خيارات البحث
النتائج 2661 - 2670 من 4,896
Simultaneous removal of nitrate/phosphate with bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin
2019
Shen, Zhanhui | Dong, Xinyi | Shi, Jialu | Ma, Yuanhao | Liu, Daoru | Fan, Jing
Given the prevalence of nitrate and phosphate in surface and groundwater, it is important to develop technology for the simultaneous removal of nitrate and phosphate. In this study, we prepared the bimetallic nanoparticles of Fe coupled with copper or nickel supported on chelating resin DOW 3N (D-Fe/Ni and D-Fe/Cu) for removing nitrate and phosphate simultaneously. XPS profiles revealed that Cu has better ability than Ni to increase the stability of Fe nanoparticles and prevent nZVI from oxidation. The results showed that nitrate removal efficiencies by D-Fe/Ni and D-Fe/Cu were 98.7% and 95.5%, respectively and the phosphate removal efficiencies of D-Fe/Cu and D-Fe/Ni were 99.0% and 93.0%, respectively. Besides adsorption and coprecipitation as reported in previous studies, the mechanism of phosphate removal also includes the adsorption of the newly formed polymeric ligand exchanger (PLE). Moreover, in previous studies, the presence of phosphate had significant negative effects on the reduction of nitrate. However, in this study, the removal efficiency of nitrate was less affected with the increasing concentration of phosphate for D-Fe/Cu. This was mainly because D-Fe/Cu had higher adsorption capacity of phosphate due to the newly formed PLE according to the XPS depth profile analysis.
اظهر المزيد [+] اقل [-]Ameliorative effect of Bacillus subtilis, Saccharomyces boulardii, oregano, and calcium montmorillonite on growth, intestinal histology, and blood metabolites on Salmonella-infected broiler chicken
2019
Abudabos, Alaeldein M. | Alhouri, Hemiar A.A. | Alhidary, Ibrahim A. | Nassan, Mohammed A. | Swelum, Ayman A.
This study evaluated the effects of Bacillus subtilis, Saccharomyces boulardii, oregano, and calcium montmorillonite on the physical growth, intestinal histomorphology, and blood metabolites in Salmonella-challenged birds during the finisher phase. In this study, a total of 600 chicks (Ross 308) were randomly distributed into the following dietary treatments: basal diet with no treatment; infected with Salmonella; T1, infected + avilamycin; T2, infected + Bacillus subtilis; T3, Saccharomyces boulardii; T4, infected + oregano; T5, infected + calcium montmorillonite. Our results indicated that feed consumption, body weight gain, total body weight, and feed conversion ratio increased significantly (P < 0.01) in T1 and T2. Villus width increased significantly (P < 0.01) in T1 while the total area was significantly (P < 0.01) higher in T1 and T2 among the treatment groups. Blood protein was significantly (P < 0.01) high in T3 and T4; however, the glucose concentration was significantly (P < 0.01) high in T2, T3, and T4. The treatments increased significantly (P< 0.01) in the treatment groups compared to the negative control. Aspirate aminotransferase (AST) was significantly (P < 0.05) low in T3 compared to the positive control. In conclusion, the results indicated that supplementation of Bacillus subtilis and calcium montmorillonite improved the production performance compared to other feed additives in broiler chicks infected with Salmonella during the finisher phase.
اظهر المزيد [+] اقل [-]Increasingly Distant from Eden—a Look at the Soils of Protected Areas Using Ecotoxicological Tests and Chemical Analysis
2019
Honscha, Laiz Coutelle | de Moura, Renata Rodrigues | Baisch, Paulo Roberto Martins | Da Silva Júnior, Flavio Manoel Rodrigues
On the basis of the assumption that legally protected areas are created to maintain environmental quality that, in turn, is indispensable for quality of life, this study aims to evaluate the soil conditions in protected areas that are located near urban regions by using ecotoxicological assays and chemical analysis. The study was carried out using surface soil samples collected from seven protected areas in southern Brazil. For the protected area to be considered “clean,” the results of the ecotoxicological tests should be within the criteria accepted for negative control according to standardized protocols, and the concentration of chemical elements should be below the maximum levels allowed by Brazilian law. On the basis of the criteria adopted for ecotoxicological assays and chemical analysis, soil from only two of the seven protected areas (28.6%) met the criteria for being considered “clean.” This probably reflects the influence of anthropogenic activities within the protected areas, demonstrating drawbacks of delimitation and management. The strategy used in this study could be used to assess the anthropogenic impact on protected areas in other parts of the world.
اظهر المزيد [+] اقل [-]Adsorption performance and mechanisms of Pb(II), Cd(II), and Mn(II) removal by a β-cyclodextrin derivative
2019
Zhang, Mengjiao | Zhu, Liyun | He, Changhua | Xu, Xiaojun | Duan, Zhengyang | Liu, Shuli | Song, Mingyao | Song, Shumin | Shi, Jiemei | Li, Yu’e | Cao, Guangzhu
In this study, the novel adsorbent PVA-TA-βCD was synthesized via thermal cross-linking between polyvinyl alcohol and β-cyclodextrin. The characterization methods SEM-EDS, FTIR, and XPS were adopted to characterize the adsorbent. The effect of pH, contact time, initial concentrations, and temperature during the adsorption of Pb(II), Cd(II), and Mn(II) onto the PVA-TA-βCD was also investigated. In a single-component system, the data fitted well to pseudo-second-order, and film diffusion and intra-particle diffusion both played important roles in the adsorption process. As for isotherm study, it showed a heterogeneous adsorption capacity of 199.11, 116.52, and 90.28 mg g⁻¹ for the Pb(II), Cd(II), and Mn(II), respectively. Competition between the ions existed in a multi-component system; however, owing to the stronger affinity of the PVA-TA-βCD for Pb(II) relative to Cd(II) and Mn(II), the Pb(II) adsorption onto the PVA-TA-βCD was less affected by the addition of the other metals, which could be effectively explained by the hard and soft acid and base theory (HSAB). Furthermore, PVA-TA-βCD showed good reusability throughout regeneration experiments.
اظهر المزيد [+] اقل [-]Bioaccumulation, antioxidative response, and metallothionein expression in Lupinus luteus L. exposed to heavy metals and silver nanoparticles
2019
Jaskulak, Marta | Rorat, Agnieszka | Grobelak, Anna | Chaabene, Zayneb | Kacprzak, Małgorzata | Vandenbulcke, Franck
Yellow-lupin (Lupinus luteus L.) was grown on soils contaminated with heavy metals during two parallel studies. In the first one, the soil was contaminated by industrial activities whereas, in the second one, the soil was artificially contaminated with a single metal including Cd, Pb, Zn, Ni (in nitrate form), and Ag (in nitrate and nanoparticles form). The study was performed to assess a plant’s response to contamination including its antioxidative response and molecular mechanisms involved in metal detoxification through the expression level of metallothioneins (MTs). Overall, the study provided insights into identification and validation of housekeeping genes (HKG) in L. luteus under exposure to metal stress and showed the effects of selected heavy metals and silver nanoparticles on the expression of metallothioneins, the activity of guaiacol peroxidase (GPX) and bioaccumulation of metals in leaves of L. luteus. As such, HKG validation using BestKeeper, NormFinder, and geNorm software allowed for the selection of four most stable reference genes in a context metal contamination for the selected plant. Moreover, a significant increase in the expression levels of MT was observed in plants grown under heavy metal stress and none on plants grown on 25 mg kg⁻¹ of silver nanoparticles. Also, the GPX activity and MT expression showed statistically significant changes between different conditions and doses which means that they can be used as highly sensitive stress markers for planning the phytoremediation process on a large scale.
اظهر المزيد [+] اقل [-]Wet Dust Sampler—a Sampling Method for Road Dust Quantification and Analyses
2019
Lundberg, Joacim | Blomqvist, Göran | Gustafsson, Mats | Janhäll, Sara | Järlskog, Ida
In northern countries, the climate, and consequently the use of studded tyres and winter traction sanding, causes accumulation of road dust over winter and spring, resulting in high PM₁₀ concentrations during springtime dusting events. To quantify the dust at the road surface, a method—the wet dust sampler (WDS)—was developed allowing repeatable sampling also under wet and snowy conditions. The principle of operation is flushing high-pressurised water over a defined surface area and transferring the dust laden water into a container for further analyses. The WDS has been used for some time and is presented in detail to the international scientific community as reported by Jonsson et al. (2008) and Gustafsson et al. (2019), and in this paper, the latest version is presented together with an evaluation of its performance. To evaluate the WDS, the ejected water amount was measured, as well as water losses in different parts of the sampling system, together with indicative dust measurement using turbidity as a proxy for dust concentration. The results show that the WDS, when accounting for all losses, have a predictable and repeatable water performance, with no impact on performance based on the variety of asphalt surface types included in this study, given undamaged surfaces. The largest loss was found to be water retained on the surface, and the dust measurements imply that this might not have as large impact on the sampled dust as could be expected. A theoretical particle mass balance shows small particle losses, while field measurements show higher losses. Several tests are suggested to validate and improve on the mass balances. Finally, the WDS is found to perform well and is able to contribute to further knowledge regarding road dust implications for air pollution.
اظهر المزيد [+] اقل [-]Shift of Soil Polycyclic Aromatic Hydrocarbons (PAHs) Dissipation Pattern and Microbial Community Composition due to Rhamnolipid Supplementation
2019
Lu, Lu | Zhang, Jing | Peng, Chao
Biosurfactants are promising substitutes for chemical surfactants during polycyclic aromatic hydrocarbon (PAH) bioremediation. However, recent studies have revealed contrasting findings and critical knowledge gaps regarding the impacts of biosurfactants on the soil PAH biodegradation efficiency and microbial community. Here, a laboratory study was conducted to evaluate the impact of rhamnolipid on the PAH dissipation efficiency and microbial community structure during the time-course incubation. The data showed that the contribution ratio of biotic loss and abiotic loss depended on the ring number of PAH. In the microcosms supplemented with 20 μg g⁻¹ rhamnolipid, the biodegradation efficiencies of phenanthrene, fluoranthene, and pyrene increased by 10.1%, 12.3%, and 22.0%, respectively, compared to those in the rhamnolipid-free treatment after incubation for 7 days. In contrast, rhamnolipid either had no impact on or inhibited PAH degradation in the later time points (21–35 days). The abundance of bacterial 16S rRNA and phnAc genes showed significant increase in soil amended of both PAH and rhamnolipid. MiSeq sequencing results revealed that potential PAHs-degrading Massilia, Bacillus, Lysobacter, Archrobacter, and Phenylobacterium became dominant genera in PAH treatment, irrespective of the rhamnolipid added. Nevertheless, PAH addition in the presence of rhamnolipid also significantly stimulated the growth of Delftia, Brevundimonas, Tumebacillus, and Geobacillus. In contrast, the rhamnolipid altered the microbial community composition through the selection of Gaiella, Solirubrobacter, Nocardioides, and Bacillus. The results reveal the intensive selectivity effect of PAH and rhamnolipid on the soil microbes that are involved in bioremediation, and highlight the positive effect on PAHs biodegradation.
اظهر المزيد [+] اقل [-]Optimization of a laccase-mediator system with natural redox-mediating compounds for pesticide removal
2019
Kupski, Larine | Salcedo, Gabriela M. | Caldas, Sergiane S. | de Souza, Taiana D. | Furlong, Eliana B. | Primel, Ednei G.
This study proposed the optimization of a laccase-mediator system to reduce pesticide levels (bentazone, carbofuran, diuron, clomazone, tebuconazole, and pyraclostrobin) on aqueous medium. Firstly, the mediator concentration of 1 mM was established (average removal of 36%). After that, seven redox-mediating compounds, namely, 2,20-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt, caffeic acid, chlorogenic acid, p-coumaric acid, ferulic acid, gallic acid, protocatechuic acid, and vanillin, were compared regarding their removal efficiency. The highest removal (77%) was achieved with the laccase-vanillin system. After this screening, the optimization was carried out by a 2² full factorial design. Variables under study were the enzyme (laccase) activity and vanillin concentration. Maximum removal (53–85%) was achieved with 0.95 U/mL laccase and 1.8 mM vanillin. Pesticide removal in reaction media was fitted to the first-order kinetics equation with an average half-time life of 2.2 h. This is the first study of the use of this natural compound as a mediator in the degradation of the pesticides under investigation. The results of this study contribute, with alternative methods, to decrease pesticide levels since they are highly persistent in aqueous samples and, as a result, mitigate the environmental impact.
اظهر المزيد [+] اقل [-]Bioaccumulation of Heavy Metals (Pb, Cd, Cr, Cu) in Fine Roots Under Three Species of Alders (Alnus spp.) Plantation at Different Soil Substrates Addition on the Reclaimed Combustion Wastes Landfill
2019
Świątek, Bartłomiej | Woś, Bartłomiej | Gruba, Piotr | Pietrzykowski, Marcin
In the study, we have analysed the impact of lead (Pb), cadmium (Cd), chromium (Cr) and copper (Cu) on fine root biomass and the associated level of bioacumulation heavy metals in fine roots under alder plantings (Alnus incana, A. glutinosa and A. viridis) growing on technosols developed from combustion wastes and extremely poor quaternary sands excavated by sand mining. The control sites were located in natural habitats in the Bieszczady Mountains within the natural range of the occurrence of the investigated alder species. Results showed that the bioaccumulation index of heavy metals in the alder roots depended on technosol properties, in particular, pH and texture, and, to a lesser extent, on the total content of heavy metals in soil. Additionally, it was found that in some concentration ranges, Pb and Cr had a stimulating effect on the growth of fine roots.
اظهر المزيد [+] اقل [-]Estimating the spatial distribution of environmental suitability for female lung cancer mortality in China based on a novel statistical method
2019
Han, Xiao | Guo, Yanlong | Gao, Hong | Ma, Jianmin | Sang, Manjie | Zhou, Sheng | Huang, Tao | Mao, Xiaoxuan
Lung cancer as one of the major causes of cancer mortality has been demonstrated to be closely related to the ambient atmospheric environment, but little has been done in the synthetic evaluation of the linkage between cancer mortality and combined impact of ambient air pollution and meteorological conditions. The present study determined the environmental suitability for female lung cancer mortality associated with air contaminants and meteorological variables. A novel fuzzy matter–element method was applied to identify the spatial distribution and regions for the environmental suitability for the female lung cancer mortality across China in 2013. The membership functions between the cancer mortality and 6 environmental factors, including PM₂.₅, NO₂, SO₂, PM₁₀, the annual mean wind speed, and mean temperature, were generated and the weights of each of the environmental factors were established by the maximum entropy (MaxEnt) model. We categorized the environmental suitability combined with GIS spatial analysis into three zones, including low-suitable, medium-suitable, and high-suitable region where the cancer mortality ranging from low to high rate was identified. These three zones were quantified by the MaxEnt model taking different air pollutants and meteorological variables into consideration. We identified that NO₂ was a most significant factor among the 6 environmental factors with the weight of 24.88%, followed by the annual mean wind speed, SO₂, and PM₂.₅. The high-suitable area, mainly in the North China Plain which is a most heavily contaminated region by air pollution in China, covers 1.6195 million square kilometers, accounting for 17.85% of the total area investigated in this study. Identification of the impact of various environmental factors on cancer mortality in the different suitable area provides a scientific basis for the environmental management, risk assessment, and lung cancer control.
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