Short-term measurements of CO, NO, NO2, organic compounds and PM10 at a motorway location in an Austrian valley

In situ measurements of CO, NOx, PM10 and certain organic compounds took place over an 11 day period encompassing a 12 h motorway blockade. Located within the Inn valley (Tirol, Austria), the monitoring site experiences varying meteorological conditions and traffic frequency throughout the day which both strongly influence air pollutant levels. Early morning increases of NOx, PM10 and aromatic hydrocarbons were clearly correlated with rising traffic. Midday minima and afternoon maxima may be explained by changing wind conditions and varying inversion layer dynamics. Night time lows in concentrations can be explained by minimal traffic activity. Classification of compound sources was made through grouping of data, separated into times when heavy duty vehicles (HDV) were permitted to use the motorway and HDV-ban periods. Increased levels of NOx and PM10 were observed from data that included periods of high HDV numbers, with levels decreasing significantly during HDV-ban periods. In contrast, the aromatic hydrocarbons and CO displayed only minor variations between these two periods. Furthermore, on typical workdays NOx levels reached a maximum that corresponded to a peak in HDV numbers, whereas the aromatic compounds peaked later when LDV numbers had reached their maximum. Our findings give strong evidence that increased NOx and PM10 levels can be predominantly attributed to HDV traffic. Principal components analyses for the separated data further support this conclusion.