线源扩散的快速模拟

提出了一种计算风向与线源成任意角时任意长地面线源大气扩散的简化模式。通过与数值积分方法计算结果的比较表明,模式的最大相对误差在风向与线源平行时最大,但不超过18％。随风向与线源夹角的增大,相对误差迅速减小,当夹角大于5°时,已小于2％。为城镇公路网大气扩散的快速、准确模拟提供了新手段。     

Accident consequence calculation of ammonia dispersion in factory area

With the widespread use of ammonia in the process industry, more and more accidents were caused by ammonia leakage and dispersion. The dispersion of ammonia is determined by its physical properties, release source conditions and atmospheric environment. Full-scale numerical simulation based on CFD theory was carried out to study the dispersion law of ammonia in a food factory. It was found that ammonia concentrated on the symmetric plane and showed an upward movement near the source. Moreover, the effect of pressure on the dispersion of ammonia was explored showing that the concentration of ammonia near the source increased with the increase of pressure, while the dispersion of ammonia far from the source is mainly influenced by wind field. Last but not the least, the dangerous area completely covers the obstacle region according to the harmful concentration, but the lethal concentration range and explosion range both only existed near the release source. Correspondingly, the concentration of ammonia in the region far from the symmetric plane can be regarded as a safe area. When the accident happens, one should stay away from the release source and evacuate towards the sides in a timely manner. We hope that this work can provide an effective method in predicting the impact of ammonia dispersion and can arouse concerns over the public safety.     

On the non-monotonic wind influence on flammable gas cloud from CFD simulations for hazardous area classification

Hazardous areas are defined as a result of a variety of variables as storage temperature, pressure, leak orifice size, physical properties of flammable substance, and wind characteristics. The potential formation of an explosive atmosphere must be accurately assessed to ensure process safety. Therefore, computational fluid dynamics (CFD) arises as an important tool for accurate predictions as recommended by the international standard IEC 60079-10-1 (2015). This study aims to analyze the influence of wind velocity magnitude and direction on the hazardous area classification. The authors evaluated the extent and volume for methane, propane, and hydrogen leakages from a CFD model. For each flammable gas, the wind velocity magnitude and direction were regularly varied. The outcomes show that the behavior of the plume size as the wind varies mainly depends on the gas concentration. Counter-flow wind directions lead to zero relative velocity closer to the release point, which concentrates the gas, and wind in the release direction promotes a higher dilution of the gas cloud increasing the hazardous extent while decreases the volume. As a consequence, the wind also influences the zone type, which was accurately predicted from CFD simulations and significant differences were found when compared to the standard analyses. These differences are, to some extent, related to the consideration of wind velocity effects on the gas jet release.     

基质固相分散-快速溶剂萃取-GC/MS法同时测定土壤中有机氯农药和多环芳烃

建立了基质固相分散-ASE提取-GC/MS法同时测定土壤中8种有机氯农药和16种多环芳烃的方法。对方法的线性、检出限、精密度、回收率及土壤质控样品进行了分析,结果表明,8种有机氯农药和16种多环芳烃线性良好,相关系数为0.997 5～0.999 8,方法检出限为0.39～1.57μg/kg,空白加标样品的相对标准偏差小于20%,实际土壤样品加标回收率为60.6%～125%,土壤质控样品结果均在范围内。该方法能够满足土壤中8种有机氯农药和16种多环芳烃的检测要求。     

A study of the atmospheric dispersion of a high release of krypton-85 above a complex coastal terrain, comparison with the predictions of Gaussian models (Briggs, Doury, ADMS4)

Atmospheric releases of krypton-85, from the nuclear fuel reprocessing plant at the AREVA NC facility at La Hague (France), were used to test Gaussian models of dispersion. In 2001-2002, the French Institute for Radiological Protection and Nuclear Safety (IRSN) studied the atmospheric dispersion of 15 releases, using krypton-85 as a tracer for plumes emitted from two 100-m-high stacks. Krypton-85 is a chemically inert radionuclide. Krypton-85 air concentration measurements were performed on the ground in the downwind direction, at distances between 0.36 and 3.3 km from the release, by neutral or slightly unstable atmospheric conditions. The standard deviation for the horizontal dispersion of the plume and the Atmospheric Transfer Coefficient (ATC) were determined from these measurements. The experimental results were compared with calculations using first generation (Doury, Briggs) and second generation (ADMS 4.0) Gaussian models. The ADMS 4.0 model was used in two configurations; one takes account of the effect of the built-up area, and the other the effect of the roughness of the surface on the plume dispersion. Only the Briggs model correctly reproduced the measured values for the width of the plume, whereas the ADMS 4.0 model overestimated it and the Doury model underestimated it. The agreement of the models with measured values of the ATC varied according to distance from the release point. For distances less than 2 km from the release point, the ADMS 4.0 model achieved the best agreement between model and measurement; beyond this distance, the best agreement was achieved by the Briggs and Doury models.     

平稳地震地面运动改进金井清谱的相关函数模型

胡聿贤平稳地震地面运动谱模型是对Kanai-Tajimi模型的一种改进。通过数学推导证明胡聿贤谱是将基岩地震动模拟为过滤白谱过程,经具有某种特性的线性单自由度土层滤波后而形成的,从而在物理上解释了胡聿贤模型的合理性;研究了低频截止频率的作用,推导出胡聿贤模型的相关函数的表达式。本文所得结果可为结构随机地震反应时域分析提供基础。     

Assessment of Air Quality, Emissions and Management in a Local Urban Environment

This paper describes one example of how the UK National Air Quality Strategy (NAQS) is implemented in a local urban environment. The paper reviews the beginning of this process, by examining the review and assessment procedures of the NAQS in the London Borough of Barnet. By the application of available UK tools of local air quality management (LAQM), the process began through analysis of the levels of local emissions and progressed onto modelling of current and future air quality. A map showing combined emission hotspot areas for the Borough indicated and higher emission rates occur in the south of the Borough and along the major transport corridors, as road sources dominate emissions. Dispersion modelling studies were also conducted for this purpose, using the screening models GRAM, PGRAM and ADMS Urban for an in-depth assessment. These analyses found that some local point sources and the majority of Borough roads with over 20,000 vehicles per day produced exceedances of the future objectives for air quality for some pollutants.Recommendations for the progression of LAQM in the Borough are made and include the update and expansion of the emissions information held for use in future modelling studies. The paper demonstrates the experience of implementing the Strategy, using the tools and procedures available for this purpose, in a local urban environment that is similar to many in the UK.     

基于磁性多壁碳纳米管的涡旋辅助分散基质固相萃取-高效液相色谱检测水中双酚A

针对分散基质固相萃取中吸附剂与液相难以彻底分离等问题,合成磁性多壁碳纳米管作为吸附剂,结合液相色谱检测,建立了基于涡旋辅助磁性分散基质固相萃取检测水中双酚A的分析方法。磁性多壁碳纳米管与液相可以实现简便、彻底的分离,省略分散基质固相萃取中的过滤或离心步骤。在优化条件下,方法检出限为0.02μg/L,线性范围为0.05~10μg/L(r=0.999 2)。将该方法用于实际水样的分析,相对回收率为89.6%。     

厌氧污泥性质对超声破解效率的影响

超声破解是污泥溶胞-隐性生长处理的一种重要前处理手段,破解效果受到超声条件及污泥性质的影响。以厌氧污泥破解后溶解性化学需氧量的增加值和污泥溶出破解率为评价指标,通过不同性质的厌氧污泥超声破解实验,探讨不同的污泥性质对厌氧污泥破解效果的影响,为厌氧污泥的下一步隐性生长处理提供良好条件。控制在超声频率为20kHz,超声声能密度1.2 W/mL,超声辐照时间20 min的条件下进行破解实验,实验结果表明,污泥的初始温度、pH值和污泥浓度等参数对厌氧污泥破解效率影响较大。     

A method for the analysis of organophosphorus pesticide residues in Mexican axolotl

A method based on matrix solid-phase dispersion (MSPD) was developed for quantitative extraction of three organophosphorus pesticides (OPPs) from the Mexican axolotl, Ambystoma mexicanum. The determination was carried out using high- performance liquid chromatography (HPLC) with diode array spectrophotometric UV detection (DAD). The MSPD extraction with octadecylsilyl (C18) sorbent combined with a silica gel clean-up and acetonitrile elution was optimised for chlorpyrifos, fenthion and methyl parathion. The method was validated, yielding recovery values higher than 90%. The precision, expressed as the relative standard deviation (RSD), was less than or equal to 6% in muscle samples at spiking levels of 10 and 5 ppm. Linearity was studied from 15 to 60 ppm for chlorpyrifos and fenthion, and from 7.5 to 30 ppm for methyl parathion. The limits of detection (LODs) were found to be less than or equal to 0.5 ppm_.This method was applied to the analysis of samples from a chlorpyrifos-exposed axolotl, demonstrating its use as an analytical tool for toxicological studies.