Representativity of air quality monitoring stations

A major concern in the Austrian Inn valley is the pollution caused by transnational traffic on a transit route between Germany and Italy in combination with considerably weaker dispersion within a valley compared to flat terrain. As a response to high air pollution levels traffic measures are discussed and executed (e.g. night ban for heavy duty vehicles). Critical traffic-related parameters regarding human health and vegetation are nitrogen-oxides as well as particulate matter.

The basis for the determination of threshold exceedances is recorded by air quality monitoring stations of the regional authority (Land Tirol), some of which have been in place for more than 20 years now. The location with respect to sources is not incidental but follows guidelines in order to represent different types and areas such as location dominated by a major emission source (e.g. highway, industry, town) or background station.

The measured station values are mostly viewed and analysed on a point-to-point basis. A connection to the relevant valley section is often implied, while the local position or the influence of a major source might be more important.

In the frame work of an Interreg IIIB programme called ALPNAP (Monitoring and Minimisation of Traffic-Induced Noise and Air Pollution Along Major Alpine Transport Routes) this aspect is studied as outlined below.

First the characteristics of each station are determined by criteria such as position relative to important sources (e.g. distance to the highway, town/open field), topography in the surroundings and valley geometry (e.g. valley width, location with respect to side valleys).

In a next step correlations of nitrogen dioxide (particulate matter) with the above mentioned and normalised (!) parameters are computed taking care of seasonal and daily variations. Important parameters are identified and if feasible merged into one equation for a certain air quality parameter, season and time of the day.

Data collected during an ALPNAP wintertime field campaign in 2005/2006 serve as a basis for more detailed studies and validation.

This study is intended to make the first steps towards an objective comparison of air quality stations based on long-term station characteristics.