首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 93 毫秒
1.
The Freundlich isotherm was used to estimate the adsorption of the herbicide linuron on 39 Japanese soils to confirm the suitability of the prediction technique used in atrazine adsorption. Linuron was adsorbed on the soils according to the Freundlich isotherm. In conjunction with the log K F prediction equation derived from the soil characteristics, it was possible to predict the linuron adsorption. Comparison of the equations for linuron with those for atrazine, indicated that the difference in the intercept of the 1 / n regression line against log K F reflected the adsorptive characteristics of the herbicides.  相似文献   

2.
The adsorption-desorption equilibrium of atrazine (2-chloro, 4-ethylamino, 6-isopropyl amino-1, 3, 5 triazine) was studied by the batch equilibration method at 27 ± 1 °C on four soils of Hyderabad. Adsorption isotherms conformed to the Freundlich equation (A = KC1/n ). K increased in the same order as the organic C content of the soils. Desorption studies were conducted by repeated replacement of 5 mL of the supernatant equilibrium solutions after adsorption, with 0.01 M CaCl2. Desorption isotherms showed considerable hysteresis which was more prominent when the desorption was carried out with higher adsorbed concentration of atrazine. Desorption from the lowest level of adsorbed atrazine (3 to 5 μg g?1 soil) was close to the adsorption isotherm. The cumulative desorption after four desorption steps covering five days was significantly different at the 1% level, for different initial adsorbed concentrations of atrazine. Desorption was significantly higher at the lowest adsorbed level of atrazine. The soils differed significantly at 6% level for desorption and the amount desorbed decreased in the inverse order of organic C. Desorption isotherms also conformed to Freundlich equation but K andn values were both higher than that for adsorption and increased with increase in initially adsorbed concentration of atrazine. Desorption thus confirmed the irreversible nature of the adsorption of atrazine on these soils. The quantitative factors and reasons for desorption are discussed.  相似文献   

3.
This study investigated the effect of different farming practices over long time periods on the sorption‐desorption behavior of Cu, Cd, and Zn in soils. Various amendments in a long‐term field experiment over 44 y altered the chemical and physical properties of the soil. Adsorption isotherms obtained from batch sorption experiments with Cu, Cd, and Zn were well described by Freundlich equations for adsorption and desorption. The data showed that Cu was adsorbed in high amounts, followed by Zn and Cd. In most treatments, Cd ions were more weakly sorbed than Cu or Zn. Generally, adsorption coefficients KF increased among the investigated farming practices in the following order: sewage sludge ≤ fallow < inorganic fertilizer without N ≈ green manure < peat < Ca(NO3)2 < animal manure ≤ grassland/extensive pasture. The impact of different soil management on the sorption properties of agricultural soils for trace metals was quantified. Results demonstrated that the soil pH was the main factor controlling the behavior of heavy metals in soil altered through management. Furthermore, the constants KF and n of isotherms obtained from the experiments significantly correlated with the amount of solid and water‐soluble organic carbon (WSOC) in the soils. Higher soil pH and higher contents of soil organic carbon led to higher adsorption. Carboxyl and carbonyl groups as well as WSOC significantly influenced the sorption behavior of heavy metals in soils with similar mineral soil constituents.  相似文献   

4.
Adsorption and desorption of the herbicides glyphosate [N-phosphonomethyl-aminoaceticacid], simazine [6-chloro-N,N′-diethyl-1,3,5-triazine-2,4-diamine] and atrazine [6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine] were studied in four sandy soils from Western Australia. Distribution coefficients (Kds) were calculated from breakthrough curves (BTCs) resulting from leaching step changes in concentrations through small saturated columns of soil at flow rates ranging from 0.3 to 30 m day–1. A comparison was made with Kds obtained after batch equilibrating solutions of the herbicides with the same soils. The Kds of herbicides in soils decreased with increasing flow rate and most strongly for glyphosate in soils rich in clay content. Resulting increases in mobility of about 40–50% were estimated for simazine and atrazine and > 50% for glyphosate at flow rates of 3 m day–1. Adsorption and desorption rates were estimated by fitting numerically simulated BTCs to experimental BTCs. Best fits were obtained with a time-dependent Freundlich adsorption equation. The resulting coefficient for time dependency in the equation suggests that the rates of adsorption and desorption are controlled mainly by diffusion in an adsorbing layer on or in soil particles.  相似文献   

5.
Atrazine [6-chloro-N-ethyl-N′-(1-methyl)-1,3,5 triazine-2,3-diamine] and alachlor [2-chloro-N-(2,6-diethylphenyl)-N-(methoxymethyl) acetamide] are agricultural herbicides used in large quantities and, as a consequence, are common contaminants in groundwater and surface water. The retention of these herbicides in soils and their degradation in aqueous environments is highly dependent upon their adsorption to solid surfaces. The adsorption of atrazine and alachlor was investigated on three typical Kansas and underlying aquifers known to be vulnerable to contamination. More alachlor was adsorbed to the soils and sediments than atrazine. The adsorption coefficients for atrazine were 2 to 5 times higher for soils than for aquifer sediments. For alachlor, the adsorption coefficients were 4 to 20 times higher for soil than for aquifer solids. Both linear and Freundlich isotherms represented the adsorption data well in all cases. The slope of the Freundlich isotherms, 1/n, was close to one, with the exception of alachlor adsorption onto the Topeka aquifer sediment (1/n = 0.67). The K d values found in these studies were comparable to the lower range of those reported in the literature.  相似文献   

6.
The adsorption kinetics and adsorption parameters of metolachlor, atrazine, deethylatrazine (DEA), deisopropylatrazine (DIA) and hydroxyatrazine (HA) were investigated in a soil profile in a maize field formed from recent alluvial deposits in a river basin in Greece. We used the batch equilibrium method modified to simulate field conditions as closely as possible for the use and practices related to soil applied pre‐emergence herbicides. Pseudo‐equilibrium times, determined by kinetic studies, were achieved after 16, 16, 24, 24 and 48 hours for metolachlor, DIA, DEA, HA and atrazine, respectively. At pseudo‐equilibrium the percentage of the adsorbed amount increased in the order of DEA (10%) < DIA (14%) < atrazine (27%) < metolachlor (43%) ≪ HA (94%) which indicates that more than 57% of all compounds except for HA are in solution and available for transport to deeper soil layers when conditions similar to those simulated in the laboratory exist in the field. Adsorption isotherms of all compounds and in most of the cases correlated well with the Freundlich model and adsorption coefficients (Kf) decreased with increased soil depth. Principal component and multiple regression analyses confirmed the importance of the soil organic carbon content on the adsorption capacity of soils for all compounds except HA in the plough layers (0–40 cm). In the subsurface soils (40–110 cm) variables such as clay content and pH were more important. For HA, the Kf values determined for the plough and subsurface soil layers were better correlated with clay content and pH. Also in the subsurface soils, the variation in organic carbon content was not correlated with the variation of Kf values. Thus calculated Koc‐f‐values misrepresent the adsorptive capacity of these soils towards the compounds studied.  相似文献   

7.
Abstract

The sorption behavior of three triazine herbicides: atrazine, metribuzin, and terbutryn was studied in two different soils. Three experimental procedures to determine the Kf values were assayed: the conventional batch equilibration method in which the sorbed concentration is calculated by difference from the change in solution concentration; an alternative mass balance equilibrium batch technique in which the solution and the sorbed phase concentration are measured directly; and the flow equilibration method in which a solution of known concentration was passed through a column of soil until the effluent reached the same concentration as the input solution. Four concentrations of each herbicide were selected and results were fitted to the linearized form of the Freundlich isotherm. Recovery of the herbicides was studied in soil and water samples using the same four concentrations employed in the sorption assays. Average recoveries ranged from 86 to 104% with standard deviations lower than 10%. The Koc (mg1–1/n kg‐1 Ll/n) values obtained ranged from 43 to 87 for atrazine, 27 to 114 for metribuzin, and 355 to 505 for terbutryn. The exponents 1/n of the Freundlich adsorption isotherms were lower than unity, with only one exception, and varied from 0.72 to 0.86 for atrazine, 0.73 to 1.12 for metribuzin, and 0.76 to 0.99 for terbutryn. The solution method gave values of Koc that were 1.25, 1.55, and 2.65 (average of both soils) times those of the mass balance method for terbutryn, atrazine and metribuzin, respectively. When adsorption was low, the mass balance calculation method is recommended if the batch equilibration method is used, since the solution method can produce a considerable overestimation of adsorption. The flow equilibration method produced similar values of adsorption than the mass balance batch equilibration method and it made the experimental procedure easier since pesticide solution concentration need not to be measured once the equilibration time has been determined to ensure that the equilibrium was reached.  相似文献   

8.
土壤和氧化铁对氟化物的吸附和解吸   总被引：5，自引：0，他引：5  
邵宗臣  陈家坊 《土壤学报》1986,23(3):236-242
本文研究了两种土壤(砖红壤和黄棕壤)和两种合成氧化铁(无定形氧化铁和针铁矿)对氟化钠溶液的吸附和解吸现象,讨论了氟离子吸附的吸附等温线特征.根据实验资料和吸附等温线的拟合情况,我们认为,砖红壤和无定形氧化铁用Langmuir公式来描述,黄棕壤和针铁矿用Freundlich公式来描述更为适宜.氟离子的解吸量均低于吸附量.研究结果表明,由于水洗和醇洗,一部分以静电引力所吸附的氟离子被洗去,造成氟离子解吸量偏低.  相似文献   

9.
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.  相似文献   

10.
A. K. DOLUI  S. S. ROY 《土壤圈》2005,15(5):611-619
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.  相似文献   

11.
Cadmium (Cd) sorption and desorption characteristics by Alfisols from different land uses were examined, and the relationships between soil and sorption/desorption characteristics were investigated. Adsorption studies were done using Cd concentrations (0–100 mg Cd kg?1) in 0.01 M CaCl2. The Cd sorbed by the soils was then subjected to two desorption runs. The soils' adsorption conformed to Freundlich and Langmuir equations. The amount of Cd sorbed by the soils varied. Two desorption runs detached more than 95% of sorbed Cd, but the first accounted for more than 80% of the total. Desorption of Cd in degraded soils was more than in soils from other land uses. The amount of Cd desorbed correlated with amount applied (r = 0.90??), solution concentration (r = 0.83??), and amount sorbed (r = 0.70??). A positive relationship exists between the adsorption maxima of the soils and soil organic matter (r = 0.13, p = 0.87). The relationship between amount of Cd desorbed and sorbed is quadratic for all the soil.  相似文献   

12.

Purpose

Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of atrazine in soils. Equilibrium batch experiments were carried out to investigate the adsorption–desorption characteristics of atrazine. The objectives of this study were to (1) determine and quantify the main soil parameters governing atrazine adsorption and desorption phenomena; (2) find the correlativity between the identified soil parameters; and (3) investigate the universal desorption hysteresis traits.

Materials and methods

Fifteen soils with contrasting physico-chemical characteristics were collected from 11 provinces in eastern China. The equilibrium time was 24 h both for adsorption and desorption experiments. Atrazine was detected by Waters 2695/UV HPLC.

Results and discussion

Adsorption isotherms of atrazine could be well described by the Freundlich equation (r?≥?0.994, p?<?0.01). The total organic carbon (TOC) was the first independent variable that described 53.0 % of the total variability of K f, followed by the pH (9.9 %), and the clay (4.0 %) and silt (1.2 %) contents, separately; while the primary soil properties that affect desorption parameters included the TOC, pH, free Fe2O3 (Fed) and the sand content, with the biggest contribution achieved by the TOC (ranged from 48.5–78.1 %). The results showed that when the content ratio of clay to TOC (RCO) was less than 40, the atrazine adsorption was largely influenced by the organic matrix, while when the RCO was greater than 40, they were vital affected by the clay content.

Conclusions

Adsorption–desorption isotherms of atrazine in soils were nonlinear. The content of TOC, clay, and iron oxides, as well as the pH value were the key soil parameters affecting the adsorption–desorption of atrazine in soil, among which the RCO especially exhibited relevance. Additionally, the desorption hysteresis existed for atrazine retention in all 15 tested soils, and the hysteretic effect enhanced with the increasing time for desorption. This would be ascribed to the heterogeneity physical–chemical properties of these soils.  相似文献   

13.
叶炳  王虹 《土壤学报》1984,21(1):21-28
目前应用Langmuir吸附等温式来探讨土壤对磷酸离子的吸附作用,较为广泛.自从Olsen(1957)系统地报道以来,从机理到结合生产实际的研究已有大量的报道,我国近年来也有研究.由于土壤本身组成的复杂性,多数学者用纯物质(如纯粘土或铁与铝的含水氧化物等)进行吸附等温式的机理研究,已取得了很多结果.  相似文献   

14.
The adsorption and desorption of dimepiperate, S-(,-dimethylbenzyl)-1-piperidinecarbothioate, on three soils of various physical and chemical properties was studied. Adsorption isotherms conformed to Freundlich equation. The k f values increased with increasing organic carbon content of the soils. To confirm the effect of organic matter, the adsorption of the herbicide was studied after removal of organic matter by peroxidation. This soil treatment caused a sequential loss of adsorptive capacity. Desorption isotherms also conformed to Freundlich equation, but K des values were higher than those for adsorption and increased with increase in concentration of initially adsorbed dimepiperate. Hysteresis was indicated by the decrease in slope of desorption compared to adsorption isotherms. Hysteresis decreased with increasing methanol content in the extracting solution. The factors involved are discussed.  相似文献   

15.
周志强  刘琛  杨红薇  鲜青松  唐翔宇 《土壤》2018,50(2):353-360
吸附-解吸是影响抗生素类污染物在土壤中迁移转化及生物有效性的重要过程,本文以川中丘陵区坡耕地紫色土为研究对象,通过批量平衡实验和柱实验研究生物炭施用（投加量0(B0)、39.75 (B1)t/hm2和198.75 (B2) t/hm2）及田间老化作用（夏季干湿交替）对三种典型磺胺类抗生素（磺胺嘧啶（SD）、磺胺二甲基嘧啶（SM2）及磺胺甲恶唑（SMZ））在紫色土中的吸附-解吸和淋溶行为的影响。结果表明：在几种处理中,三种磺胺类抗生素吸附强弱的顺序都表现为SD>SMZ>SM2;与B0处理相比,添加生物炭能增加土壤对三种抗生素的吸附能力,其中SM2的吸附显著增加（P<0.05）,但这种促进作用在经过老化过程后有所减弱。在解吸过程中,三种抗生素的Freundlich常数Kf大小顺序为SD>SMZ>SM2,表明SD在土壤中吸附容量最大且不易解吸,其次是SMZ和SM2;相应的迟滞系数H大小顺序为SD相似文献   

16.
The adsorption of a radioisotope of caesium, 137Cs, has been interpretation and ratio and solution measured on four soils with differing clay mineralogies. All measurements have been made using unwashed soils in suspensions shaken for 2 h at 20°C. The effects of concentration in potassium and caesium, the nature of the background electrolyte and the soil:solution ratio have been investigated. The results are expressed either as the distribution coefficient, KD or as Freundlich isotherms. The distribution coefficient of each of the soils decreases markedly as the concentration of caesium increases. The adsorption properties of the soils are not determined by the dominant clay mineralogy alone. Adsorption is always lower in 0.01 m CaCl2 solution than in water. The addition of potassium has relatively little effect on adsorption of trace amounts of caesium; however, KD decreases with increasing concentrations of stable caesium. The major reason for the dependence of KD on the soil: solution ratio is found to be the non-linear adsorption isotherm; the influence of the varying compositions of the solution and exchange complex is minor. The validity of the use of a single KD value as an indicator of adsorption capacity and the meaning of the relative values of the Freundlich parameters are considered. The implications of these findings for the use of radiotracers and the usefulness of KD as an indicator of bioavailability are discussed.  相似文献   

17.
通过等温吸附试验,研究不同磷含量处理暗棕壤对Zn2+的吸附解吸行为,结果表明:(1)随平衡液中Zn2+浓度的增加,3种处理暗棕壤对Zn2+的吸附作用均表现为:低浓度下(0～100 mg/L),吸附量增加迅速,随着浓度升高(100～150 mg/L),吸附量变缓并渐趋平衡,含磷量高的土壤吸附Zn2+的量较高。(2)Freundlich、Langmuir和Temkin方程均能很好描述Zn2+在3种不同磷含量暗棕壤上的吸附等温线,拟合效果依次为Freundlich>Langmuir>Temkin。经参数计算,较高磷含量有利于提高暗棕壤的最大吸附量和土壤对Zn2+的缓冲容量,而磷含量不同对Zn2+在暗棕壤上的吸附力没有太大影响。(3)3种不同磷含量处理暗棕壤吸附量与解吸量关系图形状相似,呈高度线性相关,均表现为暗棕壤对Zn2+的解吸量随吸附量的增加而增加,磷含量较高土壤有利于Zn2+的固定且不易解吸。  相似文献   

18.
土壤对镉的吸附与解吸——Ⅱ.吸附势与解吸势   总被引：7，自引：0，他引：7       下载免费PDF全文
陈怀满 《土壤学报》1988,25(3):227-235
本文提出了吸附势(logKa)和解吸势(logKd或相对解吸势logKdr)两个有关吸附和解吸的强度概念,并进行了理论推导和实验验证。logKa和logKd或logKdr是影响土壤或胶体吸附和解吸因素的综合反应。实验证实logKa可用于表征土壤胶体对Cd的相对选择性,并且对胶体吸附Cd有着良好的预测性;logKdr可用于表征土壤胶体对Cd的相对固定能力,并可用于估测Cd的污染程度。盆栽试验表明,随着土壤胶体logKa的增加,或logKdr的降低,稻草或糙米中Cd的含量下降。可以预期,吸附势和解吸势不但在土壤物理化学,土壤环境化学研究中,而且在植物营养化学、水化学、以及界面化学等方面有可能获得实际应用。  相似文献   

19.
On the relation of herbicide adsorption and soil organic fraction Freundlich adsorption isotherms were measured for four herbicides (atrazine, terbuthylazine, chlorotoluron, isoproturon) and 24 soil horizons, which are typical of Schleswig-Holstein, northern Germany. The relationship between the adsorption constant (KFr) of a chemical and the fraction of organic carbon (fOC) of the soil horizons was evaluated. Chemical specific K'OC-values, that are independent of soil organic carbon fraction varied considerably for each herbicide (CV about 50%); therefore these values as well as KOC-values, that are determined by linear regression of KFr and fOC should be evaluated critically before application. K'OC- and KOC-values derived from experiments showed decreasing affinity of the herbicides to soil horizons in the order terbuthylazine > chlorotoluron > atrazine ? isoproturon. Calculation of KOC from KOW or water solubility of each herbicide, however, led to changes in the above mentioned ranking. Hence, especially KOW or water solubility based KOC-values may lead to false conclusions concerning chemical mobility. For atrazine, terbuthylazine and isoproturon Freundlich adsorption constants increased overproportionally with increasing organic carbon content of soils. The relationships between KFr and fOC therefore were described better by a non-linear equation (second order polynom) than by a linear approach. Contrary, for chlorotoluron a linear relation between KFr and fOC holds at least for the range of fOC investigated in this study.  相似文献   

20.
The mobility, bioavailability, and environmental fate of heavy metals in soil are controlled by their adsorption onto soil minerals and solid organic matter. The adsorption is strongly affected by the presence of various low-molecular-weight organic acids. In this study, effect of hydroxamate siderophore desferrioxamine B (DFOB) on cadmium (Cd) and zinc (Zn) adsorption onto two micaceous clay minerals, muscovite and phlogopite, was evaluated in batch experiments. Results showed that the presence of DFOB diminished the adsorption of Cd and Zn onto both minerals, particularly under neutral to alkaline pH conditions. For instance, at pH 8.2, the presence of DFOB caused a decrease in the adsorption of Zn onto phlogopite by nearly 50%. The equilibrium adsorption of Cd and Zn was satisfactorily described using Freundlich isotherm. The adsorption isotherms showed that the affinity of Cd and Zn onto the minerals decreased in the presence of DFOB. For example, at pH 8.0, the presence of siderophore caused a decrease in the Freundlich adsorption isotherm coefficient KF for Zn adsorption onto muscovite and phlogopite from 4.60 to 0.07 L g-1 and from 3.56 to 0.36 L g-1, respectively. These findings confirm the potential influence of siderophore on the fate of Cd and Zn in arid soils containing substantial contributions of micaceous silicate minerals.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号