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20 July 2026
Volume 46 Issue 7
    
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    Air Pollution Control
  • Precise filling method of PM2.5 missing values based on a bidirectional XGBoost
    LI Fei, WANG Zhen, OU Chang-hong, GUO Jin-yuan, CAI Yao-ming, JIANG Pei, QU Zhi-guang, WEI Yong-chang
    China Environmental Science. 2026, 46(7): 3553-3562.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    This study introduced an innovative precise filling method of PM2.5 missing values based on a bidirectional extreme gradient boosting (XGBoost) strategy. The developed strategy could perform forward and reverse parallel predictions on time series PM2.5 data, and then a dynamic weight distribution mechanism designed based on the characteristics of the data was used for weighted integration. Then, based on constructed simulated datasets with different missing data patterns, a comparative analysis was conducted between the bidirectional XGBoost strategy and other commonly used imputation methods, including linear interpolation, diurnal cycle-constrained empirical orthogonal function (DCCEOF), random forest (RF), and XGBoost. Results showed that most models performed well under hourly random missing conditions (R2> 0.9). Among them, the linear interpolation performed the best (R2=0.99, MAE=2.23), while XGBoost performed a better ability in terms of restoring data fluctuations and cyclical features. However, in scenarios involving 24-hour continuous missing data and spatiotemporally clustered gaps, the unidirectional algorithms generally exhibited lower accuracy (R2=0.80 and 0.43, respectively). In contrast, the proposed bidirectional XGBoost strategy significantly enhances imputation performance, with corresponding R2 values increasing to 0.83 and 0.75, outperforming the single-model approaches. This advantage is especially pronounced in handling data gaps over relatively medium- to long-term time scales.
  • OMI-based estimation of ground-level NO2 concentration and dry deposition flux over the Yangtze River Basin
    ZHUANG Hao-bo, CHEN Xin, DONG Si-yuan, TIAN Ye
    China Environmental Science. 2026, 46(7): 3563-3571.
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    This study integrates tropospheric NO2 vertical column density retrieved from ozone monitoring instrument (OMI) with ground-based NO2 observations and multiple meteorological variables to develop a random forest regression model for the high-precision estimation of ground-level NO2 concentrations across the Yangtze River Basin during 2018~2022. Based on these estimates, the NO2 dry deposition flux are further quantified. The results show pronounced seasonal variability with higher ground-level NO2 concentrations in the Yangtze River Basin in winter and lower in summer. Spatially, elevated NO2 concentrations are mainly distributed in densely populated and highly urbanized regions. Comparison with the Multi-resolution Emission Inventory model for Climate and air pollution research (MEIC) emission inventory reveals that ground-level NO2 concentrations are strongly correlated with NOx emissions from the transportation and energy sectors. The NO2 dry deposition flux exhibits a slow but consistent decreasing trend over the study period, range from 2.77 to 2.66kg N/(hm2⋅a). Using a land-use classification approach, atmospheric dry deposition nitrogen flux is estimated to account for 3.5% of the nitrogen flux transported by the Yangtze River into the sea. By addressing the uneven spatial distribution and limited density of monitoring stations in the Yangtze River Basin, this study provides an effective framework for improving the quantification of NO2 dry deposition flux.
  • Study on a PM2.5 remote sensing retrieval method for northwest China integrating NRBO-XGBoost and CCHZ-DISO
    WANG Zhuo-wen, GAO Yu-xiao, LIU Shao-zhuo, CHEN Zhen-zhu
    China Environmental Science. 2026, 46(7): 3572-3584.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To address the critical challenges of sparse ground monitoring stations, complex terrain, and the inherent tendency of PM2.5 inversion models to converge to local optima in Northwest China, this study proposes a novel remote sensing inversion method that integrates the Newton-Raphson Based Optimizer (NRBO)-optimized eXtreme Gradient Boosting (XGBoost) with the CCHZ-DISO comprehensive evaluation system. Using multi-source data spanning 2017 to 2023, we constructed a 23-dimensional feature set encompassing Aerosol Optical Depth (AOD), meteorological factors, Human Activity Intensity (HAI), and temporal autocorrelation factors (T-PM2.5). First, the Random Forest-Recursive Feature Elimination with Cross-Validation (RF-RFECV) algorithm was employed to eliminate redundant features, yielding an optimal subset of 16 features. Subsequently, the NRBO algorithm was applied to perform intelligent hyperparameter optimization for XGBoost, based on which the final inversion framework was established. The results demonstrate that the proposed RF-RFECV-NRBO-XGBoost model achieves the best overall performance, with a coefficient of determination (R2) of 0.89, root mean square error (RMSE) of 13.78μg/m3, and correlation coefficient (CC) of 0.95. It significantly outperforms benchmark models including particle swarm optimization (PSO)-XGBoost, random forest (RF), and support vector machine (SVM). Seasonal evaluation based on the CCHZ-DISO system reveals that the model performs best in winter (DISO=0.0448). Furthermore, the model successfully captures the spatial heterogeneity characterized by a pronounced east-west dichotomy in air quality across Northwest China, as well as the downward trend in PM2.5 concentrations from 2017 to 2022.
  • Analysis of the impacts of boundary layer processes from meteorological tower and numerical model on the vertical characteristics of ozone in Tianjin
    ZHANG Jia-lin, JIA Dan, WANG Xin-zi, LIAO Yun-chen, SUN Shu-peng, CAI Zi-ying
    China Environmental Science. 2026, 46(7): 3585-3598.
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    Based on observations of ozone (O3), nitrogen oxides (NOx) and turbulence at ground level, 120m and 200m platforms of the Tianjin boundary layer observation tower from April to June 2025, combined with numerical simulation, this study analyzes the vertical distribution characteristics of O3 under different temporal scales, pollution levels, temperature stratifications and turbulence intensities, and explores the influence mechanisms of boundary layer processes. The results show that during the study period, the average O3 concentrations at ground, 120m and 200m heights were 138.2, 165.7 and 178.9μg/m3 in the daytime (09:00~17:00), and 80.8, 110.9 and 130.3μg/m3 at night (18:00~08:00 next day), respectively, indicating a gradual increase in O3 concentration from the surface to upper air within the surface layer. The O3 concentration variability on moderate–severe pollution days was significantly larger than that on clean days, reflecting the impacts of high-concentration O3 in the nocturnal residual layer and the middle daytime atmosphere on ground-level O3. Numerical simulations show that daytime near-surface O3 contributions in descending order were chemical formation, turbulent mixing, vertical advection and horizontal advection, with mean intensities of 36.9, -12.8, -8.4 and -5.7μg/m3 per hour; all terms except chemical formation present negative contributions. At night, chemical consumption was -8.7μg/m3, turbulent mixing droped to 0.41μg/m3, while horizontal and vertical advection were 5.7 and -3.4μg/m3, respectively. Compared with surrounding-areas, the near-surface layer in Tianjin acted as an O3 source in the daytime and an O3 sink at night. Within the 0~200m layer, a larger daytime vertical temperature difference promoted more uniform O3 mixing and raised the probability of near-surface O3 pollution. Nocturnal temperature inversion favors NOx titration near the ground, further enlarging the O3 concentration gap between the surface and the residual layer. Moderate O3 pollution occurred on May 28~29 and June 12~13, mainly due to weakened daytime turbulent mixing that eliminated the dilution effect on near-surface O3 and even caused downward transport of upper-level O3 to the ground. Moderate-severe O3 pollution was observed on June 23~25, in which subsidence- dominated vertical advection increased the hourly growth rate of daytime O3 concentration by 8~9μg/m3, accounting for the abnormal rise in ground-level O3. Observations reveal that the negative correlation between turbulence intensity and O3 concentration strengthens with height. Turbulent kinetic energy (TKE) at 120m performs better in characterizing vertical exchange than at other levels. O3 pollution tends to occur in Tianjin when daytime TKE was 1.0~3.4m2/s2 and nighttime TKE was 0.4~2.0m2/s2, reflecting the dual effects of turbulence on O3 vertical transport and precursor diffusion.
  • Pollution characteristics and source apportionment of atmospheric carbonyl compounds in a coking plant area
    NING Yi, MU Ling, ZHANG Guo-qiang, CHEN Xuan, SUN Jie-ya, XUE Zhi-gang, TIAN Gang
    China Environmental Science. 2026, 46(7): 3599-3610.
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    Aldehydes and ketones in ambient air at a coking plant were collected using 2,4-dinitrophenylhydrazine (DNPH) tubes and analyzed by high-performance liquid chromatography. Concentrations, diurnal variations, photochemical reactivity, sources, and health risks were investigated. Acetone, formaldehyde, and acetaldehyde were the most abundant species and showed higher daytime than nighttime levels; acetone was suggested as an indicator of coking emissions owing to its high concentration and low reactivity. Stronger photochemistry in summer produced higher carbonyl concentrations and average maximum incremental reactivity (MIR) values than in winter. Formaldehyde, acetaldehyde, and methacrolein were the main contributors to hydroxyl radical loss rate (LOH) and ozone formation potential (OFP). Mean C1/C2 ratios were 1.00 (winter) and 1.47 (summer), and C2/C3 ratios were 6.23 and 8.09, respectively—lower than values typical of vehicle-dominated urban areas—indicating strong industrial influence. Multivariate linear regression apportioned summer formaldehyde to primary combustion (44.4%) and secondary photochemical formation (48.4%), while acetaldehyde was attributed 11.6% and 47.7%, respectively. Observation-based modeling implicated ethylene and other olefins from coking, oxidized by hydroxyl (OH) radicals, in secondary formation of formaldehyde and acetaldehyde. Health risk assessment indicated a carcinogenic risk from occupational formaldehyde exposure, warranting stricter control of primary formaldehyde emissions and regulation of reactive olefin precursors.
  • Future BVOCs emissions characteristics in the Beijing-Tianjin-Hebei region driven by coupled climate-vegetation changes
    SHI Ji-bo, WANG Yu, CHEN Guo-lei, HAN Li-hui
    China Environmental Science. 2026, 46(7): 3611-3619.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Biogenic volatile organic compounds (BVOCs) are important precursors for the formation of ozone (O3) and secondary organic aerosols (SOA). Under China’s dual-carbon goals, large-scale ecological restoration is expected to substantially increase vegetation coverage, which may further enhance future BVOCs emissions. In this study, a multi-model coupling framework integrating FLUS, LPJ-GUESS, and WRF-MEGAN was developed to simulate BVOCs emissions in the Beijing-Tianjin-Hebei (BTH) region under three future scenarios (SSP126, SSP245, and SSP585), with both climate change and dynamic vegetation evolution considered. The results showed that BVOCs emissions increased markedly under all scenarios; compared with 2020, the 2060 emissions were increased by 8.0, 16.5, and 21.1×104t. Forests and croplands are the dominant contributors to the increase, with emission hotspots mainly located in the northern and western forested areas and the southern agricultural zones. Driver attribution analysis indicates that climate change contributes an additional 1.8~8.6×104t, while plant functional type (PFT) changes contribute (3.2~7.6)×104t. When PFT and leaf area index (LAI) changes are considered jointly, the increment increases to (7.7~9.3)×104t. Overall, jointly accounting for future climate change and vegetation dynamics provides a more realistic representation of future BVOCs emission characteristics in the BTH region.
  • Characteristics and causes of nocturnal ozone enhancement events during the warm season in Hefei
    TONG Huan-huan, DONG Hao, ZHAO Xu-hui, GENG Tian-zhao
    China Environmental Science. 2026, 46(7): 3620-3632.
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    Taking Hefei City as a typical study area, this research integrated multi-source observational data and employed the WRF-CMAQ air quality model to systematically investigate the spatiotemporal distribution, driving factors, and formation mechanisms of nighttime ozone enhancement (NOE) events during the warm season (April-September) from 2021 to 2024. The main findings are as follows: A total of 102 days of NOE events occurred in Hefei during the warm season, primarily concentrated between 23:00 and 03:00 local time, accounting for 62% of the total events. Compared with periods without NOE events (NNOE), the average nighttime concentrations of Ox (Ox = O3 + NO2) and PM2.5 were elevated during NOE events, indicating enhanced atmospheric oxidizing capacity that promotes the formation and transformation of secondary pollutants. Case studies (June 4 and June 6, 2024) revealed a decrease in CO concentration, while the contributions of vertical diffusion to near-surface O3 concentrations reached 18 and 14μg/(m3·h), respectively. Further analysis demonstrated that vertical diffusion is the dominant mechanism driving NOE events. Under conditions of increased atmospheric boundary layer height and enhanced friction velocity, the vertical transport of high-concentration O3 from the nocturnal residual layer to the near-surface layer constitutes the core factor in NOE formation. This study reveals the key formation mechanism of nighttime O3 enhancement, providing a scientific basis for regional air quality management and O3 pollution prevention and control.
  • Pollution characteristics, source-sink budgets, and environmental impacts of atmospheric low-molecular-weight aldehydes in China
    WANG Si-qi, LIU Dong-yang, WANG Ming, YUAN Bin, SHAO Min
    China Environmental Science. 2026, 46(7): 3633-3645.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Fine particulate matter (PM2.5) and ozone (O3) remained as the key pollutants limiting further improvements in air quality across China. As important oxygenated volatile organic compounds, low-molecular-weight aldehydes played a crucial role in regulating atmospheric oxidative capacity and promoting the secondary formation of PM2.5 and O3. A comprehensive synthesis of recent advances in measurement techniques, pollution characteristics, source-sink budgets, chemical transformation pathways, and environmental impacts of low-molecular-weight aldehydes in China was presented in this review. The applicability, strengths, and limitations of offline and online measurement approaches were first compared. Subsequently, the spatial patterns, seasonal variations, and long-term trends of formaldehyde, acetaldehyde, glyoxal, and methylglyoxal were summarized. Current methods for source apportionment and source-sink budget simulation were reviewed, with particular attention to differences in formation and removal pathways among these compounds. The roles of low-molecular-weight aldehydes in production of O3 and secondary organic aerosols, and health impacts were also discussed. Finally, future research directions were proposed to provide scientific guidance for subsequent studies.
  • Spatiotemporal characteristics and dynamic evolution of nitrous oxide emissions from the food system in the Yangtze River Delta region
    ZHANG Ze-qian, LIU Meng-xiao, LIU Peng, SUN Li-hui, YANG Que-ping
    China Environmental Science. 2026, 46(7): 3646-3655.
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    The food system has been identified as the largest anthropogenic source of the third most important greenhouse gas, nitrous oxide (N2O), thus establishing it as an important sector for achieving China’s “dual carbon” goals. Using the 2019 IPCC methodology for greenhouse gas inventories together with a nitrogen flow model, N2O emissions from the food system in 27 cities within the Yangtze River Delta (YRD) region were estimated for the period 2011~2020. The spatiotemporal patterns and dynamic evolution of these emissions were examined through detrended analysis, spatial autocorrelation, and Markov chains analysis. The results indicated that the N2O emissions averaged 94.2Gg/a annually and exhibited an inter-annual trend characterized by an initial increase followed by a subsequent decrease, with 2016 identified as a pivotal turning point. The contributions of each emission source varied greatly and changed over time. Synthetic fertilizer application emerged as the primary source of N2O emissions (50.6%); moreover, the contribution of food production has declined, whereas that of food consumption and waste management has increased. Significant spatial heterogeneity was observed in N2O emissions from the food system in the YRD region. The Moran’s index was calculated as 0.4095, indicating a significantly positive spatial autocorrelation. Specifically, the N2O emission intensity associated with the food system and food production was higher in the northern region compared to the southern region, while that related to food consumption and waste management was higher in the east than in the west. The relative contributions of each anthropogenic source varied substantially across cities. In 12 cities, fertilizer contributed more than 50% of total N2O emissions; however, in Shanghai and Zhoushan, the fertilizer shares were only 27.5% and 22.4%, respectively. Based on the structural characteristics of N2O emissions, 27 cities were clustered into four groups, which facilitates the formulation of differentiated mitigation strategies. The Markov transition probability matrix revealed a strong stability in the N2O emission states of the food system in the YRD region, suggesting a low likelihood of inter-state transitions. Both “club convergence” phenomenon and spatial spillover effects were observed. The main findings revealed the spatiotemporal characteristics and dynamic evolution of N2O emissions from the food system at regional scale, thereby providing a scientific basis for formulating N2O reduction strategies for regional food systems.
  • N2O emission characteristics and mechanisms of wastewater treatment using an anoxic filter-biotrickling filter process
    KONG Qiu-yu, BING Ze-tao, DING Jing, ZHANG Shi-jin, YANG Hong, HOU Bing-dong, GAO Kuo, WANG Kun, ZHAO Qing-liang
    China Environmental Science. 2026, 46(7): 3656-3667.
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    An anoxic filter-biotrickling filter (AnF-BTF) process was developed to achieve efficient nitrogen removal while mitigating greenhouse gas emissions from wastewater treatment. The nitrogen removal performance, nitrous oxide (N2O) emission characteristics, and underlying mechanisms of the AnF-BTF system were systematically investigated. The results showed that efficient nitrogen removal was achieved at hydraulic loading rates ≤ 7m3/(m2·d) and internal reflux ratios of 150%~250%. With increasing hydraulic loading, N2O emissions exhibited a decreasing-increasing trend, whereas a pronounced increase in N2O emissions was observed when the reflux ratio exceeded 200%. The lowest carbon emission level was obtained under the optimal operating conditions of a hydraulic loading rate of 7m3/(m2·d) and a reflux ratio of 200%. Metagenomic analysis revealed the nitrogen metabolic pathways within the system, showing that the relative abundance of the N2O reductase gene (nosZ) was significantly higher than that of the nitric oxide reductase gene (norB), indicating a high potential for N2O reduction. The N2O mitigation performance of the AnF-BTF process was jointly governed by operational parameters, internal functional compartmentalization, and microbial nitrogen metabolic pathways. These results demonstrate that the AnF-BTF process is a promising low-carbon configuration for nitrogen removal, providing insights for the optimization of wastewater treatment processes with reduced greenhouse gas emissions.
  • Structural design and acetone oxidation mechanism study of RuCrOx/Al2O3 catalyst
    DANG Fan, JIANG Ze-yu, AI Chun-li, WU Ya-ni, He Chi
    China Environmental Science. 2026, 46(7): 3668-3675.
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    In this paper, RuCrOx/Al2O3 catalyst with bimetallic structure was synthesized by a one-step hydrothermal method, the effect of Ru-Cr interactions on acetone (C3H6O) catalytic oxidation was systematically investigated. The activity test results demonstrated that compared with RuOx/Al2O3 and CrOx/Al2O3, RuCrOx/Al2O3 exhibited the highest activity for the oxidation of acetone and the highest CO2 selectivity. Its T90 (the temperature required for 90% conversion of acetone) was detected as 311℃, which was much lower than those of RuOx/Al2O3 (428℃) and CrOx/Al2O3 (476℃). The oxygen vacancies, acidity, and redox performance of catalysts were systematically investigated by using various characterization methods, including XPS, EPR, O2-TPD, H2-TPR, and Acetone-TPD. The activity test results indicated that the interaction between Ru and Cr can cause charge redistribution, altering the adsorption and redox properties of the catalyst, and further improving its catalytic ability. Specifically, compared with RuOx/Al2O3 and CrOx/Al2O3, the increased presence of Ruδ+ (Ruδ+/Ru0=1.51) and Cr3+ (Cr3+/Cr6+=1.41) on RuCrOx/Al2O3 enhances acetone adsorption and activation, and the sufficient surface adsorption oxygen and oxygen vacancies (OV/OL=0.64) enhance the catalyst’s oxygen activation capability, leading to superior oxygen activation ability, redox performance, and acetone adsorption ability. In addition, in-situ infrared measurements further showed that the acetone reaction pathway of acetone oxidation on RuCrOx/Al2O3 is C3H6O → CH3CHO → CH3COOH → COOH → CO2. The strong Ru-Cr interaction was found to enhance C-C bond cleavage ability and electron transfer, promoting reactant activation, rapid conversion of intermediate products, and the deep oxidation. This work provides new insights into the rational design of low-temperature catalysts for acetone oxidation reactions.
  • Anti-sulfur properties of silver-based zeolite soot catalyst (Ag/ZSM-5)
    RUAN Hong-cheng, QIAN Zhi-ling, FENG Rui-xiang, HE Rui, DONG Xi-yuan
    China Environmental Science. 2026, 46(7): 3676-3685.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The catalytic efficiency and service life of soot catalysts in diesel exhaust are typically influenced by sulfur in the exhaust, making sulfur resistance crucial.This study investigates the sulfur resistance of silver-based zeolite catalysts (Ag/ZSM-5) by modifying their silica-to-alumina ratio (SiO2/Al2O3=50/200) and incorporating single (Ag) or bimetallic (Ag-K) species. The catalysts Ag/Z-50, Ag-K/Z-50, Ag/Z-200, and Ag-K/Z-200 were tested under sulfur dioxide (SO2) atmospheres at concentrations of 0.005%, 0.01%, and 0.015%. Under 0.015% SO2 exposure, the T50 change rates were less than 1%, 2%~7%, 6%~8%, and less than 3%, respectively. The bimetallic Ag-K/Z-200 catalyst demonstrated the best sulfur resistance. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and carbon dioxide temperature-programmed desorption (CO2-TPD) were employed to characterize the physical and chemical properties of the catalyst. In-situ diffuse reflectance infrared spectroscopy (DRIFTS) was employed to monitor real-time temperature-dependent behavior under SO2 conditions, revealing the sulfur resistance mechanisms of different catalysts.
    • Water Pollution Control
  • Separate nitrification enhanced SNEDPR for simultaneous denitrification and phosphorus removal
    ZHANG Jie, LI Yao, LI Dong, DENG Dong-cai, YOU Yue
    China Environmental Science. 2026, 46(7): 3686-3695.
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    The SNEDPR process was significantly enhanced in terms of treatment efficiency for low C/N wastewater. However, it was often limited by the requirement for additional external chemical dosing, which conflicted with the goals of energy-saving wastewater treatment. In this study, a separate nitrification strategy was adopted, and operational conditions under various anaerobic drainage ratios were compared to investigate denitrification and phosphorus removal performance, endogenous carbon source conversion, and microbial enrichment across systems. It was found that at an anaerobic drainage ratio of 1:2, organic matter in the influent was effectively captured by the system, while optimal concentrations of endogenous nitrate and alkalinity were maintained, ensuring stable SNEDPR operation. Denitrification and phosphorus removal efficiencies were maintained at 92.08% and 93.1%, respectively, and the SNED rate was increased to 64.09%. However, when the anaerobic drainage ratio was further extended to 1:3, treatment performance was observed to fluctuate, and the average TP removal rate declined to 72.98%. Moreover, the pH environment of the system was regulated by the anaerobic drainage ratio, promoting the formation of inorganic precipitates such as hydroxyapatite, which contributed to enhanced sludge particle size and structural stability. Through microbial community analysis, it was revealed that at an anaerobic drainage ratio of 1:2, dominant bacterial genera represented by Candidatus Competibacter were effectively enriched, while the relative abundance of DOHOs was significantly reduced. Consequently, efficient pollutant removal and dynamic equilibrium of the microbial community were achieved. In contrast, at an anaerobic drainage ratio of 1:3, a marked increase in filamentous bacteria represented by Thiothrix was observed, leading to deterioration in system performance.
  • Machine learning driven the prediction of UV/Fenton treatment efficiency for landfill leachate treatment
    ZHAO Jian-shu, WU Zhao-jiang, JIN Wen-biao, ZHONG Quan-fa, JIN Qing-hai, MA Xiao-ming, HE Di
    China Environmental Science. 2026, 46(7): 3696-3705.
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    UV-Fenton has emerged as a prominent technology for landfill leachate treatment due to its high efficiency, operational simplicity, and absence of secondary pollution. Aiming at overcoming the limitation of traditional experimental approaches in low efficiency and difficulty in handing complex nonlinear interactions, this study employed machine learning to optimize the reaction conditions of UV-Fenton for landfill leachate treatment. The results indicate that the random forest model optimized by particle swarm optimization (PSO) achieved the best predictive performance (R2 = 0.95, RMSE = 2.88). Based on the SHAP value method, the key process parameters were ranked in descending order of importance as follows: UV irradiation time > UV lamp power > Fe2+ dosage > initial COD concentration > H2O2 dosage> initial pH > water temperature. Validation experiments conducted under the model-predicted optimum conditions showed relative errors below 5%, confirming the reliability of the model for the reverse design of UV-Fenton system. This data-driven approach proves more effective than conventional experimental optimization, thereby supporting the engineering application of UV-Fenton technology in wastewater treatment and offering theoretical and technical insights for accurate prediction and stable, efficient process operation.
  • Responses of partial nitrification and anammox to shock loading from food waste anaerobic membrane bioreactor effluent
    LI Yi-hang, WU Ya-ping, WANG Xing, TANG Xi-fang, YAN Lu-wei, LI Qian, CHEN Rong
    China Environmental Science. 2026, 46(7): 3706-3716.
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    To investigate the performance and recovery mechanisms of a partial nitrification-anammox (PN/A) system treating effluent from a food waste anaerobic membrane bioreactor (AnMBR), a two-stage PN/A system was constructed. This study focused on its operational efficiency under shock loading of AnMBR effluent, recovery strategies, and the dynamic evolution of the microbial community. Results indicated that the PN system could quickly recover stable operation after shock loading through minor adjustments, maintaining a steady effluent nitrite-to-ammonium ratio (NO2--N/NH4+-N) above 1.1. This stability was attributed to the sufficient alkalinity in the AnMBR effluent and the successful succession of the dominant ammonia-oxidizing bacteria (AOB) to the genus norank_f_Ns9_marine-group, which showed higher adaptability to the AnMBR effluent. In contrast, the performance of the Anammox system deteriorated significantly, with the total nitrogen removal rate decreasing from 86.3% to 45.1%. The accumulation of free ammonia (FA) and free nitrous acid (FNA) were identified as the main factors inhibiting the activity of anammox bacteria (AnAOB), which decreased from 0.54g-N/g-VSS/d to 0.28g-N/g-VSS/d. To restore performance, a strategy of diluting the Anammox system influent by 50% was proposed. This measure enabled the system's total nitrogen removal rate to recover to 88.5% within 4days and remain stable, demonstrating good recovery resilience. Although system performance fluctuated, the abundance of the dominant AnAOB genus Candidatus Kuenenia remained stable, providing the foundation for system recovery. Based on these findings, this study proposes an economically feasible engineering application strategy: to treat such high-strength ammonium wastewater, the PN effluent should be appropriately diluted (e.g., by 50%) before being introduced into the Anammox system, with the proportion of PN effluent gradually increased. This approach effectively avoids the inhibition caused by FA and FNA accumulation resulting from a decline in the total nitrogen removal rate, ensuring the long-term stable operation of the PN/A system.
  • The olfactory characteristics and risk differences of penetrating algal cells in new and old cast iron pipe networks
    CHENG Ya, ZHANG Xiao-xiao, ZHAO Jian-chao, SHAO Ming-yue, SUN Jie, WEN Gang, ZHANG Hai-han, HUANG Ting-lin
    China Environmental Science. 2026, 46(7): 3717-3726.
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    To reveal the differences in odor potential and key influencing factors between the new and old cast iron water distribution systems after long-term operation, a laboratory water distribution network micro-environment simulation device was constructed. The effects of water transmission duration, water flow velocity, and initial residual chlorine concentration on the generation of β-cyclo citral (β-cyclo) in the new and old cast iron pipes were mainly investigated. Combined with scanning electron microscopy and high-throughput sequencing technology, the attachment morphology of Pseudomonas aeruginosa and the characteristics of the biofilm community on the pipe walls were analyzed. The results showed that the odor-generating potential of corroded cast iron pipes was significantly higher than that of uncorroded iron pipes; after 3 stages of operation, the concentration of β-cyclo in corroded pipe sections reached 19.46ng/L (odor threshold: 16.2ng/L), which was much higher than the 7.13ng/L in uncorroded cast iron pipes. Changes in flow velocity and residual chlorine had certain effects on odor-causing risks: changes in rotation speed (simulating flow velocity) inhibited the growth and metabolism of microorganisms in the pipe network, low residual chlorine promoted odor formation, and 1.0mg/L residual chlorine reduced the producngtion of β-cyclo. The rough and porous inner wall of corroded cast iron pipes was conducive to the attachment of Microcystis aeruginosa; the relative abundance of Microcystis aeruginosa in the pipe wall biofilm was 0.48%, which was 16 times higher than that in uncorroded pipes (0.03%), and it formed a synergistic effect with iron-tolerant microorganisms, further promoting the formation of β-cyclo. The driving mechanism of cast iron pipe corrosion on the odor-causing process was quantified through simulation experiments, providing theoretical support for the precise control of algae-derived odor pollution in water distribution networks.
  • Prediction of H2S concentration in sewage grille room using a deep learning model optimized by meta-heuristic algorithms
    LOU He-zhuang, SUN Hui, GAO Jing-qi
    China Environmental Science. 2026, 46(7): 3727-3736.
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    To address the challenge of complex dynamic variations in H2S concentration within sewage grille room and the difficulty of achieving precise predictions using traditional monitoring methods, a hybrid deep learning model integrating Long Short-Term Memory (LSTM) and Gated Recurrent Unit (GRU) was developed. An Improved Whale Optimization Algorithm (IWOA) was proposed to adaptively optimize the hyperparameters of the hybrid model. Tent chaotic mapping was introduced to enable uniform population initialization, while the Levy flight mechanism and adaptive weight factors were integrated to enhance the algorithm’s global exploration and local exploitation capabilities. Findings that the IWOA-LSTM-GRU hybrid model achieves an R2 of 0.997 on the test set, with MSE and RMSE reduced to 0.021×10-6 and 0.145×10-6, respectively. This performance significantly outperforms hybrid models optimized by other meta-heuristic algorithms, including Sparrow Search Algorithm (SSA), Firefly Algorithm (FA), and Caterpillar Fungus Optimizer (CFO). Moreover, IWOA-LSTM-GRU hybrid model accurately captured the transient peaks and gradual changes of H2S concentration, and its alarm realization rate Ra (5.55%) was highly consistent with the actual value (5.58%). This study provides a reliable theoretical tool and method support for the high-precision prediction and safety monitoring system of H2S concentration in the sewage grille room.
  • Method of enhancing algae removal and water purification performance of SiQAS-MC based on composite flocculation
    ZHENG Xu, WANG Ming-jiao, JIANG Wen-bin, ZANG Xiao-miao, SONG Xiu-xian, CAO Xi-hua
    China Environmental Science. 2026, 46(7): 3737-3745.
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    This study focuses on how to further enhance the algae-removing and water-purifying properties of the novel organosilicon quaternary ammonium salt-modified clay (SiQAS-MC). Based on the comparison of composite flocculation effects, the synergistic enhancement capabilities of different types of ions were evaluated, and trivalent cations were selected as the synergistic component. By observing the Zeta potential, particle size, and SEM micromorphology of flocs during the Fe3+-enhanced flocculation process, it was found that an appropriate amount of Fe3+ could significantly improve the size, strength, and regenerability of MC flocs, which indicates that the composite system has stronger flocculation capacity. The algae-removal conditions of the composite system were optimized based on response surface methodology (RSM) experiments, and it was found that the influencing order of the total dosage, mass ratio, and premix concentration decreased sequentially. The composite system with a ratio of m(SiQAS-MC):m(FeCl3) = 3:1 at a total concentration of 0.1g/L achieved a removal rate of 91.10%±1.29% for Prorocentrum donghaiense (with an initial concentration of 1.4×108cells/L). Meanwhile, it could remove 73% of the phosphate in the algal solution and effectively alleviate the increase in pH and turbidity of seawater caused by microalgal proliferation. This study confirms that introducing ions with composite flocculation properties can effectively enhance the algae-removing and water-purifying capabilities of SiQAS-MC, providing a reference method for modified clay technology to achieve comprehensive red tide control effects.
  • Investigation of the long-term operational stability of a two-stage partial nitrificationprocess using integrated reactor-settlers
    WU Zuo-tan, XU Zhi-hui, XU Yu-dong
    China Environmental Science. 2026, 46(7): 3746-3757.
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    An alternated sequence two-stage partial nitrification process based on different inhibitions by free ammonia (FA) and free nitrous acid (FNA) was proposed. A continuous stirred-tank reactor with an integrated reaction/sedimentation design was operated continuously over 356days in two phases. The results showed that during phase I (days 1~129), three times sequence-swapping operations rapidly reduced the specific nitrite oxidation rate (SNOR) by 66.1% to 87.4% and restored the nitrite accumulation ratio (NAR) to 89.5%~95.5%. In phase II (days 130~356), after increasing the sludge concentration to (4500±100)mg/L, ammonia- oxidizing bacteria (AOB) achieved a competitive advantage due to their higher specific growth rate. Under fluctuating nitrogen loading rates ranging from 0.56 to 3.1kgN/(m3·d), the NAR remained stable at (97.3±1.2)%. After inhibition by a high COD concentration of 200mg/L, the original reactor performance was restored within 3 days via sequence swapping. The NAR was maintained above 98% even when the hydraulic retention time was extended from 10h to 28h. High-throughput sequencing results indicated that the AOB biomass remained stable throughout the 356-day operation, with Nitrosomonas and Nitrosospira alternately dominating in response to temperature changes, while no significant increase in NOB abundance. Microbial diversities for the two-stage partial nitrification reactors decreased significantly during long-term operation, with the Shannon indexes decreasing from 5.082 and 5.137 to 4.510 and 4.184, respectively. PCoA analysis revealed significant differentiation in community composition between the two reactors due to their distinct inhibition environments.
  • Treatment of chlorophenol-contaminated wastewater by immobilized mixed white-rot fungi
    CHEN Qi-yue, TAN Yu-yu, CHEN Xin-yan, ZHU Jie-yu, WANG Yi-ming, XU Ling-yi, JIN Yu-he, WANG Xue-fei, ZHONG Yi-fan, WANG Yan-ni, LIU Peng
    China Environmental Science. 2026, 46(7): 3758-3771.
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    To address the ecological risks posed by chlorophenol-contaminated wastewater, this study employed white-rot fungi as the experimental microorganisms and used a mixed-strain strategy for treatment. Immobilized pellets were prepared by adsorption-entrapment, and the immobilization parameters were optimized using response surface methodology, with the degradation rate of 2,4-dichlorophenol (2,4-DCP) as the response variable. Changes in enzyme activities were compared to determine the optimal mixing ratio and application performance of the immobilized mixed white-rot fungal system. The results showed that when Trametes versicolor and Pleurotus ostreatus were mixed at a ratio of 1:1, the mixed-culture system significantly enhanced the activities of lignin peroxidase, manganese peroxidase, and laccase, achieving a 2,4-DCP degradation rate of 86.96% within 96h. In addition, compared with free white-rot fungal cells, immobilization significantly improved microbial stress resistance and pollutant adsorption capacity. When a composite immobilization carrier was constructed using sodium alginate (10g/L), biochar (20g/L), silica, and modified zeolite, the degradation rate increased to 94.82%. After further optimization of environmental parameters, including a pellet dosage of 11.5g/L, pH 5.5, and an initial 2,4-DCP concentration of 40mg/L, the degradation rate reached 99.26% within 96h. Overall, this study achieved efficient degradation of 2,4-DCP by optimizing the immobilization conditions of mixed white-rot fungal cultures and preliminarily explored the degradation pathway, providing a theoretical basis for the treatment of chlorophenol-contaminated wastewater.
  • Research progress on cleaning-in-place of ultrafiltration membranes with micro-nano bubbles
    GAO Hua-sheng, TANG De-chao, YAO Min
    China Environmental Science. 2026, 46(7): 3772-3778.
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    Severe fouling of ultrafiltration membranes has seriously restricted the full exertion of their technical performance. Traditional physical cleaning methods failed to thoroughly clean membrane pores. Although chemical cleaning could be applied to penetrate deep into pore channels, it was associated with the aging of membrane materials, residual chemical agents and secondary pollution. Due to unique physicochemical properties, micro-nano bubbles (MNBs) exhibited prominent advantages when combined with various cleaning technologies, thereby providing a new approach for the efficient and low-consumption cleaning of ultrafiltration membranes. The research progress in the application of MNBs alone or in combination with other technologies to ultrafiltration membrane cleaning was systematically reviewed. The mechanisms of MNBs in enhancing the efficiency of physical cleaning and facilitating the synergistic effect of chemical cleaning for ultrafiltration membranes were comprehensively analyzed. The practical effects of MNBs on improving cleaning efficiency and reducing chemical dosage were also evaluated. The findings were intended to offer theoretical references and technical support for the green and efficient cleaning-in-place of ultrafiltration membranes in the field of water treatment.
  • Effects and mechanisms of microplastic leachate on the stability of algal-bacterial granular sludge
    WANG Qin-wen, YANG Juan-ru, NIE Jing-xin, WU Pan, WANG Shu-lian
    China Environmental Science. 2026, 46(7): 3779-3790.
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    This study investigated the differential impacts and underlying mechanisms of leaching chemicals from two typical microplastics, polypropylene (PP) and polylactic acid (PLA), on the stability of algal-bacterial granular sludge (ABGS). Results showed that both PP and PLA leachates contained multiple substances highly toxic to aquatic organisms. In terms of system function, PP leachate slightly inhibited the removal of PO43--P and COD. In the PP-100 and PP-300 groups, PO43--P removal decreased by 3.5% and 3.7%, and COD removal by 4.3% and 4.9%, respectively, with no significant impact on NH4+-N removal. In contrast, PLA leachate showed a clear concentration dependent effect. At the high concentration of 300mg/L, the removal rates of PO43--P, NH4+-N, and COD decreased by 50.6%, 83.2%, and 66.3%, respectively. Physiological responses indicated that both leachates induced oxidative stress in ABGS. PP leachate caused a continuous increase in malondialdehyde (MDA). After 90days, MDA activity in the PP-300 group was 1.6 times that of the control. The PLA-300 group reached its highest MDA level, 2.3 times the control, at day 15. PP leachate promoted the secretion of extracellular polymeric substances (EPS), while PLA-300 inhibited it. However, the proportion of humic acid like substances in the PLA-100 and PLA-300 groups increased from 9.1% in the control to 20.7% and 25.1%, respectively. Microbial community analysis revealed that PP leachate mainly affected the abundance of prokaryotic functional bacteria. In contrast, PLA-300 led to the loss of eukaryotic microalgae, with cyanobacteria and fungi becoming dominant, fundamentally altering the symbiotic relationship in ABGS. This study systematically reveals the distinct pathways through which PP and PLA leachates disrupt ABGS stability. It clarifies that biodegradable PLA may pose a higher short term environmental risk. The findings provide a key scientific basis for a comprehensive assessment of the environmental impact of MPs in wastewater treatment processes.
  • Release of phthalate esters (PAEs) from PE pipes and their effects on the water quality in drinking water distribution systems under chlorine and chloramine disinfection
    LIN Si-min, XU Hong-wei, QIU Fa-wei, LU Jin-suo, SHI Bao-you, WANG Hai-bo
    China Environmental Science. 2026, 46(7): 3791-3799.
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    Two sets of simulated drinking water distribution systems (DWDSs) were established using polyethylene (PE) pipes to investigate the release of phthalate esters (PAEs) from PE pipes under sodium hypochlorite (NaClO) and chloramine (NH2Cl) disinfection, as well as their impacts on water quality in the DWDSs. The results showed that the concentrations of PAEs released from PE pipes ranged from 13.32 to 30.51μg/L in the NaClO group and from 7.55 to 37.84μg/L in the NH2Cl group. In the early stage (during the first 15days), the amount of PAEs released in the NaClO group was higher than that in the NH2Cl group. However, in the later stage (after 15days), significantly higher PAEs release from PE pipes was observed in the NH2Cl group than that in the NaClO group. This change was closely associated with the oxidation of the PE pipes wall induced by chloramine. Less biofilm and extracellular polymeric substances (EPS) were formed on the pipes wall under chloramine disinfection, which allowed chloramine to more readily come into contact with the PE pipes surface and promote oxidation. Under long-term chloramine exposure, a higher degree of oxidation of the pipes wall was induced, and the surface hydrophilicity was enhanced, thereby facilitating the release of PAEs and increasing the associated water quality risks. In addition, the effects of chloramine disinfection on water quality became more pronounced in the later stage of the experiment. In particular, chloramine disinfection exhibited stronger potential hazards in terms of PAE release, cytotoxicity, and changes in the microbial community.
  • Degradation of tetracycline hydrochloride via H2O2 activation over Cu-Mn bimetallic modified desilication sludge: Performance and mechanisms
    SHENG Guang-hong, LI Song-bo, GUO Xu-jing, WANG Shi-sheng, LIU Yi-yun, LIU Ling
    China Environmental Science. 2026, 46(7): 3800-3809.
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    A heterogeneous Fenton catalyst featuring a composite Fe2O3-CuMn2O4-SiO2 structure was synthesized, utilizing desilication sludge generated from the cold-rolling spent acid regeneration process as a carrier. Copper and manganese transition metals were incorporated through co-precipitation and subsequent calcination. The prepared material was characterized by SEM, TEM, XRD, and FTIR, and its catalytic performance was evaluated using tetracycline hydrochloride (TCH) as the target pollutant. Under the conditions of initial pH 4.3, catalyst dosage 0.3g/L, H2O2 40mmol/L, and TCH 40mg/L, the TCH removal rate of 92.22% was achieved within 90min. This performance significantly surpassed that of the singlemetal catalysts modified with only copper or manganese, indicating a notable synergistic effect between Cu and Mn. Freequenching experiments and EPR tests identified ·OH and 1O2 as the primary active species responsible for degradation, with ·O2- playing a relatively minor role. XPS analysis further revealed that electron transfer between Fe2O3 and CuMn2O4 was facilitated by multiple redox cycles involving Fe2+/Fe3+, Cu+/Cu2+, and Mn2+/Mn3+/Mn4+. This interplay collectively enhanced H2O2 activation and radical generation.
  • Recent advances in machine learning-assisted prediction of adsorption performance and mechanisms of carbon-based materials for water pollutants
    XIONG Ting, TAO Jia-le, HOU Ze-min, YUAN Xing-zhong, JIANG Long-bo, LENG Li-jian
    China Environmental Science. 2026, 46(7): 3810-3819.
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    Carbon-based materials (CBMs), such as biochar, activated carbon, and carbon nanotubes, have demonstrated remarkable performance in the adsorption and removal of water pollutants, with their adsorption influenced by multiple mechanisms and factors. Traditional experimental approaches for analyzing these factors are often time-consuming and complex, while the rapid development of artificial intelligence provides new opportunities to understand the structure-performance relationships of adsorption materials. This review systematically summarizes recent research progress on machine learning (ML) techniques for predicting the adsorption performance and elucidating the mechanisms of CBMs toward heavy metals and organic pollutants in aqueous solutions. The workflow for constructing ML models is detailed, including data collection and processing, model training and evaluation, and model interpretation. A multidimensional feature descriptor system, integrating material properties, environmental parameters, and pollutant characteristics, is established to explore the influence of different features on adsorption performance. Feature analysis indicates that environmental conditions are the primary factors affecting CBMs’ adsorption of heavy metals, followed by material properties and pyrolysis conditions, whereas the adsorption of organic pollutants is more dependent on material properties. Finally, current challenges related to data quality, feature selection, material design, and engineering applications are highlighted, and the importance of interdisciplinary collaboration, data sharing, and multi-model integration is emphasized to guide the design and practical application of intelligent environmental functional materials in pollutant remediation.
    • Solid Waste
  • Comparative study on the performance optimization of anaerobic ammonium oxidation sludge and typical municipal organic solid waste for resource recovery
    WANG Zi-yi, FU Yu-lin, CUI Yong-xin, WU Yi-fan, LI Ling-hu, YAN Chen-hao, LI Yu-you, CHEN Rong, WANG Xiao-chang, XING Bao-shan
    China Environmental Science. 2026, 46(7): 3820-3829.
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    To address the challenges of efficient resource utilization of anaerobic ammonium oxidation (Anammox) sludge and typical municipal organic solid waste, as well as the optimization of methane production efficiency during anaerobic digestion, this study systematically evaluated the methane production performance of Anammox sludge in mono-digestion and co-digestion with food waste (FW) through batch experiments. The differences in methane production efficiency between mono-digestion of Anammox sludge, FW, waste activated sludge (WAS), and their co-digestion were compared, and the optimal mixing ratio for co-digestion of Anammox sludge and FW was determined. The results showed that the methane production efficiency of Anammox sludge mono-digestion was extremely low, with a cumulative methane yield of only 45.06mL/g VS. When co-digested with FW at a ratio of 1:4 (based on VS), the cumulative methane yield significantly increased to 442.98mL/g VS, with a synergistic promotion rate of 42.5%. The corresponding maximum methane production rate reached 2.37mL/(h·g VS), which was comparable to the energy production performance of the optimal FW/WAS co-digestion ratio (4:1). Furthermore, the mechanisms underlying the synergistic promotion of methane production were elucidated through metagenomic sequencing and physicochemical characterization of the sludge. The results indicated that the extracellular polymeric substances of Anammox sludge and its symbiotic microorganisms played synergistic roles in the hydrolysis, acidogenesis, and methanogenesis stages of anaerobic digestion, alleviating acidification inhibition and promoting substrate conversion. This comparative study on the synergistic resource recovery of Anammox sludge and typical municipal organic solid waste provides a novel approach for achieving closed-loop cycling in low-carbon wastewater treatment systems.
    • Soil Pollution Control
  • Effects and mechanisms of biochar loaded with Shewanella oneidensis MR-1on the leaching of vanadium (V) in soil columns
    CUI Chen-hui, WANG Xiang, MIN Qi, SI You-bin
    China Environmental Science. 2026, 46(7): 3830-3841.
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    To address the environmental risks posed by the high toxicity and mobility of pentavalent vanadium (V(V)) in soil, this study investigated the feasibility and mechanisms of remediation using Shewanella oneidensis MR-1immobilized on biochar. Soil column leaching experiments demonstrated that microbial inoculum size and environmental pH were critical factors influencing V(V) reduction. Optimal V(V) reduction and immobilization were achieved with an initial inoculum of 1.0×108 cells/mL under neutral pH conditions, whereas acidic conditions inhibited microbial activity and exacerbated V(V) leaching. Biochar was proved to be an advantageous carrier, and its porous structure provided a stable microenvironment for S. oneidensis MR-1, effectively reducing bacterial washout. Microbial immobilization significantly transformed soil vanadium speciation, decreasing the readily mobile reducible fraction (from 45.86% to 20.58%) while increasing the stable residual fraction (from 40.54% to 59.83%). Mechanistic analysis via scanning electron microscopy (SEM) confirmed that biochar’s pores offered stable attachment sites, promoting microbial-vanadium interaction. Fourier transform infrared spectroscopy (FTIR) verified that S. oneidensis MR-1 facilitated the formation and transformation of hydroxyl, carboxyl, and sulfur-containing functional groups, which collectively participated in V(V) bioreduction and immobilization. Furthermore, three-dimensional fluorescence (3D-EEM) spectroscopy revealed that the biochar- microbe complex significantly enhanced the production of tryptophan and aromatic proteins in extracellular polymeric substances (EPS), indicating that biochar provided a favorable growth environment and enhanced microbial activity. These findings demonstrate that immobilizing S. oneidensis MR-1 on biochar can significantly reduce the leaching and mobility of soil vanadium, providing a theoretical basis and technical support for the remediation of vanadium-contaminated sites.
    • Environmental Ecology
  • Analyzing the effects of variables on odor concentration determined by the percent-correct-response method based on the Weibull model
    WANG Ya-ling, SUN Cheng-yi, NIE Lei, WANG Yong-gang
    China Environmental Science. 2026, 46(7): 3842-3850.
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    The psychophysical models and technical frameworks of different odor concentration test methods were compared to identify critical variables. Based on the Weibull model, a quantitative expression of odor concentration was constructed for the Percent-Correct-Response Method. The effects of the critical variables on the determination results were quantitatively analyzed. The following results were concluded. The psychophysical model of the Percent-Correct-Response Method exhibited the inherent traits of both Method of Average Error and Method of Constant Stimuli. The fundamental distinctions between Percent-Correct-Response Method and Method of Limits lay in the experimental termination criteria and calculation variables. For pd1=0.5, the accuracy of odor concentration based on Percent-Correct-Response Method reached 80.20% at dilution step factor φ=2, and dropped to 18.03% at φ=10. For φ=2 and 3, relative deviations of measured odor concentration were at 12.27%~20.10% and 12.88%~38.96%, respectively. To maintain deviations below 40% at higher dilution factors (φ=4, 5, 10), pd1 should be confined to 0.37< pd1<0.48, 0.37<pd1<0.45, and 0.37<pd1<0.42, respectively. Diluted odor samples and odor-free air were significantly different (P<0.05) when percent correct response was above 0.5556. Experimental termination criteria of Percent-Correct-Response method (percent correct response of 0.58) was close to the statistical critical value. However, the same termination criteria (percent correct response of 0.58) will indicate a premature termination of dilution for Method of Limits. Therefore, the Percent-Correct-Response Method will underestimate odor concentration of waste gases. In practical applications, when one is faced with choosing between The Percent- Correct-Response Method and Method of Limits, efficiency demands in the specific scenario come first. Once the Percent-Correct- Response Method is applied for odor concentration measurement of ambient air, a low dilution step factor is recommended.
  • Spatial distribution patterns of riverine chromophoric dissolved organic matter in China and its key driving factors
    WANG Yu-Lai, CHENG Yi-Han, ZHU Wen-Kai, YANG Chang-Ming
    China Environmental Science. 2026, 46(7): 3851-3862.
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    Based on a comprehensive review of dissolved organic matter (DOM) data from Chinese rivers over the past two decades, this study investigated the spatial distribution patterns of DOM content and fluorescent components across four major geographical regions, including North China, South China, Northwest China, and the Tibetan Plateau. Key driving factors were identified using multiple nonlinear regression and random forest analysis. The contents of riverine dissolved organic carbon (DOC) ranged from 0.33 to 17.91mg/L, influenced by vegetation patterns, temperature, rainfall and human activities, with significantly higher contents in northern regions than in southern, northwestern, and Tibetan Plateau regions (P<0.001). In addition, humic-like components dominated in the DOM composition in Chinese rivers ((64.45±19.90)%), and the protein-like accounted for (35.55±19.90)%. Furthermore, the riverine microbial metabolism and photobleaching caused the differentiation in riverine DOM properties, resulting in higher aromaticity and lower molecular weight in northern regions, stronger humification in southern regions, and low humification in northwestern and Tibetan Plateau regions. Results from multiple nonlinear regression and random forest analysis indicated that DOM molecular composition and aquatic environmental conditions were identified as key factors in reshaping DOM characteristics. Our findings revealed that the spatial patterns of riverine DOM content and composition in China.
  • Differential photoaging behavior and mechanism of microplastics with various colors in coastal seawater
    SUN Guo-xin, CHEN Dan-ying, YE Zhi-bin, WU Xiao-wei
    China Environmental Science. 2026, 46(7): 3863-3872.
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    In this study, polyethylene microplastics (PE MPs) were selected as the target plastic material, and PE master batches containing 50% (mass fraction) white, transparent, and purple pigments were prepared separately. These masterbatches were then irradiated with ultraviolet (UV) radiation in coastal seawater for 12days. By comparing the changes in the particle size of PE MPs at different aging stages, the results showed that the photoaging and fragmentation rates of purple microplastics in coastal seawater were higher than those of white and transparent ones (fragmentation rates: purple, 0.01/d; white, 0.009/d; transparent, 0.006/d), which confirms the differential photoaging behaviors of PE MPs with different colors in coastal seawater. Furthermore, we determined the contents of reactive oxygen species (ROS), including hydroxyl radicals (·OH) and superoxide anions (O2·-), generated during the photoaging of PE MPs in seawater. It was found that under light irradiation, purple PE MPs produced higher concentrations of ·OH (purple(7.19×10-15) mol/L; white (5.13×10-15) mol/L; transparent(5.48×10-15)mol/L and O2·- (purple(169.3 ±2.06) μmol/L; white(149.3 ±3.97) μmol/L; transparent(18.36 ±0.28) μmol/L) compared with white and transparent PE MPs, which further accelerated the photoaging process of MPs. This is because the purple pigment coated on the surface of MPs can enhance the UV absorption efficiency of the polymer during photoaging. In conclusion, the findings of this study clarify the differential photoaging behaviors and mechanisms of MPs with different colors in the current marine environment, which is of great significance for a deeper understanding of the sources and formation processes of MPs in the aquatic environments.
  • Effects of cascade small hydropower development on benthic macroinvertebrate communities in headwater streams
    WU Xin-yi, ZENG Chen-jun, SHI Wen-qing, XING Ran
    China Environmental Science. 2026, 46(7): 3873-3882.
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    Cascade small hydropower development disrupts river hydrological and hydrodynamic regimes, leading to changes in benthic macroinvertebrate communities and affecting ecosystem structure and function. To elucidate the impact mechanisms in headwater streams, this study compared two adjacent, physically similar streams: Tongluowan Stream, affected by cascade hydropower development, and Yashankeng Stream, a natural reference stream. Benthic macroinvertebrate communities and environmental parameters were monitored during the wet (June) and dry (December) seasons of 2022. The results demonstrated that hydropower development not only reduced macroinvertebrate density and diversity but also altered their seasonal dynamics. In the regulated stream, benthic macroinvertebrate density decreased by approximately 50% in the dry season compared to the wet season, whereas no significant seasonal difference was observed in the natural stream. Diversity was lower in the dry season in the regulated river but higher in the natural stream. Furthermore, hydropower operations shifted dominant taxa from rheophilic, clean-water indicator species to pollution-tolerant species that prefer stagnant habitats. Flow velocity, discharge, and substrate type were identified as the primary environmental drivers structuring these communities. This study enhances the understanding of the ecological impacts of cascade small hydropower development on headwater stream ecosystems.
  • Experimental study on the transport behavior and partition characteristics of microplastics in homogeneous and heterogeneous aquifers
    XU Tian-yang, ZHANG Yan-ru, LI Wang-rui, QI Bu-ri
    China Environmental Science. 2026, 46(7): 3883-3893.
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    In this study, batch experiments and two-dimensional sand tank experiments were conducted. The effects of particle size of porous media, clay minerals and groundwater ionic strength on the solid-water distribution characteristics of different types of MPs were investigated. And a comparison in the migration behavior and spatial-temporal distribution of MPs was made between homogeneous and heterogeneous aquifers. The experimental results show that the solid-water partition coefficient Kd of MPs is positively correlated with the particle size of MPs (0.1~10μm) and the ion concentration in groundwater (1~100mmol/L), but negatively correlated with the particle size of aquifer medium (0.075~1.5mm). The presence of clay minerals promotes the partition of polystyrene microspheres (PS) and polylactic acid microspheres (PLA) to the solid phase, while the effect on polyethylene terephthalate microspheres (PET) is the opposite. In the 50-day dynamic migration experiment, the final retention percentages of MPs in simulated homogeneous and heterogeneous aquifers were 17.0% and 13.8% respectively. Due to the difference in permeability, MPs showed different spatial and temporal distribution characteristics in the two aquifers. MPs showed an obvious ‘flow around’ behavior in the heterogeneous aquifer, preferentially migrating to the upper or lower layers of the sand tank, while the concentration in the low permeability zone (LPZ) in the middle and its downstream is lower. The local focusing coefficient of the heterogeneous aquifer was much smaller than that of the homogeneous aquifer at the beginning of the experiment, but its value increased gradually with time, suggesting that the desorption and release process of MPs in LPZ lagged significantly behind that in the high-permeability zone.
  • Three-dimensional simulation of groundwater contaminant migration based on a posteriori error estimation and an octree adaptive mesh
    ZOU Yan-hong, PENG Xu, YANG Fu-qiang, YUAN Hua-qing
    China Environmental Science. 2026, 46(7): 3894-3904.
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    To address the challenge of balancing accuracy and efficiency in three-dimensional groundwater pollution simulation, a finite volume method numerical model integrating a posteriori error estimation and an octree adaptive mesh is proposed. Based on an octree data structure, the model constructs a posteriori error indicator to quantify discrete errors and drive dynamic adjustment of the local mesh. Taking Cr(VI) migration in a chromium-contaminated site as an example, a dual-module coupled framework of "solver-adaptive" is used to solve the flow field and concentration field, achieving adaptive refinement and coarsening of the octree mesh. Results show that the model can accurately capture the details of the pollution plume front. Compared with a uniform mesh, the number of computational units is reduced by approximately 60% at the same global error level, and the average absolute error of the monitoring well concentration simulation decreases from 0.295mg/L to 0.025mg/L. This method significantly improves computational efficiency while maintaining accuracy, providing a feasible solution for fine three-dimensional simulation of groundwater pollution.
  • A review on the photodegradation of emerging pollutants mediated by algal-derived dissolved organic matter in water
    WANG Xin, LI Ting-ting, QUAN Li-xia, HUANG Zhuo-chao, PENG Bo, LI Zhong-wu
    China Environmental Science. 2026, 46(7): 3905-3915.
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    Regarding the challenge of the difficult degradation of new pollutants (EPs) in water environments, the photodegradation process mediated by algal-derived dissolved organic matter (ADOM) due to its high efficiency and green characteristics, has become a research hotspot in the field of water pollution treatment. Based on a systematic review of the photophysical properties of ADOM and the mechanism of generating active intermediates, this paper focuses on summarizing the three major pathways that drive the photodegradation of new pollutants by ADOM, including direct photodegradation, indirect photodegradation, and self-sensitized photodegradation. It further explores the influence of ADOM's own characteristics and external environmental factors on the efficiency of photodegradation. Finally, it looks forward to the research direction of ADOM photodegradation of pollutants, proposing suggestions such as exploring the interactive photodegradation mechanism of multiple sources of DOM, the kinetics of photodegradation under multiple factors combined conditions, the formation and transformation pathways of degradation products, and the application of ADOM sensitization green technology, in order to provide theoretical basis for water environmental pollution prevention and ecological restoration.
  • Centennial evolution of dissolved organic matter composition and molecular characteristics in the sedimentary record of Zhushan Bay, Lake Taihu
    ZHAI Jia-yu, YAN Yong-qin, LIU Xiang-yu, WANG Qian, XING Jun-feng, LYU Rui, GAO Yun-ze, XIAO Yi-hua
    China Environmental Science. 2026, 46(7): 3916-3926.
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    To elucidate the centennial-scale evolution of dissolved organic matter (DOM) in lake sediments, a sediment core from Zhushan Bay of Lake Taihu was investigated. A multi-proxy approach, including radionuclide dating (210Pb and 137Cs), nutrient and pigment analyses, UV-Vis absorption spectroscopy, excitation-emission matrix (EEM) fluorescence spectroscopy, and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), was employed to reconstruct the compositional and molecular characteristics of sedimentary DOM over the past century. The results indicated a continuous accumulation of organic matter and nutrients since the mid-20th century, with total nitrogen (TN) increasing from 0.91 to 1.38mg/g and total phosphorus (TP) from 0.015 to 0.035mg/g. Based on multiple proxies, the sedimentary record can be divided into three stages: a natural background stage (before the 1970s), a period of intensified anthropogenic disturbance (1970s~2000s), and a recent accelerated stage (after the 2000s).DOM optical properties exhibited distinct stage-dependent variations. During the natural background stage, SUVA254 ranged from 13.26 to 20.41L/(mg·g) with relatively minor fluctuations, indicating stable DOM characteristics. During the period of intensified anthropogenic disturbance, the proportion of protein-like component (P1) increased from 18% to 27%, accompanied by enhanced microbial signatures. In the recent stage, fluorescence index (FI) increased from 1.28 to 1.47 and biological index (BIX) from 0.66 to 0.79, suggesting substantial shifts in DOM sources and structure. FT-ICR MS analysis further revealed that, toward recent sediments, the O/C ratio, nominal oxidation state of carbon (NOSC), and the relative abundance of carboxyl-rich alicyclic molecules (CRAM) all decreased. Meanwhile, the proportion of tannin-like compounds declined from 8.66% to 5.75%, whereas protein-like and lipid-like compounds increased, indicating a transition toward lower oxidation state and enhanced autochthonous contribution. Correlation analysis demonstrated that nutrient loading, particularly TN, and organic matter accumulation were significantly associated with DOM optical properties and molecular composition (P<0.05). This study provides molecular-level and sedimentary evidence for the long-term evolution of sedimentary DOM and its environmental responses, offering new insights into the regulation mechanisms of organic carbon cycling in lake systems.
  • Synergistic effects of dipotassium hydrogen phosphate and phenylalanine on humification and structural evolution during sewage sludge composting
    SUN Xiao-jie, CHEN Shu-xin, LIU Shi-qi, SHI Yun-yi, MA Cui-cui, LIAO Chen-chen, ZHANG Hong-xia, CHANG Hao-yu, HONG Zhi, WANG Yan, LIU Cheng-lang, DONG Bin, XI Bei-dou
    China Environmental Science. 2026, 46(7): 3927-3937.
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    This study investigated the synergistic effects of a composite additive (dipotassium hydrogen phosphate (KH2PO4) and phenylalanine), on humus formation and structural evolution during sewage sludge composting. The transformation of organic carbon and the structural characteristics of humic substances (HS), including humic acid (HA) and fulvic acid (FA), were systematically characterized using total organic carbon (TOC) analysis, humification index (HIX) assessment, and compositional profiling. The results revealed that the composite additive significantly promoted the transformation of organic carbon into stable humic states. At the end of composting, the accumulation of HS and HA increased by 14.7% and 18.8%, respectively, accompanied by enhanced aromaticity and molecular stability. The continuous increase in HIX (from 0.48 to 0.83) and changes in spectral indices such as SUVA indicated that the composite additive facilitated the structural complexity and maturation of humus by accelerating aromatization and condensation reactions. The synergistic effect stems from the systematic acceleration of key humification processes. On one hand, it promotes the oxidative condensation of oxygen-containing functional groups such as carboxyl and hydroxyl groups, generating stable structures including aromatic rings and quinones. On the other hand, it drives the efficient transformation of FA into the more stable HA, ultimately leading to a significant increase in the accumulation of HS, particularly HA, and enhancing the overall aromaticity and maturity of humus. In summary, the combination of dipotassium hydrogen phosphate and phenylalanine exhibits notable specificity in regulating humification pathways, providing a scientific basis for the development of efficient composting additives and the resource utilization of organic waste.
  • Influencing factors of forest carbon density and carbon sequestration rate in Beijing
    CHEN Yun-ru, LI Ling-jun, ZHANG Qiang, SU Ri-na, ZHANG Jian, ZOU Ben-dong, JIANG Lei, SHEN Xiu-e
    China Environmental Science. 2026, 46(7): 3938-3948.
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    To address the unclear driving mechanism of regional forest carbon(C) sequestration, this study was conducted in the Baihuashan and Sizuolou Nature Reserve in western and northern Beijing to clarify the driving mechanism of regional forest C sequestration. Based on the repeated surveys at 5-year intervals in 56 permanent plots, we investigated the characteristics of forest C density and C sequestration rate, as well as their correlations with species diversity and environmental factors. The results showed that the forest C density in the study area ranged from 3.77 to 8.63kg C/m2, with an average C sequestration rate of 0.20kg C/(m2·a), indicating strong overall C sequestration capacity. Species diversity was negatively correlated with C sequestration rate (P<0.05), supporting the biomass ratio hypothesis. This suggests that greater species richness may intensify competition and thereby inhibit C accumulation in temperate forests dominated by dominant species. Canopy density and slope position were the main factors influencing C density and C sequestration rate in the study area (explanation degree >10%), indirectly affecting C accumulation by regulating light-harvesting efficiency of trees. The study recommends that future regional forest management should fully consider the structural characteristics of forests dominated by young and middle-aged stands. Management should focus on maintaining and optimizing the structure and health of existing dominant populations, and optimize canopy space through appropriate tending practices, thereby enhancing tree growth potential, and ensuring the sustained functioning of ecological services.
  • Urban expansion and its regional ecological impacts in underdeveloped mountainous areas of Northern China
    ZHANG Wei-ting, SUN Cong-jian, CHEN Wei, ZHANG Xu-dong
    China Environmental Science. 2026, 46(7): 3949-3960.
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    Driven by China’s Rural Revitalization Strategy, urbanization was accelerated in the underdeveloped mountainous areas of Northern China (UMNC), including the Liupan Mountains (LPM), the Southern Greater Khingan Mountains (SGKM), the Lüliang Mountains (LLM), and the Yanshan-Taihang Mountains (YTM). However, the way in which regional thermal environments and ecological quality were shaped by plain versus mountainous expansion patterns remained not clearly understood. Using land-use and remote sensing data, plain and mountainous expansion of urban construction land was characterized, associated changes in thermal conditions and ecological quality were examined, and future risks under SSP-RCP scenarios were assessed. The following key findings were identified: from 2000 to 2024, the region was dominated by plain expansion, with a net increase of 4257.17km2 concentrated in the SGKM and YTM; high heterogeneity was observed in mountainous expansion, where clear mountainous expansion (ABCI > 0) was shown in the YTM, while no significant trend was exhibited in the LPM; local heat island effects were intensified by urban expansion, as both construction land area and ABCI were found to be strongly and positively associated with “strong” and “very strong” heat island levels, suggesting that localized heat risks were elevated under mountainous expansion; although the regional mean RSEI was improved by ecological engineering, the heat island intensification caused by urban expansion was not fully offset; and under SSP5-RCP8.5, the greatest combined pressure on ecological security and thermal environments was projected to be exerted by sprawl-type expansion, especially in the SGKM and YTM. These results were utilized to inform coordinated human-land management and urban spatial optimization in underdeveloped mountainous regions.
  • Experimental study on two-phase displacement behavior of NAPL-water in non-horizontal fractures
    XUE Song, ZHANG Xiao-song, ZHOU Ze-xiong, LU Bin, LIU Gang
    China Environmental Science. 2026, 46(7): 3961-3968.
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    Understanding the displacement behavior of immiscible two-phase fluids in fractures under gravity-driven conditions is essential for predicting groundwater flow and the migration of organic pollutants. In this study, visualization experiments of light non-aqueous phase liquid (LNAPL)-water displacement were performed using a transparent fracture model. By varying the fracture inclination angle and the LNAPL injection flow rate, the intrusion and buoyancy-driven displacement of LNAPL were systematically investigated. It was revealed that three typical modes of LNAPL ascent in saturated fractures were identified: gravity-dominated, injection-rate-dominated, and combined-drive modes. In the gravity-dominated mode, an active rise of LNAPL was observed with an unstable displacement front, and an overall fingering flow (dominant channel) morphology was exhibited. Under injection-rate dominance, LNAPL was forcibly driven upward with a relatively stable displacement front, and a steady frontal advancement was resulted. In the combined-drive mode, a transitional behavior was exhibited by LNAPL, characterized by an increase in the number of fingers and an expansion of their widths. Furthermore, a critical fracture inclination angle α*(=20°) was identified, by which the displacement patterns and migration dynamics was governed: when α<α*, dominance of injection flow over buoyancy was observed; the LNAPL ascent rate was shown to have low sensitivity to changes in fracture inclination angle, and penetration was achieved at high saturation levels; when α>α*,dominance of gravity over the ascent process was observed, which caused a significant increase in ascent rate with increasing fracture inclination angle and a rapid decrease in saturation within the intrusion zone.
  • Research progress on adsorbents for in situ preconcentration of PFAS using diffusive gradients in thin-films
    NIU Wen-ting, LYU Jian, WANG Run-mei, ZHANG Qing-xi, WU Jun
    China Environmental Science. 2026, 46(7): 3969-3980.
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    This review summarizes recent research progress on the in situ preconcentration and sampling of per- and polyfluoroalkyl substances (PFAS) using the diffusive gradients in thin-films (DGT) technique, with a particular focus on the development of adsorbent materials. Six categories comprising 54 materials—including activated carbon, carbon-based materials, bio-based materials, mineral materials, polymers, and porous organic frameworks—were compared and evaluated. Their performance was assessed in terms of physical properties, adsorption performance, chemical stability, environmental adaptability, and their behavior in real water matrices, thereby elucidating the strengths and limitations of each material class. Currently, weak-anion-exchange resins are the most widely used adsorbents in DGT applications; however, their limited affinity for short-chain PFAS and insufficient tolerance to high-salinity matrices remain significant constraints. Future efforts directed toward the rational design of highly selective adsorbents based on “fluorine-fluorine self-recognition” are expected to substantially enhance the performance of DGT for PFAS monitoring. Meanwhile, the establishment of standardized workflows for DGT adsorbent development is urgently needed to bridge the gap between material innovation and DGT deployment, thereby promoting the broader application and standardization of this technique in environmental monitoring.
    • Environmental Microbiology
  • Isolation, identification and biodegradation of a quizalofop-p-ethyl-degrading strain Bacillus cereus OsE2
    LI Meng-long, HAN Lu, SHAO Xiao-lan, YIN Zhou, LIU Kai-lin
    China Environmental Science. 2026, 46(7): 3981-3990.
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    In this study, bacterial strain OsE2 was enriched and isolated from rice grown in quizalofop-p-ethyl-contaminated soil, and it exhibited significant quizalofop-p-ethyl degradation activity as determined by HPLC. Based on its morphological, physiological, and biochemical characteristics, as well as 16S rRNA and gyrB gene sequence analyses, the strain was identified as Bacillus cereus. Under the optimal biodegradation conditions of pH 7.0 and 35℃, 91% of 20mg/L quizalofop-p-ethyl was degraded within 36h, whereas the maximum degradation rate for 200mg/L quizalofop-p-ethyl reached 1.25mg/(L·h) after 96h of cultivation. Strain OsE2 also degraded various aryloxyphenoxypropionate (AOPP) herbicides, and the order of degradation activity was determined as: cyhalofop-butyl ≈ clodinafop-propargyl ≈ diclofop-methyl ≈ haloxyfop-p-methyl > fluazifop-p-butyl > fenoxaprop-p-ethyl> metamifop. Furthermore, UHPLC/Q-TOF-MS was employed to analyze the metabolites and metabolic pathway of quizalofop-p-ethyl degraded by strain OsE2, which was converted into quizalofop-acid via ester bond cleavage. This is the first report on the biodegradation of quizalofop-p-ethyl by Bacillus cereus, indicating that strain OsE2 has the potential to mitigate environmental pollution caused by AOPP herbicides.
  • Effects of pre-culture on facultative oligotrophic aerobic denitrifying bacteria
    ZHAO Xuan, ZHAO Xue-jie, GUO Xiu-hua, WU Cong-cong, LI Ming-zhi, WANG Xiao-min, WEI Yan-fei, HE Meng-yun
    China Environmental Science. 2026, 46(7): 3991-4001.
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    In this study, aerobic denitrifying strains were isolated from oligotrophic river sediments using an improved enrichment and acclimation strategy. The facultative oligotrophic strains Rhodococcus ruber D30-2 and Acinetobacter tandoi D4-2 were selected as representative isolates to evaluate the effects of pre-culture under low-C/low-N, high-C/high-N, and nutrient-rich LB conditions on their denitrification performance. The results demonstrated that pre-culture did not affect the growth or metabolic activity of strains D30-2 and D4-2 under oligotrophic conditions, but significantly altered their nitrogen removal efficiency and metabolic pathways. Following pre-culture under low-C/low-N or high-C/high-N conditions, the total nitrogen removal rates of D30-2 and D4-2 under oligotrophic conditions ranged from 23.1% to 26.2%, which were 78.4%~87.0% higher than those observed after LB pre-culture. Nitrogen balance analysis indicated that, compared with the other two pre-culture treatments, LB pre-culture resulted in a substantially lower proportion of nitrogen converted to gaseous forms and a relatively higher proportion assimilated into biomass. Transcriptional analysis revealed that LB pre-culture significantly suppressed the expression of denitrification-related functional genes in D4-2, whereas no obvious transcriptional response was detected in D30-2.
  • Environmental drivers shaping microbial communities in surface water of tropical rainforests versus rubber plantations
    WEI Yong-yi, SUN Rui, YANG Chuan, LAN Guo-yu, WU Zhi-xiang, LI Yuan-fa
    China Environmental Science. 2026, 46(7): 4002-4015.
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    To investigate the impact of forest type conversion on microbial communities in tropical surface waters, this study employed metagenomic sequencing technology to analyze the composition, diversity characteristics, functional genes, and environmental drivers of microbial communities in surface waters from tropical rainforests and rubber plantations on Hainan Island. The results were summarised as follows: a total of 177 bacterial phyla, 31 archaeal phyla, and 36 eukaryotic phyla were detected in surface water from two forest types. Among these, core shared phyla accounted for 83.9%~96.6%, while the number of unique phyla was significantly higher in rubber plantations (6 bacterial phyla, 5 archaeal phyla) compared to tropical rainforests (1eukaryotic phylum). This pattern demonstrates "highly shared core taxa with markedly differentiated unique taxa". At the genus level, rubber plantations enriched various ammonia-oxidizing archaea and methanogenic archaea, while tropical rainforests enriched thermophilic archaea and bacterial taxa related to nitrogen fixation and degradation of recalcitrant organic matter, reflecting significant functional differentiation between the two ecosystems. Functional gene analysis revealed that the abundance of genes related to carbon, nitrogen, sulfur, and phosphorus cycling in rubber plantations was 1.57, 1.41, 1.58 and 1.65 times higher, respectively, compared with tropical rainforests. Notably, the abundance of functional genes such as K01689, K00169, K00174, K00370, K04561, K00261, K01012, K00394, K00395, K00860, and K00937 was significantly higher in rubber plantations than in tropical rainforests. Microbial community responses exhibit taxonomic heterogeneity, with archaeal communities demonstrating the highest sensitivity to stand type variations. Compared with tropical rainforests, rubber plantations exhibit significantly increased species richness in archaea and eukaryotes, along with higher bacterial community evenness. The redundancy analysis revealed that salinity (20.81% explained), sodium (20.03%), and chloride (19.98%) were key drivers of archaeal community structure. Sulfate (21.01%) and chloride (19.81%) dominated bacterial communities, while sulfate (15.63%) and total dissolved solids (15.87%) significantly influenced fungal communities. The comprehensive analysis demonstrated that forest type conversion reshapes microbial community structure and function by altering surface water physicochemical properties, providing a microbial ecological basis for tropical forest conservation and rubber plantation ecological management.
  • Regulation effects of biochar and oat on soil nitrogen and phosphorus transformation and functional microbial community in coastal saline-alkali soil
    Li Ming-yan, Hu Hai-bo, Jin Wei, Ge Zhi-wei, Sun Hai-jun, Tang Zi-lai, Liu Xin
    China Environmental Science. 2026, 46(7): 4016-4028.
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    To investigate the synergistic ecological mechanism by which biochar and salt-tolerant plants enhance nitrogen and phosphorus cycling in coastal saline-alkali soils, a field experiment was conducted in Yancheng, Jiangsu Province. Four treatments were established: control with no fertilization and no oat planting (CK), biochar application alone (B), oat planting alone (O), and the combined application of biochar and oat (BO). By analyzing soil physicochemical properties and employing functional gene high-throughput sequencing, this study systematically examined the effects of different treatments on soil basic properties, the transformation of nitrogen and phosphorus forms, and the functional microbial communities involved in nitrogen fixation (nifH), ammonia oxidation (amoA), and phosphorus solubilization (pqqC, phoD). The coupling relationships between these microbial communities and soil environmental factors were also revealed. The results indicate that the BO treatment demonstrated a significant synergistic improvement effect, which significantly reduced soil pH (by 0.77) and electrical conductivity (by 0.72mS/cm), and significantly increased the contents of soil organic matter (167.01%), total nitrogen (219.44%), and total phosphorus (166.67%); (2) Treatments B, O and BO all increased the contents of active nitrogen and phosphorus components in the soil. Among them, BO increased the contents of NO3--N, NH4+-N and AN by 117.69%, 266.50% and 183.16% respectively. The contents of labile phosphorus (Labile-P) and moderately labile phosphorus (Moderately-labile-P) were increased by 320.84% and 189.33% respectively. The proportion of labile phosphorus component in the soil was increased (6.41%), while the proportion of stable phosphorus component was reduced (-4.67%), showing the best effect. The BO treatment effectively optimized the functional microbial communities of the nitrogen and phosphorus cycle, significantly increasing the Chao1 and Shannon index of the microbial communities containing nifH, amoA, pqqC, and phoD genes. It is also enriched with nitrogen-fixing bacteria primarily represented by Methylobacter, ammonia-oxidizing archaea dominated by Thaumarchaeota, and key phosphorus-solubilizing microorganisms such as Pseudomonas and Bradyrhizobium. Redundancy analysis (RDA) indicated soil organic matter (SOM) as a key driver shaping the construction of functional microbial communities. The four functional microbial communities of the nitrogen and phosphorus cycle were positively correlated with SOM, TN, TP, NO3--N, NH4+-N, AN, Labile-P, Moderately-labile-P, stably-P, and negatively correlated with pH and EC. In conclusion, the combined application of biochar and oat (BO) can systematically shape diverse, stable and efficient functional microbial communities by improving the physical and chemical environment of the plant rhizosphere, providing carbon sources and habitats. This synergy drives the retention, transformation and activation of nitrogen and phosphorus nutrients in coastal saline-alkali soil. This provides a theoretical basis for the improvement of soil fertility and efficient carbon sequestration in coastal tidal flat saline-alkali lands.
    • Environmental Toxicology and Environmental Health
  • Study on the optimum temperature for detecting biological toxicity in water using the locomotor behavior of Daphnia magna
    LUO Yun-fei, YIN Gao-fang, GAN Ting-ting, QIN Fei-hu, YE Zi-qi, TAN Xiao-xuan, LIANG Tian-hong, ZHAO Nan-jing
    China Environmental Science. 2026, 46(7): 4029-4039.
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    This study systematically examined the effects of temperature (10, 15, 20, 25, and 30℃) on the locomotor behavior parameters (average speed, average acceleration, and fractal dimension) of Daphnia magna. A Response Efficacy Index (REI) was introduced to comprehensively evaluate in sensitivity and stability of the toxicological responses of Daphnia magna to trichlorfon (TCF) stress across different temperatures. Validation experiments were subsequently conducted using copper sulfate (CuSO4) and fluoxetine (FLX). This study aimed to elucidate the influence of temperature on the locomotor baseline, sensitivity, and stability of Daphnia magna, thereby establishing optimal conditions that balance sensitivity, stability, and throughput. The results indicated that under non-toxic conditions, Daphnia magna exhibited the highest locomotor stability at 20℃; the change rate of average speed and the relative standard deviation (RSD) were at their lowest, recorded at 3.22% and 32.98%, respectively. At this temperature, the swimming trajectories exhibited extensive coverage, high path complexity, and a uniform distribution across directions. Under TCF exposure, the inhibition rate of average speed at 20℃ showed a linear increasing trend with exposure time, indicating a stable accumulation of toxic effects over time. By integrating the results from two TCF concentrations (1.7 and 6.8μg/L), the REI reached 0.769, indicating optimal toxicological response efficacy. Validation experiments with CuSO4 and FLX further confirmed these findings, yielding the highest REI values at 20℃ (0.739 and 0.496, respectively). These findings suggest that 20℃ is the optimal temperature for toxicity detection, offering a favorable balance between sensitivity and stability.
  • Explainable machine learning for mechanistic investigation of PFAS uptake and translocation in plants and risk assessment of alternatives
    LIU Bing, SUN Hai-jie, ZOU Ke-ke, LIU Hui, SHI Kai-ge, LU Xin, CHEN Yan-min, HAN Shuai-jun, GU Li
    China Environmental Science. 2026, 46(7): 4040-4054.
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    The fate of per- and polyfluoroalkyl substances (PFAS) in plant systems is crucial for food safety and ecological risk assessment. To elucidate the driving mechanisms underlying PFAS uptake and translocation in plants, this study integrated hydroponic experimental data encompassing nine common vegetable species and 19 PFAS compounds, combining correlation analysis, principal component analysis (PCA), and interpretable machine learning (ML) approaches to systematically evaluate key factors influencing root concentration factors (RCF), shoot concentration factors (SCF), and root-to-shoot translocation factors (TF). The results demonstrated that complex nonlinear relationships exist between RCF, SCF, TF, and most physicochemical parameters. The CatBoost model exhibited excellent performance in predicting lgRCF, lgSCF, and lgTF (test set R2 ≥ 0.70), with particularly outstanding predictive capability for TF (test set R2=0.89). Interpretable ML analysis revealed the presence of a molecular weight (MW)-centric “molecular sieve” physical barrier mechanism within plants. MW contributed most significantly to RCF and TF, with a critical threshold observed around 500g/mol, beyond which root-to-shoot translocation capacity decreased sharply. Meanwhile, exposure duration emerged as the primary driver for SCF, while plant species significantly influenced TF values. Further analysis identified prevalent nonlinearities and interaction effects among key features; for instance, prolonged exposure exacerbated translocation inhibition for larger PFAS molecules. The model demonstrated strong generalization capability (R2 = 0.714~0.784) in assessing accumulation risks for PFOA, PFOS, and five substitutes (e.g., HFPO-DA, 6:2 FTSA), confirming that most alternative PFAS exhibit significantly lower root-to-shoot translocation potential compared to legacy PFAS, attributable to their larger molecular dimensions and complex functional group designs that enhance exclusion by plant barriers. This study not only provides a reliable modeling tool for PFAS plant accumulation risk assessment but also offers critical theoretical foundations for sustainable molecular design of green alternatives.
  • Accumulation dynamics, physiological responses, tissue damage and molecular adaptation mechanisms of the Mytilus coruscus under subacute exposure to heavy metal release from deep-sea polymetallic nodules mining
    QIAN Jun, PAN Yu-ying, JIA Yong-gang, FAN Zhi-han, YANG Jin-sheng, SHE Yun-yong, XIA Chao-yu, ZHOU Kai-jia, YUAN Xin
    China Environmental Science. 2026, 46(7): 4055-4067.
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    This study used the mussel Mytilus coruscus as a model organism to conduct a 21-day indoor simulation experiment of subacute toxic exposure to nodule-containing sediment. By analyzing heavy metal concentrations in seawater and organisms, measuring biochemical indicators (SOD, CAT, GPx, GST, MDA, MT), performing histopathological observation, and conducting transcriptome sequencing, its bioaccumulation behavior, physiological responses, tissue damage, and molecular adaptation mechanisms under multi-metal (Fe, Mn, Cu, Ni, Zn, Co, Cr, Pb, As, Mo, and Cd) stress were systematically evaluated. The results revealed that: Heavy metal accumulation exhibited time dependence. During early exposure, the bioconcentration factors (BCF) of Zn, Cr and Pb in the organism increased significantly. As exposure continued, the organism's excretion and defense mechanisms gradually strengthened, leading to a decline in its heavy metal accumulation capacity. However, in later stages, the BCF of Pb showed a secondary rebound in the high-concentration group (≥100mg/L). The physiological response exhibited tissue specificity and temporal dynamics. Gills responded rapidly but had limited tolerance; under prolonged high-concentration stress (≥100mg/L), the activity of antioxidant enzymes (SOD, CAT, GPx) decreased, leading to aggravated lipid peroxidation (MDA). The visceral mass relied on the scavenging effect of glutathione (GSH) to counteracted oxidative damage in the early stage, but under sustained stress, GSH became depleted due to continuous consumption, and antioxidant enzyme activity also declined, ultimately resulted in exacerbated lipid peroxidation. Histopathological analyses confirmed exacerbated structural damage in both gills and visceral mass at high exposure concentrations (≥100mg/L). At the molecular level, significant alterations were observed in the expression of genes associated with antioxidant defense (SOD2, CAT, GPX, GPX4, GST, GSTK1), energy metabolism (HK, IDH3, IDH1, PRKAA), metal detoxification (ABCC5, ATP6D), and apoptosis regulation (CASP3, BCL2). Transcriptional regulation indicated a shift from energy-conserving maintenance to active stress response, with prioritization of antioxidant defense and cellular repair processes over cell death under high metal loads, thereby preserving tissue integrity. The study revealed the integrated adaptive mechanisms of the mussel M. coruscus in response to long-term multi-metal stress, identified the ecological effects of the critical stress threshold of 100mg/L, and provided important scientific evidence for predicting the long-term ecological risks of deep-sea mining activities.
    • Emerging Contaminants
  • Toxicity to earthworms from polypropylene/polylactic acid microplastics alone and in co-exposure with cadmium
    YANG Xiao-xia, ZHANG Xue-mei, FAN Yong-yang, SHU Xiao, XIE Man-li, GONG Jiu-ping, HUANG Yong-chuan, FU Ting-ting, HUANG Cheng-lan, LI Dian-yan
    China Environmental Science. 2026, 46(7): 4068-4080.
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    The toxic effects and mechanisms of polypropylene (PP) and polylactic acid (PLA) microplastics (MPs, 2.5g/kg), individually and in combination with cadmium (Cd, 10mg/kg) on the earthworm Eisenia fetida were investigated, after 28 days of exposure by analyzing multi-scale endpoints, including growth and reproduction, activities of metabolic enzymes (CYP1A2, CYP2C9, SOD, CAT), metabolomis, bioaccumulation of Cd or MPs, and soil acidity alteration in this study. The results showed that PLA MP exposure significantly inhibited the activities of CYP1A2and CYP2C9, and downregulated steroid synthesis, lipid, and amino acid metabolism. In contrast, PP exposure alone promoted steroid synthesis, lipid metabolism, tricarboxylic acid cycle, and amino acid metabolism. Under combined exposure, earthworm growth and reproduction were significantly inhibited, and steroid synthesis was disrupted. Specifically, the energy and purine metabolism were further disturbed under the co-exposure of PLA and Cd. The interaction between PLA MPs and Cd was synergistic, whereas an antagonistic effect was observed between PP MPs and Cd.The higher retention of PLA MPs (10 particles) in earthworms compared to PP MPs (3~4 particles), along with the significantly higher bioaccumulation of Cd in the PLA+Cd group (5.4 ±0.5mg/kg) than in the Cd-alone (3.9 ±0.5mg/kg) and PP+Cd groups (3.8 ±0.5mg/kg), explains the greater toxicity of PLA MPs alone and the enhanced harmful effects under co-exposure with Cd. Although PLA MPs caused soil acidification, the soil pH (6.5~6.9) remained within the optimal range for earthworms, indicating that acidity was not the primary factor contributing to the toxicity.
    • Carbon Emission Control
  • Pathways to low-carbon energy transformation in Shanxi province under supply security and decarbonization constraints
    DI Zi-chen, LI Yu-kun, ZHOU Wen-fang, ZHU Zhi-han, WU Hai-bin, HAO Peng-cheng
    China Environmental Science. 2026, 46(7): 4081-4093.
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    To address the practical challenge of achieving low-carbon transformation in Shanxi Province under the constraint of energy security and supply guarantee, this study develops the LEAP-SHANXI regional energy system model and designs three scenarios, business-as-usual, coal control with supply security, and deep decarbonization, to analyze the evolution trends of energy consumption and carbon emissions during 2022~2060. The results show that: under the business-as-usual scenario, the share of coal consumption remains above 60% for an extended period, with carbon emissions projected to peak around 720Mt in 2035 and still remain at a high level by 2060, making it difficult to achieve carbon neutrality. Under the coal control with supply security scenario, if unconventional natural gas production increases to 40 billion m3 and the renewable electricity consumption ratio rises to 64.1%, carbon emissions can peak earlier in 2030 at approximately 616 Mt, with emissions declining by about 44% from the peak by 2060, initially achieving coordinated progress between energy supply security and carbon emission reduction. Under the deep decarbonization scenario, with further intensification of energy structure adjustment—unconventional natural gas production increasing to 80 billion m3 and renewable electricity consumption ratio reaching 80.1%—the carbon emission peak can be further advanced to 2028 at approximately 556Mt. Combined with advanced low-carbon technologies such as carbon capture, utilization and storage (CCUS) and hydrogen-based shaft furnaces, emissions can be reduced by 96% from the peak by 2060, basically achieving carbon neutrality. In conclusion, Shanxi Province's low-carbon transformation should follow a "establishing the new before abolishing the old, step-by-step implementation" pathway: in the near term (by 2030), focusing on scaled utilization of unconventional natural gas such as coalbed methane to replace scattered coal use, and orderly development of local wind and solar power; in the medium term (2031~2045), promoting the principal restructuring of the energy system with wind and solar becoming the main sources of incremental power generation, and launching hydrogen application demonstrations; in the long term (2046~2060), tackling deep decarbonization through scaled application of CCUS and other technologies to address residual emissions, ultimately building a modern energy system featuring multi-energy complementarity, cleanliness, and low carbon.
  • Research on the county-level carbon emission reduction effects of green computing infrastructure construction
    ZHOU Si-shu, WEI Chen-bo, JI Xue-qiang, ZHANG Yue-song
    China Environmental Science. 2026, 46(7): 4094-4105.
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    Developing green computing power infrastructure is a critical pathway for the synergistic realization of the “Digital China” strategy and the “Double Carbon” goals. Drawing on the pilot and construction of national green data centers as a quasi- natural experiment, this paper employs a Principal Component Analysis-Double Machine Learning (PCA-DML) model, combined with panel data from 2669 Chinese counties spanning the period 2003~2023, to empirically identify the impact of green computing power infrastructure development on carbon emissions. The findings reveal that green computing power infrastructure construction exerts a significant carbon reduction effect, with an average reduction of 3.51%. Mechanism analysis indicates that the policy leads to a 3.29-unit increase in county-level digital infrastructure, a 4.09% decrease in social energy consumption intensity, and a 4.26% advancement in industrial structure upgrading. Heterogeneity analysis further shows that this carbon reduction effect is more pronounced in regions with higher economic development, stricter environmental regulation, more optimized industrial structures, and lower resource dependence. These results provide a scientific basis for optimizing the national layout of computing power and formulating differentiated environmental policies.
  • Research on the coupling of “engy-intelligence” and its impact on the synergy of industrial pollution-carbon reduction
    TANG Li-chen, LI Jie, TU Jiang-yue, CHEN Hui, ZENG Xian-gang
    China Environmental Science. 2026, 46(7): 4106-4122.
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    This paper selected panel data from 30 provinces in China from 2011 to 2022 as the research sample. Using the entropy method, window super-efficiency EBM model, and coupling coordination degree model, it measured the coupling of “energy-intelligence” (CEI) and the synergy of industrial pollution-carbon reduction (SIPCR), and analyzed their spatial-temporal evolution characteristics. On this basis, the double machine learning model was employed to empirically examine the impacts and mechanisms of CEI on SIPCR. The results indicated that from 2011 to 2022, the national CEI increased from 0.308 to 0.470, with an average annual growth rate of 3.917%. The regional pattern exhibited a gradient characteristic of “Eastern China > Western China > Central China > Northeastern China”, while the spatial pattern improved from an imbalanced state of “heavy in the north and light in the south” to a more coordinated state, though regional disparities remained prominent. SIPCR rose from 0.595 to 0.807, with an average annual growth rate of 2.809%. The regional pattern maintained “Eastern China > Central China > Western China > Northeastern China”, and the spatial pattern shifted from partial imbalances to a fully coordinated state with balanced quality development. CEI significantly promoted SIPCR, exerting separate positive driving effects on both pollution reduction efficiency and carbon reduction efficiency. CEI indirectly enhanced SIPCR by alleviating the degree of factor distortion, optimizing the industrial agglomeration effect, and improving the level of human-machine collaboration. In western regions, regions with higher levels of green finance development, environmental regulation intensity, and economic development, the promoting effects of CEI on SIPCR were more pronounced.
    • Environmental Impact Assessment and Management
  • Climate vulnerability, green energy transition, and total factor productivity——Evidence from cross-country panel data
    SUN Yi-ming, ZHANG Geng
    China Environmental Science. 2026, 46(7): 4123-4133.
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    This study examines the impact of climate vulnerability on total factor productivity (TFP) and its underlying mechanisms using panel data from 105 countries over the period 2002~2019. The results show that climate vulnerability exerts a significant negative effect on TFP: a 1% increase in vulnerability is associated with an average decline of approximately 2.013% in TFP. Decomposition analysis indicates that this effect is primarily driven by elevated economic sensitivity and limited adaptive capacity. Further analysis reveals that the green energy transition mitigates the adverse impact of climate vulnerability on TFP, with stronger moderating effects observed in countries characterized by lower energy intensity and a smaller share of manufacturing value added. To address potential endogeneity, this study exploits the establishment of the Green Climate Fund (GCF) as a quasi-natural experiment and employs a difference-in-differences (DID) approach. The results suggest that the GCF has significantly enhanced TFP in developing countries. These findings highlight the importance of tailoring energy transition strategies to national energy intensity and industrial structure in order to jointly enhance climate resilience and productivity growth.
  • A game model of cascade utilization of power batteries considering the informal recycling channel
    WU Jia-ni, WANG Ying
    China Environmental Science. 2026, 46(7): 4134-4144.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    As the large-scale retirement wave of new energy vehicle power batteries approached, the cascade utilization of resources and environmental protection were severely hindered by the disorderly expansion of informal recycling channels (small workshops). To address the practical dilemma of the coexistence of "formal-informal" dual channels, a Stackelberg game model composed of the government, cascade utilization enterprises, formal and informal recyclers was constructed, and the impacts of government subsidies, regulatory intensity, penalty deterrence, and social environmental benefits on market equilibrium and evolution were deeply explored through numerical simulation. It was found that: First, in the early development stage of the power battery recycling market, the market was dominated by informal channels due to their channel monopoly and low-cost advantages, presenting a typical characteristic of "bad money drives out good". It was shown by the simulation that the financial subsidy mechanism was substantially triggered only when the unit social environmental benefit exceeded the policy activation threshold (v≥26), and a fundamental reversal of market share was achieved when the market reversal point (v≈50) was further crossed. Second, in scenarios with high law enforcement costs or backward regulatory technologies, a decline in total social welfare was caused by an over-reliance on high-pressure regulation (unit penalty intensity f was increased from 5 to 50) due to the surge in administrative costs, where the subsidy strategy based on the price transmission mechanism was considered more economically efficient. Third, when the cascade utilization conversion rate of formal enterprises was increased from 0.6 to 0.9, a multiple-level leap in the formal cascade utilization volume driven by the same subsidy increment was realized, which was identified as the key to achieving subsidy phase-out and the long-term market-oriented operation of the industry.
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