Degradation Of Herbicides Research Articles

Efficient degradation of organophosphorus herbicide by free‐standing 3D reduced graphene oxide supported nFe3O4 catalytic‐activated persulfate

AbstractBACKGROUNDOrganophosphorus herbicides in water are an increasingly critical environmental problem. Given this challenge, a free‐standing 3D reduced graphene oxide (GO) foam supporting Fe3O4 nanoparticles (3D‐rGO‐Fe3O4) was synthesized using GO as a precursor and applied as an efficient persulfate activator for glyphosate (GLY) degradation.RESULTSThe effects of Fe3O4 mass, pH, oxidant dosage, temperature and common ions on GLY degradation were investigated in detail. Analytical techniques using scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR) and X‐ray photoelectron spectroscopy (XPS) indicated that the 3D foam prevented aggregation of the Fe3O4 nanoparticles by in situ uniform formation on GO nanosheets. The addition of Fe was vitally important for activation of the oxidation system. The results of batch‐scale experiments illustrated that the GLY degradation efficiency reached 96.8% with initial GLY concentration 30 mg L−1, graphene:Fe3O4 mass ratio 1:7, solution pH 4 and persulfate mass 48 mg. High temperatures could significantly facilitate GLY degradation. Additionally, the 3D‐rGO‐Fe3O4 material proved highly stable according to the replicated test results. Furthermore, EPR test results revealed that Na2S2O8 catalytic activation by 3D‐rGO‐Fe3O4 mainly produced ·OH and SO4−·, and the predominant free radical was SO4−· in the current experiment.CONCLUSIONThe results indicate that 3D‐rGO‐Fe3O4 has good catalytic activity and stability, and, accordingly, has high application prospects for the remediation of organophosphorus herbicide‐contaminated water. © 2023 Society of Chemical Industry (SCI).

Citric acid modified ultrasmall copper peroxide nanozyme for in situ remediation of environmental sulfonylurea herbicide contamination.

Herbicide residues in the environment threaten high-quality agriculture and human health. Consequently, in situ remediation of herbicide contamination is vital. We synthesized a novel self-catalyzed nanozyme, ultrasmall (2-3nm) copper peroxide nanodots modified by citric acid (CP@CA) for this purpose, which can break down into H2O2 and Cu2+ in water or soil. Ubiquitous glutathione reduces Cu2+ into Cu+, which promotes the decomposition of H2O2 into •OH through a Fenton-like reaction under mild acid conditions created by the presence of citric acid. The generated •OH efficiently degrade nicosulfuron in water and soil, and the maximum degradation efficiency could be achieved at 97.58% in water at 56min. The possible degradation mechanisms of nicosulfuron were proposed through the 25 intermediates detected. The overall ecotoxicity of the nicosulfuron system was significantly reduced after CP@CA treatment. Furthermore, CP@CA had little impact on active components of soil bacterial community. Moreover, CP@CA nanozyme could effectively remove seven other sulfonylurea herbicides from the water. In this paper, a high-efficiency method for herbicide degradation was proposed, which provides a new reference for the in situ remediation of herbicide pollution.

MoS2@SiO2 enhanced persulfate oxidation for the degradation of triazine herbicides in fixed-bed reactor

A continuous flow mode fixed-bed reactor (FBR) was built for the efficient degradation of triazine herbicides (THs) in wastewater, in which MoS2@SiO2 composites were used as a co-catalyst for the Fe2+ activated persulfate (PS) oxidation. The degradation activity of this MoS2@SiO2/PS/Fe2+ FBR was evaluated by choosing atrazine (ATZ) as a model pollutant, and operation conditions were systematically optimized, including the amount of oxidant, Fe2+ concentration, initial pH, flow rate, and coexisting interferences. The degradation results showed that MoS2@SiO2 could greatly improve the degradation efficiency, and over 97.1 % of ATZ could be degraded under the optimized conditions (hydraulic residence time of 24 s). In this reaction system, sulfate radicals and hydroxyl radicals played the major roles (over 80 %) in the degradation process. Continuous treatment of 1400 mL wastewater could be achieved with 1.0 g MoS2@SiO2 composite with a degradation efficiency maintained above 80 %. Four tested THs of ATZ, simazine, ametryn and prometryn could be efficiently degraded. Furthermore, the removal rate of ATZ in pond water reached 77.6 % and the mineralization rate was about 51 %, indicating this MoS2@SiO2/PS/Fe2+ FBR was applicable in the treatment of real wastewater.

Oxygen vacancy construction and in situ reduction of metal ions to enhance the photocatalytic performance of Bi5Nb3O15

Bi-Bi5Nb3O15-550 photocatalyst was successfully synthesized by high-temperature calcination and in-situ reduction. The composition and morphology of the photocatalyst were characterized by XRD, SEM, TEM and XPS. The photocatalytic degradation of herbicide 2,4-Dichlorophenoxyacetic acid (2,4-D) by Bi-Bi5Nb3O15-550 under visible light was investigated. The results show that the introduction of oxygen vacancies and the surface plasmon resonance effect of Bi can expand the absorption range of photocatalyst in the visible light region and accelerate the transport of photogenerated carriers and inhibit their recombination. After 120 min of irradiation, 15 mg of Bi-Bi5Nb3O15-550 can degrade 92.4 % of 2,4-D (20 mg/L). The degradation rate of 2,4-D is 13.6 times that of Bi5Nb3O15 without high-temperature calcination and in-situ reduction treatment. The degradation products and path of 2,4-D were analyzed by high resolution mass spectrometry. The mechanism of oxygen vacancy and reduced bismuth enhancing the photocatalytic activity of Bi-Bi5Nb3O15-550 was revealed.

A solar photoFenton process with calcium peroxide from eggshell and ferrioxalate complexes for the degradation of the commercial herbicide 2,4-D in water

The present study focused on the degradation of the commercial herbicide 2,4-D in water by solar photoFenton assisted with ferrioxalate complex and calcium peroxide (CaO2), using an experimental system consisting of a storage tank, a water pump, a solar reactor, and a compound parabolic concentrator (CPC), which collected solar energy of 212.102 kJ/L. The CaO2 was synthesized from eggshells, the influence of the 2,4-D concentration, oxalic acid (H2C2O4), iron (Fe3+), and CaO2 on the degradation of herbicide was evaluated by HPLC, and the intermediates such as 2,4-dichlorophenol, 1,4-benzoquinone, and oxalic acid were determined to confirm the proposed reaction mechanism. The generation of hydroxyl radicals and other reactive species, depends on the molar ratios of oxalate/Fe3+, CaO2/Fe3+, and CaO2/2,4-D. The optimum concentrations for 100 % degradation were 61.5 mg/L 2,4-D, 50.5 mg/L Fe3+, 100.5 mg/L H2C2O4, and 81 mg/L CaO2 with 42.27 % COD and 44.09 % TOC. This study highlights the viability of the solar photoFenton process to degrade the 2,4-D herbicide and aims to promote: the recovery of organic waste such as eggshells, the complexing effect of H2C2O4-Fe3+, the CaO2 as an alternative oxidant, and the application of renewable energy in the treatment of similar contaminants present in wastewater for future research.

Dicamba Degradation by Fenton-Like Process Using Iron/Biochar Composites

In this work, an iron/biochar composite was evaluated as a catalyst for 3,6-dichloro2-methoxybenzoic acid (dicamba) herbicide degradation by heterogeneous Fenton-like process. The biochar was produced from pyrolysis of coffee husks. After FeII adsorption by biochar, the material was submitted to chemical reduction, via borohydride, producing zero-valent iron nanoparticles (BIO-Fe0 ). The material was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy and energy dispersive X-ray spectroscopy, Raman scattering spectroscopy, nitrogen adsorption/desorption analysis, among other techniques. The BIO-Fe0 is a heterogeneous material, and the main constituent elements are carbon (C), oxygen (O), silicon (Si), sulfur (S) and iron (Fe). The dicamba degradation was monitored by high-performance liquid chromatography and biological assays using beans (Phaseolus vulgaris) as indicator species. The commercial dicamba (500 mL; 250 mg L-1) was submitted to Fenton-like process (initial pH 3.20; BIO-Fe0 : 3 or 5 g; 1.00 mL H2O2 at 3.00 mmol L-1; 1.00 mL Al2(SO4)3 at 1.00 mol L-1; 25 °C and 5 h of reaction), presenting ca. 100% of degradation. These treated solutions were used in a biological assay. The intoxication levels were less 30%. These results show that BIO-Fe0 has the potential to be used in the dicamba degradation by Fenton-like processes.

Decomposition and mineralization of glyphosate herbicide in water by radical and non-radical pathways through peroxymonosulfate activation using Co3O4/g-C3N4: a comprehensive study

Mechanism for the degradation of glyphosate herbicide in water by peroxymonosulfate activation using Co3O4/g-C3N4.

Comparison of plasma technology for the study of herbicide degradation.

The study aimed to investigate the effects of two different plasma systems, including pinhole plasma jet and gliding arc (GA) plasma, for the degradation of herbicide, diuron, in plasma activated solutions (PAS). In the GA plasma system, air was used to generate plasma, however, Ar, oxygen and nitrogen at different gas compositions were compared in the pinhole plasma jet system. The Taguchi design model was used to study the effects of gas compositions. Results revealed that the pinhole plasma jet system was able to degrade over 50% of the diuron in 60 minutes. The optimal plasma generation condition for the highest degradation of diuron used pure Ar gas. The highest degradation percentage of herbicide in PAS corresponded to the lowest hydrogen peroxide (H2O2) content, nitrite concentration and electrical conductivity (EC) of the PAS. The diuron degradation products were identified as 3,4-dichloro-benzenamine, 1-chloro-3-isocyanato-benzene and 1-chloro-4-isocyanato-benzene via gas chromatography-mass spectrometry (GC-MS). The GA plasma system was not adequate for the degradation of herbicide in PAS.

Bismuth-doped 3D carbon felt/PbO2 electrocatalyst for degradation of diuron herbicide and improvement of pesticide wastewater biodegradability

A bismuth-doped three-dimensional networked carbon felt/PbO2 (CF/Bi-PbO2) anode was developed for the electrocatalytic degradation of diuron and treatment of real pesticide wastewater. The prepared PbO2 anodes were characterized by FESEM, XRD, EDX, BET-BJH, accelerated lifetime test, LSV, CV and EIS. Bi doping in the PbO2 matrix significantly increased the electrochemical active area (3.17 vs. 1.57 m2 g−1), oxygen evolution potential (2.3 vs. 1.95 V) and service time (143 vs. 76 h) of CF/Bi-PbO2 anode compared to pristine CF/PbO2. The results showed that the optimized degradation efficiency of diuron by CF/Bi-PbO2 anode at pH 5 and a current density of 15 mA cm−2 after 25 min of reaction is 97.6 %. However, it took 50 min to remove COD with 98.7 % efficiency. The possible pathways of electrocatalytic degradation of diuron were discussed using HPLC-mass data. The electrocatalytic performance of PbO2 anodes was compared under optimal conditions for real pesticide wastewater treatment. Accordingly, the kinetic constant of COD removal by Bi-doped anode (0.0101 min−1) was about 2.4 times higher than pristine PbO2 (0.0043 min−1). The biodegradability index (BOD/COD ratio) of pesticide wastewater after 180 min of treatment by CF/Bi-PbO2 and CF/PbO2 anodes was 0.62 and 0.29, respectively, which shows that the wastewater treated with Bi-doped anode is completely biodegradable.

Reduced Degradation of the Herbicide 4-Chloro-2-Methylphenoxyacetic Acid (MCPA) in Soil Induced by the Fungicide Mixture Mancozeb, Metalaxyl-M, and Chlorothalonil Used in Tank Mixtures and Spray Series

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.

Impact of drinking water treatment processes on the residues of plant protection products for consumer and aquatic risk assessment: theoretical and experimental studies.

Pesticides residues can occur in ground and surface waters, and potentially react with chemicals used for water disinfection treatments, such as chlorine. This can lead to the formation of unknown reaction products, which can be more toxic and/or persistent than the active substances themselves, and therefore become a potential risk for human health and environment. Thus, in the framework of the EU Regulation 1107/2009, the identification of these by-products and their potential risk should be assessed. Within the European Food Risk Assessment (EU-FORA) Fellowship Programme, the fellow studied the behaviour of herbicides belonging to the families of imidazolinones and sulfonylureas in waters treated with chlorine disinfectants. Due to their physicochemical properties, these herbicides are susceptible of reaching natural waters. In fact, some of them have been detected in water monitoring programmes. During the experimental part of the present work programme, reactions between the active substances and the most used chlorine disinfecting reactants (hypochlorite and chloramines) were performed. Degradation kinetic parameters such as half-lives and degradation constants were calculated. Results showed that herbicide degradation was both pH and chlorine/chloramines concentration dependent. In order to identify the degradation by-products, high-resolution mass spectrometry experiments were performed, and a possible route of formation of these compounds was proposed. Finally, their risk assessment was carried out by using tox/ecotoxicological properties determined by QSAR methodology and FOCUS modelling for hazard and exposure assessment, respectively. These results will contribute to the definition of a risk assessment scheme for pesticides by-products potentially occurring in drinking water.

Plant and Microorganism Combined Degradation of Bensulfuron Herbicide in Eight Different Agricultural Soils

Sulfonylurea herbicides (SH) are widely used throughout the world. In this paper, the degradation of sulfonylurea herbicides (SH) in eight different agricultural soils was studied by exploring the synergism between microbial consortium (MC) and plants. In the experiment, chlorimuron with a concentration of 50 mg/L was used as the only carbon source to domesticate and prepare the MC. The degradation of six sulfonylurea herbicides was determined, among which bensulfuron (BN), due to its better degradation effects, was selected. The best degradation conditions of BN were determined as follows: pH 7, 20 °C, and BN concentration 20 mg/L, and after 20 days, the degradation rate of BN by MC reached 90.49%. The physical and chemical properties of eight different agricultural soils were compared, and the correlation between them and the degradation effect of BN was analyzed. When plants were combined with 3% MC to remediate BN-contaminated soil, it was beneficial to plant growth, and the degradation rate of BN was the highest (81%) after 25 days. In addition, the content of soil urease and soil catalase in the soil increased to 449 ug/g and 12.19 mmol/g after 25 days of combined remediation. The results showed an effective bioremediation strategy to restore agricultural soil contaminated by BN.

Hydrogen-Rich Water Pretreatment Alleviates the Phytotoxicity of Bispyribac-Sodium to Rice by Increasing the Activity of Antioxidant Enzymes and Enhancing Herbicide Degradation

Bispyribac-sodium (BS) is an herbicide often used to control weeds in rice fields. Hydrogen-rich water (HRW) has recently been recommended for alleviating adverse effects, but whether and how HRW alleviates the injury to rice from exposure to BS is still largely unknown. In this study, a greenhouse hydroponic experiment showed that BS alone could substantially inhibit the plant height and fresh weight of both indica and japonica rice seedlings. For indica rice, its pretreatment with HRW at 75% saturation could markedly alleviate the impact on its size but not so with either 50% or 100% HRW. For japonica rice, all the concentrations of HRW used in this study (50%, 75%, and 100% HRW) were capable of reversing the plant size reductions. Further results revealed that the HRW supplement could increase the activity of antioxidative enzymes, including that of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD), which assist in the effective removal of ROS (reactive oxygen species). Subsequent results demonstrated a weaker inhibition of the acetolactate synthase (ALS) enzyme within five days by BS in rice seedlings pretreated with HRW than those receiving the BS treatment alone, and that the HRW pretreatment can hasten the rate at which BS is degraded in rice. Taken together, these findings strongly suggest that pretreatment with HRW may offer a promising and effective strategy to improve the ability of rice to tolerate BS.

Overlooked involvement of phosphate radicals in the degradation of the atrazine herbicide by sulfate radical-based advanced oxidation

Overlooked involvement of phosphate radicals in the degradation of the atrazine herbicide by sulfate radical-based advanced oxidation

Effective Fenton-like degradation of the tebuthiuron herbicide by ferrocene functionalized g-C3N4

At the present time, proper treatments of water and wastewater stand as one of the main concerns of our society due to otherwise potential health and environmental problems. Thus, this work aimed to synthesize, characterize, and use graphitic carbon nitride (g-C3N4) functionalized with ferrocenecarboxaldehyde (Fc) to assess its performance in the oxidation of the tebuthiuron (TBT) herbicide by in situ chemical activation reaction using hydrogen peroxide (H2O2 – HP) or persulfate (S2O82− – PS) as oxidant under white light irradiation. For that, the TBT concentration as well as oxidant consumption and main products in the form of carboxylic acids and inorganic ions were monitored during the oxidation experiments. Morphological, structural, and electrochemical assays confirmed that Fc functionalized g-C3N4 (g-C3N4/Fc) was indeed obtained, showing the expected activation of the Fe(III)/Fe(II) redox pair. Using g-C3N4/Fc to activate HP and PS, a complete oxidation of TBT was achieved only when using HP under acidic conditions (pH 3, [g-C3N4/Fc] = 0.250 g L−1, [HP] = 1 mmol L−1), with a total HP consumption of 50% after 120 min of treatment. However, the degree of mineralization of the organic load was low; acetic and formic acid were the main carboxylic acids produced as well as nitrate ions, but far below the theoretical value of complete mineralization. The main oxidant species leading to TBT oxidation were the hydroxyl radical and, to lesser extent, the sulfate radical. The in situ activation process mediated by g-C3N4/Fc was also dependent on produced electrons to regenerate Fe(II) ions, especially when using HP.

Evaluating phytochemical and microbial contributions to atrazine degradation

The inclusion of warm-season grasses, such as switchgrass (Panicum virgatum) and eastern gamagrass (EG) (Tripsacum dactyloides), in vegetated buffer strips has been shown to mitigate herbicide contamination in runoff and increase herbicide degradation in soil. The mode of action by which buffer strip rhizospheres enhance herbicide degradation remains unclear, but microorganisms and phytochemicals are believed to facilitate degradation processes. The objectives of this study were to: 1) screen root extracts from seven switchgrass cultivars for the ability to degrade the herbicide atrazine (ATZ) in solution; 2) determine sorption coefficients (Kd) of the ATZ-degrading phytochemical 2-β-D-glucopyranosyloxy-4-hydroxy-1,4-benzoxazin-3-one (DBG) to soil and Ca-montmorillonite, and investigate if DBG or ATZ sorption alters degradation processes; and 3) quantify ATZ degradation rates and soil microbial response to ATZ application in mesocosms containing soil and select warm-season grasses. Phytochemicals extracted from the roots of switchgrass cultivars degraded 44–85% of ATZ in 16-h laboratory assays, demonstrating that some switchgrass cultivars could rapidly degrade ATZ under laboratory conditions. However, attempts to isolate ATZ-degrading phytochemicals from plant roots were unsuccessful. Sorption studies revealed that DBG was strongly sorbed to soil (Kd = 87.2 L kg−1) and Ca-montmorillonite (Kd = 31.7 L kg−1), and DBG driven hydrolysis of ATZ was entirely inhibited when either ATZ or DBG were sorbed to Ca-montmorillonite. Atrazine degradation rates in mesocosm soils were rapid (t0.5 = 8.2–11.2 d), but not significantly different between soils collected from the two switchgrass cultivar mesocosms, the eastern gamagrass cultivar mesocosm, and the unvegetated mesocosm (control). Significant changes in three phospholipid fatty acid biomarkers were observed among the treatments. These changes indicated that different ATZ-degrading microbial consortia resulted in equivalent ATZ degradation rates between treatments. Results demonstrated that soil microbial response was the dominant mechanism controlling ATZ degradation in the soil studied, rather than root phytochemicals.

Thermal and Biological Degradation of Herbicides to Treat Wastewater and Soil Pollution

Since their discovery in 1958, atrazine and other members of s-triazine family have been extensively applied in order to control grassy and broadleaf weeds in crops. Although, it was proved by many researchers that atrazine was slow and partially degradable material. These pesticides were widely used to enhance crop quality and yield. Atrazine degradation can be achieved by the effects of air, sun, water, microorganisms and temperature. Thermal degradation plays an important role in agrochemicals elimination; so a better understanding of the role of thermal degradation of atrazine is essential. Quantitative determination of pesticide residues was studied by calculating the amount of herbicide residues left after decomposition using a simple thermo analytical technique (TG, DSC). In this study, we found that all samples undergo the process of melting, evaporation, decomposition and oxidation at a temperature higher than the maximum registered climate temperature which made us conclude that 80–90%wt) of the pesticides stay in the environment without change under 100 °C on different parts of plants like fruits, leaves, and some penetrate into the ground to reach the roots or continue to the groundwater causes toxic problems to their consumers and environmental pollution. This result gave the motivation to find a more effective approach to reduce the harmful effect of these pollutants. In this regard, biological degradation of atrazine by using two legumes roots rhizobium bacteria was investigated. It is found that both rhizobium are able to treat atrazine at moderate temperature (30 °C). In comparison to chickpea rhizobia, bean rhizobia showed a higher performance with a removal efficiency of 43.21% and 57.42% at mild and high atrazine concentrations (5 mg/L and 10 mg/L) respectively. The results from this research offer an elegant way to remove the harmful effect of herbicides through degradation and to bring the safe use of herbicides a step closer to applications.

Effect of Three Commercial Formulations Containing Effective Microorganisms (EM) on Diflufenican and Flurochloridone Degradation in Soil.

The aim of this study was to determine the influence of effective microorganisms (EM) present in biological formulations improving soil quality on degradation of two herbicides, diflufenican and flurochloridone. Three commercially available formulations containing EM were used: a formulation containing Bifidobacterium, Lactobacillus, Lactococcus, Streptococcus, Bacillus, and Rhodopseudomonas bacteria and the yeast Saccharomyces cerevisiae; a formulation containing Streptomyces, Pseudomonas, Bacillus, Rhodococcus, Cellulomonas, Arthrobacter, Paenibacillusa, and Pseudonocardia bacteria; and a formulation containing eight strains of Bacillus bacteria, B. megaterium, B. amyloliquefaciens, B. pumilus, B. licheniformis, B. coagulans, B. laterosporus, B. mucilaginosus, and B. polymyxa. It was demonstrated that those formulations influenced degradation of herbicides. All studied formulations containing EM reduced the diflufenican degradation level, from 35.5% to 38%, due to an increased acidity of the soil environment and increased durability of that substance at lower pH levels. In the case of flurochloridone, all studied EM formulations increased degradation of that active substance by 19.3% to 31.2% at the most. For control samples, equations describing kinetics of diflufenican and flurochloridone elimination were plotted, and a time of the half-life of these substances in laboratory conditions was calculated, amounting to 25.7 for diflufenican and 22.4 for flurochloridone.

Isolation and Genome Sequence of a Novel Phosphate-Solubilizing Rhizobacterium Bacillus altitudinis GQYP101 and Its Effects on Rhizosphere Microbial Community Structure and Functional Traits of Corn Seedling.

Bacillus altitudinis is a widely distributed soil bacterium that has various functional activities, including remediation of contaminated soil, degradation of herbicides, and enhancement of plant growth. B. altitudinis GQYP101 was isolated from the rhizosphere soil of Lycium barbarum L. and demonstrated potential as a plant growth-promoting bacterium. In this work, strain GQYP101 could solubilize phosphorus, and increased the stem diameter, maximum leaf area, and fresh weight of corn in a pot experiment. Nitrogen and phosphorus contents of corn seedlings (aerial part) increased by 100% and 47.9%, respectively, after application of strain GQYP101. Concurrently, nitrogen and phosphorus contents of corn root also increased, by 55.40% and 20.3%, respectively. Furthermore, rhizosphere soil nutrients were altered and the content of available phosphorus increased by 73.2% after application of strain GQYP101. The mechanism by which strain GQYP101 improved plant growth was further investigated by whole genome sequence analysis. Strain GQYP101 comprises a circular chromosome and a linear plasmid. Some key genes of strain GQYP101 were identified that were related to phosphate solubilization, alkaline phosphatase, chemotaxis, and motility. The findings of this study may provide a theoretical basis for strain GQYP101 to enhance crop yield as microbial fertilizer.

Occurrence of herbicides in the aquatic environment and their removal using advanced oxidation processes: a critical review.

Herbicides are chemicals used globally to kill unwanted plants so as to obtain high agricultural yields and good agricultural products. Herbicides are sometimes transported from the farmlands into water bodies mainly through runoffs. These chemicals are recalcitrant, and their accumulation is hazardous to abiotic and biotic components of the ecosystem. At present, the best alternative technology for elimination of herbicides in water is the usage of advanced oxidation processes (AOPs). The AOPs, which are performed homogeneously or heterogeneously, are capable of breaking down complex pollutants in water into carbon dioxide and mineral compounds. In these processes, ·OH is produced and used for degradation process. It is recommended that the total organic carbon (TOC) produced during degradation reaction be monitored because the ‧OH produced or generated can react to form intermediates before complete mineralisation is achieved. Different kinds of AOPs for degradation of herbicides have their specific advantages as well as limitations. This report shows that AOPs are excellent techniques for degradation of herbicides in aqueous solutions, and the mechanisms showed that herbicides were mineralised. The amount and type of photocatalysts, pH of the medium, surface characteristics of the photocatalysts, doping of the photocatalysts, temperature of the medium, concentration of herbicides, presence of competing ions, intensity and irradiation period, and type of oxidants have great influence on the degradation of herbicides in water. Overall, this report showed that most AOPs could not completely degrade herbicides in water and complete degradation can be achieved by developing novel and robust AOPs that will completely mineralise herbicides in water-this will pave way for water and environmental safety.