Regional radiation risk and vulnerability assessment by integration of mathematical modelling and GIS analysis

The Kola Peninsula, Russian Arctic exceeds all other regions in the world in the number of nuclear reactors. The study was aimed at estimating possible radiation risks to the population in the Nordic countries in case of a severe accident in the Kola Peninsula. Two approaches were tested: (1) probabilistic analysis of modelled possible pathways of radionuclide transport and precipitation and (2) deterministic approach (case studies) for most possible or worst-case scenarios of modelled transport and deposition of radionuclides. For the general population, Finland is at most risk with respect to the Kola nuclear power plant (NPP) because of (a) relatively high population density or proximity to the radiation-risk sites and (b) rather high probability of an airflow trajectory there and precipitation. After considering the critical group, northern counties in Norway, Finland and Sweden appear to be most vulnerable. The case scenarios demonstrate that population in many counties in each country, both near and far away from a nuclear site, might be subject to high risk depending on the meteorological situation.     

Mineralisation of Monuron photoinduced by Fe(III) in aqueous solution

The degradation of Monuron (3-(4-chlorophenyl)-1,1-dimethylurea) photoinduced by Fe(III) in aqueous solution has been investigated. The rate of degradation depends on the concentration of Fe(OH)2+, the most photoreactive species in terms of *OH radical formation. These *OH radicals are able to degrade Monuron until total mineralisation. The primordial role of the speciation of Fe(III)-hydroxy complex in aqueous solution, for the efficiency of the elimination of pollutant, was shown and explained in detail. The formation of Fe(II) in the irradiated solution was monitored and correlated with the total organic carbon evolution. Degradation photoproducts were identified and a mechanism of degradation is proposed.     

238Pu, 239,240Pu, 241Am, 90Sr and 137Cs in soils around nuclear research centre Rez, near Prague

Forty-four soil samples were taken around the nuclear research centre Rez, near Prague. The mean activity concentrations of 238Pu, 239,240Pu, 241Am, 90Sr and 137Cs in uncultivated soil were 0.010, 0.26, 0.12, 2.7 and 23 Bq.kg(-1), respectively. Contents of radionuclides in cultivated soil were lower and in forest soil higher than in uncultivated soil. The mean activity ratios of 238Pu/239,240Pu, 241Am/239,240Pu, 90Sr/239,240Pu and 239,240Pu/137Cs in uncultivated soil were 0.041, 0.47, 10.9 and 0.013, respectively. The mean activity ratios in cultivated and forest soils were close to the values given above. It follows from the results that the source of 239,240Pu, 90Sr and 137Cs in the studied area is deposition from atmospheric nuclear tests, in the case of 137Cs also deposition from Chernobyl accident. The contribution of the research centre effluents was not proved for these radionuclides. Increased activity ratio of 241Am/239,240Pu indicates the presence of 241Am in the soils studied emanating from sources other than nuclear tests. Uniform distribution of the 241Am/239,240Pu activity ratio around the nuclear research centre and the absence of an area with evidently higher activity ratio, including at sites lying in the main wind direction, suggest that the additional activity of 241Am does not originate from the nuclear research centre. The additional source might be the deposition following the Chernobyl accident.     

Assessing the economic impact of invasive species: the case of yellow starthistle (Centaurea solsitialis L.) in the rangelands of Idaho, USA

Yellow starthistle (Centaurea solsitialis L.) is an invasive weed that creates problems for the management of Idaho's rangelands. A bioeconomic approach combined with an input-output economic model is used to estimate direct and secondary economic costs of the weed in relation to its interference with agricultural and non-agricultural benefits that rangelands provide. Direct economic costs of the infestations were estimated to be of 8.2 million '05 dollars per year, and secondary costs of 4.5 million '05 dollars per year, for a total of 12.7 million '05 dollars; agricultural related economic impacts accounted for 79% of this total cost, and non-agricultural for 21%.     

Metal/metalloid contamination and isotopic composition of lead in edible mushrooms and forest soils originating from a smelting area

High metal contents in edible mushrooms growing in severely contaminated industrial areas pose an important toxicological risk. In the presented study, trace element (Pb, Cd, Zn, Cu, Ag, As, Se) contents were determined in caps and stipes of three different edible mushroom species (Boletus edulis Bull. Fr., Xerocomus badius Fr. Gilb., Xerocomus chrysenteron Bull. Quél.). Additionally, information about the chemical fractionation of metals in separate soil horizons and Pb isotopic data from soils and fruiting bodies allowed a more detailed insight on the uptake mechanisms of metals by the studied mushroom species. Total metal and metalloid concentrations in the organic soil horizons reached 36234 mg Pb kg(-1); 11.9 mg Cd kg(-1); 519 mg Zn kg(-1); 488 mg Cu kg(-1); 25.1 mg Ag kg(-1); 120 mg As kg(-1) and 5.88 Se mg kg(-1). In order to evaluate the accumulation capacity of the studied species, bioconcentration factors (BCF) were calculated for separate trace elements. For selected metals (Pb, Cd, Zn, Cu), a modified BCF calculation (using EDTA-extractable concentrations of metals in soil) was proposed. High contents of Pb (up to 165 mg kg(-1)) and Cd (up to 55 mg kg(-1)) exceeded all the regulatory limits in all the studied species. This was also the case for Se (up to 57 mg kg(-1)) in B. edulis. Intensive consumption of this species grown in such polluted areas can therefore pose toxicological risks for human health. A novel finding was that X. badius can act as an Ag accumulating species when grown at polluted sites due to the high concentrations of Ag (up to 190 mg kg(-1)) in caps. Pb isotopic data showed that Pb originating from the recent air pollution control residues is present mainly in the exchangeable/acid-extractable fraction of the organic horizons and is taken up by fruiting bodies; especially in the case of B. edulis, where fast Pb accumulation occurs. Due to the high species-dependent variations of metal contents, the studied mushrooms are not suitable as bioindicators of environmental pollution.     

Colonization of surfaces by phenolic compounds utilizing microorganisms

The aim of the present study is to determine optimal adhesive interaction of phenolic compounds utilizing Candida maltosa and Rhodococcus erythropolis when adhering to kaolin, silicone, synthetic foil (Steriking R40) and fluorinated silicones, comparing cell and support surface hydrophobicity. In parallel, the interfering effect of detergents was investigated. Data obtained show that the less hydrophobic supports display high initial cell adhesion when contacted with the cell type with a lower surface hydrophobicity (yeast cell) but most stable yeast biofilms are those formed on highly hydrophobic fluorinated silicones. On the other hand, support hydrophobicity has no effect on bacterial cell detachment; however, bacterial biofilms are denser when growing on more hydrophobic supports. Both detergents interfere (independently on the cell type) with the early and late phases of biofilm development.     

Increased thyroid volume and frequency of thyroid disorders signs in schoolchildren from nitrate polluted area

Thyroid volume (ThV) and echogenicity by ultrasound were estimated in 324 schoolchildren (aged between 10 and 13-years) from high nitrate area (HNA) located in agricultural lowland with high nitrate drinking water supply (51-274 mg/l) from shallow wells. The data were compared to children of the same age from low nitrate area (LNA) consisting of 168 children from the neighboring area with very low nitrate (< 2 mg/l) drinking water and of 596 children from the city of Kosice located in a vicinity of LNA and also supplied by low nitrate water. Blood samples were obtained from 315 willing children from HNA and 109 children from LNA and the levels of thyrotropin (TSH), total thyroxine (TT4), free triiodothyronine (FT3) and thyroperoxidase antibodies (anti-TPO) in serum were determined. ThV (mean +/- SE) in 10-year (5.10 +/- 0.14 ml) and 13-year (5.97 +/- 0.11 ml) old children from HNA was significantly higher than that in two groups of respective age from LNA, 4.58 +/- 0.17 (p < 0.02) and 5.23 +/- 0.15 ml (p < 0.05), and from the city of Kosice, 4.77 +/- 0.10 ml (p < 0.05) and 4.87 +/- 0.1 0ml (p < 0.0001). The frequency of hypoechogenicity in HNA was also significantly higher than that in pooled LNA plus Kosice, 13.7% vs. 4.7% (p < 0.01) in 10-year and 10.6% vs. 5.7% (p < 0.03) in 13-year, respectively. The frequency of TSH level in the range of subclinical hypothyroidism (> 4.0 mU/l) in pooled age groups from HNA was 13/324 (4.0%) and that of positive anti-TPO was 8/324 (2.5%), while no case of either increased TSH or positive anti-TPO was found in 109 children from LNA. Finally, no differences in the levels of TT4 and FT3 were found between HNA and LNA. It was concluded that long-term exposure to high nitrate intake by drinking water and home made meals from local products results in increased thyroid volume and increased frequency of signs of subclinical thyroid disorders (thyroid hypoechogenicity by ultrasound, increased TSH level and positive anti-TPO).