Effects of a zeolite-selective catalytic reduction system on comprehensive emissions from a heavy-duty diesel engine

The effects of a zeolite urea-selective catalytic reduction (SCR) aftertreatment system on a comprehensive spectrum of chemical species from diesel engine emissions were investigated in this study. Representative samples were collected with a newly developed source dilution sampling system after an aging process designed to simulate atmospheric dilution and cooling conditions. Samples were analyzed with established procedures and compared between the measurements taken from a baseline heavy-duty diesel engine and also from the same engine equipped with the exhaust aftertreatment system. The results have shown significant reductions for nitrogen oxides (NOx), carbon monoxide, total hydrocarbons, polycyclic aromatic hydrocarbons (PAHs), and organic carbon (OC) emissions. Additionally, less significant yet notable reductions were observed for particulate matter mass and metals emissions. Furthermore, the production of new species was not observed with the addition of the zeolite urea-SCR system joined with a downstream oxidation catalyst.     

Blast phenomena in urban tunnel systems

Traffic infrastructure in urbanised areas is increasingly projected in tunnels underground or covered over, these days. A consequence is that in case of an incident with hazardous materials the safety level for fellow road users in tunnels is considerably less than it is in surface infrastructure. To reduce the consequences of incidents for fellow tunnel users, urban tunnels are sometimes interrupted by open spaces of limited length. Open spaces allow, for instance, the release of smoke in case of a fire. In this way, possible lethal effects are limited to the tunnel section in which the incident occurred. To what extent an open space may also be effective in the mitigation of blast effects from an explosion in a tunnel system is subject of this paper.

To this end, the blast effects originating from the rupture of a 50 m³ LPG pressure vessel in an urban tunnel system have been computed by numerical simulation. The results show that an open space in a tunnel system has a significant mitigating effect on the blast effects indeed. However, as a consequence of the ingress of a high-velocity jet flow that follows on a primary blast wave, a second blast wave develops in the tunnel section following on an open space. The strength of this second blast wave is not very dependent on the length of the open space. It shows that an open space in a tunnel system may not always limit the lethal effects of explosion incidents in tunnels to the tube in which the incident occurred. The second blast wave in the tunnel section following on an open space may have lethal consequences for fellow tunnel users by car window failure.     

Acclimatization patterns in tropical reptiles: uncoupling temperature and energetics

The physiological compensation of animals in changing environments through acclimatization has long been considered to be of minor importance in tropical ectotherms due to more stable climatic conditions compared to temperate regions. Contrasting this assumption are reports about a range of metabolic adjustments in tropical species, especially during the last two decades from field acclimatized animals. Metabolic rates are strongly linked to temperature in ectotherms but they also reflect energetic requirements and restrictions. We therefore postulate that the observed variety of acclimatization patterns in tropical reptiles results from an interaction of multiple influences, including food and water availability, rather than from thermal constraints alone. We present new data from two sympatric Malagasy lizards with contrasting acclimatization patterns and, complemented with an extensive literature search, discuss the variety of acclimatization patterns in tropical reptiles with regard to thermal and energetic influences. This broad consideration of constraints allows a rearrangement of apparently controversial patterns into a scheme of decreasing metabolic costs, including two new categories for selective and selective inverse acclimatization, where metabolic shifts are restricted to body temperatures below those preferred during activity.     

Climate variability and spruce beetle (Dendroctonus rufipennis) outbreaks in south-central and southwest Alaska

We used tree ring data (AD 1601-2007) to examine the occurrence of and climatic influences on spruce beetle (Dendroctonus rufipennis) outbreaks in south-central and southwest Alaska and found evidence of regional-scale outbreaks dating from the mid-1700s, related to climate variability at multiple temporal scales. Over interannual time scales (approximately 1-3 years), El Ni?o years, combined with severe late-summer drought, appeared to contribute significantly to spruce beetle outbreaks in the study area. Over multidecadal time scales (up to approximately 40 years), cool-phase Pacific Decadal Oscillation (PDO) conditions tended to precede beetle outbreaks, regardless of the phase of El Ni?o-Southern Oscillation (ENSO). All sites showed low-severity disturbances attributed to spruce beetle damage, most notably during the 1810s. During other major periods of disturbance (i.e., 1870s, 1910s, 1970s), the effects of spruce beetle outbreaks were of moderate or higher severity. The highly synchronized timing of spruce beetle outbreaks at interannual to multidecadal scales, and particularly the association between cool-phase PDO conditions and beetle disturbance, suggests that climate (i.e., temperature, precipitation) is a primary driver of outbreaks in the study area. Our disturbance chronologies (mid-1700s to present) suggest that recent irruptions (1990s to present) in south-central and southwest Alaska are within the historical geographic range, but that outbreaks since the 1990s show greater spatiotemporal synchrony (i.e., more sites record high-severity infestations) than at any other time in the past approximatly 250 years.     

Integrating climate change adaptation into Dutch local policies and the role of contextual factors

Moving towards a more sustainable adaptation process requires closer integration of policies related to the environment. An important actor in this is the local government. This paper examines to what extend adaptation is currently being integrated into Dutch local policies, and what the role is of a municipality's size, risk and experience in the encountered manifestations of adaptation. First, it was determined that adaptations taking place only anticipate currently perceivable weather extremes – mostly increasing precipitation. Second, it was determined that the realisation of further adaptations is hindered by a strongly sectoral divided reality. Adaptation is now heavily dominated by the water department, while spatial planning and the environment are only limitedly involved. Finally, it was observed that the contextual factor size proved to most important for horizontal policy integration, whereas the contextual factor extreme-weather experience was the most definite for the realisation of adaptations. We conclude that a more sustainable adaptation should first tackle the sectoral divides which requires administrative efforts, for example, professional training. These would preferably be initiated from a vertical direction.