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Результаты 1491-1500 из 3,243
Dynamics Simulation of Vapour Assisted Ammonia Pollution Removal By Pulse Discharge Method
2015
Wang Xiaojun
Though ammonia (NH3) is one of the most highly produced inorganic chemicals in the world, its pollution disadvantage on air and water have drawn much attention. In this article, the NH3 removal is investigated through pulse discharge method. A zero dimensional molecular reaction model is established and solved. The vapour assisting effect on the NH3 gas removal is discussed due to the extremely soluble character of NH3. Simulation indicates that the vapour additive has affected the H2 and N2 generating process. For vapour with several thousand’th ratio mixed, the electron collision on H2O has been ignored. The results show that lower concentration vapour improves the removal efficiency in a very small extent, but higher vapour deteriorates it, with the optimal mixing concentration ratio between H2O and NH3 as 0.75:1000. For vapour with several tenth ratio mixed, the electron collision process on H2O molecules is considered. More H2O additive has significantly improved the NH3 removal efficiency by accelerating the H2 and N2 generation process. At the vapour ratio of 750‰, the removal efficiency is 64.28%, which is remarkably higher than that of 37.81% without vapour added. H2O additive has saving of 70% energy consumption. The initial NH3 concentration is another factor to influence the removal efficiency. The higher the initial NH3 input, the less the H2O is decomposed into OH and H by electron impact, and the removal efficiency is decreased consequently.
Показать больше [+] Меньше [-]Research on Content, Distribution and Health Risk Assessment of PAHs in Surface Dust in Shenyang City
2015
Li Yue | Zhang Le | Hou Wei | Li Yuli | Li Xiaojun
As the “source” and “collector” of PAHs, surface dust in cities, cause invisible, potential and long-term destructions to ecosystems. PAHs content in the surface dust and distributions of functional areas in Shenyang city was discussed systematically. PAHs composition differences in different functional areas were analysed. It was concluded that parks and residential districts present the least PAHs pollution, while commercial districts and roads suffer the heaviest PAHs pollution. Different functional areas show similar composition of PAHs. Most PAHs are high-ring ones, accompanied with some low-ring PAHs. The content of high-ring PAHs is proportional to the number of rings or molecular weight. PAHs pollution and health risk in Shenyang city were evaluated through various methods. Results demonstrated that PAHs pollution in Shenyang city has reached a high level, which is threatening the local ecological environment and human health significantly.
Показать больше [+] Меньше [-]Variability of Organic Matter Sources and Phytoplankton Community Structure During the 19th Century under Global Warming Background in the Chukchi Sea
2015
Qingying Zhao | Ronghua Chen | Haisheng Zhang | Peisong Yu | Bing Lu
Multi-biomarker of sediment core P7200 obtained from the Chukchi Sea during the First Chinese National Arctic Research Expedition was measured to indicate changes of the source of organic matter, the primary productivity and the phytoplankton community structure through the 19th century. The results show that the organic matters in the Chukchi Sea are mainly from the terrigenous source, marine organisms and icerafted debris, and the ratio of terrigenous and oceanic inputs has increased over the 19th century. The total primary productivity has been elevated by nearly 100% in the century and the phytoplankton community structure also exhibits significant variability. The relative abundance of diatom increases dramatically, while that of cocolith decreases obviously and almost constant for the dinoflagellate. It is suggested that the changes of the source of organic matter, the primary productivity and the phytoplankton community structure are associated with global warming. However, elevated primary productivity and the altered phytoplankton community structure may strengthen the ability of CO2 absorbing in the Chukchi Sea, which may weaken the greenhouse effect and should be regarded as one of the negative feedback mechanisms to the global warming.
Показать больше [+] Меньше [-]Effects of sand-fixing vegetation on topsoil properties in the Mu Us desert, Northwest China
2015
Fan Dongqing | Qin Shugao | Zhang Yuqing | Wu Bin | Gao Hao | Chen Dong | Zhang Jiachen | Zhu Linfeng
Planting vegetation to restore the soil environment is one of the most important methods for combating desertification. Reasonable vegetation type and vegetation coverage has an important role in sand control and the regional ecological security. The objective of this study is to clarify the appropriate type and coverage of sand-fixing vegetation in the Mu Us Desert. We identified changes in the topsoil properties as affected by different types and coverage of sand-fixing vegetation, and assessed the relationship between the soil fractal dimension (D) and major soil properties. Our results showed that: (1) with increasing cover of sand-fixing vegetation, fine soil material and soil nutrient content increased, indicating that the soil environment could accelerate restoration after planting or recovery of sand-fixing vegetation | (2) there were significant positive relationships between D and soil properties, which indicated that D was a sensitive and useful index for evaluating the influence of sand-fixing vegetation on soil physicochemical properties | and (3) recovery of natural vegetation using fencing should be given priority in areas where the soil matrix is not completely destroyed, and plant cover should be maintained at approximately 40% to 60%. We suggest that native shrubs, rather than trees, should be considered when choosing a sand-fixing vegetation.
Показать больше [+] Меньше [-]Calculation and Evaluation of Carbon Dioxide Emissions of Regional Logistics Ecosystem: A Study in China
2015
Zhou Lingyun | Gu Zhonghua | Zhao Gang | Luo Jianfeng
Regional logistics with a large quantity of energy consumption and carbon emissions has great important impacts on the regional ecological environment. Therefore, constructing the regional logistics ecosystem has become a crucial way to minimize the environmental impacts. This paper aims to accurately obtain the characteristics and causes of carbon dioxide (CO2) emissions of regional logistics ecosystem. It firstly analyses the main factors affecting carbon emissions of regional logistics ecosystem, and then builds the calculation model and the performance evaluation model of carbon emissions of regional logistics ecosystem respectively based on regional logistics activities and their energy consumption structures. According to energy consumption statistics of 30 provinces in China, it calculates the total amounts and differences of CO2 emissions of logistics activities in different regions of China. The results illustrate that the overall regional logistics ecosystem in China is in its initial stage with huge carbon emissions | and there are significant variations in CO2 emission intensities of regional logistics and CO2 emission amounts per unit of cargo turnover between different regions. This research offers accurate information for policy making of logistics industry and setting the carbon emission reduction targets in different regions of China.
Показать больше [+] Меньше [-]Adsorption of Methylene Blue by Activated Carbon from Capsicum Straw
2015
Qiu Muqing | Xuan Yannan | Luo Peichao | Wang Zebin | Shou Jianxin
Dyes are known to be toxic, carcinogenic and mutagenic. Their release into the environment can cause aesthetic pollution, and moreover, they are not degraded by conventional aerobic wastewater treatment due to their recalcitrance. Therefore, it is necessary to reduce dye concentration in the wastewater. Activated carbon was obtained from capsicum straw by chemical activation using KOH as an activator. Then it was used as an adsorbent for the removal of dye methylene blue. The adsorption of dye methylene blue by activated carbon was carried out in detail. Kinetic adsorption data were analysed by the pseudo-first-order kinetic model, the pseudo-second-order model and the intraparticle diffusion model. The experimental data were analysed by the Langmuir and Freundlich models of adsorption. The thermodynamics parameters were also calculated.
Показать больше [+] Меньше [-]Equilibrium and Thermodynamic Studies for Adsorption of 1,4-Benzoquinone by Fly Ash
2015
Li Guoting | Feng Yanmin | Chai Xiaoqi | He Xiaoshuang
Fly ash, an industrial waste from thermal power plants, was used for the adsorptive removal of 1,4-benzoquinone, one of the oxidation intermediates generated in AOPs. Effect of fly ash dosage and solution pH was investigated. The highest 1,4-benzoquinone uptake occurred at pH 7.0. Neutral and alkaline conditions were more favourable for the adsorptive removal of 1,4-benzoquinone. Isotherm data at 288, 298 and 308 K were simulated by Langmuir, Freundlich, Temkin, Redlich-Peterson, Koble-Corrigan and Dubinin-Radushkevich isotherm models. Both the Koble-Corrigan and Dubinin-Radushkevich isotherms can predict equilibrium adsorption behaviour better at different reaction temperatures. The reaction enthalpy was 29.42 kJ/mol and the entropy achieved 164.52 J/mol·K. The change of Gibbs free energy achieved -19.48 kJ/mol at 298 K. The above indicates that the sorption process was spontaneous and endothermic. This also reveals that, fly ash has the potential for the adsorptive removal of 1,4-benzoquinone.
Показать больше [+] Меньше [-]Quinalphos Induced Oxidative Stress Biomarkers in Liver and Kidney of Common Carp, Cyprinus Carpio
2015
Padmanabha A. | Reddy H. R. V. | Bhat Avinash | Khavi Muttappa
Oxidative stress responses were evaluated in liver and kidney of freshwater fish, Cyprinus carpio exposed to organophosphorus pesticide, quinalphos (25% emulsified concentration). Lipid peroxidation levels and antioxidant enzyme activities were measured spectrophotometrically in liver and kidney of fish, treated with two sub-lethal concentrations of quinalphos viz., 0.275 ppm and 0.55 ppm along with control as a reference for 4, 8, 16 and 32 days. The experimental concentration of quinalphos evoked different degrees of activity in both the tissues, the liver and the kidney. The significant increase in lipid peroxidation suggests quinalphos-mediated free radical production | the increase in the activity of glutathione-S-transferase with corresponding increase in the activity of glutathione reductase indicates the glutathione conjugation of the pesticide | activity of superoxide dismutase, catalase and glutathione peroxidase decreased drastically after 32nd day exposure to sub-lethal concentrations of pesticide. Overall, the results demonstrate that alteration in the antioxidant enzymes, glutathione system and induction of lipid peroxidation reflects the toxicity of quinalphos which may cause oxidative stress in the experimental fish. The study, therefore, provides a rational use of biomarkers of oxidative stress in biomonitoring programs.
Показать больше [+] Меньше [-]Nitrate Pollution in the Groundwater of Different Cropping Systems of Varanasi District, Uttar Pradesh, India
2015
Prasad Mahendra | Raha Priyankar
The occurrence of high nitrate levels in groundwater has to be recognized as a threat to humans and animals. Infant methaemoglobinaemia and nitrate poisoning in livestock occur at unexpected times and places. Nitrate pollution in the groundwater is one of the major pollution problems. In the last few decades nitrate concentration in groundwater has increased dramatically. Groundwater contamination by nitrate (NO3-) is a global problem and is most often associated with leachates derived from fertilizers and animal or human wastes. The study presented here was carried out in Varanasi district. The nitrate content in water was investigated during premonsoon (March-April, 2013) and postmonsoon (November-December, 2013) seasons and compared with the standard values given by WHO. Eighty four, from different cropping systems (i.e. rice-wheat, rice-vegetable, vegetable-vegetable, pulse-pulse, orchard and sugarcane) groundwater samples were collected from the bore wells. The analysis of nitrate in these water samples reveals that some villages have a high concentration of nitrate, exceeding permissible limits of WHO (45 mg/L), which is due to the more than the required quantity of nitrogen based fertilizers, water, manure and pesticides are used extensively which all contribute to the non point source contamination of nitrates in groundwater of the study area.
Показать больше [+] Меньше [-]Performance Evaluation of Sewage Treatment Plants (STPs) in Multistoried Buildings
2015
Ganesan Jayanthi | Namasivayam Vasudevan
The enormous generation of wastewater in a relatively small area i.e., in a multistoried building, makes mandatory to have a mini Sewage Treatment Plant (STP) inside the premises itself. In a developing country like India, where competition for freshwater supplies will continue to increase, it is better to reuse the treated wastewater to meet the demand. Many treatment technologies are available currently, hence it is essential to find an appropriate technology for treating the wastewater. This study is to know about the different STP’s installed in the multistoried buildings, to analyse the performance of each technology, its design concepts and the life cycle costing of each system. Four technologies, namely Extended Aeration, SBR, MBR and FBBR were selected for the study. From the study, it was observed that, extended aeration is a preferred technology as per as the efficiency of the plant in treating the wastewater. From this study, it is concluded that, even though efficiency of the system is very important, a decision is made in finding an appropriate technology based on its relative closeness to its both, positive ideal solution and negative ideal solution (using TOPSIS) and found that SBR is a best technology based on the criteria selected.
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