خيارات البحث
النتائج 6101 - 6110 من 6,546
Catalytic performance promoted on Pt-based diesel oxidation catalyst assisted by polyvinyl alcohol النص الكامل
2020
Liang, Yanli | Ding, Xinmei | Wang, Jianli | Zhao, Ming | Dan, Yi | Jiang, Long | Chen, Yaoqiang
Eliminating vehicle emission is of importance due to the severe limit value. The work reports a convenient strategy of improving dispersion of platinum-based catalyst with the assistance of polyvinyl alcohol in a varied addition amount. Following the “two-step” annealing techniques, the catalytic performance of the polymer-assisted catalysts in diesel was obviously enhanced because of the improved dispersion of the platinum. Based on experimental results, the long chains of polymer resulting in the steric effect are presumed to isolate platinum ion, inhibiting the aggregation of platinum particles and then improving its dispersion. And the hydroxyl bonding between the polymers could convey electron to platinum species, leading to the lower platinum valence state. Both effects are positive resulting in an excellent NO maximum conversion of around 65% at the optimal introduction of 5 mass% of polymer, as the diesel oxidation catalyst (DOC), which could be inclined to a good purification in the diesel aftertreatment. Hopefully, the convenient research method could initiate the exploration and application of polymer-assisted catalysts for well-dispersed noble metal nanoparticles in eliminating exhaust emission.
اظهر المزيد [+] اقل [-]Implementation of data intelligence models coupled with ensemble machine learning for prediction of water quality index النص الكامل
2020
Abba, Sani Isah | Phạm, Quó̂c Bảo | Saini, Gaurav | Linh, Nguyen Thi Thuy | Ahmed, Ali Najah | Mohajane, Meriame | Khaledian, Mohammadreza | Abdulkadir, Rabiu Aliyu | Bach, Quang-Vu
In recent decades, various conventional techniques have been formulated around the world to evaluate the overall water quality (WQ) at particular locations. In the present study, back propagation neural network (BPNN) and adaptive neuro-fuzzy inference system (ANFIS), support vector regression (SVR), and one multilinear regression (MLR) are considered for the prediction of water quality index (WQI) at three stations, namely Nizamuddin, Palla, and Udi (Chambal), across the Yamuna River, India. The nonlinear ensemble technique was proposed using the neural network ensemble (NNE) approach to improve the performance accuracy of the single models. The observed WQ parameters were provided by the Central Pollution Control Board (CPCB) including dissolved oxygen (DO), pH, biological oxygen demand (BOD), ammonia (NH₃), temperature (T), and WQI. The performance of the models was evaluated by various statistical indices. The obtained results indicated the feasibility of the developed data intelligence models for predicting the WQI at the three stations with the superior modelling results of the NNE. The results also showed that the minimum values for root mean square (RMS) varied between 0.1213 and 0.4107, 0.003 and 0.0367, and 0.002 and 0.0272 for Nizamuddin, Palla, and Udi (Chambal), respectively. ANFIS-M3, BPNN-M4, and BPNN-M3 improved the performance with regard to an absolute error by 41%, 4%, and 3%, over other models for Nizamuddin, Palla, and Udi (Chambal) stations, respectively. The predictive comparison demonstrated that NNE proved to be effective and can therefore serve as a reliable prediction approach. The inferences of this paper would be of interest to policymakers in terms of WQ for establishing sustainable management strategies of water resources.
اظهر المزيد [+] اقل [-]Unitary and binary remediations by plant and microorganism on refining oil-contaminated soil النص الكامل
2020
Fei, Jia Jia | Wan, Yun Yang | He, Xin Yue | Zhang, Zhi Huan | Ying, Yu Xi
Refining oil contaminants are complex and cause serious harm to the environment. Remediation of refining oil-contaminated soil is challenging but has significant impact in China. Two plant species Agropyron fragile (Roth) P. Candargy and Avena sativa L. and one bacterium Bacillus tequilensis ZJ01 were used to investigate their efficiency in remediating the refining oil-polluted soil sampled from an oil field in northern China. The simulated experiments of remediations by A. fragile or A. sativa alone and A. fragile or A. sativa combined with B. tequilensis ZJ01 for 39 days and by B. tequilensis ZJ01 alone for 7 days were performed in the laboratory, with B. tequilensis ZJ01 added before or after the germination of seeds. Seed germination rates and morphological characteristics of the plants, along with the varieties of oil hydrocarbons in the soil, were recorded to reflect the remediation efficiency. The results showed that the contamination was weakened in all experimental groups. A. sativa was more sensitive to the pollutants than A. fragile, and A. fragile was much more resistant to the oil hydrocarbons, especially to aromatic hydrocarbons. Adding B. tequilensis ZJ01 before the germination of seeds could restrain the plant growth while adding after the germination of A. fragile seeds notably improved the remediation efficiency. The degradation rate of oil hydrocarbons by B. tequilensis ZJ01 alone was also considerable. Together, our results suggest that the unitary remediation by B. tequilensis ZJ01 and the binary remediation by A. fragile combined with B. tequilensis ZJ01 added after the germination of seeds are recommended for future in situ remediations.
اظهر المزيد [+] اقل [-]Effects of sulfonylurea herbicides chlorsulfuron and sulfosulfuron on enzymatic activities and microbial communities in two agricultural soils النص الكامل
2020
Medo, Juraj | Hricáková, Nikola | Maková, Jana | Medová, Janka | Omelka, Radoslav | Javoreková, Soňa
Sulfonylurea herbicides are widely used for weed control in agriculture, and they are suspected to alter microbial communities and activities in the soil. This study investigates the impact of two sulfonylurea herbicides chlorsulfuron and sulfosulfuron on microbial community and activity in two different soils taken from two sites in west part of the Slovak Republic. The soil from the Malanta site was silt-loam luvisol with pH₍H₂O₎ 5.78 while the soil from the Stefanov site was sandy-loam regosol with pH₍H₂O₎ 8.25. These soils were not treated by sulfonylurea herbicides at least for 2 years prior to the study. In laboratory assay, the herbicides were applied to soil in their maximal recommended doses 26 and 25 g per hectare of chlorsulfuron and sulfosulfuron, respectively. Their effect was evaluated on the 3rd, 7th, 14th, 28th, 56th, and 112th day after application to soil. Illumina high-throughput amplicon sequencing of the 16S rRNA gene and ITS region was used to monitor changes on prokaryotic and fungal community composition. Enzymatic activity was evaluated using 11 substrates. Physiological profile of microbial community was analyzed using Biolog© ecoplates. Significant changes in enzymatic activity caused by the application of herbicides were found during the first 28 days. The application of herbicides altered the activity of cellobiohydrolase, arylsulphatase, dehydrogenase, phosphatase, and FDA hydrolase. Chlorsulfuron caused a more varying response of enzymatic activity than sulfosulfuron, and observed changes were not the same for both soils. In Malanta soil, chlorsulfuron decreased dehydrogenase activity while it was increased in the Stefanov soil. Phosphatase activity was decreased in both soils on 7th and 14th day. There were only minor changes in prokaryotic or fungal community or physiological profiles regarding pesticide application. Differences between soils and incubation time explained most of the variability in these parameters. Diversity indices, physiological parameters, and enzymatic activity decreased over time. The results have shown that chlorsulfuron and sulfosulfuron can affect the function and activity of the soil microbial community without significant change in its composition.
اظهر المزيد [+] اقل [-]The role of partisan conflict in environmental sustainability targets of the United States النص الكامل
2020
Akadiri, Seyi Saint | Alola, Andrew Adewale
The prevailing political atmosphere and partisanship in the United States depict the degree of polarization between the two major political parties of the country. Evidently, the polarization between the Democratic Party (DP) and the Republican Party will expectedly drive the partisan conflict to the higher levels. Considering this motivation, this paper examined the role of partisan conflict in the pollutant emissions in the case of the United States. For sound empirical analysis, the impacts of other environmental quality determinants are being examined over the period 1960–2015. In order to present a decent argument that is viable for policy implementation, the study adopts the combined methodologies of Johansen cointegration; the autoregressive distributed lag (ARDL) of Pesaran et al. J Am Stat Assoc 94(446):621–634 (1999); and the Toda and Yamamoto J Econ 66(1–2):225–250 (1995) Granger causality. Empirical outcomes show (i) the kg oil equivalent per capita energy consumed exercise positive and significant impacts on metric tons of per capita CO₂ emissions, and it is the principal determinant of environmental degradation in both the short-run and the long-run (ii) renewable energy consumption and economic growth also exercise negative and significant impacts on metric tons of per capita CO₂ emissions. Based on our empirical findings, we conclude that partisan conflict indirectly plays a significant role in environmental sustainability targets of the United States. Thus, we are of the opinion that the government should avoid heightened partisan conflict among the political parties in order to promote sustainable environmental policies that would enhance sound and clean environment for both the immediate and the future generation.
اظهر المزيد [+] اقل [-]Biodegradation of microcystin-RR and nutrient pollutants using Sphingopyxis sp. YF1 immobilized activated carbon fibers-sodium alginate النص الكامل
2020
Ren, Guofeng | He, Xinghou | Wu, Pian | He, Yayuan | Zhang, Yong | Tang, Shibiao | Song, Xinli | He, Yafei | Wei, Yuandan | Ding, Ping | Yang, Fei
A novel biological material named activated carbon fibers-sodium alginate@Sphingopyxis sp. YF1 (ACF-SA@YF1) was synthesized for microcystin-RR (MC-RR) and nutrient pollutant degradation in eutrophic water. The synthesized biomaterial was characterized by scanning electron microscopy (SEM). Box-Behnken design and response surface methodology (RSM) were utilized for the optimization of conditions during the MC-RR degradation. The degradation of MC-RR and nutrient pollutants was dynamically detected. The results revealed that the optimal conditions were temperature 32.51 °C, pH 6.860, and inoculum 14.97%. The removal efficiency of MC-RR, nitrogen, phosphorus, and chemical oxygen demand were 0.76 μg/mL/h, 32.45%, 94.57%, and 64.07%, respectively. In addition, ACF-SA@YF1 also performed satisfactory cyclic stability, while the MC-RR removal efficiency was 70.38% after seven cycles and 78.54% of initial activity after 20 days of storage. Therefore, it is reasonable to believe that ACF-SA@YF1 is an effective material which has a great prospect in removing MC-RR and nutrients from freshwater ecosystems.
اظهر المزيد [+] اقل [-]Multivariate statistical monitoring of subway indoor air quality using dynamic concurrent partial least squares النص الكامل
2020
Liu, Hongbin | Yang, Chong | Huang, Mingzhi | Yoo, ChangKyoo
To maintain the health level of indoor air quality (IAQ) in subway stations, the data-driven multivariate statistical method concurrent partial least squares (CPLS) has been successfully applied for output-relevant and input-relevant sensor faults detection. To cope with the dynamic problem of IAQ data, the augmented matrices are applied to CPLS (DCPLS) to achieve the better performance. DCPLS method simultaneously decomposes the input and output data spaces into five subspaces for comprehensive monitoring: a joint input-output subspace, an output principal subspace, an output-residual subspace, an input-principal subspace, and an input-residual subspace. Results of using the underground IAQ data in a subway station demonstrate that the monitoring capability of DCPLS is superior than those of PLS and CPLS. More specifically, the fault detection rates of the bias of PM₁₀ and PM₂.₅ using DCPLS can be improved by approximately 13% and 15%, respectively, in comparison with those of CPLS.
اظهر المزيد [+] اقل [-]Mercury contamination levels in the bioindicator piscivorous fish Hoplias aïmara in French Guiana rivers: mapping for risk assessment النص الكامل
2020
Maury-Brachet, Régine | Gentes, Sophie | Dassié, Emilie P. | Feurtet-Mazel, Agnès | Vigouroux, Régis | Laperche, Valérie | Gonzalez, Patrice | Hanquiez, Vincent | Mesmer-Dudons, Nathalie | Durrieu, Gilles | Legeay, Alexia
In French Guiana, native populations present high level of mercury contamination, which has been linked to the consumption of contaminated fishes. The goal of this study is to undertake a cartography of mercury contamination levels in fishes from the six main Guiana rivers. The selected species for this study is the ubiquitous piscivorous fish Hoplias aimara. A total number of 575 fishes from 134 discrete fishing sites are regrouped into 51 river sectors. Results from this study permits to rank the six main Guiana rivers by their mean level of contamination: Oyapock (0.548 mg kg⁻¹), Comté (0.624 mg kg⁻¹), Maroni (0.671 mg kg⁻¹), Approuague (0.684 mg kg⁻¹), Mana (0.675 mg kg⁻¹), and Sinnamary (1.025 mg kg⁻¹). The contamination is however not spatially homogenous along each river, and a map of the different levels of mercury contamination in fishes is provided. Sectors of low mean Hg contamination are observed both upstream (0.471 mg kg⁻¹) and downstream (0.424 mg kg⁻¹), corresponding to areas without any influence of gold mining activities and areas under the influence of estuarine dilution, respectively. Anoxia and gold mining activities are found to be the two main factors responsible for the high mercury concentration in fish muscles. While mean levels of mercury contaminations are higher in anoxia areas (1.029 mg kg⁻¹), contaminations induced by gold mining activities (0.717 mg kg⁻¹) present the most harmful consequences to human populations. No significant differences in Hg concentrations are observed between 2005 and 2014 for neither a pristine nor a gold mining area, while Hg concentration differences are observed between former (0.550 mg kg⁻¹) and current gold mining sites (0.717 mg kg⁻¹).
اظهر المزيد [+] اقل [-]Preparation and characterization of triple layer membrane for water filtration النص الكامل
2020
Nallathambi, Gobi | Baskar, Devi | Selvam, Arun Karthick
Triple layer membranes of different proportions were prepared by using the combination of electrospinning and dry-wet phase inversion technique. The polymer solution of Nylon/PEG was prepared and poured over the electrospun polyacrylonitrile (PAN) nanofibers. Thus, prepared triple layer membranes were characterized by optical microscope, scanning electron microscope, porosimeter, X-ray diffraction, and thermogravimetric analyzer to study the morphology, pore size distribution, crystallinity, and degradation properties respectively. The performance of the triple layer membranes was evaluated by pure water flux and filtration efficiency. The results revealed that the triple layer membrane with the proportion of 60/40 (Nylon/PEG) has optimal pure water flux and higher filtration efficiency than the other prepared triple layer membranes.
اظهر المزيد [+] اقل [-]Little egret (Egretta garzetta) as a bioindicator of heavy metal contamination from three different localities in Egypt النص الكامل
2020
Soliman, Kareem M. | Mohallal, Eman M. E. | Alqahtani, Abdulaziz R. M.
This work aimed at using Little Egrets (Egretta garzetta), for the first time in Egypt, as a bioindicator of heavy metal contamination from three different Egyptian land use types (Qillin within Kafr El-Sheikh (S1, agricultural), Toukh within Qalyubia (S2, semi-rural area), and Abu Rawash within Giza (S3, urban)). Concentrations of aluminum (Al), barium (Ba), cobalt (Co), cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), iron (Fe), nickel (Ni), lead (Pb), and zinc (Zn) were analyzed in liver and kidney samples of twenty-six adult Little Egrets collected from the three localities during winter 2018. Moreover, the study calculated the Metal Pollution Index (MPI) to highlight the health of the surrounding environment using birds’ internal organs as a mirror. Results revealed that, throughout the three sampling sites, the total metal concentrations in liver samples exceeded that of the kidney, indicating that the liver is the target organ of metal accumulation. The Little Egret’s liver was found to be the best-recommended organ to use in future biomonitoring of Cu, Zn, Fe, Mn, and Ni, whereas Al, Co, Cr, Ba, Pb, and Cd can be monitored in the kidney. Cu and Pb were higher in the Little Egret’s tissues collected from the agricultural site (S1), whereas Ba, Ni, and Fe were higher in the semi-rural site (S2), followed finally by Cd in the urbanized site (S3). The concentrations of trace elements reported in Little Egrets were within the known background level for water birds. However, alarming concentrations were found for Ni levels in liver (from Qillin and Toukh), as well as Pb and Cr levels in kidney samples (from the three localities). MPI of the eleven studied metals in both liver and kidney of the studied species decreased in the order Qillin (24.36) > Abu Rawash (17.98) > Toukh (3.90). In the three investigated localities, the overall calculated MPI values were higher than one, indicating that the ecosystem is polluted. The study suggested using Little Egrets as a bioindicator of metal contamination.
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