Pollution sources in Cunha Baixa uranium mining area (Viseu, Portugal)

[Abstract] One of the most significant environmental issues that have arisen in the abandoned Cunha Baixa uranium mine area is the Acid Drainage (AD). Downward the mining site AD affects surface and irrigation water quality. ln order to evaluate their contribution as a pollution source, this paper discusses: i) the composition of mine water, pit lake water and effluent water discharged after chemical treatment and settling, and ii) the conrribution of rocks and mine wastes as acid generators materials. Pit lake and mine waters are acidic (pH 3- 4) with high 226 Ra activity (1.8-12 Bq/l), sulphate (1000-2400 mg/l) and heavy metals concentration (Al: 8-70 mg/l; Mn: 4-35 mg/l; Fe: 1-55 mg/l; U: 1.2-6.3 mg/l; Zn: 0.5-2.9 mg/l). ln spite of mine water treatment and settling efficiency to remove the main dissolved species (50-80 %), the overflow effluent can be a source of pollution, due to high contents of sulphate, uranium as well fluorine and calei um. The chemical treatment was also responsible for the water hardness in this granitic region. Rocks and mine wastes submitted to static and kinetic laboratory tests (Acid-Base accounting test and Humidity Cell test) did not show capacity to generate acid drainage from sulphide oxidation through testing rime, nevertheless Thiobacillus ferrooxidans bacterium was detected in mine waters. However, the open pit wastes showed low acid neutralising potential and capacity to generate an acid leachate (pH < 5) with potentialities to release sulphate and heavy metals. The running water or the pit lake water percolating through these wastes was able to mobilise elements and increase its dispersion by contínuos contaminating leaching. The acid drainage in Cunha Baixa can be the remaining result of heap leaching process used in past, to recover uranium from low-grade ore when opening the pit area, although this process ceased in 1993

Uncertainties in import/export studies and the outwelling theory. An analysis with the support of hydrodynamic modelling

According to the “outwelling theory”, salt marshes are net exporters of primary production. This view has been contested, inducing a considerable interest in the subject. Both theses are based on annual budgets of organic matter exchange across salt marsh boundaries. These budgets are a function of integrated fluxes computed from water discharge and concentration of solutes and suspensates. Inaccuracies can follow from errors in velocity measurement and subsequent flow rate calculations as well as from analytical errors. Furthermore, the oscillatory nature of tidal transport implies that net budgets are at present one order of magnitude lower than total fluxes. Therefore, only rather more accurate methods can lead to safe conclusions on this issue. Moreover, a number of other fundamental uncertainties remain with the processing of organic matter in salt marsh sediments. These questions are discussed within the framework of the results of a European comparative salt marsh study on the Mira estuary in Portugal. Hydrodynamic modelling has been shown to be a useful tool particularly in situations where velocities are most of the time bellow the range of accuracy of commercial current meters (< 5 cm s-1)

Uranium distribution in the solid phases of soils from Cunha Baixa mining site (Portugal)

The present study concerns the application of partial chemical extraction, in a parallel procedure, to evaluate the uranium distribution in different solid phases constituents of the soils in the vicinity of Cunha Baixa mining area in order to assess its environmental risk. In the surface horizon of the soils, uranium that reached total concentrations between 9.8 to 362 mg/kg was preferential bound to non-crystalline iron oxides. These phases represent a small environmental risk. The contaminated irrigation water (>100 μg U/L) and the exchangeable complex of the acidic soils (pH <5), are important sources for the available fraction of uranium for crops (up to 30% of total U). The transference of uranium into the soil-water-plant system could be a factor of risk for Cunha Baixa population through the ingestion of vegetal foodstuffs, due to its possible uranium bioaccumulation capacity

Near-band-edge slow luminescence in nominally undoped bulk ZnO

We report the observation of slow emission bands overlapped with the near-band-edge steady-state luminescence of nominally undoped ZnO crystals. At low temperatures the time-resolved spectra are dominated by the emission of several high-energy bound exciton lines and the two-electron satellite spectral region. Furthermore, two donor-acceptor pair transitions at 3.22 and 3.238 eV are clearly identified in temperature-dependent time-resolved spectroscopy. These donor-acceptor pairs involve a common shallow donor at 67 meV and deep acceptor levels at 250 and 232 meV.FCT/FEDER - POCTI/CTM/45236/0

Limited diversity in natal origins of immature anadromous fish during ocean residency

Author Posting. © The Authors, 2009. This is the author's version of the work. It is posted here by permission of NRC Research Press for personal use, not for redistribution. The definitive version was published in Canadian Journal of Fisheries and Aquatic Sciences. 67 (2010): 1699-1707, doi:10.1139/F10-086.Variable migration patterns can play a significant role in promoting diverse life history traits among populations. However, population and stage specific movement patterns are generally unknown yet crucial aspects of life history strategies in many highly migratory species. We used a natural tag approach using geochemical signatures in otoliths to identify natal origins of one-year-old anadromous American shad (Alosa sapidissima) during ocean residency. Otolith signatures of migrants were compared to a database of baseline signatures from 20 source populations throughout their spawning range. Samples were dominated by fish from only two rivers, while all other potential source populations were nearly or completely absent. These data support the hypothesis that American shad exhibit diverse migratory behaviors and immature individuals from populations throughout the native range do not all mix on northern summer feeding grounds. Rather, our results suggest populations of anadromous fish are distributed heterogeneously at sea in the first year of life and thus may encounter different ocean conditions at a critical early life history stage.This work was funded by National Science Foundation grants OCE-0215905 and OCE-0134998 to SRT and by a WHOI Ocean Life Institute grant to BDW

Electron impact ionization of 1-propanol

Experimental measurements of the cations created in electron impact ionization have been undertaken for the primary isomer of propanol using a Hidden Quadrupole Mass Spectrometer (EPIC 300), with a mass resolution of 1 amu. The mass spectra recorded at an incident electron energy of 70 eV reveals the relative probability of forming 50 different cations, by either direct ionization or dissociative ionization. Individual partial ionization cross sections (PICS) for 31 different cations were measured for the first time in this work, for the incident electron energy range from 10 to 100eV. Also, appearance energies (AEs) and Wannier exponents for the 16 most intense cations formed in electron collisions with 1-propanol are reported. Where possible, those results are compared to those from an earlier investigation. Total Ionization Cross Sections (TICS) were also obtained from the sum of the measured PICS, for nearly all cations measured, and are compared to relevant data reported in the literature. In addition, as a part of this study, theoretical TICS were calculated using the Binary-encounter Bethe (BEB) and independent atom model with screening corrected additivity rule (IAM - SCAR) methods. Good agreement between current measured and calculated TICSs and corresponding earlier results was typically found

Condições fitossanitárias de cereais nos silos da Federação Nacional dos Produtores de trigo (V zona)

info:eu-repo/semantics/publishedVersio

Sugar bislactones by one-step oxidative dimerisation with pyridinium chlorochromate versus regioselective oxidation of vicinal diols

Synthesis of 10-membered bislactones by PCC oxidation of methyl 2,6-di-O-pivaloyl-α-D-glucopyranoside and methyl 4,6-O-benzylidene-α-D-glucopyranoside is described, with emphasis on their structure elucidation using the information gained by combination of NMR spectroscopic techniques with X-ray diffraction data. In alternative, the use of PCC and PCC adsorbed on silica gel or alumina for the regioselective oxidation of vicinal diols in sugars is also reported. Both bislactones showed antifungal activity against Candida albicans, and were slightly active against the bacteria Bacillus subtilis. The bislactone presenting pivaloyl protecting groups also promoted some growth inhibition of Staphylococcus aureus.info:eu-repo/semantics/publishedVersio