خيارات البحث
النتائج 3661 - 3670 من 4,924
The impact of electric generation capacity by renewable and non-renewable energy in Brazilian economic growth
2019
de Oliveira Noronha, Maiara | Zanini, Roselaine Ruviaro | Souza, Adriano Mendonça
Renewable sources are relevant in a country’s energy planning because they are linked to the creation of opportunities for technological, economic, and productive development guided by the principles of sustainability. Thus, the aim of this study was to investigate the relation between electric generation capacity by renewable and non-renewable energies and Brazilian socioeconomic variables. The analysis of the interrelationships between electricity generation capacity and economic growth in Brazil, from April 2009 to March 2017, was carried out by the vector autoregressive and autoregressive distributed lag methodologies. It was verified that the variance of employment is explained by renewable sources: hydroelectric in 7.71%, biomass in 1.99%, wind energy in 3.13%, and solar energy in 10.58%. While, the GDP variance is explained in 3.15% by hydroelectric energy, 0.06% by biomass, 1.70% by wind energy, and 17.38% by solar energy. The export variance is explained by renewable sources: hydroelectric 2.48%, biomass 0.39%, wind energy 2.34%, and solar energy 17.58%. Finally, the variance of the minimum wage is explained by hydroelectric energy in 1.48%, biomass in 5.09%, wind energy in 9.09%, and solar energy in 10.67%. An ARDL (1, 1, 2, 0, 0, 0, 3, 2, 0, 2, 0, 2) model was also adjusted for natural gas, with AIC (13.082) and BIC (13.739), and the ARDL (1, 0, 1, 0, 0, 0, 0, 0, 3, 0, 0, 4) model adjusted for hydroelectric power, with AIC (13.633) and BIC (14.189), considering the variables’ order cited above. Through the adjustment of the ARDL model, it was verified that there is a long-term influence of socioeconomic variables on electricity production variables, both renewable and non-renewable ones. The analysis of the impulse response function and the variance decomposition allowed us to verify that the installed capacity for production of electric energy exerts influence on Brazilian socioeconomic variables considered in this study.
اظهر المزيد [+] اقل [-]Short-term PM2.5 forecasting based on CEEMD-RF in five cities of China
2019
Liu, Da | Sun, Kun
The development of industrial civilization has greatly enriched the material and spiritual life of human beings, but it is accompanied by the intensification of the consumption of earth resources and environmental pollution. The smog that has emerged in various parts of China in recent years is a typical problem, which not only endangers human health but also affects normal human work and life. It is difficult to control smog in a short time productively, so people need to understand the rule of smog formation gradually, and effectively predict the PM2.5 index to help people continuously analyze relevant mechanisms and timely protect-related hazards. This paper proposes a hybrid model that uses the Complementary Ensemble Empirical Modal Decomposition algorithm to mine the information in the original PM2.5 sequence and then predicts the pertinent random forests. The trend of PM2.5 concentration during the decomposition process is effectively reflected, and the decomposition sequence is modeled by the high tolerance of the random forest to the noise data and the good fitting ability. In the modeling process, the parameters are optimized according to the evaluation function of the model on the verification set, and eventually, the prediction sequences are superimposed to obtain the final predicted PM2.5 concentration value. The validity of the model is verified by the data of several Chinese cities with different geographical features in the past 5 years. The results show that the recommendation model is higher than other comparison models in terms of model stability and prediction accuracy.
اظهر المزيد [+] اقل [-]Neutral polyfluoroalkyl and perfluoroalkyl substances in surface water and sediment from the Haihe River and Dagu Drainage Canal deserve more attention
2019
Hua, Xia | Luo, Jianbo | Zhao, Zhen | Wang, Qi | Sun, Hongwen
Neutral polyfluoroalkyl and perfluoroalkyl substances (nPFASs) were detected in the surface water and sediment from the Haihe River (HR) and Dagu Drainage Canal (DDC), Tianjin, China. N-methyl perfluorooctane sulfonamide ethanol (MeFOSE) and N-ethyl perfluorooctane sulfonamide ethanol (EtFOSE) were the predominant nPFASs in surface water and sediment, which was different from the composition in air. The concentrations of ΣnPFASs in water from the HR (1.88–8.21 ng/L) were lower than those from the DDC (3.72–11.32 ng/L). Concentrations of ΣnPFASs were higher in the middle of the HR in the Dongli District due to industrial activity, whereas at lower reaches of the DDC, high ΣnPFAS concentrations might be due to effluent from wastewater treatment plants (WWTPs). The detection frequency in sediment (13.5%) was less than that in water (83%). The concentrations in sediment from the DDC (below limit of qualification (LOQ) to 5.58 ng/g) were higher than those from the HR (below LOQ to 2.46 ng/g). The distribution coefficient (log KD) between water and sediment was calculated, and they were highly related to the compound structures. The contribution of nPFASs to nPFASs+PFAAs was up to 52% in sediment in the DDC, suggesting the importance of nPFASs in aquatic systems.
اظهر المزيد [+] اقل [-]The chemical form and spatial variation of metals from sediment of Jemberau mining region of Tasik Chini, Malaysia
2019
Krishnankutty, Nimisha | Mushrifah Idris, | Hamzah, Firdaus Mohamad | Manan, Yasmin
Bauxite and iron ore mining is the major contributor to metal pollution in Tasik Chini, Malaysia. Deforestation of the protected zone of reserve forest exacerbates the problem. The current study is to understand the speciation of metals spatially in sediment to analyse the risk associated in terms of its mobility and bioavailability. The samples of sediment are collected from Sungai Jemberau, Laut Jemberau, and Laut Gumum of Tasik Chini. Four samplings were conducted for a year, by collecting the surface sediment. Sequential extraction method was followed for speciation of sediment and classified it into exchangeable, reducible, Fe–Mn oxides, organic and residual fractions. The results were also analyzed using principal component analysis (PCA) and cluster analysis (CA). The result reveals that Fe, Al, Mn, Zn, and Pb are the primary constituents of sediment contributing to about 98% of residual fraction. Co, Cd, Cr, As, and Ni are found in trace metal concentration and are identified to be mainly released from anthropogenic sources nearby. Although the individual proportion is less than major metals in exchangeable and carbonate fraction, they possess geochemically significant concentration above the permissible limit. More than 70–80% of all its total concentration proportion is hence found in mobile and bioavailable state. These possess toxic and have chronic effects to aquatic life and public health even in trace elemental concentration. Hence, these metals are the most toxic and bioavailable metals pausing risk for aquatic and public health. PCA analysis highlights that the enrichment of heavy metals in bioavailable fraction is mostly contributed from anthropogenic sources. The same results are emphasized by cluster analysis.
اظهر المزيد [+] اقل [-]Selection of microalgae species based on their lipid content, fatty acid profile and apparent fuel properties for biodiesel production
2019
Deshmukh, Suchit | Bala, Kiran | Kumar, Ritunesh
Different microalgae species produce varying quantity and quality of the lipids. Fatty acid methyl ester composition, which comprises both saturated and unsaturated contents, critically affects biodiesel properties. Current study compares six locally isolated microalgae strains belonging to three classes (Trebouxiophyceae, Chlorophyceae, and Cyanophyceae) on the basis of lipid content and biodiesel properties. All the six species are grown in similar condition up to the late stationary phase, and their lipid content and fatty acid methyl ester composition are measured experimentally. Multi-criteria decision analysis (MCDA) tool has ranked Calothrix species (class Cyanophyceae) on the top, owing to better cetane number, density and oxidation stability; whereas Chlorococcum species (class Chlorophyceae) is ranked second because of its higher lipid content, better cold flow property, and low viscosity. Property analysis of these two species is extended in the enlarge temperature range for five properties, vapor pressure, latent heat of vaporization, liquid density, liquid viscosity and vapor diffusivity, which are important in spray and combustion modeling. It is found through detailed property estimation that Chlorococcum sp. is a more suitable species in comparison with Calothrix sp. as it is having better properties and its lipid content is much higher than that of Calothrix sp. Although the properties of microalgae biodiesel are poorer in comparison with conventional diesel fuel, a greater number of such studies will help in understanding the requisite changes as required for microalgae biodiesel–based engine and their properties as compared with conventional diesel.
اظهر المزيد [+] اقل [-]Correlation between pri-miR-124 (rs531564) polymorphism and congenital heart disease susceptibility in Chinese population at two different altitudes: a case-control and in silico study
2019
Yang, Wenke | Yi, Kang | Yu, Hongmiao | Ding, Yunhan | Li, Dehong | Wei, Yuping | You, Tao | Xie, Xiaodong
The development of congenital heart disease (CHD) is a complicated process and affected by multiple environmental factors, as genetic factors, and the interactions among those factors. Previous studies have shown that intrauterine hypoxic environment exposure is a risk factor of CHD, but the genetic factors involved in the process are not clear. In this study, given that tetralogy of Fallot (TOF) is a CHD with hypoxemia as its primary pathophysiological manifestation, an in silico analysis was performed to reveal the relationship between potential target genes (miR-124) with the energy metabolism in non-syndromic TOF patients’ cardiomyocyte. Furthermore, the study investigated the correlation between the primary miR-124 (rs531564) polymorphism and CHD susceptibility in 432 sporadic patients and 450 controls from two different altitude provinces (city) in China. Our study indicated that the minor C allele of rs531564 correlated with reduced risk of CHD in the low altitude city. Besides, the C allele has elevated frequency in the high-altitude group. Therefore, our findings suggest that the minor C allele of rs531564 SNP may be involved in the reduction of the risk of CHD in a way that interacts with the intrauterine hypoxic environmental factors.
اظهر المزيد [+] اقل [-]Bibliometric analysis of global research on air pollution and human health: 1998–2017
2019
Dhital, Sushma | Rupakheti, Dipesh
To give a basic overview of research publications on air pollution and human health, a bibliometric analysis of 2179 documents published during the last two decades (year 1998 to 2017) was carried out. The relevant data was retrieved from the Web of Science Core Collection (WoSCC) and analyzed by using the software such as VOSviewer 1.6.7, Tableau Public 2018.1, and Origin Pro 9.0 for visualization and mapping. The publication trend showed a drastic increase during the second decade. The most productive countries working in the field of air pollution and human health were the USA, China, Italy, England, and Canada, whereas top institutions were Chinese Academy of Sciences, US EPA, Harvard University, Peking University, and University of Sao Paulo. Likewise, leading authors in the context of number of documents published and co-citation were Michael Bell and C. Arden Pope respectively. Majority of the researches were published in the journals like Atmospheric Environment, Science of the Total Environment, and Environmental Science and Pollution Research whereas most common author keywords in the publications were “air pollution,” “particulate matter,” and “PM₂.₅.”
اظهر المزيد [+] اقل [-]The seasonal and spatial variations in diatom communities and the influence of environmental factors on three temperate reservoirs in Shandong province, China
2019
Zhang, Shasha | Pei, Haiyan | Wei, Jielin | Zhu, Yaowen | Wang, Yuting | Yang, Zhigang
Diatoms play an important role as ecological indicators, and some species of diatoms can easily cause water blooms, thereby decreasing the production capacity of water treatment plants and endangering drinking water safety. Mastering the diatom community dynamics is crucial for water supply. In this study, diatom composition, spatial distribution and succession were investigated in Datun Reservoir, Donghu Reservoir and Shuangwangcheng Reservoir, which are important drinking water sources in Shandong province, China. Results showed that the three reservoirs could be classified as being between mesotrophic and moderately eutrophic. The diatom community in each of the three reservoirs exhibited no obvious seasonal succession. The diatom communities in the three reservoirs were relatively simple in composition, with Synedra and Cyclotella being the most dominant groups all year round. Synedra had a negative relationship with NO₂-N. Cyclotella had a positive association with NO₃-N, but was negatively associated with NH₄-N and CODMₙ in the three reservoirs. Through the analysis of diatom and environmental factors, the three reservoirs have the potential of hosting diatom blooms in summer, when the higher temperature combines with reduced water flow.
اظهر المزيد [+] اقل [-]Organo-modification of montmorillonite for enhancing the adsorption efficiency of cobalt radionuclides from aqueous solutions
2019
Soliman, Mohamed A. | Rashad, Ghada M. | Mahmoud, Mamdoh R.
Montmorillonite clay was organically modified with thoron (TH) and was employed as an adsorbent for removal of cobalt(II) radionuclides from aqueous solutions. Batch adsorption experiments, under several operational parameters such as pH, contact time, initial adsorbate concentration, adsorbent dosage, ionic strength, and temperature, were conducted to determine the optimum conditions for efficient removal of cobalt(II) radionuclides. The obtained data showed that almost complete removals were achieved for cobalt(II) at pH values ≥ 3.5 using TH-modified montmorillonite (TMM), while only 63% were obtained by unmodified clay at pH ≥ 5.4. Adsorption kinetic data of cobalt(II) were better fitted by the pseudo-second order kinetic model and its adsorption rate was controlled by film diffusion. Both Langmuir and Freundlich models had the ability to well describe the equilibrium data of cobalt(II) radionuclides at the studied temperatures. The adsorption capacity of TMM (0.85 mmol/g) was found to be not only nine times that of unmodified montmorillonite (0.097 mmol/g), but also higher than those reported in literature using various unmodified and modified clays. Thermodynamic parameters (ΔH°, ΔS°, and ΔG°) were calculated. Among the examined desorbing agents, both Al³⁺ and EDTA were succeeded to desorb most of cobalt(II) radionuclides (desorption % ~ 90%) loaded onto TMM. The results of this study clarified that TMM can be considered as an effective adsorbent for removal of cobalt(II) radionuclides from aqueous solutions.
اظهر المزيد [+] اقل [-]Fabrication of phosphonium bamboo cellulose by triphenylphosphine: preparation, characterization, and adsorption of Acid Black 24
2019
Xiong, Wei | Hu, Dongying
Cellulose from bamboo shavings (BC) separated and modified by grafting triphenylphosphine, which was used as an adsorbent for the removal of Acid Black 24 from aqueous solution. The quaternary phosphonium-based bamboo cellulose (PBC) was characterized by FTIR and SEM measurements. The FTIR studies showed that the quaternary phosphonium group was successfully grafted onto the BC molecular structure. The effects of PBC dosage, contact time, initial dye concentration, temperature, and pH on the adsorption performance were studied. The nonlinear fitting kinetics and isotherms models were also conducted. The pseudo-second-order, intra-particle diffusion and Langmuir models were more suitable for analyzing the adsorption behavior of PBC for Acid Black 24 dye. The adsorption activation energy was lower than 40 kJ mol⁻¹, and the ΔH⁰ value was in the range of 20~80 kJ mol⁻¹, indicating that PBC played a dominant role in the physical purification of dye. The results of thermodynamic analysis indicated that the adsorption was a spontaneous endothermic purification process. Adsorbents had a good reusability and high adsorption performance for dye removal. The adsorbents PBC had a good reusability and could effectively remove residual Acid Black 24 dye with good development prospects in the field of biomass adsorbent materials.
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