Efficacy of Agricultural Residue-Derived Biochar for Tackling Cadmium Contamination in an Aqueous Solution.

This study aimed to investigate the efficacy of biochar, produced from different agricultural residues varying in lignin and cellulose content and subjected to different pyrolysis temperatures, in removing cadmium ions (Cd (II)) from an aqueous solution. This removal process is crucial for protecting human health and the environment. Specifically, the study focused on the adsorption behaviors of Cd (II) by the biochars made from rice husk biochar (RHB), maize straw biochar (MSB), peanut shell biochar (PSB), cottonseed shell biochar (CHB), and mulberry leaf biochar (MLB), which were prepared at 300 °C and 600 °C. The results indicated that the type of agricultural residue used to produce biochar significantly influenced the adsorption of Cd (II). Notably, mulberry leaf biochar prepared at 300 °C (MLB-300) demonstrated the highest adsorption efficiency, achieving a maximum adsorption capacity of 42.2 mg g-1. Batch adsorption experiments assessed the impact of various factors, including system pH, NO3- concentration, and adsorption duration. The adsorption kinetics were better described by the pseudo-second-order model than the pseudo-first-order model. Moreover, the study found that the lignin content of the biochar plays a major role in determining the adsorption capacity. The surface characteristics of biochar, influenced by the types of agricultural residues and preparation temperature, directly impact its adsorption mechanism and capacity. While biochar produced at 300 °C showed optimal Cd(II) adsorption, those processed at 600 °C were less effective, likely due to the loss of functional groups at higher temperatures.

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.

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.

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.

Effect of microplastics and arsenic on nutrients and microorganisms in rice rhizosphere soil.

The presence of microplastics and arsenic in soil can endanger crop growth; therefore, their effects on the properties of rhizosphere soil should be evaluated. Large (10-100 µm) and small (0.1-1 µm) polystyrene (PSMP) and polytetrafluorethylene (PTFE) particles were added to soil with different arsenic concentrations (1.4, 24.7, and 86.3 mg kg-1) to investigate the combined effect of microplastics and arsenic pollution on rice rhizosphere soil. After the addition of PSMP and PTFE, pH, arsenic (V) and arsenic (III) in the soil were observed to decrease. The interaction of arsenic with PSMP and PTFE resulted in this phenomenon, leading to a decrease of arsenic bioavailability in the soil. PSMP, PTFE, and arsenic reduced the abundance of Proteobacteria, increased the abundance of Chloroflexi and Acidobacteria, and inhibited soil urease, acid phosphatase, protease, dehydrogenase, and peroxidase activity via affecting the tertiary structure of the enzyme. PSMP, PTFE, and arsenic also reduced the available nitrogen and phosphorus content in the soil. Arsenic increased the soil organic matter content, whereas PSMP and PTFE reduced the organic matter content. Furthermore, microplastics inhibited the effects of arsenic on the microbial and chemical properties of the rhizosphere soil. This study revealed the effects of microplastic and arsenic pollution on rice rhizosphere microorganisms and nutrients, and elucidated the mechanism by which these pollutants retard crop growth in the designed growth medium.

Effects of Fe-Mn oxide-modified biochar composite applications on phthalate esters (PAEs) accumulation in wheat grains and grain quality under PAEs-polluted brown soil.

Phthalate esters (PAEs), such as dibutyl phthalate (DBP) and di-(2-ethylhexyl) phthalate (DEHP), are used extensively as additives and plasticizers, and have become ubiquitous in the environment. PAEs in the soil could have adverse effects on crop plants as well as humans via accumulations in food chain. Thus, it is important to explore strategies to reduce the bioavailability of phthalate esters. We investigated the effects of Fe-Mn oxide-modified biochar composite (FMBC) applications on the quality of wheat grown in DBP- and DEHP-polluted brown soil. The application of FMBC and biochar (BC) increased the wheat grain biomass by 9.71-223.01% and 5.40-120.15% in the DBP-polluted soil, and 10.52-186.21% and 4.50-99.53% in the DEHP-spiked soil in comparison to the controls. All FMBC treatments were better than the BC treatments, in terms of decreasing DBP and DEHP bioavailability for the wheat grains. The activities of the glutamine synthetase and glutamic-pyruvic transaminase in the flag leaves at the filling stage and of granule-bound starch synthase, soluble starch synthase, and adenosine diphosphate-glucose pyrophosphorylase in the grains at maturity increased significantly with increases in either the BC or FMBC applications. This, in turn, increased the starch, protein, and amino acid content in the wheat grains. Compared with the BC treatment, the FMBC amendment induced only slight increases in the aforementioned factors. This study offers novel insights into potential strategies for decreasing PAEs bioavailability in soil, with potential positive implications for crop quality and environmental health improvements.

Effects of di-n-butyl phthalate on rhizosphere and non-rhizosphere soil microbial communities at different growing stages of wheat.

The potential effects of dibutyl phthalate (DBP) on soil ecosystems and biological processes have recently aroused great concern because of the ubiquitous nature of this pollutant. However, the effects of DBP-associated disturbance on rhizosphere and non-rhizosphere soil microbial communities remain poorly understood. In the present study, we investigated the effects of DBP contamination on microbial function and soil enzyme activities in rhizosphere and non-rhizosphere soils throughout the growing season of wheat. We conducted pot experiments under glasshouse conditions and used different concentrations of DBP: 10, 20, and 40 mg kg-1. We found that the average well color development value and McIntosh index in rhizosphere and non-rhizosphere soils increased in the 10 and 20 mg kg-1 DBP treatments, but declined in the 40 mg kg-1 DBP treatment at the seedling and tillering stages, particularly, in the non-rhizosphere soil. DBP addition enhanced the Shannon-Wiener and Simpson indexes in rhizosphere and non-rhizosphere soils throughout the growing period of wheat. A principal component analysis clearly differentiated the treatments from the control, indicating that DBP led to different patterns of potential carbon utilization in rhizosphere and non-rhizosphere soils. The microbial use of amino acids was significantly increased in rhizosphere and non-rhizosphere soils after DBP addition, while the use of carbohydrates was significantly declined (p < 0.05). The dehydrogenase, urease, and acid phosphatase activities were significantly stimulated (p < 0.05) at the seedling stage, while the phenol oxidase and ß-glucosidase activities were inhibited. The 40 mg kg-1 DBP treatment significantly decreased the phenol oxidase and ß-glucosidase activities in rhizosphere and non-rhizosphere soils at the seedling stage, particularly in non-rhizosphere soil (p < 0.05). The microbial function and soil enzymatic activities were gradually restored following the wheat growing stage. These results offer a better understanding of the effects of DBP on the activities and functional diversity of microbial communities in farmland soils.

Effects of graphene oxide on cadmium uptake and photosynthesis performance in wheat seedlings.

Graphene oxide (GO) is extensively used in various fields because of its versatility. The presence of GO in the environment enhances the toxicity of toxicants or pollutants. Cadmium (Cd) and GO pollution is a problem in aquatic environment, which should be solved. We investigated the toxic effects of Cd on photosynthesis and oxidative stress in wheat seedlings in the presence of GO, by measuring seedling biomass, Cd content, photosynthesis, reactive oxygen species (ROS) level, antioxidant enzyme activities, and malondialdehyde (MDA) content. At low concentrations, GO alone had limited effects, but at concentrations > 20 mg L-1, seedlings were negatively affected. Under combined Cd-GO treatment, GO was significantly toxic at only 5 mg L-1 concentration, and increasing concentration significantly increased Cd accumulation and decreased biomass. The net photosynthetic rate, stomatal conductance, transpiration rate, primary maximum photochemical efficiency of photosystem II, actual quantum yield, photosynthetic electron transport rate, chlorophyll content, and ribulose-1,5-bisphosphate carboxylase/oxygenase concentration decreased significantly, whereas intercellular CO2 concentration increased significantly. These changes can be attributed to impairment of ROS level, antioxidant enzyme activities, and MDA level, and toxicity mechanisms are suggested to be due to oxidative stress. The resulting damage to the photosynthetic systems and structures likely contributed to the overall decrease in biomass.

Effects of biodegradable chelator combination on potentially toxic metals leaching efficiency in agricultural soils.

Soil washing with chelators, a viable method for treating soils contaminated with potentially toxic metals, has drawn increasing attentions. The objective of this study was to determine a new generation of mixed degradable chelating agents from N, N-bis (carboxymethyl) glutamic acid (GLDA), [S, S]-stereoisomer of ethyleneiaminedisucc--inic acid (EDDS), nitrilotriacetic acid (NTA), and citric acid (CA), and to evaluate its effectiveness and feasibility to reduce toxic metals contamination in two different agricultural soils. A comparative leaching test conducted on the four individual degradable chelating agents showed that the capacity of single chelator in mobilizing copper (Cu), zinc (Zn), cadmium (Cd), and lead (Pb) varied significantly. Using a combination of GLDA and NTA was more advantageous than using a single chelating agent in extracting potentially toxic metals. The removal efficiencies of Cu, Zn, Cd, and Pb reached 38.2, 9.8, 71.4, and 19.5% for soil 1, and 25.0, 5.2, 59.7, and 18.5% for soil 2, respectively, at mixed chelator (MC) concentrations of 3 mmol/L (GLDA) and 2 mmol/L (NTA), pH of 6.0, and a contact time of 4.0 h. The effects of washing conditions, chelator concentration, pH values, and contact time on the removal efficiencies of target toxic metals were investigated. The results showed that the combined chelating agent has a lower pH dependence, making it feasible for a wider range of applications. The effects of the chelating agents on the morphological distribution of potentially toxic metals and the soil enzyme activity before and after the treatments were also studied. After washing, the content of the water-soluble, acid-soluble, reducible, and oxidizable target metals showed a certain degree of decrease. Although the activities of catalase, urease, and invertase appeared to be inhibited during a short period of time, their activities were stimulated and later promoted with the degradation of the chelating agent. In general, the chelating agent combination has a great potential for toxic metals leaching.

Transcriptome analysis of the effects of Cd and nanomaterial-loaded Cd on the liver in zebrafish.

The wide application of engineered nanoparticles to remove heavy metals in aquatic environments has raised concerns over nanomaterial-adsorbed heavy metal toxicity. To ensure safe use of nanomaterial-heavy metal composites, understanding their biological effects at the molecular level is crucial. In the present study, we used the Illumina HiSeq technology to study the transcriptome changes induced by Cd2+ and nano-manganese dioxide- or nano-hydroxyapatite-adsorbed CdCl2 composites (nMnO2-Cd, nHAP20-Cd, and nHAP40-Cd) in zebrafish liver cells. We identified 545 differentially expressed genes (DEGs), 33 of which were in common between the nMnO2-Cd, nHAP20-Cd, and nHAP40-Cd groups. The DEGs could be classified in four categories: hydrolases (enzymes involved in various physiological functions, including digestion, immune response, blood coagulation, and reproduction), biological binding (FMN-, actin- and metal ion-binding), metabolic enzymes (e.g., ceramidase, alpha-amylase, carboxylic ester hydrolase, and carboxypeptidase), and cell structure (cell surface, intermediate filament, and muscle myopen protein). The DEGs identified in this study are potentially useful markers to understand the physiological responses induced by Cd2+ and nano-Cd composites in zebrafish liver.

Reduction of arsenic toxicity in two rice cultivar seedlings by different nanoparticles.

In this study, we investigated arsenic uptake and enzymatic activities in rice seedlings after the addition of nanoparticles. Hydroponic experiments were conducted to investigate the effects of different nanomaterials (high-quality graphene oxide, multilayer graphene oxide, 20 nm hydroxyapatite (HA20), 40 nm hydroxyapatite (HA40), nano-Fe3O4 (nFe3O4) and nano-zerovalent iron [nFe]) on the biomass, arsenic uptake, and enzyme activities in seedlings of the rice cultivars T705 and X24. Compared with the control, the addition of different nanomaterials increased seedling growth, with X24 rice growing better than T705 rice. Nanomaterials effectively reduced arsenic uptake in T705 rice seedlings under low and high arsenic concentrations; however, they were only effective at lower arsenic concentrations in X24 seedlings. nFe3O4 and nFe performed better than other nanomaterials in preventing arsenic from being transported to the aboveground parts of the rice seedlings. Different nanomaterials obviously influenced enzyme activities in the T705 seedlings at low arsenic concentrations (≤ 0.8 mg L-1). High-quality and multilayer graphene oxide decreased enzyme activities in the aboveground parts of the T705 seedlings, whereas, HA20 and HA40 increased the enzyme activities. nFe3O4 and nFe also reduced the effect of antioxidants in the aboveground parts of the T705 seedlings. Nanomaterials effectively reduced the arsenic uptake of T705 and X24 rice seedlings at low arsenic concentrations.

Arsenic removal in aqueous solution by a novel Fe-Mn modified biochar composite: Characterization and mechanism.

The aim of this study was to develop a cost-effective method for As removal from aqueous systems. To this end, pristine biochar (BC) was impregnated with Fe-Mn oxides and a comparative analysis was conducted on the adsorption capacities of BC, Fe-Mn binary oxide (FMO), and Fe/Mn modified biochar (FMBC). The ferromanganese oxides increased the specific surface areas of BC. FMBC presented greater adsorption of As (Qmax = 8.25mgg-1) than FMO and BC. Energy dispersive spectrometer analysis and electron microscope scanning revealed numerous pores of FMBC with the existence of Fe-Mn oxide using. Distinguished binding energy shifting of the As3d, Fe2p, O1s, and Mn2p3/2 regions after As sorption were found, indicating that Mn(III) oxidation and interaction of oxygen-containing function groups in the FMBC promoted the conversion of As(III) to As(V). Furthermore, chemisorption was found to be the main mechanism for As sorption on FMBC. Thus, the results suggest that FMBC could be used as an inexpensive and highly efficient adsorbent for As removal from water environment.

Adsorption Properties of Nano-MnO2-Biochar Composites for Copper in Aqueous Solution.

There is a continuing need to develop effective materials for the environmental remediation of copper-contaminated sites. Nano-MnO2-biochar composites (NMBCs) were successfully synthesized through the reduction of potassium permanganate by ethanol in a biochar suspension. The physicochemical properties and morphology of NMBCs were examined, and the Cu(II) adsorption properties of this material were determined using various adsorption isotherms and kinetic models. The adsorption capacity of NMBCs for Cu(II), which was enhanced by increasing the pH from 3 to 6, was much larger than that of biochar or nano-MnO2. The maximum adsorption capacity of NMBCs for Cu(II) was 142.02 mg/g, which was considerably greater than the maximum adsorption capacities of biochar (26.88 mg/g) and nano-MnO2 (93.91 mg/g). The sorption process for Cu(II) on NMBCs fitted very well to a pseudo-second-order model (R² > 0.99). Moreover, this process was endothermic, spontaneous, and hardly influenced by ionic strength. The mechanism of Cu(II) adsorption on NMBCs mainly involves the formation of complexes between Cu(II) and O-containing groups (e.g., COO-Cu and Mn-O-Cu). Thus, NMBCs may serve as effective adsorbents for various environmental applications, such as wastewater treatment or the remediation of copper-contaminated soils.

Chloride ions promoted the catalytic wet peroxide oxidation of phenol over clay-based catalysts.

Catalytic wet peroxide oxidation (CWPO) of phenol over clay-based catalysts in the presence and absence of NaCl was investigated. Changes in the H2O2, Cl(-), and dissolved metal ion concentration, as well as solution pH during phenol oxidation, were also studied. Additionally, the intermediates formed during phenol oxidation were detected by liquid chromatography-mass spectroscopy and the chemical bonding information of the catalyst surfaces was analyzed by X-ray photoelectron spectroscopy (XPS). The results showed that the presence of Cl(-) increased the oxidation rate of phenol to 155%, and this phenomenon was ubiquitous during the oxidation of phenolic compounds by H2O2 over clay-based catalysts. Cl(-)-assisted oxidation of phenol was evidenced by several analytical techniques such as mass spectroscopy (MS) and XPS, and it was hypothesized that the rate-limiting step was accelerated in the presence of Cl(-). Based on the results of this study, the CWPO technology appears to be promising for applications in actual saline phenolic wastewater treatment.

Effects of a manganese oxide-modified biochar composite on adsorption of arsenic in red soil.

The arsenic adsorption capacity of a manganese oxide-modified biochar composite (MBC), prepared by pyrolysis of a mixture of potassium permanganate and biochar, was investigated in red soil. Adsorption experiments using batch procedures were used to estimate the arsenic adsorption capacities of the absorbent materials. Adsorption and desorption isotherms, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) were used to characterise the prepared adsorbent materials, and a plausible mechanism for arsenic removal by MBC was proposed. Arsenic in red soil-MBC mixtures exhibited lower mobility than that in soils amended with pristine biochar. The improved removal performance of soil-MBC mixtures was attributed to a lower H/C ratio, higher O/C ratio, higher surface hydrophilicity, and higher surface sorption capacity, even though the impregnation of manganese oxide decreased the specific surface area of the biochar. Arsenic retention increased as the biochar content increased, mainly owing to an increase in soil pH. Several oxygenated functional groups, especially O-H, CO, Mn-O, and Si-O, participated in the adsorption process, and manganese oxides played a significant role in the oxidation of arsenic. This study highlights the potential of MBC as an absorbent to immobilise arsenic for use in contaminated land remediation in the red soils region.

Biochars derived from various crop straws: characterization and Cd(II) removal potential.

Five types of biochars prepared from four crop straws and one wood shaving at 600 °C were characterized, and their sorption to Cd(II) were determined to investigate the differences in capacity to function as sorbents to heavy metals. Surface areas and pore volumes of the biochars were inversely correlated to the lignin content of raw biomass. The biochars derived from crop straws displayed more developed pore structure than wood char due to the higher lignin content of wood. Sorption capacity of the biochars to Cd(II) followed the order of corn straw>cotton straw>wheat straw>rice straw>poplar shaving, which was not strictly consistent with the surface area of the chars. The surface characteristics of chars before and after Cd(II) sorption were investigated with scanning electron microscopy equipped with an energy dispersive X-ray spectroscopy and Fourier transform infrared spectroscopy, which suggested that the higher sorption of Cd(II) on corn straw chars was mainly attributed to cation exchange, surface precipitation of carbonate, and surface complexation with oxygen-containing groups. This study indicated that crop straw biochars exhibit distinct sorption capacities to heavy metals due to various surface characteristics, and thus the sorption efficiency should be carefully evaluated specific to target contaminant.

Response of wheat (Triticum aestivum L. cv.) to the coexistence of micro-/nanoplastics and phthalate esters alters its growth environment.

Micro- and nano-plastics (MPs/NPs) have emerged as a global pollutant, yet their impact on the root environment of plants remains scarcely explored. Given the widespread pollution of phthalate esters (PAEs) in the environment due to the application of plastic products, the co-occurrence of MPs/NPs and PAEs could potentially threaten the growth medium of plants. This study examined the combined effects of polystyrene (PS) MPs/NPs and PAEs, specifically dibutyl phthalate and di-(2-ethylhexyl) phthalate, on the chemical properties and microbial communities in a wheat growth medium. It was observed that the co-pollution with MPs/NPs and PAEs significantly increased the levels of oxalic acid, formic acid, and total organic carbon (TOC), enhanced microbial activity, and promoted the indigenous input and humification of dissolved organic matter, while slightly reducing the pH of the medium solution. Although changes in chemical indices were primarily attributed to the addition of PAEs, no interaction between PS MPs/NPs and PAEs was detected. High-throughput sequencing revealed no significant change in microbial diversity within the media containing both PS MPs/NPs and PAEs compared to the media with PS MPs/NPs alone. However, alterations in energy and carbohydrate metabolism were noted. Proteobacteria dominated the bacterial communities in the medium solution across all treatment groups, followed by Bacteroidetes and Verrucomicrobia. The composition and structure of these microbial communities varied with the particle size of the PS in both single and combined treatments. Moreover, variations in TOC, oxalic acid, and formic acid significantly influenced the bacterial community composition in the medium, suggesting they could modulate the abundance of dominant bacteria to counteract the stress from exogenous pollutants. This research provides new insights into the combined effects of different sizes of PS particles and another abiotic stressor in the wheat root environment, providing a critical foundation for understanding plant adaptation in complex environmental conditions.

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.

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.

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.