Journal of environmental sciences最新文献

Polyhalogenated carbazoles (PHCZs) are recently raising much attention due to their toxicity and ubiquitous environmental distribution. However, little knowledge is known about their ambient occurrences and the potential source. In this study, we developed an analytical method based on GC-MS/MS to simultaneously determine 11 PHCZs in PM_2.5 from urban Beijing, China. The optimized method provided low method limit of quantifications (MLOQs, 1.45–7.39 fg/m³) and satisfied recoveries (73.4%–109.5%). This method was applied to analyze the PHCZs in the outdoor PM_2.5 (n = 46) and fly ash (n = 6) collected from 3 kinds of surrounding incinerator plants (steel plant, medical waste incinerator and domestic waste incinerator). The levels of ∑₁₁PHCZs in PM_2.5 ranged from 0.117 to 5.54 pg/m³ (median 1.18 pg/m³). 3-chloro-9H-carbazole (3-CCZ), 3-bromo-9H-carbazole (3-BCZ), and 3,6-dichloro-9H-carbazole (36-CCZ) were the dominant compounds, accounting for 93%. 3-CCZ and 3-BCZ were significantly higher in winter due to the high PM_2.5 concentration, while 36-CCZ was higher in spring, which may be related to the resuspending of surface soil. Furthermore, the levels of ∑₁₁PHCZs in fly ash ranged from 338 to 6101 pg/g. 3-CCZ, 3-BCZ and 36-CCZ accounted for 86.0%. The congener profiles of PHCZs between fly ash and PM_2.5 were highly similar, indicating that combustion process could be an important source of ambient PHCZs. To the best of our knowledge, this is the first research providing the occurrences of PHCZs in outdoor PM_2.5.

Perfluorinated or polyfluorinated compounds (PFCs) continue entering to the environmental as individuals or mixtures, but their toxicological information remains largely unknown. Here, we investigated the toxic effects and ecological risks of Perfluorooctane sulfonic acid (PFOS) and its substitutes on prokaryotes (Chlorella vulgaris) and eukaryotes (Microcystis aeruginosa). Based on the calculated EC₅₀ values, the results showed that PFOS was significantly more toxic to both algae than its alternatives including Perfluorobutane sulfonic acid (PFBS) and 6:2 Fluoromodulated sulfonates (6:2 FTS), and the PFOS-PFBS mixture was more toxic to both algae than the other two PFC mixtures. The action mode of binary PFC mixtures on Chlorella vulgaris was mainly shown as antagonistic and on Microcystis aeruginosa as synergistic, by using Combination index (CI) model coupled with Monte Carlo simulation. The mean risk quotient (RQ) value of three individual PFCs and their mixtures were all below the threshold of 10⁻¹, but the risk of those binary mixtures were higher than that of PFCs individually because of their synergistic effect. Our findings contribute to enhance the understanding of the toxicological information and ecological risks of emerging PFCs and provide a scientific basis for their pollution control.

CO₂ hydrogenation to methanol is a significant approach to tackle the problem of global warming and simultaneously meet the demand for the portable fuel. Cu-ZnO catalysts with various kinds of promoters have received wide attention. However, the role of promoter and the form of active sites in CO₂ hydrogenation are still in debate. Here, various molar ratios of ZrO₂ were added into the Cu-ZnO catalysts to tune the distributions of Cu⁰ and Cu⁺ species. A volcano-like trend between the ratio of Cu⁺/ (Cu⁺ + Cu⁰) and the amount of ZrO₂ is presented, among which the CuZn10Zr (the molar ratio of ZrO₂ is 10%) catalyst reaches the highest value. Correspondingly, the maximum value of space-time yield to methanol with 0.65 g_MeOH/(g_cat·hr) is obtained on CuZn10Zr at reaction conditions of 220°C and 3 MPa. Detailed characterizations demonstrate that dual active sites are proposed during CO₂ hydrogenation over CuZn10Zr catalyst. The exposed Cu⁰ takes participate in the activation of H₂, while on the Cu⁺ species, the intermediate of formate from the co-adsorption of CO₂ and H₂ prefers to be further hydrogenated to CH₃OH than decomposing into the by-product of CO, yielding a high selectivity of methanol.

Flame retardants (FRs) are ubiquitous in environment and biota and may pose harm to human health. In recent years, concern regarding legacy and alternative FRs has been intensified due to their widespread production and increasing contamination in environmental and human matrices. In this study, we developed and validated a novel analytical method for simultaneous determination of legacy and alternative FRs, including polychlorinated naphthalenes (PCNs), short- and middle-chain chlorinated paraffins (SCCPs and MCCPs), novel brominated flame retardants (NBFRs), and organophosphate esters (OPEs) in human serum. Serum samples were prepared by liquid-liquid extraction using ethyl acetate, and purified with Oasis® HLB cartridge and Florisil–silica gel columns. Instrumental analyses were carried out using gas chromatography-triple quadrupole mass spectrometry, high-resolution gas chromatography coupled with high-resolution mass spectrometry, and gas chromatography coupled with quadrupole time-of-flight mass spectrometry, respectively. The proposed method was validated for linearity, sensitivity, precision, accuracy, and matrix effects. Method detection limits for NBFRs, OPEs, PCNs, SCCPs, and MCCPs were 4.6 × 10^–4–8.6 × 10^–2, 4.3 × 10^–3–1.3, 1.1 × 10^–5–1.0 × 10^–4, 1.5, and 9.0 × 10^–1 ng/mL, respectively. Matrix spike recoveries ranged from 73%–122%, 71%–124%, 75%–129%, 92%–126%, and 94%–126% for NBFRs, OPEs, PCNs, SCCPs, and MCCPs, respectively. The analytical method was applied for detection of real human serum. CPs were the dominant FRs in serum, indicating CPs were widely presented in human serum and should be pay more attention for their health risk.

The effect of combined antibiotics exposure on nitrogen removal, microbial community assembly and proliferation of antibiotics resistance genes (ARGs) is a hotspot in activated sludge system. However, it is unclear that how the historical antibiotic stress affects the subsequent responses of microbes and ARGs to combined antibiotics. In this study, the effects of combined sulfamethoxazole (SMX) and trimethoprim (TMP) pollution on activated sludge under legacy of SMX or TMP stress with different doses (0.005-30 mg/L) were investigated to clarify antibiotic legacy effects. Nitrification activity was inhibited under higher level of combined exposure but a high total nitrogen removal (∼70%) occurred. Based on the full-scale classification, the legacy effect of past antibiotic stress had a marked effect on community composition of conditionally abundant taxa (CAT) and conditionally rare or abundant taxa (CRAT). Rare taxa (RT) were the keystone taxa in the microbial network, and the responses of hub genera were also affected by the legacy of antibiotic stress. Nitrifying bacteria and genes were inhibited by the antibiotics and aerobic denitrifying bacteria (Pseudomonas, Thaurea and Hydrogenophaga) were enriched under legacy of high dose, as were the key denitrifying genes (napA, nirK and norB). Furthermore, the occurrences and co-selection relationship of 94 ARGs were affected by legacy effect. While, some shared hosts (eg., Citrobacter) and hub ARGs (eg., mdtD, mdtE and acrD) were identified. Overall, antibiotic legacy could affect responses of activated sludge to combined antibiotic and the legacy effect was stronger at higher exposure levels.

Degradation of organic matter (OM) in sediments is a key link in nutrient cycling and sedimentation processes in lakes. The aim of this study was to explore the degradation of OM in surface sediments of a shallow lake (Baiyangdian Lake, China) under seasonal temperature variations. For this, we used the amino acid-based degradation index (DI) and the spatiotemporal distribution characteristics and sources of OM. Sediment OM in the lake mainly originated from freshwater aquatic plants and terrestrial C4 plants. The sediment at some sampling sites was affected by surrounding crops. The organic carbon and total nitrogen contents, and the total hydrolyzed amino acid concentrations in the sediments were highest in summer and lowest in winter. The lowest DI occurred in spring, which indicated that the OM in the surface sediment at this time was highly degraded and relatively stable, and the highest DI occurred in winter, which showed that the sediment was fresh. The water temperature was positively correlated with the organic carbon content (p < 0.01) and total hydrolyzed amino acids concentration (p < 0.05). Seasonal variations in the overlying water temperature had a large effect on OM degradation in the lake sediments. Our results will facilitate the management and restoration of lake sediments that suffer from endogenous release of OM in a warming climate.

Adenosine triphosphate (ATP) generation of aquatic organisms is often subject to nanoparticles (NPs) stress, involving extensive reprogramming of gene expression and changes in enzyme activity accompanied by metabolic disturbances. However, little is known about the mechanism of energy supply by ATP to regulate the metabolism of aquatic organisms under NPs stress. Here, we selected extensively existing silver nanoparticles (AgNPs) to investigate their implications on ATP generation and relevant metabolic pathways in alga (Chlorella vulgaris). Results showed that ATP content significantly decreased by 94.2% of the control (without AgNPs) in the algal cells at 0.20 mg/L AgNPs, which was mainly attributed to the reduction of chloroplast ATPase activity (81.4%) and the downregulation of ATPase-coding genes atpB and atpH (74.5%-82.8%) in chloroplast. Molecular dynamics simulations demonstrated that AgNPs competed with the binding sites of substrates adenosine diphosphate and inorganic phosphate by forming a stable complex with ATPase subunit beta, potentially resulting in the reduced binding efficiency of substrates. Furthermore, metabolomics analysis proved that the ATP content positively correlated with the content of most differential metabolites such as D-talose, myo-inositol, and L-allothreonine. AgNPs remarkably inhibited ATP-involving metabolic pathways, including inositol phosphate metabolism, phosphatidylinositol signaling system, glycerophospholipid metabolism, aminoacyl-tRNA biosynthesis, and glutathione metabolism. These results could provide a deep understanding of energy supply in regulating metabolic disturbances under NPs stress.

Rational design and synthesis of highly efficient and robust photocatalysts with positive exciton splitting and interfacial charge transfer for environmental applications is critical. Herein, aiming at overcoming the common shortcomings of traditional photocatalysts such as weak photoresponsivity, rapid combination of photo-generated carriers and unstable structure, a novel Ag-bridged dual Z-scheme g-C₃N₄/BiOI/AgI plasmonic heterojunction was successfully synthesized using a facile method. Results showed that Ag-AgI nanoparticles and three-dimensional (3D) BiOI microspheres were decorated highly uniformly on the 3D porous g-C₃N₄ nanosheet, resulting in a higher specific surface area and abundant active sites. The optimized 3D porous dual Z-scheme g-C₃N₄/BiOI/Ag-AgI manifested exceptional photocatalytic degradation efficiency of tetracycline (TC) in water with approximately 91.8% degradation efficiency within 165 min, outperforming majority of the reported g-C₃N₄-based photocatalysts. Moreover, g-C₃N₄/BiOI/Ag-AgI exhibited good stability in terms of activity and structure. In-depth radical scavenging and electron paramagnetic resonance (EPR) analyses confirmed the relative contributions of various scavengers. Mechanism analysis indicated that the improved photocatalytic performance and stability were ascribed to the highly ordered 3D porous framework, fast electron transfer of dual Z-scheme heterojunction, desirable photocatalytic performance of BiOI/AgI and synergistic effect of Ag plasmas. Therefore, the 3D porous Z-scheme g-C₃N₄/BiOI/Ag-AgI heterojunction had a good prospect for applications in water remediation. The current work provides new insight and useful guidance for designing novel structural photocatalysts for environment-related applications.

Decentralized treatment of wastewater in rural areas usually has several challenges, which include large fluctuations in pollutant concentration and water quantity, complicated operation and maintenance of conventional biochemical treatment equipment, resulting in poor stability and a low compliance rate of the wastewater treatment process. In order to solve the above problems, a new integration reactor is designed, which uses gravity and aeration tail gas self-reflux technology to realize the reflux of sludge and the nitrification liquid, respectively. The feasibility and operation characteristics of its application for decentralized wastewater treatment in rural areas are explored. The results demonstrated that, under constant influent, the device showed strong tolerance to the shock of pollutant load. The chemical oxygen demand, NH₄⁺-N, total nitrogen and total phosphorus fluctuated in the ranges of 95–715 mg/L, 7.6–38.5 mg/L, 9.32–40.3 mg/L and 0.84–4.9 mg/L, respectively. The corresponding effluent compliance rates were 82.1%, 92.8%, 96.4% and 96.3%, respectively. When the wastewater discharge was non-constant and the maximum single-day Q_max/Q_min reached 5, all indicators of the effluent met the relevant discharge standard. The integrated device also demonstrated high phosphorus enrichment levels in its anaerobic zone; the concentration of phosphorus reached a maximum of 26.9 mg/L, which created a good environment for phosphorus removal. The microbial community analysis showed that sludge digestion, denitrification, and phosphorus-accumulating bacteria all played an important role in pollutant treatment.

The eutrophication of lakes is a global environmental problem. Regulating nitrogen (N) and phosphorus (P) on phytoplankton is considered to be the most important basis of lake eutrophication management. Therefore, the effects of dissolved inorganic carbon (DIC) on phytoplankton and its role in mitigating lake eutrophication have often been overlooked. In this study, the relationships between phytoplankton and DIC concentrations, carbon isotopic composition, nutrients (N and P), and hydrochemistry in the Erhai Lake (a karst lake) were investigated. The results showed that when the dissolved carbon dioxide (CO_2(aq)) concentrations in the water were higher than 15 µmol/L, the productivity of phytoplankton was controlled by the concentrations of TP and TN, especially by that of TP. When the N and P were sufficient and the CO_2(aq) concentrations were lower than 15 µmol/L, the phytoplankton productivity was controlled by the concentrations of TP and DIC, especially by that of DIC. Additionally, DIC significantly affected the composition of the phytoplankton community in the lake (p<0.05). When the CO_2(aq) concentrations were higher than 15 µmol/L, the relative abundance of Bacillariophyta and Chlorophyta was much higher than those of harmful Cyanophyta. Thus, high concentrations of CO_2(aq) can inhibit harmful Cyanophyta blooms. During lake eutrophication, when controlling N and P, an appropriate increase in CO_2(aq) concentrations by land-use changes or pumping of industrial CO₂ into water may reduce the proportion of harmful Cyanophyta and promote the growth of Chlorophyta and Bacillariophyta, which may provide effectively assist in mitigating water quality deterioration in surface waters.