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Since the introduction of low emission zones in Germany in 2008 the question of their efficiency has been debated. In this pilot study, measurement data collected before and after the introduction of the low emission zone in Munich (October 2007 until January 2008 vs. October 2008 until Januar 2009) were analysed on the basis of matched quadruples. Applying previously described methods (Morfeld et al. 2011), continuously measured half-hour fine dust concentration data (PM10) - simultaneously determined at an index station situated inside the low emission zone and a reference station outside of the zone - were contrasted and analysed (difference score method in the two-period case). Meteorological parameters (height of the inversion base, amount of precipitation, wind velocity) as well as baseline data of index and reference stations were taken into account as covariates in regression analyses. The statistical approach was successfully validated in an analysis of simulated data. 26438 quadrupels could be matched for analysis. Averages of PM10 concentration values before (after) introducing the low emission zone were 33.9 μg/m3 (39.0 μg/m3) at 5 index stations and 24.6 μg/m3 (30.5 μg/m3) at 2 reference stations. Taking covariates into account, an additive model estimated the change in concentration associated to the introduction of the low emission zone as +0.017 μg/m3 (0.95-CI: -0.33 μg/m3, +0.37 μg/m3), a multiplicative model estimated the relative effect as -0.5% (0.95-CI: -0.12%, +0.30%). The results of this study differ relevantly from the findings of an earlier investigation by Cyrys et al. (2009) who analyzed the same data. This analysis does not prove the effectiveness of Munich's low emission zone. This study also points out that the methodological approach is crucial for a scientifically reliable evaluation of the efficacy of low emission zones. Strict rules need to be followed in order to prevent from misinterpretations.

We developed a coupled code to obtain a better understanding of the role of pore pressure changes in causing fracture reactivation and seismicity during EGS. We implemented constitutive models for fractures in a continuum approach, which is advantageous because of the ease of integration in existing geomechanical codes (FLAC3D), the speed of the calculations and the flexibility of the fracture representation. For modeling the mechanical behavior of the fracture zone the softening ubiquitous joints model was used with random strength properties for the fracture zone. We implemented a hyperbolic deformation with effective stress for the reversible tensile fracture opening, and a linear relationship between plastic shear strain and ir eversible fracture opening. The effective permeability of the fracture network was described by a cubic dependence on the fracture aperture. We created a model inspired on the Soultz-la-Forêts GPK3 injection well, intersected by a dominant fracture zone. Due to injection of water, the model reproduced reactivation of the fracture zone and we observed the growth of a zone with large directional permeability. The model was used to perform a sensitivity analysis on parameters like injection rates, in-situ stress regime, fracture strength, and frictional weakening. This allowed us to evaluate the trends of their impact on fracture reactivation, including reactivated area, seismic moment and moment magnitudes.

Utrecht als Romeins fort van natuursteen De geschiedenis van de stad Utrecht begint in de eerste eeuw van onze jaartelling, als de Romeinse keizer Claudius besluit dat de Rijn de noordgrens van zijn rijk zal vormen. Ter verdediging van deze grens verrijzen forten langs de rivier. Eén van deze forten, met de naam Trajectum, ‘doorwaadbare plaats’, bevond zich op de plaats van het huidige Domplein, dichtbij een ondiepte in de Rijn. Rond dit middelpunt ontstond de stad Utrecht. Van het Romeinse fort zijn nog fundamenten en muurresten van natuursteen te zien in Café het Weeshuis en bij het Utrechts Centrum voor de Kunsten , beide aan het Domplein. De nummering vindt u terug op de kaart in deze folder.