Photocatalytic activity of ambient particle systems

Unter der Einwirkung von Sonnenstrahlung können - insbesondere im Bereich der kurzwelligen und damit energiereichen UV-Strahlung - zahlreiche persistente Stoffsysteme durch Photokatalyse an geeigneten Partikeln teilweise vollständig abgebaut werden. In dieser Arbeit wurde die photokatalytische Wirkung ambienter Partikelsysteme unter natürlichen Bedingungen untersucht und Anwendungsmöglichkeiten überprüft. Dazu wurden zwei unabhängige Verfahren angewandt. Zum einen wurde eine Screening-Methode zur Detektion photokatalytisch erzeugter Radikale am einzelnen Partikel entwickelt. Zum anderen wurde der photokatalytische Abbau des persistenten Herbizids Atrazin im Partikelverbund bilanziert. Es zeigte sich, dass der Atrazinabbau an reinen Halbleitern sehr schnell erfolgt, während der Abbau an bestrahlten partikulären Umweltproben so langsam ist, dass er in der Umwelt keinen zusätzlichen Abbauweg darstellt. Hingegen kann der photokatalytische Abbau an modifizierten Zementpartikeln einen beachtlichen Beitrag zum abiotischen Abbau von Schadstoffen in der bebauten Umwelt leisten.During photocatalysis many persistent substances are degradable by suitable particles under the influence of solar radiation - especially in the UV range. In this work, the photocatalytic effect of ambient particle systems and their possible application for environmental remediation was investigated. Therefore two different techniques were applied. On the one hand, the photocatalytic effect of single particles was measured by detection of intermediately formed radicals. On the other hand the photocatalytic degradation of the persistent herbicide atrazine in bulk particle systems was investigated. Atrazine degradation by model catalysts like TiO2 was very fast, whereas with environmental particle samples no significant photocatalytic activity was observed. Thus photocatalysis by aerosol or soil particles appears not to enhance abiotic atrazine degradation in the environment. The degradation of harmful substances by modified cement samples, however, could possess a considerable contribution to the abiotic degradation of pollutants by modified building surfaces

Supranational Banking Supervision in Europe: The Construction of a Credible Watchdog

Does the institutional design of the European Single Supervisory Mechanism (SSM) and its first assessment of systemically important bank stability bolster the credibility of supranational banking supervision in Europe? One crucial measure of credibility with regard to the SSM and NCA supervision of less significant banks — the large majority of euro area headquartered bank not subject to direct ECB supervision — is the assurance of consistent supervision in the euro area. This involves some degree of convergence of NCA supervision in order to prevent national supervisory forebearance of struggling banks. This contribution thus examines whether or not the design of the SSM provides the foundation to build convergence in euro area supervision of less significant banks, despite very different national supervisory practices and institutional frameworks. The Principal-Agent approach is used to assess the credibility of the SSM design in terms of providing the foundation for consistent supervision. This contribution also examines the credibility of the ECB’s direct supervision of significant banks. The management of the ECB’s Comprehensive Assessment of signficant banks can be seen as the first step in demonstrating the capacity of the ECB to make difficult decisions with regard to the stability of the euro area’s banks

Full scale demonstration of air-purifying pavement

Experiments concerning a full-scale demonstration of air purifying pavement in Hengelo, The Netherlands, are reported. The full width of the street was provided with concrete pavement containing TiO2 over a length of 150 m ("DeNOx street"). Another part of the street, about 100 m, was paved with normal paving blocks ("Control street"). The outdoor monitoring was done during 26 days for a period exceeding one year, and measured parameters included traffic intensity, NO, NO2 and ozone concentrations, temperature, relative humidity, wind speed and direction, and the visible and UV light irradiance. Prior and parallel to these field measurements, the used blocks were also measured in the lab to assess their performance. The NOx concentration was, on average, 19% (considering the whole day) and 28% (considering only afternoons) lower than the obtained values in the Control street. Under ideal weather conditions (high radiation and low relative humidity) a NOx concentration decrease of 45% could be observed

Nuclear-weapon-free zones

Bibliography: p. 227-238