Effects of sertraline hydrochloride with As(III) or Cd on rhizosphere micro-environment and root endophytes in rice.

This study investigated the effects of the antidepressant sertraline hydrochloride (Ser-HCI) on rice physiology when combined with arsenic (III) or cadmium. Hydroponic experiments revealed that combined lower concentrations (0.2 and 0.6 mg L-1) of Ser-HCl and As (III) or Cd increased rice biomass and reduced pH and low molecular weight organic acids. The fluorescence intensity was enhanced with Ser-HCl and As-only treatments, with a significant difference (p < 0.05) in the dissolved organic matter index. There was a decrease in endophyte-specific operational taxonomic units, with proteobacteria dominating the rice root endophytes. The addition of Ser-HCl resulted in the Verrucomicrobiota increasing by 6.4 times, which was positively correlated with malic acid and negatively correlated with pH. Functional annotation highlighted alterations in carbohydrate metabolism pathways. This study provides insights into the interactive effects of Ser-HCl on rice when combined with As (III) or Cd, addressing gaps in our understanding of the impact of antidepressants on plant systems.

Response of garlic (Allium sativum L.) to the combined toxicity of microplastics and arsenic.

The extensive utilization of mulch films in agricultural settings, coupled with the persistence of microplastic remnants in soil following the natural degradation of plastics, has given rise to detrimental microplastic impacts on crops. Arsenic (As) contamination in the environment is known to accumulate in crops through aquatic pathways or soil. Garlic (Allium sativum L.), a globally popular crop and seasoning, contains alliin, a precursor of its flavor compounds with medicinal properties. While alliin exhibits antimicrobial and antioxidant effects in garlic, its response to microplastics and arsenic has not been thoroughly investigated, specifically in terms of microplastic or As uptake. This study aimed to explore the impact of varied stress concentrations of microplastics on the toxicity, migration, and accumulation of As compounds. Results demonstrated that polystyrene (PS) fluorescent microspheres, with an 80 nm diameter, could permeate garlic bulbs through the root system, accumulating within vascular tissues and intercellular layers. Low concentrations of PS (10 and 20 mg L-1) and As (2 mg L-1) mitigated the production and accumulation of reactive oxygen species (ROS) and antioxidant enzymes in garlic. Conversely, garlic exhibited reduced root vigor, substance uptake, and translocation when treated with elevated As concentrations (4 mg L-1) in conjunction with PS concentrations of 40 and 80 mg L-1. An escalation in PS concentration facilitated As transport into bulbs but led to diminished As accumulation and biomass in the root system. Notably, heightened stress levels weakened garlic's antioxidant defense system, encompassing sulfur allicin and phytochelatin metabolism, crucial for combating the phytotoxicity of PS and As. In summary, PS exerted a detrimental influence on garlic, exacerbating As toxicity. The findings from this study offer insights for subsequent investigations involving Liliaceae plants.

Effect of cadmium on polystyrene transport in parsley roots planted in a split-root system and assessment of the combined toxic effects.

Micro and nanoplastics (MPs/NPs) coupled with heavy metals are prevalent in both aquatic and terrestrial ecosystems. Their ecological toxicity and combined adverse effects have obtained significant concern. Past studies primarily focused on how MPs/NPs influence the behavior of heavy metals. Yet, the possible effects of heavy metals on MP/NP transport and toxicity within co-contaminated systems are still not well-understood. In this study, we conducted split-root experiments to explore the transport and toxicity of polystyrene (PS) particles of varying sizes in parsley seedlings, both with and without the addition of cadmium (Cd). Both the PS-NPs (100 nm) and PS-MPs (300 nm) traveled from the PS-spiked roots (Roots-1) to the non-PS-spiked roots (Roots-2), with or without Cd, possibly because of phloem transport. Furthermore, the presence of Cd reduced the accumulation and movement of PS-NP/MP in the roots, likely due to the increased positive charge (Cd2+) on the PS surface. PS-NPs/MPs in both Roots-1 and Roots-2 were observed using transmission electron microscopy (TEM). When Cd was added to either Roots-1 (PS + Cd|H) or Roots-2 (PS|Cd), there was a minor reduction in the chlorophyll a and carotenoids content in leaves with PS|H. The adverse impacts of MPs|H on both indicators were influenced by the MP concentration. However, chlorophyll b significantly increased in the PS|H, PS + Cd|H, and PS|Cd treatments. Consequently, the chlorophyll a/b ratio declined, indicating inhibition of photosynthesis. The dehydrogenase content showed a minor change in Roots-1 and Roots-2 without Cd stress, whereas it significantly decreased on the Cd-spiked side and subsequently inhibited root growth. In contrast, the marked rise in glutathione (GSH) levels within Cd-spiked roots suggested, based on Gaussian analysis, that GSH and Cd chelation were instrumental in mitigating Cd toxicity. When Cd was introduced to both Roots-1 and Roots-2 simultaneously (PS + Cd|Cd), the aforementioned index showed a notable decline.

Less is more: A new strategy combining nanomaterials and PGPB to promote plant growth and phytoremediation in contaminated soil.

Novel combination strategies of nanomaterials (NMs) and plant growth-promoting bacteria (PGPB) may facilitate soil remediation and plant growth. However, the efficiency of the NM-PGPB combination and interactions among NMs, PGPB, and plants are still largely unknown. We used multiwalled carbon nanotubes (MWCNTs) and zero-valent iron (nZVI) combined with Bacillus sp. PGP5 to enhance the phytoremediation efficiency of Solanum nigrum on heavy metal (HM)-contaminated soil. The NM-PGPB combination showed the best promoting effect on plant growth, which also had synergistic effects on the bioaccumulation of HMs in S. nigrum. The MWCNT-PGP5 combination increased the Cd, Pb, and Zn removal efficiency of S. nigrum by 62.03%, 69.44%, and 61.31%, respectively. The underlining causes of improved plant growth and phytoremediation by NMs-PGPB combination were further elucidated. NM application promoted PGPB survival in soil. Compared with each single application, the combined application minimized disturbance to plant transcription levels and rhizosphere microbial community, resulting in the best performance on soil remediation and plant growth. The NM-PGPB-induced changes in the microbial community and root gene expression were necessary for plant growth promotion. This work reveals the "less is more" advantage of the NM-PGPB combination in soil remediation, providing a new strategy for soil management.

Impact of microplastics on microbial-mediated soil sulfur transformations in flooded conditions.

As emerging environmental pollutants, microplastics have become a crucial focus in environmental science research. Despite this, the impact of microplastics on soil in flooding conditions remains largely unexplored. Addressing this gap, our study examined the influence of polystyrene (PS) and polyphenylene sulfide (PPS) on the microbial populations in black soil, meadow soil, and paddy soil under flooded conditions. Given the significant regulatory influence exerted by microorganisms on sulfur transformations, our study was primarily focused on evaluating the microbial contributions to alterations in soil sulfur species. Our findings revealed several notable trends: In black soil, both PS and PPS led to a marked increase in the abundance of γ-proteobacteria and Subgroup_6, while reducing Clostridia. Ignavibacteria were found to be lower under PPS compared to PS. In meadow soil, the introduction of PPS resulted in increased levels of KD4-96 and γ-proteobacteria, while α-proteobacteria decreased. Chloroflexia under PPS was observed to be lower than under PS conditions. In paddy soil, our study identified a significant rise in Bacteroidia and Ignavibacteria, accompanied by a decrease in α-proteobacteria and γ-proteobacteria. γ-proteobacteria levels under PPS were notably higher than those under PS conditions. These shifts in microbial communities induced by both PS and PPS had a direct impact on adenosine 5'-phosphosulfate reductase, sulfite reductase, and polysulfide dioxygenase. Consequently, these changes led to soil organic sulfur decrease and sulfide increase. This study not only offers a theoretical framework but also provides empirical evidence for understanding the effects of microplastics on soil microorganisms and their role in regulating nutrient cycling, particularly in flood-prone conditions. Furthermore, this study underscores the importance of ensuring an adequate supply of sulfur in agricultural practices, such as rice and lotus root cultivation, to support optimal crop growth in the presence of microplastic pollution.

The impact of microplastics on sulfur REDOX processes in different soil types: A mechanism study.

Microplastics can potentially affect the physical and chemical properties of soil, as well as soil microbial communities. This could, in turn, influence soil sulfur REDOX processes and the ability of soil to supply sulfur effectively. However, the specific mechanisms driving these effects remain unclear. To explore this, soil microcosm experiments were conducted to assess the impacts of polystyrene (PS) and polyphenylene sulfide (PPS) microplastics on sulfur reduction-oxidation (REDOX) processes in black, meadow, and paddy soils. The findings revealed that PS and PPS most significantly decreased SO42- in black soil by 9.4%, elevated SO42- in meadow soil by 20.8%, and increased S2- in paddy soil by 20.5%. PS and PPS microplastics impacted the oxidation process of sulfur in soil by influencing the activity of sulfur dioxygenase, which was mediated by α-proteobacteria and γ-proteobacteria, and the oxidation process was negatively influenced by soil organic matter. PS and PPS microplastics impacted the reduction process of sulfur in soil by influencing the activity of adenosine-5'-phosphosulfate reductase, sulfite reductase, which was mediated by Desulfuromonadales and Desulfarculales, and the reduction process was positively influenced by soil organic matter. In addition to their impacts on microorganisms, it was found that PP and PPS microplastics directly influenced the structure of soil enzymes, leading to alterations in soil enzyme activity. This study sheds light on the mechanisms by which microplastics impact soil sulfur REDOX processes, providing valuable insights into how microplastics influence soil health and functioning, which is essential for optimizing crop growth and maximizing yield in future agricultural practices.

Investigating the impact of microplastics on sulfur mineralization in different soil types: A mechanism study.

Microplastics can affect the physicochemical properties of soil and soil microorganisms, potentially resulting in changes in the soil sulfur mineralization and its capacity to supply available sulfur. However, the specific mechanisms underlying these effects remain unclear. We performed soil microcosm experiments, in which the effects of polystyrene (PS) and polyphenylene sulfide (PPS) microplastics on sulfur mineralization were examined in black, meadow, and paddy soils under flooded and dry conditions. Under dry condition, the presence of PS and PPS microplastics impeded sulfur (S) mineralization in black and paddy soils, but promoted sulfur mineralization in meadow soil. The size of microplastics was identified as the primary factor influencing sulfur mineralization in black soil, while in meadow soil, it was influenced by the microplastics type. In the case of paddy soil, the concentration of microplastics was the key factor affecting sulfur mineralization. During the flooding period, PS and PPS microplastics in black and paddy soils curtailed sulfur mineralization, however expedited sulfur mineralization in meadow soil, with PS enhancing soil sulfur mineralization more pronouncedly than PPS in black soil. The type and concentration of microplastics were identified as the main factors affecting sulfur mineralization in black soil, while in paddy soil, it was influenced by the size of microplastics. The principal regulating factors of soil sulfur mineralization were the sulphatase and arylsulfatase enzymes produced by Actinobacteria, Xanthomonadales, and Rhizobiales microorganisms, while organic matter and Olsen-P also had an influential role. Additionally, microplastics directly affected the structure of soil enzymes, thereby altering soil enzyme activities. This study provided insights into the mechanism by which microplastics affect soil sulfur mineralization, offering significant implications for assessing the influence of microplastics on soil sulfur availability and making informed decisions about sulfur application in future agricultural practices.

Effective Removal of Cd from Aqueous Solutions Using P-Loaded Ca-Mn-Impregnated Biochar.

Cadmium (Cd) pollution in wastewater has become an increasingly widespread concern worldwide. Studies on Cd (II) removal using phosphate-adsorbed sorbents are limited. This study aimed to elucidate the behaviors and mechanisms of Cd (II) sorption on phosphate-loaded Ca-Mn-impregnated biochar (Ps-CMBC). The Cd (II) sorption on Ps-CMBC reached equilibrium within 2 h and exhibited a higher sorption efficiency than biochar and CMBC. Additionally, the Langmuir isotherm could better describe the Cd (II) adsorption on the sorbents. P75-CMBC had a maximum Cd (II) sorption capability of 70.13 mg·g-1 when fitted by the Langmuir isotherm model, which was approximately 3.18 and 2.86 times greater than those of biochar and CMBC, respectively. Higher pH (5-7) had minimal effect on Cd (II) sorption capacity. The results of characterization analyses, such as SEM-EDS, FTIR, and XPS, suggested that there was a considerable difference in the sorption mechanisms of Cd (II) among the sorbents. The primary sorption mechanisms for biochar, CMBC, and Ps-CMBC included electrostatic attraction and surface complexation; additionally, for Ps-CMBC, Cd (II)-π interactions and coordination of Cd (II) with P=O were critical mechanisms for Cd (II) removal. The results of this study demonstrate that phosphate-loaded CMBC can be used as an effective treatment for heavy metal pollution in aqueous media.

Enhancing rice quality and productivity: Multifunctional biochar for arsenic, cadmium, and bacterial control in paddy soil.

The perilousness of arsenic and cadmium (As-Cd) toxicity in water and soil presents a substantial hazard to the ecosystem and human well-being. Additionally, this metal (loids) (MLs) can have a deleterious effect on rice quality and yield, owing to the existence of toxic stress. In response to the pressing concern of reducing the MLs accumulation in rice grain, this study has prepared magnesium-manganese-modified corn-stover biochar (MMCB), magnesium-manganese-modified eggshell char (MMEB), and a combination of both (MMCEB). To test the effectiveness of these amendments, several pot trials were conducted, utilizing 1% and 2% application rates. The research discovered that the MMEB followed by MMCEB treatment at a 2% rate yielded the most significant paddy and rice quality, compared to the untreated control (CON) and MMCB. MMEB and MMCEB also extensively decreased the MLs content in the grain than CON, thereby demonstrating the potential to enrich food security and human healthiness. In addition, MMEB and MMCEB augmented the microbial community configuration in the paddy soil, including As-Cd detoxifying bacteria, and decreased bioavailable form of the MLs in the soil compared to the CON. The amendments also augmented Fe/Mn-plaque which captured a considerable quantity of As-Cd in comparison to the CON. In conclusion, the utilization of multifunctional biochar, such as MMEB and MMCEB, is an encouraging approach to diminish MLs aggregation in rice grain and increase rice yield for the reparation of paddy soils via transforming microbiota especially enhancing As-Cd detoxifying taxa, thereby improving agroecology, food security, and human and animal health.

Characteristics of a Novel Decomposed Corn Straw-Sludge Biochar and Its Mechanism of Removing Cadmium from Water.

The utilization of high-efficiency adsorption materials to reduce cadmium pollution in aquatic environments is the focus of current environmental remediation research. Straw waste and sludge, which are available in huge amounts, can be best utilized in the preparation of environmental remediation materials. In this study, six types of biochar (SBC, CBC, DBC, SD1BC, SRDBC, and SCDBC) were prepared from straw and sludge by co-pyrolysis, and their cadmium adsorption mechanisms were explored. Cd(II) adsorption isotherms and kinetics on the biochar were determined and fitted to different models. Kinetic modeling was used to characterize the Cd(II) adsorption of biochar, and findings revealed the process of sorption followed pseudo-second-order kinetics (R2 > 0.96). The Langmuir model accurately represented the isotherms of adsorption, indicating that the process was monolayer and controlled by chemical adsorption. SCDBC had the highest capacity for Cd(II) adsorption (72.2 mg g-1), 1.5 times greater than that of sludge biochar, and 3 times greater than that of corn straw biochar. As the pH level rose within the range of pH 5.0 to 7.0 and the ionic strength decreased, the adsorption capacity experienced an increase. SCDBC contained CaCO3 mineral crystals before Cd(II) adsorption, and CdCO3 was found in SCDBC after adsorbing Cd(II) via X-ray diffraction analysis; the peak of Cd could be observed by Fourier transform infrared spectroscopy after the adsorption of Cd(II). The possible adsorption of Cd(II) by SCDBC occurred primarily via surface complexation with active sorption sites, precipitation with inorganic anions, and coordination with π electrons. Collectively, the study suggested that the six types of biochar, particularly SCDBC, could be used as highly efficient adsorbents for Cd(II) removal from aquatic environments.

Effects of polystyrene nanoplastics with different functional groups on the accumulation and toxicity of Pb on dandelion.

Micro (Nano)plastics are ubiquitous in the environment and can potentially affect the toxic effects of other chemicals, such as heavy metals. Although the interaction of micro (nano)plastics and heavy metals as well as their effects on aquatic organisms have been widely investigated, studies on their influence on terrestrial plants are limited. Therefore, in this study, the effects of polystyrene (PS), carboxy-modified PS (CPS) and amino-modified PS (APS) nanoparticles on the accumulation and toxicity of Pb on dandelion (Taraxacum asiaticum Dahlst) were investigated using hydroponic cultivation. The presence of the three PS caused cell damage and destroyed the tertiary structure of the ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and dehydrogenase (DHA) enzymes, thereby inhibiting Rubisco and root activities, which hindered nutrient uptake and photosynthesis. The inhibition of APS on the biomass of dandelion was greater than that of PS and CPS. Confocal laser scanning microscope and transmission electron microscopy analysis showed that APS was more likely to enter the roots of dandelion than PS and CPS. The presence of Pb induced more PS, CPS, and APS to enter dandelion roots, and Pb aggravated PS and CPS toxicities on dandelion rather than APS toxicity. This is because the complex formed by CPS and Pb can affect the structure of Rubisco and DHA through covalent and coordination bonds, and Pb increased the surface positive charge on CPS, according to Gaussian analysis. The presence of both PS and CPS significantly reduced Pb uptake by dandelion, and they did not exacerbate the toxicity of Pb. In contrast, APS slightly inhibited Pb accumulation, but aggravated Pb toxicity in dandelion. Our findings revealed that the changes in the uptake of nanoplastics and Pb by dandelion potentially resulted in a cascade of events that increased the toxicity and inhibited the growth of dandelion seedlings.

Effect of co-toxicity of lead and nanoplastics on the flavonoid biosynthetic pathway in dandelion (Taraxacum asiaticum Dahlst).

MAIN CONCLUSION: Negatively charged carboxy-polystyrene (CPS) and positively charged amino-polystyrene (NPS) could significantly inhibit the biomass and flavonoid content of dandelion roots and leaves, and the inhibitory effect of NPS was stronger than that of CPS. The increasingly serious pollution of microplastics and heavy metals is likely to affect the efficacy of flavonoids synthesized by dandelion in natural medicine fields. Therefore, we combined hydroponic experiments with computational chemistry (Gaussian and autodock analysis) to explore the mechanism by which amino-polystyrene (NPS), carboxy-polystyrene (CPS), and lead affect the flavonoid biosynthetic pathway in dandelion (Taraxacum asiaticum Dahlst). Our results show that CPS and NPS could significantly inhibit the biomass and flavonoid content of dandelion roots and leaves, and the inhibitory effect of NPS was stronger than that of CPS. Mechanistic studies showed that CPS and NPS increased the content of O2- and H2O2 in dandelion roots and leaves, causing membrane lipid peroxidation, resulting in cell damage and decreased biomass. CPS and NPS inhibited related enzymatic activities by affecting their tertiary structures, resulting in a decrease in phenolic acid, coumaroyl-CoA, and flavonoid content. Dandelion preferred to absorb positively charged NPS compared to negatively charged CPS, but CPS inhibited the uptake of Pb by dandelion more strongly than NPS. Pb promoted CPS agglomeration and increased the surface positive charge of CPS through coordination bonds and hydrogen bonds, so more CPS entered dandelion under CPS + Pb treatment than under CPS alone. Although NPS and CPS reduced the uptake of Pb by dandelion, the biomass and flavonoid contents of dandelion were lower than those of single Pb treatment because of the higher toxicity of NPS and CPS than Pb. Pb significantly increased the effect of CPS on the root biomass of dandelion compared with CPS alone by increasing the positive charge of CPS. We suggest that microplastics with different charges and lead composite pollution inhibit dandelion flavonoid biosynthesis and provide a reference for the loss of dandelion medicinal components and economic value.

Effects of polystyrene nanoplastics on lead toxicity in dandelion seedlings.

Increasing rates of commercialization and industrialization have led to the comprehensive evaluation of toxic effects of microplastics on crop plants. However, research on the impact of functionalized polystyrene nanoplastics on the toxicity of heavy metals remains limited. This study investigated the effects of polystyrene, carboxy-modified polystyrene, and amino-modified polystyrene on lead (Pb) toxicity in dandelion seedlings. The results showed that carboxy -modified polystyrene with a negative charge absorbed more Pb2+ than polystyrene and amino-modified polystyrene, and their maximum adsorption amounts were 5.328, 0.247, and 0.153 µg g-1, respectively. The hydroponic experiment demonstrated that single amino-modified polystyrene was more toxic to dandelion seedlings than polystyrene and carboxy-modified polystyrene. The presence of Pb2+ was found to increase antioxidant enzymes (superoxide dismutase and catalase) and non-antioxidant enzymes (glutathione and ascorbic acid) activities in response to excessive reactive oxygen species in dandelion leaves and roots treated with polystyrene and carboxy-modified polystyrene, while it did not change much when amino-modified polystyrene was added. Interestingly, compared with single Pb2+, the addition of amino-modified polystyrene with positive charges induced an obvious decrease in the above parameters; however, they declined slightly in the treatments with polystyrene and carboxy-modified polystyrene despite a stronger adsorption capacity for Pb2+. Similarly, the bioactive compounds, including flavonoids, polyphenols, and polysaccharides in dandelion, showed a scavenging effect on O2- and H2O2, thereby inhibiting the accumulation and reducing medicinal properties. This study found that the effects of microplastics on the uptake, distribution, and toxicity of heavy metals depended on the nanoparticle surface charge.

A novel Ca/Mn-modified biochar recycles P from solution: mechanisms and phosphate efficiency.

The excessive use of phosphate leads to severe environmental issues, such as a shortage of phosphorus resources and water eutrophication. In this study, a novel Ca-Mn-impregnated biochar (CMBC) composite was synthesized by co-pyrolysis at 600 °C for P recovery from solution. The efficiency of P-sorbed CMBC as a fertilizer was assessed via pot experiments. Kinetic experiments exhibited a higher phosphate sorption efficiency for the CM1BC and CM2BC composites. Pot experiments revealed that P-sorbed CMBC treatment significantly improved plant growth and yield. Compared with those of the control, the dry weight, fresh weight, and P content of rape leaf (root) P50-CMBC1.0% treatment increased by 108.6% (350%), 88.7% (396%), and 132.8% (109.3%), respectively. This may be due to the porous surface structures that develop during the treatment and Ca-P precipitation on P-sorbed biochar partly dissolved in the slightly acidic soil (pH: 6.25). The maximum P adsorption values fitted by the Langmuir isotherm model were up to 9.15, 3.19, 15.58, and 20.84 mg g-1 for CBC, MBC, CM1BC, and CM2BC, respectively. The mechanism of phosphate recovery mainly includes electrostatic attraction, surface precipitation, and the formation of inner-sphere complexes with hydroxyl groups that were assessed using BET, zeta potential, SEM-EDS, FTIR, and XPS analyses. These mechanisms suggest that phosphate may be desorbed from the P-laden sorbent, which was consistent with the results of the pot experiments and desorption experiments in aqueous media. These results imply that P-sorbed modified biochar has the potential to be a promising P fertilizer in soil.

A novel mechanism study of microplastic and As co-contamination on indica rice (Oryza sativa L.).

Although the compound pollution of microplastics and arsenic (As) in paddy soil can affect the growth and quality of rice, relevant research on this phenomenon was limited. Therefore, we combined a pot experiment with computational chemistry to explore the effects and mechanism of polystyrene (PSMP) and polytetrafluoroethylene (PTFE) microplastics on As bioavailability. PSMP and PTFE interacted with rice root exudates through van der Waals forces, approached the rice root system, inhibited root activity, reduced the relative abundance of Geobacteria and Anaeromyxobacter, and consequently reduced the iron plaques on the root surfaces. Consequently, As uptake by the rice was inhibited. PSMP and PTFE reduced the hemoglobin content by directly destroying its tertiary structure, thereby retarding rice growth. In contrast, As increased the hemoglobin content by inducing reactive oxygen species in rice. Under the influence of PSMP, PTFE, and As, the activities of soluble starch synthase and pyrophosphorylase in rice grains were inhibited, and starch accumulation decreased. Thus, PSMP, PTFE, and As reduced rice biomass and yield owing to their physiological toxicity and adverse impacts on root activity. Grain yields in soil with an As content of 86.3 mg·kg-1, 0.5% small particle-sized PSMP, and 0.5% small particle-sized PTFE decreased by 30.7%, 20.6%, and 19.4%, respectively, compared to the control. This study determined the comprehensive mechanism through which PSMP and PTFE affect As bioavailability, which is critical for managing rice biomass and low yields in As and microplastic co-contaminated soil.

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As a carrier of environmental pollutants, microplastics have received wide concerns in recent years. However, the direct and indirect effects of the coexistence of polystyrene particles (PS) and pollutants on vegetables are still unclear. Here, the combined effects of 0.25, 0.50, 1.0 mg·mL-1 PS and 5 mg·L-1 dibutyl phthalate (DBP) on the biomass and biochemical indices of purple lettuce were investigated in hydroponic experiments. The results showed that the presence of PS increased the inhibition of DBP on lettuce biomass and increased O2-· content in roots and leaves relative to the control group with DBP alone, with positive consequences on the activities of supero-xide dismutase, ascorbic acid peroxidase, dehydroascorbate reductase and monodehydroascorbate reductase. According to transmission electron microscope analysis, plasmolysis occurred in root cells under the treatment of DBP alone, cell wall was damaged in PS-only treatment, and the negative effect was enhanced when DBP and PS coexisted. Therefore, the combined pollution of PS and DBP aggravated the toxic effect on purple lettuce.

Response of soil characteristics to biochar and Fe-Mn oxide-modified biochar application in phthalate-contaminated fluvo-aquic soils.

Biochar (BC) derived from agricultural biomass is effective at immobilizing phthalate in the agricultural soil environment. In this study, we assessed the effects of 0.5%, 1%, and 2% BC and Fe-Mn oxide-modified biochar (FMBC) addition on dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP) residues and biochemical characteristics in the rhizosphere soil of mature wheat polluted with DBP and DEHP using a pot experiment. Scanning electron microscopy showed that the surfaces and pores of BC and FMBC adhered soil mineral particles after remediation. Therefore, DBP and DEHP residues were increased in BC- and FMBC-treated soils. Illumina HiSeq sequencing showed that, compared with the control, BC and FMBC addition significantly enhanced the relative abundance of Firmicutes and reduced Proteobacteria. The abundance of Sphenodons and Pseudomonas, which degrade phthalates, tended to be higher in FMBC-amended soils than in BC-amended and control soils. This result may be related to an increase in available nutrients and organic matter following BC and FMBC application. Subsequently, the changes in soil bacterial abundance and community structure induced an increase in polyphenol oxidase, ß-glucosidase, neutral phosphatase, and protease activity in BC and FMBC remediation. In comparison with the BC treatment, FMBC addition had a significantly positive effect on enzyme activity, and the microbial structure and was therefore more effective at immobilizing DBP and DEHP in the soil. Thus, our findings strongly suggest that FMBC is a reliable remediation material for phthalate-contaminated soil.

The influence of humic and fulvic acids on polytetrafluoroethylene-adsorbed arsenic: a mechanistic study.

The large-scale use of polytetrafluoroethylene has resulted in ever-increasing amounts of polytetrafluoroethylene (PTFE) microplastic particles entering the environment. Given that the environment is polluted with arsenic (As(III)), and that the environment contains significant levels of humic acid (HA) and fulvic acid (FA), how PTFE and As(III) in water interacting in the presence of HA and FA needs to be urgently investigated. The results showed that As(III) was adsorbed by PTFE in the presence of HA and FA more markedly than the absence of them Adsorption equilibrium was reached at approximately 960 min and the adsorption isotherms were found to be best fitted by the Toth model. An increase in temperature was found to destroy hydrogen bonds, resulting in inhibited, non-spontaneous adsorption; a higher pH inhibited adsorption in the range 3-7. Computational and mechanistic studies revealed that PTFE formed π complexes with HA units, which increased the number of oxygen-containing functional groups on its surface. The surface of the PTFE-HA π complex was mostly negatively charged; however, the hydrogen atoms of the hydroxyl and carboxylic acid groups exhibited large positive potentials that enabled the adsorption of As(III). When the oxygen atom on As was close to the oxygen-containing functional group on PTFE-HA, the more electronegative oxygen atom forms a special intermolecular interaction in the form of O-H···O through the medium of hydrogen, which makes As adsorb on the surface of PTFE. Pore filling, hydrogen bonding, and covalent bonding are the main ways in which PTFE adsorbs As(III) in the presence of HA and FA. PTFE also adsorbed more As(III) in the presence of HA than in the presence of FA.

Mechanism of As(III) removal properties of biochar-supported molybdenum-disulfide/iron-oxide system.

Sulfate (SO4•-) and hydroxyl-based (HO•) radical are considered potential agents for As(III) removal from aquatic environments. We have reported the synergistic role of SO4•- and HO• radicals for As(III) removal via facile synthesis of biochar-supported SO4•- species. MoS2-modified biochar (MoS2/BC), iron oxide-biochar (FeOx@BC), and MoS2-modified iron oxide-biochar (MoS2/FeOx@BC) were prepared and systematically characterized to understand the underlying mechanism for arsenic removal. The MoS2/FeOx@BC displayed much higher As(III) adsorption (27 mg/g) compared to MoS2/BC (7 mg/g) and FeOx@BC (12 mg/g). Effects of kinetics, As(III) concentration, temperature, and pH were also investigated. The adsorption of As(III) by MoS2/FeOx@BC followed the Freundlich adsorption isotherm and pseudo-second-order, indicating multilayer adsorption and chemisorption, respectively. The FTIR and XPS analysis confirmed the presence of Fe-O bonds and SO4 groups in the MoS2/FeOx@BC. Electron paramagnetic resonance (EPR) and radical quenching experiments have shown the generation of SO4•- radicals as predominant species in the presence of MoS2 and FeOx in MoS2/FeOx@BC via radical transfer from HO• to SO42-. The HO• and SO4•- radicals synergistically contributed to enhanced As(III) removal. It is envisaged that As(III) initially adsorbed through electrostatic interactions and partially undergoes oxidation, which is finally adsorbed to MoS2/FeOx@BC after being oxidized to As(V). The MoS2/FeOx@BC system could be considered a novel material for effective removal of As(III) from aqueous environments owing to its cost-effective synthesis and easy scalability for actual applications.

Effect of Fe-Mn-La-modified biochar composites on arsenic volatilization in flooded paddy soil.

As can be volatilized naturally; however, this has adverse environmental effects. In this study, we investigated As volatilization in flooded paddy soil with the addition of biochar (BC) and Fe-Mn-La-modified BC composites (FMLBCs). The addition of BC and FMLBCs caused decreases in total As volatilization in the soil over 7 weeks. Maximum volatilization was achieved in the third week followed by stabilization. Volatilization decreased by 21.9%, 18.8%, 20.8%, and 31.1% with the addition of BC, FMLBC1, FMLBC2, and FMLBC3 (BC/Fe/Mn/La weight ratios different), respectively, in lightly contaminated soil, and by 15.2%, 20.5%, 17.6%, and 25.4%, respectively, in highly contaminated soil. The FMLBCs decreased the exchangeable As fractions and increased the non-swappable As in the soil. Furthermore, the addition of FMLBCs significantly reduced the As(III) concentration in a suspended solution (P < 0.05), whereas no significant changes were observed in the As(V) or methyl arsenic acid concentrations. Soil enzyme activity increased and the relative abundances of Proteobacteria and Actinobacteria changed with the addition of FMLBCs. Therefore, the mechanism by which FMLBCs affected As volatilization likely included the following two aspects: (1) FMLBCs affected the transformation and distribution of soil As and decreased As dissolution, crystallization, and methylation; (2) FMLBCs influenced soil properties, which directly affected microorganism activity, thereby affecting As volatilization. FMLBCs therefore can decrease As volatilization properties and be used to control As volatilization in As-contaminated paddy soils.