خيارات البحث
النتائج 5711 - 5720 من 6,489
Agriculture, dairy and fishery farming practices and greenhouse gas emission footprint: a strategic appraisal for mitigation النص الكامل
2020
Ghosh, Avijit | Misra, Sukanya | Bhattacharyya, Ranjan | Sarkar, Abhijit | Singh, Amit Kumar | Tyagi, Vikas Chandra | Kumar, Ram Vinod | Singh Meena, Vijay
Rising global population would force farmers to amplify food production substantially in upcoming 3–4 decades. The easiest way to increase grain production is through expanding cropping area by clearing uncultivated land. This is attained by permitting deadly loss of carbon (C) stocks, jeopardizing ecosystem biodiversity and deteriorating environmental quality. We aim to propose key agronomical tactics, livestock management strategy and advance approaches for aquaculture to increase productivity and simultaneously reduce the environmental impacts of farming sector. For this, we considered three major sectors of farming, i.e. agriculture, fishery and dairy. We collected literatures stating approaches or technologies that could reduce GHG emission from these sectors. Thereafter, we synthesized strategies or options that are more feasible and accessible for inclusion in farm sector to reduce GHG emission. Having comprehensively reviewed several publications, we propose potential strategies to reduce GHG emission. Agronomic practices like crop diversification, reducing summer fallow, soil organic carbon sequestration, tillage and crop residue management and inclusion of N₂-fixing pulses in crop rotations are some of those. Livestock management through changing animals’ diets, optimal use of the gas produced from manures, frequent and complete manure removal from animal housing and aquaculture management strategies to improve fish health and improve feed conversion efficiency could reduce their GHG emission footprint too. Adapting of effective and economic practices GHG emission footprint reduction potential of farming sector could make farming sector a C neutral enterprise. To overcome the ecological, technological and institutional barriers, policy on trade, tax, grazing practice and GHG pricing should be implemented properly.
اظهر المزيد [+] اقل [-]Influence of Leifsonia sp. on U(VI) removal efficiency and the Fe–U precipitates by zero-valent iron النص الكامل
2020
Xie, Shuibo | Xiao, Xue | Tan, Wenfa | Lv, Junwen | Deng, Qinwen | Fang, Qi
Zero-valent iron (ZVI) has been widely applied to the remediation of uranium (U)-contaminated water. Notably, indigenous bacteria may possess potential positive or unfavorable influence on the mechanism and stability of Fe–U precipitates. However, the focus of the researches in this field has mainly been on physical and/or chemical aspects. In this study, batch experiments were conducted to explore the effects of an indigenous bacterium (Leifsonia sp.) on Fe–U precipitates and the corresponding removal efficiency by ZVI under different environmental factors. The results showed that the removal rate and capacity of U(VI) was significantly inhibited and decreased by ZVI when the pH increased to near-neutral level (pH = 6~8). However, in the ZVI + Leifsonia sp. coexistence system, the U(VI) removal efficiency were maintained at high levels (over 90%) within the experimental scope (pH = 3~8). This revealed that Leifsonia sp. had a synergistic effect on U(VI) remove by ZVI. According to scanning electron microscope and energy dispersive X-ray detector (SEM-EDX) analysis, dense scaly uranium-phosphate precipitation was observed on ZVI + Leifsonia sp. surface. The X-photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis indicated that Leifsonia sp. facilitated the generation of U(VI)-phosphates precipitates. The X-ray diffraction (XRD) analyses further revealed that new substances, such as (Fe(II)Fe(III)₂(PO₄)₂(OH)₂), Fe(II)(UO₂)₂(PO₄)₂·8H₂O, Fe(II)Fe(III)₅(PO₄)₄(OH)₂·4H₂O, etc., were produced in the coexisting system of ZVI and Leifsonia sp. This study provides new insights on the feasibility and validity of site application of ZVI to U(VI)-contaminated subsurface water in situ. Graphical abstract
اظهر المزيد [+] اقل [-]Experimental study on the effects of chemical composite additive on the microscopic characteristics of spontaneous combustion coal النص الكامل
2020
Pan, Rongkun | Ma, Junwei | Zheng, Ligang | Wang, Jian
In order to study the effects of chemical composite additive (CCA) on the microscopic characteristics of spontaneous combustion coal, atomic force microscope and Fourier transform infrared spectroscopy technology were used to study the microstructure and active groups of spontaneous combustion coal. The roughness, three-dimensional surface morphology, microscopic pore structure, infrared spectrum, and active group content of raw coal samples and coal samples treated with water or different concentrations of CCA were analyzed. The experimental results showed that compared with the raw coal, the roughness Rq and Ra of the CCA-treated coal samples decreased with increasing CCA concentration, and the surface topography of the microscopic structure tended to be flat and smooth, and the size becomes smaller and the depth becomes shallow of pore. In the raw coal samples and coal samples treated with water and CCA, the main types of active groups remained constant. However, the contents of these groups changed, and the order of the contents of main types of active groups is water-treated > raw coal (untreated) > CCA-1% treated > CCA-5% treated > CCA-10% treated > CCA-20% treated. In addition, the mechanism of the CCA inhibition of coal spontaneous combustion was discussed and analyzed.
اظهر المزيد [+] اقل [-]Trend of the research on rare earth elements in environmental science النص الكامل
2020
Kang, Jonghoon | Kang, Albert M.
Rare earth elements (REEs) consist of 17 transition metals which are the 15 lanthanides and yttrium and scandium. These elements have great utility in the production of modern technology, especially electronics. However, these materials may pose a serious threat to the environment if handled or disposed of incorrectly; the effects of which are being studied by the field of environmental toxicology. A multitude of studies have indicated that rare earth elements have harmful impacts on biological life, making a reform to the disposal of rare earth elements increasingly pressing. Scientific interest in REEs is constantly rising due to the increased use of REEs due to their utility. In this paper, we display our meta-analysis of a scientific literature database, PubMed, to quantitatively map the temporal flux of research and interest pertaining to REEs, especially in the field of environmental science. Our findings may prove useful for planning research on REEs or predicting the future of REE usage.
اظهر المزيد [+] اقل [-]Suspended sediment load prediction using artificial neural network and ant lion optimization algorithm النص الكامل
2020
Banadkooki, Fatemeh Barzegari | Ehteram, Mohammad | Ahmed, Ali Najah | Teo, Fang Yenn | Ebrahimi, Mahboube | Fai, Chow Ming | Huang, Yuk Feng | El-Shafie, Ahmed
Suspended sediment load (SSL) estimation is a required exercise in water resource management. This article proposes the use of hybrid artificial neural network (ANN) models, for the prediction of SSL, based on previous SSL values. Different input scenarios of daily SSL were used to evaluate the capacity of the ANN-ant lion optimization (ALO), ANN-bat algorithm (BA) and ANN-particle swarm optimization (PSO). The Goorganrood basin in Iran was selected for this study. First, the lagged SSL data were used as the inputs to the models. Next, the rainfall and temperature data were used. Optimization algorithms were used to fine-tune the parameters of the ANN model. Three statistical indexes were used to evaluate the accuracy of the models: the root-mean-square error (RMSE), mean absolute error (MAE) and Nash-Sutcliffe efficiency (NSE). An uncertainty analysis of the predicting models was performed to evaluate the capability of the hybrid ANN models. A comparison of models indicated that the ANN-ALO improved the RMSE accuracy of the ANN-BA and ANN-PSO models by 18% and 26%, respectively. Based on the uncertainty analysis, it can be surmised that the ANN-ALO has an acceptable degree of uncertainty in predicting daily SSL. Generally, the results indicate that the ANN-ALO is applicable for a variety of water resource management operations.
اظهر المزيد [+] اقل [-]Carbon emission effect of energy transition and globalization: inference from the low-, lower middle-, upper middle-, and high-income economies النص الكامل
2020
Alola, Andrew Adewale | Joshua, Udi
The importance of income to environmental sustainability especially in the perspective of economic development has been rigorously examined in recent times. To further deepened the income-environmental sustainability narrative, the current study explore the cases of income-classified countries vis-à-vis the high-income, low-income, lower middle-income, and the upper middle-income countries and territories. As such, the current study examined the impact of renewable energy and fossil fuel energy consumption and globalization on CO₂ emissions over the period of 1970 to 2014 for the case of (1) the panel of income-classified countries and territories and (2) the time series of each of the income-classification. By employing the Pooled Mean Group of the Autoregressive Distributed Lag (ARDL) approach, the study found that fossil fuel consumption in the panel of examined income classification aggravates environmental hazards in both the short–long run, while the share of renewable energy usage improves the environmental quality only in the short run. Like the renewable energy consumption, globalization exacts negative and positive impacts in the short run and long run, respectively. From the second (time series) approach, the study found that fossil fuel energy worsen the environment in each of the fours income-categorized economies. Similarly, renewable energy usage exerts a significant and desirable impact on the environment in all but one (lower middle income) of the four income-categorized economies. However, globalization observably plays a significant and desirable role only in the lower middle-income economies. Hence, the study posits policy guide in the context of increased diversification of energy portfolio for each of the four income-categorized countries and territories especially the lower middle-income economies.
اظهر المزيد [+] اقل [-]Ultrasonication favors TiO2 nano-particles dispersion in PVDF ultrafiltration membrane to effectively enhance membrane hydrophilicity and anti-fouling capability النص الكامل
2020
Xie, Wanying | Li, Ji | Sun, Feiyun | Dong, Wenyi
The influence of ultrasonication on membrane performance was investigated by two ultrasonication modes, direct and indirect ultrasonication as pretreatment, and simply improved PVDF-TiO₂ membranes’ performance was systematically compared. Ultrasound intensity of 100% and ultrasonication time ranged from 1 to 2 h positively affect membrane permeability. Characterization results manifested that membrane structure was eventually optimized with an even nano-TiO₂ dispersion by direct ultrasonication. Analysis of surface roughness reflected that PVDF-TiO₂ (MS-U2) surface morphological pattern was peak-valley structure that resisted fouling greatly. A good fitting of experimental result and Tansel’s simulation illustrated that anti-fouling ability was realized direct ultrasonication modified membrane. PVDF-TiO₂ (MS-U2) membrane showing the lowest |τ| reflecting the time required to reach a certain level of the fouling degree was the lowest. Relying upon modified Hermia’s model analysis, protein blockage within the membrane pore was one major fouling mechanism; surface blockage degree of PVDF-TiO₂ (MS-U2) was relative slight. Fouling mechanism analyzed by two models reflected that PVDF-TiO₂ (MS-U2) membrane exhibited a higher anti-protein fouling ability during cross-flow filtration process.
اظهر المزيد [+] اقل [-]Effects of di (2-ethylhexyl) phthalate and high-fat diet on lipid metabolism in rats by JAK2/STAT5 النص الكامل
2020
Zhang, Yuezhu | Zhou, Liting | Zhang, Zhaoming | Xu, Qi | Han, Xu | Zhao, Yaming | Song, Xinyue | Zhao, Tianyang | Ye, Lin
Exposure to di (2-ethylhexyl) phthalate (DEHP) induces lipid metabolism disorder and high-fat diet (HD) may have joint effects with DEHP. We aim to clarify the role of JAK2/STAT5 pathway in the process and reveal the effects of HD on the toxicity of DEHP. Wistar rats (160 animals) were fed with HD or normal diet (ND) respectively and exposed to DEHP 0, 5, 50, and 500 mg/kg/day for 8 weeks. Lipid levels, as well as the morphology of liver and adipose, mRNA levels, and protein levels of JAK2, STAT5A, STAT5B, FAS, ap2, and PDK4 were detected. The results showed that DEHP exposure leads to increased weight gain. The JAK2/STAT5 pathway was activated in adipose after DEHP exposure and promoted the expression of FAS, ap2, and PDK4 in ND rats. While in the liver, JAK2 was inhibited, and lipid synthesis and accumulation were increased. However, rats exposed to DEHP in combination with HD showed a complete disorder of lipid metabolism. Therefore, we conclude that DEHP affects lipid metabolism through regulating the JAK2/STAT5 pathway and promotes adipogenesis and lipid accumulation. High-fat diet may have a joint effect with DEHP on lipid metabolism disorder.
اظهر المزيد [+] اقل [-]Operational parameters in H2S biofiltration under extreme acid conditions: performance, biomass control, and CO2 consumption النص الكامل
2020
García-Pérez, Teresa | Hernández-Jiménez, Sergio | Revah, Sergio
This paper reports the treatment of gaseous hydrogen sulfide, H₂S, in a biotrickling filter (BTF) under extreme acidic pH conditions (≈ 1.2). The effect of adding thiosulfate (Na₂S₂O₃.5H₂O) to promote biomass growth, feeding low concentrations of ozone to control excess biomass, and the carbon dioxide, CO₂, consumption by the chemolithoautotrophic consortium were evaluated. The results showed a global removal efficiency over 98.0% with loads of H₂S > 50 g m⁻³ h⁻¹ (at 639 ppmv) and a linear relation between H₂S elimination capacity with the CO₂ consumption rate of around 0.1 gCO₂/gH₂S. Supplementing sulfur in the medium with 2 g L⁻¹ thiosulfate resulted in negative effect performance. Respirometry tests proved that the consortium could not utilize this sulfur form at this pH. Additionally, continuous and intermittent O₃ feeding to the BTF in gaseous concentrations of 98 ± 5.4 mg m⁻³ caused a slight decreased in the performance but the biomass activity in the BTF was only slightly affected allowing a quick performance recovery once O₃ addition was suspended.
اظهر المزيد [+] اقل [-]Water quality in recirculating aquaculture system using woodchip denitrification and slow sand filtration النص الكامل
2020
Lindholm-Lehto, Petra | Pulkkinen, Jani | Kiuru, Tapio | Koskela, Juha | Vielma, Jouni
Water quality in recirculating aquaculture system using woodchip denitrification and slow sand filtration النص الكامل
2020
Lindholm-Lehto, Petra | Pulkkinen, Jani | Kiuru, Tapio | Koskela, Juha | Vielma, Jouni
In recirculating aquaculture system (RAS), ammonium excreted by the fish is typically transformed to less toxic nitrate by microbial activity in bioreactors. However, nitrate-nitrogen load can be harmful for the receiving water body when released from the RAS facility. A new type of water treatment system for a RAS was designed, including a passive woodchip denitrification followed by a sand filtration introduced into a side-loop of an experimental RAS, rearing rainbow trout (Oncorhynchus mykiss). In the process, woodchips acted as a carbon source for the denitrification, aiming at a simultaneous nitrogen removal and reduction of water consumption while sand filtration was used to remove organic matter and recondition the circulating water. A variety of chemical analyses and toxicological tests were performed to study the suitability of the process and to ensure the absence of harmful or toxic substances in the system. The results did not show increased toxicity, and no increased mortality was reported for the raised species. After the start-up of the system, the concentrations of fatty acids (e.g., hexadecanoic acid <LOD-1.21 mg L⁻¹) and heavy metals (e.g., Cd < LOD-0.45 μg L⁻¹, Pb < LOD-14 μg L⁻¹) remained at very low levels and below those of known toxic effects. In the beginning of the experiment, good denitrification efficiency was achieved, but it declined after 1 month, showing the need for improved stability and dimensioning of the application.
اظهر المزيد [+] اقل [-]