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Traditional pyrolysis biochar has been widely employed to treat dye wastewater. However, there are some problems in the pyrolysis process, such as the generation of harmful gases and the low content of silico-oxygen functional groups to promote adsorption. Straw biochar (Ac-BCbm) was prepared by sulfuric acid co-ball milling method. The adsorption performance and adsorption mechanism of rhodamine B (RhB) under different preparation conditions and factors were investigated. The results showed that the adsorption rate of Ac-BCbm on RhB was up to 94.9%, which was 60.5% and 55.8% higher than that of ball-milling straw (STbm) and biochar prepared by pyrolysis (STBC600), respectively. The Ac-BCbm had better adaptability under different pH and common interfering ions for remove RhB. Characterization and DFT simulation analysis revealed that the sulfuric acid co-ball milling process promoted the formation of Si–OH and Si–O-CH3 oxygen-containing functional groups of Si component in straw, which enhanced the hydrogen bonding interactions and effectively improved the adsorption efficiency. This study investigated a new strategy for biochar preparation by sulfuric acid co-ball milling, which provides an additional development direction for the efficient resource utilization of straw. [ABSTRACT FROM AUTHOR]

Increased biogas residue related to the rapid development of anaerobic fermentation has become an urgent environmental problem. The pyrolysis of biogas residue into biochar is one of the most promising treatments. In this study, biochar derived from biogas residue was prepared, and the degradation efficiency of phenol by permanganate (KMnO4) increased from 25.3% to 73.4% in 60 min in the presence of biogas residue biochar (BRB). KMnO4 reacted with BRB to produce intermediate manganese dioxide (MnO2), while BRB was activated. The specific surface area increased by 132.25%, and the oxygen-containing functional groups C=O, C−O, and COOH increased after the reaction. The generated MnO2 complexed with BRB to form MnO2@BRB. The newly formed MnO2@BRB catalyzed KMnO4 to remove phenol, which explains the high removal efficiency of phenol. A significant removal rate was also observed for antibiotics and chlorophenols, which suggested that the KMnO4/BRB system has a relatively high ability to oxidize organic pollutants. In addition, the co-existing metal ions and the natural environment had little influence on the removal efficiency of the KMnO4/BRB system. This work provides a novel technology for the resource utilization of biogas residue and improved organic pollutant removal efficiency of KMnO4 in the presence of BRB. Highlights: Phenol removal was enhanced by permanganate (KMnO4) with biogas residue biochar (BRB). Manganese dioxide (MnO2) was generated and complexed with BRB to catalyze phenol removal by KMnO4. KMnO4/BRB system can be used for the removal of other organic pollutants. [ABSTRACT FROM AUTHOR]

In this study, a new straw-iron composite material (ST@Fe) was synthesized through impregnation and freeze-drying process for persulfate (PS) activation to degrade reactive black 5 (RB5). Scanning electron microscope, Brunauer–Emmett–Teller, Fourier transform infrared spectrometry, and X-ray photoelectron spectroscopy confirmed that straw owns huge pore structure and varieties of organic functional groups, including hydroxyl carboxyl groups, which could effectively adsorb and complex iron ions. The interaction between the active iron particles in ST@Fe and straw generated Fe2+ for PS activation, effectively degrading over 94.80% of RB5 at an initial concentration of 20 ppm in 100 min with a specific degradation capacity of 18.97 min−1 per unit of iron ions. ST@Fe/PS system demonstrated high tolerance in a wide initial pH range, which could gradually attack the RB5 molecular structure and significantly reduce the mineralization of water. Quenching experiments and electron paramagnetic resonance demonstrated the efficient generation of ROS including sulfate radicals, hydroxyl radicals, and singlet oxygen, and confirmed the dominance of sulfate radicals in the degradation process. The continuous degradation capacity and reusability of ST@Fe were also evaluated, which proved that the contaminant could be effectively degraded even after multiple cycles in the simulated textile wastewater, indicating its potential for use in practical remediation. This work provided a new method for the preparation of modified functional materials for the degradation of organic pollutants in textile wastewater and posed a novel strategy for the utilization of waste biomass. [ABSTRACT FROM AUTHOR]

Purpose: Climate models predict shifts in precipitation patterns characterized by increased precipitation amount and decreased frequency for semi-arid grasslands in northeast China. However, under these novel climatic conditions, potential differences in plant biomass and its allocation among different degraded grasslands remain unclear. Methods: We conducted a mesocosm experiment to test the effects of higher precipitation amount (increased by 50% from the long-term mean) and lower frequency (decreased by 50%) on plant biomass and allocation in the lightly, moderately, and severely degraded grasslands. Results: Lower precipitation frequency promoted belowground biomass but reduced aboveground biomass through enhancing soil water variability. Higher precipitation amount enhanced aboveground biomass in the lightly and moderately degraded grasslands, but not in the severely degraded grassland due to lower soil nitrogen availability. Lower precipitation frequency weakened or ended the positive effects of higher precipitation amount on aboveground and belowground biomass, and higher precipitation amount suppressed the enhancement of lower precipitation frequency on belowground biomass, which could be attributed to temporary waterlogging. Plants in the moderately degraded grassland preferred to adjust root vertical distribution, which was impacted by the changes in plant community composition. However, adjustment of aboveground biomass vs. belowground biomass was the primary biomass allocation strategy in the other two grasslands. Conclusions: Our findings emphasized the importance of considering the degradation level of grasslands when predicting responses of ecosystem functions to the projected changes in precipitation regimes. These findings are critical for making feasible decisions for the sustainable management of degraded grasslands. Legend: + and − indicate positive and negative relationships, respectively LDG, MDG and SDG-lightly degraded, moderately degraded and severely degraded grasslands, respectively DPF-decreased precipitation frequency treatment, IPA-increased precipitation amount treatment SWC and CVSWC-mean and variation of soil water content, respectively SINC-soil inorganic nitrogen content AGB and BGB-aboveground and belowground biomass, respectively fAGB-AGB / total biomass BGB0–10 (%)-belowground biomass proportion in the 0–10 cm soil layer, BGB 0 - 10 / BGB 0 - 30 × 100 RAGB-relative aboveground biomass [ABSTRACT FROM AUTHOR]

High-efficiency and cost-effective catalysts with available strategies for persulfate (PS) activation are critical for the complete mineralization of organic contaminants in the environmental remediation and protection fields. A nanoscale zero-valent iron-embedded modified mesoporous carbon (MCNZVI) with a core-shell structure is synthesized using the hydrothermal synthesis method and high-temperature pyrolysis. The results showed that nZVI could be impregnated within mesoporous carbon frameworks with a comparatively high graphitization degree, rich nitrogen doping content, and a large surface area and pore volume. This material was used as a persulfate activator for the oxidation removal of Reactive Black 5 (RB5). The effects of the material dosage, PS concentration, pH, and some inorganic anions (i.e., Cl−, SO42−) on RB5 degradation were then investigated. The highest degradation efficiency (97.3%) of RB5 was achieved via PS (20 mmol/L) activation by the MCNZVI (0.5 g/L). The pseudo-first-order kinetics (k = 2.11 × 10−2 min−1) in the MCNZVI/PS (0.5 g/L, 20 mmol/L) was greater than 100 times than that in the MCNZVI and PS. The reactive oxygen species (ROS), including 1O2, SO4·−, HO., and ·O2−, were generated by PS activation with the MCNZVI. Singlet oxygen was demonstrated to be the primary ROS responsible for the RB5 degradation. The MCNZVI could be reused and regenerated for recycling. This work provides new insights into PS activation to remove organic contamination. [ABSTRACT FROM AUTHOR]

Waste classification is to reduce solid waste and its associated environmental pollution. This paper applied bibliometrics to assess publications related to classification technology of domestic waste from 2000 to 2019. A total of 466 publications were retrieved. The results showed the number of citations and papers increased rapidly. The major publication type regarding waste classification technology is article and English is the primary language for academic communication. The research is multidisciplinary and interdisciplinary, and its research directions are mainly divided into "Engineering," "Environmental Sciences Economics," and "Chemistry." It was identified that Waste Management (85) published most of papers in this topic. Meanwhile, China (93) contributed the most of publications, followed by the USA (42), France (40), Japan (36), and Italy (28). European countries are in the leading position in the study of garbage classification technology. Plastics and waste metals were the existing focus of waste classification technology, and waste identification and classification has become an important classification method. In addition, we also summarized the current mainstream technology progress and possible research challenges. [ABSTRACT FROM AUTHOR]

Antibiotics are emerging pollutants and increasingly present in aquaculture and industrial wastewater. Due to their impact on the environment and health, their removal has recently become a significant concern. In this investigation, we synthesized nano zero-valent iron-loaded magnetic mesoporous silica (Fe-MCM-41-A) via precipitation and applied the adsorption of oxytetracycline (OTC) from an aqueous solution. The effects of competing ions such as Na+, Ca2+ and Cu2+ on the adsorption process under different pH conditions were studied in depth to providing a theoretical basis for the application of nanomaterials. The characterization of the obtained material through transmission electron microscopy demonstrates that the adsorbent possesses hexagonal channels, which facilitate mass transfer during adsorption. The loaded zero-valent iron made the magnetic, and was thus separated under an applied magnetic field. The adsorption of OTC onto Fe-MCM-41-A is rapid and obeys the pseudo-second-order kinetic model, and the maximum adsorption capacity of OTC is 625.90 mg g−1. The reaction between OTC and Fe-MCM-41-A was inner complexation and was less affected by the Na+. The effect of Ca2+ on the adsorption was small under acidic and neutral conditions. However, the promotion effect of Ca2+ increased by the increase of pH. Cu2+ decreased the removal efficiencies continuously and the inhibitory effects decrease varied with the increase of pH. We propose that surface complexing, ion-exchange, cationic π-bonding, hydrogen bonding, and hydrophobicity are responsible for the adsorption of OTC onto Fe-MCM-41-A. [ABSTRACT FROM AUTHOR]

The behavior and characteristics of phenol adsorption by activated carbon produced from co-pyrolysis of coal tar pitch and vinasse were investigated. Coal tar pitch and vinasse (mass ratio of 1:3) were firstly co-pyrolyzed and carbonated at 400 °C for 2 h. The carbonized material produced was then soaked with saturated KOH solution and activated at 800 °C for 1 h to form activated carbon. Results from the phenol wastewater adsorption experiments suggest that pseudo-second-order kinetics and the Weber-Morris model could reflect the time-dependent adsorption behavior of phenol wastewater by the activated carbon, revealing that internal diffusion represents the rate-limiting procedure and dominant process to control the adsorption rate in the early stage of the adsorption. Monolayer adsorption played the key role during the phenol adsorption. The adsorption was an endothermic reaction in temperature ranging from 15 °C to 35 °C, indicating that the adsorption speed could be stimulated by the increasing temperature. This study establishes a theoretical foundation for the usage and the potential application of the activated carbon derived from coal tar pitch and vinasse in wastewater treatment. [ABSTRACT FROM AUTHOR]

Landfill leachate, due to its quantity and inherent risk, is generally collected and transported by piping system for advanced treatment. During the piping, the pipe materials may react with leachate, resulting in corrosion and scaling. In order to reduce possible failures and mitigate the associated consequences, this study provides an indicator system for material selection to aid the pipe system design. The material functional, economic, and environmental attributes are incorporated into the indicator system, to perform a precise selection of commercial drainage pipe materials, thus improving empirically oriented selection. Four common drainage pipe materials including high-density polyethylene (HDPE), polyvinyl chloride (PVC), galvanized steel, and seamless steel are taken as the material alternatives for the selection. Based upon their experimental data, a grey target decision-making framework is employed to perform the priority ranking of the materials. The results indicate that HDPE has the best performance, followed by PVC, galvanized steel, and seamless steel. This study discusses the validity of the selection results and the applicability of the proposed method, to provide insight into leachate piping system design. [ABSTRACT FROM AUTHOR]

To evaluate the longevity of the iron-activated persulfate (PS) oxidation degradation of 2,4-dinitrotoluene (2,4-DNT), zero-valent iron (ZVI), and three different micron-scale iron oxides were used as catalysts for the activation of PS. It was revealed that 2,4-DNT was degraded more effectively by ZVI and maghemite (γ-Fe2O3) compared to that of hematite (α-Fe2O3) and magnetite (Fe3O4) catalyst treatments. Denitration of 2,4-DNT and oxidation of nitro groups as nitrate occurred by Fe0/PS and γ-Fe2O3/PS. When the 2,4-DNT removal rate was 1%, the generated sulfate concentrations of Fe0/PS and γ-Fe2O3/PS were 2.08 mg/L and 1.27 mg/L, respectively. Only micron scale γ-Fe2O3 could activate PS for 2,4-DNT removal. ZVI was cycled and able to activate PS through multiple rounds. The size of the corrosion products of ZVI was more than 100 nm, and the particle size gradually increased in the cycling process. The first cycle of Fe0 resulted in 45% removal of 2,4-DNT in 360 min. The 2,4-DNT removal efficiency (68.15%) increased after the second cycle, reaching the best removal efficiency in the fourth cycle. Oxidation products formed during degradation covered the ZVI surface, forming a shell. Adsorption of organic pollutants to this shell aids in the removal efficiency of 2,4-DNT and longevity of ZVI in groundwater. [ABSTRACT FROM AUTHOR]

Biochar has been paid great attentions during the last two decades, because of its resources potentials and environmental benefits. A bibliometric analysis was applied to assess the publications regarding the keyword biochar from the Web of Science database during the period of 1999 to 2018. A total of 8629 publications were obtained with a rapid increase of annual citations and number of papers. The research topics were diversified, which were mainly divided into "Environmental Sciences and Ecology," "Agriculture," and "Engineering." Bioresource Technology was the journal which published most of the relevant papers. China ranked first in the number of published papers, followed by the USA, Australia, UK, and Germany. Especially, China established close collaboration with the USA in joint publication. Analysis of the keywords indicated that biochar production, comparative sorption, soil-applied black carbon, and soil management were the main research hotspots of biochar. The burst detection reflected that the innovation of biochar production and the new application field of biochar was the future research trends. These results can provide insight into the research progress regarding biochar. [ABSTRACT FROM AUTHOR]

Aims: Terrestrial plants require relative stable stoichiometry of elements for their growth. The effects of plant species and soil phosphorus (P) concentration on P:nutrient stoichiometry in plant remains still unknown. Methods: Soil and plant samples were collected from 88 sites in a P-rich area of a subtropical portion of China to examine the linkage of soil P concentration with the concentrations and stoichiometry of 12 nutrient elements (C, N, P, S, K, Ca, Mg, Fe, Al, Zn, Mn and Na) for different plant species. Results: Soil rich in P increased the concentrations of S, P, K, Ca, Fe, Mg, Mn, Al, and Na in the plants, but induced a strong antagonism to Zn. Meanwhile, the concentrations of C and N in the leaf was restrained when the plants grew in soil under high P concentration. Clustering analysis showed that plant species were categorized according to soil P concentration into P > 2 mg g−1 and P < 2 mg g−1 groups. However, insignificant dissimilarity among plant species was noticed. Conclusions: The stoichiometry of P:nutrient in the plant organs was strongly affected by soil P concentrations and this could reflect soil nutrient status over plant species. Therefore, the difference in soil P concentration is a major driver triggering the variation in elemental stoichiometry. [ABSTRACT FROM AUTHOR]

Hexachlorobenzene (HCB) dechlorination affected by humic acids (HA) was evaluated in terms of HA redox capacity, HA concentrations, and microbial community, as well as the correlation between HA redox capacity values and HCB concentrations. With addition of HA in the initial stage, redox capacity values increased by 2.19 meq/L (80 mg/L of HA addition, HA80), 2.51 meq/L (120 mg/L of HA addition, HA120), and 3.64 meq/L (200 mg/L of HA addition, HA200), respectively. The addition of HA could prominently enhance the HCB degradation rate. However, the concentration and the redox capacity of HA decreased during the anaerobic digestion process. Illumina MiSeq sequencing showed that microbial community affected by HA. Bacillus, Comamonas, and Pseudomonas were the predominant genera during the HCB dechlorination treatment. Moreover, Bacillus and Pseudomonas can improve HA electron transfer capability and promote the dechlorination of HCB. [ABSTRACT FROM AUTHOR]

Dredging has been practiced to remove sediment impacted by persistent contaminants, such as heavy metals. Of these metals, lead (Pb) is of particular concern due to its toxicity. Therefore, dredged sediment containing Pb requires further mitigation. One method for Pb mitigation is phytoremediation of dredged sediment. In this study, the partitioning of Pb in sediment during phytoremediation by willow ( Salix integra) was assessed. The results showed that, in general, the bioavailable forms of Pb declined with increased application of the standard Hoagland nutrient solution, which appeared to enhance the Fe-Mn oxide fraction and residual inert fraction. In contrast, the addition of excess phosphorus decreased the bioavailable fractions of Pb. However, the bioavailable fractions of Pb increased with additional potassium addition. Planting Salix integra was shown to promote the stabilization of Pb in sediment and led to a transformation from bioavailable forms to non-bioavailable forms. The results suggest that planting Salix integra can remediate Pb-contaminated dredged sediment via Pb immobilization by the roots. During this process, the application of Hoagland nutrient solution and the application of nutrient solutions with excess phosphorus not only promote root growth of Salix integra which would reduce Pb bioavailability, but also further enhance the immobilization of Pb in contaminated sediment, likely through the formation of Pb-containing compounds with low bioavailability. [ABSTRACT FROM AUTHOR]

Both three-dimensional excitation-emission matrix fluorescence spectroscopy and parallel factor analysis were utilized to identify dissolved organic matter (DOM) components in sediments of thirty eutrophic shallow lakes in the middle reaches of the Yangtze River in China. Four distinct DOM components were identified: two main components regarding terrestrial humic-like materials (C1 and C2), one about terrestrial fulvic/humic-like materials (C3), and one related to autochthonous tryptophan-like materials (C4). The dominance of terrestrial fluorescence materials in DOM indicated that terrestrial inputs have critical effects on the surveyed lakes. The Principal Component Analysis (PCA) and Canonical Corresponding Analysis (CCA) were applied to analyze DOM components and their relationship with the environmental variables. PCA graphs showed that there were spatial differences in DOM fluorophores among lakes with various environments. Components C1, C2, and C4 were correlated positively with PC1 axis (factor 1), while C3 was opposite. Component C1 and C3 showed positive correlations with PC2 axis (factor 2). The CCA and Pearson correlation analysis showed that sediment DOC was correlated significantly with sediment variables (TN, OM, and conductivity), water quality variables (TN, PO , and Chl a), and DOM components C1 and C3. All DOM components were related significantly to different environment variables, including water quality variables especially nutrient elements (NO , TN, Chl a, and DOC) and sediment variables (OM, NH , and HCl-P). The relationship between DOC and the lake comprehensive nutritive index TLI was marginally significant. [ABSTRACT FROM AUTHOR]

With the rise of environmentalism in China, great efforts have been devoted to environmental protection over the past several decades. Compared with urban environmental protection, rural environmental protection has not been attached enough importance in China due to the dual-track structure of socio-economic development. As a result, rural China is shouldering disproportionally heavy environmental burdens partly because of the differences and biases between urban and rural environmental protection seen in environmental policies, environmental rights and interests, environmental protection investment, and the environmental protection awareness of people. To eliminate the gap between rural and urban environmental protection, and achieve the goal of 'balanced urban-rural environmental protection' (BUREP), government should consider mapping out proper policies and strategies. In this paper we put forward an innovative strategy of BUREP against the background of China's urban-rural environmental protection. First, we review the current status of rural environmental protection status and its challenges compared with urban environmental protection in China. Secondly, we analyzed the main driving factors and reasons deeply, and then we put forward the BUREP strategy base on the unequal status between urban and rural environment. Finally, we proposed the framework of BUREP. This study may serve as a scientific reference regarding decision-making in coordinating urban and rural environmental protection and in constructing the new countryside of China. [ABSTRACT FROM AUTHOR]

Red mud as a waste material is produced in large quantities by the aluminum industry. Heat activation has been used to enhance sorption capacity of red mud for its beneficial reuse as an effective sorbent. In this study, heat-activated red mud (HARM) was investigated for its Cd(II) sorption capacity under various process conditions (Cd concentration, pH and contact time) using response surface methodology (RSM). Analysis with RSM identified pH as the most important process parameter. The positive correlation between higher pH and greater Cd(II) sorption was likely due to: (i) decreased proton competition with Cd(II) for sorption sites at higher pH; (ii) enhanced sorption via ion exchange by monovalent Cd species from hydrolysis at higher pH; and (iii) improved thermodynamics of sorption at higher pH as protons are being released as products. Further analysis indicated the sorption process was thermodynamically favorable with a negative change in Gibbs free energy. Additionally, the sorption process exhibited a positive change in enthalpy, indicative of endothermic nature of sorption; this is consistent with sorption increase at higher temperature. These findings provide needed insight into the mechanisms underlying Cd(II) sorption by HARM for more effective applications of heat-activated red mud as sorbents for Cd(II) removal. [ABSTRACT FROM AUTHOR]

While the contribution of biodiversity to supporting multiple ecosystem functions is well established in natural ecosystems, the relationship of the above- and below-ground diversity with ecosystem multifunctionality remains virtually unknown in urban greenspaces. Here we conducted a standardized survey of urban greenspaces from 56 municipalities across six continents, aiming to investigate the relationships of plant and soil biodiversity (diversity of bacteria, fungi, protists and invertebrates, and metagenomics-based functional diversity) with 18 surrogates of ecosystem functions from nine ecosystem services. We found that soil biodiversity across biomes was significantly and positively correlated with multiple dimensions of ecosystem functions, and contributed to key ecosystem services such as microbially driven carbon pools, organic matter decomposition, plant productivity, nutrient cycling, water regulation, plant-soil mutualism, plant pathogen control and antibiotic resistance regulation. Plant diversity only indirectly influenced multifunctionality in urban greenspaces via changes in soil conditions that were associated with soil biodiversity. These findings were maintained after controlling for climate, spatial context, soil properties, vegetation and management practices. This study provides solid evidence that conserving soil biodiversity in urban greenspaces is key to supporting multiple dimensions of ecosystem functioning, which is critical for the sustainability of urban ecosystems and human wellbeing., (© 2023. The Author(s), under exclusive licence to Springer Nature Limited.)