خيارات البحث
النتائج 2511 - 2520 من 4,921
Evaluation of Fe-containing Li2CuO2 on CO2 capture performed at different physicochemical conditions
2019
Yañez-Aulestia, Ana | Ovalle-Encinia, Oscar | Pfeiffer, Heriberto
Li₂CuO₂ and different iron-containing Li₂CuO₂ samples were synthesized by solid state reaction. On iron-containing samples, atomic sites of copper are substituted by iron ions in the lattice (XRD and Rietveld analyses). Iron addition induces copper release from Li₂CuO₂, which produce cationic vacancies and CuO, due to copper (Cu²⁺) and iron (Fe³⁺) valence differences. Two different physicochemical conditions were used for analyzing CO₂ capture on these samples; (i) high temperature and (ii) low temperature in presence of water vapor. At high temperatures, iron addition increased CO₂ chemisorption, due to structural and chemical variations on Li₂CuO₂. Kinetic analysis performed by first order reaction and Eyring models evidenced that iron addition on Li₂CuO₂ induced a faster CO₂ chemisorption but a higher thermal dependence. Conversely, CO₂ chemisorption at low temperature in water vapor presence practically did not vary by iron addition, although hydration and hydroxylation processes were enhanced. Moreover, under these physicochemical conditions the whole sorption process became slower on iron-containing samples, due to metal oxides presence.
اظهر المزيد [+] اقل [-]Swine Wastewater Treatment for Small Farms by a New Anaerobic-Aerobic Biofiltration Technology
2019
Escalante-Estrada, V. E. | Garzón-Zúñiga, M. A. | Valle-Cervantes, S. | Páez-Lerma, J. B.
Effluents form the swine livestock industry contain a high concentration of pollutants and require complex treatment systems. The most recurrent form to treat Swine wastewater is by a conventional anaerobic–aerobic treatment. For example, an up-flow anaerobic blanket sludge reactor followed by an activated sludge reactor. However, in many countries, a high percentage of producers are small or medium-sized farms that can afford neither complex treatment systems nor specialized operations. The present study assessed the performance of a novel and different combinations of treatment processes, based on changing the anaerobic systems that require a specialized operation for one very simple to operate for farm owners. The assessed system is composed by a septic tank in combination with an up-flow anaerobic filter packed with volcanic rocks and an aerobic biofilter packed with waste wood chips. The effect of the hydraulic residence time and the volumetric organic loading in the septic tank and up-flow anaerobic filter and the effect of surface hydraulic loading in the aerobic biofilter were also evaluated. The system efficiently removed chemical oxygen demand (86–93%), total suspended solids (91–97%), volatile suspended solids (86–97%), and ammoniacal nitrogen (86–87%), showing a constant removal efficiency under a VOL of between 5 and 14.6 kg COD m⁻³ d⁻¹in the up-flow anaerobic filter. The advantages of this system are that the packing materials can be available in rural zones and are sustainable; the whole system is cost-effective and easy to handle; thus, farmers can operate and maintain it with their own means.
اظهر المزيد [+] اقل [-]Human exposure risk to semivolatile organic compounds via soil in automobile workshops in Awka, South Eastern, Nigeria
2019
Ibeto, Cynthia | Anekwe, Chibuzor | Ihedioha, Janefrances
Evaluation of the human exposure risk to semivolatile organic compound (SVOC) levels in soil from automobile workshops in Awka was investigated. Soil samples were collected in both dry and rainy seasons. Solvent extraction of the soil samples was carried out using n-hexane: acetone mixture (1:1). Concentrations of SVOCs were determined using gas chromatography-mass spectrometry. There were higher concentrations of SVOCs in the dry season than in the rainy season. The concentrations of the SVOCs were compared with standards for industrial soils. Concentrations of pentachlorophenol in the samples for dry and rainy seasons were below the Canadian Council of Ministers of Environment (CCME) acceptable limit of 7.6 mg/kg. Eighty percent of soil samples for the dry season and all the soil samples for the rainy season had benzo(a)pyrene concentrations lower than the CCME acceptable limit of 0.7 mg/kg. However, incremental lifetime cancer risk (ILCRdₑᵣ) of PAHs and pentachlorophenol for dry seasons exceeded 1.0 × 10⁻⁶ WHO acceptable limit in all the sampling stations, which indicates potential risk via dermal contact. ILCRs of pentachlorophenol were above 1.0 × 10⁻⁶ in 60% of the samples for soil ingestion and all the samples for dermal contact. Hazard quotient of phenolics, phthalates, 1,3-dichlorobenzene and 1,4-dichlorobenzene for soil samples were less than 1 for both seasons, which indicates no non-cancer risk. Results suggest that the SVOCs were highest at the centre of the automobile workshop and the main route of exposure was dermal contact with the soil.
اظهر المزيد [+] اقل [-]Target and non-target botanical pesticides effect of Trichodesma indicum (Linn) R. Br. and their chemical derivatives against the dengue vector, Aedes aegypti L
2019
Chellappandian, Muthiah | Senthil-Nathan, Sengottayan | Vasantha-Srinivasan, Prabhakaran | Karthi, Sengodan | Thanigaivel, Annamalai | Kalaivani, Kandaswamy | Sivanesh, Haridoss | Stanley-Raja, Vethamonickam | Chanthini, Kanagaraj Muthu-Pandian | Shyam-Sundar, Narayanan
The effects of crude ethanol derived leaf extract Trichodesma indicum (Linn) (Ex-Ti) and their chief derivatives were accessed on the survival and development of the dengue mosquito Ae. aegypti also their non-toxic activity against mosquito predator. T. indicum is recognized to be the vital weed plant and a promising herb in the traditional ayurvedic medicine. In this study, the GC-MS chromatogram of Ex-Ti showed higher peak area percentage for cis-10-Heptadecenoic acid (21.83%) followed by cycloheptadecanone (14.32%). The Ex-Ti displayed predominant mortality in larvae with 96.45 and 93.31% at the prominent dosage (200 ppm) against III and IV instar. Correspondingly, sub-lethal dosage against the enzymatic profile of III and IV instar showed downregulation of α,β-carboxylesterase and SOD protein profiles at the maximum concentration of 100 ppm. However, enzyme level of GST as well as CYP450 increased significantly dependent on sub-lethal concentration. Likewise, fecundity and hatchability of egg rate of dengue mosquito decreased to the sub-lethal concentration of Ex-Ti. Repellent assay illustrates that Ex-Ti concentration had greater protection time up to 210 min at 100 ppm. Also, activity of Ex-Ti on adult mosquito displayed 100% mortality at the maximum dosage of 600, 500 and 400 ppm within the period of 50, 60 and 70 min, respectively. Photomicrography screening showed that lethal dosage of Ex-Ti (100 ppm) produced severe morphological changes with dysregulation in their body parts as matched to the control. Effects of Ex-Ti on the Toxorhynchites splendens IV instar larvae showed less mortality (43.47%) even at the maximum dosage of 1500 ppm as matched to the chemical pesticide Temephos. Overall, the present research adds a toxicological valuation on the Ex-Ti and their active constituents as a larvicidal, repellent and adulticidal agents against the global burdening dengue mosquito.
اظهر المزيد [+] اقل [-]Electrochemical modification of activated carbon fiber as 3-D particle electrodes: characterization and enhancement for the degradation of m-cresol
2019
Liu, Weijun | Hu, Xiang | Sun, Zhirong | Duan, Pingzhou
Commercial activated carbon fiber (ACF) has been employed as particle electrodes to degrade aqueous m-cresol in 3-D electrode systems. To enhance the electrooxidation performance, three types of new ACF modification modes (anodic oxidation, cathodic reduction, and aqueous oxidation with concentrated HNO₃) were introduced in this paper. These pretreated samples were characterized by N₂ adsorption, scanning electron microscopy (SEM), cyclic voltammetry (CV), temperature-programmed desorption mass (TPD-MS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FT-IR). It was revealed that the two new modification methods could efficiently modify the surface morphology as well as the chemical property. Eight types of surface oxygen groups (SOGs) were identified on the surface of ACF, and the types and amount of SOGs might be related to the oxidation effect of ACF on the 3-D electrodes. The effect and mechanism of these SOGs on electrooxidation performance were discussed with the aid of the frontier molecular orbital theory. It was demonstrated that the H₂O₂–·OH reaction mechanism was improved in the 3-D electrode system and the mechanism was elucidated.
اظهر المزيد [+] اقل [-]Activation of endoplasmic reticulum stress in rat brain following low-intensity microwave exposure
2019
Ranjeet Kumar, | Deshmukh, Pravin S. | Sharma, Sonal | Banerjee, BasuDev
The present study was designed to explore the effects of low-intensity microwave radiation on endoplasmic reticulum stress and unfolded protein response. Experiments were performed on male Wistar rats exposed to microwave radiation for 30 days at 900 MHz, 1800 MHz, and 2450 MHz frequencies on four groups of animal: sham-exposed group, 900 MHz exposed (SAR 5.84 × 10⁻⁴ W/kg), 1800 MHz exposed (SAR 5.94 × 10⁻⁴ W/kg), and 2450 MHz exposed (SAR 6.7 × 10⁻⁴ W/kg) groups. Expressions of mRNA were estimated at the end of exposure in rat brain by real-time quantitative PCR. Microwave exposure at 900, 1800, and 2450 MHz with respective SAR values as mentioned above significantly (< 0.05) altered mRNA expression of transcription factors ATF4, CHOP, and XBP1 in accordance with increasing microwave frequency. The result of the present study reveals that low-intensity microwave exposure at frequencies 900, 1800, and 2450 MHz induces endoplasmic reticulum stress and unfolded protein response.
اظهر المزيد [+] اقل [-]Windbreak Wall-Vegetative Strip System to Reduce Air Emissions from Mechanically Ventilated Livestock Barns: Part 2—Swine House Evaluation
2019
ʻAjamī, ʻAlī | Shah, Sanjay B. | Wang-Li, Lingjuan | Kolar, Praveen | Castillo, Miguel S.
Air emissions from animal feeding operations (AFOs) can affect public health, environment, and quality of life. Although regulations or lawsuits may force AFOs to reduce air emissions, treatment options are limited and expensive. Trapping particulate matter (PM) emitted from AFOs is important for reducing emissions since many odorous and environmentally important gases are also transported on PM. Since PM emitted by AFOs have relatively high particle density and diameter, its partial filtration might be feasible and effective in reducing air emission. A porous windbreak wall made of lumber and mosquito screen, coupled with a vegetative strip of switchgrass (Panicum virgatum) covering three fans, was evaluated in a tunnel-ventilated swine finishing barn. The system imposed acceptable pressure on the fan (< 13 Pa) and was readily cleaned by rain. The system reduced total suspended particulate (TSP) emission moderately (average reduction of 28%), while reduction in ammonia emissions was low. Odor 10 m downstream of the fans was reduced greatly by 71%. Soil inside the system and vegetation accumulated appreciable amounts of nitrogen and sulfur; the vegetation also trapped appreciable amounts of PM. Overall, this low-cost, retrofittable, and modular system could be used by swine farmers to reduce their emissions, alone or in combination with other mitigation methods to obtain greater reduction in emissions.
اظهر المزيد [+] اقل [-]Dynamic simulation of the optimal allocation of water resources via the introduction of integrated water environmental policies in Baoding, China
2019
Mou, Siyu | Yan, Jingjing | Sha, Jinghua | Li, Shule | Ma, Yufang | He, Gengyu | Song, Ci
With rapid industrialization and urbanization, regional water shortages and water quality deterioration have posed great challenges for the sustainable development of cities in North China, especially those with a large demand for agricultural irrigation water. Based on an input-output analysis, this paper develops a dynamic optimization model consisting of three sub-models and multiple constraint conditions to solve the water crisis of Baoding, a typical city experiencing water shortages and serious water pollution in North China. The water resource carrying capacity (WRCC) indicator is introduced in the analysis of the results to comprehensively assess the effect of integrated water environmental policies (IWEPs) from 2013 to 2025. In the optimal scenario, the annual chemical oxygen demand (COD) discharge and annual water demand in Baoding can be reduced by 2.6% and 0.6%, respectively, with an annual gross regional product (GRP) growth rate of 7.52%. The WRCC can be improved from moderately overloaded to weakly unsaturated, which indicates that water resources can meet the socioeconomic development requirements. The results demonstrate the effectiveness of the linear optimization model with input-output analysis in coordinating the relationships among water demand, water environment protection, and economic development, and the IWEPs provide an applicable reference for decision-makers in Baoding and other similar cities in North China to address deteriorating water systems.
اظهر المزيد [+] اقل [-]Vulnerability assessment of areas allocated for municipal solid waste disposal systems: a case study of sanitary landfill and incineration
2019
Ngamsang, Thittaya | Yuttitham, Monthira
This study was conducted to assess the vulnerability of areas allocated for sanitary landfill in Nakhon Ratchasima and for incineration in Phuket, Thailand, and to investigate the factors contributing to their vulnerability. Analysis was conducted to develop a vulnerability index using a composite index approach and the Intergovernmental Panel on Climate Change (IPCC) framework approach, while correlation and t tests were applied to identify the relationships and differences between the two systems. Additionally, vulnerability indices were developed using the IPCC vulnerability definition. The results suggested that the vulnerability of the areas allocated for sanitary landfill and incineration were not significantly different. The factor that had the greatest impact on the vulnerability of the sanitary landfill was nuisance, while sub-component correlation analysis revealed that cadmium in groundwater was significantly negatively correlated with vulnerability (r = − 0.958, p < 0.05). Furthermore, the factor that had the greatest effect on vulnerability from incineration was leachate. Similarly, correlation analysis suggested that the chemical oxygen demand in leachate and solid waste residues was significantly positively correlated with vulnerability (r = 0.981, 0.975 respectively, p < .05). It is hoped that these findings can be used to establish measures for preventing environmental problems, as well as to prioritize and identify issues that need to be resolved urgently, and to help policy makers select appropriate systems for different regions of Thailand.
اظهر المزيد [+] اقل [-]Estimation of methane and nitrous oxide emission from wetland rice paddies with reference to global warming potential
2019
Gorh, Dipti | Baruah, Kushal Kumar
Methane (CH₄) and nitrous oxide (N₂O) are two important greenhouse gases (GHG) and contribute largely to global warming and climate change. The impact of physiological characteristics of rice genotypes on global warming potential (GWP) and greenhouse gas intensity (GHGI) is not well documented. A 2-year field experiment was conducted with eight summer rice varieties: Dinanath, Joymoti, Kanaklata, Swarnabh, IR 64, Tapaswami (modern varieties), Number 9, and Jagilee Boro (indigenous varieties) for two successive seasons (December–June, 2015–2016 and December–June, 2016–2017) to estimate their GWP and GHGI. The GWP of the rice varieties ranged from 841.52 to 1288.67 kg CO₂-equiv. ha⁻¹ and GHGI from 0.184 to 0.854 kg CO₂-equiv. kg⁻¹ grain yield. Significant differences (p < 0.05) in seasonal GHG emission, GWP, GHGI, CEE (carbon equivalent emission), photosynthetic efficiency, stomatal conductance, transpiration rate, and grain productivity among the rice varieties were observed during the investigation. A good correlation of GWP (p < 0.01) was recorded with rate of stomatal conductance and transpiration rate of the varieties. The present study reveals a strong relationship between plant biomass (p < 0.01) with GWP and CEE of the rice varieties. The variety IR 64 and Number 9 are identified as the most suitable variety with lowest GWP (909.85 and 876.68 kg CO₂-equiv. ha⁻¹ respectively) and GHGI (0.192 and 0.227 kg CO₂-equiv. kg⁻¹ grain yield respectively) accompanied by higher grain productivity (4839 and 3867 kg ha⁻¹ respectively). Observations from the study suggest that agricultural productivity and GHG mitigation can be simultaneously achieved by proper selection of rice genotypes.
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