خيارات البحث
النتائج 1201 - 1210 من 1,310
Effect of nuclear power on CO₂ emission from power plant sector in Iran النص الكامل
2011
Kargari, Nargess | Mastouri, Reza
INTRODUCTION: It is predicted that demand for electricity in Islamic Republic of Iran will continue to increase dramatically in the future due to the rapid pace of economic development leading to construction of new power plants. At the present time, most of electricity is generated by burning fossil fuels which result in emission of great deal of pollutants and greenhouse gases (GHG) such as SO₂, NOₓ, and CO₂. The power industry is the largest contributor to these emissions. Due to minimal emission of GHG by renewable and nuclear power plants, they are most suitable replacements for the fossil-fueled power plants. However, the nuclear power plants are more suitable than renewable power plants in providing baseload electricity. The Bushehr Nuclear Power Plant, the only nuclear power plant of Iran, is expected to start operation in 2010. This paper attempts to interpret the role of Bushehr nuclear power plant (BNPP) in CO₂ emission trend of power plant sector in Iran. MATERIALS AND METHODS: In order to calculate CO₂ emissions from power plants, National CO₂ coefficients have been used. The National CO₂ emission coefficients are according to different fuels (natural gas, fuels gas, fuel oil). RESULTS AND DISCUSSION: By operating Bushehr Nuclear Power Plant in 2010, nominal capacity of electricity generation in Iran will increase by about 1,000 MW, which increases the electricity generation by almost 7,000 MWh/year (it is calculated according to availability factor and nominal capacity of BNPP). CONCLUSIONS: Bushehr Nuclear Power Plant will decrease the CO₂ emission in Iran power sector, by about 3% in 2010.
اظهر المزيد [+] اقل [-]Interpreting methamphetamine levels in a high-use community النص الكامل
2011
Chiaia-Hernandez, Aurea C. | Banta-Green, Caleb J. | Field, Jennifer A.
INTRODUCTION: Illicit drug use is a largely hidden phenomenon, and population measures are notoriously problematic. Reliable and valid data for local, regional, and national public health and other interventions are needed. METHODS: To address this information, we examined temporal trends within and across weeks in methamphetamine (MA) in a single location in order to inform a sampling plan for understanding long-term trends in MA use based on sampling raw influent to wastewater treatment plants. The measured concentrations in the wastewater are used to estimate the total mass of MA consumed rather than the number of doses due to the uncertainty surrounding methamphetamine purity, mass of MA per dose, and the number of doses used per day. RESULTS: Results from a region with high levels of MA use indicate that MA levels do not differ significantly between weekdays and weekends (p = 0.1), consistent with a predominately regular, daily use pattern use. The potential contribution of legal sales of D: - and L: -MA to the mass of MA consumed within the community was estimated to range from 3–8%. Limitations and uncertainties associated with estimating the mass of MA consumption include small contributions of prescription and over-the-counter drugs that are metabolized to MA as well as measurement and sampling variability.
اظهر المزيد [+] اقل [-]Toxic effect of tetracycline exposure on growth, antioxidative and genetic indices of wheat (Triticum aestivum L.) النص الكامل
2011
Xie, Xiujie | Zhou, Qixing | Lin, Dasong | Guo, Jianmian | Bao, Yanyu
Introduction More attention has been paid to tetracycline contamination in view of its rapid increasing concentration in the environment. Therefore, it is important to set up rapid, simple, and accurate methods for monitoring tetracycline ecotoxicity. Methods In the present study, a hydroponics experiment was conducted to examine toxic effects of tetracycline at the concentration range of 0.5 to 300 mg L⁻¹ on growth, antioxidative, and genetic indices of wheat (Triticum aestivum L.). Results The results indicated that tetracycline at 0.5-10 mg L⁻¹ could stimulate seed germination, cell mitotic division, and growth of wheat seedlings and did not induce a significant increase in the activity of antioxidative enzymes. However, tetracycline at the high concentrations (10-300 mg L⁻¹) could significantly inhibit these parameters in the concentration-dependent manner, including germination percentage (≥100 mg L⁻¹), shoot height (≥100 mg L⁻¹), root length (≥50 mg L⁻¹), and mitotic index (≥50 mg L⁻¹), and increased the activity of antioxidative enzymes (≥25 mg L⁻¹) in the dose-dependent manner, including superoxide dismutase, catalase, and peroxidase. Tetracycline at 5 mg L⁻¹ and above significantly augmented chromosome aberration frequency and malondialdehyde (MDA) content. On the other hand, MDA has positive correlation with the inhibition rates of seed germination, root length, shoot length, mitotic index, and antioxidative enzyme activities. Conclusion Tetracycline may have potential physiological, biochemical, and genetic toxicity to plant cells, and chromosome aberration and MDA might be sensitive bioindicators for tetracycline contamination than the other plant characteristics.
اظهر المزيد [+] اقل [-]The performance of nature reserves in capturing the biological diversity on Hainan Island, China النص الكامل
2011
Wu, Ruidong | Ma, Guangzhi | Long, Yongcheng | Yu, Jiehua | Li, Shining | Jiang, Haisheng
Purpose The performance of nature reserves depends on the degree to which they represent a region's full biodiversity. Here, we conducted a study on Hainan Island, China, to assess how well Hainan's biodiversity features were captured by existing nature reserves. We also explored the driving forces behind the current protection pattern so as to provide guidelines for improving the island's conservation system. Methods We integrated the information on nature reserves, ecological variables, and human activities into a spatial database, then assessed the performance of nature reserves in representing natural variation, vegetation types, and species, and examined the impacts of human activities and land ownership on the current protection pattern. Results About 8.4% of Hainan Island was protected by nature reserves; the coverage was geographically biased toward its central mountainous areas with higher elevation, rugged terrain, and fertile soils. We found that 60% of the environmental units and 39.4% of the natural vegetation types had more than 10% of their area protected, respectively. Lowlands tended to have higher animal species richness, and the protection for endangered species was less efficient. Nature reserve coverage was negatively correlated with amount of converted habitats, human population density, and road density, and 82.4% of the total reserved area was allocated on state-owned land. Conclusions Nature reserve coverage was not enough to capture lowlands biodiversity features. The current protection pattern was significantly driven by several major conservation targets, human development, planning methods, and land ownership. To improve its conservation system, Hainan should enhance protection in the north and northeast plains and coastal regions, implement systematic planning approaches to define clear visions for guiding future conservation actions, and develop flexible management and funding mechanisms toward sustainable use of natural resources.
اظهر المزيد [+] اقل [-]Statistical analysis and isotherm study of uranium biosorption by Padina sp. algae biomass النص الكامل
2011
Khani, Mohammad Hassan
Introduction The application of response surface methodology is presented for optimizing the removal of U ions from aqueous solutions using Padina sp., a brown marine algal biomass. Methods Box-Wilson central composite design was employed to assess individual and interactive effects of the four main parameters (pH and initial uranium concentration in solutions, contact time and temperature) on uranium uptake. Results and discussion Response surface analysis showed that the data were adequately fitted to second-order polynomial model. Analysis of variance showed a high coefficient of determination value (R ² = 0.9746) and satisfactory second-order regression model was derived. Conclusion The optimum pH and initial uranium concentration in solutions, contact time and temperature were found to be 4.07, 778.48 mg/l, 74.31 min, and 37.47°C, respectively. Maximized uranium uptake was predicted and experimentally validated. The equilibrium data for biosorption of U onto the Padina sp. were well represented by the Langmuir isotherm, giving maximum monolayer adsorption capacity as high as 376.73 mg/g.
اظهر المزيد [+] اقل [-]Microbial communities to mitigate contamination of PAHs in soil—possibilities and challenges: a review النص الكامل
2011
Fernández-Luqueño, F. | Valenzuela-Encinas, C. | Marsch, R. | Martínez-Suárez, C. | Vázquez-Núñez, E. | Dendooven, L.
BACKGROUND, AIM, AND SCOPE: Although highly diverse and specialized prokaryotic and eukaryotic microbial communities in soil degrade polycyclic aromatic hydrocarbons (PAHs), most of these are removed slowly. This review will discuss the biotechnological possibilities to increase the microbial dissipation of PAHs from soil as well as the main biological and biotechnological challenges. DISCUSSION AND CONCLUSIONS: Microorganism provides effective and economically feasible solutions for soil cleanup and restoration. However, when the PAHs contamination is greater than the microbial ability to dissipate them, then applying genetically modified microorganisms might help to remove the contaminant. Nevertheless, it is necessary to have a more holistic review of the different individual reactions that are simultaneously taking place in a microbial cell and of the interactions microorganism–microorganism, microorganism–plant, microorganism–soil, and microorganisms–PAHs. PERSPECTIVES: Elucidating the function of genes from the PAHs-polluted soil and the study in pure cultures of isolated PAHs-degrading organisms as well as the generation of microorganisms in the laboratory that will accelerate the dissipation of PAHs and their safe application in situ have not been studied extensively. There is a latent environmental risk when genetically engineered microorganisms are used to remediate PAHs-contaminated soil.
اظهر المزيد [+] اقل [-]Selective recovery of chromium, copper, nickel, and zinc from an acid solution using an environmentally friendly process النص الكامل
2011
Machado, Manuela D. | Soares, Eduardo V. | Soares, Helena M. V. M.
PURPOSE: Real electroplating effluents contain multiple metals. An important point related with the feasibility of the bioremediation process is linked with the strategy to recover selectively metals. In this work, a multimetal solution, obtained after microwave acid digestion of the ashes resulted from the incineration of Saccharomyces cerevisiae contaminated biomass, was used to recover selectively chromium, copper, nickel, and zinc. RESULTS: The acid solution contained 3.8, 0.4, 2.8, and 0.2 g/L of chromium(III), copper, nickel, and zinc, respectively. The strategy developed consisted of recovering copper (97.6%), as a metal, by electrolyzing the solution at a controlled potential. Then, the simultaneous alkalinization of the solution (pH 14), addition of H2O2, and heating of the solution led to a complete oxidation of chromium and nickel recovery (87.9% as a precipitate of nickel hydroxide). After adjusting the pH of the remaining solution at pH 10, selective recovery of zinc (82.7% as zinc hydroxide) and chromium (95.4% as a solution of cromate) was achieved. CONCLUSION: The approach, used in the present work, allowed a selective and efficient recovery of chromium, copper, nickel, and zinc from an acid solution using a combined electrochemical and chemical process. The strategy proposed can be used for the selective recovery of metals present in an acid digestion solution, which resulted from the incineration of ashes of biomass used in the treatment of heavy metals rich industrial effluents.
اظهر المزيد [+] اقل [-]Natural radionuclides in trees grown on a uranium mill tailings waste pile النص الكامل
2011
Štrok, Marko | Smodiš, B (Borut) | Eler, Klemen
Objective The purpose of the study was to investigate natural radionuclide uptake and allocation by trees. Materials and methods Samples from six Scots pines (P. sylvestris), six Norway spruces (Picea abies) and one sycamore maple (Acer pseudoplatanus) tree, growing on the Boršt uranium mill tailings waste pile in Slovenia were collected. ²³⁸U, ²³⁰Th, ²²⁶Ra and ²¹⁰Pb activity concentrations in wood, shoots and 1-year-old needles or leaves were determined. Particular radionuclides were separated from the samples by appropriate radiochemical procedures and their activity concentrations measured with an alpha spectrometry system. In addition, concentration ratios for different plant parts were calculated. Results and conclusions Results showed that for all radionuclides, the highest activity concentrations were found in foliage, followed by shoots and wood. The activity concentrations in trees were from 0.01 to 5.4 Bq kg⁻¹ for ²³⁸U, 0.03-11.3 Bq kg⁻¹ for ²³⁰Th, 2.7-2,728 Bq kg⁻¹ for ²²⁶Ra and 5.1-321 Bq kg⁻¹ for ²¹⁰Pb. All activity concentrations were calculated on dry weight basis. The calculated concentration ratios were from 1.05E-5 to 5.39E-3 for ²³⁸U, 7.65E-6-2.88E-3 for ²³⁰Th, 3.10E-4-3.16E-1 for ²²⁶Ra and 6.70E-4-4.22E-2 for ²¹⁰Pb.
اظهر المزيد [+] اقل [-]Pharmaceuticals in the environment: an educational perspective النص الكامل
2011
PURPOSE: Pharmaceuticals are an integral part of a dignified life. However, a lack of degradability and threats to the welfare of living beings cause concern due to their emission into the environment. There is also a lack of knowledge about cause and consequence. Therefore, we intend to contribute to the development of educational programmes which should increasingly include the topic ‘pharmaceuticals in the environment’. METHODS: Considering the current literature, we developed a corresponding series of worksheets (Online Resource) and sample solutions on an introductory level and integrated them into our curriculum. RESULTS: The material compiled for the worksheets was arranged in a logical order and considers several subtopics. The worksheets aim to support the examination of related aspects such as environmental effects, emissions, wastewater treatment plants, degradation, degradation by-products, advanced oxidation processes, hydraulic retention times, half-life times, biosolids, exposition pathways, precautionary principle, classification schemes for pharmaceuticals and, related to the structure–activity relationship, the design for degradability. The students managed to work on the tasks in an appropriate manner and received a good overview of the occurrence and fate of pharmaceuticals in the environment. CONCLUSIONS: Tasks that were presented to students regarding the topic ‘pharmaceuticals in the environment’ contributed to a better understanding of the possible risks of medical care on an introductory level. The tasks have been incorporated into a logic series of worksheets (Online Resource) with sample solutions available. Alternatively, the material would be appropriate for the preparation of a corresponding lecture on this topic.
اظهر المزيد [+] اقل [-]Characterization of dioxin-like contamination in soil and sediments from the “hot spot” area of petrochemical plant in Pancevo (Serbia) النص الكامل
2011
Kaisarevic, Sonja | Hilscherova, Klara | Weber, Roland | Sundqvist, Kristina L. | Tysklind, Mats | Voncina, Ernest | Bobic, Stanka | Andric, Nebojsa | Pogrmic-Majkic, Kristina | Vojinović-Miloradov, Mirjana | Giesy, John Paul | Kovačević, Radmila
Purpose Combinatorial bio/chemical approach was applied to investigate dioxin-like contamination of soil and sediment at the petrochemical and organochlorine plant in Pancevo, Serbia, after the destruction of manufacturing facilities that occurred in the spring of 1999 and subsequent remediation actions. Materials and methods Soil samples were analyzed for indicator polychlorinated biphenyls (PCBs) by gas chromatography/electron capture detection (GC/ECD). Prioritized soil sample and sediment samples from the waste water channel were analyzed for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS). Microethoxyresorufin o-deethylase (Micro-EROD) and H4IIE-luciferase bioassays were used for monitoring of dioxin-like compounds (DLC) and for better characterization of dioxin-like activity of soil samples. Results Bioanalytical results indicated high dioxin-like activity in one localized soil sample, while the chemical analysis confirmed the presence of large quantities of DLC: 3.0 × 10⁵ ng/g d.w. of seven-key PCBs, 8.2 ng/g d.w. of PCDD/Fs, and 3.0 × 10⁵ ng/g d.w. of planar and mono-ortho PCBs. In the sediment, contaminant concentrations were in the range 2-8 ng/g d.w. of PCDD/Fs and 9-20 ng/g d.w. of PCBs. Conclusions This study demonstrates the utility of combined application of bioassays and instrumental analysis, especially for developing and transition country which do not have capacity of the expensive instrumental analysis. The results indicate the high contamination of soil in the area of petrochemical plant, and PCDD/Fs contamination of the sediment from the waste water channel originating from the ethylene dichloride production.
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