Underlying Mechanisms for Low-Molecular-Weight Dissolved Organic Matter to Promote Translocation and Transformation of Chlorinated Polyfluoroalkyl Ether Sulfonate in Wheat

Concentration-dependent cellular responses of coontail (Ceratophyllum demersum) during the substitutions to perfluorooctanoic acid by its two alternatives

The substitutions of alternatives to legacy per- and polyfluoroalkyl substances (PFASs) may lead to unknown and variational joint toxicity on ecosystems. To comprehensively understand the effects of substitutions on aquatic ecosystems, the single and joint effects of perfluorooctanoic acid (PFOA) and its alternatives (perfluorobutanoic acid, PFBA; 2,3,3,3-tetrafluoro-2-(1,1,2,2,3,3,3,heptafluoropropoxy)propanoic acid, GenX) with various concentrations and compositions on a primary producer, coontail (Ceratophyllum demersum), were investigated at cellular level. Results showed that the substitutions of PFBA/GenX could alleviate the inhibition of PFOA on plant length, hydrogen peroxide accumulation, and chlorophyll b, due to the shifts of reactive oxygen species and their less toxicity to antioxidants. Significant up-regulations of superoxide dismutase, glutathione, and carotenoid implied their primary roles in defensing against PFASs (p < 0.05). Catalase/peroxidase was significantly up-regulated in PFBA/GenX substitutions (p < 0.05) to help alleviate stress. PFBA substitutions reduced 23.9 % of PFOA in organelle and GenX reduced the subcellular concentrations of PFOA by 1.8-17.4 %. Redundancy analysis suggested that PFOA, PFBA, and GenX in cell wall and organelle, as well as GenX in soluble fractions, were responsible for the cellular responses. These findings were helpful to understand the integrated effects on aquatic ecosystems during the substitutions to legacy PFASs by alternatives.

A review of per- and polyfluoroalkyl substances (PFASs) removal in constructed wetlands: Mechanisms, enhancing strategies and environmental risks

PER: Polyfluoroalkyl substances (PFASs), typical persistent organic pollutants detected in various water environments, have attracted widespread attention due to their undesirable effects on ecology and human health. Constructed wetlands (CWs) have emerged as a promising, cost-effective, and nature-based solution for removing persistent organic pollutants. This review summarizes the removal performance of PFASs in CWs, underlying PFASs removal mechanisms, and influencing factors are also discussed comprehensively. Furthermore, the environmental risks of PFASs-enriched plants and substrates in CWs are analyzed. The results show that removal efficiencies of total PFASs in various CWs ranged from 21.3% to 98%. Plant uptake, substrate absorption and biotransformation are critical pathways in CWs for removing PFASs, which can be influenced by the physiochemical properties of PFASs, operation parameters, environmental factors, and other pollutants. Increasing dissolved oxygen supply and replacing traditional substrates in CWs, and combining CWs with other technologies could significantly improve PFASs removal. Further, CWs pose relatively lower ecological and environmental risks in removing PFASs, which indicates CWs could be an alternative solution for controlling PFASs in aquatic environments.

Metabolism of isodecyl diphenyl phosphate in rice and microbiome system: Differential metabolic pathways and underlying mechanisms

Isodecyl diphenyl phosphate (IDDP) is among the emerging aromatic organophosphate esters (aryl-OPEs) that pose risks to both human beings and other organisms. This study aims to investigate the translocation and biotransformation behavior of IDDP in rice and the rhizosphere microbiome through hydroponic exposure (the duration of hydroponic exposure was 10 days). The rhizosphere microbiome 9-FY was found to efficiently eliminate IDDP, thereby reducing its uptake in rice tissues and mitigating the negative impact of IDDP on rice growth. Furthermore, this study proposed the first-ever transformation pathways of IDDP, identifying hydrolysis, hydroxylation, methylation, methoxylation, carboxylation, and glucuronidation products. Notably, the methylation and glycosylation pathways were exclusively observed in rice, indicating that the transformation of IDDP in rice may be more complex than in microbiome 9-FY. Additionally, the presence of the product COOH-IDDP in rice suggested that there might be an exchange of degradation products between rice and rhizobacteria, implying their potential interaction. This finding highlights the significance of rhizobacteria's role which cannot be overlooked in the accumulation and transformation of organic pollutants in grain crops. The study revealed active members in 9-FY during IDDP degradation, and metagenomic analysis indicated that most of the active populations contained IDDP-degrading genes. Moreover, transcriptome sequencing showed that cytochrome P450, acid phosphatase, glucosyltransferase, and methyltransferases genes in rice were up-regulated, which was further confirmed by RT-qPCR. This provides insight into the intermediate products identified in rice, such as hydrolysis, hydroxylated, glycosylated, and methylated products. These results significantly contribute to our understanding of the translocation and transformation of organophosphate esters (OPEs) in plants and the rhizosphere microbiome, and reveal the fate of OPEs in rice and microbiome system to ensure the paddy yield and rice safety.

A fast solid-phase microextraction scheme for in vivo monitoring of bio-accumulation and bio-transformation of arbidol in living plants

Large quantity of the antiviral drug arbidol is used for resisting virus infection like the Corona Virus Disease 2019 and influenza, resulting in unanticipated environmental pollution. Herein, to investigate the environmental risks of the unanticipated arbidol contamination, a novel in vivo sampling probe was developed based on a bromo-substituted porous organic polymer (Br-POP) and then adopted for tracking the bio-accumulation and bio-transformation of arbidol in living plants by coupling with a nano-electrospray ionization fourier-transform ion cyclotron resonance mass spectrometry (Nano-ESI-FT-ICR-MS) method. The established method showed good extraction performance towards arbidol with limit of detection (LOD) of 0.48 ng g-1, and relative standard deviation (RSD) of single-and multiple- probe of 2.2 and 14 %. Owing to the interactions between the Br-POP and the target analytes, as well as the fast analysis process of Nano-ESI-FT-ICR-MS, <6 min was cost for total sampling and analysis duration, achieving hourly tracking of arbidol and its metabolites in this work. During 21-d in vivo tracking, the concentration of arbidol in living plant stems increased rapidly within 6 h and peaked at 413.93 ± 47.09 ng g-1. Meanwhile, it was found that dissolved organic matters (DOM) had significant effect on arbidol behaviors in living plants, resulting in a decrease of the maximum concentration of arbidol in plant stems (152.70 ± 42.44 ng g-1) and the change of dominant metabolite of arbidol that the S-oxidation rather than N-demethylation product of arbidol was dominant with DOM participation. Additionally, the plant root secretion was found to be significantly altered by arbidol exposure. To summarized, the combination of in vivo SPME and the FT-ICR-MS analysis provide new and important information regarding arbidol contamination and related alternation of plant root metabolism.

Multimedia and Full-Life-Cycle Monitoring Discloses the Dynamic Accumulation Rules of PFAS and Underestimated Foliar Uptake in Wheat near a Fluorochemical Industrial Park

The escalating concern of perfluoroalkyl and polyfluoroalkyl substances (PFAS), particularly at contaminated sites, has prompted extensive investigations. In this study, samples of multimedia including air, rhizosphere soil, and tissues of wheat at various growing stages were collected near a mega fluorochemical industrial park in China. Perfluorooctanoic acid (PFOA) was predominant in both air and soil with a strong correlation, highlighting air deposition as an important source in the terrestrial system. PFAS concentrations in wheat decreased in the stem and ear but increased in the leaves as wheat matured. Specifically, perfluorobutanoic acid (PFBA) dominated in the aboveground tissues in the full-life-cycle, except that PFOA surpassed and became predominant in leaves during the filling and maturing stages, hinting at an airborne source. For all PFAS, both bioaccumulation factors and translocation factors (TFs) were inversely correlated with the carbon chain length during the full-life-cycle. The obtained TF values were considerably higher than those obtained from ambient sites reported previously, further suggesting an unneglectable foliar uptake from air, which was estimated to be 25% for PFOA. Moreover, spray irrigation remarkably enhanced the absorption of PFAS in wheat via foliar uptake relative to flood irrigation. The estimated daily intake of PFBA via wheat consumption and air inhalation was 0.50 μg/kg/day for local residents, at least one magnitude higher than the corresponding threshold, suggesting an alarmingly high exposure risk.

Effect of Co-exposure to Additional Substances on the Bioconcentration of Per(poly)fluoroalkyl Substances: A Meta-Analysis Based on Hydroponic Experimental Evidence

A consensus has yet to emerge regarding the bioconcentration responses of per(poly)fluoroalkyl substances under co-exposure with other additional substances in aqueous environments. This study employed a meta-analysis to systematically investigate the aforementioned issues on the basis of 1,085 published datasets of indoor hydroponic simulation experiments. A hierarchical meta-analysis model with an embedded variance covariance matrix was constructed to eliminate the non-independence and shared controls of the data. Overall, the co-exposure resulted in a notable reduction in PFAS bioaccumulation (cumulative effect size, CES =  - 0.4287, p < 0.05) and bioconcentration factor (R2 = 0.9507, k < 1, b < 0) in hydroponics. In particular, the inhibition of PFAS bioconcentration induced by dissolved organic matter (percentage form of the effect size, ESP =  - 48.98%) was more pronounced than that induced by metal ions (ESP =  - 35.54%), particulate matter (ESP =  - 24.70%) and persistent organic pollutants (ESP =  - 18.66%). A lower AS concentration and a lower concentration ratio of ASs to PFASs significantly promote PFAS bioaccumulation (p < 0.05). The bioaccumulation of PFASs with long chains or high fluoride contents tended to be exacerbated in the presence of ASs. Furthermore, the effect on PFAS bioaccumulation was also significantly dependent on the duration of co-exposure (p < 0.05). The findings of this study provide novel insights into the fate and bioconcentration of PFAS in aquatic environments under co-exposure conditions.

Plant Root Secretion Alleviates Carbamate-Induced Molecular Alterations of Dissolved Organic Matter

Studying the interaction between pesticide contamination in the plant system and the dissolved organic matter (DOM) composition is important to understand the impact of pesticides and plants on the ecological function of DOM. The present study investigated the effects of DOM on the bioaccumulation and biotransformation of carbamates in plants, carbamate exposure on DOM composition, and plant root secretion on the interaction between DOM and carbamates. The concentrations of carbamates and their metabolites in living cabbage plants were continuously tracked through an in vivo analytical method. The presence of DOM was found to reduce the highest bioconcentrations and shorten the time it took to reach the highest bioaccumulated amounts of isoprocarb and carbofuran in plants, while it showed no significant effect on the uptake behavior of carbaryl. DOM profiling results indicated that carbamate exposure substantially decreased the number and molecular diversity of DOM. Notably, plant root secretion alleviated carbamate-induced DOM molecular alterations by inducing a higher turnover rate of DOM compared to that in the uncontaminated group, highlighting the role of plants in mitigating the effects of exogenous pesticide exposure on DOM composition and maintaining DOM molecular homeostasis.

Characterization of the Bioavailability of Per- and Polyfluoroalkyl Substances in Farmland Soils and the Factors Impacting Their Translocation to Edible Plant Tissues

In this study, various crops and farmland soils were collected from the Fen-Wei Plain, China, to investigate the bioavailability of perfluoroalkyl substances (PFAS), their accumulation in edible plant tissues, and the factors impacting their accumulation. PFAS were frequently detected in all of the crops, with total concentrations ranging from 0.61 to 35.8 ng/g. The results of sequential extractions with water, basic methanol, and acidic methanol indicate that water extraction enables to characterize the bioavailability of PFAS in soil to edible plant tissues more accurately, especially for the shorter-chain homologues. The bioavailability of PFAS was remarkably enhanced in the rhizosphere (RS) soil, with the strongest effect observed for leafy vegetables. The water-extracted Σ16PFAS in RS soil was strongly correlated with the content of dissolved organic carbon in the soil. Tannins and lignin, identified as the main components of plant root exudates by Fourier transform-ion cyclotron resonance mass spectrometry, were found to enhance the bioavailability of PFAS significantly. Redundancy analysis provided strong evidence that the lipid and protein contents in edible plant tissues play important roles in the accumulation of short- and long-chain PFAS, respectively. Additionally, the high water demand of these tissues during the growth stage greatly facilitated the translocation of PFAS, particularly for the short-chain homologues and perfluorooctanoic acid.

Insights into the Enantiomeric Uptake, Translocation, and Distribution of Triazole Chiral Pesticide Mefentrifluconazole in Wheat (Triticum aestivum L.)

The uptake, translocation, and accumulation of mefentrifluconazole (MFZ), an innovative chiral triazole fungicide, in plants at the enantiomeric level are still unclear. Herein, we investigated the patterns and mechanisms of enantiomeric uptake, bioaccumulation, and translocation through several experiments. Rac-MFZ shows the strongest uptake and bioaccumulation capacity in wheat compared with its enantiomers, while S-(+)-MFZ has the highest translocation potential. Molecular docking provided evidence of the stronger translocation ability of S-(+)-MFZ than R-(-)-MFZ. Split-root experiments showed that MFZ and its enantiomers could undergo long-distance transport within the wheat. Active transport or facilitated and simple diffusion may be involved in the wheat uptake of MFZ. The limited acropetal translocation capability of MFZ may be attributed to the dominant uptake pathway of apoplastic. The concentrations of Rac-MFZ in different subcellular fractions varied greatly. In summary, this study provides novel insights for further understanding the behaviors of MFZ and its enantiomers in plants.

The bioaccumulation and ecotoxicity of co-exposure of per(poly)fluoroalkyl substances and polystyrene microplastics to Eichhornia crassipes

Gen X and F-53B have been popularized as alternatives to PFOA and PFOS, respectively. These per(poly)fluoroalkyl substances pervasively coexist with microplastics (MPs) in aquatic environments. However, there are knowledge gaps regarding their potential eco-environmental risks. In this study, a typical free-floating macrophyte, Eichhornia crassipes (E. crassipes), was selected for hydroponic simulation of a single exposure to PFOA, PFOS, Gen X, and F-53B, and co-exposure with polystyrene (PS) microspheres. F-53B exhibited the highest bioaccumulation followed by Gen X, PFOA, and PFOS. In the presence of PS MPs, the bioavailabilities of the four PFASs shifted and the whole plant bioconcentration factors improved. All four PFASs induced severe lipid peroxidation, which was exacerbated by PS MPs. The highest integrated biomarker response (IBR) was observed for E. crassipes (IBR of shoot: 30.01, IBR of root: 22.79, and IBR of whole plant: 34.96) co-exposed to PS MPs and F-53B. The effect addition index (EAI) model revealed that PS MPs showed antagonistic toxicity with PFOA and PFOS (EAI < 0) and synergistic toxicity with Gen X and F-53B (EAI > 0). These results are helpful to compare the eco-environmental impacts of legacy and alternative PFASs for renewal process of PFAS consumption and provide toxicological, botanical, and ecoengineering insights under co-contamination with MPs.

Effects of long-chained perfluoroalkyl acids (PFAAs) on the uptake and bioaccumulation of short-chained PFAAs in two free-floating macrophytes: Eichhornia crassipes and Ceratophyllum demersum

Short-chained perfluoroalkyl acids (PFAAs, CnF2n+1-R, n ≤ 6) have merged as global concerns due to their extensive application and considerable toxicity. However, long-chained PFAAs (n ≥ 7) featured with high persistence are still ubiquitously observed in aquatic environment. To understand the uptake behavior of short-chained PFAAs in aquatic macrophytes, the uptake kinetics, bioconcentration, and translocation of short-chained PFAAs (3 ≤n ≤ 6) in two typical free-floating macrophytes (Eichhornia crassipes and Ceratophyllum demersum) were investigated in the treatments with and without long-chained PFAAs (7 ≤n ≤ 11). Results showed that short-chained PFAAs can be readily accumulated in both E. crassipes and C. demersum, and the uptake of short-chained PFAAs fit the two-compartment kinetic model well (p < 0.05). In the treatments with long-chained PFAAs, significant concentration decreases of all concerned short-chained PFAAs in E. crassipes and PFAAs with n ≤ 5 in C. demersum were observed. Long-chained PFAAs could hinder the uptake rates, bioconcentration factors, and translocation factors of most short-chained PFAAs in free-floating macrophytes (p < 0.01). Significant correlations between bioconcentration factors and perfluoroalkyl chain length were only observed when long-chained PFAAs were considered (p < 0.01). Our results underlined that the effects of long-chained PFAAs should be taken into consideration in understanding the uptake and bioaccumulation behaviors of short-chained PFAAs.

Bio-accumulation and health risk assessments of per- and polyfluoroalkyl substances in wheat grains

Per- and polyfluoroalkyl substances (PFASs) have been widely detected in various food, which has attracted worldwide concern. However, the factors influencing the transfer and bio-accumulation of PFASs from soils to wheat in normal farmland, is still ambiguous. We investigated the PFASs accumulation in agricultural soils and grains from 10 cites, China, and evaluated the health risks of PFASs via wheat consumption. Our results show that ∑PFASs in soils range from 0.34 μg/kg to 1.59 μg/kg with PFOA and PFOS dominating, whilst ∑PFASs in wheats range from 2.74 to 6.01 μg/kg with PFOA, PFBA and PFHxS dominating. The lower pH conditions and high total organic carbon (TOC) could result in the higher accumulation of PFASs in soils and subsequently in wheat grains, whilst the bioaccumulation factors of PFASs increase with increasing pH conditions but not with TOC. The estimated daily intake (EDI) values of PFBA, PFOA, and PFHxS are relatively high, but data supports that ingesting wheat grains does not result in any potential risk to the human beings. Our studies provided more information about PFASs accumulation in wheat grains, and help us understand the current potential risks of PFASs in food.

Comparative uptake, translocation and metabolism of phenamacril in crops under hydroponic and soil cultivation conditions

Many studies investigate the plant uptake and metabolism of xenobiotics by hydroponic experiments, however, plants grown in different conditions (hydroponic vs. soil) may result in different behaviors. To explore the potential differences, a comparative study on the uptake, translocation and metabolism of the fungicide phenamacril in crops (wheat/rice) under hydroponic and soil cultivation conditions was conducted. During 7-14 days of exposure, the translocation factors (TFs) of phenamacril were greatly overestimated in hydroponic-wheat (3.6-5.2) than those in soil-wheat systems (1.1-2.0), with up to 3.3 times of difference between the two cultivation systems, implying it should be cautious to extrapolate the results obtained from hydroponic to field conditions. M-144 was formed in soil pore water (19.1-29.9 μg/L) in soil-wheat systems but not in the hydroponic solution in hydroponics; M-232 was only formed in wheat shoots (89.7-103.0 μg/kg) under soil cultivation conditions, however, it was detected in hydroponic solution (20.1-21.2 μg/L), wheat roots (146.8-166.0 μg/kg), and shoots (239.2-348.1 μg/kg) under hydroponic conditions. The root concentration factors (RCFs) and TFs of phenamacril in rice were up to 2.4 and 3.6 times higher than that in wheat for 28 days of the hydroponic exposure, respectively. These results highlighted that cultivation conditions and plant species could influence the fate of pesticides in crops, which should be considered to better assess the potential accumulation and transformation of pesticides in crops.

Macronutrient and PFOS bioavailability manipulated by aeration-driven rhizospheric organic nanocapsular assembly

Ubiquitous presence of the extremely persistent pollutants, per- and polyfluoroalkyl substances, is drawing ever-increasing concerns for their high eco-environmental risks which, however, are insufficiently considered based on the assembly characteristics of those amphiphilic molecules in environment. This study investigated the re-organization and self-assembly of perfluorooctane sulfonate (PFOS) and macronutrient molecules from rhizospheric organic (RhO) matter induced with a common operation of aeration. Atomic force microscopy (AFM) with infrared spectroscopy (IR)-mapping clearly showed that, after aeration and stabilization, RhO nanocapsules (∼ 1000 nm or smaller) with a core of PFOS-protein complexes coated by "lipid-carbohydrate" layers were observed whereas the capsule structure with a lipid core surrounded by "protein-carbohydrate-protein" multilayers was obtained in the absence of PFOS. It is aeration that exerted the disassociation of pristine RhO components, after which the environmental concentration PFOS restructured the self-assembly structure in a conspicuous "disorder-to-order" transition. AFM IR-mapping analysis of faeces combined with quantification of component uptake denoted the decreased ingestion and utilization of both PFOS and proteins compared with lipids and carbohydrates when Daphnia magna were fed with RhO nanocapsules. RhO nanocapsules acted as double-edged swords via simultaneously impeding the bioaccessibility of hazardous PFOS molecules and macronutrient proteins; and the latter might be more significant, which caused a malnutrition status within merely 48 h. Elucidating the assembly structure of natural organic matter and environmental concentration PFOS, the finding of this work could be a crucial supplementation to the high-dose-dependent eco-effect investigations on PFOS.

Transformation process and phytotoxicity of sulfamethoxazole and N4-acetyl-sulfamethoxazole in rice

Sulfonamide antibiotics, extensively used in human and veterinary therapy, accumulate in agroecosystem soils through livestock manure and sewage irrigation. However, the interaction between sulfonamides and rice plants remains unclear. This study investigated the transformation behavior and toxicity of sulfamethoxazole (SMX) and its main metabolite, N4-acetyl-sulfamethoxazole (NASMX) in rice. SMX and NASMX were rapidly taken up by roots and translocated acropetally. NASMX showed higher accumulating capacity, with NASMX concentrations up to 20.36 ± 1.98 μg/g (roots) and 5.62 ± 1.17 μg/g (shoots), and with SMX concentrations up to 15.97 ± 2.53 μg/g (roots) and 3.22 ± 0.789 μg/g (shoots). A total of 18 intermediate transformation products of SMX were identified by nontarget screening using Orbitrap-HRMS, revealing pathways such as deamination, hydroxylation, acetylation, formylation, and glycosylation. Notably, NASMX transformed back into SMX in rice, a novel finding. Transcriptomic analysis highlights the involvements of cytochrome P450 (CYP450), acetyltransferase (ACEs) and glycosyltransferases (GTs) in these biotransformation pathways. Moreover, exposure to SMX and NASMX disrupts TCA cycle, amino acid, linoleic acid, nucleotide metabolism, and phenylpropanoid biosynthesis pathways of rice, with NASMX exerting a stronger impact on metabolic networks. These findings elucidate the sulfonamides' metabolism, phytotoxicity mechanisms, and contribute to assessing food safety and human exposure risk amid antibiotic pollution.

Novel Insights into the Promoted Accumulation of Nitro-Polycyclic Aromatic Hydrocarbons in the Roots of Legume Plants

Substituted polycyclic aromatic hydrocarbons (sub-PAHs) are receiving increased attention due to their high toxicity and ubiquitous presence. However, the accumulation behaviors of sub-PAHs in crop roots remain unclear. In this study, the accumulation mechanism of sub-PAHs in crop roots was systematically disclosed by hydroponic experiments from the perspectives of utilization, uptake, and elimination. The obtained results showed an interesting phenomenon that despite not having the strongest hydrophobicity among the five sub-PAHs, nitro-PAHs (including 9-nitroanthracene and 1-nitropyrene) displayed the strongest accumulation potential in the roots of legume plants, including mung bean and soybean. The nitrogen-deficient experiments, inhibitor experiments, and transcriptomics analysis reveal that nitro-PAHs could be utilized by legumes as a nitrogen source, thus being significantly absorbed by active transport, which relies on amino acid transporters driven by H+-ATPase. Molecular docking simulation further demonstrates that the nitro group is a significant determinant of interaction with an amino acid transporter. Moreover, the depuration experiments indicate that the nitro-PAHs may enter the root cells, further slowing their elimination rates and enhancing the accumulation potential in legume roots. Our results shed light on a previously unappreciated mechanism for root accumulation of sub-PAHs, which may affect their biogeochemical processes in soils.

Using regular and transcriptomic analyses to investigate the biotransformation mechanism and phytotoxic effects of 6:2 fluorotelomer carboxylic acid (6:2 FTCA) in pumpkin (Cucurbita maxima L.)

Although 6:2 fluorotelomer carboxylic acid (6:2 FTCA), which is one of the most popular substitutes for perfluorooctanoic acid (PFOA), has been widely distributed in environments, little is known about its biotransformation mechanism and phytotoxic effects in plants. Here, we showed that 6:2 FTCA could be taken up by pumpkin (Cucurbita maxima L.) roots from exposure solution and acropetally translocated to shoots. Biotransformation of 6:2 FTCA to different carbon chain perfluorocarboxylic acid (PFCA) metabolites (C2-C7) via α-and β-oxidation in pumpkin was observed, and perfluorohexanoic acid (PFHxA) was the major transformation product. The results of enzyme assays, enzyme inhibition experiments and gene expression analysis indicated that cytochrome P450 (CYP450), glutathione-S-transferase (GST) and ATP-binding cassette (ABC) transporters were involved in the metabolism of 6:2 FTCA in pumpkin. Plant-associated rhizobacteria and endophyte also contributed to 6:2 FTCA degradation through β-oxidation. The chlorophyll (Chl) content and genes involved in photosynthesis were significantly improved by 6:2 FTCA. The reductions of antioxidant and metabolic enzyme activities reflected the antioxidant defense system and detoxification system of pumpkin were both damaged, which were further confirmed by the down-regulating associated genes encoding phenylpropanoid biosynthesis, endoplasmic reticulum-related proteins, ascorbate-glutathione cycle and ABC transporters. This study is helpful to understand the environmental behaviors and toxicological molecular mechanisms of 6:2 FTCA in plants.

Novel Insights into Uptake, Translocation, and Transformation Mechanisms of 2,2',4,4'-Tetra Brominated Diphenyl Ether (BDE-47) in Wheat (Triticum aestivum L.): Implication by Compound-Specific Stable Isotope and Transcriptome Analysis

The uptake, translocation, and transformation of 2,2',4,4'-tetra brominated diphenyl ether (BDE-47) in wheat (Triticum aestivum L.) were comprehensively investigated by hydroponic experiments using compound-specific stable isotope analysis (CSIA) and transcriptome analysis. The results indicated that BDE-47 was quickly adsorbed on epidermis of wheat roots and then absorbed in roots via water and anion channels as well as an active process dependent on energy. A small fraction of BDE-47 in roots was subjected to translocation acropetally, and an increase of δ13C values in shoots than roots implied that BDE-47 in roots had to cross at least one lipid bilayer to enter the vascular bundle via transporters. In addition, accompanied by the decreasing concentrations, δ13C values of BDE-47 showed the increasing trend with time in shoots, indicating occurrence of BDE-47 transformation. OH-PBDEs were detected as transformation products, and the hydroxyl group preferentially substituted at the ortho-positions of BDE-47. Based on transcriptome analysis, genes encoding polybrominated diphenyl ether (PBDE)-metabolizing enzymes, including cytochrome P450 enzymes, nitrate reductases, and glutathione S-transferases, were significantly upregulated after exposure to BDE-47 in shoots, further evidencing BDE-47 transformation. This study first reported the stable carbon isotope fractionation of PBDEs during translocation and transformation in plants, and application of CSIA and transcriptome analysis allowed systematically characterize the environmental behaviors of pollutants in plants.

Occurrences and fates of per- and polyfluoralkyl substances in textile dyeing wastewater along full-scale treatment processes

Industrial wastewater is a substantial source of per- and polyfluoroalkyl substances (PFASs) in the environment. However, very limited information is available on the occurrences and fates of PFASs along industrial wastewater treatment processes, particularly for the textile dyeing industry where PFASs occur extensively. Herein, the occurrences and fates of 27 legacy and emerging PFASs were investigated along the processes of three full-scale textile dyeing wastewater treatment plants (WWTPs) based on UHPLC-MS/MS in combination with self-developed solid extraction protocol featuring selective enrichment for ultrasensitive analysis. The total PFASs ranged at 630-4268 ng L-1 in influents, 436-755 ng L-1 in effluents, and 91.5-1182 μg kg-1 in the resultant sludge. PFAS species distribution varied among WWTPs, with one WWTP dominated by legacy perfluorocarboxylic acids while the other two dominated by emerging PFASs. Perfluorooctane sulfonate (PFOS) was trivial in the effluents from all the three WWTPs, indicating its diminished use in textile industry. Various emerging PFASs were detected at different abundances, demonstrating their use as alternatives to legacy PFASs. Most conventional processes of the WWTPs were inefficient in removing PFASs, especially for the legacy PFASs. The microbial processes could remove the emerging PFASs to different extents, whereas commonly elevated the concentrations of legacy PFASs. Over 90% of most PFASs could be removed by reverse osmosis (RO) and was enriched into the RO concentrate accordingly. The total oxidizable precursors (TOP) assay revealed that the total concentration of PFASs was increased by 2.3-4.1 times after oxidation, accompanied by formation of terminal perfluoroalkyl acids (PFAAs) and degradation of emerging alternatives to various extents. This study is believed to shed new light on the monitoring and management of PFASs in industries.

Phytoextraction of per- and polyfluoroalkyl substances (PFAS) by weeds: Effect of PFAS physicochemical properties and plant physiological traits

Phytoextraction is a promising technology that uses plants to remediate contaminated soil. However, its feasibility for per- and polyfluoroalkyl substances (PFAS) and the impact of PFAS properties and plant traits on phytoextraction efficacy remains unknown. In this study, we conducted greenhouse experiment and evaluated the potential of weeds for phytoextraction of PFAS from soil and assessed the effects of PFAS properties and plant traits on PFAS uptake via systematic correlation analyses and electron probe microanalyzer with energy dispersive spectroscopy (FE-EPMA-EDS) imaging. The results showed that 1) phytoextraction can remove 0.04%- 41.4%wt of PFAS from soil, with extracted PFAS primarily stored in plant shoots; 2) Weeds preferentially extracted short-chain PFAS over long-chain homologues from soil. 3) PFAS molecular size and hydrophilicity determined plant uptake behavior, while plant morphological traits, particularly root protein and lipid content, influenced PFAS accumulation and translocation. Although plants with thin roots and small leaf areas exhibited greater PFAS uptake and storage ability, the impact of PFAS physicochemical properties was more significant. 4) Finally, short-chain PFAS were transported quickly upwards in the plant, while uptake of long-chain PFOS was restricted.

Latest development in the fabrication and use of lignin-derived humic acid

Humic substances (HS) are originated from naturally decaying biomass. The main products of HS are humic acids, fulvic acids, and humins. HS are extracted from natural origins (e.g., coals, lignite, forest, and river sediments). However, the production of HS from these resources is not environmentally friendly, potentially impacting ecological systems. Earlier theories claimed that the HS might be transformed from lignin by enzymatic or aerobic oxidation. On the other hand, lignin is a by-product of pulp and paper production processes and is available commercially. However, it is still under-utilized. To address the challenges of producing environmentally friendly HS and accommodating lignin in valorized processes, the production of lignin-derived HS has attracted attention. Currently, several chemical modification pathways can be followed to convert lignin into HS-like materials, such as alkaline aerobic oxidation, alkaline oxidative digestion, and oxidative ammonolysis of lignin. This review paper discusses the fundamental aspects of lignin transformation to HS comprehensively. The applications of natural HS and lignin-derived HS in various fields, such as soil enrichment, fertilizers, wastewater treatment, water decontamination, and medicines, were comprehensively discussed. Furthermore, the current challenges associated with the production and use of HS from lignin were described.