Radioactivity and metal concentrations in marine sediments associated with mining activities in Ierissos Gulf, North Aegean Sea, Greece.

Marine sediment samples were collected from Ierissos Gulf, N Aegean Sea, close to the coastal mining facilities. Measurements of radionuclide and metal concentrations, mineral composition and grain size distribution were performed. The concentrations of (226)Ra, (235)U and trace metals showed enhanced values in the port of Stratoni compared with those obtained near to Ierissos port. The dose rates received by marine biota were also calculated by the ERICA Assessment Tool and the results indicated no significant radiological risk.

Competitive adsorption of boric acid and chromate onto alumina in aqueous solutions.

The competitive adsorption of boric acid and chromate from aqueous solutions by alumina has been investigated by spectrophotometry at pH 8, ionic strength = 0.0, 0.1 and 1.0 M NaClO4, T = 22 ± 3 °C and under normal atmospheric conditions. The experimental data show that addition of excess boric acid in the system leads to the increase of Cr(VI) concentration in solution, indicating the replacement of adsorbed chromate by boron on the alumina surface. Data evaluation results in the determination of the competition reaction constant and the formation constant of the Cr(VI) surface complexes, which are logKCr(VI)-B(III) = -3.5 ± 0.2 and logß*Cr = 7.6 ± 0.3, respectively.

Copper(II) removal from aqueous solutions by adsorption on non-treated and chemically modified cactus fibres.

The adsorption efficiency of a biomass by-product (cactus fibres) regarding the removal of copper(II) from aqueous solutions has been investigated before and after its chemical treatment. The chemical treatment of the biomass by-product included phosphorylation and MnO2-coating. The separation/removal efficiency has been studied as a function of pH, Cu(II) concentration, ionic strength, temperature and contact time. Evaluation of the experimental data shows that the MnO2-coated product presents the highest adsorption capacity, followed by the non-treated and phosphorylated material. Regarding the effect of ionic strength/salinity on the adsorption, in contrast to the removal efficiency of the phosphorylated product, which is significantly affected, the MnO2-coated and non-treated material don't show any effect, indicating the formation of inner-sphere surface complexes. The adsorption reaction is in all cases endothermic and relatively fast, particularly the adsorption on the MnO2-coated product. The results of the present study indicate that for the removal of bivalent metal-ions from contaminated waters the MnO2-coated material is expected to be the most effective adsorbent and an alternative to MnO2 resins for the treatment of environmentally relevant waters.

Hydrophilic olive cake extracts: characterization by physicochemical properties and Cu(II) complexation.

Disposed olive cake generates hydrophilic components that can be mobilized in the aquatic environment. This paper deals with the characterization of such components, isolated by alkaline extraction. It is shown that these substances possess properties very much resembling humic acid, including a substantial inventory of proton exchanging groups. Extraction and purification of the hydrophilic components from the disposed olive cake was performed by the standard approach for isolation of humic acids from solid sources, i.e. alternating alkaline dissolution and acid flocculation, leaving the purified extract in the protonated form. The purified sample was characterized by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Fourier Transform Infra Red Spectroscopy (FTIR), UV-vis, Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and Asymmetrical Flow Field-Flow Fractionation (AFFFF). The complex formation properties were investigated by potentiometry using Cu(II) ion selective electrode under atmospheric conditions at I=0.1M NaClO(4) (aqueous solution) and pH 6. The formation constant for the CuHA complex is found to be logbeta=5.3+/-0.4 which is close to the corresponding value (logbeta=5.2+/-0.4) obtained from similar investigations with the commercially available Aldrich humic acid (this study) and corresponding published values for various humic acids. Both, structural properties and complex formation data show that the olive cake extract has considerable similarities with humic acids from different sources, pointing towards potential similarities in environmental behavior and impact.

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 (2x10(-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.

Uranium chemistry in stack solutions and leachates of phosphogypsum disposed at a coastal area in Cyprus.

The effect of the matrix composition (main constituents) on the concentration and chemical behavior of uranium in phosphogypsum stack solutions and leachates has been investigated. Solid and aqueous samples were taken from three different sub-areas of a phosphogypsum stack at a coastal area in Vasilikos (Cyprus). The sub-areas are characterized whether by their acidity (e.g. "aged" and "non-aged" phosphogypsum) or by their salt content, originating from pulping water during wet stacking or (after deposition) from the adjacent sea. Measurements in stack solutions and leachates showed that phosphogypsum characteristics affect both, the concentration and the chemical behavior of uranium in solution. Uranium concentration in solutions of increased salinity is up to three orders of magnitude higher than in solutions of low salinity and this is attributed to the effect of ionic strength on the solubility of phosphogypsum. Modelling showed that uranium in stack solutions is predominantly present in the form of uranium(VI) phosphate complexes (e.g. UO(2)(H(2)PO(4))(2), UO(2)HPO(4)), whereas in leachates uranium(VI) fluoro complexes (e.g. UO(2)F(2), UO(2)F(3)(-)) are predominant in solution. The latter indicates that elution of uranium from phosphogypsum takes places most probably in the form of fluoro complexes. Both, effective elution by saline water and direct migration of uranium to the sea, where it forms very stable uranium(VI) carbonato complexes, indicate that the adjacent sea will be the final receptor of uranium released from Vasilikos phosphogypsum.

Radon levels in Cyprus.

Radon levels in atmospheric and aquatic systems in Cyprus have recently been measured using the radon monitor Alpha Guard. Indoor and outdoor radon levels were obtained in situ, whereas analysis of radon concentrations in water was performed using tap and ground water samples collected from several areas of the island. The average value for outdoor and indoor radon concentration is 11+/-10 and 7+/-6 Bq m(-3), respectively, and for tap and ground water 0.4 Bq l(-1) and 1.4 Bq l(-1), respectively. From these data the annual dose equivalent of airborne radon to the Cypriot population is about 0.19 mSv y(-1), which is quite low compared to the total dose equivalent of natural and man-made ionising radiation in Cyprus. Radon levels in aquatic systems are relatively low due to an exhaustive utilisation of ground water resources and also to the increased input of desalinated sea water in the water distribution network and eventually into the ground water reservoirs.

Molecular factors affecting the complex formation between deferiprone (L1) and Cu(II). Possible implications on efficacy and toxicity.

Deferiprone (1,2-dimethyl-3-hydroxypyrid-4-one, L1, CAS 30652-11-0) is a new chelating drug used worldwide for the treatment of iron overloading conditions. Spectrophotometric and potentiometric measurements were carried out to investigate the interaction of L1 with Cu(II) ions under different conditions. The complexation of Cu(II) ions with L1 in aqueous solution leads predominantly to the formation of the Cu(L1)2 species at a pH range of 4-9. The experimental results indicate that L1 has high affinity for Cu(II) with stability constants log beta 11 = 10.3 +/- 0.9 and log beta 12 = 19.2 +/- 0.6. The effect of Cu(II) ions on the affinity of L1 for Fe(III) ions by competition reactions in vitro indicate displacement of Fe(III) in a concentration dependent manner by Cu(II). Similarly, the presence of different buffers at various pH values resulted in the formation of different stoichiometry L1 complexes with Cu(II) and of mixed complexes with buffer anions. The strong interaction of L1 with Cu(II) may have implications on the therapeutic and toxicological properties of this chelating drug. In particular, L1 may be used in the treatment of copper overloading conditions, such as Wilson's disease or other conditions where copper toxicity is implicated.