大型相连容器中火焰传播的研究

为了进一步了解相连装置中粉尘爆炸的火焰传播行为和压力发展,为该结构的安全防护设计提供有价值的信息,采用大型实验装置对相连容器中玉米淀粉/空气混合物爆炸时的火焰传播行为进行了实验研究,同时采用已开发的数值模型对实验进行仿真计算。实验表明:粉尘浓度的变化对粉尘爆炸的火焰传播行为有重要影响;在粉尘浓度很低的情况下,火焰仍然能够在管道中加速传播且爆炸发展的最终结果相当猛烈。数值模型采用欧拉-拉格朗日方法模拟两相流现象,通过求解非稳态的湍流两相反应流守恒方程对实验进行二维仿真,计算结果与实验结果符合性较好,表明该模型可以很好地应用于粉尘爆炸火焰传播的研究。     

Mathematical Modeling of Column and Field Dense Nonaqueous Phase Liquid Tracer Tests

Mathematical models for the simulation of dense nonaqueous phase liquid tracer tests (DTTs) in laboratory columns and in the field are developed and examined. The DTT technique is a means of estimating the quantity of dense nonaqueous phase liquid (DNAPL) in a domain of interest in an aquifer. The two-dimensional field DTT model uses the Method of Principal Directions and an asymmetrical upwind algorithm for describing advective transport. Both models include diffusion transport of tracer into and from low-permeability porous structures such as clay lenses, as well as the mass transport kinetics of partitioning tracer to and from the DNAPL droplets. The dependence of the effluent tracer concentration curves on the parameters of the models is explored, and conclusions are drawn regarding the applicability of, and several possible problems with, the DTT technique. Model results indicate that the DTT performs well at locating distributed droplets of DNAPL, but is unlikely to be useful in the assessment of pooled DNAPL.     

Benzene Exposure Assessment at Indoor, Outdoor and Personal Levels. The French Contribution to the Life MACBETH Programme

Many VOC represent hazards to human health through chronic exposure. Recent European and world-wide legislation proposes limit values for ambient concentrations of these compounds. However, very little experimental data exists for true population exposure. In 1996, the European MACBETH initiative set out to measure population exposure to benzene in six European cities. This study details the French contribution to this program. Six campaigns were carried out, each comprising measurements at 100 outdoor sites and the participation of 50 non-smoking volunteers who wore personal samplers and had passive monitors installed in their homes. Iso-concentration maps were drawn for each campaign and the results showed that outdoor concentrations were significantly lower than indoors. Almost 75% of the volunteers were exposed to mean concentrations higher than the limit value of 5µgm³. It is demonstrated that personal exposure levels cannot be deduced simply by combining indoor and outdoor background concentrations. It is also shown that there is need for better knowledge of the contributions to overall exposure of outdoor microenvironments and the authors hope that future European directives will take this into account.     

Air Quality Monitoring and Management in Lisbon

The environmental decision-making process is related with the interpretation of data both in spatial and temporal dimensions. This paper presents a methodology that integrates the time-space framework of air quality data to infer the temporal pattern and spatial variability that could be interpreted for environmental decision purposes. Variograms that accommodate time and space lags were used for the analysis and proved to be effective. Its environmental meaning, in particular its relationship with traffic patterns is discussed. Data from air quality monitoring stations located in the central part of Lisbon were used in this study. It describes a strategy to identify the type of vehicles responsible for certain pollutant levels, particularly for nitrogen oxides, and discusses the application of new air quality European legislation to the city of Lisbon, Portugal.     

Adaptation Scenarios of Agriculture in Poland to Future Climate Changes

This paper demonstrates the ability of Polish agriculture to adapt to predicted climate change according to GISS and GFDL scenarios. Both climate-change scenarios will significantly affect farming conditions in Poland through water deficit, shifts in planting and harvesting seasons, changes in crop yields and crop structure. Neither scenario seems to endanger the self-sufficiency of Poland as long as preventative measures are taken. Moreover, the realization of GISS creates the possibility of a surplus in production. It must be emphasized that regardless of the scenario, the adaptation of agriculture to an expected climate change cannot be handled by the farming community itself.     

Characterisation of Particulate Matter Sampled during a Study of Children's Personal Exposure to Airborne Particulate Matter in a UK Urban Environment

The personal exposure of children aged 9 – 11 years to particulate matter (PM₁₀ and PM_2.5) was carried out between January and September 1997 in the London Borough of Barnet. Personal sampling along with home, garden and classroom microenvironmental monitoring was completed for all ten children. Each child was monitored for five days during winter, spring and summer. All children completed daily time activity diaries to provide information on any potential activities that could influence their exposure to particulate matter. Each evening a household activity questionnaire was also completed by the parents. Personal Environmental Monitors were used to sample personal exposure to PM₁₀ and PM_2.5. Harvard Impactors were used for the microenvironmental sampling of both size fractions. The children's mean personal exposure concentrations for PM₁₀ during winter, spring and summer were 72, 54 and 35 µg/m³ respectively and for PM_2.5 22, 17 and 18 µg/m³ respectively. In order to determine the potential sources of particulate matter, analysis of the Teflon filters has been undertaken. The physical characteristics of the particles have been identified using Scanning Electron Microscopy. The relationships between personal exposure concentrations and the different microenvironments will be discussed.     

Modelling the contribution of different sources of sulphur to atmospheric deposition in the United Kingdom

In order to understand relationships between sources and receptors of atmospheric deposition, computer models must be used. This paper describes a Lagrangian acid deposition model that represents emissions of trace species across Northern Europe. The chemistry of sulphur dioxide, dimethyl sulphide and hydrogen sulphide is represented and the model tested against estimates of UK wet and dry deposition. Mean UK wet and dry deposition for the period 1992–1994 was 206 and 145 ktonne S yr^-1, respectively. The model predicted wet and dry deposition of 222 and 166 ktonne S yr^-1, in good agreement with measurements. The model has been used to examine the sources of deposited S to the UK. For a base year of 1992, 86% of the UK's SO₂ emissions are exported. The S deposition attributable from mainland European sources was 36% of the UK total S deposition, in good agreement with other UK models but this differs substantially from the calculations of the EMEP model. Natural sources of S deposition from planktonic emissions of dimethyl sulphide, biological emissions of hydrogen sulphide and non-eruptive volcanic emissions of sulphur dioxide contributed approximately 1% of the modelled UK S deposition, of which 95% originated from dimethyl sulphide. The explicit chemical scheme for dimethyl sulphide incorporated into the model showed that 24% of the resultant deposited S was methane sulphonic acid. Boundary conditions of the model were tested and it was found that initialisation of sulphur dioxide and sulphate concentrations to representative ambient conditions had a very small effect. The modelled contribution of UK and European sources to UK S deposition was approximately 40 and 60%, respectively, showing the dramatic change arising from projected UK SO₂ emissions in 2010. This revised version was published online in July 2006 with corrections to the Cover Date.     

INASUD project findings on integrated assessment of climate policies

This communication summarizes the main findings of INASUD, an European-wide research project on integrated assessment of climate policies. The project aimed at improving the framing of climate policy analysis through the parallel use of various existing integrated assessment models. It provides a comprehensive examination of the link between uncertainty regarding damages and inertia in economic systems. Results show that the Kyoto targets and timing are consistent with the precautionary principle but offers little insurance for longer-term climate protection. Flexibility mechanisms offer potentials for cooperation with developing countries, and are necessary to tap the environmental and economic benefits of joint carbon and sulfur emissions abatement.     

Water quality assessment of Almatti Reservoir of Bijapur (Karnataka State, India) with special reference to zooplankton

The present investigation deals with the limnobiotic status of Almatti reservoir from February, 2003 to January, 2005. The study revealed that, the distribution and population density of zooplankton species depend upon the physico-chemical factors of the environment. Statistical analysis showed that there exists a significant relation between the biological and non-biological factors. The benthic fauna constituting the food of fish can be utilized for extensive culture operation so that the nutrients in the reservoir are not only properly cycled but also serve as a check on further eutrophication.