Pollutants In Aquatic Environment Research Articles

Mechanism of macroalgae Gracilaria bailiniae responding to cadmium and lanthanum.

Macroalgae can accumulate a wide array of metals, leading to their appliance as biomonitors of aquatic environments. With the rapid development of industrial and agricultural-based activities, Cd pollution in aquatic environments is considered an increasingly severe problem worldwide. Although La could alleviate the Cd stress in higher terrestrial plants, the response mechanisms of macroalgae to Cd and La are unknown. Along these lines, in this work, Cd significantly affected the growth, internal cellular structure, photosynthesis, pigment content, antioxidant enzyme activity, and lipid peroxidation level of G. bailiniae. However, the presence of La alleviated these adverse effects from Cd. Furthermore, the response mechanism of G. bailiniae to Cd was attributed to the self-antioxidant ability enhancement, membrane defense, and programmed-cellular regulation. However, the presence of La mediated the biosynthesis of both flavonoids and lipids, which inhibited the Cd accumulation, modulated algal stress signalling networks, renewed the impaired chlorophyll molecule, maintained the activity of the crucial enzyme, enhanced antioxidant ability, and maintained the stabilization of redox homeostasis, alleviating the adverse impact from Cd and improve the growth of G. bailiniae. The experimental results successfully demonstrate a new detoxicant to alleviate Cd stress, promoting a more comprehensive array of macroalgal applications.

Simultaneous photocatalytic removal of heavy metal and organic dye over nitrogen and sulfur co-doped hierarchical ZnSnO3/Zn2SnO4 hollow octahedrons

A series of hierarchical N, S co-doped ZnSnO3/Zn2SnO4 porous hollow octahedrons (NS/ZnSnO3/Zn2SnO4) were constructed using the strategy of combining acid-etching technique with in-situ decoration method for the removal of various pollutants in aqueous environment. The optimized NS/ZnSnO3/Zn2SnO4 exhibited an enhanced photocatalytic activity under simulated sunlight, removing heavy metal ion Cr(VI) in 140 min and rhodamine B (RhB) in 50 min, outperforming hollow Zn2SnO4 and ZnSnO3/Zn2SnO4 octahedrons. This raise could be attributed to the synergetic effect of ZnSnO3/Zn2SnO4 heterojunctions, the introduction of N, S elements and unique hierarchical porous hollow morphology. In addition, the photocatalytic activities of NS/ZnSnO3/Zn2SnO4 for removing Cr(VI) and RhB from mixed pollutant solutions were 1.94 and 1.53-folds as high as those of single system, and it also displayed good reusability and stability in co-existing system, suggesting its potential practical applications in the simultaneous removal of various pollutants from contaminated water.

Adverse Impacts of Toxic Metal Pollutants on Sex Steroid Hormones of Siganus rivulatus (Teleostei: Siganidae) from the Red Sea

Toxic metal pollutants in aquatic environments negatively affect the natural characteristics of water and living organisms. Herein, 254 and 232 specimens (8–14/month) of the fish Siganus rivulatus (Teleostei: Siganidae) were caught alive during four successive seasons in the Red Sea, Egypt, from a chronically polluted bay and from an unpolluted bay, respectively. In each bay, the monthly water temperature was recorded, and the seasonal concentrations of Cd and Pb were determined in the water and in the intestine, liver, and gonads of both fish sexes. In the polluted bay, Cd and Pb were found in significantly high concentrations in the water and in the fish’s intestine, liver, and gonads, and the concentrations only significantly increased in the fish gonads during the spring (spawning season). In each bay, seasonal levels of sex steroid hormones (testosterone T, 17β-estradiol E2, and progesterone P4) in both fish sexes were determined, and they only peaked in both sexes during the spring. In male fish, the serum levels of these hormones throughout the year were in the order T > E2 > P4, while in the females, they were in the order E2 > T > P4. Compared to those in the fish from the unpolluted bay, the levels of these hormones in the fish from the polluted bay were greatly altered. Our results strongly suggest that the serum levels of sex steroid hormones are sensitive biomarkers for detecting heavy metal pollutants in aquatic environments and their effect on fish reproduction.

A Study on the Behavior Evaluation and Control of Midge Larvae in the Filtration Process

Recently, midge larvae, which are indicators of aquatic environmental pollution, have been detected in tap water in some areas, resulting in controversy. Therefore, the objective of this study is to analyze the behavioural features of midge larvae in sand, GAC (granular activated carbon) and GAC/sand processes, which are mainly operated in domestic water purification plants, and suggest effective operating methods for larval control. In this study, a pilot-scale square column (W300×L300×H3500~5000 mm) was used for the filtration experiment and was used with a filter height of 2.5 m as well as in the field. The water to be treated was the sand filtered from the water purification plant G, and midge larvae from the Han River were injected periodically and operated for an estimated 40 to 50 days. As a result, no larvae were detected during the first five operational days in the sand filter and GAC and 14 days in the case of GAC/sand. However, after backwashing, larvae were detected from the 9th day of operation for sand and GAC, and from the 15th day for GAC/sand. In the case of sand laying under the GAC, larvae detection was delayed by approximately 6 days compared to the operation of the GAC alone. Following examination of larval distribution in relation to the height of the activated carbon layer after approximately 50 days of operation, it was found that the larvae were distributed on 17% in the upper layer, 7% in the middle layer, 19% in the lower layer and 0.2% in the lower water collection device. Therefore, it is necessary to shorten the backwashing cycle from the initial stage of larval introduction and to increase the rate of expansion of GAC during the backwashing to quickly flush out the larvae. The results of this study also confirmed that when the backwash speed was 0.57 m/min or more, the rate of expansion of GAC was 30% or more, and larval rejection increased approximately twice when compared with a washing rate of 0.45 m/min. Consequently, as a method of effective functioning of the filtration process for larval control, in the case of sand filtration, when it is difficult to expand the filter media, it is necessary to increase the rinsing time, and in the case of GAC, it is necessary to quickly discard the larvae by increasing the backwashing rate and shortening the backwashing cycle.

Preparation of magnetic Fe3O4@PDA/CuS core-shell nanocomposite as a green photocatalyst

To solve the emerging aromatic organic pollutants in aqueous environment, in this study, the efficient recyclable core-shell structured photocatalyst Fe3O4@PDA/CuS was prepared by in situ reduction method. Firstly, Fe3O4 as cores were prepared to provide magnetic recovery. Through the self-polymerization of dopamine (DA), polydopamine (PDA) was coated on Fe3O4 as shells to protect Fe3O4 cores. Then, Cu2+ coordinated with PDA on the surface of Fe3O4@PDA and in situ reduced by Na2S to obtain core-shell structural Fe3O4@PDA/CuS with CuS uniformly growing on the PDA. CuS with a narrow band gap will endow Fe3O4 @PDA/CuS excellent photocatalytic performance for organic dyes degradation. The decomposition rate of methylene blue (MB) reached to 92.1 % within 180 min under visible light irradiation of Fe3O4@PDA/CuS as photocatalyst without any cocatalyst. When pH= 10, the decomposition rate of MB can reach to 92.7 % in 60 min, indicated Fe3O4@PDA/CuS was more suitable for use under alkaline conditions. The capture experiment determined that·OH was the main active substance. This also explained that under alkaline conditions, numerous OH- was conducive to the formation of ·OH, thus accelerated the degradation rate. And the decomposition rate of MB by Fe3O4@PDA/CuS can still reach 83.95 % after reused three times.

Environmental magnetic signatures in mangrove ecosystems in northern Persian Gulf: Implication for pollution assessment in marine environment

Magnetic properties of root, bark, and leaf of mangrove (Avicenna marina) and sediment were determined for pollution assessment at three locations in the northern coast of the Persian Gulf. The study revealed that the sources of the particles deposited on leaf surfaces can be discriminated via saturation isothermal remanent magnetization (SIRM) values and heavy metal. However, different factors including wind direction, size of the magnetic particles and crown density, play a role using SIRM for biomonitoring of atmospheric particulate matter. For leaves, the significant correlations between SIRM and leaf elemental contents indicated that the deposited particles on their surface mainly have geogenic sources. The magnetic analyses revealed that leaves are more suitable than bark for monitoring atmospheric pollution using mangrove trees due to the effect of different factors including dense crown of trees, washing of tree trunk by sea waves, and elements translocation from roots and sediments. Instead, the positive and significant correlation between the SIRM values for sediments and mangrove roots, and no or negative correlation between sediments and roots with barks and leaves indicates that the magnetic properties of the sediments and mangrove roots are suitable indicators of pollution in aquatic environment.

Expression of genes related to antioxidation, immunity, and heat stress in Gambusia affinis exposed to the heavy metals Cu and Zn

Water pollution is an increasingly serious problem. Here, Cu and Zn ions were used as stress factors, and G. affinis served as a test organism. Fluorescence quantitative PCR was used to detect changes in the expression of antioxidant genes (SOD, GST, CAT), heat stress genes (Hsp70, Hsp90, Hspd1, Hsc70), and immune system-related genes (IL-1β, IL-8) in G. affinis exposed to Cu and Zn ions over time. To explore the toxic effects of Cu and Zn on G. affinis. The results showed that the 48 h LC50 concentrations of the heavy metals Cu and Zn to G. affinis were 0.17 mg/L and 44.67 mg/L, respectively. Within 48 h, with prolonged Cu exposure, the relative expression levels of the Hsp70, Hsp90, Hspd1, Hsc70, SOD, GST, and CAT genes in the gill tissue first showed a significant increase and then gradually decreased. Gene expression peaked between 9 and 36 h. The relative expression levels of SOD and GST genes in liver tissue showed a gradual decline. Within 48 h, with prolonged Zn exposure, the expression levels of SOD, CAT, and GST genes in G. affinis first increased and then fell before finally rising. The expression levels of IL-1β and IL-8 mRNA showed varying degrees of upward trends, and the expression of IL-8 was the highest for all gill tissue. To sum up, Cu and Zn have strong toxic effects on G. affinis, which makes it possible to use G. affinis as indicator organisms for aquatic environmental pollution.

Microplastics pollution from wastewater treatment plants: A critical review on challenges, detection, sustainable removal techniques and circular economy

The wastewater treatment plants (WWTPs) have long been recognized as a potentially significant source of microplastic (MPs) pollution in aquatic environments. It is challenging to precisely detect and efficiently remove MPs from wastewater due to the lack of standard protocol and removal technologies. Although many advances have been made in the characterization and quantification of MPs in wastewater, the polydisperse and degradation-resistant properties of MPs and WWTPs’ broad nature and lack of specific design allow MPs to pass through treatment processes. This review highlights the current understanding on the occurrence, fate and expulsion of MPs, recent detection status, advanced and sustainable removal technologies for MPs in WWTPs and conversion of MPs into renewable energy sources. Specifically, different techniques to collect MPs from sewage sludge and wastewater, pre-treatment, classification approaches and retention of MPs in wastewater are reviewed and analyzed. Previous MPs studies have undoubtedly improved our understanding, but many unanswered questions need to be answered. The main challenges appear to be the harmonization of detection methods and the removal levels of MPs in wastewater and sewage sludge. To address this challenge, an alternative methodological approach for WWTPs effluent sampling was developed that eliminate sample contamination by synthetic fibre deposition during aquatic sample processing. In parallel, the sustainable methodology was developed for the treatment of sewage sludge samples that effectively separates the MPs from the organic and organometal compositions of the sludge samples, achieving an average extraction efficiency of 81.9%. The studies determined that synthetic fibres were released in greater quantities than MPs over the short period during which the samples were collected. Recommendations for further methodological refinement are formulated and the need for authoritative methodological standardization is recognized. • Current understanding on the occurrence, fate and expulsion of MPs from WWTPs. • Assessment of analytical techniques used for MPs identification in samples of WWTPs. • Use of sustainable removal technologies for MPs in WWTPs. • Microplastic into renewable energy sources to facilitate the circular economy.

Comparative Study of pesticides effects on Artemia salina (Leach, 1819) survival and morphology

The use of pesticides has grown over the years and their effects on ecosystems, especially aquatic ones, have been increasingly observed. Agricultural pesticides are responsible for a large part of pollution in aquatic environments, and can reach non-target organisms, harming biodiversity. In this research, the effects of common pesticides on mortality rate and morphology of the model specie Artemia salina were evaluated. Commercial eggs of A. salina were hatched during 24-36 hours, at 37⸰C. Then, nauplli were exposed to different concentrations of insecticides Bifenthrin, Imidacloprid, Diflubenzuron, and Glyphosate herbicide. The mortality rate and lethal concentrations (LC) of each pesticide were established after 24 hours of treatment. Morphological analyses were made after treatment with the LC25 and LC50 of each pesticide. The results obtained show that Bifenthrin, Imidacloprid and Glyphosate promote linear mortality of the non-target species A. salina, while for insecticide Diflubenzuron, the mortality curve followed a logarithmic model. In addition, Diflubenzuron and Glyphosate induce changes in the morphological parameters of this specie. These results contribute to highlight the harmful effects of agricultural pollutants upon aquatic invertebrates. Besides, the present study confirms that Diflubenzuron does not affect only target species, but also has negative interference with the morphology of non-target species. This result has environmental implication since several invertebrates, including those not harmful to agriculture, can contact with Diflubenzuron in agricultural places.

Facile preparation of activated carbon supported nano zero-valent iron for Cd(Ⅱ) removal in aqueous environment

Activated carbon-supported nano-zero-valent iron (nZVI@AC) is considered to be one of the most promising materials for in-situ remediation of pollutants in aqueous environment, while liquid phase reduction (LPR) is one of the most commonly used preparation methods for nZVI@AC. However, the complex operation and the requirement of various agents limit the practical application of the traditional liquid-phase reduction (TLPR). In this study, an improved liquid phase reduction method (ILPR) was proposed, which was characterized by solid-state dosing of reducing agents. Compared with TLPR, ILPR simplified the preparation process, while there was no requirement of polyethylene glycol and ethanol. When the Cd(II) removal efficiency was used as the evaluation index, the preferred parameters of ILPR were as follows: AC/FeSO4·7H2O mass ratio was 15:1; NaBH4 dosage was 8 g; ultrasonic time was 1 h; stirring time was 20 min. Moreover, the Cd(II) removal efficiency of nZVI@AC prepared by ILPR (nZVI@AC-I) was greater than 92.00%, which was superior to that of nZVI@AC prepared by TLPR (nZVI@AC-T). The characterization results showed that the pore parameters, surface functional groups and iron contents of nZVI@AC-I and nZVI@AC-T were basically the same. However, the distribution of iron-containing particles on the surface of nZVI@AC-I was more uniform. Furthermore, the Fe0 in nZVI@AC-I had a smaller particle size and a higher content. Overall, this study provided a promising approach for nZVI@AC preparation.

Designing a novel metal-organic framework@covalent organic framework composite for the selective removal of fluoroquinolones: Adsorption behaviors and theoretical investigation

Increasing fluoroquinolone (FQ) pollution in aquatic environments is a growing global concern owing to its extensive use as therapeutic agents and growth promoters. This study aims to present a highly selective adsorbent for the removal of FQs. A binary metal-organic framework (MOF) and covalent organic framework (COF) composite (NH2-MIL-125@TpPa-SO3H) was successfully synthesized by a solvothermal method, wherein MOF comes from the NH2-MIL-125 of the Material of Institute Lavoisier (MIL) family and COF from SO3H-anchored Schiff-base TpPa-SO3H. The adsorption outcomes showed that the as-synthesized adsorbent considerably improved the removal efficiency of FQs in water environments compared to independent MOFs or COFs. The adsorbent also displayed remarkable stability after 8 cycles of adsorption-desorption. According to the Sips isotherm model, the maximum adsorption capacities were 444.7, 455.7, 457.5, and 429.1 mg·g−1 for enoxacin, norfloxacin, ciprofloxacin, and sparfloxacin, respectively, and the adsorption kinetics were in accordance with the pseudo-second-order model. Moreover, the selective adsorption mechanism was intensively explored through characterizations and density functional theory, showing the synergistic effects of electrostatic interaction, hydrogen bonding, C–H⋯π interaction, and hydrophilic interaction. This study provides a new strategy for designing composite adsorbents for the removal of organic pollutants in the field of environmental remediation.

Donnan dialysis for phosphate recovery from diverted urine

There is a critical need to shift from existing linear phosphorous management practices to a more sustainable circular P economy. Closing the nutrient loop can reduce our reliance on phosphate mining, which has well-documented environmental impacts, while simultaneously alleviating P pollution of aquatic environments from wastewater discharges that are not completely treated. The high orthophosphate, HxPO4(3−x)−, content in source-separated urine offers propitious opportunities for P recovery. This study examines the use of Donnan dialysis (DD), an ion-exchange membrane-based process, for the recovery of orthophosphates from fresh and hydrolyzed urine matrixes. H2PO4− transport against an orthophosphate concentration gradient was demonstrated and orthophosphate recovery yields up to 93% were achieved. By adopting higher feed to receiver volume ratios, DD enriched orthophosphate in the product stream as high as ≈2.5 × the initial urine feed concentration. However, flux, selectivity, and yield of orthophosphate recovery were detrimentally impacted by the presence of SO42− and Cl− in fresh urine, and the large amount of HCO3− rendered hydrolyzed urine practically unsuitable for P recovery using DD. The detrimental effects of sulfate ions can be mitigated by utilizing a monovalent ion permselective membrane, improving selectivity for H2PO4− transport over SO42− by 3.1 × relative to DD with a conventional membrane; but the enhancement was at the expense of reduced orthophosphate flux. Critically, widely available and low-cost/waste resources with sufficiently high Cl− content, such as seawater and waste water softening regenerant rinse, can be employed to improve the economic viability of orthophosphate recovery. This study shows the promising potential of DD for P recovery and enrichment from source-separated urine.

Effects of natural nanoparticles on the acute toxicity, chronic effect, and oxidative stress response of phenicol antibiotics in Daphnia magna.

Natural nanoparticles (NNP) are ubiquitous in natural water and can interact with other contaminants, causing ecotoxic effects on aquatic nontarget organisms. However, the impact of NNPs on the ecotoxicity of antibiotics remains largely unknown. This work investigated the acute toxicity, chronic effect, and oxidative response and damage in Daphnia magna co-exposed to phenicol antibiotics (chloramphenicol, thiamphenicol) and different concentrations of NNPs (10mg/L: environmentally relevant concentration; 100mg/L: a high concentration that caused no apparent immobilization in D. magna). The results showed that the acute toxicity of chloramphenicol was increased by 10mg/L NNPs but decreased by 100mg/L NNPs; both concentrations of NNPs increased and decreased acute toxicities of thiamphenicol and chloramphenicol + thiamphenicol treatments, respectively. After long-term exposure, phenicol antibiotics (1μg/L) and NNP (10mg/L) mixtures in environmentally relevant concentrations significantly affected the reproduction of D. magna but did not influence their growth. The catalase activity, reduced glutathione level, and malonaldehyde content in D. magna also varied with the NNPs concentrations. Notably, the lowest concentration of thiamphenicol and chloramphenicol + thiamphenicol combined with NNPs significantly increased the malondialdehyde content in D. magna compared with the control, indicating membrane lipid peroxidation occurred in daphnids. This study suggests that the toxic effects of contaminants and NNPs on aquatic organisms should be considered thoroughly to avoid underestimating the hazard of these pollutants in the actual aquatic environment.

Editorial: Toxic effects and ecological risk assessment of typical pollutants in aquatic environments

Editorial: Toxic effects and ecological risk assessment of typical pollutants in aquatic environments

Microplastic pollution in aquatic environments may facilitate misfeeding by fish

Numerous recent studies have documented ingestion of microplastics (MPs) by many aquatic animals, yet an explanation for misfeeding by fish remains unexplained. Here we tested the hypothesis that biofilm (biofouling) on MP surfaces due to exposure in the aquatic environment facilitates misfeeding in fish. Spherical polystyrene (PS) was cultured for 0–22 weeks in a freshwater environment to grow a biofilm on the MPs. Goldfish were employed in a simple feeding experiment with and without provision of genuine food at ecologically relevant MP concentrations. Absorbance (ABS), which is a proxy for biofilm formation, increased exponentially within three weeks of initiation and reached a plateau after approximately five weeks. Although fish did not swallow the MPs, “capture” occurred when food pellets were in the vicinity and significantly increased in probability with aging. Duration of capture also increased significantly with increasing aging. These results suggest that drifting of MPs in aquatic environments may facilitate fish misidentification of MPs as edible prey.

Synthesis of a novel visible-light active Gd2O3/GdVO4/V2O5 photocatalyst for rapid purification of industrial wastewater containing organic dyes and bacteria

In the past decades, population growth and industrial development have posed a significant threat to the aquatic environment and water pollution, considerably influencing our living standards. In the present study, novel visible light-responsive nano photocatalysts Gd2O3/GdVO4/V2O5 were synthesized by mechanical alloying and sintered at different elevated temperatures. All the structural and microstructural parameters of the mechanosynthesized C12.6N0.6VO3 phase have been modified from the reported values. XRD, TEM, SEM, XPS, and FTIR are employed to characterize the as-obtained nanocomposites with elemental mapping. The surface or grain boundary defects, bandgap, and Urbach energy of the nanocomposites are revealed by diffused reflectance spectroscopy (DRS) and BET analysis. The photodegradation and quantum efficiency of the samples are investigated by analyzing UV–Vis spectra, using Rhodamine B (RhB), Congo Red (CR), and Methylene Blue (MB) as model organic dye pollutants. Experimental results reflect that the 5 h milled and sintered sample shows better photocatalytic degradation efficiency of almost 100% within 150 min - nearly twice that of pure precursor materials. Scavenger tests ensure the oxidative radical species involved in the photodegradation mechanism. The antibacterial study reveals that the Gd2O3/GdVO4/V2O5 nanocomposite efficiently prohibits gram-positive bacterial growth in the wastewater. These Gd2O3 /GdVO4 /V2O5 nanocomposites may be utilized as an efficient tool for wastewater treatment in industrial areas and prohibiting bacterial growth in wastewater.

Novel 3D multi-layered carbon nitride/indium sulfide heterostructure for boosted superoxide anion radical generation and enhanced photocatalysis under visible light

Superoxide anion radical (O2−) plays an important role in the selective photocatalytic degradation of recalcitrant organic pollutants in a complex aquatic environment. However, the yield of O2− is low due to the low charge utilization and limited visible light absorption. Here, we built a novel there-dimension (3D) multi-layered CNIS (carbon nitride/indium sulfide) heterostructure via a facile molecular self-assembly route, in which morphological engineering and heterostructure construction were synergistically used. Results showed that the formation of the type-II heterojunction between CN and In2S3 via In-N bonds significantly shifted the band positions and increased the density of band tail, facilitating high absorption of visible light and suppressing the charge carrier recombination. Additionally, the ordered sheet-to-sheet architecture of 3D multi-layered CNIS heterostructure with strong anisotropy accelerated exciton dissociation and provided abundant diffusion channels. Therefore, the novel 3D multi-layered CNIS heterostructure exhibited effective photocatalytic activity towards O2− generation (11.54 μmol/L min−1), causing 83 % removal of tetracycline (TC) in 10 min under visible light.

Life Cycle Assessment of Management Scenarios for Dredged Sediments: Environmental Impacts Caused during Landfilling and Soil Conditioning

The management of dredged sediments is a challenging issue since it involves the interconnection of complex economic, social, technical and environmental aspects. The EU LIFE SURE project aimed to apply a more sustainable dredging technique to Malmfjärden Bay in Kalmar/Sweden (a shallow urban water body with a high content of nutrients) and, additionally, it involved beneficial uses for the dredged material, in line with the circular economy concept. To achieve this, a life cycle assessment (LCA) study was carried out to assess the potential environmental impacts associated with two scenarios: sediment landfilling (S1) and soil conditioning (S2). This LCA study also aimed to evaluate and compare the costs related to each scenario. S1 contemplated the construction and operation of the landfill for 100 years, including the collection and discharge of leachate and biogas. S2 included the use of sediments in soils and the avoidance of producing and using fertilisers. Results showed that (S2) soil conditioning (total impact: −6.4 PE) was the scenario with fewer environmental impacts and the best economic evaluation. The S2 scenario was mainly related to the positive environmental savings produced by reducing fertiliser consumption (which also avoided purchase costs). However, S2 was also linked to potential negative effects associated with eutrophication and toxicity categories of impacts due to the possible spread of nutrients and pollutants in terrestrial and aquatic environments. In order to mitigate this problem, the sediments could be pre-treated to reduce their risk of pollution. Moreover, the main impact of the landfilling scenario (S1, total impact: 1.6 PE) was the emission of global warming-contributing gases during the operation of the facility. Implementing the soil conditioning scenario was therefore recommended, in line with the aim of the LIFE SURE project. Finally, it was recommended that LCA studies should be applied more often in the future when selecting beneficial uses for dredged sediments. The decision-making process is facilitated when the positive and negative impacts produced by each handling option are considered.

N and S co-doped pine needle biochar activated peroxydisulfate for antibiotic degradation

A low-cost nitrogen and sulfur doped biochar (CNS) was prepared by oxygen limiting method using pine needles. In the CNS/PDS system, the degradation rate of tetracycline hydrochloride (TCH) reached 85.6% in 20 min when the pyrolysis temperature was 800 °C. X-ray photoelectron spectroscopy and Raman spectroscopy showed that high-temperature pyrolysis produced more carbonyl and defect, which enhanced the activation efficacy of CNS for PDS. Electron paramagnetic resonance and radical quenching have demonstrated that O2•- and 1O2 played key roles in radical pathway. A novel mechanism for degradation of TCH by electron transfer pathway was proposed by linear sweep voltammetry and electrochemical impedance spectroscopy. CNS served as a transport mediator and the electrons of TCH were continuous transferred to PDS via CNS, which accelerated its oxidation. Moreover, density functional theory demonstrated that pyrrolic N combined with the H atom of PDS to form an N–H structure and generated a PDS-catalyst complex. The projected density of state results showed that pyrrolic N and thiophene S further speeded up the electron transfer process due to their closer proximity to 0 Fermi level. This study provides insight into the reaction mechanism of heteroatom doped biochar for treatment of organic pollutants in aquatic environments.

Adverse effects of polystyrene microplastics in the freshwater commercial fish, grass carp (Ctenopharyngodon idella): Emphasis on physiological response and intestinal microbiome

Microplastics (MPs) pollution in aquatic environment has attracted global attention in recent years. To evaluate the potential toxic effects of MPs in freshwater cultured fish, grass carps (Ctenopharyngodon idella) (body length: 7.7 ± 0.1 cm, wet weight: 6.28 ± 0.23 g) were exposed to different sizes (0.5 μm, 15 μm) and concentrations (100 μg/L, 500 μg/L) of polystyrene microplastics (PS-MPs) suspension for 7 and 14 days, followed by 7 days of depuration, detecting the variations in growth rate, histological structure, oxidative response and intestinal microbiome. Our results indicate that MP toxicity elicited significant size- and concentration-dependent responses by grass carp. MP exposure caused obvious decrease in growth rate on day 14 but not on day 7. Additionally, MPs with large size and high concentration caused more severe intestinal damage and less weight gain, while MP particles with small size and high concentration induced more severe liver congestion and stronger oxidative stress. MP exposure dramatically shifted the gut microbial composition, with the top 10 genera in abundance being associated with the diameter and concentration of the MPs. After 7 days of depuration, only superoxide dismutase and malondialdehyde in liver, showed a tendency to recover to the initial values. Even though the differences in the gut microbial community between the control and treatment groups disappeared, and the proportion of potential pathogenic bacteria in intestine was still high. Thus, it is clear that a short-term depuration period of 7 days is not enough for complete normalization.