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Zheng Z.,CAS Beijing National Laboratory for Molecular | Kang M.,CAS Beijing National Laboratory for Molecular | Wang C.,CAS Beijing National Laboratory for Molecular | Liu C.,CAS Beijing National Laboratory for Molecular | And 3 more authors.
Chemosphere | Year: 2014

Arsenazo III is a widely used reagent for the concentration measurement of uranium and other actinides in aqueous samples. This study indicates that, for routine aqueous samples, due to the strong complexing ability with Arsenazo III, Fe(III) can significantly decrease the UV-Vis absorbance of the U(VI)-Arsenazo III complex, whereas the influence of Fe(II) on the absorbance is negligible. However, when Fe(II) is present in a gamma-irradiated U(VI) aqueous sample, it can give rise to the Fenton reaction, which produces oxidizing radicals that decompose the subsequently added Arsenazo III, leading to a sharp decrease in the absorbance of the U(VI)-Arsenazo III complex. The decrease in absorbance depends on the iron content and irradiation dose. Furthermore, the oxidizing radicals from the Fenton reaction induced by gamma irradiation can be continually produced. Even if the irradiated solution has been aged for more than one month in the absence of light at room temperature and without the exclusion of oxygen, the reactivity of the radicals did not decrease toward the subsequently added Arsenazo III. This finding demonstrates that the presence of Fe(II) in gamma-irradiated U(VI) aqueous samples can lead to incorrect U(VI) measurement using the Arsenazo III method, and a new method needs to be developed for the quantitative determination of U(VI) in the presence of gamma radiation and ferrous iron. © 2014 Elsevier Ltd. Source

Ortega M.F.,Technical University of Madrid | Rincones M.,Technical University of Madrid | Elio J.,Technical University of Madrid | Del Olmo G.J.,Technical University of Madrid | And 8 more authors.
Global Nest Journal | Year: 2014

CO2 capture and storage (CCS) projects are presently developed to reduce the emission of anthropogenic CO2 into the atmosphere. CCS technologies are expected to account for the 20% of the CO2 reduction by 2050. Geophysical, ground deformation and geochemical monitoring have been carried out to detect potential leakage, and, in the event that this occurs, identify and quantify it. This monitoring needs to be developed prior, during and after the injection stage. For a correct interpretation and quantification of the leakage, it is essential to establish a pre-injection characterization (baseline) of the area affected by the CO2 storage at reservoir level as well as at shallow depth, surface and atmosphere, via soil gas measurements. Therefore, the methodological approach is important because it can affect the spatial and temporal variability of this flux and even jeopardize the total value of CO2 in a given area. In this sense, measurements of CO2 flux were done using portable infrared analyzers (i.e., accumulation chambers) adapted to monitoring the geological storage of CO2, and other measurements of trace gases, e.g. radon isotopes and remote sensing imagery were tested in the natural analogue of Campo de Calatrava (Ciudad Real, Spain) with the aim to apply in CO2 leakage detection; thus, observing a high correlation between CO2 and radon (r=0,858) and detecting some vegetation indices that may be successfully applied for the leakage detection. © 2014 Global NEST Printed in Greece. All rights reserved. Source

Smith G.M.,GMS Abingdon Ltd. | Smith K.L.,RadEcol Consulting Ltd. | Kowe R.,Radioactive Waste Management Directorate | Thorne M.,Mike Thorne and Associates Ltd | And 3 more authors.
Journal of Environmental Radioactivity | Year: 2014

Decisions on permitting, controlling and monitoring releases of radioactivity into the environment rely on a great variety of factors. Important among these is the prospective assessment of radionuclide behavior in the environment, including migration and accumulation among and within specific environmental media, and the resulting environmental and human health impacts. Models and techniques to undertake such assessments have been developed over several decades based on knowledge of the ecosystems involved, as well as monitoring of previous radionuclide releases to the environment, laboratory experiments and other related research.This paper presents developments in the assessment of radiation doses and related research for some of the key radionuclides identified as of potential significance in the context of releases to the biosphere from disposal facilities for solid radioactive waste. Since releases to the biosphere from disposal facilities involve transfers from the geosphere to the biosphere, an important aspect is the combined effects of surface hydrology, near-surface hydrogeology and chemical gradients on speciation and radionuclide mobility in the zone in which the geosphere and biosphere overlap (herein described as the geosphere-biosphere subsystem). In turn, these aspects of the environment can be modified as a result of environmental change over the thousands of years that have to be considered in radioactive waste disposal safety assessments. Building on the experience from improved understanding of the behavior of the key radionuclides, this paper proceeds to describe development of a generic methodology for representing the processes and environmental changes that are characteristic of the interface between the geosphere and the biosphere. The information that is provided and the methodology that is described are based on international collaborative work implemented through the BIOPROTA forum, www.bioprota.org. © 2013 Elsevier Ltd. Source

Elio J.,Technical University of Madrid | Ortega M.F.,Technical University of Madrid | Nisi B.,CNR Institute of Geosciences and Earth Resources | Mazadiego L.F.,Technical University of Madrid | And 3 more authors.
International Journal of Greenhouse Gas Control | Year: 2015

Natural analogs offer a valuable opportunity to investigate the long-term impacts associated with the potential leakage in geological storage of CO2.Degassing of CO2 and radon isotopes (222Rn-220Rn) from soil, gas vents and thermal water discharges was investigated in the natural analog of Campo de Calatrava Volcanic Field (CCVF; Central Spain) to determine the CO2-Rn relationships and to assess the role of CO2 as carrier gas for radon. Furthermore, radon measurements to discriminate between shallow and deep gas sources were evaluated under the perspective of their applicability in monitoring programs of carbon storage projects.CO2 flux as high as 5000gm-2d-1 and 222Rn activities up to 430kBqm-3 were measured; 220Rn activities were one order of magnitude lower than those of 222Rn. The 222Rn/220Rn ratios were used to constrain the source of the Campo de Calatrava soil gases since a positive correlation between radon isotopic ratios and CO2 fluxes was observed. Thus, in agreement with previous studies, our results indicate a deep mantle-related origin of CO2 for both free and soil gases, suggesting that carbon dioxide is an efficient carrier for Rn. Furthermore, it was ascertained that the increase of 222Rn in the soil gases was likely produced by two main processes: (i) direct transport by a carrier gas, i.e., CO2 and (ii) generation at shallow level due to the presence of relatively high concentrations of dissolved U and Ra in the thermal aquifer of Campo de Calatrava.The diffuse CO2 soil flux and radon isotopic surveys carried out in the Campo de Calatrava Volcanic Fields can also be applicable to geochemical monitoring programs in CCS (Carbon Capture and Storage) areas as these parameters are useful to: (i) constrain CO2 leakages once detected and (ii) monitor both the evolution of the leakages and the effectiveness of subsequent remediation activities. These measurements can also conveniently be used to detect diffuse leakages. © 2014 Elsevier Ltd. Source

Elio J.,Fundacion Ciudad de la Energia CIUDEN | Elio J.,Technical University of Madrid | Nisi B.,CNR Institute of Geosciences and Earth Resources | Ortega M.F.,Technical University of Madrid | And 3 more authors.
International Journal of Greenhouse Gas Control | Year: 2013

From the end of 2013 and during the following two years, 20kt of CO2sc are planned to be injected in a saline reservoir (1500m depth) at the Hontomín site (NE Spain). The target aquifers are Lower Jurassic limestone formations which are sealed by Lower Cretaceous clay units at the Hontomín site (NE Spain). The injection of CO2 is part of the activities committed in the Technology Development phase of the EC-funded OXYCFB300 project (European Energy Program for Recovery - EEPR, http://www.compostillaproject.eu), which include CO2 injection strategies, risk assessment, and testing and validating monitoring methodologies and techniques.Among the monitoring works, the project is intended to prove that present-day technology is able to monitor the evolution of injected CO2 in the reservoir and to detect potential leakage. One of the techniques is the measurement of CO2 flux at the soil-atmosphere interface, which includes campaigns before, during and after the injection operations.In this work soil CO2 flux measurements in the vicinity of oil borehole, drilled in the eighties and named H-1 to H-4, and injection and monitoring wells were performed using an accumulation chamber equipped with an IR sensor. Seven surveys were carried out from November 2009 to summer 2011. More than 4000 measurements were used to determine the baseline flux of CO2 and its seasonal variations.The measured values were low (from 5 to 13gm-2day-1) and few outliers were identified, mainly located close to the H-2 oil well. Nevertheless, these values cannot be associated to a deep source of CO2, being more likely related to biological processes, i.e. soil respiration. No anomalies were recognized close to the deep fault system (Ubierna Fault) detected by geophysical investigations. There, the CO2 flux is indeed as low as other measurement stations. CO2 fluxes appear to be controlled by the biological activity since the lowest values were recorded during autumn-winter seasons and they tend to increase in warm periods. Two reference CO2 flux values (UCL50 of 5gm-2d-1 for non-ploughed areas in autumn-winter seasons and 3.5 and 12gm-2d-1 for in ploughed and non-ploughed areas, respectively, in spring-summer time, and UCL99 of 26gm-2d-1 for autumn-winter in not-ploughed areas and 34 and 42gm-2d-1 for spring-summer in ploughed and not-ploughed areas, respectively) were calculated. Fluxes higher than these reference values could be indicative of possible leakage during the operational and post-closure stages of the storage project. © 2013 Elsevier Ltd. Source

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