Journal of Environmental Sciences-china最新文献

Freshwater lakes globally are witnessing an escalation in the frequency and intensity of cyanobacterial harmful blooms. However, underlying factors influencing the succession or coexistence of cyanobacteria, especially filamentous ones, remain poorly understood. Lake Honghu, a Ramsar Wetland of International Importance with degrading aquatic ecological quality, served as a case study to elucidate the intricate relationship between environmental changes and cyanobacterial dynamics. Our analysis revealed a significant increase in the dominance of filamentous cyanobacteria, marked by high spatiotemporal variability in community structure. This dominance of filamentous diazotrophic cyanobacteria is attributed to a decrease in the ratio of dissolved inorganic nitrogen to total phosphorus and their capacity to utilize organic phosphorus in phosphorus-deficient conditions. Species-specific density variations were linked to diverse environmental factors, with total nitrogen or total phosphorus concentration remaining as a crucial factor influencing dominant cyanobacterial density fluctuations. The dominance of low-temperature-tolerant Aphanizomenon and Pseudanabaena was evident in spring and winter, whereas Dolichospermum and Cylindrospermopsis, which prefer higher temperatures, thrived in summer and autumn. Additionally, non-algal turbidity and heterogeneity can potentially alter the competitive outcome among filamentous cyanobacteria or foster coexistence under conditions of elevated temperatures and nutrient limitation. This study predicts that filamentous cyanobacteria may spread and persist in lakes spanning a wide trophic range. Current findings enhance our comprehension of the dynamic responses exhibited by filamentous bloom-forming cyanobacteria in the face of environmental changes within shallow eutrophic lakes and provide valuable insights for lake managers involved in the remediation of degraded shallow lakes.

Anaerobic ammonium oxidation coupled to iron(III) reduction (Feammox) process has recently been recognized as an important pathway for removing ammonium in various natural habitats. However, our understanding for Feammox in river–estuary continuum is limited. In this study, stable isotope tracers and high-throughput amplicon sequencing were employed to determine Feammox rates and identify associated microbial communities in sediments along the Yangtze river–estuary continuum. Feammox rates averaged 0.0058 ± 0.0069 mg N/(kg·d) and accounted for approximately 22.3% of the ammonium removed from the sediments. Sediment Fe(III), ammonium (NH₄⁺), total organic carbon (TOC), and pH were identified as important factors influencing Feammox rates. Additionally, Spirochaeta, Caldilineaceae_uncultured, and Ignavibacterium were found potentially associated with Feammox, which had not been documented as Feammox-associated microbial taxa previously. This study demonstrates that Feammox plays a vital role in ammonium removal within the Yangtze river–estuary continuum, providing greater insight into nitrogen removal and cycling in aquatic ecosystems.

Two kinds of oxide-zeolite composite support, Ce-beta and Zr-beta were prepared by a simple wet impregnation method and adopted for the preparation of palladium-based catalysts for catalytic oxidation of methane. The Pd/6.8Zr-beta catalyst showed superior methane oxidation performance, achieving T₅₀ and T₉₀ of 417 °C and 451 °C, respectively, together with robust hydrothermal stability. Kinetic analysis has shown that incorporating Zr into the catalyst significantly enhanced its efficiency, nearly tripling the turnover frequency (TOF) for methane combustion compared to the Pd/beta catalyst. This enhanced performance was attributed to the dispersion of Zr on the zeolite surface, which not only promoted the formation of active PdO sites but also helped maintain the high Pd²⁺ content via facilitating the oxygen migration during the reaction, thus improving both the catalyst's activity and stability. In the Pd/8.6Ce-beta catalyst, doped CeO₂ tended to aggregate in the zeolite's pores, adversely affecting the catalyst's efficiency. This aggregation promoted the formation of inactive Pd⁴⁺ species, a result of the enhanced metal-support interaction. This finding is critical for understanding the implications of dopant selection in the design of high-activity methane oxidation catalysts.

Manganese (Mn) has been characterized as an environmental pollutant. Excessive releases of Mn due to human activities have increased Mn levels in the environment over the years, posing a threat to human health and the environment. Long-term exposure to high concentrations of Mn can induce neurotoxicity. Therefore, toxicological studies on Mn are of paramount importance. Mn induces oxidative stress through affecting the level of reactive oxygen species (ROS), and the overabundance of ROS further triggers ferroptosis. Additionally, Mn²⁺ was found to be a novel activator of the cyclic guanosine-adenosine synthase (cGAS)−stimulator of interferon genes (STING) pathway in the innate immune system. Thus, we speculate that Mn exposure may promote ROS production by activating the cGAS−STING pathway, which further induces oxidative stress and ferroptosis, and ultimately triggers Mn neurotoxicity. This review discusses the mechanism between Mn-induced oxidative stress and ferroptosis via activation of the cGAS−STING pathway, which may offer a prospective direction for future in-depth studies on the mechanism of Mn neurotoxicity.

In eutrophic shallow lakes, cyanobacterial blooms will occur frequently and then settle into sediment, leading the formation of fluid sediment. Several factors including temperature can influence surface sediment properties. In this study, the influence of temperatures on surface sediment properties was determined in microcosm experiments through monitoring sediment physicochemical and rheological properties. During one-month incubation, it was found that surface sediment density and water content varied exponentially with increase in temperatures from 10 to 35 ℃. The results of particle size distribution indicated that cyanobacterial blooms biomass (CBB) degradation in sediment led to sediment flocculation and agglomeration. In the meantime, there were high ratios polysaccharide/protein in extracellular polymeric substances (EPSs), which enhanced the sediment particle agglomeration. Further, the yield stress in rheological test for sediment with (R² = 0.97) and without (R² = 0.85) CBB presented an exponential decay with increase in temperatures. And a threshold value at 20 ℃ for sediment critical shear stress (τ_cr) indicated that sediment could be resuspended easier when temperature was more than 20 ℃. Altogether, this study showed that the increase in temperatures with a threshold at 20 ℃, can cause sediment particle flocculation, resulting in a loose and fragile structure. And the results would be helpful to sediment management considering environmental effects of sediment suspension for eutrophication shallow lakes.

Vertical detection of volatile organic compounds (VOCs) is essential to expend our understanding of the distribution characteristics of VOCs and improve the predictive ability of existing air quality models. In this work, we report the development of a sorbent tube sampler based on an unmanned aerial vehicle (UAV) platform. Vertical profile measurement of VOCs with a vertical resolution of 25 m was achieved. The sampler consists of five lightweight VOC sorbent tubes and a 5-way solenoid valve, making it available for collecting five atmospheric VOC samples in a single flight with a time response of less than 30 min. The sampler weighed ∼ 1.45 kg and had dimensions of 240 mm × 220 mm × 100 mm with small penetration loss (< 10%) under 4-liter sampling conditions (flow rate of 200 mL/min). Commercialized SUMMA canisters were used as experimental controls to investigate the possible loss of self-made sampler for target compounds in the same sampling process. Comparison experiment on the ground showed that the concentration differences for all VOC species were lower than 0.14 μg/m³, proving the good reliability for VOCs measurements using sorbent tube sampler. The UAV platform also incorporated online instruments for meteorological parameters and O₃ measurement. The sampler was successfully applied to characterize the vertical profiles of VOCs up to 100 m in October 2023 in the Huaihe River Basin of China. The UAV platform and the sorbent tube sampler demonstrate good performance and will be a valuable and reliable tool for vertical VOCs measurement.

Anaerobic ammonia oxidation (Anammox) is an economical and sustainable wastewater nitrogen removal technology, and its application in the mainstream process is the inevitable trend of the development of Anammox. However, how to effectively enriching Anammox bacteria from the activated sludge remains challenging and restricts its extensive applications. In this study, the rapid and efficient enrichment of Anammox bacteria was achieved by raising the reflux ratio and nitrogen loading rate (NLR) using conventional activated sludge as the inoculant. In the screening phase (days 1–90), the reflux ratio was increased to discharge partial floc sludge, resulting in the relative abundance of Candidatus Brocadiaceae increased from 0.04% to 22.54%, which effectively reduced the matrix and spatial competition between other microorganisms and Anammox bacteria. On day 90, the stoichiometric ratio of the Anammox process closely approached the theoretical value of 1:1.32:0.26, indicating that the Anammox reaction was the primary nitrogen removal process in the system. In the enrichment phase (days 91–238), the NLR increased from 0.43 to 1.20 kgN/(m³·d) and removal efficiency was 71.89%, resulting in the relative abundance of Candidatus Brocadiaceae increased to 61.27% on day 180. The reactor operated steadily from days 444 to 498, maintaining the nitrogen removal rate (NRR) of 3.00 kgN/(m³·d) and achieving successful sludge granulation with the particle size of 392.4 µm. In short, this study provided a simple and efficient approach for enriching Anammox bacteria from the activated sludge, supporting to start an Anammox process efficiently.

Magnetic iron oxide nanoparticles (Fe_xO_y NPs, mainly Fe₃O₄ and γ-Fe₂O₃) are nanomaterials ubiquitously present in aquatic, terrestrial, and atmospheric environments, with a high prevalence and complex sources. Over the past decade, numerous reports have emerged on the presence of exogenous particles in human body, facilitated by the rapid development of separation and detection methods. The health risk associated with magnetic Fe_xO_y NP have garnered escalating attention due to their presence in human blood and brain tissues, especially for their potential association with neurodegenerative diseases like Alzheimer's disease. In this paper, we provide a comprehensive overview of sources, analysis methods, environmental impacts, and health risks of magnetic Fe_xO_y NP. Currently, most researches are primarily based on engineered Fe_xO_y NP, while reports about magnetic Fe_xO_y NP existing in real-world environments are still limited, especially for their occurrence levels in various environmental matrices, environmental transformation behavior, and biotoxic effects. Our study reviews this emerging pollutant, providing insights to address current research deficiencies and chart the course for future studies.

Highly dispersed noble metals are acknowledged for its pivotal role in influencing the efficiency of catalysts during the HCHO oxidation process. Interestingly, in this work, an innovative approach was employed to augmenting the stabilization of noble metals on irreducible carriers supported noble metal catalyst (Pd/SiO₂) by adding alkali metal potassium (K). A formidable promotion effect was observed when the K doping to Pd/SiO₂ catalysts. It achieves a conversion rate of 93% for 270 ppmV of HCHO to harmless CO₂ and H₂O at a weight hourly space velocity (WHSV) of 300,000 mL/(g·hr) at 25°C. Multiple characterization results illustrated that a strong interaction between added K and Pd species was formed after K addition, which not only stabilized Pd species on the carrier surface but also markedly enhanced its dispersal on the SiO₂ carrier. The increasing Pd dispersion induced more oxygen vacancies on the surfaces of the Pd/SiO₂ catalysts. The formation of these oxygen vacancies can be attributed to the phenomenon of hydrogen spillover, which also contributed to elevating the electron density on the Pd sites. Meanwhile, the oxygen vacancies favored the O₂ activation to form more reactive oxygen species participating in the HCHO oxidation reaction, thus improving the performance of Pd/SiO₂ catalysts displayed for HCHO oxidation. This study provides a simple strategy to design high-performance irreducible carriers supported noble metal catalysts for HCHO catalytic oxidation.

Monotonic pore size and particles inseparability of metal-organic frameworks (MOFs) caused serious effects on its light absorption ability and charge separation, restricting its application for antibiotic such as levofloxacin (LEV) degradation in water. In this study, a magnetically detachable nano-photocatalyst (ZnFe₂O₄@MIL-88A(Fe)) was synthesized using a simple two-step hydrothermal technique. The morphology and microstructure analyses showed that n-type ZnFe₂O₄ catalyst particles were efficiently assembled onto the surface of MIL-88A(Fe) crystal. Photocatalytic activity studies indicated that the ZnFe₂O₄@MIL-88A(Fe) plus H₂O₂ exhibiting a significantly boosted photo-Fenton activity toward LEV at visible light irradiation, compared to the pure ZnFe₂O₄ and MIL-88A(Fe), the degradation efficiency accordingly reached up to nearly 82% and 25% within 60 min. This excellent photocatalytic performance was ascribed to the synergistic effects of the heterogeneous structure of ZnFe₂O₄ and MIL-88A(Fe), whereby the efficient separation of charge carriers in the catalytic system is mutually reinforced with the efficient reduction of Fe³⁺ and Fe²⁺. Meanwhile, the degradation mechanism and intermediates of LEV during the photo-Fenton reaction process were also studied in depth through free radical burst, electron paramagnetic resonance, and mass spectrometry analyses, etc. Additionally, the ZnFe₂O₄@MIL-88A(Fe) composite catalyst displayed significant stability and ease of separation, indicating potential for the photo-oxidative degradation of organic pollutants.