上海土壤磷的吸附特性及缓冲性能的研究

本文以上海土壤为对象,研究选定了土壤磷等温吸附试验条件为:水土比10,平衡时间6天,控温25℃,磷加入量为100,200,400,600μgP/g土,溶液基质为0.01M CaCl₂。磷缓冲能力试验条件为:平衡时间2天,磷加入量为20,40,100,200μgP/g土。根据Freundlich, Tempkin和Langmuir方程计算的土壤吸附指标与土壤类型及土壤性质有密切关系,是土壤磷素肥力的重要指标。反映土壤缓冲能力的“磷肥指标”与土壤有机质、粘粒、活性铝及pH值相关较好。上海几种主要土壤中以青紫泥的最大吸附量(X_m),0.2ppm P吸附量和“磷肥指标”为最高,其次为青黄土,沟干泥和黄泥头,最小为夹沙泥。应用磷吸附指标与“磷肥指标”来预测土壤需磷量,初步试验是可行的,但实际应用还需进一步试验研究。     

Phosphate sorption by red mediterranean soils from Greece

Abstract

In nineteen surface horizons of red Mediterranean soils from various locations of Greece, phosphorus (P) sorption experiments were conducted and the sorption characteristics were studied in relation to soil properties. Phosphate sorption data were fitted both to the Langmuir and Freundlich equations. From these equations, the following P sorption parameters were determined from the Freundlich equation, X = ACⁿ, the parameters A (the phosphate sorbed at C = 1 mg P/L), n (the P sorption intensity), the P sorption index (PS = X/log C) and maximum P sorption (Xmfr). From the Langmuir equation, C/X = 1/KXm + C/Xm, the parameters K (showing the bonding energy), maximum P sorption (Xmla), the quantity of P adsorbed at a standard concentration of 0.2 mg P/L (P0.2), and P maximum buffering capacity (PMBC). The Freundlich parameter A was strongly correlated to the clay and sesquioxides ("free”; iron and aluminum oxides and amorphous iron oxides) content. Seventy‐four percent of the variance of this parameter was explained by clay and “free”; iron (Fe) content. The Freundlich parameter n was significantly correlated with pH and amorphous iron oxides content, while 52% of its variance was explained by amorphous Fe and dithionite extrac‐table aluminum (Al). The P sorption maxima calculated from the Freundlich equation were in general lower than those calculated by the Langmuir equation. Both these parameters were strongly correlated with clay and more slightly with sesquioxides content. About 50% of their variance was explained by clay content of the soils. The P sorption index was strongly correlated with the clay content and less strongly with dithionite‐extractable Fe and Al. The P‐buffering capacity calculated from the data of Langmuir equation was also strongly correlated with these two parameters. In addition, clay content and dithionite‐extractable Fe and Al were well correlated to the amounts of P required to obtain an equilibrium concentration of 0.2 mg P/L while 61% of the variation of this parameter was explained by the clay and the dithionite‐extractable Fe content. From these findings, it seems that for the red Mediterranean soils from Greece, P sorption is affected by clay content and iron and aluminum oxide contents.     

Describing the effect of time on sorption of phosphate by iron and aluminium hydroxides

Iron and aluminium hydroxides were precipitated both in the presence and absence of kaolinite. The reaction between phosphate and these hydroxides was measured for periods which ranged from 5 min to 72 h. The effect of time on phosphate sorption was examined by plotting the sorption data according to different, simple, kinetic equations such as the first order, second order, the parabolic diffusion equation, the Elovich equation and the modified Freundlich equation. The effect of time on sorption was also examined by the mechanistic model recently developed by Barrow (1983b) for the sorption and desorption of phosphate by soils. The sorption of phosphate by iron and aluminium hydroxides increased with time and the reaction continued through the period of observation without reaching a true equilibrium. Curvilinear relationships were obtained when the data were plotted according to the simple kinetic equations. These simple kinetic equations fail to describe the effect of time on sorption partly because the mechanism is different from that postulated and partly because they do not consider electrostatic effects when phosphate ions react with a charged surface. The mechanistic model of Barrow (1983b), which takes this effect into account, described effect of both concentration and time on phosphate sorption. According to this model, the increase in phosphate sorption with time was caused by a redistribution of adsorbed phosphate into the interior of the particles of iron and aluminium hydroxides by solid-state diffusion.     

印度Chattisgarh州两种新开发土和一种淋溶土中磷酸盐吸附-解析特征研究

Two Inceptisols and an Alfisol of the Indravati Catchment area in Chattisgarh, India, comprising several gradients in physical and chemical properties were studied to relate phosphate sorption and desorption to soil properties. From the P isotherm curve, the standard P requirement （SPR） of the soils was determined. Phosphate sorption data were also fitted both to the Langmuir and Freundlich Equations. The mean sorption maximum values for three different soil series were： Bastar 〉 Geedam 〉 Mosodi. The fraction of added phosphate sorbed for the 3 series followed this same trend as did SPR; the phosphate sorption maximum and the maximum phosphate buffering capacity, which were estimated by the Langmuir isotherm; and the Freundlich constant 1/n. However, phosphate desorption, as well as the maximum recovery percent did not follow this order. The phosphate affinity constant （K） was also different following the same progression for the 3 soil series as the Freundlich constant K＇, which measured sorption strength. Meanwhile, an inverse order existed for K and K＇ versus the percent desorbed relative to the sorbed as well as the maximum recovery percent. In addition, significant correlation coefficients among sorption parameters of P and soil factors were found.     

稻作制、有机肥和地下水位对红壤性水稻土磷的吸持作用的影响

从１９８２～１９９４年,对稻作制,有机肥和地下水位三因素多水平的定位试验土壤,进行磷的恒温吸附试验,研究不同稻作制和地下不位以及施用有机肥对红壤性水稻土对磷的吸持作用的影响,结果表明,各处理土壤磷的恒温吸附曲线形状都很相似,均属于高亲和力的“Ｌ”型曲线,所有吸附资料与三个已知吸附模型的拟合程度的均达极显著水平,其中以一元Ｌａｎｇｍｕｉｒ模型优于Ｆｒｅｕｎｄｌｉｃｈ和Ｔｅｍｋｉｎ两个模型,三种稻作制     

THE USE OF ADSORPTION EQUATIONS TO DESCRIBE COPPER COMPLEXING BY HUMIFIED ORGANIC MATTER

Samples of humified organic matter were extracted from several sources by water or alkali, and divided into colloidal and dialysable fractions. The variation of the concentration of complexed copper with that of added copper was determined for these fractions using a cupric ion-sensitive electrode. A computer program fitted five equations often used to describe adsorption of ions on soil surfaces to the results. The data did not fit Langmuir or Temkin equations very well, probably because of the heterogeneity of adsorption sites of the organic matter; they fitted double Langmuir, Gunary and Freundlich equations almost equally well, leaving very small residual sums of squares. The Freundlich isotherm is preferred as it has only two parameters and the values of these are fairly stable to changes in the range of copper concentrations considered, or to doubling of the complexant concentration.     

土壤对磷的吸持特性及其与土壤供磷指标之间的关系

本试验测定了浙江省几种代表性土壤对磷的等温吸持特性。实测值与Frundlich、Langmuir、两项式Langmuir和Temkin方程都很符合,相关系数变化范围在0.919-0.999之间,都达到极显著水平。其中以简单Langmuir等温式与本实验资料最为吻合。从Langmuir方程得到的土壤吸持特性值(k×q_m)被认为与土壤供磷特性有关。几种供试样品的(k×q_m)值是:针铁矿21100>黄筋泥4218>黄筋泥田991>青紫泥798>粉泥田660>高岭石485>老黄筋泥田423>泥质田298。根据土壤吸持特性值以田菁进行盆栽试验来估算作物磷肥需要量,结果表明,供磷强度0.3ppm P基本能满足田菁早期生长的需要。为使不同土壤达到相同的供磷强度,(k×q_m)值大的土壤要求更高的有效磷值。供试土壤的几种磷素指标:E值、Bray1-P值和(NaOH-Na₂C₂O₄)法值对(k×q_m)值的变化比较敏感,而EDTA-P和Olsen-P指标对(k×q_m)值的变化较为迟钝。     

Sorption of phosphorus in field-moist and air-dried samples from four weakly developed cultivated soil profiles

Sorption of phosphorus (P) in complete soil profiles in northern Europe is not adequately documented. I measured the sorption in genetic horizons of four cultivated soils (Inceptisols, Spodosol) in Finland using both field‐moist and air‐dried soil samples, fitted modified Freundlich equations (Q = a × I^b ? q) to the data, and presented the results in quantity/intensity (Q/I) graphs. Least‐squares‐estimates for the parameters of the modified Freundlich equation (a, b, q) were found to be imprecise measures of sorption. Values derived from the fitted equations (the amount of P sorbed at the P concentration of 2 mg litre^?1 and P buffering capacity at the same concentration) were more precise. Both were correlated with concentrations of oxalate‐extractable iron and aluminium. In all soils, there was a distinct difference in sorption between the fertilized Ap horizons and the subsurface horizons, which retained P strongly. Most of the sorption capacity was located in the B horizons at depths between 0.3 and 0.7 m. The results demonstrate the effects of soil‐forming processes and human impact on the sorption of P in the soils. Drying the samples prior to the sorption experiments altered the shape of the Q/I graphs. It increased dissolution of P at small P concentrations, sorption at large P concentrations, and the estimates for P buffering capacity. The effects of drying soil samples on the results and the imprecision of the parameters estimated with the modified Freundlich equation should be taken into account when interpreting results of Q/I experiments.     

Comparison of Five Adsorption Isotherms for Prediction of Zinc Retention in Calcareous Soils and the Relationship of their Coefficients with Soil Characteristics

Abstract

Zinc (Zn) deficiency is believed to be a consequence of reactions taking place between soluble Zn and the soil solid phase. This study was carried out to obtain quantitative relationships between Zn in equilibrium solution and that retained by the soil solids in calcareous soils. Twenty calcareous soils (saturated paste pH 6.9–7.9; calcium carbonate equivalent 4.64–22.80%) from Tehran province, Iran, were equilibrated with varying solution concentrations of Zn, and the amounts removed from the solution were used to check the fit to five adsorption isotherms, namely, Freundlich, Langmuir, Temkin, Gunary, and two‐surface Langmuir. Adsorption data of all soils showed statistically significant fit to the first four adsorption isotherms, but only 7 of the 20 soils tested showed fit to the two‐surface Langmuir. Coefficients of the adsorption isotherms showed statistically significant relationship with soil characteristics. Clay percentage, calcium carbonate equivalent percentage, and cation exchange capacity appeared to be the most influential soil characteristics with regard to Zn adsorption, whereas soil organic matter seemed to be of no importance under the conditions of this study.     

Modifications to the Freundlich equation to describe anion sorption over a large range and to describe competition between pairs of ions

We measured sorption of selenite and phosphate, both separately and in competition, in a Chilean Andisol. We also used previously published data for competitive sorption of arsenate and phosphate by a clay subsoil. We wrote computer programs that allowed us to compare the fits of differing versions of equations to describe individual sorption and competitive sorption. For the selenite–phosphate data, the index term of the Freundlich equation decreased as concentration increased. This was described using the Sibbesen modification of the Freundlich equation. This modification was then included in competition equations. For both the selenite–phosphate and the arsenate–phosphate data, competition was not ‘symmetrical’, that is, the competition terms were not reciprocals of each other. We think this occurred because competition between ions is not only competition for adsorption sites but also involves electrical effects that follow penetration of the surface.     

Evaluating Binary Sorption of Phenol/Aniline fromAqueous Solutions onto Granular Activated Carbon and Hypercrosslinked Polymeric Resin (MN200)

Sorption equilibrium of phenol and aniline onto the granular activated carbon and hyperreticulated un-functionalized polymeric resin (MN200) was investigated in single and binary component aqueous systems. Higher loading was obtained for aniline than phenol onto both sorbents, which is probably due to hydrophobic difference between both solutes and the greater electronic density of the aromatic ring of the aniline. Granular activated carbon reported larger uptake than resin MN200 for both solutes, which may be attributed to the better physical properties of the granular activated carbon, for instance, larger surface area. The experimental sorption could be properly described by the Langmuir and Freundlich isotherms. Five models for predicting the binary equilibrium sorption isotherm were compared in order to determine the best fit model to correlate binary experimental data: the extended Langmuir isotherm with and without a constant interaction factor, a simplified model based on the single equilibrium factors, the empirical extended Freundlich isotherm and the modified extended Langmuir equation, which considers the synergistic interactions between sorbate–sorbate and not only the competition between them defined by the extended Langmuir model. The modified extended Langmuir model provides the best agreement between predicted and experimental data indicating that the synergistic interactions between solutes play an important role in the binary phenol/aniline sorption system.     

MECHANISMS OF PHOSPHATE SORPTION BY SOILS AND HYDROUS FERRIC OXIDE GEL

Data for the sorption of added inorganic phosphate (P) by contrasting soils and iron oxide gel were resolved by a method of successive approximation of the Langmuir sorption constants. Three distinct Langmuir equations described the overall isotherm irrespective of the experimental conditions used. Free energies of sorption (ΔG) for a particular region were similar for each soil and for iron oxide gel under all experimental conditions. In contrast, the sorption maximum for each region was influenced by the sorbent and experimental conditions. Because of the pronounced similarities in their P sorption characteristics iron oxide gel was used as a model surface for P sorption by soils. Three mechanisms for P sorption by iron oxide gel and by soils are proposed: (i) chemisorption at protonated surface sites, (ii) chemisorption by replacement of surface hydroxyls, and (iii) a more-physical sorption of P as a potential-determining ion.     

宁夏灌淤土对磷吸附的初步研究

本文报道了宁夏灌淤土12个代表性土样对磷的等温吸附与解吸特性。实测吸附曲线与Preundlich、Langmuir和Temkin三种等温吸附方程都很吻合。全部供试样品的相关系数变化在0.931-0.999之间,均达极显著水平(p<0.01)。其中Langmuir等温式与本实验资料最为吻合。供试土壤对磷的最大吸附量(X_m)变化在172-460μgP/g之间,平均为347±28μgP/g。影响其大小的因子主要是物理性粘粒和CaCO₃,含量,均达极显著正相关。灌淤土不同土层的吸磷量大小依次为:剖面24>23>21>22,而解吸磷能力大小依次为:剖面23>22>21>24。磷的解吸量与吸附量之间呈极显著正相关。根据本试验数据,土壤对磷的等温吸附曲线可以用来预测土壤需磷量。     

Evaluation of phosphorus sorption by an allophanic soil

Solutions containing different P concentrations were equilibrated with samples of an allophanic soil from Navarra (Spain) to determine whether P sorption conformed qualitatively and quantitatively to the Langmuir, Freundlich and Sokolowska isotherms.Phosphorus sorption conformed to the Langmuir isotherm. When the sorption d data were plotted according to the conventional and Hofstee forms, two linear relationships were obtained. At the lower equilibrium P concentrations the K₁ parameter determined by regression analysis was higher than those corresponding to higher equilibrium P concentrations. The values obtained for K₁ and K₂ by the conventional and Hofstee equations were different. A procedure for evaluating the coefficients for higher equilibrium P concentrations was proposed. The K₁ and K₂ values so obtained allowed us to generate an experimental curve by addition of calculated adsorption data. This suggests that the curve-splitting technique is satisfactory.The sorption data also conformed to the Freundlich and Sokolowska equations, but in the latter it was necessary to evaluate two different sets of parameters.The same experimental data can be adjusted to the three different equations, in one case with only one set of constants and in the other two cases with two different sets of parameters, one for the lower P concentrations and the other for the higher ones. Besides, to fit the experimental data to the Langmuir and Sokolowska equations, it was necessary to split the isotherm into two regions and these two regions were different for the Langmuir and the Sokolowska equations. This suggests that the parameters do not have any chemical signification and that they are only “curve fitting”.A study of the effect of pH on the P sorption indicated that low pH notably increased the P sorption.The soil samples had very high phosphate sorption capacity probably due to the very large specific surface and reactivity of the allophane.     

Sorption of phosphorus by some surface soils from Quebec in relation to their properties

Abstract

Surface horizons from Podzolic and Gleysolic soils were collected in various parts of the province of Quebec, Canada, and equilibrated with various amounts of KH₂PO₄ in 0.01 M CaCl₂ for 48 hours. P sorption data conformed to the linear form of the Langmuir and Freundlich equations. P solubility isotherms showed evidence of hydroxyapatite formation in most samples studied, whereas equilibration solutions of only few samples were saturated with respect to either dicalcium phoshate dihydrate or octocalcium phosphate. These reaction products were associated to soil pH and levels of added phosphate. The average values of the Langmuir sorption maximum for these studied Gleysolic and Podzolic samples were 763 and 1096 μg/g respectively. These values were higher than those obtained by the segmented and modified Freundlich models.

Relationships between the soil characteristics and P sorption parameters were evaluated by regression analysis. Among all variables, oxalate‐extractable Fe plus Al content of the Podzolic samples and the ratio of oxalate—extractable Al to clay of the Gleysolic samples gave the best significant correlation coefficients. Furthermore, soil pH and various ratios such as pyrophosphate‐extractable Fe and Al, oxalate‐extractable Fe and organic matter to clay were found to be significantly correlated only with the P sorption parameters of the Gleysolic samples.     

Adsorption isotherms of copper and zinc in clay minerals of calcareous soils and their effects on X-ray diffraction

Reactions of elements with the water mineral interface are important and affect their bioavailability and transportation within soil. Effects of metal sorption on X-ray-diffraction (XRD-photographs) of clay minerals have been not studied. Therefore, sorption experiments were done on clay fractions of two calcareous soils using 12 concentrations of 0–2000 mg L^?1 Zn(NO₃)₂ and Cu(NO₃)₂. Langmuir and Freundlich isotherms’ coefficients were determined. After sorption, XRD-diffraction were prepared and compared with those of initial samples. Langmuir (R² = 0.996–0.999 and SE = 0.001–0.002) and Freundlich equation were the best-model for Zn and Cu-sorption, respectively. Sorption energy was higher for Zn than Cu, whereas the maximum concentration of sorbed-Cu was higher than that of Zn. Distribution coefficient (K_d) of Cu were more (threefold) than that of Zn. The K_d values representing the slope of Freundlich isotherms decreased according to linear regression equations (R² = 0.72–0.91) as the equilibrium concentrations of metals increased. No significant differences were observed among XRD-photographs of applied concentrations (some negligible differences were found in position/sharpness of peaks). Dry-XRD-method resulted in omission of intensity peaks at 2θ which may interfere in recognition of clays that show a maximum intensity >1.4 nm in the mentioned 2θ. Zinc can become more leachable especially in Shekarbani-soil-series, whereas, Cu highly adsorb on clay minerals and can show less tendency to transportation.     

Boron adsorption and desorption in some acid soils of West Bengal,India

Laboratory and greenhouse experiments were conducted to determine the influence of soil properties on adsorption and desorption of boron (B) as well as to estimate the degree of reversibility of adsorption reactions. The utility of Freundlich and Langmuir equations for characterizing the plant availability of applied B in soils was established using soybean [Glycine max (L.) Merr.] as a test crop. The adsorption-desorption study revealed that Fe₂O₃ and clay were primarily responsible for retaining added B in all the 25 different soils under investigation. Organic carbon, pH and cation exchange capacity (CEC) positively influenced the adsorption of B while free Fe₂O₃, organic carbon and clay retarded release of B from these soils. The degree of irreversibility (hysteresis) of B adsorption/desorption increased with increase in organic carbon and CEC of these soils. Freundlich isotherm proved more effective in describing B adsorption in soils as compared to Langmuir equation. The split Langmuir isotherm demonstrated that any of the adsorption maxima, calculated from lower, upper or entire isotherm, could be of practical use. Contrary, bonding energy coefficient, calculated either at lower or higher equilibrium concentration failed to show any practical benefit. Regression models as a function of B application rate and adsorption equation parameters to predict B uptake from applied B, demonstrated the utility of Langmuir and Freundlich equation parameters.     

A statistical study of seven curves for describing the sorption of phosphate by soil

Seven mathematical models, which have been advanced for describing phosphate sorption by soils, are studied here with respect to their statistical behaviour in estimation. These seven non-linear regression models include the Langmuir equation and two extensions of it, the Freundlich equation and two extensions of it, and Gunary's equation. Measures of non-linear behaviour, such as the Bates & Watts (1980) curvature measure of intrinsic non-linearity and the Lowry & Morton (1983) asymmetry measure of non-linearity, were calculated for each model in combination with each of six data sets. It was found that the Freundlich equation and the extension of it proposed by Sibbesen behaved best, with Gunary's equation also having acceptable statistical properties, whereas the Langmuir equation and its extensions behaved worse, exhibiting properties which indicate that the estimators of their parameters would be severely biased and non-normal in distribution. It is believed that similar conclusions may apply to other processes involving surface adsorption.     

Phosphate sorption by Greek alkaline soils evaluated with a modified Freundlich Equation

Phosphate adsorption of calcareous and non calcareous alkaline Greek soils was studied using the Freundlich Equation modified as to take also into account q, the quantity of phosphorus (P) already existing in these soils. Relatively high amounts of phosphate added were adsorbed, with a minimum of 44.5% at the highest level of P addition, being 600 μg P/g soil. The fit of the modified Freundlich Equation to the experimental data was best, when the values of bicarbonate extractable P were assigned to q, in comparison to both lower and higher values, Correction for q as above, resulted also in a statistically significant positive relationship between the Freundlich coefficient a, a capacity term with respect to P adsorption, and OM of the soils studied.