羧甲基壳聚糖/改性膨润土复合载体对莠去津释放和淋溶的影响

首次尝试将羧甲基壳聚糖与改性膨润土复合用作除草剂莠去津的载体,制备得到控释型颗粒剂,以延缓莠去津的释放,减少淋溶损失,提高药效及控制其污染。通过水中释放实验研究了制剂配方对莠去津释放速率的影响,并借助半经验方程探讨了其释放机理,采用土壤薄层实验考察了复合载体对降低莠去津淋溶的效果。 结果表明,采用复合载体时莠去津的半数释放时间(t 50)可达700 h 以上,比对照采用单一羧甲基壳聚糖作载体时延长了1倍以上。莠去津由颗粒剂向水相释放的过程主要受费克扩散(Fickian diffusion)控制,且经9次淋洗后莠去津的累计淋出率仅为6.0%,表明该复合载体控释制剂可显著减少莠去津对地下水的污染。     

Movement of metolachlor in soil: effect of new organo-clay formulations

The use of commercially available formulations of metolachlor has resulted in its leaching and migration to water sources. Formulations of metolachlor designed to reduce its leaching in soil have been prepared by adding the herbicide dissolved in an organic solvent or in water to organo-clay complexes. Best formulations were made when the organo-clay complex was formed by adsorbing the monovalent organic cations benzyltrimethylammonium (BTMA) or benzyltriethylammonium (BTEA) onto sodium montmorillonite (Mont) at 0.5 or 0.8 mole kg⁻¹ clay. Adsorption of metolachlor to organo-clays followed the sequence Mont-BTMA 0.5 > Mont-BTMA 0.8 > Mont-BTEA 0.8 > Mont-BTEA 0.5 > Mont. Fourier transform infrared (FTIR) analysis demonstrated the occurrence of shifts of several peaks of adsorbed metolachlor relative to the free herbicide, indicating the existence of strong interactions between metolachlor molecules and the organo-clay surface. Leaching studies employing organo-clay and commercial formulations were carried out under greenhouse and field conditions. Metolachlor applied as organo-clay formulations leached less than the commercial formulation. Organo-clay formulations prepared by adding the herbicide as a water solution showed less leaching in the soil profile than those made by using organic solvent. Under greenhouse conditions, the herbicidal activity of organo-clay formulations was similar to that of the commercial one. Under field conditions, leaching from Mont-BTMA 0.5-metolachlor was less than that from the commercial formulation, demonstrating the environmental and agricultural advantages of the organo-clay formulations of metolachlor. © 1999 Society of Chemical Industry     

Transformation of fenuron induced by photochemical excitation of humic acids

When neutral solutions containing the herbicide 3-phenyl-1,1-dimethylurea (fenuron) and a humic acid are irradiated at 365 nm, 3-(4-hydroxyphenyl)-1,1-dimethylurea and three biphenyl products are formed as main products. The apparent quantum yield of fenuron disappearance is evaluated as 6·2 × 10⁻⁵ mole E⁻¹. Upon irradiation of the same mixture at 253·7 nm, both direct and induced phototransformations of fenuron occur. Direct photooxidation yields 2- and 4-amino-N,N-dimethylbenzamide. The induced phototransformation leads to 2- and 4-hydroxylation of the aromatic ring in accordance with the fact that hydroxyl radicals are involved in the oxidation.     

Simazine dynamics in a vineyard soil at Casablanca valley, Chile

Field dissipation, soil movement and laboratory leaching studies were performed to elucidate the effect of two rainfall amounts in the behaviour and environmental fate of simazine under climatic conditions at Casablanca Valley, Chile. Dissipation and soil movement were studied in a field vineyard with a sandy loam soil (Inceptisol; 74.08% sand; 14.87% silt and 11.04% clay). Simazine was applied to bare soil at 2.0 kg AI ha(-1), and its concentration was measured using immunoassay (ELISA) at 0, 10, 20, 40 and 90 days after application under two rainfall amounts, natural field conditions (39 mm) and modified conditions (39 + 180 mm). Simazine leaching was studied using soil core PVC lysimeters (0.9 m height; 0.22 m diameter). Field dissipation data were adjusted with a bi-exponential model. Half-life (DT(50)) values varied between 31.3 (+/-2.5) and 19.0 (+/-4.2) days under natural and modified conditions, respectively. Simazine K(d) varied from 0.42 to 2.15 (K(oc) 32.6-216.2) in the soil profile. Simazine was detected at a 90-cm soil depth in concentrations of 0.0085 (+/-0.0043) mg kg(-1) and 0.0321 (+/-0.001) mg kg(-1) under field and modified conditions, respectively. The maximum simazine leachate concentrations were 0.013 (+/-0.00084) mg litre(-1) (0.012% of total applied simazine) and 0.0084 (+/-0.00082) mg litre(-1) (0.11% of total applied simazine) for field and modified conditions respectively. These data indicate that water quantity has a significant effect on the DT(50) and the amount of simazine that moved through the soil profile, but not on the soil depth reached by this herbicide.     

复合改性粘土对除草剂2,4-D的控制释放作用研究

采用无机/有机复合改性粘土作制剂载体,探讨了其对阴离子型除草剂2,4-D的控制释放作用,目的在于延长2,4-D的持效期,同时减轻其污染。利用无机和有机改性的结合优势,复合改性粘土具有更强的吸附性能,能够显著延缓2,4-D在水中和土壤中的释放。分析其水中释放动力学数据得出,2,4-D释放50%所需时间(t50)长达73.8 h,远大于有机改性粘土作载体时的1 h。土壤层释放实验表明,当2,4-D载药量在20~80 mg/g之间时,复合改性粘土均能保持良好的控制释放效果。     

Aminocyclopyrachlor sorption–desorption and leaching in soil amended with organic materials from sugar cane cultivation

The correct application of a new herbicide depends on knowledge concerning its behaviour within the cultivation system. The objective of this study was to evaluate the sorption–desorption process of aminocyclopyrachlor in soils with the addition of three aged organic materials from sugar cane and their transport via leaching. Sugar cane straw (12 t/ha), filter cake (90 t/ha) and vinasse (200 m³/ha) were added to a clayey soil 15, 30 and 60 days before herbicide application. Sorption and desorption were evaluated by the batch equilibrium method. For leaching assessments, the materials were applied to the soil surface. Sorption was relatively low in all treatments (K_d = 0.17–0.41 L/kg), although significantly higher in soil without organic material addition. A negative correlation between herbicide sorption and increased soil base saturation was observed, indicating competition for sorption sites. With the addition of vinasse, 71% of the herbicide reached the leachate, while <50% reached the leachate in the other treatments. Aminocyclopyrachlor availability was not reduced with organic material addition to the soil, which may be favourable for weed control. However, the presence of vinasse leads to the risk of leaching to deeper soil layers than the seed bank.     

Controlled release of isoproturon from an alginate–bentonite formulation: water release kinetics and soil mobility

The herbicide isoproturon [3‐(4‐isopropylphenyl)‐1,1‐dimethylurea] was incorporated in alginate‐based granules to obtain controlled‐release (CR) properties. The basic formulation (sodium alginate (1.87%)–isoproturon (0.67%) in water) was modified by addition of different sorbents. The effect on isoproturon release rate, modified by the incorporation of natural and acid‐treated bentonite in alginate formulation, was studied by immersion of the granules in water while shaking. The release of isoproturon was diffusion‐controlled. The time taken for 50% of the active ingredient to be released into water, T₅₀, was longer for those formulations containing added bentonite (5.98 and 7.43 days, for natural and acid‐treated (1 M H₂SO₄) bentonite, respectively) than for the preparation without bentonite (3.78 days). The mobilities of non‐formulated technical grade (98%) and formulated isoproturon were compared using soil columns. The use of alginate‐based CR formulations containing bentonite reduced isoproturon movement compared with the technical product. Sorption capacity of the soil for isoproturon was measured using batch experiments (0.29 litre kg⁻¹) and the results obtained here in agreement with those obtained under dynamic conditions. © 2000 Society of Chemical Industry     

Effect of aggregate size on leaching of herbicide in soil columns

In a column experiment with dry aggregated soils, the effect of aggregate size on leaching of metribuzin from the upper soil layer (2.5 cm) was studied. The penetration of the herbicide was less than predicted by the equilibrium retardation factor. The penetration was less for large than for smalt aggregates due to kinetic effects induced by the aggregates. These kinetic effects overruled the effect of adsorption. Although the mean herbicide penetration was limited, part of the herbicide moved freely with the water as the herbicide was found throughout the column and in the leachate.     

农艺措施和除草剂用量对化感稻产量及杂草生物量的影响

为实现水稻生产减施除草剂的目标,将化感材料与农艺措施相结合取得对稻田杂草有效控制的效果,田间采用再裂区试验法研究了化感稻3号和N两优201两个水稻化感材料和非化感材料五山丝苗在不同水分管理、移栽密度和除草剂不同用量下,对水稻产量和田间杂草生物量的影响。结果表明:无论早季稻田还是晚季稻田,施用常规除草剂量的小区杂草生物量均为0,施用常规剂量50%除草剂且仅在孕穗期晒田的小区和常规密度小区有少量杂草发生。不施除草剂的水稻材料小区杂草生物量依次为化感稻3号N两优201五山丝苗。移栽后75 d,不施除草剂的小区相同水稻材料孕穗期不晒田比晒田处理、高密度比常规密度处理的杂草生物量小。早季稻田不晒田和高密度提高了水稻的产量,晚季稻田则相反。化感材料化感稻3号和N两优201在田间的抑草效果较五山丝苗要好。在水稻生产中,水稻化感材料结合农艺措施,可以实现水稻不减产,田间杂草得到有效控制,除草剂量减50%的目标。     

Reduced metribuzin pollution with phosphatidylcholine-clay formulations

BACKGROUND: Metribuzin is a widely used herbicide that has been identified as a groundwater contaminant. In this study, slow‐release formulations of metribuzin were designed by encapsulating the active ingredient in phosphatidylcholine (PC) vesicles and adsorbing the vesicles onto montmorillonite. RESULTS: The maximum active ingredient content in the slow‐release formulations was 246 g kg^?1. Infrared spectroscopy results revealed that the hydrophobic interactions between metribuzin and the alkyl chains on PC were necessary for encapsulation. In addition, water bridges connecting the herbicide and the PC headgroup enhanced the solubility of metribuzin in PC. Adsorption experiments in soils were performed to evaluate the relationship between sorption and leaching. Funnel experiments in a sandy soil revealed that the herbicide was not irreversibly retained in the formulation matrix. In soil column experiments, PC–clay formulations enhanced herbicide accumulation and biological activity in the top soil layer relative to a commercial formulation. PC–clay formulations also reduced the dissipation of metribuzin by a factor of 1.6–2.5. CONCLUSIONS: A reduction in the recommended dose of metribuzin can be achieved by employing PC–clay formulations, which reduces the environmental risk associated with herbicide applications. Moreover, PC and montmorillonite are non‐toxic and do not negatively affect the environment. Copyright © 2010 Society of Chemical Industry     

Monitoring the efficacy and metabolism of phenylcarbamates in sugar beet and black nightshade by chlorophyll fluorescence parameters

Desmedipham, phenmedipham and a 50% mixture of the two decreased the maximum quantum efficiency of photosystem II (F(v)/F(m)) and the relative changes at the J step (F(vj)) immediately after spraying in both sugar beet and black nightshade grown in the greenhouse. Sugar beet recovered more rapidly from phenmedipham and the mixture than from desmedipham. Desmedipham and the mixture irreversibly affected F(v)/F(m) and F(vj) in black nightshade at much lower doses than in sugar beet. Black nightshade recovered from phenmedipham injury at the highest dose in the first experiment (120 g AI ha(-1)) but not in the second experiment (500 g AI ha(-1)). The dry matter dose-response relationships and the energy pipeline presentation confirmed the same trend. There was a relatively good correlation between F(vj) taken 1 day after spraying and dry matter taken 2 or 3 weeks after spraying. The differential speed of herbicide metabolism between weed and crop plays an important role in herbicide selectivity and can be studied by using appropriate chlorophyll a fluorescence parameters.     

控制释放制剂的组成对异丙甲草胺释放速率的影响

将海藻酸盐与膨润土复合作为载体制备除草剂异丙甲草胺的控制释放制剂,研究了载药量、载体原料配比、膨润土类型等制剂组成因素对异丙甲草胺释放速率的影响。采用Ritger和Peppas方程分析释放动力学过程,计算50%的异丙甲草胺被释放所需时间(t50),并以此表征释放速率。结果表明,采用海藻酸盐/膨润土复合载体时, t50随载药量和载体原料配比不同介于29.4~68.0 h 之间,控制释放效果明显优于单纯以有机改性膨润土作载体(t50=5.9 h)。将有机改性膨润土与海藻酸盐复合作载体时,t50可达110 h。释放动力学方程的n值(0.436~0.496)接近Fickian扩散模型,说明该控制释放制剂中异丙甲草胺的释放过程主要受到扩散控制。     

Relationships between substituted urea herbicides and soil urease activity

Fenuron, monuron, diuron, siduron, linuron and neburon were tested for their inhibition of soil urease activity in order to investigate relationships between fertilizers and herbicides. The inhibition of urea hydrolysis in the selected soils was 10–33% for fenuron, 10–39% for monuron, 10–35% for diuron, 8–38% for siduron, 9–36% for linuron and 12–30% for neburon. In the field greater effects might be expected since the fertilizer/herbicide ratio would be lower than the one considered here. Some agronomic aspects of the relationship between fertilizers and herbicides are discussed.     

复合改性粘土对除草剂2,4-D的控制释放作用研究

采用无机/有机复合改性粘土作制剂载体,探讨了其对阴离子型除草剂2,4-D的控制释放作用,目的在于延长2,4-D的持效期,同时减轻其污染.利用无机和有机改性的结合优势,复合改性粘土具有更强的吸附性能,能够显著延缓2,4-D在水中和土壤中的释放.分析其水中释放动力学数据得出,2,4-D释放50%所需时间(t_(50))长达73.8 h,远大于有机改性粘土作载体时的1 h.土壤层释放实验表明,当2,4-D载药量在20～80 mg/g之间时,复合改性粘土均能保持良好的控制释放效果.     

Release of atrazine and alachlor from clay-oxamide controlled-release formulations

Controlled-release herbicide formulations have been shown to decrease the leaching potential of several herbicides under laboratory and field conditions. The utility and efficacy of these formulations may be improved by combining several herbicides and a fertilizer source in a single formulation. The objective of these studies was to develop granular alginate formulations that were composed of a combination of the herbicides atrazine and alachlor with the slow-release nitrogen source oxamide (ethanediamide). Controlled release of the herbicides was obtained by addition of selected minerals, including calcium bentonite, fine-grind bentonite, montmorillonite K10, kaolinite and iron (III) oxide. A formulation without clay was used as a comparison. The formulations tested had herbicide active ingredient contents ranging from ∽0·02 to 0·54% and a nitrogen content of 21%. Release of the herbicides was studied by equilibrating the formulations with deionized water on a rotary shaker at 200 rev min^-1 and sampling at regular time intervals up to 104 hours. The minerals used in the different formulations influenced the herbicide active ingredient composition, as well as the release properties of the individual formulations. The atrazine content of the formulations decreased in the order calcium bentonite>fine-grind bentonite>kaolinite>montmorillonite=iron oxide>no clay. For alachlor the content decreased in the order of calcium bentonite>fine-grind bentonite>montmorillonite>iron oxide>kaolinite>no clay. Controlled release of atrazine (i.e. reduction in release rate) varied in the order calcium bentonite>iron oxide>montmorillonite>fine-grind bentonite= kaolinite>no clay, and for alachlor fine-grind bentonite>calcium bentonite>montmorillonite>no clay=kaolinite=iron oxide. A certain percentage of the applied active ingredient of both alachlor and atrazine was not recovered. From 5 to 27% of the active ingredient was not released, with the greatest retention by the bentonite formulations. Release of nitrogen was not strongly influenced by mineral type, although a trend indicated greater release with formulations containing kaolinite. © 1998 SCI     

Preparation of controlled-release formulations of 14C-labelled thiobencarb herbicide and study of their environmental behaviour

Controlled-release formulations of ¹⁴C-labelled thiobencarb herbicide were prepared in calcium alginate using kaolin as an inexpensive filler. The rates of release of the herbicide from these and from a commercial granular formulation were studied in static distilled water contained in open and closed vessels. The rate of release of the herbicide was much higher from the commercial formulation than from the controlled-release formulations. Increasing the proportion of kaolin to calcium alginate in controlled-release formulations reduced the rate of release of the herbicide. There was a significant loss of thiobencarb-related radioactivity from the water solution when the vessels containing the solutions were left uncovered and exposed to light. The loss of the herbicide seemed to be due to degradation and evaporation.     

Efficacy and fate of glyphosate on Swedish railway embankments

The herbicide glyphosate, N-(phosphonomethyl)glycine, as Spectra (240 g AI litre(-1) SL; Monsanto Europe AB), RoundUp (360 g AI litre(-1) SL; Monsanto) and RoundUp Bio (360 g AI litre(-1) SL; Monsanto), have been used for weed control on Swedish railway embankments since 1986. This article summarizes results from studies of the weed effect and behaviour of glyphosate for the period 1984-2003. Studies on a railway embankment with a range of application rates showed excellent weed control at 5 litre ha(-1) of RoundUp Bio. The appearance of glyphosate and its metabolite AMPA [(aminomethyl)phosphonic acid] in the embankment, eg mobility and persistence, was also studied. Mobility was low in most cases, the main proportion of both glyphosate and AMPA being found in the upper 30-cm layer although minor amounts penetrated to lower depths. The 50% disappearance time of glyphosate was generally <5 months in railway embankments but cases with longer persistence were found. Transport to the groundwater was observed for glyphosate and AMPA in groundwater pipes along tracks. Downward transport appears to be dependent on the application rate, which should not exceed 3 litre ha(-1) of RoundUp Bio to avoid groundwater contamination. A lower rate of glyphosate mixed with a low rate of another herbicide may achieve acceptable weed control and be environmentally safer.     

Effects of formulation on the run-off of imidacloprid from turf

Imidacloprid is a pesticide often used to control insect pests on residential lawns and golf courses. To investigate its potential to be transported into non-target aquatic systems by rainfall events, imidacloprid was applied as 5.0 g kg-1 GR and 750 g kg-1 WP to 12 plots planted with bermuda grass set on a 5% slope. The dimethylamine salt of the herbicide 2,4-D was applied simultaneously to the plots in order to normalize the results to prior trials conducted with other pesticides. At a rate of 2.5 cm h-1, 5-cm rainfall events were simulated at 24 and 48 h after application and 2.5-cm events were simulated at 96 and 192 h. After each event water was collected from each plot and analyzed by HPLC for residual insecticide or herbicide. Approximately 1.4% of the insecticide formulated as WP and 1.9% of that formulated as GR was lost from the plots after four run-off events. Of the total mass lost, 64% and 30% respectively occurred in the first and second run-off events for the WP formulation versus 75% and 20% for the GR formulation. These values compare with a total mass export of 2.6% for 2,4-D, of which 95% and 4% of the loss occurred respectively in the first and second run-off events. The maximum concentration of imidacloprid detected in run-off water was 0.49 mg litre-1 and occurred during the first run-off event.     

Dissipation and movement of flumioxazin in soil at four field sites in Chile

BACKGROUND: Flumioxazin is a soil-applied herbicide recommended for broadleaf weed control in soybeans and peanuts, and was recently introduced for vineyard weed management. Considering the limited information available in relation to flumioxazin field soil behaviour, the main objectives of this study were to determine the persistence, adsorption and movement of flumioxazin in soil in four Chilean vineyard production areas. RESULTS: DT(50) values ranged from 10.6 +/- 1.0 to 32.1 +/- 3.1 days between localities, being correlated with rain events, time between herbicide application and first heavy rain event, and soil pH. Flumioxazin soil residue found at 90 days after application (DAA) varied from 9.6 to 24.9% of the initial amount applied, and depended on the total rainfall amount that occurred during the first 90 DAA. Herbicide leaching below 15 cm was approximately 45% of the flumioxazin detected at 90 DAA in the whole soil profile. Flumioxazin maximum leaching soil depth was 45 cm at all locations. K(d) values varied from 2.54 to 6.51 mg L(-1), depending on localities and soil profile depth, and correlated positively with organic carbon and clay content. CONCLUSIONS: These results indicate that flumioxazin is a herbicide with low environmental risk owing to its short DT(50), reduced soil residues 3 months after application and low effective dose.     

Efficacy of four corn (Zea mays L.) herbicides when applied with flat fan and air induction nozzles

Twelve field experiments were conducted over a 4 year (2002–2005) period to determine the influence of the herbicide dose, nozzle type, spray volume, and spray pressure on herbicide efficacy in field corn ( Zea mays L.). The control of Abutilon theophrasti (velvetleaf ), Ambrosia artemisiifolia (common ragweed), Chenopodium album (common lambsquarters), Amaranthus powellii (green pigweed), and Echinochloa crus-galli (barnyard grass) was improved with the use of full herbicide doses compared to half doses of bromoxynil, glufosinate, dicamba, and nicosulfuron. The yield was increased for bromoxynil, glufosinate, and nicosulfuron when the full herbicide dose was used. When applied at the manufacturer's recommended dose, flat fan nozzles, compared to air induction (AI) nozzles, provided better control of A. theophrasti , A. artemisiifolia , and C. album with bromoxynil, A. artemisiifolia and C. album with dicamba, and E. crus-galli with nicosulfuron. Bromoxynil, in relation to weed control, was the only herbicide that was affected by the water carrier volume. By increasing the spray pressure with an AI nozzle, there was an improvement in the control of A. theophrasti , A. artemisiifolia, and C. album with the application of bromoxynil and E. crus-galli with the application of nicosulfuron, with a yield increase with bromoxynil. Overall, this study concludes that the optimum nozzle type, water carrier volume, and spray pressure is herbicide- and weed species-specific.