Degradation Of Fenamiphos Research Articles

Metalorganic Polyhedra Polyoxometalate Hybrid Salts for Tandem Photooxidative‐Hydrolytic Pesticide Detoxification

AbstractThe extensive use of pesticides to ensure global food production presents significant threats to both human health and the environment. In this study, the photochemical, redox, and acid‐base properties of Zr‐metal‐organic polyhedra (Zr‐MOP) and polyoxometalates (POM) are utilized to fabricate functional hybrid salts, denoted as [Zr‐MOP][POM], designed for pesticide detoxification. Upon light irradiation, [Zr‐MOP][POM] salts generate a charge‐separated state with oxidizing properties. This activated state selectively photooxidizes highly toxic and persistent fenamiphos into fenamiphos sulfoxide and subsequently hydrolytically breaks down it into non‐toxic 3‐methyl‐4‐(methylsulfinyl)phenol and phosphate components. The hydrolytic degradation of fenamiphos is facilitated by the reduced basicity of the 3‐methyl‐4‐(methylsulfinyl)phenolate residue (ΔpKb = ‐2.4) in the photooxidized form of the pesticide molecule. Furthermore, the hybrid salts demonstrate efficacy in the breakdown of multicomponent pesticide mixtures such as fenamiphos and methylparaoxon.

Synthesis of WO3 nanorods through anodization in the presence of citric acid: Formation mechanism, properties and photoelectrocatalytic performance

In this study, WO 3 nanorods have been fabricated by simple anodization in the presence of different amounts of citric acid and at different anodization times. A comprehensive morphological, structural, electrochemical and photoelectrochemical characterization of different samples has been carried out. Moreover, a formation mechanism for WO 3 nanorods has been proposed. Finally, these nanostructures have been proven to be excellent visible-light photoelectrocatalysts to remove persistent organic pollutants present in wastewaters, such as fenamiphos. Almost the 80% of this molecule was eliminated from the test solution after 180 min of irradiation, indicating the great potential of these WO 3 nanorods, fabricated following a very simple and unexpensive procedure, in the energy and environmental fields as photoelectrocatalysts. • Citric acid influences the type and size of WO 3 nanostructures formed by anodization. • Large nanoplatelets were obtained in the absence of citric acid. • Nanorods formed with citric acid whose size decreased with increasing concentration. • WO 3 nanorods were used as photoelectrocatalysts for the degradation of fenamiphos. • After 180 min, almost the 80% of initial fenamiphos was degraded.

Photoelectrocatalyzed degradation of organophosphorus pesticide fenamiphos using WO3 nanorods as photoanode.

In this study, WO3 nanostructures were synthesized by the electrochemical anodization technique to use them on the degradation of persistent organic compounds such as the pesticide fenamiphos. The acids electrolyte used during the anodization were two different: 1.5M H2SO4 - 0.05M H2O2 and 1.5M CH4O3S - 0.05M H2O2. Once the samples have been manufactured, they have been subjected to different tests to analyze the properties of the nanostructures. With Field Emission Scanning Electron Microscopy (FE-SEM) the samples have been examined morphologically, their composition and crystallinity has been studied through Raman Spectroscopy and their photoelectrochemical behaviour by Photoelectrochemical Impedance Spectroscopy (PEIS). Finally, degradation tests have been carried out using the technique known as photoelectrocatalysis (PEC). The conditions that were applied in this technique were a potential of 1 VAg/AgCl and simulated solar illumination. The degradation process was monitored by UV-Visible and High-Performance liquid Chromatography (HPLC) to control the course of the experiment. The nanostructures obtained with 1.5M CH4O3S - 0.05M H2O2 electrolyte showed a better photoelectrochemical behaviour than nanostructures synthesized with 1.5M H2SO4 - 0.05M H2O2. The fenamiphos degradation was achieved at 2h of experiment and the intermediate formation was noticed at 1h of PEC experiment.

Supported TiO2 on Borosilicate Glass Plates for Efficient Photocatalytic Degradation of Fenamiphos

Supported titanium dioxide (TiO2) was investigated for the photodegradation of the insecticide fenamiphos in water. The photocatalyst was immobilised on borosilicate glass plates and the kinetics of degradation were studied in a stirred tank reactor under UV irradiation. Two types of TiO2, for example, Millennium PC500 (100% anatase) and Degussa P25 (80% anatase, 20% rutile), were used. Their activities have been based on the rates of insecticide disappearance. Experiments were investigated to evaluate the effect of pH and initial concentrations of fenamiphos as well as catalyst doses on the photocatalytic degradation of fenamiphos. Kinetic parameters were experimentally determined and an apparent first-order kinetic was observed. For photolysis process of fenamiphos, two photoproducts were identified and characterized using high performance liquid chromatography/mass spectrometry (HPLC/MS). The plausible mechanism of photolysis involved is the oxidation of sulfonamide group. In presence of photocatalyst TiO2, photodegradation was observed. Under identical conditions, Degussa P25 shows higher photocatalytic activity in regard to PC500 Millennium and complete degradation was observed after 180 min.

Semiconductor oxides-sensitized photodegradation of fenamiphos in leaching water under natural sunlight

The photocatalytic degradation of fenamiphos in leaching water has been studied using zinc oxide (ZnO), different mixed-phase titanium dioxide (TiO2), tungsten(VI) oxide (WO3), and tin(IV) oxide (SnO2) at pilot plant scale under natural sunlight. Photocatalytic experiments showed that the addition of semiconductors in tandem with the oxidant (Na2S2O8) strongly enhances the degradation rate of fenamiphos in comparisons carried out with photolytic tests. The primary degradation of fenamiphos followed a pseudo-first order kinetics. The time required for 50% degradation was in the range 1–3min for ZnO and TiO2. The main photocatalytic intermediates (fenamiphos-sulfoxide and fenamiphos sulfone) detected during the degradation of fenamiphos were identified. Comparison of catalysts showed that ZnO is the most efficient for catalyzing the removal of fenamiphos and their metabolites. Thus, complete disappearance of all the compounds studied achieved after 240min of illumination in the ZnO/Na2S2O8 system.

Isolation and characterization of fenamiphos degrading bacteria

The biological factors responsible for the microbial breakdown of the organophosphorus nematicide fenamiphos were investigated. Microorganisms responsible for the enhanced degradation of fenamiphos were isolated from soil that had a long application history of this nematicide. Bacteria proved to be the most important group of microbes responsible for the fenamiphos biodegradation process. Seventeen bacterial isolates utilized the pure active ingredient fenamiphos as a carbon source. Sixteen isolates rapidly degraded the active ingredient in Nemacur 5GR. Most of the fenamiphos degrading bacteria were Microbacterium species, although Sinorhizobium, Brevundimonas, Ralstonia and Cupriavidus were also identified. This array of gram positive and gram negative fenamiphos degrading bacteria appeared to be pesticide-specific, since cross-degradation toward fosthiazate, another organophosphorus pesticide used for nematode control, did not occur. It was established that the phylogenetical relationship among nematicide degrading bacteria is closer than that to non-degrading isolates.

Simultaneous enantioselective determination of fenamiphos and its two metabolites in soil sample by CE

The enantioseparation of fenamiphos and its two main metabolites (fenamiphos sulfoxide and fenamiphos sulfone) were simultaneously achieved by CE by using a dual CD system. A mixture of 25 mM carboxymethyl-beta-CD and 10 mM hydroxypropyl-alpha-CD was added to the acetic acid/ammonia (ionic strength=50 mM, pH 5) buffer and was suitable for the baseline resolution of all stereoisomers of analytes. A further addition of 5% methanol to the BGE increased significantly the resolution between the diastereoisomers of fenamiphos sulfoxide. An overimposed pressure (0.2 psi) was applied during the analysis in order to have better peak efficiencies and small run time. The composition of the sample solvent was found to be a crucial parameter. An amount of 15% MeOH added to the sample was a good alternative to ensure the total solubility of fenamiphos and the baseline separation of fenamiphos sulfoxide enantiomers. The extraction of pesticides from soil samples was also investigated. A methanolic extraction allowed recovering 50-75% of pesticides, which were detected by CE at the parts per million concentration level (3-100 mg/kg) with a good precision (5.1-13.2% RSD). This method was applied to soil samples and was found to be suitable to monitor the enantiomeric degradation of fenamiphos in environmental samples.

Photodegradation of fenamiphos on the surface of clays and soils

The photodegradation of the organophosphorus fenamiphos was studied in various clay matrices: montmorillonite, kaolin and the mineral components of two soils collected from two different sites: Settat (S) and Berrechid (B). The degradation was shown to be mainly due to the direct excitation of fenamiphos and was similar for all the matrices with a two-step kinetics : a fast and a slower one. The first step rate obtained at the surface of montmorillonite was slightly lower than that determined at the surface of kaolin. The fenamiphos degradation process clearly depended on the amount of humic substances and iron(III). The latter component accelerated the disappearance of fenamiphos, while humic substances clearly inhibited the process. The degradation rate increased in the presence of water and was mainly due to the involvement of the photohydrolysis process leading to the scission of the P–O bond. The formation of the main by-products, sulfoxide, sulfone and phenol derivatives, were elucidated by HPLC/MS.

Degradation of fenamiphos in soils collected from different geographical regions: The influence of soil properties and climatic conditions

The persistence of fenamiphos (nematicide) in five soils collected from different geographical regions such as Australia, Ecuador and India under three temperature regimes (18, 25 and 37°C) simulating typical environmental conditions was studied. The effect of soil properties (soil pH, temperature and microbial biomass) on the degradation of fenamiphos was determined. The rate of degradation increased with increase in temperature. Fenamiphos degradation was higher at 37°C than at 25 and 18°C (except under alkaline pH). The degradation pathway differed in different soils. Fenamiphos sulfoxide (FSO) was identified as the major degradation product in all the soils. Fenamiphos sulfone (FSO2), and the corresponding phenols: fenamiphos phenol (FP), fenamiphos sulfoxide phenol (FSOP) and fenamiphos sulfone phenol (FSO2P) were also detected. The degradation of fenamiphos was faster in the alkaline soils, followed by neutral and acidic soils. Under sterile conditions, the dissipation of the pesticide was slower than in the non-sterile soils suggesting microbial role in the pesticide degradation. The generation of new knowledge on fenamiphos degradation patterns under different environmental conditions is important to achieve better pesticide risk management.

Bioremedial potential of fenamiphos and chlorpyrifos degrading isolates: Influence of different environmental conditions

Previously isolated bacterial strains for chlorpyrifos and fenamiphos degradation were used to examine their potential as bioremedial agents in soils and water containing pesticide residues. Both, chlorpyrifos-degrading Enterobacter sp and fenamiphos-degrading consortium rapidly degraded pesticides when inoculated into natural and sterile water and soils. Degradation rate was slower in lower pH soils in comparison with natural and alkaline soils. Soil organic matter had no impact on pesticide degrading ability of isolates. Soil moisture <40% of maximum water-holding capacity slowed down degradation rate. The bacterial isolates were able to rapidly degrade fenamiphos and chlorpyrifos between 15 and 35 °C but their degradation ability was sharply reduced at 5 and 50 °C. Both groups of bacterial systems were also able to remove a range of pesticide degradation. An inoculum density of 10 4 cells g −1 of soil was required for initiating rapid growth and degradation. Ageing of pesticide in soils prior to inoculation produced contrasting results. Ageing of fenamiphos had no impact on subsequent degradation by the inoculated consortium. However, degradation of chlorpyrifos by Enterobacter sp after aging resulted in persistence of ∼10% of pesticide in soil matrix. Higher K oc value of chlorpyrifos may have resulted in a lack of bioavailability of a smaller percentage of chlorpyrifos to degrading bacteria. Overall, this paper confirms bioremedial potential of a fenamiphos degrading consortium and a chlorpyrifos degrading bacterium under different soil and water characteristics.

Cross-enhancement of accelerated biodegradation of organophosphorus compounds in soils: Dependence on structural similarity of compounds

Rates of degradation of seven organophosphate nematicides and insecticides were examined in two soils known to show accelerated biodegradation of fenamiphos and one soil known to show accelerated biodegradation of chlorpyrifos. The results indicated that several organophosphate insecticides and one nematicide were susceptible to cross-enhanced degradation in the soil showing accelerated biodegradation of chlorpyrifos. No cross-enhancement was observed in the two soils showing accelerated degradation of fenamiphos. Fumigation resulted in the complete inhibition of pesticide degradation in all soils. The data suggested that the cross-enhancement of selected pesticides in chlorpyrifos-degrading soil was dependent on the structural similarity of the compounds. Mechanisms of degradation of pesticide in soil support this hypothesis, where structurally similar compounds (diazinon, parathion, coumaphos and isazofos) were hydrolysed by microbial activity in chlorpyrifos-degrading soil but the degradation products were accumulated. Enhanced degradation of chlorpyrifos and fenamiphos was found to be stable in the laboratory condition for a period of one year.

Role of soil pH in the development of enhanced biodegradation of fenamiphos.

Repeated treatment with fenamiphos (ethyl 4-methylthio-m-tolyl isopropylphosphoramidate) resulted in enhanced biodegradation of this nematicide in two United Kingdom soils with a high pH (>/= 7.7). In contrast, degradation of fenamiphos was slow in three acidic United Kingdom soils (pH 4.7 to 6.7), and repeated treatments did not result in enhanced biodegradation. Rapid degradation of fenamiphos was observed in two Australian soils (pH 6.7 to 6.8) in which it was no longer biologically active against plant nematodes. Enhanced degrading capability was readily transferred from Australian soil to United Kingdom soils, but only those with a high pH were able to maintain this capability for extended periods of time. This result was confirmed by fingerprinting bacterial communities by 16S rRNA gene profiling of extracted DNA. Only United Kingdom soils with a high pH retained bacterial DNA bands originating from the fenamiphos-degrading Australian soil. A degrading consortium was enriched from the Australian soil that utilized fenamiphos as a sole source of carbon. The 16S rRNA banding pattern (determined by denaturing gradient gel electrophoresis) from the isolated consortium migrated to the same position as the bands from the Australian soil and those from the enhanced United Kingdom soils in which the Australian soil had been added. When the bands from the consortium and the soil were sequenced and compared they showed between 97 and 100% sequence identity, confirming that these groups of bacteria were involved in degrading fenamiphos in the soils. The sequences obtained showed similarity to those from the genera Pseudomonas, Flavobacterium, and CAULOBACTER: In the Australian soils, two different degradative pathways operated simultaneously: fenamiphos was converted to fenamiphos sulfoxide (FSO), which was hydrolyzed to the corresponding phenol (FSO-OH) or was hydrolyzed directly to fenamiphos phenol. In the United Kingdom soils in which enhanced degradation had been induced, fenamiphos was oxidized to FSO and then hydrolyzed to FSO-OH, but direct conversion to fenamiphos phenol did not occur.

Kinetics and hydrolysis of fenamiphos, fipronil, and trifluralin in aqueous buffer solutions.

Hydrolyses of fenamiphos, fipronil, and trifluralin were studied in aqueous buffer solutions of pH 4.1, 7.1, and 9.1 at different temperatures, 5, 22 +/- 1, 32 +/- 1, and 50 +/- 1 degrees C. Fenamiphos, fipronil, and trifluralin were found to be more stable in acidic and neutral buffer solutions at temperatures of 5 and 22 +/- 1, and dissipation is rapid at 50 +/- 1 degrees C. In basic buffer and at higher temperature, degradation of fenamiphos was found to be very rapid when compared with fipronil and trifluralin. The rate constants calculated at 32 degrees C for fenamiphos were 2349.4 x 10(-)(8) (pH 4.1), 225.2 x 10(-)(8) (pH 7.1), and 30476.0 x 10(-)(8) (pH 9.1); for fipronil 1750.0 x 10(-)(8) (pH 4.1), 3103.0 x 10(-)(8) (pH 7.1), and 3883.0 x 10(-)(8) (pH 9.1); and for trifluralin 2331.0 x 10(-)(8) (pH 4.1), 2360.0 x 10(-)(8) (pH 7.1), and 3188.0 x 10(-)(8) (pH 9.1). On the basis of rate constant values, these pesticides appeared to be more susceptible to hydrolysis than synthetic organophosphorus compounds such as chlorpyriphos, diazinon, malathion, and ronnel. DT(50) values calculated at 32 degrees C were 228 (pH 4.1), 5310.24 (pH 7.1), and 37.68 (pH 9.1) h for fenamiphos; 608.6 (pH 4.1), 373.9 (pH 7.1), and 270.2 (pH 9.1) h for fipronil; and 502.1 (pH 4.1), 496.8 (pH 7.1), and 355.7 (pH 9.1) h for trifluralin.

Stability of pesticides stored on polymeric solid-phase extraction cartridges

The stability of four pesticides (desethylatrazine, fenamiphos, fenitrothion and fonofos) was examined under different storage conditions after preconcentration in disposable solid-phase extraction (SPE) cartridges containing new polymer sorbent materials (Hysphere-1, IST EnviroLut and LiChrolut). Complete recovery for all the compounds was observed in precolumns kept at −20°C for 1 month when preconcentrating 26 ml of ground water sample spiked at 10 μg/l. Degradation of fenamiphos and fenitrothion occurred in precolumns stored at 4°C and at room temperature after 1 month. Fonofos was stable when compared to their storage in C 18 precolumns. Problems in the quantification of the analytes after storage at 4°C and at room temperature were encountered due to the presence of many interfering peaks in the chromatograms. Analysis of blanks with C 18 precolumns was carried out, to determined the interferences. The stability of the pesticides was also examined in acidified and non-acidified ground water in order to compare it to the stability of pesticides stored on SPE cartridges. Significant losses of fenamiphos and fenitrothion were achieved and were related to the pH of the water sample and their chemical structure. Finally, the new polymeric sorbent Hysphere-1 was evaluated in terms of breakthroughs and compared with those of C 18, obtaining higher recoveries for desethylatrazine.

Degradation of Fenamiphos and Folpet in Water

The degradation of the pesticides fenamiphos and folpet was examined in distilled water and water from Albufera de Adra, a lake which is located along the west coast of Almeria (Spain). pH value, ultraviolet (UV) light and activity of microorganisms affected the persistence of both fenamiphos and folpet in the Albufera de Adra water. The results showed a faster degradation in that water than in distilled water. Fenamiphos was more stable than folpet.

Determination and stability of pesticides in freeze-dried water samples by automated on-line solid-phase extraction followed by liquid chromatography with diode-array detection

The determination of selected pesticides, atrazine, simazine, carbaryl, propanil, linuron and fenamiphos, was carried out in freeze-dried water using automated on-line solid-phase extraction (Prospekt) followed by liquid chromatography with diode-array detection. The concentration of the pesticides in the water varied from 1.2 to 20.5 μg/l after reconstitution of the freeze-dried water sample. A stability study was undertaken using freeze-dried water for a period of 1.5 months at three different storage temperatures (4, −20 and 20°C). It was shown that the degradation of fenamiphos, linuron and simazine observed at 4 and 20°C was correlated with various parameters such as Henry's law constant, hydrolysis, photolysis and temperature.

Stability of organophosphorus pesticides on disposable solid-phase extraction precolumns

The stability of 19 organophosphorus (OP) pesticides was performed using precolumns from the Prospekt (automated on-line solid-phase extraction system) filled with C 18 . Several different storage conditions were tested, which included storage at 4 °C, at -20 °C, and a combination of two conditions where precolumns were stored at 4 °C for 1.5 months and held at room temperature until analysis (0.5 and 1 month). Complete recoverywas observed in precolumns kept in at -20 °C for 8 months except for mevinphos, dichlorvos, and phosmet, which had recoveries from 22 to 58%. Degradation also occurred for these same OP pesticides when precolumns were stored at 4 °C for 2 months and at room temperature for 1 month, with losses varying from 21 to 78% and from 41 to 61%, respectively. Complete degradation of fenamiphos and fonofos occurred in precolumns stored at 4 °C and at room temperature. The stability of the pesticides in each storing treatment is related to the hydrolytic processes, to K oc , and to their solubility in water.

Degradation of Fenamiphos in Soil with a History of Continuous Fenamiphos Applications

AbstractThe efficacy of the nematicide fenamiphos [ethyl‐3‐methyl‐4‐(methylthio)phenyl (1‐methylethyl) phosphoramidate] often is reduced when applied annually or biannually for extended periods to turfgrasses in Florida. This study was conducted near Gainesville, FL, on a Blichton sand (loamy, siliceous, hyperthermic Arenic Plinthic Paleaquults) to determine whether the degradation of fenamiphos was enhanced by long‐term applications to a turfgrass golf course fairway and putting green. 14C‐fenamiphos was used for determination of mineralization rates, metabolites, and mass balance. Initial mineralization of 14C‐fenamiphos in soil collected from the turfgrass site was more rapid than in soil collected from the rough (untreated). Fenamiphos sulfoxide (FSO) was the main metabolite detected, whereas fenamiphos sulfone (FSO2) was either not detected or only occasionally detected in trace amounts. Half‐life values for total toxic residues (TTR, fenamiphos + FSO + FSO2) in soil samples collected from the site were all small, ranging from 0.9 to 4.2 d, and half‐life values for TTR in soil collected after the fenamiphos application were smaller than in soil collected before the application. Total 14C recovery from 14C‐fenamiphos‐treated surface soil collected 0.7 mo after the annual application was well below 100%. Rapid initial mineralization of fenamiphos was also observed in this sample. Applications of fenamiphos to the same site for prolonged periods appear to increase the potential for enhanced degradation of TTR.

Microbial Degradation of Fenamiphos After Repeated Application To a Tomato-Growing Soil

Soil was obtained from a tomato-growing field near Bowen, Queensland, where the nematicide fenamiphos was reported to have lost its effectiveness following 14 years of regular use. A bioassay using the fungal-feeding nematode Aphelenchus avenae demonstrated that nematicidal activity in this soil was lost in 2 wk, whereas similar soil that had never been treated with fenamiphos retained significant nematicidal activity for at least 6 wk. Results of further experiments with the bioassay suggested that microorganisms were responsible for enhanced degradation of fenamiphos. Significant nematicidal activity was retained for 6 wk following autoclaving or gamma-irradiation, but was lost in untreated soil in less than 2 wk. Furthermore, nematicidal activity of fenamiphos in mixtures of autoclaved and non-autoclaved tomato-growing soil decreased as the proportion of non-autoclaved soil was increased. Despite evidence that enhanced microbial degradation was occurring, the degradative organisms were not isolated. Twelve fungal and 70 bacterial isolates were obtained from the soil by enrichment with fenamiphos, but none degraded the nematicide when added individually or as mixtures to autoclaved soil.

Interactions of Microorganisms and Soil during Fenamiphos Degradation

AbstractEnhanced degradation of a number of pesticides occurs in soils with a history of previous exposure to the chemical. Little is known, however, about the duration of enhanced degradation after a single field application of a pesticide or the microorganisms responsible for the enhancement. Soil samples collected 2, 3, and 4 yr after one application of the nematicide fenamiphos [ethyl‐3‐methyl‐4‐(methylthio)phenyl (1‐methylethyl) phosphoramidate] at a rate of 4.48 kg ha−1 to an experimental site planted in potato (Solanum tuberosum L.) near Hastings, FL, were used to determine mineralization rates and total‐toxic‐residue (TTR) disappearance rates. Both mineralization rates and TTR disappearance rates in samples collected 2 and 3 yr after field application were enhanced compared with the corresponding control samples. Half‐lives for TTR in soil samples collected 2 and 3 yr after field application of fenamiphos were 22 and 89 d, respectively, while half‐life values for the corresponding control samples were 131 and 130 d. During a 70‐d incubation period, 67.2, 27.8, and 9.8% of applied 14C‐fenamiphos was mineralized in soil samples collected 2, 3, and 4 yr after field application, while 10.8, 11.5, and 9.5% of applied 14C‐fenamiphos in the corresponding control samples was mineralized. Mineralization rates in soil collected 4 yr after field application were the same as in the control sample. Microorganisms capable of degrading fenamiphos could not be isolated from the soils. A mixed bacterial culture derived from soil collected 2 yr after the field application, in the presence of a small amount of this soil, however, did mineralize fenamiphos. Without the small amount of soil, the mixed culture did not mineralize the nematicide.