pH对土壤重金属吸附动力学的影响

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-brown soil from Nanjing, 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 increasing pH. The sorptions were more sensitive to pH in red soil than in yellow-brown soil.     

An evaluation of methods for characterizing phosphate sorption in rice soils

Abstract

Two single value methods of indexing P sorption were compared to parameters derived from P adsorption isotherms in a range of waterlogged and dry rice soils. These measures of P sorption capacity correlated closely with one another. However, they did not correlate equally with several other soil properties (pH, extractable Fe and Al). Because relationships between P sorption and soil properties proved to be method dependent, results from different methods must be compared with caution.

It is suggested that the single value method of Bache and Williams² be adopted when the rapid analyses of many samples is required. It is suited to routine analysis of soils with markedly different P sorption capacities, from both waterlogged and dry conditions.

Close correlations between the single value methods and P sorbed at a standard supernatant concentration suggest they may be useful in testing soils for P fertilizer requirements.     

Effects of equilibrating salt solutions on phosphate sorption by soils

Abstract

Several equilibrating salt solutions have been used in the studies of P sorption by soils and sediments. This study was conducted to evaluate the effects of 10 salt solutions on estimation of P sorption by soils. Results obtained showed that, when the equilibrating solution was made to contain 0.01M with respect to CaCl₂, Ca(NO₃)₂, CaSO₄, MgCl₂, KCl, LiCl, Nacl, or KHCO₃, the amount of P sorbed by soil always exceeded the amount sorbed from the soil‐water system. In comparison with the amount of P sorbed from water, 0.01M NaHCO₃ reduced P sorption by soils. Use of THAM buffer (0.05M pH 7.0) to control the pH increased P sorption by some soils and decreased P sorption by others, relative to that sorbed from the soil‐water system. The results indicated that inclusion of salts in the equilibrating solution for P‐sorption studies should be avoided, especially in studies related to water quality.     

Phosphate sorption in some representative soils of Bangladesh

An experiment was conducted to observe the phosphate sorption potential of some soils of Bangladesh. Three soil series of calcareous origin, namely Sara (Aquic Eutrochrept), Gopalpur (Aquic Eutrochrept) and Ishurdi (Aeric Haplaquept), and two soil series of non-calcareous origin, namely Tejgaon (Rhodic Paleustult) and Ghatail (Aeric Haplaquept), were selected. The soils were equilibrated with dilute solution of calcium chloride containing graded concentrations of phosphate (0, 1, 2, 5, 10, 25 and 50?μg?P?mL^?1), and the amount of phosphate sorbed or desorbed was determined. Although all the soils showed potential for sorbing phosphate from applied phosphorus, their ability to sorb phosphorus differed. Increasing rates of phosphate application increased the amount of P sorption but reduced phosphate sorption percentage in all soils except Tejgaon. Phosphate was sorbed by the soils in the order: Tejgaon > Ghatail > Ishurdi > Gopalpur > Sara at 50?μg?P?mL^?1 application. Soils possessing higher amounts of free iron oxide and clay sorbed more phosphate from applied phosphorus.     

The Langmuir parameters of orthophosphate and pyrophosphate sorption for ammoniated tropical soils

Abstract

The Langmuir parameters of orthophosphate (OP) and pyrophosphate (PP) sorption for the ammoniated tropical soils were determined. Positive linear relationships between OP and PP sorption maxima and amounts of anhydrous NH₃ added were noticed. Indexes of bonding energy of OP and PP increased exponentially as ammoniation level of the soils increased from 33 to 100% of ammonia retention capacity.     

Phosphorus sorption kinetics in different types of alkaline soils

This study investigated phosphorus sorption kinetics of three different soils from three sites within the Sahel region of Tunisia; iso-humic soils from Chott-Mariem site, calcic-magnesic soils from Enfidha site and saline-sodic soils from Kondar site. Soils from all sites were sampled (0–25 cm) and analysed for their physico-chemical proprieties. In previous works, we determined the adsorption efficiency of these different soils. In this study, we focused on the influence of contact time on phosphorus adsorption by the different soils. The analytic data were approached from the following kinetics models: pseudo-first-order, pseudo- second-order and Elovich model. The second order model was shown to be the best fit for describing phosphorus adsorption by each soil sample, as seen from the correlation coefficient R² which ranged from 0.68 to 0.96 for the pseudo-first-order model, 0.91 to 0.99 for pseudo-second-order model and 0.84 to 0.94 for Elovich model.     

Relationship between Gu(II) sorption and active H+ sorption sites of soils

Sorption characteristics of Cu(PI) were investigated using six soils coPBected in Korea (JUF9 SUM, and HHM) and in Japan (HNG, TWD, and ISM). The Cu(IH) sorption amount increased with increasing initial Cu(II) concentration. The maximnm sorption amount of @u(PI) increased in the order of KHM< ISK< JUM < JUF < TWD < KNG, and was related to the pH and BZSE of soils. The H⁺ release curves due to Cu(II) sorption apparently were characterized by a two or three step pattern. The amount of H⁺ released due do Cu(II) sorption increased with the increase in the Cu(II) sorption amount. The amount of protons released per Cu(II) sorbed onto soils with a larger Gu(II) sorption amount tended to be smaller compared with soils with a smaller Cu(HHQ sorption amount. The W⁺ sorption amount of the original soils and those with Cu(II) sorption at the PZSE, which was referred to as σ_P (Sakurai et al. 1988: Soil Sci. Plant Nutr., 34, 171–182; 1996: Jpn. J. Soil Sci. Plant Nutr., 67, 32–39), was determined by the STPT method proposed by Sakurai et al. (4988: Soil Sci. Plant Nutp., 34, 171–182). The active H⁺ sorption sites of soils were used for Cu(II) sorption and their amount decreased after Cu(II) sorption because they were covered with Cu(II). Soils with a larger amount of active H⁺ sorption sites exhibited a higher aEamity to Cu(II) khan those with a smaller amount of active H⁺ sorption sites. The Cu(II) sorption created a positive charge in soils, causing the decrease in the amount of active H⁺ sorption sites.     

Characterization of clay and fine silt fractions of forest soils by standardized K/Ca sorption isotherms

For better comparison of selectivity characteristics of clay and fine silt fractions sorption isotherms standardized on the cation exchange capacity (CEC) are useful. Due to the effect of the CEC on the sorption isotherms, it is necessary to characterize the exchanging substance with regard to different ion selectivities with standardized potassium/calcium‐(K/Ca) sorption isotherms. This procedure helps to complete the knowledge about the mineralogical composition, which is obtained by X‐ray powder diffractometry. A Haplic Luvisol from boulder marl shows distinct differences in its K selectivity both between different particle size fractions and different horizons. This is partly due to the presence of smectites and vermiculites which are differently distributed within the particle size fractions. The increase of K selectivity with increasing particle diameter in the calcareous C horizon can be attributed to the marginal expansion of mica/illite by Ca²⁺ ions. The K selectivity of individual particle size fractions in different horizons of a Gleyic Cambisol from glacial sand shows major similarities. If pedogenic chlorite is formed, no changes in selectivity characteristics can be observed.     

Effects of soil organic matter on pH-dependent phosphate sorption by soils

Effects of soil organic matter (80M) on P sorption of soils still remain to be clarified because contradictory results have been reported in the literature. In the present study, pH-dependent P sorption on an allophanic Andisol and an alluvial soil was compared with that on hydrogen peroxide (H₂0₂)-treated, acid-oxalate (OX)-treated, and dithionite-citrate- bicarbonate (DCB)-treated soils. Removal of 80M increased or decreased P sorption depending on the equilibrium pH values and soil types. In the H₂O₂ OX-, and DCB-treated soils, P sorption was pH-dependent, but this trend was not conspicuous in the untreated soils. It is likely that 80M affects P sorption of soils through three factors, competitive sorption, inhibition of polymerization and crystallization of metals such as AI and Fe, and flexible structure of metal-80M complexes. As a result, the number of available sites for P sorption would remain relatively constant in the wide range of equilibrium pH values in the presence of 80M. The P sorption characteristics were analyzed at constant equilibrium pH values (4.0 to 7.0) using the Langmuir equation as a local isotherm. The maximum number of available sites for P sorption (Q _max) was pH-dependent in the H₂0₂-, OX-, and DCBtreated soils, while this trend was not conspicuous in the untreated soils. Affinity constants related to binding strength (K) were less affected by the equilibrium pH values, soil types, and soil treatments, and were almost constant (log K ≈ 4.5). These findings support the hypothesis that 80M plays a role in keeping the number of available sites for P sorption relatively constant but does not affect the P sorption affinity. By estimating the Q _max and K values as a function of equilibrium pH values, pH-dependent P sorption was well simulated with four or two adjustable parameters. This empirical model could be useful and convenient for a rough estimation of the pH-dependent P sorption of soils.     

Effect of reducing conditions on P sorption of soils

Abstract

The phosphate sorption (P _sor) capacity of soils increased when the soils were reduced (Willet and Higgins, Aust. J. Soil Res., 16, 319–326, 1978). The present study aimed at the elucidation of this mechanism using Na₂S₂O₄ and 5 different soils. The P _sor of the 5 soils increased with the addition of a small amount of Na₂S₂O₄. Fe(II) was released from the soils with the addition of the same small amount of Na₂S₂O₄. Furthermore, when the amount of FeCl₂ corresponding to the amount of Fe(II) released along with the small amount of Na₂S₂O₄ was added, the P _sor of the soil increased. However, the P _sor of the lowland soils, of which the hydrous Fe oxide content was lower than the others, decreased when the amount of Na₂S₂O₄ addition was increased up to 150–200 g kg^?1. Based on these results, the following process is inferred for the increase in the P _sor of the soils when they are reduced. Hydrous Fe oxide in soil takes the form of very fine, high-density particles and reacts with P mainly on their surface. When a small amount of Na₂S₂O₄ is added, the hydrous Fe oxide is partially reduced, dissolved and finally re-precipitates with P by oxidation with O₂ from the air during the experiment.     

Specific sorption of trace amounts of cadmium by soils

Abstract

Sorption of trace quantities of Cd in four soils of different chemical and mineralogical properties, was studied. Initial Cd concentrations were between 15 to 150 μg. 1^?1. The sorption isotherms were linear and had a positive intercept in three of the soils, indicating a constant partition‐high affinity sorption isotherm (Giles et. al⁶). The data also followed the Freundlich sorption isotherm, and the Freundlich K parameter was taken as a measure of the relative affinity of the different soils for the Cd metal sorbed. Cadmium sorbed was extracted by IN‐NH₄C1 followed by 0.1N HC1, and the fraction remaining in the soils was considered specifically sorbed Cd. This fraction also followed a linear sorption isotherm, and was around 30% for the four soils studied. The sorption order for the amount of specifically sorbed Cd showed that the Boomer soil (kaolinite‐iron oxides) had the lowest affinity for specific sorption of this metal. This was taken as evidence that kaolinite and iron oxides have a lower capacity for retaining cadmium through specific sorption mechanism(s) than the materials present on the other soils (2:1 layer silicates and humic substances). The existence of specific mecha‐nism(s) responsible by the sorption of trace quantities of Cd in soil solutions has important implications on soil‐plant relationships, Cd mobility in soil profiles and control of Cd activity in soil solutions.     

综述: 酸性硫酸盐土壤的环境风险评价分析方法

Assessment of acid sulfate soil risk is an important step for acid sulfate soil management and its reliability depens very much on the suitability and ccuracy of various analytical methods for estimating sulfide-derived potential acidity,actual acidity and-neutralizing capacity in acid sulfate soils.This paper cirtically reviews various nalytical methods that are currently used for determination of the above parameters,as well as their implications for environmental risk assessment of acid sulfate soils.     

Kinetics of sorption of orthophosphate and pyrophosphate by ammoniated tropical soils

Abstract

A laboratory experiment was conducted to study kinetics of sorption of orthophosphate (OP) and pyrophosphate (PP) from dilute solutions by three ammoniated tropical soils. Milligrams of P sorbed by soil (?P) and shaking time (t) showed a linear relationship: ?P = a + b √t. The data suggested two diffusion — controlled processes during P sorption. In general, due to ammoniation, initial sorption rate of OP (in linear region I) increased while that of PP decreased. PP was sorbed more than OP. Sorption rate of OP and PP in linear region II showed a tendency to decrease with increasing ammoniation levels.     

Organic matter effects on phosphorus sorption in sandy soils

Phosphorus (P) sorption processes in soils contribute to important problems in agriculture: a deficiency of this plant nutrient and eutrophication in aquatic systems. Soil organic matter (SOM) plays a major role in sorption processes, but its influence on P sorption remains unclear and needs to be elucidated to improve the ability to effectively manage soil P. The aim of this research was to investigate the influence of SOM on P sorption. The study was conducted in sandy soil profiles and in topsoils before and after removal of SOM with H₂O₂. The results were interpreted with the Langmuir and Freundlich isotherms. Our results indicated that SOM affected P sorption in sandy soils, but that P sorption also depended on specific soil properties (e.g. values of the degree of P saturation (DPS), P sorption capacity (PSC) and pH) often related to land use. Removal of SOM decreased PSC in most of the topsoils tested; other soil properties became important in controlling P sorption. An increase in P desorption observed after SOM removal indicated that SOM was potentially that soil constituent which increased P binding and limited P leaching from these sandy soils.     

中国典型设施栽培土壤Cu、Zn累积特征及风险预测

为了探明铜(Cu)和锌(Zn)在设施栽培土壤中的累积现状及潜在风险,该研究基于中国8个省16个州市典型区域的设施栽培土壤全量和有效态含量,系统分析了Cu、Zn的累积现状及风险特征,并采用分段线性模型(Split-line Model)拟合了土壤Cu、Zn有效态累积量与种植年限的关系,预测了土壤Cu、Zn累积量超风险限量...     

可溶性有机物对土壤中绿麦隆吸附与解吸的影响

A batch equilibrium techniques was used to examine the effect of dissolved organic matter （DOM） extracted from both non-treated sludge （NTS） and heat-expanded sludge （HES） on the sorption and desorption of chlorotoluron （3-（3-chloro-p-tolyl）-1,1-dimethylurea） in two types of soils, a yellow fluvo-aquic and a red soil from China. Without DOM,sorption of chlorotoluron was significantly greater （P 〈 0.05） in the red soil than in the yellow fluvo-aquic soil. However,with DOM the effect was dependent on the soil type and nature of DOM. Chlorotoluron sorption was lower in the yellow fluvo-aquic soil than in the red soil, suggesting that with the same DOM levels the yellow fluvo-aquic soil had a lower sorption capacity for this herbicide. Application of DOM from both NTS and HES led to a general decrease in sorption to the soils and an increase in desorption from the soils. Desorption of chlorotoluron also significantly increased （P 〈 0.05） with an increase in the DOM concentration. Additionally, for sorption and desorption, at each DOM treatment level the NTS treatments were significantly lower （P 〈 0.05） than the HES treatments. This implied that non-treated sludge had a greater effect on the sorption and desorption of chlorotoluron than heat-expanded sludge.     

土壤组分对广东省酸性水稻土磷吸附参数的影响

Soil components affecting phosphate sorption parameters were studied using acid paddy soils derived from basalt, granite, sand-shale and the Pearl River Delta sediments, respectively, in Guangdong Province.For each soil, seven 2.50 g subsamples were equilibrated with 50 mL 0.02 mol L-1 (pH=7.0) of KCl containing 0, 5, 10, 15, 25, 50 and 100 ng P kg-1, respectively, in order to derive P sorption parameters (P sorption maximum, P sorption intensity factor and maximum buffer capacity) by Langmuir isotherm equation. It was shown that the main soil components influencing phosphate sorption maximum (Xm) included soil clay, pH,amorphous iron oxide (Feo) and amorphous aluminum oxide (Alo), with their effects in the order of Alo ＞Feo ＞ pH ＞ clay. Among these components, pH had a negative effect, and the others had a positive effect.Organic matter (OM) was the only soil component influencing P sorption intensity factor (K). The main components influencing maximum phosphate buffer capacity (MBC) consisted of soil clay, OM, pH, Feo and Alo, with their effects in the order of Alo ＞ OM ＞ pH ＞ Feo ＞ clay. Path analysis indicated that among the components with positive effects on maximum phosphate buffer capacity (MBC), the effect was in the order of Alo ＞ Feo ＞ Clay, while among the components with negative effects, OM ＞ pH. OM played an important role in mobilizing phosphate in acid paddy soils mainly through decreasing the sorption intensity of phosphate by soil particles.     

The effect of soil type on phosphorus sorption capacity and desorption dynamics in Irish grassland soils

Abstract. The phosphorus (P) sorption and desorption dynamics of eleven major agricultural grassland soil types in Ireland were examined using laboratory techniques, so that soils vulnerable to P loss might be identified. Desorption of P from soil using the iron-oxide paper strip test (Pfeo), water extractable P (Pw) and calcium chloride extractable P (Pcacl₂) depended on soil P status in all soils. However, soil types with high organic matter levels (OM), namely peat soils (%OM >30), had lower Pfeo and Pw but higher Pcacl₂ values compared to mineral soils at similar soil test P levels. Phosphorus sorption capacity remaining (PSCr) was measured using a single addition of P to soils and used to calculate total P sorption capacities (PSCt) and degree of P saturation (DPS). Phosphorus sorption capacities correlated negatively with % OM in soils indicating that OM may inhibit P sorption from solution to soil. High organic matter soils exhibited low P sorption capacities and poor P reserves (total P, oxalate extractable P) compared to mineral soils. Low P sorption capacities (PSCt) in peat soils were attributed to OM, which blocked or eliminated sorption sites with organic acids, therefore, P remained in the soil solution phase (Pcacl₂). In this work, peat and high organic matter soils exhibited P sorption and desorption characteristics which suggest that these soils may not be suitable for heavy applications of manure or fertilizer P owing to their low capacities for P sorption and storage.     

Biochar concomitantly increases simazine sorption in sandy loam soil and lowers its dissipation

Biochar application has been receiving much attention as pesticide pollution mitigator because it reduces harmful chemicals. However, direct comparisons between the effect of biochar and straw on the simazine fate in soils remain poorly understood. We explored the impact of biochars and straw on the simazine behavior in a soil using a ¹⁴C labeling approach. Biochar was produced by the thermal treatment of wheat straw at four contrasting temperatures (250, 350, 450 and 550°C) and was incorporated into a sandy loam soil. The sorption of simazine in the biochar soil from 83.9% to 87.5% was significantly higher than 43.0% in the unamended soil and 35.7% in the soil amended with unprocessed straw, thus resulting in low samizine leaching from 21.8% to 42.6% in the biochar soil. However, biochar application suppressed the simazine decomposition, which is contrast in the straw soil. Furthermore, the biogeochemical behavior of simazine varied with the pyrolysis temperature. These results indicate biochar application can significantly increase simazine adsorption and reduce leaching, which is benefit to the environmental pollution. In conclusion, the simazine behaviors in the soil are strongly influenced by the biochar properties. In comparison to straw, biochar has potential to mitigate simazine pollution.