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1.
Sulfentrazone and metolachlor have been detected in groundwater due to extensive leaching. To reduce herbicide leaching and increase weed control, we have developed, designed, and tested controlled release formulations (CRFs) for both herbicides based on their solubilizion in cationic micelles and adsorption of the mixed micelles (surfactant and herbicide) on a clay mineral, montmorillonite. A better understanding of solubilizing anionic (sulfentrazone) and nonionic (metolachlor) organic molecules in cationic micelles was reached. The percent of active ingredient in the formulations was much higher than previously designed CRFs due to the enhanced solubilization of the herbicides in the micelles and due to their adsorption on the clay. Both CRFs demonstrated controlled release (compared to the commercial formulations) when applied to a thin soil layer. A bioassay in soil columns determined that the new sulfentrazone and metolachlor CRFs significantly improve weed control and reduce leaching (for the latter) in comparison with the commercial formulations.  相似文献   

2.
The herbicide sulfentrazone is classified as highly mobile and persistent and this study aimed to examine degradation of this compound on a Typic Hapludox soil that is representative of regions where sulfentrazone is used in Brazil. Soil samples were supplemented with sulfentrazone (0.7 μg active ingredient (a.i.) g?1 soil), and maintained at 27 °C. Soil moisture was corrected to 30%, 70%, or 100% water-holding capacity (WHC) and maintained constant until the end of the experimental period. Soils without added herbicide were used as controls. Aliquots were taken after 14, 30, 60, 120, 180, and 255 days of incubation for quantitative analysis of sulfentrazone residues by gas chromatography. Another experiment was conducted in soil samples, with and without the herbicide, at different temperatures (15, 30, and 40 °C), with moisture kept constant at 70% of WHC. The sulfentrazone residues were quantified by gas chromatography after 14, 30, 60, and 120 days of incubation. Sulfentrazone degradation was not affected by soil moisture. A significant effect was observed for the temperature factor after 120 days on herbicide degradation, which was higher at 30 °C. A half-life of 146.5 days was recorded. It was observed that the herbicide stimulated growth of actinomycetes, whereas bacterial and fungal growth was not affected. The microorganisms selected as potential sulfentrazone degraders were Rhizobium radiobacter, Ralstonia pickettii, Methylobacterium radiotolerans, Cladosporium sp., Eupenicillium sp., and Paecilomyces sp.  相似文献   

3.
Slow release formulations of the anionic herbicide sulfosulfuron (SFS) were prepared by incorporating it in micelles of an organic cation octadecyltrimethylammonium, which adsorb on the clay-mineral montmorillonite. The fraction of SFS adsorbed on the micelle-clay complex reached 98%, whereas for monomer-clay complexes, its adsorption was insignificant. Fluorescence studies showed surface contact between the micelles and the clay surface. The rate of SFS release from the micelle-clay formulations in aqueous suspensions was slow (<1%, 72 h). Spraying SFS formulations on a thin soil layer in a funnel, followed by irrigations (50 mm), resulted in complete elution of SFS from the commercial formulation (dispersible granular) versus 4% from the micelle-clay formulation. A plant bioassay in Rehovot soil showed that these respective formulations yielded 23 and 65% of shoot growth inhibition of foxtail. Consequently, the slow release micelle-clay formulations of SFS yield significantly reduced leaching and enhanced biological activity, thus providing environmental and agricultural advantages.  相似文献   

4.
The development of controlled-release formulations of alachlor to diminish its leaching in sandy soils, avoiding groundwater contamination and maintaining its efficacy, was studied. For this purpose, ethylcellulose (EC) microencapsulated formulations (MEFs) of alachlor were prepared under different conditions and applied to soil columns to study their mobility. The results show that in all cases the release into water of alachlor from MEFs was retarded when compared with commercial formulation. Total leaching losses in soil columns were reduced to 59% from 98%. The mobility of alachlor from EC microspheres into soil columns has been greatly diminished in comparison with its current commercial formulation (CF), above all with increasing EC/herbicide ratios. Distribution of alachlor applied as MEFs at different depths in the soil was higher in the soil surface (66.3-81.3% of herbicide applied at the first 12 cm). In contrast, the residues from CF along the complete soil column were only 20.4%. From the results of bioassays, MEFs showed a higher efficacy than CF at 30 days after the treatment. The use of ME formulations could provide an advantage in minimizing the risk of groundwater contamination by alachlor and reducing the application rates, as a result of maintaining the desired concentration of the herbicide in the top soil layer, obtaining longer periods of weed control.  相似文献   

5.
Five ethylcellulose (EC) microencapsulated formulations (MEFs) of norflurazon were prepared and applied in soil to study their mobility, dissipation, activity, and persistence. The results show that the release into water of norflurazon from EC microspheres was retarded when compared with that of commercial herbicide. The mobility of norflurazon from MEFs into soil columns has been greatly diminished in comparison with that of its current commercial formulation (CF). Norflurazon distribution at different depths in the soil was higher in the upper ring (up to 50% of the initial application). In contrast, the residues from commercial norflurazon along the complete soil column were only about 2%. Degradation and bioassay experiments showed that the MEFs had greater persistence (t1/2 values were 7.72 and 30.83 weeks for CF and MEFs, respectively) and herbicidal activity than the commercial formulation. The use of these formulations can be advantageous, because they can minimize the risk of groundwater contamination and permit herbicide use at reduced rates, maintaining the desired concentrations of herbicide in the topsoil layer for longer periods of weed control.  相似文献   

6.
The herbicide norflurazon was encapsulated in ethylcellulose (EC(40)) microspheres by the solvent evaporation technique to obtain controlled release formulations. The kinetics of release of the active ingredient into the aqueous solution from different preparations was determined. It was found that the percentage release of the incorporated herbicide was a function of the composition and formation conditions of the formulations (amount of emulsifying agent, EC(40)/herbicide ratio, stirring speed, and percentage of pore-forming agent). The percentage of the herbicide release was related to the properties of the different microspheres obtained, such as particle size distribution, herbicide loading, or surface morphology. The release percentage depended inversely on the particle size of the microspheres and directly on the content of active ingredient and emulsifying and pore-forming agents. An empirical equation was used to fit the herbicide release data, indicating that the release of norflurazon from the various formulations is controlled by a diffusion mechanism. The time taken for 50% of the active ingredient to be released into water (T(50)) was calculated, showing a wide variation among the different preparations (0.95-16.4 days).  相似文献   

7.
The risk of ground water contamination resulting from rapid leaching of highly soluble pesticides can be minimized through the application of the pesticide adsorbed on a matrix or carrier, which limits the amount of pesticide immediately available for undesirable losses. The use of natural materials for this purpose is of special interest in terms of economy and sustainability. In this work the adsorption of the herbicide hexazinone by two montmorillonites saturated with various inorganic and organic cations was determined and the ability of the two clays displaying the highest adsorption capacities [Fe(3+)-saturated Wyoming montmorillonite, (Fe-SW) and hexadecyltrimethylammonium-saturated Arizona montmorillonite (HDTMA-SA)] to act as carriers for slow release of hexazinone and to reduce herbicide leaching losses was evaluated. Hexazinone formulations based on Fe-SW and HDTMA-SA displayed slow release properties in water and soil/water suspensions, reduced herbicide leaching in soil columns, and maintained herbicidal activity, as compared with the currently available commercial hexazinone formulation (wettable powder). Loosely bound hexazinone-HDTMASA formulations, which led to the slowest breakthrough of hexazinone in soil columns along with the greatest amounts of herbicide released from the clay particles, displayed the most interesting characteristics for their use as slow release formulations and to prevent ground water contamination.  相似文献   

8.
The design and tests of slow-release formulations of sulfometuron (SFM), an anionic sulfonylurea herbicide, are described. The formulations are based on incorporation of the herbicide in octadecyltrimethylammonium (ODTMA) micelles, which adsorb on a clay mineral, montmorillonite. An optimization of herbicide/micelle clay ratios yielded high adsorption of SFM (95%), and at a 1% (w/w) water suspension only 0.5% of the adsorbed SFM was released at times varying from hours to 9 days. An analytical test in Seville soil showed that under excessive irrigation (400 mm) 100% of the commercial formulation leached, whereas the micelle-clay formulations showed only 50-65% elution. A plant bioassay in Rehovot soil showed that the commercial dispersible granule formulation (Oust, 75% ai sulfometuron methyl) yielded only 23% root elongation inhibition at the top 5 cm of the soil, whereas complete inhibition was achieved with the micelle-clay formulation. The detected concentration of SFM for the micelle-clay formulation at a depth of 15-20 cm was half of that detected for the commercial one, indicating a reduction in leaching when applying the micelle-clay formulation. A 10-fold reduction in the applied dose of SFM in the micelle-clay formulations resulted in good herbicidal activity of 60-87% inhibition. These characteristics make the new formulation promising from the environmental and economic points of view.  相似文献   

9.
The herbicide diuron was incorporated in alginate-based granules to obtain controlled release (CR) properties. The standard formulation (alginate-herbicide-water) was modified by the addition of different sorbents. The effect on diuron release rate caused by incorporation of natural and acid-treated bentonites in alginate formulation was studied by immersion of the granules in water under static conditions. The release of diuron was diffusion-controlled. The time taken for 50% release of active ingredient to be released into water, T(50), was calculated for the comparison of formulations. The addition of bentonite to the alginate-based formulation produced the higher T(50) values, indicating slower release of the diuron. The mobility of technical and formulated diuron was compared by using soil columns. The use of alginate-based CR formulations containing bentonite produced a less vertical distribution of the active ingredient as compared to the technical product and commercial formulation. Sorption capacities of the various soil constituents for diuron were also determined using batch experiments.  相似文献   

10.
Current knowledge about the behavior of forest species under herbicide treatment regarding selectivity, resistance, and fitotoxic effects is insufficient. This study assesses the selectivity of sulfentrazone and glyphosate on Hymenaea courbaril L. seedlings (jatoba) and the effects of this herbicide on the rhizospheric microbial activity of those plants. For this assessment, two experiments were conducted. In the first one, 10 treatments were compounded by the combination of two herbicides (glyphosate and sulfentrazone) applied in five doses (0.00, 0.09, 0.18, 0.35, and 0.70 L ha?1). The second experiment assessed effects of the combination of five doses of the herbicide sulfentrazone and two types of substrate (rhizospheric and nonrhizospheric cultivated with jatoba seedling). To assess the selectivity of seedling to the herbicide, visual assessments of toxicity were carried out 15, 30, 45, and 60 days after the application. To determine the effect of sulfentrazone on rhizospheric activity, the basal respiration and of microbial biomass carbon (CBM) associated with substrates was evaluated. A good tolerance of the seedling with the herbicide was observed even at higher doses, indicating potential use in control of weeds in areas of jatoba planting in the initial phase of development. Regarding microbiological indicators, it is verified that the evolution of carbon dioxide carbon (C-CO2) and CBM were effective in the presence of herbicides, which can constitute auxiliary tools for environmental-impact monitoring of the herbicides.  相似文献   

11.
To assess the persistence and dissipation kinetics of sulfentrazone in soil, terminal residues in soybean and carryover effect on bioindicator species, field experiment was carried out under Indian tropical conditions. The sulfentrazone was applied at 360, 480 and 720?g a.i. ha?1 rates as pre-emergence herbicide. Its residues in soil and in soybean at harvest were analyzed by high pressure liquid chromatography. Results showed that the sulfentrazone dissipation in soil followed first-order reaction kinetics with the half-lives of 5.5 to 14.8 days. Terminal residue in shoot and grain showed that sulfentazone at 360?g ha?1 can be safely applied for weed control in soybean since there was no phytotoxicity injury to the crop. The residue in soybean grain was within the safe limits (0.05?µg g?1) as proposed by US. However, the detection of sulfentrazone residue in soil at harvest and carryover injury to bioindicator signified the risk for crops in succession. Hence the use of this herbicide in soil with low organic matter and coarse texture is questionable as it is highly mobile. Further biomagnifications of sulfentrazone residue in soil and crop produce under continuous use and interaction of climatic variables and soil properties on its persistence, sorption and leaching behavior need to be investigated.  相似文献   

12.
The estrogenic isoflavones of soybeans and their glycosides are products of the shikimate pathway, the target pathway of glyphosate. This study tested the hypothesis that nonphytotoxic levels of glyphosate and other herbicides known to affect phenolic compound biosynthesis might influence levels of these nutraceutical compounds in glyphosate-resistant soybeans. The effects of glyphosate and other herbicides were determined on estrogenic isoflavones and shikimate in glyphosate-resistant soybeans from identical experiments conducted on different cultivars in Mississippi and Missouri. Four commonly used herbicide treatments were compared to a hand-weeded control. The herbicide treatments were (1) glyphosate at 1260 g/ha at 3 weeks after planting (WAP), followed by glyphosate at 840 g/ha at 6 WAP; (2) sulfentrazone at 168 g/ha plus chlorimuron at 34 g/ha applied preemergence (PRE), followed by glyphosate at 1260 g/ha at 6 WAP; (3) sulfentrazone at 168 g/ha plus chlorimuron at 34 g/ha applied PRE, followed by glyphosate at 1260 g/ha at full bloom; and (4) sulfentrazone at 168 g/ha plus chlorimuron at 34 g/ha applied PRE, followed by acifluorfen at 280 g/ha plus bentazon at 560 g/ha plus clethodim at 140 g/ha at 6 WAP. Soybeans were harvested at maturity, and seeds were analyzed for daidzein, daidzin, genistein, genistin, glycitin, glycitein, shikimate, glyphosate, and the glyphosate degradation product, aminomethylphosphonic acid (AMPA). There were no remarkable effects of any treatment on the contents of any of the biosynthetic compounds in soybean seed from either test site, indicating that early and later season applications of glyphosate have no effects on phytoestrogen levels in glyphosate-resistant soybeans. Glyphosate and AMPA residues were higher in seeds from treatment 3 than from the other two treatments in which glyphosate was used earlier. Intermediate levels were found in treatments 1 and 2. Low levels of glyphosate and AMPA were found in treatment 4 and a hand-weeded control, apparently due to herbicide drift.  相似文献   

13.
Use of activated bentonites in controlled-release formulations of atrazine   总被引：3，自引：0，他引：3  
The herbicide atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) was incorporated in alginate-based granules to obtain controlled-release (CR) properties. The basic formulation [sodium alginate (1.40%)-atrazine (0.60%)-water] was modified by the addition of sorbents. The effect on atrazine release rate caused by the incorporation of acid-treated bentonite (0.5 and 2.5 M H2SO4) in alginate formulation was studied by immersion of the granules in water under static conditions. The water uptake, sorption capacity of the sorbent, permeability, and time taken for 50% of the active ingredient to be released into water, t50, were calculated for the comparison of the preparations. t50 values were longer for those formulations containing acid-treated bentonite (36.78 and 29.01 days for 0.5 and 2.5 M H2SO4 treatments, respectively) than for the preparation without bentonite (9.69 days). On the basis of a parameter of an empirical equation used to fit the herbicide release data, it appears that the release of atrazine from the various formulations into water is controlled by diffusion mechanism. The sorption capacity of the sorbents and the permeability of the formulations (ranging from 4.99 to 20.83 mg day(-1) mm(-1)) were the most important factors affecting herbicide release.  相似文献   

14.
Atrazine and alachlor formulations were designed by encapsulating the herbicide molecules into phosphatidylcholine (PC) vesicles, which subsequently were adsorbed on montmorillonite. PC and montmorillonite are classified as substances of minimal toxicological risk by the U.S. EPA. PC enhanced alachlor and atrazine solubilities by 15- and 18-fold, respectively. A 6 mM PC:5 g/L clay ratio was found as optimal for PC adsorption on the clay. Active ingredient contents of the PC-clay formulations ranged up to 8.6% for atrazine and 39.5% for alachlor. Infrared spectroscopy showed hydrophobic interactions of herbicide molecules with the alkyl chains of PC, in addition to hydrophilic interactions with the PC headgroup. Release experiments in a sandy soil showed a slower rate from the PC-clay formulations than the commercial ones. Soil column experiments under moderate irrigation and bioactivity experiments indicate that a reduction in the recommended dose of alachlor and atrazine can be accomplished by using PC-clay formulations.  相似文献   

15.
Controlled-release formulations of the herbicide acetochlor were prepared by using carboxylmethylcellulose (CMC) gel and different types of clay, which were obtained by acid activation, pillared with metal hydroxides, or saturated with organic cations. The effect of formulation parameters (amount and type of clay used, cross-linking time, and drying of the hydrogel formulations) on the acetochlor release rate from different formulations was evaluated by water-release studies. The time taken for 50% of acetochlor to be released, t 50, showed a wide variation (151-522 h) for dried gel formulations, the largest value corresponding to the formulation incorporating aluminum hydroxide pillared clay into CMC gels. The release rate of acetochlor from clay/CMC hydrogel formulations decreased with the increase of the hydrogels' cross-linking time (t50 values ranged from 2.18 to 14.0 h for cross-linking times ranging from 2.0 to 120 min). The performance of inorganic clays in dried gel formulations on slowing the release of acetochlor is related to their sorption capacities, but the addition of organic clay did not lead to the slowest release despite its highest sorption capacity. According to the parameters of an empirical equation used to fit herbicide-release data, the release of acetochlor from clay/CMC gel formulations is controlled by diffusion mechanism.  相似文献   

16.
Studies were conducted to examine the effects of soil properties on sulfentrazone phytotoxicity and dissipation under laboratory conditions. The pH values of five soils from Saskatchewan were altered through acidification with hydrochloric acid (HCl) and alkalization with calcium carbonate (CaCO3). The phytotoxicity of sulfentrazone to sugar beet (Beta vulgaris L. Beta 1385), determined using a shoot length bioassay, was reduced when soil pH was lowered and was greater when soil pH increased. Concentrations corresponding to 50% inhibition (I50 values) obtained from the dose–response curves were correlated with soil pH, demonstrating the relationship between soil pH and sulfentrazone phytotoxicity. Dissipation of sulfentrazone was examined in soils incubated at 25 °C and moisture content of 85% field capacity. Sulfentrazone dissipation followed a two-compartment model, and sulfentrazone half-lives estimated from the dissipation curves ranged from 21 to 111 days. Half-lives were correlated with soil pH (R = –0.857, p = 0.014) and soil organic carbon content (R = 0.790, p = 0.034) but not with clay content (R = 0.287, p = 0.533). Soil characteristics, particularly soil pH and organic carbon content, affect the bioactivity of sulfentrazone and influence both sulfentrazone efficacy in weed control and its potential for carry-over injury to subsequent crops.  相似文献   

17.
A Mg/Al layered double hydroxide (LDH) was intercalated with the anionic herbicides 2,4-D, MCPA, and picloram by using three different methodologies: (i) direct synthesis (DS), (ii) regeneration (RE), and (iii) ion exchange (IE). The resulting complexes were characterized and assayed by batch release and column leaching tests, aiming at the controlled release of these herbicides. All the tested LDH-herbicide complexes displayed similar slow herbicide release properties in water, although the IE method seemed to result in complexes with a greater fraction of herbicide in a readily available form. Apparently, the LDH-herbicide complexes released most of the active ingredient present in the complexes at the end of the batch release experiment. This was attributed to the replacement of the intercalated herbicide by carbonate and hydroxyl anions from the aqueous solution. Compared to the free herbicides, the application of the three LDH-herbicide complexes (RE) to soil columns resulted in reduction in the maximum herbicide concentration in leachates and led to the retardation of herbicide leaching through the soil. All LDH-herbicide complexes presented an herbicidal efficacy similar to that of the free (technical) herbicides. Our results indicated the potential applicability of LDHs as supports for the preparation of slow release formulations of acid herbicides such as 2,4-D, MCPA, or picloram.  相似文献   

18.
This study aimed to evaluate new methodology for designing ecologically acceptable formulations of acetochlor. Modification of montmorillonite with phenyltrimethylammonium chloride (PTMA) or benzyltrimethylammonium chloride (BTMA) and organoclay formulations of acetochlor were prepared in the presence of high concentrations of sodium chloride (150 g/L). Acetochlor concentration in the equilibrium solutions was determined by HPLC. Release of acetochlor in a water system was performed by a funnel experiment. Leaching of acetochlor in soil was determined by a bioassay using a column technique and Setaria viridis as a test plant. The adsorbed amounts of acetochlor on montmorillonite exchanged by PTMA or BTMA were increased as NaCl concentration increased in the equilibrium solution. Leaching of acetochlor from organoclay formulations was significantly inhibited to the top soil layer (0-5 cm) when the formulations were prepared at extreme NaCl concentration (100-150 g/L). These results are in accord with a funnel experiment that showed a reduction in acetochlor release from the montmorillonite-based formulations. The application of this method for herbicide formulation would produce ecologically acceptable herbicide formulations that can significantly minimize the risk to groundwater pollution.  相似文献   

19.
Research on organoclays as sorbents of pesticides has shown the usefulness of these materials as pesticide supports to prolong the efficacy of soil-applied pesticides and to reduce the large transport losses that usually affect pesticides applied in an immediately available form. Nevertheless, little information exists on the availability of organoclay-formulated pesticides for bacterial degradation. In this work, laboratory experiments were conducted to determine the adsorption-desorption behavior of two hexadecyltrimethylammonium-treated Arizona montmorillonites (SA-HDTMA50 and SA-HDTMA100) for the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D), and to evaluate the ability of these organoclays to slow the release of the herbicide and to reduce herbicide leaching losses as compared to the free (technical) compound. The kinetics of mineralization of free and formulated 2,4-D by adapted bacteria was also determined. Organoclay-based formulations of 2,4-D displayed slow release properties in water and reduced herbicide leaching through soil columns, while maintained a herbicidal efficacy similar to that of the free (technical) 2,4-D. The total amount of 14C-2,4-D mineralized at the end of the biodegradation experiment (t=130 h) ranged between 30% and 46% of the formulated herbicide, which represented 53-81% of the amount of free 2,4-D mineralized in the same conditions. The release, leaching, and mineralization patterns of the formulated herbicide were found to depend both on the affinity of the organoclay for the herbicide and on the degree of interaction promoted during the preparation of the herbicide-organoclay complex. This suggests the possibility to select diverse preparations to achieve the desired release, leaching and biodegradation behavior.  相似文献   

20.
Controlled release (CR) formulations of the insecti-nematicide carbofuran have been prepared using commercially available rosin, sodium carboxymethylcellulose and sodium carboxymethylcellulose with clay (bentonite, kaolinite, and Fuller's earth). The kinetics of carbofuran release in soil from the different formulations were studied in comparison with that of the commercially available granules (3G). Release from the commercial formulation was faster than with the new CR formulations. Addition of clay in the biodegradable polymer matrix reduced the rate of release. The diffusion exponent (n value) of carbofuran in soil ranged from 0.462 to 0.740 in the tested formulations. The half-release (t1/2) values ranged between 4.79 and 25.11 days, and the period of optimum availability (POA) of carbofuran ranged from 15.10 to 43.97 days. The mean EC50 of the commercial formulation against Meloidogyne incognita was quite high as compared to those of CR formulations. The effective duration (te) of carbofuran from the CR and commercial formulations was predicted by fitting the mean EC50 values of test formulations in the model (M(infinity) - Me)/M(infinity) = Kdte. It was 0.7 day in commercial 3G in comparison with 17.8 days for CMC-bentonite. The bioassay studies revealed that with the rosin-yellow polymer, the dose of carbofuran could be reduced to half of its recommended dose for nematode control. Overall, a comparison of CR formulations with the commercial one showed an earlier degradation of carbofuran in the latter and relatively prolonged activity in the former.  相似文献   

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