With rapid industrialization and urbanization, China is facing a great challenge with regard to severe fog-haze pollutions, which were characterized by high fine particulate concentration level and ...visibility impairment. The control strategies for atmosphere pollutions in China were not only cutting-edge topics of atmospheric research, but also an urgent issue to be addressed by the Chinese government and the public. Focused on the core scientific issues of the haze and fog pollution, this paper reviews the main studies conducted in China, especially after 2010, including formation mechanisms, evolution features, and factors contributing to the fog-haze pollutions. Present policy and control strategies were synoptically discussed. The major challenges ahead will be stated and recommendations for future research directions are proposed at the end of this Review.
Display omitted
•The effect of the haze and fog events on air quality, climate change and health risk in China are reviewed.•Factors contributing to formation of fog-haze events in China are reviewed.•Advances in the studies of haze and fog pollutions in China are reviewed.•Future directions of haze pollutions in China are suggested.
Display omitted
•Transition-metal based MOFs as electrocatalysts for OER are introduced.•Recent achievements of MOF-based materials for OER are discussed.•The perspectives for the future development ...of MOF-based materials for OER are shown.
Exploiting advanced electrocatalysts for oxygen evolution reaction (OER) is of vital importance for the development of metal-air batteries, fuel cells and water electrolyzers. Rational design and fabrication of electrocatalysts with high specific areas, abundant expose active sites, and porous structures is an effective approach to improve the electrocatalytic performances. Metal-organic frameworks (MOFs), an emerging class of porous crystalline materials, which possess large surface areas, high porosities, componential and structural diversity, has shown great potential as efficient OER electrocatalysts. This review focus on the recent progress of fabrication and utilization of transition metal (e.g., Fe, Co, and Ni) based MOF materials including pristine MOFs, MOF composites and their derivatives for OER. A variety of typical strategies, including synthetic designs, compositional, and structural modifications for activity improvement of the MOF-based materials in the OER are outlined and discussed. Based on the previous achievements, the current state of the art and the perspectives for the future development of the field are summarized.
Algae is a very promising source for renewable energy production since it can fix the greenhouse gas (CO2) by photosynthesis and does not compete with the production of food. Compared to microalgae, ...researches on biofuel production from macroalgae in both academia and industry are at infancy for economically efficient and technological solutions. This review provides up to-date knowledge and information on macroalgae-based biofuels, such as biogas, bioethanol, biodiesel and bio-oils respectively obtained from anaerobic digestion, fermentation, transesterification, liquefaction and pyrolysis technique methods. It is concluded that bioethanol and bio-oils from wet macroalgae are more competitive while biodiesel production seems less attractive compared to high lipid content microalgae biomass. Finally, a biorefinery concept based on macroalgae is given.
The greater abundances of antibiotic resistance genes (ARGs) in point-of-use tap and reclaimed water than that in freshly treated water raise the question whether residual disinfectants in ...distribution systems facilitate the spread of ARGs. This study investigated three widely used disinfectants (free chlorine, chloramine, and hydrogen peroxide) on promoting ARGs transfer within Escherichia coli strains and across genera from Escherichia coli to Salmonella typhimurium. The results demonstrated that subinhibitory concentrations (lower than minimum inhibitory concentrations MICs) of these disinfectants, namely 0.1-1 mg/L Cl
for free chlorine, 0.1-1 mg/L Cl
for chloramine, and 0.24-3 mg/L H
O
, led to concentration-dependent increases in intragenera conjugative transfer by 3.4-6.4, 1.9-7.5, and 1.4-5.4 folds compared with controls, respectively. By comparison, the intergenera conjugative frequencies were slightly increased by approximately 1.4-2.3 folds compared with controls. However, exposure to disinfectants concentrations higher than MICs significantly suppressed conjugative transfer. This study provided evidence and insights into possible underlying mechanisms for enhanced conjugative transfer, which involved intracellular reactive oxygen species formation, SOS response, increased cell membrane permeability, and altered expressions of conjugation-relevant genes. The results suggest that certain oxidative chemicals, such as disinfectants, accelerate ARGs transfer and therefore justify motivations in evaluating disinfection alternatives for controlling antibiotic resistance. This study also triggers questions regarding the potential role of environmental chemicals in the global spread of antibiotic resistance.
The COVID-19 epidemic broke out in Wuhan, Hubei in December 2019 and in January 2020 and was later transmitted to the entire country. Quarantine measures during Chinese New Year effectively ...alleviated the spread of the epidemic, but they simultaneously resulted in a decline in anthropogenic emissions from industry, transportation, and import and export of goods. Herein, we present the major chemical composition of non-refractory PM2.5 (NR-PM2.5) and the concentrations of gaseous pollutants in an urban site in Shanghai before and during the quarantine period of the COVID-19 epidemic, which was Jan. 8―23 and Jan. 24―Feb. 8, respectively. The observed results show that the reduction in PM2.5 can be mainly attributed to decreasing concentrations of nitrate and primary aerosols. Nitrate accounted for 37% of NR-PM2.5 before the quarantine period when there was no emission reduction. During the quarantine period, the nitrate concentration decreased by approximately 60%, which is attributed to a reduction in the NOx concentration. Ammonium, as the main balancing cation, showed an approximately 45% simultaneous decrease in concentration. The concentrations of chloride and hydrocarbon-like organic aerosols from primary emissions also declined due to limited human activities. By contrast, sulphate and oxygenated organic aerosols showed a slight decrease in concentration, with their contributions increasing to 27% and 18%, respectively, during the quarantine period, which resulted in two pollution episodes with PM2.5 exceeding 100 μg/m3. This study provides a better understanding of the impact of quarantine measures on variations of the PM2.5 concentration and chemical compositions. Atmospheric oxidation capacities based on the oxidant (Ox = O3 + NO2) and oxidation ratios have been discussed for elucidating the source and formation of haze in an environment with lower anthropogenic emissions. With increasing contribution of secondary aerosols, lower NOx and nitrate concentrations did not completely avoid haze in Shanghai during the epidemic.
Display omitted
•Quarantine measures led to a reduction in the concentrations of PM2.5, SO2, NOx, and CO in Shanghai.•Reduction in NOx led to increasing O3 and decreasing nitrate.•Reduction in PM2.5 is attributed to the decreasing concentrations of primary aerosols and nitrate.•The increasing contribution of sulphate and OOA inhibited further PM2.5 reduction.
Although widespread antibiotic resistance has been mostly attributed to the selective pressure generated by overuse and misuse of antibiotics, recent growing evidence suggests that chemicals other ...than antibiotics, such as certain metals, can also select and stimulate antibiotic resistance via both co-resistance and cross-resistance mechanisms. For instance, tetL, merE, and oprD genes are resistant to both antibiotics and metals. However, the potential de novo resistance induced by heavy metals at environmentally-relevant low concentrations (much below theminimum inhibitory concentrations MICs, also referred as sub-inhibitory) has hardly been explored. This study investigated and revealed that heavy metals, namely Cu(II), Ag(I), Cr(VI), and Zn(II), at environmentally-relevant and sub-inhibitory concentrations, promoted conjugative transfer of antibiotic resistance genes (ARGs) between E. coli strains. The mechanisms of this phenomenon were further explored, which involved intracellular reactive oxygen species (ROS) formation, SOS response, increased cell membrane permeability, and altered expression of conjugation-relevant genes. These findings suggest that sub-inhibitory levels of heavy metals that widely present in various environments contribute to the resistance phenomena via facilitating horizontal transfer of ARGs. This study provides evidence from multiple aspects implicating the ecological effect of low levels of heavy metals on antibiotic resistance dissemination and highlights the urgency of strengthening efficacious policy and technology to control metal pollutants in the environments.
Display omitted
•Sub-inhibitory heavy metals promoted conjugative transfer of ARGs between E. coli strains.•Mechanisms included ROS formation, SOS response, membrane permeability and altered gene expression.•This study provides evidence of low levels of heavy metals on antibiotic resistance dissemination.
•Combining HTL with subsequent technologies should be an important research direction.•Formic acid and formaldehyde are promising reagent for lignin depolymerization.•A breakthrough is needed in the ...development of new materials for advanced reactor.•Finding multifunctional catalysts is important for cutting down energy consumption.•Novel technologies for bio-oil refining and upgrading should be developed.
Hydrothermal liquefaction has been widely applied to obtain bioenergy and high-value chemicals from biomass in the presence of a solvent at moderate to high temperature (200–550°C) and pressure (5–25MPa). This article summarizes and discusses the conversion of agricultural and forestry wastes by hydrothermal liquefaction. The history and development of hydrothermal liquefaction technology for lignocellulosic biomass are briefly introduced. The research status in hydrothermal liquefaction of agricultural and forestry wastes is critically reviewed, particularly for the effects of liquefaction conditions on bio-oil yield and the decomposition mechanisms of main components in biomass. The limitations of hydrothermal liquefaction of agricultural and forestry wastes are discussed, and future research priorities are proposed.
Graphene （G） was dispersed uniformly in water and used as an inhibitor in waterborne epoxy coatings. The effect of dispersed G on anticorrosion performance of epoxy coatings was evaluated. The ...composite coatings displayed outstanding barrier properties against H20 molecule compared to the neat epoxy coating. Open circuit potential （OCP）, Tafel and electrochemical impedance spectroscopy （EIS） analysis confirmed that the corrosion rate exhibited by composite coatings with 0.5 wt% G was an order of magnitude lower than that of neat epoxy coating. Salt spray test results revealed superior corrosion resistance offered by the composite coating.
•A novel magnetic porous carbon with γ-Fe2O3 particles was prepared from hydrochar.•Activation and magnetization of hydrochar can be simultaneously obtained.•The as-prepared magnetic porous carbon ...could remove tetracycline efficiently.
In the present work, a novel magnetic porous carbon (MPC) with maghemite (γ-Fe2O3) particles is facilely prepared from hydrochar (a solid residue of hydrothermal carbonization of biomass) in one step through simultaneous activation and magnetization. The resultant MPC is characterized and utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. The BET surface area and micropore volume of the MPC are found to be 349m2g−1 and 0.16cm3g−1, respectively. The adsorption kinetics data could be well described by the pseudo-second-order model, and the TC adsorption onto MPC is an endothermic and spontaneous process. The enhanced surface area of the MPC, as well as its graphite-like structure, may contribute to the adsorption capacity of TC. After adsorption, MPC could be effectively separated by applying a magnetic field.
“Structural superlubricity” is an important fundamental phenomenon in modern tribology that is expected to greatly diminish friction in mechanical engineering, but now is limited to achieve only at ...nanoscale and microscale in experiment. A novel principle for broadening the structural superlubricating state based on numberless micro‐contact into macroscale superlubricity is demonstrated. The topography of micro‐asperities on engineering steel substrates is elaborately constructed to divide the macroscale surface contact into microscale point contacts. Then at each contact point, special measures such as pre‐running‐in period and coating heterogeneous covalent/ionic or ionic/ionic nanocomposite of 2D materials are devised to manipulate the interfacial ordered layer‐by‐layer state, weak chemical interaction, and incommensurate configuration, thereby satisfying the prerequisites responsible for structural superlubricity. Finally, the robust superlubricating states on engineering steel–steel macroscale contact pairs are achieved with significantly reduced friction coefficient in 10−3 magnitude, extra‐long antiwear life (more than 1.0 × 106 laps), and good universality to wide range of materials and loads, which can be of significance for the industrialization of “structural superlubricity.”
A novel principle is proposed to assemble numberless “microscale superlubricity” into “macroscale superlubricity,” where the elaborately constructed micro‐asperities of rough engineering substrate play the role of splitting macro‐surface into micro‐points. Then, at each contact point, special measures, such as pre‐running‐in and heterogeneous 2D materials are devised to manipulate the interfacial ordered state, chemical interaction, and incommensurate configuration, thereby achieving robust macroscale superlubricity.
PDF
