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1.
The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing.  相似文献   

2.
The widespread use of sodium p-perfluorous nonenoxybenzene sulfonate(OBS), a typical alternative to perfluorooctane sulfonate, has resulted in potential threats to the environment, but the adsorption behavior of OBS in soils has not yet been reported. In this study, the adsorption behaviors of OBS on five soils with different physicochemical properties were investigated. The rate of OBS adsorption was fast, and most of the OBS uptake was completed within 12 h. The good model fit of OBS adsorption to the pseudo-second-order and Elovich models indicated the occurrence of chemical adsorption. The adsorption isotherms of OBS on the soils were better described by the Freundlich model than by the Langmuir model, suggesting that the OBS adsorption sites on the soils were heterogeneous. This is possibly associated with various adsorption mechanisms including hydrophobic, π-π, hydrogen bonding, and electrostatic interactions,further confirmed by the good model fit to the D-R isotherm. Adsorption of OBS occurred on the soils, and the adsorption process was spontaneous and endothermic. In addition, the soils were more suitable for OBS adsorption at lower pH values due to the stronger electrostatic adsorption. The OBS adsorption on the soils decreased with the increase of soil depth from 0 to 30 cm. Moreover, the presence of organic matter and ammonia nitrogen in the soils was favorable for OBS adsorption, and these parameters decreased with increasing soil depth, making OBS adsorption less prominent in the deeper soil. This study indicates that OBS is easily enriched in surface soils, and that soil organic matter and ammonia nitrogen significantly affect OBS migration in soil.  相似文献   

3.
Adsorption and desorption of exogenous rare earth elements (REE) in soils were studied.Results showed that soils had strong adsorbability for REE and the rate of adsorption of REE was over 95% of the added REE in these tests.The characteristics of adsorption isotherms corresponded well with the both Freundlich and Temkin equations,but deviated from the Langmuir equation.The adsorption of REE tended to increase with the rising of soil pH.A sequential extraction method used for studing the desorption and distribution of REE sorbed in soils are also discussed.  相似文献   

4.
有机配体、竞争阳离子和pH对土壤中Zn分解的影响   总被引：1，自引：0，他引：1  
A series of experiments were conducted to examine the interactive effects of an organic ligand, a competing cation, and pH on the dissolution of zinc （Zn） from three California soils, Maymen sandy loam, Merced clay, and Yolo clay loam. The concentrations of soluble Zn of the three soils were low in a background solution of Ca（NO3）2. Citric acid, a common organic ligand found in the rhizosphere, was effective in mobilizing Zn in these soils; its presence enhanced the concentration of Zn in soil solution by citrate forming a complex with Zn. The ability of Zn to form a complex with citric acid in the soil solution was dependent on the concentration of citric acid, pH, and the concentration of the competing cation Ca^2＋. The pH of the soil solution determined the extent of desorption of Zn in solid phase in the presence of citric acid. The amounts of Zn released from the solid phase were proportional to the concentration of citric acid and inversely proportional to the concentration of Ca（NO3）2 background solution, which supplied the competing cation Ca^2＋ for the formation of a complex with citrate. When the soil suspension was spiked with Zn, the adsorption of Zn by the soils was retarded by citric acid via the formation of the soluble Zn-citrate complex. The dissolution of Zn in the presence of citric acid was pH dependent in both adsorption and desorption processes.  相似文献   

5.
湿地土壤NH4+吸附解吸对冻融循环的响应   总被引：3，自引：0，他引：3  
Nitrogen (N) cycling in boreal peatland ecosystems may be influenced in important ways by freeze-thaw cycles (FTCs).Adsorption and desorption of ammonium ions (NH + 4) 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 + 4 and reduced the desorption potential of NH + 4 in the wetland soils.There were significant differences in the NH + 4 adsorption amount between the soils with and without freeze-thaw treatment.The adsorption amount of NH + 4 increased with increasing FTCs.The palustrine wetland soil had a greater adsorption capacity and a weaker desorption potential of NH + 4 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 NH + 4 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 NH + 4,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.  相似文献   

6.
As one of the most toxic heavy metals with persistence, bioaccumulation, and toxicity in environment, mercury and its envi- ronmental problems have caused a global concern. To fully understand the behavior and fate of mercury (Hg)(Ⅱ) in forest soils, a series of batch experiments were conducted to determine the adsorption and desorption characteristics of Hg(Ⅱ) by three dark brown forest soils from Mount Taishan, Laoshan Mountain, and Fanggan Village in Shandong Province, China. The adsorption solution was prepared using 0.1 mol L-1 NaNO3 as background electrolyte, with Hg(Ⅱ) at rising concentration gradients of 0.0, 2.0, 4.0, 6.0, 8.0, and 10.0 mg L-1 . Fourier transform infrared (FTIR) spectroscopy was adopted to characterize the soil samples and soil-Hg complexes. It was found that Hg(Ⅱ) adsorption isotherms could be well fitted with both Langmuir and Freundlich equations. The soil from Mount Taishan had the largest potential Hg(Ⅱ) adsorption capacity, though with less adsorptive intensity. The percentages of Hg(Ⅱ) desorbed from all soil samples were less than 0.6%, which suggested that all the soils studied had a high binding strength for Hg(Ⅱ). The soil from Mount Taishan had a higher Hg(Ⅱ) desorption capacity than the other soils, which indicated that the Hg(Ⅱ) deposited on the topsoil of Mount Taishan from atmosphere may easily discharge to surface water through runoff. Results of the FTIR spectroscopy showed that the three soils contained the same functional groups. The relative absorbencies of soil-Hg complexes changed significantly compared with those of the soil samples and the adsorption of Hg(Ⅱ) mainly acted on the O-H, C-O, and C=O groups of the soils.  相似文献   

7.
可溶性有机物对土壤中绿麦隆吸附与解吸的影响   总被引：7，自引：0，他引：7  
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.  相似文献   

8.
初始浓度对六氯苯在土壤中的吸附-解吸的影响及解吸   总被引：1，自引：0，他引：1  
GAO Hong-Jian  JIANG Xin 《土壤圈》2010,20(1):104-110
Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equilibrium batch experiments were carried out using two soils (red soil and paddy soil) with different initial HCB concentrations (0.25, 0.50, 0.75, 1.00, 1.50, 2.50, 3.50, and 5.00 mg L-1) by using 0.01 mol L-1 calcium chloride as the background solution. The successive desorption experiments (48, 96, 144, 192, and 240 h) were conducted after each adsorption equilibrium experiment. The results revealed that adsorption and desorption isotherms of HCB on two soils were nonlinear, which can be best described by the Freundlich equation with the square of the correlation coefficient (r2) ranging from 0.97 to 0.99. Desorption of HCB from the two soils exhibited hysteresis at all HCB concentrations because the Freundlich desorption coefficients were always higher than the Freundlich adsorption coefficients. The hysteretic effect was enhanced with increasing initial HCB concentration, and positive hysteresis was observed at different concentrations.  相似文献   

9.
Adsorption of Potassium and Sodium Ions by Variable Charge Soils   总被引：4，自引：2，他引：4  
Adsorption of potassium and sodium ions by four typical variable charge soils of South China was studied.The results indicated that the variable charge soils saturated with H and Al showed a much higher preference for potassium ions relative to sodium ions,and this tendence could not be changed by such factors as the pH,the concentration of the cations,the dielectric constant of solvent,the accompanying anions and the iron oxide content etc.,suggesting that this difference in affinity is caused by the difference in the nature of the two cations.It was observed that a negative adsorption of sodium ions by latosol and lateritic red soil in a mixed system containing equal amount of potassium and sodium ions at low pH,which is caused by a competitive adsorption of potassium and sodium ions and repulsion of positive charge on the surfaces of soil particles for cations.The adsorption of potassium and sodium ions increased with the decreases in the dielectric constant of solvent and the iron oxide content.Sulfate affected the adsorption of potassium and sodium ions through changing the surface properties of the soils.  相似文献   

10.
亚热带土壤不同矿物组分中铬的吸附   总被引：1，自引：0，他引：1  
Safe application of chromium (Cr)-containing organic industrial wastes to soil requires considering the ability of the soil to adsorb Cr.In this study,the maximum Cr adsorption capacity was assessed for the bulk samples and their clay and iron-free clay fractions of four subtropical soils differing in mineralogy.To this end,the samples were supplied with Cr(Ⅲ) nitrate solutions at pH 4.5 or 5.5.The results of Cr(Ⅲ) adsorption fitted to a Freundlich equation and the adsorption capacity was positively correlated with soil organic matter and iron oxide contents.The clay fractions adsorbed more Cr per unit mass than the bulk soils and the iron-free clay fractions.The Cr(Ⅲ) adsorption capacity increased with increasing soil pH due to more charges on adsorbing surfaces.Our results suggest that the soils rich in organic matter and iron oxides and having a pH above 4.5 are suitable for application of Cr(Ⅲ)-loaded industrial wastes.  相似文献   

11.
Liming is a practice commonly used to modify soil acidity, neutralize aluminum, and increase calcium and magnesium in the soil. Liming can change herbicide retention processes and consequently weed control and potential environmental contamination. The effects of liming on the sorption and desorption of hexazinone in different soils were evaluated. Samples from seven Brazilian soils were collected and separated into two subsamples, with and without limestone incubation. Hexazinone was quantified using ultra high-performance liquid chromatography. The sorption and desorption coefficients were determined in soils using Freundlich isotherms. Increasing the pH did not alter the sorption kinetics of hexazinone in the same soil class. The shortest sorption time of hexazinone occurred in soils with higher organic matter (OM) and clay content. Liming reduced the sorption and increased the desorption of hexazinone in the soils, which was caused by the increase in pH and reduction of OM content. Although the application of limestone increased desorption, the rate at which this process occurred was less than the sorption rate of hexazinone in most cases. In alkaline soils, the recommended dose of hexazinone for pre-emergence application should be low to avoid leaching and reduce the contamination of groundwater resources.  相似文献   

12.
Adsorption and desorption of triasulfuron by soil   总被引：10，自引：0，他引：10  
The adsorption and desorption of the herbicide triasulfuron [2-(2-chloroethoxy)-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carbonyl]benzenesulfonamide] by three soils, soil organic matter (H(+) and Ca(2+)-saturated), and an amorphous iron oxide were studied. Adsorption isotherms conformed to the Freundlich equation. It was found that pH is the main factor influencing the adsorption in all of the systems. Indeed, the adsorption on soils was negatively correlated with pH. The highest level of adsorption was measured on soils with low pH and high organic carbon content. Moreover, it was found that humic acid is more effective in the adsorption compared with calcium humate (the pH values of the suspensions being 3.5 and 6, respectively). Experiments on amorphous iron oxide confirmed the pH dependence. Desorption was hysteretic on soils having high organic carbon content.  相似文献   

13.
Adsorption-desorption studies of norflurazon on 17 soils of very different characteristics have been performed using a batch equilibration method and correlated to its mobility, activity, and persistence in soils. The influence of different soil properties and components on norflurazon adsorption was determined. The significant variables were organic matter (OM) content and iron and aluminum oxides, which accounted for 85 and 11% of the variability, respectively. Norflurazon desorption from soils was hysteretic in all cases, being more irreversible at the lowest herbicide concentrations adsorbed. The percentage of norflurazon eluted from columns of selected soils reached almost 100% in soils with sand content >80% and OM <1%, but in the soil which gave the highest sorption, herbicide residues were not detected at depths >16 cm. The herbicidal activity of norflurazon was followed by measuring its bleaching effect on soybean plants, and the herbicide concentration required to give 50% chlorophyll inhibition (CI(50)) was calculated. CI(50) was achieved on a sandy soil with 0.08 mg x kg(-)(1), whereas 1.98 mg x kg(-)(1) was necessary for the soil that presented maximum norflurazon adsorption.  相似文献   

14.
Adsorption/desorption characteristics of the herbicide 2,4-D on various types of soils were investigated. Batch equilibrium techniques were used in the laboratory experiments. Data were fitted to the linear and Freundlich sorption equations. K and Kf values ranged between 0.32–1.89 L- 1 mg and 2.6 × 10-3 – 7.4 mg kg- 1, respectively. Results showed that both for linear and Freundlich adsorption equations, for all soils, K and Kf were correlated to the organic matter content (r = 0.87 and r = 0.66, respectively). Adsorption was also positively correlated with silt and clay content of soils (r = 0.53) and negatively correlated with sand content.  相似文献   

15.
Adsorption and mobility of the herbicide linuron (3-3, 4-dichlorophenyl-1-methoxy-1-methylurea) in 35 irrigated soils with organic matter (OM) contents in the 0.43-2.59% range and in four natural soils with OM contents in the 4.16-11.69% range were studied using the batch equilibration technique. The adsorption isotherms were found to conform to the Freundlich adsorption equation. The Freundlich constant, K, and the distribution coefficient, K(d), were seen to be highly significantly correlated (p < 0.001) with the OM content when all soils or only those with an OM content above 2% were considered. There was also a significant correlation of K and K(d) with the OM content (p < 0.05) and of K(d) with the clay and silt plus clay contents (p < 0.1) when the soils with a OM content below 2% were considered. On the basis of the R(f)() values obtained by soil TLC, the pesticide was found to be slightly mobile in 77% and moderately mobile in 23% of the soils studied. The results of the leaching of linuron in soil columns unmodified and modified with two organic agricultural amendments, a city refuse compost, and two surfactants (one of them cationic and the other anionic) revealed that the leaching rate and the mass transfer of the herbicide to water were affected, increasing or decreasing according to the characteristics of the amendments and the doses added. These results also point to the usefulness of selected organic materials and surfactants in the development of physicochemical methods for preventing the pollution of soils, sediments and aquifers by hydrophobic pesticides.  相似文献   

16.
Adsorption and desorption of imazosulfuron by soil   总被引：12，自引：0，他引：12  
Understanding and quantifying the adsorption and desorption of herbicides by soil is important for predicting their fate and transport in the environment. Here we report a study concerning the adsorption and desorption, by four different soils, of imazosulfuron, 1-(2-chloroimidazo[1,2-a]pyridin-3-ylsulfonyl)-3-(4, 6-dimethoxypyrimidin-2-yl)urea, a new sulfonylurea herbicide. Both phenomena are well-described by the Freundlich equation, which shows this herbicide to be little adsorbed by each of the four soils investigated. The Freundlich adsorption constants, K(f-ads), ranged from 1.46 to 3.02. Distribution coefficients between soil and water, Kd, measured on soils of different organic matter contents and pH values showed an important effect of these two parameters on imazosulfuron retention. The Freundlich desorption data indicated that a significant amount of the imazosulfuron sorbed is not easily desorbed. The desorption process showed an evident hysteresis phenomenon, which may contribute to the persistence of imazosulfuron in soil.  相似文献   

17.
Azimsulfuron sorption--desorption on soil   总被引：11，自引：0，他引：11  
The sorption and desorption of the herbicide azimsulfuron, N-[[(4-dimethoxypyrimidin-2-yl)amino]carbonyl]1-methyl-4-(2-methyl-2H-tetrazole-5-yl)1H-pyrazole-5-sulfonamide, were studied using five soils. Sorption isotherms conformed to the Freundlich equation. It was found that pH is the main factor influencing the sorption and that the sorption on soils was negatively correlated with pH. The highest level of sorption was measured on soils with low pH and high organic carbon content. Moreover, inorganic soil colloids, for example, smectite clay minerals and iron oxides, contributed to the sorption of azimsulfuron. Desorption was hysteretic on soils with high organic and inorganic colloid contents.  相似文献   

18.
Abstract

The adsorption and mobility of herbicide, metamitron, in 41 soils samples from the province of Salamanca (Spain) was studied. Thirty‐four of the samples assayed were from irrigated soils and seven were from natural, uncultivated soils with organic matter contents above 3%. The correlations between the Freundlich K constants, Kd distribution coefficients, and Rf mobility parameters and the soils parameters were determined. Considering all the soils, the soils with organic matter contents above 2% or the soils with organic matter contents below 2%, significant correlations (p<0.001 to p<0.05) were found between K and Kd and the organic matter content of the soils. There were also a significant correlations (p<0.05) of K and Kd with clay+silt and clay contents of soils with organic matter contents below 2%. The adsorption of the herbicide by isolated soil components confirmed the results obtained with the soils and point to the importance of the exchangeable cation nature of the samples in the adsorption process. Based on Rf values obtained by TLC, the herbicide was found to be moderately mobile in 74% and mobile in 26% of the soils studied. The results of metamitron leaching by thin layer chromatography (TLC) and in undisturbed soil columns indicated the influence of organic matter content and of soil texture on the mobility of this herbicide.  相似文献   

19.
除草剂咪草烟在土壤上吸附-脱附过程及作用机理   总被引：2，自引：0，他引：2  
本文研究了咪唑啉酮类除草剂咪草烟在不同土壤固－液相间的分配及与土壤组分作用的定量相关性。结论指出：咪草烟在土壤固－液相的分配主要受土壤粘粒,有机质及土壤ｐＨ的影响。它们在土壤上的吸附－脱除均可用Ｆｒｅｕｎｄｌｉｃｈ方程描述;通过运用红外及Ｘ－衍射技术,从分子水平研究了咪草烟与蒙脱石的作用机理,发现咪草烟与蒙脱的作用不仅发生在表面,而且咪草烟还能进入蒙脱石内层与其层间阳离子形成配合物。  相似文献   

20.
The effect of beta-cyclodextrin (beta-CD) on the removal of the herbicide norflurazon (NFL) from soils has been investigated. The interaction of NFL with beta-CD in solution yielded the formation of a water-soluble inclusion complex at 1:1 stoichiometric ratio, which gave an increase in NFL solubility. Desorption studies of NFL previously adsorbed on six soils of different characteristics have been performed in the presence of 0.01 M beta-CD or 0.01 M Ca(NO(3))(2) as extractant solutions. Positive hysteresis was observed in all soils when 0.01 M Ca(NO(3))(2) solution was used, indicating that desorption of NFL from these soils was not completely reversible. On the contrary, the application of beta-CD solutions to soils where NFL had been previously adsorbed increased very much its desorption, and a negative hysteresis was obtained for all soils studied; that is, more NFL was desorbed with respect to NFL adsorption isotherm. A clear relationship was observed between the physicochemical characteristics of the soils and the beta-CD concentration necessary to remove the herbicide, the percentages of desorption observed for each soil being inversely related to the values obtained for the Freundlich sorption capacity parameter of the herbicide, K(f). In general, high desorption yields can be obtained with very low beta-CD concentrations, which is an important advantage from an economic point of view, although in those soils that present an extremely high NFL adsorption, higher amounts of beta-CD should be used. The results obtained indicate the high extracting power of beta-CD toward the herbicide previously adsorbed on the soils and the potential use of beta-CD for in situ remediation of pesticide-contaminated soils.  相似文献   

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