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

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.

Coupled effects of redox-active substances and microbial communities on reactive oxygen species in rhizosphere sediments of submerged macrophytes

Reactive oxygen species (ROS) play crucial roles in element cycling and pollutant dynamics, but their variations and mechanisms in the rhizosphere of submerged macrophytes are poorly investigated. This study investigated the light-dark cycle fluctuations and periodic variations in ROS, redox-active substances, and microbial communities in the rhizosphere of Vallisneria natans. The results showed sustained production and significant diurnal fluctuations in the O2•- and •OH from 27.6 ± 3.7 to 61.7 ± 3.0 μmol/kg FW and 131.0 ± 6.8 to 195.4 ± 8.7 μmol/kg FW, respectively, which simultaneously fluctuated with the redox-active substances. The ROS contents in the rhizosphere were higher than those observed in non-rhizosphere sediments over the V. natans growth period, exhibiting increasing-decreasing trends. According to the redundancy analysis results, water-soluble phenols, fungi, and bacteria were the main factors influencing ROS production in the rhizosphere, showing contribution rates of 74.0, 17.3, and 4.4 %, respectively. The results of partial least squares path modeling highlighted the coupled effects of redox-active substances and microbial metabolism. Our findings also demonstrated the degradation effect of ROS in rhizosphere sediments of submerged macrophytes. This study provides experimental evidence of ROS-related rhizosphere effects and further insights into submerged macrophytes-based ecological restoration.

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.

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.

Elucidating the degradation mechanisms of perfluorooctanoic acid and perfluorooctane sulfonate in various environmental matrices: a review of green degradation pathways

Given environmental persistence, potential for bioaccumulation, and toxicity of Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS), the scientific community has increasingly focused on researching their toxicology and degradation methods. This paper presents a survey of recent research advances in the toxicological effects and degradation methods of PFOA and PFOS. Their adverse effects on the liver, nervous system, male reproductive system, genetics, and development are detailed. Additionally, the degradation techniques of PFOA and PFOS, including photochemical, photocatalytic, and electrochemical methods, are analyzed and compared, highlighted the potential of these technologies for environmental remediation. The biotransformation pathways and mechanisms of PFOA and PFOS involving microorganisms, plants, and enzymes are also presented. As the primary green degradation pathway for PFOA and PFOS, Biodegradation uses specific microorganisms, plants or enzymes to remove PFOA and PFOS from the environment through redox reactions, enzyme catalysis and other pathways. Currently, there has been a paucity of research conducted on the biodegradation of PFOA and PFOS. However, this degradation technology is promising owing to its specificity, cost-effectiveness, and ease of implementation. Furthermore, novel materials/methods for PFOA and PFOS degradation are presented in this paper. These novel materials/methods effectively improve the degradation efficiency of PFOA and PFOS and provide new ideas and tools for the degradation of PFOA and PFOS. This information can assist researchers in identifying flaws and gaps in the field, which can facilitate the formulation of innovative research ideas.

Removal of perfluoroalkyl acids (PFAAs) from aqueous solution by water hyacinth (Eichhornia crassipes): Uptake, accumulation, and translocation

Although Eichhornia crassipes, commonly known as water hyacinth, has been widely used in wastewater treatment, further investigations are still needed to explore the removal efficiency of perfluoroalkyl acids (PFAAs) from the aqueous environment using this floating aquatic plant. In this study, a hydroponic experiment was conducted to assess accumulation, bioconcentration factors (BCFs), translocation factors (TFs), and removal rates of eight PFAAs by water hyacinth. The obtained results indicated that all PFAAs, including five perfluoroalkyl carboxylic acids (PFCAs) with chain lengths C4-C8 and three perfluoroalkyl sulfonic acids (PFSAs) with C4, C6, and C8, were readily accumulated in water hyacinth. Throughout the duration of the experiment, there was a noticeable increase in PFAA concentrations and BCF values for different plant parts. For the root, PFAAs with more carbon numbers showed a higher uptake than the shorter homologues, with PFSAs being more readily accumulated compared to PFCAs with the same carbon number in the molecules. In contrast, the levels of long-chain PFAAs were comparatively lower than those of short-chain substances in the stem and leaf. Notably, PFAAs with less carbon numbers, like PFPeA, PFBA, and PFBS, showed a remarkable translocation from the root to the stem and leaf with TFs >1. For the whole plant, no significant correlation was found between BCFs and organic carbon-water partition coefficients (Koc), octanol-water partition coefficients (Kow), membrane-water distribution coefficients (Dmw), or protein-water distribution coefficients (Dpw). The removal rates of PFAAs ranged from 40.3 to 63.5 % throughout the three weeks of the experiment while the removal efficiencies varied from 48.9 % for PFHxS to 82.6 % for PFPeA in the last week.

Ecotoxicity of perfluorooctanoic acid and perfluorooctane sulfonate on aquatic plant Vallisneria natans

Perfluorinated compounds (PFCs) are persistent organic contaminants that are highly toxic to the environment and bioaccumulate, but their ecotoxic effects on aquatic plants remain unclear. In this study, the submerged plant Vallisneria natans was treated with short-term (7 days) and long-term (21 days) exposures to perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of 0, 0.01, 0.1, 1.0, 5.0, and 10 mg/L, respectively. The results showed that both high concentrations of PFOA and PFOS inhibited the growth of V. natans and triggered the increase in photosynthetic pigment content in leaves. The oxidative damage occurred mainly in leaves, but both leaves and roots gradually built up tolerance during the stress process without serious membrane damage. Both leaves and roots replied to short-term stress by activating superoxide dismutase (SOD), catalase (CAT) and polyphenol oxidase (PPO), while peroxidase (POD) was involved under high concentration stress with increasing exposure time. Leaves showed a dose-effect relationship in integrated biomarker response (IBR) values under short-term exposure, and the sensitivity of roots and leaves to PFOS was higher than that of PFOA. Our findings help to increase knowledge of the toxic effects of PFCs and have important reference value for risk assessment and environmental remediation of PFCs in the aquatic ecosystem.

Submersed macrophytes Vallisneria natans and Vallisneria spinulosa improve water quality and affect microbial communities in sediment and water columns

Healthy aquatic ecosystems are essential for human beings. However, anthropogenic activities severely worsen water quality. In this study, using assembling mesocosms, we developed an efficient and easy-to-handle method to monitor the water quality by measuring the electrical conductivity (EC) of water. Our data demonstrate that the growth of two submersed macrophytes, Vallisnerianatans and Vallisneria spinulosa, improves water quality by decreasing EC. Furthermore, using high-throughput DNA sequencing, we analyzed the microbial community abundance and structure in sediment and water columns with or without plant growth. We generated 33,775 amplicon sequence variants from 69 samples of four sediment groups (BkM, CtM, VnR, and VsR) and three water column sample groups (CtW, VnW, and VsW). The results show that the relative abundance of bacteria was higher in the sediment than in the water column. Moreover, the diversity and composition of microbiomes were altered by Vallisneria spp. growth, and the α-diversity of the microbial communities decreased due to submersed macrophytes in both the sediment and water columns. The β-diversity of the microbial communities also varied significantly with or without Vallisneria spp. growth for both the sediment and water columns.

Effect of luminescent materials on the biochemistry, ultrastructure, and rhizobial microbiota of Spirodela polyrhiza

Fluorescent materials and technologies have become widely used in scientific research, and due to the ability to convert light wavelengths, their application to photosynthetic organisms can affect their development by altering light quality. However, the impacts of fluorescent materials on aquatic plants and their environmental risks remain unclear. To assess the effects of luminescent materials on floating aquatic macrophytes and their rhizosphere microorganisms, 4-(di-p-tolylamino)benzaldehyde-A (DTB-A) and 4-(di-p-tolylamino)benzaldehyde-M (DTB-M) (emitting blue-green and orange-red light, respectively) were added individually and jointly to Spirodela polyrhiza cultures and set at different concentrations (1, 10, and 100 μM). Both DTB-A and DTB-M exhibited phytotoxicity, which increased with concentration under separate treatment. Moreover, the combined group exhibited obvious stress relief at 10 μM compared to the individually treated group. Fluorescence imaging showed that DTB-A and DTB-M were able to enter the cell matrix and organelles of plant leaves and roots. Peroxidation induced cellular damage, contributing to a decrease in superoxide dismutase (SOD) and peroxidase (POD) activities and malondialdehyde (MDA) accumulation. Decomposition of organelle structures, starch accumulation in chloroplasts, and plasmolysis were observed under the ultrastructure, disrupting photosynthetic pigment content and photosynthesis. DTB-A and DTB-M exposure resulted in growth inhibition, dry weight loss, and leaf yellowing in S. polyrhiza. A total of 3519 Operational Taxonomic Units (OTUs) were identified in the rhizosphere microbiome. The microbial communities were dominated by Alphaproteobacteria, Oxyphotobacteria, and Gammaproteobacteria, with the abundance and diversity varied significantly among treatment groups according to Shannon, Simpson, and Chao1 indices. This study revealed the stress defense response of S. polyrhiza to DTB-A and DTB-M exposures, which provides a broader perspective for the bioremediation of pollutants using aquatic plants and supports the further development of fluorescent materials for applications.

Temporal variations in reactive oxygen species in biofilms of submerged macrophytes: The key role of microbial metabolism mediated by oxygen fluctuations

Reactive oxygen species (ROS) play a crucial role in the biogeochemistry of aquatic environments, yet their occurrence and accumulation in the biofilm of submerged macrophytes have been poorly documented. Herein, we first investigated the light-dark cycling fluctuations of biofilm microenvironment and the temporal variations of a representative ROS (O2•-) during biofilm succession on the macrophyte leaves and subsequently quantified the photochemical processes in biofilms. The sustained production of O2•- exhibited a distinct rhythmic fluctuation from 32.49 ± 0.56 μmol/kg to 72.56 ± 0.92 μmol/kg FW, which simultaneously fluctuated with the dissolved oxygen, redox potential, and pH, all driven by the alternating oxic-anoxic conditions of biofilms. The intensities of O2•- and ROS firstly increased and then decreased throughout biofilm succession. The O2•- concentrations in biofilms from different waters followed the order of rural river water > landscape lake water > aquaculture pond water, and the leaf photosynthesis and microbial community played a key role. ROS production was significantly associated with Actinobacteria, Proteobacteria and Bacteroidetes, with contributions of 44.6%, 32.8%, and 15.2%, respectively. Partial least squares path modeling structural equation analysis showed that ROS production in leaf biofilms was mainly related to the microenvironment and microbial metabolism. These findings will facilitate the development of ecological restoration strategies in aquatic environments.

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.

Source, transport, and toxicity of emerging contaminants in aquatic environments: A review on recent studies

Emerging contaminants (ECs) are gaining global attention owing to their widespread presence and adverse effects on human health. ECs comprise numerous composite types and pose a potential threat to the growth and functional traits of species and ecosystems. Although the occurrence and fate of ECs has been extensively studied, little is known about their long-term biological effects. This review attempts to gain insights into the unhindered connections and overlaps in aquatic ecosystems. Microplastics (MPs), one of the most representative ECs, are carriers of other pollutants because of their strong adsorption capacity. They form a complex of pollutants that can be transmitted to aquatic organisms and humans through the extended food chain, increasing the concentration of pollutants by tens of thousands of times. Adsorption, interaction and transport effects of emerging contaminants in the aquatic environment are also discussed. Furthermore, the current state of knowledge on the ecotoxicity of single- and two-pollutant models is presented. Herein, we discuss how aquatic organisms within complex food networks may be particularly vulnerable to harm from ECs in the presence of perturbations. This review provides an advanced understanding of the interactions and potential toxic effects of ECs on aquatic organisms.

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.

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.

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.

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.

Aquaculture—Production System and Waste Management for Agriculture Fertilization—A Review

Aquaculture is the fastest growing animal food production sector worldwide and is becoming the main source of aquatic animal foodstuff for human consumption. However, the aquaculture sector has been strongly criticized for its environmental impacts. It can cause discharge and accumulation of residual nutrients in the areas surrounding the production farms. This is because, of the total nutrients supplied to production ponds, only 30% are converted into product, while the rest is usually discharged into the environment to maintain water quality in aquaculture culture systems, thereby altering the physic-chemical characteristics of the receiving water. In contrast, this same accumulation of nutrients is gaining importance within the agricultural sector, as it has been reported that the main nutrients required by plants for their development are found in this aquaculture waste. The purpose of this review article is to indicate the different aquaculture production systems, the waste they generate, as well as the negative effects of their discharge into the environment. Biofiltration and bioremediation processes are mentioned as alternatives for aquaculture waste management. Furthermore, the state of the art in the treatment and utilization of aquaculture waste as a mineral source for agricultural nutrition through biodigestion and biomineralization processes is described. Finally, aquaponics is referred to as a biological production approach that, through efficient use of water and recycling of accumulated organic nutrients in aquaculture systems, can contribute to addressing the goals of sustainable aquaculture development.

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.