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Frontier Progresses from Chinese-American Professors of Environmental Engineering and Science (Eds. Xing Xie, Jinkai Xue & Hongliang Zhang)
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  • RESEARCH ARTICLE
    Gaosheng Xi, Xiaojiang Gao, Ming Zhou, Xiangmei Zhai, Ming Chen, Xingxiang Wang, Xiaoying Yang, Zezhen Pan, Zimeng Wang
    Frontiers of Environmental Science & Engineering, 2023, 17(8): 102. https://doi.org/10.1007/s11783-023-1702-4

    ● Column experiments with an inclined slope were applied to simulate NH4–N transport.

    ● The transport of NH4–N was simulated via HYDRUS-2D.

    ● The chemical non-equilibrium model well described the transport process.

    ● The lateral flow led to the preferential loss of surface NH4–N.

    ● Flow rate and rainfall intensity affected the adsorption and leaching of NH4–N.

    Ion-absorbed rare earth mines, leached in situ, retain a large amount of ammonium nitrogen (NH4–N) that continuously releases into the surrounding environments. However, quantitative descriptions and predictions of the transport of NH4–N across mining area with hill slopes are not fully established. Here, laboratory column experiments were designed with an inclined slope (a sand box) to examine the spatial temporal transport of NH4–N in soils collected from the ionic rare earth elements (REE) mining area. An HYDRUS-2D model simulation of the experimental data over time showed that soils had a strong adsorption capacity toward NH4–N. Chemical non-equilibrium model (CNEM) could well simulate the transport of NH4–N through the soil-packed columns. The simulation of the transport-adsorption processes at three flow rates of leaching agents revealed that low flow rate enabled a longer residence time and an increased NH4-N adsorption, but reduced the extraction efficiency for REE. During the subsequent rainwater washing process, the presence of slope resulted in the leaching of NH4–N on the surface of the slope, while the leaching of NH4–N deep inside the column was inhibited. Furthermore, the high-intensity rainfall significantly increased the leaching, highlighting the importance of considering the impact of extreme weather conditions during the leaching process. Overall, our study advances the understanding of the transport of NH4–N in mining area with hills, the impact of flow rates of leaching agents and precipitation intensities, and presents as a feasible modeling method to evaluate the environmental risks of NH4–N pollution during and post REE in situ mining activities.

  • CORRECTION
    Zeou Dou, Maria Vitoria Bini Farias, Wensi Chen, Dongjing He, Yuhang Hu, Xing Xie
    Frontiers of Environmental Science & Engineering, 2023, 17(8): 104. https://doi.org/10.1007/s11783-023-1704-2
  • RESEARCH ARTICLE
    Chen Zhou, Ermias Gebrekrstos Tesfamariam, Youneng Tang, Ang Li
    Frontiers of Environmental Science & Engineering, 2023, 17(9): 107. https://doi.org/10.1007/s11783-023-1707-z

    ● EPS immobilizes U(VI) via adsorption, bioreduction and desorption.

    ● This work provides a framework to quantify the three immobilization processes.

    ● The non-equilibrium adsorption of U follows pseudo-second-order kinetics.

    ● The equilibrium adsorption of U followed Langmuir and Freundlich isotherms.

    Hexavalent uranium (U(VI)) can be immobilized by various microbes. The role of extracellular polymeric substances (EPS) in U(VI) immobilization has not been quantified. This work provides a model framework to quantify the contributions of three processes involved in EPS-mediated U(VI) immobilization: adsorption, bioreduction and desorption. Loosely associated EPS was extracted from a pure bacterial strain, Klebsiella sp. J1, and then exposed to H2 and O2 (no bioreduction control) to immobilize U(VI) in batch experiments. U(VI) immobilization was faster when exposed to H2 than O2 and stabilized at 94% for H2 and 85% for O2, respectively. The non-equilibrium data from the H2 experiments were best simulated by a kinetic model consisting of pseudo-second-order adsorption (ka = 2.87 × 10−3 g EPS·(mg U)−1·min−1), first-order bioreduction (kb = 0.112 min−1) and first-order desorption (kd = 7.00 × 10−3 min−1) and fitted the experimental data with R2 of 0.999. While adsorption was dominant in the first minute of the experiments with H2, bioreduction was dominant from the second minute to the 50th min. After 50 min, adsorption was negligible, and bioreduction was balanced by desorption. This work also provides the first set of equilibrium data for U(VI) adsorption by EPS alone. The equilibrium experiments with O2 were well simulated by both the Langmuir isotherm and the Freundlich isotherm, suggesting multiple mechanisms involved in the interactions between U(VI) and EPS. The thermodynamic study indicated that the adsorption of U(VI) onto EPS was endothermic, spontaneous and favorable at higher temperatures.

  • RESEARCH ARTICLE
    Zhou Zhang, Kai Huo, Tingxuan Yan, Xuwen Liu, Maocong Hu, Zhenhua Yao, Xuguang Liu, Tao Ye
    Frontiers of Environmental Science & Engineering, 2023, 17(8): 101. https://doi.org/10.1007/s11783-023-1701-5

    ● TiO2/ZSM-11 was prepared by a facile solid state dispersion method.

    ● Mechanism for photocatalytic degradation of dyes was investigated.

    ● Both experimental and MD simulations were conducted.

    ● Chemisorption instead of electrostatic interaction played a critical role.

    Photocatalytic degradation is a promising way to eliminate dye contaminants. In this work, a series of TiO2/ZSM-11 (TZ) nanocomposites were prepared using a facile solid state dispersion method. Methyl orange (MO), methylene blue (MB), and rhodamine B (RhB) were intentionally chosen as target substrates in the photocatalytic degradation reactions. Compared to pristine TiO2, negative effect was observed on MO degradation while promoted kinetics were collected on MB and RhB over TZ composites. Moreover, a much higher photocatalytic rate was interestingly achieved on RhB than MB, which indicated that a new factor has to be included other than the widely accepted electrostatic interaction mechanism to fully understand the selective photodegradation reactions. Systematic characterizations showed that TiO2 and ZSM-11 physically mixed and maintained both the whole framework and local structure without chemical interaction. The different trends observed in surface area and the photo-absorption ability of TZ composites with reaction performance further excluded both as the promotion mechanism. Instead, adsorption energies predicted by molecular dynamics simulations suggested that differences in the adsorption strength played a critical role. This work provided a deep mechanistic understanding of the selective photocatalytic degradation of dyes reactions, which helps to rationally design highly efficient photocatalysts.

  • RESEARCH ARTICLE
    Zeou Dou, Maria Vitoria Bini Farias, Wensi Chen, Dongjing He, Yuhang Hu, Xing Xie
    Frontiers of Environmental Science & Engineering, 2023, 17(5): 53. https://doi.org/10.1007/s11783-023-1653-9

    ● A controlled-release fertilizer was developed based on chitosan biopolymer scaffold.

    ● Chitosan-MMT scaffold achieved a well-controlled nutrient release.

    ● Highly water-absorbing chitosan-MMT hydrogels enhanced the soil water retention.

    ● Physically crosslinked chitosan-MMT hydrogels exhibited excellent degradability.

    Fertilizer consumption is increasing drastically along with the rapid expansion of farming in response to the ever-growing population. However, a significant portion of the nutrients in traditional fertilizers is lost during leaching and runoff causing economic loss and environmental threats. Polymer-modified controlled-release fertilizers provide an opportunity for mitigating adverse environmental effects and increasing the profitability of crop production. Here, we present a cheap and easy-to-fabricate controlled-release fertilizer excipient based on hydrogels scaffolded by safe and biodegradable chitosan and montmorillonite (MMT) nanoclays. By introducing elastic and flexible physical crosslinking induced by 2-dimensional (2D) MMT nanoflakes into the chitosan hydrogel, highly swellable and degradable chitosan-MMT nanocomposites were fabricated. The addition of MMT into the chitosan hydrogels enhanced the total release of phosphorous (P) and potassium (K), from 22.0 % to 94.9 % and 9.6% to 31.4 %, respectively, compared to the pure chitosan gel. The chitosan-MMT nanocomposite hydrogel achieved a well-controlled overall fertilizer release in soil. A total of 55.3 % of loaded fertilizer was released over 15 d with a daily release of 2.8 %. For the traditional fertilizer podwer, 89.2 % of the fertilizer was washed out during the first irrigation under the same setup. In the meantime, the nanocomposites improved the water retention of the soil, thanks to its excellent water absorbency. Moreover, the chitosan-MMT nanocomposite hydrogels exhibited high degradation of 57 % after swelling in water for 20 d. Such highly degradable fertilizer excipient poses minimal threat to the long-term fertility of the soil. The engineered Chitosan-MMT biopolymer scaffold as a controlled-release fertilizer excipient provides a promising opportunity for advancing sustainable agriculture.

  • RESEARCH ARTICLE
    Mourin Jarin, Zeou Dou, Haiping Gao, Yongsheng Chen, Xing Xie
    Frontiers of Environmental Science & Engineering, 2023, 17(2): 16. https://doi.org/10.1007/s11783-023-1616-1

    ● Present a general concept called “salinity exchange”.

    ● Salts transferred from seawater to treated wastewater until completely switch.

    ● Process demonstrated using a laboratory-scale electrodialysis system.

    ● High-quality desalinated water obtained at ~1 mL/min consuming < 1 kWh/m 3 energy.

    Two-thirds of the world’s population has limited access to potable water. As we continue to use up our freshwater resources, new and improved techniques for potable water production are warranted. Here, we present a general concept called “salinity exchange” that transfers salts from seawater or brackish water to treated wastewater until their salinity values approximately switch, thus producing wastewater with an increased salinity for discharge and desalinated seawater as the potable water source. We have demonstrated this process using electrodialysis. Salinity exchange has been successfully achieved between influents of different salinities under various operating conditions. Laboratory-scale salinity exchange electrodialysis (SEE) systems can produce high-quality desalinated water at ~1 mL/min with an energy consumption less than 1 kWh/m3. SEE has also been operated using real water, and the challenges of its implementation at a larger scale are evaluated.

  • RESEARCH ARTICLE
    Qianqian Gao, Xiaojing Zhu, Qihuang Wang, Kaili Zhou, Xiaohui Lu, Zimeng Wang, Xiaofei Wang
    Frontiers of Environmental Science & Engineering, 2023, 17(1): 10. https://doi.org/10.1007/s11783-023-1610-7

    ● Compositional patterns of PAHs in dust aerosol vary from soil during dust generation.

    ● The EF of PAH in dust aerosol is affected by soil texture and soil PAH concentration.

    ● The sizes of dust aerosol play an important role in the enrichment of HMW-PAHs.

    Polycyclic aromatic hydrocarbons (PAHs) are major organic pollutants in soil. It is known that they are released to the atmosphere by wind via dust aerosol generation. However, it remains unclear how these pollutants are transferred through the air/soil interface. In this study, dust aerosols were generated in the laboratory using soils (sandy loam and loam) with various physicochemical properties. The PAH concentrations of these soils and their generated dust aerosol were measured, showing that the enrichment factors (EFs) of PAHs were affected by soil texture, PAH contamination level, molecular weight of PAH species and aerosol sizes. The PAHs with higher EFs (6.24–123.35 in dust PM2.5; 7.02–47.65 in dust PM10) usually had high molecular weights with more than four aromatic rings. In addition, the positive correlation between EFs of PAHs and the total OCaerosol content of dust aerosol in different particle sizes was also statistically significant (r = 0.440, P < 0.05). This work provides insights into the relationship between atmospheric PAHs and the contaminated soils and the transfer process of PAHs through the soil-air interface.

  • RESEARCH ARTICLE
    Haoduo Zhao, Min Liu, Junjie Yang, Yuyang Chen, Mingliang Fang
    Frontiers of Environmental Science & Engineering, 2023, 17(1): 4. https://doi.org/10.1007/s11783-023-1604-5

    ● Metabolomic temporal profiling of cells exposed to xenobiotics.

    ● Global metabolome dysregulation patterns with time-resolved landscapes.

    ● Synchronized regulation behavior and specific dysregulation sensitivity.

    ● Temporal metabolic adaptions indicated cellular emphasis transition.

    The biochemical consequences induced by xenobiotic stress are featured in dose-response and time-resolved landscapes. Understanding the dynamic process of cellular adaptations is crucial in conducting the risk assessment for chemical exposure. As one of the most phenotype-related omics, metabolome in response to environmental stress can vary from seconds to days. Up to now, very few dynamic metabolomics studies have been conducted to provide time-dependent mechanistic interpretations in understanding xenobiotics-induced cellular adaptations. This study aims to explore the time-resolved metabolite dysregulation manner and dynamically perturbed biological functions in MCF-7 cells exposed to bisphenol A (BPA), a well-known endocrine-disrupting chemical. By sampling at 11 time points from several minutes to hours, thirty seven significantly dysregulated metabolites were identified, ranging from amino acids, fatty acids, carboxylic acids and nucleoside phosphate compounds. The metabolites in different pathways basically showed distinct time-resolved changing patterns, while those within the common class or same pathways showed similar and synchronized dysregulation behaviors. The pathway enrichment analysis suggested that purine metabolism, pyrimidine metabolism, aminoacyl-tRNA biosynthesis as well as glutamine/glutamate (GABA) metabolism pathways were heavily disturbed. As exposure event continued, MCF-7 cells went through multiple sequential metabolic adaptations from cell proliferation to energy metabolism, which indicated an enhancing cellular requirement for elevated energy homeostasis, oxidative stress response and ER-α mediated cell growth. We further focused on the time-dependent metabolite dysregulation behavior in purine and pyrimidine metabolism, and identified the impaired glycolysis and oxidative phosphorylation by redox imbalance. Lastly, we established a restricted cubic spline-based model to fit and predict metabolite’s full range dysregulation cartography, with metabolite’ sensitivity comparisons retrieved and novel biomarkers suggested. Overall, the results indicated that 8 h BPA exposure leaded to global dynamic metabolome adaptions including amino acid, nucleoside and sugar metabolism disorders, and the dysregulated metabolites with interfered pathways at different stages are of significant temporal distinctions.

  • RESEARCH ARTICLE
    Yujia Huang, Ting Zhang, Jianing Lou, Peng Wang, Lei Huang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 66. https://doi.org/10.1007/s11783-022-1545-4

    ● Education and subsidy were effective interventions during short-term heat exposure.

    ● A new index was defined to evaluate the intervention performance.

    ● Blood pressure and sleep duration were more heat-sensitive for the elderly.

    Due to climate change, the heatwave has become a more serious public health threat with aging as an aggravating factor in recent years. There is a pressing need to detect the most effective prevention and response measures. However, the specific health effects of interventions have not been characterized on an individual scale. In this study, an intervention experiment was designed to explore the health effects of heat exposure at the individual level and assess the effects of different interventions based on a comprehensive health sensitivity index (CHSI) in Xinyi, China. Forty-one subjects were recruited randomly, and divided into one control group and three intervention groups. Interventions included education (Educate by lecturing, offering relative materials, and communication), subsidy support (offer subsidy to offset the cost of running air conditioning), and cooling-spray (install a piece of cooling-spray equipment in the yard). Results showed that systolic blood pressure (SBP) and deep sleep duration (DSD) were significantly affected by short-term heat exposure, and the effects could be alleviated by three types of interventions. The estimated CHSI indicated that the effective days of the education group were longer than other groups, while the lower CHSI of the subsidy group showed lower sensitivity than the control group. These findings provide feasible implementation strategies to optimize Heat-health action plans and evaluate the intervention performance.

  • RESEARCH ARTICLE
    Yi Xiong, Boya Wang, Chao Zhou, Huan Chen, Gang Chen, Youneng Tang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 62. https://doi.org/10.1007/s11783-022-1567-y

    ● Evaluated three methods for determining the consortia’s growth kinetics.

    ● Conventional method is flawed since it relies on the total biomass concentration.

    ● Considering only selected bacterial taxa improved the accuracy.

    ● Considering oligotrophs and copiotrophs further improved the accuracy.

    The conventional method for determining growth kinetics of microbial consortia relies on the total biomass concentration. This may be inaccurate for substrates that are uncommon in nature and can only be degraded by a small portion of the microbial community. 1,4-dioxane, an emerging contaminant, is an example of such substrates. In this work, we evaluated an improved method for determining the growth kinetics of a 1,4-dioxane-degrading microbial consortium. In the improved method, we considered only bacterial taxa whose concentration increase correlated to 1,4-dioxane concentration decrease in duplicate microcosm tests. Using PEST (Parameter Estimation), a model-independent parameter estimator, the kinetic constants were estimated by fitting the Monod kinetics-based simulation results to the experimental data that consisted of the concentrations of 1,4-dioxane and the considered bacterial taxa. The estimated kinetic constants were evaluated by comparing the simulation results with experimental results from another set of microcosm tests. The evaluation was quantified by the sum of squared relative residual, which was four orders of magnitude lower for the improved method than the conventional method. By further dividing the considered bacterial taxa into oligotrophs and copiotrophs, the sum of squared relative residual further decreased.

  • SHORT COMMUNICATION
    Elizabeth Eastman, Kelly A. Stevens, Cesunica Ivey, Haofei Yu
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 63. https://doi.org/10.1007/s11783-022-1542-7

    ● We evaluated the accuracy of iPhone data in capturing time-activity patterns.

    ● iPhone data captured the most important microenvironments and time spent in them.

    ● iPhone data also accurately captured daily exposure to ambient PM pollution.

    ● A considerable fraction of the population in the USA may have iPhone data available.

    ● iPhone data has great potential in air pollution health studies.

    In many air pollution health studies, the time-activity pattern of individuals is often ignored largely due to lack of data. However, a better understanding of this location-based information is expected to decrease uncertainties in exposure estimation. Here, we showcase the potential of iPhone’s Significant Location (iSL) data in capturing the user’s historical time-activity patterns in order to estimate exposure to ambient air pollutants. In this study, one subject carried an iPhone in tandem with a reference GPS tracking device for one month. The GPS device recorded locations in 10 second intervals while the iSL recorded the time spent in locations the subject visited frequently. Using GPS data as a reference, we then evaluated the accuracy of iSL data in capturing the subject’s time-activity patterns and time-weighted air pollution concentration within the study time period. We found the iSL data accurately captured the time the subject spent in 16 microenvironments (i.e. locations the subject visited more than once), which was 93% of the time during the study period. The average error of time-weighted aerosol optical depth value, a surrogate of particle pollution, is only 0.012%. To explore the availability of iSL data among iPhone users, an online survey was conducted. Among the 349 surveyed participants, 72% of them have iSL data available. Considering the popularity of iPhones, iSL data may be available for a significant portion of the general population. Our results suggest iSL data have great potential for characterizing historical time-activity patterns to improve air pollution exposure estimation.

  • RESEARCH ARTICLE
    Bingdi Liu, Lin Zhang, Jason H. Knouft, Fangqiong Ling
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 64. https://doi.org/10.1007/s11783-022-1543-6

    ● Riverine microbiomes exhibited hyperlocal variation within a single transect.

    ● Certain family-level taxa directionally associated with river center and bank.

    ● Taxon accumulation curves within a transect urges more nuanced sampling design.

    Microbial communities inhabiting river ecosystems play crucial roles in global biogeochemical cycling and pollution attenuation. Spatial variations in local microbial assemblages are important for detailed understanding of community assembly and developing robust biodiversity sampling strategies. Here, we intensely analyzed twenty water samples collected from a one-meter spaced transect from the near-shore to the near-center in the Meramec River in eastern Missouri, USA and examined the microbial community composition with 16S rRNA gene amplicon sequencing. Riverine microbiomes across the transect exhibited extremely high similarity, with Pearson’s correlation coefficients above 0.9 for all pairwise community composition comparisons. However, despite the high similarity, PERMANOVA revealed significant spatial differences between near-shore and near-center communities (p = 0.001). Sloan’s neutral model simulations revealed that within-transect community composition variation was largely explained by demographic stochasticity (R2 = 0.89). Despite being primarily explained by neutral processes, LefSe analyses also revealed taxa from ten families of which relative abundances differed directionally from the bank to the river center, indicating an additional role of environmental filtering. Notably, the local variations within a river transect can have profound impacts on the documentation of alpha diversity. Taxon-accumulation curves indicated that even twenty samples did not fully saturate the sampling effort at the genus level, yet four, six and seven samples were able to capture 80% of the phylum-level, family-level, and genus-level diversity, respectively. This study for the first time reveals hyperlocal variations in riverine microbiomes and their assembly mechanisms, demanding attention to more robust sampling strategies for documenting microbial diversity in riverine systems.

  • SHORT COMMUNICATION
    Peng Wang, Shengqiang Zhu, Mihalis Vrekoussis, Guy P. Brasseur, Shuxiao Wang, Hongliang Zhang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 65. https://doi.org/10.1007/s11783-022-1544-5

    ● This study summarizes and evaluates different approaches that indicate O3 formation.

    ● Isopleth and sensitivity methods are useful but have many prerequisites.

    ● AOC is a better indicator of photochemical reactions leading to O3 formation.

    Tropospheric ozone (O3) concentration is increasing in China along with dramatic changes in precursor emissions and meteorological conditions, adversely affecting human health and ecosystems. O3 is formed from the complex nonlinear photochemical reactions from nitrogen oxides (NOx = NO + NO2) and volatile organic compounds (VOCs). Although the mechanism of O3 formation is rather clear, describing and analyzing its changes and formation potential at fine spatial and temporal resolution is still a challenge today. In this study, we briefly summarized and evaluated different approaches that indicate O3 formation regimes. We identify that atmospheric oxidation capacity (AOC) is a better indicator of photochemical reactions leading to the formation of O3 and other secondary pollutants. Results show that AOC has a prominent positive relationship to O3 in the major city clusters in China, with a goodness of fit (R2) up to 0.6. This outcome provides a novel perspective in characterizing O3 formation and has significant implications for formulating control strategies of secondary pollutants.

  • PREFACE
    Xing Xie, Jinkai Xue, Hongliang Zhang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 67. https://doi.org/10.1007/s11783-022-1546-3
  • RESEARCH ARTICLE
    Mahsa Kheirandish, Chunjiang An, Zhi Chen, Xiaolong Geng, Michel Boufadel
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 61. https://doi.org/10.1007/s11783-022-1540-9

    ● An approach for assessing the transport of benzene on the beach was proposed.

    ● The behavior of benzene in the subsurface of the beach was impacted by tide.

    ● Tidal amplitude influenced the travel speed and the benzene biodegradation.

    ● Hydraulic conductivity had the impact on plume residence time and biodegradation.

    ● Plume dispersed and concentration decreased due to high longitudinal dispersivity.

    The release and transport of benzene in coastal aquifers were investigated in the present study. Numerical simulations were implemented using the SEAM3D, coupled with GMS, to study the behavior of benzene in the subsurface of tidally influenced beaches. The transport and fate of the benzene plume were simulated, considering advection, dispersion, sorption, biodegradation, and dissolution on the beach. Different tide amplitudes, aquifer characteristics, and pollutant release locations were studied. It was found that the tide amplitude, hydraulic conductivity, and longitudinal dispersivity were the primary factors affecting the fate and transport of benzene. The tidal amplitude influenced the transport speed and percentage of biodegradation of benzene plume in the beach. A high tidal range reduced the spreading area and enhanced the rate of benzene biodegradation. Hydraulic conductivity had an impact on plume residence time and the percentage of contaminant biodegradation. Lower hydraulic conductivity induced longer residence time in each beach portion and a higher percentage of biodegradation on the beach. The plume dispersed and the concentration decreased due to high longitudinal dispersivity. The results can be used to support future risk assessment and management for the shorelines impacted by spill and leaking accidents. Modeling the heterogeneous beach aquifer subjected to tides can also be further explored in the future study.

  • RESEARCH ARTICLE
    Wei Tan, Shaohua Xie, Wenpo Shan, Zhihua Lian, Lijuan Xie, Annai Liu, Fei Gao, Lin Dong, Hong He, Fudong Liu
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 60. https://doi.org/10.1007/s11783-022-1539-2

    • CeO2 doping significantly improved low-temperature NH3-SCR activity on FeTiOx.

    • The crystallinity of FeTiOx was decreased dramatically after CeO2 doping.

    • Unique Ce-O-Fe structure in FeCe0.2TiOx accounted for its superior redox property.

    • Facile activation of NH3 to-NH2 on FeCe0.2TiOx promoted the DeNOx efficiency.

    FeTiOx has been recognized as an environmental-friendly and cost-effective catalyst for selective catalytic reduction (SCR) of NOx with NH3. Aimed at further improving the low-temperature DeNOx efficiency of FeTiOx catalyst, a simple strategy of CeO2 doping was proposed. The low-temperature (<250℃) NH3-SCR activity of FeTiOx catalyst could be dramatically enhanced by CeO2 doping, and the optimal composition of the catalyst was confirmed as FeCe0.2TiOx, which performed a NOx conversion of 90% at ca. 200℃. According to X-ray diffraction (XRD), Raman spectra and X-ray absorption fine structure spectroscopy (XAFS) analysis, FeCe0.2TiOx showed low crystallinity, with Fe and Ce species well mixed with each other. Based on the fitting results of extended X-ray absorption fine structure (EXAFS), a unique Ce-O-Fe structure was formed in FeCe0.2TiOx catalyst. The well improved specific surface area and the newly formed Ce-O-Fe structure dramatically contributed to the improvement of the redox property of FeCe0.2TiOx catalyst, which was well confirmed by H2-temperature-programmed reduction (H2-TPR) and in situ XAFS experiments. Such enhanced redox capability could benefit the activation of NO and NH3 at low temperatures for NOx removal. The detailed reaction mechanism study further suggested that the facile oxidative dehydrogenation of NH3 to highly reactive-NH2 played a key role in enhancing the low-temperature NH3-SCR performance of FeCe0.2TiOx catalyst.

  • RESEARCH ARTICLE
    Yang Yang, Qi Zhang, Baiyang Chen, Liangchen Long, Guan Zhang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 55. https://doi.org/10.1007/s11783-021-1489-0

    • UV/VUV/I induces substantial H2O2 and IO3 formation, but UV/I does not.

    • Increasing DO level in water enhances H2O2 and iodate productions.

    • Increasing pH decreases H2O2 and iodate formation and also photo-oxidation.

    • The redox potentials of UV/VUV/I and UV/VUV changes with pH changes.

    • The treatability of the UV/VUV/I process was stronger than UV/VUV at pH 11.0.

    Recently, a photochemical process induced by ultraviolet (UV), vacuum UV (VUV), and iodide (I) has gained attention for its robust potential for contaminant degradation. However, the mechanisms behind this process remain unclear because both oxidizing and reducing reactants are likely generated. To better understand this process, this study examined the evolutions of hydrogen peroxide (H2O2) and iodine species (i.e., iodide, iodate, and triiodide) during the UV/VUV/I process under varying pH and dissolved oxygen (DO) conditions. Results show that increasing DO in water enhanced H2O2 and iodate production, suggesting that high DO favors the formation of oxidizing species. In contrast, increasing pH (from 6.0 to 11.0) resulted in lower H2O2 and iodate formation, indicating that there was a decrease of oxidative capacity for the UV/VUV/I process. In addition, difluoroacetic acid (DFAA) was used as an exemplar contaminant to verify above observations. Although its degradation kinetics did not follow a constant trend as pH increases, the relative importance of mineralization appeared declining, suggesting that there was a redox transition from an oxidizing environment to a reducing environment as pH rises. The treatability of the UV/VUV/I process was stronger than UV/VUV under pH of 11.0, while UV/VUV process presented a better performance at pH lower than 11.0.

  • RESEARCH ARTICLE
    Jiuli Yang, Mingyang Liu, Qu Cheng, Lingyue Yang, Xiaohui Sun, Haidong Kan, Yang Liu, Michelle L. Bell, Rohini Dasan, Huiwang Gao, Xiaohong Yao, Yang Gao
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 56. https://doi.org/10.1007/s11783-021-1490-7

    • The impact of air pollution on AMI/COPD hospital admissions were examined.

    • Significant connection was found between air pollutants and AMI/COPD in Qingdao.

    • Nonlinearity exists between air pollution and AMI/COPD hospital admissions.

    Air pollution has been widely associated with adverse effects on the respiratory and cardiovascular systems. We investigated the relationship between acute myocardial infarction (AMI), chronic obstructive pulmonary disease (COPD) and air pollution exposure in the coastal city of Qingdao, China. Air pollution in this region is characterized by inland and oceanic transportation sources in addition to local emission. We examined the influence of PM2.5, PM10, NO2, SO2, CO and O3 concentrations on hospital admissions for AMI and COPD from October 1, 2014, to September 30, 2018, in Qingdao using a Poisson generalized additive model (GAM). We found that PM2.5, PM10, NO2, SO2 and CO exhibited a significant short-term (lag 1 day) association with AMI in the single-pollutant model among older adults (>65 years old) and females, especially during the cold season (October to March). In contrast, only NO2 and SO2 had clear cumulative lag associations with COPD admission for females and those over 65 years old at lag 01 and lag 03, respectively. In the two-pollutant model, the exposure-response relationship fitted by the two-pollutant model did not change significantly. Our findings indicated that there is an inflection point between the concentration of certain air pollutants and the hospital admissions of AMI and COPD even under the linear assumption, indicative of the benefits of reducing air pollution vary with pollution levels. This study has important implications for the development of policy for air pollution control in Qingdao and the public health benefits of reducing air pollution levels.

  • RESEARCH ARTICLE
    Xuesong Liu, Jianmin Wang, Yue-Wern Huang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 59. https://doi.org/10.1007/s11783-021-1493-4

    • A two-compartment model is able to quantify the effect of nano-TiO2 on Pb toxicity.

    • Nano-TiO2 reduces Pb tolerance level and increased the killing rate for C. dubia.

    • Thus, nano-TiO2 synergistically enhances Pb toxicity.

    • Algae reduce Pb transfer rate to the body tissue and the killing rate.

    Nano-TiO2 can remarkably increase lead (Pb) toxicity in aquatic organisms. However, the mechanism of this toxicity, additive or synergistic, is not well understood. To explore this mechanism, we inspected the role of nano-TiO2 in the toxicity of Pb on Ceriodaphnia dubia (C. dubia), a model water flea species typically used for ecotoxicity studies. The effect of algae, a diet for aquatic organisms, on the effect of this binary mixture was also investigated. A two-compartment toxicokinetic (TK)-toxicodynamic (TD) modeling approach was used to quantify the Pb toxicity under these complex conditions and to develop critical parameters for understanding the mechanism of toxicity. This two-compartment modeling approach adequately described the Pb accumulation in the gut and in the rest of the body tissue under different nano-TiO2 concentrations, with and without algae, and predicted the toxicity response of C. dubia. It indicated that increasing the nano-TiO2 concentration reduced the Pb tolerance level and concurrently increased the killing rate constant of C. dubia. Therefore, nano-TiO2 synergistically enhanced Pb toxicity. Algae remarkably reduced the toxicity of this binary mixture through reducing the Pb transfer rate to the body tissue and the killing rate, although it did not affect the Pb tolerance level. This two-compartment modeling approach is useful in understanding the role of nanoparticles when assessing the overall toxicity of nanoparticles and other toxic elements in the environment.

  • RESEARCH ARTICLE
    Feng Chen, Shihao Guo, Yihao Wang, Lulu Ma, Bing Li, Zhimin Song, Lei Huang, Wen Zhang
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 57. https://doi.org/10.1007/s11783-021-1491-6

    • A high-efficiency N-doped porous carbon adsorbent for Cr(VI) was synthesized.

    • The maximum adsorption capacity of Cr(VI) reached up to 285.71 mg/g at 318K.

    • The potential mechanism for Cr(VI) adsorption by NHPC was put forward.

    • DFT analyzed the adsorption energy and interaction between NHPC and Cr(VI).

    To develop highly effective adsorbents for chromium removal, a nitrogen-doped biomass-derived carbon (NHPC) was synthesized via direct carbonation of loofah sponge followed by alkali activation and doping modification. NHPC possessed a hierarchical micro-/mesoporous lamellar structure with nitrogen-containing functional groups (1.33 at%), specific surface area (1792.47 m2/g), and pore volume (1.18 cm3/g). NHPC exhibited a higher Cr(VI) adsorption affinity than the HPC (without nitrogen doping) or the pristine loofah sponge carbon (LSC) did. The influence of process parameters, including pH, dosage, time, temperature, and Cr(VI) concentration, on Cr(VI) adsorption by NHPC were evaluated. The Cr(VI) adsorption kinetics matched with the pseudo-second-order model (R2≥0.9983). The Cr(VI) adsorption isotherm was fitted with the Langmuir isotherm model, which indicated the maximum Cr(VI) adsorption capacities: 227.27, 238.10, and 285.71 mg/g at 298K, 308K, and 318K, respectively. The model analysis also indicated that adsorption of Cr(VI) on NHPC was a spontaneous, endothermal, and entropy-increasing process. The Cr(VI) adsorption process potentially involved mixed reductive and adsorbed mechanism. Furthermore, computational chemistry calculations revealed that the adsorption energy between NHPC and Cr(VI) (−0.84 eV) was lower than that of HPC (−0.51 eV), suggesting that nitrogen doping could greatly enhance the interaction between NHPC and Cr(VI).

  • REVIEW ARTICLE
    Jinkai Xue, Seyed Hesam-Aldin Samaei, Jianfei Chen, Ariana Doucet, Kelvin Tsun Wai Ng
    Frontiers of Environmental Science & Engineering, 2022, 16(5): 58. https://doi.org/10.1007/s11783-021-1492-5

    • 23 available research articles on MPs in drinking water treatment are reviewed.

    • The effects of treatment conditions and MP properties on MP removal are discussed.

    • DWTPs with more steps generally are more effective in removing MPs.

    • Smaller MPs (e.g.,<10 μm) are more challenging in drinking water treatment.

    Microplastics (MPs) have been widely detected in drinking water sources and tap water, raising the concern of the effectiveness of drinking water treatment plants (DWTPs) in protecting the public from exposure to MPs through drinking water. We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment (DWT), including laboratory- and full-scale studies. This article summarizes the major MP compositions (materials, sizes, shapes, and concentrations) in drinking water sources, and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes. The discussed drinking water treatment processes include coagulation-flocculation (CF), membrane filtration, sand filtration, and granular activated carbon (GAC) filtration. Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water. Various influential factors to MP removal are discussed, such as coagulant type and dose, MP material, shape and size, and water quality. It is anticipated that better MP removal can be achieved by optimizing the treatment conditions. Moreover, the article framed the major challenges and future research directions on MPs and nanoplastics (NPs) in DWT.