Agricultural Herbicides Research Articles

Agricultural Extension and Herbicide toxicity awareness among smallholder farmers in Malawi

Agricultural Extension and Herbicide toxicity awareness among smallholder farmers in Malawi

Digital image processing: a useful tool in the analysis of lung injuries caused by chronic inhalation of agricultural herbicides.

The herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) is widely used in agriculture to control various weeds. The objective of this study was to use the digital image processing method to identify alveolar lesions in the lungs of rats submitted to chronic 2,4-dichlorophenoxyacetic acid (2,4-D) inhalation exposure. We used forty adult male Wistar rats. The rats were divided into four groups: control group (CG), low concentration group (LCG), medium concentration group (MCG), and high concentration group (HCG). In a 6-month exposure period, we used two boxes connected to ultrasonic nebulizers for herbicide spraying. After this period, the rats were euthanized for the collection and study of lung tissue. For each image, counts of injuries and blisters were performed automatically using a methodology based on digital image processing techniques. For analysis of the results, an electronic database (Excel®) was created. We used the Pearson method for correlation analysis; values of p <0.05 were considered significant. In the evaluation of healthy alveoli, we recorded positive and significant correlations between analysis from a pathologist and computational analysis. In the evaluation of injured alveoli, we recorded a positive but non-significant correlation between analysis from a pathologist and computational analysis. These results show the effectiveness of digital image processing when evaluating alveolar integrity.

Molecular mechanisms underlying glyphosate resistance in bacteria.

Glyphosate is a nonselective herbicide that kills weeds and other plants competing with crops. Glyphosate specifically inhibits the 5-enolpyruvyl-shikimate-3-phosphate (EPSP) synthase, thereby depleting the cell of EPSP serving as a precursor for biosynthesis of aromatic amino acids. Glyphosate is considered to be toxicologically safe for animals and humans. Therefore, it became the most-important herbicide in agriculture. However, its intensive application in agriculture is a serious environmental issue because it may negatively affect the biodiversity. A few years after the discovery of the mode of action of glyphosate, it has been observed that bacteria evolve glyphosate resistance by acquiring mutations in the EPSP synthase gene, rendering the encoded enzyme less sensitive to the herbicide. The identification of glyphosate-resistant EPSP synthase variants paved the way for engineering crops tolerating increased amounts of the herbicide. This review intends to summarize the molecular mechanisms underlying glyphosate resistance in bacteria. Bacteria can evolve glyphosate resistance by (i) reducing glyphosate sensitivity or elevating production of the EPSP synthase, by (ii) degrading or (iii) detoxifying glyphosate and by (iv) decreasing the uptake or increasing the export of the herbicide. The variety of glyphosate resistance mechanisms illustrates the adaptability of bacteria to anthropogenic substances due to genomic alterations.

Design and Fabrication of Yttrium Ferrite Garnet-Embedded Graphitic Carbon Nitride: A Sensitive Electrocatalyst for Smartphone-Enabled Point-of-Care Pesticide (Mesotrione) Analysis in Food Samples.

As the use of pesticides in agriculture is increasing at an alarming rate, food contamination by pesticide residues is becoming a huge global problem. It is essential to develop a sensitive and user-friendly sensor device to quantify trace levels of pesticide and herbicide residues in food samples. Herein, we report an electrocatalyst made up of yttrium iron garnet (Y3Fe5O12; YIG) and graphitic carbon nitride (GCN) to attain picomolar-level detection sensitivity for mesotrione (MTO), which is a widely used herbicide in agriculture. First, YIG was prepared by a hydrothermal route; then, it was loaded on GCN sheets via a calcination method. The surface structures, composition, crystallinity, and interfacial and electrocatalytic properties of the YIG and YIG/GCN were analyzed. As the YIG/GCN displayed better surface and catalytic properties than YIG, YIG/GCN was modified on a screen-printed carbon electrode to fabricate a sensor for MTO. The YIG/GCN-modified electrode displayed a detection limit of 950 pM for MTO. The method was demonstrated in (spiked) fruits and vegetables. Then, the modified electrode was integrated with a miniaturized potentiostat called KAUSTat, which can be operated wirelessly by a smartphone. A first smartphone-based portable sensor was demonstrated for MTO that is suitable for use in nonlaboratory settings.

A dual electro-optical biosensor based on Chlamydomonas reinhardtii immobilised on paper-based nanomodified screen-printed electrodes for herbicide monitoring

The indiscriminate use of herbicides in agriculture contributes to soil and water pollution, with important endangering consequences on the ecosystems. Among the available analytical systems, algal biosensors have demonstrated to be valid tools thanks to their high sensitivity, cost-effectiveness, and eco-design. Herein, we report the development of a dual electro-optical biosensor for herbicide monitoring, based on Chlamydomonas reinhardtii whole cells immobilised on paper-based screen-printed electrodes modified with carbon black nanomaterials. To this aim, a systematic study was performed for the selection and characterisation of a collection among 28 different genetic variants of the alga with difference response behaviour towards diverse herbicide classes. Thus, CC125 strain was exploited as case study for the study of the analytical parameters. The biosensor was tested in standard solutions and real samples, providing high sensitivity (detection limit in the pico/nanomolar), high repeatability (RSD of 5% with n = 100), long lasting working (10 h) and storage stability (3 weeks), any interference in the presence of heavy metals and insecticides, and low matrix effect in drinking water and moderate effect in surface one.

Selective β-Mono-Glycosylation of a C15-Hydroxylated Metabolite of the Agricultural Herbicide Cinmethylin Using Leloir Glycosyltransferases.

Cinmethylin is a well-known benzyl-ether derivative of the natural terpene 1,4-cineole that is used industrially as a pre-emergence herbicide in grass weed control for crop protection. Cinmethylin detoxification in plants has not been reported, but in animals, it prominently involves hydroxylation at the benzylic C15 methyl group. Here, we show enzymatic β-glycosylation of synthetic 15-hydroxy-cinmethylin to prepare a putative phase II detoxification metabolite of the cinmethylin in plants. We examined eight Leloir glycosyltransferases for reactivity with 15-hydroxy cinmethylin and revealed the selective formation of 15-hydroxy cinmethylin β-d-glucoside from uridine 5′-diphosphate (UDP)-glucose by the UGT71E5 from safflower (Carthamus tinctorius). The UGT71E5 showed a specific activity of 431 mU/mg, about 300-fold higher than that of apple (Malus domestica) UGT71A15 that also performed the desired 15-hydroxy cinmethylin mono-glycosylation. Bacterial glycosyltransferases (OleD from Streptomyces antibioticus, 2.9 mU/mg; GT1 from Bacillus cereus, 60 mU/mg) produced mixtures of 15-hydroxy cinmethylin mono- and disaccharide glycosides. Using UDP-glucose recycling with sucrose synthase, 15-hydroxy cinmethylin conversion with UGT71E5 efficiently provided the β-mono-glucoside (≥95% yield; ∼9 mM) suitable for biological studies.

Analysis of Biomechanical Parameters of Muscle Soleus Contraction and Blood Biochemical Parameters in Rat with Chronic Glyphosate Intoxication and Therapeutic Use of C60 Fullerene.

The widespread use of glyphosate as a herbicide in agriculture can lead to the presence of its residues and metabolites in food for human consumption and thus pose a threat to human health. It has been found that glyphosate reduces energy metabolism in the brain, its amount increases in white muscle fibers. At the same time, the effect of chronic use of glyphosate on the dynamic properties of skeletal muscles remains practically unexplored. The selected biomechanical parameters (the integrated power of muscle contraction, the time of reaching the muscle contraction force its maximum value and the reduction of the force response by 50% and 25% of the initial values during stimulation) of muscle soleus contraction in rats, as well as blood biochemical parameters (the levels of creatinine, creatine phosphokinase, lactate, lactate dehydrogenase, thiobarbituric acid reactive substances, hydrogen peroxide, reduced glutathione and catalase) were analyzed after chronic glyphosate intoxication (oral administration at a dose of 10 μg/kg of animal weight) for 30 days. Water-soluble C60 fullerene, as a poweful antioxidant, was used as a therapeutic nanoagent throughout the entire period of intoxication with the above herbicide (oral administration at doses of 0.5 or 1 mg/kg). The data obtained show that the introduction of C60 fullerene at a dose of 0.5 mg/kg reduces the degree of pathological changes by 40–45%. Increasing the dose of C60 fullerene to 1 mg/kg increases the therapeutic effect by 55–65%, normalizing the studied biomechanical and biochemical parameters. Thus, C60 fullerenes can be effective nanotherapeutics in the treatment of glyphosate-based herbicide poisoning.

Single-cell RNA sequencing reveals adverse effects of paraquat on the fate commitment of murine neural stem cells

Paraquat (PQ), widely used as an agricultural herbicide, is a known neurotoxicant and linked to neurodegenerative diseases including Parkinson's disease. However, the mechanisms of PQ neurotoxicity remain to be determined. Herein, we explored the PQ neurotoxicity by focusing on its effect during murine neural stem cell (mNSC) differentiation. Based on our extensive single-cell RNA sequencing (scRNA-seq) analyses, we classified the differentiated mNSCs into eight cell subtypes, namely immature neuron, NSC, astrocyte, Purkinje cell, neuroblast, ependymal cell, OPC, and oligodendrocyte, and obtained unique transcriptome in each cell type. Significantly, PQ exposure changed the proportions of these subtypes, with decreased neurons and increased astrocytes. Such changes suggested PQ impacting neurogenesis for neurotoxicity. Besides, we analyzed the unique transcript signature (differentially expressed genes) in each cell subtype and unveiled PQ-altered cell-specific-responses in immature neurons. PQ increased intracellular and mitochondrial reactive oxygen species (ROS) in a dose-dependent manner. Intriguingly, pretreatment with mitochondria-targeted antioxidant MitoTEMPO ameliorated PQ-altered neuronal reduction. In addition, PQ dysregulated cell-to-cell communications. Taken together, our results showed that PQ altered differentiation of mNSCs and ROS played a key role in PQ-altered neuronal reduction. This study provided new insights into better understanding the neurotoxicity of PQ.

An ABCC-type transporter endowing glyphosate resistance in plants

Glyphosate is the most widely used herbicide in world agriculture and for general vegetation control in a wide range of situations. Global and often intensive glyphosate selection of very large weedy plant populations has resulted in widespread glyphosate resistance evolution in populations of many weed species. Here, working with a glyphosate-resistant (GR) Echinochloa colona population that evolved in a Western Australia agricultural field, we identified an ATP-binding cassette (ABC) transporter (EcABCC8) that is consistently up-regulated in GR plants. When expressed in transgenic rice, this EcABCC8 transporter endowed glyphosate resistance. Equally, rice, maize, and soybean overexpressing the EcABCC8 ortholog genes were made resistant to glyphosate. Conversely, CRISPR/Cas9-mediated knockout of the EcABCC8 ortholog gene OsABCC8 increased rice susceptibility to glyphosate. Subcellular localization analysis and quantification of glyphosate cellular levels in treated ABCC8 transgenic rice plants and isolated leaf protoplasts as well as structural modeling support that EcABCC8 is likely a plasma membrane-localized transporter extruding cytoplasmic glyphosate to the apoplast, lowering the cellular glyphosate level. This is a report of a membrane transporter effluxing glyphosate in a GR plant species, and its function is likely conserved in crop plant species.

Nanomaterial-enhanced 3D-printed sensor platform for simultaneous detection of atrazine and acetochlor

The widespread use of herbicides in agriculture and gardening causes environmental and safety issues such as water pollution. Thus, efficient and convenient analysis of the levels of herbicide residues is of significant importance. Here, we employed 3D-printing to design a multiplex immunosensor for simultaneous detection of two widely used herbicides, atrazine and acetochlor. Multiplexing was achieved through customization of a lateral flow immunoassay, and then integrated with an electrochemical analyzer for ultrasensitive detection. Quantification of herbicide residues was realized through the detection of a novel nanomaterial label, the mesoporous core-shell palladium@platium nanoparticle (Pd@Pt NP), for its outstanding peroxidase-like property. During the electrochemical analysis, the catalytic activity of Pd@Pt NPs on the redox reaction between thionin acetate and hydrogen peroxide provided an electrochemically driven signal that accurately indicated the level of herbicide residues. Using this Nanomaterial-enhanced multiplex electrochemical immunosensing (NEMEIS) system, simultaneous detection of atrazine and acetochlor was realized with a limit of detection of 0.24 ppb and 3.2 ppb, respectively. To further evaluate the feasibility, the optimized NEMEIS was employed for detection in atrazine and acetochlor residue-containing spiked samples, and an overall recovery with 90.8% – 117% range was obtained. The NEMEIS constructed with the aid of 3D-printing provides a rapid, precise, economical, and portable detection device for herbicides, and its success suggests potential broad applications in chemical analysis, biosensors and point-of-care monitoring.

Paraquat Poisoning and AKI –A Rare Pediatric Case Report in a Tertiary Care Hospital

Paraquat is a widely used synthetic herbicide in agriculture. Ingestion of toxic doses of paraquat can be fatal with life threatening effects on the kidneys, lungs, gastrointestinal tract (GIT), liver, heart, and other organs. There is no specific antidote or effective life saving treatment for paraquat poisoning and its prognosis is very poor worldwide. Here we report a case that presented with acute renal failure, shock, GIT bleeding with oral mucosal ulceration, and pulmonary involvement due to accidental paraquat poi soning and delayed hospitalization after poison ingestion. In spite of partial improvement, the patient expired after two weeks of admission. Therefore, any case of paraquat poisoning must be hospitalized and, if needed, referred to equipped centers as early as possible after poison ingestion

Simultaneous determination and dietary risk assessment of clethodim and its metabolites in different fruits and vegetables

ABSTRACT Clethodim is one of the most widely used herbicides in agriculture and, after field application, is metabolised to several metabolites. The potential toxicological negative effects of these compounds are poorly understood. Thus, recently, within the risk assessment framework, the European Food Safety Authority (EFSA) proposed to include the minor metabolites in the definition of clethodim residue. In this work, an easy to use and reliable UHPLC method coupled with a triple quadrupole MS/MS was developed and validated for the detection and quantification of the herbicide clethodim and related metabolites clethodim sulphone, clethodim sulphoxide, metabolites M17R and M18R in apple, grape, olive and rice. The five analytes were extracted by using a modified QuEChERS procedure, while the active ingredients were determined in multiple reaction monitoring (MRM) ion-switching mode. The proposed method showed calibration curve linearity with r2 ≥ 0.990 for all active ingredients (a.is.) both in solvent and matrix extracts. Limits of quantitation (LOQ) of the five compounds ranged from 9.44 µg/kg for M17R in olive extract to 11.01 µg/kg for clethodim in apple extract. Recoveries values ranged from 86% to 119% at two concentration levels (LOQ and 10xLOQ), while the intraday and interday precisions of the method were both below 10% in all cases. The method was successfully used for the quantification of the five a.is. in different food matrices. Furthermore, chronic dietary risk was investigated using a hazard quotients (HQ) method based on European dietary habits. The chronic dietary exposure risk quotients ranged from 1.0 × 10−5 (lower bound scenario) to 2.7 × 10−4 (upper bound scenario) which were significantly lower than 1. Data obtained indicate that the dietary exposure risks were acceptable for clethodim and its major and minor metabolites applied in apple, table grape, rice and table olive.

Developmental atrazine exposure in zebrafish produces the same major metabolites as mammals along with altered behavioral outcomes

Atrazine (ATZ) is the second most commonly applied agricultural herbicide in the United States. Due to contamination concerns, the U.S. EPA has set the maximum contaminant level in potable water sources at 3 parts per billion (ppb; μg/l). Depending on the time of year and sampling location, water sources often exceed this limit. ATZ is an endocrine disrupting chemical in multiple species observed to target the neuroendocrine system. In this study the zebrafish vertebrate model was used to test the hypothesis that a developmental ATZ exposure generates metabolites similar to those found in mammals and alters morphology and behavior in developing larvae. Adult AB zebrafish were bred, embryos were collected, and exposed to 0, 0.3, 3, or 30 ppb ATZ from 1 to 120 h post fertilization (hpf). Targeted metabolomic analysis found that zebrafish produce the same major ATZ metabolites as mammals: desethyl atrazine (DEA), deisopropyl atrazine (DIA), and diaminochloroatrazine (DACT). The visual motor response test at 120 hpf detected hyperactivity in larvae in the 0.3 ppb treatment group and hypoactivity in the 30 ppb treatment group (p < 0.05). Further analysis into behavior during the dark and light phases showed zebrafish larvae exposed to 0.3 ppb ATZ had an increase in total distance moved in the first light phase and time spent moving in the first dark and light phases (p < 0.05). Alternatively, a decrease in total distance moved was observed in the second and third dark phases in zebrafish exposed to 30 ppb ATZ (p < 0.05). No significant differences were observed for any of the morphological measurements following ATZ exposure from 1 to 120 hpf (p > 0.05). These findings suggest that a ATZ exposure during early development generates metabolite profiles similar to mammals and leads to behavioral alterations supporting ATZ as a neurodevelopmental toxicant.

Explaining Growing Glyphosate Use: The Political Economy of Herbicide-Dependent Agriculture

The growing use of chemical herbicides for weed control has become a dominant feature of modern industrial agriculture and a major environmental and health concern in agricultural systems worldwide. This paper seeks to explain how and why glyphosate-based agricultural herbicides have become so entrenched in modern agriculture. It shows that a complex interplay among technological, market, and regulatory developments have encouraged a lock-in of glyphosate linked technologies in agricultural systems. These are: (1) the repurposing of glyphosate for use with genetically modified crops; (2) the rise of the generic glyphosate market, which globalized the chemical’s use and encouraged new agricultural uses; (3) new technologies such as digital agriculture and genome editing that interface with glyphosate use; and (4) growing corporate market power and declining public investment in agricultural research programs that constrained innovation in non-herbicide weed control technologies.

Can Glyphosate-Based Herbicides Contribute to Sustainable Agriculture?

Glyphosate-based herbicides (GBHs) have become the leading agricultural herbicides used globally since the development of genetically engineered herbicide-tolerant crops. This paper investigates whether GBHs are consistent with or supportive of sustainable agriculture. Agricultural sustainability is defined by generally agreed upon goals: (1) promoting agroecology; (2) protecting soils and the Earth’s natural resources; (3) protecting biodiversity; and (4) enhancing the quality of life and health of farmers, farm workers, and society. Through an in-depth examination of the scholarly literature, the paper explores whether the scientific studies of GBHs are consistent with their sustainable applications in agriculture in the areas of human health, non-tillage agriculture, soil quality, aquatic ecosystems and beneficial, non-target species. Based on the four generally agreed upon goals listed above for agricultural sustainability, the paper finds that GBHs are not consistent with sustainability goals.

Role of 2‒13C Isotopic Glyphosate Adsorption on Silver Nanoparticles Based on Ninhydrin Reaction: A Study Based on Surface—Enhanced Raman Spectroscopy

Glyphosate is one of the most commonly used and non-selective herbicides in agriculture, which may directly pollute the environment and threaten human health. A simple and effective approach to its detection is thus quite necessary. Surface-enhanced Raman scattering (SERS) spectroscopy was shown to be a very effective method to approach the problem. However, sensitivity in SERS experiments is quite low, caused by different orientation/conformation of the adsorbed molecules on the metal surface, which limit its detection by using SERS. In this paper, 2‒13C‒glyphosate (hereafter: 13–GLP) was designed as a model molecule for theoretical and experimental studies of the molecule structure. Vibrational modes were assigned based on the modeling results obtained at the B3LYP/6-311++G** level by density functional theory (DFT) calculations, which were performed to predict the FT‒IR and Raman spectra. Band downshifts were caused by 13C atom isotopic substitution with mass changed. Moreover, SERS spectra of 13–GLP by combining ninhydrin reaction on Ag NPs were obtained. Isotopic Raman shifts are helpful in identifying the components of each Raman band through vibrations across the molecular system. They are coupled by probe molecules and thus bind to the substrates, indirectly offering the opportunity to promote interactions with Ag NPs and reduce the complex equilibrium between different orientation/conformation of glyphosate molecules on the metal surface.

Epigenome-wide association study for atrazine induced transgenerational DNA methylation and histone retention sperm epigenetic biomarkers for disease

Atrazine is a common agricultural herbicide previously shown to promote epigenetic transgenerational inheritance of disease to subsequent generations. The current study was designed as an epigenome-wide association study (EWAS) to identify transgenerational sperm disease associated differential DNA methylation regions (DMRs) and differential histone retention regions (DHRs). Gestating female F0 generation rats were transiently exposed to atrazine during the period of embryonic gonadal sex determination, and then subsequent F1, F2, and F3 generations obtained in the absence of any continued exposure. The transgenerational F3 generation males were assessed for disease and sperm collected for epigenetic analysis. Pathology was observed in pubertal onset and for testis disease, prostate disease, kidney disease, lean pathology, and multiple disease. For these pathologies, sufficient numbers of individual males with only a single specific disease were identified. The sperm DNA and chromatin were isolated from adult one-year animals with the specific diseases and analyzed for DMRs with methylated DNA immunoprecipitation (MeDIP) sequencing and DHRs with histone chromatin immunoprecipitation (ChIP) sequencing. Transgenerational F3 generation males with or without disease were compared to identify the disease specific epimutation biomarkers. All pathologies were found to have disease specific DMRs and DHRs which were found to predominantly be distinct for each disease. No common DMRs or DHRs were found among all the pathologies. Epimutation gene associations were identified and found to correlate to previously known disease linked genes. This is one of the first observations of potential sperm disease biomarkers for histone retention sites. Although further studies with expanded animal numbers are required, the current study provides evidence the EWAS analysis is effective for the identification of potential pathology epimutation biomarkers for disease susceptibility.

PSVIII-17 Modeling of glyphosate speciation in rumen fluid of cattle

Abstract Glyphosate, the active ingredient in Roundup® agricultural herbicides, is used on crops that are commonly grown for animal feed. Even though there has not been empirical data to suggest that animal productivity and health are affected when glyphosate-based products are used as labeled, accusations based on hazard identification alone have circulated widely. One of these accusations originates regarding a patent that was never held by Monsanto (now part of the Bayer Group) that did not include glyphosate. This claim hypothesizes that glyphosate could chelate minerals in the gut and prevent absorption. Formation constants measure the strength of complexation between metal ions and ligands and can be used to model the speciation in mixtures of minerals, amino acids, VFAs, and glyphosate as they exist in the rumen. The amines and carboxylic acids of all amino acids and functional side chains such as the imidazole group of histidine are potential donors for binding minerals. Likewise, carboxylic acid groups from VFAs are prevalent sources for binding of minerals. Literature references of concentrations of minerals and amino acids were used along with a measurement of glyphosate, and speciation calculations were performed at three pH’s commonly encountered in the rumen (5.8, 6.3 and 6.8). This calculation identified all species present at ≥0.01%. Using pH=6.3 as an example, 55.1% of cobalt is present as free Co2+, 28.6% is bound to a VFA (acetate, propionate or butyrate), and 13.1% is bound to histidine. The remaining 1.6% is distributed among Ala, Asp, Cys, Glu, Gly, Lys, Met, Ser, Thr, NH3 and OH. Similar results by ligand will be presented for Fe, Zn, Cu, Mn, Ca, His, Cys, and Glu. Data from these models confirm that glyphosate is a relatively weak chelator that should not have deleterious effects in the rumen.

Impact of long-term conservation agriculture induced changes in soil properties on persistence of pendimethalin under different cropping systems

Increasing use of herbicides in modern agriculture poses potential risks of crop phytotoxicity, contamination of land and water resources, and adverse impacts on human and ecosystem health. Apart from climatic conditions and soil properties, agronomic practices can significantly influence the persistence of herbicides in soil. Therefore, we assessed the impact of 13-year conservation agriculture (CA) on soil properties as well as on the fate (persistence and leaching) of pendimethalin herbicide in an alluvial sandy loam soil (Typic Haplustept) in comparison with an intensively tillage-based conventional system. The experiment involved two cropping systems (mungbean (Vigna radiata L.)–wheat (Triticum aestivum L.) and sorghum (Sorghum bicolor L.)–wheat as summer and winter crops respectively) and three tillage practices: zero tillage with crop residue retention in both summer and winter seasons (ZT-ZT), conventional tillage in summer and zero tillage with residue retention in winter (CT-ZT) and conventional tillage in both seasons (CT-CT). The adoption of ZT-ZT system resulted in a 24% increase in infiltration rate, 13% greater moisture retention and 69% higher organic carbon content in surface (0–0.05 m) soil over CT-CT. In contrast, under the CT-ZT treatment, only a small change in the above soil properties was observed, which indicated that the benefits associated with CA were negated as soon as the soil was tilled in the subsequent season. In terms of herbicide leaching, under ZT-ZT, a greater fraction (4.1% vs 2.6%) of pendimethalin residues percolated down into the subsurface soil (0.15–0.30 m) than under the CT-CT system, most likely due to greater pore connectivity with the zero-till situation. However, there was a non-significant difference in the overall dissipation of the herbicide from the surface soil (0–0.05 m) under different systems. The field study illustrated that long-term adoption of CA under mungbean–wheat and sorghum–wheat cropping systems can lead to a significant change in soil properties and these in turn can influence the fate of herbicides in soils.

Synthesis of Thiol modified magMCM-41 nanoparticles with rice husk ash as a robust, high effective, and recycling magnetic sorbent for the removal of herbicides

The presence of agricultural herbicides in the aquatic environment is one of the most important problems of water resource ecosystems. The present study was performed to remove 2,4-Dichlorophenoxyacetic acid and glyphosate herbicides from aqueous solutions by Thiol modified the magnetic mesoporous silica (magMCM-41) nanoparticles using extracted silica from rice husk ash, and the modification was performed by the 3-Mercaptopropyltrimethoxysilane (Thiol) functional group. The properties of the synthesized nanoparticles were investigated using XRD, FT-IR, TGA, VSM, pHZPC and TEM analyzes. The efficiency of the synthesized adsorbent was also studied by investigating the effect of pH, time, adsorbent dose, and initial concentrations of contaminants. The results of this study showed that the highest rate of elimination of 2,4-Dichlorophenoxyacetic acid and glyphosate was observed at herbicides the concentrations of 20 mg L−1, adsorbent dose of 0.2 gL−1, the contact time of 30 and 60 min and pH of 6 and 5 respectively. Under optimum conditions, 83.44 % and 79.38 % were removed for 2,4-Dichlorophenoxyacetic acid and glyphosate, respectively. Also, the adsorption capacity of SH-mgMCM-41 for 2,4-Dichlorophenoxyacetic acid and glyphosate is 120.36 and 108.53 mg/g, respectively. The results of the adsorption isotherms showed that the Langmuir model had a little better fit for 2,4-Dichlorophenoxyacetic acid and glyphosate with a correlation coefficient of 0.99 and 0.98, respectively. The thermodynamic results showed that the adsorption process is endothermic and spontaneous. After 5 consecutive adsorption-resorption cycles for 2,4-Dichlorophenoxyacetic acid and glyphosate, the removal efficiency was 72 % and 65 %, respectively. SH-magMCM-41 nano-adsorbent can be an effective adsorbent for the removal of 2,4-Dichlorophenoxyacetic acid and glyphosate herbicides.