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Surface enhanced Raman spectroscopy (SERS) is a powerful analytical technique that has found application in the trace detection of a wide range of contaminants. In this paper, we report on the fabrication of 2D silver nanodendrites, on silicon chips, synthesized by electrochemical reduction of AgNO3 at microelectrodes. The formation of nanodendrites is tentatively explained in terms of electromigration and diffusion of silver ions. Electrochemical characterization suggests that the nanodendrites do not stay electrically connected to the microelectrode. The substrates show SERS activity with an enhancement factor on the order of 106. Density functional theory simulations were carried out to investigate the suitability of the fabricated substrate for pesticide monitoring. These substrates can be functionalized with cyclodextrin macro molecules to help with the detection of molecules with low affinity with silver surfaces. A proof of concept is demonstrated with the detection of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA). [ABSTRACT FROM AUTHOR]

Background: Urea fertilizer and MCPA herbicide are widely used agrochemicals in pastures. Even though urea hydrolysis impacts soil pH, potentially affecting MCPA dissipation, little is known about the effects of their co-application into the rhizosphere. Hence, we aimed to analyze the dynamics of urea transformation and MCPA dissipation when both are co-applied to the soil. Methods: A greenhouse experiment was conducted with a planted control and treatments incorporating urea and/or MCPA. Subsequently, pH changes, urea transformation into N-NH4+ and N-NO3−, the enzymatic activity of urease and dehydrogenase, and MCPA dissipation were monitored for 30 d. Results: Urea application induced a significant (p < 0.05) pH change, production of N-NH4+ (from 50 and 250 mg kg−1) and N-NO3− (from 206 to 347 mg kg−1), and urease (from 12 to 35 µmol N-NH4+g−1 h−1) and dehydrogenase (from 0.5 to 2.5 mg TPF g−1 h−1) activities. Urea also decelerated MCPA dissipation in the latter half of the experiment, whereas MCPA reduced urease activity when urea and herbicide were co-applied. Conclusions: Urea was the primary factor modifying the properties of the rhizosphere by stimulating the activity of microbial enzymes, shaping the pH changes during its mineralization, and decelerating MCPA dissipation. MCPA did not reduce urea mineralization but slowed urease activity, constituting an insight that requires further study. [ABSTRACT FROM AUTHOR]

Herbicides, such as MCPA and clopyralid, may be transported to surface waters via runoff, which can have unintended environmental consequences. A split herbicide application strategy, wherein applications are spread across a season, may improve herbicide effectiveness, although impacts of this strategy on runoff mitigation have not been investigated. Therefore, this study aimed to (1) quantify the impact of split‐dose applications of MCPA and clopyralid on herbicide losses in surface runoff and (2) assess the impact of split‐dose applications of MCPA on the quantity and classification of MCPA‐degrading soil bacteria. Intact grassed soil sods were placed in 1 m‐long × 0.25 m‐wide × 0.1 m‐deep laboratory flumes, onto which either MCPA or clopyralid were applied in one full‐dose (13.5 kg MCPA ha−1; 2 kg clopyralid ha−1) or two split‐doses (each 6.75 kg MCPA ha−1; 1 kg clopyralid ha−1) 42 days apart. On days 2, 7 and 21 following herbicide applications, flumes were subjected to controlled rainfall simulations at an intensity of 11 mm h−1, and the herbicides in the runoff were quantified. MCPA and clopyralid concentrations in the runoff were highest immediately after the initial application. Both herbicides were below the limit of detection (0.1 μg l−1 for MCPA and 0.45 μg l−1 for clopyralid) by 44 days. No herbicides were detected in the runoff following the second split‐dose application. For MCPA, this was attributed to an adaptation in the microbial community with the emergence of bacteria possessing the tfdA class III gene in the soil. These results support split‐dose herbicide application as a strategy for agricultural management. [ABSTRACT FROM AUTHOR]

Delayed sowing of winter cereals or unfavorable weather conditions in autumn may make it impossible to carry out herbicide treatment in autumn. In such cases, weed control should be started in the spring. During this time, the plantation should be protected as effectively as possible because the weeds are at an advanced stage of growth. Therefore, they are less sensitive to applied herbicides. In the treatment, it is worth using a mixture of different mechanisms of action. Studies were conducted to evaluate the effectiveness of a band of tribenuron-methyl, and MCPA applied as soluble granules in spring control of dicotyledonous in winter cereals. The biological efficacy of herbicides was estimated in the 25 field experiments on winter cereals in Poland. Postemergence, a spring application of tribenuron-methyl + MCPA, effectively controls the majority of weed species present in spring: Anthemis arvensis, Brassica napus, Capsella bursa-pastoris, Centaurea cyanus, Lamium purpureum, Matricaria chamomilla, Tripleurospermum inodorum, Stellaria media and Thlaspi arvense. Satisfactory control was confirmed for Veronica persica, Viola arvensis, and Galium aparine. Tribenuron-methyl with MCPA is recommended for application to winter cereals in spring. To prevent the development of resistance in weeds, it is advantageous to combine two active substances.

Abstract This study encompasses a quick, efficient, repeatable and reproducible analytical method for simultaneous determination of Bromoxynil (3, 5-Dibromo-4-hydroxybenzonitrile) and MCPA (2-methyl-4-chlorophenoxyacetic acid) using RP-HPLC with UV-Detector. Bromoxynil + MCPA is one of the most selective post emergent herbicide formulations for the control of important broad leaf weeds infesting small grains (wheat, barley, oats, rye), conservation reserve program areas and grass grown for seed. Optimum weed control is achieved when Bromoxynil + MCPA is applied to actively growing weed seedlings. So, a simple, repeatable, reproducible and efficient simultaneous analytical method was developed for Bromoxynil + MCPA. The developed method was applied for the detection and quantitation of these pesticides in formulations and raw materials with excellent recoveries. It was validated according to ICH Guidelines with excellent linearity R2 = 0.992 for Bromoxynil and 0.998 for MCPA. For Bromoxynil, LOD = 1.57 mg/L and LOQ = 5.22 mg/L while for MCPA the LOD = 1.08 mg/L and LOQ = 3.62 mg/L was found. The proposed method has shown high precision (RSD %) 0.06% and 0.11% for Bromoxynil and MCPA respectively while the trueness has been calculated in terms of recovery percentage obtained as “mean value of Bromoxynil 99.53% and MCPA 100.10%” which is excellent under optimized conditions. For repeatability and reproducibility, five replicate readings of standard and sample were taken and had found within acceptable limits of relative standard deviation (RSD ≤ ± 2%). Finally, the robustness of the developed method was determined by changing flow rate and mobile phase ratios that has found within the permissible limits (% RSD NMT 1.5). So, the proposed analytical method has found to be more precise, valid and accurate at commercial scale. Graphical Abstract

2-methyl-4-chlorophenoxyacetic acid (MCPA) was successfully intercalated into zinc layered hydroxide (ZLH) by anion exchange technique followed by hydrothermal treatment, resulting in the formation of nanoherbicide, zinc-layered hydroxide-2-methyl-4-chlorophenoxyacetic acid (ZMCPA). Fourier-transform infrared spectroscopy (FTIR) and Powder X-ray diffraction (PXRD) was used to confirm the intercalation of herbicide into ZLH, while Ultraviolet-visible spectroscopy (UV-vis) was employed to assess the plant's protein content and amino acid composition before and after 1 h treatment with ZnO, MCPA and ZMCPA via the foliar technique and direct soil application. The basal spacing of ZMCPA in this study is 21.6 Å at 4.0815°, revealing the triumphant incorporation of MCPA into the ZLH host. The zinc oxide (ZnO) fingerprint from 30° to 60° that certainly vanished in the ZMCPA diffractogram indicates that all ZnO has successfully converted to ZLH matrices. The FTIR spectrum of ZMCPA shows the similarity of most MCPA spectra, but with the COO-peaks at 1610 and 1700 cm-1 replacing the intense C=O band at 1742.21 cm-1, implying that the herbicide has assimilated into the host. The protein level of the plant treated with ZMCPA was discovered to be more significant, which signifies that ZLH has effectively acted as a herbicide carrier. This study has depicted the potential of ZMCPA as a more unassailable agrochemical agent in increasing crop productivity while minimizing environmental consequences. [ABSTRACT FROM AUTHOR]

The conventional herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA) provide substantial risk to the environment such as contamination of soil and groundwater. The overuse application of conventional herbicide can leave harmful residues in soil and be washed off as runoff, thus causes toxic effect to nontarget organism. For instance, MCPA can cause toxicity to the freshwater organisms such as Daphnia magna and alga Selenastrum capricornutum. Zinc oxide as nanomaterials that are intercalated with 2-methyl-4-chlorophenoxyacetic acid (ZMCPA) herbicide may be useful to resolve the problems associated with MCPA. Nanoherbicide are known to provide a better penetration of active substances hence reduces the amount of herbicide to be applied. The nanostructured herbicide such as ZMCPA could substantially replace the conventional herbicide MCPA if it able to kill the targeted weeds efficiently and have a low risk to the environment. Therefore, it is important to compare the differences of herbicidal activity of MCPA and ZMCPA. The objective of this research is to determine the effects of MCPA and ZMCPA on growth and pigment content of Sphagneticola trilobata. The 2nd objective of this research is to measure the physiological effect and effectiveness of herbicidal activity between the conventional and nanoformulation against Sphagneticola trilobata. The preliminary study was conducted to determine a minimal concentration for MCPA to exert its effect on Sphagneticola trilobata. Then, in the main research, Sphagneticola trilobata was exposed to different concentrations of MCPA and ZMCPA in low, medium and high concentrations. The effect of MCPA and ZMCPA on growth and pigment content of Sphagneticola trilobata was observed at 7, 14 and 21 days, respectively. The results indicated there were no obvious differences in plant growth and pigment content observed between treatment of MCPA and ZMCPA at the same exposure concentration at 7, 14 and 21 days, respectively. MCPA showed higher herbicide efficacy than ZMCPA. [ABSTRACT FROM AUTHOR]

Background: Urea fertilizer and MCPA herbicide are widely used agrochemicals in pastures. Even though urea hydrolysis impacts soil pH, potentially affecting MCPA dissipation, little is known about the effects of their co-application into the rhizosphere. Hence, we aimed to analyze the dynamics of urea transformation and MCPA dissipation when both are co-applied to the soil. Methods: A greenhouse experiment was conducted with a planted control and treatments incorporating urea and/or MCPA. Subsequently, pH changes, urea transformation into N-NH4+ and N-NO3−, the enzymatic activity of urease and dehydrogenase, and MCPA dissipation were monitored for 30 d. Results: Urea application induced a significant (p < 0.05) pH change, production of N-NH4+ (from 50 and 250 mg kg−1) and N-NO3− (from 206 to 347 mg kg−1), and urease (from 12 to 35 µmol N-NH4+g−1 h−1) and dehydrogenase (from 0.5 to 2.5 mg TPF g−1 h−1) activities. Urea also decelerated MCPA dissipation in the latter half of the experiment, whereas MCPA reduced urease activity when urea and herbicide were co-applied. Conclusions: Urea was the primary factor modifying the properties of the rhizosphere by stimulating the activity of microbial enzymes, shaping the pH changes during its mineralization, and decelerating MCPA dissipation. MCPA did not reduce urea mineralization but slowed urease activity, constituting an insight that requires further study.

In the last 30 years, the area occupied by pearorchards, in Romania, is decreasing from 9974 ha to 4827.05 ha. Favorable conditions for pear cultivation can be found in 14 counties. Orchards are annually infested with weeds that compete with fruit trees for nutrients, space, water, light and reduce growth, vigor, flowering, production and fruit quality. Herbicides are an effective, easy and relatively cheap method of weed control. The effectiveness of herbicides against weeds is different for each species. The aim of this study was to reduce populations of Lamium purpureum and Ranunculus repens by using MCPA and Fluroxypyr-methyl. The testing of herbicides against the two weed species (Ranunculus repens and Lamium purpureum, was carried out in the Orchards Experimental Research Station - Lugoj Herindești (Timiș county). The experimental field included 5 variants: three treated with the hormonal herbicide MCPA 50% DMA (0.9 l/ha, 1.2 l/ha, 1.5 l/ha), one in which the herbicide Cerlit was applied (1.0 l/ha) and a control untreated variant. These herbicides were applied post-emergence (21.04.2022). The impact of MCPA and fluroxypyr, in the control of Ranunculus repens and Lamium purpureum species, was determined 10-38 days after application. 10 days after applying the treatments, the species Lamium purpureum was reduced by 70-75%, regarding the species Ranunculus repens it was observed that the product MCPA 50% DMA 1.5 l/ha managed to reduce the population in percentage of 80%. At 38 days after application, an increase in the effectiveness of herbicides in the control of segetal species was observed. [ABSTRACT FROM AUTHOR]

Pesticides and personal care products are two very important groups of contaminants posing a threat to the aquatic environment and the organisms living in it.. Therefore, this study aimed to describe the effects of widely used pesticides and parabens on aquatic non-target biota such as fish (using model organisms Danio rerio and Cyprinus carpio) and amphibians (using model organism Xenopus laevis) using a wide range of endpoints. The first part of the experiment was focused on the embryonal toxicity of three widely used pesticides (metazachlor, prochloraz, and 4-chloro-2-methyl phenoxy acetic acid) and three parabens (methylparaben, propylparaben, and butylparaben) with D. rerio, C. carpio, and X. laevis embryos. An emphasis was placed on using mostly sub-lethal concentrations that are partially relevant to the environmental concentrations of the substances studied. In the second part of the study, an embryo-larval toxicity test with C. carpio was carried out with prochloraz using concentrations 0.1, 1, 10, 100, and 1000 µg/L. The results of both parts of the study show that even the low, environmentally relevant concentrations of the chemicals tested are often able to affect the expression of genes that play either a prominent role in detoxification and sex hormone production or indicate cell stress or, in case of prochloraz, to induce genotoxicity. [ABSTRACT FROM AUTHOR]

Biochar activation methods have attracted extensive attention due to their great role in improving sorptive properties of carbon-based materials. As a result, chemically modified biochars gained application potential in the purification of soil and water from xenobiotics. This paper describes changes in selected physicochemical properties of high-temperature wheat-straw biochar (BC) upon its deashing. On the pristine and chemically activated biochar (BCd) retention of five pesticides of endocrine disrupting activity (carbaryl, carbofuran, 2,4-D, MCPA and metolachlor) was studied. Deashing resulted in increased sorbent aromaticity and abundance in surface hydroxyl groups. BCd exhibited more developed meso- and microporosity and nearly triple the surface area of BC. Hydrophobic pesticides (metolachlor and carbamates) displayed comparably high (88–98%) and irreversible adsorption on both BCs, due to the pore filling, whereas the hydrophilic and ionic phenoxyacetic acids were weakly and reversibly sorbed on BC (7.3 and 39% of 2,4-D and MCPA dose introduced). Their removal from solution and hence retention on the deashed biochar was nearly total, due to the increased sorbent surface area and interactions of the agrochemicals with unclogged OH groups. The modified biochar has the potential to serve as a superabsorbent, immobilizing organic pollutant of diverse hydrophobicity from water and soil solution. [ABSTRACT FROM AUTHOR]

The biological efficacy of herbicides MCPA+tribenuron-methyl (code name: MT-565 SG) and diflufenican+chlorotoluron (Legato Pro 425 SC) was estimated in eighteen field experiments on winter cereals in Poland and Germany to control broadleaf weeds. Postemergence application of tribenuron-methyl in combination with MCPA, applied at the 3-leaf stage to 3 tillers detectable in autumn in winter cereals, resulted in the majority of weed species occurring in autumn being effectively eliminated with MCPA+tribenuron-methyl applied at 1.0 kg∙ha–1. It also provided an acceptable (82.4–94.1%) and comparable level of control to commonly occurring weeds Brassica napus, Capsella bursa-pastoris, Centaurea cyanus, Lamium purpureum, Tripleurospermum inodorum, Stellaria media, and Thlaspi arvense. A satisfactory level of control of 66.3 to 88.3% was confirmed for Veronica persica, Viola arvensis, and Galium aparine. According to these results, the formulation of tribenuron-methyl combined with MCPA can be recommended for application in winter cereals in the autumn as an alternative to commonly available herbicides. [ABSTRACT FROM AUTHOR]

Pesticides are extensively used in agriculture to prevent infestation of crops, control plant-associated diseases and pests, and increase crop productivity. With regards to typical agricultural practice, tank mixing of two or more plant protection products or the subsequent applications of herbicides, fungicides, and insecticides are common application strategies to improve pest control. Our study provides evidence that the fungicide mixture consisting of mancozeb, metalaxyl-M, and chlorothalonil, each applied according to their recommended field rates, retarded the degradation of the phenoxy herbicide 4-chloro-2-methylphenoxyacetic acid (MPCA) in soil. MCPA dissipation times were between 1.6 and 1.9 days without and 2.5–3.5 days with co-applied fungicides. Furthermore, the proportions of extractable residues, non-extractable residues, mineralization, volatile organic compounds, and MPCA metabolism were altered by the fungicide mixture, i.e., considerably lower amounts of the main transformation product of MCPA, 4-chloro-2-methylphenol, were formed. The effects induced by the fungicides persisted throughout the experiment. Our results demonstrate that the current situation of considering individual active substances in the authorization process for plant protection products could lead to a discrepancy in the exposure assessment for humans and the environment. For specifically these cases, this calls into question whether the legally required level of protection is provided. [ABSTRACT FROM AUTHOR]

The carbon black N-220 surface was subjected to modification through H2O2 oxidation and deposition of aminopropyltriethoxysilane. The pristine (CB-NM) and modified materials (CB-Ox and CB-APTES) were characterized by N2 adsorption–desorption isotherms, scanning electron microscopy, energy-dispersive X-ray spectroscopy (SEM-EDS), thermogravimetry, and FTIR spectroscopy. Carbon black samples were applied as adsorbents for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) herbicides from aqueous solutions. The influence of their surface properties on adsorption efficiency was analyzed and discussed. The results showed that the adsorption of the herbicides was pH-dependent, and the most favorable adsorption was observed in an acidic environment. The experimental data best fit pseudo-second-order and Langmuir models for kinetic and equilibrium data, respectively. The adsorption rate of both the herbicides increased in the order of CB-APTES < CB-Ox < CB-NM and was closely correlated with the mesopore volume of the carbon blacks. The monolayer adsorption capacities were found to be 0.138, 0.340, and 0.124 mmol/g for the adsorption of 2,4-D and 0.181, 0.348, and 0.139 mmol/g for the adsorption of MCPA on CB-NM, CB-APTES, and CB-Ox, respectively. The results showed that the surface chemistry of the adsorbent plays a more important role than its porous structure. Both herbicides were preferably adsorbed on APTES-modified carbon black and were adsorbed the worst on oxidized carbon black (CB-APTES > CB-NM > CB-Ox). [ABSTRACT FROM AUTHOR]

Agricultural pesticides are known to significantly impact the non-target aquatic communities and key ecosystem processes of stream ecosystems such as litter decomposition. The unresolved questions are remaining of how such stressors interact to alter ecosystem structure and function, and how impacted ecosystems are able to maintain their ecological balance. Hence, this paper discusses the effects of the insecticide Profenofos and herbicide MCPA on Ficus racemosa and Panicum maximum litter breakdown in 40 days of indoor microcosm systems. Litter breakdown rates were analysed in microcosms treated with pesticide concentrations of 0.010, 0.025, 0.100, 0.250, 1.000 mg/L and in control tanks with no pesticides. The results of the study indicated a significant alteration of litter breakdown rate of MCPA-treated tanks compared to the control tanks in terms of reduction percentage of dry weight, remaining organic matter content, microbial community sporulation, and remaining nutrient content (p < 0.05). The herbicide MCPA accelerated the structural impairment of leaf material by destructing the leaf material. No significant differences were observed between Profenofos-treated leaf packs and control leaf packs (p < 0.05). Aquatic hyphomycetes have degraded the applied Profenofos by consuming the nutrients from the litter. These alterations were modulated by the litter quality and microbial colonizations on leaf materials. The findings of the study emphasize the effects of pesticides on the structure and functional properties of lower levels organisms in the ecological food chain and the importance of considering indirect effects of pesticides in ecological processes. [ABSTRACT FROM AUTHOR]

2-methyl-4-chlorophenoxyacetic acid (MCPA) is herbicide in group of phenoxyherbicides. It has been widely used in agriculture industry to control the weeds population especially thistle and dock. The toxicity of MCPA may impact the environment and harmful for living organisms especially human and aquatic life. This research aimed to intercalate MCPA herbicide with zinc layered hydroxide (ZLH) to form a composites (ZMCPA) and its controlled release properties. In this study, ZMCPA was prepared as an advanced delivery system by ion exchange method and further by hydrothermal treatment. The intercalations of zinc oxide were done with various MCPA concentration of 0.1 M, 0.3 M, 0.5 M, 0.7 M and 0.9 M. Intercalation performances were detected using powder X- ray diffraction (PXRD) and supported by Fourier Transform infrared spectroscopy (FTIR). The study for porosity of the composite was performed by BET analyzer. Among all of these concentrations, 0.5M represented the successful intercalation due to the presence of four sharp and intense harmonic peaks at 2θ with basal spacing of 24.6 Å, 12 Å, 8 Å and 6 Å, respectively. Herbicides release study was conducted in three salt solution, sodium chloride, sodium carbonate and sodium phosphate. Sustain release of MCPA was faster in sodium phosphate solution by 85%. This controlled release study was determined by UV-Vis spectrometry.

Photoelectron spectroscopy (PES) investigation of two widely used herbicide compounds MCPA and 2,4-D is reported. The GW calculations are shown to offer a good description of their electronic structure. There is excellent agreement between the experimental and theoretical energies of the HOMO states of 2,4-D and MCPA, which are at 8.7 eV and 8.5 eV binding energy, respectively. The low energy tail of the HOMO state extends to about 8 eV. The good agreement between the UPS (ultraviolet photoelectron spectroscopy) spectra and the simulation validates the proposed conformer. The presented gas phase data will help researchers to analyze data from liquid and diluted samples of these herbicide molecules and perform additional theoretical modelling. • The UPS spectra of two widespread herbicides MCPA and 2,4-dichlorophenoxyacetic acid have been obtained and analyzed. • A side-by-side comparison of the geometric and electronic structures is presented. • There is excellent agreement between the experimental and theoretical energies of the HOMO states of 2,4-D and MCPA, which are at 8.7 eV and 8.5 eV binding energy, respectively. [ABSTRACT FROM AUTHOR]

Metabolism data for MCPA in rat, dog and human shows a single oral dose is quantitatively and rapidly absorbed with evidence of non-linear kinetics at >100 mg/kg bw. The extent of metabolism is low and consistent between rat and human, with substantially higher metabolic conversion in dog. Parent accounts for 50%–67% dose in rat, ∼40% in human and 2%–27% in dog. No dog specific metabolite is apparent. In rat and human, MCPA and metabolites are rapidly eliminated in urine (65%–70% within 24 h) but in dog, excretion is via urine and faeces (20%–30% within 24 h), with renal excretion saturating between 5 and 100 mg/kg bw. The species difference in excretion is reflected in pharmacokinetics. Terminal half-life is similar in rat and human (15–17 h) but higher in dog (47 h). Modelling shows species differences in single dose kinetics profoundly affect systemic exposure following repeat dosing. The difference in renal excretion and systemic exposure of MCPA between dogs and rats has been attributed to species differences in active transporters (OAT1/OAT3). A new in vitro flux study in renal proximal tubules supports this hypothesis with net secretion in rat and human of a similar magnitude but significantly less in dog. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the influence of syringic acid (SA), a plant secondary metabolite (PSM), on the properties of soil contaminated with 2-methyl-4-chlorophenoxyacetic acid (MCPA) and the condition of two cucurbit species zucchini (C. pepo L. 'Atena Polka') and cucumber (C. sativus 'Cezar') grown on that soil. It was found that amendment with MCPA and MCPA + SA modified the soil physico-chemical properties. Content of N and K was significantly higher for variants amended with SA and/or MCPA, while P content was lower in variant amended with SA. The cucurbits demonstrated varied efficiencies in mitigating the phytotoxicity of the MCPA-treated soil. For soil amended with MCPA + SA, samples remediated with cucumber were characterized as slightly toxic or toxic (45.2%–81.5%), while those planted with zucchini were nontoxic or slightly toxic (−40.6%−47.8%). Development of cucumber seedlings was fully inhibited by MCPA, regardless of SA application, zucchini demonstrated enhanced growth in soil treated with MCPA + SA and no statistically significant differences between morphological parameters of MCPA + SA-treated zucchini in comparison to control plants were observed. The obtained findings suggest that the application of SA is a promising way to mitigate the toxic influence of MCPA in the soil, depending on the cultivated plant species. Novelty statement: The study meets the criteria of novelty and innovativeness. Most importantly, the study is focused on: phytotoxicity studies to inform about the limitations of phytotechnology based on PSMs. Additionally, this manuscript provides an interdisciplinary description of the effects of MCPA and naturally occurring PSM- SA on cucurbits and soil parameters. Such studies, which combine the interactions between cucurbits, their secondary metabolite (SA) and their role in mitigation of phytotoxicity in MCPA-contaminated soil, has not been performed before. [ABSTRACT FROM AUTHOR]

Pesticides and personal care products are two very important groups of contaminants posing a threat to the aquatic environment and the organisms living in it.. Therefore, this study aimed to describe the effects of widely used pesticides and parabens on aquatic non-target biota such as fish (using model organisms Danio rerio and Cyprinus carpio) and amphibians (using model organism Xenopus laevis) using a wide range of endpoints. The first part of the experiment was focused on the embryonal toxicity of three widely used pesticides (metazachlor, prochloraz, and 4-chloro-2-methyl phenoxy acetic acid) and three parabens (methylparaben, propylparaben, and butylparaben) with D. rerio, C. carpio, and X. laevis embryos. An emphasis was placed on using mostly sub-lethal concentrations that are partially relevant to the environmental concentrations of the substances studied. In the second part of the study, an embryo-larval toxicity test with C. carpio was carried out with prochloraz using concentrations 0.1, 1, 10, 100, and 1000 µg/L. The results of both parts of the study show that even the low, environmentally relevant concentrations of the chemicals tested are often able to affect the expression of genes that play either a prominent role in detoxification and sex hormone production or indicate cell stress or, in case of prochloraz, to induce genotoxicity.

Pesticides are extensively used in agriculture to prevent infestation of crops, control plant-associated diseases and pests, and increase crop productivity. With regards to typical agricultural practice, tank mixing of two or more plant protection products or the subsequent applications of herbicides, fungicides, and insecticides are common application strategies to improve pest control. Our study provides evidence that the fungicide mixture consisting of mancozeb, metalaxyl-M, and chlorothalonil, each applied according to their recommended field rates, retarded the degradation of the phenoxy herbicide 4-chloro-2-methylphenoxyacetic acid (MPCA) in soil. MCPA dissipation times were between 1.6 and 1.9 days without and 2.5–3.5 days with co-applied fungicides. Furthermore, the proportions of extractable residues, non-extractable residues, mineralization, volatile organic compounds, and MPCA metabolism were altered by the fungicide mixture, i.e., considerably lower amounts of the main transformation product of MCPA, 4-chloro-2-methylphenol, were formed. The effects induced by the fungicides persisted throughout the experiment. Our results demonstrate that the current situation of considering individual active substances in the authorization process for plant protection products could lead to a discrepancy in the exposure assessment for humans and the environment. For specifically these cases, this calls into question whether the legally required level of protection is provided.

The biological efficacy of herbicides MCPA+tribenuron-methyl (code name: MT-565 SG) and diflufenican+chlorotoluron (Legato Pro 425 SC) was estimated in eighteen field experiments on winter cereals in Poland and Germany to control broadleaf weeds. Postemergence application of tribenuron-methyl in combination with MCPA, applied at the 3-leaf stage to 3 tillers detectable in autumn in winter cereals, resulted in the majority of weed species occurring in autumn being effectively eliminated with MCPA+tribenuron-methyl applied at 1.0 kg∙ha–1. It also provided an acceptable (82.4–94.1%) and comparable level of control to commonly occurring weeds Brassica napus, Capsella bursa-pastoris, Centaurea cyanus, Lamium purpureum, Tripleurospermum inodorum, Stellaria media, and Thlaspi arvense. A satisfactory level of control of 66.3 to 88.3% was confirmed for Veronica persica, Viola arvensis, and Galium aparine. According to these results, the formulation of tribenuron-methyl combined with MCPA can be recommended for application in winter cereals in the autumn as an alternative to commonly available herbicides.

The development of biofilms on modified natural zeolites was investigated with purpose to obtain biocomposites with biodegradation activity towards pesticides MCPA (2-methyl-4-chlorophenoxyacetic acid) and glyphosate (N-(phosphonomethyl)glycine) for potential application in bioaugmentation of polluted agricultural soils. Microbial communities were selected from agricultural pesticide-contaminated soil/water samples and enriched on the basis of their ability to biodegrade the pesticides. In order to enhance affinity of microbial communities to the support material, the natural mineral zeolite was modified by nontoxic environmentally friendly cations (Li+, Na+, K+, NH4+, H+, Mg2+, Ca2+, Fe3+) by methods preserving its structure and characterised using powder XRD, surface area measurement and chemical composition analysis. Kinetics of pesticide degradation by the biocomposites was studied in liquid media. Results showed that according to zeolite modifications, the microbial activity and biodiversity changed. The best biodegradation rate of MCPA and glyphosate reached 0.12–0.13 mg/h with half-life of 16–18 h, which is considerably quicker than observed in natural environment. However, in some cases, biodegradation activity towards pesticides was lost which was connected to unfavourable zeolite modification and accumulation of toxic metabolites. High-throughput sequencing on the 16S rRNA genes of the biofilm communities highlighted the selection of bacteria genera known to metabolise MCPA (Aminobacter, Cupriavidus, Novosphingobium, Pseudomonas, Rhodococcus, Sphingobium and Sphingopyxis) and glyphosate (Pseudomonas). Altogether, results suggested that zeolites do not only have a passive role of biofilm support but also have protective and nutrient-supportive functions that consequently increase biodiversity of the pesticide degraders growing in the biofilm and influence the pesticide biodegradation rate. [ABSTRACT FROM AUTHOR]

Ten ionic liquids containing the (4-chloro-2-methylphenoxy)acetate (MCPA) anion and domiphen derived phenoxyethylammonium cation were synthesized. The obtained compounds differed in terms of the substitution of the phenoxyethylammonium group in the ring (the presence of a methyl group in the meta or para positions and the presence of chlorine in the para position) as well as the length of the alkyl chain (from hexyl to tetradecyl). The basic physicochemical properties of the obtained ionic liquids (solubility and thermal stability) were characterized and their structures were confirmed. The herbicidal activity of the compounds was tested under greenhouse conditions using cornflower (Centaurea cyanus L.) as the test plant. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess control effects of 2-methyl-4-chlorophenoxyacetic acid (MCPA) dosage, application timing and crop presence on the weed Cirsium arvense. Swedish farmers are recommended to control C. arvense chemically when most shoots are 10-20 cm tall, and mechanically at the compensation point (CP). Recent studies have shown that the CP occurs before shoots reach the three-leaf stage. We hypothesised that (i) herbicide application near the three-leaf stage gives the strongest control, (ii) crop presence increases herbicide effects, and (iii) a 50% herbicide dose gives the same effect as 100%. Treatments of the pot experiment consisted of MCPA 750; 0%, 50% and 100% of the recommended dose applied at leaf stages 3-8, with and without barley. The strongest control was obtained at four leaves and a maximum shoot height of 13 cm, using the recommended dose and with spring barley. In a field population, a maximum shoot height of 13 cm corresponded to a medium height of 6 cm. The 50% dose gave poorer control. Spraying with the recommended dose at the four-leaf stage reduced the development of C. arvense most effectively. Based on this, we recommend that herbicide spraying should be performed at earlier leaf stages/median heights than previously recommended.

An emulsification liquid–liquid microextraction (ELLME) method was successfully developed using phenolic-based deep eutectic solvent (DES) as an extraction solvent for the determination of phenoxy acid herbicides, 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 2-methyl-4-chlorophenoxyacetic acid (MCPA) in environmental water samples. Five different phenolics-based DESs were successfully synthesized by using phenol (DES 1), 2-chlorophenol (DES 2), 3-chlorophenol (DES 3), 4-chlorophenol (DES 4) and 3,4-dichlorophenol (DES 6) as the hydrogen-bond donor (HBD) and choline chloride as the hydrogen-bond acceptor (HBA). The DESs were mixed at 1 : 2 ratio. A homogeneous solution (clear solution) was observed upon the completion of successful synthesis. The synthesized DESs were characterized by using Fourier transform infrared and nuclear magnetic resonance (NMR). Under optimum ELLME conditions (50 µl of DES 2 as extraction solvent; 100 µl of THF as emulsifier solvent; pH 2; extraction time 5 min), enrichment factor obtained for dicamba and MCPA were 43.1 and 59.7, respectively. The limit of detection and limit of quantification obtained for dicamba were 1.66 and 5.03 µg l−1, respectively, meanwhile for MCPA were 1.69 and 5.12 µg l−1, respectively. The developed ELLME-DES method was applied on paddy field water samples, with extraction recoveries in the range of 79–91% for dicamba and 82–96% for MCPA.

Effective removal of 4-chloro-2-methylphenoxyacetic acid (MCPA), an emerging agrochemical contaminant in water with carcinogenic and mutagenic health effects has been reported using hydrothermally synthesized MIL-101(Cr) metal-organic framework (MOF). The properties of the MOF were ascertained using powdered X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM) and surface area and porosimetry (SAP). The BET surface area and pore volume of the MOF were 1439 m2 g−1 and 0.77 cm3 g−1, respectively. Artificial neural network (ANN) model was significantly employed for the accurate prediction of the experimental adsorption capacity (qe) values with minimal error. A rapid removal of the pollutant (99%) was recorded within short time (approx. 25 min), and the reusability of the MOF (20 mg) was achieved up to six cycles with over 90% removal efficiency. The kinetics, isotherm and thermodynamics of the process were described by the pseudo-second-order, Freundlich and endothermic adsorption, respectively. The adsorption process is spontaneous based on the negative Gibbs free energy values. The significant correlation between the experimental findings and simulation results suggests the great potential of MIL-101(Cr) for the remediation of MCPA from water matrices.

Leptospira is a genus of spirochete bacteria highly motile that includes pathogenic species responsible to cause leptospirosis disease. Chemotaxis and motility are required for Leptospira infectivity, pathogenesis, and invasion of bacteria into the host. In prokaryotes, the most common chemoreceptors are methyl-accepting chemotaxis proteins that have a role play to detect the chemical signals and move to a favorable environment for its survival. Here, we report the first crystal structure of CACHE domain of the methyl-accepting chemotaxis protein (McpA) of L. interrogans. The structural analysis showed that McpA adopts similar α/β architecture of several other bacteria chemoreceptors. We also found a typical dimerization interface that appears to be functionally crucial for signal transmission and chemotaxis. In addition to McpA structural analyses, we have identified homologous proteins and conservative functional regions using bioinformatics techniques. These results improve our understanding the relationship between chemoreceptor structures and functions of Leptospira species. Image 1 • The first chemoreceptor structure from L. interrogans was determined to 1.75 Å. • McpA structure revealed a CACHE_1 domain with dimeric interface. • McpA structure showed some structural characteristics with bacterial chemoreceptors. • McpA protein showed evolution similarity with several microorganisms. [ABSTRACT FROM AUTHOR]

4-chloro-2-methylphenoxyacetic acid (MCPA) is one of the high toxic herbicide that may cause the potential environmental risks for sediment. Thus, a simple and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for determination of MCPA in sediment samples. The best conditions for analysis were as follow: sediment sample was treated by ultrasonic extraction with the acidified acetonitrile solution; the extract was then cleaned up with GCB-NH2 solid phase extraction column; furthermore, the mobile phase consisting of acetonitrile and ultrapure water was used under gradient elution to isolate MCPA from impurities with HSS T3 column as the separator. The mass spectrometric detection was conducted in negative electrospray ionization with multiple reaction monitoring mode. The quantification of MCPA was performed using the matrix matched / external standard method. With the established method, an excellent linear relationship between chromatographic peak area and mass concentration of MCPA was obtained in the range of 1-100 μg/L (R2 = 0.9997), and the quantitation limit (LOQ) sensitively reached 0.1 μg/kg. Under the fortified level of 0.1-5 μg/kg MCPA, the satisfactory relative recoveries (80%-108%) of MCPA in sediment were achieved with relative standard deviations of 3.6%-8.2%. During the establishment of UPLC-MS method, the contradiction between 'column retention' and 'mass spectrometry ionization' of MCPA was worked out by strengthening the binding forces between MCPA and chromatographic column. This method is rapid, accurate and sensitive, and is suitable for the analysis of trace MCPA residues in sediment [ABSTRACT FROM AUTHOR]

Humic substances (HSs) as a major part of soil organic matter (SOM) are complex combinations of natural organic matter, which are ubiquitous in the environment and occur predominantly in soils, residues and natural water. They play a crucial role in the fate and behaviour of contaminants in the environment. In this work, an HS nanopore model was based on a structural motif containing polar and nonpolar domains. The polar domain was represented by the carboxyl groups that predominate in the composition of HSs, whereas the nonpolar domain was constructed by aliphatic chains. The effect of hydrophobic/hydrophilic interactions on sorption in HSs was analysed by the inclusion of the nonpolar polycyclic aromatic hydrocarbon naphthalene and the polar herbicide 2‐methyl‐4‐chlorophenoxyacetic acid (MCPA) in the nanopore. Water cluster was also included to allow the formation of the water molecular bridges (WaMB), which stabilized the whole system. Thermodynamic potential‐of‐mean‐force (PMF) calculations by means of classical molecular dynamics simulations were performed to investigate the effect of polar and nonpolar domains in the adsorption mechanism. The polar MCPA molecule was stabilized at the hydrophilic water–HS interface, whereas nonpolar naphthalene was stabilized inside of the hydrophobic nanovoid of the HS nanopore model. The obtained results demonstrated that the adsorption strength of HSs regarding polar and nonpolar species is similar, but the adsorption mechanisms differ. Highlights: The work elucidates the adsorption mechanism of polar and nonpolar species in SOM at the molecular scale.The derived HS model was suitable to describe and explain the adsorption properties of SOM by means of constrained molecular dynamics simulations.Adsorption mechanisms for polar and nonpolar species in SOM differ. Polar molecules prefer the water–SOM interface, whereas nonpolar molecules are trapped in hydrophobic nanovoids of SOM.Molecular dynamics simulation is an effective method providing a detailed description of the adsorption processes in SOM. [ABSTRACT FROM AUTHOR]

The adsorption of the phenoxy herbicides including 2-(4-chloro-2-methylphenoxy)acetic acid (MCPA), 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP), and 4-(4-chloro-2-methylphenoxy) butanoic acid (MCPB) on the activated carbons with different surface chemical properties was investigated. The activated carbon was demineralized (AC–NM) and modified by nitric acid oxidation to produce oxidized adsorbent (AC–OX) which possesses acidic surface. Basic activated carbon (AC–AM) was prepared by heat treatment in ammonia at 900°C. Adsorption of the herbicides was strongly pH dependent; no effect of ionic strength was observed. The adsorption kinetics was analyzed using pseudo-first-order and pseudo-second-order models, while the equilibrium data were examined using Langmuir and Freundlich isotherm equations. The obtained results showed that the pseudo-second-order kinetic and Langmuir isotherm models were that best fitted to the experimental data. The adsorption rate, as well as the adsorption efficiency of the herbicides on all of the adsorbents, increased in the order: MCPA < MCPP < MCPB. All of the adsorbates were preferably adsorbed on the basic activated carbon (AC–AM) although it had the lowest specific surface area, indicating that in the adsorption process the availability of the functional groups on the adsorbent surface was more important than the surface area. [ABSTRACT FROM AUTHOR]

This study deals with the evaluation of soil sorption and degradation of Agritox herbicide formulation, which contains Na-K-DMA MCPA salt (dimethyl ammonium-potassium-sodium salt of (4-chloro-2-methylphenoxy)acetic acid) as an active ingredient. It is important to quantify these two processes as they are crucial for the migration of undesirable organic compounds into surface- and groundwater. Three agricultural soils were tested using column experiments to determine the sorption of MCPA salt and incubation batch experiments to measure its dissipation kinetics. The sorption of MCPA salt in these soils was relatively low with Freundlich constant values between 0.33–4.87 mgl–1/n×l1/n/kg. Despite the small number of soil samples tested, the effect of clay and organic carbon content on MCPA salt sorption was demonstrated. This herbicide was subject to rapid degradation in soil with half-lives of 4.5–7 days and degraded most rapidly in the soil with the highest microbial activity. Due to its rapid degradation, MCPA salt could be classified as a non-leacher into groundwater [ABSTRACT FROM AUTHOR]

Monitoring and quantifying organic chemicals in the environment play a vital role in understanding their behavior and ensuring environmental safety. MCPA (2-methyl-4-chlorophenoxyacetic acid) is a commonly used phenoxy herbicide that poses potential risks to aquatic life. In this study, we present an innovative analytical approach for MCPA quantification, employing molecularly imprinted polymers (MIPs) for selective extraction and ambient plasma mass spectrometry for direct on-line analysis. To synthesize functional MIPs, we employed a post-polymerization strategy based on a thiol-ene click reaction conducted on a short-chain poly[2-(3-butenyl)-2-oxazoline] (poly(ButenOx)) that allowed attachment of 3-mercaptopropionic acid (MPA) to polymer side chains. The incorporation of MPA groups into polymer structure enabled the attainment of elevated maximum adsorption capacities and enhanced selectivity towards MCPA. Utilizing a specially designed ambient plasma mass spectrometry setup, we successfully quantified MCPA in water samples, achieving significantly improved detection limits compared to conventional solution-based analysis, whereas the quantification of MCPA in real-life river water samples demonstrated excellent recoveries. In conclusion, this novel analytical method employing MIPs and ambient plasma mass spectrometry provides an effective and sensitive approach for accurate MCPA detection in environmental water samples. The technique holds promise for facilitating reliable monitoring and management of MCPA levels in aquatic ecosystems. [Display omitted] • Poly(ButenOx) was functionalized with 3-mercaptopropionic acid with click reaction. • The obtained materials were cross-linked to obtain MIPs imprinted with MCPA. • MIPs with the highest modification degrees showed the highest adsorption properties. • Ambient mass spectrometry was used to quantify the analate adsorbed by MIPs. • Real-life sample analysis proved applicability of the proposed analytical procedure. [ABSTRACT FROM AUTHOR]

Abstract Background Impact of two widely used commercial herbicides, i.e. Aminopielik D 450 SL and Chwastox 300 SL, on the uptake and translocation of selected heavy metals in wheat plants Triticum aestivum L. cultivated in the laboratory pot experiments was investigated. Mineral-humus, loamy sand soil representative for the central part of Poland was applied. Bioavailable, exchangeable and total forms of Cd, Co, Cu, Zn, Pb, and Mn were determined. Transfer coefficients, translocation, and bioaccumulation factors illustrating metal migration in the plant were investigated. Results Administration of commercial herbicides significantly altered heavy metals uptake by wheat in a way distinctively different than that observed for the parent chemically pure synthetic auxins, i.e. 2,4-D and MCPA. In particular, Aminopielik D 450 SL and Chwastox 300 SL prompted heavy metals accumulation in roots as indicated by their high transfer coefficients. Further transport to above ground part of the plant was limited and element dependent. Conclusions This work clearly shows that commercial herbicide formulations may act in a distinctively different way than pure active ingredients alone.

The ability of microorganisms to degrade xenobiotics can be exploited to develop cost-effective and eco-friendly bioremediation technologies. Microorganisms can degrade almost all organic pollutants, but this process might be very slow in some cases. A promising way to enhance removal of recalcitrant xenobiotics from the environment lies in the interactions between plant exudates such as plant secondary metabolites (PSMs) and microorganisms. Although there is a considerable body of evidence that PSMs can alter the microbial community composition and stimulate the microbial degradation of xenobiotics, their mechanisms of action remain poorly understood. With this in mind, our aim was to demonstrate that similarity between the chemical structures of PSMs and xenobiotics results in higher micropollutant degradation rates, and the occurrence of corresponding bacterial degradative genes. To verify this, the present study analyses the influence of syringic acid, a plant secondary metabolite, on the bacterial degradation of an herbicide, 4-chloro-2-methylphenoxyacetic acid (MCPA). In particular, the presence of appropriate MCPA degradative genes, MCPA removal efficiency and changes in samples phytotoxicity have been analyzed. Significant MCPA depletion was achieved in samples enriched with syringic acid. The results confirmed not only greater MCPA removal from the samples upon spiking with syringic acid, and thus decreased phytotoxicity, but also the presence of a greater number of genes responsible for MCPA biodegradation. 16S rRNA gene sequence analysis revealed ubiquitous enrichment of the β-proteobacteria Rhodoferax, Achromobacter, Burkholderia and Cupriavidus. The obtained results provide further confirmation that plant metabolites released into the rhizosphere can stimulate biodegradation of xenobiotics, including MCPA.

The present study was focused on the application of an electrochemical oxidation process combined with biodegradation for the removal of novel Herbicidal Ionic Liquids (HILs) –promising protection plant products which incorporate herbicidal anions and ammonium cations. The influence of carbon chain length (n = 8, 10, 12, 14, 16, 18) in the dialkyldimethylammonium cations on electrochemical oxidation kinetics, degradation efficiency and biodegradation by activated sludge was investigated. It was established that the applied cation influenced the heterogeneous rate constant and diffusion coefficient of electrochemical oxidation. The oxidation efficiency ranged from 17% in case of HILs with C8 alkyl chain to approx. 60% in case of HILs comprising C14 and C16 alkyl chains after 3 h of electrochemical treatment. Subsequent biodegradation studies revealed that electrochemical oxidation improved the mineralization efficiency of the studied HILs. The mineralization efficiency of electrochemically-treated HILs ranged from 28% in case of HILs comprising the C8 alkyl chain to 57% in case of HILs with C14 and C16 alkyl chains after 28 days. In case of untreated HILs, the corresponding mineralization efficiency ranged from 0 to 8%, respectively. This confirms the feasibility of a hybrid electrochemical-biological approach for treatment of herbicidal ionic liquids based on MCPA. Image 1 • Novel MCPA-based herbicidal ionic liquids (HILs) were synthesized. • Electrochemical oxidation combined with biodegradation of HILs was studied. • Oxidation efficiency of HILs ranged from 17 to 60% depending on alkyl chain length. • Biodegradation efficiency of electrochemically-treated HILs ranged from 28 to 57. • Biodegradation efficiency of untreated HILs ranged from 0 to 8%. [ABSTRACT FROM AUTHOR]

Summary: Recently, a new implement for controlling weeds in cereals (CombCut) has been developed. It cuts weeds in growing cereals without damaging them by using the physical differences (in height, stem thickness, straw stiffness and branching pattern) between crops and weeds. To evaluate and compare the effects of selective cutting with different timings of herbicide application on Cirsium arvense in spring barley, a randomised block experiment was conducted in Sweden in 2015–2017, in a field with a naturally occurring C. arvense population. Treatments consisted of control (C), herbicide application at 4–5‐leaf stage of C. arvense (H1), herbicide application at 8–10‐leaf stage (H2) and selective cutting at 10‐leaf stage (S). The treatments were performed in 2015 and repeated in 2016 in the same plots, and a final evaluation was performed in 2017. Compared to the control, S, H1 and H2 were equally efficient in reducing above‐ground biomass production of C. arvense and increasing spring barley grain yield per unit area. The number of C. arvense shoots per area was, however, higher in S compared to H1 and H2. No differences in control effects on shoot number were observed between H1 and H2. Our study indicates that (i) selective cutting (S) reduces C. arvense equally efficient as herbicide application and (ii) early herbicide spraying is as efficient as spraying later in the season. [ABSTRACT FROM AUTHOR]

2-Methyl-4-chlorophenoxyacetic acid has been widely used as herbicide in the United States and Europe. This study aims to quantify its effects at concentrations of 0–100 mg/L for up to 48 h on the physiological status of the lichen Ramalina fraxinea. 2-Methyl-4-chlorophenoxyacetic acid exposure induced a reduction in the maximum capacity of PSII, in chlorophyll content along with chlorophyll degradation, and in adverse effects on cell membrane integrity, and induced oxidative stress in a dose- and time-dependent manner. [ABSTRACT FROM AUTHOR]

Purpose: MCPA (2-methyl-4-chlorophenoxy acetic acid) and 2,4-D (2,4-dichlorophenoxy acetic acid) have a relatively high water solubility (> 20,000 mg L−1 at 20 °C) and a few studies have examined the affinity of these herbicides for river sediments. The aim of this study was to evaluate whether the concentrations of MCPA and 2,4-D quantified in bottom sediments were associated with the characteristics and herbicide sorption-desorption parameters determined for these sediments. Materials and methods: Sixty surface bottom sediments samples (15 cm3) and water column samples (1 L) were collected from 12 sampling sites distributed across selected rivers in a prairie province of Canada, with each site being sampled four to seven times during the summer 2016. The concentrations of MCPA and 2,4-D in the sediment and water column samples were quantified by a gas chromatography coupled to triple quadrupole mass spectrometry. Sediment characteristics included determinations of the organic carbon content (OC), the percentages of sand, silt, and clay by the pipette method, as well as detailed particle size distributions (PSD) as determined using a laser diffraction particle size analyzer. Sorption of 2,4-D and MCPA by sediments was determined using standard batch equilibrium method. Results and discussion: Sediments with larger OC contents had relatively larger sorption and smaller desorption when their unimodal PSD had a narrow range (1 to 60 μm), but relatively smaller sorption and larger desorption when their unimodal PSD had a broader range (1 to 1000 μm) thus coarser particle sizes. Sediments with smaller OC contents always had relatively smaller sorption and larger desorption. The detection frequencies and concentrations in sediments were substantially greater for MCPA than 2,4-D even though batch-equilibrium experiments showed that sediments sorbed significantly less MCPA than 2,4-D. Neither MCPA nor 2,4-D concentrations detected in sediments were significantly correlated with sediment properties or their sorption-desorption characteristics. However, the detection frequencies and concentrations in water column samples were also substantially greater for MCPA than 2,4-D. Conclusions: Relatively to 2,4-D, MCPA was more frequently detected in the sediments and in greater concentrations because the more frequent presence of MCPA in the water column allowed for greater opportunities for MCPA to partition to sediments. Thus, the water column loadings of MCPA and 2,4-D, and not sediment characteristics, are the driving force for determining their frequency and concentrations in sediments. [ABSTRACT FROM AUTHOR]

This study examines the photocatalytic activity of titanium dioxide (TiO2) semiconductor supported on borosilicate tubes (cut-off 290 nm) towards removal of a mix of persistent organic pollutants (POPs) from water. For this purpose, two widely used analgesic and anti-inflammatory drugs (NSAIDs), ibuprofen (IBU) and mefenamic acid, along with MCPA sodium monohydrate, which is a common herbicide frequently used in the agricultural activities, were selected as a case study. Borosilicate tubes were coated with titanium oxide through two different approaches: sol-gel dip-coating and a hybrid nanoparticle dip-coating and plasma-enhanced chemical vapour deposition (PECVD) process. The photochemical reactor that hosts the titania-coated tubes was designed to permit continuous throughput of liquid feed stream. The photodegradation experiments were performed in laboratory conditions under artificial irradiation simulating solar light. The efficiency of direct photolysis and heterogeneous photocatalysis (TiO2) was investigated, and the performance of each coating method was evaluated. Kinetic studies for each experiment were accomplished, the overall results showed poor efficiency and insufficient removal for NSAIDs through direct photolysis, whereas applying heterogeneous photacatalysis with TiO2 coated on borosilicate tubes was found to accelerate their degradation rate with complete decomposition. Concomitantly, kinetic experimental results showed a critical difference of performance for the two coating methods used; in particular, the degradation rates of pollutants by the sol-gel-coated tubes were much faster than the degradation by the nanoparticle/PECVD-coated tubes. Using TiO2 supported on borosilicate tubes appears to be a promising alternative to conventional TiO2 suspension and avoid post-separation stages. The results achieved in this study can be used to optimise large-scale applications, and expanding the study to cover a wide range of pollutants will lead to achieve more representative results. [ABSTRACT FROM AUTHOR]

Abstract Bensulfuron-methyl (BM) and 4-chloro-2-methylphenoxyacetic acid (MCPA) are herbicides widely used in rice agroecosystems, and are commonly found in their environments, especially in water resources. The objective of this study was to evaluate the sorption-desorption, leaching, and dissipation of BM and MCPA under aerobic and anaerobic rice cropping conditions. For this purpose, a three-year field experiment was conducted in SW Spain using four management systems: aerobic with sprinkler irrigation and tillage (ST), sprinkler irrigation and no-tillage (SNT), long-term sprinkler irrigation and no-tillage (SNTLT), and anaerobic with flooding and tillage (FT). At the end of the experiment, the partition coefficients (K d -values) in ST were (2.7, 3.1, and 3.9) and (1.2, 1.5, and 1.9) times significantly lower than the values in {SNT, SNTLT, and FT} for BM and MCPA, respectively. Greater sorption was related to lower values of soil pH for both herbicides and to higher contents in humic acids for BM and fulvic acids for MCPA. The persistence was much longer for BM (t 1/2 = 26.9–52.1 days) than for MCPA (t 1/2 = 1.54–21.1 days) in all management systems, and both herbicides' dissipation rates were generally greater under aerobic than under anaerobic conditions. The mobility of MCPA was much greater than that of BM. Compared with SNT and SNTLT, leaching losses of the applied BM were greater by 51% for ST, and of the applied MCPA by 55% and 99% for ST and FT, respectively. Therefore, only aerobic rice production with no-tillage in the short- or long-terms could be considered as alternative management strategies with which to reduce water contamination by BM and MCPA in rice-growing environments. Highlights • Aerobic rice production modifies soil properties leading to changes in MCPA and BM behaviour. • Soil pH, OC, and humified fractions were major factors contributing to behaviour of both herbicides. • MCPA and BM persistence was greater under aerobic than under anaerobic conditions. • Aerobic rice production under no-tillage reduced the risk of water contamination by MCPA. • Aerobic rice under tillage may increase the risk of water contamination by BM. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The CuS/Bi 4 Ti 3 O 12 p-n heterojunction material were synthesized. • Flower like hierarchical structures with improved visible light absorption. • Intra-electric field and microscopic contact are vital for photocatalytic activity. • CuS/Bi 4 Ti 3 O 12 materials highly active for MCPA degradation under visible light. • The mechanistic details of MCPA degradation is illustrated. Abstract In this study, a series of CuS/Bi 4 Ti 3 O 12 p-n heterojunction materials were synthesized by a two-step process. Initially, the Aurivillius phase Bi 4 Ti 3 O 12 (BT) was synthesized by a facile combustion route using urea as a fuel. The Bi 4 Ti 3 O 12 was subsequently modified by deposition of CuS (5–20 wt%) using a hydrothermal route to prepare the heterojunction materials. The methods of synthesis and calcination temperature were important factors which influenced the morphology, particle size and phase purity of Bi 4 Ti 3 O 12 material. Phase pure BT nanoplates with planar dimension of 150–200 nm and thickness between 50 and 70 nm were obtained at a calcination temperature of 600 °C. Pure CuS prepared by hydrothermal method, contained hierarchical microspheres with diameter in the range of 1.2–1.6 μm. The heterostructure materials exhibited hierarchical flower like structure consisting of ultrathin CuS nanosheets and BT-nanoflakes. HRTEM and microstructural study revealed microscopic close interaction between the two phases. The optical and electrical measurement study suggested significant improvement in visible light absorption (400–800 nm) and charge carrier separation due to heterojunction formation. The CuS/Bi 4 Ti 3 O 12 materials showed excellent photocatalytic activity for aqueous phase degradation of 2-methyl-4-chlorophenoxyacetic acid (MCPA) herbicide under visible light (>95% degradation in 3 h). The rate constant for CuS/Bi 4 Ti 3 O 12 materials was 4.5 times higher than the pure BT material towards MCPA degradation. The OH and O 2 – radicals have been identified as the reactive species, the formation of which was confirmed by spectrometric method using terephthalic acid and nitroblue tetrazolium as molecular probes. The mechanism of MCPA degradation over the photocatalyst surface has also been elucidated using LC-ESI-MS, TOC and scavenger experiments. [ABSTRACT FROM AUTHOR]

The aim of this study is to assess control effects of 2-methyl-4-chlorophenoxyacetic acid (MCPA) dosage, application timing and crop presence on the weed Cirsium arvense. Swedish farmers are recommended to control C. arvense chemically when most shoots are 10-20 cm tall, and mechanically at the compensation point (CP). Recent studies have shown that the CP occurs before shoots reach the three-leaf stage. We hypothesised that (i) herbicide application near the three-leaf stage gives the strongest control, (ii) crop presence increases herbicide effects, and (iii) a 50% herbicide dose gives the same effect as 100%. Treatments of the pot experiment consisted of MCPA 750; 0%, 50% and 100% of the recommended dose applied at leaf stages 3-8, with and without barley. The strongest control was obtained at four leaves and a maximum shoot height of 13 cm, using the recommended dose and with spring barley. In a field population, a maximum shoot height of 13 cm corresponded to a medium height of 6 cm. The 50% dose gave poorer control. Spraying with the recommended dose at the four-leaf stage reduced the development of C. arvense most effectively. Based on this, we recommend that herbicide spraying should be performed at earlier leaf stages/median heights than previously recommended. [ABSTRACT FROM AUTHOR]

The ability of microorganisms to degrade xenobiotics can be exploited to develop costeffective and eco-friendly bioremediation technologies. Microorganisms can degrade almost all organic pollutants, but this process might be very slow in some cases. A promising way to enhance removal of recalcitrant xenobiotics from the environment lies in the interactions between plant exudates such as plant secondary metabolites (PSMs) and microorganisms. Although there is a considerable body of evidence that PSMs can alter the microbial community composition and stimulate the microbial degradation of xenobiotics, their mechanisms of action remain poorly understood. With this in mind, our aim was to demonstrate that similarity between the chemical structures of PSMs and xenobiotics results in higher micropollutant degradation rates, and the occurrence of corresponding bacterial degradative genes. To verify this, the present study analyses the influence of syringic acid, a plant secondary metabolite, on the bacterial degradation of an herbicide, 4-chloro-2-methylphenoxyacetic acid (MCPA). In particular, the presence of appropriate MCPA degradative genes, MCPA removal efficiency and changes in samples phytotoxicity have been analyzed. Significant MCPA depletion was achieved in samples enriched with syringic acid. The results confirmed not only greaterMCPAremoval from the samples upon spiking with syringic acid, and thus decreased phytotoxicity, but also the presence of a greater number of genes responsible for MCPA biodegradation. 16S rRNA gene sequence analysis revealed ubiquitous enrichment of the β-proteobacteria Rhodoferax, Achromobacter, Burkholderia and Cupriavidus. The obtained results provide further confirmation that plant metabolites released into the rhizosphere can stimulate biodegradation of xenobiotics, including MCPA. [ABSTRACT FROM AUTHOR]