An experimental investigation of an inertization effectiveness of fluorinated hydrocarbons in relation to premixed H2–N2O and CH4–N2O flames

An experimental investigation of an influence of trifluoromethane CHF_3, pentafluoroethane C₂HF₅ and perfluorobutane C₄F₁₀ on near-limit hydrogen-nitrous oxide and methane-nitrous oxide premixed flames was performed. Flammability limits, a maximum explosion pressure ΔP_max, maximum rate of pressure rise (dP/dt)_max, and a laminar burning velocity S_u were determined. The flammability area in the case of N₂O as an oxidizer is substantially wider than for the case of the oxidizer which is the mixture of oxygen and nitrogen with the O₂ content 25% (vol.). The dependences of S_u, ΔP_max and (dP/dt)_max on concentration of the fluorinated hydrocarbons are characterizing by an availability of maxima which positions are close to the peak concentrations of the flammability regions. A qualitative interpretation of the results obtained is given.     

Effect of self-inhibition at a flame propagation in rich gaseous mixtures of combustible–air–diluent

An analysis of published experimental data characterizing the influence of diluents of various chemical nature (both halogenated and chemically inert) on upper flammability limits of flammable gases in air (methane and hydrogen have been considered as examples) has been done. Dependences of critical oxygen concentration and critical fuel equivalence ratio _cr for mixtures combustible–air–diluent at upper flammability limits on diluent concentration were determined. The obtained data were interpreted on the basis of the concept of self-inhibition at combustion of rich mixtures of organic combustibles in air. A method for evaluation of relative effectiveness of various inhibitors and for determination of availability of self-inhibitive properties of a combustible gas has been proposed.     

乙醇汽油自燃温度及爆炸极限测试

为评估不同标号乙醇汽油(E10)的燃爆危险特性,补充完善乙醇汽油的技术指标,首次采用AIT551自燃温度测试仪和FRTA爆炸极限测试仪测试了E10的自燃温度和爆炸极限,并分析了温度对乙醇汽油爆炸极限的影响规律。结果表明:90号、93号、97号E10自燃温度分别为373℃、339℃、373℃,对应着火延迟时间为8 s、9 s、8s;90号、93号、97号E10的爆炸范围分别为1.223%~8.292%、1.343%~8.893%、1.294%~8.546%;温度从20℃升高至120℃,93号E10的爆炸范围从1.491%~8.765%变宽至1.318%~9.103%,即E10蒸气爆炸极限范围随温度升高而变宽;推导了测量E10蒸气爆炸极限时待测样品量预估计的公式。     

Relationship of traffic fatality rates to maximum state speed limits

Objectives: The objective of this study was to examine the safety effects of increases in U.S. state maximum speed limits during the period 1993–2013.

Methods: Poisson regression was used to model state-by-state annual traffic fatality rates per mile of travel as a function of time, the unemployment rate, the percentage of the driving age population that was younger than 25, per capita alcohol consumption, and the maximum posted speed limit on any road in the state. Separate analyses were conducted for all roads, interstates and freeways, and all other roads.

Results: A 5 mph increase in the maximum state speed limit was associated with an 8% increase in fatality rates on interstates and freeways and a 4% increase on other roads. In total, there were an estimated 33,000 more traffic fatalities during the years 1995–2013 than would have been expected if maximum speed limits had not increased. In 2013 alone, there were approximately 1,900 additional deaths—500 on interstates/freeways and 1,400 on other roads.

Conclusions: There is a definite trend of increased fatality risk when speed limits are raised. As roadway sections with higher speed limits have become more ubiquitous, the increase in fatality risk has extended beyond these roadways. The increase in risk has been so great that it has now largely offset the beneficial effects of some other traffic safety strategies. State policy makers should keep this trade-off in mind when considering proposals to raise speed limits.     

根据循证医学理论和方法研制我国的《非常规工作制条件下职业接触限值调整指南》

对我国现行的职业接触限值及其制订依据进行梳理,系统研究美国、加拿大等国家职业接触限值调整的原理及方法,根据循证医学的理论和方法,确定我国《非常规工作制条件下职业接触限值调整指南》的制定依据、基本框架,梳理重要术语以及核心技术参数等,并对722种化学有害因素进行分类,包括修改魁北克模型第三版中73种物质的分类,比较核对我国现行职业接触限值标准（GBZ2.1-2007）,依据GBZ2.1的编制说明以及其他相关资料,补充魁北克模型中尚未涵盖的36种物质及其分类,在此基础上,进一步讨论《指南》解决的核心问题及需进一步配套进行的科学研究。     

水中几种有机污染物的SPE-HPLC联用测定技术

酚类及硝基苯是水中一类重要的优先控制污染物。通过对固相萃取 (SPE)技术与高效液相色谱 (HPLC)联用技术的研究 ,得出对于含酚类及硝基苯的水样采用 2 0 0mg的键合硅胶C1 8柱在水样pH值为 3 .0和过柱水样为 40mL时可得到较好的萃取及测定结果 ,从而提出一种对水中酚类物质及硝基苯测定具有灵敏度高、准确性好的分析方法。     

汽车涂料生产环节VOCs的排放特征及安全评价

选择某汽车涂料的生产车间为研究对象,根据汽车涂料生产工艺的不同环节,在3个生产车间选定了8个采样点,用气质联用仪分析了汽车涂料车间内不同生产环节的挥发性有机物(volatile organic compounds,VOCs)的种类及浓度水平,并通过比较各种VOC的浓度与国家卫生部规定的工作场所有毒物质职业接触限值中短时接触容许浓度,对车间工人健康的影响进行了评价.结果表明,汽车涂料生产车间内共检测出15种主要的VOCs,包括苯、甲苯、乙苯、二甲苯、乙酸乙酯、乙酸丁酯、甲基异丁基酮、丙二醇甲醚醋酸酯、三甲苯、乙二醇丁醚等,其浓度检出范围为0.51~593.14 mg·m-3.生产车间各生产环节处TVOCs浓度显著不同,同一生产环节不同批次的气体样品中VOCs浓度也存在较大差异.二甲苯和乙酸丁酯是生产车间室内空气的主要VOCs.在生产高峰期部分VOCs浓度超过了工作场所有毒物质职业接触限值,需采取相应控制措施以保障工人健康.     

美国工业点源排放控制经验对中国的借鉴研究

文章分析了以排放限值为主要手段的美国工业水污染控制体系.美国工业水污染控制体系包括基于水质的排放限值和基于技术的排放限值,两者相辅相成,互为补充,不仅促使工业点源排放量不断降低,而且按照水质标准维护自然水体健康.在此基础上,文章提出了美国经验对中国水污染控制政策的三点启示:一是基于水质的排放限值与基于技术的排放限值分开设置,二是基于技术的排放限值始终保持先进性,三是重视统计学方法在排放限值制定中的应用.     

我国农村生活污水处理地方标准现状、问题及对策建议

农村生活污水处理设施水污染排放标准关系到农村生活污水治理技术的选取、建设投资及运行维护,科学合理地制定排放标准具有重要意义。对我国30个省（区、市）已发布的农村生活污水处理设施水污染物排放地方标准的适用范围、分级分类情况、污染物控制指标选取及限值、监测采样方法等进行了对比分析,发现我国农村生活污水污染物排放地方标准存在适用范围及分级分类不科学、指标限值区域化不明显、监测及采样方法不明确等问题。针对上述问题提出根据功能分区及处理规模科学制定分级分类标准,因地制宜地选取污染物控制指标,指标限值应做到宽严相济,进一步明确监测频次及采样方法,强化标准的基准研究等相关建议,以期为完善农村生活污水处理标准体系提供指导与借鉴。     

Heavy Metal Load Of Soil, Water And Vegetables In Peri-Urban Delhi

Peri-urban lands are often used for production of vegetables for better market accessibility and higher prices. But most of these lands are contaminated with heavy metals through industrial effluents, sewage and sludge, and vehicular emission. Vegetables grown in such lands, therefore, are likely to be contaminated with heavy metals and unsafe for consumption. Samples of vegetables i.e., spinach (Spinacia oleracea L.) and okra (Abelmoschus esculentus L.); soil and irrigation water were collected from 5 peri-urban sites of New Delhi to monitor their heavy metal loads. While heavy metal load of the soils were below the maximum allowable limit prescribed by the World Health Organization (WHO), it was higher in irrigation water and vegetable samples. The spinach and okra samples showed Zn, Pb and Cd levels higher than the WHO limits. The levels of Cu, however, were at their safe limits. Metal contamination was higher in spinach than in okra. Spatial variability of metal contamination was also observed in the study. Bio-availability of metals present in soil showed a positive relationship with their total content and organic matter content of soil but no relationship was observed with soil pH. Washing of vegetables with clean water was a very effective and easy way of decontaminating the metal pollution as it reduced the contamination by 75 to 100%.