Glyphosate Degradation Research Articles

Complete and rapid degradation of glyphosate with Fe3Ce1Ox catalyst for peroxymonosulfate activation at room temperature

Glyphosate, a common broad-spectrum herbicide, is a serious environmental pollutant that causes a significant threat to humans. Hence, there is a pressing task to remove glyphosate from the environment. Here, we report an excellent Fe3Ce1Ox catalyst synthesized via the one-step co-precipitation method for activating peroxymonosulfate (PMS) to degrade glyphosate at 25 °C. As a result, glyphosate is completely degraded with a high degradation rate of 400 mg L−1·h−1, and the TOC and TN removals are 85.6% and 80.8%, respectively. As proven by systematic characterizations, the Fe–Ce synergistic effect plays a significant role in promoting PMS activation. The main reactive oxygen species for glyphosate oxidation are surface-bound SO4−· and ·OH, produced by activating PMS by electron transfer between Fe2+/Fe3+ and Ce3+/Ce4+ of Fe3Ce1Ox. In light of the products determined, the possible degradation process of glyphosate is also speculated: C–N and C–P bonds of glyphosate molecules are attacked to form aminomethylphosphonic acid (AMPA) and orthophosphate (PO43−) by surface-bound SO4−· and ·OH that continuously mineralize and dephosphorylate AMPA to generate small molecules and inorganic ions, such as H2O and PO43−. The results of this work suggest that Fe3Ce1Ox/PMS could provide a potential candidate for efficiently removing organic compounds containing nitrogen or phosphorus from wastewater.

Citric acid-assisted ultrasmall CeO2 nanoparticles for efficient photocatalytic degradation of glyphosate

Degradation of glyphosate has attracted much attention all over the world, since glyphosate has been demonstrated to affect the human health through the accumulation in food chain. Herein, we use citric acid as capping agent to synthesize highly-stable aqueous dispersions of monodispersed CeO2 nanoparticles (NPs) with ultrasmall controllable size of 2.1–4.8 nm, high surface areas and rich oxygen defects, which were firstly used as photocatalyst for efficient degradation of glyphosate. The obtained CeO2 NPs display a significantly size-dependent catalytic activity and a good stability performance. Ultrasmall 2.1 nm CeO2 NPs have 6 times (UV) and 20 times (visible light) degradation rates of 4.8 nm counterpart, which can rapidly remove glyphosate from water at pH = 4 in 5 min (UV) and 20 min (visible light). And the related degradation kinetics data at pH = 4 are well related to the pseudo-first-order kinetic model. In this highly-efficient photocatalytic degradation process, the grafted citric acid can initiate the electron transfer to accelerate the regeneration of Ce3+ sites as electron donors and enhance photocatalytic performance via ligand-to-metal charge transfer. This work provides a new method to prepare high-performance CeO2 photo-nanocatalysts for the removal of glyphosate and emphasizes the important role of modifier, oxygen defects and particle size in seeking efficient photocatalytic materials.

Temperature and Aging Affect Glyphosate Toxicity and Fatty Acid Composition in Allonychiurus kimi (Lee) (Collembola).

Glyphosate is the most used herbicide worldwide, but enormous use of glyphosate has raised concerned about its environmental loadings. Although glyphosate is considered non-toxic, toxicity data for soil non-target organisms according to temperature and aging are scarce. This study examined the toxicity of glyphosate with the temperature (20 °C and 25 °C) and aging times (0 day and 7 days) in soil using a collembolan species, Allonychiurus kimi (Lee). The degradation of glyphosate was investigated. Fatty acid composition of A. kimi was also investigated. The half-life of glyphosate was 2.38 days at 20 °C and 1.69 days at 25 °C. At 20 °C with 0 day of aging, the EC50 was estimated to be 93.5 mg kg−1. However, as the temperature and aging time increased, the glyphosate degradation increased, so no significant toxicity was observed on juvenile production. The proportions of the arachidonic acid and stearic acid decreased and increased with the glyphosate treatment, respectively, even at 37.1 mg kg−1, at which no significant effects on juvenile production were observed. Our results showed that the changes in the glyphosate toxicity with temperature and aging time were mostly dependent on the soil residual concentration. Furthermore, the changes in the fatty acid compositions suggest that glyphosate could have a chronic effect on soil organisms.

Degradation of boscalid, pyraclostrobin, fenbuconazole, and glyphosate residues by an advanced oxidative process utilizing ultraviolet light and hydrogen peroxide

Recently an advanced oxidative process (AOP) combining H2O2 and UV-C light was observed to be effective at controlling Listeria monocytogens and Escherichia coli O157:H7 and degrading chlorpyrifos residues on the surface of apples. Little is known about the application of AOP for the degradation of other pesticide residues. This study examined degradation of boscalid, pyraclostrobin, fenbuconazole and glyphosate by 3% (w/v) H2O2, UV-C (254 nm) irradiation and their combination on apple skin and glass. The extent of degradation was not significantly different between the AOP and optimal individual treatment. However, treatment susceptibility was different with glyphosate most effectively degraded by H2O2 exposure (up to 98 % on apple, 3% (w/v) H2O2 at 30 °C for 15 min) while boscalid, pyraclostrobin and fenbuconazole were more effectively degraded by UV-C (up to 88 %, 100 % and 70 % degradation after ∼11,000 mJ/cm2). Suggestions for possible causes of degradation are proposed.

Photoelectrocatalytic degradation of glyphosate on titanium dioxide synthesized by sol-gel/spin-coating on boron doped diamond (TiO2/BDD) as a photoanode

The construction of a photoanode with several layers of titanium oxysulfate as a precursor to form titanium dioxide-TiO2 on boron doped diamond-BDD (TiO2/BDD), and its application for the photoelectro-degradation of glyphosate in aqueous medium are presented. The study was divided into three stages: i) optimization of the number of layers of the TiO2 precursor to modify BDD using a novel method combining Sol-gel/Spin-Coating; ii) characterization of the TiO2/BDD electrodes, by scanning electron microscopy-SEM, dispersive energy spectroscopy-EDX, Ray diffraction-XRD, contact angle, and electrochemical response by cyclic voltammetry using [Fe(CN)6]3-/4- system; iii) degradation of glyphosate (50 mg L−1) by electrochemical oxidation on BDD and photoelectrocatalysis on TiO2/BDD in dark and UV-light conditions, at different current densities, for 5 h. The glyphosate degradation and mineralization were evaluated by High-Performance Liquid Chromatography, Total Organic Carbon, Chemical Oxygen Demand and inorganic-ions concentration (NO3−, PO43−, and NH4+). Also, the aminomethylphosphonic acid-AMPA was quantified by HPLC, as a degradation intermediate. Using five layers of the TiO2 precursor, in the construction of TiO2/BDD photoanode, and a lower contact angle, greater photoelectrocatalysis against the [Fe(CN)6]3-/4- redox system and better degradation of glyphosate compared to BDD without modification were achieved. The formation of TiO2 nanoparticles (14.79 ± 3.43 nm) in anatase phase on BDD was verified by SEM and XRD. Additionally, glyphosate degradation and mineralization were 2.3 times faster by photoelectrocatalysis on TiO2/BDD, relative to BDD, at 3 mA cm−2 and UV-light. Thus, the presence of TiO2 on BDD increases the rate and efficiency of glyphosate degradation with respect to electrochemical oxidation on BDD.

Glyphosate Biodegradation Potential in Soil Based on Glycine Oxidase Gene (thiO) from Bradyrhizobium.

Despite the intensive use of glyphosate(GP) and its ubiquitous presence in the environment, studies addressing the presence of microbial genes involved in glyphosate degradation in natural conditions are scarce. Based on the agronomical importance of Bradyrhizobium genus and its metabolic versatility, we tested the hypothesis that species or genotypes of Bradyrhizobium could be a proxy for GP degrader potential in soil. A quantitative PCR assay was designed to target a specific region of the glycine oxidase gene (thiO), involved in the oxidation of glyphosate to AMPA, from known sequences of Bradyrhizobium species. The abundance of the thiO gene was determined in response to herbicide application in soils with different GP exposure history both under field and microcosm conditions. The gene coding for RNA polymerase subunitB (rpoB) was usedas a reference for the abundance of total Bradyrhizobia. The assay using the designed primers was linear over a very large concentration range of the target and showed high efficiency and specificity. In a field experiment, there was a differential response related to the history of glyphosate use and the native Bradyrhizobium genotypes. In a soil without previous exposure to herbicides, thiO gene increased over time after glyphosate application with most genotypes belonging to the B. jicamae and B. elkanni supergroups. Conversely, in an agricultural soil with more than 10 years of continuous glyphosate application, the abundance of thiO gene decreased and most genotypes belonged to B. japonicum supergroup. In a microcosm assay, the amount of herbicide degraded after a single application was positively correlated to the number of thiO copies in different agricultural soils from the Pampean Region. Our results suggest that Bradyrhizobium species are differently involved in glyphosate degradation, denoting the existence of metabolically versatile microorganisms which can be explored for sustainable agriculture practices. The relationship between the abundance of thiO gene and the GP degraded in soil point to the use of thiO gene as a proxy for GP degradation in soil.

Bacterial isolates from Argentine Pampas and their ability to degrade glyphosate

Glyphosate is a synthetic phosphonate compound characterized by a carbon‑phosphorus bond. Glyphosate based herbicides (GBH) are widely distributed in most of the economically productive lands in which crop production is mainly based on glyphosate-resistant genetically modified plants. Naturally, glyphosate is remediated by soil microorganisms, which accelerate its degradation. Technology based on microorganisms is considered highly efficient, low-cost and eco-friendly to remediate contaminated environments, denoting the importance of characterizing new bacterial strains able to degrade glyphosate to perform its bioremediation. In this work, 13 different bacterial strains able to grow in GBH as only phosphorous source were isolated from different environmental samples from the Argentine vastly productive glyphosate-resistant soybean crop area. These strains were identified and they belong to the genera Acinetobacter, Achromobacter, Agrobacterium, Ochrobactrum, Pantoea and Pseudomonas. Their ability to grow and consume GBH, glyphosate or the aminomethylphosphonic acid (AMPA), another phosphonate derived from glyphosate degradation, was evaluated. The best degradation performance was observed for bacteria from the genera Achromobacter, Agrobacterium and Ochrobactrum. The genome of the highly efficient GBH degrader Agrobacterium tumefaciens CHLDO was sequenced revealing the presence of a phn cluster, responsible for phosphonate metabolization. Expression analysis of A. tumefaciens CHLDO phn genes in the presence of 1.5 mM GBH compared to inorganic phosphorous showed that most of them are highly expressed during growth in the presence of the herbicide, suggesting a strong participation of phn cluster in GBH degradation. The importance of discovering new bacterial strains and the value of deciphering molecular determinants of GBH degradation give promising tools for bioremediation techniques to be used in glyphosate-contaminated environments is discussed.

W-Doped ZnO Photocatalyst for the Degradation of Glyphosate in Aqueous Solution

In this paper, the photocatalytic degradation of glyphosate by zinc oxide (ZnO) photocatalysts doped with tungsten (W) was investigated under solar simulated light. The photocatalysts were successfully synthesized through a simple precipitation method and subsequently characterized by different techniques: Raman spectroscopy, UV–Vis, N2 adsorption at −196 °C, X-ray diffraction, and SEM analysis. In particular, all the prepared catalysts were characterized by a crystallite size of about 28 nm and a hexagonal wurtzite structure. After the W doping, the bandgap energy decreased from 3.22 of pure ZnO to 3.19 for doped ZnO. This allowed us to obtain good results in terms of glyphosate degradation and simultaneous mineralization under solar simulated lamps, making the process environmentally friendly and with almost zero energy costs. In particular, the best photocatalytic performance was obtained with 100 W-ZnO (prepared with 1.5 mol% of W). With this catalyst, after 180 min of exposure to solar simulated light, the glyphosate degradation and mineralization was equal to 74% and 30%, respectively. Furthermore, it has been shown that the best catalyst dosage was equal to 1.5 g/L. The study on the influence of pH evidenced that the best photocatalytic performances are obtained at spontaneous (neutral) pH conditions. Finally, to determine the main reactive species in the glyphosate oxidation, the effects of different radical scavengers were tested. The results evidenced that the glyphosate oxidation mechanism seems to be related mainly to the O2•− generated under simulated solar light irradiation, but also in minor part to h+.

The fate of a hazardous herbicide: a DFT-based ab initio study on glyphosate degradation.

Glyphosate degradation has been extensively examined; however, only a few detailed computational studies have been performed on the topic so far. There are substantial differences between the degradation products of glyphosate, as AMPA (aminomethylphosphonic acid) is toxic while sarcosine intermediate is non-toxic. These species can have different effects on the environment and, indirectly, on the human body. We performed calculations using density functional theory and post-Hartree-Fock correlated ab initio methods to find the possible mechanisms for the degradation process by small (hydroxyl, peroxyl, and superoxide) radicals. We found that direct sarcosine formation is strongly dependent on the concentration of the radical species. AMPA and glycine were mostly formed as aldehyde derivatives, while in addition to the former, glyoxylate and bicarbonate are formed alternatively. A significant pH effect was also found for the competitive reactions determined by the calculated rate constants of the elementary steps. Overall barriers showed similarities by DFT but ab initio methods could separate them.

CLUSTERED ZnO NANOPARTICLES SYNTHESIZED VIA PRECIPITATION FOR PHOTOCATALYTIC DEGRADATION OF METHYL ORANGE AND GLYPHOSATE

Precipitation of clustered ZnO nanoparticles was performed from low-cost starting materials. Morphological and particle size analyses show the cluster formation accumulating with nanoparticles. Chemical composition detection refers the ZnO formation. Hexagonal wurtzite structures are confirmed with low crystal size, high dislocation density, and spherical growth. Optical band gap shows red shift affecting to low required activating energy for photocatalytic activity. Photocatalytic degradation of methyl orange and glyphosate presents degradation rate constants of 3.28×10-3 min-1 and 2.45×10-3 min-1 , respectively, which is caused by the synergy of small particle size, small crystal size, high dislocation density, and low optical band gap. Therefore, clustered ZnO nanoparticles were demonstrated as a potential photocatalytic material for the decomposition of methyl orange and glyphosate.

Role of soil bacterial consortia on glyphosate degradation and growth of maize seedlings

Pre-growing weed control by glyphosate herbicides is effective for increasing yield, but glyphosate residues in the soil might reduce soil quality and can accumulate in agricultural products. Naturally, microbes are able to breakdown glyphosate into nontoxic substances orthophosphate and glycine. Glyphosate degradation in soil by single soil microbes are reported elsewhere, but the information about glyphosate removal by soil bacterial consortia was limited. The objective of this research was to determine the effect of carbon (C), nitrogen (N), and phosphorus (P) composition in liquid media to increase glyphosate degradation and its degradation product by soil bacterial consortia and 2) verify the effect of bacterial consortia on maize seedlings growth, their N and P uptake, as well as total and soluble P in soil. Glyphosate degradation test was set up by incubating bacterial consortia in a different composition of C-N-P liquid basal media. Greenhouse experiment has been performed in a randomized block design to treat maize grown in Inceptisols with bacterial and glyphosate application. The results showed that C-N-P composition of liquid media affected the concentration of glyphosate, as well as orthophosphate and glycine as by-products. In-planta experiment verified that inoculation of glyphosate-degrading bacterial to maize seedling grown in glyphosate-contaminated soil enabled to enhance shoot dry weight of maize seedling and N and P uptake at 4 weeks after inoculation.

Binding interaction of glyphosate with glyphosate oxidoreductase and C–P lyase: Molecular docking and molecular dynamics simulation studies

Widespread application of glyphosate poses a threat to living organisms. Microbial strains are able to degrade glyphosate via contrasting metabolic pathways with the help of enzymes. Glyphosate oxidoreductase (GOX) and C–P lyase are the key enzymes for the biodegradation of glyphosate and its intermediate metabolite aminomethylphosphonic acid (AMPA) in microbes. The microbial degradation of glyphosate has been reported, but the underlying molecular mechanism is still unclear. Therefore, in this study, the interaction mechanism of GOX and C–P lyase with glyphosate and AMPA were investigated by using molecular docking and molecular dynamics (MD) simulations. The results indicate that glyphosate contacts with the active site of GOX and C–P lyase by hydrogen bonds as well as hydrophobic and van der Waals interactions in aqueous solution to maintain its stability. The presence of glyphosate and AMPA in the active site significantly changes the conformation of GOX and C–P lyase. The results of the MD simulations confirm that GOX and C–P lyase complexes are stable during the catalytic reaction. This study offers a molecular level of understanding of the expression and function of GOX and C–P lyase for the bioremediation of glyphosate.

Enhanced photocatalytic degradation of glyphosate over 2D CoS/BiOBr heterojunctions under visible light irradiation

Two-dimensional (2D) heterojunction photocatalysts can shorten the carrier transfer pathway. In this study, CoS nanoparticles were deposited on the surface of 2D BiOBr nanosheets to fabricate novel ultrathin and intimate-contact 2D heterojunction photocatalysts by a two-step solvothermal route. Under visible-light (λ > 400 nm) irradiation, the apparent reaction rate constant of glyphosate degradation over 10%CoS/BiOBr reaches 0.0074 min–1 (74.7% glyphosate was degraded within 3 h), which is about 5.3 times that of pure BiOBr (0.0014 min–1). The extraordinary photocatalytic performance is attributed to the strong visible-light absorption, the effective charge separation and low charge transfer resistance. The possible photocatalytic reaction process and mechanism over CoS/BiOBr heterojunctions are proposed. Moreover, the 10%CoS/BiOBr sample shows good reusability and stability. This work could provide a new insight for the design and development of 2D heterojunction photocatalysts.

Preparation of multifunctional cellulosic fabric based on graphene/TiO2 nanocoating

Photocatalysts in powder form commonly cannot have a high photocatalytic efficiency without strong agitation in traditional photocatalytic process. It is also inconvenient for recovery of the photocatalysts in powder form after usage. This consequently, results in a secondary pollution which limits their application in water treatment for heavily polluted natural waterways. In this work, coating GO and TiO2 nanomaterials over large-scale cellulose substrates which can easily float on water was performed in the presence of crosslinker by applying a simple dip-coating method. The photocatalytic activities were evaluated by studying the degradation of two models of organic pollutants, methylene blue and glyphosate under visible light irradiation. The nanomaterial wrapped substrates endured over 40 times reuse at an optimum photocatalyst concentration of 0.1 g/L GO and 15% TiO2 based on fabric weight. The highest degradation rate was obtained at this point and a further increase in concentration decreased the degradation rate. The efficient degradation of glyphosate by the nanomaterial loaded substrate confirms its industrial application in treating pesticide and herbicide polluted waters. Remarkably, this study has established a feasible practical way for direct degradation of pollutants in lakes or rivers using mechanically floating large-scale cellulose-supported photocatalysts.

Bacillus aryabhattai FACU: A promising bacterial strain capable of manipulate the glyphosate herbicide residues.

Glyphosate is a commonly used organophosphate herbicide that has an adverse impact on humans, mammals and soil microbial ecosystems. The redundant utilize of glyphosate to control weed growth cause the pollution of the soil environment by this chemical. The discharge of glyphosate in the agricultural drainage can also cause serious environmental damage and water pollution problems. Therefore, it is important to develop methods for enhancing glyphosate degradation in the soil through bioremediation. In this study, thirty bacterial isolates were selected from an agro-industrial zone located in Sadat City of Monufia Governorate, Egypt. The isolates were able to grow in LB medium supplemented with 7.2 mg/ml glyphosate. Ten isolates only had the ability to grow in a medium containing different concentrations of glyphosate (50, 100, 150, 200 and 250 mg/ml). The FACU3 bacterial isolate showed the highest CFU in the different concentrations of glyphosate. The FACU3 isolate was Gram-positive, spore-forming and rod-shape bacteria. Based on API 50 CHB/E medium kit, biochemical properties and 16S rRNA gene sequencing, the FACU3 isolate was identified as Bacillus aryabhattai. Different bioinformatics tools, including multiple sequence alignment (MSA), basic local alignment search tool (BLAST) and primer alignment, were used to design specific primers for goxB gene amplification and isolation. The goxB gene encodes FAD-dependent glyphosate oxidase enzyme that responsible for biodegradation process. The selected primers were successfully used to amplify the goxB gene from Bacillus aryabhattai FACU3. The results indicated that the Bacillus aryabhattai FACU3 can be utilized in glyphosate-contaminated environments for bioremediation. According to our knowledge, this is the first time to isolate of FAD-dependent glyphosate oxidase (goxB) gene from Bacillus aryabhattai.

The Degradation of Glyphosate and Its Effect on the Microbial Community of Agro-Sod–Podzolic Soil under Short-Term Model Experiment Conditions

Under laboratory conditions, the decomposition of glyphosate with the formation of aminomethylphosphonic acid (AMPA) and its effect on the total abundance of bacteria and fungi as well as the number of copies of genes encoding the enzymes C–P lyase of α-proteobacteria (phnJ), acid and alkaline phosphatase (phoC and phoD) and Fe protein of nitrogenase (nifH) in agro-sod-podzolic soil (Epialbic Retisol) were determined. It was shown that when applying glyphosate in recommended doses (5–10 mg/kg), only 5–7% of the introduced herbicide were detected after 14 days, but when the dose was increased to 100 mg/kg, this value increased up to 23%. Decreasing the rate of the herbicide degradation was observed only during the first week of incubation and was accompanied by a decrease in the number of copies of the phoC, phoD, and nifH genes and an increase in the abundance of fungi. The obtained results indicate that glyphosate was mainly degraded by means of C–P bond breaking and the formation of phosphates, and also suggest possible inhibition of the nitrogen fixation process. It is shown that at an application dose of glyphosate of 100 mg/kg may lead to the accumulation of AMPA, the first metabolite of the herbicide degradation pathway, formed after the C–N bond break. Bioassay using wheat showed that when applying glyphosate at a dose of 100 mg/kg, an inhibition of plant development was observed: the length of the roots and the biomass of the shoots reduced by 60 and 20% compared to the control, respectively. Based on the data obtained, it was proposed to use the reduction in the content of copies of the phoC gene and the increase in the number of copies of ITS rRNA as indicators of the predominant decomposition of glyphosate through the sarcosine pathway. The decrease in the number of copies of ITS rRNA gene by 40% or more can be used as an indicator of the possibility of AMPA accumulation during glyphosate degradation.

Electrochemical monitoring of the oxidative degradation of glyphosate with UV/H2O2

A voltammetric method optimized for the sensitive and reliable study of the UV/H2O2 oxidation of glyphosate (N- (phosphonomethyl) glycine) (GPS). The cell consisted of three electrodes in a compartment, silver wire coated with silver chloride as a pseudo reference electrode, platinum electrode as working electrode and stainless steel as auxiliary electrode. GPS cyclic voltammetric analysis suggests the formation of a GPS-Pt complex on the electrode surface, with an enhanced signal in perchloric acid between 1.3 to -1.3V; sensitive to protonation of the amino group, no response observed at pH values greater than 5.00. The oxidative degradation of GPS with UV/H2O2 is evident at pH 3.0, it exhibits first order pseudo kinetics with a half-life of 40 ± 4min. Two degradative routes are estimated depending on the concentration of H2O2: at low concentrations (H2O2/GPS 1: 100 ratio), the formation of sarcosine and then glycine is favored; at H2O2/GPS 1:20 and 1:10 ratios predominate the formation of glycine.

Invasive species versus pollutants: Potential of Limnoperna fortunei to degrade glyphosate-based commercial formulations.

The intensive use of glyphosate in industrial agriculture may lead to freshwater contamination, encouraging studies of its toxic effect on non-target aquatic organisms. Glyphosate-based commercial formulations contain adjuvants, making them even more toxic than the active ingredient (a.i.) itself. The golden mussel Limnoperna fortunei is a freshwater invasive species which has been found to increase glyphosate dissipation in water and to accelerate eutrophication. The aim of this study is to evaluate the capability of L. fortunei to reduce the concentration of glyphosate in two commercial formulations, Roundup Max® and Glifosato Atanor®. Results were compared with the decay of the a.i. alone and in presence of mussels. Evasive response and toxicity tests were performed in a first set of trials to analyze the response of L. fortunei exposed to Roundup Max® and Glifosato Atanor®. Subsequently, we conducted a 21-day degradation experiment in 2.6-L microcosms applying the following treatments: 6mgL-1 of technical-grade glyphosate (G), Glifosato Atanor® (A), Roundup Max® (R), 20 mussels in dechlorinated tap water (M), and the combination of mussels and herbicide either in the technical-grade (MG) or formulated form (MA and MR) (all by triplicate). Samples were collected at days 0, 1, 7, 14 and 21. No significant differences in glyphosate decay were found between treatments with mussels (MG: 2.03±0.40mgL-1; MA: 1.60±0.32mgL-1; MR: 1.81±0.21mgL-1), between glyphosate as a.i. and the commercial formulations, and between the commercial formulations, suggesting that the adjuvants did not affect the degrading potential of L. fortunei. In addition to the acceleration of glyphosate dissipation in water, there was an increase in the concentration of dissolved nutrients in water (N-NH4+ and P-PO43-) even higher than that caused by the filtering activity of the mussels, probably resulting from stress or from the degradation of glyphosate and adjuvants. We believe that a larger bioavailability of these nutrients due to glyphosate metabolization mediated by mussels would accelerate eutrophication processes in natural water bodies. The approach used here, where L. fortunei was exposed to two commercial formulations actually used in agricultural practices, sheds light on the potential impact of glyphosate decay on water bodies invaded by this species.

Cyclodextrins grafted MoS2/g-C3N4 as high-performance photocatalysts for the removal of glyphosate and Cr (VI) from simulated agricultural runoff

The hydrophobicity of MoS2/g-C3N4 based photocatalysts remains a major hurdle to their successful application for the remediation of water-soluble contaminants such as herbicides and heavy metals. Herein, we develop new photocatalysts based on the graft of three different cyclodextrins (α-CD, β-CD and γ-CD) on MoS2/g-C3N4 composites (CDs/MoS2/g-C3N4) for the removal of glyphosate and Cr (VI) from simulated agricultural runoff. CDs/MoS2/g-C3N4 show remarkably enhanced photocatalytic activities for glyphosate degradation and Cr (VI) reduction compared to pristine MoS2/g-C3N4. In addition, γ-CD/MoS2/g-C3N4 exhibits the highest hydrophilicity and photocatalytic activity among these three different cyclodextrins grafted MoS2/g-C3N4. The mechanistic investigation indicates that cyclodextrins can not only increase the accumulation of glyphosate and Cr (VI) onto the surface of CDs/MoS2/g-C3N4 but also facilitate the fleet separation of photo-induced electron-hole pairs. In summary, these results collectively imply that the graft of cyclodextrins could be an effective strategy to improve the photocatalytic efficiency of MoS2/g-C3N4 composites for the removal of glyphosate and Cr (VI) from simulated agricultural runoff.

Monoammonium Phosphate Effects on Glyphosate in Soils: Mobilization, Phytotoxicity, and Alteration of the Microbial Community

Application of monoammonium phosphate has been demonstrated to re-immobilize glyphosate sorbed by soil under model laboratory experiment conditions. This effect was most pronounced in the gray forest soil (Haplic Phaeozem), where the concentration of herbicide in the presence of fertilizer was 3.6 times higher than in its absence. For soddy-podzolic soil (Albic Retisol) and leached Chernozem (Luvic Chernozem), this ratio was 1.5 and 2.8, respectively. Thus, the introduction of monoammonium phosphate into soils contaminated with glyphosate may result in an increase of the risk of herbicide migration into the neighboring environments. The estimated number of functional genes of bacteria responsible for glyphosate degradation by means of the C–P bond cleavage did not show statistically significant effect of the fertilizer on the number of copies of the phnJ gene, encoding the C–P lyase of α- and γ-proteobacteria. The release of glyphosate was not accompanied by any adverse effects on the length and biomass of wheat plants.