A mobile laboratory for monitoring non-exhaust emissions in Finland

Local vehicular traffic is responsible for a substantial fraction of PM10 in urban air mainly due to non-exhaust traffic emissions and resuspension from street surfaces (e.g. Zhao et al., 2006). In Northern areas (e.g. Scandinavia) street dust levels are especially high during spring, and the diurnal average PM10 value (the EU directive) is exceeded more than the allowed 35 times per year. In this paper we introduce the sampling system of a mobile research laboratory SNIFFER for studying emission levels of respirable dust from street surfaces. We have measured a unique time series of the street level PM10 concentrations in a city of Helsinki, Finland, during the last five springs. A special 20 km route in downtown was selected to cover main streets including bus lanes, tram lanes, canyon streets, open transit streets and some cobblestone covered streets. For every spring the maximun emission level averaged over the whole route was 2000-4500 mg/m-3 and occurred in the turn from March to April, after which the clear decreasing trend was found. The most highest street concentrations were measured on the street canoyns as well as on the streets covered by copplestone and on the sections which were under work construction