Determination and interpretation of environmental water samples contaminated by uranium mining activities (original) (raw)
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Use of the Eurachem guide on method validation for determination of uranium in environmental samples
Accreditation and Quality Assurance, 2005
Three analytical methods for determination of uranium in environmental samples by a fluorescence technique have been validated and compared in accordance with the Eurachem Guide on method validation. The first method depends on uranium separation from iron using the mercury anode technique; in the other two methods uranium is separated from iron on an anion exchange column by use of either a solution of hydrochloric acid containing ascorbic acid and hydrazine hydrate or a dilute sulfuric acid solution. Detection limits, repeatability, reproducibility, and recovery coefficient were the main validation characteristics. The results showed that better statistical values can be achieved by using the third method. Control charts for in-house control samples and international intercomparison samples have also shown that the third method is more statistically stable with time. In addition, uncertainties of measurement were estimated and compared for the three methods. It was found that the Eurachem Guide and comparison of quality statistical validation data can be good tools for selection of the appropriate method for an application.
Complete and unequivocal preservation of natural water samples is a practical impossibility. The physico-chemical and biological changes continue inevitably after sample collection. In this paper, the various aspects which cause changes in the content of uranium, major cations and anions with reference to the time interval between sample collection and analysis are presented. These parameters warrant the need and use of Mobile Geochemical Laboratory for quick analysis of water samples. The reliability/quality of measurement results of water samples depends on strict adherence to each step of sampling, preservation of samples, time-interval between sampling and analysis for filtered but un-acidified water samples, and on the methodology adopted, and not simply analyzed by any person or lab or any technique. Interpretation and conclusions of hydrogeochemical reconnaissance survey will depend on the quality of measurement results. In addition to this, self-evaluation of data from collecting samples to reporting results should be carried out to ensure reliability and accuracy of analytical data of water samples.
Distribution of Natural Uranium in Surface and Groundwater Resources: A Review
Keeping in view the toxicity of uranium and to reduce exposure to uranium and avoid high doses, it is essential to examine on routine bases the concentration of natural radionuclide uranium (U) in surface and groundwater resources. In this approach, the concentrations of U (total U) were summarized in worldwide surface and groundwater resources. U(+6) is the major form of U in oxic surface waters, while U(+4) is the major form in anoxic waters. An efficient way of uranium measurement in all water sources must be utilized to obtain reliable results. For this purpose a summary of available analytical techniques for U determination has also been presented. On the basis of the available data, the chemical exposures from these contaminated water sources were specified and some important epidemiological cross-sectional, ecological, and case-control studies and influence of heavy metal mining on water quality were also included. The literature review results revealed that the concentrations of natural U are higher in many parts of the world than the prescribed limit of World Health Organization. Ground and surface water in different areas of the world is contaminated with U and available data is not enough regarding water-related diseases possibly due to the lack of diagnostic facilities. Regular surveys need to be conducted in various parts of the world to obtain a clear picture of water-linked diseases.
Activity concentration of uranium in groundwater from uranium mineralized areas and its neighborhood
Journal of Radioanalytical and Nuclear Chemistry, 2013
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Environmental Earth Sciences, 2017
The Caldas Uranium Mine (CUM), located on the Poços de Caldas Plateau in the southeastern region of Brazil, is presently undergoing a decommissioning process. The aim of the present investigation is to identify and characterize the effects of acid mine drainage (AMD) originating from the CUM on surface water quality. To achieve these aims, sampling stations were located at two AMD sources: the retention pond at the foot of waste rock pile#4 (WRP#4) and the settling pond that receives effluents from the tailings dam (TD). Ten additional sampling stations were located along watercourses in the vicinity, both downstream and upstream of the mine. Sampling was performed during the rainy and dry seasons in 2010 and 2011. The water analysis detected significant changes in pH, electrical conductivity, F − , Cd, U, Zn, Al, Mn, As, Ca, SO 4 2− , Pb, 238 U, 226 Ra, 210 Pb, 232 Th, 228 Ra, and Mo in waters downstream of both pond discharge sites. It was demonstrated that the disequilibrium between 226 Ra and 238 U can be used to trace the extent of AMD impacts in nearby streams. Variations in 18 O and 2 H enabled the flow of mining-impacted water to be traced from the ponds to nearby streams. Multivariate analysis yielded a three-factor model: Factor 1 was interpreted as being associated with AMD (from WRP#4) and Factor 2 with a Ca-Mo relationship associated with the chemical constitution of the ore and with the treatment of tailings wastes in the area (from TD); Factor 3 was interpreted as being associated with the natural influence of geogenic processes on water quality in the area. The results of this study provide a scientific basis for recommending appropriate remedial actions during mine decommissioning.
AIP Conference Proceedings, 2008
Uranium is an element that has the solely characteristic to behave as significant hazard both from a chemical and radiological point of view. Exclusively of natural occurrence, its distribution into the environment may be influenced by human activities, such as nuclear fuel cycle, military use of depleted uranium, or coal and phosphate fertilizer use, which finally may impact freshwater ecosystems. Until now, the associated environmental impact and risk assessments were conducted separately. We propose here to apply the same methodology to evaluate the ecological risk due to potential chemotoxicity and radiotoxicity of uranium. This methodology is articulated into the classical four steps (EC, 2003: problem formulation, effect and exposure analysis, risk characterisation). The problem formulation dealt both with uranium viewed as a chemical element and as the three isotopes 234, 235 and 238 of uranium and their main daughters. Then, the exposure analysis of non-human species was led on the basis of a common conceptual model of the fluxes occurring in freshwater ecosystems. No-effect values for the ecosystem were derived using the same effect data treatment in parallel. A Species Sensitivity Distribution was fitted : (1) to the ecotoxicity data sets illustrating uranium chemotoxicity and allowing the estimation of a Predicted-No-Effect-Concentration for uranium in water expressed in Hg/L; (2) to radiotoxicity effect data as it was done within the ERICA project, allowing the estimation of a Predicted No-Effect-Dose-Rate (in |aGy.h'). Two methods were then applied to characterize the risk to the ecosystem: a screening method using the risk quotient approach, involving for the radiological aspect back calculation of the water limiting concentration from the PNEDR for each isotope taken into account and a probabilistic risk assessment. A former uranium ore mining case-study will help in demonstrating the application of the whole methodology.
Environmental Earth Sciences, Springer, 2022
The presence of uranium (U) in potable groundwater must be treated with extreme care because of its health concerns. The study area consists of complex lithology and various land use activities including natural and anthropogenic processes. The present study aims to assess the seasonal distribution, probable sources and factors responsible for U mobilization in groundwater and provides a holistic picture of geochemical processes in the study area. To achieve these objectives, a total of 680 groundwater samples were collected during four different seasons (pre-monsoon, southwest monsoon, monsoon and post-monsoon). The samples were collected with lithological differences to determine the effects of natural geochemical processes in addition to the anthropogenic impacts. The trend of anions reflected the following order during PRM and NEM: Cl > HCO 3 − > NO 3 > SO 4 > PO 4 , and cations Na > Ca > Mg > K during PRM and SWM. The U concentration in the samples ranged from 10 to 70 ppb, being higher during the NEM season. The samples were classified into three groups based on U concentration (< 10 ppb, 10-15 ppb and > 15 ppb) and studied using various geochemical diagrams, statistical application, thermodynamic study and saturation states for different minerals. The maximum concentration of U in groundwater during different seasons reflects that NEM > POM > SWM > PRM. The higher U values were observed in the hornblende-biotitegneiss irrespective of the season. U in groundwater migrates away from the source due to its high solubility, where it tends to form complexes, especially in the presence of phosphates or carbonates. Analysis of the data shows that the majority of the samples in the monsoon season reflect dilution and recharge processes. In contrast, during SWM and PRM, ion exchange and anthropogenic influences predominate the processes. The PCA study shows that secondary salt leaching, weathering, anthropogenic influences and ion exchange play a significant role in determining the groundwater chemistry in this region.
Some Aspects of the Influence of Uranium Exploitation on the Environment
Fiabilitate şi Durabilitate, 2012
Gamma-ray spectrometric measurements of samples of riverbed sediments and soil samples taken along the valley of a river, which runs very close to a uranium mine retaining dam are performed. The content of 238U, 226Ra, 210 Pb, 232Th, and 40K is analyzed. Up to a distance of about 6 km away from the retaining dam, 238U, 226Ra and 210Pb have high concentrations and the content in the sediments samples is consistently higher than the content in the soil samples. In the same interval are observed considerable fluctuations in the contents related to the swamping of the river. Receding at a greater distance from the retaining dam, the concentration of 238U, 226Ra and 210Pb decreases and has values close to the average ones. A very close correlation is established between the contents of the three radioactive nuclides. Regarding 232Th and 40K, the distribution characteristics along the profile are different in comparison with those of the 238U family members. The performed research contrib...
Predictive modeling for U and Th concentrations in mineral and thermal waters, Serbia
Environmental Earth Sciences, 2020
The objective of this paper was to determine background values (BV) and anomalous values (AV) of U and Th in groundwater and to establish hydrogeochemical conditions which lead to the elevated concentrations of these elements in groundwater. The methodology included planning and collecting of water samples, laboratory work, and assessment of BV and AV concentrations in accordance with the dataset distribution, based on consideration of hydrogeochemical conditions in the hydrogeological system. Groundwater sampling included 144 occurrences of mineral and thermal water from Serbian territory, belonging to different hydrogeological systems. Field parameters were measured for temperature (T), pH, electrical conductivity (EC), oxidation-reduction potential (ORP), dissolved oxygen (DO), and carbon dioxide (CO 2). Standard laboratory measurements were applied for the determination of major chemical components (Ca, Mg, Na, K, Cl, HCO 3 , and SO 4) and U and Th concentrations were measured by ICP-MS. The first step for obtaining U and Th threshold values was based on non-parametric statistical analysis on the data sets. Further analysis of threshold values enabled establishing hydrogeochemical conditions influencing elevated concentrations of U and Th and setting up the logistic regression (LR) model. Differences in the hydrochemical properties of U and Th can be observed based on predictor variables from LR models. Physico-chemical parameters Eh and pH, groundwater type, and geochemical environment (cretaceous igneous rocks) were significant predictors for elevated uranium concentrations, while significant predictors in the thorium LR model were the pH value, the concentration of SO 4 in the solution, and the water-bearing rocks (tertiary igneous rocks).