Mobility and efficacy of 2,4-D herbicide from slow-release delivery systems based on organo-zeolite and organo-bentonite complexes

This research aimed to develop slow-release formulations (SRFs) of 2,4-dichlorophenoxyacetic acid (2,4-D) using zeolite and bentonite minerals modified with cetyltrimethylammonium (CTMA) surfactant. Adsorption–desorption, greenhouse bioassay and column experiments were carried out to assess the potential of the SRFs to control weeds while reducing the herbicide leaching losses to deep layers of soil. The results showed that only 6.5 mmol 2,4-D kg^?1 was retained by Na-bent, and the herbicide was not adsorbed by Na-zeol at all. The surface modification with CTMA surfactant, however, improved the 2,4-D adsorption capacity of the zeolite and bentonite up to 207.5 and 415.8 mmol kg^?1, respectively. The synthesized organo-minerals slowly released the retained 2,4-D discharging 22 to 64% of the adsorbed 2,4-D to the solution phase within 7 days. The SRFs significantly (P = 0.05) reduced the herbicide mobility within the soil columns keeping a great portion of the herbicide active ingredient in the upper 5 cm soil layer. The SRFs were significantly (P = 0.05) as effective as the free technical herbicide in weed control without harming the ryegrass as the main plant. Therefore, the synthesized SRFs could be considered as useful tools for weed control in sustainable agriculture.     

Herbicide activity of monosulfuron and its mode of action

Monosulfuron was developed for weed control in the field of wheat( Triticum, aestivum L.) and millet( Panicum miliaceum L.)with the application rate ranging from 15 to 60 g ai/hm^2 . Herbicidal.activity of monosulfuron was evaluated systematically by bioassay using maize( Zea mays L. ) taproot as indicator and weed fresh weight of Acalypha australis L. and Echinochloa phyllopogon. Maize CAU 3138 was the most tolerant cultivars to monosulfuron with IC50 (concentration of .50% inhibition) of 8.5μg/kg, Yedan 13 was one of the most sensitive cultivars to monosulfuron with IC50 of 6.4 μg/kg. Monosulfuron inhibited the growth of Acalypha australis L. strongly comparing with that of Echinochloa phyllopogon. Monosulfuron was a good acetolactate synthase(ALS) inhibitor in vitro, the 150 (50% of inhibition) of monosulfuron, chlorsulfuron, tdbenuron-methyl and nicosulfuron for CAU 3138 were 32, 2, 19 and 26 nmol/L respectively, for Yedan 13 the /50 were 1.5, 3, 17 and 6.5 nmol/L respectively. In vivo ALS inhibition occurred only in higher concentration of 4 sulfonylurea herbicide tested. Comparison study of this test indicated that the mode of action of monosulfuron was the same as that of other sulfonylurea herbicides such as chlorsulfuron, tribenuron-methyl and nicosulfuron, they were all inhibitors targeted at the ALS.     

稳杀得(Fluazifop-butyl)环境行为研究

采用田间试验和模拟试验的方法,研究了稳杀得及稳杀得酸的降解动态规律;鉴定了部分降解产物,推测了部分降解途径;借助红外光谱及电子自旋共振谱研究了稳杀得及稳杀得酸与土壤金属离子Cu~(2+)、Fe~(3+)及Al~(3+)的相互作用。为探明稳杀得在我国的安全使用提供了科学依据。     

除草剂对氮肥反硝化损失与N2O排放的影响

在华北平原潮土上,采用原状土柱培养乙炔抑制法研究玉米地氮肥反硝化损失和N2O排放量以及喷施3种除草剂(乙莠、丁莠和旱锄)的影响.结果表明,氮肥的反硝化损失量为2.66kgN/hm2,占施肥量的1.77%;氮肥产生的N2O排放量为3.14kgN/hm2,占施氮量的2.09%,反硝化不是该地区旱作系统氮肥损失的主要途径,但氮肥的施用大大增加N2O排放量.喷施除草剂显著或极显著降低氮肥的N2O排放量和反硝化损失量,比单施尿素处理分别降低2.01~2.85kgN/hm2和2.56~3.16kgN/hm2.     

spatial analysis of herbicide decay rates in louisiana

This analysis presents results based on a five-yearstudy recently supported by the Louisiana Departmentof Transportation and Development (DOTD) in which theacute toxicity, fate and effect of herbicide mixtureson human health and the environment were assessed. Three sites were routinely sprayed by DOTD to killweeds along the roadsides. Two herbicide mixtures wereused, 2,4-D and Roundup, and Garlon 3A and Roundup.Water, vegetation, soil and sediment samples werecollected quarterly for three years and were analyzedfor pesticide content to study the fate and impact ofherbicides in the environment. Results indicate acorrelation between soil type, herbicide type, andpersistence of the herbicide in the environment. Usingthe correlations found in these data, spatial analysisidentified areas where herbicide use may potentiallycause surface water and sediment contamination, basedon soil composition/properties, type of herbicideapplied, and proximity of water bodies to sprayed areas.     

Nitrite and nitrate induced photodegradation of monolinuron in aqueous solution

Here we evidenced the photo-induced degradation of monolinuron, a phenylurea herbicide, through the 300–450 nm light excitation of nitrite and nitrate species. The degradation pathways were compared to those obtained under direct photolysis at 254 nm. When using NO₃^– and NO₂^– as photoinducers, hydroxyphenyl-substituted photodegradation products were found to be formed specifically through the involvement of OH° radicals. NO^– and NO₂-phenyl substituted compounds were also observed as a result of the production of NO° and NO₂° radicals. Half-lives of monolinuron in aqueous solutions were measured in various conditions of concentrations of substrate and inducer, oxygen content and pH.     

Atrazine and metolachlor residues in brookston Cl following conventional and conservation tillage culture

Atrazine and metolachlor are extensively used in Ontario, Canada for control of broadleaf weeds and annual grasses in corn. Conservation tillage may alter the physical and biological environment of soil affecting herbicide dissipation. The rate of dissipation of these two herbicides in soil from conventional, ridge and no-tillage culture was followed. Herbicide dissipation was best described by first order reaction kinetics. Half life, the time for herbicide residues to dissipate to half their initial concentration, was unaffected by tillage. Half life for atrazine and metolachlor was similar and ranged from 31 to 66 d. The rate of dissipation decreased in dry years when soil moisture content was low. In a dry year, herbicide residues during the growing season were significantly greater on ridge tops than in the other tillage treatments. However, after harvest no differences in herbicide residues were detected among tillage treatments. Residues of atrazine (6 to 9% of applied) and metolachlor (4 to 6%) were detected in soil before planting a year after application. De-ethyl atrazine, the primary degradation product of atrazine, increased in concentration during the growing season with the greatest concentrations measured at harvest and in years when atrazine dissipated fastest. De-ethyl atrazine one year after application accounted for about 12% of the remaining triazine residue. These herbicide residues would not be phytotoxic to subsequent crops but are a potential source for leaching to ground and surface waters.     

土壤中20种磺酰脲类除草剂的超高效液相色谱-串联质谱测定方法

建立了加速溶剂提取、凝胶渗透色谱法净化-超高效液相色谱/串联质谱快速测定土壤中20种磺酰脲类除草剂的方法。土壤经过冷冻干燥、粉碎过筛,用加速溶剂仪提取(ASE),经凝胶渗透色谱净化(GPC),以超高效液相色谱/串联质谱(UPLC-MS/MS)多级监测模式(MRM)外标法进行定性定量分析。结果表明:土壤中20种磺酰脲类除藻剂的检出限为2～5 ng/kg。对同一环境样品进行了3个不同添加量(1、5、10μg/L)的加标回收实验,平均回收率为65. 7%～106. 1%,相对标准偏差为2. 3%～12. 1%。该方法快速、灵敏、准确,可有效应用于土壤中20种磺酰脲类除草剂的快速监测。     

Bioherbicidal activity of a germacranolide sesquiterpene dilactone from Ambrosia artemisiifolia L.

Ambrosia artemisiifolia L. (common ragweed) is an invasive plant whose allelopathic properties have been suggested by its field behaviour and demonstrated through phytotoxicity bioassays. However, the nature of the molecules responsible for the allelopathic activity of common ragweed has not been explored. The main objective of this study was to identify the phytotoxic molecules produced by A. artemisiifolia. A preliminary investigation has indicated that a methanol extract of A. artemisiifolia completely inhibited the germination of cress and radish. Semi-preparative fractionation of the methanol extract allowed separating of phytotoxic fraction which contained a single compound. The structure of this compound was elucidated by liquid chromatography–mass spectrometry (LC-MS)/MS, high-resolution mass spectral, nuclear magnetic resonance, and Fourier transform infrared spectra as sesquiterpene lactone isabelin (C₁₅H₁₆O₄). The effect of pure isabelin was tested on four different weed species, confirming the inhibitory activity of molecule. The results indicate directions for the future studies about herbicidal specific activity of isabelin, as pure molecule or in the crude extract, as a potential candidate for biological weed control.     

Atrazine degradation by fungal co-culture enzyme extracts under different soil conditions

This investigation was undertaken to determine the atrazine degradation by fungal enzyme extracts (FEEs) in a clay-loam soil microcosm contaminated at field application rate (5 μg g^?1) and to study the influence of different soil microcosm conditions, including the effect of soil sterilization, water holding capacity, soil pH and type of FEEs used in atrazine degradation through a 2⁴ factorial experimental design. The Trametes maxima–Paecilomyces carneus co-culture extract contained more laccase activity and hydrogen peroxide (H₂O₂) content (laccase = 18956.0 U mg protein^?1, H₂O₂ = 6.2 mg L^?1) than the T. maxima monoculture extract (laccase = 12866.7 U mg protein^?1, H₂O₂ = 4.0 mg L^?1). Both extracts were able to degrade atrazine at 100%; however, the T. maxima monoculture extract (0.32 h) achieved a lower half-degradation time than its co-culture with P. carneus (1.2 h). The FEE type (p = 0.03) and soil pH (p = 0.01) significantly affected atrazine degradation. The best degradation rate was achieved by the T. maxima monoculture extract in an acid soil (pH = 4.86). This study demonstrated that both the monoculture extracts of the native strain T. maxima and its co-culture with P. carneus can efficiently and quickly degrade atrazine in clay-loam soils.