خيارات البحث
النتائج 3021 - 3030 من 4,935
Performance of an aquaponics system using constructed semi-dry wetland with lettuce (Lactuca sativa L.) on treating wastewater of culture of Amazon River shrimp (Macrobrachium amazonicum) النص الكامل
2019
de Farias Lima, Jô | Duarte, Sting Silva | Bastos, Argemiro Midonês | Carvalho, Taina
Aquaponics is a science that integrates animal aquatic production with vegetable culture in recirculating water systems. The performance of an aquaponics system using constructed semi-dry wetland with lettuce (Lactuca sativa L.) planted on treating wastewater of culture of shrimp Macrobrachium amazonicum was evaluated. Each aquaponics module consisted in four culture tanks (1 m³ tank⁻¹), conical sedimentation tank (0.1 m³), circular holding tank (0.2 m³), and constructed semi-dry wetland (0.2 m × 1.0 m × 4.0 m). Post larvae (PL) shrimps with an initial average mass of 314 ± 4.75 mg were stocked at density treatments in quadruplicate: (A) 40 shrimps m⁻², (B) 80 shrimps m⁻², and (C) 120 shrimps m⁻². Our results showed the average final mass of shrimps had a slight reduction at the density 80 and 120 shrimps. However, it did not differ significantly between the treatments. The ultimate survival and productivity were higher in density 80 and 120 shrimps. The maximum biomass productivity occurred at the treatment with density 120 shrimps. The aquaponics recirculation system using constructed semi-dry wetlands with lettuce adequately treated the water at the densities tested. Various water quality parameters were deemed suitable for shrimp culture, but for lettuce not, especially the temperature. The shrimp density was inappropriate which limited the system to accumulate and increase the concentration of nutrients to vegetables with lessening the yield. Nonetheless, the system with higher density has higher nutrient content that plants demonstrated significantly better growth and yield. The results showed the potential use of organics waste generated in a family lettuce hydroponic production, but for a commercial production is indicated supplementation with nutrients like calcium, magnesium, and potassium in the water.
اظهر المزيد [+] اقل [-]The economic and environmental benefits analysis for food waste anaerobic treatment: a case study in Beijing النص الكامل
2019
Guo, Xiaopeng | Yang, Xiaoyu
The disposal of food waste has attracted worldwide attention. Each year, the amount of wasted food accounts for an estimated one third of annual food production globally. This large amount of food waste has caused serious land, water, and air pollution. In the past, most research on food waste was focused solely on food waste disposal processing. Only a few studies analysed the flow of materials in food waste treatment processes. Therefore, this paper focused on the process of food waste anaerobic treatment in Beijing and investigated the treatment. According to a life cycle theory, the food waste treatment process is divided into three processes: “collection and transportation, disposal, and resource utilization.” This paper analysed the input and output of food waste treatment in different processes and evaluated the economic and environmental costs and benefits of food waste treatment. The study found that 200 t of food waste anaerobic treatment can obtain benefits 66,888 Chinese yuan, generate electricity energy 43,350 kW⋅h, and reduce carbon dioxide emissions 16,087 kg. Generally, the economic and environmental benefits of the food waste anaerobic treatment project are considerable. However, the economic benefits are mainly from government subsidies. There are many impurities in food waste, which indicates some problems in food waste treatment. Thus, the proposals to strengthen waste classification, optimize the layout of garbage collection and transportation, and accelerate the development of waste treatment plants have been put forward.
اظهر المزيد [+] اقل [-]Oxidation stability of yeast biodiesel using Rancimat analysis: validation using infrared spectroscopy and gas chromatography–mass spectrometry النص الكامل
2019
Biodiesel and single cell oils obtained from oleaginous yeasts grown in industrial waste are attractive alternatives to the conventional fuels. However, there are only few articles dealing with the stability of the microbial biofuels. Hence, this study aimed at characterizing the storage time of biodiesels using Rancimat methods. The microbial oil and the biodiesel obtained from microbial oil have been characterized with storage stability due to various oxidizing and thermal damage. Here, the microbial fuels were subject to Rancimat analysis and found to have high thermal-oxidative stability of 18 and 8.78 h for biodiesel and oil, respectively. The storage stability resulting from storage conditions was extrapolated for biodiesel and oil and has been found to be 1.62 and 0.54 years, respectively. The infrared spectroscopic analysis reveals the degree of oxidation found after the induction time was reached and shows the characteristic peaks for degradation products. Gas chromatography revealed the compounds that were responsible for the stability as well as the amount of degradation products left.
اظهر المزيد [+] اقل [-]Efficacy of two actinomycete extracts in the amelioration of carbon tetrachloride–induced oxidative stress and nephrotoxicity in experimental rats النص الكامل
2019
Actinomycetes are a group of the Gram-positive bacteria famous for their antimicrobial, anticancer, anti-parasitic, and anti-inflammatory activities. This study aimed to investigate the efficacy of two bacterial extracts derived from two soil actinomycete strains (S19 and G30) against carbon tetrachloride (CCl₄)–induced nephrotoxicity in experimental rats. Sixty-four male rats were assigned to four groups of 16 rats in each group. The 1st group was kept as a normal (control) group and given corn oil combined with the used production medium, while the 2nd group received only CCl₄ (CCl₄ group). On the other hand, the 3rd group (CCl₄+S19) was administered CCl₄ and the extract of the actinomycete strain S19 and the 4th group (CCl₄+G30) received CCl₄ and the extract of the actinomycete strain G30, both treatments for 8 weeks. The results revealed that the two actinomycete extracts S19 and G30 could significantly (p < 0.01) lower the elevated levels of serum creatinine, urea, and uric acid caused by the CCl₄ administration. Additionally, the two actinomycete extracts improved the decreased serum total protein. Interestingly, treatment of the CCl₄-intoxicated rats with S19 and G30 extracts remarkably reversed the lowered renal glutathione (GSH), glutathione peroxidase (GSH-Px), peroxidase (Px) and superoxide dismutase (SOD) activities, and the elevated lipid peroxidation (LPO) levels. The histopathological examination of the treated kidney revealed that the two actinomycete extracts improved rats against CCl₄-induced kidney lesions. The present results suggested that the protective effect of the two actinomycete extracts may rely on its effect on reducing the oxidative stress and improving the antioxidant defense system.
اظهر المزيد [+] اقل [-]Development of the specific emission factors for buses in Hanoi, Vietnam النص الكامل
2019
This paper develops the specific emission factors for buses in the real-world traffic conditions in the inner city of Hanoi, Vietnam. An engine stationary cycle consisting of 14 modes was developed based on the typical driving cycle of Hanoi buses which had been constructed with the application of Markov chain theory. This is the first engine stationary emissions test cycle constructed for heavy-duty engine in Vietnam. Based on this cycle, the country-specific emission factors (CSEFs) of air pollutants including CO, HC, NOₓ, CO₂, and PM for buses in Hanoi have been developed using the emission measurements on the engine test bed. It is found that almost all developed emission factors are higher than those derived from the emission measurements to the ECE R49 on the same engine. These emission factors, therefore, can be used to improve the quality of the emission inventory of buses in Hanoi.
اظهر المزيد [+] اقل [-]Establishment of suitable separation distance by using different methods for malodor mitigation from palm oil mill النص الكامل
2019
Malaysia is the second-largest producer and exporter of palm oil amounting to 39% of world palm oil production and 44% of world exports (MPOB, 2014). An enormous amount of palm oil mill effluent is released during palm oil milling, and the effluent causes a major odor problem. Many methods, such as biofiltering, can be adopted to manage the malodor. However, these methods are expensive and require high maintenance. The separation distance method can be used as an alternative due to its low cost and effectiveness. This research was conducted to verify the performance of three different methods, namely, in-field monitoring by using an olfactometer, CALPUFF model, and Gaussian plume model. Given that no research has compared the three methods, this study examined the effectiveness of the methods and determined which among them is suitable for use in Malaysia. The appropriate separation distances were 1.3 km for in-field monitoring, 1.2 km for the CALPUFF model, and 0.5 for the Gaussian plume model. These different values of separation distance were due to the various approaches involved in each method. This research determined an appropriate means to establish a proper separation distance for reducing odor nuisance in areas around palm oil mills.
اظهر المزيد [+] اقل [-]Sequential determination and chemical speciation analysis of inorganic As and Sb in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by HG AAS النص الكامل
2019
In this work, fast sequential determination and chemical speciation analysis of inorganic arsenic and antimony in airborne particulate matter collected in outdoor and indoor environments using slurry sampling and detection by hydride generation atomic absorption spectrometry (HG-AAS) is proposed. A Doehlert design was applied to optimise the hydride generation conditions of As and Sb for fast sequential determination in the same aliquot of particulate matter samples after preparation of the slurry. The limits of quantification (LoQ) obtained for As and Sb were 0.3 and 0.9 ng m⁻³, respectively. The accuracy of the analytical method was confirmed by analysis of the certified reference material of urban particulate matter (SRM NIST 1648a), presenting concordance with certified values of 92.7±7.7% for As and 91.2±9.5% for Sb. Precision was expressed as relative standard deviation (% RSD, n=3), with our results presenting values better than 3.4% and 4.2% for total inorganic As and Sb, respectively. For all analysed samples, total As concentrations and its inorganic species were below the LoQ of the analytical method (<0.3 ng m⁻³). However, the averages of total inorganic Sb concentrations in airborne particulate matter, collected as total suspended outdoor particles (TSPₒᵤₜdₒₒᵣ), inhalable particulate matter (PM₁₀), and total suspended indoor particles (TSPᵢₙdₒₒᵣ), were 3.1±0.5, 2.4±0.6, and 2.6±0.4 ng m⁻³, respectively. Trivalent Sb (Sb³⁺) was the predominant inorganic species in all samples investigated, with mean percentages of 76%, 72%, and 73% in TSPₒᵤₜdₒₒᵣ, PM₁₀, and TSPᵢₙdₒₒᵣ, respectively. The presence of Sb and its predominant inorganic form (Sb³⁺) can be attributed to vehicular traffic close to the sampled urban areas. Therefore, fast sequential determination of As and Sb and their inorganic species in particulate matter samples prepared as slurry by FS-HG-AAS is an efficient, accurate, and precise method and can be successfully applied to routine analysis.
اظهر المزيد [+] اقل [-]2,4-D causes oxidative stress induction and apoptosis in human dental pulp stem cells (hDPSCs) النص الكامل
2019
2,4-Dicholorophenoxy acetic acid (2,4-D) is a worldwide used hormone herbicide. Human dental pulp stem cells (hDPSCs) as a potential source of mesenchymal stem cells provide a confident model system for the assessments of chemicals in vitro. The main objective of this study was to examine the biological effects and damages attributed to 2,4-D on hDPSCs. hDPSCs were isolated from third molar pulp tissues and their mesenchymal identity were evaluated. Then, hDPSCs were treated with increasing concentrations of 2,4-D (0.1 μM–10 mM). Cell viability assay and cumulative cell counting were carried out to address 2,4-D effects on biological parameters of hDPSCs. Cell cycle distribution, ROS level and ALP activity were measured before and after treatment. AO/EB staining and caspase 3/7 activity were investigated to detect the possible mechanisms of cell death. Flow-cytometric immunophenotyping and differentiation data confirmed the mesenchymal identity of cultivated hDPSCs. 2,4-D treatment caused a hormetic response in the viability and growth rate of hDPSCs. G0/G1 cell cycle arrest, enhanced ROS level, and reduced ALP activity were detected in hDPSCs treated with EC50 dose of 2,4-D. AO/EB staining showed a higher percentage of alive cells in lower concentrations of the herbicide. The increment in 2,4-D dose and the number of early and late apoptotic cells were increased. DAPI staining and caspase 3/7 assay validated the induction of apoptosis. 2,4-D concentrations up to 100 μM did not affect hDPSCs viability and proliferation. The intense cellular oxidative stress and apoptosis were observed at higher concentration.
اظهر المزيد [+] اقل [-]Toxicity of three emerging contaminants to non-target marine organisms النص الكامل
2019
da Silva, Allyson Q. | de Souza Abessa, Denis Moledo
Coastal areas are continually impacted by anthropic activities because they shelter large urban conglomerates. Urban effluents directly or indirectly end up reaching the marine environment, releasing a large number of pollutants which include the so-called contaminants of emerging concern (CECs), since the conventional treatment plants are not effective in removing these compounds from the effluents. These substances include hormones, pharmaceuticals and personal care products, nanoparticles, biocides, among others. The aim of this study was to evaluate the toxicity of the 17α-ethinylestradiol (EE2), acetylsalicylic acid (ASA), and bisphenol-A (BPA) to two marine crustaceans and one echinoderm, evaluating the following parameters: survival (Artemia sp. and Mysidopsis juniae), embryo-larval development (Echinometra lucunter). The LC₅₀ values calculated in the acute toxicity tests showed that the compounds were more toxic to M. juniae than to the Artemia sp. Among the three contaminants, EE2 was the most toxic (LC₅₀₋₄₈ₕ = 18.4 ± 2.7 mg L⁻¹ to Artemia sp.; LC₅₀₋₉₆ₕ = 0.36 ± 0.07 mg L⁻¹ to M. juniae). The three tested compounds affected significantly the embryonic development of the sea urchin in all tested concentrations, including ecologically relevant concentrations, indicating the potential risk that these contaminants may present to the marine biota.
اظهر المزيد [+] اقل [-]Dryland cyanobacterial exopolysaccharides show protection against acid deposition damage النص الكامل
2019
Gao, Xiang | Liu, Li-Tao | Liu, Bin
Soil surface-dwelling cyanobacteria constitute an important part of the dryland ecosystem. The exopolysaccharide (EPS) matrix they establish plays multiple roles in helping cells cope with harsh environments and also improves soil physicochemical properties. Anthropogenic atmospheric nitrogen or sulfur depositions have arisen as an important environmental change in drylands. The acid moisture derived from the depositions will be absorbed by cyanobacterial EPS matrix and thus may pose a threat to cells. In this communication, we evaluated this potential impact in a dryland cyanobacterium, Nostoc flagelliforme, which is a representative polysaccharide-rich species and shows remarkable resistance to desiccation stress. A strong and resilient pH buffering property was found for the EPS matrix, mainly of the polysaccharide’s role, and this could protect the cells from acid damage of pH 4–6, a general acidity range of rainwater in the world. Unlike in acid aquatic environments, terrestrial xeric environments ensure N. flagelliforme unlikely to undertake lasting severe acidification. Thus, protection of the EPS matrix for dryland cyanobacteria would be conducive to sustain their growth and ecological roles in face of atmospheric acid pollution.
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