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Segal-Rozenhaimer M Shavit U Vengosh A Gavrieli I Farber E Holtzman R Mayer B Shaviv A 《Journal of environmental quality》2004,33(4):1440-1451
The Lower Jordan River is located in the semiarid area of the Jordan Valley, along the border between Israel and Jordan. The implementation of the water sections of the peace treaty between Israel and Jordan and the countries' commitment to improve the ecological sustainability of the river system require a better understanding of the riverine environment. This paper investigates the sources and transformations of nitrogen compounds in the Lower Jordan River by applying a combination of physical, chemical, isotopic, and mathematical techniques. The source waters of the Lower Jordan River contain sewage, which contributes high ammonium loads to the river. Ammonium concentrations decrease from 20 to 0-5 mg N L(-1) along the first 20 km of the Lower Jordan River, while nitrate concentrations increase from nearly zero to 10-15 mg N L(-1), and delta(15)N (NO(3)) values increase from less than 5 per thousand to 15-20 per thousand. Our data analysis indicates that intensive nitrification occurs along the river, between 5 and 12 km from the Sea of Galilee, while further downstream nitrate concentration increases mostly due to an external subsurface water source that enters the river. 相似文献
293.
Holtzman R Shavit U Segal-Rozenhaimer M Gavrieli I Marei A Farber E Vengosh A 《Journal of environmental quality》2005,34(3):897-906
The flow rate of the Lower Jordan River has changed dramatically during the second half of the 20th century. The diversion of its major natural sources reduced its flow rate and led to drying events during the drought years of 2000 and 2001. Under these conditions of low flow rates, the potential influence of external sources on the river discharge and chemical composition became significant. Our measurements show that the concentrations of chloride, calcium, and sodium in the river water decrease along the first 20-km section, while sulfate and magnesium concentrations increase. These variations were addressed by a recent geochemical study, suggesting that ground water inflow plays a major role. To further examine the role of ground water, we applied mass-balance calculations, using detailed flow rate measurements, water samplings, and chemical analyses along the northern (upstream) part of the river. Our flow-rate measurements showed that the river base-flow during 2000 and 2001 was 500 to 1100 L s(-1), which is about 40 times lower than the historical flow rates. Our measurements and calculations indicate that ground water input was 20 to 80% of the river water flow, and 20 to 50% of its solute mass flow. This study independently identifies the composition of possible end-members. These end-members contain high sulfate concentration and have similar chemical characteristics as were found in agricultural drains and in the "saline" Yarmouk River. Future regional development plans that include the river flow rate and chemistry should consider the interactions between the river and its shallow ground water system. 相似文献
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高层建筑发生火灾后,保护人员的安全是个十分重要的问题。把楼内的一定区域设计为避难区或安全区,并对该区进行正压送凤,可以防止火灾烟气进入,从而使人们免受烟气的影响。本文讨论了避难区内外压差的计算方法,指出此压差取在25-85Pa范围内为宜,分析了外界风速、建筑物的窗户破裂及门的开启或关闭对压差产生的影响,并对间接加压方案作了探讨. 相似文献
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隧道火灾纵向通风下羽流触顶区温度变化研究 总被引:5,自引:1,他引:5
根据Boussinesq相似性,利用流体力学基本方程,建立隧道火灾羽流三维模型,并借助量纲分析方法,推导了触顶区温升公式.在假设的隧道模型下,通过改变火源功率和纵向风速设计了多个算例,利用温升公式进行计算,并与场模拟结果比较,归纳了触顶区温度的变化规律.结果表明,同一火源功率下,触顶区温度随纵向风速增加而降低,并趋于一稳定值,其大小约为最高温度的1/3.还对温降过程中的突变现象进行了分析,讨论了中心低温区及不同羽流对温度的影响.最后对火灾救援的通风策略提出了建议. 相似文献
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A laboratory study was performed to assess the biodegradation of lube oil in bio-reactor with 304# stainless steel as a biofilm carrier.Among 164 oil degrading bacterial cultures isolated from oil contaminated soil samples, Commaonas acidovorans Pxl, Bacillus sp.Px2, Pseudomonas sp. Px3 were selected to prepare a mixed consortium for the study based on the efficiency of lube oil utilization.The percentage of oil degraded by the mixed bacterial consortium decreased slightly from 99% to 97.2% as the concentration of lube oil was increased from 2000 to 10,000 mg/L. The degradation of TDOC (total dissolved organic carbon) showed a similar tendency compared with lube oil removal, which indicated that the intermediates in degradation process hardly accumulated. Selected mixed bacterial consortium showed their edge compared to activated sludge. Scanning electron microscopy (SEM) photos showed that biofilms on stainless steel were robust and with a dimensional framework constructed by EPS (extracellular polymeric substances),which could promote the biodegradation of hydrocarbons. The increase of biofilm followed first-order kinetics with rate of 0.216 μg glucose/(cm~2·day) in logarithm phase. With analysis of Fourier transform infrared spectroscopy (FT-IR) and gas chromatography-mass spectrometry (GC-MS) combined with removal of lube oil and TDOC, mixed bacterial consortium could degrade benzene and its derivatives, aromatic ring organic matters with a percentage over 97%. 相似文献
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