Hydrostatic pressure drives microbe-mediated biodegradation of microplastics in surface sediments of deep reservoirs: Novel findings from hydrostatic pressure simulation experiments

Dynamic process of UV-aging polystyrene microplastics, simultaneous adsorption of drugs, and subsequently coagulative removal together

The aging of plastics and their adsorptive interactions with the residual contaminants in water has attracted increasing attentions. In this study, the dynamic process of UV-aging polystyrene (PS) microplastics (MPs) were semi-quantitatively analyzed using a coulter counter, and the adsorptive interactions between the aged PS MPs and two popular drugs[norfloxacin (NOR) and chloroquine phosphate (CQ)] were investigated simultaneously. The MPs presented a rapid size downtrend, reduced from micrometer to nanometer, and the particle number concentration increased about 2 -3 times after a 36.0 h aging effect. The apparent UV-aging process of PS MPs mainly obeyed the pseudo-first order kinetic model in currently measured MPs' size range. The drug uptakes of the aged MPs were fully consistent with the contents of oxygen-containing groups on MPs surface rather than MPs' size. The involved adsorption mechanisms were investigated in detail mainly including electrostatic attraction, hydrogen bonding, and π-π electron donor-acceptor interaction. The drug adsorbed MPs were subsequently efficiently removed by an enhanced coagulation together owing to the synergistic effects of the two pollutants. This study provides a novel and comprehensive perspective on the fundamental understanding the UV-aging process of MPs and the simultaneous adsorption behaviors, furthermore, a strategy was proposed for their collaborative removal.

Aging behaviors intensify the impacts of microplastics on nitrate bioreduction-driven nitrogen cycling in freshwater sediments

Microplastics (MPs) inevitably undergo aging processes in natural environments; however, how aging behaviors influence the interactions between MPs exposures and nitrate bioreduction in freshwater sediments remains poorly understood. Here, we explored the distinct impacts of virgin and aged MPs (polystyrene (PS) and polylactic acid (PLA)) on nitrate bioreduction processes in lake sediments through a long-term microcosm experiment utilizing the 15N isotope tracing technique and molecular analysis. Compared to virgin MPs, aged PLA significantly increased the rates of denitrification, anaerobic ammonium oxidation (anammox), and dissimilatory nitrate reduction to ammonium (DNRA) (p < 0.05), facilitating sediment nitrogen loss, while aged PS only significantly improved the rates of DNRA by 272-297 % and contributed to nitrogen retention in sediments. Metagenomic sequencing demonstrated that a more significant enrichment of functional genes responsible for nitrate bioreduction pathways occurred with aged MPs exposures than with virgin MPs. By combining analyses of MPs aging traits and the key drivers of nitrate bioreduction, we revealed that aging behaviors directly regulated sediment nutrient status (e.g., DOC/NOx- ratio) and microbiological properties (from genes to bacteria), thereby further determining the activity of nitrate bioreduction. This work provides new insights into the impacts of aged MPs on sediment nitrate reduction and highlights the role of MPs aging in future assessments of long-term MPs pollution in freshwater ecosystems.

Enhanced ecological risk of microplastic ingestion by fish due to fragmentation and deposition in heavily sediment-laden river

The widespread occurrence of microplastics (MPs) in rivers has aroused increasing concerns. However, there remains a significant gap about its effect on fish with different species, especially in highly-sediment-laden rivers. Here, through a large-scale investigation of microplastics in the Yellow River, our research highlighted effects of heavily sediments on MPs contamination in fish gut. MPs were 100 % tested in water, sediment and fish gut samples, with MPs in the lower reach 2∼3 times larger than that of the upper reach. Most of the microplastics were small (<1 mm), fibrous and blue fragments, composed of polyethylene, polypropylene, and polyethylene terephthalate. Feeding habitat and environment significantly controlled MPs ingestion by fish (p < 0.05), of which filter feeders and species with broader dietary preferences exhibited higher ingestion abundance, omnivorous fish abundance up to 24.9 items/individual. Heavily sediment load accelerated the fragmentation and deposition of MPs (p < 0.05), leading to the generation of more and smaller MPs particles, increasing ecological risks to aquatic organisms. Downstream, smaller sediment size and higher organic matter content also facilitated microplastic accumulation. The prevalence of highly toxic polyvinyl chloride polymers was emerged as the major contributor to environmental risks. Our results suggested that the contribution and ecological risks of small microplastics are worth attention in the mid and lower reaches of the Yellow River.

Neurotoxic effects of chronic exposure to perfluorobutane sulfonate in adult zebrafish (Danio Rerio)

Per and polyfluoroalkyl substances (PFAS) are synthetic compounds extensively utilized in industrial applications and consumer products. Long-chain PFAS has been linked to negative health impacts, prompting the introduction of shorter-chain alternatives like perfluorobutane sulfonate (PFBS). While long-chain PFAS are known to induce oxidative stress, neuroinflammation, and neuronal apoptosis, the neurotoxic potential of short-chain PFAS like PFBS was not well studied. This study aims to evaluate the neurotoxic effect and bioaccumulation of PFBS on adult zebrafish. In this study, adult zebrafish were exposed to PFBS at concentrations of 0.14, 1.4, and 14 μM for 28 days. PFBS accumulation in zebrafish brain tissue was confirmed by specific mass spectrum peaks. Behavioral assays revealed significant anxiety-like behavior, with PFBS (14 μM) exposed zebrafish spending more time in the bottom zone of the novel tank diving test (179.33 ± 1.03 s) and in the light and dark preference results showed increased time spent in the dark zone (165.17 ± 10.89 s). Learning and memory deficits were evident in the T-maze test, where PFBS-exposed zebrafish spent less time in the favorable zone (0.67 ± 1.15 s). Biochemical analysis showed significant inhibition of acetylcholinesterase (AChE) activity in the male and female brains (0.06 μmol/min and 0.09 μmol/min). Antioxidant enzyme levels were reduced, with superoxide dismutase (SOD) 5.45 U/mg protein in the male brain and 4.06 U/mg protein in the female brain, leading to increased oxidative stress biomarkers like lipid peroxidation and nitric oxide levels in male (0.99 μmol/mg/ml and 8.85 μM) and female brain (1.83 μmol/mg/ml and 8.74 μM), respectively. Gene expression analysis demonstrated the downregulation of SOD, CAT, GSR, and GPx, indicating impaired antioxidant defense mechanisms. Histopathological analysis of PFBS exposure groups revealed vacuolation and increased pyknotic neurons in the optic tectum region of the brain. Our study suggests that PFBS exposure leads to bioaccumulation in the brain, causing histopathological changes and cognitive impairment. In conclusion, PFBS induces neurotoxicity which can be a potential risk as they are incorporated into a range of consumer products.

Organic substitution enhances soil quality, soil microbial community stability, foxtail millet productivity, and grain quality in North China

Excessive use of chemical fertilisers has reduced crop productivity and adversely affected agroecosystems. Partial substitution of chemical fertilisers with organic fertilisers can sustainably increase cereal yields; however, its effect on soil microbial characteristics in foxtail millet fields remains unclear. A two-year (2022-2023) experiment was conducted to investigate the effects of four fertilisation regimes (chemical fertiliser only, CF; 25 % organic substitution, ZF25; 50 % organic substitution, ZF50; and 75 % organic substitution, ZF75) on foxtail millet productivity, soil quality, and soil microorganism properties. The organic substitution groups promoted plant nitrogen uptake by 4.16 %-10.09 % and 3.79 %-12.88 % and improved soil fertility, increasing the crop productivity index (CPI) by 7.46 %-12.79 % and 3.78 %-6.39 % and soil quality index (SQI) by 36.48 %-125.46 % and 12.04 %-87.25 % in 2022 and 2023, respectively, compared to that in the chemical fertiliser group. ZF25 and ZF50 increased the annual millet yield by 1.39 %-6.53 % in 2022 and 2.80 %-7.87 % in 2023 compared to that of CF. Organic substitution altered the structure of the soil bacterial and fungal communities. Compared with CF, the Shannon index of soil bacteria and fungi increased by 0.28 %-1.68 % and 8.88 %-14.10 %, respectively. The biomarkers enriched in the organic substitution and chemical fertiliser groups had similar associated soil biochemical metrics, but the associated trends were reversed. Organic substitution also improved soil carbon and nitrogen metabolism. Bacteria and fungi indirectly influenced yield variations via enzyme activity and nutrient interactions. This study has important theoretical implications for scientific fertiliser management and the development of microbial fertilisers in agricultural practice.

A potentially fruitful path toward a cleaner and safer environment: MXenes uses in environmental remediation

The rapid industrialization of the world has resulted in severe environmental pollution, necessitating the development of new materials such as pollution remediation. Two-dimensional (2D) MXenes have emerged as a promising family of materials due to their unique physicochemical properties, making them ideal for environmental remediation. The article sheds light on the new opportunities of MXenes in the removal of organic and inorganic contaminants, including organic dyes, pharmaceuticals, heavy metals, radionuclides, and gas pollutants. MXenes also show excellent performance in photocatalytic degradation, adsorption, and microbial inactivation with environmental safety. Moreover, their application in recovering valuable elements from waste streams is also being explored. While these advances are promising, challenges remain in surface chemistry, semiconducting behavior, interfacial effects, and large-scale synthesis. This review highlights the tremendous potential of MXenes in environmental remediation while also outlining the key challenges that need to be resolved to fully realize MXenes capabilities. By providing this comprehensive survey of MXene-based technologies, the paper stimulates further research and innovation in this rapidly evolving field.

Microbial degradation potential of microplastics in urban river sediments: Assessing and predicting the enrichment of PE/PP-degrading bacteria using SourceTracker and machine learning

Microplastic mitigation strategies that adapt to various actual aquatic environments require the ability to predict their microbial degradation potential. However, the sources and enrichment characteristics of the degrading bacteria in the plastisphere from river sediments, and their relationship with environmental conditions remain poorly understood. Here, SourceTracker analysis was adopted to investigate the sources and distribution characteristics of total PE/PP-degrading bacteria (TD) and local PE/PP-degrading bacteria (LD) in the plastisphere and surrounding sediments of the urban river. To better characterize the enrichment property of PE/PP-degrading bacteria in the plastisphere, two specific indices, the enrichment ratios of TD (ERTD) and LD (ERLD) separately, were first defined in this study. Furthermore, machine learning models were constructed to predict these enrichment ratios. The results showed that river sediments represented an important reservoir of PE/PP-degrading bacteria within the plastisphere (representing 81.8 %). Both the enrichment ratio of TD (R2 = 0.720) and the enrichment ratio of LD (R2 = 0.537) showed a significant positive correlation with the carbonyl index of PE/PP, indicating that the enrichment ratios can effectively reflect the microbial degradation potential of PE/PP in sediments. Compared to gradient boosting regression tree, multilayer perceptron, and support vector machines, the random forest (RF) model demonstrated superior accuracy in predicting both the enrichment ratio of TD (R2Test = 0.954, MSE = 0.180) and the enrichment ratio of LD (R2Test = 0.924, MSE = 0.009. It was also observed that the enrichment ratios were higher in river bends, indicating that river bends were potential hot zones for microbial degradation of PE/PP. SHAP analysis highlighted that the key environmental factors exhibited synergistic effects on both enrichment ratios of TD and LD. Finally, the concentration range of key environmental factors that maximize the enrichment ratio was determined. This study constitutes a powerful example of predicting microplastic microbial degradation potential across various scientific disciplines and provides a basis for the effective management of microplastics.

Influence of tulsi Ocimum sanctum extract on fish health: Growth, hematology, serum immune parameters, and antioxidant status in Common Carp

OBJECTIVE

In aquaculture, the trend is shifting towards using plant-derived alternatives that are abundant in phytochemicals as effective replacements for traditional antibiotics and synthetic feed additives. In the present study, the effects of tulsi Ocimum sanctum extract on growth performance, hemato-biochemical indices, serum immune parameters, and antioxidant parameters in Common Carp Cyprinus carpio were investigated.

METHODS

Common Carp (mean body weight ± SD = 10.6 ± 0.13 g) were fed experimental diets that contained tulsi leaf extract at 0.0 (control), 0.5, 1.0, and 1.5% for 60 d (25 fish/treatment).

RESULTS

The findings revealed a considerable enhancement in growth performance and a decreased feed conversion ratio, especially for the 1.0% tulsi-based diet. Additionally, weight gain and feed conversion ratio exhibited significance at both the linear and quadratic levels, as indicated by polynomial contrasts. The hematological and biochemical profiles exhibited improvements in groups receiving tulsi-enriched diets. The antioxidant status of fish serum exhibited a notable increase, as evidenced by elevated activities of total antioxidant capacity, superoxide dismutase, and catalase in fish that received the 1.0% and 1.5% tulsi-based diets. Tulsi-supplemented diets led to remarkable enhancements in serum lysozyme activity, alternative complement activity, and total immunoglobulin content. Moreover, tulsi supplementation at 1.0% and 1.5% showcased a significant reduction in serum glucose and cortisol levels compared to the other groups.

CONCLUSIONS

In conclusion, tulsi extract emerged as a valuable asset, positively influencing growth, blood parameters, antioxidant balance, and serum immune response in Common Carp, particularly at supplementation levels ranging from 1.0% to 1.5% in the diet.

Using biochar, compost, and dry-based organic amendments in combination with mycorrhizae for mitigating heavy metal contamination in soil

Water scarcity has led to the increased use of untreated wastewater for irrigation, contributing to heavy metal (HM) accumulation in soils and crops. This study evaluated the effectiveness of organic amendments and arbuscular mycorrhizal fungi (AMF) in reducing HM bioavailability and enhancing plant growth. A two-year pot experiment (2022-2023) was conducted using eight treatments (T1-T8) and three replicates each. Treatments included: T1 (Control), T2 Rice straw, T3, rice straw compost, T4, rice straw biochar, T5, AMF, T6, Straw + AMF, T7, compost + AMF, and T8, biochar + AMF. Post-harvest analysis showed that T7 and T8 significantly reduced soil and plant HM levels. T8 was the most effective, reducing Pb, Cd, and Ni in grains by up to 93%, 76%, and 83%, respectively. Shoot HM concentrations declined by 22%-52%, and grain uptake dropped by 58%-92%. T8 also improved shoot and root dry weights by 66% and 48%, and grain yield by 56%. Root colonization and mycorrhizal intensity increased significantly, along with urease (78%) and catalase (156%) activities. Results highlight the potential of T8 (biochar + AMF) as a sustainable strategy for remediating contaminated soils and improving crop productivity.

Impact of polyethylene microplastics on the nitrogen removal and bacterial community in sequencing batch reactor at different hydraulic retention times

Both hydraulic retention time (HRT) and microplastics (MPs) are factors affecting the performance of biological wastewater treatment processes, but how MPs affect the role of HRT in biological wastewater treatment performance has not been investigated. In this study, the effects of polyethylene MPs (PE-MPs) on the nitrogen removal performance in a sequencing batch reactor (SBR) at different HRTs were investigated by analyzing the changes in the content and composition of extracellular polymer substances (EPS) and in the bacterial communities and metabolic pathways. In the PE-MPs absence, the HRT was shortened from 1440 to 720 min, resulting in a decrease in the average elimination of chemical oxygen demand and ammonia nitrogen by 13.21 % and 3.78 %, respectively. Whereas the presence of 0.5 mg/L PE-MPs enhanced the reduction by 73.36 % and 93.85 %, respectively. PE-MPs did not change the promotional impacts of HRT shortening on the levels of protein (PN) and polysaccharide (PS) within EPS, while amplified this effect. Aromatic PN of EPS was more sensitive to PE-MPs and HRT than tryptophan-like PN. PE-MPs resulted in a lower enzyme level in nitrification and denitrification metabolism pathways at different HRTs compared to no PE-MPs. This research offers novel perspectives for understanding how PE-MPs intervene in the influence of HRT on biological wastewater treatment performance.

Aerobic biofilm systems outperform anaerobic and anoxic regimes in 2,4-dimethylphenol degradation: Microbial synergy and metabolic mechanisms

The efficient biodegradation of 2,4-dimethylphenol (2,4-DMP), a toxic and recalcitrant phenolic pollutant, remains a critical challenge in wastewater treatment, with ongoing debate regarding the optimal dissolved oxygen (DO) regime for biofilm-based systems. To resolve this, four biofilm reactors-anaerobic (R1), anoxic (R2), microaerobic (R3), and aerobic (R4)-were operated under a DO gradient (0.3-8.0 mg/L). When influent 2,4-DMP concentrations increased from 25 to 300 mg/L, removal efficiencies declined significantly in R1-R3 (9.0 %, 44.8 %, and 58.8 %, respectively), whereas R4 maintained 100 % removal regardless of loading. Rapid degradation occurred within 8-16 h in R4, correlating with DO consumption from 8.0 to 5.0 mg/L. Aerobic conditions eliminated dependence on extracellular polymeric substances (EPS) for pollutant sequestration, as complete mineralization negated intermediate accumulation. Microbial analysis revealed Zoogloea (18.92 % abundance), Prosthecobacter, and Ferruginibacter as keystone aerobic bacteria, encoding aromatic ring-hydroxylating dioxygenases (RHDs) for 2,4-DMP hydroxylation and β-ketoadipate pathway activation. Concurrently, fungal genera Cutaneotrichosporon (74.50 %) and Kalenjinia were enriched in R4, contributing laccase-mediated ring cleavage. Synergy between bacterial oxidative pathways and fungal ligninolytic systems enabled sustained COD removal (95.54 %) without biofilm destabilization. These findings conclusively demonstrate aerobic biofilms' superiority in 2,4-DMP treatment, driven by metabolic completeness, energy-efficient respiration, and cross-kingdom functional partitioning.

Evaluation of machine learning models for accurate prediction of heavy metals in coal mining region soils in Bangladesh

Coal mining soils are highly susceptible to heavy metal pollution due to the discharge of mine tailings, overburden dumps, and acid mine drainage. Developing a reliable predictive model for heavy metal concentrations in this region has proven to be a significant challenge. This study employed machine learning (ML) techniques to model heavy metal pollution in soils within this critical ecosystem. A total of 91 standardized soil samples were analyzed to predict the accumulation of eight heavy metals using four distinct ML algorithms. Among them, random forest model outer performed in predicting As (0.79), Cd (0.89), Cr (0.63), Ni (0.56), Cu (0.60), and Zn (0.52), achieving notable R squared values. The feature attribute analysis identified As-K, Pb-K, Cd-S, Zn-Fe2O3, Cr- Fe2O3, Ni-Al2O3, Cu-P, and Mn- Fe2O3 relationships resembled with correlation coefficients among them. The developed models revealed that the contamination factor for metals in soils indicated extremely high levels of Pb contamination (CF ≥ 6). In conclusion, this research offers a robust framework for predicting heavy metal pollution in coal mining soils, highlighting critical areas that require immediate conservation efforts. These findings emphasize the necessity for targeted environmental management and mitigation to reduce heavy metal pollution in mining sites.

Evaluating degradation efficiency of pesticides by persulfate, Fenton, and ozonation oxidation processes with machine learning

Quantifying organic properties is pivotal for enhancing the precision and interpretability of degradation predictive machine learning (ML) models. This study used Binary Morgan Fingerprints (B-MF) and Count-Based Morgan Fingerprints (C-MF) to quantify pesticide structure, and built the ML model to forecast degradation rates of pesticides by persulfate (PS), Fenton (FT) and ozone oxidation (OZ). The result demonstrated that the C-MF-XGBoost model excelled, achieving R2 of 0.914, 0.934, and 0.971 on test-sets for the above three processes, respectively. The model accurately linked molecular structural variations to degradation rates, demonstrating that impact of molecular structure on the degradation rate was observed to be 12.4 %, 15.2 %, and 21.6 % respectively, across a broader range of SHAP values. Additionally, optimal pH ranges were identified for PS (3.5-5.5) and FT (2.5-4.0), while OZ showed a positive correlation with pH. The model identified electron gain/loss groups' promoting/inhibiting effects on degradation rates and highlighted the significance of N atomic structures in PS. Then, Tanimoto coefficient was used to evaluate the applicability of the model. This study lays a groundwork for quantifying organic compound structures and predicting their degradation impacts, presenting a novel framework to assess future organic pollutants' degradation performance.

Effectiveness of waste-derived MIL type MOFs in removing PFOA and PFAS pollutants for environmental remediation

Elimination of perfluorooctanoic acid (PFOA), a persistent pollutant that is toxic to human and ecosystem health, is important. In this study, three adsorbents, C-101, W-101, and NW-101, were evaluated. W-101 was modified by diamine ethyl modification to enhance the number of PFOA adsorption sites. The results showed that W-101 (42.7 mg g-1) had better PFOA adsorption capacity than C-101 (12.3 mg g-1), and NW-101 (698.4 mg g-1) was the best. The Langmuir model correctly described the isotherms of PFOA adsorption, and the pseudo-second-order kinetic model fitted the process. NW-101 exhibited an excellent adsorption efficiency, as it reached the equilibrium within 7 min, and also revealed higher reusability due to the stable structure of the amine-grafted structure; therefore, NW-101 proved very efficient in PFOA removal. The new method used the bark of poplar trees to prepare MIL-101(Cr) adsorbents with surface areas of 3341, 2767, and 2374 m2 g-1 for C-101, W-101, and NW-101, respectively. This cost-effective, eco-friendly method utilizes renewable raw materials, minimizes environmental impact, and represents a significant advance in PFOA removal and thermal material research.

The Evolution of Nutrient and Microbial Composition and Maturity During the Composting of Different Plant-Derived Wastes

Composting is an environmentally friendly treatment technology that recycles and sanitizes organic solid waste. This study aimed to assess the evolution of nutrients, maturity, and microbial communities during the composting of different plant-derived wastes. The composting process was conducted over 49 days using three types of plant-derived waste: wheat bran (WB), peanut straw (PS), and poplar leaf litter (PL). This process was examined through physical, chemical, and biological parameters. The results revealed that after 49 days of composting, the three groups experienced significant changes. They were odorless, were insect-free, exhibited a dark brown color, had an alkaline pH value, and had an electrical conductivity (EC) value of less than 4 mS/cm. These characteristics indicated that they had reached maturity. Nutrient content was the most significant factor influencing the degree of humification of the different composting materials, while changes in microbial community diversity were the key driving factors. Significantly, the compost PS, derived from peanut straw, entered the thermophilic phase first, and by the end of composting, it had the lowest organic matter (OM) loss rate (17.4%), with increases in total nitrogen (TN), total phosphorus (TP), and total potassium (TK) in the order of PS > PL > WB. The increase in humus carbon (HSC) content and the humic acid/fulvic acid (HA/FA) ratio followed the order PS > WB > PL. FTIR spectra indicated that PS had greater aromatic characteristics compared to the other samples. The abundance and diversity of bacterial and fungal communities in the compost increased significantly, accompanied by more complex community structures. Crucially, there were no phytotoxic effects in any of the three composting treatments, and the compost PS boasted a high germination index (GI) of 94.79%, with the lowest heavy metal contents. The findings indicate that the compost PS has the highest potential for resource utilization and is suitable for agricultural applications. Our results demonstrate that composting technology for plant-derived waste has the potential to enhance soil fertility and provide a reference for the composting treatment and resource utilization of other plant-derived waste.

Enhanced Enzymatic Hydrolysis of Tobacco Stalk via Simultaneous Deconstruction and Modification through Triton X-100-Mediated Organosolv Pretreatment

Tobacco stalks (TS) present substantial potential for biofuel and biochemical production; however, their complex lignin structures and tightly bound carbohydrates pose significant challenges for enzymatic hydrolysis due to high recalcitrance. This study explores Triton-X 100-mediated 1,4-butanediol combined with AlCl3 pretreatment for TS fractionation towards improving enzymatic hydrolysis. Optimized pretreatment conditions achieved a significant removal of 87.8 % of hemicellulose and 81.0 % of lignin while maintaining a high cellulose retention of 90.1 %. Subsequently, the pretreated biomass recorded 91.2 % glucose yield after enzymatic hydrolysis at 10 % w/w solid with 12 FPU/g enzyme loadings, substantially outperforming controls. The presence of Triton-X 100 in pretreatment reduced enzyme requirements by up to 33.3 %. Structural characterization of the pretreated TS indicated effective disruption of lignin-carbohydrate complexes and an increase in biomass porosity by 1.2-2.3 folds, contributing to improved cellulose accessibility and enzymatic hydrolysis efficiency. Moreover, structural characterization of lignin revealed that Triton-X 100 grafted onto lignin by etherification, yielding a 21 % reduction in phenolic hydroxyl content and enhancing surface negative charge. These modifications effectively weaken both hydrogen bonding and electrostatic interactions between lignin and cellulase, thereby improving enzymatic hydrolysis efficiency. Overall, the proposed pretreatment presents a promising strategy for efficient fractionation and hydrolysis of TS biomass.

Impact of heavy metals on health and quality of Oreochromis niloticus cultured in biofloc and earthen pond systems

Heavy metal contamination in aquaculture threatens fish health and consumer safety, with bioaccumulation differing between farming systems. The study compares heavy metal (Cd, Cr, Pb and Cu) contamination in fish feed, water and organs (muscle, gills and liver) of Nile tilapia (Oreochromis niloticus) from biofloc and pond farming systems. Samples were collected from ten biofloc tanks and ten earthen ponds, with heavy metals quantified using atomic absorption spectrophotometry. Heavy metal levels in fish feed were below permissible limits, while pond water showed significantly higher (P < 0.05) contamination than biofloc water. Pond-reared tilapia exhibited higher heavy metal accumulation in muscles, gills and liver compared to biofloc-reared fish. The liver showed the highest bioaccumulation, followed by gills, in both systems. Cd levels exceeded standard limits in the liver and gills of pond-reared fish. Principal component analysis (PCA) and cluster analysis revealed strong correlations between heavy metals in gills, water and liver, while muscles and feed formed a separate cluster. Pb, Cd and Cu were closely associated, suggesting a common contamination source. The health index (HI) for muscle was <1 in both systems, indicating safety for consumption. Overall, biofloc-reared tilapia was found safer for human consumption compared to pond-reared fish.

Carbon Cycling in Wetlands Under the Shadow of Microplastics: Challenges and Prospects

Wetlands are one of the most crucial ecosystems for regulating carbon sequestration and mitigating global climate change. However, the disturbance to carbon dynamics caused by microplastics (MPs) in wetlands cannot be overlooked. This review explores the impacts of MPs on the carbon cycles within wetland ecosystems, focusing on the underlying physicochemical and microbial mechanisms. The accumulation of MPs in wetland sediments can severely destabilize plant root functions, disrupting water, nutrient, and oxygen transport, thereby reducing plant biomass development. Although MPs may temporarily enhance carbon storage, they ultimately accelerate the mineralization of organic carbon, leading to increased atmospheric carbon dioxide emissions and undermining long-term carbon sequestration. A critical aspect of this process involves shifts in microbial community structures driven by selective microbial colonization on MPs, which affect organic carbon decomposition and methane production, thus posing a threat to greenhouse gas emissions. Notably, dissolved organic matter derived from biodegradable MPs can promote the photoaging of coexisting MPs, enhancing the release of harmful substances from aged MPs and further impacting microbial-associated carbon dynamics due to disrupted metabolic activity. Therefore, it is imperative to deepen our understanding of the adverse effects and mechanisms of MPs on wetland health and carbon cycles. Future strategies should incorporate microbial regulation and ecological engineering techniques to develop effective methodologies aimed at maintaining the sustainable carbon sequestration capacity of wetlands affected by MP contamination.

Response of sedimentary microbial community and antibiotic resistance genes to aged Micro(Nano)plastics exposure under high hydrostatic pressure

Several studies reported that the presence of microplastics (MPs)/nanoplastics (NPs) in marine environments can alter microbial community and function. Yet, the impact of aged MPs/NPs on deep sea sedimentary ecosystems under high hydrostatic pressure remains insufficiently explored. Herein, the sedimentary microbial community composition, co-occurrence network, assembly, and transfer of antibiotic resistance genes (ARGs) in response to aged MPs/NPs were investigated. Compared with the control, NPs addition significantly reduced bacterial alpha diversity (p < 0.05), whereas MPs showed no significant impact (p > 0.05). Moreover, networks under NPs exhibited decreased complexity than that under MPs and the control, including edges, average degree, and the number of keystone. The assembly of the microbial community was primarily governed by stochastic processes, and aged MPs/NPs increased the importance of stochastic processes. Moreover, exposure to MPs/NPs for one month decreased the abundance of antibiotic resistance genes (ARGs) (from 94.8 to 36.2 TPM), while exposure for four months increased the abundance (from 40.6 to 88.1 TPM), and the shift of ARGs in sediment was driven by both functional modules and microbial community. This study is crucial for understanding the stress imposed by aged MPs/NPs on sedimentary ecosystems under high hydrostatic pressure.

The synchronized dynamic release behavior of microplastics during farmland soil erosion process

Microplastics (MPs) are widespread in farmland soil. However, the risks associated with their loss through soil erosion remain unknown. This study investigates the occurrence and behavior of MPs in farmland soil in a southeastern coastal area of China, focusing on their synchronized dynamic release during soil erosion scenarios. The results showed that the abundance of MPs in the tested farmland soil ranged from 2.40 × 104 to 1.04 × 105 items·kg-1. MPs predominantly appear as fragments and particles, with sizes concentrated between 30 and 100 μm. During the process of soil erosion, characterized by rapid soil subsidence, the amount of MPs released into water bodies initially decreases, averaging a reduction of 1.08 × 104 items·kg-1. This is followed by an average increase of 1.89 × 104 items·kg-1. The competition between the adsorption, collision, and sedimentation of soil particles and the desorption and release of settled particles, determines this behavior. This pattern is strongly related to the physicochemical properties and mechanical composition of the soil. Deep learning predictions revealed that, without external influences, 49.42% of MPs in farmland soil could be synchronously released into water bodies during erosion. The analysis shows that MPs exhibit dynamic behavior in time and space, posing serious threats to aquatic ecosystems. Controlling soil erosion in farmland is crucial for the source management of MP migration.

Distribution, characteristics, and ecological risks of microplastics in the Hongyingzi sorghum production base in China

Microplastics (MPs), an emerging pollutant of global concern, have been studied in the Hongyingzi sorghum production base. In this study, we investigated MPs in the surface soil (0-10 cm) and deeper soil (10-20 cm) in the Hongyingzi sorghum production base. Pollution characterization and ecological risk evaluation were conducted. The results revealed that the MP abundance ranged from 1.31 × 102 to 4.27 × 103 particles/kg, with an average of 1.42 ± 1.22 × 103 particles/kg. There was no clear correlation between the MP abundance and soil depth, and the ordinary kriging method predicted a range of 1.26 × 103-1.28 × 103 particles/kg in most of the study area, indicating a relatively uniform distribution. Among the 12 types of MPs detected, acrylates copolymer (ACR), polypropylene (PP), polyurethane (PU), and polymethyl methacrylate (PMMA) were the most frequently detected. These MPs primarily originated from packaging and advertising materials made from polyurethane and polyester used by Sauce Wine enterprises, as well as plastic products made from polyolefin used in daily life and agricultural activities. The particle size of MPs was primarily 20-100 μm. Overall, the proportion of the 20-100 μm MP was 95.1% in the surface soil layer and 86.7% in the deeper soil layer. Based on the pollution load index, the MP pollution level in the study area was classified as class I. Polymer hazard index evaluation revealed that the risk levels at all of the sampling sites ranged from IV to V, and ACR, PU, and PMMA were identified as significant sources of polymer hazard. Potential ecological index evaluation revealed that most of the soil samples collected from the study area were dangerous or extremely dangerous, and the surface soil posed a greater ecological risk than the deeper soil. These findings provide a scientific foundation for the prevention, control, and management of MP pollution in the Hongyingzi sorghum production base.

Insight into the removal of nanoplastics and microplastics by physical, chemical, and biological techniques

Plastic pollutants create health crises like physical damage to tissues, upset reproductive processes, altered behaviour, oxidative stress, neurological disorders, DNA damage, gene expression, and disrupt physiological functions, as the biosphere accumulates them inadvertently through the food web. Water resources have become the generic host of plastic wastes irrespective of their particle size, resulting in widespread distribution in aquatic environments. The pre-treatment step of the traditional water treatment process can easily remove coarse-sized plastic wastes. However, the fine plastic particles, with sizes ranging from nanometres to millimetres, are indifferent to the traditional water treatment. To address the escalating problems, the upgradation of different traditional physical, chemical, and biological remediation techniques offers a promising avenue for tackling tiny plastic particles from the water environment. Further, new techniques and hybrid incorporations to the existing water treatment techniques have been explored, specifically removing tiny plastic debris. A detailed understanding of the sources, fate, and impact of plastic wastes in the environment, as well as an evaluation of the above treatment techniques and their limitations and challenges, can only show the way for their upgradation, hybridization, and development of new techniques. This review paper provides a comprehensive overview of the current knowledge and techniques for the remediation of nanoplastics and microplastics.

Hotspots lurking underwater: Insights into the contamination characteristics, environmental fates and impacts on biogeochemical cycling of microplastics in freshwater sediments

The widespread presence of microplastics (MPs) in aquatic environments has become a significant concern, with freshwater sediments acting as terminal sinks, rapidly picking up these emerging anthropogenic particles. However, the accumulation, transport, degradation and biochemical impacts of MPs in freshwater sediments remain unresolved issues compared to other environmental compartments. Therefore, this paper systematically revealed the spatial distribution and characterization information of MPs in freshwater (rivers, lakes, and estuaries) sediments, in which small-size (<1 mm), fibers, transparent, polyethylene (PE), and polypropylene (PP) predominate, and the average abundance of MPs in river sediments displayed significant heterogeneity compared to other matrices. Next, the transport kinetics and drivers of MPs in sediments are summarized, MPs transport is controlled by the particle diversity and surrounding environmental variability, leading to different migration behaviors and transport efficiencies. Also emphasized the spatio-temporal evolution of MPs degradation processes and biodegradation mechanisms in sediments, different microorganisms can depolymerize high molecular weight polymers into low molecular weight biodegradation by-products via secreting hydrolytic enzymes or redox enzymes. Finally, discussed the ecological impacts of MPs on microbial-nutrient coupling in sediments, MPs can interfere with the ecological balance of microbially mediated nutrient cycling by altering community networks and structures, enzyme activities, and nutrient-related functional gene expressions. This work aims to elucidate the plasticity characteristics, fate processes, and potential ecological impact mechanisms of MPs in freshwater sediments, facilitating a better understanding of environmental risks of MPs in freshwater sediments.

Response of microbial communities and biogeochemical cycling functions to sediment physicochemical properties and microplastic pollution under damming and water diversion projects

Understanding the interactions among flow-sediment, microorganisms, and biogeochemical cycles is crucial for comprehending the ecological response mechanisms of dams and water diversion. This study focused on the spatial patterns of carbon, nitrogen, phosphorus, and sulfur (CNPS) cycle functional genes in the water resource for the middle route of the South-to-North Water Diversion Project in China, specifically the Danjiangkou Reservoir (comprising the Han and Dan reservoirs). The investigation incorporated sediment physicochemical properties and microplastic pollution. Numerous microbial species were identified, revealing that microbial communities demonstrated sensitivity to changes in sedimentary mud content. The communities exhibited greater β diversity due to finer sediment particles in the Han Reservoir (HR), whereas in the Dan Reservoir (DR), despite having higher sediment nutrient content and MPs pollution, did not display this pattern. Regarding the composition and structure of microbial communities, the study highlighted that sediment N and P content had a more significant influence compared to particle size and MPs. The quantitative microbial element cycling (QMEC) results confirmed the presence of extensive chemolithotrophic microbes and strong nitrogen cycle activity stemming from long-term water storage and diversion operations. The denitrification intensity in the HR surpassed that of the DR. Notably, near the pre-dam area, biological nitrogen fixation, phosphorus removal, and sulfur reduction exhibited noticeable increases. Dam construction refined sediment, fostering the growth of different biogeochemical cycling bacteria and increasing the abundance of CNPS cycling genes. Furthermore, the presence of MPs exhibited a positive correlation with S cycling genes and a negative correlation with C and N cycling genes. These findings suggest that variations in flow-sediment dynamics and MPs pollution have significant impact the biogeochemical cycle of the reservoir.

Biofilms on Plastic Debris and the Microbiome

Plastic pollution has become a global environmental problem, and the large number of microorganisms attached to plastic debris in the environment has become a hot topic due to their rapid response to pollutants and environmental changes. In this study, we used high-throughput sequencing to investigate the microbial community structure of and explore the metagenome in the biofilm of two types of plastic debris, polystyrene (PS) and polyethylene terephthalate (PET), and compared them with a water sample collected at the sampling site. The phylum Proteobacteria dominated both the PET and PS samples, at 93.43% and 65.95%, respectively. The metagenome data indicated that the biofilm is enriched with a number of hydrocarbon (petroleum, microplastics, etc.) degrading genes. Our results show that the type of plastic determined the bacterial community structure of the biofilm, while the environment had relatively little effect.

Distribution characteristics and microbial synergistic degradation potential of polyethylene and polypropylene in freshwater estuarine sediments

The microbial degradation of polyethylene (PE) and polypropylene (PP) resins in rivers and lakes has emerged as a crucial issue in the management of microplastics. This study revealed that as the flow rate decreased longitudinally, ammonia nitrogen (NH4+-N), heavy fraction of organic carbon (HFOC), and small-size microplastics (< 1 mm) gradually accumulated in the deep and downstream estuarine sediments. Based on their surface morphology and carbonyl index, these sediments were identified as the potential hot zone for PE/PP degradation. Within the identified hot zone, concentrations of PE/PP-degrading genes, enzymes, and bacteria were significantly elevated compared to other zones, exhibiting strong intercorrelations. Analysis of niche differences revealed that the accumulation of NH4+-N and HFOC in the hot zone facilitated the synergistic coexistence of key bacteria responsible for PE/PP degradation within biofilms. The findings of this study offer a novel insight and comprehensive understanding of the distribution characteristics and synergistic degradation potential of PE/PP in natural freshwater environments.

Understanding microplastic pollution: Tracing the footprints and eco-friendly solutions

Microplastics (MPs) pollution has emerged as a critical environmental issue with far-reaching consequences for ecosystems and human health. These are plastic particles measuring <5 mm and are categorized as primary and secondary based on their origin. Primary MPs are used in various products like cosmetics, scrubs, body wash, and toothpaste, while secondary MPs are generated through the degradation of plastic products. These have been detected in seas, rivers, snow, indoor air, and seafood, posing potential risks to human health through the food chain. Detecting and quantifying MPs are essential to understand their distribution and abundance in the environment. Various microscopic (fluorescence microscopy, scanning electron microscopy) and spectroscopy techniques (FTIR, Raman spectroscopy, X-ray photoelectron spectroscopy) have been reported to analyse MPs. Despite the challenges in scalable removal methods, biological systems have emerged as promising options for eco-friendly MPs remediation. Algae, bacteria, and fungi have shown the potential to adsorb and degrade MPs in wastewater treatment plants (WWTPs) offering hope for mitigating this global crisis. This review examines the sources, impacts, detection, and biological removal of MPs, highlighting future directions in this crucial field of environmental conservation. By fostering global collaboration and innovative research a path towards a cleaner and healthier planet for future generations can be promised.

Polyethylene microplastics induced inflammation via the miR-21/IRAK4/NF-κB axis resulting to endoplasmic reticulum stress and apoptosis in muscle of carp

As a widespread environmental pollutant, microplastics pose a great threat to the tissues and organs of aquatic animals. The carp's muscles are necessary for movement and survival. However, the mechanism of injury of polyethylene microplastics (PE-MPs) to carp muscle remains unclear. Therefore, in this study, PE-MPs with the diameter of 8 μm and the concentration of 1000 ng/L were used to feed carp for 21 days, and polyethylene microplastic treatment groups was established. The results showed that PE-MPs could cause structural abnormalities and disarrangement of muscle fibers, and aggravate oxidative stress in muscles. Exposure to PE-MPs reduced microRNA (miR-21) in muscle tissue, negatively regulated Interleukin-1 Receptor Associated Kinase 4 (IRAK4), activated Nuclear Factor Kappa-B (NF-κB) pathway, induced inflammation, and led to endoplasmic reticulum stress and apoptosis. The present study provides different targets for the prevention of muscle injury induced by polyethylene microplastics.