WIT Press

Small-scale Differences Of Urban NOx Exposition In Field Measurement Data


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1513 - 1522




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É. V. P. Rácz, Z. Horváth


Local differences in air pollution levels of different positions of even close points along a street can be dramatic due to mainly meteorological parameters and local geometry. Air pollution monitoring systems provide a huge amount of temporal data, but the number of monitoring sites is far from sufficient for fine spatial investigations. On the other hand, for reliable air pollution modelling and correct prediction of expositions, a more detailed spatial distribution of samples is needed. Small-scale differences and street canyons are often investigated by models. However, such small-scale real field data from direct measurements are rarely available. In this paper we provide evidence by measurements to the existence of significant small-scale differences in air pollution levels and provide data for model validation. Hence, we performed measurements inside a single crossing and along three main roads in the city of Győr. Air samples were sucked into Tedlar bags and NOx concentration was determined by a gas analyser using a chemiluminescent method. On the sampling days manual traffic counting and noise measurements were performed and meteorological data were also taken at the same time. Daily rhythm and spatiotemporal variation of NOx expositions were investigated and compared to traffic data and data from the two monitoring containers of Győr. We observed a similar daily profile as expected in an average workday out of heating season: a sharp peak in the morning and a wider rise of nitrogen oxide concentration in the afternoon. Canyon effects were detected inside the investigated crossing. It caused a difference in pollutant levels of the two sides of the street. Despite a relatively small number of sampling sites, significant differences were detected both inside the crossing level and between main streets at p = 0.055.


NOx, street canyon, field measurement, traffic pollution, Hungary