不同土壤对不同形态氮肥吸持状况的影响

以黄土高原旱塬区黑垆土和黄绵土为材料,研究了不同土壤对硝态氮肥、铵态氮肥、酰胺态氮肥的吸持情况。结果表明黑垆土对NO-3-N、NH+4-N和CO(NH2)2的吸持力分别为:4.835mgN/100g、4.960mgN/100g、4.980mgN/100g;黄绵土对NO-3-N、NH+4-N和CO(NH2)2的吸持力分别为:4.803mgN/100g、4.947mgN/100g、4.975mgN/100g,且黑垆土对氮肥的吸持力总体高于黄绵土对氮肥的吸持力。对于同一种土壤来说,氮肥的吸附力大小为:CO(NH2)2>NH+4-N>NO-3-N.

Effects of Sorbed Phosphate on Kinetics of Cn^（2＋） Sec－ondary Adsorption in Soils

The effects of sorbed phosphate on the kinetics of Cu￣2+ secondary adsorption on three major types ofsoils in southern and Central China were studied using the batch method and flow (or miscible displacement)techniques. Both of the methods showed that diffusions were the ratedetermining steps in the Cu￣2+ adsorp-tion by the soils. By the flow method, the course of Cu￣2+ adsorption kinetics consisted of two steps-sn initialrapid process and a later slow process of Cu￣2+ adsorption; while by the batch method, the 90% of Cu￣2+adsorption reaction was found to finish within first 1 minute. The results obtained using the flow method alsoindicated that for red soil and yellow-brown soil, Cu￣2+ adsorptions during the initial reaction periods wererestrained when the soils sorbed phosphate, whereas the adsorption reactions were stimulated at the finaltime. For grey Chao soil, sorbed phosphate retarded the Cu￣2+ adsorption in the whole reaction period. Theresults obtained using the batch method and flow techniques all implied that the different effects of sorbedphosphate would be attributed to its effects on Cu￣2+ ion diffusion in soil solution.

Temperature Effect on Boron Adsorption-Desorption Kinetics in Soils

The effect of temperature on the properties of boron adsorption-desorption in brown-red soil, yellowbrown soil and calcareous alluvial soil of Hubei Province was investigated with the mobile displacement technique. The experimental data of B adsorption-desorption amounts and reaction t line at 25 and 40℃ were fitted by the zero-order, first-order and parabolic diffusion kinetic equations. The adsorption process was in conformity with the parabolic diffusion law at both the temperatures, and the values of rate constant of the parabolic diffusion equation in B adsorption were 0.138, 0.124 and 0.105 mg kg-1 min-1/2 at 25℃, and 0.147, 0.146 and 0.135 mg kg-1 min-1/2 at 40℃ for the brown-red soil, yellow-brown soil, and calcareous alluvial soil, respectively. The relationship between amount of B desorption and reaction time could be well described by the first-order kinetic equation, and the corresponding values of rate constant were 0.0422, 0.0563 and 0.0384 min-1 at 25℃, and 0.0408, 0.042 3 and 0.0401 min-1 at 40℃ for the brown-red soil, the yellow-brown soil and the calcareous alluvial soil, respectively. Therefore, the desorption process of B might be related to the amount of B adsorbed in soil. The higher the temperature, the lower the amount of B adsorption for the same soil in the same reaction time. The values of the apparent activation energy of B adsorption in the three soils calculated with the rate constants of parabolic diffusion equation were 3.27, 8.44 and 12.99 kJ mol-1, respectively, based on the experimental data of B adsorption amounts and reaction time at 25 and 40℃.

Kinetic Equations of Potassium Desorption and the Ap－plication of Equation Constants

Elovich, parabolic diffusion, power function and exponential equations were used to describe K desorptionkinetics of 12 soils in a constant electric field of electro-ultrafiltration (EUF). Results showed that the Elovich,parabolic diffusion and power function equations could describe K desorption kinetics well owing to their highcorrelatfon coefficients and low standard errors; but the exponential equation was not suitable to be usedin this study due to its relatively low correlation coefficients and relatively high standard errors. This workestablished successfully the relationships between the constants (slope or intercept) of kinetic equations andthe barley responses to K fertilizer in the multiple-site field experiments and K-supplying status of soils, theconstants of Elovich, parabolic diffusion and power function equations were very significantly or significantlycorrelated to the soil available K, relative yield of barley and K uptake of barley in NP plot. It was suggestedthat the kinetic equation constants could be used to estimate K-supplying power of soils.

pH Effect on kinetics of Heavy Metal Sorption in Soils

The pH effect on the sorption kinetics of heavy metals in soils was studied using a Constant flow leaching method. The soil samples were red soil collected from Yingtan, Jiangxi, and yellow-browp soil from Nabing,Jiangsu. The heavy metals tested were zinc and cadmium.Assuming that the experimental data fitted to the following kinetic rate equation: 1/c dx/dt=kx∞-kx,the rate constant k of sorption could be determined from the slope of the straight line by plotting of 1/c.dx/dt vs. x. The results showed that the pH effect on the rate constants of heavy mental sorption in soils was very significant. The values of k decreased with inpeasing pH. The sorptions were more sensitive to pH in red soil than in yellow-brown soil.

Removal of Cu^2＋ Ions from Aqueous Solutions by Adsorption on Libyan Soil

Heavy metals are well recognized as potential health hazards as they can neither be degraded nor biologically detoxified. This experimental study aims to investigate the possible use of Libyan local soil, Ashkida soil, mined in the Southern Province of Libya as a low cost adsorbent to remove copper ions from aqueous solutions. In this work, the effects of various parameters such as adsorbent dosage, initial concentration of copper, agitation rate, contact time and solution pH level on the adsorption efficiency are investigated through batch experiments at room temperature. The results indicate that the optimum conditions for copper removal from aqueous solutions are 60 minutes contact time, 10 g/L adsorbent dose and 500 rpm agitation rate at natural pH value. The results are fitted to Freundlich, Langmuir, Temkin and Dubinin-Radushkevich isotherms. A satisfactory agreement between the experimental data and the model-predicted values is expressed by the correlation coefficient, r^2, and the total mean error, E%. Freundlich model offers the best representation of adsorption process revealing a monolayer adsorption capacity, qmax, of 27.03 mg/g. A comparison of kinetic models applied to the adsorption of copper ions on the adsorbent is evaluated by simple first order, pseudo first order and pseudo second order kinetic models. Kinetic parameters, rate constant, equilibrium sorption capacities and related correlation coefficients for each kinetic model are determined revealing that the pseudo second order kinetic model is in a better correlation with the experimental data in comparison with the other isotherms.

Kinetics of K Desorption from Soils in a Constant Electric Field (Electro-Ultrafiltration) and Its Application

Kdesorption from soils in a constant electric field(field strength:44.5Vcm-1) by means of electro-ultrafil-tration (EUF) followed second-order kinetics and could be described by the equation dd/dt = k(D-d)2. From theequation, such kinetic parameters relating to K desorption from soils as the maximum desorbable quantity D, quantity of K desorbed within 40 minutes d40, initial desorption rate Vo, desorption rate constant k and half-time t1/2 could be calculated. An expression which describes the relationships between the kinetic parameters on the one hand and the responses of barley to fertilizer-K in the field experiments in different sites and the potassium-supplying power of soils on the other was established. Vo, D and d40 were significantly correlated with barley relative yield, K uptake by barley and the content of soil available potassium. The rate constants of K desorption varied between 4.42 × 10-4-1.80 × 10-3kg mg-1 min-1 and highly correlated with the relative yield of barley. The kinetic parameters including Vo, D, d40 and k were successfully used to estimate the K-supplying power of soils.

Relationship Between Soil Boron Adsorption Kinetics and Rape Plant Boron Response

The boron adsorption kinetic experiment in soil by means of a flow displacement technique showed that the kinetic data could be described with some mathematic equations. The average values of the correlation coefficient for zero-order, first-order, parabolic diffusion, Elovich, power function and exponential equations were 0.957, 0.982, 0.981, 0.984, 0.981 and 0.902, respectively. The correlation between adsorbed boron or its other expression form and time were the highest for first-order, parabolic diffusion, Elovich, and power function equations, the second for the zeroorder equation, and the lowest for the exponential equation. The parabolic diffusion equation fitted well the experimental results, with the least standard error among the six kinetic equations, showing that the movement of boron from soil solution to soil colloid surface may be controlled by boron diffusion speed. The boron content of rape seedling obtained from soil cultivation was correlated with the rate constants of the kinetic equations. The constants of first-order, parabolic diffusion,and exponential equations were significantly correlated with the boron content of the crop of NPK treatment at a 95% probability level, with correlation coefficients being 0.686, 0.691 and 0.641, respectively. In the case of zero-order equation, it was significant at 99% probability level (r =0.736). These results showed that the absorption kinetic constants of soil boron were closely related with the rape plant response to boron.

Effect of Anions on Adsorbability and Extractability of Lead Added in Soil

The effect of accompanying anions on the adsorbability and extractability of Pb added in soils was studied by using bach equilibria and incubation-extraction mothods.Pb concentration ranged between 0.48-2.41 mM in the adsorption experiment,and Pb added to soil from 2.14 to 19.31mM Pb/kg with an incubation time of 2-16 weeks in the incubation-extraction test in which 1M NH4OAc(pH 7) was taken as an extraction agent,and the Pb compounds used are PbCl2,Pb(NO3)2 and Pb(OAc)2.The values of pH50 for Pb retention and the parameters,b and k values,of Langmuir equation were used to distinguish the difference of adsorbability and extractability of Pb affected by anions,respectively.Judging from the results of either pH50 value or b value,the influences of Cl^- and NO3^- on the adsorbability and extractability of Pb in soils were similar but quite different from those of OAc^-.The relative loading capacities of soils to Pb calculated according to the extraction rate showed that the values of Pb(OAc)2 were higher than those of PbCl2 and Pb(NO3)2.

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals: Ⅱ. Equations for Describing Experimental Data

Different mathematical methods, including linearization, differential, integration and nonlinear least squares approximation (Newton-Marquardt method), were used to fit different kinetic equations, such as zero-order, first-order (i. e, membrane diffusion), second-order, parabolic-diffusion, Elovich, two-constant equations, to the experimental data of Pb2+ and Cu2+ adsorption on variable charge soils and kaolinite. Assuming each M2+ occupied two adsorption sites, two more equations, the so-called surface second-order equation and third-order equation were derived and compared with the above equations according to the fitting results, which showed that the second-order equation and surface second-order equation, being one equation in different expressions under some conditions, were better than the other equations in describing the Pb2+ and Cu2+ adsorption kinetics, and the latter was the best.

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: Ⅲ. Adsorption Kinetics of Pb^(2+) Within 30 Minutes

The adsorption kinetics of Pb^2+ 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.The higher the suspension pH,the faster the adsorption occurred.The meaning of Xm got by the two ion-selective electrode technique(one kind of batch technique) was different from that by the miscible displacement technique in that the former was only the equilibrium adsorption amount at a definite concentration and pH,but the latter was almost equal to the adsorption capacity at a definite pH with much less influence of concentration.One Pb^2+ was supposed to occupy two adsorption sites as the adsorption mechanism is concerned.

Kinetics comparison on simultaneous and sequential competitive adsorption of heavy metals in red soils

To compare the adsorption kinetics of Cu, Zn and Cd introduced into red soils simultaneously and sequentially as well as their distribution coefficients, the ability of red soils to retain heavy metals was evaluated by performing batch experiments. The results indicate that Cu is preferentially adsorbed by red soils no matter in simultaneous or in sequential situation. The adsorption amount of Cd is the minimum in simultaneous competitive adsorption experiment. As heavy metals are added into red soils sequentially, the heavy metal adsorptions are relatively hard to reach equilibrium in 2 h. Red soils retain more Cd than Zn, which is opposite to the result in simultaneous adsorption. The addition sequences of heavy metals affect their adsorbed amounts in red soils to a certain extent. The joint distribution coefficients of metals in simultaneous adsorption are slightly higher than those in sequential adsorption.

施用沼液对农林土壤生态系统影响的研究进展

目前,沼液排放量逐年增加,对农林土壤的影响也在增大,笔者就施用沼液对土壤的影响研究现状进行了综合分析,总结归纳施用沼液对农林土壤理化与生物学特性的影响及其机制。认为:①适当沼液施用条件下农林土壤动物、微生物的数量,全氮、全钾、全磷、速效氮、速效磷和速效钾的含量都有所提高;②土壤的理化性质和结构及施用沼液的质量浓度、用量、使用时间都是影响农林土壤生态系统的重要因素;③施用沼液可能增加土壤重金属含量,不同土层各种重金属含量增加程度不一;④不同的沼液处理方式、发酵时间,对农林土壤的重金属积累、土壤动物的影响各异,稀释后的沼液比原沼液灌溉土壤更易造成Cd、Cu的积累,新鲜沼液比陈放沼液对土壤动物的抑制作用更明显。因此,施用沼液是资源可持续循环利用的重要途径之一,合理施用沼液不仅可以提高农林土壤生产力,也可以保护生态环境;同时,因土壤生物学特性、理化性质等不同,长期施用沼液对不同类型农林土壤的影响结果有所不同,尤其对土壤生态系统的生物学与生态学的过程与机制尚不清楚。在研究施用沼液对农林土壤的影响及其响应机制过程中,一方面要做2 a甚至更长时间的定位观测与分析;另一方面要考虑不同处理沼液的理化性质以及实验土壤的理化和生物学特性的差异,深入探究沼液内含物在土壤中的迁移、转化过程以及吸附作用,以达到长期维持土壤生产力的目的。

Adsorption and Desorption of Ammonium in Wetland Soils Subject to Freeze-Thaw Cycles

Nitrogen （N） cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles （FTCs）. Adsorption and desorption of ammonium ions （NH4＋） were examined in a controlled laboratory experiment for soils sampled from palustrine wetland, riverine wetland, and farmland reclaimed from natural wetland in response to the number of FTCs. The results indicate that freeze-thaw significantly increased the adsorption capacity of NH： and reduced the desorption potential of NH4＋ in the wetland soils. There were significant differences in the NH4＋ adsorption amount between the soils with and without freeze-thaw treatment. The adsorption amount of NH4＋ increased with increasing FTCs. The palustrine wetland soil had a greater adsorption capacity and a weaker desorption potential of NH4＋ than the riverine wetland soil because of the significantly higher clay content and cation exchange capacity （CEC） of the riverine wetland soil. Because of the altered soil physical and chemical properties and hydroperiods, the adsorption capacity of NH4＋ was smaller in the farmland soil than in the wetland soils, while the desorption potential of the farmland soil was higher than that of the wetland soils. Thus, wetland reclamation would decrease adsorption capacity and increase desorption potential of NH4＋, which could result in N loss from the farmland soil. FTCs might mitigate N loss from soils and reduce the risk of water pollution in downstream ecosystems.

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.