Cation-π Interactions with Coexisting Heavy Metals Enhanced the Uptake and Accumulation of Polycyclic Aromatic Hydrocarbons in Spinach

Effects of zeolite imidazole frameworks on rice seedlings (Oryza sativa L.): Phytotoxicity, transformation, and bioaccumulation

Zeolite imidazole frameworks (ZIFs), a class of the metal organic framework, have been extensively studied in environmental applications. However, their environmental fate and potential ecological impact on plants remain unknown. Here, we investigated the phytotoxicity, transformation, and bioaccumulation processes of two typical ZIFs (ZIF-8 and ZIF-67) in rice (Oryza sativa L.) under hydroponic conditions. ZIF-8 and ZIF-67 in the concentration of 50 mg/L decreased root and shoot dry weight maximally by 55.2% and 27.5%, 53.5% and 37.5%, respectively. The scanning electron microscopy (SEM) imaging combined with X-ray diffraction (XRD) patterns revealed that ZIFs on the root surface gradually collapsed and transformed into nanosheets with increasing cultivation time. The fluorescein isothiocyanate (FITC) labeled ZIFs were applied to trace the uptake and translocation of ZIFs in rice. The results demonstrated that the transformed ZIFs were mainly distributed in the intercellular spaces of rice root, while they cannot be transported to culms and leaves. Even so, the Co and Zn contents of rice roots and shoots in the ZIFs treated groups were increased by 1145% and 1259%, 145% and 259%, respectively, compared with the control groups. These findings suggested that the phytotoxicity of ZIFs are primarily attributed to the transformed ZIFs and to a less extent, the metal ions and their ligands, and they were internalized by rice root and increased the Co and Zn contents of shoots. This study reported the transformation of ZIFs and their biological effectiveness in rice, highlighting the potential environmental hazards and risks of ZIFs to crop plants.

Root-zone regulation and longitudinal translocation cause intervarietal differences for phthalates accumulation in vegetables

Selecting and cultivating low-accumulating crop varieties (LACVs) is the most effective strategy for the safe utilization of di-(2-ethylhexyl) phthalate (DEHP)-contaminated soils, promoting cleaner agricultural production. However, the adsorption-absorption-translocation mechanisms of DEHP along the root-shoot axis remains a formidable challenge to be solved, especially for the research and application of LACV, which are rarely reported. Here, systematic analyses of the root surface ad/desorption, root apexes longitudinal allocation, uptake and translocation pathway of DEHP in LACV were investigated compared with those in a high-accumulating crop variety (HACV) in terms of the root-shoot axis. Results indicated that DEHP adsorption was enhanced in HACV by root properties, elemental composition and functional groups, but the desorption of DEHP was greater in LACV than HACV. The migration of DEHP across the root surface was controlled by the longitudinal partitioning process mediated by root tips, where more DEHP accumulated in the root cap and meristem of LACV due to greater cell proliferation. Furthermore, the longitudinal translocation of DEHP in LACV was reduced, as evidenced by an increased proportion of DEHP in the root apoplast. The symplastic uptake and xylem translocation of DEHP were suppressed more effectively in LACV than HACV, because DEHP translocation in LACV required more energy, binding sites and transpiration. These results revealed the multifaceted regulation of DEHP accumulation in different choysum (Brassica parachinensis L.) varieties and quantified the pivotal regulatory processes integral to LACV formation.

Potential hazards of typical small molecular organic matters in shale gas wastewater for wheat irrigation: 2-butoxyethanol and dimethylbenzylamine

2-butoxyethanol (BE) and dimethylbenzylamine (DMBA) are small molecular organic compounds commonly found in shale gas wastewater (SGW) and environmental samples, yet their environmental risks in exposure and irrigation reuse have not been thoroughly studied. From the perspectives of physicochemical properties and toxicity, seven groups of irrigation treatment were designed for wheat irrigation according to the concentration gradient. Overall, wheat growth was normal, but higher DMBA concentrations resulted in more severe growth inhibition. The absorption of BE by various tissues of wheat was positively correlated with its concentration, while the absorption of DMBA by wheat stems showed the same trend. Interestingly, there was no significant difference in the absorption of DMBA by wheat grains in different groups. The detection results of nutritional and heavy metal elements in wheat tissues showed that the presence of organic compounds changed the relative sensitivity of wheat leaves and grains to some elements (such as Mg, Mn, Mo, etc.) enrichment. The Cd and Pb contents of wheat grains in all groups complied with national safety standards, but the As or Cr concentration in wheat grains treated with BE or DMBA exceeded the limits in some cases. Transcriptome sequencing, GO annotation, and KEGG enrichment analysis revealed similar gene functions and metabolic pathways enriched by BE and DMBA. The safe and sustainable agricultural reuse of SGW still has great potential as a promising water resources management strategy.

Insights into relationships between polycyclic aromatic hydrocarbon concentration, bacterial communities and organic matter composition in coal gangue site

Coal mining usually brought polycyclic aromatic hydrocarbons (PAHs) contamination. Relationships between the concentration of PAHs, bacterial communities and soil environmental factors were important for bioremediation of PAHs in soil. Total 4 kinds of soil samples with different concentrations of PAHs were selected from 7 typical coal gangue（CG） sites in Huainan, Anhui Province. The relationships between microorganisms, dissolved organic matter (DOM) composition and PAHs concentration were systematically analyzed in this work. Total 11 kinds of PAHs were enriched in the soil surface layer. That was attributed to the strong binding of soil organic matter (SOM) to PAHs. PAHs contamination reduced the diversity of soil microbial. The abundance of PAHs-degrading genera such as Arthrobacter decreased with the increasing concentration of PAHs. Mycobacterium increased with the increasing concentration of PAHs in all samples. The microbial activities decreased with increasing concentration of PAHs. The increasing contents of LWM-PAHs and DOM were beneficial to improve the activities of soil microbial. The increasing DOM aromaticity was beneficial to improve the bioavailability of PAHs according to the correlation analysis between PAHs content and DOM structural parameters. The obtained results provide a basis for better understanding the contamination characteristics and microbial communities of coal gangue PAH-contaminated sites.

Effect of natural soil nanocolloids on the fate and toxicity of cadmium to rice (Oryza sativa L.) roots

Toxic heavy metals are common contaminants and will most likely interact with ubiquitous natural nanocolloids (Ncs) in the soil environment. However, the effect of soil Ncs on the fate and health risk of cadmium (Cd) have not been well addressed. Here, the interaction between Ncs and Cd is investigated using two-dimensional correlation spectroscopy (2DCOS) combined with synchronous fluorescence and Fourier transform infrared spectroscopy. Our results reveal that Cd binding to the soil Ncs surface is mainly driven through strong hydrophilic effects and π - π interactions, which contribute to a high adsorption capacity (366-612 mg/g) and strong affinity (K_L = 4.3-9.7 L/mg) of Cd to soil Ncs. Interestingly, soil Ncs and Cd coexposure can significantly mediate the phytotoxicity (e.g., uptake, root growth, and oxidative stress) of Cd to rice (Oryza sativa L.) roots after 7 days of exposure. At the molecular level, metabolomic analysis reveals that the downregulated metabolic pathways (e.g., isoquinoline alkaloid and aminoacyl-tRNA biosynthesis, glycine, serine and threonine metabolism) may contribute to the above adverse phytotoxicity. This study provides new insight into the effect of natural Ncs on the fate and health risks of toxic heavy metals in soil environments.

The physiological effect of organophosphate flame retardants (OPFRs) on wheat (Triticum aestivum L.) seed germination and seedling growth under the presence of copper

This study investigated the physiological and biochemical impacts of organophosphate flame retardants (OPFRs) on wheat (Triticum aestivum L.) germination and growth performance in the presence and absence of copper. The study evaluated seed germination, growth, OPFRs concentrations, chlorophyll fluorescence index (F_v/F_m and F_v/F₀), and antioxidant enzyme activity. It also calculated the root accumulation of OPFRs and their root-stem translocation. At the germination stage, at a concentration of 20 μg·L^-1 OPFR exposure, wheat germination vigor, root, and shoot lengths were significantly decreased compared to the control. However, the addition of a high concentration of copper (60 mg·L^-1) decreased by 80%, 82%, and 87% in the seed germination vitality index and root and shoot elongation, respectively, compared to 20 μg·L^-1 of OPFR treatment. At the seedling stage, a concentration of 50 μg·L^-1 of OPFRs significantly decreased by 42% and 5.4% in wheat growth weight and the photochemical efficiency of photosystem II (Fv/Fm) compared to the control. However, the addition of a low concentration of copper (15 mg·L^-1) slightly enhanced the growth weight compared to the other two co-exposure treatments, but the results were not significant (p > 0.05). After 7 days of exposure, the activity of superoxide dismutase (SOD) and malondialdehyde (MDA) (indicates lipid peroxidation) content in wheat roots significantly increased compared to the control and was higher than in leaves. MDA contents in wheat roots and shoots were decreased by 18% and 6.5% when OPFRs were combined with low Cu treatment compared with single OPFRs treatment, but SOD activity was slightly improved. These results suggest that the co-exposure of copper and OPFRs enhances reactive oxygen species (ROS) production and oxidative stress tolerance. Seven OPFRs were detected in wheat roots and stems, with root concentration factors (RCFs) and translocation factors (TFs) ranging from 67 to 337 and 0.05 to 0.33, respectively, for the seven OPFRs in a single OPFR treatment. The addition of copper significantly increased OPFR accumulation in the root and aerial parts. In general, the addition of a low concentration of copper promoted wheat seedling elongation and biomass and did not significantly inhibit the germination process. OPFRs could mitigate the toxicity of low-concentration copper on wheat but had a weak detoxification effect on high-concentration copper. These results indicated that the combined toxicity of OPFRs and Cu had antagonistic effects on the early development and growth of wheat.

Atomically Dispersed ZnN5 Sites Immobilized on g-C3 N4 Nanosheets for Ultrasensitive Selective Detection of Phenanthrene by Dual Ratiometric Fluorescence

Ultrasensitively selective detection of trace polycyclic aromatic hydrocarbons (PAHs) like phenanthrene (PHE) is critical but remains challenging. Herein, atomically dispersed Zn sites on g-C₃ N₄ nanosheets (sZn-CN) are constructed by thermal polymerization of a Zn-cyanuric acid-melamine supramolecular precursor for the fluorescence detection of PHE. A high amount (1.6 wt%) of sZn is grafted in the cave of CN with one N vacancy in the form of unique Zn(II)N₅ coordination. The optimized sZn-CN achieves a wide detection range (1 ng L^-1 to 5 mg L^-1 ), ultralow detection limit (0.35 ng L^-1 , with 5-order magnitude improvement over CN), and ultrahigh selectivity toward PHE even among typical PAHs based on the built PHE-CN dual ratiometric fluorescence method. By means of in situ Fourier transform infrared spectroscopy, time-resolved absorption and fluorescence spectroscopy, and theoretical calculations, the resulting superior detection performance is attributed to the favorable selective adsorption of PHE on as-constructed atomic Zn(II)N₅ sites via the ionic cation-π interactions (Zn^δ+ C₂ ^δ- type), and the fluorescence quenching is dominated by the inner filter effect (IFE) from the multilayer adsorption of PHE at low concentrations, while it is done by the protruded photogenerated electron-transfer process, as well as IFE from the monolayer adsorption of PHE at ultralow concentration.

Influence mechanism of organic matter and low-molecular-weight organic acids on the interaction between minerals and PAHs

Investigate the effect of soil organic matter (SOM) and low molecular weight organic acids (LMWOAs) on minerals adsorption of PAHs. Batch adsorption experiments have been carried out to study the adsorption of PAHs (Naphthalene (NaP), Phenanthrene (Phe) and Pyrene (Pyr)) by minerals (Montmorillonite (Mnt), kaolinite (Kln) and calcite (Cal)). This research found that compared with Kln and Cal, Mnt showed the maximum adsorption capability for PAHs. And the order of PAHs adsorption by Mnt was: Pyr > Phe > Nap, which corresponds to the octanol-water partition coefficient (K_ow) of different PAHs. The adsorption kinetic and isotherm were well fitted by Pseudo-second-order kinetic model, Freundlich and Linear isotherm model. Furthermore, inorganic ions (Ca²⁺) impacted PAHs adsorption by competitive adsorption and cation-π interactive. Cal has the maximum desorption of PAHs among three minerals, and there was desorption hysteresis phenomenon. Field emission-scanning electron microscope (Fe-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared (FTIR) analysis indicated that SOM enhanced the sorption of PAHs by van der Waals, hydrogen bonding, π-π interactions, and chemical bonding. LMWOAs significantly inhibited PAHs adsorption and promote PAHs desorption from the minerals. As a result, LMWOAs increased of PAHs bioavailability, which provide a new strategy to improve PAHs cleanup efficiency.

Distribution and ecological risk assessment of heavy metals in sediments of Dajiuhu Lake Wetland in Shennongjia, China

The rapid development of modern society has resulted in discharge of large, heavy metal quantities into wetlands that have been continuously accumulating, causing severe pollution. Dajiuhu, located in the Shennongjia Forest District of Hubei Province in China, is a wetland of significant value internationally, serving as a model wetland ecosystem with heightened scientific research value. In this study, 27 surface sediment samples from nine sub-lakes in Dajiuhu were collected in August 2020. The concentrations of Cd, Cr, Cu, Ni, Pb, and Zn in the sediments were determined. The heavy metal occurrence and speciation characteristics were analyzed by an improved BCR (European Community Bureau of Reference) extraction method. Four methods were used to evaluate heavy metals' pollution degree and ecological risk. The possible source of heavy metals was inferred using correlation analysis and principal component analysis. The heavy metal content in the lake sediments of Dajiuhu wetland was from the highest to the lowest concentration as follows: Zn [Formula: see text] Cr [Formula: see text] Ni [Formula: see text] Pb [Formula: see text] Cu [Formula: see text] Cd. The average Cd content exceeded the national nature reserve threshold values, while the other heavy metals measured were below their respective threshold values. However, due to the occurrence of Pb and Cd in different forms, they still pose certain pollution and ecological risk to the lake wetlands. On the other hand, Zn, Cr, Ni, and Cu do not pose an ecological risk in the lakes of the Dajiuhu wetland. The spatial distribution of heavy metal content in the nine sub-lakes did vary significantly. Regarding the heavy metal sources in the lake sediments, Ni, Cr, and Cu originate from natural factors, and Cd and Pb have mainly anthropogenic origins. In contrast, Zn has both natural and anthropogenic origins. This study provides further insights into the study of heavy metal pollution in lake wetlands. It provides a framework and a direction for managing heavy metal pollution in the Dajiuhu wetland.

Bioaccumulation and emission of organophosphate esters in plants affecting the atmosphere's phosphorus cycle

The imbalance of atmospheric, terrestrial and aquatic phosphorus budgets remains a research conundrum and global concern. In this work, the uptake, distribution, bioaccumulation and emission of organophosphate esters (OPEs) by clove trees (Syzygium aromaticum), lemon trees (Citrus limon) and cape jasmine trees (Gardenia jasminoides var. fortuniana) was investigated as conduits for phosphorus transfer or sinks and sources. The objective was to assess the role OPEs in soils play as atmospheric phosphorus sources through plant bioaccumulation and emission. Results demonstrated OPEs in experimental soil plots ranging from 0.01 to 81.0 ng g^-1 dry weight, were absorbed and transported through plants to the atmosphere. The total emission of OPEs varied greatly from 0.2 to 588.9 pg g^-1 L^-1 h^-1, with a mean of 47.6 pg g^-1 L^-1 h^-1. There was a negative linear relationship between the concentrations of total phosphorus and four OPEs, tri-iso-butyl phosphate, tri-n-butyl phosphate, tris (2-chloroisopropyl) phosphate and tripentyl phosphate. Trimethyl phosphate levels were positively correlated with total nitrogen, and the concentrations of tri-iso-butyl phosphate, tri-n-butyl phosphate, tris (2-chloroisopropyl) phosphate and tripentyl phosphate decreased along with available potassium in leaves after 72 h. There was a significantly positive linear relationship between higher emission concentrations of OPEs and the emission factor of OPEs concentration (F = 4.2, P = 0.002), with lower emissions of OPEs and the bioaccumulation of OPEs in leaves (F = 4.8, P = 0.004). OPEs releases to the atmosphere were enriched in aerosols, and participate in atmospheric chemical reactions like photolysis, thereby affecting the phosphorus balance and cycling in the atmosphere.

The simultaneous removal of co-contaminants pyrene and Cu (II) from aqueous solutions by Fe/Mn bimetallic functionalized mesoporous silica

In recent years, the co-contamination of heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs) has attracted more and more attention, and finding efficient and coordinated removal method has been the hot focus. In this study, Fe/Mn-SBA15 bimetallic mesoporous silica adsorbent (Fe/Mn-SBA15) was prepared by hydrothermal method with the functional groups Fe and Mn simultaneously doped into the framework structure of SBA15. Fe/Mn-SBA15 was systematically characterized by XRD, TEM, and BET and used in removal of typical PAHs-pyrene and heavy metal-Cu (II) from aqueous solutions simultaneously. The single and binary adsorption behaviors were studied by kinetics, isotherm, pH, and ionic strength. The results showed that the functional groups of Fe and Mn were successfully loaded into the structure of SBA15 and the prepared adsorbent was still a typical mesoporous adsorbent. The adsorption of pyrene and Cu (II) onto Fe/Mn-SBA15 was fast and the adsorption equilibrium was achieved in 100 min. The Langmuir model fitted the adsorption isotherm better and the maximum adsorption capacities for pyrene and Cu (II) were 120 mg/g and 10.52 mg/g, respectively. The increase of ionic strength could enhance and decrease the adsorption capacity of pyrene and Cu (II), which may be attributed to salting-out effect and potassium competitive. With the increase of pH values, the negative charge on the surface of the adsorbent increased, resulting in the decrease and increase of adsorption capacity of pyrene and Cu (II) onto Fe/Mn-SBA15. In addition, Fe/Mn-SBA15 was found to have a synergistic effect on the adsorption of pyrene and Cu (II). This result is mainly due to the formation of hydration complex by pyrene-Cu (II) through cation-π interaction, which increases the adsorption capacity by occupying each other's adsorption sites of adsorbent. This study provides a new method for the synergistic removal of PAHs and HMs from aqueous solutions.

Distribution and Relationships of Polycyclic Aromatic Hydrocarbons (PAHs) in Soils and Plants near Major Lakes in Eastern China

The distributions and correlations among polycyclic aromatic hydrocarbons (PAHs) in soils and plants were analyzed. In this study, 9 soil samples and 44 plant samples were collected near major lakes (Hongze Lake, Luoma Lake, Chaohu, Changhu, Danjiangkou Reservoir, Wuhan East Lake, Longgan Lake, Qiandao Lake and Liangzi Lake) in eastern China. The following results were obtained: The total contents of PAHs in soil varied from 99.17 to 552.10 ng/g with an average of 190.35 ng/g, and the total contents of PAHs in plants varied from 122.93 to 743.44 ng/g, with an average of 274.66 ng/g. The PAHs in soil were dominated by medium- and low-molecular-weight PAHs, while the PAHs in plants were dominated by low-molecular-weight PAHs. The proportion of high-molecular-weight PAHs was the lowest in both soil and plants. Diagnostic ratios and principal component analysis (PCA) identified combustion as the main source of PAHs in soil and plants. The plant PAH monomer content was negatively correlated with Koa. Acenaphthylene, anthracene, benzo[k]fluoranthene, benzo[b]fluoranthene and dibenzo[a,h]anthracene were significantly correlated in plants and soil. In addition, no significant correlation between the total contents of the 16 PAHs and the content of high-, medium-, and low-molecular-weight PAHs in plants and soil was found. Bidens pilosa L. and Gaillardia pulchella Foug in the Compositae family and cron in the Poaceae family showed relatively stronger accumulation of PAHs, indicating their potential for phytoremediation.

Biochar Effect on the Benzo[a]pyrene Degradation Rate in the Cu Co-Contaminated Haplic Chernozem under Model Vegetation Experiment Conditions

The research of the fundamentals of the behavior of behavior in the soil–plant system during their co-contamination is of high interest because of the absence of technologies for the creation of effective, environmentally friendly and cost-effective remediation methods, as well as integrated systems for predicting the quality of soils co-contaminated with HMs and PAHs. The unique model vegetation experiment was studied with Haplic Chernozem contaminated by one of the priority organic toxicants, benzo[a]pyrene (BaP), applied alone and co-contaminated with Cu with the subsequent vegetation of tomato (Solanum lycopersicum) and spring barley plants (Hordeum sativum Distichum). Biochar obtained from sunflower husks was used as a sorbent for the remediation of the contaminated soil. It was established that by increasing the BaP amount applied to the soil, the rate of BaP degradation improved. The effect was enhanced in the presence of biochar and decreased in the case of joint co-contamination with Cu, which is especially expressed for the soil of tomato plants. The half-degradation time of the BaP molecule varied from 8 up to 0.2 years for tomatoes and barley.

Effect of nitrilotriacetic acid and tea saponin on the phytoremediation of Ni by Sudan grass (Sorghum sudanense (Piper) Stapf.) in Ni-pyrene contaminated soil

Phytoremediation is commonly used in the remediation of soils co-contaminated by heavy metals and polycyclic aromatic hydrocarbons (PAHs) because of its economy and effectiveness. Sudan grass (Sorghum sudanense (Piper) Stapf.) has well-developed roots and strong tolerance to heavy metals, so it has been widely concerned. In this study, nitrilotriacetic acid (NTA) and tea saponin (TS) were used as enhancers and combined with Sudan grass for improving the remediation efficiency of Ni-pyrene co-contaminated soil. The results of the pot experiment in soils showed that enhancers promoted the enrichment of Ni in plants. With the function of enhancers, more inorganic and water-soluble Ni were converted into low-toxic phosphate-bonded and residual Ni, so as to reinforce the tolerance of Sudan grass to Ni. In the pot experiment based on vermiculite, it was found that enhancers increased the accumulation of Ni in cell wall by 49.71-102.73%. Enhancers also had the positive effect on the relative abundance of Proteobacteria, Patescibacteria and Bacteroidetes that could tolerate heavy metals at phylum level. Simultaneously, the study found that pyrene reduced the exchangeable Ni in soils. More Ni entered the organelles and transfer to more high-toxic forms in Sudan grass when pynere coexisted. The study manifested that enhancers improved the phytoremediation effect of Ni significantly, yet the co-existence of pyrene weakened the process. Our results provided meaningful references for remediating actual co-contaminated soil of heavy metals and PAHs.

Bioremediation of PAHs and heavy metals co-contaminated soils: Challenges and enhancement strategies

Systemic studies on the bioremediation of co-contaminated PAHs and heavy metals are lacking, and this paper provides an in-depth review on the topic. The released sources and transport of co-contaminated PAHs and heavy metals, including their co-occurrence through formation of cation-π interactions and their adsorption in soil are examined. Moreover, it is investigated that co-contamination of PAHs and heavy metals can drive a synergistic positive influence on bioremediation through enhanced secretion of extracellular polymeric substances (EPSs), production of biosynthetic genes, organic acid and enzymatic proliferation. However, PAHs molecular structure, PAHs-heavy metals bioavailability and their interactive cytotoxic effects on microorganisms can exert a challenging influence on the bioremediation under co-contaminated conditions. The fluctuations in bioavailability for microorganisms are associated with soil properties, chemical coordinative interactions, and biological activities under the co-contaminated PAHs-heavy metals conditions. The interactive cytotoxicity caused by the emergence of co-contaminants includes microbial cell disruption, denaturation of DNA and protein structure, and deregulation of antioxidant biological molecules. Finally, this paper presents the emerging strategies to overcome the bioavailability problems and recommends the use of biostimulation and bioaugmentation along with the microbial immobilization for enhanced bioremediation of PAHs-heavy metals co-contaminated sites. Better knowledge of the bioremediation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of PAHs and heavy metals co-contamination in the near future.

Synergistic leaching of heavy metal-polycyclic aromatic hydrocarbon in co-contaminated soil by hydroxamate siderophore: Role of cation-π and chelation

Exploring a novel green efficient bioeluant is a golden key to unlock the ex-situ scale remediation of soil contaminated with heavy metals (HMs) and polycyclic aromatic hydrocarbons (PAHs). Hydroxamate siderophore (HDS) produced by Pseudomonas fluorescens HMP01, with certain hydrophobicity and strong coordination because of its special chemical structure (e.g., hydroxamic acid and dihydroxy quinoline chromophore), was used to investigate the bioleaching efficiency of HMs and PAHs from actual contaminated soils and underlying mechanisms. Results showed that leaching efficiency for HMs and PAHs from the co-contaminated soil was higher than that of single contaminated soil due to the cation-π interaction and coordination, which was closely related to the spacial configuration changes of the complex. HDS not only increased the bioleaching efficiency of cationic HMs by chelation (the leaching amount of Cd²⁺, Pb²⁺, Hg²⁺, Cu²⁺, Zn²⁺, and Ni²⁺ achieved 27.5, 110.4, 6.9, 477.7, 10,606.9, and 137.4 mg/kg HDS, respectively) but also enhanced the bioleaching amount of PAHs by solubilization (the leaching amount of phenanthrene reached 90.2 mg/kg HDS. Also, the residual HDS in soils caused no significant ecological risk. As expected, HDS is a desirable bioeluant to promote the scale application of the ex-situ remediation of soil contaminated with HMs and PAHs.

Engineered macroalgal and microalgal adsorbents: Synthesis routes and adsorptive performance on hazardous water contaminants

Colourants, micropollutants and heavy metals are regarded as the most notorious hazardous contaminants found in rivers, oceans and sewage treatment plants, with detrimental impacts on human health and environment. In recent development, algal biomass showed great potential for the synthesis of engineered algal adsorbents suitable for the adsorptive management of various pollutants. This review presents comprehensive investigations on the engineered synthesis routes focusing mainly on mechanical, thermochemical and activation processes to produce algal adsorbents. The adsorptive performances of engineered algal adsorbents are assessed in accordance with different categories of hazardous pollutants as well as in terms of their experimental and modelled adsorption capacities. Due to the unique physicochemical properties of macroalgae and microalgae in their adsorbent forms, the adsorption of hazardous pollutants was found to be highly effective, which involved different mechanisms such as physisorption, chemisorption, ion-exchange, complexation and others depending on the types of pollutants. Overall, both macroalgae and microalgae not only can be tailored into different forms of adsorbents based on the applications, their adsorption capacities are also far more superior compared to the conventional adsorbents.

Selenium improved the combined remediation efficiency of Pseudomonas aeruginosa and ryegrass on cadmium-nonylphenol co-contaminated soil

Most chemical plant wastewater contains both organic and inorganic pollutants, which are easy to diffuse along with surface runoff. The combined pollution of nonylphenol (NP) and cadmium (Cd) in soil is a serious problem that has not attracted enough attention. Based on the effects of selenium (Se) and Pseudomonas aeruginosa (P. aeruginosa) on plant and soil microbial communities, we speculated that the application of Se and P. aeruginosa in soil could improve the phytoremediation efficiency of ryegrass on contaminated soil. In this study, pot experiments with Cd and NP co-contaminated soil were conducted, and the results showed that application of P. aeruinosa alone could improve the removal rates of NP and Cd by ryegrass, and the supplementary of Se further enhanced the effect of micro-phyto remediation, with the highest removal rates of NP and Cd were 79.6% and 49.4%, respectively. The application of P. aeruginosa plus Se reduced the adsorption of Cd and NP through C-O and Si-O-Fe of the soil, changed the enzyme activity, and also affected the changing trend of the microbial community in soil. Pseudomonas, Sphingomonadales, Nitrospira, and other beneficial bacteria were enriched after a 60-day period with P. aeruginosa and Se treatment, thus promoting the removal of NP and Cd. In light of the above results, we suggest that P. aeruginosa application can efficiently facilitate the phytoremediation of ryegrass on Cd-NP co-contaminated soil, and Se supplementation in soil showed the synergistic effect on the remediation.

Uptake and translocation of organophosphate esters by plants: Impacts of chemical structure, plant cultivar and copper

Organophosphate esters (OPEs) are normally used as flame retardants, plasticizers and lubricants, but have become environmental pollutants. Because OPEs are normally present alongside heavy metals in soils, the effects of interactions between OPEs and heavy metals on plant uptake of OPEs need to be determined. In this study, we investigated the effects of OPEs chemical structure, plant cultivar and copper (Cu) on the uptake and translocation of OPEs by plants. The bioaccumulation of OPEs varied among plant cultivars. They were preferentially enriched in carrot, with the lowest concentrations observed in maize. OPEs with electron-ring substituents (ER-OPEs) exhibited a higher potential for root uptake than did OPEs with open-chain substituents (OC-OPEs), which could be attributed to the higher sorption of ER-OPEs onto root charged surfaces. This was explained by the stronger noncovalent interactions with the electron-rich structure of ER-OPEs. The presence of Cu slightly reduced the distinct difference in the ability of roots to take up OC-OPEs and ER-OPEs. This was explained by the interactions of Cu ions with the electron-rich structure of ER-OPEs, which suppressed the sorption of ER-OPEs on the root surface. A negative relationship between the logarithms of the translocation factor and octanol-water partition coefficient (K_ow) was observed in treatments with either OPEs only or OPEs + Cu, implying the significant role of hydrophobicity in the OPEs acropetal translocation. The results will improve our understanding of the uptake and translocation of OPEs by plant cultivars as well as how the process is affected by the chemical structure of OPEs and Cu, leading to improvements in the ecological risk assessment of OPEs in the food chain.