Theoretical study of the atrazine pesticide interaction with pyrophyllite and Ca2+-montmorillonite clay surfaces

MAPK/NF-κB signaling mediates atrazine-induced cardiorenal syndrome and antagonism of lycopene

Atrazine (ATZ) is the most prevalent herbicide that has been widely used in agriculture to control broadleaf weeds and improve crop yield and quality. The heavy use of ATZ has caused serious environmental pollution and toxicity to human health. Lycopene (LYC), is a carotenoid that exhibits numerous health benefits, such as prevention of cardiovascular diseases and nephropathy. However, it remains unclear that whether ATZ causes cardiorenal injury or even cardiorenal syndrome (CRS) and the beneficial role of LYC on it. To test this hypothesis, mice were treated with LYC and/or ATZ for 21 days by oral gavage. This study demonstrated that ATZ exposure caused cardiorenal morphological alterations, and several inflammatory cell infiltrations mediated by activating NF-κB signaling pathways. Interestingly, dysregulation of MAPK signaling pathways and MAPK phosphorylation caused by ATZ have been implicated in cardiorenal diseases. ATZ exposure up-regulated cardiac and renal injury associated biomarkers levels that suggested the occurrence of CRS. However, these all changes were reverted, and the phenomenon of CAR was disappeared by LYC co-treatment. Based on our findings, we postulated a novel mechanism to elucidate pesticide-induced CRS and indicated that LYC can be a preventive and therapeutic agent for treating CRS by targeting MAPK/NF-κB signaling pathways.

Atrazine Desorption Mechanism from an Hydrated Calcium Montmorillonite-A DFT Molecular Dynamics Study

Atrazine is one of the most widely used herbicide molecules in the triazine family. Despite its interdiction in the European Union in 2004, atrazine and its main degradation products remain among the most frequently found molecules in freshwater reservoirs in many European Union countries. Our study aims in obtaining insight into the desorption process of atrazine from the main soil absorbent material: clay. Constrained Molecular Dynamics simulations within the Density Functional Theory framework allow us to obtain a free energy desorption profile of atrazine from a Ca2+-montmorillonite surface. The results are interpreted in terms of atrazine inclination to the clay surface and moreover, in terms of hydration states of the cations present in the clay interlayer as well as the hydration state of the atrazine. The desorption mechanism is driven by atrazine alkyl groups and their sizes because of dispersion stabilizing effects. The highest barrier corresponds to the loss of the isopropyl interaction with the surface.

Selective Adsorption of Organic Micro-Pollutants by Smectite Clays Revealed from Atomistic Simulations

In this study, atomistic simulations were carried out to study the difference in the adsorption process between two similar molecules, diazepam and oxazepam, on Na+-montmorillonite. Kinetic and XRD measurements showed a contrasting adsorption mechanism of these two molecules, differing only by the presence/absence of methyl and hydroxyl groups, with a larger adsorption amount and intercalation for the oxazepam. The structural characterization of these molecules was investigated through DFT calculations and showed the vicinity of hydroxyl and carbonyl groups for only the chair conformation of oxazepam compared to the boat conformation. Classical molecular dynamics simulations of diazepam and the two forms of oxazepam on the external surface of Na+-montmorillonite highlighted the better coordination of the oxazepam-chair conformation, compared to its boat counterpart and diazepam. This has been confirmed through DFT calculations, from which a coordination energy that is greater by 10 kcal·mol-1 is observed. This strongly suggests that the experimentally observed intercalation of oxazepam occurs only in the chair form because of the strong coordination with the Na+ cation present in the Na-Mt interlayer. Classical MD simulations of the intercalated oxazepam chair molecule in the Na-Mt interlayer allowed the evaluation of the interlayer spacing d001, which was in very good agreement with the experimental XRD measurement.

Global qualitative and quantitative distribution of micropollutants in the deep sea

Micropollutants (MPs) include a wide range of biological disruptors that can be toxic to wildlife and humans at very low concentrations (<1 μg/L). These mainly anthropogenic pollutants have been widely detected in different areas of the planet, including the deep sea, and have impacts on marine life. Because of this potential toxicity, the global distribution, quantity, incidence, and potential impacts of deep-sea MPs were investigated in a systematic review of the literature. The results showed that MPs have reached different zones of the ocean and are more frequently reported in the Northern Hemisphere, where higher concentrations are found. MPs are also concentrated in depths up to 3000 m, where they are also more frequently studied, but also extend deeper than 10,000 m. Potentially toxic metals (PTMs), polychlorinated biphenyls (PCBs), dichlorodiphenyltrichloroethane (DDTs), organotins, and polycyclic aromatic hydrocarbons (PAHs) were identified as the most prevalent and widely distributed MPs at ≥200 m depth. PTMs are widely distributed in the deep sea in high concentrations; aluminum is the most prevalent up to 3000 m depth, followed by zinc and copper. PCBs, organotins, hexachlorocyclohexanes (HCHs), PAHs, and phenols were detected accumulated in both organisms and environmental samples above legislated thresholds or known toxicity levels. Our assessment indicated that the deep sea can be considered a sink for MPs.

Toxic effects of atrazine on immune function in BALB/c mice

This study was aimed to evaluate the toxic effects of different concentrations (23, 90, 360 mg/kg BW) of atrazine (ATZ) on immune function in BALB/c mice. Some parameters of general immunotoxicity, humoral immunity, cellular immunity, and non-specific immunity were tested. The studies showed that the high-dose ATZ induced a significant reduction in the final body weight of mice, the absolute and relative weights of spleen, the counts of white blood cell (WBC), lymphocyte (LYM), monocyte (MON), and the number of splenocyte. An increase in the level of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), and cholesterol (CHO) in the high-dose ATZ group was observed. Pathological examination showed that the medium- and high-doses of ATZ caused atrophy and destruction of thymus, spleen, and hepatorenal toxicity. The serum interleukin-5(IL-5) level of mice and the number of plaque-forming cell (PFC) in spleen cells in the high-dose ATZ group decreased significantly while there was a significant increase of the serum immunoglobulin G (IgG) in the high-dose ATZ group when compared to the negative control group. In the high-dose ATZ group, the proliferation ability of T and B lymphocytes as well as the delayed-type hypersensitivity (DTH) response were significantly decreased. The low-dose ATZ (23 mg/kg BW) caused a significant decrease in the number of WBC and neutrophil (NEUT), as well as the proportion of polychromatic and normoblast. In summary, we thought the low-dose ATZ has a slight effect on the immune system; it can be preliminarily concluded that the lowest observed adverse effect level (LOAEL) of atrazine is 23 mg/kg BW in mice. Atrazine can cause immunotoxicity mainly through cellular and humoral immunity pathways.

Stability of Atrazine–Smectite Intercalates: Density Functional Theory and Experimental Study

Atrazine (A) is one of the most applied herbicides and has a negative impact on the environment and health. Density functional theory (DFT) and experimental methods were used in the study of the immobilization of atrazine in two smectites, montmorillonite (Mt) and beidellite (Bd), as well as in their organically modified structures. Four systems were examined: A-Mt and A-Bd, as well as the structures modified by tetramethylphosphonium cation (TMP), A-TMP-Mt and A-TMP-Bd. The calculations revealed a flat arrangement of the atrazine in the interlayer space of both smectites with higher stability of beidellite structures. The presence of the TMP cation increased the fixation of atrazine in both organically modified smectites. The calculated vibrational spectra allowed a detailed analysis of the overlapping bands observed in the experimental FTIR spectra and their correct assignment. Further, selected FTIR bands unambiguously assigned to atrazine and both smectites served for the estimation of the adsorbed amount of atrazine. It was shown that the adsorption capacity of both TMP-modified smectites did not increase in comparison to the adsorption capacity of unmodified smectite samples.

DFT Simulation of the Water Molecule Interaction with the (00l) Surface of Montmorillonite

Montmorillonite is one of the principal mineralogical phases in clay minerals, where its interaction with water and other molecules represents one of the most important aspects and properties for basic science and specific applications. In fact, montmorillonite has many uses in various scientific and technological fields, ranging from environmental remediation to ceramics, food science, and construction/building materials. Several efforts have characterized its structure and physico-chemical properties, especially at the Tetrahedral-Octahedral-Tetrahedral TOT surface. For this purpose, in this work, the authors investigated the structural and electrostatic potential features of the (00l) surface of montmorillonite and the water adsorption process by first principle methods (density functional theory, DFT), considering both static and molecular dynamics approaches. The provided data further extend the knowledge of the modulation of the water molecule adsorption with this important clay mineral.

Effects of electrolyzed water treatment on pesticide removal and texture quality in fresh-cut cabbage, broccoli, and color pepper

The effects of alkaline and acidic electrolyzed water (AlEW, AcEW) treatment on the removal of pesticides (phorate, chlorpyrifos, lambda-cyhalothrin, cyfluthrin, procymidone, and chlorothalonil) and texture quality of fresh-cut cabbage, broccoli, and color pepper were investigated. AlEW efficiently removed pesticides from color pepper, whereas AcEW was the optimal treatment for pesticide removal from cabbage and broccoli. AcEW resulted in greater losses of pyrethroid and organophosphates than fungicides, while AlEW was superior for removing fungicides. The best pesticide removal from cabbage (72.28%-91.04%) was achieved by continuous oscillation treatment, while intermittent oscillation for 20 min achieved optimal results for broccoli and color pepper (72.28%-90.11% and 72.24%-88.12%, respectively). No significant deterioration in texture was detected in samples treated with electrolyzed water for 5-25 min. The results suggest that electrolyzed water treatment is effective for removing organophosphate, pyrethroid, and fungicide residues from fresh-cut vegetables while not negatively affecting their texture quality.

Adsorption of two β-blocker pollutants on modified montmorillonite with environment-friendly cationic surfactant containing amide group: Batch adsorption experiments and Multiwfn wave function analysis

The novel environment-friendly hexadecanoamide propyltrimethy lammonium chloride (NQAS16-3) surfactant with different amounts (0.2, 0.4, 0.6, 0.8, 1.0, 1.2 CEC) was firstly used to modify montmorillonite, and the obtained organomontmorillonite (N-Mt) with the amount of surfactant equal to 1.0 CEC was utilized to adsorb two β-blocker pollutants- Atenolol (ATE) and acebutolol (ACE). The experimental results indicated that the equilibrium adsorption capacity of N-Mt(the organo-montmorillonite that the amount of modifier was 1.0 CEC) for ATE and ACE was 93.47 mg/g and 84.55 mg/g, respectively, which was more than twice that of raw montmorillonite for two pollutants, the adsorption was better fitted with the pseudo-second-order model and Langmuir isotherms model, and the adsorption was the spontaneous and exothermic process. Moreover, combining with the Zeta potential values of N-Mt, and with the help of Multiwfn wave function program based on density functional theory (DFT), the electrostatic interaction and the hydrophobic partitioning between N-Mt and two pollutant molecules were verified, p-π/π interaction between NQAS16-3 and ATE (or ACE) may be contributed to the increasing adsorption capacity of N-Mt for two β-blocker pollutants. The work provided novel organomontmorillonite for the removal of non-degradable β-blocker pollutants and the insight of the adsorption mechanism from the atomic level.

Interaction of Metamitron and Fenhexamid with Ca2+ -Montmorillonite Clay Surfaces: A Density Functional Theory Molecular Dynamics Study

Metamitron (Meta), an herbicide, and fenhexamid (Fen), a fungicide, are authorized by the European Union to be used in agriculture. This article reports theoretical calculations about Meta and Fen in interaction with a clay surface: a Ca-montmorillonite (Mont). Conformational searches have been performed thanks to Car-Parrinello molecular dynamics simulations from which geometries have been extracted. Interaction and adsorption energies have been calculated for isomers of Meta or Fen in interaction with Mont to understand the relative stability of various kinds of complexation. Substantial adsorption energies are comparable for Meta and Fen: around -40 kcal/mol. For Fen-Mont, the CO monodentate family is surprisingly the lowest in energy. Moreover, the 10 lowest-energy isomers involve complexation on Fen carbonyl oxygens. The Meta-Mont lowest-energy family, N-N, does not involve π delocalization breaking within Meta. At the same time, the stronger the interaction energy is, the larger the structural modifications within Mont are, particularly concerning the interacting cation distance to the surface. The non-negligible charge transfer and the magnitude of the adsorption energy speak in favor of the chemisorption of the pesticide on the surface. © 2019 Wiley Periodicals, Inc.

Multivariate analysis reveals significant diuron-related changes in the soil composition of different Brazilian regions

Sorption and desorption determine the amount of an herbicide in soil solution. Therefore, knowledge of the sorption and desorption coefficients in different soils is an essential factor to estimate the potential for environmental contamination by herbicides. We evaluated the feasibility of multivariate and linear discriminant analyses to predict the sorption and desorption capacity of a soil for diuron, one of the most used herbicides on sugarcane plantations. The adsorptive capacity in twenty-seven Brazilian soil samples was estimated using the sorption constant (Kfs) and desorption constant (Kfd) obtained by the Freundlich isotherms. The regression model was created from the sorbed and nonsorbed concentrations of diuron in soils. Ultra-performance liquid chromatography was applied to quantify the diuron concentrations. The multivariate analysis separated the soils into four groups considering the similarity of the following attributes: pH, organic matter, clay, and base saturation. The groups showed a similar pattern of sorption and desorption for diuron: Lom-Lclay: low sorption (5.9 ± 1.2) and high desorption (10.9 ± 0.6); Lclay: low sorption (7.5 ± 1.1) and high desorption (11.4 ± 1.3); Hom-Hclay: high sorption (11.2 ± 1.2) and low desorption (13.8 ± 1.2); HpH-Hclay: high sorption (10.1 ± 1.1) and medium desorption (11.5 ± 1.4). Linear discriminant analysis of these soil attributes was used to classify other soils described in the literature with adsorption capacity. This analysis was able to identify soils with high and low sorption using the pH, organic matter, clay, and base saturation, demonstrating the enormous potential of the technique to group soils with different contamination risks for subterranean waters. Sugarcane crops in northeastern Brazil showed a higher pollution risk through the leaching of diuron. Multivariate analysis revealed significant diuron-related changes in the soil composition of different Brazilian regions; therefore, this statistical analysis can be used to improve understanding of herbicide behavior in soils.

Structural effect of imidazolium-type ionic liquid adsorption to montmorillonite

The adsorption of 1-alkyl-3-methylimidazolium-type ionic liquids (ITILs) coupled with different counteranions (Tf₂N^-, PF₆^-, BF₄^-, and Cl^-) with variational cation alkyl chain lengths (n = 2, 4, 6, and 8) to montmorillonite was investigated to explore the structural effect of ITILs on their adsorption. A series of montmorillonite with different cation exchange capacities (CECs) and possessing a set of homoionic K- and Cs-exchanged interlayer cations were also examined to assess the influence of montmorillonite structure and characteristics. The adsorption of ITILs to Na-saturated montmorillonite (Na-MAz) was counteranion-independent but increased with the increase in the alkyl chain length of the imidazolium cation. X-ray diffraction results indicated that ITIL cations with different alkyl chains lay flat between the montmorillonite interlayers with different contact angles. The uptake of ITILs by Na-MAz increased with the increase in the solution pH and decrease in ionic strength. Na-MAz exhibited greater adsorption than K- and Cs-saturated MAz due to the larger hydrated radii of Na⁺ than those of K⁺ and Cs⁺. The uptake of ITILs to Na-MZj (CEC = 64 mmol/100 g) was almost half compared with that of Na-MAz (CEC = 117 mmol/100 g). Consequently, this work demonstrated that the ITIL adsorption to montmorillonite was dependent on the structures of both adsorbate and adsorbent.

Photo-transformation of atrazine in aqueous solution in the presence of Fe3+-montmorillonite clay and humic substances

As one of the most troublesome herbicides, the natural behavior of atrazine has drawn great attentions. Currently, most studies investigated the adsorption of atrazine on clay minerals and humic substances (HSs), whereas, the transformation of atrazine catalyzed by clay and HSs was still unknown. In the present study, photo-degradation of atrazine in the presence of Fe³⁺-montmorillonite and Suwannee river fulvic acid (SRFA) in aqueous solution was systematically studied. In the Fe³⁺-montmorillonite system, the hydroxyl radical (OH) induced removal of atrazine was strongly pH-dependent and the reaction rate increased with the decrease of pH. The presence of SRFA suppressed the atrazine degradation by Fe³⁺-montmorillonite at pH 3 but promoted its removal rate in the pH range of 4-6. Our results demonstrated that both OH and singlet oxygen are responsible for the degradation process in the Fe³⁺-montmorillonite/SRFA hybrid system. The degradation of atrazine followed the cleavage of the CN bonds in aliphatic chains of atrazine, and three major products, desethylatrazine, desisopropylatrazine and desethyldesisopropylatrazine were detected. The toxicity assessment showed that the toxicity of the reaction solution significantly decreased after the radical reactions, indicating that the transformation of atrazine on natural clay minerals with/without HSs could be considered as a detoxification pathway, which might be important to evaluate the environmental risk of atrazine in a natural system.

Lignin peroxidase ligand access channel dysfunction in the presence of atrazine

Studies have determined that the white-rot basidiomycete Phanerochaete chrysosporium is capable of biodegrading the atrazine herbicide with its broad-specificity enzymes, but the particular role of biocatalysts is still unclear. In the case of lignin peroxidase, a ligand access channel connected to the active heme cofactor provides access to the active site for potential small-sized substrates. Experimental results show that lignin peroxidase is unable to degrade atrazine, therefore, the primary goal was to determine whether there is any connection between the structural and dynamical properties of the enzyme and its incapability to degrade atrazine. The results of protein-ligand docking and molecular dynamics study correlate with relevant, published NMR and molecular dynamics data, and give the answer to the lack of atrazine degradation by lignin peroxidase which has already been established by numerous authors using experimental methods. Atrazine has no access to heme edge due to the electric charges of the delocalized s-triazine ring. The detected phenomenon suggests that the small size of the ligands only is not a sufficient condition to access the active site. Their physicochemical properties influence the structural behaviour of the channel.

Polyurethane foams containing residues of petroleum industry catalysts as recoverable pH-sensitive sorbents for aqueous pesticides

To investigate ways of mitigating the contamination of water with herbicides, which is a well-recognized global problem, we prepared natural resource-based polyurethane foams containing different amounts of petroleum industry catalyst residue (RC) and tested them as atrazine (ATZ, a common herbicide) sorbents in aqueous solutions. The above sorbents were characterized by infrared spectroscopy, electron microscopy, microtomography, thermogravimetric analysis, and X-ray diffraction. The adsorption/desorption of ATZ thereon was investigated as a function of foam composition, pH, initial ATZ concentration, and time. The obtained results showed that the porosity, pore size, and pore interconnectivity of the prepared sorbents were well suited for optimal ATZ removal. At pH 2, foams with high RC contents achieved higher ATZ removal efficiencies (e.g., 25%) than the pristine foam (12%). Conversely, ATZ removal was disfavored at high pH, which was attributed to restricted ATZ-sorbent interactions due to changes in the sorbent surface charge. The presence of other species (such as pectin, which is usually found in fruits) did not interfere with ATZ removal. ATZ desorption was most effective at high pH, enabling the regeneration and re-use of sorbents and thus reducing large-scale application costs.

Determination of triazine herbicides and their metabolites in multiple medicinal parts of traditional Chinese medicines using streamlined pretreatment and UFLC-ESI-MS/MS

A rapid, sensitive, and reliable ultra-fast liquid chromatography combined with electrospray ionization tandem mass spectrometry (UFLC-ESI-MS/MS) method was established and applied to simultaneous determination of 31 triazine herbicides and their metabolites in multiple medicinal parts of traditional Chinese medicines (TCMs). A streamlined pretreatment approach using one-step extraction and dilution was proposed, which provided high-throughput processing, excellent recovery, and negligible interference. Afterwards, multiple-reaction monitoring (MRM) and information-dependent acquisition (IDA) triggered enhanced product ion spectra (EPI) was adopted to identify and quantify the targets in a single analysis. The optimized method was then validated according to the guidelines of the European Commission for the following parameters: Matrix effects, specificity, accuracy, precision, linearity, range, and stability. The LOD and LOQ for the 31 triazine herbicides were 0.1-10 μg kg^-1 and 0.5-25 μg kg^-1, respectively. Recoveries at three concentration levels were within 67.9-120.3% with an associated precision RSD <20%. Using the proposed approach, trazines herbicides were determined from 44 commercially available TCMs. The detection rate of triazine herbicides residues was 15.9% of the total samples. Among them, atrazine, simeton, and simetryn were found in the radix, herba, and seed TCMs with values far below the referenced maximum residue limits (MRLs), but no residues were detected in either the flos or fructus. Taken together, this method has the potential to provide a means for triazines screening in extensive matrices, thereby laying the foundation for pesticide registration on TCMs. Moreover, it has the potential to guide further triazine residue control in TCMs.

Can Carbamates Undergo Radical Oxidation in the Soil Environment? A Case Study on Carbaryl and Carbofuran

Radical oxidation of carbamate insecticides, namely carbaryl and carbofuran, was investigated with spectroscopic (electron paramagnetic resonance [EPR] and UV-vis) and theoretical (density functional theory [DFT] and ab initio orbital-optimized spin-component scaled MP2 [OO-SCS-MP2]) methods. The two carbamates were subjected to reaction with ^•OH, persistent DPPH^• and galvinoxyl radical, as well as indigenous radicals of humic acids. The influence of fulvic acids on carbamate oxidation was also tested. The results obtained with EPR and UV-vis spectroscopy indicate that carbamates can undergo direct reactions with various radical species, oxidizing themselves into radicals in the process. Hence, they are prone to participate in the prolongation step of the radical chain reactions occurring in the soil environment. Theoretical calculations revealed that from the thermodynamic point of view hydrogen atom transfer is the preferred mechanism in the reactions of the two carbamates with the radicals. The activity of carbofuran was determined experimentally (using pseudo-first-order kinetics) and theoretically to be noticeably higher in comparison with carbaryl and comparable with gallic acid. The findings of this study suggest that the radicals present in soil can play an important role in natural remediation mechanisms of carbamates.

Toxic effects of atrazine on porcine oocytes and possible mechanisms of action

Because atrazine is a widely used herbicide, its adverse effects on the reproductive system have been extensively researched. In this study, we investigated the effects of atrazine exposure on porcine oocyte maturation and the possible mechanisms. Our results showed that the rates of oocyte maturation significantly decreased after treatment with 200 μM atrazine in vitro. Atrazine treatment resulted in abnormal spindle morphology but did not affect actin distribution. Atrazine exposure not only triggered a DNA damage response but also decreased MPF levels in porcine oocytes. Our results also revealed that atrazine worsened porcine oocyte quality by causing excessive accumulation of superoxide radicals, increasing cathepsin B activity, and decreasing the GSH level and mitochondrial membrane potential. Furthermore, atrazine decreased developmental competence of porcine oocytes up to the blastocyst stage and changed some properties: cell numbers, apoptosis, and related gene expression levels. Collectively, our results indicate that porcine oocyte maturation is defective after atrazine treatment at least through disruption of spindle morphology, MPF activity, and mitochondrial function and via induction of DNA damage, which probably reduces developmental competence.