review provides state-of-the-art groundwater contamination with U and As in different zones of India based on geology and soil texture. The average concentration of U in different zones of India was in the order: West Zone (41.07 μg/L) > North Zone (37.7 μg/L) > South Zone (13.5 μg/L)> Central Zone (7.4 μg/L) > East Zone (5.7 μg/L) >Southeast Zone (2.4 μg/L). The average concentration of As in groundwater of India is in the order: South Zone (369.7 μg/L)>Central Zone (260.4 μg/L)>North Zone (67.7 μg/L)>East Zone (60.3 μg/L)>North-east zone (9.78 μg/L)>West zone (4.14 μg/L). The highest concentration of U and As were found in quaternary sediments, but U in clay skeletal and As in loamy skeletal. Results of health risk assessment showed that the average health quotient of U in groundwater for children and adults was less than unity. In contrast, it was greater than unity for As posing a harmful impact on human health. This review provides the baseline data regarding the U and As contamination status in groundwater of India, and appropriate, effective control measures need to be taken to control this problem.},

keywords = {Arsenic, Geology, Groundwater, Health risk, Soil texture, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{grozeva_reactive_2022,

title = {Reactive transport modeling of U and Ra mobility in roll-front uranium deposits: Parameters influencing 226Ra/238U disequilibria},

author = {Niya G. Grozeva and Jean Radwan and Catherine Beaucaire and Michaël Descostes},

url = {https://www.sciencedirect.com/science/article/pii/S037567422200019X},

doi = {https://doi.org/10.1016/j.gexplo.2022.106961},

issn = {0375-6742},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Geochemical Exploration},

volume = {236},

pages = {106961},

abstract = {Uranium reserve estimates in ore deposits can be significantly impacted by 226Ra/238U disequilibria arising from the differential mobility of uranium and radium during groundwater transport. 1D reactive transport models were developed to investigate the long-term effects of retention processes (UO2(am) precipitation, U(VI) and Ra sorption on smectite, Ra co-precipitation with barite) on the repartitioning of 238U and 226Ra during formation of roll-front type deposits. Analytical solutions to radioactive decay chains were used in complement to examine the influence of geochemical parameters, including fluid 234U/238U activity ratios and α-recoil loss, on 226Ra/238U disequilibria in uranium ores. Model results demonstrate that smectite and barite can produce 226Ra/238U ratios >1 at low uranium contents and may explain 226Ra/238U disequilibria occurring in altered rock up- and downstream of roll-front deposits. The capacity of these phases to take up Ra and generate 226Ra/238U disequilibria depends on both mineral contents and groundwater compositions, and is thus expected to be site-specific. Simulations of ore deposits that advance downstream with time demonstrate the formation of stronger 226Ra/238U disequilibria, as expected, in the downgradient side or nose of the ore, reflecting both younger mineralization ages and the presence of active uranium precipitation. Whether disequilibria are positive or negative with respect to secular equilibrium, however, depends on the 234U/238U activity ratio in the fluid from which uranium minerals precipitate. Smaller hydraulic conductivities are shown to generate a narrower range in 226Ra/238U activity ratios with distance, and may explain the occurrence of disequilibria in the limb ore that are less pronounced than those in the nose. Furthermore, the ability of α-recoil loss to decrease 226Ra/238U activity ratios at secular equilibrium may account for negative disequilibria in high grade ores. The South Tortkuduk uranium deposits (Kazakhstan) are subsequently used as a case study to identify the processes and parameters that may contribute to 226Ra/238U disequilibria at this site. Variations in multiple parameters, including clay contents, barite contents, and mineralization ages, are found to reproduce measured 226Ra/238U activity ratios in the roll-front ore. Prioritization of these parameters will necessitate field measurements targeting both groundwater fluids and the host rock. Results from this study will ultimately aid geologists in building appropriate hydrogeochemical data sets to more efficiently locate and exploit uranium ore deposits.},

keywords = {Ra/U, Radioactive disequilibria, Radium, Reactive transport modeling, Roll-front uranium deposit},

pubstate = {published},

tppubtype = {article}

}

@article{zhang_case_2022,

title = {Case studies of radioactivity of drilling mud for in situ leaching uranium mining in China},

author = {Hui Zhang and Jie Gao and Lechang Xu and Xueli Zhang},

url = {https://www.sciencedirect.com/science/article/pii/S0265931X22001734},

doi = {https://doi.org/10.1016/j.jenvrad.2022.106982},

issn = {0265-931X},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Environmental Radioactivity},

volume = {251-252},

pages = {106982},

abstract = {The drilling mud from in situ leaching uranium mining is a type of low-radioactivity waste that contains natural nuclides and other harmful substances. In order to determine whether the drilling mud can meet the requirements of radioactive exemption management standards, field investigations and data simulations were conducted in this study. Two typical uranium mines were selected for onsite investigations. Drilling mud from different layers (i.e., the upper covering layer and ore-bearing layer) and from different stages (e.g., logging stage mud, drilling expansion stage mud, and mixed mud) was sampled. For each sample, the 238U and 226Ra concentrations of the solid components and the U and 226Ra concentrations of the supernatant were analyzed. The results revealed that the highest 238U and 226Ra concentrations of the solid components were 4122 Bq/kg and 4077 Bq/kg, while the 238U and 226Ra concentrations of the mixed drilling mud were all less than 300 Bq/kg. A radioactivity estimation model was established for scenario analysis. Exemption management screening lines of waste drilling mud, which can be used to classify and treat the drilling project according to the deposit's grade and conditions, were proposed for in situ leaching drilling projects.},

keywords = {Drilling mud, Exemption management, In situ leaching, Radioactivity},

pubstate = {published},

tppubtype = {article}

}

@article{zeng_fractal_2022,

title = {Fractal kinetic characteristics of uranium leaching from low permeability uranium-bearing sandstone},

author = {Sheng Zeng and Yuan Shen and Bing Sun and Kaixuan Tan and Shuwen Zhang and Wenhao Ye},

url = {https://www.sciencedirect.com/science/article/pii/S1738573321005970},

doi = {https://doi.org/10.1016/j.net.2021.10.013},

issn = {1738-5733},

year  = {2022},

date = {2022-01-01},

journal = {Nuclear Engineering and Technology},

volume = {54},

number = {4},

pages = {1175–1184},

abstract = {The pore structure of uranium-bearing sandstone is one of the critical factors that affect the uranium leaching performance. In this article, uranium-bearing sandstone from the Yili Basin, Xinjiang, China, was taken as the research object. The fractal characteristics of the pore structure of the uranium-bearing sandstone were studied using mercury intrusion experiments and fractal theory, and the fractal dimension of the uranium-bearing sandstone was calculated. In addition, the effect of the fractal characteristics of the pore structure of the uranium-bearing sandstone on the uranium leaching kinetics was studied. Then, the kinetics was analyzed using a shrinking nuclear model, and it was determined that the rate of uranium leaching is mainly controlled by the diffusion reaction, and the dissolution rate constant (K) is linearly related to the pore specific surface fractal dimension (DS) and the pore volume fractal dimension (DV). Eventually, fractal kinetic models for predicting the in-situ leaching kinetics were established using the unreacted shrinking core model, and the linear relationship between the fractal dimension of the sample's pore structure and the dissolution rate during the leaching was fitted.},

keywords = {Fractal characteristics, In-situ leaching, Leaching kinetics, Pore structure, Uranium mine},

pubstate = {published},

tppubtype = {article}

}

@article{wang_ion_2022,

title = {Ion migration in in-situ leaching (ISL) of uranium: Field trial and reactive transport modelling},

author = {Bing Wang and Yue Luo and Jin-hui Liu and Xun Li and Zhi-hong Zheng and Qian-qian Chen and Li-yao Li and Hui Wu and Qi-ren Fan},

url = {https://www.sciencedirect.com/science/article/pii/S0022169422012045},

doi = {https://doi.org/10.1016/j.jhydrol.2022.128634},

issn = {0022-1694},

year  = {2022},

date = {2022-01-01},

journal = {Journal of Hydrology},

volume = {615},

pages = {128634},

abstract = {Acid in-situ leaching (ISL) can be used as a mining technique for in situ uranium recover from underground. Acids and oxidants as lixiviants were continuously injected into a sandstone-type uranium deposit in Bayan-Uul (China). It was conducted to facilitate the dissolution of uranium minerals to generate uranyl ions, which could then be extracted for the recovery of uranium resources by the pumping cycle. A reactive transport model based on PHAST was developed to investigate the dynamic reactive migration process of uranium. The simulated results well reproduce the fluid dynamic evolution in the injecting and pumping units, as well as the dynamic release of uranium. The simulated leaching area indicates that the uranium ore leaching area was much larger than the acidification area. In addition, the pollution plume of uranium and acid water was larger than that of the leaching area, which can be used as a reference for uranium mining schemes. Furthermore, the parameter sensitivity analysis indicates the volume fraction of uranium ore and the reaction rate were the main factors affecting uranium leaching efficiency. Without considering the blockage of pores by precipitation, the Fe2+ in the reinjection fluid had a significant negative influence on uranium leaching.},

keywords = {Acid in situ leaching, Banyan-Uul uranium deposit, Influence area, Reactive transport, Sensitivity analysis},

pubstate = {published},

tppubtype = {article}

}

@article{jana_-situ_2022,

title = {In-situ polymerization into the basal spacing of LDH for selective and enhanced uranium adsorption: A case study with real life uranium alkaline leach liquor},

author = {Animesh Jana and Anand Unni and Shanmuk Srinivas Ravuru and Abhijit Das and Diptendu Das and Sujoy Biswas and H. Sheshadri and Sirshendu De},

url = {https://www.sciencedirect.com/science/article/pii/S1385894721027613},

doi = {https://doi.org/10.1016/j.cej.2021.131180},

issn = {1385-8947},

year  = {2022},

date = {2022-01-01},

journal = {Chemical Engineering Journal},

volume = {428},

pages = {131180},

abstract = {Uranium is used as a fuel for nuclear power plant and can be extracted from different ores, mainly acidic (silicious ore) and alkaline (carbonate ore). Recovery of uranium through acid leaching from silicious ore is well established, whereas, alkaline leaching from carbonate ore is challenging due to the excessive salinity of leach liquor and high concentration of carbonate, bicarbonate and sulphate. Herein, two monomers, acrylic acid (AA) and N, N-methylene bisacrylamide (BAM), selective towards uranyl were intercalated in-situ into the interlayer, followed by their polymerization and cross-linking to form novel polymer intercalated hybrid layered double hydroxide (LDH). The LDH acts as a backbone to overcome coiling and swelling of polymer and anchors them as free-standing. Various parameters, like, the type of metal ions, monomer ratio (AA: BAM) and metal ion ratio (M2+:M3+), were studied to determine the optimum conditions for effective intercalation and polymerization of monomers. Magnesium aluminum (MgAl) LDH with a cross-linked polymer having a monomer ratio of 3:2 (AA: BAM) as intercalating species showed maximum efficiency of uranyl adsorption (1456 mg/g at 30 °C) with highest capacity so far. The distribution coefficient (Kd, l/mg) in the order of 105 suggested that the adsorbent was highly selective for uranyl in the presence of different cations, anions and humic acid. The adsorbent extracts uranium effectively and selectively from a real-life alkaline leach liquor with an efficiency of 96% at 5 g/l dose. Uranium can be recovered from the adsorbent in the form of sodium di-uranate using 2(M) NaOH and was reused for eight cycles.},

keywords = {In-situ polymerization, Layered double hydroxide, Leach liquor, Uranium adsorption, Uranium recovery},

pubstate = {published},

tppubtype = {article}

}

@article{milena-perez_uranium_2021,

title = {Uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes},

author = {A. Milena-Pérez and F. Piñero-García and J. Benavente and V. M. Expósito-Suárez and P. Vacas-Arquero and M. A. Ferro-García},

url = {https://www.sciencedirect.com/science/article/pii/S0265931X20307499},

doi = {https://doi.org/10.1016/j.jenvrad.2020.106503},

issn = {0265-931X},

year  = {2021},

date = {2021-01-01},

journal = {Journal of Environmental Radioactivity},

volume = {227},

pages = {106503},

abstract = {This paper studies the uranium content and uranium isotopic disequilibria as a tool to identify hydrogeochemical processes from 52 groundwater samples in the province of Granada (Betic Cordillera, southeastern Spain). According to the geological complexity of the zone, three groups of samples have been considered. In Group 1 (thermal waters; longest residence time), the average uranium content was 2.63 ± 0.16 μg/L, and 234U/238U activity ratios (AR) were the highest of all samples, averaging 1.92 ± 0.30. In Group 2 (mainly springs from carbonate aquifers; intermediate residence time), dissolved uranium presented an average value of 1.34 ± 0.13 μg/L, while AR average value was 1.38 ± 0.25. Group 3 comes from pumping wells in a highly anthropized alluvial aquifer. In this group, where the residence time of the groundwater is the shortest of the three, average uranium content was 5.28 ± 0.26 μg/L, and average AR is the lowest (1.17 ± 0.12). In addition, the high dissolved uranium value and the low AR brought to light the contribution of fertilizers (Group 3). In the three groups, 235U/238U activity ratios were similar to the natural value of 0.046. Therefore, 235U detected in the samples comes from natural sources. This study is completed with the determination of major ions and physicochemical parameters in the groundwater samples and the statistical analysis of the data by using the Principal Component Analysis. This calculation indicates the correlation between uranium isotopes and bicarbonate and nitrate anions.},

keywords = {234U/238U, Betic cordillera, Groundwater, Hydrogeochemistry, Uranium natural isotopes},

pubstate = {published},

tppubtype = {article}

}

@article{n_spatio-temporal_2021,

title = {Spatio-temporal variations of Uranium in groundwater: Implication to the environment and human health},

author = {Devaraj N and Banajarani Panda and Chidambaram S and Prasanna M. V and Dhiraj Kr Singh and Ramanathan A. L and S. K. Sahoo},

url = {https://www.sciencedirect.com/science/article/pii/S0048969721008548},

doi = {https://doi.org/10.1016/j.scitotenv.2021.145787},

issn = {0048-9697},

year  = {2021},

date = {2021-01-01},

journal = {Science of The Total Environment},

volume = {775},

pages = {145787},

abstract = {Groundwater overexploitation has resulted in huge scarcity and increase in the demand for water and food security in India. Groundwater in India has been observed to have experienced various water quality issues like arsenic, fluoride, and Uranium (U) contamination, leading to risk in human health. Markedly, the health risk of higher U in drinking water, as well as its chemical toxicity in groundwater have adverse effects on human. This study has reported occurrence of U as an emerging and widespread phenomenon in South Indian groundwater. Data on U in groundwater were generated from 284 samples along the Cretaceous Tertiary boundary within 4 seasons viz. pre-monsoon (PRM), southwest monsoon (SWM), northeast monsoon (NEM), and post-monsoon (POM). High U concentrations (74 μgL−1) showed to be above the World Health Organization's provisional guideline value of 30 μgL−1. The geochemical, stable isotope and geophysical studies suggested that U in groundwater could vary with respect to season and was noted to be highest during NEM. The bicarbonate (HCO3) released by weathering process during monsoon could affect the saturation index (SI)Calcite and carbonate species of U. However, the primary source of U was found to be due to geogenic factors, like weathering, dissolution, and groundwater level fluctuation, and that, U mobilization could be enhanced due to anthropogenic activities. The findings further indicated that groundwater in the study area has reached the alarming stage of chemical toxicity. Hence, it is urgent and imperative that workable management strategies for sustainable drinking water source be developed and preventive measures be undertaken, relative to these water quality concerns to mitigate their disconcerting effect on human health.},

keywords = {Groundwater, Health risk, Speciation, Stable isotopes, Statistics, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{ponter_early_2021,

title = {Early diagenesis of anthropogenic uranium in lakes receiving deep groundwater from the Kiruna mine, northern Sweden},

author = {Simon Pontér and Ilia Rodushkin and Emma Engström and Katerina Rodushkina and Cora Paulukat and Elsa Peinerud and Anders Widerlund},

url = {https://www.sciencedirect.com/science/article/pii/S0048969721035130},

doi = {https://doi.org/10.1016/j.scitotenv.2021.148441},

issn = {0048-9697},

year  = {2021},

date = {2021-01-01},

journal = {Science of The Total Environment},

volume = {793},

pages = {148441},

abstract = {The uranium (U) concentrations and isotopic composition of waters and sediment cores were used to investigate the transport and accumulation of U in a water system (tailings pond, two lakes, and the Kalix River) receiving mine waters from the Kiruna mine. Concentrations of dissolved U decrease two orders of magnitude between the inflow of mine waters and in the Kalix River, while the concentration of the element bound to particulate matter increases, most likely due to sorption on iron‑manganese hydroxides and organic matter. The vertical distribution of U in the water column differs between two polluted lakes with a potential indication of dissolved U supply from sediment's pore waters at anoxic conditions. Since the beginning of exposure in the 1950s, U concentrations in lake sediments have increased >20-fold, reaching concentrations above 50 μg g-1. The distribution of anthropogenic U between the lakes does not follow the distribution of other mine water contaminants, with a higher relative proportion of U accumulating in the sediments of the second lake. Concentrations of redox-sensitive elements in the sediment core as well as Fe isotopic composition were used to re-construct past redox-conditions potentially controlling early diagenesis of U in surface sediments. Two analytical techniques (ICP-SFMS and MC-ICP-MS) were used for the determination of U isotopic composition, providing an extra dimension in the understanding of processes in the system. The (234 U)/(238 U) activity ratio (AR) is rather uniform in the tailings pond but varies considerably in water and lake sediments providing a potential tracer for U transport from the Kiruna mine through the water system, and U immobilization in sediments. The U mass balance in the Rakkurijoki system as well as the amount of anthropogenic U accumulated in lake sediments were evaluated, indicating the immobilization in the two lakes of 170 kg and 285 kg U, respectively.},

keywords = {Isotope ratios, Mine water, Sediments, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{mathuthu_radiological_2021,

title = {Radiological safety of groundwater around a uranium mine in Namibia},

author = {Manny Mathuthu and Vera Uushona and Vaino Indongo},

url = {https://www.sciencedirect.com/science/article/pii/S1474706520303612},

doi = {https://doi.org/10.1016/j.pce.2020.102915},

issn = {1474-7065},

year  = {2021},

date = {2021-01-01},

journal = {Physics and Chemistry of the Earth, Parts A/B/C},

volume = {122},

pages = {102915},

abstract = {Uranium mining activities produce the main element used in nuclear energy production. However, it can also negatively affect the environment including groundwater by release of residues or effluent containing radioactive elements. The study investigated the concentration and radiological hazard of uranium in groundwater and seepage water from the tailings of a uranium mine in Namibia. Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to assess the concentration of uranium in the groundwater and seepage water and the radiological hazards were determined. The radiological hazard indices Radium equivalent activity (Raeq), Absorbed dose (D), Annual Effective Dose equivalent (AEDE), External hazard index (Hex) and Internal hazard index (Hin) were determined and compared to limits recommended by United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The calculated average value of D and Hin of groundwater is 108.11nGyh−1 and 1.26, respectively and are above the UNSCEAR values (55 nGyh−1 and 1). Further, the average values of Raeq, AEDE and Hex were below the recommended values. The isotopic ratio of uranium radionuclides in groundwater indicates that the uranium in the sampled groundwater is below 1 suggesting it is not natural uranium present but a possible contamination from the mine seepage. The radiological hazard parameters of the seepage water were above the recommended values and thus pose a radiation risk to human and environment.},

keywords = {Groundwater, ICP-MS, Radiological hazard, Uranium mining},

pubstate = {published},

tppubtype = {article}

}

@article{moreau_defining_2021,

title = {Defining natural baselines for rates of change in New Zealand's groundwater quality: Dealing with incomplete or disparate datasets, accounting for impacted sites, and merging into state of the-environment reporting},

author = {Magali Moreau and Chris Daughney},

url = {https://www.sciencedirect.com/science/article/pii/S0048969720368236},

doi = {https://doi.org/10.1016/j.scitotenv.2020.143292},

issn = {0048-9697},

year  = {2021},

date = {2021-01-01},

journal = {Science of The Total Environment},

volume = {755},

pages = {143292},

abstract = {To effectively manage sustainably groundwater bodies, it is essential to establish what the naturally occurring ranges of chemical concentrations in groundwaters are and how they change over time. We defined baseline trends for New Zealand groundwaters using: 1) pattern recognition techniques to deal with inconsistent monitoring suites between the national (110 sites) and the denser regional network (>1000 sites), and 2) multivariate statistics to identify and remove impacted sites from the enhanced dataset. Rates of changes were calculated for 13 parameters between January 2005 and December 2014 at more than 1000 groundwater quality monitoring sites. The resulting dataset included 262 complete cases (CC), which was enhanced using Machine-Learning (ML) techniques to a total of 607 sites. Hierarchical cluster analysis was used to identify trend clusters that were consistent between the CC, ML-enhanced datasets and a 2006 study based on solely on the national network. The largest cluster (WR) consisted of low magnitude changes across all parameters and was attributed to water-rock interaction processes. The second largest cluster (I) exhibited fast changes particularly for parameters linked to human-induced impact. The third largest cluster (D) comprised decreases of all parameters and was associated with dilution processes. Trend clusters were further refined using groundwater quality state information, enabling the identification of impacted sites outside of Cluster I in the ML-enhanced and CC datasets. Corresponding trend baselines were subsequently derived at unimpacted sites using univariate quantile distribution (5th and 95th percentile thresholds). Finally, we developed classifications combining baselines (state and trend) and natural variability to enhance state of the environment reporting. This allowed the new identification of deteriorating trends at sites where groundwater quality state is not yet affected in addition to trend reversals. These classifications can be adapted to incorporate new knowledge or align with surface water quality reporting.},

keywords = {Baseline, Groundwater quality, Machine-learning, Monitoring, New Zealand, Trends},

pubstate = {published},

tppubtype = {article}

}

@article{rallakis_conditions_2021,

title = {Conditions for uranium biomineralization during the formation of the Zoovch Ovoo roll-front-type uranium deposit in East Gobi Basin, Mongolia},

author = {Dimitrios Rallakis and Raymond Michels and Michel Cathelineau and Olivier Parize and Marc Brouand},

url = {https://www.sciencedirect.com/science/article/pii/S0169136821003772},

doi = {https://doi.org/10.1016/j.oregeorev.2021.104351},

issn = {0169-1368},

year  = {2021},

date = {2021-01-01},

journal = {Ore Geology Reviews},

volume = {138},

pages = {104351},

abstract = {The Zoovch Ovoo uranium roll-front-type deposit is hosted in the Sainshand Formation, a Late Cretaceous siliciclastic reservoir, which constitutes the upper part of the post-rift infilling of the Mesozoic East Gobi Basin in SE Mongolia. The Sainshand Formation consists of unconsolidated medium-grained sand, silt and clay intervals deposited in fluvial-lacustrine settings. The uranium deposit is confined within a 60–80 m thick siliciclastic sequence inside aquifer-driven systems. The overall system experienced shallow burial and was never subjected to temperatures higher than 40 °C. This study proposes a comprehensive metallogenic model for this uranium deposit. Sedimentological and mineralogical observations from drill core samples to the microscopic scale (optical and Scanning Electron Microscopy) together with in situ geochemistry of late-formed phases (Laser Ablation–Inductively Coupled Plasma Mass Spectrometry, Electron Probe Microanalysis, Fourier Transform–Infrared Spectroscopy) were considered for the reconstruction of the main stages of U trapping. In the mineralized zone, the uranium ore is expressed as Ca–enriched uraninite (UO2) and less commonly as Ca–enriched phospho-coffinite (U, P)SiO4. Trapping mechanisms include i) complexation (i.e. uranyl-carboxyl complexes), ii) adsorption on organic or clay particles) and iii) reduction by pyrite and by bacterial activity to amorphous uraninite. In all cases, the organic matter plays either the role of trap for uranium or nutrient for bacteria that can trap uranium through their metabolism. The shallow burial diagenesis conditions do not allow direct reduction of U(VI) by organic carbon. The δ34S values of the iron disulfide are very diverse, fluctuating in extreme cases between −50 to + 50‰, with an average δ34S value for framboidal pyrite at 2‰, and −20‰ for euhedral pyrite. The positive and negative values reflect close versus open fractionation systems, while bacterial sulphate reduction (BSR) is active during the whole diagenetic history of the deposit as an essential source of reduced sulfur. Therefore, using detrital organic matter as a carbon source, microorganisms play a significant role in uranium trapping, either as a direct reducing agent for uranium or pyrite formation, which will trap uranium through redox driven epigenetic processes.},

keywords = {Bioreduction, East Gobi Basin, Mongolia, Organic matter, Roll-front, Sulfur isotopes, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{zeng_pore_2021,

title = {Pore structure evolution characteristics of sandstone uranium ore during acid leaching},

author = {Sheng Zeng and Yuan Shen and Bing Sun and Ni Zhang and Shuwen Zhang and Song Feng},

url = {https://www.sciencedirect.com/science/article/pii/S1738573321003326},

doi = {https://doi.org/10.1016/j.net.2021.06.011},

issn = {1738-5733},

year  = {2021},

date = {2021-01-01},

journal = {Nuclear Engineering and Technology},

volume = {53},

number = {12},

pages = {4033–4041},

abstract = {To better understand the permeability of uranium sandstone, improve the leaching rate of uranium, and explore the change law of pore structure characteristics and blocking mechanism during leaching, we systematically analyzed the microstructure of acid-leaching uranium sandstone. We investigated the variable rules of pore structure characteristics based on nuclear magnetic resonance (NMR). The results showed the following: (1) The uranium concentration change followed the exponential law during uranium deposits acid leaching. After 24 h, the uranium leaching rate reached 50%. The uranium leaching slowed gradually over the next 4 days. (2) Combined with the regularity of porosity variation, Stages I and II included chemical plugging controlled by surface reaction. Stage I was the major completion phase of uranium displacement with saturation precipitation of calcium sulfate. Stage II mainly precipitated iron (III) oxide-hydroxide and aluminum hydroxide. Stage III involved physical clogging controlled by diffusion. (3) In the three stages of leaching, the permeability of the leaching solution changed with the pore structure, which first decreased, then increased, and then decreased.},

keywords = {Acid method, In situ leaching, Nuclear magnetic resonance, Pore characteristic, Sandstone uranium ore},

pubstate = {published},

tppubtype = {article}

}

@article{uugulu_estimation_2020,

title = {Estimation of groundwater recharge in savannah aquifers along a precipitation gradient using chloride mass balance method and environmental isotopes, Namibia},

author = {S. Uugulu and H. Wanke},

url = {https://www.sciencedirect.com/science/article/pii/S1474706518301074},

doi = {https://doi.org/10.1016/j.pce.2020.102844},

issn = {1474-7065},

year  = {2020},

date = {2020-01-01},

journal = {Physics and Chemistry of the Earth, Parts A/B/C},

volume = {116},

pages = {102844},

abstract = {The quantification of groundwater resources is essential especially in water scarce countries like Namibia. The chloride mass balance (CMB) method and isotopic composition were used in determining groundwater recharge along a precipitation gradient at three sites, namely: Tsumeb (600 mm/a precipitation); Waterberg (450 mm/a precipitation) and Kuzikus/Ebenhaezer (240 mm/a precipitation). Groundwater and rainwater were collected from year 2016–2017. Rainwater was collected monthly while groundwater was collected before, during and after rainy seasons. Rainwater isotopic values for δ18O and δ2H range from −10.70 to 6.10‰ and from −72.7 to 42.1‰ respectively. Groundwater isotopic values for δ18O range from −9.84 to −5.35‰ for Tsumeb; from −10.85 to −8.60‰ for Waterberg and from −8.24 to −1.56‰ for Kuzikus/Ebenhaezer, while that for δ2H range from −65.6 to −46.7‰ for Tsumeb; −69.4 to −61.2‰ for Waterberg and −54.2 to −22.7‰ for Kuzikus/Ebenhaezer. Rainwater scatters along the GMWL. Rainwater collected in January, February and March are more depleted in heavy isotopes than those in November, December, April and May. Waterberg groundwater plots on the GMWL which indicates absence of evaporation. Tsumeb groundwater plots on/close to the GMWL with an exception of groundwater from the karst Lake Otjikoto which is showing evaporation. Groundwater from Kuzikus/Ebenhaezer shows an evaporation effect, probably evaporation occurs during infiltration since it is observed in all sampling seasons. All groundwater from three sites plot in the same area with rainwater depleted in stable isotopic values, which could indicates that recharge only take place during January, February and March. CMB method revealed that Waterberg has the highest recharge rate ranging between 39.1 mm/a and 51.1 mm/a (8.7% – 11.4% of annual precipitation), Tsumeb with rates ranging from 21.1 mm/a to 48.5 mm/a (3.5% – 8.1% of annual precipitation), and lastly Kuzikus/Ebenhaezer from 3.2 mm/a to 17.5 mm/a (1.4% – 7.3% of annual precipitation). High recharge rates in Waterberg could be related to fast infiltration and absence of evaporation as indicated by the isotopic ratios. Differences in recharge rates cannot only be attributed to the precipitation gradient but also to the evaporation rates and the presence of preferential flow paths. Recharge rates estimated for these three sites can be used in managing the savannah aquifers especially at Kuzikus/Ebenhaezer where evaporation effect is observed that one can consider rain harvesting.},

keywords = {Chloride mass balance, Groundwater recharge, Isotopic values, Precipitation gradient},

pubstate = {published},

tppubtype = {article}

}

@article{belz_leaf_2020,

title = {The leaf wax biomarker record of a Namibian salt pan reveals enhanced summer rainfall during the Last Glacial-Interglacial Transition},

author = {Lukas Belz and Irka Schüller and Achim Wehrmann and Jürgen Köster and Heinz Wilkes},

url = {https://www.sciencedirect.com/science/article/pii/S0031018219304110},

doi = {https://doi.org/10.1016/j.palaeo.2019.109561},

issn = {0031-0182},

year  = {2020},

date = {2020-01-01},

journal = {Palaeogeography, Palaeoclimatology, Palaeoecology},

volume = {543},

pages = {109561},

abstract = {Conventional continental geoarchives are rarely available in arid southern Africa. Therefore, palaeoclimate data in this area are still patchy and late Quaternary climate development is only poorly understood. In the western Kalahari, salt pans (playas, ephemeral lakes) are common and can feature quasi-continuous sedimentation. This study presents the first climate-related biomarker record using sediments from the Omongwa Pan, a Kalahari salt pan located in eastern Namibia. Our approach to reconstruct vegetation and hydrology focuses on biogeochemical bulk parameters and plant wax-derived lipid biomarkers (n-alkanes, n-alkanols, and fatty acids) and their compound-specific carbon and hydrogen isotopic compositions. The presented record reaches back to 27 ka. During the glacial, rather low δ2H values of n-alkanes and low sediment input exclude a strong influence of winter rainfall. n-Alkane and n-alkanol distributions and δ13C values of n-hentriacontane (n-C31) indicate a shift to a vegetation with a higher proportion of C4 plants at the end of the Last Glacial Maximum until the end of Heinrich Stadial I (ca. 18–14.8 ka), which we interpret to indicate an abrupt excursion to a short wetter period likely to be caused by a temporary southward shift of the Intertropical Convergence Zone. Shifts in δ2H values of n-C31 and plant wax parameters give evidence for changes to drier conditions during early Holocene. Comparison of this dataset with representative continental records from the region points to a major influence of summer rainfall at Omongwa Pan during the regarded time span and demonstrates the potential of southern African salt pans as archives for biomarker-based climate proxies.},

keywords = {-Alkanes, -Alkanols, Late Quaternary, Organic geochemistry, Palaeohydrology, Southern Africa},

pubstate = {published},

tppubtype = {article}

}

@article{ammar_uranium_2020,

title = {Uranium isotopes as tracers of groundwater evolution in the Complexe Terminal aquifer of southern Tunisia},

author = {Friha Hadj Ammar and Pierre Deschamps and Najiba Chkir and Kamel Zouari and Aissa Agoune and Bruno Hamelin},

url = {https://www.sciencedirect.com/science/article/pii/S1040618220300252},

doi = {https://doi.org/10.1016/j.quaint.2020.01.024},

issn = {1040-6182},

year  = {2020},

date = {2020-01-01},

journal = {Quaternary International},

volume = {547},

pages = {33–49},

abstract = {The Complexe Terminal (CT) multi-layer aquifer is formed by Neogene/Paleogene sand deposits, Upper Senonian (Campanian-Maastrichtian limestones) and Turonian carbonates. The chemical composition and isotopes of carbon and uranium were investigated in groundwater sampled from the main hydrogeological units of the (CT) aquifer in southern Tunisia. We paid special attention to the variability of uranium contents and isotopes ratio (234U/238U) to provide a better understanding of the evolution of the groundwater system. Uranium concentrations range from 1.5 to 19.5 ppb, typical of oxic or mildly reducing conditions in groundwaters. The lowest concentrations are found southeast of the study area, where active recharge is supposed to take place. When looking at the isotope composition, it appears that all the samples, including those from carbonate levels, are in radioactive disequilibrium with significant 234U excess. A clear-cut distinction is observed between Turonian and Senonian carbonate aquifers on the one hand, with 234U/238U activity ratios between 1.1 and 1.8, and the sandy aquifer on the other hand, showing higher ratios from 1.8 to 3.2. The distribution of uranium in this complex aquifer system seems to be in agreement with the lithological variability and are ultimately a function of a number of physical and chemical factors including the uranium content of the hosting geological formation, water-rock interaction and mixing between waters having different isotopic signatures. Significant relationships also appear when comparing the uranium distribution with the major ions composition. It is noticeable that uranium is better correlated with sulfate, calcium and magnesium than with other major ions as chloride or bicarbonate. The 14C activities and δ13C values of DIC cover a wide range of values, from 1.1 pmc to 30.2 pmc and from −3.6‰ to −10.7‰, respectively. 14C model ages estimated by the Fontes and Garnier model are all younger than 22 Ka and indicate that the recharge of CT groundwater occurred mainly during the end of the last Glacial and throughout the Holocene.},

keywords = {CT southern Tunisia, Holocene, Mixing, Radicarbon, Uranium isotopes, Water-rock interaction},

pubstate = {published},

tppubtype = {article}

}

@article{su_petrology_2020,

title = {Petrology, mineralogy, and ore leaching of sandstone-hosted uranium deposits in the Ordos Basin, North China},

author = {Xuebin Su and Zhengbang Liu and Yixuan Yao and Zhiming Du},

url = {https://www.sciencedirect.com/science/article/pii/S0169136819302628},

doi = {https://doi.org/10.1016/j.oregeorev.2020.103768},

issn = {0169-1368},

year  = {2020},

date = {2020-01-01},

journal = {Ore Geology Reviews},

volume = {127},

pages = {103768},

abstract = {The Nalinggou–Daying uranium metallogenic belt is situated at the northern Ordos Basin, China. Petrographical, mineralogical and geochemical techniques were used to study the ore-bearing sandstones and host rocks in the Nalinggou–Daying uranium metallogenic belt. The present study shows that uranium minerals, i.e., coffinite, pitchblende, and brannerite, are mostly disseminated around pyrite and detrital particles. The ore-bearing sandstones are enriched in organic matter, with which this reductive environment influenced uranium leaching. The carbonate concentration of the uranium ores is markedly higher than that of the host rocks, and intense carbonatization occurs in the ore-bearing sandstones. In this case, the usage of the classical in-situ leach uranium mining technique by injecting H2SO4 + H2O2 solution produces calcium sulfate precipitate, which can lead to blocking of the ore-bearing strata. For this reason, laboratory and field uranium mining tests were conducted using CO2 + O2 in-situ leaching technology and were demonstrated to be successful, illustrating that this approach is technically feasible. Inhibiting ore bed blockage and increasing the amount of injected O2 are important for uranium leaching in this setting.},

keywords = {Geochemical composition, leach mining, Mineralogy, Ordos Basin, Sandstone-hosted uranium deposit},

pubstate = {published},

tppubtype = {article}

}

@article{sahoo_scientific_2020,

title = {Scientific background and methodology adopted on derivation of regulatory limit for uranium in drinking water – A global perspective},

author = {S. K. Sahoo and V. N. Jha and A. C. Patra and S. K. Jha and M. S. Kulkarni},

url = {https://www.sciencedirect.com/science/article/pii/S266676572030020X},

doi = {https://doi.org/10.1016/j.envadv.2020.100020},

issn = {2666-7657},

year  = {2020},

date = {2020-01-01},

journal = {Environmental Advances},

volume = {2},

pages = {100020},

abstract = {Guideline values are prescribed for drinking water to ensure long term protection of the public against anticipated potential adverse effects. There is a great public and regulatory agencies interest in the guideline values of uranium due to its complex behavior in natural aquatic system and divergent guideline values across the countries. Wide variability in guideline values of uranium in drinking water may be attributed to toxicity reference point, variation in threshold values, uncertainty within intraspecies and interspecies, resource availability, socio-economic condition, variation in ingestion rate, etc. Although guideline values vary to a great extent, reasonable scientific basis and technical judgments are essential before it could be implemented. Globally guideline values are derived considering its radiological or chemical toxicity. Minimal or no adverse effect criterions are normally chosen as the basis for deriving the guideline values of uranium. In India, the drinking water limit of 60 µg/L has been estimated on the premise of its radiological concern. A guideline concentration of 2 µg/L is recommended in Japan while 1700 µg/L in Russia. The relative merit of different experimental assumption, scientific approach and its methodology adopted for derivation of guideline value of uranium in drinking water in India and other countries is discussed in the paper.},

keywords = {Drinking water, Global policy, Regulatory limits, Toxicity, Uranium},

pubstate = {published},

tppubtype = {article}

}

@article{lartigue_aqueous_2020,

title = {Aqueous inorganic uranium speciation in European stream waters from the FOREGS dataset using geochemical modelling and determination of a U bioavailability baseline},

author = {J. E. Lartigue and B. Charrasse and B. Reile and M. Descostes},

url = {https://www.sciencedirect.com/science/article/pii/S0045653520304951},

doi = {https://doi.org/10.1016/j.chemosphere.2020.126302},

issn = {0045-6535},

year  = {2020},

date = {2020-01-01},

journal = {Chemosphere},

volume = {251},

pages = {126302},

abstract = {The concentration of the bioavailable uranium fraction (Ubio) at the European scale was deduced by geochemical modelling considering several definitions found in the literature and the FOREGS European stream waters geochemical atlas dataset to produce a Ubio baseline. A sensitivity analysis was performed using three thermodynamic databases. We also investigated the link between total dissolved uranium (Uaq) concentrations, speciation and global stream water chemistry on the one hand, and the lithology and ages of the surrounding rocks on the other. The more U-enriched the stream sediments or rock type contexts are, which tends to be the case with rocks containing silicates (4.1 mg/kg), the less U-concentrated the stream waters are (0.15 μg/L). Sedimentary rocks lead to slightly higher Uaq concentrations (0.34 μg/L) even if the concentration in sediment (Used) is relatively low (1.6 mg/kg). This trend is reversed for Ubio, with higher concentrations in a crystalline context. The mean estimated Ubio value ranges from 1.5.10−3 to 65.3 ng/L and can fluctuate by 3 orders of magnitude depending on the considered definition as opposed to by 2 orders of magnitude accountable to differences between thermodynamic databases. The classification of the water in relation to the two surrounding rock lithologies makes it possible to reduce the mean variability for the Ubio concentrations. Irrespective of the definition of Ubio considered, in 59% of cases the Ubio fraction represents less than 1% of Uaq. Several threshold values relating to Ubio were proposed, assuming knowledge only of the aqueous concentrations of the major elements and Uaq.},

keywords = {Bioavailable fraction, Geochemical mapping / baseline, Modelling, Speciation, Stream water, Uranium},

pubstate = {published},

tppubtype = {article}

}