液氧储罐爆炸事故树分析

采用安全系数工程的方法,对液氧储罐爆炸进行丁事故树分析,通过求事故树最小割集,进行结构重要度分析,从而对液氧储罐爆炸的事故原因进行分析、预测,并提出了相应的预防控制措施。     

水体沉积物质量基准研究现状

沉积物质量基准是对水质基准的补充,对水质管理具有重要意义。目前国际上沉积物质量基准计算方法有十几种。对各种方法的理论基础、数据需求、适用范围等方面进行了概述之后,综合分析了各种方法的理论基础。研究结果认为,应将建立沉积物质量基准的方法分为以生物效应数据为基础的生物效应数据库法和以相平衡分配原理为依据的相平衡分配法。而根据统计方法不同,生物效应数据库法又分为单值基准、双值基准和三轴图法。同时还对美国、加拿大、荷兰、英国、澳大利亚和新西兰的沉积物质量基准研究发展和应用概况进行了分析。结合我国实际情况认为,依赖于大量生物效应数据的生物效应数据库法,目前在我国的适用范围有限,只能用于推导少数几种污染物的基准值。相平衡分配法具有可靠的理论基础而且不需要大量的生物效应数据,具有很大的发展潜力。因此,对于目前沉积物质量基准研究处于初级阶段的我国,更适合使用相平衡分配法计算污染物沉积物质量基准。     

包埋固定化微生物的特性研究

文章通过实验研究了PVA与海藻酸钠混合载体包埋固定化微生物系统降解有机物的过程,并对其特性进行了分析。结果发现运行初期凝胶体有凝胶溶出现象,第一天凝胶有机物溶出高达2 173 mg,随后溶出量减少,7～8天溶出停止;同时发现包埋后的微生物活性有损伤和恢复的过程,损伤时相对活性为0.27经过恢复可达到0.85;另外,凝胶的粒径和比重等物理特性也随时间变化,最后趋于稳定。一年多运行实验发现包埋凝胶体的抗持久性也较好。这些特性的探讨将为工程应用提供理论指导。     

我国职业伤害经济损失研究

结合国情 ,在全面、系统地研究了我国工业企业职业伤害的经济损失的基础上 ,对需要明确的若干问题进行了阐述。主要内容有 :国内外职业伤害的经济损失研究现状 ;职业伤害的经济损失的调查、统计与分析技术 ;工伤事故的经济损失估算方法及其主要规律等。     

沉积物中六氯苯对颤蚓(淡水单孔蚓)的毒性效应研究

以淡水底栖动物颤蚓(淡水单孔蚓)为受试生物,研究了沉积物中六氯苯(HCB)对淡水单孔蚓14 d和28 d的毒性效应.结果表明,沉积物中HCB对颤蚓致死效应较低,当HCB浓度为190 mg· kg-,连续暴露28 d时,致死率低于8％.但HCB对颤蚓具有较强的慢性毒性效应,当HCB浓度为190 mg·kg-1,连续暴露28 d时,身体自断率高达90％,并且随着浓度升高和暴露时间延长,颤蚓自断率明显增高.HCB对颤蚓自断14 d和28 d的EC50分别为＞190 mg·kg-1和97.1 mg· kg-1.HCB对颤蚓行为(运动和挖掘)产生明显抑制作用.随着HCB浓度增加和暴露时间延长,颤蚓运动强度减弱,并伴随摄食量减少与体重减轻现象.     

基于NetLogo平台的室内学生疏散过程仿真研究

为了保证学生在突发事件发生时能够安全迅速的疏散,本文基于多主体仿真平台NetLogo,利用瓦片建立真实教室模型,赋予海龟自主移动能力,对不同出口条件、不同人数的教室内学生疏散过程进行了模拟。计算结果表明,随着学生人数的增加,疏散用时随之增大,双出口条件学生疏散用时较单出口条件可平均节约53.8%,可提高学生的安全逃生概率,并利用计算结果对教室出口条件进行了优化。     

Joint effects of Penta-BDE and heavy metals on Daphnia magna survival, its antioxidant enzyme activities and lipid peroxidation

The joint toxicity of Penta-BDE (Pe-BDE) and heavy metals including cadmium and copper on Daphnia magna (D. magna) was evaluated on the basis of determining the 48 h survival, antioxidative enzyme responses, and lipid peroxidation. The response was classified as additive, greater than additive, or less than additive by comparing the measured ??toxic units, TU?? with one. Based on the survival of D. magna, less-than-additive interactions were found in most of mixtures treatments. This may be attributed to the different toxicity mechanism between Pe-BDE and metals. Cu and Cd played a greater role in toxicity than what Pe-BDE did. As for the superoxide dismutase (SOD) and catalase (CAT) activity, most response was less than additive. For the glutathione S-transferases (GST) activity, most of the greater-thanadditive responses were found in the Cu plus Pe-BDE treatments, but the additive responses occurred in Cd plus Pe-BDE treatments and binary metal treatments. For lipid peroxide levels, which were measured as malondialdehyde (MDA) levels, less-than-additive response occurred in the 50% Cd plus 50% Cu and ternary mixture treatments. Results suggested that Pe-BDE, Cd, and Cu could induce different patterns of antioxidant enzyme responses, such as antioxidant/prooxidant responses, depending on their capability to produce reactive oxygen species and antioxidant enzymes to detoxify them.     

沉积物中Pb和Cd对泥鳅的毒性效应及其基准阈值的验证

为探讨沉积物中AVS(acid volatile sulfide,酸挥发性硫化物)和SEM(simultaneously extracted metals,同时提取金属)对重金属生物有效性和基准验证的影响,以泥鳅为受试生物,以死亡率、鳃部渗血率和体质量变化为测试终点,研究了沉积物和上覆水中重金属Pb、Cd对底栖生物的毒性效应,并对文献中Pb、Cd沉积物基准阈值进行了验证. 结果表明:沉积物中Pb、Cd对泥鳅21 d的LC₅₀(半数致死浓度)分别为391、37.0 mg/kg;上覆水中ρ(Pb2+)和ρ(Cd2+)较低,对生物毒性效应贡献可以忽略. 经验证,Pb和Cd的TEL(threshold effect level,临界效应浓度)和PEL(probable effect level,必然效应浓度)基本符合其所代表的意义,Pb、Cd加标浓度(以w计)低于其对应的TEL时不具有毒性,高于其对应的PEL时具有明显毒性,介于二者之间时毒性不确定. SEM/AVS(物质的量比)和生物死亡率有明显的相关性,当该比值大于1.00时,重金属对泥鳅有明显的毒性效应.      

Distribution, source and risk assessment of polychlorinated biphenyls (PCBs) in urban soils of Beijing, China

The concentration of PCBs in urban soils of Beijing across six land types including business districts (BD), cultural and educational areas (CE), classical gardens (CG), public green (PG), residential areas (RA), and roadsides (RD) was investigated. The total concentrations of PCBs ranged from below method detection limit (M.D.L.) to 37.11 × 10⁻³ mg kg⁻¹ dry weight (mean: 11.70 × 10⁻³ mg kg⁻¹; median: 13.28 × 10⁻³ mg kg⁻¹), which was at a medium level compared with other cities around the world. In general, the levels of PCBs decreased from the center of Beijing city to the suburb, suggesting the increasing PCBs concentrations with the age of the urban area. For different types of land use, the highest level of PCBs was observed in CG soils which have the oldest age, and the homologue profiles were similar, which were predominated by lowly chlorinated congeners including di-, tri- and tetra-CBs. Principal component analysis indicated that local sources such as Aroclor 1016, 1242, and 1248 were important sources in addition to long-range transport of PCBs all over the world. Although the toxic equivalency (TEQ) concentrations of dioxin-like PCBs in all soil samples of Beijing were higher than those in other urban areas of China, they met the Canadian soil quality standard.     

Rheology of Concentrated Cellulose Solutions in 1-Butyl-3-methylimidazolium Chloride

Rheological behavior of the concentrated cellulose/1-butyl-3-methylimidazolium chloride ([BMIM]Cl) solutions was investigated. As polymeric fluid, solutions of cellulose in [BMIM]Cl display a marked elastic behavior under shear flow. The dependence of the shear viscosity η, and of the dynamic modulus, on concentration, average degree of polymerization (DP) and temperature is discussed. At lower concentrations and degrees of polymerization (DP), cellulose solutions show viscous, inelastic behavior at low frequencies and low shear rate. At higher concentration and DP, cellulose solutions are more elastic at higher frequencies and shear rate. Such solutions also have some usual rheological properties. The dynamic rheological responses revealed that the Cox–Merz rule did not hold for these cellulose solutions at high deformation rate. Plotting storage modulus G′ against loss modulus G″ gave almost a master curve which is independent of temperature and concentration, with the slope of about 1.651 for 10 wt% cellulose solutions. This value indicates the existence of microheterogeneity in the solution system.