Surface Retention and Photochemical Reactivity of the Diphenylether Herbicide Oxyfluorfen (original) (raw)
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Photochemical behaviour of oxyfluorfen: a diphenyl-ether herbicide
Journal of Photochemistry and Photobiology A-chemistry, 1999
The photochemical behaviour in different solvents of the herbicide oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene (CAS RN 42874–03–3)] was studied. Photochemical reactions were carried out by using a high pressure mercury arc and a solar simulator. Kinetic parameters and quantum yields were determined. Identification of the photoproducts was performed by GC-MS and the main compounds were confirmed by [1H] NMR. The photochemical reactions were also carried out in the presence of either a singlet or a triplet quencher, and in the presence of either a radical initiator or a radical inhibitor. Results indicate that the first excited singlet state can undergo both homolytic and heterolytic cleavage of the ethyl-oxygen bond in the side chain of oxyfluorfen. Moreover, the presence of reduction products in the reaction mixture is supposed to occur via a monoelectron transfer process with the formation of a transient exciplex during the reaction.
Persistence and carryover effect of oxyfluorfen residues in red sandy clay loam soil
Journal of Pharmacognosy and Phytochemistry, 2017
A Field experiments were conducted for two years at Agricultural Research Station, Bhavanisagar of Tamil Nadu Agricultural University, Coimbatore, India during kharif season of 2010 and 2011 to evaluate the new formulation of oxyfluorfen (23.5% EC) on weed control in onion and their residual effect on succeeding crops. Herbicides are being chemical in nature, excessive and repeated use may pose phytotoxicity to crop plants, carryover effects on succeeding crops and also leads to adverse effects on non-target organisms. This might due to causes of health hazards to humans, animals and the environment. Many herbicides are bound residues which make them not only unavailable to the targets, but also polluting the soil ecosystem in a number of ways. Thus monitoring of herbicides residue in soil, plant and other matrixes are very much important. Therefore, a laboratory and field experiments were undertaken to investigate the persistence of oxyfluorfen in soil and onion crop under red sand...
Journal of Environmental Science and Health, Part B, 2009
A four-year field study was conducted to determine the effect of pluviometric conditions on pendimethalin and oxyfluorfen soil dynamics. Adsorption, dissipation and soil movement were studied in a sandy loam soil from 2003 to 2007. Pendimethalin and oxyfluorfen were applied every year on August at 1.33 and 0.75 kg ha −1 , respectively. Herbicide soil concentrations were determined at 0, 10, 20, 40, 90 and 340 days after application (DAA), under two pluviometric regimens, natural rainfall and irrigated (30 mm every 15 days during the first 90 DAA). More than 74% of the herbicide applied was detected at the top 2.5 cm layer for both herbicides, and none was detected at 10 cm or deeper. Pendimethalin soil half-life ranged from 10.5 to 31.5 days, and was affected mainly by the time interval between application and the first rain event. Pendimethalin soil residues at 90 DAA fluctuated from 2.5 to 13.8% of the initial amount applied, and it decreased to 2.4 and 8.6% at 340 DAA. Oxyfluorfen was more persistent than pendimethalin as indicated by its soil half-life which ranged from 34.3 to 52.3 days, affected primarily by the rain amount at the first rainfall after application. Oxyfluorfen soil residues at 90 DAA ranged from 16.7 to 34.8% and it decreased to 3.3 and 17.9% at 340 DAA. Based on half-life values, herbicide soil residues after one year, and soil depth reached by the herbicides, we conclude that both herbicides should be considered as low risk to contaminate groundwater. However, herbicide concentration at the top 2.5 cm layer should be considered in cases where runoff or soil erosion could occur, because of the potential for surface water contamination.
Journal of Agricultural and Food Chemistry, 2010
This study was conducted to assess the effects of solarization and biosolarization on the degradation of oxyfluorfen, ethalfluralin, trifluralin, propyzamide, and pendimethalin. The experimental design consisted of 17 L pots filled with clay-loam soil, which were contaminated with the studied herbicides. Then, soil disinfection treatments were applied during the summer season, including a control without disinfection (C), solarization (S), and biosolarization (BS). Soil from five pots per treatment was sampled periodically up to 90 days. Herbicide dissipation rates were higher in both S and BS treatments with regard to the control. Similar dissipation rates were observed under S and BS for most of the herbicides studied, except oxyfluorfen and pendimethalin, which were degraded to a greater extent in the BS than in the S treatment. The obtained results showed that both solarization and biosolarization can be considered, in addition to soil disinfection techniques, such as bioremediation tools for herbicide-polluted soils.
Leaching Behavior of Oxyfluorfen and Oxdiargyl in Red and Black Soils
Leaching studies of herbicides in soil columns are simple and reliable methods to assess their environmental fate and contamination potential. Pretilachlor and metribuzin are popular herbicides used in transplanted rice and vegetables crops (tomato, carrot, potato) respectively. A lab experiment was conducted for two years (2012 and 2013) in red and black soils to study leaching behavior of oxyfluorfen and oxdiargyl with soil columns (PVC tubes of 10 cm diameter and 65 cm length). Retention time of oxadiargyl was 6.95 min. Recovery of in the soil varied from 86.8 to 90.2 %. LOD was 0.005 mg/kg and LOQ was 0.015 mg/kg. Retention time of oxyfluorfen was 9.17 min. recovery of oxyfluorfen in the soil varied from 90.2 to 94.8 %. LOD was 0.005 mg/kg and LOQ was 0.025 mg/kg. Oxadiargyl and oxyfluorfen leached only up 5-10 cm layer in red and black soils at the recommended rates of application (100 g and 125 g a.i./ha). Hence, these herbicides did not present any threat of contaminating the ground water when used at recommended rates. At double the recommended rates of application oxyfluorfen and oxadiargyl leached up to 10-15 cm depth in red soils. In black soils the leaching was restricted to top 10 cm layer in double dose also.
Photodegradation of chlorpyrifos, malathion, and dimethoate by sunlight in the Sudan
Environmental Earth Sciences, 2019
The potential of sunlight photolysis in remediation of pesticide-polluted soils in Sudan was studied. Chlorpyrifos, malathion and dimethoate, common pollutants, were exposed to sunlight over glass and soil surfaces with periodic samples drawn for GC and GC-MS analysis. Photo-degradation followed a biphasic model. Alpha half-lives of direct photolysis over glass surface range between 1.99 and 9.36 days while the range in soil surfaces is 1.88-10.77 days. Respective values for indirect photolysis with β-carotene are 0.96-2.40 days whereas for benzophenone are 0.38-2.37 days (not including malathion as starting material was completely lost after 3 days). Values for soil β-carotene sensitized photolysis are 0.85-4.02 days while respective values for soil benzophenone sensitized photolysis are 0.88-3.74 days. Metrological factors did not have a significant impact on photolysis rates. No photoproducts detected in direct photolysis. However, many photoproducts were detected on the indirect sets. Photo-degradation efficiency can be ordered as; benzophenone > β-carotene > direct exposure.
Journal of Xenobiotics
Photodegradation (photolysis) causes the breakdown of organic pesticides molecules by direct or indirect solar radiation energy. Flucetosulfuron herbicide often encounters water bodies. For this reason, it is important to know the behavior of the compound under these stressed conditions. In this context, photodegradation of flucetosulfuron, a sulfonylurea-based herbicide, has been assessed in aqueous media in the presence of photocatalyst TiO2 and photosensitizers (i.e., H2O2, humic acid, and KNO3) under the influence of ultraviolet (UV) irradiation. The influence of different water systems was also assessed during the photodegradation study. The photodegradation followed the first-order reaction kinetics in each case. The metabolites after photolysis were isolated in pure form by column chromatographic method and characterized using the different spectral data (i.e., XRD, IR, NMR, UV-VIS, and mass spectrometry). The structures of these metabolites were identified based on the spect...
Photodegradation study of some triazine-type herbicides
Microchemical journal, 2003
Triazines are amongst the most widely used herbicides. Since triazines can be found in many environmental compartments, their fate in ecosystems and the characterization of their degradation pathways in the environment are to be determined. In this paper we report on a study intended to investigate the photodegradation of some triazine-type herbicides: atrazine, cyanazine, terbuthylazine and terbutryn. The rate of photodegradation process was determined, and degradation schemes were outlined for the compounds studied. Moreover, experiments with different degrading energies were carried out in order to gain information about the effect of total degrading energy on the photodegradation process. The most significant processes of photodegradation of triazines are the partial or complete loss of side-chains, or rather the substitution of the heteroatom-containing side-chain to hydroxyl-group. Besides consecutive processes, loss of the different side-chains takes place parallely also, thus, different metabolites will be formed having mixed side-chains, until the cyanuric acid and 2-amino-4,6-dihydroxy-1,3,5-s-triazine are formed by losing all the side-chains. The presence of the dimer products could be detected during the degradation of all triazines. This proves the radical character of processes occurring during the photodegradation. Increasing the degradation energy (15 to 125 W) has raised the degradation rate by 2–5, and the chlorine containing metabolite—which was still present in the completely degraded mixture during the low-energy experiments—has completely disappeared from the mixture, thus, the increased degrading energy is favorable to the formation of less dangerous, nature identical metabolites.
Photo‐Fenton and Riboflavin‐photosensitized Processes of the Isoxaflutole Herbicide
Photochemistry and Photobiology, 2018
The pro-herbicide Isoxaflutole (IXF) hydrolyses spontaneously to diketonitrile (DKN) a phytotoxic compound with herbicidal activity. In this work, the sensitized degradation of IXF using Riboflavin (Rf), a typical environmentally friendly sensitizer, Fenton and photo-Fenton processes have been studied. The results indicate that only the photo-Fenton process produces a significant degradation of the IXF. Photolysis experiments of IXF sensitized by Riboflavin is not a meaningful process, IXF quenches the Rf excited triplet (3 Rf*) state with a quenching rate constant of 1.5 10 7 M-1 s-1 and no reaction is observed with the species O 2 (1 g) or O 2 generated from 3 Rf*. Similarly, the Fenton reaction no produce changes in the IXF concentration. While the photo-Fenton process of the IXF, under typical conditions, it produces a degradation of 99% and a mineralization to CO 2 and H 2 O of 88%. A rate constant value of 1.0 x 10 9 M-1 s-1 was determined for the reaction between IXF and HO . The photo-Fenton process degradation products were identified by UHPLC-MS/MS analysis.
Orbital the Electronic Journal of Chemistry, 2010
A field study was carried out to investigate persistence and dissipation kinetics of Trifluralin (48 EC) applied pre emergently in Green gram (Variety T-44) @ 1 Kg ai ha-1 (T 1) and 2 Kg ai ha-1 (T 2) for the control of broad leaf weeds during kharif 2006. The dissipation on 90 days was around 71.56-64.55% in T 1 and T 2. Kinetics studies revealed that dissipation of Trifluralin residues followed first order kinetics. The half life values observed were 60.21 days in T 1 and 75.56 days in T 2. Irrespective of any dose no residues were detected in cropped soil as well as plant samples at harvest.