Speciation and spectrophotometric determination of uranium in seawater

A series of ion-exchange and extraction procedures for the separation of uranium from seawater samples and subsequent spectrophotometric determination of uranium in seawater by means of arsenazo(III) is described. According to the measurements performed by means of traced samples at every stage of separation, the yield of the pre-analytical procedures is generally over 90% and the separation of uranium very selective. The mean uranium concentration in seawater samples collected from five different coastal areas in Cyprus was found to be 3.2 ± 0.2 & micro; g L-1. Uranium in seawater is stable in its hexavalent oxidation state and UO2 (CO3)34- is the predominant species under normal coastal conditions (pH ≥ 8, EH ≥ 0.35 mV, 1 atm and 0.03% CO2)

My Private Cloud Overview: A Trust, Privacy and Security Infrastructure for the Cloud

Based on the assumption that cloud providers can be trusted (to a certain extent) we define a trust, security and privacy preserving infrastructure that relies on trusted cloud providers to operate properly. Working in tandem with legal agreements, our open source software supports: trust and reputation management, sticky policies with fine grained access controls, privacy preserving delegation of authority, federated identity management, different levels of assurance and configurable audit trails. Armed with these tools, cloud service providers are then able to offer a reliable privacy preserving infrastructure-as-a-service to their clients

Quantitative description and local structures of trivalent metal ions Eu(III) and Cm(III) complexed with polyacrylic acid

The trivalent metal ion (M(III) = Cm, Eu)/polyacrylic acid (PAA) system was studied in the pH range between 3 and 5.5 for a molar PAA-to-metal ratio above 1. The interaction was studied for a wide range of PAA (0.05 mg L−1–50 g L−1) and metal ion concentrations (2×10−9–10−3 M). This work aimed at 3 goals (i) to determine the stoichiometry of M(III)–PAA complexes, (ii) to determine the number of complexed species and the local environment of the metal ion, and (iii) to quantify the reaction processes. Asymmetric flow-field-flow fractionation (AsFlFFF) coupled to ICP-MS evidenced that size distributions of Eu–PAA complexes and PAA were identical, suggesting that Eu bound to only one PAA chain. Time-resolved laser fluorescence spectroscopy (TRLFS) measurements performed with Eu and Cm showed a continuous shift of the spectra with increasing pH. The environment of complexed metal ions obviously changes with pH. Most probably, spectral variations arose from conformational changes within the M(III)–PAA complex due to pH variation. Complexation data describing the distribution of complexed and free metal ion were measured with Cm by TRLFS. They could be quantitatively described in the whole pH-range studied by considering the existence of only a single complexed species. This indicates that the slight changes in M(III) speciation with pH observed at the molecular level do not significantly affect the intrinsic binding constant. The interaction constant obtained from the modelling must be considered as a mean interaction constant

A two-sample model for the comparison of radiation doses

The t-test is one of the most well known parametric statistical procedures that can be applied to the problem of two-sample comparison. However, it relies on several assumptions that might not be satisfied in practice and therefore alternative methods are called for. The contribution of this article is to present a relatively new technique for the comparison of two samples in the context of semiparametric statistical inference and apply the new method to the comparison of external radiation doses in the region of Cyprus. Accordingly, without specifying the parametric form of the distribution of the two samples, it is assumed that their log likelihood ratio is linear in some parameters. This in turn leads to empirical likelihood estimation and comparison. Real data analysis shows that the external dose rate does not vary upon the type of rock formation—a fact which does not hold for the terrestrial radiation

Determination of uranium concentration in ground water samples of Northern Greece

The activity concentration of 238U and 234U has been determined in groundwater samples of hot springs and deep wells from the region of Northern Greece. The analysis was performed by alpha spectroscopy after pre-concentration and separation of uranium by cation exchange (Chelex 100 resin) and finally its electro-deposition on stainless steel discs. The uranium concentration in deep wells and springs varies strongly between 0.15 and 7.66 μg l−1. Generally the springs present higher uranium concentration than the deep wells, except of the Apol-lonia spring, which has shown the lowest value of 0.15 mg l−1. 238U and 234U activity concentration ranged between 1.8–95.3 mBq l−1 and 1.7–160.1 mBq l−1, respectively. The obtained isotopic ratio 234U/238U varies between 0.95 and 1.74 which means that the two isotopes are not in radioactive equilibrium. The highest 234U/238U activity ratio values correspond to the Langada springs, indicating most probably old-type waters. On the other hand, ground waters from wells with relatively low uranium activity concentration and low 234U/238U isotopic ratios, point to the presence of younger waters with a stronger contribution of a local recharge component to the groundwater

KINETIC-STUDY OF PHOSPHORUS DESORPTION BY ALFISOLS AND ENTISOLS

The kinetics of phosphorus (P) desorption by six Greek soils, four Alfisols and two Entisols, have been studied. By the addition of several amounts of P fertilizers at different water/soil rations and different contact times, that amount of P fertilizer required for the two major categories for Greek soils in order to avoid enviromental pollution from overdoses was determined. The experimental data lead to the same desorption model as given by Sharpley (1981): Pd = kPot(partial derivative)w(b); where, Pd is the amount of P desorption from the soil in mug P/g soil, Po the amount of P fertilizers in grams added into the soil, t the contact time of P fertilizers with the soil, w the water/soil rations, and k, partial derivative, and b constants. The values of the partial derivative, k, and b constants for each soil are, nearly the same for all the experimental conditions. For the Entisols, the partial derivative values are lower than for the Alfisols. Calcium carbonate (CaCO3) and exchangeable Ca of the Entisols influenced negatively the desorption-time relationship, while exchangeable Fe and Mn, and the low CEC of the Alfisols had a positive influence. For the Entisols, the b values are higher than for the Alfisols, except for the Agrinio B soil. The clay silty soils with high CECs and low exchangeable Fe and Mn had a positive influence on the the desoption water-soil relationship. Since the values for the partial derivative, K, and b constants for each soil are almost the same, the average of these values can be used in the Shapley model for the determination of desorbed P for each agricultural use for the two major categories of Greek soils