A Novel Mobile Laboratory for “Chasing” City Traffic 2004-01-1962

A mobile laboratory was designed and built in Helsinki Polytechnic, in close co-operation with the University of Helsinki, to measure traffic pollutants with high temporal and spatial resolution under real world conditions. The laboratory provides measurements of gaseous pollutants and particle size number distributions as well as meteorological and geographical parameters. Two inlet systems are employed to enable the “chasing” of different type of vehicles. This paper introduces the construction and technical details of the mobile laboratory, and presents the results from “chasing” experiments performed in the Helsinki metropolitan area during a field campaign in June, 2003. New particle formation was found while driving in the exhaust plume of vehicles. Approximately 75% of the total particle number concentration was due to particles smaller than 50 nm in size. The shorter the distance from the “chased” vehicle, the higher nuclei mode number concentration was recorded owing to the reduced potential dilution time. Typical modal mean particle diameters were 7-15 nm and 70 nm.