Degradation Of Chlorpyrifos Research Articles

Potential of formulated Dyadobacter jiangsuensis strain 12851 for enhanced bioremediation of chlorpyrifos contaminated soil

Chlorpyrifos (O, O-diethyl O-3, 5, 6-trichloropyridin-2-yl phosphorothioate) is a toxic and chlorinated organic contaminant in soils across the globe. The present study examines the chlorpyrifos (CP) degrading potential of gram-negative bacterium Dyadobacter jiangsuensis (MTCC 12851), to be a promising and sustainable remedial approach. The proliferation of D. jiangsuensis in the chlorpyrifos spiked minimal salt media indicated the ability of this strain to utilize CP as a sole carbon source and also confirmed the utilization of 3,5,6- trichloro-2-pyridinyl (TCP) through silver nitrate assay. The strain 12851 degraded 80.36% and 76.93% chlorpyrifos (CP) in aqueous medium and soil environment, respectively. The water dispersible granules (WDG) of 45% (v/w) inoculum (bacterial suspension) were developed using talcum powder, acacia gum and alginic acid as key ingredients. The formulated strain (12851) achieved 21.13% enhanced CP degradation in soil under microcosm condition as compared to the unformulated one on 15th day of the treatment. The intermediate metabolites namely 3,5,6-trichloro-2-pyridinol (TCP), tetrahydropyridine, thiophosphate and phenol, 1, 3-bis (1,1-dimethylethyl) were detected during the CP degradation. The current investigation reveals D. jiangsuensis as a potential microbe for CP degradation and opens up the possibility of exploiting its formulations to remediate the CP polluted soils.

Removal of chlorpyrifos and its hydrolytic metabolite in microcosm-scale constructed wetlands under soda saline-alkaline condition: Mass balance and intensification strategies.

Chlorpyrifos (CP) is a typical organophosphorus insecticide, which poses serious threats to the natural environment and human health. Strategies for the fast elimination of CP and its toxic hydrolytic metabolite 3,5,6-trichloro-2(1H)-pyridianol (TCP) in drainage water are urgently needed. The fate of CP and TCP in microcosm-scale subsurface batch constructed wetlands (SSBCWs) was quantified with different macrophyte species under soda saline-alkaline (SSA) condition and effective intensification strategies were developed. The macrophyte species Canna indica outperformed Phragmites australis and Typha orientalis for CP and TCP removal in SSBCWs. Mass balance calculation indicates the fate of CP in SSBCWs was residue in water (≤8%), alkaline hydrolysis (18.93-57.42%), microbial degradation (37.75-61.91%), substrate adsorption (~4-14%), and macrophyte uptake (≤3%). The addition of ferric-carbon (Fe-C) as a substrate amendment in SSBCWs increased the CP removal percentage by 35% and reduced the effluent TCP concentration by ~70% during Day 1-4 on average compared with the unintensified control. Fe-C addition simplified the microbial community diversity, while increasing the relative abundance of Proteobacteria which tolerates the microelectrolytic environment. A single application of liquid microbial agent improved CP removal percentage by 84% and decreased the effluent TCP concentration by two orders of magnitude during Day 1-4. The hydraulic retention time for thorough removal of TCP reduced from over 8d to 4d. Although only two dominant microbial genera (i.e., Sphingomonas and Pseudomonas) adapted to the environment with CP and SSA, they accelerated CP and TCP degradation via their own metabolism and co-metabolism with other indigenous microorganisms.

Molecular Characterization of Chlorpyrifos Degrading Bacteria Isolated from Contaminated Dairy Farm Soils in Nakuru County, Kenya

Chlorpyrifos [O, O-diethyl O-(3,5,6-trichloro-2-pyridinyl) phosphonothioate] is an organophosphate widely used as an insecticide against a broad spectrum of pests, including as an acaricide against ticks and mites. Due to environmental persistence and toxicity, it should be eliminated quickly from contaminated sites through biodegradation. Microbial bioremediation is one of the most viable ways of removing Chlorpyrifos (CP) from the environment. However, few studies have been conducted on the bacterial diversity that degrades Chlorpyrifos. The enrichment culture technique conducted in this study isolated chlorpyrifos degrading bacteria in soils from dairy farms in Nakuru County, Kenya. The growth response of the bacteria and degradation of Chlorpyrifos was monitored every five days using UV-VIS Spectrophotometer (600nm). Sequential soil and liquid culture enrichments led to the isolation of eighteen (MA1-MA18) bacterial chlorpyrifos degraders with DNA sequences homologous to members of the genera Pseudomonas, Stenotrophomonas, Bacillus, Alicaligenes, and Achromobacter. The efficacy of four (4) strains was further investigated using Gas Chromatography-Mass Spectrometry (GC-MS) analysis. The results showed that all four strains significantly degraded Chlorpyrifos in Minimum Salt Medium (MSM), Lysinibacillus sp.HBUM206408 (79.52%), Stenotrophomonas maltophilia (71.43%), Pseudomonas putida (73.32%), and Achromobacter insuavis (71.03%), producing 2-Hydroxy-3,5,6-trichloropyridine (TCP) as a metabolite in MSM as the only source of carbon. Therefore, these strains can be used for the bioremediation of Chlorpyrifos in contaminated soil. There is a need for further studies to determine the possible mechanisms and other metabolites of Chlorpyrifos degradation by the isolates obtained in the study. Besides, future studies should explore the efficacy and survival of the organisms in the contaminated environment.

Chlorpyrifos induced proteome remodelling of Pseudomonas nitroreducens AR-3 potentially aid efficient degradation of the pesticide

Bacteria respond to xenobiotics in their immediate environment and can either tolerate/ evade high concentrations of it, or are capable of their removal through degradation. A highly efficient and rapid chlorpyrifos (CP) degrader Pseudomonas nitroreducens AR-3 was previously reported, and the current work focused on elucidating the molecular mechanisms by which the bacterium achieves this. The bacterial response to CP included remodelling of the proteome and induction of global response pathways. Sixty-four out of the 794 significantly up-regulated proteins were specifically involved in carbohydrate metabolism, environmental and genetic information processing, biosynthesis of secondary metabolites and metabolism in diverse environments. There was an induction of (mainly) periplasmic proteins, and those involved in chemical degradation pathways. Interestingly, an unprecedented repression of stress responsive pathways and xenobiotic transporter elements were also observed, presumably due to the non-recognition of CP as a stress factor. A presumptive MBL-fold metallo-hydrolase protein showing 44% sequence similarity to an organophosphate hydrolase (ophC2) was identified from the genome. Understanding of the dynamic changes in the protein profiles shed light into the basic cellular and molecular mechanisms underlying CP degradation and enabling the organism to sustain under adverse conditions.

Chlorpyrifos degradation by plant growth-promoting Alcaligenes faecalis bacteria isolated from oil-contaminated soil

Chlorpyrifos (Chlp), one of the major organophosphates is extensively used in agriculture to control pests. With a half-life of 7–120 d, it may persist for up to one year in soil depending on the soil conditions and affect the soil microflora. Chlp degradation by soil microbes proves to be an effective and environment friendly method to remove it from the soil. This study aims to identify and characterize Chlp degrading soil microbes. Total 173 bacteria isolated from different soil samples were screened for Chlp degradation. Characterization of 10 selected samples showed that all the strains produced excessive exo-polysaccharides (EPSs), which positively correlated with the Chlp degradation under in vitro conditions. Among these 10 bacterial strains, the most potent Chlp degrading bacteria was identified to be Alcaligenes faecalis (NBRI OSS2-5) which paired with the Chlp degrading Pseudomonas in the phylogenetic tree. The strain was shown to possess opd gene reported for Chlp degradation. From the study, it was concluded that EPS production may be a common feature of Chlp degrading microbes which may have some role in the Chlp biodegradation process and the pesticide-contaminated fields may not necessarily be the ideal source of isolating pesticide degrading microbes.

Chlorpyrifos remediation in agriculture runoff with homogeneous solar photo-Fenton reaction at near neutral pH: phytotoxicity assessment.

This study represents the first application of Fe-citrate-based photo-Fenton chemistry for the degradation of chlorpyrifos (CPF) spiked into agricultural runoff, and its phytotoxicity assessment. The effects of the initial CPF concentration, time and ratio of Fe-citrate/H2O2 on CPF removal during the photo-Fenton reaction were investigated and modeled with analysis of variance using R software by the response-surface methodology package. According to the stationary point in original units, the optimal condition for 70.00% CPF removal was as follows: CPF = 2.5 mg L-1 (0.0), time = 48.0 min (0.585) and Fe-citrate/H2O2 = 0.075 (0.539). Beside running the system at near-neutral pH, another strength of this study is related to the treatment of agricultural runoff contaminated with CPF with a raceway pond reactor, which has the advantages of simplicity of the facilities and procedures, as well as the possibility of using sunlight more efficiently in the field of applications. Finally, untreated and treated agriculture runoffs were used as irrigation to determine their phytotoxic effects on seed germination of cress (Lepidium sativum). Solar photo-Fenton treatment greatly reduced phytotoxicity of agriculture runoff and showed the highest germination percentage (70%) compared to both raw agricultural runoff (60%) and untreated CPF-spiked runoff (35%).

Novel CuO/TiO2/PANI nanocomposite: Preparation and photocatalytic investigation for chlorpyrifos degradation in water under visible light irradiation

Visible light active photocatalyst, copper oxide/titanium dioxide/polyaniline (CuO/TiO2/PANI) nanocomposite, have been synthesized and utilized for chlorpyrifos degradation in water. The nanocomposite was characterized by some techniques including field emission scanning electron microscopy (FE-SEM), Fourier-transform infrared spectroscopy (FT-IR), and diffuse reflectance spectroscopy (DRS). The structural properties confirmed that the nanocomposite was successfully prepared and optical properties revealed that the nanocomposite can be operated by visible light irradiation. The resulting nanocomposite was employed as photocatalyst to degrade chlorpyrifos in water and 95 % of pesticide was photo-degraded within 90 min illumination. Some parameters affecting the photocatalytic reaction such as pH, pesticide initial concentration, irradiation time and photocatalyst amount were optimized. The CuO/TiO2/PANI nanocomposite presented higher photocatalytic activity in comparison with CuO/TiO2 and TiO2/PANI under the same conditions. According to the obtained results, the nanocomposite band gap has been decreased, leading to decrease the recombination rate of photo-generated charges. That is why the nanocomposite catalytic efficiency has been improved.

Coupling between laser irradiation and TiO2 nanoparticles on efficient decontamination of some pesticide's residues from orange and tomato puree

In this paper, we focused on the development of photocatalytic degradation to be a promising method for the treatment of decontaminated fruits and vegetables with pesticides. We investigate the coupling between Laser irradiation with TiO2 nanoparticles catalyst in order to study the photocatalytic degradation of metalaxyl, chlorpyrifos, and diazinon from artificially contaminated tomato puree and orange puree. Degradation products were identified by gas chromatography-mass spectrometry (GC–MS). The influences of different parameters such as catalyst concentration, irradiation time on the reaction rate were ascertained and optimum conditions for maximum degradation were determined. The degradation percentage of all pesticides was achieved under optimized conditions (1g/L catalyst at the irradiation time of 120 min). The study proved that the coupling between TiO2 nanoparticles and laser irradiation has a high potential for photocatalytic degradation of diazinon, chlorpyrifos, and metalaxyl from orange puree and tomato puree. And also, proved that the efficient degradation of pesticide residues increased with an increase in laser irradiation time (for 60 min) and catalyst (TiO2nanoparticles) dosage in all experiments. Maximum reduction >80% was observed in diazinon in all puree treatments. The processing factor (PFs) was generally less than one which indicates that all processes can reduce pesticide residues in all puree treatments. The less efficient removal of pesticides residues from all treatments without Laser irradiation (dark TiO2100mg) We concluded that the optimum conditions for the photodegradation of diazinon, chlorpyrifos, and metalaxyl in all puree treatments were TiO2100mg catalyst concentration and after 60 min of laser irradiation.

Remediation of Wastewater from Chlorpyrifos Pesticide by Nano-Gold Photocatalyst

AbstractSuccessful disintegration of Chlorpyrifos pesticide by nearly monodisperse nano-gold photcatalyst (∼10 nm) for remediation of wastewater has been reported in current studies. Nano-Gold dispersion reaction with Chlorpyrifos solutions completes in 45 minutes at ambient temperature under the normal daylight and exhibit systematic variations in the solution color from wine red to pink to light sky blue and finally transforming into a transparent solution with fine precipitates. UV-Vis absorption studies correlates well with the systematic color changes as observed in the nano-gold treated Chlorpyrifos solutions with time. The characteristic localized surface plasmon resonance peak of nanogold dispersion observed at 529 nm red shifts to weak, medium and strong intensity peaks at ∼ 640 nm, 740 nm and 890 nm on increasing chlorpyrifos concentration owing to the aggregation of gold nanoparticles in small to bigger sized clusters. The fine turbidity in final transparent solution further confirms the aggregation of nanogold particles into stable bigger ensembles. IR transmission spectra of final transparent solutions showed disappearance of Chlorpyrifos νC-Cl and phosphorothioate functional group peaks indicating degradation of chlorpyrifos.

Synthesis and photocatalytic activity of porous ZnO stabilized by TiO2 and Fe3O4 nanoparticles: investigation of pesticide degradation reaction in water treatment.

The present research studies the photocatalytic degradation of a pesticide using TiO2 and Fe3O4 nanoparticles supported on ZnO mesoporous (mZnO) substrate. Chlorpyrifos is an organophosphate pesticide with a C9H11Cl3NO3PS chemical formula. It is broadly utilized in agricultural fields to control product pests. The chlorpyrifos toxicity is acute and still dangerous to any aquatic organisms. The mZnO/TiO2-Fe3O4 material was characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), and N2 adsorption and desorption (Brunauer-Emmett-Teller; BET). In order to optimize three important operating parameters, i.e., chlorpyrifos concentration, mZnO/TiO2-Fe3O4 nanocomposite amount, and pH, for photocatalytic degradation of chlorpyrifos, response surface methodology (RSM) was applied. The central composite design (CCD) including 20 experiments was used to conduct experiments. The highest photodegradation performance of about 94.8% was obtained for a chlorpyrifos concentration of 8ppm, a pH of 10, and an amount of mZnO/TiO2-Fe3O4 nanocomposite of 60mg. The degradation of chlorpyrifos using mZnO/TiO2-Fe3O4 presented good performance (more than 94%). The photocatalytic reaction followed pseudo-first-order kinetics with a rate constant of 0.058min-1 for chlorpyrifos degradation. The results propose that mZnO/TiO2-Fe3O4 nanocomposite is a suitable alternative for the degradation of chlorpyrifos in aqueous solution. The improved photocatalytic efficiency could be attributed to the effective separation of electron-hole pairs via a Z-scheme mechanism.

Degradation of chlorpyrifos formulation in water by the UV/H2O2 process: Lumped kinetic modelling of total organic carbon removal

The degradation of a commercial chlorpyrifos (CP) formulation solution under the UV/H2O2 process was predicted through a lumped kinetics modelling approach (LKA). The proposed models are based on different reaction schemes that include the hydroxyl radical reaction rate with the Total Organic Carbon (TOC). TOC represents the concentration of the mixture of CP and “unknown organic matter”, both components present in CP formulation. TOC is one of the most practical parameter that can be used to quantify organic pollution in a complex matrix. A one-step model was selected and a second-order reaction rate constant between hydroxyl radical and TOC was obtained by optimization: 1.75 × 107 M−1 s−1. According to computed performance metrics, the chosen model well fitted the concentrations evolution of the reactants (TOC and H2O2). The model could be useful to predict the behaviour of reaction systems with different configuration for wastewater treatment applications.

Biodegradation of organophosphorus pesticide chlorpyrifos by Sphingobacterium sp. C1B, a psychrotolerant bacterium isolated from apple orchard in Himachal Pradesh of India.

A psychrotolerant Sphingobacterium sp. was isolated from the apple orchard situated in the Kufri region of Shimla, Himachal Pradesh, India using an enrichment culture technique having chlorpyrifos (CP) as the sole source of carbon and energy. Based on biochemical characterization and 16S rRNA analysis, the strain was identified as Sphingobacterium sp. C1B. The bacterium C1B was able to degrade chlorpyrifos ≥ 42ppm and ≥ 36ppm within 14days at 20°C and 15°C, respectively. The strain was also able to degrade chlorpyrifos ≤ 35ppm at 28°C within 14days. The enzyme organophosphorus hydrolase might be responsible for the initial degradation of CP by the strain C1B. Based on the HPLC and GCMS analysis, a probable degradation pathway has been proposed, which followed the path from chlorpyrifos to 3,5,6-trichloro-2-pyridinol to benzene, 1,3-bis (1,1-dimethylethyl) and then entered into the TCA cycle. Our current study revealed that the bacterium C1B was found to be a useful strain for the degradation of pesticide chlorpyrifos in the cold climatic environment.

Daily temperature variation lowers the lethal and sublethal impact of a pesticide pulse due to a higher degradation rate

Daily temperature variation (DTV) is an important warming-related stressor that may magnify pesticide toxicity. Yet, it is unknown whether the pesticide impact under DTV is partly ameliorated by a faster pesticide degradation caused by cyclically higher temperatures under DTV. As synergisms may be more likely under energy-limiting conditions, the impact of the pesticide chlorpyrifos was tested under DTV on the mosquito Culex pipiens in the absence and presence of interspecific competition with the water flea Daphnia magna. Chlorpyrifos exposure at a constant temperature without interspecific competition caused considerable mortality, decreased development time, and increased pupal mass of C. pipiens. Competition with D. magna had negative sublethal effects, but it did not affect the toxicity of chlorpyrifos. In contrast, the presence of C. pipiens decreased the impact of chlorpyrifos on D. magna probably due to corporal absorption of chlorpyrifos by C. pipiens. A key finding was that chlorpyrifos no longer caused lethal effects on C. pipiens under DTV, despite DTV on its own being mildly lethal. Additionally, chlorpyrifos exposure under DTV decreased development time less and had no effect anymore on pupal mass compared to chlorpyrifos exposure at a constant temperature. Similarly, the negative chlorpyrifos impact on adult survival of D. magna was less under DTV than at the constant temperature. This could be explained by a faster chlorpyrifos degradation under DTV. This antagonism between pesticide exposure and DTV is likely widespread because organisms experience DTV, many pesticides are applied in pulses, and pesticide degradation is faster at higher temperatures.

Synergistic effect of Ficus-zero valent iron supported on adsorbents and Plantago major for chlorpyrifos phytoremediation from water

Chlorpyrifos and the metabolite 3, 5, 6-trichloro-2-pyridinol (TCP) are widespread contamination of aquatic environments especially freshwater fish. The objectives of this study were to evaluate the contribution of using Ficus zero-valent iron nanoparticles supported on adsorbents (F-Fe0 ad) as green nanotechnology and Plantago major as phytoremediation for removing chlorpyrifos and degradation product TCP polluted water. The shapes of F-Fe0 were circular, with sizes from 2.46 nm to 11.49 nm. Wheat bran (WB) showed the highest extent of removal of chlorpyrifos, while Rice straw ash (RSA) showed the lowest extent of removal. F-Fe0 supported on adsorbents has demonstrated faster removal toward chlorpyrifos compared with tested adsorbents or F-Fe0. Chlorpyrifos was removed more quickly and effectively by P. major L. plus F-Fe0 supported on different adsorbents (nearly 100%) than that by P. major (43.76%) or F-Fe0 (81.69%). The degradation product TCP was more greatly accumulated in water treated with F-Fe0 than that P. major alone or F-Fe0 supported with adsorbents and combined with P. major. Furthermore, TCP significantly accumulated in P. major roots and leaves in the water treated with F-Fe0 supported with adsorbents plus P. major more than that in the P. major roots and leaves alone, this is attributed to the role of F-Fe0 adsorbents for the degradation of chlorpyrifos to TCP, Which strongly accumulated in the P. major roots and leaves. It can be concluded that the contribution of using F-Fe0 supported on adsorbents, especially WB as green nanotechnology and P. major as phytoremediation would be a major role for the complete removal of chlorpyrifos from the water with a significant reduction in the toxic degradation product TCP.

Chlorpyrifos degradation efficiency of Bacillus sp. laccase immobilized on iron magnetic nanoparticles.

The present study explored the immobilization of laccase onto iron magnetic nanoparticles (MNPs) to enhance its enzymatic properties and applications. The immobilization process was optimized using Box-Behnken design (BBD). BBD showed significance towards the quadratic model with experimental data. Maximum laccase activity recovery (99%) of the predicted model was observed at 0.75mg/mL of laccase concentration, 200mg/mL of MNPs, 0.3% cross linking with carbodiimide, and 3h of cross-linking time. The magnetization activity of MNPs (8emu/g) and the immobilized laccase with MNPs (4emu/g) was analyzed using vibrating sample magnetometer (VSM). Maximum activity of immobilized laccase was observed at pH 7.0 and 55°C. The immobilized laccase has greater stability (100h) and significant chlorpyrifos (pesticide) degradation activity. High-performance liquid chromatography (HPLC) results confirmed the degraded metabolic products of chlorpyrifos. In all, the immobilized laccase was superior to free laccase, showing promising structural and application characteristics.

Plasmid-Mediated Biodegradation of Chlorpyrifos and Analysis of Its Metabolic By-Products.

Organophosphate pesticide persistence is an emerging menace to the environment and despite this fact, its use has been enhanced due to its high efficiency. Bioremediation using microorganisms would be the only means by which these hazardous compounds could be wiped out without disturbing the environmental harmony. The current work studied the molecular mechanism of degradation of Chlorpyrifos (CP) by a bacterial consortium C5 comprising of three soil isolates Staphylococcus warneri (CPI 2), Pseudomonas putida (CPI 9) and Stenotrophomonas maltophilia (CPI 15), which unveiled that the property is plasmid borne. All the isolates were found to possess a 4kb plasmid which could be cured only by using sodium azide. The Escherichia coli JM109 cells when transformed individually with the plasmid of the isolates showed CP degradation in mineral salts medium (MSM) that contained CP as the sole carbon source. The degradative enzyme organophosphorus hydrolase (~ 60 KDa) of the isolates was extracted and purified to 31.85, 26 and 37.74 fold, respectively. The possible metabolic by-products of CPdegradation by the consortium C5, were also analysed. The LC-Q-Tof MS analysis revealed the presence of the major metabolite 3, 5, 6 -trichloropyridine (TCP) with the formation of chlorpyrifos oxon as the intermediate. The isolates also showed trichloropyridine degradation (> 80%) individually in MSM-TCP medium proving its efficiency to remediate both CP and TCP.

PHOTOCATALYTIC DEGRADATION OF CHLORPYRIFOS BY USING SYNTHESIZED NANO TITANIUM

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Photocatalytic Degradation of Chlorpyrifos with Mn-WO3/SnS2 Heterostructure

Tungsten trioxide (WO3) is a photocatalyst that has gained interest amongst researchers because of its non-toxicity, narrow band gap and superior charge transport. Due to its fast charge recombination, modification is vital to counteract this limitation. In this paper, we report on the fabrication of Mn-doped WO3/SnS2 nanoparticles, which were synthesised with the aim of minimising the recombination rates of the photogenerated species. The nanomaterials were characterised using spectroscopic techniques (UV-Vis-diffuse reflectance spectroscopy (DRS), Raman, XRD, photoluminescence (PL) and electrochemical impedance spectroscopy (EIS)) together with microscopic techniques (FESEM-EDS and high resolution transmission electron microscopy selected area electron diffraction (HRTEM-SAED)) to confirm the successful formation of Mn-WO3/SnS2 nanoparticles. The Mn-doped WO3/SnS2 composite was a mixture of monoclinic and hexagonal phases, confirmed by XRD and Raman analysis. The Mn-WO3/SnS2 heterojunction showed enhanced optical properties compared to those of the un-doped WO3/SnS2 nanoparticles, which confirms the successful charge separation. The Brunauer–Emmett–Teller (BET) analysis indicated that the nanoparticles were mesoporous as they exhibited a Type IV isotherm. These nanomaterials appeared as a mixture of rectangular rods and sheet-like shapes with an increased surface area (77.14 m2/g) and pore volume (0.0641 cm3/g). The electrochemical measurements indicated a high current density (0.030 mA/cm2) and low charge transfer resistance (157.16 Ω) of the Mn-WO3/SnS2 heterojunction, which infers a high charge separation, also complemented by photoluminescence with low emission peak intensity. The Mott–Schottky (M-S) plot indicated a positive slope characteristic of an n–n heterojunction semiconductor, indicating that electrons are the major charge carriers. Thus, the efficiency of Mn-WO3/SnS2 heterojunction photocatalyst was monitored for the degradation of chlorpyrifos. The effects of pH (3–9), catalyst loading (0.1–2 g) and initial chlorpyrifos concentration (100 ppb–20 ppm) were studied. It was observed that the degradation was purely due to photocatalysis, as no loss of chlorpyrifos was observed within 30 min in the dark. Chlorpyrifos removal using Mn-WO3/SnS2 was performed at the optimum conditions of pH = 7, catalyst loading = 1 g and chlorpyrifos concentration = 1000 ppb in 90 min. The complete degradation of chlorpyrifos and its major degradation by-product 3,5,6-trichloropyridin-2-ol (TCP) was achieved. Kinetic studies deduced a second order reaction at 209 × 10−3 M−1s−1.

Endocrine disruption: molecular interactions of chlorpyrifos and its degradation products with estrogen receptor

Chlorpyrifos is an extensively used organophosphate pesticide showing broad-spectrum effectiveness on various target pests. Long-term sublethal exposure to this pesticide is reported to produce detrimental effects on sex hormone metabolism and nervous system functioning. It is a suspected endocrine-disrupting chemical and causes abnormal developmental patterns, gonadal atrophy, and neurodevelopmental problems. The degradation products formed during environmental degradation of chlorpyrifos are also capable of binding with steroid hormone receptors such as estrogen receptor alpha (ER-α) and can disrupt estrogen signaling in humans. In the present study, chlorpyrifos and four of its degradation products viz. CPYO, DEC, TCP, and TMP were chosen to study their ability to bind with estrogen receptors. The molecular docking and dynamics simulation carried out to understand the molecular interaction of chlorpyrifos and its environmental degradation products with human ER reveal the risk of potential disruption in estrogen signaling in humans by these compounds.

TOXICITY, NATURAL AND INDUCED DEGRADATION OF CHLORPYRIFOS

The increase in demand for agricultural products due to the growing population led to excessive inputs of pesticides in the agriculture field which resulted in contamination of the environmental segments of life i.e. air, water, and soil. Chlorpyrifos is one of the most extensively used broad-spectrum organophosphate insecticides. The usage and broad-spectrum applicability of chlorpyrifos lead to widespread contamination in the environment and serious damage to non-target organisms. Moreover, metabolites of chlorpyrifos i.e. chlorpyrifos-oxon and 3,5,6-trichloro-2-pyridinol are found to be more toxic than its parent compound. This review emphasizes on various toxic effects of chlorpyrifos and its metabolites on living organisms. The efforts put to develop the efficient methods for the degradation of the insecticide in soil and water i.e. photocatalytic, biodegradation, electrochemical and others have been discussed. Analytical techniques used for the study of degraded products and various intermediates formed during degradation under different conditions are summarized. It also includes the general pathway for the degradation of chlorpyrifos. The review will help in the development of tools for degradation and mineralization of organophosphate pesticides by knowing the mechanism of degradation and applicability of the developed process at a large scale.