Study of the explosion parameters of vapor–liquid diethyl ether/air mixtures

The knowledge of the vapor–liquid two-phase diethyl ether (DEE)/air mixtures (mist) on the explosion parameters was an important basis of accident prevention. Two sets of vapor–liquid two-phase DEE/air mixtures of various concentrations were obtained with Sauter mean diameters of 12.89 and 22.90 μm. Experiments were conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at an ignition energy of 40.32 J and at an initial room temperature and pressure of 21 °C and 0.10 MPa, respectively. The effects of the concentration and particle size of DEE on the explosion pressure, the explosion temperature, and the lower and upper flammability limits were analyzed. Finally, a series of experiments was conducted on vapor–liquid two-phase DEE/air mixtures of various concentrations at various ignition energies. The minimum ignition energies were determined, and the results were discussed. The results were also compared against our previous work on the explosion characteristics of vapor–liquid two-phase n-hexane/air mixtures.     

Improving the prediction of air pollution peak episodes generated by urban transport networks

This paper illustrates the early results of ongoing research developing novel methods to analyse and simulate the relationship between trasport-related air pollutant concentrations and easily accessible explanatory variables. The final scope is to integrate the new models in traditional traffic management support systems for a sustainable mobility of road vehicles in urban areas.This first stage concerns the relationship between the hourly mean concentration of nitrogen dioxide (NO₂) and explanatory factors reflecting the NO₂ mean level one hour back, along with traffic and weather conditions. Particular attention is given to the prediction of pollution peaks, defined as exceedances of normative concentration limits. Two model frameworks are explored: the Artificial Neural Network approach and the ARIMAX model. Furthermore, the benefit of a synergic use of both models for air quality forecasting is investigated.The analysis of findings points out that the prediction of extreme concentrations is best performed by integrating the two models into an ensemble. The neural network is outperformed by the ARIMAX model in foreseeing peaks, but gives a more realistic representation of the concentration's dependency upon wind characteristics. So, the Neural Network can be exploited to highlight the involved functional forms and improve the ARIMAX model specification. In the end, the study shows that the ability to forecast exceedances of legal pollution limits can be enhanced by requiring traffic management actions when the predicted concentration exceeds a lower threshold than the normative one.     

Use of Population Viability Analysis to Evaluate CITES Trade‐Management Options for Threatened Marine Fishes

Abstract: Achieving multiple conservation objectives can be challenging, particularly under high uncertainty. Having agreed to limit seahorse (Hippocampus) exports to sustainable levels, signatories to the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) were offered the option of a single 10‐cm minimum size limit (MSL) as an interim management measure for all Hippocampus species (≥34). Although diverse stakeholders supported the recommended MSL, its biological and socioeconomic implications were not assessed quantitatively. We combined population viability analysis, model sensitivity analysis, and economic information to evaluate the trade‐off between conservation threat to and long‐term cumulative income from these exploited marine fishes of high conservation concern. We used the European long‐snouted seahorse (Hippocampus guttulatus) as a representative species to compare the performance of MSLs set at alternative biological reference points. Our sensitivity analyses showed that in most of our scenarios, setting the MSL just above size at maturity (9.7 cm in H. guttulatus) would not prevent exploited populations from becoming listed as vulnerable. By contrast, the relative risk of decline and extinction were almost halved—at a cost of only a 5.6% reduction in long‐term catches—by increasing the MSL to the size reached after at least one full reproductive season. On the basis of our analysis, a precautionary increase in the MSL could be compatible with sustaining fishers' livelihoods and international trade. Such management tactics that aid species conservation and have minimal effects on long term catch trends may help bolster the case for CITES trade management of other valuable marine fishes.     

Limitations in the SAR Use

Summary The paper discusses several aspects of the practical application of the SAR. It is shown that the unit is an ideal solution for basic research and laboratory experiments. SAR is directly nonmeasurable unit. Although methods and devices based upon indirect SAR measurements may widen our knowledge about EM energy distribution and absorption within a body. It is shown that for practical applications the temperature SAR measurement methods are not sensitive enough while methods based upon E(H) measurement are less accurate than traditional approaches. As a result of assumption SAR = 4 W/kg as a basic restriction the present protection standards are illogical and nonrealiazable. A return to traditional units (E, H, S) in the standards and surveying metrology is suggested.     

关于中国在用汽车排污控制的若干问题--柴油车部分

文章结合《点燃式发动机汽车排气污染物排放限值及测量方法（双怠速法及简易工况法）》（GB18285—2005）修订中的重大问题阐述中国在用汽油车排气烟度控制方面的新要求。主要包括：增加高怠速排污检测、对电喷汽车增加过量空气系数（λ）的限定、新规定了国1以来的在用汽油车双怠速排放限值、双燃料车要对两种燃料分别检测、对简易工况检测法作了规定、制定简易工况检测法排放限值的基本原则和方法、供地方参考的排放限值等。     

Detection limits can influence the interpretation of pesticide monitoring data in Canadian surface waters

Water quality monitoring programs rely on residue data that are frequently left censored, due to some observations occurring below the Method Detection Limit (MDL). Our objective was to determine the influence the MDL has on the interpretation of pesticide residues in surface waters. Water samples from tributaries in southern and central Ontario were collected by Environment Canada from 2003 to 2008 and were analyzed for 27 pesticides, with MDLs that averaged 7.02 ng⁻¹ L (range 0.39-25.1 ng⁻¹ L). We then simulated MDLs ranging from 25 to 1700 ng⁻¹ L, to determine the impact this would have on the reporting of pesticide concentrations and detections. The mean number of pesticides detected simultaneously declined with increasing, i.e. less sensitive MDLs, from 5.02 pesticides (native MDL) to 0.08 pesticides detected (MDL < 1700 ng⁻¹ L). We compared the proportion of sites where pesticides were detected in surface waters under five MDL scenarios for 13 selected pesticides. The proportions decreased sharply with increasing MDLs. We calculated detection probabilities in an effort to compensate for higher MDLs using maximum likelihood; while adjusting for detection probabilities generally improved estimates of the presence of pesticides, as the MDLs increased the ability to compensate for detection probabilities deteriorated and became unviable at high MDLs. Depending on the method of substitution for observations below MDL (replacement with ½ × or 0 × MDL), the mean and median pesticide residues became increasingly over- and underestimated, respectively, at higher MDLs. Although monitoring programs that are focused on exceedences of water quality guidelines may not require low MDLs, the achievable goals of monitoring programs oriented towards other ecological and toxicological objectives may be limited by higher MDLs.     

Development of a theoretical framework for the evaluation of risk connected to accidental oxygen releases

A short-cut methodology for a fast estimation of hazards from oxygen releases and the evaluation of safety distances is presented. Starting from a historical survey on accidents involving oxygen releases and consequent scenarios, the approach includes analytical models for the quantification of incremental hazards due to oxygen releases, in non-obstructed areas, both for continuous and nearly instantaneous scenarios, adopting a simple Gaussian dispersion model. An example of the application of the model in a real case-study and relevant quantitative results are presented.     

我国《非常规工作制条件下职业接触限值调整指南》的核心内容

对我国现行的职业接触限值进行梳理,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,提出我国非常规工作制条件下职业接触限值的调整,进行系统综述,确定标准框架及实施难点和技术问题,建立722种职业性化学有害因素数据库,确定其调整分类,专家评议。确定我国《非常规工作制条件下职业接触限值调整指南》的核心内容,包括调整原则、步骤、调整系数的计算以及根据健康损害类型、生物半减期（如果已知）、建立职业接触限值的依据以及毒理学及药（毒）代动力学数据对722种职业性化学有害因素的非常规工作制调整分类及调整方法等。调整方法包括4种:不需调整、日调整、周调整及日调整或周调整（选择2者中较严格的1种）。建议尽快以推荐性标准发布《非常规工作制条件下职业接触限值调整指南》,并加快多种接触联合作用研究。     

农村生活污水处理设施水污染物排放标准制订探讨

农村生活污水处理设施水污染物排放标准是农村环境管理的重要依据,关系到污水处理技术和工艺的选择,以及污水处理设施建设和运行维护成本.通过对北京市、重庆市及浙江省等地区农村生活污水排放标准进行对比,发现现有标准存在适用范围不清晰、分类分级思路不全面及控制指标选择不合理等问题.因此,基于优化农村生活污水处理设施水污染物排放标准的制订提出3点建议:①明确标准适用于规模 < 500 m3/d的农村生活污水处理设施.②根据排水去向、处理设施规模以及尾水资源化利用因素等的不同进行标准分级.③建议选择pH、ρ（SS）、ρ（COD_Cr）、ρ（NH₃-N）、ρ（TN）、ρ（TP）及ρ（动植物油）等作为控制指标,其中ρ（TN）和ρ（TP）适用于出水直接排入封闭水体或超标因子为氮、磷的不达标水体的处理设施,ρ（动植物油）适用于含农家乐废水的处理设施,有条件的地区可在上述控制指标的基础上适当增加,如阴离子表面活性剂浓度、类大肠菌群数、色度等.因此,提出因地制宜、及时修订、完善农村生活污水处理技术评估方法以及加强处理设施资金保障等建议,确保标准的顺利实施,切实做到污染物减排.      

Experimental and simulation studies on the influence of carbon monoxide on explosion characteristics of methane

In underground coal mining, methane explosions often can cause tremendous disasters. In the meantime, carbon monoxide (CO), generated during the process of coal oxidation, may appear in the air. Therefore, the explosion characteristics of the mixture of CH₄ and CO must be investigated to prevent gas explosion accidents in coal mines. We conducted experiments by using a 20-L nearly spherical gas explosion testing device. The software FLACS was used to simulate the explosion of the mixture of CH₄ and CO at various mixing concentrations, and the simulation results corresponded to experimental results. With the increase of CO concentration, both upper and lower explosive limits of CH₄ decreased. On the whole, the explosion characteristic parameters of CH₄ and the mixture are similar. When CH₄ concentration was below the stoichiometric concentration, the addition of CO could promote the intensity of gas explosion; oppositely, excessive CO would inhibit the gas explosion reaction. The inhibitory effects become more significant as the concentration of CH₄ increases.