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The responses of trace elements and secondary metabolites to stress can reflect plant adaptation to the environment. If and how the imperative trace element Fe and the defensive secondary metabolite 2,4-dihydroxy-7-methoxy-2

A new perspective was put forward to alleviate the potential toxicity of herbicide (R)-imazethapyr ((R)-IM) to non-target plant wheat by active regulation between auxin and secondary metabolite 2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazine-3(4H)-one (DIMBOA) in this study. (R)-IM effortlessly disrupted the balance between wheat growth and defense, which not only reduced 32.4% auxin content in wheat leaves, but also induced 40.7% DIMBOA accumulation compared to the control group. Transcriptomic results indicate that restoration of the auxin level in plants promotes the up-regulation of growth-related genes and increased accumulation of DIMBOA increases the expression of defense-related genes. Auxin and DIMBOA are in two divergent paths and alleviate herbicide stress on wheat primarily through effects on growth and defense, respectively. Additionally, as a common precursor of both auxin and DIMBOA, indole adopted a combined growth and defense strategy in response to (R)-IM toxicity, i.e., both restoring growth development and enhancing the defense system. It might be possible to find appropriate ways to regulate the plant growth-defense balance under herbicide stress by regulating auxin and DIMBOA levels in plants. Our insight into the interference mechanism of herbicides to the plant growth-defense system will facilitate the design of improved strategies for herbicide detoxification.

The cell walls of microalgae have an impact on the toxic effects of Cu. The addition of Cu increased the accumulation of Fe Mn, and Zn by both cell types.

Iron is an essential microelement in plants that is involved in several growth processes. The use of herbicides may cause the abnormal aggregation of iron in leaves, but the regulatory mechanisms underlying this phenomenon remain unclear. Here, we show that chiral herbicide (R)-dichlorprop ((R)-DCPP) triggers ferroptosis-like death in Arabidopsis thaliana. (R)-DCPP led to reactive oxygen species (ROS) accumulation and iron aggregation, and these processes were iron dependent. Under (R)-DCPP treatment, ROS, lipid hydrogen peroxides, and malondialdehyde were significantly accumulated. In addition, (R)-DCPP induced the depletion of glutathione, ascorbic acid, and glutathione peroxidase as well as the accumulation of toxic lipid peroxides. Thus, oxidation imbalance led to cell death, and this mode of action could be inhibited by the ferroptosis inhibitor ferrostatin-1 or ciclopirox olamine. NADPH oxidases were found to be involved in herbicide-induced ROS accumulation, and lipoxygenase and NADPH cytochrome P450 oxidase were shown to positively regulate (R)-DCPP-induced lipid peroxidation. Overall, these results indicate that the iron- and ROS-dependent signaling cascades were involved in the (R)-DCPP-induced phytotoxicity pathway, which disrupted the structure of plant cell membranes and triggered ferroptosis. Generally, this study provides new insight into the mechanisms of pesticide phytotoxicity and suggests new therapeutic directions to protect nontarget plants.

Given the recent extensive synthesis and application of ionic liquids (ILs), finding a sensitive and visual indicator to provide a fast-initial risk assessment of IL use has become a pressing issue. In this study, we verified that the phototaxis of Chlamydomonas reinhardtii is a valid indicator of the environmental risk associated with chiral ILs L-(+)- and D-(-)-1-butyl-3-methylimidazolium lactate (BMIM L). Briefly, C. reinhardtii was exposed to a 4000-lx side light source for varying lengths of time. Following the allotted exposure time, the algae aggregation was photographed, and then quantitative analysis was conducted using Image-J software to obtain the corresponding relationship between IL stimulation and C. reinhardtii phototaxis. The gray areas from each treatment were measured and the percentage was calculated. After 16 h of side lighting, for control, the percentage of gray areas was - 22%, while for L-(+)- and D-(-)- BMIM L were 17% and 33%, respectively. Then, after 8 h of darkness, where D-(-)-BMIM L and the control showed the positive phototaxis, but the L-(+)-BMIM L-treated group showed virtually no change. This phenomenon is consistent with excessive production of reactive oxygen species (ROS). Moreover, atomic force microscope (AFM) results indicated distinct aggregation between D-(-)- and L-(+)-BMIM L, which caused changes in cell permeability that induced a change in ROS transfer. Furthermore, relationship between phototaxis and changes in cell ultrastructure and photosynthetic efficiency was also investigated. This work demonstrates the potential of phototaxis to serve as a sensitive, convenient, and cost effective qualitative assessment of ILs' toxic impact, with the understanding that quantitative evaluation requires further improvement.

The Fe(III)/Fe(II) redox cycle is the main factor limiting the effectiveness of Fe-mediated advanced oxidation processes (AOPs) for the degradation of organic pollutants. In this study, the promoting effects of thin-layer Al

Plant fatty acids have indispensable physiological functions and nutritional value. However, the overuse of herbicides may cause phytotoxic disturbances of fatty acids in nontarget plants while spraying for weeds. Evidence has shown that the herbicide dichlorprop can inhibit the activity of acetyl-CoA carboxylase (ACCase), a key enzyme involved in fatty acid synthesis. However, the enantioselective phytotoxic effects of dichlorprop enantiomers ((R)-dichlorprop and (S)-dichlorprop) on fatty acids and their related mechanisms remain unclear. To solve this issue, the enantioselective phytotoxicity of dichlorprop in the model plant species Arabidopsis thaliana (A. thaliana) with a focus on fatty acids was evaluated for the first time. The results indicated a significant difference in enantioselectivity and that exposure to (R)-dichlorprop can cause marked fatty acid disturbances in nontarget plant species. Specifically, (R)-dichlorprop decreased the content of three fatty acids by more than 50% by inhibiting the activity of ACCase. In addition, increased malondialdehyde (MDA) and lipid hydroperoxides (LOOHs) contents and membrane permeability reflected herbicide-induced lipid peroxidation, which decreased the unsaturation of fatty acids in membranes and further influenced membrane composition and function. Moreover, an increased level of glutathione peroxidase (GPX) and cytochrome P450 (CYP450) reflected a plant stress-induced response. To summarize, fatty acids represent a new perspective for evaluating the toxicity of chiral pesticides, contributing to a better understanding of the enantioselective phytotoxicity and mechanisms of dichlorprop, and providing evidence for herbicide security and risk assessments.

Iron is an essential microelement in plants that is involved in several growth processes. The use of herbicides may cause the abnormal aggregation of iron in leaves, but the regulatory mechanisms underlying this phenomenon remain unclear. Here, we show that chiral herbicide (

The Fenton reaction has the advantages of short reaction time, low cost, no toxicity, and straightforward application and control. The Fenton reaction generates highly reactive HO•, which has been applied effectively. However, the effect of the generated Fe3+ has not been investigated widely. In this study, the Fenton reaction was used to improve the Cr(VI) adsorption and detoxification capacities of chitosan. After the Fenton modification, chitosan efficiently adsorbed Cr(VI) and transformed it into the less toxic Cr(III) in a wide pH range as a result of layer formation, which was described by a sandwich model. The adsorption of Cr(VI) onto the Fenton modified chitosan was in good agreement with the Freundlich adsorption model, and the adsorption capacity exceeded 120 mg/g. During the Fenton reaction, H2 O2 and HO• with high oxidative activity broke the hydrogen bonds in the chitosan structure, resulting in the release of free amine groups for Fe3+ to form metal-binding biopolymers. The distance between the chitosan polymers increased, and additional adsorption sites were created. HCrO4- entered the gap between the chitosan polymer and was adsorbed on the newly created adsorption sites. The sandwich adsorption model indicated that the Fenton modified chitosan provided a high concentration of active sites for Cr(VI) capture and detoxification. PRACTITIONER POINTS: Fenton reaction was used to improve the adsorption ability of chitosan. The formed Fe3+ in Fenton reaction was utilized. HO· broke the hydrogen bonds and Fe3+ ions chelated with chitosan in modification. Cr(VI) could be adsorbed and reduced efficiently by Fenton modified chitosan. The Fenton modified chitosan provided a high concentration of active sites for Cr(VI) capture and detoxification.

The enantioselective effects of chiral herbicides on aquatic organisms have received increasing attention. As one kind of freshwater algae responsible for most algal blooms, Microcystis aeruginosa can produce hepatotoxic microcystin and cause serious health concerns for drinking water. Thus, the effects of chiral herbicides on M. aeruginosa are of vital significance but poorly understood, especially as the structures of chiral herbicides become more complex. In this study, the enantioselective effects of four metolachlor enantiomers based on carbon center and axis chirality on M. aeruginosa were investigated for the first time at an enantiomeric level. The results of the investigation into algal growth inhibition, chlorophyll a content, and cell integrity indicated that ( S)-metolachlor [( S)-Met] was significantly more toxic than any other isomer. The toxicity ranking of different enantiomers at the highest concentration (15 mg/L) against M. aeruginosa was ( S)-Met > (α R,1' S)-Met > (α S,1' S)-Met > (α S,1' R)-Met > (α R,1' R)-Met, with (α S,1' S)-Met and (α R,1' S)-Met displaying a synergistic effect. Additionally, the Fe distribution in M. aeruginosa presented distinct enantioselectivity, which may contribute to the enantioselective toxicity of metolachlor. Furthermore, metolachlor upregulated the expression of genes mcyD and mcyH in an enantioselective manner, indicating that this herbicide can potentially promote the synthesis and efflux of microcystin, thus aggravating agricultural water contamination to different extents. Overall, this study will help to understand the ecotoxicity of metolachlor at a deeper level and provide theoretical insights into the enantioselective behaviors of metolachlor.

Pharmacologically active compounds found in reclaimed wastewater irrigation or animal manure fertilizers pose potential risks for agriculture. The mechanism underlying the effects of ketoprofen on rice (Oryza sativa L.) seedlings was investigated. The results showed that low concentrations (0.5 mg L−1) of ketoprofen slightly stimulate growth of rice seedlings, while high concentrations can significantly inhibit growth by reducing biomass and causing damage to roots. Ketoprofen affects photosynthetic pigment content (Chla, Chlb, and carotenoids) and chlorophyll synthesis gene (HEMA, HEMG, CHLD, CHLG, CHLM, and CAO) expression. Fluorescence parameters such as minimum fluorescence (F0), maximum fluorescence (Fm), variable fluorescence (Fv), potential photosynthetic capacity (Fv/F0), maximum quantum efficiency of PSII photochemistry (Fv/Fm), electron transfer rate (ETR), and Y(II), Y(NPQ), Y(NO) values were affected, showing photosynthetic electron transfer was blocked. Active oxygen radical (O2•−and H2O2), malondialdehyde and proline content increased. Superoxide dismutase, catalase and ascorbate peroxidase activities, glutathione content and antioxidant-related gene (FSD1, MSD1, CSD1, CSD2, CAT1, CAT2, CAT3, APX1, APX2) expression were induced. Higher integrated biomarker response values of eight oxidative stress response indexes were obtained at higher ketoprofen concentrations. Ultrastructure observation showed that ketoprofen causes cell structure damage, chloroplast swelling, increase in starch granules, and reduction in organelles. This study provides some suggested toxicological mechanisms and biological response indicators in rice due to stress from pharmacologically active compounds.

Persulfates are recognized as promising oxidants and an alternative to Fenton reaction for water treatment. However, activation methods in hand restrict the practical application. Herein, we explore the possibility of Fe-N complexes being a catalyst for persulfate activation for the first time. The catalyst denoted as Fe-Im-SBA was synthesized from ferric chloride, imidazole, and SBA-15 at high temperature. The internal pore structure of Fe-Im-SBA was maintained well; Fe, N and C elements are evenly distributed on the catalyst. This catalyst presents an extraordinarily catalytic activity for Rh B removal by PMS activation with a removal rate of Rh B that reached up to 97.0% in the first 5 min. It also performed well in a wide pH range with complete removal of Rh B in pH ranged from 0.5 to 10, suggesting the stability of this catalyst in both acidic and alkaline conditions. It also showed high adaptability to degrade different kinds of pollutants, which could give an attractive advantage of Fe-Im-SBA for environmental implications. Through X-ray absorption spectroscopies analysis, it shows that the active sites of Fe-Im-SBA are composed of Fe-N4 sites and Fe2–N2 sites. 1O2 were proved to generate in the Fe-Im-SBA/PMS system and serve as the major ROS. Meanwhile, graphitic carbon can accelerate the transfer of electrons, which may also be the reason for its high catalytic performance.

Cyanobacterial bloom has been rising as a worldwide issue owing to its adverse effects to water quality and ecological health. To solve this problem, hydrogen peroxide (H2O2) has been considered as a potential algaecide because no by-products are generated after treatment and because it kills cyanobacteria selectively. In addition, cytochromes P450 (CYPs) was reported to be related with H2O2, but the roles of CYPs in the regulation of H2O2 in cyanobacteria have yet to be investigated. In this study, the CYPs suicide inhibitor 1-aminobenzotriazole (ABT) was added to the representative cyanobacteria Microcystis aeruginosa (M. aeruginosa) exposed to H2O2. The results showed that CYPs mediates the effects of H2O2 on M. aeruginosa. To be exact, the addition of ABT induced greater inhibitory effects on the growth and higher reactive oxygen species levels in M. aeruginosa comparing to those treated with H2O2 alone. At the same time, photosynthetic parameters significantly decreased, and the content of extracellular microcystins (MCs) increased but the total MCs decreased due to the combined effect of H2O2 and ABT. ABT also intensified the aggregation of Fe, which might explain the effects on photosynthesis and synthesis of MCs. Furthermore, the transcriptional levels of MCs-synthesis genes (mcyA and mcyD) decreased but MCs-release gene (mcyH) increased, and photosynthetic genes (psaB, psbD1 and rbcL) decreased, which confirmed the effects on the MC production/release and electron transport of photosynthesis, respectively. In summary, this study illuminated the mediation role of CYPs in the adverse effects on M. aeruginosa induced by H2O2, thus providing new theoretical basis for the explanation of H2O2 as potential algaecide.

Efficient cycling of Fe3+/Fe2+ is a key step for the Fenton reaction. In this exploration, from microalgae, we have prepared a novel Fe-N-graphene wrapped Al2O3/pentlandite composite which showed high Fenton catalytic ability through accelerating of Fe3+ reduction. The catalyst exhibits high activity, good reusability along with stability, and wide adaptation for the organics degradation under neutral pH. High TON and H2O2 utilization efficiency have also reached by this catalyst. Characterization results disclose a unique structure that the layered Fe-N-graphene structure tightly covers on Al2O3/pentlandite particles. Mechanistic evidence suggests that the accelerated Fe3+/Fe2+ redox cycle originates from the enhanced electron transfer by the synergistic effect of Fe, Ni and Al in the catalyst, and it causes the low H2O2 consumption and high •OH generation rate. Moreover, organic radicals formed in the Fenton process also participate in the Fe3+ reduction, and this process may be accelerated by the N dop...

The chiral compound 2-(2,4-dichlorophenoxy) propionic acid (DCPP) is a widely used herbicide; the active ( R )-DCPP enantiomer has been reported to often be preferentially degraded, whereas the inactive ( S )-DCPP with greater toxicity remains in the environment. In this study, we achieved efficient enantioselective recognition and controllable degradation of ( S )-DCPP on a photoelectrocatalytic (PEC) surface by introducing a molecular imprinting technique. We fabricated an ( S )-DCPP-molecular-imprinted single-crystalline TiO 2 ( S -TiO 2 (SC)) photoelectrode in situ by constructing ( S )-DCPP molecular imprinting sites on the surface of 1D single-crystalline TiO 2 nanorods. The results revealed that the S -TiO 2 (SC) exhibited higher PEC oxidation activity (0.500 mA/cm 2 ) and electrochemical surface adsorption (4.37 × 10 −12 mol cm −2 mg) against the target ( S )-DCPP than against the non-target ( R )-DCPP. Additionally, the S -TiO 2 (SC) achieved excellent enantioselective PEC degradation of ( S )-DCPP in both the single component and racemic systems. The k value of ( S )-DCPP was 0.156 h −1 after 6 h, which was 2.6 times greater of ( R )-DCPP (0.060 h −1 ). Finally, when ( S )-DCPP was present with 100-fold concentration of ( R )-DCPP and five other contaminants, a greater anti-interference ability was demonstrated by S -TiO 2 (SC). This study highlights the need for further investigations on the enantioselective degradation of a specific enantiomer in chiral enantiomers.

Heterogeneous Fe-N complexes are a kind of promising catalysts for the Fenton-like reaction. The present study selected a stable and inexpensive g-C 3 N 4 as the chelating agent and combined with the graphitized mesoporous carbon (GMC). The fabricated Fe-g-C 3 N 4 /GMC composite was characterized by several techniques including FTIR, XRD, XPS, TEM and STXM. Results showed clear sheets of g-C 3 N 4 and graphite with Fe evenly distributed mostly in the Fe-N coordination form. The catalyst expressed high activity in the Fenton-like reaction in a wide pH range of 4–10. 99.2% removal of Acid Red 73 was obtained in 40 min, and the degradation data well fitted with the pseudo-first-order kinetics model. By correlating the constant of reaction rates calculated from the model and the Fe speciation contents of the samples prepared at different conditions, we deduced that Fe-N species are the most important active sites for the Fenton-like reaction. More importantly, hydroxyl radicals played a great role in the whole reaction yet their generation was independent of visible light. Cyclic voltammetry results confirmed that the GMC can accelerate the Fe(III)/Fe(II) redox cycle by enhancing electron transfer, and thus enable this Fenton-like catalyst to perform well in a wide pH range.

Plant fatty acids have indispensable physiological functions and nutritional value. However, the overuse of herbicides may cause phytotoxic disturbances of fatty acids in nontarget plants while spraying for weeds. Evidence has shown that the herbicide dichlorprop can inhibit the activity of acetyl-CoA carboxylase (ACCase), a key enzyme involved in fatty acid synthesis. However, the enantioselective phytotoxic effects of dichlorprop enantiomers ((

Cu

The secondary metabolism of plants is key for mediating responses to environmental stress, but few studies have examined how the relationship between secondary metabolism and the stress response of plants is affected by exposure to chiral herbicides. Here, we studied the enantioselective disturbance of the chiral herbicide imazethapyr (IM) on the secondary metabolism and nutrient levels of wheat seedlings. The bioactive enantiomer R-IM significantly increased the contents of major secondary metabolites, including phenolic acids, flavonoids, and carotenoids but greatly inhibited the production of benzoxazine. The antioxidant system also responded strongly to R-IM; specifically, the activities of SOD, CAT, and GPX enzymes were all significantly induced, and the GSH content initially increased but then decreased. Furthermore, the nutrient levels of wheat seedlings were also affected; dietary fiber content decreased, while the contents of the microelements Fe, Mn, and Zn increased. In sum, this study provides new insight into the phytotoxic effects of IM and raises new questions on the role of secondary metabolites and nutrients in mediating enantioselective effects.

Powdered activated carbons (PACs) with micrometer size are showing great potential for enabling and improving technologies in water treatment. The critical problem in achieving practical application of PAC involves simple, effective fabrication of magnetic PAC and the design of a feasible reactor that can remove pollutants and recover the adsorbent efficiently. Herein, we show that such materials can be fabricated by the combination of PAC and magnetic Fe3O4 with chitosan-Fe hydrogel through a simple co-precipitation method. According to the characterization results, CS–Fe/Fe3O4/PAC with different micrometers in size exhibited excellent magnetic properties. The adsorption of tetracycline was fast and efficient, and 99.9% removal was achieved in 30 min. It also possesses good usability and stability to co-existing ions, organics, and different pH values due to its dispersive interaction nature. Finally, the prepared CS–Fe/Fe3O4/PAC also performed well in the fluidized bed reactor with electromagnetic separation function. It could be easily separated by applying a magnetic field and was effectively in situ regenerated, indicating a potential of practical application for the removal of pollutants from water.

Effective remediation technologies which can converse the harmful organic pollutants to high-value chemicals are crucial both for wastewater treatment and energy regeneration. This study provides an evidence that extracting useful chemicals from wastewater is feasible through selective conversion of p-chlorophenol to high value formic acid as an example. The reported system works with a readily available Fe-containing ZSM-5 catalyst, water as the solvent and hydrogen peroxide as the oxidant. The yield of formic acid reached up to 50.7% when the Si/Al ratio of ZSM-5 was 80 and the Fe-content was 1.4%. By X-ray adsorption fine structure (XAFS), NH3 temperature-programmed desorption (NH3-TPD) technique, the pyridine adsorption Fourier-transition infrared (Py-IR) spectroscopy and adsorption measurements, it was concluded that the controllable degradation of p-CP could be approached through selective adsorption, the moderate Brønsted acid sites for H2O2 activation and the properly selective conversion control due to extra-framework coordination unsaturated sites (CUS) of Fe. This approach might provide a new avenue for the field of organic pollutant remediation.

Stomata in plants play vital roles in water transpiration and gas exchange necessary for photosynthesis, which are critical for the plants growth. Until now, however, the effect of chiral herbicides on the response of stomata was poorly understood. To unveil this puzzle, the enantioselective effect of chiral herbicide dichloroprop (DCPP) on stomata in Arabidopsis thaliana was investigated. It was found that (R)-DCPP preferentially promoted the extent of stomatal opening in Arabidopsis leaves, resulting in 59.84% enhancement at 0.3μmol·L(-1) comparing to the control, where (S)- and (Rac)-DCPP exhibited no significant differences. Enantioselectivity was also observed in the response of stomata to DCPP. To better understand the mechanism involved, the reactive oxygen species (ROS) production and antioxidant system defense were measured. Interestingly, the ROS production in Arabidopsis leaves was also enantioselective. The (R)-DCPP treatments resulted in 6.08-fold enhancement compared with the control, whereas 1.35- and 2.51-fold increases occurred in (S)-DCPP and (Rac)-DCPP treatments, respectively. The promoting of stomatal opening was positively correlated with ROS production. In addition, the antioxidant system response provided evidence of oxidative stress and damage caused by DCPP. This study confirmed that the ROS produced by DCPP promoted stomatal opening and suggested a potential sight to elucidate the phytotoxicity of chiral herbicides.

In order to prevent health risk from potential exposures to phthalates, a glow discharge plasma (GDP) process was applied for phthalate degradation in aqueous solution. The results revealed that the phthalate derivatives 4-hydroxyphthalic acid, 4-methylphthalic acid and 4-tert-butylphthalic anhydride could be degraded efficiently in GDP process (498 V, 0.2 A) with high removal efficiencies of over 99% in 60 minutes. Additionally, pyrite as a promising heterogeneous iron source in the Fenton reaction was found to be favorable for GDP process. The phthalate degradation reaction could be significantly enhanced by the continuous formation of •OH and the inhibition of the quenching reaction in the pyrite Fenton system due to the constant dissolution of Fe(II) from pyrite surface. Meanwhile, the initial pH value showed little impact on the degradation of phthalates and the energy efficiency of GDP system for phthalate degradation ranged between 0.280 × 10−9 and 1.210 × 10−9 mol/J, which is similar to the GDP system with phenol, bisphenol A and methyl tert-butyl ether as the substrates. Further, the X-ray diffraction and scanning electron microscopy with energy dispersive X-ray spectroscopy analyses indicated that the pyrite was relatively stable in GDP system and there was no obvious polymeric compound formed on the catalyst surface. Overall, this GDP process offers high removal efficiency, simple technology, considerable energy efficiency and the applicability to salt-containing phthalate wastewater.

The toxic effects of Cu (II) on the freshwater green algae Chlorella vulgaris and its chloroplast were investigated by detecting the responses of photosynthesis and oxidant stress. The results showed that Cu (II) arrested the growth of C. vulgaris and presented in a concentration- and time-dependent trend and the SRichards 2 model fitted the inhibition curve best. The chlorophyll fluorescence parameters, including qP, Y (II), ETR, F v /F m , and F v /F 0, were stimulated at low concentration of Cu (II) but declined at high concentration, indicating the photosystem II (PSII) of C. vulgaris was destroyed by Cu (II). The chloroplasts were extracted, and the Hill reaction activity (HRA) of chloroplast was significantly decreased with the increasing Cu (II) concentration under both illuminating and dark condition, and faster decline speed was observed under dark condition. Activities of superoxide dismutase (SOD) and catalase (CAT) and malondialdehyde (MDA) content were also significantly decreased at high concentration Cu (II), companied with a large number of reactive oxygen species (ROS) production. All these results indicated a severe oxidative stress on algal cells occurred as well as the effect on photosynthesis, thus inhibiting the growth of algae, which providing sights to evaluate the phytotoxicity of Cu (II).

Unlike the removal of chromium (Cr) ions, the efficient treatment of Cr complexes with organic ligands is a challenging issue in wastewater treatment. The generation and accumulation of highly toxic Cr(VI) species should be minimized. In this study, well-dispersed Cu2O and Fe3O4 nanoparticles inlaid in chitosan beads were prepared. This catalyst demonstrated dual functions, i.e., catalytic oxidation of Cr(III)-organic complexes and efficient inhibition of Cr(VI) accumulation in the presence of H2O2. More than 85% of the Cr(III)-organic complexes were removed in a wide pH range and a negligible amount of Cr(VI) remained in solution in the presence of 20 mmol/L H2O2. The synergistic effect of Cu2O, Fe3O4, and the chitosan matrix was the key factor for the ligand disruption and Cr removal. X-ray photoelectron spectroscopy (XPS) and electron spin resonance (ESR) analysis were used to determine the underlying mechanism. The results showed that the generated Cu+ species of Cu2O transferred electrons to accelerate the Fe(III)/Fe(II) cycle during the Fenton reaction, which favored the production of OH radicals. The generated Cr(VI) in the Fenton-like reaction was efficiently adsorbed by chitosan and reduced to Cr(III) by chitosan and Cu2O. The reduced Cr(III) was then incorporated into the surface structure of Fe3O4 and generated a stable complex oxides of Fe and Cr(III). Overall, this paper demonstrated a new method for the treatment of Cr(III)-organic complexes from wastewater.

The enantioselective toxic mechanisms of chiral herbicides in photosynthetic organisms are closely related to the production of reactive oxygen species (ROS) production, however, there are few reports on how the enantioselective production of ROS can be triggered. In suboptimal conditions, photosynthesis is one of the most important processes in the production of ROS, especially in the process of light utilization and electron transfer. In this study, we investigated the interactions between chiral herbicide dichlorprop (DCPP) enantiomers and the chiral macroaggregates of the photosynthetic light-harvesting chlorophyll a/b pigment-protein complexes (LHCII) in Scenedesmus obliquus, which is of great significance in capturing and utilizing sun light, and also in dissipating the excess excitation energy. The results of the circular dichroism indicated that DCPP induced the structural changes of the LHCII chiral macroaggregates in an enantioselective manner and that the (R)-DCPP treated-group showed a bigger change accompanied by a changed enantioselective dissipation of the excitation energy. The excitation energy was excessed in DCPP treated-groups and the degree of excess was enantioselective and the detrimental non-chemical energy triggered the enantioselective production of ROS, that induced the enantioselective toxicity to green algae S. obliquus. Overall, this study has identified that how the enantioselective production of ROS can be triggered in chloroplasts; this can help to reveal the enantioselective mechanisms of chiral herbicides to photosynthetic organisms.

Efficient cycling of Fe

Heterogeneous Pd catalytic Fenton-like systems with in-situ-generated H 2 O 2 have recently gained significant attention for wastewater treatment. Intense research efforts have been focused on developing highly efficient Fenton-like catalysts. It is known that nanoparticle size and appropriate coordination of active compositions are important for the fabrication of a highly efficient multicomponent catalyst. Unfortunately, effects of these factors on Fenton-like reaction are still unknown. To decipher the puzzle, we designed multicomponent Pd/PdO/Fe 2 O 3 nanoparticles in SBA-15 (denoted as FePd-SBA) as a Fenton-like catalyst which possesses uniform and highly dispersed nanoparticles (small size about 5 nm) in space-confined channels of SBA-15. The fabricated catalyst shows high catalytic activities in Fenton-like reaction for dye degradation. For example, 98.6% removal of dye Acid Red 73 was obtained under in-situ generation of hydrogen peroxide. In contrast, when the catalyst loaded on SiO 2 without channels or pores (FePd–SiO 2 ) was prepared, and compared with FePd–SBA, FePd–SiO 2 showed noticeably poor performance (51.6%) under same conditions. Obviously, such a difference in results is due to the confinement effect of SBA-15 porous channels. It was also found that Fe and Pd played important roles in the synergistic effect, that is, Pd worked in in-situ H 2 O 2 generation and Fe species worked in decompose H 2 O 2 to degrade organic pollutants. When we applied this catalyst for Fenton-like reaction with addition of H 2 O 2 , it was also found that Pd and PdO played important roles and the synergistic effect between Fe and Pd species actually existed in dye removal. The unique nanostructure makes the catalyst to be a novel and welcoming choice for H 2 O 2 favorite reactions.

A novel CS2-modified chitosan encapsulated magnetic Fe3O4 nanoparticles (CMCS@Fe3O4) was prepared for the removal of Cd(II) from aqueous solution. The adsorption behavior of the CMCS@Fe3O4 toward Cd(II) was studied using batch method. The CMCS@Fe3O4 showed a rapid process and a superior adsorption capacity for Cd(II). The adsorption kinetics followed the pseudo-second-order and the equilibrium data were well described by the Langmuir isotherm for the CMCS@Fe3O4. The maximum adsorption capacity of CMCS@Fe3O4 for Cd(II) was 200 mg g−1 from the Langmuir isotherm. Based on Fourier transform infrared spectroscopy analysis, the –NH2 and –SH groups on the CMCS@Fe3O4 mainly participated in the Cd(II) adsorption process. In addition, the common coexisting ions had a negligible impact on Cd(II) adsorption on the CMCS@Fe3O4. Overall, the results reported herein indicated that the CMCS@Fe3O4 is very attractive and implies a potential of practical application for the removal of toxic heavy metals.

In this study, despite the high adsorption ability, efficient catalytic activity of a chitosan–metal complex has been developed through the chelation of chitosan polymer with bimetals Cu(II) and Fe(III). The removal of C. I. Reactive Black 5 (RB 5) by the chitosan–Cu–Fe complex/H2O2 system was studied in the pH range from 4 to 12. The maximal dye removal rate was achieved at an optimal concentration of Cu and Fe in the chitosan–Cu–Fe matrix, demonstrating the combination of sorptive enrichment and catalytic degradation. The results indicated that TOC removal and discoloration of the dye achieved 89.9% and 96.5% in a short reaction time. The pH sensitivity of the chitosan complex, the effect of the coexisting ions and the adsorption of other anionic dyes were also studied. X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) were analyzed to study the structure of the chitosan bi-metal complex and a possible mechanism was proposed.

A novel adsorbent of carbonaceous sulfur-containing chitosan–Fe(III) was developed for copper (II) removal from water. This adsorbent showed an excellent performance in copper removal due to its fast kinetic behavior, high adsorption capacity and relatively good ability to resist acidic conditions. The adsorption of Cu2+ was observed to be fast in the beginning 2.5 min followed by a slower adsorption process, and eventually equilibrium was reached in about 15 min. The Cu2+ adsorption isotherm was well described by Langmuir model. The calculated adsorption capacity of carbonaceous sulfur-containing chitosan–Fe(III) for Cu2+ was up to 413.2 mg/g, which is higher than most (of the) values reported before. The main mechanism of Cu2+ adsorption is chelation with the O as well as small contribution from S atoms in the molecules. During the preparation process of this adsorbent, the majority of the sulfur binds with iron. Both sulfur and Fe contribute to the formation of a stable and regular matrix with macropores, which increase the access to the adsorption sites for Cu2+. Overall, this study indicates that there is potential to use carbonaceous sulfur-containing chitosan–Fe(III) to remove Cu2+ from water in practical applications.

A high-dispersive FeS2 micro-cube crystal on graphene oxide (FeS2@GO) was fabricated by a one-pot hydrothermal method. The catalytic degradation of 4-chlorophenol (4-CP) and its mechanism in a FeS2@GO-based Fenton system was investigated. Under acidic to slight alkaline conditions, FeS2@GO demonstrated an excellent capacity to remove 4-CP. More than 97% of 4-CP was eliminated within 60 min in pH 7.0 reaction solutions initially containing 0.2 g L−1 FeS2@GO, 128.6 mg L−1 4-CP and 100 mM H2O2 at 25 ± 1 °C, and the removal of 4-CP was further enhanced with increasing FeS2@GO loadings. In the meantime, the FeS2@GO also achieved lower iron leaching and a more complete TOC removal compared with pure synthetic FeS2 without graphene oxide. Furthermore, acetic acid and oxalic acid were identified as the primary products. The remarkable capacity of the FeS2@GO-based Fenton system in removing 4-CP displays its potential application in the treatment of organic compound-contaminated water.

For dewatering and resource utilization of sewage sludge, catalyst preparation paralleled with sewage sludge dewatering, was explored. In order to obtain a better understanding of this strategy, an anaerobic sludge based MnOx catalyst (MnOx/HCAS) was characterized, and tested in activation of Oxone for dye degradation in aqueous solution. The multi-valence oxidation states of manganese were formed in MnOx/HCAS. The catalyst exhibits high catalytic activity towards Oxone for the degradation of dyes in aqueous solution. The kinetic data followed first order kinetics with an activation energy of 21.87 kJ mol−1. The evaluation of the reusability of MnOx/HCAS showed that MnOx/HCAS exhibited high stability in recycled tests without losing its activity. The removal of a variety of anionic dyes also demonstrates an excellent catalytic performance of MnOx/HCAS. To investigate stabilization of heavy metals in the catalyst, a leaching test was conducted, and the result showed that heavy metals can be solidified to prevent their leaching into solution. The effect of different kinds of wet sludge was investigated. And all these sludge based MnOx catalysts exhibit good catalytic performance with azo dyes with degradation rates more than 98%, which decides its unquestionable possibility for fabrication of MnOx heterogeneous catalysts from wet sludge and its practical applications.

A green efficient strategy for the combination of biodegradation and adsorption methods is urgently desired nowadays to degrade dyes in an economical and effective way. In this study, a kind of novel, environmentally friendly and efficient hybrid for the fungus and chitosan–Fe membrane has been fabricated by the alginate approach. Myrothecium verrucaria I-5 and C-1, deuteromycete fungi capable of producing laccase to degrade dyes, have been used. It is found that the chitosan–Fe membrane can excellently immobilize the fungi mycelia and enzyme, and after the immobilization, the fungi and enzyme still maintain a high activity after the dye decolorization. Also, the immobilized fungi membranes have been proved to have a high efficiency for dye decolorization. Simultaneously, the decolorization ability of the crude enzymes, which are extracted from I-5 and C-1 medium, and the decolorization ability of chitosan–Fe membrane are also investigated, respectively. The results demonstrate that the dyes can be removed by the fungi and the membrane synergistically. In addition, different kinds of dyes are successfully removed with chitosan–Fe immobilized fungi membranes. These results demonstrate that dyes are first adsorbed on the chitosan–Fe membrane, decreasing the toxicity to the fungus, and then bio-degraded by the laccase produced from the fungi on the membrane.

The ecotoxicology effects of chiral herbicides have long been recognized and have drawn increasing attention. The toxic mechanisms of herbicides in plants are involved in production of reactive oxygen species (ROS) and cause damage to target enzymes, but the relationship between these two factors in the enantioselectivity of chiral herbicides has rarely been investigated. Furthermore, even though cytochromes P450 enzymes (CYP450s) have been related to the phytotoxicity of herbicides, their roles in the enantioselectivity of chiral herbicides have yet to be explored. To solve this puzzle, the CYP450s suicide inhibitor 1-aminobenzotriazole (ABT) was added to an exposure system made from dichlorprop (DCPP) enantiomers in the model plant Arabidopsis thaliana. The results indicated that different phytotoxicities of DCPP enantiomers by causing oxidative stress and acetyl-CoA carboxylase (ACCase) damage were observed in the presence and the absence of ABT. The addition of ABT decreased the toxicity of (R)-DCPP but was not significantly affected that of (S)-DCPP, resulting in smaller differences between enantiomers. Furthermore, profound differences were also observed in Fe uptake and distribution, exhibiting different distribution patterns in A. thaliana leaves exposed to DCPP and ABT, which helped bridge the relationship between ROS production and target enzyme ACCase damage through the function of CYP450s. These results offer an opportunity for a more-comprehensive understanding of chiral herbicide action mechanism and provide basic evidence for risk assessments of chiral herbicides in the environment.

Nowadays, silver nanoparticles (AgNP) have been widely used and there are raising concerns about their potential adverse effects on organism. As for the exact toxicity mechanism of AgNP, opinions still vary and whether the released silver ions (Ag+) or AgNP themselves are responsible for the toxicity remains debatable. In the present study, we have designed two exposure systems where Ag+ and AgNP coexisted but differed in quantification by using photo-reduced method with cysteine enantiomers, and their toxicities to freshwater microalgae Scenedesmus obliquus and model plant Arabidopsis thaliana were determined. In the results, Ag+ was in suit photo-reduced by cysteine enantiomers, and the UV–Vis and circular dichroism spectrum evidence confirmed the quantification difference between Ag- l -cysteine (Ag- l -Cys) and Ag- d -cysteine (Ag- d -Cys), where there was more AgNP and less Ag+ in Ag- l -Cys. Furthermore, the toxicity assay data revealed that Ag- d -Cys was more toxic to S. obliquus but A. thaliana was more susceptible to Ag- l -Cys. The metal element distribution in Arabidopsis leaves was also influenced in an enantioselective manner, which was related to the oxidative stress. Considering the quantification difference between Ag- l -Cys and Ag- d -Cys, it can be concluded that AgNP exhibited their toxicity to S. obliquus by the action of Ag+, but toxicity brought to A. thaliana was attributed to AgNP themselves rather than Ag+. The results of the present study help to better clarify the role of Ag+ in AgNP toxicity and offer a chiral tool and a new sight to investigate the toxicity mechanism of AgNP.

As the most essential element, nitrogen play a pivotal role in plant physiological process, which is susceptible to contaminants. However, the enantioselective effects of chiral herbicides on nitrogen metabolism have not been comprehensively understood. In this study, effects of chiral herbicide dichlorprop (DCPP) on the nitrogen behaviors in Arabidopsis thaliana were investigated. The results revealed that the uptakes of inorganic nitrogen (NO3- and NH4+) were preferentially impacted by herbicidal active (R)-DCPP, where the transportation of beneficial NO3- was inhibited but the toxic NH4+ was accumulated. As for nitrogen assimilation, enantioselectivity was disappeared and reoccurred when NO3- was assimilated into NH4+. Furthermore, the pathways of NH4+ assimilation differed in Arabidopsis exposed to DCPP enantiomers, where (S)-DCPP remained almost the same to the control relying on GS-GOGAT cycle, but the dominant pathway in (R)-DCPP group was shifted to glutamate dehydrogenase route. Consequently, a profound enantioselectivity was also observed in the effects on amino acids synthesis. As for nitrogen stable isotope fractionation, (R)-DCPP led to more negative δ15N values than (S)-DCPP at 0.3μM, indicating the selective uptake of toxic NH4+ and different discrimination of δ15N was also observed between DCPP enantiomers. Moreover, stable isotopic evidence also revealed the disturbance caused by DCPP to the balance of nitrogen demand and consumption in A. thaliana. All these results may contribute to the final enantioselective toxicity, providing a new sight into the better understanding the action mechanism of chiral herbicides.

The disposal of sewage sludge is one of the most pressing environmental issues with increasing amount of sewage sludge. Among these methods, carbonized sludge is thought to be a potential approach for resource utilization and becomes one of the most widely used adsorbent for wastewater treatment. However, effects of environmental factors and its relative mechanism for pollutant removal have not been thoroughly studied. In this study, carbonized sludge derived from sewage sludge was investigated. The adsorption of C. I. Acid Red 73 (AR 73) on the carbonized sludge was a rapid process and fit well to the Langmuir model with a maximum adsorption capacity of 137.95 mg g−1 at pH 6.8. In addition, the common coexisting ions had a negligible negative impact on dye adsorption on the carbonized sludge. The magnetic carbonized sludge also exhibited high adsorption efficiency for other anionic dyes. Furthermore, the adsorption mechanism was proposed by analysis Fourier transform infrared spectroscopy (FTIR) and X-ra...

Nicotine is an important environmental toxicant in tobacco waste. Shinella sp. strain HZN7 can metabolize nicotine into nontoxic compounds via variations of the pyridine and pyrrolidine pathways. However, the catabolic mechanism of this variant pathway at the gene or enzyme level is still unknown. In this study, two 6-hydroxynicotine degradation-deficient mutants, N7-M9 and N7-W3, were generated by transposon mutagenesis. The corresponding mutant genes, designated nctB and tnp2 , were cloned and analyzed. The nctB gene encodes a novel flavin adenine dinucleotide-containing ( S )-6-hydroxynicotine oxidase that converts ( S )-6-hydroxynicotine into 6-hydroxy- N -methylmyosmine and then spontaneously hydrolyzes into 6-hydroxypseudooxynicotine. The deletion and complementation of the nctB gene showed that this enzyme is essential for nicotine or ( S )-6-hydroxynicotine degradation. Purified NctB could also convert ( S )-nicotine into N -methylmyosmine, which spontaneously hydrolyzed into pseudooxynicotine. The kinetic constants of NctB toward ( S )-6-hydroxynicotine ( K m = 0.019 mM, k cat = 7.3 s −1 ) and nicotine ( K m = 2.03 mM, k cat = 0.396 s −1 ) indicated that ( S )-6-hydroxynicotine is the preferred substrate in vivo . NctB showed no activities toward the R enantiomer of nicotine or 6-hydroxynicotine. Strain HZN7 could degrade ( R )-nicotine into ( R )-6-hydroxynicotine without any further degradation. The tnp2 gene from mutant N7-W3 encodes a putative transposase, and its deletion did not abolish the nicotine degradation activity. This study advances the understanding of the microbial diversity of nicotine biodegradation.

The current problem of excess fluoride in drinking water around the world makes people looking toward low-cost but efficient adsorbents. In the present study, aluminum and doping chitosan–Fe(III) hydrogel (Al–CS–Fe) was prepared and investigated as a possible adsorbent for the removal of fluoride from aqueous solutions. Besides, a series of single metal impregnated chitosan were also synthesized to compare their defluorination ability with Al–CS–Fe. These adsorbents were characterized using FTIR, SEM, EDS and STXM and the adsorption of fluoride is well described by the pseudo-second-order model and Langmuir isotherm model. The results indicate that Al–CS–Fe has a good ability to resist co-existing anions and the change of pH value, and owns a relatively high adsorption capacity of 31.16 mg/g. After regeneration, this adsorbent performs higher defluorination efficiency than before. The mechanism of adsorption may be described by the ligand and ions exchange happened on the active sites. Overall, the results obtained in this study indicate Al–CS–Fe possesses a potential of practical application for fluoride removal from aqueous solutions.

Cu+-based catalysts have great potential in Fenton reactions under neutral pH conditions. However, cuprous (Cu+) materials are instable in the aqueous environment. Herein, using the cheap precursors, a Cu+-graphitic carbon nitride complex with an efficient Fenton-like activity as well as relative stability was prepared. 99.2% removal of Rhodamine B with an initial concentration of 50 mg/L could be attained in 1 h. Several experimental techniques are employed to study the structure of this catalyst. Results show that after the addition of Cu, the graphitic carbon nitride (g-C3N4) network is partially destroyed and the reduced Cu is therefore firmly embedded in the fragmentary g-C3N4 sheet. The X-ray adsorption fine spectra illustrates the chemical state and the local structure of the bonded Cu. Due to the strong orbital hybridization, Cu+ could be stabilized through the coordination with pyridinic N. A two-coordinate structure with a bond length of 1.90 A is confirmed and this structure is not changed even after the Fenton-like reaction. Singlet oxygen (1O2) and hydroxyl radicals (HO•) are produced by the rapid interaction of bonded Cu+ with H2O2 and the resulting Cu2+ can be easily reduced to its cuprous state due to its structure stability, leading to its high activity in the Fenton-like reaction.

Pseudomonas sp. strain HZN6 utilizes nicotine as its sole source of carbon, nitrogen, and energy. However, its catabolic mechanism has not been elucidated. In this study, self-formed adaptor PCR was performed to amplify the upstream sequence of the pseudooxynicotine amine oxidase gene. A 1,437-bp open reading frame (designated nox ) was found to encode a nicotine oxidase (NOX) that shows 30% amino acid sequence identity with 6-hydroxy-l-nicotine oxidase from Arthrobacter nicotinovorans . The nox gene was cloned into a broad-host-range cloning vector and transferred into the non-nicotine-degrading bacteria Escherichia coli DH5α (DH-nox) and Pseudomonas putida KT2440 (KT-nox). The transconjugant KT-nox obtained nicotine degradation ability and yielded an equimolar amount of pseudooxynicotine, while DH-nox did not. Reverse transcription-PCR showed that the nox gene is expressed in both DH5α and KT2440, suggesting that additional factors required for nicotine degradation are present in a Pseudomonas strain(s), but not in E. coli . The mutant of strain HZN6 with nox disrupted lost the ability to degrade nicotine, but not pseudooxynicotine. These results suggested that the nox gene is responsible for the first step of nicotine degradation. The ( RS )-nicotine degradation results showed that the two enantiomers were degraded at approximately the same rate, indicating that NOX does not show chiral selectivity. Site-directed mutagenesis revealed that both the conserved flavin adenine dinucleotide (FAD)-binding GXGXXG motif and His456 are essential for nicotine degradation activity.

The use of earthworms as a sublethal endpoint has significantly contributed to the ecological risk assessment of contaminated soils. Few studies have focused on the potential toxicity of PFOS to earthworms in the soil. In this work, artificial soils were tested, and contact filter paper studies were used. The results showed that earthworm growth was generally inhibited. The antioxidant activities of the enzymes superoxide dismutase, peroxidase, catalase and glutathione peroxidase were initially activated and then inhibited. Reduced glutathione content was observed, and malondialdehyde content was elevated over the duration of the exposure. These results suggested that PFOS induced oxidative stress in earthworms. In addition, the values of olive tail moment, tail DNA% and tail length using SCGE showed similar frequency distributions and increased with increases in the PFOS concentration. These results suggest that all concentrations of PFOS cause DNA damage.

Pesticide residues and nitrogen overload (which caused cyanobacteria blooms) have been two serious environmental concerns. In particular, chiral pesticides with different structures may have various impacts on cyanobacteria. Nitrogen may affect the behavior between pesticides and cyanobacteria (e.g., increase the adverse effects of pesticides on cyanobacteria). This study evaluated the impacts of Rac- and S-metolachlor on the cell integrity and toxin release of Microcystis aeruginosa cells at different nitrogen levels. The results showed that (both of the configurations: Rac-, S-) metolachlor could inhibit M. aeruginosa cell growth under most conditions, and the inhibition rates were increased with the growing concentrations of nitrogen and metolachlor. However, cyanobacterial growth was promoted in 48 h under environmental relevant condition (1 mg/L metolachlor and 0.15 mg/L nitrogen). Therefore, the water authorities should adjust the treatment parameters to remove possible larger numbers of cyaonbacteria under that condition. On the other hand, the inhibition degree of M. aeruginosa cell growth by S-metolachlor treatments was obviously larger than Rac-metolachlor treatments. S-metolachlor also had a stronger ability in compromising M. aeruginosa cells than Rac-metolachlor treatments. Compared to control samples, more extracellular toxins (12%–86% increases) were detected after 5 mg/L S-metolachlor treatment for 72 h at different nitrogen levels, but the variations of extracellular toxins caused by 5 mg/L Rac-metolachlor addition could be neglected. Consequently, higher concentrations of metolachlor in source waters are harmful to humans, but it may prevent cyanobacterial blooms. However, the potential risks (e.g. build-up of extracellular toxins) should be considered.

Metal-biopolymer complexes has recently gained significant attention as an effective adsorbent used for the removal of Cr(VI) from water. Unfortunately, despite increasing research efforts in the field of removal efficiency, whether this kind of complex can reduce Cr(VI) to less-toxic Cr(III) and what are the mechanisms of detoxification processes are still unknown. In this study, despite the highly adsorption efficiency (maximum adsorption capacity of 173.1 mg/g in 10 min), the significant improvement of Cr(VI) reduction by chitosan-Fe(III) complex compared with normal crosslinked chitoan has been demonstrated. In addition, the structure of chitosan-Fe(III) complex and its functional groups concerned with Cr(VI) detoxification have been characterized by the powerful spectroscopic techniques X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS). The XPS spectra indicated that the primary alcoholic function on C-6 served as an electron donor during Cr(VI) reduction and was oxidized to a carbonyl group. The X-ray adsorption near edge spectra (XANES) of the Cr(VI)-treated chitosan-Fe(III) complex revealed the similar geometrical arrangement of Cr species as that in Cr(III)-bound chitosan-Fe(III). Overall, a possible process and mechanism for highly efficient detoxification of Cr(VI) by chitosan-Fe(III) complex has been elucidate.