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

The distinctive population structure of Colletotrichum species associated with olive anthracnose in the Algarve region of Portugal reflects a host–pathogen diversity hot spot

Anthracnose (Colletotrichum spp.) is an important disease of olive fruits. Diversity and biogeographic relationships of the olive anthracnose pathogens in the Algarve (Portugal) were investigated, along with host association patterns and disease levels during 2004–2007, to test the hypothesis that this region is a host–pathogen diversity hot spot. Diverse Colletotrichum acutatum and Colletotrichum gloeosporioides populations were identified based on rRNA-internal transcribed spacer and partial β-tubulin 2 gene sequences of 95 isolates. Spatial and temporal variations in the occurrence of the eight genetic entities of the pathogens were linked to olive biogeography. Disease occurrence patterns suggest that C. acutatum populations are more stable pathogens, while C. gloeosporioides populations appear to be more influenced by favourable conditions. Three unique C. acutatum populations were identified, but none of the eight populations were dominant, with the most frequent type representing only 27%. Thus, the population structure of olive anthracnose pathogens in the Algarve is distinct from other parts of Portugal and other world locations, where only one or two genetic entities are dominant. This pattern and level of genetic diversity in a restricted area, where oleaster (wild olive tree), ancient landraces and modern cultivars of olive occur in close proximity, suggests the Algarve as a centre of diversity of the anthracnose pathogens and corroborates recent work suggesting western Mediterranean as an important centre of olive diversity and domestication

Uptake of uranium by lettuce (Lactuca sativa L.) in natural uranium contaminated soils in order to assess chemical risk for consumers

Uranium mining activity in Cunha Baixa (Portugal) village has left a legacy of polluted soils and irrigation water. A controlled field experiment was conducted with lettuce (Lactuca sativa L.) in an agricultural area nearby the abandoned mine in order to evaluate uranium uptake and distribution in roots and leaves as well as ascertain levels of uranium intake by the local inhabitants from plant consuming. Two soils with different average uranium content (38 and 106 mg/kg) were irrigated with non-contaminated and uranium contaminated water (100 μg/l). A non-contaminated soil irrigated with local tap water (<1 μg/l uranium) was also used as a control. Uranium in lettuce tissues was positively correlated with soil uranium content, but non-significant differences were obtained from contaminated soils irrigated with different water quality. Uranium in plants (dry weight) growing in contaminated soils ranged from 0.95 to 6 mg/kg in roots and 0.32 to 2.6 mg/kg in leaves. Lettuce bioconcentration is more related to available uranium species in water than to its uranium concentration. Translocated uranium to lettuce leaves corresponds to 30% of the uranium uptake whatever the soil or irrigation water quality. A maximum uranium daily intake of 0.06 to 0.12 μg/kg bodyweight day was estimated for an adult assuming 30 to 60 g/day of lettuce is consumed. Although this value accounts for only 10% to 20% of the recommended Tolerable Daily Intake for ingested uranium, it still provides an additional source of the element in the local inhabitants’ die

Metastability and Nucleation for the Blume-Capel Model. Different mechanisms of transition

We study metastability and nucleation for the Blume-Capel model: a ferromagnetic nearest neighbour two-dimensional lattice system with spin variables taking values in -1,0,+1. We consider large but finite volume, small fixed magnetic field h and chemical potential "lambda" in the limit of zero temperature; we analyze the first excursion from the metastable -1 configuration to the stable +1 configuration. We compute the asymptotic behaviour of the transition time and describe the typical tube of trajectories during the transition. We show that, unexpectedly, the mechanism of transition changes abruptly when the line h=2*lambda is crossed.Comment: 96 pages, 44 tex-figures, 7 postscript figure

Are uranium-contaminated soil and irrigation water a risk for human vegetable consumers? A study case with Solanum tuberosum L., Phaseolus vulgaris L. and Lactuca sativa L.

The knowledge of uranium concentration, in the products entering the human diet is of extreme importance because of their chemical hazard to health. Controlled field experiments with potatoes, beans and lettuce (Solanum tuberosum L., Phaseolus vulgaris L. and Lactuca sativa L.) were carried out in a contaminated soil used by local farmers located near a closed Portuguese uranium mine (Cunha Baixa, Mangualde). The soil with high average uranium levels (64–252 mg/kg) was divided in two plots, and irrigated with non-contaminated and uranium-contaminated water (\20 and [900 lg/L). Uranium maximum average concentration in the edible vegetables parts (mg/kg fresh weight) ranged in the following order: lettuce (234 lg/kg)[green bean (30 lg/kg)[potatoes without peel (4 lg/kg). Although uranium in soil, irrigation water and vegetables was high, the assessment of the health risk based on hazard quotient indicates that consumption of these vegetables does not represent potential adverse (no carcinogenic) effects for a local inhabitant during lifetime