Phytoextraction of diuron, hexazinone, and sulfometuron-methyl from the soil by green manure species

Sensitivity and antioxidant response of forest species seedlings to the atrazine under simulated conditions of subsurface water contamination

Atrazine is an herbicide with a high soil leaching capacity, contaminating subsurface water sources. Once the water table is contaminated, riparian species can be exposed to atrazine. In this way, understanding the impacts of this exposure must be evaluated for planning strategies that minimize the effects of this herbicide on native forest species. We aimed to evaluate forest species' sensitivity and antioxidant response to exposure to subsurface waters contaminated with atrazine, as well the dissipation this herbicide. The experiment was conducted in a greenhouse in a completely randomized design, with three replications and one plant per experimental unit. The treatments were arranged in a 2 × 10 factorial. The first factor corresponded to the presence or absence (control) of the atrazine in the subsurface water. The second factor comprised 10 forest species: Amburana cearensis, Anadenanthera macrocarpa, Bauhinia cheilantha, Enterolobium contortisiliquum, Hymenaea courbaril, Libidibia ferrea, Mimosa caesalpiniifolia, Mimosa tenuiflora, Myracrodruon urundeuva, and Tabebuia aurea. The forest species studied showed different sensitivity levels to atrazine in subsurface water. A. cearensis and B. cheilantha species do not have efficient antioxidant systems to prevent severe oxidative damage. The species A. macrocarpa, E. contortisiliquum, L. ferrea, and M. caesalpiniifolia are moderately affected by atrazine. H. courbaril, M. urundeuva, and T. aurea showed greater tolerance to atrazine due to the action of the antioxidant system of these species, avoiding membrane degradation events linked to the production of reactive oxygen species (ROS). Among the forest species, H. courbaril has the most significant remedial potential due to its greater tolerance and reduced atrazine concentrations in the soil.

Canavalia ensiformis enhances the phytoremediation of remineralized and sulfentrazone-contaminated tropical soils

The objective of the study was to assess the phytoremediation potential in two remineralized soils contaminated with sulfentrazone. Two soil types were evaluated: Oxisol (clayey) and Inceptisol (sandy loam), in pots, with and without the incorporation of the rock powder, at rates of 0, 4, and 8 t ha-1. Following this, sulfentrazone was applied at rates of 200, 400, 600, and 800 g a. i. ha-1, in addition to the control treatment without herbicide application, followed by the sowing of Canavalia ensiformis (jack bean). Injury level (IL) was assessed at 42 days after emergence (DAE), and biometric evaluations of the phytoremediating species were conducted at 70 and 120 DAE in the Oxisol and Inceptisol, respectively, for the following variables: height (HT), diameter (DM), trifoliate leaf number (TN), leaf area (LA), above-ground dry biomass (DB), and root dry biomass (RDB). At the end of the phytoremediation experiment, the soils were analyzed using High-Performance Liquid Chromatography (HPLC) and with Sorghum bicolor (sorghum) as a bioindicator to verify the residue of sulfentrazone. IL and DB assessments of the bioindicator species were conducted at 21 DAE. In both soils, higher herbicide rates (600 and 800 g a. i. ha-1) resulted in greater IL and reduced HT, LA, DB, and RDB of the phytoremediating species. C. ensiformis reduced the sulfentrazone residues in the soils. Although it did not directly influence phytoremediation, the rock powder improved soil fertility. In conclusion, C. ensiformis has the potential for effective phytoremediation of soils contaminated with sulfentrazone, providing safety for cultivating sensitive crops and benefiting the environment.

Phytoremediation: A green and low-cost technology to remediate herbicides in the environment

Pesticide dependence is one of the main disadvantages of agriculture. Despite the advances in biological control and integrated management of plant pests and diseases in recent years, herbicides are still essential for weed control and constitute the main class of pesticides worldwide. Herbicide residues in water, soil, air, and non-target organisms are among the biggest agricultural and environmental sustainability obstacles. Therefore, we suggest an environmentally viable alternative to reduce the harmful effects of herbicide residues, a technology called phytoremediation. Remediating plants were grouped into herbaceous, arboreal, and aquatic macrophytes. Phytoremediation can reduce the loss of at least 50% of all herbicide residues to the environment. Among the herbaceous species reported as phytoremediators of herbicides, the Fabaceae family was mentioned in more than 50% of reports. This family is also among the main species of trees reported. Regarding the most reported groups of herbicides, it is observed that most of them, regardless of the group of plants, are triazines. Processes such as extraction or accumulation are the best known and reported for most herbicides. The phytoremediation may be effective against chronic or unknown herbicide toxicity. This tool can be included in proposals for management plans and specific legislation in countries, guaranteeing public policies to maintain environmental quality.

Phytotoxicity of 2,4-D and fipronil mixtures to three green manure species

Sugarcane expansion has been associated with soil contamination by agrochemicals. Pesticides can affect plant growth, and their mixture might have potentiated effects on exposed species. This research aimed to evaluate the influence of fipronil on the phytotoxicity of 2,4-D on three green manure plant species: Canavalia ensiformis, Dolichos lablab, and Lupinus albus. Plants were exposed (for 21 days, at 25 °C) to a control soil and five concentrations of each pesticide and their combinations (36 treatments, considering a full-factorial approach). Effect concentrations of 50% growth inhibition (EC₅₀) were estimated. No phytotoxicity effects were identified when plants were exposed to different fipronil concentrations (up to 0.12 mg kg^-1). All species exposed to 2,4-D showed a decrease in shoot and root length and fresh/dry biomass. L. albus and D. lablab roots showed the highest sensitivity when exposed to 2,4-D among the endpoints (EC₅₀ = 0.02 and 0.05 mg kg^-1, respectively), while C. ensiformis roots were the most tolerant (EC₅₀ = 0.98 mg kg^-1). However, the interference of fipronil on the toxicity of 2,4-D was not detected in different mixture proportions, indicating no interaction between pesticides. Residues of 2,4-D might also impair other crops' growth, compromise productivity, and limit phytotechnologies for soil recovery.

Effects of Green Manures on Rhizosphere Fungal Community Composition of Cucumber Seedlings

Green manures are usually used to improve soil health and increase crop productivity. The activity and composition of the soil microbial community could be altered by green manures. High-throughput amplicon sequencing was used to assess the effects of green manures of wheat (Triticum aestivum) and Indian mustard (Brassica juncea) on the rhizosphere fungal community composition of cucumber (Cucumis sativus L). Results showed that green manures of wheat and Indian mustard altered the composition but not the diversity of rhizosphere fungal communities of cucumber Contents of inorganic N, Olsen P, and available K in bulk soil decreased by green manure treatments. Ascomycota, Zygomycota, and Basidiomycota were the predominant phyla in soil, and their relative abundance changed after treatment with wheat and Indian mustard. The relative abundance of Basidiomycota was increased in the green manure of wheat, while that of Zygomycota was decreased in the green manure of Indian mustard. The relative abundance of Ascomycota increased in both wheat and Indian mustard. Green manures of wheat and Indian mustard also increased the relative abundances of unclassified Sordariomycetes and Fusarium spp., whereas they decreased the relative abundances of Pseudallescheria, Mortierella, Kernia, and unclassified Chaetomiaceae spp. Compared with other treatments, green manures of wheat increased the relative abundance of Waitea sp. and decreased the relative abundance of Cephaliophora sp. Indian mustard increased the relative abundance of Humicola sp.

Development of monoclonal antibodies for the detection of diuron in water and sugarcane and their application in immunochromatographic strips

Diuron (DR) as a chemical herbicide persists in soil and water for a long time and causes extensive harm to humans. We have produced an excellent monoclonal antibody (mAb) with the ability to sensitively and specifically recognize DR in water and sugarcane samples. The semi-inhibitory concentration (IC₅₀) of this mAb was 0.28 ng mL^-1, and the limit of detection (LOD) was 0.07 ng mL^-1. Based on the mAb, an immunochromatographic assay (ICA) strip was developed. The visual detection limits of the strip assay were estimated, and the critical values of DR in water and sugarcane samples were determined to be 5 and 10 ng mL^-1, respectively, when assessed by the naked eye. The ICA strip was validated by HPLC-MS for water and sugarcane samples which had been spiked with DR. This ICA strip could be a useful tool for in-site and rapid detection of DR in water and sugarcane samples.

Effects of sulfometuron-methyl on zebrafish at early developmental stages

Sulfometuron methyl (SM) is a widely used herbicide and thus leading to accumulation in the environment. The toxicity assessments of SM in model organisms are currently rare. In the present study, zebrafish were utilized for evaluating the detrimental effects of SM in aquatic vertebrates. Zebrafish embryos were exposed to 0, 10, 20, and 40 mg/L SM from 5.5 to 72 h post-fertilization (hpf), respectively. Consequently, SM exposure resulted in increasing the mortality rate and reducing hatching rate in larval zebrafish at 10, 20, and 40 mg/L SM-treated groups. The reduced numbers of immune cells (neutrophils and macrophages) were observed after SM exposure by a dose-dependent manner. The inflammatory responses (TLR4, MYD88, IL-1β, IL-6, IL-8, IFN-γ, IL-10, and TGF-β) were measured to estimate immune responses. Anti-inflammatory factors (IL-10 and TGF-β) were down-regulated in all the treated groups and significantly altered at 40 mg/L exposure group. Additionally, behavioral tests suggested that SM treatment significantly increased the total distance, average speed, and maximum acceleration of larval zebrafish during light-dark transition and subsequently enzymology test displayed the same trend to locomotor behaviors. The content significantly increased in oxidative stress, as reflected in ROS level in all the treated groups. The numbers of cell apoptosis were significantly increased at 20, and 40 mg/L and the highest concentration group induced the substantial increment (P < 0.001) of apoptosis-related genes including p53, Bax/Bcl-2, caspase-9, and caspase-3. In summary, our results demonstrated that exposure to SM caused toxicity of development, immune system, locomotor behavior, oxidative stress, and cell apoptosis at the early developmental stages of zebrafish.

Emerging Strategies for the Bioremediation of the Phenylurea Herbicide Diuron

Diuron (DUR) is a phenylurea herbicide widely used for the effective control of most annual and perennial weeds in farming areas. The extensive use of DUR has led to its widespread presence in soil, sediment, and aquatic environments, which poses a threat to non-target crops, animals, humans, and ecosystems. Therefore, the removal of DUR from contaminated environments has been a hot topic for researchers in recent decades. Bioremediation seldom leaves harmful intermediate metabolites and is emerging as the most effective and eco-friendly strategy for removing DUR from the environment. Microorganisms, such as bacteria, fungi, and actinomycetes, can use DUR as their sole source of carbon. Some of them have been isolated, including organisms from the bacterial genera Arthrobacter, Bacillus, Vagococcus, Burkholderia, Micrococcus, Stenotrophomonas, and Pseudomonas and fungal genera Aspergillus, Pycnoporus, Pluteus, Trametes, Neurospora, Cunninghamella, and Mortierella. A number of studies have investigated the toxicity and fate of DUR, its degradation pathways and metabolites, and DUR-degrading hydrolases and related genes. However, few reviews have focused on the microbial degradation and biochemical mechanisms of DUR. The common microbial degradation pathway for DUR is via transformation to 3,4-dichloroaniline, which is then metabolized through two different metabolic pathways: dehalogenation and hydroxylation, the products of which are further degraded via cooperative metabolism. Microbial degradation hydrolases, including PuhA, PuhB, LibA, HylA, Phh, Mhh, and LahB, provide new knowledge about the underlying pathways governing DUR metabolism. The present review summarizes the state-of-the-art knowledge regarding (1) the environmental occurrence and toxicity of DUR, (2) newly isolated and identified DUR-degrading microbes and their enzymes/genes, and (3) the bioremediation of DUR in soil and water environments. This review further updates the recent knowledge on bioremediation strategies with a focus on the metabolic pathways and molecular mechanisms involved in the bioremediation of DUR.

Potential of Egeria densa and Pistia stratiotes for the phytoremediation of water contaminated with saflufenacil

Saflufenacil is an herbicide that is leachable in soil and has the potential to contaminate groundwater, besides having moderate toxicity to aquatic organisms. Some macrophyte species may interfere with the availability of herbicides in water, increasing dissipation in this environment. Thus, the objective of this work was to evaluate the absorption and dissipation of ¹⁴C-saflufenacil in water by Egeria densa and Pistia stratiotes. Dissipation was performed with ¹⁴C-saflufenacil applied directly in water and quantified by liquid scintillation spectrometry (LSS). The evaluation times were 0, 3, 6, 24, 48, 72 and 96 h after application (HAA) for E. densa and 0, 12, 24, 36, 48, 60, 84 and 108 HAA for P. stratiotes. Absorption was analyzed through plant combustion in a biological oxidizer. The presence of the macrophytes increased the dissipation of ¹⁴C-saflufenacil in water. The half-life time (DT₅₀) of the herbicide decreased by 82.6% in the presence of E. densa at 96 HAA. For P. stratiotes, the reduction in DT₅₀ was 94.8% at 108 HAA. The absorption of ¹⁴C-saflufenacil was low for both macrophytes during the evaluated time. However, the macrophytes E. densa and P. stratiotes showed potential for the phytoremediation of water contaminated with saflufenacil.

Phytoremediation of quinclorac and tebuthiuron-polluted soil by green manure plants

Quinclorac and tebuthiuron are residual herbicides that may remain in the soil longer than for the cropping season. The objective of this research was to evaluate the use of green manure plants to remediate soils treated with quinclorac and tebuthiuron. Soils were separately treated with ¹⁴C-quinclorac and ¹⁴C-tebuthiuron at 266.4 and 132 g ha^-1, respectively. After 21 days, four green manure plants, namely Crotalaria spectabilis, Canavalia ensiformis, Stizolobium aterrimum, and Lupinus albus, were separately sown in the treated soils. Overall, all four species absorbed more ¹⁴C-tebuthiuron [C. ensiformes (22.49%), S. aterrimum (16.71%), L. albus (15%), and C. spectabilis (4.48%)] than ¹⁴C-quinclorac [C. ensiformis (13.44%), L. albus (10.02%), S. aterrimum (6.2%), and C. spectabilis (1.75%)]. Quinclorac translocation in all four plants was greater in young leaves compared to old leaves, cotyledons, or roots, and ¹⁴C-tebuthiuron translocation in all four plant species was greater in old leaves and cotyledons compared to young leaves or roots. Regardless of the differences in translocation between the two herbicides, the four green manure plants are capable to remediate soils that have been treated with quinclorac and tebuthiuron. However, C. ensiformis is more efficient for the remediation of tebuthiuron-treated soil compared to the other plants.