柠檬酸盐和磷酸盐存在下酸性磷素酶在矿物和土壤胶体上的吸附

The aim of this work was to study the influence of phosphate and citrate, which are common inorganic andorganic anions in soils, on the adsorption of acid phosphatase by kaolin, goethite and the colloids separatedfrom yellow-brown soil (YBS) and latosol (LS) in central-south China. The YBS colloid has the major claymineral composition of 1.4 nm mineral, illite and kaolinite while the LS colloid mainly contains kaolinite andoxides. The adsorption isotherm of acid phosphatase on the examined soil colloids and minerals fitted tothe Langmuir model. The amount of enzyme adsorbed in the absence of ligands was in the order of YBScolloid ＞LS colloid＞kaolin≈goethite. In the presence of phosphate or citrate, the amounts of the enzymeadsorbed followed the sequence YBS colloid＞kaolin＞LS colloid＞goethite. The presence of ligands alsodecreased the binding energy between the enzyme and soil colloids or minerals. With the increase of ligandconcentration from 10 mmol L-1 to 400 m mol L-1, different behaviors for the adsorption of enzyme werefound in the colloid and mineral systems studied. A sharp decrease in enzyme adsorption was observed ongoethite while gradual decreases of enzyme adsorption were recorded in the two soil colloid systems. However,no any decrease was found for the amount of enzyme adsorbed on kaolin at higher ligand concentrations.When phosphate or citrate was introduced to the system before the addition of enzyme, the ligands usuallyenhanced the adsorption of enzyme. The results obtained in this study suggested the important role ofkaolinite mineral in the adsorption of enzyme molecules in acidic soils in the presence of various ligands.     

有机酸对高岭石, 针铁矿和水铝英石吸附镉的影响

Effects of organic acids （oxalic, acetic, and citric） on adsorption characteristics of Cadmium （Cd） on soil clay minerals （kaolinite, goethite, and bayerite） were studied under different concentrations and different pH values. Although the types of organic acids and minerals were different, the effects of the organic acids on the adsorption of Cd on the minerals were similar, i.e., the amount of adsorbed Cd with an initial solution pH of 5.0 and initial Cd concentration of 35 mg L^-1 increased with increasing concentration of the organic acid in solution at lower concentrations, and decreased at higher concentrations. The percentage of Cd adsorbed on the minerals in the presence of the organic acids increased considerably with increasing pH of the solution. Meanwhile, different Cd adsorption in the presence of the organic acids, due to different properties on both organic acids and clay minerals, on kaolinite, goethite, or bayerite for different pHs or organic acid concentrations was found.     

七种钾释放动力学方程的比较和动力学参数的应用

Batch equilibrium experiments were conducted to investigate cadmium （Cd） sorption by two permanent-charge soils, a yellow-cinnamon soil and a yellow-brown soil, and two variable-charge soils, a red soil and a latosol, with addition of selected organic acids （acetate, tartrate, and citrate）. Results showed that with an increase in acetate concentrations from 0 to 3.0 mmol L^-1, Cd sorption percentage by the yellow-cinnamon soil, the yellow-brown soil, and the latosol decreased. The sorption percentage of Cd by the yellow-clnnamon soil and generally the yellow-brown soil （permanent-charge soils） decreased with an increase in tartrate concentration, but increased at low tartrate concentrations for the red soil and the latosol. Curves of percentage of Cd sorption for citrate were similar to those for tartrate. For the variable-charge soils with tartrate and citrate, there were obvious peaks in Cd sorption percentage. These peaks, where organic acids had maximum influence, changed with soil type, and were at a higher organic acid concentration for the variable-charge soils than for the permanent charge soils. Addition of cadmium after tartrate adsorption resulted in higher sorption increase for the varlable-charge soils than permanent-charge soils. When tartrate and Cd solution were added together, sorption of Cd decreased with tartrate concentration for the yellow-brown soil, but increased at low tartrate concentrations and then decreased with tartrate concentration for the red soil and the latosol.     

离子强度和三氧化物对土壤吸附Bt毒素的影响

Chemical reactions and fate of the toxins of Bacillus thuringiensis(Bt) in the soil environment are causing increasing concerns due to the large-scale cultivation of transgenic Bt plants.In this study,the effect of ionic strength(0-1 000 mmol kg 1) adjusted by NaCl or CaCl 2 on adsorption of Bt toxin by a lateritic red soil,a paddy soil and these soils after chemical removal of organic-bound or free Fe and Al oxides,as well as by pure minerals(goethite,hematite and gibbsite) which are widespread in these soils,were studied.The results indicated that when the supporting electrolyte was NaCl,the adsorption of Bt toxin by the lateritic red soil and paddy soil increased rapidly until the ionic strength reached 250 mmol kg 1 and then gradually slowed down with the increase of ionic strength;while in case the supporting electrolyte was CaCl 2,the adsorption of Bt toxin enhanced significantly at low ionic strength(< 10 mmol kg 1) and then decreased as the ionic strength increased.The adsorption of Bt toxin by the tested minerals and soils after the removal of organic-bound or free Fe and Al oxides also increased with increasing ionic strength controlled by NaCl.Removing organic-bound Fe and Al oxides obviously increased the adsorption of Bt toxin in the tested soils.Differently,removing free Fe and Al oxides increased the Bt adsorption by the paddy soil,but decreased the adsorption by the lateritic red soil.The study indicated that the varieties of ionic strength and the presence of Fe and Al oxides affected the adsorption of Bt toxin by the soils,which would contribute to the further understanding of the fate of Bt toxin in the soil environment and provide references for the ecological risk assessment of transgenic Bt plants.     

Adsorption of Potassium and Calcium Ions by Variable Charge Soils

Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.     

Effect of low-molecular-weight organic acids on Cl- adsorption by variable charge soils

Low-molecular-weight (LMW) organic acids exist widely in soils and have been implicated in many soil processes.The objective of the present paper was to evaluate effect of two LMW organic acids, citric acid and oxalic acid, on Cl^- adsorption by three variable charge soils, a latosol, a lateritic red soil and a red soil, using a batch method. The results showed that the presence of citric acid and oxalic acid led to a decrease in Cl- adsorption with larger decreases for citric acid. Among the different soils Cl- adsorption in the lateritic red soil and the red soil was more affected by both the LMW organic acids than that in the latosol.     

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

The study results of the effects of temperature and ionic strength on the adsorption kinetics of Pb2+ and Cu2+ by latosol, red soil and kaolinite coated with Mn oxide showed that Pbr" and Cur" adsorption by all samples, as a whole, increased with raising temperature. Temperature also increased both values of Xm (the amount of ion adsorbed at equilibrium) and k (kinetics constant) of Pb2+ and Cu2+ The activation energies of Pb2+ adsorption were kaolin-Mn>red soil>goethite and those of Cu2+ were latosol>red soil>kaolin-Mn>goethite. For a given single sample the activation energy of Cu2+ was greater than that of Pb2+. Raising ionic strength decreased the adsorption of Pb2+ and Cu2+ by latosol, red soil and kaolinite coated with Mn oxide but increased Pb2+ and Cu2+ adsorption by goethite. The contrary results could be explained by the different changes in ion forms of Pb2+ or Cu2+ and in surface charge characteristics of latosol, red soil, kaolin-Mn and goethite. Increasiclg supporting electrolyte concentration in-creased Xm and k in goethite systems but decreased and k in kaolin-Mn systems. All the timedependent data fitted the surface secondorder equation very well.]     

Adsorption Kinetics of Pb2+ and Cu2+ on Variable Charge Soils and Minerals: Ⅲ. Adsorption Kinetics of Pb2+ Within 30 Minutes

The adsorption kinetics of Pb2+ on different soils and minerals with variable charges was studied by the two ion-selective electrode technique at different pH and concentrations. The results showed that more than 95% of adsorption on all the samples occurred during the first 5 minutes. All adsorption time-dependent data could fit the surface second-order equation very well. The values of Xm were goethite > kaolinite, and latosol > red soil at the same initial reaction concentration. The values of k were kaolinite > > goethite, and latosol > red soil at the same reaction pH and initial concentration.     

铁铝氧化物和高岭石对转化酶的吸附及活性的影响

Experiments were conducted to study the influences of synthetic bayerite, non-crystalline aluminum oxide (N-AlOH), goethite, non-crystalline iron oxide (N-FeOH) and kaolinite on the adsorption, activity, kinetics and thermal stability of invertase. Adsorption of invertase on iron, aluminum oxides fitted Langmuir equation. The amount of invertase held on the minerals followed the sequence kaolinite > goethite > N-AlOH > bayerite > N-FeOH. No correlation was found between enzyme adsorption and the specific surface area of minerals examined. The differences in the surface structure of minerals and the arrangement of enzymatic molecules on mineral surfaces led to the different capacities of minerals for enzyme adsorption. The adsorption of invertase on bayerite, N-AlOH, goethite, N-FeOH and kaolinite was differently affected by pH. The order for the activity of invertase adsorbed on minerals was N-FeOH > N-AlOH > bayerite > reak goethite > kaolinite. The inhibition effect of minerals on enzyme activity was kaolinite > crystalline oxides > non-crystalline oxides. The pH optimum of iron oxide- and aluminum oxide-invertase complexes was similar to that of free enzyme (pH 4.0), whereas the pH optimum of kaolinite-invertase complex was one pH unit higher than that of free enzyme. The affinity to substrate and the maximum reaction velocity as well as the thermal stability of combined invertase were lower than those of the free enzyme.     

Types of Crystalline Iron Oxides and Phosphate Adsorption in Variable Charge Soils

The types,contents and morphologies of crystalline Fe oxides and their relations to phosphate adsorption on the clay fractions in soils with varable charge in southern China were investigated by means of XRD,TEM,EMA and chemical analysis methods.Results indicated that the types and contents of crystalline Fe oxides varied with the soils examined.The dominant crystaline Fe oxide was hematite in the latosols and goethites in the red soils.In yellow-brown soils,the only crystalline Fe oxide was goethite.The difference between Ald and Alo came mainly from the Al Substituting for Fe in the Fe oxides.The crystal morphology of goethite appeared mainly as subrounded flat or iso-dimensional rather than acicular particles,Hematities occurred in plates of various thickness,Their MCDa/MCDc ratios in the latosols and red soils were generally above 1.5 and below 1.5,respectively.The MCD values of goethites and hematites were 15-25nm and 20-35nm,and their specific surface areas were 80-120m^2/g and 35-75m^2/g,respectively.The goethite crystals were generally smaller,Variations of the total amounts of crystalline Fe oxides in clay fractions were not related to plhophats adsorption.The types,contents and morphologies of crystalline Fe oxides in the soils remarkably affected phosphate adsorption characteristics of the soils.The phosphate adsorption of goethite was much greater than that of hematite,The higher th MCDa/MCDc ratio of hematite,the lower the phosphate adsorption.     

几种有机酸对可变电荷和恒电荷土壤吸附镉的影响

The objectives of this study were to illustrate the reaction processes, to identify and quantify the precipitates formed, and to estimate the porosity losses in order to eliminate drawbacks during remediating monochlorobenzene （MCB） and trichloroethylene （TCE）-contaminated aquifers using the ORC-GAC-Fe^0-CaCO3 system. The system consisted of four columns （112 cm long and 10 cm in diameter） with oxygen-releasing compound （ORC）, granular activated carbon （GAC）, zero-valent iron （Fe^0）, and calcite used sequentially as the reactive media. The concentrations of MCB in the GAC column effluent and TCE in the Fe^0 column effluent were below the detection limit. However, the concentrations of MCB and TCE in the final calcite column exceeded the maximum contaminant level （MCL） under the Safe Drinking Water Act of the US Environmental Protection Agency （US EPA） that protects human health and environment. These results suggested that partitioning of MCB and TCE into the gas phase could occur, and also that transportation of volatile organic pollutants in the gas phase was important. Three main precipitates formed in the ORC-GAC-Fe^0-CaCO3 system： CaCO3 in the ORC column along with Fe（OH）2 and FeCO3 in the Fe^0 column. The total porosity losses caused by mineral precipitation corresponded to about 0.24% porosity in the ORC column, and 1% in the Fe^0 column. The most important cause of porosity losses was anaerobic corrosion of iron. The porosity losses caused by gas because of the production and entrapment of oxygen in the ORC column and hydrogen in the Fe^0 column should not be ignored. Volatilization, precipitation and porosity losses were considered to be the main drawbacks of the ORC-GAC-Fe^0-CaCO3 system in remediating the MCB and TCE-contaminated aquifers. Thus, measurements such as using a suitable oxygen-releasing compound, weakening the increase in pH using a buffer material such as soil, stimulating biodegradation rates and minimizing the plugging caused by the relatively high dissolved oxygen levels should be taken to eliminate the drawbacks and to improve the efficiency of the ORC-GAC-Fe^0-CaCO3 system.     

Effects of Addition Sequence and pH of Oxalate on the Adsorption and Activity of Acid Phosphatase on Soil Colloids and Minerals

The adsorption and specific activities of acid phosphatase on soil colloids and minerals in oxalate systems with different pH values were studied using the batch method. Results indicated that the amount of phosphatase adsorption decreased in the following order: goethite ? yellow-brown soil (YBS) > kaolinite > latosol, and the specific activities of immobilized phosphatase were goethite > latosol > kaolinite > YBS. The profiles of enzymatic adsorption and specific activity on soil minerals were bell shaped, and their change tendencies were out of sync. The optimal pH for phosphatase adsorption was located between the isoelectric point of phosphatase and the zero point of charge of the studied soil minerals, and the optimal pH for the specific activity of the immobilized enzyme either did not change or shifted toward alkalinity. Enzymatic adsorption amounts and specific activities were greater when the enzyme was added before oxalate than when enzyme was added after oxalate.     

酒石酸对黏粒矿物上酸性磷酸酶吸附及活性的影响

采用平衡批处理法,研究了模拟根系分泌物——酒石酸溶液的浓度(0~80 mmol L-1)、pH(2.5~7.0)对酸性磷酸酶在针铁矿、高岭石及黄棕壤和砖红壤胶体(<2μm)上的吸附及比活性影响。结果表明,当酒石酸浓度由0 mmol L-1(作为对照)升高至80 mmol L-1时,酸性磷酸酶在供试土壤胶体和矿物表面的吸附量先急剧降低(0~5mmol L-1之间),后逐渐达到平衡;以羟基化表面为主的针铁矿对酸性磷酸酶的吸附百分率受酒石酸浓度的影响最大,吸附百分率从对照的96.2%降至80 mmolL-1酒石酸浓度时的33.7%,其他以层状铝硅酸盐矿物为主的供试土壤胶体和高岭石则受影响较小,吸附百分率从对照的76.3%~60.6%降至80 mmol L-1酒石酸浓度时的56.2%~41.6%。酸性磷酸酶在酒石酸体系中的最大吸附pH点均在该酶的等电点酸侧,这可能与酒石酸对矿物表面的电荷性质改变有关;酒石酸体系中,针铁矿上酸性磷酸酶的比活性远高于其它供试土壤胶体,该酶的最适比活性点随胶体类型的不同而无变化或有所高移。     

Immobilization and species of heavy metals in soils in the absence and presence of rhizobia

Abstract

The effect of bacterial inoculation of Rhizobium fredii HN01 on the immobilization and speciation of Cu, Zn, and Cd was studied in Red and Cinnamon soil which are typical Chinese soils. The soil was mixed with bacterial suspension for one week followed by an immobilization of each heavy metal for another week. The total binding and fractionation of heavy metals in soils were analyzed. As compared with the control, the retention of total Cu, Zn, and Cd in Red soil increased by 28, 16, and 28%, respectively, in the presence of rhizobia. The amount of exchangeable, NH₄OAc-extractable, Mn oxides-bound and organic matter-bound Cu increased by 23–123%. There were significant decrease of exchangeable Cu and marked increases of NH₄OAc-extractable and Mn oxide-bound Cu in Cinnamon soil with the presence of rhizobial cells, although no changes for the total retention of Cu were observed. The amount of exchangeable Zn in Red soil-rhizobia composite was 20% greater than that of the no-rhizobia soil. Addition of rhizobia also increased exchangeable Cd and specifically-adsorbed Cd by 25 and 93%, respectively, in Red soil. No considerable differences were found for the total immobilization of Zn and Cd as well as their distribution in various solid fractions of Cinnamon soil in the absence and presence of rhizobial cells. In terms of soil components, it is assumed that bacterial biomass had a relatively less impact on the species of heavy metals bound with Fe oxides. Results suggested that the retention and speciation of heavy metals in soil are governed largely by the interactions of bacteria with various inorganic and organic soil constituents. The data are useful in understanding the impact of microorganisms on the behavior, mobility and transformation of heavy metals in soil environments.     

土壤对镉的吸附与解吸——Ⅰ.土壤组份对镉的吸附和解吸的影响

采用选择溶解法研究了有机质、游离铁、无定型硅、铝等土壤组份对青黑土、黄棕壤、红壤和砖红壤胶体吸附和解吸Cd的影响。结果表明,去除有机质后胶体吸附Cd减少,这可能是由于交换吸附的减少所致;游离铁的去除使得黄棕壤、红壤和砖红壤的吸附量显著减少,显示了在这些土壤中游离氧化铁专性吸附的重要性;随着无定形铝含量的上升,吸附量下降,这是因为铝离子占据了高能量的吸附位。经不同处理后的土壤胶体,其Cd的解吸顺序(解吸%)大致为:去无定型硅、铝者>去游离铁者>去有机质者>原胶体,但在不同土壤和不同pH条件下该顺序略有差别。研究结果为控制和改造土壤Cd污染提供了理论依据。     

土壤和粘粒矿物对亚硒酸盐的吸附和解吸

本文研究了三种土壤(砖红壤、红壤和黄棕壤)、高岭土和两种合成氧化铁(无定形氧化铁和针铁矿)对亚硒酸盐的吸附和解吸作用。讨论了亚硒酸盐的吸附特征,以及土壤中氧化铁对亚硒酸盐吸附和解吸的影响,根据实验资料与吸附等温方程式的拟合情况,作者认为以Freundlich和Langmuir公式为宜。此外,供试样品对亚硒酸盐的吸附和解吸结果表明,Se的吸附量随Se的添加量的增加而增加,但由于矿物组成各异,吸附量的差异显著。其吸附量的大小顺序为:无定形氧化铁>针铁矿>砖红壤>红壤>黄棕壤>高岭土;而被吸附Se的解吸能力则是高岭土>黄棕壤>红壤>砖红壤>针铁矿>无定形氧化铁。实验结果还表明,在各种矿物组成中,亚硒酸盐的吸附和解吸受氧化铁的影响很明显,三个土壤样品的吸附等温线都表现出氧化铁在初始阶段对亚硒酸盐吸附快而强烈的特征,而在去除氧化铁以后,这一特征也随之消失,硒的吸附量显著降低,而解吸率则明显上升。     

Contparison of the influence of Cu,Zn, and Cd on the activity and kinetics of free and intntobilized acid phosphatase

The influence of Cu, Zn, and Cd on the activity and kinetics of acid phosphatase immobilized by two soil clays, kaolin or goethite was investigated. The ability of Cu to inhibit the enzyme activity was higher than that of Zn in all the enzyme complexes examined. The ability of Cd was negligible. The inhibitory effects of Cu and Zn on the two soil clay- and kaolin-enzyme complexes were much stronger than those on the goethite-enzyme complex. The V _max and K _m values of the enzyme complexes indicated that both Cu and Zn decreased the maximum reaction velocity of the enzymes, but increased the affinity of the enzymes for the substrate. The degree of the decrease and increase was higher in the Cu systems than in the Zn systems.