Degradation Of Organophosphorus Pesticides Research Articles

Photocatalytic degradation of four organophosphorus pesticides in aqueous solution using D-cys/Au NPs modified TiO2 by natural sunlight

The widespread use of organophosphorus pesticides (OPPs) in foods, poses a serious threat to human and environmental health, it is crucial to develop methods that can efficiently degrade residual OPPs. Herein, a chiral TiO2 photocatalyst was developed by modification TiO2 with D-cys/Au NPs (DAT) for the simultaneous degradation of four OPPs (chlorpyrifos, chlorpyrifos-methyl, malathion, and parathion) by natural light. The influence of D-Au NPs concentration on the degradation process was optimized, along with the initial pesticide concentration. Under optimal conditions, the photocatalytic degradation efficiencies of DAT for four OPPs were 96.7 %, 56.9 %, 42.6 %, and 49.2 %, respectively, after 12 h of natural light exposure. 12 degradation products of OPPs were identified, among which three products were identified for the first time. The degradation pathway revealed that the degradation of OPPs by DAT involves the oxidation of the P═S bond and the cleavage of the P-O bond and C-O bond. This study establishes a theoretical foundation for applying chiral TiO2 nanomaterials for the photocatalytic degradation of OPPs in foods.

Effective degradation of organophosphorus pesticide by photo-Fenton and in-situ recovery/utilization of the generated phosphorus: Dual function of iron ions

Efficient recovery and utilization of the generated phosphorus during the process of organophosphorus pesticides degradation is promising but still challenging. In this study, a photo-Fenton-crystallization sequential processes were developed to achieve the degradation of organophosphorus pesticides and simultaneous recovery/utilization of the generated phosphate. In this system, iron ions exhibited dual functionality: activator of the photo-Fenton reaction and crystallizing agent of the generated phosphate and the crystals obtained were proved to be vivianite by X-ray Diffraction and Scanning Electron Microscopy. The results showed that a trichlorfon degradation rate exceeding 90% and a vivianite yield of 85.1% was achieved. Parameters such as pH and the Fe-P ratio play pivotal roles in phosphorus recovery efficiency from wastewater. In addition, the toxicity of the degradation by-products was much less than that of trichlorfon by the Toxicity Estimation Software Tool. Additionally, the recovered vivianite exhibits advantageous catalytic properties to activate peroxymonosulfate for the degradation of different pollutants. This study provides a novel perspective for the treatment and utilization of organophosphorus pesticides.

Distribution of organophosphorus pesticides and its potential connection with probiotics in sediments of a shallow freshwater lake

Despite the serious health threats due to wide use of organophosphorus pesticides (OPPs) have been experimentally claimed to be remediated by probiotic microorganisms in various food and organism models, the interactions between OPPs and probiotics in the natural wetland ecosystem was rarely investigated. This study delves into the spatial and temporal distribution, contamination levels of OPPs in the Baiyangdian region, the diversity of probiotic communities in varying environmental contexts, and the potential connection with OPPs on these probiotics. In typical shallow lake wetland ecosystem—Baiyangdian lake in north China, eight OPPs were identified in the lake sediments, even though their detection rates were generally low. Malathion exhibited the highest average content among these pesticides (9.51 ng/g), followed by fenitrothion (6.70 ng/g). Conversely, chlorpyrifos had the lowest detection rate at only 2.14%. The region near Nanliu Zhuang (F10), significantly influenced by human activities, displayed the highest concentration of total OPPs (136.82 ng/g). A total of 145 probiotic species spanning 78 genera were identified in Baiyangdian sediments. Our analysis underscores the relations of environmental factors such as phosphatase activity, pH, and electrical conductivity (EC) with probiotic community. Notably, several high-abundance probiotics including Pseudomonas chlororaphis, Clostridium sp., Lactobacillus fermentum, and Pseudomonas putida, etc., which were reported to exhibit significant potential for the degradation of OPPs, showed strongly correlations with OPPs in the Baiyangdian lake sediments. The outcomes of this research offer valuable insights into the spatiotemporal dynamics of OPPs in natural large lake wetland and the probability of their in-situ residue bioremediation through the phosphatase pathway mediated by probiotic such as Lactic acid bacteria in soils/sediments contaminated with OPPs.

Highly efficient photocatalytic decomposition of triazophos using novel In2O3/WO3 nanocomposites with oxygen defects and S-Scheme heterojunctions

Confronted with the substantial environmental threat posed by organophosphorus pesticides, the urgency to develop reliable and efficient mitigation strategies is paramount. Photocatalytic technology, which catalyzes the generation of potent oxidizing radicals, emerges as a promising solution. In this study, we have successfully synthesized In2O3/WO3 (IO/WO) nanocomposites, endowed with oxygen defects and S-scheme heterojunctions, exhibiting exceptional photocatalytic degradation activity and mineralization efficiency. Notably, the WO material synthesized in this study is blue in color, unlike the traditional yellow color of WO, indicating a rich presence of oxygen defects. The 60-IO/WO nanocomposite, containing 60 % IO, achieved superior photocatalytic degradation, reducing triazophos pesticide from 100 % to 21.29 % within 60 min, outperforming the individual materials IO (56.97 %) and WO (48.02 %). This nanocomposite also exhibited remarkable corrosion resistance across multiple cycles, showcasing significantly enhanced stability compared to the individual IO and WO materials. Electron paramagnetic resonance (EPR) spectroscopy confirmed the presence of oxygen defects in the blue WO, while both EPR and theoretical calculations substantiated the formation of the S-scheme heterojunction in the 60-IO/WO nanocomposite. The new nanocomposite's excellent photocatalytic degradation activity is influenced by various factors such as differing surface areas, composite amounts, photocurrent responses, and resistances, all of which impact the degradation performance of triazophos. Compared to traditional photocatalytic materials, the IO/WO nanocomposite demonstrates a significant edge in photocatalytic efficiency and chemical stability, offering considerable potential for environmental remediation, especially in the degradation of organophosphorus pesticides.

Schiff base stabilized palladium nanoparticles: Synthesis, characterization, catalytic degradation of organophosphorus pesticides, and fluorometric detection of Cr6+ in aqueous media

As a stabilizing and reducing agent, the Schiff base (2-(4-(trifluoromethoxy)phenylimino)methyl)-6-methoxyphenol) was used to synthesize palladium nanoparticles (PdNPs) with an average particle size (12 ± 2 nm) and a spherical shape. The numerous methods, including UV–vis absorption spectroscopy, photoluminescence (PL), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) were used to characterize the PdNPs. The Schiff base capped PdNPs have FCC structure with 10 ± 3 nm particle size was estimated from XRD and TEM analysis. The catalytic, sensing, antibacterial, and antioxidant abilities of the created PdNPs were assessed. The findings demonstrated that PdNPs followed pseudo-first-order kinetics and had superior catalytic activity in the degradation of pesticides (monocrotophos (MCP), 99.9%) and chlorpyrifos (CLP), 98.2%) using NaBH4 as a reducing agent in 1 h reaction. PdNPs were still stable and exhibited a high catalytic activity with only a marginal decrease from maximum degradation (99.9% of MCP and 98.2% of CLP) using the fresh catalyst to 92.6% (MCP) and 90.1% (CLP) of the used catalyst (recycled after 5 times) was observed. Additionally, at a concentration range of 10–100 µM, the PdNPs demonstrated selective fluorescence sensing for Cr6+ metal ions in aqueous media. The significant antimicrobial action was also shown by the PdNPs against pathogens such S. aureus, B. subtilis, E. coli, P. aeruginosa, A. niger, and C. albicans. The PdNPs also demonstrated antioxidant activity in the DPPH free radical scavenging assay, with a 78.06% scavenging efficiency. This technique is efficient and cost-effective, and it may be used as an effective biological agent, sensor, and catalyst for a variety of environmental applications.

Efficient degradation of diazinon and adsorption of released phosphate through activating peroxymonosulfate by Zr-doped ZIF-8 encapsulated CoFe2O4 composite

The widespread application of organophosphorus pesticides (OPPs) has caused pollution in many aqueous environments. Sulfate radical-based advanced oxidation processes (SR-AOPs) are effective for degrading refractory organic pollutants. However, only a limited number of studies have been conducted in the field of OPP removal using SR-AOPs. The residue of phosphate generated by the degradation of OPPs is also a problem worth considering. Herein, Zr-doped ZIF-8 encapsulated CoFe2O4 magnetic composite was successfully synthesized (CoFe2O4 @Zr/ZIF-8) to activate peroxymonosulfate (PMS) for the degradation of diazinon (DZ) and adsorb released phosphate. CoFe2O4 @Zr/ZIF-8 demonstrated excellent catalytic performance, with 100% DZ degradation (20 mg/L); most of the phosphates produced during degradation were also adsorbed. The wrapping of ZIF-8 effectively inhibited the leaching of cobalt ions. Different factors affecting DZ removal were investigated. Further study demonstrated that sulfate radicals (SO4•−), hydroxyl radicals (•OH), and singlet oxygen (1O2) are responsible for the degradation of DZ, with SO4•− and 1O2 playing pivotal roles. This study presents a potential strategy for both OPP degradation and phosphate adsorption and provides a new concept for utilizing multifunctional materials in environmental remediation.

Multifunctional Fe-doped carbon dots and metal-organic frameworks nanoreactor for cascade degradation and detection of organophosphorus pesticides

Organophosphorus pesticides (OPs) are the most widely used pesticides, hence it is crucial to effectively prevent and control OPs residues for agricultural product safety and ecological development. In this work, the nanoreactor consisting of Fe-doped carbon dots (Fe-CDs) and metal-organic framework (MOF-808) were developed for selective degradation as well as sensitive detection of paraoxon and parathion. MOF-808 was selected as the host and used to rapidly degrade paraoxon due to its excellent organophosphorus hydrolase activity. Fe-CDs were severed as guest molecules not only for photocatalytic degradation of parathion, but also for sensing to detect OPs. Through host–guest interaction, Fe-CDs/MOF-808 and Fe-CDs@MOF-808 were synthesized for cascade degradation and detection of paraoxon and parathion, respectively. Paraoxon and parathion were detoxified by catalytic hydrolysis and photocatalytic degradation by Fe-CDs/MOF-808 and Fe-CDs@MOF-808, respectively. Meanwhile, the fluorescence of the nanocomposites was quenched by the internal filtering effect with 4-nitrophenol (4-NP), the degradation product of OPs. Fe-CDs/MOF-808 has a wide linear range for detection of paraoxon from 0.001 to 360 μM, with a limit of detection (LOD) as low as 0.3 nM. Fe-CDs@MOF-808 exhibited a linear range of 0.01–100 μM for parathion, with an LOD about 3.3 nM. The reliability of the nanoreactor was verified by testing the recovery rate of OPs spiked water sample. Meanwhile, the nanoreactors were applied for degradation and detection of OPs in pakchoi. The OPs in pakchoi can be fully degraded within 5 min, and the analytical results are consistent with those by standard method (HPLC). Therefore, the proposed nanoreactor provides a feasible alternative for effective degradation and timely detection of OPs during agricultural production.

Degradation kinetics and transformation pathway of methyl parathion by δ-MnO2/oxalic acid reaction system

Methyl parathion (MP) is a typical organophosphorus pesticide that is widely used worldwide, and hydrolysis, oxidation and reduction are the main abiotic degradation processes. Manganese dioxide (MnO2) and organic acid can participate in various geochemical processes of pollutants, a reaction system was constructed to degrade MP using δ-MnO2 and oxalic acid. The δ-MnO2/oxalic acid reaction system could efficiently degrade MP, and the removal rate of MP (20 μM) reached 67.83% within 30 h under the optimized conditions (pH 5, [δ-MnO2] = 2 mM, [oxalic acid] = 100 mM). MP was hydrolyzed by substitution reactions of SN@P and SN@C, and reduced by conversion of the nitro groups (-NO2) in MP and its hydrolysates to amino groups (-NH2). The primary active substance produced in the reaction system was the complexes dominated by Mn(III)-oxalic acid. This study provides a scientific basis for the degradation of organophosphorus pesticides using MnO2 and an organic acid. The results have important theoretical significance and application value for pollution control and remediation of organophosphorus pesticides.

Gold nanoclusters-manganese dioxide composite-based fluorescence immunoassay for sensitive monitoring of fenitrothion degradation in Chinese cabbage

Understanding the residues and degradation of organophosphorus pesticides (OPs) in crops has attracted increasing attention. Herein, we designed a sensitive fluorescence immunoassay (FIA) by employing nanobody-linked alkaline phosphatase (Nb-ALP) and gold nanoclusters anchored manganese dioxide (AuNCs-MnO2) composite. In immunoassay protocol, Nb-ALP is used to competitively recognize the coating antigen and pesticide. After competitive immunoreaction, alkaline phosphatase catalyzes l-ascorbic acid-2-phosphate to produce ascorbic acid that can trigger the decomposition of the AuNCs-MnO2 composite, regulating the fluorescence response. As a proof-of-concept, fenitrothion (FNT) is chosen as the target analyte. As a result, the developed FIA exhibits high detection sensitivity (IC10 = 5.78 pg/mL), which is about 56-times higher than that of the conventional enzyme-linked immunosorbent assay. The developed FIA has been successfully applied for precisely monitoring the degradation of FNT in Chinese cabbage with excellent anti-interference ability and reproducibility, paving the way for the determination of pesticide residues in real food samples.

“Unity and Struggle of Opposites” as a Basis for the Functioning of Synthetic Bacterial Immobilized Consortium That Continuously Degrades Organophosphorus Pesticides

This work was aimed at the development of an immobilized artificial consortium (IMAC) based on microorganisms belonging to the Gram-positive and Gram-negative bacterial cells capable of jointly carrying out the rapid and effective degradation of different organophosphorus pesticides (OPPs): paraoxon, parathion, methyl parathion, diazinon, chlorpyrifos, malathion, dimethoate, and demeton-S-methyl. A cryogel of poly(vinyl alcohol) was applied as a carrier for the IMAC. After a selection was made between several candidates of the genera Rhodococcus and Pseudomonas, the required combination of two cultures (P. esterophilus and R. ruber) was found. A further change in the ratio between the biomass of the cells inside the granules of IMAC, increasing the packing density of cells inside the same granules and decreasing the size of the granules with IMAC, gave a 225% improvement in the degradation activity of the cell combination. The increase in the velocity and the OPP degradation degree was 4.5 and 16 times greater than the individual P. esterophilus and R. ruber cells, respectively. Multiple uses of the obtained IMAC were demonstrated. The increase in IMAC lactonase activity confirmed the role of the cell quorum in the action efficiency of the synthetic biosystem. The co-inclusion of natural strains in a carrier during immobilization strengthened the IMAC activities without the genetic enhancement of the cells.

Water-Regulated Mechanisms for Degradation of Pesticides Paraoxon and Parathion by Phosphotriesterase: Insight from QM/MM and MD Simulations.

The enzymatic degradation of pesticides paraoxon (PON) and parathion (PIN) by phosphotriesterase (PTE) has been investigated by QM/MM calculations and MD simulations. In the PTE-PON complex, Znα and Znβ in the active site are five- and six-coordinated, respectively, while both zinc ions are six coordinated with the Znα -bound water molecule (WT1) for the PTE-PIN system. The hydrolytic reactions for PON and PIN are respectively driven by the nucleophilic attack of the bridging-OH- and the Znα -bound water molecule on the phosphorus center of substrate, and the two-step hydrolytic process is predicted to be the rate-limiting step with the energy spans of 13.8 and 14.4 kcal/mol for PON and PIN, respectively. The computational studies reveal that the presence of the Znα -bound water molecule depends on the structural feature of substrates characterized by P=O and P=S, which determines the hydrolytic mechanism and efficiency for the degradation of organophosphorus pesticides by PTE.

Zwitterionic polymer-mediated immobilization of organophosphorus hydrolase enhances hydrolysis of methyl parathion by substrate enrichment

Organophosphorus pesticides (OPPs) degradation is highly demanded due to the toxic nature of the pesticides that have caused serious environmental concerns. Biocatalytic hydrolysis using organophosphorus hydrolase (OPH) is an important way to OPPs degradation, but the poor stability of OPH severely hindered its extensive applications in environmental bioremediation. It is well known that immobilization is an efficient way of enzyme stabilization, so this work has proposed to immobilize OPH onto mesoporous silica nanoparticles coated with a zwitterionic polymer containing short hydrophobic chains. It is found that the zwitterionic polymer coating significantly modified the microenvironment, leading to the stabilization of the immobilized enzyme while keeping its activity toward methyl parathion hydrolysis. More importantly, the coating resulted in the substrate enrichment onto the carrier (capacity, 49.7 mmol·g−1; dissociation constant, 11.7 μM), so the immobilized OPH presented a much lower Michaelis constant (0.09 mM) than its free counterpart (0.34 mM) as revealed by kinetic studies. Consequently, the catalytic efficiency (kcat/Km) of the immobilized OPH was 2.41 times higher than free OPH. Thus, this work demonstrated the promise of the zwitterionic polymer-mediated immobilization strategy for OPH in enhancing the enzyme performance for the hydrolysis of OPPs that are of low concentration in open environments.

Ratiometric fluorescent hydrogel for point-of-care monitoring of organophosphorus pesticide degradation

The residues of organophosphorus pesticides have caused the potential risk in environment and human health, arousing worldwidely great concern. Herein, we fabricated a robust gold nanoclusters/MnO2 composites-based hydrogel portable kit for accurate monitoring of paraoxon residues and degradation in Chinese cabbages. With the immobilization of gold nanoclusters/MnO2 composites into a hydrogel, a ratiometric fluorescent signal is generated by catalyzing the oxidation of o-phenylenediamine, which possesses a built-in correction with low background interference. Coupling with acetylcholinesterase catalytic reactions and pesticide inhibition effect, the portable kit can sensitively detect paraoxon residues with a detection limit of 5.0 ng mL−1. For on-site quantification, the fluorescent color variations of portable kit are converted into digital information that exhibits applicative linear range toward pesticide. Notably, the hydrogel portable kit was successfully applied for precisely monitoring the residue and degradation of paraoxon in Chinese cabbage, providing a potential pathway toward practical point-of-care testing in food safety monitoring.

Correlation of bacterial community with phosphorus fraction drives discovery of Actinobacteria involved soil phosphorus transformation during the trichlorfon degradation

Trichlorfon (TCF) is a broad-spectrum phosphorus (P)-containing pesticide, yet its effects on soil P fraction transformation and bacterial communities during the TCF degradation in soils is unknown. In this study, we investigated soil TCF degradation behavior at different contents of 50, 100 and 200 mg/kg, and analyzed residual TCF contents and metabolites by gas chromatography mass spectrometry after 216-h incubation. Our results suggested that TCF was gradually degraded in soils and was be initially hydrolyzed to dichlorvos via P–C bond cleavage and then other P-containing metabolites. By analyzing different P fractions and soil microbial community composition, we found significant increases of soil available phosphorus contents from 2.76 mg/kg (control) to 3.23 mg/kg (TCF-50), 5.12 mg/kg (TCF-100) and 5.72 mg/kg (TCF-200), respectively. Inorganic CaCl2–P was easily and instantly transformed to primary mineral inorganic P (Pi) forms of HCl–P and citrate-P, while the proportion of enzyme-P (a labile organic P) fluctuated throughout TCF degradation process. Soil available P contents and Pi fractions were significantly correlated with the relative abundance of Actinobacteria. These results highlighted that Actinobacteria is the dominant soil species utilizing TCF as P sources to increase its community richness, and subsequently affect the transformation of P fractions to regulate soil P cycle. Our study gives new understanding on the microorganisms can involve soil P transformation during organophosphorus pesticides degradation in soils, highlighting the importance of bacteria in P transformation and pesticides soil decontamination.

Visible light assisted enzyme-photocatalytic cascade degradation of organophosphorus pesticides

The worldwide application of organophosphorus pesticides (OPs) has promoted agricultural development, but their gradual accumulation in soil and water can seriously affect the central nervous system of humans and other mammals. Organophosphorus hydrolase (OPH) is an effective enzyme that can catalyze the degradation of the residual OPs. However, the degradation products such as p-nitrophenol (p-NP) is still toxic. Thus, it is of great significance to develop a multi-functional support that can be simultaneously used for the immobilization of OPH and the further degradation of p-NP. Herein, a visible light assisted enzyme-photocatalytic integrated catalyst was constructed by immobilizing OPH on hollow structured Au-TiO2 (named OPH@H-Au-TiO2) for the degradation of OPs. The obtained OPH@H-Au-TiO2 can degrade methyl parathion to p-NP by OPH and then degrade p-NP to hydroquinone with low toxicity by using H-Au-TiO2 under visible light. OPH molecules were immobilized on H-Au-TiO2 through adsorption method to prepare OPH@H-Au-TiO2. After 2.5 h of reaction, methyl parathion is completely degraded, and about 82.64% of the generated p-NP is further degraded into hydroquinone. After reused for 4 times, the OPH@H-Au-TiO2 retains more than 80% of the initial degradation activity. This research presents a new insight in designing and constructing multi-functional biocatalyst, which greatly expands the application scenarios and industrial value of enzyme catalysis.

Sequential photocatalytic degradation of organophosphorus pesticides and recovery of orthophosphate by biochar/α-Fe2O3/MgO composite: A new enhanced strategy for reducing the impacts of organophosphorus from wastewater

Photocatalysis is regarded as one of the most promising techniques for degrading organophosphorus pesticides (OPs) from wastewater given its low-cost and environmental benignity. Yet, photocatalytic degradation of OPs is an incomplete process, since PO43− is produced after photocatalysis. Here, biochar-supported α-Fe2O3/MgO composite (BC-α-Fe2O3/MgO) is developed for sequential photocatalytic degradation of OPs and recovery of the produced PO43−. The degradation efficiency of N-phosphonomethyl iminodiacetic acid (NPA) by BC-α-Fe2O3/MgO based photocatalysis reaches 90.1% within 80 min, and the recovery ratio of the produced PO43− by BC-α-Fe2O3/MgO is as high as 82.3%. Besides, the as-prepared BC-α-Fe2O3/MgO used in this integrated photocatalysis and adsorption process maintain a high stability towards NPA degradation and PO43− recovery during five cycling experiments. The mechanistic study reveals that holes, •OH, and •O2– radicals generated in the photocatalytic process are responsible for NPA degradation. UV light can activate persistent free radicals on BC-α-Fe2O3/MgO surface, which provide O2 withelectrons for the generation of •O2– and subsequent yield of •OH. Moreover, the presence of α-Fe2O3 and MgO on the surface of biochar leads to the excellent P adsorption performance of BC-α-Fe2O3/MgO. This study opens new possibilities for the recovery of P resource from organophosphorus polluted wastewater.

Design of metalloenzyme mimics based on self-assembled peptides for organophosphorus pesticides detection

Organophosphorus pesticides (OPs) detection has attracted considerable attention because of the extensive application of OPs. In this research, non-toxic and high-performance metalloenzyme mimics of Zn2+-bonding peptides were developed by obtaining inspiration from phosphotriesterase (PTE) and nanofiber formation. Furthermore, based on the electrochemical activity of p-nitrophenol (PNP), the electrochemical sensor of metalloenzyme mimics was developed. By examining the effect of the active sites of peptides and fibril formation on the degradation of OPs, the optimal metalloenzyme mimic was selected. Furthermore, optimal metalloenzyme mimics were combined with NiCo2O4 to develop an electrochemical sensor of OPs. By monitoring square wave voltammetry (SWV) signals of PNP degraded from OPs, the amounts of OPs in actual samples could be determined in 15 min. We discovered that both the active sites of α metal and β metal were required for metalloenzyme mimics; Zn2+ promoted peptide fibrosis and especially acted as a cofactor for degrading OPs. Compared to traditional methods, the electrochemical sensor of metalloenzyme mimics was sensitive, reliable, and non-toxic; furthermore, the detection limit of methyl paraoxon was as low as 0.08 µM. The metalloenzyme mimics will be a promising material for detecting OPs in the food industry and environment fields.

Tailored design of three-dimensional rGOA-nZVI catalyst as an activator of persulfate for degradation of organophosphorus pesticides

In this study, three-dimensional reduced graphene oxide aerogel (rGOA)-supported nanozero-valent iron (rGOA-nZVI) was successfully synthesized via tailored design and applied to activate persulfate (PS) to degrade three organophosphorus pesticides (OPPs; phorate, terbufos and parathion) in water and a historically contaminated soil. The results showed that loading nZVI nanoparticles on rGOA could prevent the aggregation of nZVI. rGOA-nZVI presented a better catalytic performance for PS activation to degrade the three OPPs than bare nZVI and rGOA, with degradation efficiencies of greater than 99.5% within 5 min. pH had negligible effects on the PS activated by rGOA-nZVI (rGOA-nZVI/PS). EPR measurements and radical quenching experiments showed that ·SO4- and ·OH were the main radicals responsible for OPP removal in the rGOA-nZVI/PS system. Furthermore, nine intermediates were identified, and the oxidation and scission of C-S-C, P-S/O and PS were the dominant degradation pathways of the three OPPs in aqueous solutions treated with rGOA-nZVI/PS. Additionally, rGOA-nZVI/PS achieved degradation efficiencies of 95.1% for phorate, 79.9% for terbufos and 89.1% for parathion in the contaminated soil, and the detected intermediates could be further degraded except triethylphosphate. Overall, this study provides practical knowledge for OPP removal by rGOA-nZVI/PS in wastewater and actual contaminated soil.

Application of Hi-throat/Hi-volume SPE technique in assessing organophosphorus pesticides and their degradation products in surface water from Tai Lake, east China

Organophosphorus pesticides (OPPs) are among the most commonly used pesticides worldwide. However, these compounds pose a serious threat to aquatic environments. Here, thirty-seven pesticides and eight degradation products were determined in surface water samples from Tai Lake, East China, using a high-volume solid phase extraction technique (Hi-throat/Hi-volume SPE). Surface water was pumped in-situ through a portable sampler, and OPPs in the water retained on the Hi-volume SPE adsorption column, finally extracted for analysis. This technique efficiently reduced the detection limits to below 0.3 ng/L. In total, 40 out of 45 OPP congeners were detected, which far exceeded the amount of OPPs in previous studies. The total concentration of OPPs ranged between 101.4 and 1530 ng/L (median: 378.9 ng/L). Parathion exhibited the highest concentration (median: 112.0 ng/L), followed by paraoxon-methyl (median: 90.3 ng/L), as well as carbophenothion, fenthion, and mevinphos. Agricultural areas were more polluted than residential and industrial regions. However, degradation products persisted in residential and industrial waters. The ecological risks of OPPs in these areas were estimated based on the risk quotient index (RQ). Parathion, fenthion, carbophenothion, and tolclofos-methyl occurred at high-risk levels, and the levels of degradation products were also non-trivial. Our findings thus indicated that OPP degradation products pose a potential threat to natural environments and should therefore be closely monitored.

Color-coded detection of malathion based on enzyme inhibition with dark-field optical microscopy

Malathion is widely applied in agriculture as one of organophosphorus pesticides (OPs) and easily causes a number of health and environmental problems. Traditional methods for analyzing malathion residues have failed to meet the current requirements of detection. To address this challenge, we designed a colorimetric-based single particle detection (SPD) method to quantify malathion using MnO2-coated gold nanoparticles (GNP@MnO2 NPs) as the probe. In the existence of alkaline phosphatase (ALP), p-aminophenyl phosphate (p-APP) can be hydrolyzed to p-aminophenol (p-AP), which employs as a reductant to induce MnO2 to Mn2+ and make the gold core exposure. With the dark field optical microscopy (DFM), the color change of the probe can be readily observed at the single particle level. However, malathion is able to inhibit the activity of ALP and makes the color of the probe remain. Thus, the content of malathion can be accurately quantified by monitoring the changes in color and scattering intensity of the probe. The linear range of this assay is 0.001–0.1 ng/mL and the limit of detection (LOD) is as low as 0.82 pg/mL. In addition, degradation of malathion can be achieved due to the interaction between malathion and ALP. Therefore, this strategy offers new insights on the design of an ultrasensitive assay for OPs detection and degradation in the future.