阴-阳离子有机膨润土制备及其对铅离子的吸附

用十八烷基三甲基溴化铵（STAB）和十二烷基苯磺酸钠（SDBS）共同改性膨润土制备阴．阳离子有机膨润土,并用红外光谱分析法、热分析法和X粉晶衍射分析进行了表征;考察了阴-阳离子有机膨润土对铅离子的吸附性能。结果表明,用0．5CEC（cationexchangecapacity）十八烷基三甲基溴化铵和0．4CEC十二烷基苯磺酸钠改性的膨润土吸附铅的效果最佳;阴-阳离子有机膨润土吸附铅离子的能力比改性前明显增加,达到吸附平衡所需要的时间缩短;pH值强烈影响有机膨润土对铅离子吸附;有机膨润土对铅离子等温吸附过程符合Langmuir吸附模型;吸附热力学分析表明该吸附是一个放热过程,降低温度有利于铅离子的吸附。     

Distance-dependent varieties of microbial community structure and metabolic functions in the rhizosphere of Sedum alfredii Hance during phytoextraction of a cadmium-contaminated soil

Environmental Science and Pollution Research - The recovery of microbial community and activities is crucial to the remediation of contaminated soils. Distance-dependent variations of microbial...     

Classification and identification of metal-accumulating plant species by cluster analysis

Identification and classification of metal-accumulating plant species is essential for phytoextraction. Cluster analysis is used for classifying individuals based on measured characteristics. In this study, classification of plant species for metal accumulation was conducted using cluster analysis based on a practical survey. Forty plant samples belonging to 21 species were collected from an ancient silver-mining site. Five groups such as hyperaccumulator, potential hyperaccumulator, accumulator, potential accumulator, and normal accumulating plant were graded. For Cd accumulation, the ancient silver-mining ecotype of Sedum alfredii was treated as a Cd hyperaccumulator, and the others were normal Cd-accumulating plants. For Zn accumulation, S. alfredii was considered as a potential Zn hyperaccumulator, Conyza canadensis and Artemisia lavandulaefolia were Zn accumulators, and the others were normal Zn-accumulating plants. For Pb accumulation, S. alfredii and Elatostema lineolatum were potential Pb hyperaccumulators, Rubus hunanensis, Ajuga decumbens, and Erigeron annuus were Pb accumulators, C. canadensis and A. lavandulaefolia were potential Pb accumulators, and the others were normal Pb-accumulating plants. Plant species with the potential for phytoextraction were identified such as S. alfredii for Cd and Zn, C. canadensis and A. lavandulaefolia for Zn and Pb, and E. lineolatum, R. hunanensis, A. decumbens, and E. annuus for Pb. Cluster analysis is effective in the classification of plant species for metal accumulation and identification of potential species for phytoextraction.     

Survival of Escherichia coli O157:H7 in soils under different land use types

Laboratory studies on Escherichia coli O157:H7 survival in soils from four different land use types: forest, tea plantation, bamboo grove, and vegetable garden were investigated at 25?±?1 °C with the field capacity (soil water content at ?33 kPa). Results showed that E. coli O157:H7 declined quickly in the test soils, but its survival dynamics varied in the soils under different land use types. The survival time needed to reach the detection limit (t _d) in the test soils ranged from 2.1 to 3.6 days, with slightly longer t _d values being observed in soils from the bamboo grove. Stepwise multiple regression analysis revealed that the t _d values were shorter in sandy, lower pH, and lower organic carbon content soils. Different E. coli O157:H7 survival time in the soils under different land uses suggests that it is important to adapt proper management practices for reducing the potential risks of pathogen contamination when diary manure is applied to agricultural land.