Impact of dust loads in long railway tunnels: In-situ measurements and consequences for tunnel facilities and operation

Reliable information concerning rail tunnel dust emissions dependent on parameters such as train type, train speed, operating conditions, etc. is quite rare. Thus, in order to quantify the effect of heavy metals on the environment, specific data is needed when designing air filtration systems inside the tunnel, or in carrying out environmental assessment studies. Detailed investigations were therefore carried out in a test installation in an Austrian rail tunnel. In order to be able to use these data for the long railway tunnels currently under construction, train-specific emission factors were determined. It was found that emissions from freight trains are up to 6.68 times higher than those from passenger trains. Bulk freight transport in open cars produces the highest emissions, while the short regional passenger trains exhibit the lowest emission levels. Chemical analysis of the samples came up with a mass fraction of 60% related to metals, of which, iron is the dominating component. Based on these findings, maintenance intervals for high quality dust filters were derived. In addition, the knowledge gained on train type-dependent emission factors greatly helps to improve upon the very poor data now used in environmental studies, particularly when determining railway particulate matter emissions.