Bench-scale soil column experiments were carried out to evaluate the effectiveness of Cr（VI） bioremediation process in soils by using indigenous bacteria with the addition of bacteria nutrient media. Effects of part...Bench-scale soil column experiments were carried out to evaluate the effectiveness of Cr（VI） bioremediation process in soils by using indigenous bacteria with the addition of bacteria nutrient media. Effects of particle size, spray intensity, initial Cr（VI） concentration, circulation mode and soil depth on Cr（VI） remediation were studied. Results show that soils after 6 d remediation with spray intensity controlled in the range of 29.6-59.2 mL/min could well fulfill the requirement of concrete aggregate and roadbed material usage, for the leaching toxicity concentration of the Cr（VI） in treated soils under the chosen condition is far less than 5 mg/L The leaching toxicity and fractions of both hexavalent chromium and trivalent chromium from remediated soils were determined and compared with that of untreated soil. The results show that water soluble Cr（VI） declines from 1520.54 mg/kg to 0.68 mg/kg, exchangeable Cr（VI） decreases from 34.83 mg/kg to 0.01 mg/kg and carbonates-bonded Cr（V1） falls from 13.55 mg/kg to 0.68 mg/kg. Meanwhile, a corresponding increase in carbonate-bonded Cr（III）, Fe and Mn oxides-bonded Cr（III） and organic matter-bonded Cr（III） are found. It reveals that indigenous bacteria can leach out water soluble Cr（VI）, exchangeable Cr（VI） and carbonates-bonded Cr（VI） from contaminated soil followed by converting into carbonate-bonded Cr（III）, Fe and Mn oxides-bonded Cr（IlI）, organic matter-bonded Cr（III） and residual Cr（III）.展开更多
The amount of microbeads ingested by Daphnia magna decreases on exposure to toxic materials; tins oenawor was used to develop a toxicity test. To determine the toxicity of seven metals, D. magna were collected and hom...The amount of microbeads ingested by Daphnia magna decreases on exposure to toxic materials; tins oenawor was used to develop a toxicity test. To determine the toxicity of seven metals, D. magna were collected and homogenized, and the fluorescence intensity of the microbeads ingested by D. magna was measured. The amount of ingestion was determined from fluorescence intensity. The fluorescence intensity was half of that of the controls which was measured as the 30 min-FI50, and these data correlated well with those from an acute immobilization method （24 h-EC50）. An advantage of the method using fluorescent beads is that an estimate of the 24 h-EC50 can be obtained.展开更多
基金Project(50925417) supported by the National Funds for Distinguished Young Scientist, ChinaProject(50830301) supported by the Key Program of National Natural Science Foundation of ChinaProject(51074191) supported by the National Natural Science Foundation of China
文摘Bench-scale soil column experiments were carried out to evaluate the effectiveness of Cr（VI） bioremediation process in soils by using indigenous bacteria with the addition of bacteria nutrient media. Effects of particle size, spray intensity, initial Cr（VI） concentration, circulation mode and soil depth on Cr（VI） remediation were studied. Results show that soils after 6 d remediation with spray intensity controlled in the range of 29.6-59.2 mL/min could well fulfill the requirement of concrete aggregate and roadbed material usage, for the leaching toxicity concentration of the Cr（VI） in treated soils under the chosen condition is far less than 5 mg/L The leaching toxicity and fractions of both hexavalent chromium and trivalent chromium from remediated soils were determined and compared with that of untreated soil. The results show that water soluble Cr（VI） declines from 1520.54 mg/kg to 0.68 mg/kg, exchangeable Cr（VI） decreases from 34.83 mg/kg to 0.01 mg/kg and carbonates-bonded Cr（V1） falls from 13.55 mg/kg to 0.68 mg/kg. Meanwhile, a corresponding increase in carbonate-bonded Cr（III）, Fe and Mn oxides-bonded Cr（III） and organic matter-bonded Cr（III） are found. It reveals that indigenous bacteria can leach out water soluble Cr（VI）, exchangeable Cr（VI） and carbonates-bonded Cr（VI） from contaminated soil followed by converting into carbonate-bonded Cr（III）, Fe and Mn oxides-bonded Cr（IlI）, organic matter-bonded Cr（III） and residual Cr（III）.
文摘The amount of microbeads ingested by Daphnia magna decreases on exposure to toxic materials; tins oenawor was used to develop a toxicity test. To determine the toxicity of seven metals, D. magna were collected and homogenized, and the fluorescence intensity of the microbeads ingested by D. magna was measured. The amount of ingestion was determined from fluorescence intensity. The fluorescence intensity was half of that of the controls which was measured as the 30 min-FI50, and these data correlated well with those from an acute immobilization method （24 h-EC50）. An advantage of the method using fluorescent beads is that an estimate of the 24 h-EC50 can be obtained.
