Analyzing the spatiotemporal variation and influencing mechanisms of dry deposition is crucial for identifying pollution sources, atmospheric pollution control, soil environmental management, and agricultural pollution prevention. Focusing on the Xiangjiang River Basin, a vital grain producing region in China, this study estimated PM_2.5 dry deposition fluxes using empirical parameterization formulas and multi-source data, including remote sensing PM_2.5 concentrations, ERA5 reanalysis meteorological data, and ground-based monitoring. The long-term spatiotemporal characteristics of dry deposition across the basin and three zones delineated by three lines for land use (agricultural zones, ecological preservation zones, and urban development zones) were investigated. Furthermore, the random forest model was employed to quantify the contributions of influencing factors and elucidated the dominant mechanisms driving dry deposition. Results show thatthe dry deposition fluxes presented a spatial pattern of high in the north and central areas, low in the south and periphery. Urban development zones had the highest dry deposition flux (1.42g/m²), followed by agricultural zones (1.06g/m²) and ecological preservation zones (0.80g/m²). Since 2000, dry deposition fluxes have shown a declining trend at a rate of -0.017g/(m²·a), with significant decreases in high PM_2.5 concentration areas. Residential emissions (2.43±0.04), air temperature (0.71±0.01), industrial emissions (0.69±0.02), and relative humidity (0.59±0.01) were identified as dominant factors influencing PM_2.5 dry deposition. Considering the spatial heterogeneity of mechanisms in influencing factors, tailored atmospheric pollution control measures are recommended to achieve targeted pollution mitigation.

In order to investigate the impact of future climate change on high temperatures and ozone pollution, summer temperatures and O₃ concentrations for different years in the 21st century were simulated using downscaling based on the CMIP6-WRF/Chem model. The results of the study indicated that, in comparison with 2014, the rate of temperature increased in typical cities within the Beijing-Tianjin-Hebei region would slow down by 2100 under the SSP2-4.5 scenario with peak warming rates of 0.29℃/decade, 0.46℃/decade, and 0.33℃/decade for Beijing, Tianjin, and Shijiazhuang respectively. Under the SSP5-8.5 scenario, warming accelerated markedly, with rates of 0.63℃/decade, 0.80℃/decade, and 0.72℃/decade for the three cities. Under both scenarios, daily average O₃ concentrations and MDA8O₃ concentrations in Beijing, Tianjin, and Shijiazhuang all exhibited increasing trends, with growth rates of 1.1μg/(m³·decade), 1.5μg/(m³·decade) and 0.9μg/(m³·decade), and 1.2μg/(m³·decade), 1.3μg/(m³·decade) and 1.1 μg/(m³·decade), respectively. However, the number of days exceeding O₃ standards exhibited differing patterns, potentially linked to variations in O₃ concentrations between hot and non-hot days. Non-hot-day O₃ concentrations exhibited an increasing trend across all cities, with the largest increment occurring in Beijing under the SSP5-8.5 scenario by 2035, rising by 12.9μg/m³. Conversely, O₃ concentrations decreased to varying degrees on high-temperature days, with the largest reduction occurring in Tianjin under the SSP2-4.5 scenario by 2100, decreasing by 13.9μg/m³. Under all scenarios, Tianjin's temperature penalty factor was lower than in 2014, indicating a consistent high-temperature suppression effect on O₃ across scenarios and years. The influence of air temperature on O₃ is non-linear, and relative humidity may modulate the relationship between high temperatures and O₃ concentrations.

Using the hourly atmospheric visibility and relative humidity observations in Chengdu from October to December 2017, along with simultaneous data of black carbon (BC), particulate matter (PM), and nitrogen dioxide (NO₂) mass concentrations, the response of aerosol extinction coefficients to the changes of multiple factors was analyzed through correlation analysis, variance inflation factor analysis and the GAM model. The results revealed that the explanatory variable set for aerosol extinction coefficients included ρPM_2.5, RH, ρBC/ρPM_2.5, ρPM₁/ρPM_2.5, and ρPM_2.5/ρPM₁₀ (where ρBC, ρPM₁, ρPM_2.5, and ρPM₁₀ represent the mass concentrations of BC, PM₁, PM_2.5, and PM₁₀, respectively). Each variable demonstrated a significant nonlinear relationship with aerosol extinction coefficients. Compared to traditional bivariate models, the multivariate GAM model incorporating ρPM_2.5, RH, ρBC/ρPM_2.5, ρPM₁/ρPM_2.5, and ρPM_2.5/ρPM₁₀ as explanatory variables significantly improved simulation accuracy, particularly in reducing high-humidity-related biases. The adjusted R² values of the GAM models were 0.659, 0.683, 0.738, and 0.938 for slight, light, moderate, and heavy haze conditions, respectively. The coefficient of determination (R²) values were 0.686, 0.737, 0.777, and 0.961, with mean relative errors (MRE) of 0.091, 0.041, 0.071, and 0.016. The above results revealed the complexity of the multifactorial influence of the aerosol extinction coefficient and its intrinsic relationship with the change of haze intensity.

Assessment of photochemical losses is essential for characterizing VOC pollution and apportioning its sources. Continuous online monitoring of VOCs was conducted in urban Wuhan from September 8 to 18, 2021, capturing two ozone pollution episodes with active photochemical reactions. The parameterized method based on photochemical age was employed to correct observed VOC concentrations (Ob) for photochemical losses, deriving initial concentrations (In) for pollution characterization. Source apportionment was performed using the Positive Matrix Factorization (PMF) model. Results indicate that alkenes exhibited the highest photochemical loss concentrations and ozone formation potential (OFP) among VOC categories, identifying them as key species governing ozone pollution. PMF analysis based on initial and observed values identified six major emission sources with concentration contributions (initial, observed) as follows: vehicle emissions (16.5%, 17.7%), industrial chemical emissions (14.7%, 13.7%), biogenic sources (4.6%, 4.0%), combustion sources (20.2%, 33.1%), LPG/NG usage (21.1%, 18.9%), and solvent use (22.9%, 12.6%). The PMF results were significantly influenced by photochemical reactions, underscoring the necessity of employing initial VOC concentrations in source apportionment to avoid underestimating contributions from solvent use, LPG/NG sources, biogenic emissions, and industrial chemical sources.

The present study took the two typical haze/fog low visibility episodes in Tianjin as a point of departure for the following investigation, developed data assimilation methods applicable to visibility observations, in order to improve the numerical forecast effect of visibility through the simulation optimization of PM_2.5 concentration, relative humidity and fog water content. Theresults showed that the visibility change of typical haze episode was primarily influenced by PM_2.5 concentration, the minimum value of visibilitywas approximately 1km, with the daily change about 2~3km in the result of relative humidity change. The relative humidity of the haze-fog mixing episode was high, and visibility was lower than 50min localities due to the significant influence of fog during nighttime. The typical characteristic of the haze-fog episode were largedaily change and extreme value being low in visibility. The simulation of haze-fog low visibilitywas significantly enhanced with assimilation of visibility observation, root mean square error of the two episodes reduced from 7km and 4km to approximately 2km. Furthermore, the simulation deviation was corrected in time with 6-hour interval assimilation, with an enhancement effect observed to be more pronounced during specific time periods. Through the assimilation to achieve the optimization of the PM_2.5 concentration and the relative humidity simulation, the deviation of the haze visibility simulation was reduced by a maximum of 6~8km.By adding fog water content correction, combined with relative humidity assimilation improvement, the underestimate of fog water content was reduced during nocturnal periods, the visibility simulation deviation was reduced from 1~2km to 300~500m and the degree and range of the low visibility was significantly improved. One-month simulation showed that the root mean square error of visibility below 10 km was reduced from 4.4 km to 3.2 km.

Based on high-resolution measurements of aerosol number concentration and meteorological data that had been obtained at Tangkou Meteorological Station on Mts. Huangshan from April to June 2023, the wet scavenging efficiency of submicron aerosol particles (with a particle diameter range of 0.01~1μm) across the four modes (nucleation mode, Aitken mode, condensation mode, and droplet mode) and its influencing factors were analyzed in this study. The results showed that the number concentration of submicron aerosol particles on precipitation days was averagely 27.8% lower as compared to non-precipitation days (the difference even reached 36.32% for particles in the diameter range of 0.1~1μm), and the scavenging efficiency was found to increase with aerosol particle size. It was also shown that the differences in precipitation intensity influenced the scavenging efficiency of different size particles differently. During light rainfall events, the impact of precipitation intensity on the removal rate of particles larger than 0.1μm was observed to weaken as particle size increased, whereas heavy rain was found to exhibit a higher overall removal efficiency as compared to moderate rain. The scavenging effect was found to vary with initial particle concentration and precipitation duration: Under high initial concentrations, the removal efficiency of particles larger than 0.03μm was shown to increase significantly, while prolonged precipitation (39h) was found to enhance the scavenging effect across all four modes. At different stages of the precipitation process, the removal and resuspension of smaller particles (with a particle size<0.1μm) were determined to be correlated with temperature and local wind speed at the beginning and end of precipitation events. Accumulation-mode particles (0.1~1μm) were more effectively removed during the periods of high rainfall intensity, with particles larger than 0.6μm being observed to show no significant concentration rebound after precipitation. This study revealed the efficiency of precipitation in removing submicron aerosols and its environmental dependence, and provided theoretical support for understanding the wet removal mechanism of atmospheric aerosols.

To investigate the pollution characteristics and formation mechanisms of ozone episodes in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) during autumn, ozone (O₃) concentrations and emission characteristics of volatile organic compounds (VOCs) were analyzed during three ozone episodesin Hong Kong.Observational data combined withobservation-based model(OBM) and the empirical kinetics modeling approach (EKMA) wasemployed to assess the impact of VOCs on O₃ formation sensitivity mechanisms and contribution to O₃ formation. The peak O₃ values recorded during the three episodes were 382.65, 302.67, and 301.76μg/m³, with corresponding concentrations of VOCs measuring 23.6×10^-9, 25.4×10^-9, and 32.1×10^-9, respectively. Oxygenated volatile organic compounds (OVOCs)were the most dominant of the observed species, with methanol, formaldehyde, and acetone being the three most prevalent by volume fraction. EKMA curves confirmedthat the nonlinear relationship among O₃-nitrogen oxides (NO_x)-VOCs depends ontheir instantaneous concentrations. The morning hours were characterized as VOC-limited regimes, while the afternoon hourswerethe transitional regime. The photochemical initial concentration (PIC) was 8.2×10^-9 higher than measured concentration, indicating that neglecting photochemically VOCs consumption may lead to an underestimation of the contribution of local VOCs photochemical reactions to O₃ formation. Furthermore, differences in the types and concentrations of O₃ precursors and radicals resulted in varying O₃ formation and loss rates, confirming the promoting effect of VOCs as precursors on net O₃ formation. Based on O₃ formation potential (OFP) and OH loss rate (L_OH) calculations, the VOCs with the highest contribution to the OFP were OVOCs (68.9%), alkenes (17.5%), and aromatics (13.6%). Formaldehyde and isoprene were the dominant species driving O₃ formation and hydroxyl radical (OH) consumption in the autumn in Hong Kong, respectively. The OFP of formaldehyde ranged from 42.1 to 73.1μg/m³, and the L_OH of isoprene varied from 1.35 to 2.12s^-1. Backward trajectory cluster analysis revealed that Hong Kong’s background site was primarily influenced by three air mass types driven by northeasterly winds: long-range transport (52%), short-range transport (28%), and local sources (20%). Results reveal that the photochemical reactions of VOCs, the response characteristics of different VOCs to the sensitivity of O₃ formation, and the synergistic effect of regional transport and local emissions have a significant impact on the O₃ pollution in Hong Kong during autumn.

Sea salt aerosols is critical particles in natural world that influence climate regulation, chemical processes of atmospheric, and cloud condensation nuclei formation. Accurate quantification of emission fluxes in these three areas and the development of reliable source function models are essential for climate modeling and environmental assessment. In this paper, major sea salt aerosol source function estimation methods, including the whitecap coverage method, the steady-state dry deposition method, and micrometeorological approaches, were reviewed, and environmental variables such as wind forcing, wave breaking intensity, water temperature, and surface organic enrichment in sea salt aerosol generation were analyzed. In addition, the main source function formulations derived from different methods are summarized. Recent literature indicates that current source function models cannot be widely applied at the global scale. It is expected that future studies will integrate deep learning techniques with remote sensing and reanalysis datasets to develop widely applicable source function models of sea salt aerosols.

In this paper, a time-series simulation prediction study of pollen concentration in Shunyi District, Beijing, China, for the period of 2018~2024 was carried out based on machine learning and time-series algorithms. The study integrates traditional statistical models, machine learning models and deep learning models, and introduces 36 meteorological elements and their variables as covariates to improve the prediction accuracy. The results show that AutoGluon-TimeSeries (AG-TS) significantly reduces the risk of overfitting through model integration, and performs well in short-term prediction (1day), with DLinear model having the best overall performance with R=0.68 and RMSE=206.5. In contrast, some models overestimated or underestimated the predictions. It was found that the pollen concentration showed double peaks in spring (March~May) and fall (August~October), and the correlation with meteorological variables reflected the complex effects of meteorological conditions and vegetation phenology. In addition, the modeling performance declined with the extension of prediction time, e.g., the R-value of DLinear decreased by 18% and the RMSE increased by 15% in the 3-day prediction. By eliminating the inefficient models and optimizing the remaining models, the direction of model optimization and scientific support for pollen allergy early warning were provided.

A high-resolution aircraft emission inventory for Qingdao Jiaodong Airport based on real flight trajectory datawas established.Concurrently, the three-dimensional non-steady-state puff dispersion model (CALPUFF) was improved to accommodate high-dynamic aircraft mobile sources, and the sensitivity of pollutant simulation results to the temporal and spatial resolution of aircraft emissionswas investigated. Building upon this, a quantitative assessment of the environmental impacts of aircraft emissionswasperformed. The results indicated that nitrogen oxides (NO_x), sulfur dioxide (SO₂), and fine particulate matter (PM_2.5) emissionsexhibited similar temporal variation characteristics in relation to flight takeoffs and landings, with low emissions observed from 03:00 to 05:00 and high emissions occurring from 15:00 to 17:00. The spatial distribution of emissions was closely related to the airport layout and the approach and departure tracks, with high emissions concentrated in critical areas of the airport flight area, including the runway, taxiway, and apron. The spatiotemporal resolution of the aircraft emission inventory significantlyaffectedthe simulation results of pollutant concentrations, withthe effect of temporal resolution becoming increasingly pronounced at higher spatial resolutions. An emission inventory based on a 1-hourtemporal resolution and a 100-meter spatial resolution effectively captured short-term variations in local emissions and better characterized the fine-scale pollutant concentration distributions associated with airport operations. The annual mean contributions of aircraft emissions to NO_x, SO₂, and PM_2.5 concentrations at Jiaodong Airport were 4.21, 0.53 and 0.07μg/m³, respectively, with regional maximum values of 220.25, 33.46 and 4.69μg/m³. These emissions were concentrated within a radius of 10~15km around the airport. Influenced by both meteorological factors and emissions, significant seasonal variations in the contributions of these three pollutants were observed. The impact was more widespread in winter; in contrast, during summer, it was primarily concentrated around the airport and its northwestern region.

In this study, based on the urban statistical yearbook and multi-source remote sensing data—including pollutant concentrations, nighttime light intensity, and land cover—the spatiotemporal distribution characteristics of PM_2.5-O₃ compound pollution across 274 prefecture-level cities in China were examined from an integrated perspective of meteorological, socioeconomic, and urban form factors. The results showed that from 2005 to 2020, PM_2.5 concentrations in Chinese cities followed a 'rise-then-fall' trend, while O₃ exhibited a 'rise-fall- rise' trend. Both the spatial distribution and the synergistic relationship between PM_2.5 and O₃ displayed pronounced regional heterogeneity. High PM_2.5 concentrations were mainly concentrated in the North China Plain, whereas high O₃ concentrations occurred in both the North China Plain and the eastern coastal urban agglomerations. Positive correlations between PM_2.5 and O₃ concentrations were predominant in the humid regions of southern and northeastern China, while negative correlations were more common in the semi-humid and semi-arid regions of northern China. Geodetector analysis revealed that the spatial differentiation drivers of PM_2.5 and O₃ concentrations was primarily shaped by urban form factors, followed by meteorological and socioeconomic conditions. Specifically, PM_2.5 concentrations were strongly influenced by the proportion of ecological space (q=0.627) and agricultural land (q=0.610), whereas O₃ concentrations were significantly affected by the proportion of ecological space (q=0.512) and topography (q = 0.466). The synergistic relationship between PM_2.5 and O₃ was mainly controlled by the single factors such as precipitation (q=0.396) and temperature (q=0.374), with significant enhancement observed under dual-factor interactions, such as temperature-topography (q=0.718) and precipitation-Shannon's evenness index (q=0.708). These findings highlight the nonlinear synergistic effects arising from the coupling of 'urban form constraints' and 'meteorological disturbances' on PM_2.5-O₃ compound pollution, and provide a scientific basis for the precise and coordinated prevention and control of such pollution.

This study establishes two sets of experiments to compare the performance of the latest version of the Community Earth System Model (CESM2) in simulating atmospheric pollutants over East Asia. The first set employs the MUSICA simulation with regional refinement over East Asia (SE), while the second set utilizes the conventional grid configuration of CESM (FCSD). Both simulations are evaluated against satellite and surface observations to assess the advantages of the variable-resolution approach in modeling regional air pollution over East Asia.Results demonstrate that while FCSD exhibits superior performance in simulating tropospheric ozone column concentrations due to its finer vertical resolution, the SE configuration outperforms FCSD in capturing surface O₃, CO, and NO₂levels over China. Compared to observational data from the China National Environmental Monitoring Centre (CNEMC), SE reduces mean seasonal biases by approximately 5.0%, 6.4%, and 52.9% for O₃, CO, and NO₂, respectively, relative to FCSD. Furthermore, the Earth System Model framework provides a comprehensive representation of stratospheric chemistry and dynamics, offering a powerful tool for investigating stratosphere-troposphere exchange processes. This capability holds significant implications for both global climate change research and regional air quality management.

This study focuses on East China, establishing a 15-indicator system to investigate the driving mechanisms of traffic-related CO₂ emissions and their contributions to ozone (O₃) concentrations. First, the Lasso regression model is employed to screen key variables. Then, feature importance is assessed using Random Forest (RF) and Extreme Gradient Boosting (XGBoost) models, with the SHAP method used to visualize the marginal contributions of each factor. A systematic framework for identifying and ranking driving factors is thus constructed. Results indicate that traffic-related CO₂ emissions in East China have shown a continuous upward trend, with Shanghai, Jiangsu, and Shandong together accounting for 62.18% of total emissions by 2022. High O₃ concentration zones are primarily located in the northeastern subregion, with Anhui Province experiencing a remarkable increase of 92.25%. In terms of model performance, the RF model outperforms XGBoost in both explanatory power and stability, achieving R² values above 0.8 for both CO₂ and O₃, with MSE values of 0.001 and MAE values below 0.1. SHAP analysis reveals that the main drivers of CO₂ emissions include population density, freight turnover, tertiary industry output, and urbanization level; while O₃ concentrations are primarily influenced by total population, transport sector output, the number of freight vehicles, and urban road length.

Nitrate wastewater was considered a potential threat to human health and the ecological environment. The adsorption method was regarded as promising for nitrate removal due to its high efficiency and low cost. The interlayer spacing characteristics of layered metal hydroxides were found to be favorable for nitrate adsorption. Nickel-iron layered double hydroxides (NiFe LDHs) was prepared by coprecipitation-hydrothermal method. The optimal preparation conditions were determined through orthogonal experiments as follows: nickel-to-iron molar ratio of 4:1, hydrothermal time of 12hours, and hydrothermal temperature of 1201C. The adsorption capacity of NiFe LDHs for nitrate can reach 37.48mg/g. The adsorption kinetics curve conforms to the quasi second order kinetic equation, and the adsorption process conforms to the Langmuir model. The predicted maximum adsorption capacity is 38.88mg/g. High nitrate adsorption efficiency was maintained by NiFe LDHs within the pH range of 3~10, and a considerable nitrate adsorption capacity was observed even in the presence of high concentrations of coexisting anions, with HCO₃^- identified as having the most significant impact. The optimal desorption of the adsorbent was achieved using 0.1mol/L NaCl solution, and after five consecutive adsorption-desorption cycles, a nitrate removal rate of 87.1% was retained. Characterization results indicated that the layered structure of NiFe LDHs was essentially maintained before and after adsorption, and the primary adsorption mechanisms were determined to be electrostatic attraction, surface complexation, and ion exchange.

In this study, a catalyst with bimetallic CuCo-MOF-74 dispersed on semi-coke (SC) (CuCo-MOF-74_x/SC) was successfully prepared by one-pot hydrothermal synthesis, and the degradation behavior and mechanism for aqueous bisphenol A (BPA) via persulfate (PMS) activation was systemically studied. The characterization results showed that CuCo-MOF-74 was uniformly dispersed onto the surface of semi-coke activated carbon, and the specific surface area of CuCo-MOF-74₂/SC was 582.04m²/g. For BPA degradation, under the optimum conditions (0.2g/L PMS, 0.1g/L catalyst), the CuCo-MOF-74₂/SC/PMS system achieved a degradation efficiency of 95.01% for 20mg/L BPA in 30min and the mineralization rate of 54.7%, which was significantly higher than that of the CuCo-MOF-74/PMS system, and the reaction rate constant of CuCo-MOF-74₂/SC (0.1113min^-1) was 3.4 times of CuCo-MOF-74 (0.0324min^-1). After 5 cycles, the degradation efficiency of CuCo-MOF-74₂/SC decreased from 94.83% to 72.56%, which was remarkably higher than that of CuCo-MOF-74 (from 76.95% to 21.49%). In the CuCo-MOF-74₂/SC/PMS system, both free radicals (·OH, and ) and non-radicals (¹O₂ and electron transfer) were involved in the degradation of BPA, and free radicals oxidation played a major role. The loading of CuCo-MOF-74 on SC significantly enhances the stability and improves specific surface area of CuCo-MOF-74, thereby elevating the degradation efficiency for BPA in water. This study provides the important guiding significance for the development of MOF-based catalysts.

In this study, fluorine-defective covalent triazine frameworks (CTFs) were designed and synthesized to improve adsorption performance for per-and polyfluoroalkyl substances (PFAS). Compared with pristine CTFs, the fluorine-defective CTFs exhibited a 55% increase in adsorption capacity. A systematic evaluation of different particle sizes revealed that CTF-F10 (246.421mg/g) achieved a 59% higher capacity than CTF-F595 (154.403mg/g). These results demonstrate that reducing the adsorbent particle size not only substantially increases the equilibrium adsorption capacity, but also accelerates the adsorption rate. At pH 2, CTF-F10 achieved a C7HFPO-TA removal efficiency of 89.55%, significantly higher than that at pH 6 (50.15%) and pH 10 (26.35%). The presence of NaCl or fulvic acid (FA) reduced removal efficiency by about 20%. DFT calculations indicated that the adsorption of C7HFPO-TA onto fluorine-defective CTFs is primarily governed by electrostatic and fluorophilic interactions. Regeneration experiments also excellent recyclability and reusability of powdered CTFs. This work establishes a novel design strategy for fluorine-defective CTFs for PFAS removal from water and provides a first comparative evaluation of the particle size effects on C7HFPO-TA adsorption, providing scientific and technical guidance for mitigating PFAS contamination in aquatic environments.

3-aminopropyltriethoxysilane (KH550) was used to modify Fh, yielding organosilane-modified ferrihydrite (KH-Fh). The Pb(Ⅱ) adsorption performance and underlying mechanisms of KH-Fh were systematically explored.Results demonstrate that the modification successfully introduced Si-OH and -NH₂ functional groups onto the Fh surface, enhancing the maximum adsorption capacity from 50.51mg/g of the unmodified Fh to 102.85mg/g of KH-Fh, representing a 103.6% increase. Adsorption kinetics and isotherm studies indicate that the adsorption processes of both Fh and KH-Fh for Pb(Ⅱ) conform to the pseudo-second-order kinetic model and the Langmuir isotherm model, suggesting that chemisorption is the dominant mechanism. The positive value of the thermodynamic parameter ΔH indicates that elevated temperatures promote the adsorption reaction. Compared with unmodified Fh, KH-Fh maintains higher and more stable adsorption efficiency across a wide pH range (3.0~7.0) and is less affected by ionic strength and common coexisting ions (Na⁺, K⁺, Ca²⁺). X-ray photoelectron spectroscopy (XPS) analysis confirms that Pb(Ⅱ) is immobilized through coordination with Si-OH, Fe-OH, and -NH₂ functional groups on the surface of KH-Fh, significantly enhancing the adsorption stability. These results offer novel theoretical insights and practical guidance for the functional modification of iron oxides and the remediation of Pb(Ⅱ)-contaminated environments.

The effect of scrap iron on the nitrogen removal performance of theanaerobic ammonium oxidation (ANAMMOX) system under different salinity influents was investigated using anUpflow Anaerobic Sludge Blanket (UASB) reactor. The results showed that scrap iron had a positive effect on enhancing the nitrogen removal efficiency of the ANAMMOX process. Under salinity conditions ranging from 2.75% to 3%, the nitrogen removal rate (NRR) increased from 0.39±0.12kg/(m³·d) to 2.88±0.09kg/(m³·d). However, when the salinity reached 3.5%, the system collapsed. With the addition of scrap iron, the specific anammox activity (SAA) first increased and then decreased at 3.5% salinity. Extracellular Polymeric Substances (EPS) analysis indicated that the addition of scrap iron contributed to a decrease in theProtein/polysaccharide(PN/PS)ratio, promoting the formation of dense granular sludge. Microbial community analysis revealed that high salinity reduced the abundance of AnAOB(CandidatusKuenenia) in the reactor. Notably, a potentially novel AnAOB (Brocadiaceaeunclassified), consistently dominated the community (accounting for 54.1%), suggesting that this strain may play a key role in maintaining nitrogen removal performance under high-salinity conditions. The results of this paper could provide theoretical support for the treatment of high-salt wastewater by the ANAMMOX process.

The phosphorus recovery efficiency through calcium phosphate (Ca-P) crystallization in wastewater demonstrates significant susceptibility to carbonate alkalinity (CO₃^2-), a predominant coexisting impurity in wastewater. To elucidate the influence of CO₃^2- alkalinity on phosphorus recovery of Ca-P crystallization, the variation of pH, conductivity, alkalinity, and Ca morphology in Ca-P crystalline systems with difference CO₃^2- alkalinity levels were systematically analyzed by integrated potentiometric titration and jar testing. Meanwhile, the influence mechanism of CO₃^2- alkalinity was explored based on the kinetics of phosphorus recovery and XRD results of crystallization products. The results indicate that, provided crystallization reaction time long enough, phosphorus recovery efficiency was less affected by CO₃^2- alkalinity, but mainly determined by the thermodynamic properties of Ca-P crystallization product itself. Under extended reaction durations (7200s), phosphorus recovery efficiencies stabilized at around 40% across all experimental and control groups. CO₃^2- alkalinity changed the kinetics of Ca-P crystallization. CO₃^2- alkalinity with low level promoted Ca-P crystallization by providing alkalinity, compared to delay of Ca-P crystallization by consuming free Ca²⁺ through calcium carbonate (Ca-C) crystallization while at high level. Driven by thermodynamic properties, Ca-C ion clusters and crystals would dissolve and release free Ca for continuous crystallization of Ca-P. The research results provide a direct theoretical basis for eliminating the influence of CO₃^2- alkalinity on the phosphorus recovery efficiency of Ca-P crystalline from wastewater.

An airlift internal circulation reactor was used, and laboratory-cultivated full-nitrification granular sludge was inoculated into a continuous-flow reactor. During long-term operation, a suppression strategy based on a free nitrous acid (FNA) concentration of 150mg/L formed at pH 2.5 was applied to investigate the impact of high FNA concentrations under weak acid conditions on the nitritation of granular sludge. The results showed that this suppression strategy strongly inhibited both aerobic ammonia-oxidizing bacteria (AOB) and nitrite-oxidizing bacteria (NOB), but AOB exhibited a greater recovery capacity than NOB, enabling the successful initiation of nitritation in the granular sludge reactor within one day. During stable operation, the ammonium removal rate (ARR) reached 0.2~0.5kg/(m³·d), and the nitrite accumulation efficiency (NAE) reached 100%. However, the granular sludge nitritation process exhibited a cyclical deterioration pattern during long-term operation, necessitating periodic repetition of the suppression strategy. Under weak acid conditions, the secretion of extracellular polymeric substances from granular sludge gradually decreased, leading to the continuous deterioration of its structure. High-throughput sequencing results indicated that throughout the duration of the experiment, the Nitrosomonas genus consistently dominated the AOB community in the granular sludge, while the relative abundance of the NOB genus Candidatus_Nitrotoga decreased from 5.2% to approximately 0%.

An airlift transverse internal loop reactor (ATIR) was operated for the treatment of synthetic municipalwastewater. The nitrogen removal performance and internal recycle ratio of the ATIR with four different ratios of the cross-sectional areas of the downcomer to the riser (A_d/A_r) were investigated. The results indicated that the ATIR achieved high internal recycle ratio (52~176) by utilizing aeration kinetic energy. The efficient nitrogen removal was obtained at an A_d/A_r of 1:1.5 and a hydraulic retention time (HRT) of 9h, with the effluent total nitrogen of (8.12 ± 1.21) mg/L. Compared to the conventional internal recycle mode, the ATIR at this A_d/A_r demonstrated a 27.5% reduction in aeration rate. Furthermore, the ratio of specific nitrite utilization rate to specific ammonia utilization rate decreased from 1.31 to 0.95 and the abundance of nitrite-oxidizing bacteria (NOB-Nitrospira) decreased from 3.66% to 0.88%. Meanwhile, the simultaneous nitrification-denitrification efficiency increased to 26.77%, and the contribution of partial nitrification and denitrification to nitrogen removal corresponding increased to 16.71%. These indicate that spontaneous nitrite-oxidizing bacteria washout in the ATIR had occurred and the nitrogen removal pathway at an A_d/A_r of 1.5 tends towards simultaneous partial nitrification and denitrification.

Polyethylene terephthalate (PET) and humic acid (HA), commonly present in water, were selected to represent microfibers and organic foulants, respectively. The interaction forces of each type of foulant with the membrane surface were measured, which combined with the results of the fouling layer structure and the dynamic adsorption behavior of HA on the PET and membrane surface, to unravel the influence mechanism of microfibers on the organic fouling behavior of membranes. The results revealed that the interaction force between PET microfibers and the ultrafiltration membrane surface was more than ten times stronger than that of HA. However, the micrometer-scale size of PET induced a steric hindrance effect, leading to a disordered distribution of microfibers on the membrane surface, which had only a limited impact on the flux of the ultrafiltration membrane. In the PET-HA co-existing systems, strong interactions of PET-HA enabled microfibers to preferentially adsorb HA, effectively decreasing initial-stage membrane fouling rate by reducing the concentration of free HA. However, the dissolved HA could penetrate microfiber interstices under hydrodynamic forces and form a "membrane-HA-PET" gradient fouling layer, making the membrane fouling behavior of the mixed system comparable to that of the single HA system during the stable operation stage.

In this study, a bibliometric analysis was conducted by identifying and analyzing relevant research from the core database of Web of Science in the past 20 years with the goal of identifying and characterizing critical knowledge gaps, gluts, and trends in application of biological predation in residual sludge reduction. Results showed that most relevant research was published in China, accounting for averagely 35% of the global total articles, with the highest proportion reaching 66% (in 2025). Furthermore, in the past two decades, three development stages with distinct themes and trends were identified, i.e. 2005~2011, 2011~2017 and 2017~2025; namely, (i) predator dynamics and their mechanisms in sludge reduction and pollutant degradation, (ii) enhancement of the reactors and strategies for sludge reduction that uses predation, and (iii) understanding the microbial community structure and function under the influence of predation. It is recommended that future research and practice should investigate the multi-scale effects of predation in sludge reduction systems and evaluate their stability, maintenance and regulation mechanisms. Additional research should evaluate microbial food web response and risk assessment under pollution stress. Moreover, spatiotemporal constraints, sustainability and carbon emission reduction accounting issues faced by engineering practices will be important challenges in this field.

To accurately predict the migration process of acidic minedrainage (AMD) in fractured media and its discharge intensity into the surface environment, an novel simulation technique based on the Upscaled Discrete Fracture-Matrix (UDFM) method is proposedinthisstudy, which involves locally refining the fracture structure and mapping it onto an equivalent continuum model. Building upon this approach, we construct a series of numerical casesfor AMD reactive transport in carbonate fracture networks. By integrating AMD discharge flux analysis with Damkohler number(Da_I), we quantitatively elucidate the influence of key fracture parameters (fracture direction, fracture density P₃₂) on AMD migration patterns and meticulously characterize the hydrogeochemical interactions and their dynamic evolution between fractures and the rock matrix. The simulation results demonstrate that: The higher the fracture density and the smaller the fracture angle (i.e., direction concentrating)correlate with the faster AMD migration rates and increased discharge intensity; conductive fractures dominates preferential flow under high-density conditions, AMD diffuses through the matrix into adjacent non-conductive fractures near preferential pathways, triggering a transition from reaction-dominated (highDa_I) to advection-dominated (lowDa_I) regimes within these fractures. Connectivity to the downstream boundary subsequently amplifies AMD discharge; lower fracture density and greater orientation alignment result in a higher proportion of reaction- dominated simulation units after system stabilization, indicating larger zones of incomplete neutralization.

Moisture distribution and dewatering performance are critical indicators in the study of deep dewatering of bio-waste. Traditional characterization methods have several drawbacks such as large sample consumption, low detection efficiency, poor reproducibility of results, high costs, and difficulty in identifying the turning points of the water loss curve. To address these issues, the low-field nuclear magnetic resonance technique (LF-NMR) was conducted to calibrate the drying test for moisture distribution analysis and Fourier transform infrared spectroscopy (FTIR) was conducted for dewatering performance analysis. The results indicated that the turning point of the water loss curve could be accurately located by referring the LF-NMR detection results. Moreover, a conceptual model of the water loss curve for solid waste was proposed to refine the traditional "four stage curve". At the same time, the FTIR analysis result showed that the water band spectrum related to the O-H bending vibration of FTIR (1550~1750cm^-1) could be deconvoluted into six sub-peaks. The area proportions of sub-peak 2 (p2) and sub-peak 4 (p4) in the water band spectrum of anaerobic digestate were significantly correlated with capillary suction time, and the summed ratio ∑p1~2/∑p4~6could characterize the dewatering performance of anaerobic digestate. The results of this study may provide a theoretical foundation and technical support for relevant research and applications regarding deep dewatering of bio-mass waste.

To address the resource utilization of agricultural wastes such as straw and livestock and poultry manure, this study investigated the effects of biochar addition on anaerobic digestion of a straw-manure mixture, using pig manure and wheat straw as raw materials. The biochar was devrived from the digestate obtained after anaerobic digestion of pig manure and wheat straw and its modification forms. The results showed that the addition of digestate-derived biochar played an important role in promoting electron transfer between species and providing more attachment sites for microorganisms. Specifically, biochar hydrolyzed with a manure-to- straw ratio of 1:1 and a solid content of 8% in the digestion system yielded the best gas production performance, increasing methane production by 17.59% compared to the control group without biochar. Furthermore, co-modification of this biochar with urea (as a nitrogen source) and nano zero-valent iron greatly enhanced its specific surface area and electron transfer capacity, leading to a 41.03% increase in methane production compared to the control. Additionally, the larger pore volume of digestate-derived biochar allowed it to adsorb volatile fatty acids from the digestate, thereby balancing the acidity and alkalinity of the system. The biochar also adsorbed up to 28.2% of ammonium nitrogen and 35.01% of nitrate nitrogen from the digestate, mitigating ammonium inhibition and potentially rectifying an imbalanced carbon-to-nitrogen ratio in the system. In conclusion, digestate-derived biochar and its modification represent an effective strategy for enhancing methane yield in anaerobic digestion systems.

The aims of this study are to assess the high-value characteristics of vermicompost products derived from organic wastes and to explore their potential as bio-organic fertilizers. For this purpose, 8 samples of sludge-based vermicompost and 16 samples of cow manure-based vermicompost were collected to compare their nutrient content, dissolved organic matter (DOM) characteristics, microbial community structure, and ecological functions. The results showed that both types of vermicompost were rich in water-soluble nitrogen and phosphorus, however, only half of the samples met the organic matter content standard specified in the “Organic Fertilizers” (NY/T525). Cow manure-based vermicompost was weakly alkaline, while sludge-based vermicompost was acidic. The content of humic substances in sludge-based vermicompost was 40.3% significantly higher than that in cow manure- based vermicompost (P<0.01), and the biochemical index and freshness index of DOM in sludge-based vermicompost were significantly higher than those in cow manure-based vermicompost (P<0.001). Additionally, the Chao1index and Shannon index in cow manure-based vermicompost were 1.31 times and 1.10 times higherthan those in sludge-based vermicompost (P<0.001), respectively. Moreover, significant differences in β-diversity of microbial community were observed between two types of vermicompost (P<0.01), particularly in the dominant bacterial genera. The dominant bacterial phyla in both types of vermicompost were Proteobacteria, Bacteroidetes, and Actinobacteria.Functional prediction indicated that the carbon and nitrogen cycling functions of microorganisms in sludge-based vermicompost were more abundant than in cow manure-based vermicompost. In conclusion, the DOM characteristics and microbial community structure in vermicomposts are closely related to theirsource type, with sludge-based vermicompost showing superior nutrient and humic substance content, relative to cow manure-based vermicompost.

Field plot experiments were conducted to study the intercropping systems of the hyperaccumulator Sedum plumbizincicola and passion fruit. Three planting densities of S. plumbizincicola were tested: low (D1: 30cm×30cm), medium (D2: 25cm×25cm), and high (D3: 15cm×15cm). Additionally, two microbial agents, Bacillus megaterium (Bm) and Bacillus mucilaginosus (Bmk), were applied at the medium density (D2). The effects of different treatments on the plant growth, heavy metal accumulation, and phytoextraction efficiency were investigated. The results showed that under the intercropping system, high density planting (D3) significantly increased the aboveground biomass of S. plumbizincicola and its phytoextraction efficiency for soil Cd and Zn, with annual extraction rates increased by 62.5% and 72.7%, respectively, compared with low density planting (D1) (P<0.05). The Cd content in passion fruit pulps decreased with increasing planting density of S. plumbizincicola and met the national food safety standards. Moreover, the application of Bmk in the intercropping system had a better effect on the growth of S. plumbizincicola and its ability to absorb Cd and Zn. Compared with CK, the aboveground biomass of S. plumbizincicola in Bmk treatment increased by 43.2%, and the uptake of Cd and Zn in the aboveground parts increased by 7.02% and 20.9%, respectively. The microbial application significantly reduced the pH value and significantly increased the available Cd and Zn content in both rhizosphere and non-rhizosphere soils, while Bmk had better effect than Bm. In all, this study provides a theoretical basis for improving soil heavy metal remediation under the intercropping system of hyperaccumulators and fruits.

As a core drinking water source in Beijing, the response mechanism of Total Nitrogen (TN) exceedance to Net Anthropogenic Nitrogen Input (NANI) in Miyun Reservoir is not clear. In this study, NANI was constructed based on multi-source data from 2007 to 2023 to systematically reveal the spatial and temporal dynamics of nitrogen input and its influence on TN output in the watershed. The results showed that the average NANI of Miyun Reservoir was 2768.80kg/(km²·a), with an overall decreasing trend year by year, and the high value of the input area was mainly distributed in the east, while the nitrogen input in the west was more stable; fertilizer application dominated the contribution structure of nitrogen input sources for a long period of time (67.32% of the peak value), and the contribution of the net nitrogen input from food was slowly decreasing; and the nitrogen buffer mechanism of the basin weakened the linear response of anthropogenic inputs to TN outputs. The linear response between anthropogenic inputs and TN outputs was weakened by the watershed nitrogen buffering mechanism, with the short-term bioretention capacity (SBI) enhanced by 57.90%, while the long-term buffering capacity (LBI) was reduced by 86.46% due to historical nitrogen accumulation, suggesting that saturated nitrogen retention may exacerbate the risk of water quality in the future. The study clarified the spatial and temporal patterns of nitrogen input and buffer lag effect in Miyun Reservoir, and provided scientific basis for nitrogen control strategy and dynamic early warning.

Valley-type municipal solid waste (MSW) landfill sites were characterized by a large hydraulic gradient, high groundwater flow velocity and rapid contamination migration. It was challenging for traditional permeable reactive barriers (PRBs) to efficiently capture contamination plumes under these conditions. According to the contamination migration characteristics of valley-type landfill sites, a novel passive overflow-PRB was proposed in this paper. The passive overflow-PRB was composed of a low-permeability cutoff wall and a high-permeability PRB, with the PRB situated in the upper-middle section of the cutoff wall. Upstream groundwater would be captured by the cutoff wall, then the groundwater level would be elevated and the contaminated groundwater would be forced through the PRB for remediation. This design was suitable for installation at the downstream outflow of a valley, effectively preventing further migration of the contamination plume off-site, and solving the problem of excessive construction depth required for the PRB. To validate the effectiveness of the passive overflow-PRB, the groundwater ammonium nitrogen (NH₄⁺-N) from two valley-type landfill sites in Guangdong Province and Zhejiang Province was taken as the remediation target. NaCl-modified zeolite was applied as the reactive material of the PRB, and MODFLOW and MT3DMS models were employed to simulate the collection and remediation effects after construction of passive overflow-PRB. The simulation results indicated that the passive overflow-zeolite PRB could effectively prevent the further migration of NH₄⁺-N contamination plume to the downstream, maintaining concentrations below 20.0mg/L or 1.5mg/L for 5years.

The effects of in-situ coverage of aluminum oxide (Al group) and iron oxide (Fe group) on phosphorus release from Erhai Lake sediments were evaluated through an indoor laboratory study. Base on sediment total phosphorus (TP), phosphorus forms, dissolved organic matter (DOM), and sediment water interface characteristic parameters, the differences and mechanisms of phosphorus control effects between the two materials were analyzed. The results showed that compared to the control group (CK group), both the Al and Fe groups significantly inhibited the maximum release amount (Q_max) of TP and reactive phosphorus (SRP), reducing them by 42.61% and 40.64% for TP, 45.04% and 46.29% for SRP, respectively. The downward migration and burial of TP in sediments were promoted by both types of material coverage, while the transformation of active phosphorus in upper sediments (weakly adsorbed phosphorus (NH₄Cl-P), reducible phosphorus (BD-P), and metal-oxide bound phosphorus (NaOH-P)) into inert phosphorus, namely(calcium bound phosphorus (HCl-P) and insoluble phosphorus (Residual-P), was simultaneously enhanced , thereby reducing the direct source of phosphorus release from sediments. The changes in DOM content in the Al and Fe groups followed the same trend as TP content. The molecular weight and aromatic structural complexity of DOM increased in both groups, and the mineralization rate of DOM was inhibited. The degree of DOM humification was enhanced in the Fe group, while the opposite trend was observed in the Al group, where phosphorus release produced by DOM decomposition was reduced. The diffusion boundary layer (DBL) thickness, oxidation-reduction potential (E_h), and decay rate of the sediment water interface in both the Al and Fe groups were all increased. Oxygen penetration depth (OPD) was markedly greater in Fe group than in the CK group, whereas it was lower in the Al group. Overall both materials changed the interface thickness and oxidation environment, increasing the channel resistance for phosphorus release from sediments. These findings demonstrate that both alumina and iron oxide can effectively control phosphorus release from lake sediments, although through distinct mechanisms, providing a scientific basis for selecting in-situ remediation materials in eutrophic lake sediments.

To address the challenge of heightened uncertainty in water-floating garbage trajectory prediction caused by multiple influencing factors, a multi-feature dynamic weighted fusion model for water-floating garbage trajectory prediction was proposed. Firstly, a multi-factor feature dynamic weighted fusion layer was designed to thoroughly analyze the complex mapping relationships among various influencing factors. Secondly, a bidirectional spatial-temporal weighted attention network was introduced to perform weighted fusion of features extracted by BiLSTM, thereby capturing richer temporal-spatial characteristics of drift trajectories. Finally, a learnable nonlinear output layer was proposed to fully integrate information from diverse input factors and trajectory data, significantly enhancing the model's generalization capability and prediction reliability. Experimental results on the Yinggezui Reservoir trajectory dataset show that compared with baseline model, the R² index of the proposed method has improved by 0.1085, and the MAE, MAPE, and MBE indices have decreased by 0.0112, 3.715, and 0.000624. This method can fully integrate multiple factor data and achieve high-precision prediction of the trajectory of water-floating garbage, providing a reliable model for the salvage and management of water-floating garbage.

Based on the long-series normalized vegetation index (NDVI) and climate, topographic and human activity factor data, this study studied the dynamic change characteristics and temporal stability of vegetation NDVI in China's first-class watersheds from 2000~2022 by using Theil-Sen Media trend analysis+Mann-Kendall test, geographic detector and temporal stability, and identified the representative sub-watersheds of nine first-class watersheds in China. The findings indicated that: in terms of time, the NDVI values of vegetation in the nine major river basins of China showed a significant upward trend. Among them, the Yellow River Basin had the highest growth rate of 0.0052a^-1, followed by the Songliao River Basin with a growth rate of 0.0032a^-1, while the Huaihe River Basin had the lowest growth rate, at only 0.0010a^-1. Spatially, the NDVI of vegetation exhibited a declining trend from the southeast to the northwest, and the vegetation change was mainly improved, accounting for 52.02%, and the flow between different levels of vegetation cover was mainly to the higher grades. The representative sub-basins of vegetation stability in the major river basins of China are as follows: Southwest River Basins (No. 35 Lancang River Basin), Inland River Basins (No. 15 Tarim River Basin), Yangtze River Basin (No. 8 Han River Basin), Southeast River Basins (No. 24 Min River Basin), Huai River Basin (No. 16 Yi River Basin), Hai River Basin (No. 32 Daqing River Basin), Songliao River Basin (No. 21 Songhua River Basin), Pearl River Basin (No. 12 Xijiang River Basin), and Yellow River Basin (No. 7 Fen River Basin). Based on the mutation methods of different river basins, it was concluded that the ordered clustering method and the sliding T-test were more suitable for the detection of vegetation change mutations in most of the river basins, among which the Pettt test was suitable for the southeast river basins, the Haihe River, inland rivers, Songliao River and Yangtze River basins, the Huaihe River and Southwest river basins were suitable for the ordered clustering method and the sliding T-test method, and the Yellow River basin was suitable for the sliding T-test.

The Hanjiang River, the largest tributary of the Yangtze River, is crucial for sustaining socio-economic production and human livelihoods in its basin due to its sound aquatic ecological conditions. This study analyzed aquatic ecological survey data from the middle-lower reaches of the Hanjiang River during the dry season (April) and wet season (August) of 2023. Fifty-four candidate metrics were calculated across multiple dimensions, including community composition, biodiversity, pollution tolerance, and functional traits. Unlike traditional biotic integrity index methods, this study did not establish reference sites. Core metrics were screened through statistical analyses (zero-value distribution) and correlation analyses (sensitivity and redundancy analyses), significantly simplifying the screening process. The Index of Biotic Integrity of Benthic Macroinvertebrate (B-IBI) was validated via correlation analysis with reference metrics. Results indicated higher macroinvertebrate biodiversity during the wet season compared to the dry season, with an overall "fair" biotic integrity status. In the dry season, 53.8% of sampling sites were classified as "fair", while 53.8% achieved "good" status during the wet season. Regression analysis identified pH, total phosphorus (TP), and water temperature (WT) as significant factors influencing B-IBI. This systematic assessment provides foundational data for ecological conservation and restoration in the Hanjiang River Basin.

This study focused on the high-hydrodynamic sandy shoal Sanba Tan and the slow-flow sedimentary clay shoal Wugui Zhou in the Jingjiang section of the Yangtze River. The response mechanisms between the composition of SDOM and phosphorus forms were analyzed using EEMs-PARAFAC and sequential extraction methods. Significant compositional differences were observed between the SDOM from Sanbatan and Wuguizhou. Sanbatan was dominated by protein-like components, whose high biological activity, coupled with a high proportion of Fe/Al-P, was found to jointly govern the distribution of phosphorus forms. In contrast, the SDOM from Wuguizhou was primarily characterized by humic-like components, whose high aromaticity and strong chelating capacity were identified to promote the accumulation of organic phosphorus, which was significantly higher than that in Sanbatan. A significant negative correlation was observed between protein-like components and Fe/Al-P (P<0.05), while the humification index was significantly positively correlated with organic phosphorus (P<0.05). These results suggested that SDOM influences phosphorus forms through two primary pathways: competition with metal oxides for adsorption sites and alteration of microbial metabolism. At Sanba Tan, SDOM was more readily precipitated with iron-aluminum oxides, thereby retaining more Fe/Al-P. Conversely, the low-to-medium molecular weight protein-like SDOM in Wuguizhou accelerated the decomposition and mineralization of organic phosphorus. The influence of SDOM on phosphorus forms in sandbars of the mid-Yangtze River was elucidated for the first time in this study, providing theoretical support for the phosphorus trapping function associated with the hydrological regulation of large rivers.

The dynamic changes of soil organic matter (SOM) in alpine ecosystems were investigated using lignin as a molecular marker. Soils from a swamp meadow (WQZ) and a subalpine meadow (AMX) in Hongyuan County, on the northwestern Sichuan Plateau, were analyzed to examine the vertical distribution, degradation state, and environmental drivers of lignin within the soil profile. The results indicated that: In AMX, soil pH was observed to increase with depth, while water content remained low. Both SOM and lignin contents were found to decrease with depth, and soil texture exhibited clear vertical variation. In contrast, WQZ soils showed minimal inter-layer pH variation and high water content ((3times that of AMX). Affected by seasonal waterlogging, SOM and lignin in WQZ initially decreased and then increased with depth. All WQZ profiles were identified as clay loam, with fine particle content exceeding 90%. High lignin content in the AMX surface layer was attributed to root input and declined markedly with depth. In WQZ, long-term flooding was associated with lignin accumulation in deeper layers via leaching or bioturbation, resulting in higher relative lignin contribution to SOM at depth compared to surface layers. Ratios of guaiacyl (Ad/Al)v and syringyl (Ad/Al)s monomers in both soil types exceeded 0.6across all layers, indicating significant oxidative degradation of lignin side chains, which intensified with depth. Demethylation/methoxylation degradation was more pronounced in AMX than in WQZ. Lignin stability was regulated by soil texture: absolute lignin content (Σ8) was higher in clay silt, while sand content was positively correlated with the lignin contribution to SOM (Λ8) within the same layer. Prokaryotic and eukaryotic abundances were influenced by soil water content and pH. Proteobacteria dominated the surface layer of AMX, whereas Acidobacteria were more abundant in deeper layers. In WQZ, Chloroflexi were enriched with depth, and basidiomycete abundance was significantly higher in AMX than in WQZ.

Low desalination rates and water production efficiency are key factors limiting the commercial application of freeze desalination (FD) technology. To investigate the effect of refrigeration temperature on freshwater production efficiency in freeze-gravity desalination (GD) technology, experiments were conducted with three refrigeration temperatures and two melting methods to study salt distribution patterns during freezing and melting. Results indicate that during freezing, salt concentration in ice crystals increases with decreasing the refrigeration temperature, yet the minimum desalination rate remains around 40%. During GD melting, total dissolved solids (TDS) in meltwater exhibit exponential decay increasing meltwater volume. A hypothesis for gravity-driven desalination of mixed ice meltwater was proposed. It was found that when TDS value of the mixed ice meltwater equaled the target (1000mg/L), the water production (WP₂) and water production rate (WPR₂) were significantly higher than those (WP₁ and WPR₁) when the instantaneous TDS value of ice meltwater was below 1000mg/L, with the water production rate increasing by over 21%. When combining FD and GD technologies for desalination and collecting meltwater using the method proposed in the mixed meltwaterhypothesis, the freshwater production efficiency (FP) significantly increases with decreasing refrigeration temperature. This resolves the conflict between the limitation of desalination rate during the freezing process imposed by regrigeration temperature and the users' demand for faster ice production efficiency (IP).

In this study, water samples of lakes with different salinities (fresh, saline and salt) lakes in the QTP were collected to analyze the structural characteristics and driving mechanisms of algae communities, and the Null model was used to quantify the process of algal community assembly processes. The results indicated: The abundance indices of algae in fresh lakes were the highest (average Shannon and Chao1 were 3.60 and 390.01, respectively), while that in salt lakes were the lowest (average Shannon and Chao1 were 1.96 and 184.84, respectively). With the increase of water salinity, the diversity and abundance of algal communities decreased significantly. The Average Variation Degree (AVD) index of algal community in different salinities lakes was different, and AVD in saline lakes was the lowest, indicating that the stability of algal community is the highest. At the phylum taxonomic level, the algae in the lakes of the QTP were mainly composed of Bacillariophyta (28.78%), Chlorophyta (14.28%), Euglenozoa (2.88%), Haptophyta (1.89%), including the species of uncultured_organism、Tetraselmis_cordiformis、Nannochloropsis_oculata、Rhizosolenia_sp. and the proportions were 31.94%, 9.06%, 6.30% and 3.58%, respectively. The community structure of algae in lakes with different salinities was significantly different (ANOSIM: P<0.001). Biological oxygen demand (BOD) was the most significant driving factor for variations in the community structure of algae in lakes with different salinities. Variational partition analysis (VPA) revealed that the contributions of geographic factors in shaping algae in lakes (1.02%) was lower than that of water environmental factors (36.95%). The algal community assembly process was varied in lakes with different salinity gradients. The community assembly processes of algae in fresh lakes were dominated by the deterministic processes, while the algae in saline and salt lakes were mainly dominated by the stochastic processes. The results of this study could provide theoretical support for the planning, utilization, and management strategies of water resources in lakes on the QTP, and also provided scientific basis for the assessment of water pollution risks in this region.

Aquifer heterogeneity characterization was recognized as crucial for enhancing the accuracy of groundwater models and the reliability of resource assessments and pollution control strategies. The Nugusitai Water Source, located in the Horqin District of Tongliao City, Inner Mongolia, was selected as a case study. Spatial distributions of hydraulic conductivity (K) and storativity (S_s) in a confined aquifer were characterized using three methods: Parameter Zoning, Ordinary Kriging (OK), and Sequential Gaussian Simulation (SGS). Heterogeneous isotropic models for flow and transport were constructed to evaluate the predictive impacts of each method.Results indicated that K fields generated through OK and SGS were associated with improved fits to observed hydraulic heads compared to Zoning, as evidenced by higher R² and Nash-Sutcliffe efficiency (NSE) values and lower root mean square error (RMSE). In pumping scenarios, the Zoning approach was found to cause abrupt changes in hydraulic gradients along sub-zone boundaries due to discontinuities in K values, resulting in distorted equipotential lines. The oversimplification inherent in Zoning also led to high sensitivity of predicted contaminant plume extent to the estimated K values within sub-zones. By contrast, SGS, which preserved spatial variance, produced more conservative and spatially constrained plume predictions. Storativity characterization methods were determined to have a negligible effect on model outcomes. Under common constraints such as limited borehole density, it was concluded that method selection should be aligned with specific objectives of the numerical simulation: OK was more suitable for delinerating the maximum Pollution risk Control zone, while SGS was more suitable for balancing spatial variability with local uncertainty, such as in precision remediation applications. This study provided empirical support for the selection of appropriate modeling methods in groundwater management and pollution risk mitigation efforts.

This study reveals the mechanism by which MoO₃/MoO_3-x photocatalyst inactivate algal cells. The photocatalysts were synthesized via hydrothermal and thermal polymerization methods without introducing foreign metal ions, and their physicochemical properties were characterized using XRD, XPS, SEM, and UV-Vis spectroscopy. The photocatalytic performance for algae removal was evaluated under visible light. Results demonstrated that 98.36% chlorophyll a was removed by 0.2g/L MoO₃/MoO_3-x within 6hours and the photocatalyst exhibited effective algal inhibition across a broad pH range (4.0~11.0). Additionally, the photocatalyst maintained stable performance at various initial algal concentrations. Quenching experiments confirmed that photogenerated holes (h⁺), hydroxyl radicals (·OH), and superoxide radicals (·O₂^-) were the primary reactive species responsible for algal cells inactivation. This result clarifies the core mechanism of MoO₃/MoO_3-x in photocatalytic algae removal.

This study was conducted within the area enclosed by the Third Ring Road of Nanchang, China. The Green View Index (GVI) was calculated using semantic segmentation of panoramic street view imagery, while Land Surface Temperature (LST) was retrieved through the Google Earth Engine (GEE) platform. Hotspot analysis, profile analysis, and Geographically Weighted Regression (GWR) model were employed to investigate the spatiotemporal patterns of GVI and LST and explore the scale-dependent impact of GVI on LST. The main conclusions are as follows: (1) From 2017 to 2021, the entire study area showed a declining trend, with 60.9% of the area experiencing a reduction in GVI. However, the local GVI had been enhanced and had formed a continuous green advantage zone, and the proportion of statistically significant hotspots increased from 31.6% to 41.1%. (2) During the same period, the overall LST had increased, and the Urban Heat Island (UHI) effect had intensified. The proportion of high and sub-high temperature areas rose sharply from 6.5% to 25.0%, and the proportion of strong and extremely strong UHI areas expanded from 46.0% to 50.8%. (3) The relationship between GVI and LST was foundto be spatial non-stationarity, with R² values varyingacross different grid scales. At the 500m5500m resolution, the GWR model achieved the best performance, with R² values of 0.58, 0.65, and 0.70 in 2017, 2019, and 2021, respectively. (4) A significant scale effect was identified in the impact of GVI on LST, and the 500m×500m grid was identified as the optimal analysis scale within the study area. The researchresults reveal the spatiotemporal variations of urban GVI and its multi-scale impacts on LST. This not only helps to understandthe impactof urban greening on LST from the perspective of three-dimensional greenvolume, but also providestheoretical references for urban planning.

Using ciprofloxacin (CIP) as a representative antibiotic, ciprofloxacin-resistant Serratia marcescens (CRSM) strains were isolated and characterized from the tertiary oxidation pond of an aquaculture wastewater treatment facility. The CRSM strains were systematically identified at the species level, and their resistance genes were comprehensively characterized using a third-generation sequencing platform. The inactivation efficiency was evaluated by examining the efficacy of Cu(Ⅲ) and hydroxyl radicals (·OH) generated by a Cu complex-activated PMS-based Fenton-like oxidation system on CRSM cells and genetic material in aqueous environments. The cytotoxic effects and molecular mechanisms of highly reactive oxidants in the homogeneous Cu-based Fenton-like oxidation system on CRSM were systematically investigated through a comprehensive analysis employing plate coating, scanning electron microscopy, transmission electron microscopy, and three-dimensional fluorescence spectroscopy. The results indicated that in the Cu(Ⅱ)+PMS+CIP+CRSM system, the bactericidal efficiency of CRSM was significantly enhanced, approximately 8-fold higher than that of the PMS+CIP+CRSM system. Specifically, the concentration of surviving bacteria decreased from 3.2×10⁷CFU/mL to 1.5×10²CFU/mL. The inactivation efficiency of CRSM reached approximately 97% within the initial 10-minutes, and exceeded 99.99% after a 30-minute treatment. Cu(Ⅲ) and ·OH achieved sterilization by compromising the integrity of CRSM cell membrane and cell wall, inducing damage to DNA bases (T, A, C, and G), inhibiting both intracellular and extracellular resistance genes, and degrading total DNA (both intracellular and extracellular).

The influence of Ag doping ratio on the antibacterial properties of CoP/CNx composite photocatalysts was studied from dual perspectives: photocatalyst structure-activity relationships and bacterial response mechanisms. Ag/CoP/CNx composite materials were fabricated using the photodeposition method. The crystal structure, morphology and optical properties were systematically characterized through X-ray diffraction, transmission electron microscopy, and UV-visible diffuse reflectance spectroscopy. The separation efficiency of photogenerated carriers was enhanced when Ag was introduced, which resulted in improved photocatalytic activity. Complete E. coli inactivation was accomplished within 20minutes when 2wt% Ag doping was employed with an initial bacterial concentration of 10⁴CFU/mL. The bactericidal efficiency was sustained at 100%, 99.99%, 98.60%, and 97.51% over four successive cycles, whereby remarkable stability was demonstrated. Through free radical quenching experiments, holes (h⁺) were determined to be the dominant active species, while superoxide radicals (·O₂^-) were identified as secondary active species. The sterilization efficiency was decreased to 71.9% and 23.7% after radical scavenger were introduced, respectively. The K⁺ release concentration was elevated from 2.64mg/L to 5.47mg/L (CoP/CNx) and 7.30mg/L (Ag-CoP/CNx). The destruction of cell membrane structures was verified by scanning electron microscopy and Fourier transform infrared spectroscopy analyses. This damage was induced by holes and superoxide radicals, whereby intracellular contents were leaked. Cell penetration was subsequently observed, oxidative damage to biomolecules, including DNA and proteins, was triggered. The research findings were established as theoretical and technical foundations for the implementation of Ag-based nanocomposite photocatalysts in wastewater treatment and environmental disinfection applications.

In this study, 16commercial microbial samples were collected. Leveraging available phosphorus content as the screening criterion, we conducted preliminary screenings of phosphate-solubilizing efficiency in different microbial sources, optimized inoculation quantities, and developed composite microbial consortia through strain combination. Pot experiments were then carried out to evaluate the effects of tailings with composite microbial consortia on the growth and quality of Chinese cabbage. The results show that four efficient phosphorus-solubilizing bacteria were identified after delicately screening and then three composite bacterial agents (numbered as C3, C4 and C6) were obtained by orthogonal experiments. After cultivating for 7d, the phosphate-solubilizing efficiencies of these inoculants were increased by 7.1~7.6 times compared with that of comparison group. The pot experiment indicated that with phosphate tailings and composite microbial inoculant C4 were significantly improved in comparison group, that is the chlorophyll content and yield increased by 15.96% and 40.78%, respectively. Moreover, the contents of soluble protein and vitamin C in Chinese cabbage were significantly increased by 18.52% and 229.36%, respectively. In summary, the composite microbial inoculants significantly increased the available phosphorus content in phosphate tailings and demonstrated an important theoretical significance and a broad application potential in managing harmless treatment and efficient utilization of phosphate tailings.

In the present study, a comprehensive investigation of PAHs in surface dust from Beijing was conducted through the integration of the Positive Matrix Factorization (PMF) model, Health Risk Assessment (HHRA) model, Monte Carlo simulation, and bootstrap uncertainty analysis. This integrated approach enabled a systematic analysis of the occurrence characteristics, health risks, and primary risk sources of 16 priority PAHs, while simultaneously quantifying uncertainties inherent in both risk assessment and source apportionment processes. Results indicated that the total concentrations of PAHs in Beijing’s surface dust ranged from 2.33 to 19.22μg/g, with high-ring PAHs being the dominant component (mean concentration: 6.43μg/g). Specifically, traffic-dominated zones within core urban areas exhibited the highest PAH levels (13.39μg/g), whereas ecological zones displayed the lowest concentrations (5.24μg/g). Probabilistic analysis revealed that the probability of moderate carcinogenic risk associated with PAH exposure reached 90.02% for adults and 94.97% for children, respectively. Children were found to be more susceptible to PAH-related health risks via the hand-to-mouth ingestion pathway, whereas adults faced greater vulnerability through dermal contact. Key driving factors influencing PAH exposure risks included duration of exposure and skin contact area. Source apportionment results identified three primary contributors to PAHs in surface dust: vehicle exhaust emissions (37.4%), non-combustion vehicle-related emissions (26.6%), and biomass/coal combustion (33.8%). Notably, although biomass/coal combustion accounted for 33.84% of the total PAH concentrations, its contribution to associated health risks was only approximately 15%. This observation highlights a significant discrepancy between concentration-based and risk-based source apportionment outcomes. Collectively, these findings provide valuable scientific insights to support the development of targeted pollution control measures for PAHs in Beijing.

Heavy metals in mainstream cigarette smoke can pose risks to smokers and other exposed populations. Although international standards have released to control of hazardous substances in tobacco products, no recognized standard currently exists for quantitative management of heavy metals in cigarettes. The scientific and precise exposure modeling and health risk assessment of heavy metals in mainstream smoke from best-selling cigarettes could provide theoretical support for developing targeted quantitative control strategies on both government and smoker scales. The basic levels of arsenic (As), cadmium (Cd), and lead (Pb) in the 15best-selling brands of cigarettes in Hubei Province were investigated, and a comparative analysis of the content in different cigarette types was conducted. Further, the human respiratory tract model was introduced to calculate the deposition rates of particulate matter of different sizes in mainstream smoke, and then the deposition doses in each part of the human respiratory tract were estimated. Finally, integratedly using inhalation exposure feature of mainstream smoke, the regional exposure parameters and triangular fuzzy numbers, an optimized health risk assessment model was established and carried out. The results showed that the mean values and ranges of As, Cd, and Pb in mainstream smoke were as follows: Cd (1.95mg/kg, 0.623~2.81mg/kg), As (1.33mg/kg, 0.172~2.88mg/kg) and Pb (1.13mg/kg, 0.413~1.65mg/kg). PM_2.5 accounted for 75%~85% of the particulate matter released from mainstream smoke, and the deposition rates in respiratory tract after fuzzy number operation were [27.48%, 29.19%] for PM_2.5and [28.50%, 30.46%] for PM₅. The carcinogenic risk of As, Cd, and Pb in mainstream smoke was ranked as follows: Cd (Ⅱ-Ⅴ) > As (Ⅱ-Ⅳ) > Pb (Ⅰ), hence As and Cd were identified as the priority heavy metals for control. Based on the annual mortality rates attributed to tobacco consumption, the standard value of Class Ⅱ risk (1×10^-5) was chosen as the risk control value for daily smokers. And according to the inverse calculation of the total exposure of mainstream smoke, the daily smoking amount based on this survey should be controlled at 3~4 cigarettes for thick cigarettes and menthol cigarettes, and 1~2 cigarettes for thin cigarettes. Advise all types of smokers to quit smoking as soon as possible.

The relationship between ethylene oxide (EO) and cardiovascular disease risk was investigated in this article. A total of 5041 adults were enrolled, and ethylene oxide levels were measured in serum using hemoglobin ethylene oxide conjugate (HbEO) as a biomarker. Data were obtained from the National Health and and Nutrition Examination Survey (NHANES) database in the United States between 2013 and 2018. Weighted logistic regression models and restricted cubic spline plots were used to examine the dose-response relationship between HbEO and cardiovascular disease risk. Subgroup analyses were conducted to evaluate heterogeneity in the study. Through multiple regression analysis, it was found that serum HbEO levels were positively associated with cardiovascular disease risk, and statistical significance was maintained after adjustment for multiple confounders (OR: 1.15, [95% CI: 1.02~1.30], P=0.021). For most cardiovascular diseases, increased exposure to ethylene oxide was associated with elevated OR values, although this increase was not always statistically significant. Additionally, HbEO was positively correlated with the incidence of angina pectoris and heart attack, with the highest OR values observed after full adjustment (OR=1.36 [95% CI: 1.11~1.68] and OR=1.35 [95% CI: 1.14~1.60], respectively). Angina pectoris was the most affected outcome.A significant non-linear relationship was identified between HbEO and overall cardiovascular disease risk (P-overall=0.002, P-non-linear=0.006). Dose-response analysis indicated that elevated serum HbEO levels were associated with an increased risk of angina, with evidence supporting a linear relationship (p-overall=0.012, p-non-linear=0.748). A significant non-linear association was also observed between HbEO and heart attack risk (p-overall<0.001, p-non-linear=0.011).In summary, ethylene oxide metabolites in the blood were associated with an increased incidence of cardiovascular diseases, particularly angina pectoris and heart attack. Further research is needed to confirm these findings.

In the context of global climate change, the health impacts of heatwave events exhibit marked regional heterogeneity, posing a severe threat to public health. This study analyzed daily respiratory disease outpatient data, meteorological monitoring data, and air pollution data from Handan City (2016~2021) using a Generalized Additive Model (GAM) to evaluate the risk of respiratory disease visits under 12 heatwave definitions (based on P96-P99 percentile thresholds lasting 2~4 days). Results demonstrate significant definition-dependent variability in heatwave frequency and duration: extreme heatwaves (P99 threshold, 4days) occurred only twice (9 cumulative days) over six years, while moderate heatwaves (P96 threshold, 2days) reached 20 occurrences (66 cumulative days). During heatwave periods, temperatures were significantly higher with reduced variability compared to non-heatwave periods, accompanied by statistically significant differences in daily outpatient volumes.Forheatwaves lasting 2~3 days, health risks initially increased and then decreased with rising intensity, whereas for events lasting 4 days, risks progressively declined with increasing intensity. Peak risks for P96-P98-defined heatwaves occurred at lag 3~5 days, while P99-defined extreme heatwaves showed immediate peak risks at lag1day. Long-duration heatwaves ((4days) posed significantly higher and more prolonged risks compared to short-duration events ((2days). All heatwave types exhibited a "bimodal lag pattern" with acute (lag 0~3) and delayed (lag 5~7) effect phases. The risk profile for low-intensity, short-duration heatwaves was relatively stable, whereas high-intensity, long-duration events demonstrated greater risk fluctuations. These findings provide regionally tailored evidence to inform the development of dynamic heatwave health early warning systems.

The benefits of the ultra-low emission retrofit (ULER) in Suzhou’s iron and steel industry in 2023 were evaluated in this study. Following the retrofits, annual emissions of SO₂, NO_x, and PM declined by 66.67%, 65.64%, and 53.48%, respectively, with substantial reductions in key processes such as sintering, coking, and blast furnace ironmaking. Evaluated by the mesoscale atmospheric chemical model WRF-Chem, the average concentrations of SO₂, NO₂, PM_2.5 and PM₁₀ in Suzhou and its surrounding urban agglomerations decreased by 5.02%, 1.83%, 5.16% and 5.06% respectively, while O₃ levels increased slightly by 0.93%. Suzhou exhibited the largest reductions in SO₂ and NO₂ concentrations, whereas the most significant decreases in PM_2.5 and PM₁₀occurred in Taizhou. Given that PM_2.5 pollution in China is the most severe in winter, the exposure-response relationship function was used to quantify the health benefits. The total number of premature deaths due to PM_2.5 pollution from all causes, cardiovascular diseases and respiratory diseases was reduced by 105 (95%CI: 88~122), 31 (27~36) and 12 (10~14) respectively. Geographically, the reductions in premature mortality showed a pattern of "higher in the north and lower in the south"; Nantong achieved the greatest health gain, with premature deaths from all causes reduced by 24 (15~32).

Using the data from Food and Agriculture Organization of the United Nations (FAO) and the China Statistical Yearbook spanning 1961 to 2021, this paper systematically analyzes the current status and evolution patterns of methane (CH₄) emissions from rice, nitrous oxide (N₂O) emissions from wheat, and N₂O emissions from maize in the world's five major grain-producing countries. It further explores the long-term trends and driving factors of CH₄ and N₂O emissions from China’s three staple grain crops. The results show that in recent years, China’s rice CH₄ emissions and wheat N₂O emissions consistently ranked highest among the five countries while maize N₂O emissions and the corresponding emissions per unit grain mass both ranked second. However, the carbon emissions per unit grain mass for both crops was in the middle-to-lower range among the five nations. Between 1961 and 2021, China’s rice CH₄ emissions, wheat N₂O emissions, and maize N₂O emissions increased by 13.9%, 474.0%, and 831.5%, respectively. Conversely, their non-CO₂ carbon emissions per unit grain mass significantly decreased by 69.9%, 40.5%, and 38.3%, respectively. The heavy application of chemical nitrogen fertilizer was identified as the key driver that triggers the rapid increase in wheat and maize N₂O emissions. This study reveals that China has made significant progress in reducing carbon emissions from its three major grain crops. Nevertheless, the rapid rise in N₂O emissions from wheat and maize has become a major constraint hindering further progress in decarbonizing China’s grain production.

The composite quasi-natural experiment empowered by the "dual-carbon linkage" was reconstructed based on carbon emission trading and low-carbon city construction. Using panel data from 280 prefecture-level cities in China from 2011 to 2022, a double machine learning model was employed to examine the impact of the "dual-carbon linkage" on urban green transformation. It was found that the "dual-carbon linkage" had a significant positive effect on both urban economic transformation performance and green innovation performance, with coefficients of 0.027 and 0.083, respectively, significant at the 1% statistical level. This indicated that the "dual-carbon linkage" contributed to comprehensively accelerating urban green transformation and demonstrated a more pronounced empowering effect compared to single institutional innovations. Mechanism analysis based on the "government-market-society" three-dimensional framework revealed that the "dual-carbon linkage" indirectly facilitated urban green transformation through government environmental improvement effects by reducing environmental pollution and enhancing environmental enforcement (with coefficients of -0.727 and 0.721, respectively), market resource allocation effects by promoting industrial upgrading and accelerating economic agglomeration (with coefficients of 0.134 and 0.332, respectively), and social participation and governance effects by raising public environmental awareness and optimizing public service environments (with coefficients of 0.487 and 0.052, respectively). Heterogeneity analysis showed that the incentivizing effects of the "dual-carbon linkage" on green transformation were more pronounced in cities with lower bureaucratic redundancy (coefficients of 0.110 and 0.147, respectively), greater financial technology support (coefficients of 0.039 and 0.067, respectively), higher market integration (coefficients of 0.057 and 0.102, respectively), better sci-tech business environments (coefficients of 0.121 and 0.138, respectively), as well as in cities located in the Yangtze River Economic Belt (coefficients of 0.041 and 0.069, respectively) and eastern regions (coefficients of 0.063 and 0.046, respectively). This study provided empirical evidence and decision-making insights for local governments to coordinate and unleash the synergistic force of "dual carbon" institutional innovations and accelerate the comprehensive green transformation of the economy and society during the "15th Five-Year Plan" period.

This study focused on Handan, a representative steel industry city, where the characteristics of ozone pollution were systematically analyzed based on atmospheric pollutant and meteorological data from 2014 to 2023. The Random Forest model was utilized to investigate the correlation between key meteorological factors and O₃ concentrations, as well as their relative contributions. Furthermore, the WRF-CAMx model, combined with the EKMA curve method, was employed to examine O₃ formation sensitivity and corresponding precursor emission reduction strategies in different districts. The results indicated that the monthly average O₃-8h concentration exhibited distinct seasonal variations (summer > spring > autumn > winter), with the highest levels of exceedance occurring between June and July. Hourly O₃ concentrations followed a unimodal trend, which peaked between 15:00 and 16:00. Correlation analysis revealed that relative humidity (RH), solar radiation (SR), and temperature (T) were significantly correlated with O₃ concentrations, with correlation coefficients of -0.69, 0.68, and 0.58, respectively. Their relative contributions were determined to be (24.90±2.41)%, (18.66±2.30)%, and (25.56±2.02)%. It was found that O₃ pollution was more likely to occur when T > 30℃ and 36% < RH < 56%. The O₃ control zone analysis showed that Handan’s central and western areas were VOCs-controlled, with an optimal VOCs-to- NO_x emission reduction ratio of 1.5:1. The eastern districts were identified as NO_x-controlled, while other areas required coordinated control of both VOCs and NO_x, with an optimal reduction ratio of 1:1.5. These findings provided a scientific basis and policy recommendations for the emission reduction and control of O₃ pollution in industrial cities.

This study constructs an indicator system for China's "zero-waste cities" construction. It uses the entropy weight method to measure the system's level across 30 provinces (autonomous regions and municipalities) from 2011 to 2022. The coupling coordination model is employed to analyze the development coordination between subsystems, while the gravity model and social network analysis explore the spatial network characteristics of the system. Lastly, the quadratic assignment procedure (QAP) is used to identify the driving factors behind the system. The results show that: the coupling correlation and coordination between subsystems have improved over time, with regional coordination levels in the order of: Class Ⅰ > Class Ⅱ > Class Ⅲ > Class Ⅳ > Class Ⅴ. The spatial network connectivity of each region in China's "zero waste city" construction system shows an upward trend, with increasing network density and more strong connection networks. However, the overall network remains at a low level and is unevenly developed. The network connection level of Class Ⅰ regions is higher than others, with network efficiency tending towards stability. Economic development, urbanization, innovation capacity, and industrial structure coordination significantly influence the spatial network. Economic development has a greater impact on Class Ⅰ and Class Ⅴ regions, whereas urbanization affects Class Ⅱ and Class Ⅲ regions more significantly.

This study, based on the 2017 multi-regional input-output table of China, constructed an Environmentally Extended Multi-Regional Input-Output (EE-MRIO) model to track the virtual cropland flow paths. It then quantified the value of land ecological products using the equivalent factor method and designed a “Beneficiary Pays” compensation standard. The research findings include: The Huang-Huai-Hai Plain (Henan, Shandong) and the Northeast Plain (Heilongjiang), leveraging their resource endowment advantages and policy support effects, have formed core virtual cropland supply regions; meanwhile, the Huang- Huai-Hai Plain (Henan, Shandong) and the Yangtze River Delta (Jiangsu) have emerged as centers of land resource use due to population concentration and industrial transformation needs. The national net virtual cropland flow shows a “gradient transfer” characteristic, moving from north to south and from west to east, basically adhering to the “proximity effect”. Major grain-producing regions such as Heilongjiang, Jilin, and Inner Mongolia are the main net outflow sources of virtual cropland, while economically developed regions like Guangdong and Zhejiang are the core net inflow destinations. Key path analysis reveals significant transfers of land ecological products along cross-provincial flow chains such as Heilongjiang-Jilin, Inner Mongolia-Shanxi, and Heilongjiang-Zhejiang, highlighting the dependence of developed regions on the land ecological products of major grain-producing areas. By constructing a modified matrix incorporating compensation for land ecological products in each region, the study not only clarifies the accountability for land ecological protection, but also provides a scientifically sound basis for compensation. This opens up a new path for the sustainable utilization of land resources and the harmonious coexistence of economic development.