金属污染土壤中锌铜交互作用对锌吸附和植物有效性的影响

In a previous greenhouse experiment,we showed that there was an interaction between cu and Zn,which affected growth and metal uptake by young barley plants grown on soil to which Cd,Cu,Pb,and Zn had been added.We suggested that the underlying mechanism was the control of the amount of plant-available Zn by competitive adsorption between Cu and Zn,In order to test this hypothesis,the adsorption of Zn alone,and in the presence of added Cd,Cu and Pb,has been measured using the same soil.Following adsorption,the extractability of the Zn in CaCl2 solution was measured .The adsorption isotherms showed that of the added metals only Cu had a large effect on Zn adsorption.The effect of Cu was to reduce Zn adsoption and to increase the amount of CaCl2-extractable(i.e.plant-available) Zn,in agreement with the conclusions from the greenhouse experiment.The magnitude of the effect of Cu on plant-avalilable Zn was similar in both experiments.     

Effect of Zn Adsorption on Charge of Variable Charge Soils

The variation in appa rent carge of two typical variable charge soils resulting from Zn adsorption were studied by KCl saturation and NH4NO3 replacement methods.Results showed that zinc were adsorbed specifically to those sites with negative charge.As in different pH ranges,the percantages of specific and electrostatic adsorptions of zine and the mechanisms of specific adsorption were different,the effects of Zn adsorption on apparent charge were varied and could be characterized as:when 1 mmol Zn^2 was adsorbed,a change about 1 mmol in the apparent charge was observed in the low pH range(1),1.4 to 1.5mmol in the moderate pH range(II) and 0.55 to 0.6mmol in the high pH range (III).These experimental data,in terms of soil charge,proved once more author‘s conclusion in the preceding paper(Sun,1993) that in accordance with the behaviors of Zn adsorption by the variable charge soils in relation to pH,three pH ranges with different adsorption mechanisms were delineated;that is,in Range I,specific adsorption was the predominant mechanism,in Ranges II and III,specific and electrostatic adsorptions co-existed,but their specific adsorption mechanisms were not identical.     

重重金属离子与简育湿润淋溶土和铁质湿润淋溶土间的结合能和吸附能

Gibbs free binding energy and adsorption energy between cations and charged soil particles were used to evaluate the interactions between ions and soil particles. The distribution of Gibbs free adsorption energies could not be determined experimentally before the development of Wien effect measurements in dilute soil suspensions. In the current study, energy relationships between heavy metal ions and particles of Hapli-Udic Argosol （Alfisol） and Ferri-Udic Argosol were inferred from Wien effect measurements in dilute suspensions of homoionic soil particles （〈 2 μm） of the two soils, which were saturated with ions of five heavy metals, in deionized water. The mean Gibbs free binding energies of the heavy metal ions with Hapli-Udic Argosol and Ferri-Udic Argosol particles diminished in the order of Pb^2＋ 〉 Cd^2＋ 〉 Cu^2＋ 〉 Zn^2＋ 〉 Cr^3＋, where the range of binding energies for Hapli-Udic Argosol （7.25-9.32 kJ mol^-1） was similar to that for Ferri-Udic Argosol （7.43-9.35 kJ mol^-1）. The electrical field-dependent mean Gibbs free adsorption energies of these heavy metal ions for Hapli-Udic Argosol and for Ferri-Udic Argosol descended in the order： Cu^2＋ 〉 Cd2^＋ 〉 Pb^2＋ 〉 Zn^2＋ 〉 Cr^3＋, and Cd^2＋ 〉 Cu^2＋ 〉 Pb^2＋ 〉 Zn^2＋ 〉 Cr^3＋, respectively. The mean Gibbs free adsorption energies of Cu^2＋, Zn^2＋, Cd^2＋, Pb^2＋, and Cr^3＋ at a field strength of 200 kV cm^-1, for example, were in the range of 0.8-3.2 kJ mo1^-1 for the two soils.     

可变电荷或永久电荷土壤上的电荷特征与土壤对Cu2+的吸附－解吸之间的交互作用

Charge characteristics and Cu^2 adsorption-desorption of soils with variable charge(latosol)and permanent charge(brown soil)and the relationship between them were studied by means of back-titration and adsorption equilibrium respectively.The amount of variable negative charge was much less in variable-charge soil than in permanent-charge soil and increased with the pH in the system,but the opposite trend occurred in the points of zero charge(PZCs).The amount of Cu^2 ions sorbed by permanent-charge soil was more than that by variable-charge soil and increased with the increase of Cu^2 concentration within a certain range in the equilibrium solution.The amount of Cu^2 ions desorbed with KCl from permanent-charge soil was more than that from variable-charge soil,but the amount of Cu^2 ions desorbed with de-ionized water from permanent-charge soil was extremely low whereas there was still a certain amount of desorption from variable-charge soil.The increase of PZC of soils with variable or permanent change varied with the increment of Cu^2 ions added.When the same amount of Cu^2 ions was added,the increments of PZC and variable negative surface chargc of permanent-charge soil were different from those of variable-charge soil.     

磷的吸附对老成土和淋溶土中Cu、Zn离子吸附-解吸及其有效性的影响

Surface charge,secondary adsorption-desorption and form distribution of Cu^2 and Zn^2 in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration,adsorption equilibrium and sequential extraction method,respectively,The soil surface negative charges increased whereas the amount sequential extraction method,respectively.The soil surface ngative charges increased whereas the amount of positive charges decreased with increase of P adsorbed,The soil secondary adsorption capacity for Cu^2 and Zn^2 was positively significantly correlated with the amount of P adsorbed by the soils,which could be described by the Langmuir equation.The amounts of Cu^2 and Zn^2 desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear,After the soils adsorbed P,form distribution of Cu^2 and Zn^2 in soils changed remarkably.     

Zn Adsorption by Variable Charge Soils in Relation to pH

Zn adsorption by pure oxides or in the presence of a high concentration of inner electrolyte has been extensively studied.But,in studies on Zn adsorption in the complicated soil system,especially in variable charge soils,profound knowledge about the absorption mechanism still lacks.In this paper,taking Zn ion adsorption by two typical variable charge soils as the object of the study,author discusses the relation between Zn adsorption and pH and possible adsorption mechanisms.The results showed that in the low pH range where the amount of Zn adsorbed did not exceed 50% of Zn added,the specific adsorption was the diminant mechanism.The species of Zn specifically adsorbed was free Zn^2 ion.In the middle and high pH ranges,the mechanisms of specific and electrostatic adsorptions co-existed,accounting for about 70% and 30%,respectively.Noteworthily,in the high pH range,the hydroxyl Zn ion (ZnOH^ ) from Zn^2 hydrolysis probably was a preferable species for specific absorption.     

长期重金属胁迫下的土壤微生物特征: 沈阳张士污灌区的案例研究

Soil samples were collected from Zhangshi Wastewater Irrigation Area in the suburb of Shenyang City, China, an area with a 30-year irrigation history with heavy metal-containing wastewater. The chemical properties and microbial characteristics of the soils were examined to evaluate the present situation of heavy metal pollution and to assess the soil microbial characteristics under long-term heavy metal stress. In light of the National Environmental Quality Standards of China, the soil in the test area was heavily polluted by Cd and to a lesser degree by Zn and Cu, even though wastewater irrigation ceased in 1993. Soil metabolic quotient （qCO2） had a significant positive correlation, while soil microbial quotient （qM） had a negative correlation with content of soil heavy metals. Soil microbial biomass carbon （MBC） had significantly negative correlation with Cd, but soil substrate~induced respiration （SIR）, dehydrogenase activity （DHA）, cellulase activity, and culturable microbial populations had no persistent correlations with soil heavy metal content. Soil nutrients, except for phosphorous, showed positive effects on soil microbial characteristics, which to a certain degree obscured the adverse effects of soil heavy metals. Soil Cd contributed more to the soil microbial characteristics, but qM and qCO2 were more sensitive and showed persistent responses to heavy metals stress. It could be concluded that qM and qCO2 can be used as bioindicators of heavy metal pollution in soils.     

Effect of Electrolytes on Surface Charge Characteristics of Red Soils

The zero point of charge (ZPC) and the remaining charge σp at ZPC are two important parameters characterizing surface charge of red soils.Fourteen red soil samples of different soil type and parent material were treated with dithionite-citrate-dicarbonate (DCB) and Na2CO3 respectively.ZPC and σp of the samples in three indifferent electrolytes (NaCl,Na2SO4,and NaH2PO4) were determined.Kaolinite was used as reference.The results showed that ZPC of red soils was affected by the composition of parent materials and clay minerals and in significantly positive correlation with the content of total iron oxide (Fet),free iron oxide (Fed),amorphous iron oxide (Feo),aluminum oxide (Alo) and clay,but it was negatively correlated with the content of total silica (Sit).The σp of red soils was also markedly influenced by mineral components.Organic components were also contributing factor to the value of σp.The surface charges of red soils were evidently affected by the constitution of the electrolytes.Specific adsorption of anions in the electrolytes tended to make the ZPC of red soils shift to a higher pH value and to increase positive surface charges of the soils,thus leading to change of the σp value and decrease of the remaining net negative charges,even to the soils becoming net positive charge carriers.The effect of phosphate anion was greater than that of sulfate ion.     

红壤重金属的复合污染

The effects of combined heavy metal pollution of red soil on the growth of wetland rice and the transfer of Pb,Cd,Cu and Zn from soil into plants were sudied by greenhouse pot experiment,The results showed that the plantyields were markedly affected by heavy metals,with the exception of Pb,in soils under the experimental conditions,without taking into consideration all the interactions among the elements.The concentrations of the elemets in plants were mainly affected by the specific element added to the soil.The effect of interactions among the heavy metals was very significant either on plant yields or on the concentration of the elements in plants.The risk assessment of a combined pollution by heavy metals in the soil is discussed preliminarily in terms of the relative pollution equivalent.     

Cu^2＋、Zn^2＋复合条件下Cd^2＋在陕西5种土壤中的吸附

通过平衡吸附的方法,研究了Cd2＋在单一及与Cu2＋、Zn2＋复合条件下,在陕西塿土、黄绵土、黑垆土、黄褐土、砂土5种土壤中的吸附特征,并通过多重相关分析探讨了其吸附机制。结果表明,在20、30℃条件下,Cd2＋在各供试土样中吸附等温线总体上呈H或L型等温线形式,黑垆土对Cd2＋总是吸附最强,而砂土的吸附总是最弱;Cd2＋吸附的温度效应呈现升温负效应特征,塿土土样中,Cu2＋的共存对其温度效应影响较大,而在其他4种土样中Zn2＋的共存具有较大影响;Cu2＋、Zn2＋的共存均降低了Cd2＋的吸附量,具有显著的拮抗作用;Freundlich模型是描述Cd2＋吸附等温线最佳模型。相关分析结果表明,Cd2＋在土壤中的吸附主要以电性引力吸附为主,Cu2＋的共存主要和其与土壤有机质之间的络和吸附等化学吸附作用有关,因此其对Cd2＋以化学竞争性吸附的影响相对较弱,而Zn2＋共存吸附与Cd2＋吸附机制类似,因此表现出Zn2＋共存对Cd2＋吸附影响较大的特点。     

富啡酸对石灰性潮土中磷吸附-解吸及其对锌次级吸附-解吸的影响

通过吸附和解吸试验,研究了富啡酸（Fulvic acid,FA）对石灰性潮土中磷吸附一解吸的影响,并进行了吸附富啡酸和磷后对锌次级吸附一解吸的影响。结果表明：同时吸附不同磷和富啡酸后,土壤对磷的吸附量随磷初始浓度的增加而增加,而随富啡酸吸附初始浓度的增加而降低;石灰性潮土磷等温吸附曲线用Langumir方程式描述时,土壤对磷的吸附反应常数K、最大吸附量Xm、最大缓冲容量KxXm均随富啡酸初始浓度的增加而降低;KNO_3、KOH、HCI对吸附磷的解吸量所占比例及磷的总解吸量均随富啡酸浓度的增加而增加。土壤对Zn^2＋的吸附率随磷和富啡酸吸附初始浓度的增加而降低;而其解吸率随磷和富啡酸吸附浓度的增加而增加,说明磷和富啡酸减少了土壤对Zn^2＋的吸附,且增加了其在土壤中的解吸量。所以,石灰性潮土中富啡酸提高了土壤中磷的有效性,而且磷和富啡酸提高石灰性土壤中锌的有效性。     

Cadmium,copper, and zinc adsorption by a forest soil in the presence of sludge leachate

Samples from three genetic horizons of an acidic forest soil were equilibrated with solutions containing Cd, Cu, and Zn in the presence and absence of a municipal sewage sludge leachate. Copper adsorption was greater than Cd and Zn in all three horizons, while Cd and Zn adsorption was quite similar. Relative to a NaN0₃ background solution, sludge leachate reduced Cu adsorption in all horizons; however, in the presence of leachate Zn adsorption increased in the B2 and C horizons, while Cd adsorption decreased in the Al and was unaffected in the B2 and C horizons. Distribution coefficients generally increased as solution concentration and adsorption increased. In all horizons additions of Cd and Zn were able to reduce apparent surface charge. Copper not only reduced surface charge in the Al horizon, but caused a charge reversal in the 132 and C horizons. Adsorption data were best fit by linear or Freundlich equations. Differences in adsorption between sludge leachate and NaN0₃ solutions could not be explained simply by differences in metal activities as calculated using the GEOCHEM program. Competition from cations and organics present m the sludge leachate appears to contribute to lower metal adsorption.     

离子专性吸附对可变电荷土壤的动电学性质的影响

Studies were carried out by using electrophoretic method on the effects of the specific adsorption of the anions,such as SO4^2-,PO4^3-,and F^- ions,the cations,such as Ca^2 ,Mn^2 ,Zn^2 ,and Cu^2 ,ions,and the anions and cations coexisting,such as Zn^2 and SO4^2= ions,on electrokinetic properties of the red soils as typical variable charge soils in China concerning variation in the specific ion species and concentrations,with an emphasis on the interaction between soil colloid surfaces and the ions in soil solutions.The results showed that the adsorption of specific ions led to a very pronounced decrease in zeta potentials of the soil colloids and a shift of the IEPs to lower values for specific anions,and an obvious increase in zeta potentials of the soil colloids and a shift of the IEPs to higher values for specific cations.Under circumstances of the specific anions and cations coexisting,for instance,Zn^2 and SO4^2- ions,the zeta potentials changed with values higher than the value for SO4^2- alone and lower than that for Zn^2 alone,and the IEP was between that for Zn^2 and that for SO4^2-.The adsorption of Zn^2 and Cu^2 ions resulted in a reversal of the zeta potentials,and appearance of two IEPs for Zn^2 and no IEP for Cu^2 ,exhibiting interesting special effects of these kinds of metal ions.The higher the concentrations of the ions,the greater the change of the electrokinetic properties.     

草酸对不同土壤中Cd Zn吸附及其交互作用影响的初步研究

研究了草酸对Cd2＋、Zn2＋单一及复合条件下在陕西塿土、黄绵土、黑垆土、黄褐土、砂土5种土壤中的吸附特征,并探讨了草酸的影响机制。结果表明,除在低Zn2＋平衡浓度下,5种土壤中草酸促进了Zn2＋的吸附外,总体上在Cd2＋、Zn2＋单一处理及其复合处理中,草酸降低了土壤对Cd2＋、Zn2＋的吸附。草酸既没有改变塿土、黑垆土吸附能力最强、砂土吸附能力最弱的结果,也没有改变Cd2＋、Zn2＋之间的相互拮抗作用。草酸对Cd2＋、Zn2＋吸附的影响机制主要在于其与Cd2＋、Zn2＋形成络合物。草酸主要通过降低电性引力的方式减弱土壤对Cd2＋的吸附能力,而对于Zn2＋,在低平衡浓度下,草酸对Zn2＋吸附的促进作用来源于在土壤氧化物矿物表面形成少量的三元表面络合物的桥键合效应,在高平衡浓度下,对Zn2＋吸附的抑制作用来源于草酸对土壤有机质化学吸附点位的竞争。对Cd2＋、Zn2＋吸附起决定作用的依然是土壤本身性质。     

Untersuchungen zur Schwermetalladsorption in einem sauren Waldboden

Investigations of heavy metal adsorption in an acid forest soil To examine the adsorption of heavy metals in an acid forest soil (Pseudogley-Pelosol), undisturbed soil columns of 5 cm length were treated over a period of 276 days with solutions containing Pb, Cu, Zn and Cd. It can be shown that the heavy metals added were preferably adsorbed in the humus-rich, upper part of the soil. When treating the soil with the four heavy metals simultaneously, Pb, Cu and Cd were completely adsorbed in the soil matrix. However 20% of given Zn were leached out of the soil columns. Lowering pH in the percolation solution from pH 4 to 3 led to the mobilisation of previously adsorbed Cu, Cd and Zn, whereas Pb completely remained in the soil.     

Additive effects of copper and zinc on cadmium toxicity on phosphatase activities and ATP content of soil as estimated by the ecological dose (ED50)

The ecological dose (ED₅₀) of Cd on alkaline and acid phosphatase activity and the ATP content of three contrasting forest soils was measured with or without Cu and Zn to assess the additive toxic effects of these two metals. Soils polluted with Cu and/or Zn were treated with increasing Cd concentrations to give the following metal combinations: Cd, Cd+Cu, Cd+Zn and Cd+Cu+Zn. Alkaline and acid phosphatase activities and ATP content of the three soils were analysed 4 h, 7 and 28 days after the metal additions. The ED₅₀ values were obtained by interpolating the enzyme activities or ATP data with a kinetic model and the goodness of fit was satisfactory.Generally, the ED₅₀ values of both acid and alkaline phosphatase activities for Cd were lower (higher toxicity) with than without Cu and Zn and the effect of Cu and Zn was particularly adverse when these two metals were both added to soils. The alkaline phosphatase was more sensitive in the acid and neutral soil whereas the acid phosphatase was more sensitive in the alkaline soil. Both phosphatase activities and the ATP content were more sensitive in the sandy than in the finer textured soils. The ATP content was less sensitive to the additive effects. Increasing toxicity was observed during the incubation.Analysis of 1 M NH₄NO₃-extractable Cd, Cu and Zn revealed that Cd competed with Zn for the adsorption sites but not with Cu. However, the lower ED₅₀ values for Cd of the two phosphatase activities and of the ATP content in the presence of heavy metal combinations could be not explained by the heavy metal solubility data. It is concluded that the ED₅₀ may be a sensitive tool for assessing additve toxic effects to soil biochemical parameters.     

Effect of iron oxide removal on heavy metal sorption by acid subsoils

The adsorption of Cd, Cu, Pb, and Zn from 0.025 M NaClO₄ solutions by two ferruginous subsoils, Christiana silty clay loam and Dothan sandy clay, was investigated. Under acidic conditions, selective dissolution and removal of the Fe oxide soil component by dithionite-citrate-bicarbonate (DCB) generally increased heavy metal adsorption by the soils. This effect was attributed to increased electrostatic attraction of cations to the DCB-washed soils as evidenced by substantial reduction in the zero point of charge (ZPC) for the Dothan soil following DCB extraction. Alternately, the DCB extraction stripped Fe and Al species bound to structural exchange sites or eliminated coatings which reduce cation accessibility to such sites. Addition of low levels (10^?6 M) of ferric iron suppressed heavy metal adsorption capacity of the DCB-extracted Christiana soil to values comparable to the unmodified whole soil system. While hydrous oxide surfaces represent highly reactive sites for cation binding, Fe oxides can modify both the pH-dependent and structural exchange sites in a manner which hinders heavy metal adsorption. Thus, a soil's Fe-oxide content is unlikely to be a reliable guide to heavy metal adsorption capacity.