خيارات البحث
النتائج 4261 - 4270 من 4,924
Prevalence of antibiotic resistance genes in cell culture liquid waste and the virulence assess for isolated resistant strains
2019
Wang, Haichao | Wang, Jin | Li, Shuming | Li, Jinzhao | Jing, Chuanyong
Cell culture liquid waste containing antibiotic resistance genes (ARGs) and microbial community were still not received enough recognition, which pose potential risks to human health. Sixty-eight resistance genes and intl1 were detected in eight samples by Quantitative real-time PCR, while intl1 was only detected in hospital group. Meanwhile, the bacterial community was complex and diverse in each sample by 16S rRNA gene high-throughput sequencing, in addition, Morganella and Enterococcus presented a significant difference between two groups. Whole genome shotgun sequencing revealed that Morganella morganii had more resistance genes and virulence factors in hospital group, and three extended-spectrum beta-lactamase (ESBL) genotypes were found to be blaDHA-5, blaOXA-1, and blaTEM-1. This study provided a preliminary report on ARGs and resistant strains, which reminded people attention to the health risks of potential pathogens in this waste.
اظهر المزيد [+] اقل [-]Using stress wave technology for leakage detection in a landfill impervious layer
2019
Chen, Yayu | Sun, Huanyi | Zhang, Wei | Huang, Xiaosong
This paper proposes a stress wave monitoring method for monitoring and locating leakage through the impervious layer at a landfill to resolve the “first pollution, then discovery” problem caused by the existing electrical monitoring method. The experimental results show that the linear distance to the geophones from the leak point should be less than 31.5 m to provide a well-defined rupture signal. The amplitudes of the stress wave signals generated during the yield and rupture stages of the high-density polyethylene (HDPE) film are more obvious and easily identified by the geophones; the rupture signal duration is approximately 100 ms, and the bandwidth is distributed within 0 kHz to 1 kHz. By studying the stress wave first arrival times calculated by the picking model, the average error of the picking model is approximately 0.35 ms, and the iteration of the model is ceased when the thresholds of the discriminating indices are 3.5 and 0.9. Experiments reveal that the positioning model should stop iterating when the absolute value of each element in the calibration vector is less than 140. The average positioning error is 0.248 m, and the maximum fiducial errors of the positioning model in the X-axis and Y-axis directions are 0.32% and 0.58%, respectively.
اظهر المزيد [+] اقل [-]High-efficient adsorption and removal of elemental mercury from smelting flue gas by cobalt sulfide
2019
Liu, Hui | You, Zhiwen | Yang, Shu | Liu, Cao | Xie, Xiaofeng | Xiang, Kaisong | Wang, Xiaoyang | Yan, Xu
Nonferrous metal smelting produces a large amount of Hg⁰ in flue gas, which has caused serious damage to the environment and human health. In this work, amorphous cobalt sulfide was synthesized by a liquid-phase precipitation method and was used for capturing gaseous Hg⁰ from simulated smelting flue gas at low temperatures (50~150 °C). In the adsorption process, Hg⁰ can be transformed into the stable mercury compound, which is confirmed to be HgS by X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption of Hg (Hg-TPD) analysis. Meanwhile, XPS results also demonstrate that S₂²⁻ species on the surface of cobalt sulfide play an important role in Hg⁰ transformation. At the temperature of 50 °C (inlet Hg⁰ concentration of 214 μg·m⁻³), the Hg⁰ adsorption capacity of cobalt sulfide (penetration rate of 25%) is as high as 2.07 mg·g⁻¹, which is much higher than that of popular adsorbents such as activated carbons and metal oxides. In addition, it was found that the Hg⁰ removal efficiency by cobalt sulfide in the flue gas with high concentration of SO₂ (5%) remained more than 94%. The good adsorption and Hg⁰ removal performance guarantee cobalt sulfide the great superiority and application potential in the treatment of Hg⁰ in smelting flue gas with high concentration of SO₂.
اظهر المزيد [+] اقل [-]Preparation and characterization of activated carbon produced from tannery solid waste applied for tannery wastewater treatment
2019
Mella, Bianca | Benvenuti, Jaqueline | Oliveira, Renata F. | Gutterres, Mariliz
The removal of toxic compounds (azo dyes) from dyeing wastewater was investigated by an environmentally friendly activated carbon produced from solid waste generated in the tannery process, the cattle hair (CHW), activated with H₃PO₄ (AC-CHW), suggesting a life cycle extension for this material from leather processing. Preliminary tests with aqueous solutions containing Acid Brown 414 (AB-414) and Acid Orange 142 (AO-142) removed 71.06% and 73.05%, respectively. The activated carbon was characterized by zeta potential (ZP), functional groups (FTIR), elemental composition, sorbent specific surface area, and pore size distribution (BET/BJH). The specific surface area showed low values when compared to commercial activated carbon, but average pore diameter was higher, which facilitates the adsorption of larger and complex molecules, such as those present in real wastewaters. Through SEM and FTIR, the presence of the toxic compounds studied in the AC-CHW after sorption process was observed, where the results indicated that the functional groups of -CH=CH- participated in the removal process for these compounds. The removal efficiency obtained with AC-CHW was 51.94% and 49.73% for the dyeing wastewater containing AB-414 and AO-142, respectively. The obtained results open a promising via to use AC-CHW as efficient eco-friendly sorbent for the treatment of leather wastewater.
اظهر المزيد [+] اقل [-]Biosorption of dysprosium (III) using raw and surface-modified bark powder of Mangifera indica: isotherm, kinetic and thermodynamic studies
2019
Devi, Aparna Prabha | Mishra, Pravat Manjari
In this paper, we have used HDTMA-Br- and NaOH-treated bark powder of Mangifera indica as bio-sorbents for the removal of dysprosium (III) from its aqueous solution. The adsorption process was investigated at different experimental parameters such as contact time, temperature, pH, adsorbent dose, and initial metal concentration. The amount of chemically modified bark powder required was almost two times lesser than raw bark to get a higher percentage removal of the metal ion. The kinetics results revealed the adsorption process follows the nonlinear form a pseudo-second-order model. The negative values of Gibbs free energy change (∆G°) indicated the spontaneity of the adsorption process. The enthalpy change (∆H°) and entropy change (∆S°) of adsorption were 60.97 kJ/mol and 0.48 J/mol K, respectively signified it as an endothermic process. The maximum adsorption capacity was found to be 55.04 mg/g for sorption of Dy (III) on NaOH-treated bark powder and was better fitted to Langmuier model. It was confirmed to follow physisorption process and the activation energy of the system was found to be 41.07 kJ/mol. The possibility of adsorbent and adsorbate interactions were indicated by the FTIR and SEM/EDX analysis.
اظهر المزيد [+] اقل [-]Effects of individual ozone exposure on lung function in the elderly: a cross-sectional study in China
2019
Zhang, Jiayao | Sun, Hong | Chen, Qi | Gu, Jie | Ding, Zhen | Xu, Yan
The aim of this study was to assess the acute health effects of individual ozone (O₃) exposure on the respiratory system in the elderly. A total of 40 non-smoking elderly volunteers completed personal 24 h of measurement for O₃ and fine particulate matter (PM₂.₅). To assess health effects, we measured the pulmonary function and five inflammatory biomarkers in exhaled breath condensate (EBC), including interleukin-2 (IL-2), interferon-γ (IFN-γ), prostaglandin E₂ (PGE₂), and tumor necrosis factor α/β (TNFα/β). We used the generalized additive model to analyze the association between O₃ and these health effects, after adjusting PM₂.₅, BMI, and sex as confounders. As a result, we found a negative correlation between O₃ and forced vital capacity (FVC) or forced expiratory volume-one second (FEV1). With the increasing of O₃ by 10 μg/m³, FVC and FEV1 decreased by 0.13 L (95% CI 0.01, 0.26) and 0.11 L (95% CI 0.02, 0.20), respectively. We found no statistical significance between O₃ and biomarkers in EBC. The results suggested that individual 24-h O₃ exposure was associated with decreased pulmonary function in the elderly.
اظهر المزيد [+] اقل [-]Physiological responses of three mono-species phototrophic biofilms exposed to copper and zinc
2019
Loustau, Emilie | Ferriol, Jessica | Koteiche, Shams | Gerlin, Léo | Leflaive, Joséphine | Moulin, Frédéric | Girbal-Neuhauser, Elisabeth | Rols, Jean-Luc
In freshwater ecosystem, phototrophic biofilms play a crucial role through adsorption and sequestration of organic and inorganic pollutants. However, extracellular polymeric substance (EPS) secretion by phototrophic biofilms exposed to metals is poorly documented. This work evaluated the physiological responses of phototrophic biofilms by exposing three microorganisms (cyanobacterium Phormidium autumnale, diatom Nitzschia palea and green alga Uronema confervicolum) to 20 and 200 μg L⁻¹ of Cu or 60 and 600 μg L⁻¹ of Zn, both individually and in combination. Analysis of metal effects on algal biomass and photosynthetic efficiency showed that metals were toxic at higher concentrations for these two parameters together and that all the strains were more sensitive to Cu than to Zn. U. confervicolum was the most impacted in terms of growth, while P. autumnale was the most impacted in terms of photosynthetic efficiency. In consequence to metal exposure at higher concentrations (Cu200, Zn600 and Cu200Zn600), a higher EPS production was measured in diatom and cyanobacterium biofilms, essentially caused by an overproduction of protein-like polymers. On the other hand, the amount of secreted polysaccharides decreased during metal exposure of the diatom and green alga biofilms. Size exclusion chromatography revealed specific EPS molecular fingerprints in P. autumnale and N. palea biofilms that have secreted different protein-like polymers during their development in the presence of Zn600. These proteins were not detected in the presence of Cu200 despite an increase of proteins in the EPS extracts compared to the control. These results highlight interesting divergent responses between the three mono-species biofilms and suggest that increasing protein production in EPS biofilms may be a fingerprint of natural biofilm against metal pollutants in freshwater rivers.
اظهر المزيد [+] اقل [-]Detection of Alcanivorax spp., Cycloclasticus spp., and Methanomicrobiales in water column and sediment samples in the Gulf of Mexico by qPCR
2019
Hernández-López, Edna L. | Gasperin, Jahaziel | Bernáldez-Sarabia, Johanna | Licea-Navarro, Alexei F. | Guerrero, Abraham | Lizárraga-Partida, Marcial Leonardo
Water column and sediment samples were collected in the southern Gulf of Mexico (GoMex) during 3 oceanographic cruises: XIXIMI-04 (September 2015), XIXIMI-05 (June 2016), and XIXIMI-06 (August 2017). DNA that was extracted from the samples was analyzed by qPCR to detect and quantify bacterial groups that have been reported to metabolize alkanes (Alcanivorax) and aromatic hydrocarbons (Cycloclasticus) and are involved in methane production (Methanomicrobiales). The results were then analyzed with regard to the water masses that are currently detected in the GoMex. Generally, we observed a decrease in the proportion of Alcanivorax and a rise in those of Cycloclasticus and Methanomicrobiales in samples from the surface to deep waters and in sediment samples. Scatterplots of the results showed that the relative abundance of the 3 groups was higher primarily from the surface to 1000 m, but the levels of Cycloclasticus and Methanomicrobiales were high in certain water samples below 1000 m and in sediments. In conclusion, oil-degrading bacteria are distributed widely from the surface to deep waters and sediments throughout the southern GoMex, representing a potential inoculum of bacteria for various hydrocarbon fractions that are ready for proliferation and degradation in the event of an oil spill from the seafloor or along the water column.
اظهر المزيد [+] اقل [-]Constituent transformation mechanism of concentrated leachate after incineration at different temperatures
2019
Ren, Xu | Song, Kai | Xiao, Yu | Chen, Weiming | Liu, Dan
Spraying concentrated leachate into an incineration furnace and burning is encouraged by the Chinese government as a harmless method for leachate treatment. In this research, the constituent transformation mechanism was studied, by X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectrometry (EDS), of residues after burning the concentrated leachate in a muffle furnace at different temperatures (750 °C, 850 °C, 900 °C, 1000 °C, and 1100 °C). XRD results showed that the main components of the residues were metal chlorides and calcium salt crystals and that the peak position of most of these crystals changed little because their crystal structure was stable at high temperatures. SEM results illustrated that the higher the burning temperature, the smaller the solid particles, and the looser the structures of the residues. EDS analysis showed that S atoms in the concentrated leachate were usually transformed into gaseous compounds during incineration, whereas most of the Cl atoms could be fastened onto solid residues if an appropriate temperature was maintained. This study concluded that 900 °C was the best burning temperature for spraying concentrated leachate into the furnace. In addition, this study suggested that material selection for the nozzle and flue gas pipelines must pay more attention to corrosion caused by gaseous sulfur compounds. Similarly, material selection for the inner wall of the incinerator furnace should pay more attention to corrosion caused by Cl atoms. This means that the municipal solid waste (MSW) incineration power plants should incorporate various and appropriate corrosion-resistant materials according to the different regions of the incinerator.
اظهر المزيد [+] اقل [-]Self-templated microwave-assisted hydrothermal synthesis of two-dimensional holey hydroxyapatite nanosheets for efficient heavy metal removal
2019
Su, Yiping | Wang, Jing | Li, Shun | Zhu, Jianhua | Liu, Weishu | Zhang, Zuotai
Heavy metals have caused serious environmental problems and threat to human health. Ultrathin and holey two-dimensional (2D) nanosheets have recently drawn significant attention as superb adsorbent material to remove heavy metal ions due to their unique physicochemical properties. Herein, we report a self-template-directed ultrafast reaction route to synthesis porous hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) nanosheets via a microwave-assisted hydrothermal method using poly(allylamine hydrochloride) as an additive. The resulting hydroxyapatite nanosheets showed a high specific surface area (92.9 m² g⁻¹) and excellent adsorption performance for various heavy metal ions including Pb(II), Cu(II), and Cd(II), with maximum adsorption capacities of 210.5, 31.6, and 24.9 mg g⁻¹, respectively. The adsorption kinetics fitted well with the pseudo-second-order equation and the equilibrium data showed a high correlation coefficient with the Langmuir model. Based on the experimental results and analysis, we can conclude that the sorption of heavy metal ions with the hydroxyapatite nanosheets mainly attributes to surface complexation and cation exchange. The present synthetic strategy allows the fast and massive production of porous hydroxyapatite ultrathin nanosheets and may also potentially be applicable to the fabrication of other metal phosphates with assembled or hierarchical porous structures towards various applications such as water purification.
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