Enargite (Cu 3 AsS 4 ) was leached faster by bacteria in sulfuric acid medium (pH 1.6) with added... more Enargite (Cu 3 AsS 4 ) was leached faster by bacteria in sulfuric acid medium (pH 1.6) with added ferric sulfate than by chemical leaching at the same or higher iron concentration. During chemical leaching with ferric iron, the copper dissolution rate decreased from an initial value of 0.03% per hour to a value of 0.002% per hour. Enargite is oxidized to elemental sulfur and dissolved arsenic (As 3+ and As 5+ ). Less than 10% of sulfur is oxidized to sulfate. The arsenic and copper dissolutions observed in bacterial leaching experiments suggest the existence of a specific bacterial action on the leaching of enargite, demonstrated by the ability of bacteria to oxidize enargite at very low concentration of dissolved iron and by the higher dissolution rate obtained in bacterial leaching compared to chemical ferric leaching.
Enargite (Cu3AsS4) was leached at 70 °C by Sulfolobus BC in shake-flasks. The highest copper diss... more Enargite (Cu3AsS4) was leached at 70 °C by Sulfolobus BC in shake-flasks. The highest copper dissolution (52% after 550 h of leaching) was obtained with bacteria and 1 g l−1 ferric ion. In the absence of ferric ion, Sulfolobus BC catalyzes the bioleaching of enargite through a direct mechanism after adhesion onto the mineral surface. In ferric bioleaching, arsenic precipitated as ferric arsenate and arsenic remained associated to the solid residues, preventing the presence of a high dissolved arsenic concentration in the leaching solution. About 90% inhibition of bacterial growth rate and activity was observed for dissolved arsenic concentrations above 600 mg l−1 for As(III) and above 1000 mg l−1 for As(V). Arsenic-bearing copper ores and concentrates could be leached by Sulfolobus BC in the presence of ferric iron due to the favourable precipitation of arsenic ion as ferric arsenate, avoiding significant bacterial inhibition.
Stressors of various kinds constantly affect fish both in the wild and in culture, examples being... more Stressors of various kinds constantly affect fish both in the wild and in culture, examples being acute water temperature and quality changes, predation, handling, and confinement. Known physiological responses of fish to stress such as increases in plasma cortisol and glucose levels, are considered to be adaptive, allowing the animal to cope in the short term. Prolonged exposure to stressors however, has the potential to affect growth, immune function, and survival. Nonetheless, little is known about the mechanisms underlying the long-term stress response. We have investigated the metabolic response of juvenile Atlantic salmon (Salmo salar) to long-term handling stress by analyzing fish plasma via 1H nuclear magnetic resonance spectroscopy and ultra high performance liquid chromatography–mass spectrometry (UPLC–MS), and comparing results with controls. Analysis of NMR data indicated a difference in the metabolic profiles of control and stressed fish after 1 week of stress with a maximum difference observed after 2 weeks. These differences were associated with stress-induced increases in phosphatidyl choline, lactate, carbohydrates, alanine, valine and trimethylamine-N-oxide, and decreases in low density lipoprotein, very low density lipoprotein, and lipid. UPLC-MS data showed differences at week 2, associated with another set of compounds, tentatively identified on the basis of their mass/charge. Overall the results provided a multi-faceted view of the response of fish to long-term handling stress, indicating that the metabolic disparity between the control and stress groups increased to week 2, but declined by weeks 3 and 4, and revealed several new molecular indicators of long-term stress.
Enargite (Cu 3 AsS 4 ) was leached faster by bacteria in sulfuric acid medium (pH 1.6) with added... more Enargite (Cu 3 AsS 4 ) was leached faster by bacteria in sulfuric acid medium (pH 1.6) with added ferric sulfate than by chemical leaching at the same or higher iron concentration. During chemical leaching with ferric iron, the copper dissolution rate decreased from an initial value of 0.03% per hour to a value of 0.002% per hour. Enargite is oxidized to elemental sulfur and dissolved arsenic (As 3+ and As 5+ ). Less than 10% of sulfur is oxidized to sulfate. The arsenic and copper dissolutions observed in bacterial leaching experiments suggest the existence of a specific bacterial action on the leaching of enargite, demonstrated by the ability of bacteria to oxidize enargite at very low concentration of dissolved iron and by the higher dissolution rate obtained in bacterial leaching compared to chemical ferric leaching.
Enargite (Cu3AsS4) was leached at 70 °C by Sulfolobus BC in shake-flasks. The highest copper diss... more Enargite (Cu3AsS4) was leached at 70 °C by Sulfolobus BC in shake-flasks. The highest copper dissolution (52% after 550 h of leaching) was obtained with bacteria and 1 g l−1 ferric ion. In the absence of ferric ion, Sulfolobus BC catalyzes the bioleaching of enargite through a direct mechanism after adhesion onto the mineral surface. In ferric bioleaching, arsenic precipitated as ferric arsenate and arsenic remained associated to the solid residues, preventing the presence of a high dissolved arsenic concentration in the leaching solution. About 90% inhibition of bacterial growth rate and activity was observed for dissolved arsenic concentrations above 600 mg l−1 for As(III) and above 1000 mg l−1 for As(V). Arsenic-bearing copper ores and concentrates could be leached by Sulfolobus BC in the presence of ferric iron due to the favourable precipitation of arsenic ion as ferric arsenate, avoiding significant bacterial inhibition.
Stressors of various kinds constantly affect fish both in the wild and in culture, examples being... more Stressors of various kinds constantly affect fish both in the wild and in culture, examples being acute water temperature and quality changes, predation, handling, and confinement. Known physiological responses of fish to stress such as increases in plasma cortisol and glucose levels, are considered to be adaptive, allowing the animal to cope in the short term. Prolonged exposure to stressors however, has the potential to affect growth, immune function, and survival. Nonetheless, little is known about the mechanisms underlying the long-term stress response. We have investigated the metabolic response of juvenile Atlantic salmon (Salmo salar) to long-term handling stress by analyzing fish plasma via 1H nuclear magnetic resonance spectroscopy and ultra high performance liquid chromatography–mass spectrometry (UPLC–MS), and comparing results with controls. Analysis of NMR data indicated a difference in the metabolic profiles of control and stressed fish after 1 week of stress with a maximum difference observed after 2 weeks. These differences were associated with stress-induced increases in phosphatidyl choline, lactate, carbohydrates, alanine, valine and trimethylamine-N-oxide, and decreases in low density lipoprotein, very low density lipoprotein, and lipid. UPLC-MS data showed differences at week 2, associated with another set of compounds, tentatively identified on the basis of their mass/charge. Overall the results provided a multi-faceted view of the response of fish to long-term handling stress, indicating that the metabolic disparity between the control and stress groups increased to week 2, but declined by weeks 3 and 4, and revealed several new molecular indicators of long-term stress.
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Papers by Elizabeth Huenupi