Polystyrene microplastics accumulation in lab-scale vertical flow constructed wetlands: impacts and fate

Management strategies to reduce microbial mercury methylation in constructed wetlands: Potential routes and future challenges

Constructed wetlands (CWs) are widely recognized as the potential hotspots for producing highly toxic methylmercury (MeHg). This presents an obstacle to the widespread application of CWs. A comprehensive discussion on strategies to control mercury methylation in CWs is currently lacking. This review highlighted the potential impacts of differences in oxygen supply and consumption in various CWs, the characteristics of influent quality, the interactions between different substrates and mercury (including mercury adsorption, reduction), and plants on microbial mercury methylation in CWs. We also proposed the potential strategies for human intervention in regulating or controlling microbial mercury methylation in CWs, including oxygenation, nitrate inhibition, selection of substrates with high adsorption capacity, weak reducibility and low organic matter release, and plant management. Knowledge summarized in this review would help achieve a comprehensive understanding of various research gaps in previous studies and point out future research directions by focusing on CWs types, influent quality, substrates selection and plants management, to reduce the mercury methylation in CWs.

The substrate configuration influences pollutant removal in constructed wetlands: From the aspects of submerged status of substrate and carbon-felt distribution

Redox regulation dominates the pollutant removal in constructed wetlands (CWs). To enhance efficient and cost-effective nitrogen removal, this study intended to build an unsaturated zone and add carbon-felt material for electron donor/acceptor adjustment. The unsaturated zone heights (0, 10, 20 cm) and carbon-felt distribution patterns (evenly scattered (CWSE), continuously linked (CWL), and head-tail linked like microbial fuel cells (CWMFC)) were simultaneously adjusted. Moreover, their effects and underlying microbial mechanisms on water purification were investigated. Results indicated that CWs with a 20 cm unsaturated zone achieved over 99 % ammonia nitrogen removal. CWSE facilitated optimal pollutant-microbe contact, enabling efficient in-situ electron utilization for 64.27 % total nitrogen removal through simultaneous nitrification-denitrification and anammox. In CWL, continuous carbon-felt distribution allowed efficient electron transport at a relatively macro-area and enhanced electron consumption by oxygen at the surface, leading to superior ammonia oxidation (82.97 %) in the middle area of CWL. Conversely, CWMFC facilitated direct electron transfer through the whole CW, enriched Geobacter at the top and Vibrio at the bottom, achieving 84.23 % total nitrogen removal through nitrification-denitrification under high oxygenation. This study elucidated microbial community niche differentiation in CWs mediated by carbon-felt electron transport and proposed optimal application scenarios for different carbon-felt configurations.

Effects of multi-microplastic mixtures on the performance of constructed wetland microbial fuel cells for wastewater treatment

This study examined the effects of microplastics (MPs) on constructed wetland (CW) and constructed wetland microbial fuel cell (CW-MFC) with different configurations. Four mixed MP types including polyethylene, polypropylene, polystyrene, and polyvinyl chloride were introduced. Planted CW-MFC demonstrated the highest MP removal efficiency of 96.7 % and power density of 14.90 mW m-2, outperforming both unplanted CW-MFC and conventional CW. MPs had minimal impact on COD removal, but the removal efficiencies of NH4+-N and TN were significantly inhibited, with TN removal decreasing by approximately 20 % compared to MP-free conditions. TP removal initially decreased but later increased, remaining slightly lower than pre-MP levels. Reduced chlorophyll content in plant leaves indicated MP-induced stress on plant growth. Microbial analysis revealed dominant phyla including Proteobacteria, Patescibacteria, and Bacteroidota contributed to nitrogen removal. In planted systems, genera such as Denitratisoma, Sulfuritalea, and Endomicrobium contributed to denitrification. In CW-MFCs, Geobacter and Candidatus Falkowbacteria dominated, with Geobacter linked to electricity generation and Candidatus Falkowbacteria associated with carbon and nitrogen cycles. MPs negatively affected denitrification by suppressing key denitrifiers such as Denitratisoma but enhanced electricity generation by enriching electroactive bacteria like Geobacter. These findings reveal complex MP-driven interactions influencing microbial communities and system performance.

The influencing mechanisms of different characteristics of polystyrene microplastics on Saccharomyces cerevisiae: functional group, particle size and dosage

ABSTRACTBased on the well-documented hazards of microplastics and the importance and typicality of Saccharomyces cerevisiae (S. cerevisiae) in the environment, in this study, the influencing mechanisms of functional group, particle size and dosage of polystyrene microplastics (PS MPs) on S. cerevisiae were studied systematically. The results showed that compared with the bigger particle size and lower concentration of carboxylated PS MPs, the smaller particle size and higher concentration of aminated PS MPs had the most serious inhibition of the growth of S. cerevisiae, and their cell morphology was more abnormal, the more PS MPs attached to the yeast cells. The results of orthogonal experiment showed that the inhibitory effects of PS MPs on S. cerevisiae followed the order: functional groups > concentrations > particle sizes. Through the analysis of the antioxidant properties of S. cerevisiae, it was found that the activities of superoxide dismutase and catalase were first stimulated and then inhibited, and the concentrations of superoxide dismutase enzymes in the environment with bigger particle size and lower concentration of PS MPs was higher than that in the environment with smaller particle size and higher concentrations of PS MPs. catalase enzyme showed an opposite trend in particle sizes and a similar trend in concentrations. The concentrations of malondialdehyde increased with the increase of PS MPs concentrations and the decrease of particle sizes, indicating that PS MPs could induce S. cerevisiae to produce a large amount of reactive oxygen species, resulting in severe oxidative damage to S. cerevisiae.

Co-Exposure to Polystyrene Microplastics and Bisphenol A Contributes to the Formation of Liver Fibrosis in Mice through Inhibition of the BMAL1/E-Cad Signaling Pathway

The food safety risks posed by exposure to polystyrene microplastics (PS-MPs) and bisphenol A (BPA) have become an issue worldwide. However, the toxic effects of PS-MPs and BPA coexposure on the mammalian liver remain elusive. In this study, we found that PS-MPs and BPA coexposure have synergistic toxic effects on AML12 cells and the mouse liver. Histopathological staining revealed excessive accumulation of the extracellular matrix in the coexposure liver. Co-exposure to PS-MPs and BPA downregulated Bmal1 and E-cad both in vitro and in vivo. Additionally, Bmal1-/- AML12 cells and liver-specific Bmal1-/- mice exhibited significantly reduced E-cad levels, with no significant reduction under PS-MPs and BPA coexposure. Notably, overexpression of BMAL1 and CLOCK significantly enhanced luciferase activity driven by the E-cad gene intron region (containing an E-box cis-element). These results demonstrated that coexposure to PS-MPs and BPA contributed to the development of liver fibrosis by inhibiting the BMAL1/E-cad signaling pathway.

Effect of polystyrene micro/nanoplastics on PCBs removal in constructed wetlands planted with Myriophyllum aquaticum

The co-occurrence of microplastics (MPs) and nanoplastics (NPs) with polychlorinated biphenyls (PCBs) is an emerging environmental concern. Wetland plants, with their unique anaerobic-aerobic environments, offer a promising approach for PCBs removal. However, the impact of MPs and NPs on PCBs dynamics in constructed wetlands is not well understood. This study examined the influence of polystyrene MPs and NPs of two different sizes on PCBs fate in constructed wetlands featuring Myriophyllum aquaticum. Results showed that although there was no significant difference in overall PCBs removal rates, the presence of MPs increased residues of highly chlorinated PCBs from 331 μg/kg to 379 μg/kg, while the presence of NPs increased residues of lightly chlorinated PCBs from 125 μg/kg to 153 μg/kg. Additionally, MPs and NPs increased plant uptake of PCBs from 0.08% to 0.10-0.14%, despite potential inhibition of plant growth. While MPs/NPs elevated microorganism counts, they did not affect microbial diversity or community structure. Importantly, MPs significantly inhibited the main PCB-dechlorinating bacteria (Dehalococcoidia) and had a greater impact on PCB-degrading enzymes (dioxygenase, K03381) compared to NPs. This study highlights the complex interactions between MPs/NPs and PCBs in wetland environments and their implications for bioremediation strategies.

Research progress on the origin, fate, impacts and harm of microplastics and antibiotic resistance genes in wastewater treatment plants

Previous studies reported microplastics (MPs), antibiotics, and antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs). There is still a lack of research progress on the origin, fate, impact and hazards of MPs and ARGs in WWTPs. This paper fills a gap in this regard. In our search, we used "microplastics", "antibiotic resistance genes", and "wastewater treatment plant" as topic terms in Web of Science, checking the returned results for relevance by examining paper titles and abstracts. This study mainly explores the following points: (1) the origins and fate of MPs, antibiotics and ARGs in WWTPs; (2) the mechanisms of action of MPs, antibiotics and ARGs in sludge biochemical pools; (3) the impacts of MPs in WWTPs and the spread of ARGs; (4) and the harm inflicted by MPs and ARGs on the environment and human body. Contaminants in sewage sludge such as MPs, ARGs, and antibiotic-resistant bacteria enter the soil and water. Contaminants can travel through the food chain and thus reach humans, leading to increased illness, hospitalization, and even mortality. This study will enhance our understanding of the mechanisms of action among MPs, antibiotics, ARGs, and the harm they inflict on the human body.

Microplastics removal mechanisms in constructed wetlands and their impacts on nutrient (nitrogen, phosphorus and carbon) removal: A critical review

Microplastics (MPs) are now prevalent in aquatic ecosystems, prompting the use of constructed wetlands (CWs) for remediation. However, the interaction between MPs and CWs, including removal efficiency, mechanisms, and impacts, remains a subject requiring significant investigation. This review investigates the removal of MPs in CWs and assesses their impact on the removal of carbon, nitrogen, and phosphorus. The analysis identifies crucial factors influencing the removal of MPs, with substrate particle size and CWs structure playing key roles. The review highlights substrate retention as the primary mechanism for MP removal. MPs hinder plant nitrogen uptake, microbial growth, community composition, and nitrogen-related enzymes, reducing nitrogen removal in CWs. For phosphorus and carbon removal, adverse effects of MPs on phosphorus elimination are observed, while their impact on carbon removal is minimal. Further research is needed to understand their influence fully. In summary, CWs are a promising option for treating MPs-contaminated wastewater, but the intricate relationship between MPs and CWs necessitates ongoing research to comprehend their dynamics and potential consequences.