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Pyrene and fluoranthene, when supplied as the sole carbon source, were not degraded by Burkholderia sp. VUN10013. However, when added in a mixture with phenanthrene, both pyrene and fluoranthene were degraded in liquid broth and soil. The amounts of pyrene and fluoranthene in liquid media (initial concentrations of 50 mg l À1 each) decreased to 42.1% and 41.1%, respectively, after 21 days. The amounts of pyrene and fluoranthene in soil (initial concentrations of 75 mg kg À1 dry soil each) decreased to 25.8% and 12.1%, respectively, after 60 days. None of the high molecular weight (HMW) polycylic aromatic hydrocarbons (PAHs) tested adversely affected phenanthrene degradation by this bacterial strain and the amount of phenanthrene decreased rapidly within 3 and 15 days of incubation in liquid broth and soil, respectively. Anthracene also stimulated the degradation of pyrene or fluoranthene by Burkholderia sp. VUN10013, but to a lesser extent than phenanthrene. The extent of anthracene degradation decreased in the presence of these HMW PAHs.

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Four selected plants (corn, groundnut, cow pea, and mungbean) were tested for their ability to germinate and grow in an acidic soil contaminated with phenanthrene or pyrene, two typical polycyclic aromatic hydrocarbons (PAHs). The growth of corn root was the least sensitive to, but its germination rate was the lowest in the presence of, contaminants. Among the legumes, the growth of groundnut root was better than others. Corn and groundnut were selected to further test their ability to tolerate a mixture of phenanthrene and pyrene in the acidic soil. The presence of both PAHs led to a greater decrease in the lengths of shoot and root of groundnut than phenanthrene or pyrene alone, but the lengths of shoot and root of corn were decreased to a similar extent as when phenanthrene or pyrene was present alone. The growth of corn root was also better than that of groundnut root when they were grown in oil-contaminated soil. Based on these results, we conclude that corn is the most suitable to be grown in PAH-contaminated acidic soil.

Accidental inhalation of selenium by humans has been associated with damage of respiratory tissues that is lacking a detailed histological definition. We have investigated the natural history of injury to the tracheal epithelium and lungs induced by a single intratracheal instillation of CD-1 mice with two different doses of dimethyl selenide (0.05 and 0.1 mg Se/kg of body weight). The animals were sacrificed 1, 7, 14, and 28 days after the single selenium treatment. Samples of the trachea and lungs were studied by light microscopy. The tracheal epithelium showed loss of cilia and acute necrosis that was followed by metaplastic transformation. Edema and diffuse alveolar damage was observed in the lungs. Our data suggest that: i) severity of respiratory lesions caused by selenium is dose dependent; ii) selenium causes transient metaplastic transformation of the tracheal epithelium; iii) chronic inflammation and increased thickness of alveolar septa occur in the lungs; iv) 4 weeks after selenium treatment, mice recover from the tracheal injury, whereas no amelioration of pulmonary lesions was observed.