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1.
BACKGROUND: Sorption largely controls pesticide fate in soils because it influences its availability for biodegradation or transport in the soil water. In this study, variability of sorption and desorption of isoxaflutole (IFT) and its active metabolite diketonitrile (DKN) was investigated under conventional and conservation tillage. RESULTS: According to soil samples, IFT KD values ranged from 1.4 to 3.2 L kg?1 and DKN KD values ranged from 0.02 to 0.17 L kg?1. Positive correlations were found between organic carbon content and IFT and DKN sorption. IFT and DKN sorption was higher under conservation than under conventional tillage owing to higher organic carbon content. Under conservation tillage, measurements on maize and oat residues collected from the soil surface showed a greater sorption of IFT on plant residues than on soil samples, with the highest sorbed quantities measured on maize residues (KD ≈ 45 L kg?1). Desorption of IFT was hysteretic, and, after five consecutive desorptions, between 72 and 89% of the sorbed IFT was desorbed from soil samples. For maize residues, desorption was weak (<50% of the sorbed IFT), but, after two complementary desorptions allowing for IFT hydrolysis, DKN was released from maize residues. CONCLUSION: Owing to an increase in organic carbon in topsoil layers, sorption of IFT and DKN was enhanced under conservation tillage. Greater sorption capacities under conservation tillage could help in decreasing DKN leaching to groundwater. Copyright © 2012 Society of Chemical Industry  相似文献   

2.
BACKGROUND: The fate of isoxaflutole (IFT) in soil is closely related to soil sorption. Sorption and transformation of IFT were investigated in laboratory incubations with four soils, and these results were used to interpret greenhouse studies using IFT to control several weed species. RESULTS: Degradation proceeded by previously observed pathways to form diketonitrile (DKN) and benzoic acid (BA) derivatives, as well as traces of unidentified products. Over the course of the incubation, DKN was the dominant active form of the herbicide present in the experimental system, and was thus critical to the soil activity of the herbicide for weed control. CONCLUSION: Control of most weed species appeared to be a function of both sorption and biodegradation of DKN, with greatest weed control being observed in soils in which a significant portion of the DKN that was formed persisted and remained bioavailable over the course of the incubation. Copyright © 2009 Society of Chemical Industry  相似文献   

3.
Isoxaflutole is a relatively new herbicide used for weed control in maize. The objective of this research was to increase the understanding of the behaviour and environmental fate of isoxaflutole and its diketonitrile (DKN) degradate in soil, including determination of the strength of sorption to soil and whether sorption is affected by ageing. In sandy loam (SL) and silty clay (SiCl) soils, 14C‐isoxaflutole was found to dissipate rapidly after application to soil; recovery ranged from ～42% to 68% at week 0, and recovery had decreased to <10% at week 12. Decreases in 14C isoxaflutole residues over time in SL and SiCl soils are consistent with hydrolysis of isoxaflutole and formation of bound DKN residues in the soil. DKN recovery from freshly treated SiCl and SL soils was 41% to 52%. After a 12‐week incubation in SL soil at pH 7.1 and 8.0, recoveries were similar, ～40%. However, at week 12 in SL soil pH 5.7, DKN recovery decreased to ～28%. DKN recovery in SiCl soil at week 12 was <10%. Increases in sorption of DKN in SL at pH 5.7 and SiCl soil over time indicate that the DKN degradate is tightly bound to the soil and sorption is affected by soil pH and soil type. Sorption of 14C‐DKN in the SiCl soil more than doubled with ageing compared with the lower Kd sorption coefficient values of the SL soils. In the SiCl soil at time 0, the Kd was 0.6; at 1 week, Kd increased to 2; and at the end of the 12‐week incubation period, Kd was 4.5. This strong binding of DKN to the soil may be due to chelate formation in the interlayer of the clay.  相似文献   

4.
为评价氯胺嘧草醚的环境安全性,采用批量平衡法测定了氯胺嘧草醚在5种土壤中的吸附-解吸行为,并运用数学模型对其吸附-解吸特性及移动性能进行了分析。结果表明:氯胺嘧草醚在5种土壤中的等温吸附-解吸曲线符合Freundlich模型,吸附常数（Kf值）范围在6.991~18.49之间;不同土壤对其的吸附作用强弱依次为:黑土 > 水稻土 > 褐土 > 潮土 > 红土。氯胺嘧草醚在5种土壤中的有机碳吸附常数（KOC）范围在704.4~1 579之间,推测其在土壤中具有低移动性;薄层层析试验也表明,氯胺嘧草醚在土壤中的移动性较弱。氯胺嘧草醚在5种土壤中的吸附自由能绝对值均小于40 kJ/mol,表明其吸附机理主要是物理吸附。其Kf值与土壤有机质含量、黏粒含量呈正相关,而与土壤pH值呈负相关。解吸试验表明,氯胺醚在其中3种土壤中的解吸过程存在滞后现象。研究表明,在正常使用情况下,氯胺嘧草醚不易对地表水或地下水造成污染风险。  相似文献   

5.
BACKGROUND: Sorption‐desorption processes govern the movement of pesticides in soil. These processes determine the potential hazard of the pesticide in a given environment for groundwater contamination and need to be investigated. RESULTS: In the present study, sorption‐desorption processes of benfuracarb were investigated using a batch method in two mollisols. The kinetics of benfuracarb sorption in mollisols conformed to two‐compartment (1 + 1) first‐order kinetics. The fast sorption rate constant was about 3 times higher for silt loam than for loam soil. However, the slow sorption rate constants were statistically similar for both soils. The concentration‐dependent sorption‐desorption isotherms of benfuracarb could not closely conform to the Freundlich isotherm in mollisols of high organic C content. The computed values of both the sorption (log K) and desorption (log K′) capacities were higher for silt loam than for loam soil. The desorption index (n′/n) values in the range 30.0–41.3 indicated poor reversibility of sorbed benfuracarb in mollisols. CONCLUSION: In view of the strong sorption of benfuracarb in mollisols with only partial desorption, the possibility of the leaching of soil‐applied benfuracarb to contaminate groundwaters appears to be low. Copyright © 2010 Society of Chemical Industry  相似文献   

6.
BACKGROUND: Variations in soil properties with depth influence retention and degradation of pesticides. Understanding how soil properties within a profile affect pesticide retention and degradation will result in more accurate prediction by simulation models of pesticide fate and potential groundwater contamination. Metolachlor is more persistent than other acetanilide herbicides in the soil environment and has the potential to leach into groundwater. Reasonably, information is needed about the dissipation and eventual fate of metolachlor in subsoils. The objectives were to evaluate the adsorption and desorption characteristics and to determine the dissipation rates of metolachlor in both surface and subsurface soil samples. RESULTS: Adsorption of metolachlor was greater in the high‐organic‐matter surface soil than in subsoils. Lower adsorption distribution coefficient (Kads) values with increasing depth indicated less adsorption at lower depths and greater leaching potential of metolachlor after passage through the surface horizon. Desorption of metolachlor showed hysteresis, indicated by the higher adsorption slope (1/nads) compared with the desorption slope (1/ndes). Soils that adsorbed more metolachlor also desorbed less metolachlor. Metolachlor dissipation rates generally decreased with increasing soil depth. The first‐order dissipation rate was highest at the 0–50 cm depth (0.140 week?1) and lowest at the 350–425 cm depth (0.005 week?1). Degradation of the herbicide was significantly correlated with microbial activity in soils. CONCLUSION: Metolachlor that has escaped degradation or binding to organic matter at the soil surface might leach into the subsurface soil where it will dissipate slowly and be subject to transport to groundwater. Copyright © 2009 Society of Chemical Industry  相似文献   

7.
为研究三氟苯嘧啶的吸附-解吸附特性,采用振荡平衡法研究了三氟苯嘧啶在采集于吉林通化、江苏扬州、江西萍乡、广西南宁和海南海口等地的5种土壤中的吸附-解吸附行为及其环境影响因素。结果表明:三氟苯嘧啶在土壤中的吸附动力学符合Elovich模型,吸附和解吸附等温线符合Freundlich模型,吸附常数在1.886~7.626。温度的升高更有利于吸附,土壤对三氟苯嘧啶的吸附主要是物理吸附;随着溶液中pH值的升高,土壤对三氟苯嘧啶的吸附能力逐渐下降。除广西南宁黏壤土外,三氟苯嘧啶在5种土壤中的解吸附过程中存在滞后现象,不易在土壤中长期积累,具有一定的迁移特性。  相似文献   

8.
磺酰脲类除草剂是应用较为广泛的农药之一,其在土壤中迁移、降解、转化和滞留等多个过程受其吸附、解吸行为的影响。本文以嗪吡嘧磺隆为研究对象,采用批量平衡法研究了其在8种不同类型土壤中的吸附、解吸附行为。结果表明:嗪吡嘧磺隆与土壤溶液接触4 h内为快速吸附阶段。Freundlich模型可较好地拟合嗪吡嘧磺隆在土壤中的等温吸附解吸过程,相关系数 (r) 值在0.9584~0.9973之间。8种土壤对嗪吡嘧磺隆的吸附能力均为弱,吸附常数 (Kf-ads) 在0.281~3.515之间。其中,以黑龙江白浆土对嗪吡嘧磺隆的吸附能力最强,且远高于其他土壤。除广西赤红壤外,嗪吡嘧磺隆在其他7种类型土壤中的滞后系数 (H) 均小于1,解吸过程存在滞后现象,存在潜在环境风险。单因素试验结果表明,嗪吡嘧磺隆在土壤中的吸附行为受腐殖酸的影响极显著 (P＜0.01),受pH值和Mn2 + 的影响显著 (P＜0.05),受高岭土和稻壳生物炭的影响不显著 (P＞0.05)。采用中心复合试验设计,建立了具有一定预测功能的嗪吡嘧磺隆在土壤中的吸附过程BP神经网络模型,并进行了验证,拟合结果较好。  相似文献   

9.

The behavior in competitive adsorption-desorption reactions of Cu and Zn was studied in four calcareous soils. Cu and Zn were added to the soil by Cu, Zn, and Cu+Zn sulfate solutions in a CaSO4 background. Soil sorption of these cations was described by equilibrium isotherms that fitted either Freundlich- or Langmuir type equations, although Cu desorption data fitted only Freundlich isotherms. Cu and Zn competition was quantified by distribution coefficients, Kd, relating cation distribution between soil and solute and by the competitive Langmuir equation. The competitive Langmuir equation was the better suited to describe the Cu-Zn competitive adsorption in these soils. Distribution coefficients presented lower values when both cations were present, decreasing when the Cu and Zn concentration in solution increased (decreasing soil affinity for these cations), thereby increasing their mobility through the soil. However, the distribution coefficient of specifically adsorbed Cu in equilibrium with cations extracted by a Mg (NO) solution increased with Cu concentration. Cu adsorption was more depres 3 se 2 d by Zn than Zn adsorption by Cu. The different behavior of Cu and Zn seems dependent on the percentage Ca (CO) and, to a lesser degree, on Cu and Zn organic matter complexes, free iro 3 n 2 content, and surface precipitation on oxides and carbonates.  相似文献   

10.
Adsorption, incubation and soil-column experiments with bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] were carried out in ten different soils from the marches surrounding the Doñana National Park (Huelva, SW Spain). Adsorption isotherms for the different soils showed a good fit with the Freundlich equation. Bentazone was poorly adsorbed in all the soils studied, with no significant relationship between theKf values and soil characteristics. A significant correlation was obtained between the soil organic matter content and the distribution constant values (Kd) calculated at an equilibrium concentration of 200 μg cm−3. The low adsorption and non-degradation of bentazone on these soils suggest that the herbicide readily percolates through soils to reach the surface and ground waters. The mobility of bentazone through three soil columns was also studied. The mass balances carried out showed that bentazone was totally eluted from the soil columns. The theoretical model applied to explain bentazone leaching under our experimental conditions seems to be suitable for soil columns with a uniform water-flow rate.  相似文献   

11.
The adsorption of carbofuran on soils from water‐methanol mixtures has been evaluated by batch shake testing. Two uncontaminated soils having different physicochemical properties were used in these experiments. The volume fraction of methanol in the liquid phase (fs) was varied from 0.25 to 1.0. Higher adsorption of carbofuran was observed in medium black (silt loam) soil than in alluvial (sandy loam) soil; calculated values of the Freundlich constant (Km) and distribution coefficient (Kd) showed that adsorption of carbofuran in both soils decreased with increase in fS values. The decreased carbofuran adsorption in methanol–water mixtures meant a greater potential of ground‐water contamination through leaching from potential sites. The data have been used to evaluate the co‐solvent theory for describing adsorption of carbofuran in methanol–water mixtures. The aqueous phase partition coefficient Kdw (mol g−1) normalized with respect to foc and the aqueous phase adsorption constant Kw for carbofuran were evaluated by extrapolating to fS = 0. © 2000 Society of Chemical Industry  相似文献   

12.
BACKGROUND: The behavior of the termiticide fipronil in soils was studied to assess its potential to contaminate ground and surface water. This study characterizes (1) adsorption of fipronil in three different soils, (2) transport of fipronil through leaching and runoff under simulated rainfall in these soils and (3) degradation of fipronil to fipronil sulfide and fipronil sulfone in these soils. RESULTS: The adsorption experiments showed a Freundlich isotherm for fipronil with Koc equal to 1184 L kg?1. In the leaching experiments, the concentration of fipronil and its metabolites in leachate and runoff decreased asymptotically with time. The concentration of fipronil in the leachate from the three soils correlated inversely with soil organic carbon content. The degradation experiment showed that the half‐life of fipronil in the soils ranged from 28 to 34 days when soil moisture content was 75% of field capacities, and that 10.7–23.5% of the degraded fipronil was transformed into the two metabolites (fipronil sulfide and fipronil sulfone). CONCLUSION: Fipronil showed large losses through leaching but small losses via runoff owing to low volumes of runoff water generated and/or negligible particle‐facilitated transport of fipronil. The half‐life values of fipronil in all three soils were similar. Copyright © 2011 Society of Chemical Industry  相似文献   

13.
精异丙甲草胺在土壤中的吸附行为及 环境影响因素研究   总被引：1，自引：1，他引：1  
采用平衡振荡法研究了精异丙甲草胺在粘壤土、粘土及砂壤土中的吸附和解吸附行为。结果表明,3种土壤的吸附等温线均属L型并符合Freundlich模型,吸附常数(Kf)分别为4.01、6.15及8.62,且Kf 和1/n(n为经验常数)的乘积与土壤有机质含量呈正相关性。解吸附实验结果表明,精异丙甲草胺在土壤中的解吸附与吸附并不一致,显示出明显的滞后性。温度及pH值等环境因素对吸附影响的结果显示,随温度升高精异丙甲草胺在土壤中的吸附量有所减少,中性环境下土壤吸附量较低。  相似文献   

14.
不同形态氧化铁对黄土性土壤吸附铅的影响   总被引：1，自引：0，他引：1  
针对土壤含氧化铁的普遍性以及氧化铁对土壤理化性质的重要影响,探求氧化铁对土壤吸附重金属离子的作用与影响。采用了化学选择性溶提技术,分别去除黄土性母质上发育的古土壤、淋溶褐土和黄褐土中不同形态的氧化铁,采用了等温吸附试验,并以Langmuir和Freundlich方程拟合参数为指标,分析去除不同形态氧化铁前后土壤对Pb~(2+)的吸附特征。结果表明:原土壤对Pb~(2+)的吸附曲线逐渐递增,并无明显阶段特征,且更符合Freundlich方程;而去除不同形态氧化铁后的3类土壤对Pb~(2+)的吸附曲线均为L型,阶段特征显著,更加符合Langmuir方程,且土壤对Pb~(2+)的亲和力(KL)成倍增加;去除络合态铁和无定形氧化铁后,土壤对Pb~(2+)的最大吸附量均有不同程度增加,其中去除无定形氧化铁之后,古土壤对Pb~(2+)的最大吸附量增幅最大,增加了14.71 mg·g-1;去除游离态氧化铁后古土壤、淋溶褐土对Pb~(2+)的吸附量分别下降了5.95、3.10 mg·g-1,黄褐土对Pb~(2+)的吸附量则增加了2.98 mg·g-1。土壤中氧化铁对Pb~(2+)吸附能力与吸附容量的影响不完全依赖于氧化铁的含量,在很大程度上依赖于土壤中氧化铁的形态。对于不同氧化铁形态的土壤采用相应的化学溶提技术,能够获得具有较高吸附性能的粘土矿物环境材料。  相似文献   

15.
Inclusion complex formation of 2,4‐dichlorophenoxyacetic acid (2,4‐D) with hydroxypropyl‐β‐cyclodextrin (HP‐β‐CD) has been proposed as a way of modifying the behaviour of the pesticide in the soil environment. The present study assesses the effect of complex formation on 2,4‐D physicochemical properties (aqueous solubility, crystallinity and dissolution rate) and its behaviour on soils. The solid complexes were prepared using different methods (spray drying, kneading and heating in a sealed container). To confirm the complex formation in the solid state differential scanning calorimetry, hot stage microscopy and x‐ray diffraction techniques were employed. Complex formation in solution was studied by phase solubility. The presence of HP‐β‐CD increased the 2,4‐D solubility nine times approximately. The apparent stability constant was determined as 98.6 M −1. The dissolution rates of the 2,4‐D/HP‐β‐CD complexes were examined and compared with that of the pure pesticide. The results indicated that the complex may have great utility as a rapid way of dissolving the pesticide. Batch experiments were performed to study the adsorption–desorption of 2,4‐D on soils and the influence of the HP‐β‐CD over these processes. The results showed that HP‐β‐CD could increase the desorption of 2,4‐D previously adsorbed on soils. © 2000 Society of Chemical Industry  相似文献   

16.
Five soils with different organic matter contents ranging from 0.48 to 10.4% were used to study the adsorption and desorption of alachlor, metolachor, EPTC, chlorothalonil and pirimiphos-methyl in batch experiments. The isotherm shapes according to Giles classification were S-type for alachlor, metolachlor and chlorothalonil, changing to L-type for the latter as the level of soil organic matter increased, and L-type for EPTC and pirimiphos-methyl. The adsorption isotherms fitted the Freundlich equation x/m = KfCe1/n. The Kf values increased with the increase of organic matter content. The amounts of pesticides adsorbed over a range of concentrations of 0.1-20 mg litre-1 reached 63.1% for alachlor, 69.2% for metolachlor, 89.3% for EPTC, 98.4% for chlorothalonil and 96.3% for pirimiphos-methyl. The increase of the amounts desorbed with acetone indicated that the sorption of organic compounds onto organic matter occurred principally via weak London-type induction forces, or dispersion forces which are characteristics of the physical adsorption process.  相似文献   

17.
Adsorption–desorption characteristics of 2,4-dichlorophenoxyacetic acid (2,4-D) on pure montmorillonite and synthetic chlorite-like complexes [Al(OH)x-montmorillonite complexes, obtained by coating montmorillonite surfaces with different amounts of Al(OH)x] were investigated. The equilibrium adsorption of 2,4-D was described by both Langmuir and Freundlich type isotherms. The extent of adsorption as well as the type of interaction between adsorbate and adsorbent was affected by the nature of incubation buffer and the charge characteristics of supports. At pH 5·6 and in acetate buffer, 2,4-D was negatively adsorbed by montmorillonite and herbicide adsorption capacity increased with increasing amounts of Al(OH)x species loaded on montmorillonite surfaces. When adsorption experiments were performed at the same pH but in phosphate buffer, strong reductions of both the amount of adsorbed pesticide and its affinity for the adsorbents were measured. Evidently, phosphate anions competed strongly with 2,4-D anions for the sorption site on chlorite-like complexes. Furthermore, desorption tests revealed that a large amount (about 60%) of the pesticide was firmly bound to the clay and was not removed even after repeated washings or 24 h exposure to desorption solution. Both electrostatic interactions between the negative COO- moieties of 2,4-D and the positive sites on clays, and ligand exchanges of COO- groups with -OH or water at the clay surface were probably involved in the adsorption process. ©1997 SCI  相似文献   

18.
施磷对不同生育期棉田土壤磷素吸持特性的影响   总被引：1，自引：0，他引：1  
以两种质地棉田土壤为材料,研究不同施磷处理对不同生育期棉田土壤磷吸附与解吸的影响.结果表明:各生育期磷素等温吸附曲线与Langmuir,Temkin和Freundlich方程拟合度均达极显著水平,尤以Freundlich方程拟合度最高,相关系数均在0.96以上;磷的吸附饱和度(DPS)、零净吸附浓度磷(EPC_0)、吸附量、解吸量和解吸率随施磷量的增加均呈增长趋势,而标准需磷量(SPR)呈下降趋势;以Freundlich方程估算原状棉田土壤各个生育期的需磷量,壤质棉田苗期、花铃期和吐絮期的需磷量(按含P_2O_5 46%的磷肥折算)分别为143.7,137.4 kg/hm~2和160.2 kg/hm~2,砂壤质棉田苗期、花铃期和吐絮期的需磷量分别为106.6,251.1 kg/hm~2和173.0 kg/hm~2.  相似文献   

19.
鱼藤酮在3种土壤中的吸附-解吸附特性   总被引：2，自引：0，他引：2  
为了综合评价鱼藤酮在土壤环境中的吸附-解吸附特性,采用批量平衡法,系统研究了鱼藤酮在砂壤土、黏壤土及壤土3种农业土壤中的吸附-解吸附行为。结果表明,鱼藤酮在3种土壤中的吸附-解吸附行为符合Freundlich模型 (R2≥0.946 8),吸附常数 (Kf-ads) 在1.52~11.39之间,吸附能力为:黏壤土 > 砂壤土 > 壤土;而解吸附常数 (Kf-des) 在1.02~4.55之间,解吸附强弱次序为壤土 > 黏壤土 > 砂壤土。鱼藤酮在砂壤土、黏壤土和壤土3种土壤中有机碳吸附常数 (KOC) 分别为982、101 7和219,而滞后系数 (H) 分别为0.687 3、0.556 9和0.892 3,表明鱼藤酮在黏壤土及砂壤土中移动性较弱,有正迟滞作用,而在壤土中移动性较强,无迟滞作用。该研究将对鱼藤酮的环境风险评估具有一定的理论指导意义。  相似文献   

20.
低分子量有机酸对二氯喹啉酸在土壤中吸附-解吸的影响   总被引：2，自引：0，他引：2  
采用高效液相色谱仪及批量平衡试验方法,研究了乙酸、苹果酸、酒石酸、草酸、丁二酸和柠檬酸6种低分子量有机酸对麻沙泥和第四纪红土红壤吸附-解吸二氯喹啉酸的影响。结果表明:低分子量有机酸可推迟二氯喹啉酸在土壤中的吸附平衡时间,其吸附动力学过程可用准二级动力学方程描述。Linear和Freundlich方程能较好地拟合二氯喹啉酸在供试两种土壤中的吸附等温线;二氯喹啉酸在麻沙泥中的吸附能力(lg Kf值)从大到小依次为苹果酸柠檬酸草酸=乙酸丁二酸酒石酸,在第四纪红土红壤中为苹果酸丁二酸乙酸草酸柠檬酸酒石酸;低分子量有机酸浓度对二氯喹啉酸解吸的影响因有机酸种类和供试土壤的不同而差异较大,6种供试有机酸均促进了第四纪红土红壤对二氯喹啉酸的解吸,且其解吸率均明显高于麻沙泥对二氯喹啉酸的解吸率,但在麻沙泥中呈现不同的影响模式。  相似文献   

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