Funding: NORPAC, MISTRA

Objectives: To characterise and establish particle emission factors from traffic. To link established traffic emissions to monitoring trace gases as substitutes for estimates of particle health impact.

Description: How the concentration of particles in the surrounding air is affected by changes in emissions is usually calculated by models, and the result is thus directly affected by the emission data used in the model. It is well known that traffic is a dominant source of ultrafine particles, however, the access to emission factors for size-segregated particles, or even total number of particles, is limited. The emissions from specific vehicles are frequently measured in laboratories, as dynamometer studies, where specified driving patterns are used to mimic real-world driving conditions. For a typical traffic source (e.g. a road segment) the vehicle to vehicle variation cannot be distinguished. The average line source can be estimated using data from individual vehicles, if traffic composition and driving pattern are known. The line source can also be measured directly, either on road, e.g., following the traffic with a measuring van, or stationary at the road side.

Recently, we developed a method that can extract traffic emission in relation to trace gases. The method has so far only been applied on a limited data set and we will now continue using extensive measurement data set from Stockholm and Köpenhamn to verify this method. In addition, this project has lead to the development of a measurement method that can give emission factor of specific compounds, e.g. selection of trace elements or organic compounds from a specific road segments. This can then be used as tracer compounds in source receptor evaluations.