Contaminants In Aquatic Environment Research Articles

Eco-endocrinological dynamics: Unraveling dexamethasone's influence on the interrenal axis in juvenile carp Cyprinus carpio

This study delves into the eco-endocrinological dynamics concerning the impact of dexamethasone (DXE) on the interrenal axis in juvenile carp, Cyprinus carpio. Through a comprehensive analysis, we investigated the effects of DXE exposure on oxidative stress, biochemical biomarkers, gene expression, and bioaccumulation within the interrenal axis. Results revealed a concentration-dependent escalation of cellular oxidation biomarkers, including 1) hydroperoxides content (HPC), 2) lipid peroxidation level (LPX), and 3) protein carbonyl content (PCC), indicative of heightened oxidative stress. Concurrently, the activity of critical antioxidant enzymes, superoxide dismutase (SOD), and catalase (CAT), significantly increased, underscoring the organism's response to oxidative insult. Notable alterations were observed in biochemical biomarkers, particularly Gamma-glutamyl-transpeptidase (GGT) and alkaline phosphatase (ALP) activity, with GGT displaying a significant decrease with increasing DXE concentrations. Gene expression analysis revealed a significant upregulation of stress and inflammation response genes, as well as those associated with sensitivity to superoxide ion presence and calcium signaling, in response to DXE exposure. Furthermore, DXE demonstrated a concentration-dependent presence in interrenal tissue, with consistent bioconcentration factors observed across all concentrations tested. These findings shed light on the physiological and molecular responses of juvenile carp to DXE exposure, emphasizing the potential ecological implications of DXE contamination in aquatic environments. Understanding these dynamics is crucial for assessing the environmental impact of glucocorticoid pollutants and developing effective management strategies to mitigate their adverse effects on aquatic ecosystems.

Indirect Impact of Eutrophication on Occurrence, Air-Water Exchange, and Vertical Sinking Fluxes of Antibiotics in a Subtropical River.

A significant challenge that warrants attention is the influence of eutrophication on the biogeochemical cycle of emerging contaminants (ECs) in aquatic environments. Antibiotics pollution in the eutrophic Pearl River in South China was examined to offer new insights into the effects of eutrophication on the occurrence, air-water exchange fluxes (Fair-water), and vertical sinking fluxes (Fsinking) of antibiotics. Antibiotics transferred to the atmosphere primarily through aerosolization controlled by phytoplankton biomass and significant spatiotemporal variations were observed in the Fair-water of individual antibiotics throughout all sites and seasons. The Fsinking of ∑AB14 (defined as a summary of 14 antibiotics) was 750.46 ± 283.19, 242.71 ± 122.87, and 346.74 ± 249.52 ng of m-2 d-1 in spring, summer, and winter seasons. Eutrophication indirectly led to an elevated pH, which reduced seasonal Fair-water of antibiotics, sediment aromaticity, and phytoplankton hydrophobicity, thereby decreasing antibiotic accumulation in sediments and phytoplankton. Negative correlations were further found between Fsinking and the water column daily loss of antibiotics with phytoplankton biomass. The novelty of this study is to provide new complementary knowledge for the regulation mechanisms of antibiotics by phytoplankton biological pump, offering novel perspectives and approaches to understanding the coupling between eutrophication and migration and fate of antibiotics in a subtropical eutrophic river.

In silico Structural Features of the CgNR5A: CgDAX Complex and Its Role in Regulating Gene Expression of CYP Target Genes in Crassostrea gigas

Contamination of aquatic environments has been steadily increasing due to human activities. The Pacific oyster Crassostrea gigas has been used as a key species in studies assessing the impacts of contaminants on human health and the aquatic biome. In this context, cytochrome P450 (CYPs) play a crucial role in xenobiotic metabolism. In vertebrates many of these CYPs are regulated by nuclear receptors (NRs) and little is known about the NRs role in C. gigas. Particularly, the CgNR5A represents a homolog of SF1 and LRH-1 found in vertebrates. Members of this group can regulate genes of CYPs involved in lipid/steroid metabolism, with their activity regulated by other NR, called as DAX-1, generating a NR complex on DNA response elements (REs). As C. gigas does not exhibit steroid biosynthesis pathways, CgNR5A may play other physiological roles. To clarify this issue, we conducted an in silico investigation of the interaction between CgNR5A and DNA to identify potential C. gigas CYP target genes. Using molecular docking and dynamics simulations of the CgNR5A on DNA molecules, we identified a monomeric interaction with extended REs. This RE was found in the promoter region of 30 CYP genes and also the NR CgDAX. When the upstream regulatory region was analyzed, CYP2C39, CYP3A11, CYP4C21, CYP7A1, CYP17A1, and CYP27C1 were mapped as the main genes regulated by CgNR5A. These identified CYPs belong to families known for their involvement in xenobiotic and lipid/steroid metabolism. Furthermore, we reconstructed a trimeric complex, previously proposed for vertebrates, with CgNR5A:CgDAX and subjected it to molecular dynamics simulations analysis. Heterotrimeric complex remained stable during the simulations, suggesting that CgDAX may modulate CgNR5A transcriptional activity. This study provides insights into the potential physiological processes involving these NRs in the regulation of CYPs associated with xenobiotic and steroid/lipid metabolism.

Synergistic effect on simultaneous treatment of Cr(VI) and chloramphenicol using a non-thermal plasma technology

Toxic organic and heavy metal contaminants commonly exist in industrial waste stream and the treatment is of great challenge. In this study, a dielectric barrier discharge (DBD) non-thermal plasma was employed for the simultaneous treatment of two important contaminants, chloramphenicol (CAP) and Cr(VI) in an aqueous solution through redox transformations. More than 70% of CAP and 20% of TOC were degraded in 60 min, while Cr(VI) was completely removed in 10 min. The hydroxyl radicals could be the main active species for the degradation. Meanwhile, the consumption of hydroxyl radicals was beneficial to the reduction of Cr(VI). The synergistic effect was investigated between CAP degradation and Cr(VI) reduction. The reduction of Cr(VI) would be enhanced in the presence of CAP with a low concentration and could be inhibited under a high concentration of CAP, because part of hydroxyl radicals could be consumed by a low concentration of CAP and the obtained intermediates with a higher kinetic rate. However, CAP with a high concentration could also react with some reductive species, such as eaq- and •H, which could compete with Cr(VI) and inhibit the reduction of Cr(VI). In addition, the presence of Cr(VI) could enhance the degradation and mineralization of CAP, and the identification of obtained intermediates indicated that the presence of Cr(VI) could change the degradation path of CAP as Cr(VI) would react with reductive species and enhance the generation of hydroxyl radicals, leading to more hydroxylation reactions. Moreover, the mechanism for the simultaneous redox transformations of CAP and Cr(VI) was illustrated. This study indicates that the DBD non-thermal plasma technology could be one of better solutions for simultaneous elimination of heavy metal and organic contaminants in aquatic environment.

Efficient Adsorbents for Oil Spill Removal using a Cellulose Acetate-based Natural Fibers Developed by Zinc Oxide Bionanocomposites

Due to the rising use of crude oil and its derivatives, there is a growing apprehension over the contamination of aquatic environments by oil. Hence, it is important to devise efficient methodologies and substances for the purpose of cleansing and eliminating oil from the surroundings. This work aimed to create an environmentally acceptable oil sorbent by combining cellulose acetate (CA) biopolymer with varied amounts of natural date palm fiber (DPF) (10, 20, and 30 wt %) and modifying the surface with ZnO nanoparticles at various ratios (2, 5, 10, and 20 wt %). This study examines the adsorption capabilities of untreated diesel particulate filters (DPF) and modified DPFs for diesel oil. The results showed that the experimental maximum sorption capacity of the composite material, DPF-CA/ZnO, made using CA polymer with 30 wt % DPF and 10 wt % ZnO nanomaterials, was significantly higher (66.4 mg/g) than that of the raw DPF (26.5 mg/g). The fabricated materials were characterized using scanning electron microscopy, energy dispersive X-ray analysis (SEM-EDX), transmission electron microscopy (TEM), thermogravimetric analysis (DTA-TGA), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller analysis (BET). Isothermal studies demonstrated that the adsorption of oil followed the Langmuir and Dubinin‐Radushkevich models, with R2 values of 0.99 and 0.93, and the calculated maximum adsorption capacities (qcal) from these models were 64.6 mg/g and 65.7 mg/g, respectively. Furthermore, the kinetic studies revealed that oil adsorption obeyed pseudo-second-order kinetics infer from R2 values 0.99 and (qcal) 66.7 mg/g aligning closely with (qexp). In addition, the sorption efficiency of this sorbent after five sorption cycles indicated good reusability. This study successfully employed a DPF to efficiently remove oil from water, presenting a commercially viable and environmentally friendly solution.

Environmentally friendly zero-valent iron-modified biochar beads for high-performance antimonite removal from aqueous solution

Antimony (Sb) contamination in aquatic environments has emerged as a significant environmental concern because of extensive industrial activities involving Sb and its associated health hazards. Nano-zero-valent iron (nFe) is recognised for its efficacy in heavy metal remediation; however, its application is often hindered by poor dispersion and suboptimal adsorption properties. We designed an innovative approach in which nFe is calcined with biochar to mitigate agglomeration and subsequently amalgamated with sodium alginate to form composite gel spheres (PEI/SA/BCFe) in a calcium chloride solution. The ability of these gel spheres to remove antimonite (Sb(III)) from water was evaluated under various conditions, including pH, initial concentration, the presence of competing ions, temperature, and cycling experiments. The R2 fitted to the Langmuir isotherm were 0.99, 0.96 and 0.97, respectively. The adsorption was carried out under thermostatic shaking conditions, and the maximum adsorption capacity was 621.04 mg g-1, 509.34 mg g-1, and 373.10 mg g-1 at 10, 25, and 40 °C, respectively, which corresponded to removal efficiencies of 72.5%, 65.3% and 63.7%, respectively. The underlying mechanisms driving the adsorption process were primarily attributed to the oxidation of Sb(III), inner-sphere complexation, and coprecipitation. This comprehensive study not only highlights the potential of PEI/SA/BCFe as an effective solution for mitigating antinomy contamination in water but also contributes valuable insights into the mechanistic aspects of heavy metal adsorption.

Microplastic contamination in urban aquatic environments: Occurrence characteristics in urban streams and stormwater runoff from urban surfaces

This study investigates microplastics in urban environments, focusing on their abundance, types, and relationships with hydrological parameters. Microplastic analyses encompassed two steps: (1) examining urban streams including discharges from a wastewater treatment plant (WWTP) during non-rainy seasons, and (2) analyzing stormwater runoff from urban surfaces for microplastic content during rainy seasons. In urban streams, WWTP discharge exhibited higher microplastic concentrations compared to other streams, indicating WWTP discharge is a dominant source of microplastic pollution. The most prevalent microplastics detected were polypropylene, polyethylene, and their copolymer, although a variety of other types were also found. Concentrations of microplastics were notably influenced by specific urban land uses, as evidenced by a strong correlation (0.95) between microplastic concentrations and areas characterized by industrial and transportation activities. During rainy seasons, microplastics followed the pattern of stormwater runoff, but the highest concentrations, significantly exceeding those in urban streams, were observed before the peak runoff. These maximum concentrations and their timing of occurrence were linked to antecedent dry days, rain intensity, and runoff rate, showing significant statistical correlations. Regardless of their sizes, a diverse range of microplastic types was identified in these conditions, with no consistent pattern across different rain events. This highlights the complex nature of urban microplastic pollution. This study reveals that aquatic ecosystems are significantly affected by two primary factors: (1) the consistent contribution of microplastics from WWTP discharges, and (2) the short-term, but severe, impacts of microplastic pollution associated with stormwater runoff. Furthermore, it suggests the development of alternative strategies to mitigate microplastic pollution in aquatic ecosystems, informed by the findings on the characteristics of microplastics in urban environments. This research underscores the urgent need for integrated urban environmental management strategies, paving the way for future studies to further explore and address the multifaceted challenges posed by microplastic pollution in aquatic ecosystems.

Understanding the detrimental effects of heavy metal pollution in shrimp farming and treatment methods – a review

Abstract High levels of heavy metals in the environment pose a significant risk to the aquatic ecosystem and its organisms. The non-biodegradable nature and lengthy persistence of heavy metals in the environment lead to toxicity in shrimp. Using aquatic animals as bio-indicators of metal contamination provides valuable data on acute and chronic toxicity in aquatic species and environmental quality. This review aims to provide insights into the sources, impacts, diseases and mitigation strategies related to heavy metal pollution in shrimp farming and the dangers to humans. Shrimp growth and development at each stage exhibit distinct responses to toxicity, which can vary depending on the species, types of metals, their mechanisms of action, as well as the concentration of heavy metals and duration of exposure. While several heavy metals are considered essential nutrient elements that enhance shrimp growth and feed efficiency, exceeding the maximum tolerable limit threatens shrimp health, human consumers, and ecological systems’ stability. Shrimp species subjected to lethal toxic metal concentrations experience significant effects on accumulation in histopathology. Heavy metal toxicity has been linked to high mortality rates, malformation rates, oxidative stress, moulting issues, and decreased reproduction with increasing concentrations in shrimp. Various methods have been reported for removing heavy metal ions from aquatic environments, including filtration, adsorbents, removal efficacy, operating conditions, and the pros and cons of each technique. Therefore, this review provides an overview of how heavy metals can affect shrimp physiology and dangers to consumers. It aims to increase awareness about the importance of preventing and regulating their contamination in aquatic environments.

Cerium/sulfur co-doped spinel iron-cobalt oxide@carbon interconnected mesh networks as superior peroxymonosulfate activator for tetracycline degradation

Transition metal spinel oxides have potential applications in activating peroxymonosulfate (PMS) to generate reactive substances for degrading organics in polluted water. However, many catalytic materials have low efficiency, indicating the need for advancements in material design. In this study, we present the one-step fabrication of Ce, S-codoped spinel iron-cobalt oxide@carbon (Ce-FeCo2O4@SxC) with interconnected mesh networks for efficient PMS activation in degrading tetracycline hydrochloride (TCH). Among the Ce-FeCo2O4@SxC samples, Ce-FeCo2O4@S1.5C demonstrates the highest catalytic performance, achieving a TCH degradation efficiency of 97.2 % in 30 min. Moreover, the catalytic system also exhibits anti-interference abilities against various anions and shows universality in degrading organic pollutants. Characterization and experimental tests confirm the co-existence of radical (SO4•−, •OH and O2•−) and non-radical pathways (1O2 and direct electron transfer), with 1O2 identified as the primary reactive species. Three plausible pathways for TCH removal are proposed based on detected intermediate products. Toxicity evaluation reveals a significant reduction in the toxicity of the original TCH solution during the degradation process with the PMS activator. This study introduces a simple yet effective co-doping strategy to enhance the catalytic properties of spinel oxides for PMS activation in degrading organic contaminants in aquatic environments.

Molecularly imprinted polymer photoelectrochemical sensor for the detection of triazophos in water based on carbon quantum dot-modified titanium dioxide.

Widely used organophosphorus pesticide triazophos (TAP) can easily cumulate in aquatic system due to its high stability chemically and photochemically and thus posing significant threat to aquatic creatures and humans' health. Urging demand for rapid determiningTAP in water has risen. Photoelectrochemical (PEC) sensing turns out to be a good candidate for its simplicity in fabrication and swiftness in detection. Nevertheless, traditional PEC sensors often lack selectivity as their signal generation primarily relies on the oxidation of organic compounds in the electrolyte by photo-induced holes. To address this limitation, molecularly imprinted polymers (MIPs) can be in combined with PEC sensors to significantly enhance the selectivity. Here, we present a novel approach utilizing a PEC sensor enhanced by carbon-modified titanium dioxide molecularly imprinted polymers (MIP/C/TiO2 NTs). Carbon quantum dot (CQD) modification of titanium dioxide nanotube arrays (C/TiO2 NTs) was achieved through a one-step anodization process, effectively enhancing visible light absorption by narrowing the band gap of TiO2, and CQDs also function as sensitizer accelerating charge transfer for improved and stable photocurrent signals during detection. Our method further incorporates MIPs to heighten the selectivity of the PEC sensor. Electro-polymerization using cyclic voltammetry was employed to polymerize MIPs with pyrrole as the functional monomer and triazophos as the target molecule. The resultant MIP/C/TiO2 NT sensor exhibited remarkable sensitivity, with a detection limit of 0.03nM (S/N = 3), alongside exceptional selectivity and stability for triazophos detection in water. This offers a promising avenue for efficient, cost-effective, and rapid monitoring of pesticide contaminants in aquatic environments, contributing to the broader goals of environmental preservation and public health.

Microalgae enhanced co-metabolism of sulfamethoxazole using aquacultural feedstuff components: Co-metabolic pathways and enzymatic mechanisms

The application of antibiotics in freshwater aquaculture leads to increased contamination of aquatic environments. However, limited information is available on the co-metabolic biodegradation of antibiotics by microalgae in aquaculture. Feedstuffs provide multiple organic substrates for microalgae-mediated co-metabolism. Herein, we investigated the co-metabolism of sulfamethoxazole (SMX) by Chlorella pyrenoidosa when adding main components of feedstuff (glucose and lysine). Results showed that lysine had an approximately 1.5-fold stronger enhancement on microalgae-mediated co-metabolism of SMX than glucose, with the highest removal rate (68.77% ± 0.50%) observed in the 9-mM-Lys co-metabolic system. Furthermore, we incorporated reactive sites predicted by density functional theory calculations, 14 co-metabolites identified by mass spectrometry, and the roles of 18 significantly activated enzymes to reveal the catalytic reaction mechanisms underlying the microalgae-mediated co-metabolism of SMX. In lysine- and glucose-treated groups, five similar co-metabolic pathways were proposed, including bond breaking on the nucleophilic sulfur atom, ring cleavage and hydroxylation at multiple free radical reaction sites, together with acylation and glutamyl conjugation on electrophilic nitrogen atoms. Cytochrome P450, serine hydrolase, and peroxidase play crucial roles in catalyzing hydroxylation, bond breaking, and ring cleavage of SMX. These findings provide theoretical support for better utilization of microalgae-driven co-metabolism to reduce sulfonamide antibiotic residues in aquaculture.

Assessment of aluminium toxicity on Dugesia tigrina: implications for reproduction, behaviour, and enzymatic metabolism

ABSTRACT Aluminium (Al) is the eighth most prevalent metallic contaminant in global aquatic environments. This study explores the toxicity of Al and the acidity generated in the aquatic environment, using Dugesia tigrina, elucidating its environmental repercussions. The research uniquely highlights reproductive, behaviours and enzymatic effects pertinent to Al toxicity. The paper evaluated median lethal concentration [LC50 (96 h)], planarian mobility (pLmV), reproductive effects, glycogen content, and enzymes activities. The LC50 (96 h) was 348.08 µM. The aqueous extract produced a 74.6% reduction in mobility after acute exposition, and a 34.3% decrease in glycogen content after 14 days at 100 µM Al. Fertility and fecundity decreased by 47.8% and 67.8%, respectively, after 30 days at 50 µM Al (pH 7.0), with a complete absence of cocoons at pH 5.9. Hatching time increased by 24.8% at 50 µM Al (pH 7.0). Exposure to 100 µM Al for 24 h increase enzyme activities: catalase (49%), superoxide dismutase (89.7%), and acetylcholinesterase (46%). The observed changes in enzyme activity underscore Al's adverse effects on reproduction, behaviour, and enzymatic metabolism in planarians, urging the implementation of effective environmental management strategies to mitigate potential implications for various species and ecosystems.

A novel continuous-flow photocatalytic device for antibiotic degradation

The presence of antibiotic contaminants in water reservoirs and aquatic environments poses considerable risks to public and ecosystem health. Despite its high mineralization efficiency and environmental friendliness, photocatalytic technology has limited practical applications due to low energy efficiency, intermittent operation, and inconvenient catalyst recovery. Here, we developed a continuous-flow photocatalytic device (CFP-D) with outstanding activity, stability, and university towards antibiotic wastewater degradation. Complete removal of total organic carbon was achieved for multiple antibiotic wastewaters using CFP-D in a continuous flow process. The unique combination of continuous-flow reactor and highly photo-permeable F-Ti-SiO2 aerogel with abundant TiO5 active sites overcomes the limitations of conventional photocatalytic devices. This study provides new insights for the design of highly efficient monolithic catalysts and continuous flow reaction devices, and showcases the immense potential of CFP-D in medical and organic wastewater treatment.

Removal of Cephalexin-Antibiotic from Drinking Water by Designing CaCl2 Incorporated Chitosan Co- Tragacanth Gum Composite Hydrogel

Background: The prevalence of antibiotic contaminants in aquatic environments presents a critical challenge to public health, necessitating the development of efficient removal methods. Emerging pollutants, especially antibiotics, have been implicated in the rise of antibiotic-resistant bacteria, threatening ecological balance and human well-being. Objective: This study aims to synthesize and evaluate the efficacy of a CaCl2-based composite hydrogel using chitosan as a biopolymer for the adsorption of antibiotic pollutants from water, targeting the improvement of water purification technologies in healthcare settings. Methods: Chitosan-based composite hydrogels were synthesized via free radical polymerization, incorporating CaCl2 and utilizing techniques such as Field Emission Scanning Electron Microscopy (FESEM) for morphology analysis, Energy-dispersive X-ray (EDX) analysis for elemental verification, Fourier-transform infrared spectroscopy (FTIR) for functional group identification, and X-ray diffraction (XRD) to determine crystallinity. Physicochemical parameters, including contact time, pH, temperature, reusability, and swelling behavior in various media, were systematically assessed to ascertain the hydrogel's adsorptive performance. Results: The synthesized hydrogels demonstrated a porous and rough surface ideal for adsorption, with an initial antibiotic removal rate of 80% within 30 minutes of contact time. FTIR analysis confirmed the presence of functional groups corresponding to absorption bands at 1053, 1415, 1601, 2600, 2900, 3300, and 3500 cm-1. EDX and XRD analyses affirmed the incorporation of CaCl2, with a crystalline phase characterized by sharp peaks. The hydrogel's maximum adsorption efficiency reached 95% at an optimized adsorbent dose of 0.05 g. Conclusion: The CaCl2-based composite hydrogel exhibits significant potential for the removal of antibiotic pollutants from water, suggesting a viable approach to mitigate the environmental impact of pharmaceutical contaminants and enhance human health by reducing the spread of antibiotic resistance.

Exposure to flutolanil at environmentally relevant concentrations can induce image and non-image-forming failure of zebrafish larvae through neuro and visual disruptions

Numerous pesticides pose a threat to aquatic ecosystems, jeopardizing aquatic animal species and impacting human health. While the contamination of aquatic environment by flutolanil and its adverse effects on animal in the treatment of rich sheath blight have been reported, the neuro-visual effects of flutolanil at environmentally relevant concentrations remain unknown. In this study, we administered flutolanil to zebrafish embryos (0, 0.125, 0.50 and 2.0 mg/L) for 4 days to investigate its impact on the neuro and visual system. The results revealed that flutolanil induced abnormal behavior in larvae, affecting locomotor activity, stimuli response and phototactic response. Additionally, it led to defective brain and ocular development and differentiation. The disruption extended to the neurological system and visual phototransduction of larvae, evidenced by significant disturbances in genes and proteins related to neurodevelopment, neurotransmission, eye development, and visual function. Untargeted metabolomics analysis revealed that the GABAergic signaling pathway and increased levels of glutamine, glutamate, andγ-aminobutyric acid were implicated in the response to neuro and visual system injury induced by flutolanil, contributing to aberrant development, behavioral issues, and endocrine disruption. This study highlights the neuro-visual injury caused by flutolanil in aquatic environment, offering fresh insights into the mechanisms underlying image and non-image effects.

CRISPR/Cas12a powered air-displacement enhanced evanescent wave fluorescence fiber-embedded microfluidic biochip for nucleic acid amplification-free detection of Escherichia coli O157:H7

Simple yet ultrasensitive and contamination-free quantification of environmental pathogenic bacteria is in high demand. In this study, we present a portable clustered regularly interspaced short palindromic repeats-associated protein 12a (CRISPR/Cas12a) powered Air-displacement enhanced Evanescent wave fluorescence Fiber-embedded microfluidic Biochip (AEFB) for the high-frequency and nucleic acid amplification-free ultrasensitive detection of Escherichia coli O157:H7. The performance of AEFB was dramatically enhanced upon employing a simple air-solution displacement process. Theoretical assays demonstrated that air-solution displacement significantly enhances evanescent wave field intensity on the fiber biosensor surface and increases the V-number in tapered fiber biosensors. Consequently, light-matter interaction is strengthened, and fluorescence coupling and collection efficiency are improved, considerably enhancing sensitivity. By integrating the CRISPR biosensing mechanism, AEFB facilitated rapid, accurate, nucleic acid amplification-free detection of E.coli O157:H7 with polymerase chain reaction (PCR)-level sensitivity (176 cfu/mL). To validate its practicality, AEFB was used to detect E.coli O157:H7 in surface water and wastewater. Comparison with RT-PCR showed a strong linear relationship (R2 = 0.9871), indicating the excellent accuracy and reliability of this technology in real applications. AEFB is highly versatile and can be easily extended to detect other pathogenic bacteria, which will significantly promote the high-frequency assessment and early-warning of bacterial contamination in aquatic environments.

Influences of dissolved organic matters on the adsorption and bioavailability of sulfadiazine: Molecular weight- and type-dependent heterogeneities

The bioavailability of contaminants in aquatic environments was highly related with the existing forms (soluble or adsorbed) and properties of dissolved organic matters (DOMs). In this study, the molecular weight (MWs)-dependent effects of DOMs on the adsorption and bioavailability of sulfadiazine were explored. Colloid ZnO and Al2O3 were employed as the representative colloidal particles, and algae-derived organic matter (AOM) and humic acid (HA) were selected as typical autochthonous and allochthonous DOMs. The ultrafiltration procedure was applied to divide the bulk DOMs into high MW (HMW-, 1 kDã0.45 μm) and low MW (LMW-, <1 kDa) fractions. Results showed that HMW-DOM contained more aromatic and protein-like substances as compared to the LMW counterparts. In addition, presence of AOM promoted sulfadiazine adsorption capabilities by 1.19–4.54 folds and mitigated the inhibition ratio by 0.56–0.78 folds, whereas those of HA inhibited sulfadiazine adsorption by 0.27–0.84 folds and enhanced the biotoxicity by 1.21–1.45 folds. Regardless of different DOM types, HMW-fraction exhibited highest effects on sulfadiazine adsorption and bioavailability, followed by the bulk- and LMW-fractions. Two-dimensional correlation spectroscopy showed that sulfadiazine was adsorbed on colloidal surfaces prior to AOM, and the subsequent adsorption of AOM can provide additional sites for sulfadiazine adsorption, which decreased the concentrations of aqueous sulfadiazine as well as the biotoxicity to Microcystis aeruginosa (M. aeruginosa). The HA, however, was preferentially adsorbed on colloidal surfaces, which hindered the subsequent sulfadiazine adsorption and resulted in a high sulfadiazine abundance in aqueous solution as well as the enhanced biotoxicity to M. aeruginosa. This study highlighted the importance of the types and MWs of DOMs in influencing the behaviors and ecological effects of aquatic contaminants.

Regulation of GeCu/Zn-SOD, GeMn-SOD, GeHsp90, and GeMT in Gymnocypris eckloni in Response to Copper and Lead Ion Challenges

The contamination of aquatic environments by heavy metals can have detrimental effects on fish, impacting their growth and overall health, including the regulation of antioxidant genes. An investigation was carried out to assess the distribution and habitat of Gymnocypris eckloni in the Yellow River basin. Simultaneously, heavy metal concentrations in its habitat and in selected locations within the upper Yellow River were measured. In an effort to explore the potential roles of specific genes in antioxidant responses, G. eckloni was exposed to low concentrations of copper (Cu2+) and lead (Pb2+) for varying durations (12, 24, and 48 hours). The mRNA levels of GeCu/Zn-SOD, GeMn-SOD, GeHsp90, and GeMT were quantified in the gills, kidneys, and liver through qRT-PCR. The findings suggest that the habitat of G. eckloni is generally safe; however, occasional exceedances of safety standards could pose a potential threat to its growth. Importantly, the expression of GeCu/Zn-SOD, GeMn-SOD, GeHsp90, and GeMT exhibited responses to the low concentrations of copper-induced and lead-induced stress. Notably, GeCu/Zn-SOD, GeMn-SOD, and GeMT demonstrated heightened sensitivity to lead compared to copper. Furthermore, the expression of these genes displayed tissue-specific responses under identical metal stress conditions. These results indicate that GeCu/Zn-SOD, GeMn-SOD, GeHsp90, and GeMT genes have the potential to serve as early, sensitive biomarkers for the detection of metal toxicity induced by Cu2+ and Pb2+. This study also provides valuable insights into the functioning of antioxidant genes under oxidative stress in fish.

Unraveling the photochemical behavior of dissolved organic matter derived from hydrothermal carbonization process water: Insights from molecular transformation and photoactive species

Hydrothermal carbonization process water (HTPW) has been utilized as a substitute for chemical fertilizers in agricultural applications. However, the input of HTPW into paddy water, particularly the significant proportion of dissolved organic matter (DOM) in HTPW (DOM-HTPW), directly engages in photochemical transformations, a phenomenon often overlooked. This study observed a consistent decrease in humification (SUVA280, 7.7–53.9%) and aromaticity (SUVA254, 6.1–40.0%) of DOM-HTPW after irradiation. The primary active photobleaching components of DOM-HTPW varied depending on the feedstock, such as protein for chicken manure DOM-HTPW and lignin for rice straw DOM-HTPW. The photochemical activity of DOM-HTPW was augmented by its lower molecular weight and higher hydrophilic composition, particularly evident in chicken manure DOM-HTPW, which exhibited higher generation rates for 1O2 (35.1–37.1%), 3DOM* (32.8–43.9%), and O2•− (28.6–48.8%) as measured by molecular probes. DOM-HTPW effectively facilitated the phototransformation of tetracycline, with the contribution of O2•− being more significant than 3DOM* and 1O2. These findings shed new light on the understanding the photochemical processes of DOM-HTPW as exogenous DOM and the interconnected fate of contaminants in aquatic environments.

Thermal sensitivity of Rhinella arenarum tadpole at low concentrations of dimethoate pesticides

One of the main causes of contamination of aquatic environments, which affects biotic communities, is the use of pesticides in agricultural regions. Amphibians are considered good bio-indicators of aquatic pollution, because they are one of the most susceptible groups to pollution. Several studies suggest that both pollution and climate change produce synergistic effects in amphibians which amplify the toxicity afecting survival, and malformations with an increase in temperature. We studied the sensitivity of sublethal concentrations of dimethoate in Rhinella arenarum tadpoles on two fitness related thermal traits including locomotor swimming performance and thermal tolerance limits (CTmax = critical thermal maximum and CTmin = critical thermal minimum). The locomotor performance of R. arenarum tadpoles decreased with increasing sublethal dimethoate concentrations up to ∼60 % at intermediates dimethoate concentration. The tadpoles showed a tendency to decrease their tolerance to high temperatures (CTmax) with increasing dimethoate concentration around ∼0.5 °C, however no significant differences were found among treatments. Similarly, tadpoles showed decreases in their cold resistance (CTmin) with dimethoate concentrations, around 1 °C the high concentrations of dimethoate. The increase of atypical climatic events, such as heat waves may put R. arenarum tadpoles at greater risk when exposed to dimethoate. Our results show that the sublethal concentrations of the dimethoate pesticide may affect the fitness and survival of the larvae of R. arenarum in natural, and seminatural enviroments.