Removal of perfluoroalkyl acids (PFAAs) in constructed wetlands: Considerable contributions of submerged macrophytes and the microbial community

Unravelling the mechanisms of PFAS toxicity to submerged macrophytes and epiphytic biofilms at metabolic and molecular levels

Per- and poly-fluoroalkyl substances (PFAS) are an emerging class of persistent organic pollutants that are widespread in aquatic ecosystems and pose a serious threat to aquatic organisms. It is thus crucial to explore the toxicity mechanisms of PFAS to submerged macrophytes and biofilms. In this study, Vallisneria natans (V. natans) was exposed to environmentally relevant concentrations of perfluorooctanoic acid (PFOA) and perfluorooctane sulphonate (PFOS). Results showed that PFAS induced the excessive production of reactive oxygen species, triggering antioxidant responses. V. natans exhibited an improved stress tolerance by altering the biosynthesis of several plant secondary metabolites and the histidine, arginine, proline pathways in response to PFAS exposure. Moreover, PIP1-1, PIP2-2, SLAH1 and SLAH2 genes were upregulated, indicating the activation of aquaporins and slow-type anion channels. The uptake of PFOA and PFOS by V. natans was 41.74 % and 52.31 %, respectively. Notably, PFAS bound to functional proteins (GSTF10), promoting the detoxification of plants. Exposure to PFAS also altered the structure of biofilms by inducing the synthesis of large amounts of polysaccharides and proteins. The diversity and richness of the microbial community within periphytic biofilms changed significantly. These results provide a comprehensive description of the responses of aquatic plants and periphytic biofilms to PFAS and the removal mechanism of PFAS, contributing to the environmental risk assessments and removal of PFAS in aquatic ecosystems.

Ecological risk of per-and polyfluorinated alkyl substances in the phytoremediation process: a case study for ecologically keystone species across two generations

The potential ecological risk of per- and polyfluorinated alkyl substances (PFASs) in phytoremediation has raised social concerns, promoting a need to better understand their distribution and risks in the recovery process of aquatic plants. Herein, we aim to fill this knowledge gap by investigating the distribution and ecotoxicological effects of PFASs on the structure and function of water-macrophyte-sediment microcosm systems. Among the entire system, 63.0 %-73.1 % PFOA was found in sediments and submerged plants, however, 52.5 %-53.0 % of PFPeA and 47.0 %-47.5 % of PFBS remained in the water under different treatments. PFOA was more bioavailable than the other substances, as demonstrated by the bioaccumulation factors (BAF) with ranges exposed to PFPeA and PFBS. Bioaccumulation PFASs induced plant oxidative stress which generates enzymes to suppress superoxide, and disturbed the processes of lysine biosynthesis, in which allysine, meso-2,6-diaminoheptanedioate, and Nsuccinyl-2-amino-6-ketopimelate were downregulated. PFASs were detected in the propagator (turions) of an ecological restoration species, where short-chain PFASs (70.1 % and 45.7 % for 2 or 20 μg/L PFAS exposure, respectively) were found to spread further into new individuals and profoundly influence ecological processes shaping populations. PFASs significantly enhanced the number of microbial species in the sediment, but the degree of differentiation in the microbial community structure was not significantly different. This study enhances our understanding of the ecological mechanisms of PFASs in the water-macrophyte-sediment systems and potential threats to the recovery process of macrophytes.

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.

Release of perfluoroalkyl acids from sediments under the effects of the discharge ratio and flow flux at a Y-shaped confluence

The sediments in riverine environments contain notably high concentrations of perfluoroalkyl acids (PFAAs), which may be released into the water body under different hydrodynamic forces, such as those occurring at Y-shaped confluences. The release of PFAAs may pose a significant risk to the surrounding aquatic ecosystems. However, our understanding of the release and transport of PFAAs from sediments at Y-shaped confluences remains unclear. Thus, in this study, we performed a series of flume experiments to explore the effects of discharge ratio and total flow flux on the release and redistribution of PFAAs. The results indicated that these two parameters significantly affected the hydrodynamic features of confluences and the water physicochemical parameters. PFAA concentrations in the dissolved phase and suspended particulate matter (SPM) rose significantly as the discharge ratio and total flow flux increased. The dissolved phase was the predominant loading form of PFAAs, with short-chain PFAAs being the main kind, while long-chain PFAAs were dominant in the SPM. The spatial distribution pattern of PFAAs in sediments at the confluence exhibited a high degree of correspondence with hydrodynamic zones. The separation zone and maximum velocity zone were consistent with sediment regions with low and high capacities to release PFAAs, respectively. The patterns of variation in PFAA distribution were comparable to those observed in hydrodynamic zones as the discharge ratio and total flow flux varied. Furthermore, these two parameters altered the partitioning behaviors of PFAAs; specifically, the PFAAs in sediments tended to be released into the pore-water, while the liberated PFAAs tended to attach to SPM. Linear regression and correlation analyses suggested that the stream-wise and vertical flow velocity components near the sediment-water interface were the primary contributors to sediment suspension and PFAA exchange between the water column and pore-water. These findings will help us to understand the patterns of PFAA release in sediments at Y-shaped confluences and assist in the management of PFAA-contaminated sediments at these locations.

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.

Integration of Nontarget Screening and QSPR Models to Identify Novel Organophosphate Esters of High Priority in Aquatic Environment

With the development of large numbers of novel organophosphate esters (OPEs) alternatives, it is imperative to screen and identify those with high priority. In this study, surface water, biofilms, and freshwater snails were collected from the flow-in rivers of Taihu Lake Basin, China. Screened by target, suspect, and nontarget analysis, 11 traditional and 14 novel OPEs were identified, of which 5 OPEs were first discovered in Taihu Lake Basin. The OPE concentrations in surface water ranged from 196 to 2568 ng/L, with the primary homologue tris(2,4-ditert-butylphenyl) phosphate (TDtBPP) being newly identified, which was likely derived from the transformation of tris(2,4-ditert-butylphenyl) phosphite. The majority of the newly identified OPEs displayed substantially higher bioaccumulation and biomagnification potentials in the biofilm-snail food chain than the traditional ones. Quantitative structure-property relationship models revealed both hydrophobicity and polarity influenced the bioaccumulation and biomagnification of the OPEs, while electrostatic attraction also had a contribution to the bioaccumulation in the biofilm. TDtBPP was determined as the utmost priority by toxicological priority index scheme, which integrated concentration, bioaccumulation, biomagnification, acute toxicity, and endocrine disrupting potential of the identified OPEs. These findings provide novel insights into the behaviors of OPEs and scientific bases for better management of high-risk pollutants in aquatic ecosystem.

Constructed wetlands as nature-based solutions in managing per-and poly-fluoroalkyl substances (PFAS): Evidence, mechanisms, and modelling

Per- and poly-fluoroalkyl substances (PFAS) have emerged as newly regulated micropollutants, characterised by extreme recalcitrance and environmental toxicity. Constructed wetlands (CWs), as a nature-based solution, have gained widespread application in sustainable water and wastewater treatment and offer multiple environmental and societal benefits. Despite CWs potential, knowledge gaps persist in their PFAS removal capacities, associated mechanisms, and modelling of PFAS fate. This study carried out a systematic literature review, supplemented by unpublished experimental data, demonstrating the promise of CWs for PFAS removal from the influents of varying sources and characteristics. Median removal performances of 64, 46, and 0 % were observed in five free water surface (FWS), four horizontal subsurface flow (HF), and 18 vertical flow (VF) wetlands, respectively. PFAS adsorption by the substrate or plant root/rhizosphere was deemed as a key removal mechanism. Nevertheless, the available dataset resulted unsuitable for a quantitative analysis. Data-driven models, including multiple regression models and machine learning-based Artificial Neural Networks (ANN), were employed to predict PFAS removal. These models showed better predictive performance compared to various mechanistic models, which include two adsorption isotherms. The results affirmed that artificial intelligence is an efficient tool for modelling the removal of emerging contaminants with limited knowledge of chemical properties. In summary, this study consolidated evidence supporting the use of CWs for mitigating new legacy PFAS contaminants. Further research, especially long-term monitoring of full-scale CWs treating real wastewater, is crucial to obtain additional data for model development and validation.

Intense Turbulent Bursts Promote the Release of Perfluoroalkyl Acids from Sediments at High Flow Velocity

Despite frequent detection of high levels of perfluoroalkyl acids (PFAAs) in sediments, research on the environmental fate of PFAAs in sediments, particularly under hydrodynamic conditions, is rather limited, challenging effective management of PFAA loadings. Therefore, this study investigated the release and transport of 15 PFAAs in sediments under environmentally relevant flow velocities using recirculating flumes and revealed the underlying release mechanisms by identifying related momentum transfer. An increased velocity enhanced the release magnitude of total PFAAs by a factor of 3.09. The release capacity of short-chain PFAAs was notably higher than that of long-chain PFAAs, and this pattern was further amplified by flow velocity. Pore-water drainage was the major pathway for PFAA release, with the release amount predominantly determined by flow velocity-induced release intensity and depth, as well as affected by the perfluorocarbon chain length and sediment size. The weak anion exchanger-diffusion gradients in the thin-film technique confirmed that the release depth of PFAAs increased with flow velocity. Quadrant analysis revealed that the rise in the frequency and intensity of turbulent bursts driven by sweeps and ejections at high flow velocity was the underlying cause of the increased release magnitude and depth of PFAAs.

Constructed wetlands for the removal of organic micropollutants from wastewater: Current status, progress, and challenges

In this work, the practical utility of constructed wetlands (CWs) is described as a promising treatment option for micropollutants (MPs) in wastewater with the aid of their eco-friendly, low-energy, economically feasible, and ecologically sustainable nature. This paper offers a comprehensive review on CW technology with respect to the key strategies for MP removal such as phytoremediation, substrate adsorption, and microbial degradation. It explores the important factors controlling the performance of CWs (e.g., in terms of configurations, substrates, plant-microbe interactions, temperature, pH, oxygen levels, hydraulic loading rate, and retention time) along with the discussions on the pivotal role of microbial populations in CWs and plant-microbe cooperative remediation dynamics, particularly in relation to diverse organic MP patterns in CWs. As such, this review aims to provide valuable insights into the key strategies for optimizing MP treatment and for enhancing the efficacy of CW systems. In addition, the process-based models of constructed wetlands along with the numerical simulations based on the artificial neural network (ANN) method are also described in association with the data exploratory techniques. This work is thus expected to help open up new possibilities for the application of plant-microbe cooperative remediation approaches against diverse patterns of organic MPs present in CWs.

Life in the PFAS lane: The impact of perfluoroalkyl substances on photosynthesis, cellular exudates, nutrient cycling, and composition of a marine microbial community

Perfluoroalkyl substances (PFAS) are of great ecological concern, however, exploration of their impact on bacteria-phytoplankton consortia is limited. This study employed a bioassay approach to investigate the effect of unary exposures of increasing concentrations of PFAS (perfluorooctane sulfonate (PFOS) and 6:2 fluorotelomer sulfonate (6:2 FTS)) on microbial communities from the northwestern Gulf of Mexico. Each community was examined for changes in growth and photophysiology, exudate production and shifts in community structure (16S and 18S rRNA genes). 6:2 FTS did not alter the growth or health of phytoplankton communities, as there were no changes relative to the controls (no PFOS added). On the other hand, PFOS elicited significant phototoxicity (p < 0.05), altering PSII antennae size, lowering PSII connectivity, and decreasing photosynthetic efficiency over the incubation (four days). PFOS induced a cellular protective response, indicated by significant increases (p < 0.001) in the release of transparent exopolymer particles (TEP) compared to the control. Eukaryotic communities (18S rRNA gene) changed substantially (p < 0.05) and to a greater extent than prokaryotic communities (16S rRNA gene) in PFOS treatments. Community shifts were concentration-dependent for eukaryotes, with the low treatment (5 mg/L PFOS) dominated by Coscinodiscophyceae (40 %), and the high treatment (30 mg/L PFOS) marked by a Trebouxiophyceae (50 %) dominance. Prokaryotic community shifts were not concentration dependent, as both treatment levels became depleted in Cyanobacteriia and were dominated by members of the Bacteroidia, Gammaproteobacteria, and Alphaproteobacteria classes. Further, PFOS significantly decreased (p < 0.05) the Shannon diversity and Pielou's evenness across treatments for eukaryotes, and in the low treatment (5 mg/L PFOS) for prokaryotes. These findings show that photophysiology was not impacted by 6:2 FTS but PFOS elicited toxicity that impacted photosynthesis, exudate release, and community composition. This research is crucial in understanding how PFOS impacts microbial communities.

Evaluation of ecological impacts with ferrous iron addition in constructed wetland under perfluorooctanoic acid stress

In this study, ferrous ion (Fe(II)) had the potential to promote ecological functions in constructed wetlands (CWs) under perfluorooctanoic acid (PFOA) stress. Concretely, Fe(II) at 30 mg/L and 20-30 mg/L even led to 11.37% increase of urease and 93.15-243.61% increase of nitrite oxidoreductase respectively compared to the control. Fe(II) promotion was also observed on Nitrosomonas, Nitrospira, Azospira, and Zoogloea by 1.00-6.50 folds, which might result from higher expression of nitrogen fixation and nitrite redox genes. These findings could be explanation for increase of ammonium removal by 7.47-8.75% with Fe(II) addition, and reduction of nitrate accumulation with 30 mg/L Fe(II). Meanwhile, both Fe(II) stimulation on PAOs like Dechloromonas, Rhodococcus, Mesorhizobium, and Methylobacterium by 1.58-2.00 folds, and improvement on chemical phosphorus removal contributed to higher total phosphorus removal efficiency under high-level PFOA exposure. Moreover, Fe(II) raised chlorophyll content and reduced the oxidative damage brought by PFOA, especially at lower dosage. Nevertheless, combination of Fe(II) and high-level PFOA caused inhibition on microbial alpha diversity, which could result in decline of PFOA removal (by 4.29-12.83%). Besides, decrease of genes related to nitrate reduction demonstrated that enhancement on denitrification was due to nitrite reduction to N2 pathways rather than the first step of denitrifying process.

The uptake and degradation of polychlorinated biphenyls in constructed wetlands planted with Myriophyllum aquaticum

The unregulated dismantling and improper disposal of electronic waste lead to severe soil contamination by polychlorinated biphenyls (PCBs). Constructed wetlands (CWs) play an important role in PCBs removal as a result of the co-existence of anaerobic and aerobic conditions. However, the effects and mechanisms of different PCBs concentrations in soils on plant uptake and PCBs degradation within CWs are unclear. We evaluated the uptake and degradation of PCBs at different concentrations by Myriophyllum aquaticum (Vell.) Verdc. Planting significantly increased PCBs removal by 8.70% (p < 0.05) in soils with 1500 and 2500 μg/kg PCBs, whereas no significant effect was observed at 500 and 1000 μg/kg. PCBs levels did not significantly affect plant growth and PCBs accumulation. The contribution of plant uptake to PCBs removal was only 0.10-0.12%, indicating that microbial degradation was the dominant pathway for PCBs removal after planting with M. aquaticum. In the treatments with PCBs ≥ 1500 μg/kg, M. aquaticum increased the microbial population, altered the microbial community structure and enriched PCB-degrading bacteria. Functional prediction revealed that microbes in M. aquaticum rhizosphere secreted more peroxidase and glycosyltransferase than non-plant control, which were likely involved in PCBs metabolism.

Submerged macrophyte promoted nitrogen removal function of biofilms in constructed wetland

Biofilm is one of the important factors affecting nitrogen removal in constructed wetlands (CWs). However, the impact of submerged macrophyte on nitrogen conversion of biofilms on leaf of submerged macrophyte and matrix remains poorly understood. In this study, the CWs with Vallisneria natans and with artificial plant were established to investigate the effects of submerged macrophyte on nitrogen conversion and the composition of nitrogen-converting bacteria in leaf and matrix biofilms under high ammonium nitrogen (NH4+-N) loading. The 16S rRNA sequencing method was employed to explore the changes in bacterial communities in biofilms in CWs. The results showed that average removal rates of total nitrogen and NH4+-N in CW with V. natans reached 71.38% and 82.08%, respectively, representing increases of 24.19% and 28.79% compared with the control with artificial plant. Scanning electron microscope images indicated that high NH4+-N damaged the leaf cells of V. natans, leading to the cellular content release and subsequent increases of aqueous total organic carbon. However, the specific surface area and carrier function of V. natans were unaffected within 25 days. As a natural source of organic matters, submerged macrophyte provided organic matters for bacterial growth in biofilms. Bacterial composition analysis revealed the predominance of phylum Proteobacteria in CW with V. natans. The numbers of nitrifiers and denitrifiers in leaf biofilms reached 1.66 × 105 cells/g and 1.05 × 107 cells/g, as well as 2.79 × 105 cells/g and 7.41 × 107 cells/g in matrix biofilms, respectively. Submerged macrophyte significantly increased the population of nitrogen-converting bacteria and enhanced the expressions of nitrification genes (amoA and hao) and denitrification genes (napA, nirS and nosZ) in both leaf and matrix biofilms. Therefore, our study emphasized the influence of submerged macrophyte on biofilm functions and provided a scientific basis for nitrogen removal of biofilms in CWs.

Interactions between biofilms and PFASs in aquatic ecosystems: Literature exploration

Perfluoroalkyl and polyfluoroalkyl substances (PFASs) have been detected in most aquatic environments worldwide and are referred to as "forever chemicals" because of their extreme chemical and thermal stability. Biofilms, as basic aquatic bioresources, can colonize various substratum surfaces. Biofilms in the aquatic environment have to interact with the ubiquitous PFASs and have significant implications for both their behavior and destiny, which are still poorly understood. Here, we have a preliminary literature exploration of the interaction between PFASs and biofilms in the various aquatic environments and expect to provide some thoughts on further study. In this review, the biosorption properties of biofilms on PFASs and possible mechanisms are presented. The complex impact of PFASs on biofilm systems was further discussed in terms of the composition and electrical charges of extracellular polymeric substances, intracellular microbial communities, and overall contaminant purification functions. Correspondingly, the effects of biofilms on the redistribution of PFASs in the aqueous environment were analyzed. Finally, we propose that biofilm after adsorption of PFASs is a unique ecological niche that not only reflects the contamination level of PFASs in the aquatic environment but also offers a possible "microbial pool" for PFASs biodegradation. We outline existing knowledge gaps and potential future efforts for investigating how PFASs interact with biofilms in aquatic ecosystems.

Removal of intI1, ARGs, and SARS-CoV-2 and changes in bacterial communities in four sewage treatment facilities

Currently, discharge regulations for wastewater treatment plants (WWTPs) are based on conventional parameters, but more is needed to ensure safe water reuse. In particular, emerging pollutants, as antimicrobials and antibiotic resistance genes (ARGs), are not considered. This research focuses on the fate of emerging biological contaminants during wastewater treatment in Mexico City. intI1 and the ARGs cphA-02, OXA-10 and sul1 were analyzed by qPCR; pathogenic bacteria species were characterized by high throughput sequencing of complete 16S rRNA gene, and fragments of SARS-CoV-2 were quantified by RT-qPCR. Conventional parameters (chemical oxygen demand and coliform bacteria) were also determined. Two sampling campaigns (rainy and dry seasons) were carried out in four municipal WWTPs in Mexico City, representing five biological treatment processes: conventional activated sludge, extended aeration activated sludge, membrane bioreactor, direct anaerobic digestion, and constructed wetland, followed by ultraviolet light or chlorine disinfection. In most cases, gene fragments of SARS-CoV-2 were eliminated below the detection limit of RT-qPCR. The abundance of intI1 positively correlated with the sul1, OXA-10, and cphA-02 abundances; intI1 and the ARGs here studied were partially removed in the WWTPs, and in most cases, the number of copies per second discarded in the sludge were higher those in the effluent. The treatment processes decreased the abundance of dominant bacterial groups in the raw wastewater, while enriching bacterial groups in the effluent and the biological sludge, with possible pollutant removal capabilities. Bacterial communities in the raw wastewater showed the predominance of the genus Arcobacter (from 62.4 to 86.0 %) containing potentially pathogenic species. Additionally, DNA of some species persisted after the treatment processes: A. johnsonii, A. junii, A. caviae, A. hydrophila, A. veronii, A. butzleri, A. cryaerophilus, Chryseobacterium indologenes, Hafnia paralvei, M. osloensis, Pseudomonas putida and Vibrio cholerae, which deserves special attention in future regulation for safe water reuse.

Iron-Nitrogen Amendment Reduced Perfluoroalkyl Acids' Phyto-Uptake in the Wheat-Soil Ecosystem: Contributions of Dissolved Organic Matters in Soil Solution and Root Extracellular Polymeric Substances

Understanding the mechanisms underlying perfluoroalkyl acids (PFAAs) translocation, distribution, and accumulation in wheat-soil ecosystems is essential for agricultural soil pollution control and crop ecological risk assessment. This study systematically investigated the translocation of 13 PFAAs under different iron and nitrogen fertilization conditions in a wheat-soil ecosystem. Short-chain PFAAs including PFBA, PFPeA, PFHxA, and PFBS mostly accumulated in soil solution (10.43-55.33%) and soluble extracellular polymeric substances (S-EPS) (11.39-14.77%) by the adsorption to amino- (-NH2) and hydroxyl (-OH) groups in dissolved organic matter (DOM). Other PFAAs with longer carbon chain lengths were mostly distributed on the soil particle surface by hydrophobic actions (74.63-94.24%). Iron-nitrogen amendments triggered (p < 0.05) soil iron-nitrogen cycling, rhizospheric reactive oxygen species fluctuations, and the concentration increases of -NH2 and -OH in the DOM structure. Thus, the accumulation capacity of PFAAs in soil solution and root EPS was increased. In sum, PFAAs' translocation from soil particles to wheat root was synergistically reduced by iron and nitrogen fertilization through increased adsorption of soil particles (p < 0.05) and the retention of soil solution and root EPSs. This study highlights the potential of iron-nitrogen amendments in decreasing the crop ecological risks to PFAAs' pollution.

Combined toxic effects of perfluorooctanoic acid and microcystin-LR on submerged macrophytes and biofilms

Perfluorooctanoic acid (PFOA) and microcystin-LR (MCLR) are pervasive pollutants in surface waters that induce significant toxic effects on aquatic organisms. However, the combined environmental risk of PFOA and MCLR remains unclear. To assess the toxic effects of PFOA and MCLR on submerged macrophytes and biofilms, Vallisneria natans was exposed to different concentrations of PFOA and MCLR (0.01, 0.1, 1.0 and 10.0 μg L-1). Vallisneria natans was sensitive to high concentrations of MCLR (10 μg L-1): plants exposed to 10 μg L-1 of MCLR measured a biomass of 3.46 g, which was significantly lower than the 8.71 g of the control group. Additionally, antagonistic interactive effects were observed in plants exposed to combined PFOA and MCLR. Exposure to these pollutants adversely affected photosynthesis of the plants and triggered peroxidation that promoted peroxidase, superoxide dismutase and catalase activities, and increased malondialdehyde and glutathione concentrations. The total chlorophyll content was lower in the highest concentration of the combined treatment group (0.443 mg g-1) than in the control group (0.534 mg g-1). Peroxidase activity increased from 662.63 U mg-1 Pr to 1193.45 U mg-1 Pr with increasing PFOA concentrations. Metabolomics indicated that the stress tolerance of Vallisneria natans was improved via altered fatty acid metabolism, hormone metabolism and carbon metabolism. Furthermore, PFOA and MCLR influenced the abundance and structure of the microbial community in the biofilms of Vallisneria natans. The increased contents of autoinducer peptide and N-acylated homoserine lactone signaling molecules indicated that these pollutants altered the formation and function of the biofilm. These results expand our understanding of the combined effects of PFOA and MCLR in aquatic ecosystems.

Combined toxic effects of polypropylene and perfluorooctanoic acid on duckweed and periphytic microorganisms

Microplastics and perfluorooctanoic acid coexist in the aquatic environment. Duckweed was exposed to a range of concentrations (0.1-1000 μg L-1) of solutions containing polypropylene (PP) and perfluorooctanoic acid (PFOA) for 14 days to measure their toxicity. The result showed the single and combined PP and PFOA treatments did not significantly influence the growth of duckweed. The greatest PP and PFOA concentrations of combined pollution affect plant chlorophyll. Moreover, the combined treatment of duckweed consistently resulted in increased malondialdehyde (MDA) levels, indicating oxidative damage. As an antioxidant stress response, the combination-treated plants were encouraged to produce superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT). Meanwhile, 3519 Operational Taxonomic Units (OTUs) were identified in the duckweed rhizosphere. Proteobacteria was the most predominant microbial community. Shannon, Simpson, and Chao1 discovered that microbial communities changed in response to single and combination PP and PFOA treatments, with decreased diversity and increased abundance. In addition, SEM analysis also revealed that the combined treatment significantly phyllosphere microorganisms. The findings of this investigation add to our knowledge of how PP and PFOA affect duckweed and the rhizospheric microorganisms, expanding the theoretical basis for employing duckweed in complex contamination.

Potential impact of bacteria on the transport of PFAS in porous media

The transport and fate of per- and poly-fluoroalkyl substances (PFAS) in soil and groundwater is a topic of critical concern. A number of factors and processes may influence the transport and fate of PFAS in porous media. One factor that has received minimal attention to date is the impact of bacteria on the retention and transport of PFAS, which is the focus of this current study. The first part of this work comprised a critical review of prior studies to delineate observed PFAS-bacteria interactions and to summarize the mechanisms of PFAS sorption and retention by bacteria. Retention of PFAS by bacteria can occur through sorption onto cell surfaces and/or by incorporation into the cell interior. Factors such as the molecular structure of PFAS, solution chemistry, and bacterial species can affect the magnitude of PFAS sorption. The influence of bacteria on the retention and transport of PFAS was investigated in the second part of the study with a series of batch and miscible-displacement experiments. Batch experiments were conducted using Gram-negative Pseudomonas aeruginosa and Gram-positive Bacillus subtilis to quantify the sorption of perfluorooctane sulfonic acid (PFOS). The results indicated that both bacteria showed strong adsorption of PFOS, with no significant difference in adsorption capacity. Miscible-displacement experiments were then conducted to examine the retention and transport of PFOS in both untreated sand and sand inoculated with Pseudomonas aeruginosa or Bacillus subtilis for 1 and 3 days. The transport of PFOS exhibited greater retardation for the experiments with inoculated sand. Furthermore, the enhanced sorption was greater for the 3-day inoculation compared to the 1-day, indicating that biomass is an important factor affecting PFOS transport. A mathematical model representing transport with nonlinear and rate-limited sorption successfully simulated the observed PFOS transport. This study highlights the need for future studies to evaluate the effect of bacteria on the transport of PFAS in soil and groundwater.

Microbe-mediated simultaneous nitrogen reduction and sulfamethoxazole/N-acetylsulfamethoxazole removal in lab-scale constructed wetlands

Constructed wetlands (CWs) are increasingly used to treat complex pollution such as nitrogen and emerging organic micropollutants from anthropogenic sources. In this study, the denitrification, anaerobic ammonium oxidation, dissimilatory nitrate reduction to ammonium, and nitrous oxide release rates following exposure to the frequently detected sulfonamides sulfamethoxazole (SMX) and its human metabolite, N-acetylsulfamethoxazole (N-SMX), were investigated in lab-scale CWs. Over a period of 190 d, the denitrification rates were noticeably inhibited in the SMX and N-SMX groups at week 5. Subsequently, the denitrification rates recovered, accompanied by an increase in the relevant nitrogen reduction and antibiotic resistance genes (ARGs). The composition of the microbial community also changed during this process. After the denitrification rates recovered, Burkholderia_Paraburkholderia and Gordonia exhibited a significant positive correlation with SMX exposure, which simultaneously reduced nitrate concentrations and degraded antibiotics. Burkholderia_Paraburkholderia is a key carrier of ARGs. Finally, nitrogen reduction (> 90%) and antibiotic removal (> 80%) also recovered in both SMX- and N-SMX-exposed lab-scale CWs during the operation, which revealed the interaction of SMX or N-SMX removal and nitrogen reduction.

Plant responses to per- and polyfluoroalkyl substances (PFAS): a molecular perspective

Per- and polyfluoroalkyl substances (PFAS) constitute a large class of toxic manmade compounds that have been used in many industrial and household products. Dispersion of PFAS in the environment has raised concerns because of their persistence and toxicity for living organisms. Both terrestrial and aquatic plants have been shown to take up PFAS from contaminated soil and groundwater, and to accumulate these compounds inside their tissues. Although PFAS generally exert a low toxicity on plants at environmentally relevant concentrations, they frequently impact biomass growth and photosynthetic activity at higher levels. Uptake, translocation, and toxicity of PFAS in plants have been well covered in literature. Although less attention has been given to the molecular mechanisms underlying the plant response to PFAS, recent studies based on -omics approaches indicate that PFAS affects the plant metabolism even a low concentration. The objective of this review is to summarize the current knowledge about the effects of PFAS on plants at the molecular level. Results from recent transcriptomics, proteomics, and metabolomics studies show that low levels of PFAS induce oxidative stress and affect multiple plant functions and processes, including photosynthesis and energy metabolism. These potentially harmful effects trigger activation of defense mechanisms.

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.

Occurrence of per- and polyfluoroalkyl substances in aquatic environments and their removal by advanced oxidation processes

Per- and polyfluoroalkyl substances (PFAS), one of the main categories of emerging contaminants, are a family of fluorinated organic compounds of anthropogenic origin. PFAS can endanger the environment and human health because of their wide application in industries, long-term persistence, unique properties, and bioaccumulation potential. This study sought to explain the accumulation of different PFAS in water bodies. In aquatic environments, PFAS concentrations range extensively from <0.03 (groundwater; Melbourne, Australia) to 51,000 ng/L (Groundwater, Sweden). Additionally, bioaccumulation of PFAS in fish and water biota has been stated to range from 0.2 (Burbot, Lake Vättern, Sweden) to 13,900 ng/g (Bluegill samples, U.S.). Recently, studies have focused on PFAS removal from aqueous solutions; one promising technique is advanced oxidation processes (AOPs), including microwaves, ultrasound, ozonation, photocatalysis, UV, electrochemical oxidation, the Fenton process, and hydrogen peroxide-based and sulfate radical-based systems. The removal efficiency of PFAS ranges from 3% (for MW) to 100% for UV/sulfate radical as a hybrid reactor. Therefore, a hybrid reactor can be used to efficiently degrade and remove PFAS. Developing novel, efficient, cost-effective, and sustainable AOPs for PFAS degradation in water treatment systems is a critical area of research.

Joint toxicity mechanisms of perfluorooctanoic acid and sulfadiazine on submerged macrophytes and periphytic biofilms

Hazardous chemicals, such as perfluoroalkyl substances (PFASs) and antibiotics, coexist in aquatic environments and pose a severe threat to aquatic organisms. However, research into the toxicity of these pollutants on submerged macrophytes and their periphyton is still limited. To assess their combined toxicity, Vallisneria natans (V. natans) was exposed to perfluorooctanoic acid (PFOA) and sulfadiazine (SD) at environmental concentrations. Photosynthetic parameters such as chlorophyll a, chlorophyll b, total chlorophyll, and carotenoids were lower in the SD exposure group, indicating that SD had a significant effect on the photosynthesis of aquatic plants. Single and combined exposures effectively induced antioxidant responses, with increases in superoxide dismutase, peroxidase activities, and ribulose-1,5-bisphosphate carboxylase concentrations, as well as malondialdehyde content. Accordingly, antagonistic toxicity was assessed between PFOA and SD. Furthermore, metabolomics revealed that V. natans improved stress tolerance through changes in enoic acid, palmitic acid, and palmitoleoyloxymyristic acid related to the fatty acid metabolism pathway responding to the coexisting pollutants. Additionally, PFOA and SD in combination induced more effects on the microbial community of biofilm. The alternation of α- and β-D-glucopyranose polysaccharides and the increased content of autoinducer peptides and N-acylated homoserine lactones indicated that PFOA and SD changed the structure and function of biofilm. These investigations provide a broader perspective and comprehensive analysis of the responses of aquatic plants and periphyton biofilms to PFAS and antibiotics in the environment.

The addition of iron-carbon enhances the removal of perfluoroalkyl acids (PFAAs) in constructed wetlands

Hazardous perfluoroalkyl acids (PFAAs), particularly perfluorooctane sulfonate (PFOS) and perfluorooctanoate (PFOA), have become ubiquitous environmental persistent organic contaminants, posing serious threats to environmental health, which has led to the development of PFAA treatment methods. Wetland construction in combination with iron-carbon (CW-I), a low-maintenance and high-efficiency technology, may be capable of removing PFAAs through physico-biochemical processes. In this study, we aim to investigate the removal efficiency of PFAAs by CW-I as well as the critical functions of all components within the wetlands. Pairwise comparisons of iron-carbon and control groups revealed that iron-carbon significantly enhanced 15.9% for PFOA and 17.9% for PFOS absorption through phytouptake and substrate adsorption, with respective removal efficiencies of 71.8% ± 1.03% and 85.8% ± 1.56%. The generated iron ions stimulated plant growth and further enhanced phytouptake of PFAAs, with PFAAs accumulated primarily in root tissues with limited translocation. Observations of batch adsorption suggest that chemical and electrostatic interactions are involved in the iron-carbon adsorption process, with film and intraparticle diffusions being the rate-limiting events. Fourier transform infrared spectrometer and X-ray photoelectron spectroscopy revealed that PFAA adsorption by substrates occurs at the molecular level, as well as the occurrence of hydrophobic force effects and ligand exchanges during the iron-carbon adsorption process. Additionally, iron-carbon significantly altered the genera, phyla, and community structure of microorganisms, and some microorganisms and their extracellular polymers may possess ability to bind PFAAs. The information provided in this study contributes to our understanding of the PFAA removal processes in CW-I and enriched the classical cases of PFAA removal by CWs.

Enhanced nitrogen removal via biochar-mediated nitrification, denitrification, and electron transfer in constructed wetland microcosms

This study investigated the effect of biochar on real domestic wastewater treatment by constructed wetlands (CWs). To evaluate the role of biochar as a substrate and electron transfer medium on nitrogen transformation, three treatments of CW microcosms were established: conventional substrate (T1), biochar substrate (T2), and biochar-mediated electron transfer (T3). Nitrogen removal increased from 74% in T1 to 77.4% in T2 and 82.1% in T3. Nitrate generation increased in T2 (up to 2 mg/L) but decreased in T3 (lower than 0.8 mg/L), and the nitrification genes (amoA, Hao, and nxrA) in T2 and T3 increased by 132-164% and 129-217%, respectively, compared with T1 (1.56 × 10⁴- 2.34 × 10⁷ copies/g). The nitrifying Nitrosomonas, denitrifying Dechloromonas, and denitrification genes (narL, nirK, norC, and nosZ) in the anode and cathode of T3 were significantly higher than those of the other treatments (increased by 60-fold, 35-fold, and 19-38%). The genus Geobacter, related to electron transfer, increased in T3 (by 48-fold), and stable voltage (~150 mV) and power density (~9 uW/m²) were achieved. These results highlight the biochar-mediated enhancement of nitrogen removal in constructed wetlands via nitrification, denitrification, and electron transfer, and provide a promising approach for enhanced nitrogen removal by constructed wetland technology.

Enhancement of perfluorooctanoic acid and perfluorooctane sulphonic acid removal in constructed wetland using iron mineral: Performance and mechanisms

Polyfluoroalkyl substance (PFAS) pose a threat to the aquatic environment due to their environmental persistence. The removal of PFAS using constructed wetlands (CWs) has received interest, but the adsorption saturation and limited removal capacity of the substrate is frequently challenging. To enhance the microbial degradation and performance of the substrate, different configurations of iron minerals were used as substrate to remove perfluorooctane sulphonic acid (PFOS) and perfluorooctanoic acid (PFOA) from CWs. The addition of iron minerals resulted in elimination of 57.2% and 63.9% of PFOS and PFOA in the effluent, respectively, which were 35.0% and 36.8% higher than that of control. Moreover, up to 85.4%, 86%, and 85.1% of NH₄⁺, NO₃^-, and phosphorus, respectively, was removed using iron minerals. The enhanced electron transfer in iron mineral-based CWs was confirmed by a 61.2% increase in cytochrome C reductase content and an increased Fe(III)/Fe(II) ratio. Microbial analysis showed that the proportions of microbes with PFAS removal capacity (e.g. Burkholderiae and Pseudomonas), and the key pathways of the TCA cycle and glycolysis were increased in iron mineral-based CW. Based on these findings, we conclude that supplementation with iron mineral could enhance PFOA and PFOS removal in CWs.

Nitrogen addition enhanced Per-fluoroalkyl substances' microbial availability in a wheat soil ecosystem

Per-fluoroalkyl substances (PFASs) have been widely detected in farmland soils and are understood to pose toxicological threats to soil microbiomes and crop safety. Meanwhile, farmland ecosystems have experienced increasing nitrogen loading caused by soil fertilization. Yet it is still unclear how nitrogen additions affect soil's microbial responses to PFASs. In this study, using a laboratory-based ecological experiment, we assessed the microbial availability of PFASs in soils receiving ammonium, nitrate, and urea nitrogen amendments by quantifying the translocation factors of PFASs from soil particle to soil extracellular polymeric substances (EPS). Our results showed that nitrogen, specifically ammonium, significantly increased the PFASs' microbial availability (p < 0.05). Second, nitrogen fertilization in PFASs-polluted soils decreased the microbial community diversity and stability at the structural, species, and functional levels (p < 0.05). For soil microbial activities, nitrogen enhanced the activity of superoxide dismutase (SOD) while it inhibited the catalase (CAT) and peroxidase (POD) (p < 0.01). Congruently, PFASs, as well as the nitrate and nitrite nitrogen, were shown to be the predominant abiotic drivers regulating the soil fungal succession (p < 0.05), while bacteria were mostly regulated by dissolved organic carbon (DOC) (p < 0.01). Furthermore, we revealed that the nitrogen cycling gene hmp (dominates the transformation from NO to NO₃^-) was the hub gene integrating the microbially available PFASs and the soil nitrogen cycling processes (p < 0.01), indicating that hmp could be the core regulator affecting the accumulation of PFASs in soil EPS. Our study highlighted that decreasing ammonia's amendments could mitigate China's national initiatives to reduce nitrogen fertilization in farmlands, reduce the PFASs' availability to the soil microbiome, and protect the microbial community stability in soil.

Bioaccumulation of Per- and Polyfluoroalkyl Substances (PFAS) in Ferns: Effect of PFAS Molecular Structure and Plant Root Characteristics

The present study assessed the bioaccumulation potential of per- and polyfluoroalkyl substances (PFAS) in ferns and linked root uptake behaviors to root characteristics and PFAS molecular structure. Tissue and subcellular-level behavioral differences between alternative and legacy PFAS were compared via an electron probe microanalyzer with energy dispersive spectroscopy (EPMA-EDS) and differential centrifugation. Our results show that ferns can accumulate PFAS from water, immobilize them in roots, and store them in harvestable tissue. The PFAS loading in roots was dominated by PFOS; however, a substantial amount of associated PFOS could be rinsed off by methanol. Correlation analyses indicated that root length, surface and project area, surface area per unit length of the root system, and molecular size and hydrophobicity of PFAS were the most significant factors affecting the magnitude of root uptake and upward translocation. EPMA-EDS images together with exposure experiments suggested that long-chain hydrophobic compounds tend to be adsorbed and retained on the root epidermis, while short-chain compounds are absorbed and quickly translocated upward. Our findings demonstrated the feasibility of using ferns in phytostabilization and phytoextraction initiatives of PFAS in the future.

Impact of biological activated carbon filtration and backwashing on the behaviour of PFASs in drinking water treatment plants

PFASs are present in surface water, tap water and even commercial drinking water and pose a risk to human health. In this study, the treatment efficiency of 14 PFASs was studied in a large drinking water treatment plant (DWTP) using Taihu Lake as the source, and it was found that the ozone/biological activated carbon (O₃-BAC) process was the most effective process for the removal of PFASs in DWTPs. For the O₃-BAC process, there were differences in the removal of PFASs by BACs (1,4,7,13 years) of different ages. The sterilization experiments revealed that for GAC, its physical adsorption capacity reached saturation after one year, while for BAC with mature biofilms, biosorption was the main mechanism for the removal of PFASs. The abundance of Alphaproteobacteria and Gammaproteobacteria in biofilms was positively correlated with the age of the BAC. The microbial community with higher abundance is beneficial to the biodegradation of organic matter and thus provides more active sites for the adsorption of PFASs. PFASs can leak in the early stage of filtration after backwashing, so it is necessary to pay close attention to the influent and effluent concentrations of PFASs during biofilm maturation after backwashing.

Direct evidence of the important role of proteins in bioconcentration and biomagnification of PFASs in benthic organisms based on comparison with OPEs

Despite the wide acceptance that bioconcentration and biomagnification of per/polyfluoroalkyl substances (PFASs) is related to proteins in organisms, few direct evidences are available. Here, bioconcentration and biomagnification of 9 organophosphate esters (OPEs) and 16 PFASs, which have similar range of log K_ow (octanol-water partitioning coefficient) values, were compared in the benthic food chain of biofilm-snail in Taihu Lake, China. The ∑OPEs level in water (150-23,036 ng/L) was significantly higher than ∑PFASs (57.3-351 ng/L). Although the logarithm of bioconcentration factors of both OPEs and PFASs in biofilm positively correlated with their log K_ow, the slope of PFASs was 4 times of that of OPEs, which might be due to the strong interactions of PFASs with biofilm extracellular proteins. Additionally, PFASs exhibited distinctly greater biomagnification factors from biofilm to snails (3.09-17.8) than OPEs (0.39-3.48). Significant correlations between the concentrations and protein contents in snails were observed for most long-chain PFASs, but not for any OPEs. Multiple receptor models identified polyurethane foam (77.9 %) and food packaging/metal plating (56.9 %) were the primary sources of OPEs and PFASs in Taihu Lake, respectively. We provided strong and direct evidences that proteins facilitated bioconcentration and biomagnification of PFASs.

Curbing per- and polyfluoroalkyl substances (PFASs): First investigation in a constructed wetland-microbial fuel cell system

The presence of per- and polyfluoroalkyl substances (PFASs) in water environments has been linked to a slew of negative health effects in both animals and humans, but the green and eco-sustainable removal technologies remain largely unknown. Constructed wetland coupled microbial fuel cell (CW-MFC) is termed a "green process" to control pollutants and recover energy. However, so far, no study has investigated the removal of PFASs and their effects on the performance of the CW-MFC systems. Here, we investigated the removal performance of PFOA and PFOS in the CW-MFC systems both in the absence and presence of electricity circuit, and explored the distribution and fate of PFASs and their interactions with other elements in the systems. Our findings demonstrated excellent removal efficiency of >96% PFOA and PFOS in CW-MFC systems. PFOA and PFOS were distributed throughout the system via wastewater flow, while electrode material and plants are the main enrichment sites in which MFC enhanced up to 10% PFASs removal. However, a loss of 7.2-13.5% of nitrogen removal and a decrease of 7.3% in bioelectricity output were observed when PFASs were introduced in the system. The driven force led to the loss of nitrogen removal and bioelectricity generation lies in the accumulation of PFASs in system composition, which affected microbial activity and community composition, damaging the health of the plant, and in turn reducing CW-MFC's functioning. No doubt, CW-MFC systems provide an alternative technique for PFASs removal, alleviating some limitations to the physical and chemical techniques, but further investigation is highly needed.

Impacts of iron amendments and per-fluoroalkyl substances' bio-availability to the soil microbiome in wheat ecosystem

Per-fluoroalkyl substances (PFASs) have become ubiquitous in farmland ecosystems and pose risks to agricultural safety, and iron is often applied to farmland soils to reduce the availability of pollutants. However, the effects of iron amendment on the availability of PFASs in the soil and on the soil microbiome are not well understood. Here, we investigated the responses of wheat soil containing PFASs to iron addition using a 21-day experiment. Our results showed that iron amendment enhanced PFAS availability (p < 0.05) and stimulated superoxide dismutase (SOD) activity in the wheat soil (p < 0.05), but iron amendment decreased the activities of soil catalase (CAT) and peroxidase (POD) (p < 0.05). Soil bacterial community was more structurally stable than fungal community in response to iron addition, while species' pools were more stable in fungi than in bacteria (p < 0.05). Finally, PFPeA's availability in the wheat soil was the most important abiotic factors driving community succession of iron-cycling bacteria (p < 0.05). These results highlighted the potential interactions among PFASs' availability and microbial iron cycling in wheat farmland soil ecosystems and provided guidance in farmland environmental conservation and management.

Removal of Per-, Poly-fluoroalkyl substances (PFASs) and multi-biosphere community dynamics in a bacteria-algae symbiotic aquatic ecosystem

The presence of Per-, Poly-fluoroalkyl substances (PFASs) in aquatic ecosystems has drawn broad concerns in the scientific community due to their biological toxicity. However, little has been explored regarding PFASs' removal in phytoplankton-dominated environments. This study aimed to create a simulated bacteria-algae symbiotic ecosystem to observe the potential transportation of PFASs. Mass distributions showed that sand (63-2000 μm), silt & clay (0-63 μm), the phycosphere (>3 μm plankton), and the free-living biosphere (0.22-3 μm plankton) contained 19.00, 7.78, 5.73 and 2.75% PFASs in their total mass, respectively. Significant correlations were observed between carbon chain lengths and removal rates (R² = 0.822, p < 10^-4). Structural equation models revealed potential PFAS transportation pathways, such as water-phycosphere- free-living biosphere-sand-silt&clay, and water-sand-silt&clay (p < 0.05). The presence of PFASs decreased the bacterial density but increased algal density (p < 0.01) in the planktonic environment, and PFASs with longer carbon chain lengths showed a stronger enhancement in microbial community successions (p < 0.05). In algal metabolisms, chlorophyll-a and carotenoids were the key pigments that resisted reactive oxygen species caused by PFASs. PFBA (perfluorobutyric acid) (10.38-14.68%) and PFTeDA (perfluorotetradecanoic acid) (10.33-15.96%) affected bacterial metabolisms in phycosphere the most, while in the free-living biosphere was most effected by PFPeA (perfluorovaleric acid) (13.21-13.99%) and PFDoA (perfluorododecanoic acid) (10.04-10.50%). The results of this study provide new guidance measures for PFAS removal and management in aquatic environments.

Adsorption of perfluoroalkyl acids on granular activated carbon supported chitosan: Role of nanobubbles

The safety threat posed by Perfluoroalkyl acids (PFAAs) in drinking water is a growing concern. In this study, we loaded chitosan (CS) on granular activated carbon (GAC) to adsorb PFAAs, and we explored the role of nanobubbles in the adsorption process through experiments and density functional theory (DFT) calculations. Compared with GAC, we found that the use of the composite adsorbent (CS/GAC) enhanced the removal rate of perfluorooctanoic acid by 136% with the assistance of nanobubbles. PFAAs with different chain lengths have different adsorption mechanisms owing to surface activity differences. PFAAs with longer C-F chains can be directly enriched with amino groups on the CS or air-water interface on composite adsorbents. Additionally, PFAAs can be enriched with nanobubbles in solution to form nanobubble-PFAA colloids, which are adsorbed by protonated amino groups on CS through electrostatic interactions. We found that PFAAs with shorter C-F chains are less affected by nanobubbles, and DFT calculations indicated that the adsorption of short-chain PFAAs is mainly affected by electrostatic interactions. We also proved that the electrostatic interactions between CS and PFAAs are mainly derived from the abundant protonated amino groups.

Unraveling the ecological mechanisms of bacterial succession in epiphytic biofilms on Vallisneria natans and Hydrilla verticillata during bioremediation of phenanthrene and pyrene polluted wetland

In wetland ecosystem, the microbial succession in epiphytic biofilms of submerged macrophytes remains to be fully elucidated, especially submerged macrophytes used to remediate organic pollutants contaminated sediment. Herein, 16 S rRNA gene sequencing was used to investigate the bacterial dynamics and ecological processes in the biofilms of two typical submerged macrophytes (Vallisneria natans and Hydrilla verticillata) settled in sediment polluted by polycyclic aromatic hydrocarbons (PAHs) at two growth periods. The results presented that the variations of bacterial community in the biofilms were influenced by attached surfaces (explanation ratio: 17.30%), incubation time (32.30%) and environmental factors (39.10%). Bacterial community assembly was mainly driven by dispersal limitation which triggered more positive co-occurrence associations in microbial networks, maintaining ecological stability in the process of bioremediation of PAHs. Additionally, the functional redundancy strength of bacterial community was more affected by attached surface than incubation time. The structural equation model illustrated that community assembly drove β-diversity and explained a part of ecological functions. Environmental factors, community assembly, and β-diversity jointly affected microbial networks. Overall, our study offers new insights into the microbial ecology in biofilms attached on the submerged macrophytes settled in PAH-polluted sediment, providing important information for deeply understanding submerged macrophyte-biofilm complex and promoting sustainable phytoremediation in shallow lacustrine and marshy ecosystems.

Removing nutrients from wastewater by constructed wetlands under perfluoroalkyl acids stress

Constructed wetlands (CWs) are often used to treat wastewater discharged from wastewater treatment plants (WWTPs), while emerging contaminants (such as perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS)) have been commonly discovered in WWTPs. However, no research has examined whether PFOA/OS (i.e. PFOA and PFOS) affects the performance of CW. Therefore, this study compared the nutrient removal efficiencies of four CWs with varied configurations under PFOA/OS and no PFOA/OS stress conditions. We found that CW containing plants or/and iron-carbon had higher removal efficiency for nutrients (except NH₄⁺-N) than conventional CW in stable operation under wastewater without PFOA/OS. Plants or/and iron increased the nutrient removal efficiency by plant uptake, chemical reaction, and co-precipitation of iron hydroxides. In contrast, the iron-carbon inhibited the nitrification of nitrifying bacteria by consuming dissolved oxygen, converting NO₃^--N to NH₄⁺-N. Although the removal efficiencies of nutrients by CWs differed after introducing PFOA/OS, the removal order was consistent with those before adding PFOA/OS. Plants or/and iron-carbon effectively increased CWs' resistance to PFOA/OS loading and toxicity, and the function of iron-carbon was superior to the plants. In addition, PFOA/OS reduced the abundances of microbes Hydrogenophaga, Pseudomonas, Sphingomonas, Nitrospira, and Candidatus_Accumulibacter that contributed to nutrient removal.

Perfluoroalkyl acids in representative edible aquatic species from the lower Yangtze River: Occurrence, distribution, sources, and health risk

Perfluoroalkyl acid (PFAA) exposure poses a potential hazard to wildlife and humans. Food consumption is one of the main routes of PFAA exposure for the general population, with aquatic organisms being the major contributors. To evaluate the risk of coastal residents' intake of wild aquatic organisms, 14 PFAAs were detected in crucian carp and oriental river prawn from 18 sampling sites from the lower reaches of Yangtze River. The total PFAA (∑PFAA) concentrations ranged from 5.9 to 51.3 ng/g wet weight (ww) in the muscle of crucian carp and river prawn, suggesting the potential risk to human and wildlife. Perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and long-chain PFAAs (C ≥ 10) were the main pollutants in the tissues of crucian carp and river prawn, which are known for their higher bioaccumulation capacity. The ∑PFAA concentration in all the samples showed an increasing trend from upstream to downstream and was higher in the south bank, owing to population density, prevailing winds, background pollution and industrial emission. Principal component analysis-multiple linear regression and Pearson correlation analysis showed that WWTP effluent, industrial pollution and surface runoff ware the main sources of PFAAs in the aquatic organisms and industrial pollution highest contributor, suggesting better regulation is needed to manage them. The assessment of risk to human health and wild life suggested a low risk for most residents of cities along the Yangtze River except for resident of Nantong, where frequent consumption of wild aquatic organisms may cause potential risk to human health, especially for traditional eaters and middle-aged people.

Removal of perfluoroalkyl acids and dynamic succession of biofilm microbial communities in the decomposition process of emergent macrophytes in wetlands

Perfluoroalkyl acids (PFAAs) are emerging contaminants that pose significant environmental and health concerns. Water-sediment-macrophyte residue systems were established to clarify the removal efficiency of PFAAs, explore possible removal pathways, and profile the dynamic succession of biofilm microbial communities in the decomposition process. These systems were fortified with 12 PFAAs at three concentration levels. Iris pseudacorus and Alisma orientale were selected as the decomposing emergent macrophytes. The removal rates in the treatments with residues of I. pseudacorus (IP) and A. orientale (AO) were 34.4% to 88.9% and 36.5% to 89.9%, respectively, which were higher than those in the control groups (CG) (30.3% to 86.9%), suggesting that decomposition could alter the removal of PFAAs. Sediment made the greatest contributions (preloaded 14.5% to 77.8% of PFAAs in IP, 14.3% to 78.2% in AO, and 27.4% to 71.9% in CG). PFAAs could also be removed by macrophyte residue sorption (0.0190% to 13.0% in IP and 0.016% to 15.6% in AO) and bioaccumulation of residual biofilm (the contributions of biofilm microbes and their extracellular polymeric substances were 0.0110% to 3.93% and 0.918% to 34.4%, respectively, in IP and 0.0141% to 4.65% and 1.49% to 34.1%, respectively, in AO). Significant correlations were observed between sediment/residue adsorption and bioaccumulation of biofilm microbes, and were significantly correlated with perfluoroalkyl chain length (p < 0.05). The dynamic succession of residual biofilm microbial communities was investigated. The largest difference was found at the preliminary stage. The most similar communities were found in AO on day 70 (with specific genera Macellibacteroides and WCHB1-32) and in IP on day 35 (with specific genera Aeromonas and Flavobacterium). This study is useful to understand the removal of PFAAs during the decomposition process, providing further assistance in removing PFAAs during the life cycle of macrophytes in wetlands.

Evaluation of the ecological impacts of short- and long-chain perfluoroalkyl acids on constructed wetland systems: Perfluorobutyric acid and perfluorooctanoic acid

Perfluoroalkyl substances (PFASs) contamination of aquatic system has attracted widespread attention in recent years. From both plant and microbial perspectives, the ecological risk of CWs by comparing PFASs with different chain lengths have not been fully understood. In this study, the influences of perfluorobutyric acid (PFBA) and perfluorooctanoic acid (PFOA) as typical of short- and long-chains on the ecological effect of CWs have been specifically studied. The results showed that plants produced oxidative stress response and the activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves were stimulated by 17.23-28.13% and 10.49-14.17% upon 10 mg/L PFBA and PFOA exposure. Under the high level of PFBA and PFOA stress, the chlorophyll content was reduced by 15.20-39.40% and lipid peroxidation was observed in leaves with the accumulation of malondialdehyde (MDA) at 1.20-1.22 times of the control. Dehydrogenase (DHA) exhibited the most sensitivity in the presence of PFBA and PFOA with an inhibition ratio of over 90%. The biotoxicity of PFOA was higher than that of PFBA in terms of the inhibition degree of several substrate enzymes. The information of Illumina Miseq sequencing indicated that the diversity and structure of microbial community in CWs were significantly altered by PFBA and PFOA addition and led to an enrichment of more PFASs-tolerant bacteria.

Ecotoxicological responses and removal of submerged macrophyte Hydrilla verticillate to multiple perfluoroalkyl acid (PFAA) pollutants in aquatic environments

The ubiquitous existence of perfluoroalkyl acids (PFAAs) in aquatic environments might pose toxic potential to ecosystems. To assess the ecotoxicological responses and removal of submerged macrophyte to multiple PFAA pollutants in aquatic environments, a typical submerged macrophyte, Hydrilla verticillate, was exposed to solutions with 12 typical PFAAs in the present study. The results showed that PFAAs at concentrations higher than 10 μg/L had significantly passive effects on biomass, relative growth rates, chlorophyll contents, and chlorophyll autofluorescence. PFAAs could induce the accumulation of hydrogen peroxide and lipid peroxidation in H. verticillate. Significant upregulation of CAT was observed in treatments with more than 10 μg/L PFAAs (p < 0.05). The results also showed that 13.53-20.01% and 19.73-37.72% of PFAAs could be removed in treatments without plants and with H. verticillate, respectively. The removal rates of PFAAs were significantly correlated with perfluoroalkyl chain length in treatments with H. verticillate. The removal of PFAAs was suggested to be related to the uptake of plant tissues and biosorption of microbiota. Furthermore, the dominant microbiota and biomarkers were identified in water and biofilm. Betaproteobacteriales was the most dominant microbiota at the order level. The presence of PFAAs could significantly increase the relative abundance of Micrococcales, Verrucomicrobiales, Rhizobiales, Sphingomonadales, Roseomonas, Cyanobium_PCC_6307, and Synechococcales. Our results provide scientific basis for evaluating the ecotoxicological responses and removal of submerged macrophytes in response to multiple PFAA pollutants at environmentally relevant levels, thereby providing insights into PFAA management and removal.

Interactions between dissolved organic matter and perfluoroalkyl acids in natural rivers and lakes: A case study of the northwest of Taihu Lake Basin, China

Understanding the interactions between dissolved organic matter (DOM) and perfluoroalkyl acids (PFAAs) is essential for predicting the distribution, transport, and fate of PFAAs in aquatic environments. Based on field investigations in the northwest of Taihu Lake Basin combined with laboratory experiments, we obtained DOM and PFAA concentrations as well as compositions and investigated key factors of DOM affecting PFAA variability and capture of PFAAs by DOM. Results indicated that the total concentrations of PFAAs were 73.4-689 ng/L in surface water and that PFAAs were dominated by C3-7 perfluoroalkyl carboxylic acids and perfluorooctane sulfonic acid. The main components of DOM included tyrosine-, fulvic-, and tryptophan-like substances. The Mantel test revealed a significant positive correlation between DOM and PFAAs (P = 0.0001). Fulvic-like substances were identified as the most crucial factors affecting PFAA variability. The laboratory experiments revealed that DOM can spontaneously aggregate into a microgel. Furthermore, 19.1-50.9% of PFAAs, DOM characteristic peaks, and several metals (Ca, Mg, Cu, and Fe) can be removed during aggregation, indicating the capacity of DOM binding organic/inorganic substances. The fulvic-like substances were more effectively removed than the protein-like substances. The distribution coefficients of all PFAAs except perfluorohexanoic acid significantly correlated with their perfluorinated carbon numbers (r = 0.975, p<0.001). Our results provided insights into the interactions between DOM and PFAAs, improving the understanding of the distribution, transport, and fate of PFAAs in aquatic environments.

Natural biofilm as a potential integrative sample for evaluating the contamination and impacts of PFAS on aquatic ecosystems

Natural biofilm can be a suitable medium for the monitoring of pollutants. Limited information is currently available regarding the occurrence of per- and polyfluoroalkyl substances (PFAS) in periphytic biofilm and low-trophic level organisms of freshwater ecosystems. In this study, surface water, biofilm, phytoplankton, and freshwater snails were collected from Taihu Lake, China, and characterized for 16 PFAS, including legacy compounds (PFSAs/PFCAs) and PFAS of emerging concern (fluorotelomer sulfonates and F-53B). The colonized biofilms effectively bioaccumulated PFAS from water, with the total concentration (∑PFAS) in the range of 1.96-20.1 ng/g wet weight, and the bioaccumulation factor increased with the PFAS log K_ow values. As compared with phytoplankton, the ∑PFAS in biofilms displayed a stronger correlation with those in water. PFAS distinctly biomagnified from the biofilm to freshwater snail, with the biomagnification factor in the range of 3.09 ± 2.03 - 17.8 ± 10.2, implying the important role of biofilm in PFAS transfer in aquatic environment. Extracellular proteins production in biofilm increased with the water PFAS concentrations. The total extracellular polymeric substances (EPS) content increased with the water PFAS concentration firstly and then declined to a steady level, while the algal chlorophyll level exhibited a similar relationship with the PFAS in biofilm. High PFAS levels were also associated with depressed alpha diversity of fungal community in biofilms. Biofilm appears as a relevant indicator to characterize the occurrence of PFAS in aquatic ecosystems.

Emerged macrophytes to the rescue: Perfluoroalkyl acid removal from wastewater and spiked solutions

This study evaluated the potential for three emergent aquatic macrophytes to remove perfluoroalkyl acids (PFAAs) from contaminated waters in constructed wetland systems. Three plants (Iris pseudacorus L., Phragmites australis (Cav.) Trin. Ex Steud., and Typha latifolia L.) were exposed to an effluent from a tannery wastewater treatment plant (WWTP) that contained residual PFAAs, and to three spiked solutions with increasing concentrations of 11 perfluorocarboxylic acids (PFCAs) and three perfluorosulfonic acids (PFSAs) (500, 2500, and 5000 ng L^-1, each). Thirty-six lightweight expanded clay aggregate- and vegetation-filled tanks (0.35 × 0.56 × 0.31 m) were exposed to the tested solutions at the Acque del Chiampo SpA WWTP in Arzignano (NE Italy). Throughout the experiment, PFAA concentrations and physicochemical water parameters were monitored via measures of the clay material, plastic tank inner surfaces, and below- and above-ground biomasses (after harvest). Vegetation growth was shown to be unaffected by increased PFAA levels in the spiked solutions. Alternatively, total biomass was significantly reduced when WWTP water was used, although we attribute this finding to the relatively high salinity that mainly restricted Typha and Iris development. The tested macrophytes were found to remove a significant PFAA mass from the contaminated waters (36% to ca. 80%, on average) when Phragmites was subjected to the highest PFAA concentrations. Such large accumulations were primarily associated with long C-chain PFAA stabilization in belowground biomass (26%, on average). Most PFAA translocations were observed in Typha, which accumulated mostly short perfluorinated C-chain PFBA, PFPeA, and PFHxA in the aboveground biomass (16%, on average). Despite some growth limitations, Iris was still the most efficient macrophyte for translocating PFBS under WWTP.

A novel fate and transport model for evaluating the presence and environmental risk of per-/poly-fluoroalkyl substances (PFASs) among multi-media in Lingang hybrid constructed wetland, Tianjin, China

Accurately revealing and predicting the presence and risks of per-/poly-fluoroalkyl substances (PFASs) in constructed wetlands (CWs) is great significant for the construction and management of CWs, but very challenging. In this work, a novel fate and transport model was for the first time established to evaluate the spatially continuous distribution and environmental risks of PFASs among multi-media in Lingang hybrid CW fed by industry tailwater. 20 PFASs were detected from the Lingang CW, and the total concentration of the detected PFASs in water and sediments were in the range of 38.94-81.65 ng/L and 1.23-4.31 ng/g, respectively. PFOA, PFOS and PFBS were the main pollutants in water and sediments. A fate and transport model describing the distribution characteristics and fate of PFASs in Lingang hybrid CW was constructed, and its reliability was verified. The simulated results suggested that PFASs were mainly accumulated in sediments and long-chain PFASs were more easily adsorbed by sediments compared with short-chain PFASs. According to the principal component analysis-multiple linear regression (PCA-MLR), PFASs mainly came from the tailwater from the surrounding sewage treatment plants. Besides, the environmental risks were predicted by this novel model, suggesting that the risks still cannot be neglected due to the accumulation and continuous input of PFASs although the environmental risks of Lingang CW were low. This work provides a novel model for the understanding of presence and risks of PFASs among multi-media in CWs.

Removal potential of multiple perfluoroalkyl acids (PFAAs) by submerged macrophytes in aquatic environments: Tolerance of Vallisneria natans and PFAA removal in submerged macrophyte-microbiota systems

Perfluoroalkyl acids (PFAAs) have emerged as a global concern in aquatic environment remediation due to their abundance, persistence, bioaccumulation, and toxicity. To comprehensively understand the removal potential of multiple PFAAs by submerged macrophytes in aquatic environments, systematic investigations into the tolerance of the typical submerged macrophyte Vallisneria natans to 12 typical PFAAs and the removal capacity to PFAAs in V. natans-microbiota systems were carried out. Results showed that although PFAAs could induce the accumulation of hydrogen peroxide and malondialdehyde, V. natans was overall resistant to multiple PFAAs with natural concentrations. Catalase is one of the main strategies of V. natans to alleviate PFAA stress. Microbiota can remove 18.10-30.84% of the PFAAs from the water column. 24.35-73.45% of PFAAs were removed from water in V. natans-microbiota systems. The uptake of plant tissues and the bioaccumulation of microbiota were proposed as the main removal processes. The removal rates were significantly correlated with the perfluorinated carbon atoms numbers (p < 0.05). PFAAs and V. natans increased the relative abundance of Betaproteobacteria, Nostocales, Microscillaceae, Sphingobacteriales, SBR1031, Chlamydiales, Phycisphaerae, Caldilineales, Rhodobacterales, and Verrucomicrobiales. The present study suggested that V. natans can be a potential species to remove multiple PFAAs in aquatic environments, and further providing insights into the PFAAs' remediation.

Occurrence, distribution, and risk assessment of perfluoroalkyl acids in drinking water sources from the lower Yangtze River

The occurrence, spatial distribution, potential sources, and risk assessment of 14 perfluoroalkyl acids (PFAAs), including 11 perfluoroalkyl carboxylic acids and 3 perfluoroalkyl sulfonates acids, were investigated in 21 drinking water sources from the lower Yangtze River in November 2019. The total PFAAs (∑PFAAs) concentrations ranged from 39.3 to 220.3 ng/L, and perfluorooctanoic acid and perfluorooctanesulfonate were predominant with average concentrations of 19.4 and 15.4 ng/L, respectively. The higher ∑PFAAs concentrations in the southern shore and downstream could be attributed to industrial development and surface runoff/tide currents, respectively. Principal component analysis-multiple linear regression revealed that the primary sources of PFAAs were fluororesin coatings/metal plating, surface runoff/textile, effluent discharge/food packaging, and leather/fabrics. Human intake risks of PFAAs were assessed by target hazard quotient (THQ), which showed that human health risks of PFAAs decreased with increasing age, excluding 13-17 years age group. Moreover, the total exposure risks of PFOA/PFOS in all sampling sites to people aged over 18 years calculated based on contribution from drinking water were noted to be at safe level. The results obtained were helpful for improving our understanding of human health risks of PFAAs, and expanding our knowledge on PFAAs in drinking water.

Perfluorinated compounds (PFCs) in regional industrial rivers: Interactions between pollution flux and eukaryotic community phylosymbiosis

Perfluorinated compounds (PFCs) pose serious threats to aquatic ecosystems, especially their microbial communities. However, little is known about the phylosymbiosis of aquatic fungal and viridiplantae communities in response to PFC accumulation. We quantified the distribution of 14 PFCs in rivers and found that PFBA was dominant in the transition from water to sediment. High through-put sequencing revealed that phyla Ascomycota, Basidiomycota, Anthophyta, and Chlorophyta were the predominant in eukaryotic community. The effects of PFCs on spatial community coalescence at taxonomic and phylogenetic levels (p < 0.05) were revealed. Fungal community coalescence triggered the spatial assembly of fungal and viridiplantae communities in riverine environments (p < 0.05). Null modeling indicated that PFBA, PFTrDA and PFOS, etc, mediated phylogenetic assembly (p < 0.05) and stochastic processes (86.67-100%) maintain phylogenetic turnover in the fungal community. Meanwhile, variable selection (27.78-54.44%) explained the viridiplantae community assemblage. Finally, we identified fungal genera Hannaella, Naganishia, Purpureocillium and Stachybotrys as indicators for PFC pollution (p < 0.001). These results help explain the effects of PFCs on riverine ecological remediation.

Ship navigation disturbance alters multiphase distribution of perfluoroalkyl acids and increases their ecological risk in waterways

As a global persistent organic pollutant, perfluoroalkyl acids (PFAAs) have aroused great public concern. However, little is known regarding the effect of ship navigation disturbance on the transport and fate of PFAAs in inland waterways developed regions. In the present study, overlying water, pore water, suspended particulate matter (SPM), and sediment were collected from waterways (WWs), non-navigable channels (NCs), and ports (PTs) in Taihu Lake Basin. The results revealed that the total concentrations of PFAAs (ΣPFAAs) in WWs, NCs, and PTs varied considerably in different media. In overlying water, the mean ΣPFAAs in WWs were the highest, while those of NCs were relatively higher in the remaining three media. A comparison of PFAA distribution coefficients revealed that the values in NCs were generally higher than those of WWs and PTs, suggesting the critical role of ship navigation in PFAA transport. Furthermore, a structural equation model was applied to estimate direct and indirect effects of environmental factors on PFAA partitioning behavior. The results revealed that ship traffic volume (STV) exerted indirect effects on PFAA distribution between solid and dissolved phases by influencing dissolved oxygen, total suspended solid concentration, clay and sand contents, and median diameter. PFAAs were more readily to be released into overlying water from pore water than in sediment, and the ΣPFAAs carried per gram of SPM decreased with an increase in STV. Ecological risk assessment and Monte Carlo simulation results revealed that ship navigation could exert adverse effects on aquatic organisms, making the average probability of RQ_mix values to exceed corresponding risk values in WWs, which were 1.3-2-fold higher than in NCs. The present study provides crucial information for simulating the environmental behaviors of PFAAs under the influence of ship navigation and is significant for the integration of inland water transport development and aquatic environmental protection.