罗尔斯通菌去除土壤重金属铅的效能及机制

从矿区土壤分离得到的罗尔斯通菌(Ralstonia Bcul-1)对重金属离子具有广谱抗性,可在重金属铅含量为87.35 mg·kg^(-1)的酸性土壤生长(pH 5.62)。低浓度Pb^(2+)可诱导部分重金属抗性基因表达,但高浓度Pb^(2+)(>15 mg·L^(-1))则抑制这些基因的表达。在Pb^(2+)胁迫下,一些蛋白质的表达同样受到诱导或者抑制。重金属抗性基因和抗性蛋白的表达使Ralstonia Bcul-1能够适应重金属铅污染的生存环境。在含Pb^(2+)的液体培养基中(pH<6.50),Ralstonia Bcul-1菌体对Pb^(2+)的去除效率高达8.22%~29.09%。将Ralstonia Bcul-1接菌到受重金属铅污染的酸性菜园土壤中(pH 5.32,重金属铅总含量为94.37 mg·kg^(-1)),在没有添加任何营养物质的条件下,Ralstonia Bcul-1能持续生长达12 d,并且对土壤悬浮物(包括泥浆)重金属铅的去除效率达到12.71%~24.71%(土壤悬浮物的重金属铅含量为32.67 mg·kg^(-1))。研究结果表明,Ralstonia Bcul-1能在重金属铅污染的酸性菜园土壤中存活,并对土壤悬浮物的重金属铅有较强的去除效率,具有修复土壤重金属铅污染的潜力。

Effects of different conditions on Pb^(2+) adsorption from soil by irrigation of sewage in South China

Pb2＋ adsorption onto a soil by irrigation of sewage in the Pearl River Delta of South China was examined as a function of the reaction time, solution pH, initial lead concentration, organic matter （humic acid） and competitive ions （Cu2＋）. The adsorption of Pb2＋ onto the soil was investigated on batch equilibrium adsorption experiments. Results show that the Pb2＋ adsorption on the soil is relatively rapid in the first 30 min and reaches equilibrium at 2 h, and the kinetics of the adsorption process on the soil is well characterized by the pseudo-second order reaction rate. Langmuir, Freundlich and Temkin isothermal models are fit for the adsorption of Pb2＋ onto the soil, and the maximum amount of Pb2＋ adsorption （Qm） is 7.47 mg/g. The amount of Pb2＋ adsorption increases with increasing the pH at the range of 1.2-4.5 and reaches a plateau at the range of 4.5-12. The presence of humic acid in soil decreases the adsorption of Pb2＋ onto the soil at solution pH of 8 since the negatively charged humic acid with Pb2＋ is difficult to be adsorbed on the negatively charged soil surface. The adsorption of Pb2＋ onto the soil also decreases in the presence of Cu2＋ due to file competition adsorption between Pb2＋ and Cu2＋.

Adsorption Kineties of Pb￣(2+) and Cu￣(2+) on Variable Charge Soils andMinerals V .Effects of Temperature and Ionic Strength￣*1

The study results of the effects of temperature and ionic strength on the adsorption kineties of Pb￣2+ and Cu￣2+ bylatosol, red soil and kaolinte coated with Mn oxide showed that Pb￣2+ and Cu￣2+ adsorption by all samples, as awhole, increased with missing temperature. Temperature also increased both values of X_m (the amount of ionadsorbed at equilibrium) and k (kinetica constant) of Pb￣2+ and Cu￣2+. The activation energies of Pb￣2+ adsorption werekaolin-Mn >red soil>goethite and those of Cu￣2+ were latosol> red soil > kaolin-Mn >goethite. For a given singlesample the activation energy of Cu￣2+ was greater than that of Pb￣2+. Raising ionic strength decreased the adsorptionof Pb￣2+ and Cu￣2+ by latosol, red soil and kaolinite coated with Mn oxide but increased Pb￣2+ and Cu￣2+ adsorption bygoethite. The contrary results could be explained by the different changes in ion forms of Pb￣2+ or Cu￣2+ and in surfacecbarge characteristics of latosol, red soil, kaolin-Mn and goethite. Increasing supporting electrolyte concentration in-creased X_m and k in goethite systems but decreased X_m and k in kaolin-Mn systems. All the time-dependent data fit-ted the surface second-order equation very well.

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals:Ⅰ.Technique

A new technique for studying the adsorption kinetics of heavy metals,Pb^2+ and Cu^2+,on variable charge surfaces was established with two selective electrodes and microcomputer control system.Feasibility of the technique,including interference of other ions (mainly Fe^3+ and Al^3+),response time of electrodes,and the pH range of testing,was studied.Comparision with the most widely used miscible displacement technique,which was considered insufficient in studying 30-minute rapid reactions,at present time showed that the new technique was more advantageous in testing in situ,easy to operate,and economic.

Nickel,Lead and Zinc Sorption in a Reclaimed Settling Pond Soil

The wastes used to amend soils sometimes have high concentrations of metals such as nickel(Ni), lead(Pb) and zinc(Zn). To determine the capacity of soils to retain these metals, the sorption capacities of different mine soils with and without reclamation treatments(tree vegetation and waste amendment) for Ni, Pb and Zn in individual and competitive situations were evaluated using the batch sorption technique. The untreated settling pond soil had low capacity for Ni, Pb and Zn retention. The site amended with wastes(sewage sludges and paper mill residues) increased the sorption capacity most, probably because of the higher concentrations of soil components with high retention capacity such as carbon and clay fraction. No significant competition was observed between metals in the competitive sorption experiment, indicating that the maximum of sorption was not achieved by adding 0.5 mmol L^(-1) of metal. We can conclude that, despite the possible additions of Ni, Pb and Zn from wastes to degraded soils, sewage sludges and paper mill residues have a high sorption capacity that would prevent the metals from being in a mobile form.