Computational fluid dynamics simulation of fog clouds due to ambient air vaporizers

Ambient air vaporizers (AAVs) are widely used to regasify liquefied industrial gases, which are liquefied for transport and storage. Depending on the conditions (temperature and relative humidity) of ambient air and AAV effluent, the potential exists for the formation of fog as the two fluids mix with each other. This has raised some regulatory and environmental concerns that the fog cloud may impact human activities in the vicinity of the AAV arrays.This paper describes a CFD-based modeling approach to predict the formation, dispersion and dissipation of a fog cloud due to AAV operation. The model uses the psychrometrics equations to determine when saturated air conditions are reached and to calculate mass and energy transfer between the moist air and the fog cloud. A parametric study is presented, based on an array of 6 AAVs, to demonstrate the effects of wind speed and AAV discharge elevation on the behavior of the fog cloud.     

Evaluation of Direct-Oxidative DNA Damage on Human Lung Epithelial Cells Exposed to Urban Airborne Particulate Matter

Airborne particulate matter (PM) extracts were investigated for their content of organic compounds and for the direct and oxidative DNA damage induced on lung epithelial cells A549. PM₁₀ was seasonally collected at two monitoring sites (Stations 1 and 2), characterized by different traffic loads. The cells were exposed for 30 min to extracts of PM₁₀ diluted at 0.025%, 0.05%, and 0.1% for summer samples, and at 0.05%, 0.1%, and 0.15% for winter samples. Oxidative and direct DNA damage were evaluated by formamidopyrimidine glycosylase (fpg) comet assay analyzing tail moment (TM) values from fpg-enzyme-treated cells (TMenz) and enzyme untreated cells (TM) respectively and by comet percentage analysis. Measurements relating to Station 2 showed higher levels of polycyclic aromatic hydrocarbons (PAHs), and their methyl-(methyl-PAHs) and nitro-(nitro-PAHs) derivatives in both the seasons. Nitro-PAH concentrations were higher in summer than in winter at both the stations. We found a significant increase of comet percentages at the highest dose of extract from both stations in summer and from Station 2 in winter. The TM and TMenz values relative to the summer sampling showed an early oxidative DNA damage induction also followed by direct DNA damage more evident at Station 2, that seems to correlate with the presence of higher nitro-PAH concentrations during the warm season. At both monitoring stations, the results from winter sampling campaign showed a direct DNA damage induction at 0.1% of extract and oxidative-direct DNA damage at the highest dose (0.15%).     

Quantification of source-level turbulence during LNG spills onto a water pond

The use of computational fluid dynamics (CFD) models to simulate LNG vapor dispersion scenarios has been growing steadily over the last few years, with applications to LNG spills on land as well as on water. Before a CFD model may be used to predict the vapor dispersion hazard distances for a hypothetical LNG spill scenario, it is necessary for the model to be validated with respect to relevant experimental data. As part of a joint-industry project aimed at validating the CFD methodology, the LNG vapor source term, including the turbulence level associated with the evaporation process vapors was quantified for one of the Falcon tests.This paper presents the method that was used to quantify the turbulent intensity of evaporating LNG, by analyzing the video images of one of the Falcon tests, which involved LNG spills onto a water pond. The measured rate of LNG pool growth and spreading and the quantified turbulence intensity that were obtained from the image analysis were used as the LNG vapor source term in the CFD model to simulate the Falcon-1 LNG spill test. Several CFD simulations were performed, using a vaporization flux of 0.127 kg/m² s, radial and outward spreading velocities of 1.53 and 0.55 m/s respectively, and a range of turbulence kinetic energy values between 2.9 and 28.8 m²/s². The resulting growth and spread of the vapor cloud within the impounded area and outside of it were found to match the observed behavior and the experimental measured data.The results of the analysis presented in this paper demonstrate that a detailed and accurate definition of the LNG vapor source term is critical in order for any vapor cloud dispersion simulation to provide useful and reliable results.     

An integrated analysis of production costs and net energy balance of biofuels

Up to now, the “low” price of oil has prevented the development of alternative fuels but with the current high price and increasing scarcity, biofuels could become an economically attractive alternative. However, the economic assessment of biofuels has to take into account total production costs, including impact on agriculture, and the energy balance of first generation alternative fuels (biodiesel and bioethanol). Moreover, plans to produce biofuels from agriculture should not be achieved without considering the latest developments and reforms of the common agricultural policy, which promotes a change towards sustainable rural development based on multifunctional agriculture. From the analysis carried out, it emerges that first generation biofuels do not seem to be the best solution because of high production cost, limited land availability and low net energy balance. Furthermore, only a small quantity of biofuels can be produced as alternative to fossil oil because an incremental production will lead to the rising of agri-food prices. Only second generation biofuels could be a possible solution, although they still require much supplementary research and analysis.     

Ozone sensitivity of Fagus sylvatica and Fraxinus excelsior young trees in relation to leaf structure and foliar ozone uptake

During the summer of 2001, 2-year-old Fraxinus excelsior and Fagus sylvatica plants were subjected to ozone-rich environmental conditions at the Regional Forest Nursery at Curno (Northern Italy). Atmospheric ozone concentrations and stomatal conductance were measured, in order to calculate the foliar fluxes by means of a one-dimensional model. The foliar structure of both species was examined (thickness of the lamina and of the individual tissues, leaf mass per area, leaf density) and chlorophyll a fluorescence was determined as a response parameter. Stomatal conductance was always greater in Fraxinus excelsior, as was ozone uptake, although the highest absorption peaks did not match the peaks of ozone concentration in the atmosphere. The foliar structure can help explain this phenomenon: Fraxinus excelsior has a thicker mesophyll than Fagus sylvatica (indicating a greater photosynthesis potential) and a reduced foliar density. This last parameter, related to the apoplastic fraction, suggests a greater ability to disseminate the gases within the leaf as well as a greater potential detoxifying capacity. As foliar symptoms spread, the parameters relating to chlorophyll a fluorescence also change. PI (Performance Index, Strasser, A., Srivastava, A., Tsimilli-Michael, M., 2000. The fluorescence transient as a tool to characterize and screen photosynthetic samples. In: Yunus, M., Pathre, U., Mohanty, P., (Eds.) Probing Photosynthesis: Mechanisms, Regulation and Adaptation. Taylor & Francis, London, UK, pp. 445-483.) has proved to be a more suitable index than Fv/Fm (Quantum Yield Efficiency) to record the onset of stress conditions.     

The cost of success: reproductive effort in male southern elephant seals (<Emphasis Type="Italic">Mirounga leonina</Emphasis>)

Reproductive effort is a key parameter of life history because it measures the resources allocated to reproduction at the expense of growth and maintenance. Male reproductive effort always had a minor role with respect to female effort both in the development of theories and in field research. Elephant seals are an ideal subject for reproductive effort studies because they fast during the breeding season, splitting the phase of energy acquisition from the phase of energy use for breeding. In this paper, we present results on male reproductive effort (weight loss estimated by photogrammetry) in southern elephant seals (Mirounga leonina), the most dimorphic and polygynous of all mammal species. We show that total reproductive effort increases with age, with no sign of late decrease or senescence. Male reproductive effort in this species depends mostly on behavioral factors, i.e., the success in competition with other males, and the intensity of interaction with females. A large effort results in large gains in both mating success and fertilizations. The large reproductive success that a few males are able to achieve come at a big cost in terms of energy expenditure, but this cost does not seem to affect the likelihood of survival to the following breeding season.     

Post-conflict behaviour among wild long-tailed macaques (Macaca fascicularis)

Summary A procedure originally developed for the study of post-conflict behaviour in captive groups was used to study a group of long-tailed macaques (Macaca fascicularis) in the wild. During 5 months, 156 post-conflict observations on victims of agonistic conflicts were collected and compared with matched-control observations. The findings reported previously for a captive group of the same species were confirmed. After a conflict victims scratched themselves more often and received more attacks than in control periods. Reconciliation and redirection were found to be characteristic of post-conflict situations. Their occurrence seemed to follow similar patterns in captivity and in the wild. The frequency of reconciliation, but not that of redirection, seemed to be lower after conflicts over food than in other situations. No evidence for consolation was found. In the wild, victims have the option of leaving the (sub)group in order to avoid the former aggressor. No evidence for this behaviour was actually found, but within the (sub)group victims tended to keep the former aggressor at a distance. Victims also seemed to suffer ecological costs in that they spent less time foraging than in control periods.     

Visible injury, crown condition, and growth responses of selected Italian forests in relation to ozone exposure

The impact of ozone on forest ecosystems in Italy is monitored within the CONECOFOR programme. Ozone levels are measured in 30 plots using passive samplers. Response parameters used are: crown condition (transparency), BAI (basal area increment), and visible symptoms on spontaneous vegetation. Levels of AOT40 are above the concentration-based critical level of 5 ppmh in all sites, but the evidence of impact on forest vegetation remains limited. Ozone is a predictor of crown transparency residuals in beech sites over two consecutive years, but the variance explained amounts to less than 10%. The relation between BAI reduction and ozone is even less certain. Transparency and BAI are more readily explainable in terms of ecological conditions of the site and climate fluctuations. The interpretation of visible symptoms is doubtful, and is conditioned by the prevailing ecological factors in the areas.     

Ozone and forests in South-Western Europe

The paper provides basic information about background, objectives and structure of O3SWE (Ozone at the permanent monitoring plots in South-Western Europe), an international co-operative project aimed at evaluating O3 concentrations, cumulative exposure, uptake and effects on forest vegetation in four countries of South-Western Europe (France, Italy, Luxenbourg, Spain and Switzerland). The project covers a total of 83 permanent plots of the EU and UN/ECE intensive forest monitoring programme and span over three years of investigation (2000-2002). The O3SWE project aims to demonstrate how, using data collected routinely in an intensive forest monitoring network, O3 exposure, flux and effects can be assessed and exceedances critically evaluated.