BayCEER Workshop 2016

Urban aerosol flux measurements in Innsbruck, Austria

Introduction

Air quality in the Inn valley is influenced by high traffic emissions along the Brenner motorway, a main transport route across the Alps. In order to contribute to a better understanding of air pollution mechanisms in an alpine region, reactive trace gas and particle fluxes were measured during the Innsbruck Air Quality Study (iNNAQS). The objectives of the presented particle flux measurements were the quantification of turbulent emission and deposition fluxes and the determination of sources and sinks of aerosol particles.

Material and Methods

Aerosol flux measurements were conducted 38 m above ground level near the city center of Innsbruck. The Eddy Covariance setup consisted of a sonic anemometer (CSAT3) for measuring 3D wind speed and direction and a condensation particle counter (CPC, TSI 3772) for particle number concentrations.

Results

The particle number fluxes and exchange velocities in Innsbruck showed a typical diurnal pattern with net emission during the day and decreasing net exchange and sporadic deposition in the evening. The highest net emissions came from the city center, lying in the main daytime wind direction (NE-E). NO_x fluxes were positively correlated to the particle fluxes, although the total particle fluxes were dominated by individual extreme values, originating from gust-like motions in the vertical wind and concurrent extraordinary large particle concentration peaks (“events”).

Conclusions

The city center of Innsbruck acts as a source of particles and road traffic is supposed to be the dominant emission source. The characteristics of the single events and their contribution to particle fluxes will be subject of further research.