Elevated Uranium Concentrations Research Articles

Uranium enrichment in a paleo-karstic bauxite deposit, Yunfeng, SW China: Mineralogy, geochemistry, transport – deposition mechanisms and significance for uranium exploration

Elevated concentrations of uranium have been found in many bauxite deposits, but the status of uranium in the ores and the mechanisms of enrichment have not been well understood. In this paper, we report a new case of uranium enrichment in a paleo-karstic bauxite deposit at Yunfeng, southwestern China, present electron probe micro-analyzer (EPMA) and Raman spectroscopic evidence for the presence of separate U-minerals, and propose a model in which uranium was enriched through successive processes from chemical weathering through early to burial diagenesis. The Yunfeng bauxite ores, developed in Lower Carboniferous mudrocks overlying Middle to Upper Cambrian carbonate rocks, contain 18.0 to 62.4 ppm (average 35.1 ppm) U, which is much high than the abundances in average crustal rocks (1–3 ppm). Micron-sized uraninite occurs as rims of Ti-oxides, fillings of micro-fractures in kaolinite, and disseminated grains in association with sulfides in the matrix of diaspore and kaolinite. Trace and rare earth elements analysis indicates that the bauxite ores could not be produced by in-situ weathering of the carbonates underlying the orebodies. Instead, the precursor rocks of the bauxite ores are inferred to be black shales originally enriched in uranium that were exposed tens of kilometers away. Detrital grains of the black shales were transported and accumulated in depressions above karstified carbonates in the Yunfeng area, where they were subjected to intense weathering to form bauxite ores. The weathering of the shale clasts liberated much of the uranium due to oxidation of uranium from U4+ to U6+. However, the majority of the U6+ was reduced to U4+ again due to availability of reducing agents such as organic matter and sulfides originally in the shales, forming nanocrystals of UO2+x in close association with Ti-oxides disseminated in Al-hydroxides and clay minerals. These nanocrystals of UO2+x were converted to uraninite during diagenesis, together with the convention of gibbsite and boehmite to diaspore and the formation of anhedral to euhedral pyrite and various Cu-, Pb-, Ni- and Co-rich sulfides. The recognition of uraninite in the bauxite ores is important for uranium exploration and for evaluation of the economic value of uranium as a byproduct of bauxite deposits.

Effects of the discharge of uranium mining effluents on the water quality of the reservoir: an integrative chemical and ecotoxicological assessment

The water quality of the Antas reservoir, under the influence of treated effluents from a uranium mining area Ore Treatment Unit (UTM) with acid mine drainage, was investigated. Samples were collected every 3 months from the Antas reservoir (CAB, P41-E and P14) and from the UTM (P41-S). Chemical and acute 48 h toxicity tests using Ceriodaphnia silvestrii and Daphnia magna analyses were carried out to determine the potential environmental risks due to discharging the uranium mine effluents into this reservoir. All the water samples taken from the treated effluent (P41-S) were positively correlated with elevated concentrations of uranium, manganese, aluminum, zinc and fluoride and with high electrical conductivity and pH values, being considered toxic. In November 2014 water samples taken from the reservoir showed chemical concentrations above the legislation limits for fluoride (4.5 mg L−1) uranium (0.082 mg L−1), sulfate (662.4 mg L−1), manganese (1.125 mg L−1) and aluminum (1.55 mg L−1), and in July 2015 for fluoride (2.55 mg L−1), uranium (0.01 mg L−1) and manganese (0.36 mg L−1). The extremely high average value for hardness (543.55 mg L−1) possibly reduced the toxicity potential of this chemical species mixture with respect to the bioindicators. The influence of the variation in water hardness on the toxicity of the cladocerans was discussed.

Distribution of uranium in groundwaters of Bathinda and Mansa districts of Punjab, India: inferences from an isotope hydrochemical study

This paper presents the isotope hydrochemical results of groundwaters from southwest Punjab for assessing the uranium contamination and evaluating the factors leading to elevated uranium concentration. A total of 35 samples covering shallow and deep zones were collected for hydrochemistry and isotopes. Uranium concentration ranges between 2.3 and 357 µg L−1 and 66% of the samples are contaminated. Both shallow and deep zones show U contamination but high incidences are noticed in shallow zone. Hydrochemical correlations infer geological sources rather than anthropogenic sources responsible for U contamination. Isotopically there is no clear distinction between high and low U groundwater.

Distribution of natural and anthropogenic radionuclides in northwest Mediterranean coastal sediments

The distribution of radionuclides in NW Mediterranean coastal sediments, and the processes controlling their abundance were investigated in three cores taken near the island of Porquerolles and one offshore Monaco. The sediments collected near Porquerolles were strongly anoxic due to diagenetic processes involved in the decomposition of organic matter, whereas they transitioned from oxic to anoxic at a depth of 4 cm beneath the seawater interface at Monaco. Organic carbon (OC) was more abundant in sediments at Porquerolles (by about a factor of 3–5) than at Monaco and elsewhere in the coastal NW Mediterranean. Sediment cores collected NE of Porquerolles also possessed elevated uranium concentrations that correlated with high OC content and strong reducing conditions. The 239,240Pu and 241Am activities in surficial sediments ranged from 1 to 5.7 Bq kg−1 and 0.3 to 1 Bq kg−1, respectively, while the 137Cs activity ranged from 0.3 to 6.2 Bq kg−1. The mean activity ratios of 241Am/239,240Pu and 238Pu/239,240Pu in Porquerolles and Monaco sediments were similar to the global fallout ratios. Sediment inventories of global fallout 239,240Pu (430–800 Bq m−2) and 241Am (150–285 Bq m−2) were by about a factor of 5–10 higher at Porquerolles, whereas the inventory of 137Cs (430–1000 Bq m−2) was substantially lower at the investigated stations than have been reported elsewhere at similar latitudes. Specific local conditions characterised by high OC sediment loads due to the growth and mortality of Posidonia oceanica have been responsible for deposition of large amounts of seagrass tissues at the NE corner of Porquerolles, which have had a profound effect on the distribution of radionuclides in the sediments.

Geochemistry and hydrology of perched groundwater springs: assessing elevated uranium concentrations at Pigeon Spring relative to nearby Pigeon Mine, Arizona (USA)

The processes that affect water chemistry as the water flows from recharge areas through breccia-pipe uranium deposits in the Grand Canyon region of the southwestern United States are not well understood. Pigeon Spring had elevated uranium in 1982 (44 μg/L), compared to other perched springs (2.7–18 μg/L), prior to mining operations at the nearby Pigeon Mine. Perched groundwater springs in an area around the Pigeon Mine were sampled between 2009 and 2015 and compared with material from the Pigeon Mine to better understand the geochemistry and hydrology of the area. Two general groups of perched groundwater springs were identified from this study; one group is characterized by calcium sulfate type water, low uranium activity ratio 234U/238U (UAR) values, and a mixture of water with some component of modern water, and the other group by calcium-magnesium sulfate type water, higher UAR values, and radiocarbon ages indicating recharge on the order of several thousand years ago. Multivariate statistical principal components analysis of Pigeon Mine and spring samples indicate Cu, Pb, As, Mn, and Cd concentrations distinguished mining-related leachates from perched groundwater springs. The groundwater potentiometric surface indicates that perched groundwater at Pigeon Mine would likely flow toward the northwest away from Pigeon Spring. The geochemical analysis of the water, sediment and rock samples collected from the Snake Gulch area indicate that the elevated uranium at Pigeon Spring is likely related to a natural source of uranium upgradient from the spring and not likely related to the Pigeon Mine.

Groundwater Contamination by Uranium and Mercury at the Ridaura Aquifer (Girona, NE Spain).

Elevated concentrations of uranium and mercury have been detected in drinking water from public supply and agricultural wells in alluvial and granitic aquifers of the Ridaura basin located at Catalan Coastal Ranges (CCR). The samples showed high concentrations of U above the U.S. standards and the World Health Organization regulations which set a maximum value of 30 µg/L. Further, high mercury concentrations above the European Drinking Water Standards (1 μg/L) were found. Spatial distribution of U in groundwater and geochemical evolution of groundwater suggest that U levels appear to be highest in granitic areas where groundwater has long residence times and a significant salinity. The presence of high U concentrations in alluvial groundwater samples could be associated with hydraulic connection through fractures between the alluvial system and deep granite system. According to this model, oxidizing groundwater moving through fractures in the leucocratic/biotitic granite containing anomalous U contents are the most likely to acquire high levels of U. The distribution of Hg showed concentrations above 1 μg/L in 10 alluvial samples, mainly located near the limit of alluvial aquifer with igneous rocks, which suggests a possible migration of Hg from granitic materials. Also, some samples showed Hg concentrations comprised between 0.9 and 1.5 μg/L, from wells located in agricultural areas.

Elevated uranium concentrations in Lake Baikal sediments: Burial and early diagenesis

The water column of Lake Baikal (Siberia) is pervasively oxic and O2 penetrates several cm into the sediment, followed by distinct layers of Fe/Mn oxide that undergo reductive-dissolution/oxidative-precipitation cycles. Uranium (U) contents of the oxic surface sediment layers were ~15μgg−1, which is unparalleled in oxygenated lakes. To understand the processes leading to this enrichment we investigated the geochemical composition of the particulate matter and pore water of four sediment cores from different locations in the lake and performed mass balance calculations based on sediment mass accumulation rates and published loads from major tributaries. The comparison of loads and export of U in Lake Baikal suggested that current estimates of loads are too low by a factor of about 3 compared to sediment mass accumulation rates. Peak loads during spring ice melt in tributaries that are difficult to monitor and quantify might be the main cause for the deviation. The high U concentrations in the lake sediments originated from the scavenging of U in the water column through association with settling organic particles and particulate Fe(III)- and, to a lesser extent, Mn(IV)-oxides. We outline the hypothesis that two distinct U phases, lithogenic and non-lithogenic U reach the lake sediment and that authigenic U is subsequently formed under reducing conditions within the sediment. In some cores we found that most U was remobilized during the degradation of organic matter, in particular within the top oxygenated layer of the sediment. Significant enrichments prevailed due to U adsorption to and/or co-precipitation with Fe-oxides. When Fe-oxides and, to a lesser extent, Mn-oxides were reductively dissolved, they released U to the pore water, leading to peak dissolved U concentrations in the anoxic sediment, which in turn, precipitated as authigenic U under predominantly sulphate-reducing conditions. The onset of the accumulation of authigenic U coincided with the formation of distinct Fe/Mn oxide layers above. We argue that the resilience of Fe-oxides (especially crystalline goethite and hematite), in association with phosphate, even within reducing (but non-sulfidic) sediments support the burial of substantial amounts of U.

The long-term effect of uranium and pH on the community composition of an artificial consortium.

In the environment, microorganisms are living in diverse communities, which are impacted by the prevailing environmental conditions. Here, we present a study investigating the effect of low pH and elevated uranium concentration on the dynamics of an artificial microbial consortium. The members (Caulobacter sp. OR37, Asinibacterium sp. OR53, Ralstonia sp. OR214 and Rhodanobacter sp. OR444) were isolated from a uranium contaminated and acidic subsurface sediment. In pure culture, Ralstonia sp. OR214 had the highest growth rate at neutral and low pH and only Caulobacter sp. OR37 and Asinibacterium sp. OR53 grew in the presence uranium. The four strains were mixed in equal ratios, incubated at neutral and low pH and in the presence uranium and transferred to fresh medium once per week for 30 weeks. After 30 weeks, Ralstonia sp. OR214 was dominant at low and neutral pH and Caulobacter sp. OR37 and Asinibacterium sp. OR53 were dominant in the presence of uranium. After 12 weeks, the cultures were also transferred to new conditions to access the response of the consortia to changing conditions. The transfers showed an irreversible effect of uranium, but not of low pH on the consortia. Overall, the strains initially tolerant to the respective conditions persisted over time in high abundances in the consortia.

Alpha spectroscopy substrates based on thin polymer films

The objective of this work was to prepare a novel substrate for the simultaneous concentration of actinides and sample preparation for alpha spectroscopy. Substrate preparation involved forming ultrathin films (10–180 nm) of quaternary amine anion-exchange polymers on glass and silicon by dip-coating. Samples were loaded by submerging the polymer-coated substrates into acidified solutions of 238Pu or natural water with elevated uranium concentrations. High resolution (25–30 keV) alpha spectra were acquired from these substrates under certain loading conditions indicating that through further development they may be a useful, inexpensive, and potentially field deployable platform serving national security and environmental sampling applications.

On the distribution of uranium in hair: Non-destructive analysis using synchrotron radiation induced X-ray fluorescence microprobe techniques

In the present study the distribution of uranium in single human hair shafts has been evaluated using two synchrotron radiation (SR) based micro X-ray fluorescence techniques; SR μ-XRF and confocal SR μ-XRF. The hair shafts originated from persons that have been exposed to elevated uranium concentrations. Two different groups have been studied, i) workers at a nuclear fuel fabrication factory, exposed mainly by inhalation and ii) owners of drilled bedrock wells exposed by ingestion of water. The measurements were carried out on the FLUO beamline at the synchrotron radiation facility ANKA, Karlsruhe. The experiment was optimized to detect U with a beam size of 6.8μm×3μm beam focus allowing detection down to ppb levels of U in 10s (SR μ-XRF setup) and 70s (SR confocal μ-XRF setup) measurements. It was found that the uranium was present in a 10–15μm peripheral layer of the hair shafts for both groups studied. Furthermore, potential external hair contamination was studied by scanning of unwashed hair shafts from the workers. Sites of very high uranium signal were identified as particles containing uranium. Such particles, were also seen in complementary analyses using variable pressure electron microscope coupled with energy dispersive X-ray analyzer (ESEM–EDX). However, the particles were not visible in washed hair shafts.These findings can further increase the understanding of uranium excretion in hair and its potential use as a biomonitor.

Hydromineral Resources of Saline Lakes of Mongolia and Russian Altai

Soda lakes located close to uranium deposits of West Mongolia contain elevated concentrations of uranium, reaching, in some cases, 1 to 3 mg/l. The concentration of uranium in the lakes of Russian Altai is lower and varies from 0.001 to 0.03 mg/l. The greatest uranium resources (about 6000 tons) are stored in Hyargas Nuur Lake, Western Mongolia. In addition to uranium and salts of sodium and magnesium increased contents of boron (up to 250 mg/l), bromine (up to 1.1 g/l), lithium (up to 600 mg/l), strontium (up to 8 mg/l) were determined in the lake waters. A scheme for complex processing of uranium-bearing lake waters, the first stage of which includes extraction of uranium using iron-containing sorbents or anion exchange resins is considered. Uranium compounds, bromine, iodine, boron, lithium and other elements found in salt lakes are an important raw material base for the production of advanced materials.

Environmental Radioactivity in the Sabugal Region and Impact of Past Uranium Mining

An environmental radioactivity survey carried out in the Sabugal region, Portugal, showed enhanced radioactivity levels in surface water streams related to water discharges from old uranium mines. Water from irrigation wells in this region displayed variable radionuclide levels due to natural occurrence of radionuclides and also to contamination by mine water drainage. Horticulture products grown near the uranium mine sites contained elevated radium (226Ra) concentrations but lower concentrations of uranium and other radionuclides. Despite relatively elevated radioactivity in irrigation water, the absorption and accumulation of radionuclides in plants was limited. Taking into consideration the volume of uranium waste piles, the improved management of mine waste and mine drainage is needed in order to prevent the increase of environmental radioactivity in the area.

Uranium theoretical speciation for drinking water from private drilled wells in Sweden – Implications for choice of removal method

Elevated concentrations of uranium (U) from natural sources have been measured in drinking water from private drilled wells in Sweden and many other countries world-wide. Although U is a radioactive element, radioactivity is not the main concern, but rather chemical toxicity, e.g. kidney damage. Uranium chemistry is complex and U in water has a very high tendency to form complexes with other compounds. Since speciation is crucial for the properties of U, and therefore the removal efficiency, this study determined theoretical U species in drinking water from private drilled wells using the geochemical model Visual MINTEQ. The drinking water samples used in modelling were from two datasets: (1) 76 water samples selected from a previous survey of 722 wells; and (2) samples of drinking water from 21 private wells sampled in May 2013. The results showed that neutrally charged U complexes dominated in the pH range 6.7–7.8, which is common in private drilled wells. This has important implications for removal method, since charge is an important factor for U removal efficiency. In the alkaline pH range, one of two calcium-UO2 carbonate complexes dominated and calcium (Ca) concentration proved to be a key factor determining the Ca-UO2 carbonate complex formed: the neutral Ca2UO2(CO3)30(aq) or the negative CaUO2(CO3)32−. Complexes with organic carbon (C) varied greatly in the acidic range, indicating that it is crucial to measure organic C content in the water since it is critical for the dissolved organic matter (DOM)-UO2 complex formation. Therefore before U removal method is selected, some crucial parameters for complex formation should be measured. Based on our results, such measurements should include pH, Ca, alkalinity and organic C concentration, as these determine the type of complexes formed and their charge.

Elevated Uranium and Toxic Elements Concentration in Groundwater in Punjab State of India: Extent of the Problem and Risk Due to Consumption of Unsafe Drinking Water

The article provides the first ever Statewise information on uranium and other toxic elements (Pb, As, Cd, Al, Hg, Se, and Ni) present in excess quantity in groundwater in Punjab State of India. It undertakes detailed analysis of 252 ground water samples, out of total 1,686 samples, which were found exceeding guideline value for uranium in drinking water as specified by different regulating agencies like Atomic Energy Regulatory Board (AERB) India, United States Environmental Protection Agency (USEPA), and World Health Organization (WHO). The groundwater samples were collected from 14 districts for analysis of uranium following suspected high level of uranium in groundwater and possible co-relationship of uranium in drinking water with high incidences of cancer, kidney problem, birth defects, and other abnormalities in some areas in Punjab State of India. Basic information on cancer-related incidences is also given. Keeping in view that there could be multiple reasons of cancer-related incidences and other health hazards, data on pesticide consumption in the State were also collected, and test results of other toxic elements (Pb, As, Cd, Al, Hg, Se, and Ni) in 7,176 groundwater-based drinking water sources are also presented.The analysis reveals that groundwater at many villages, which is used for drinking purpose, is contaminated with uranium and other toxic metals, and consumption of drinking water contaminated with many toxic elements may be one of the reason of high incidences of cancer, kidney problem, birth defects, and other abnormalities in some areas in Punjab State of India.

Characterization of groundwater composition in Punjab state with special emphasis on uranium content, speciation and mobility

Abstract Groundwaters (borewell and handpump) were sampled from two districts (Bathinda and Mansa) of Punjab state and analyzed for their major ionic concentrations and uranium isotope compositions in order to assess the possible origins of the waters and water–rock interactions that occurred in the deep aquifer system. The major ionic concentrations of waters were plotted on a Piper diagram and grouped into four dominant hydrochemical facies as (Na+K)-SO4+Cl type (69% – 73%), (Ca+Mg)-SO4+Cl type (6% – 21%), (Ca+Mg)–HCO3 type (4% – 6%) and (Na+K)-HCO3 type (2% – 19%). It was observed that mobility of uranium in groundwater was very much influenced by TDS (total dissolved solids). To investigate the various mechanisms for deriving the elevated uranium concentrations in groundwater, 234U/238U activity ratios (ARs) were calculated using the determined activity levels of 234U and 238U. The mean ARs was found to be near unity (i.e. secular equilibrium) in the study regions confirmed that uranium in groundwaters was mainly resulted from its host/parent rocks through weathering processes. The concentration of HCO3 − in ground water showed one order of magnitude higher than the total dissolved SiO2 indicates that carbonate weathering was the dominant process due to major water–rock interaction. The uranium speciation in groundwaters was investigated by an equilibrium model calculation using MEDUSA (make equilibrium diagrams using sophisticated algorithms) under the influence of redox conditions and complexant concentration. At the observed range of pH values, the predominant redox speciation of uranium was observed as hydroxo-carbonato complexes of (UO2)2(CO3)(OH)3 − and hydroxyl complexes of UO2(OH)3 − which might be caused for increasing the solubility of uranium. Due to very low concentration of phosphate in groundwater, its effects on U(VI)-aqueous speciation was negligible.

Perched-water analysis related to deep vadose zone contaminant transport and impact to groundwater

A series of calculations and model predictions were used to evaluate the controls on perched-water conditions and constraints on perching occurrence, persistence, and potential impact on groundwater contamination. These simulations considered perched-water conditions that have been observed in the vadose zone above a fine-grained layer located just a few meters above the water table beneath the B-Complex Tank Farms area at the Hanford Site. The perched water, containing elevated concentrations of uranium and technetium-99, is important to consider in evaluating the future flux of contaminated water into the groundwater. A study was conducted to examine the perched-water conditions and quantitatively evaluate (1) factors that control perching behavior, (2) contaminant flux toward groundwater, and, (3) associated groundwater impact. Based on the current vertical transport pathways and large areal extent of the perched system, the evaluation was conducted using a one-dimensional analysis. Steady-state analytical calculations showed that the perching-layer hydraulic conductivity is likely to be up to two orders of magnitude lower than the value obtained from Hanford site material property estimates. Numerical flow and transport simulations provided both steady-state and transient system estimates of water and contaminant behavior and were used to further refine the range of conditions consistent with current observations of perched water height and to provide estimates of future water and contaminant flux to groundwater. Near-term removal of perched water by pumping can decrease the total contaminant mass that will discharge to the groundwater, but will have only a moderate effect on the near-term discharge rate and corresponding contaminant concentration in groundwater. Combining pumping with a decrease in the recharge rate will be most effective in minimizing the impact to groundwater. These results provide a framework for constraining the behavior of perched aquifer systems especially related to impacts on contaminant transport.

Establishing the Origin of Elevated Uranium Concentrations in Groundwater near the Central Ogcheon Metamorphic Belt, Korea

We examined the origin of the U-enriched groundwater in Daejeon, near the Ogcheon U zone in Korea. For this study, groundwater ionic species and C, S, and Sr isotopic compositions were analyzed. The U-enriched groundwater occurred only in the Daejeon granite region, while all the groundwater in the Ogcheon Supergroup showed very low U concentrations. In the granite region, the pedospheric or atmospheric origin of dissolved C and S means that the aquifer has been well connected to the oxidized surface environment. The Sr/Sr ratios indicated a lithospheric origin of Sr. Groundwater isotopic compositions in the Ogcheon belt varied greatly, indicating their complex sources. In this region, dissolved C originated from graphite-rich slate and limestone. The broad range of δS suggested that the composite sources included atmospheric SO for most groundwater, lithogenic SO for mine drainage and quarry water, and anthropogenic SO for polluted groundwater. This study indicates that the U-enriched groundwater is not related to the present U ores in the Ogcheon belt but is genetically associated with the granite body itself. The varying but considerable U contents within the granite body can be present as isolated groups. We infer that locally high U contents in the Daejeon granite might inherently be due to assimilation of the Ogcheon U-mineralized zone into granitic melt during the Mesozoic; however, the pH and Eh conditions except aquifer geology were very important factors in developing highly enriched U groundwater in the Daejeon granite region. Thermodynamic modeling highlights the importance of dissolved Ca and (bi-)carbonate in U geochemistry.

Occurrence of uranium in Swiss drinking water

The results of a nationwide survey of uranium in Swiss drinking water are reported. Elevated concentrations of uranium in groundwater are found mainly in the alpine regions and can be traced back to the geology of the bedrock. Water sources were systematically surveyed and analysed for the presence of Li, B, Si, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Sr, Cd, Sn, Sb, Ba, Tl, Pb and U and the results were analysed to determine if any correlation with uranium concentration was apparent. No correlation was found. The results are interpreted in relation to the current WHO guideline and those of other countries with a view to determining which areas would be affected if a maximum value were to be adopted and which areas require further investigation. Uranium content varied considerably, from below the limit of detection to almost 100 μg L −1. Of the 5548 data samples, 98% are below the 2004 WHO provisional guideline value of 15 μg L −1 and 99.7% below the revised (2011) value of 30 μg L −1.

URANIUM INDUCED EFFECTS ON DEVELOPMENT AND MINERAL NUTRITION OF ARABIDOPSIS THALIANA

This study aimed to investigate effects on growth and development and alterations in the nutrient profiles for Arabidopsis thaliana seedlings following uranium exposure. Seventeen-day-old Arabidopsis thaliana seedlings, grown in hydroponics, were exposed to 0, 0.1, 1, 10 and 100 μM uranium for one, three and seven days. Fresh weight of leaves and roots decreased after exposure to 100 μM uranium for one and three days and after exposure to 1, 10 and 100 μM uranium for seven days. Anthocyanous-colored leaves and stunted yellow roots were observed after exposure to 100 μM uranium. The uranium content of the roots highly increased but the root-to-shoot transfer of uranium was limited. Uranium exposure resulted in disturbed macro- and micronutrient profiles, especially following exposure to 100 μM. This study indicates that elevated uranium concentrations can cause important morphological and physiological effects and disturb the nutrient profiles in Arabidopsis thaliana seedlings.

TRLFS study on the speciation of uranium in seepage water and pore water of heavy metal contaminated soil.

In situ leaching of uranium ores with sulfuric acid during active uranium mining activity on the Gessenheap has caused longstanding environmental problems of acid mine drainage and elevated concentrations of uranium. To study there remediation measures the test site Gessenwiese, a recultivated former uranium mining heap near Ronnenburg/East Thuringia/Germany, was installed as a part of a research program of the Friedrich-Schiller University Jena to study, among other techniques, the phytoremediation capacity of native and selected plants towards uranium. In the first step the uranium speciation in surface seepage and soil pore waters from Gessenwiese, ranging in pH from 3.2 to 4.0, were studied by time-resolved laser-induced fluorescence spectroscopy (TRLFS). Both types of water samples showed mono-exponential luminescence decay, indicating the presence of only one major species. The detected emission bands were found at 477.5, 491.8, 513.0, 537.2, 562.3, and 590.7 nm in case of the surface water samples, and were found at 477.2, 493.2, 513.8, 537.0, 562.4, and 590.0 nm in case of the soil water samples. These characteristic peak maxima together with the observed mono-exponential decay indicated that the uranium speciation in the seepage and soil pore waters is dominated by the uranium (VI) sulfate species UO2SO4(aq). Due to the presence of luminescence quenchers in the natural water samples the measured luminescence lifetimes of the UO2SO4(aq) species of 1.0–2.6 μs were reduced in comparison to pure uranium sulfate solutions, which show a luminescence lifetime of 4.7 μs. These results convincingly show that in the pH range of 3.2–4.0 TRLFS is a suitable and very useful technique to study the uranium speciation in naturally occurring water samples.Electronic supplementary materialThe online version of this article (doi:10.1007/s10967-011-1389-z) contains supplementary material, which is available to authorized users.