Numerical simulation of far-field blast loads arising from large TNT equivalent explosives

Large TNT equivalent explosions usually arise from accidents occurring during the transportation, storage, and manufacturing of chemicals relevant to process industries. The blast wave generated by the explosion will spread and interact with the surrounding factories and storehouses, damaging the building structures within several kilometers and causing significant casualties and property losses. This study aims to develop an efficient numerical simulation method to predict blast loads to estimate the consequences of accidents involving far-field free air bursts or surface burst explosions. Before its interaction with the interested target, a blast wave is generated in the numerical model by specifying the initial and boundary conditions of the disturbed air. Based on empirical data of incident overpressure, an explicit formula to calculate the air particle velocity is derived from the governing equations of a perfect inviscid gas. A simplified path line method is proposed to calculate the air density. The proposed method is applied to the LS-DYNA CESE solver to simulate the blast loads on building structures in the far field. Validations against empirical data and experiments indicate that the proposed method is sufficiently accurate for engineering applications and, through a case study, presents a more efficient performance than the LOAD_BLAST_ENHANCED (LBE) and mapping methods.     

Public perception of air pollution sources across Europe

Air pollution is one of the primary concerns of our society for its effect on human health and the environment. Among the policy measures that can be put in place to limit air pollutant emissions, end-of-pipe technologies and/or regulatory instruments may be implemented through legislative acts. Also, equally important are behavioural measures, requiring citizens’ active involvement. The success of any measure to limit pollutant emissions requires the acceptance by the citizens that, in turn, implies a correct perception of the main pollutant emission drivers. We present here the comparison between the public perception of air pollution sources and the real-world situation through a survey carried out in seven European countries and involving 16 101 respondents. Our study shows a dramatic underestimation of the contribution of the agri-food sector to air pollution. This result is common to all respondents in the seven countries examined and only to a small extent depends on gender, age and socio-economic status of the respondents.     

基于水质水量的城镇污水处理厂工艺运行稳定性研究

采用四川省2座位于不同排水服务区域的城镇污水处理厂的样本数据,统计分析了日处理水量,COD、TN、TP浓度及负荷和C/N、C/P等统计量的累积频率分布规律,并分析了各统计量的分布特征对工艺运行稳定性的影响。结果表明,污水处理厂A进水污染物负荷的累积频率分布范围较大,其采用的周期循环活性污泥(CASS)工艺基本能适应进水水质的随机变化,但因存在碳源随机性不足情况,可能导致其脱氮稳定性降低;污水处理厂B进水污染物负荷的累积频率分布范围较小,虽然其采用的厌氧—缺氧—好氧(A2/O)工艺的调控能力较低,但也基本能适应其服务区域内进水水质的随机变化;2座污水处理厂的日处理水量累积频率分布与污染物浓度及负荷的累积频率分布之间均存在显著的差异,日处理水量的累积频率分布比较集中,而污染物浓度及负荷的累积频率分布的离散范围较大,这也潜在威胁到工艺运行的稳定性。总体来看,2座污水处理厂的处理工艺选择恰当,均能较好适应其服务区域的进水水质和水量的要求。     

Monitoring of environmental exposure to polycyclic aromatic hydrocarbons: a review

Polycyclic aromatic hydrocarbons (PAHs) are a large group of organic compounds with two or more fused aromatic rings. They have a relatively low solubility in water, but are highly lipophilic. Most of the PAHs with low vapour pressure in the air are adsorbed on particles. When dissolved in water or adsorbed on particulate matter, PAHs can undergo photodecomposition when exposed to ultraviolet light from solar radiation. In the atmosphere, PAHs can react with pollutants such as ozone, nitrogen oxides and sulfur dioxide, yielding diones, nitro- and dinitro-PAHs, and sulfonic acids, respectively. PAHs may also be degraded by some microorganisms in the soil. PAHs are widespread environmental contaminants resulting from incomplete combustion of organic materials. The occurrence is largely a result of anthropogenic emissions such as fossil fuel-burning, motor vehicle, waste incinerator, oil refining, coke and asphalt production, and aluminum production, etc. PAHs have received increased attention in recent years in air pollution studies because some of these compounds are highly carcinogenic or mutagenic. Eight PAHs (Car-PAHs) typically considered as possible carcinogens are: benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene (B(a)P), dibenzo(a,h)anthracene, indeno(1,2,3-cd)pyrene and benzo(g,h,i)perylene. In particular, benzo(a)pyrene has been identified as being highly carcinogenic. The US Environmental Protection Agency (EPA) has promulgated 16 unsubstituted PAHs (EPA-PAH) as priority pollutants. Thus, exposure assessments of PAHs in the developing world are important. The scope of this review will be to give an overview of PAH concentrations in various environmental samples and to discuss the advantages and limitations of applying these parameters in the assessment of environmental risks in ecosystems and human health. As it well known, there is an increasing trend to use the behavior of pollutants (i.e. bioaccumulation) as well as pollution-induced biological and biochemical effects on human organisms to evaluate or predict the impact of chemicals on ecosystems. Emphasis in this review will, therefore, be placed on the use of bioaccumulation and biomarker responses in air, soil, water and food, as monitoring tools for the assessment of the risks and hazards of PAH concentrations for the ecosystem, as well as on its limitations.     

Do new health conditions support mortality–air pollution effects?

Epidemiological research underlying US air quality regulations documents significant associations between measures of fine particles and premature mortality. Recent studies examine potential mechanistic pathways, related to heart and lung functioning, that may contribute to the observed deaths. Our results support these pathophysiological analyses. We examine whether the onset of serious health conditions, consistent with disease pathways, is related to current and long-term exposure to particulate matter and ozone. Associations between air pollution and alternative indicators of health status are also evaluated. The 1996 wave of the Health and Retirement Study is used with a two-step estimator acknowledging limitations in our ability to measure individual exposures. The findings suggest significant current and long-term effects of particulates on new cases of heart attacks and angina, reinforcing the disease pathways identified in epidemiological studies. Long-term air pollution exposure is also a determinant of recently diagnosed chronic lung conditions and reports of shortness of breath.     

Did the Clean Air Act cause the remarkable decline in sulfur dioxide concentrations?

Over the last three decades, ambient concentrations of sulfur dioxide (SO₂) air pollution have declined by approximately 80%. This paper tests whether the 1970 Clean Air Act and its subsequent amendments caused this decline. The centerpiece of this legislation is the annual assignment of all counties to SO₂ nonattainment or attainment categories. Polluters face stricter regulations in nonattainment counties. There are two primary findings. First, regulators pay little attention to the statutory selection rule in their assignment of the SO₂ nonattainment designations. Second, SO₂ nonattainment status is associated with modest reductions in SO₂ air pollution, but a null hypothesis of zero effect generally cannot be rejected. This finding holds whether the estimated effect is obtained with linear adjustment or propensity score matching. Overall, the evidence suggests that the nonattainment designation played a minor role in the dramatic reduction of SO₂ concentrations over the last 30 years.     

溴水氧化-磷钼蓝分光光度法测定水和废水中元素磷

对元素磷水样的采集方法进行了比对；对其测定条件进行了试验；提出有机磷农药对元素磷测定无干扰；在应急监测时可减少水样的清洗次数；该方法的检出限为0．019mg／L、样品的加标回收率为92．69％～97．70％。     

X－射线荧光光谱法测定道路扬尘中21种元素

本文用Ｘ－射线荧光光谱法，一次测定道路扬尘中Ｎａ等２１种元素。人工配制标样，回归法求取校准曲线常数，用散射线内标法和经验系数法校正基体效应。方法的准确度、精密度较好，分析结果令人满意。     

An analytical solution of the advection-diffusion equation considering non-local turbulence closure

Atmospheric air pollution turbulent fluxes can be assumed to be proportional to the mean concentration gradient. This assumption, along with the equation of continuity, leads to the advection-diffusion equation. Moreover, large eddies are able to mix scalar quantities in a manner that is counter to the local gradient. We present a general solution of a two-dimension steady state advection-diffusion equation, considering non-local turbulence closure using the General Integral Laplace Transform Technique. We show some examples of applications of the new solution with different vertical diffusion parameterisations.     

大气有机物GC分析预处理中的组分损失

大气有机物在脱水，富集过程中的组分损失造成ＧＣ分析的系统误差。回收率测定表明，在本实验条件下，疏水性有机组分在填充碱石棉与碳酸钾的脱水预柱上的损失率分别为２５％和１５％左右，亲水性的乙醇的损失经高达６０％左右。