High Bioaccumulation Potential Research Articles

Exposure pathways (diet, dissolved or particulate substrate) of rare earth elements to aquatic organisms.

The global extraction and use of rare earth elements (REEs) continue to rise as they are implemented in technologies that improve human and environmental livelihoods. However, the general understanding of transfer processes and fates of REEs in aquatic systems remains limited. Here, we aim to determine the REEs' main exposure pathways, e.g., particulate fraction, diet, or dissolved (ionic) fractions, to three benthic and three pelagic organisms. They were maintained under laboratory conditions and exposed to natural river water, with or without a sand substrate and an adapted diet. The organisms include northern clearwater crayfish (Faxonius propinquus), chinese mystery snail (Cipangopaludina chinensis), black sandshell mussel (Ligumia recta), striped shiner minnows (Luxilus chrysocephalus), Daphnia magna, and Euglena gracilis. The combined results of REE concentrations, fractionations, and anomalies highlighted that pelagic organisms are characterized by heavy REEs enrichment indicating they mainly uptake REEs in the dissolved form with high bioaccumulation potential, i.e., bioconcentration (BCF) > 1 and diet accumulation factors (DAF) < 1. Pelagic organisms exhibited relatively low REE concentrations in their tissues ([La] ranging from 4.6 to 57.7 µg kg-1 in minnows, 18.4 µg kg-1 in whole body D. magna, and 32.2 µg kg-1 in E. gracilis). On the other hand, snails and mussels were enriched in light REEs showing they mainly uptake REEs through their respective diets and particulate sand substrate. Relative to pelagic organisms, mussels and snails have higher DAFs (161.2 and 18.6, respectively) and REE levels in their soft tissues ([La] of 5700 µg kg -1 and 650 µg kg -1, respectively), but DAF for crayfish remains < 1. In summary, under environmental-relevant conditions, the six aquatic organisms has the potential to accumulate REEs through various uptake pathways. Nevertheless, our results confirming preferential uptake pathways of the six organisms can help select appropriate species in future studies to monitor REE exposure from vaious fractions: dissolved, particulate forms or in the food webs (i.e., diet).

Performance of Persicaria amphibia (L.) for Phytoremediation of Heavy Metals Contaminated Water.

Fast-paced global industrialization due to population growth poses negative water implications, such as pollution by heavy metals. Phytoremediation is deemed as an efficient and environmentally friendly alternative which utilizes different types of hyperaccumulator plants known as macrophytes for the removal of heavy metal pollutants from contaminated water. In this study, the removal of Cu(II), Ni(II), Pb(II), and Cd(II) heavy metal ions contaminated water was studied by using an aquatic plant, Persicaria amphibia (L.) collected from Ladik Lake, Samsun, Turkiye. The experiments were carried out hydroponically in the laboratory conditions. Synthetic heavy metals contaminated water (5, 10, 25, 50, 100mg kg- 1), and domestic and industrial water were used in the experiments. The domestic and industrial water samples were taken from Aksu and Batlama streams in Giresun province. All physical plant changes were noted, and pH, conductivity, and dissolved oxygen levels of the hydroponic system were measured regularly during the experiments. In order to determine the effects of heavy metals on the plant, the chlorophyll (a, b and total) and carotenoid contents as well as the biomass of the plant, were measured. According to the phytoremediation experiments the amounts of accumulated heavy metals in plants were found as Cd(II) > Ni(II) > Cu(II) > Pb(II) in single systems and as Cd(II) > Ni(II) > Pb(II) > Cu(II) in competitive systems. The maximum amounts of heavy metals accumulated in plants were determined as 171 ± 9mg kg-1 for Cd(II), 143 ± 7mg kg-1 for Ni(II), 134 ± 8mg kg-1 for Cu(II) and 55 ± 4mg kg-1 for Pb(II). In addition, bioconcentration factor (BCF) values ​​were calculated to make comparisons with the phytoextraction potential of the plant. This study emphasizes the importance of P. amphibia with high bioaccumulation potential for phytoremediation and suggests that it could be employed to restore water in heavy metal-contaminated areas.

Risk assessment of pesticide residues ingestion in food offered by institutional restaurant menus.

The chronic ingestion of pesticide residues through food appears to be a global public health issue, especially in Brazil. This study evaluates 120 menus across six Brazilian institutional restaurants, estimating the allowance of active pesticide ingredients, residue characterization, and chronic exposure risk through food. Data analysis reveals 263 authorized active ingredients, predominantly insecticides (43%), fungicides (40%), and herbicides (14%) for use in 40 foods. Notably, 4% of residues are extremely toxic, 5% highly toxic, and 14% moderately toxic. Forty-two compounds, especially those permitted in animal-source foods, exhibit high bioaccumulation potential. Some foods harbor multiple pesticide residues, raising concerns, despite 99% of residues falling within the Acceptable Daily Intake. Methomyl insecticide poses potential ingestion risks during lunch, warranting attention. The pervasive presence of pesticide residues in daily consumed foods underscores the necessity for greater attention to the source of the food, ensuring access to healthy and safe collective consumption.

Unraveling the promotive mechanism of nitrogen-doped porous carbon from wasted lignin for Cr (VI) removal

Persistent environmental pollution by heavy metals, particularly Cr (VI), poses significant risks to ecosystems and human health due to its high toxicity and bioaccumulation potential. The development of high-performance, cost-effective adsorbents from sustainable materials remains a critical challenge in the field of Cr (VI) remediation. This study investigates the influence of pyrrolic-N (N-5) within nitrogen-doped hierarchical porous carbon (N-HPC) on its adsorption capacity. Results indicate that N-HPC variants with a higher N-5 content exhibit superior adsorption abilities. The optimal sample demonstrated an exceptional adsorption capacity of 386.2 mg/g for Cr (VI). Even after seven regeneration cycles, this N-HPC variant maintained a remarkable 77.8 % removal efficiency for Cr (VI), highlighting its robust stability and selectivity. The relationship between the physicochemical properties of N-5 and N-HPC was thoroughly examined, revealing that N-5 plays a crucial role in the adsorption process. Due to its high electronegativity, nitrogen-doping into the carbon framework generates a dipole moment, enhancing the electronegativity of N-HPC, altering its local electron density and polarity, increasing specific surface area, carbon defect density, and ion exchange capacity. These factors collectively contribute to significant improvements in pore filling, ion exchange efficiency, and electrostatic adsorption by N-HPC. The reduction complexation mechanism emerges as the dominant factor in the adsorption process. N-5 not only provides reducing electrons as an electron donor, facilitating the continuous conversion of Cr (VI) to Cr (III), but also acts as an adsorption active site, complexing Cr to the surface of N-HPC. This synergistic effect strengthens the reduction complexation, enhances adsorption performance, and improves the regeneration cycle and adsorption selectivity for Cr.

Critical analysis of enhanced microbial bioremediation strategies of PAHs contaminated sites: Toxicity and techno-economic analysis

Polycyclic aromatic hydrocarbons (PAHs) pose significant threats to environmental integrity and public health due to their high toxicity, persistence, and potential for bioaccumulation. In contaminated soils, PAH concentrations typically range from 1 to 100 mg/kg, with severely polluted areas reaching up to 1000 mg/kg. Conventional bioremediation techniques, limited to 30–50% efficiency, underscore the need for more effective solutions. This review highlights recent advancements in microbial bioremediation strategies, demonstrating removal efficiencies of 80–90% through the utilization of functional microorganisms, which metabolize PAHs into non-toxic compounds. Innovative techniques such as genetic engineering, microbial immobilization, and nanotechnology are shown to achieve over 90% pollutant removal. The review discusses key metabolic pathways and enzymatic processes driving PAH degradation, such as ring-hydroxylation and oxygenation. Techno-economic assessments indicate up to 40% cost savings and improved energy efficiency compared to conventional methods, facilitating scalability for large-scale environmental restoration projects. Microbial solutions for groundwater pollution, where PAH levels often exceed the maximum contaminant level (MCL) of 0.2 μg/L, are found to be highly effective in mitigating ecological risks and protecting public health. This comprehensive analysis highlights the promising role of advanced microbial bioremediation techniques in addressing PAH contamination across diverse ecosystems, including soils, sediments, and aquatic environments.

Metabolism of Benzo[a]pyrene by Paenibacillus sp. PRNK-6 through novel metabolite phenalene-1,9-dicarboxylic acid

Benzo[a]pyrene (BaP) is a persistent carcinogenic environmental pollutant with high bioaccumulation potential and is resistant to bacterial biodegradation. Therefore, its removal from the biosphere is a priority. In the current study, the bacterial culture Paenibacillus sp. PRNK-6 was evaluated for the degradation of BaP. Paenibacillus sp. PRNK-6 efficiently utilizes BaP as a sole carbon source and degrades 89.43% of BaP within 120 h at an initial concentration of 100 mg L−1. Maximum growth was observed at 96 h with 28.96 × 107 colony-forming units (CFU). The BaP metabolic intermediates were characterized by High-performance liquid chromatography (HPLC) and, Gas chromatography-mass spectrometry (GC-MS). Based on the metabolite characterization, utilization of probable metabolic intermediates, and investigation of the enzyme involved, a putative pathway of the BaP degradation in PRNK-6 was proposed. The metabolites formed includes a novel ring cleavage metabolite phenalene-1,9-dicarboxylic acid. The two terminal monoaromatic metabolites catechol and protocatechuate (PCA) undergo ring fission by catechol 1,2-dioxygenase and protocatechuate 3,4-dioxygenase, individually and get into the tricarboxylic acid (TCA) cycle. In both pathways there is no accumulation of any dead-end products. The results suggest that the strain PRNK-6 could be a promising biodegradation tool for high molecular weight polycyclic aromatic hydrocarbons (HMW PAHs) like BaP and may be equally used for bioremediation of other polycyclic aromatic hydrocarbons (PAHs).

Comparison among native floating aquatic macrophytes for bioconcentration of heavy metals

This work was aimed to show the development of a comparative study of the capability of bioindicators to reveal the presence of heavy metals among species of floating aquatic macrophytes such as Spirodela sp (giant duckweed), Pistia stratiotes (water lettuce), Salvinia sp used as a parameter for bioconcentration factors plant / sediment. We performed a simple sampling at six sites in the region of Pelotas, southern Brazil, in which it was collected sediments and plants. The plants experienced the nitric perchloric acid digestion method, while the sediment suffered pseudo total acid digestion method. The determination of Cr, Cu, Pb and Zn in the extracts was conducted by atomic absorption spectrophotometry in flame. In general, the floating aquatic macrophytes studied showed better bioconcentration factor for metals from the sediment in the following order: Cu&gt;Zn&gt;Pb&gt;Cr. For copper, the figures obtained with Pistia stratiots ranged from 5.7 to 82.8. The BCF for Zn ranged from 3.0 to 11.6 and Salvinia sp. For the Pb bioconcentration factor, it ranged from 5.4 to 0.6 in Spirodela sp. The in situ study showed that all species had high bioaccumulation potential, especially Pistia stratiotes that was employed to remove copper.

Exploring Prenatal Exposure to Halogenated Compounds and Its Relationship with Birth Outcomes Using Nontarget Analysis.

Halogenated organic compounds (HOCs) are a class of contaminants showing high toxicity, low biodegradability, and high bioaccumulation potential, especially chlorinated and brominated HOCs (Cl/Br-HOCs). Knowledge gaps exist on whether novel Cl/Br-HOCs could penetrate the placental barrier and cause adverse birth outcomes. Herein, 326 cord blood samples were collected in a hospital in Jinan, Shandong Province from February 2017 to January 2022, and 44 Cl/Br-HOCs were identified with communicating confidence level above 4 based on a nontarget approach, covering veterinary drugs, pesticides, and their transformation products, pharmaceutical and personal care products, disinfection byproducts, and so on. To our knowledge, the presence of closantel, bromoxynil, 4-hydroxy-2,5,6-trichloroisophthalonitrile, 2,6-dibromo-4-nitrophenol, and related components in cord blood samples was reported for the first time. Both multiple linear regression (MLR) and Bayesian kernel machine regression (BKMR) models were applied to evaluate the relationships of newborn birth outcomes (birth weight, length, and ponderal index) with individual Cl/Br-HOC and Cl/Br-HOCs mixture exposure, respectively. A significantly negative association was observed between pentachlorophenol exposure and newborn birth length, but the significance vanished after the false discovery rate correction. The BKMR analysis showed that Cl/Br-HOCs mixture exposure was significantly associated with reduced newborn birth length, indicating higher risks of fetal growth restriction. Our findings offer an overview of Cl/Br-HOCs exposome during the early life stage and enhance the understanding of its exposure risks.

Alternating water sources to minimize contaminant accumulation in food plants from treated wastewater irrigation

The use of treated wastewater (TWW) for agricultural irrigation is a critical measure in advancing sustainable water management and agricultural production. However, TWW irrigation in agriculture serves as a conduit to introduce many contaminants of emerging concern (CECs) into the soil-plant-food continuum, posing potential environmental and human health risks. Currently, there are few practical options to mitigate the potential risk while promoting the safe reuse of TWW. In this greenhouse study, the accumulation of 11 commonly occurring CECs was evaluated in three vegetables (radish, lettuce, and tomato) subjected to two different irrigation schemes: whole-season irrigation with CEC-spiked water (FULL), and half-season irrigation with CEC-spiked water, followed by irrigation with clean water for the remaining season (HALF). Significant decreases (57.0–99.8 %, p < 0.05) in the accumulation of meprobamate, carbamazepine, PFBS, PFBA, and PFHxA in edible tissues were found for the HALF treatment with the alternating irrigation scheme. The CEC accumulation reduction was attributed to reduced chemical input, soil degradation, plant metabolism, and plant growth dilution. The structural equation modeling showed that this mitigation strategy was particularly effective for CECs with a high bioaccumulation potential and short half-life in soil, while less effective for those that are more persistent. The study findings demonstrate the effectiveness of this simple and on-farm applicable management strategy that can be used to minimize the potential contamination of food crops from the use of TWW and other marginal water sources in agriculture, while promoting safe reuse and contributing to environmental sustainability.

Abstract 1478: Chronic perfluorooctanesulfonic acid exposure promotes proliferation of colorectal cancer cells

Abstract Background: Chronic exposure to long-term exposures to per- and polyfluoroalkyl substances (PFAS), widely known as “forever chemicals”, has been associated with multiple negative health outcomes including increased risk of cancer. Perfluorooctanesulfonic acid (PFOS), a “long-chain” subtype of PFAS, has high bioaccumulation potential with a long elimination half-life. PFOS is frequently detected in drinking water leading to its high absorption through the gastrointestinal tract. Recent studies demonstrate that PFAS exposures promote intestinal inflammation and gut barrier dysfunction. However, how a long-term PFOS exposure affects colorectal cancer (CRC) progression is not known. Therefore, the purpose of this study is to delineate the effect of PFOS exposure on CRC cell proliferation and test the potential mitigation strategy for the harmful effects of PFOS. Methods: SW480 and HCT116 cells have been treated with 1 ug/mL PFOS and proliferation was measured at 1, 2, and 3 months using the Presto Blue Cell Viability Reagent fluorescence assay. Proliferation markers were assessed by qPCR and Western blot. Control and PFOS exposed cells were treated with sulforaphane, a nuclear factor erythroid 2-related factor 2 (Nrf-2) inducer, at concentration 5, 10 and 20 uM for 72 hours. Results: We show that chronic, low-dose PFOS exposure promotes proliferation of SW480 and HCT116 cell lines starting at 3 months since the first exposure. The increase in proliferation is associated with upregulation of Cyclin D, pAkt and FASN. We also show that sulforaphane significantly decreases proliferation of HCT116 and SW480 cells, and its efficacy is significantly higher in PFOS exposed CRC cells. The current studies show no effect on sulforaphane on normal colon epithelium cells. Conclusion: Our studies suggest that chronic PFOS exposure promotes proliferation of CRC cells by increasing pro-carcinogenic gene expression and signaling. Furthermore, our findings suggest that supplementation of diet sulforaphane can potentially mitigate the harmful effects from PFOS exposure. Our studies warrant further investigation of the mechanisms behind the effect of PFOS exposure on cancer progression that would guide development of effective intervention strategies to mitigate the harmful effects of the exposure to “forever chemicals”. Citation Format: Jerika Durham, Josiane Weber Tessmann, Bernhard Hennig, Yekaterina Zaytseva. Chronic perfluorooctanesulfonic acid exposure promotes proliferation of colorectal cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1478.

Species-specific profiles of per- and polyfluoroalkyl substances (PFAS) in small coastal sharks along the South Atlantic Bight of the United States

Per- and polyfluoroalkyl substances (PFAS) have gained widespread commercial use across the globe in various industrial and consumer products, such as textiles, firefighting foams, and surface coating materials. Studies have shown that PFAS exhibit a strong tendency to accumulate within aquatic food webs, primarily due to their high bioaccumulation potential and resistance to degradation. Despite such concerns, their impact on marine predators like sharks remains underexplored. This study aimed to investigate the presence of 34 PFAS in the plasma (n = 315) of four small coastal sharks inhabiting the South Atlantic Bight of the United States (U.S). Among the sharks studied, bonnetheads (Sphyrna tiburo) had the highest ∑PFAS concentration (3031 ± 1674 pg g − 1 plasma, n = 103), followed by the Atlantic sharpnose shark (Rhizoprionodon terraenovae, 2407 ± 969 pg g − 1, n = 101), blacknose shark (Carcharhinus acronotus, 1713 ± 662 pg g − 1, n = 83) and finetooth shark (Carcharhinus isodon, 1431 ± 891 pg g − 1, n = 28). Despite declines in the manufacturing of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA), the long-chain (C8 – C13) perfluoroalkyl acids (PFAAs) were frequently detected, with PFOS, perfluorodecanoic acid (PFDA), and perfluorotridecanoic acid (PFTrDA) present as the most dominant PFAS. Furthermore, males exhibited significantly higher ∑PFAS concentrations than females in bonnetheads (p < 0.01), suggesting possible sex-specific PFAS accumulation or maternal offloading in some species. The results of this study underscore the urgency for more extensive biomonitoring of PFAS in aquatic/marine environments to obtain a comprehensive understanding of the impact and fate of these emerging pollutants on marine fauna.

Distinctive biotransformation and biodefluorination of 6:2 versus 5:3 fluorotelomer carboxylic acids by municipal activated sludge

Fluorotelomer carboxylic acids (FTCAs) represent an important group of per- and polyfluoroalkyl substances (PFAS) given their high toxicity, bioaccumulation potential, and frequent detection in landfill leachates and PFAS-impacted sites. In this study, we assessed the biodegradability of 6:2 FTCA and 5:3 FTCA by activated sludges from four municipal wastewater treatment plants (WWTPs) in the New York Metropolitan area. Coupling with 6:2 FTCA removal, significant fluoride release (0.56∼1.83 F-/molecule) was evident in sludge treatments during 7 days of incubation. Less-fluorinated transformation products (TPs) were formed, including 6:2 fluorotelomer unsaturated carboxylic acid (6:2 FTUCA), perfluorohexanoic acid (PFHxA), perfluoropentanoic acid (PFPeA), and perfluorobutanoic acid (PFBA). In contrast, little fluoride (0.01∼0.09 F-/molecule) was detected in 5:3 FTCA-dosed microcosms, though 25∼68% of initially dosed 5:3 FTCA was biologically removed. This implies the dominance of “non-fluoride-releasing pathways” that may contribute to the formation of CoA adducts or other conjugates over 5:3 FTCA biotransformation. The discovery of defluorinated 5:3 FTUCA revealed the possibility of microbial attacks of the C-F bond at the γ carbon to initiate the transformation. Microbial community analysis revealed the possible involvement of 9 genera, such as Hyphomicrobium and Dechloromonas, in aerobic FTCA biotransformation. This study unraveled that biotransformation pathways of 6:2 and 5:3 FTCAs can be divergent, resulting in biodefluorination at distinctive degrees. Further research is underscored to uncover the nontarget TPs and investigate the involved biotransformation and biodefluorination mechanisms and molecular basis.

B-esterases activities in several tissues of the marine fish: sea bass and hake, as potential biomarkers of bisphenol A derivatives

In the marine environment, a new threat linked to plastic pollution relates to plastic additives. This threat encompasses multiple chemical compound groups with a high bioaccumulation potential for these chemical mixtures. Hence, informative biomarkers are needed to indicate the effects of environmentally realistic mixtures of these additives. This study proposes an in vitro approach using tissue homogenates of two marine fish, the European sea bass and hake, which are both of interest in aquaculture and fisheries. The selected biomarkers are B-esterase activities comprising acetylcholinesterase (AChE) and carboxylesterases (CEs). The physiological role of AChE in brain and muscle is mainly neural transmission, while CEs participate in liver detoxification processes. However, B-esterases are also widely distributed in other tissues/organs, where their role is yet to be determined, but their inhibition may have undesired biological consequences. Here, we compared the interaction of the plastic additives, bisphenol A and some of its derivatives, like tetrabromobisphenol A (TBBPA), with B-esterase activities. We particularly focused not only on the robust and broadly distributed CE enzymes in brain, gonad, liver, kidney, and plasma tissues of two marine fish, but also on the use of two commercial substrates, p-nitrophenyl butyrate and α-naphthyl butyrate, tentatively representing two CE isoforms. The results evidenced specific species and tissue responses that could be due to a diverse isoform composition. They identified sea bass as better protected against neurotoxic exposures, at least in terms of B-esterase composition. The flame retardant TBBPA was the most reactive to B-esterases inhibition, although Bisphenol A bis (2,3-dihydroxy propyl) ether and Bisphenol F bis (3-chloro-2-hydroxypropyl) ether warrant further toxicology assessments.

Distribution of cadmium and lead in soil–rice systems and their environmental driving factors at the island scale

Toxic elements, such as Cd and Pb are of primary concern for soil quality and food security owing to their high toxicity and potential for bioaccumulation. Knowledge of the spatial variability of Cd and Pb in soil–rice systems across the landscape and identification of their driving factors are prerequisites for developing appropriate management strategies to remediate or regulate these hazardous contaminants. Considering the role of rice (Oryza sativa) as a dietary staple in China, this study aimed to examine the distribution patterns and drivers of Cd and Pb in tropical soil–rice systems across Hainan Island. To achieve this goal, 229 pairs of representative paddy soil and rice samples combined with a set of environmental covariates at the island scale were systematically analyzed. Arithmetic mean values (AMs) of Cd and Pb in rice were 0.080 and 0.199 mg kg−1, and exceeded the standard limits by 27.1% and 22.7%, respectively. We found that the AMs of Cd and Pb concentrations in paddy soil were 0.294 and 43.0 mg kg−1. Additionally, Cd in 29.26% of soil samples and Pb in 11.35% of soil samples exceeded the risk screening value for toxic elements. The enrichment factor generally showed that soil Cd and Pb on Hainan Island were both moderately enriched. Results obtained from both Spearman's correlation and stepwise regression analyses suggest that the concentrations of soil Cd and Pb are significantly influenced by the soil Na and Fe concentrations. Specifically, an increment of 1 g kg−1 in soil Na caused a rise of soil Cd and Pb by 57.1 mg kg−1 and 34.4 mg kg−1, respectively, while an increase of 1 g kg−1 in soil Fe resulted in a rise by 25.0 mg kg−1 and 14.5 mg kg−1. Similarly for rice grains, an increment of 1 g kg−1 in soil Ca resulted in a rise of rice Pb by 30.8 mg kg−1, whereas an increase of 1 g kg−1 in soil Mg led to a decrease in rice Pb by 14.8 mg kg−1. However, no significant correlation between soil Se and rice Cd concentrations was found. Furthermore, the result of geographically weighted regression revealed that the impacts of soil Na, Ca, Fe, and Mg on rice Cd were more significant in the western region, whereas the effects of soil Na and Fe on rice Pb were stronger in the northeastern region. This study provides new insights for the identification of factors influencing the distribution and accumulation of Cd and Pb in tropical island agroecosystems.

Phenolic compounds in the freshwater environment in South Korea: Occurrence and tissue-specific distribution

In this study, we investigated the occurrence and distribution of phenolic compounds, including phenol, cresols, chlorophenols, nitrophenol, and bromophenols, in freshwater environments. We also focused on phenolic compounds in crucian carp (Carassius auratus) tissues, specifically the muscle, gills, brain, blood, liver, and gonads, to assess their potential bioaccumulation in fish and human health risks. Phenolic compounds were found to be widespread in various freshwater environments throughout South Korea. Phenol was predominant in all matrices, with median concentrations of 57.0 ng/L in freshwater, 54.3 ng/g dry weight (dw) in sediment, and ranging from 71 ng/g wet weight (ww) to 621 ng/g ww in crucian carp tissues. Cresols were the second most dominant compound, with m-cresol exhibiting the highest prevalence. Most of the compounds detected in crucian carp samples were also detected in freshwater and sediment, whereas pentachlorophenol and 2,4,6-tribromophenol were exclusively detected in crucian carp tissues. A high bioaccumulation potential in the liver was observed for most phenolic compounds [median log bioconcentration factor (BCF): 3.2–3.7]. Interestingly, only m-cresol showed high bioaccumulation potential in the gills (median log BCF: 3.1). The estimated daily intake of phenolic compounds suggested that it does not pose an immediate concern for human exposure owing to crucian carp consumption. These findings enhance our understanding of the exposure status, distribution, and bioaccumulation potency of phenolic compounds in aquatic ecosystems and emphasize the importance of ongoing monitoring and risk assessment efforts.

Phosphorus conditions change the cellular responses of Microcystis aeruginosa to perfluorooctanoic acid

Perfluorooctanoic acid (PFOA), a widespread and emerging organic contaminant of aquatic environments, has high bioaccumulation potential and high toxicity. Consequently, major concerns have been raised worldwide regarding the management of this pollutant in aquatic ecosystems. To thoroughly understand PFOA's toxic effects on aquatic organisms, systematic investigations were conducted on the cellular responses of Microcystis aeruginosa to the environmental concentrations of PFOA under various concentrations as well as phosphorus (P) conditions (concentrations and forms). The results showed that P conditions remarkably affected cyanobacterial growth as well as photosynthetic pigment content, triggered oxidative stress to disrupt the function and structure of the cell membrane, and caused changes in the extracellular and intracellular contents of microcystin-LR (MC-LR). Furthermore, PFOA (100 μg/L) was absorbed by cyanobacterial cells through the stimulation of the secretion of extracellular polymeric substances (EPS) by M. aeruginosa. After entering the cyanobacterial cells, PFOA inhibited photosynthesis, reduced P absorption, induced oxidative damage, lead to a loss of cell integrity evident in scanning electron microscope images, and increased mcyA gene expression to promote MC-LR production. Moreover, the limited P concentration and forms conditions led to increased PFOA absorption by cyanobacterial cells, which further upregulated mcyA gene expression and increased the risk of MC-LR diffusion into the aquatic environment. Our present study provided a theoretical basis and new ideas for understanding and addressing safety issues related to the presence of PFOA in aquatic environments with varying nutritional statuses.

Toxicological evaluation of TBBPA by common carp (Cyprinus carpio) about the in vivo/vitro disturbance of the AHR pathway

Tetrabromobisphenol A (TBBPA) is a widely used plastic additive with high bioaccumulation potential and toxicity on both humans and wildlife. Currently, research on its ecotoxicity and the underlying mechanism is limited. Using common carp (Cyprinus carpio), we evaluated the toxicity of TBBPA, especially focusing on its alteration of a key metabolism-related pathway aryl hydrocarbon receptor (AHR), using in vivo/vitro assays and in silico simulation. The 96 h LC50 of TBBPA of common carp was 4.2 mg/L and belonged to the acute toxic level II. The bioaccumulation potential of TBBPA follows the role of liver > gill > brain and varies between 3- and 14-day exposure. On the AHR pathway respect, as expected, the metabolism-related cyp1a1 and cyp1b1 were upregulated in the liver and brain. Ahr2, the receptor, was also upregulated in the brain under TBBPA exposure. The alteration of gene expression was tissue-specific while the difference between 3- or 14-day exposure was minor. AHR inhibition assay indicated the 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD)-induced AHR transactivation can be inhibited by TBBPA suggesting it is not a potent agonist but a competitive antagonist. In silico analysis indicated TBBPA can be successfully docked into the binding cavity with similar poses but still have AHR-form-specific interactions. Molecular dynamics simulation proved TBBPA can be more flexible than the coplanar ligand TCDD, especially in ccaAHR1b with greater root-mean-square deviation (RMSD), of which TCDD-induced transactivation seemed not to be blocked by TBBPA. This research increased the understanding of TBBPA toxicity and alteration of the AHR pathway, and pointed out the need to perform additional toxicology evaluation of emerging contaminants, especially on non-model species.

Biochemical characterization and mercury methylation capacity of Geobacter sulfurreducens biofilms grown in media containing iron hydroxide or fumarate

Geobacter species are common in iron-rich environments and can contribute to formation of methylmercury (MeHg), a neurotoxic compound with high bioaccumulation potential formed as a result of bacterial and archaeal physiological activity. Geobacter sulfurreducens can utilize various electron acceptors for growth including iron hydroxides or fumarate. However, it remains poorly understood how the growth on these compounds affects physiological properties of bacterial cells in biofilms, including the capacity to produce MeHg. The purpose of this study was to determine changes in the biochemical composition of G. sulfurreducens during biofilm cultivation in media containing iron hydroxide or fumarate, and to quantify mercury (Hg) methylation capacity of the formed biofilms. Biofilms were characterized by Fourier-transform infrared spectroscopy in the attenuated total reflection mode (ATR-FTIR), Resonance Raman spectroscopy and confocal laser scanning microscopy. MeHg formation was quantified by mass spectrometry after incubation of biofilms with 100 nM Hg. The results of ATR-FTIR experiments showed that in presence of fumarate, G. sulfurreducens biofilm formation was accompanied by variation in content of the energy-reserve polymer glycogen over time, which could be cancelled by the addition of supplementary nutrients (yeast extract). In contrast, biofilms cultivated on Fe(III) hydroxide did not accumulate glycogen. The ATR-FTIR results further suggested that Fe(III) hydroxide surfaces bind cells via phosphate and carboxylate groups of bacteria that form complexes with iron. Furthermore, biofilms grown on Fe(III) hydroxide had higher fraction of oxidized cytochromes and produced two to three times less biomass compared to conditions with fumarate. Normalized to biofilm volume, the content of MeHg was similar in assays with biofilms grown on Fe(III) hydroxide and on fumarate (with yeast extract and without). These results suggest that G. sulfurreducens biofilms produce MeHg irrespectively from glycogen content and cytochrome redox state in the cells, and warrant further investigation of the mechanisms controlling this process.

Application of catalytic hydrodechlorination for the fast removal of chlorinated azole pesticides in drinking water

Catalytic hydrodechlorination (HDC) is regarded as a promising purifying technology for drinking water treatment. So far, it has proved to be highly effective for the removal of different groups of chlorinated micropollutants including pharmaceuticals, neonicotinoid pesticides, personal care products or chloroacetic acids. The azole pesticides, recently included in the EU Watch Lists (Decisions 2020/1161 and 2022/1307), are a group of micropollutants of particular concern for drinking water given their high toxicity, persistence, and bioaccumulation potential. In this work, the feasibility of HDC for the removal of a representative group of chlorinated azole pesticides tebuconazole (TEB), tetraconazole (TET), prochloraz (PCZ), penconazole (PEN), metconazole (MET) and imazalil (IMZ)) is demonstrated, and their reactivity is compared with that observed for other halogenated micropollutant groups. Notably, all the pesticides investigated in this work (100 μg L−1) were completely dechlorinated within 30 min under ambient conditions using a 1 wt% Pd/Al2O3 catalyst concentration of 0.25 g L−1 and a H2 feeding of 50 mL N min−1. The experimental data were accurately described by a pseudo-first order kinetic equation and rate constant values in the range from 1.08 to 2.60 L gcat−1 min−1 were obtained. These values are quite close to those achieved for the most reactive neonicotinoid pesticides and significantly higher than the obtained for chloroacetic acids and most pharmaceuticals (e.g. diclofenac, sertraline or chlorpromazine). From the identification of the generated reaction intermediates and the final non-chlorinated products, sequential reaction pathways were proposed for each pollutant. Remarkably, despite the high toxicity exhibited by the azole pesticides tested, with LC50 values within the 0.4–7.0 mg L−1 range using A. salina, HDC effluents were non-toxic in all cases. Furthermore, the catalyst showed a remarkable stability upon three consecutive runs. Finally, the versatility of the process was demonstrated in the treatment of real aqueous matrices such as DWTP and tap water, where no significant differences were found either in terms of activity or stability.

Accumulation characteristics, driving factors, and model prediction of cadmium in soil-highland barley system on the Tibetan Plateau

Cadmium (Cd) poses major human health problems due to its high toxicity and organ bioaccumulation potential. This study collected and analysed 130 pairs of representative soil-highland barley samples on the Tibetan Plateau. The total soil Cd content (Cd-soil), available soil Cd (Cd-ava), and highland barley Cd contents (Cd-barley) ranged from 0.03 to 0.46 mg kg−1, 0.006–0.185 mg kg−1, and 0.57–13.62 μg kg−1, with mean values of 0.19 ± 0.01 mg kg−1, 0.045 ± 0.003 mg kg−1, and 4.57 ± 0.17 μg kg−1, respectively. Redundancy analysis (RDA) demonstrated that geographic factors and soil properties explained 28.46% of the variation in Cd-soil and Cd-ava, and precipitation (14.6%) and pH (9.1%) were the dominant factors. The structural equation model (SEM) indicated that Cd-soil and Cd-ava were predominantly controlled by pH. Furthermore, the Cd-soil, Cd-ava, and Cd-barley with significantly different environmental conditions were more accurately predicted by conditional inference trees-multiple linear regression (CITs-MLR). When Cd-soil is more than 0.376 mg kg−1, Cd-ava obtains the most accurate predictor (R2 =0.64, P < 0.01). This study provides new scientific insight into understanding the environmental biogeochemical nexus of Cd in the complex and fragile plateau environment and evaluating food security on the Tibetan Plateau under the self-sufficiency model of highland barley.