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Although many German monitoring sites report declines of NOx concentrations, NO 2-concentrations actually stagnate or even increase quite often. Various analyses have identified the altered compositions of nitrogen oxides (NO 2 /NOx-ratio) emitted by motor vehicles (resulting in an increase of primary NO 2-emissions) as well as the chemical environmental conditions (mainly ground level ozone) as the main causes. The chemical conversion of NO to NO 2 is often parameterized in dispersion calculations of exhaust emissions. A widely applied conversion model is the so-called Romberg approach from 1996. However, the Romberg approach has to be re-evaluated to accommodate the above-mentioned conditions. This article presents an adjustment to the Romberg approach in accordance with the measured data from 2000 to 2006, taking into consideration substantially higher NO 2 /NOx-ratios especially for higher NOx-concentrations. Model calculations with OSPM (Operational Street Pollution Model) including its internal chemistry module are able to reproduce very well the trends in the measured annual NO 2-concentrations over a 10 year period. The relevant parameters for variations between the years are the NOx-emissions, primary NO 2-emissions, ozone concentrations, wind conditions, and background concentrations. A simplified chemistry model based on annual mean NOx-and NO 2-concentrations, and background ozone concentrations, as well as primary NO 2-emissions is presented as a better method than the updated Romberg approach. This model simulates the annual mean NO 2-concentrations much more accurately than the conventional and the updated Romberg approaches. Zusammenfassung An vielen deutschen Messstationen wird zwar ein Rückgang der NOx-Konzentrationen, aber häufig eine Stagnation der NO 2-Konzentrationen oder gar deren Anstieg beobachtet. Verschiedene Untersuchungen identifizierten als Hauptursachen eine geänderte Zusammensetzung der seitens der Kraftfahrzeuge emittierten Stickoxide (NO 2 /NOx-Verhältnis) und die daraus folgende Erhöhung der primären NO 2-Emissionen des Kfz-Verkehrs sowie die chemischen Umgebungsbedingungen (insbesondere bodennahes Ozon). Die chemische Umwandlung von NO in NO 2 wird innerhalb von Ausbreitungsrechnungen für Autoabgase oft parametrisiert. Ein häufig angewendetes Konversionsmodell stellt hierbei die so genannte Romberg-Formel aus dem Jahr 1996 dar. Unter den o. g. veränderten Randbedingungen steht die Romberg-Formel derzeit auf dem Prüfstand. Eine Anpassung der Romberg-Formel an Messdaten aus den Jahren 2000 bis 2006 wird aufgezeigt. Diese zeigt insbesondere bei hohen NOx-Konzentrationen deutlich höhere NO/NO 2-Umwandlungsraten. Modellrechnungen mit OSPM inkl. nachgeschalteten Chemiemodell können die Trends der NO 2-Jahresmittelwertë uber einen Zeitraum von 10 Jahren gut reproduzieren. Die relevanten Einflussgrößen auf die Variationen zwischen den Jahren sind die NOx-Emissionen, die primären NO 2-Emissionen, die Ozonkonzentrationen, die Windverhältnisse und die Hintergrundbelastungen. Als möglichen...

Measuring and characterizing airborne particulate matter (PM) is an important research area because PM can lead to impacts on health and to visibility reduction, material damage and groundwater pollution. In regard to road dust, suspension and re-suspension and the contribution of non-exhaust PM to total traffic emissions are expected to increase as a result of predicted climate scenarios. European environmental regulations have been enforced to reduce exhaust particle emissions from road traffic, but little attention has been paid to reducing non-exhaust coarse particle emissions due to traffic. Therefore, a monitoring program for coarse PM has been initiated in early 2013 to assess the predicted increase in the abundance of non-exhaust particles. Particle sampling was performed with the passive-sampler technique Sigma-2. The subsequent single-particle analysis allows for characterization of individual particles, determination of PM size distribution, and calculation of PM mass concentrations. Two motorways near Cologne (Köln), Germany were selected as sampling sites, and the experimental setup in the field was realized with a so-called twin-site method. The present study reports single-particle analysis data for samples collected between May 31, 2013 and May 30, 2014. Coarse PM, generated through multi-source mechanisms, consists of, e.g., tire-wear, soot aggregates, and mineral dust. The highest mass concentration occurs at both motorways in spring, and the observed PM mainly contains traffic-abrasion particles. The field measurements show that the minimum PM concentration was found in the 5 to 12°C temperature range, whereas the maximum concentration was observed in both the -5 to 5°C and the 12 to 24°C ranges, in agreement with previous laboratory measurements. Correlation between super-coarse (d p 10-80 µm, geometric equivalent diameter) PM concentration and precipitation displays a significant increase in concentration with decreasing number of precipitation events (dry weather periods).

Air quality measurements usually consist of ground-based instrumentation at fixed locations. However, vertical profiles of pollutants are of interest for understanding processes, distribution, dilution and concentration. Therefore, a multicopter system has been developed to investigate the vertical distribution of the concentration of aerosol particles, black carbon, ozone, nitrogen oxides (NOx) and carbon monoxide and the meteorological parameters of temperature and humidity. This article presents the requirements by different users, the setup of the quadrocopter system, the instrumentation and the results of first applications. The vertical distribution of particulate matter next to a highway was strongly related to atmospheric stratification, with different concentrations below and above the temperature inversion present in the morning. After the qualification phase described in this article, two identically equipped multicopters will be used upwind and downwind of line or diffuse sources such as highways or urban areas to quantify the influence of their emissions on the local air quality.

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