● A 2D finite-element solute transport model, PRB-Trans, is developed.

The passive convergence-permeable reactive barrier (PC-PRB) was proposed to address the limitations of traditional PRB configurations. To evaluate the hydraulic and pollutant removal performance of the PC-PRB system, we developed a simulation code named PRB-Trans. This code uses the two-dimensional (2D) finite element method to simulate groundwater flow and solute transport. Case studies demonstrate that PC-PRB technology is more efficient and cost-effective than continuous permeable reactive barrier (C-PRB) in treating the same contaminated plume. Implementation of PC-PRB technology results in a 33.3% and 72.7% reduction in PRB length (L_PRB) and height (H_PRB), respectively, while increasing 2D horizontal and 2D vertical pollutant treatment efficiencies of PRB by 87.8% and 266.8%, respectively. In addition, the PC-PRB technology has the ability to homogenize the pollutant concentration and pollutant flux through the PRB system, which can mitigate the problems arising from uneven distribution of pollutants in the C-PRB to some extent. The L_PRB required for PC-PRB decreases as the water pipe length (L_p) increases, while the H_PRB required initially decreases and then increases with increasing L_p. The effect of passive well height (H_w) on H_PRB is not as significant as that of L_p on H_PRB. Overall, PC-PRB presents a promising and advantageous PRB configuration in the effective treatment of various types of contaminated plumes.

● Four scenarios were used to project heat-related excess mortality in China.

Climate change is one of the biggest health threats of the 21st century. Although China is the biggest developing country, with a large population and different climate types, its projections of large-scale heat-related excess mortality remain understudied. In particular, the effects of climate change on aging populations have not been well studied, and may result in significantly underestimation of heat effects. In this study, we took four climate change scenarios of Tier-1 in CMIP6, which were combinations of Shared Socioeconomic Pathways (SSPs) and Representative Concentration Pathways (RCPs). We used the exposure-response functions derived from previous studies combined with baseline age-specific non-accidental mortality rates to project heat-related excess mortality. Then, we employed the Logarithmic Mean Divisia Index (LMDI) method to decompose the impacts of climate change, population growth, and aging on heat-related excess mortality. Finally, we multiplied the heat-related Years of Life Lost (YLL) with the Value of a Statistical Life Year (VSLY) to quantify the economic burden of premature mortality. We found that the heat-related excess mortality would be concentrated in central China and in the densely populated south-eastern coastal regions. When aging is considered, heat-related excess mortality will become 2.8–6.7 times than that without considering aging in 2081–2100 under different scenarios. The contribution analysis showed that the effect of aging on heat-related deaths would be much higher than that of climate change. Our findings highlighted that aging would lead to a severe increase of heat-related deaths and suggesting that regional-specific policies should be formulated in response to heat-related risks.

● Bioaugmentation and low-dose persulfate were effective in degrading PAHs.

Polycyclic aromatic hydrocarbon (PAH)-contaminated soils are usually complex and characterized by a lack of nutrition and soil salinization, resulting in difficulties in soil remediation. In this study, bioaugmentation with a PAH-degrading Bacillus PheN7 (BA) and low-dose persulfate oxidation (PS), along with natural biodegradation, were utilized to remediate alkaline PAH-contaminated soil. The soil used in the study had a pH of 9.35, and the total PAH content was 568.8 ± 31.0 mg/kg dry soil. After 42 d of remediation, the degradation efficiency of PAHs was 96.72% and 93.88% using persulfate oxidation and bioaugmentation, respectively, whereas 38.66% of PAHs were degraded in natural attenuation (NA). Bacillus was the dominant genera throughout the process of bioremediation with the relative abundance of 79.3% on day 42 in the BA system, whereas, Alcanivorax was enriched and became the dominant genera in PS systems. In the meantime, PAH degradation genes were detected with remarkably higher level in the BA system than in PS system during the remediation. In addition to the degradation of contaminants, persulfate oxidation promotes microbial bioremediation efficiency mainly by lowering the pH to neutral and increasing the active phosphorus content in the soil. Microbial species and ecological niches were less reduced in the PS system than in the BA system. Collectively, persulfate oxidation had a better impact on the soil microbiome and is more suitable for long-term soil health than bioaugmentation through PheN7 addition.

● Photochemical conversion of chlorobenzene (CB) on α-Fe₂O₃ was evaluated.

Despite the large emission of chlorinated volatile organic compounds (CVOCs) into the atmosphere, the ultimate fate of these compounds remains largely unknown. Herein, we explore the photochemical conversion of an important class of CVOCs, namely chlorobenzene (CB), on mineral α-Fe₂O₃ particulates under atmospheric relevant conditions. A series of chamber reactions composed of the CB with/without SO₂ or NO₂ are performed, followed by in situ diffuse reflectance infrared Fourier transform spectroscopy measurements and density functional theory calculations. We show that CB can be considerably degraded by α-Fe₂O₃ under light irradiation, whereas the reaction is markedly suppressed by adding SO₂ or NO₂ owing to their competitive adsorption and surface acidification. In particular, we discover that CB can be ultimately converted into polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) under dark state or light irradiation, suggesting a possible origin of atmospheric PCDD/Fs from this overlooked photochemical source.

● Data-driven approach was used to simulate VFA production from WAS fermentation.

Riboflavin is a redox mediator that promotes volatile fatty acids (VFAs) production from waste activated sludge (WAS) and is a promising method for WAS reuse. However, time- and labor-consuming experiments challenge obtaining optimal operating conditions for maximal VFA production. In this study, three machine learning (ML) models were developed to predict the VFAs production from riboflavin-mediated WAS fermentation systems. Among the three tested ML algorithms, eXtreme Gradient Boosting (XGBoost) presented the best prediction performance and excellent generalization ability, with the highest testing coefficient of determination (R² of 0.93) and lowest root mean square error (RMSE of 0.070). Feature importance analysis and their interactions using the Shepley Additive Explanations (SHAP) method indicated that pH and soluble protein were the top two input features for the modeling. The intrinsic correlations between input features and microbial communities corroborated this deduction. On the optimized ML model, genetic algorithm (GA) and particle swarm optimization (PSO) solved the optimal solution of VFA output, predicting the maximum VFA output as 650 mg COD/g VSS. This study provided a data-driven approach to predict and optimize VFA production from riboflavin-mediated WAS fermentation.

● The PCDD/F distribution patterns of the FW-AD process were investigated.

Food waste (FW) is a major component of municipal solid waste (MSW) in developing countries such as China. Anaerobic digestion (AD) is a widely-applied FW biological treatment method following MSW classification. With FW diversion from conventional incineration plants, the environmental risk caused by trace toxic pollutants, such as polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), should be reevaluated. This study investigated a full-scale FW-AD plant in Shenzhen, China, and addressed two important underexplored issues: the distribution patterns of PCDD/Fs during the FW-AD process and PCDD/F emission characteristics of the biogas utilization exhaust gas. Mass balance demonstrated a negative balance of 2.48 μg I-TEQ/t of raw FW (RFW), thus indicating that AD produced moderate PCDD/F emissions. The detailed findings were as follows: 1) PCDD/F toxic equivalents (TEQs) in pure FW (RFW without impurities) were lower than in RFW, indicating that MSW source separation is crucial for decreasing the PCDD/F input into the AD system; 2) PCDD/F contents (6.20–8.27 pg I-TEQ/g dry weight) in solid digestate were near the screening value of development land in China’s national standard (GB36600-2018), thus indicating that the potential environmental risk from the land application of solid digestate should be considered; and 3) PCDD/F TEQs (0.001–0.022 ng I-TEQ/Nm³) in biogas utilization exhaust gas were roughly equivalent to those produced by MSW incinerators in Shenzhen. This study indicated that compared with co-incineration with other waste, FW-AD will reduce PCDD/F emissions (air) from MSW incineration plants by 12.5%–21.3% at the national level under an FW separation scenario.

● Factor analysis of ammonium nitrate formation based on thermodynamic theory.

High levels of fine particulate matter (PM_2.5) is linked to poor air quality and premature deaths, so haze pollution deserves the attention of the world. As abundant inorganic components in PM_2.5, ammonium nitrate (NH₄NO₃) formation includes two processes, the diffusion process (molecule of ammonia and nitric acid move from gas phase to liquid phase) and the ionization process (subsequent dissociation to form ions). In this study, we discuss the impact of meteorological factors, emission sources, and gaseous precursors on NH₄NO₃ formation based on thermodynamic theory, and identify the dominant factors during clean periods and haze periods. Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution. The dust source is dominant emission source in clean periods; while a combination of coal combustion and vehicle exhaust sources is more important in haze periods. And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate. The findings of this work inform the design of effective strategies to control particulate matter pollution.

● A novel integrated machine learning method to analyze O₃ changes is proposed.

Surface ozone (O₃) is influenced by regional background and local photochemical formation under favorable meteorological conditions. Understanding the contribution of these factors to changes in O₃ is crucial to address the issue of O₃ pollution. In this study, we propose a novel integrated method that combines random forest, principal component analysis, and Shapley additive explanations to distinguish observed O₃ into meteorologically affected ozone (O_{3_MET}), chemically formed from local emissions (O_{3_LC}), and regional background ozone (O_{3_RBG}). Applied to three typical stations in Shanghai during the warm season from 2013 to 2021, the results indicate that O_{3_RBG} in Shanghai was 48.8 ± 0.3 ppb, accounting for 79.6%–89.4% at different sites, with an overall declining trend of 0.018 ppb/yr. O_{3_LC} at urban and regional sites ranged from 5.9–9.0 ppb and 8.9–14.6 ppb, respectively, which were significantly higher than the contributions of 2.5–7.4 ppb at an upwind background site. O_{3_MET} can be categorized into those affecting O₃ photochemical generation and those changing O₃ dispersion conditions, with absolute contributions to O₃ ranging from 13.4–19.0 ppb and 13.1–13.7 ppb, respectively. We found that the O₃ rebound in 2017, compared to 2013, was primarily influenced by unfavorable O₃ dispersion conditions and unbalanced emission reductions; while the O₃ decline in 2021, compared to 2017, was primarily influenced by overall favorable meteorological conditions and further emissions reduction. These findings highlight the challenge of understanding O₃ change due to meteorology and regional background, emphasizing the need for systematic interpretation of the different components of O₃.

● We tracked Chinese cities’ MSW disposal infrastructure development history.

Rapid urbanization in Chinese cities has led to a surge in municipal solid waste (MSW) generation, necessitating the development of high-quality MSW disposal facilities. This study utilizes multi-source data and regression models to examine the status, development pathways, and driving forces of MSW disposal facilities in China. Our findings reveal an inverted U-shaped relationship between the capacities or numbers of MSW disposal facilities and GDP per capita of cities. Historical data show that cities in East and Southeast China preferred incineration, while cities in West and Central China developed landfills more, largely shaped by the imbalance of development levels and endowments among regions in China. The study also identifies mixed and differentiated influences of socio-economic factors on capacity expansion and increases in the number of MSW disposal facilities. The results suggest the need for updated construction guidelines and regulations, as well as enhanced technological and managerial capabilities for MSW infrastructure. These findings can inform policymakers and practitioners in their efforts to promote sustainable waste management practices in China.

● MD simulations unveil the transport mechanism for TFP-water mixture through CNTs.

Fluorinated alcohols exhibit promising prospects in chemical industry because of their special structure and many exciting properties, in which tetrafluoropropanol (TFP) is extensive applied in synthesis of pesticides, dyestuffs, variety of solvents and detergents. However, the presence of TFP in water garners increasing attention globally because of their intrinsic potential to threat ecosystems and human health. Carbon nanotubes (CNTs) membranes are burgeoning candidates for TFP-water separation owing to well-endowed extraordinary structural and transport properties. However, a grand challenge lies in the rational design of CNTs for improving separation performance. Herein, molecular dynamics (MD) simulations were performed to investigate the effects of various parameters on the separation of TFP-water mixtures including feed temperature, CNTs pore diameters, and fluorine functionalization position. It was found that TFP was pre-selected in CNTs ranging from 9.48 to 18.98 Å due to preferential adsorption and diffusion mechanism. Excellent separation factor of 16 was achieved by (7,7) CNTs and the mass fraction of TFP was purified from 75% to 97.51%. Fluorine modified CNTs separated TFP and water by preferentially permeating water due to hydrogen bonding interaction. Simulation results showed that CNTs modified at both the entrance and interior had better separation performance than CNT modified only at one of these positions. The 100wt% water content in permeate was achieved by (11,11) CNTs modified with fluorine at the entrance and interior. These findings provide valuable insights for designing potential candidates for fluorinated alcohol-water azeotropic mixtures membrane separation, and promise extensive application aspects for the reclamation of fluorinated alcohol.

● Spartina abundance decreases over time by chemical control.

Invasions by Spartina species pose serious threats to global coastal ecosystems. Although many studies have examined the effectiveness and ecological impacts of invasive Spartina management, no comprehensive global synthesis has been conducted to assess the effects of management on Spartina per se and on wider non-targets. Here, we conducted a global meta-analysis of 3,459 observations from 102 studies to quantify the effects of different management interventions (physical, chemical, biological, and integrated control) on Spartina per se and native biodiversity and environments. We found that physical measures quickly suppressed Spartina but that their effectiveness declined over time. By contrast, chemical measures decreased the abundance and growth of Spartina to a lesser degree in the early stage, but the effectiveness increased over time. Different management measures did not significantly decrease the diversity of native biota on the whole, but native-plant diversity significantly decreased with time after physical control. Different management measures did not affect abiotic factors differently. These results support the use of chemical measures to control invasive Spartina, although their effectiveness would depend on the time since the management intervention. Addressing the problem of Spartina regrowth following physical control requires improved techniques. We hold that initial states of invaders and subsequent environmental changes after management interventions should be weighed in evaluating control efficacy.

● A fine portrayal of organic pollutants in a retired industrial park is provided.

The overall cross-media risk evaluation of organic pollutants in retired industrial parks is insufficiently recognized. In this study, 11 semi-volatile organic compounds (SVOCs) and 27 volatile organic compounds (VOCs) were measured in 531 soil and groundwater samples taken from a retired industrial park by coast in Zhejiang Province, China. Total petroleum hydrocarbons (TPHs), Di (2-ethylhexyl) phthalate (DEHP), benzene, and ethylbenzene were identified as the critical pollutants in the soil, while TPHs, 1,2-dichloropropane (1,2-DCP), toluene, benzo[a]anthracene (BaA), and benzo[b]fluoranthene (BbF) were identified as critical pollutants in the groundwater for exceeding China national standards. The spatial correlation between the concentrations of organic pollutants in soil and groundwater was explored by employing the Geodetector model. Based on the results of spatial interpolation, high-risk hotspots regarding soil and groundwater pollution were identified. Moreover, the possible harm to human health of the critical pollutants were also under evaluation. Among various critical pollutants, benzene, ethylbenzene, and DEHP in soil, and 1,2-DCP in groundwater, were the main contributors to the overall health risk of multimedia pollution. This study developed a comprehensive approach to assess the risks posed by specific organic toxicants in various environmental media. The findings of this work can serve as a valuable reference for future management strategies in retired industrial parks.

● Microplastics (MPs) undergo photoaging in natural water under light irradiation.

Plastic products widespread in natural water can be broken into smaller-sized microplastics (MPs, < 5 mm) under light irradiation, thermal degradation and biodegradation, posing a serious threat to aquatic ecosystems and human health. This perspective concludes that MPs can generate reactive oxygen species (ROS) through initiation, propagation and termination steps, which can attack the polymer resulting in the photoaging and breakdown of C–C and C–H bonds under ultraviolet (UV) irradiation. Free radical generation and weathering degree of MPs depend on their physicochemical properties and environmental conditions. In general, UV irradiation and co-existed MPs can significantly accelerate MP photoaging. With plentiful chromophores (carbonyl, carboxyl and benzene rings, Dissolved organic matter (DOM) mainly absorbs photons (300–500 nm) and generates hydrated electrons, ³DOM* and ROS, which may affect MP photoaging. However, whether DOM may transfer the electron and energy to MPs under UV irradiation, affect ROS generation of MPs and their photoaging pathway are inadequately studied. More studies are needed to elucidate MP photoaging pathways and mechanisms, consider the influence of stabilization capacity, photosensitization and photoionization of DOM as well as their competitive light absorption with MPs, which provides valuable insights into the environmental behavior and ecological risk of MPs in natural water.