Composition,distribution and sources of polycyclic aromatic hydrocarbons in sediments of the western harbour of alexandria,egypt

Aim and Background  Little data are available on the levels of polycyclic aromatic hydrocarbons (PAHs) in the sediments of the Mediterranean Sea Coast of Egypt in general and the Alexandria coastal zone in particular. It was therefore deemed necessary to set up a monitoring programme to determine the current concentrations of PAHs in bottom sediments, and to identify any area where high concentrations of these potential hazardous contaminants were present in the Western Harbour of Alexandria. Methods  The composition, distribution and the source of PAHs in surficial sediments of the harbour were investigated. To document the spatial PAH input, surficial sediment samples from 23 locations throughout the harbour were analysed. as]Results and Discussion The total PAH load determined in the surficial sediment samples ranged from 8 to 131150 ng g¹ dry wt, generally with most of the samples having total concentrations of PAHs greater than 5000 ng g¹ dry weight. The highest concentration of total PAHs was recorded in sediments of the inner harbour. Ratio values of specific compounds such as phenanthrene to anthracene, fluoranthrene to pyrene, methyl-phen-anthrene to phenanthrene, methyl-dibenzothiophenes to dibenzothiophenes, alkylated to non-alkylated and high molecular weight to low molecular weight PAH, were calculated to evaluate the possible source of PAH contamination in the harbour sediments. Conclusions  Two main sources of PAH in the study area have been found: pyrolytic and petrogenic. Interferences of rather petrogenic and pyrolytic PAH contaminations were noticed for most samples. The dominant sources of PAH appear to be the combustion processes through run-off, industrial and sewage discharges, and atmospheric input. The concentrations of PAHs were generally above levels expected to cause adverse biological effects. Recommendations and outlook  Information from this study and any other relevant studies should be useful in designing future strategies for environmental protection and management of the harbour.     

原油罐金属底板的腐蚀与防护

针对原油罐区的腐蚀现状，分析了原油罐底板的腐蚀机理，通过对原油一罐的腐蚀调查、底板测厚，以及对罐底脱水中腐蚀介质及沉积物样的化学分析，提出了使用WF－50防腐涂料加阴极保护的方案，该方案可有效地防止原油罐金属底板的腐蚀。     

IDS在维护图书馆网络安全中的缺陷及改进

文章分析了图书馆网络安全,并就IDS存在的缺陷以及降低IDS误报率提出了改进的方法,最后结合工作实际提出把改进后的DIDS应用于目前图书馆的网络安全管理.     

数据库规范化技巧

提供了一系列分析和处理数据的技巧及相应的步骤，使用这些技巧可以在设计数据表时避免某些问题。     

盛花期调节群体底层透光率对棉花产量的影响

在生育稳健、盛花期叶面积指数偏大的棉田 ,以整枝为手段 ,把群体底层透光率调节到 2 2 3%、5 18%和 8 90 % 3个水平。测产表明 ,透光率为 5 18%的处理的成铃率和子棉产量都极显著高于透光率过低和过高的处理 ,其中透光率为 8 90 %的处理子棉产量最低 ,比透光率为 2 2 3%的处理减产达显著水平     

罐底提离时的下节点应力计算

当安装于罐顶上的呼吸阀失灵，或罐内液体的汽化速度增大而又不能及时排放时，罐内的压力增高，部分罐底可能会离开基础而发生罐底提离现象。此时，在下节点处存在着较大的应力，甚至会造成油罐在下节蹼处的破坏。     

Prolonged elevated atmospheric CO2 does not affect decomposition of plant material

Prolonged elevated atmospheric CO₂ might alter decomposition. In a 90-day incubation study, we determined the long-term (9 years) impact of elevated CO₂ on N mineralization of Lolium perenne and Trifolium repens plant material grown at ambient and elevated CO₂ and low- and high-¹⁵N fertilizer additions. No significant differences were observed in recovery rates between any of the treatments, except an N addition effect was observed for L. perenne (0.4 versus 0.5% day⁻¹ in high versus low N). The results suggest that elevated CO₂ did not change plant N mineralization in any of the soils, because of a surplus of available N in the fertilized and leguminous systems, and because of insignificant plant responses to elevated CO₂ in the low soil N availability systems.     

水库调洪演算图解法在施工导流中的应用

混凝土或浆砌石坝施工中,底孔导流被广泛采用。底孔导流施工中的二期围堰高程的确定需要考虑水库调蓄作用,进行调洪演算。     

弧底梯形明渠正常水深的简化计算法

弧底梯形断面明渠正常水深计算涉及高次方程求解,无法直接完成。由于目前工程上采用的试算法及图表法存在计算烦琐且精度不高问题,而利用计算机求解又涉及编程不便实际应用。本文采用多参数优化拟合的方法,以标准剩余差最小为目标函数,在工程适用参数范围内,经逐次逼近拟合计算获得了表达形式简单、求解精度较高的近似公式,具有一定的实用意义。     

高层建筑物的防雷

简要介绍了直击雷、侧击雷、雷电波侵入的相关知识及防雷措施,并举例说明防雷措施在高层建筑物中的应用。