B.6 Determination of the impact of traffic related sources

This action is aimed at estimating the contribution of road traffic to PM levels in the five AIRUSE cities and at improving the knowledge of emission processes such as road dust resuspension, brake wear and tire wear.

The first goal is achieved after a 1 year PM10 and PM2.5 sampling campaign in each AIRUSE city, with a complete chemical characterization of PM samples and application of the Positive Matrix Factorization (PMF) model (Action B2) for source apportionment.

Results show that the total contribution from road traffic emissions to PM10 varies significantly in absolute terms (6.2-13.0 µg m-3) being the POR-TR a traffic station, but the traffic-related percentage of PM10 is quite narrow among the Mediterranean basin (31-37%). Similarly in PM2.5 absolute annual contributions vary within 3.0-10.4 µg m-3 but the percentage is quite constant within 30-41%. These results show unequivocally that road traffic is the main source of PM10 (at all sites) and PM2.5 (first source in MLN-UB, FI-UB, and POR-TR) except in ATH-SUB and BCN-UB where it is the second most important after Secondary sulphate (which however it is not identified with a specific source).

Three different traffic sources were identified at each city: vehicle exhaust, vehicle non-exhaust and traffic-related secondary nitrate. Among the three, vehicle exhuast is still in general the highest contributor to PM10. The only exceptions are ATH-SUB for PM10 and in MLN-UB for PM2.5 where the highest contribution is from traffic-related secondary nitrate, due probably to a lower share of primary exhaust emissions in Athens (low diesel fleet). The second most important traffic-source is non-exhaust, whose importance has been increasing during the last decade due to the lack of mitigation measures.

The second goal has been achieved through intensive road dust sampling campaigns at four AIRUSE cities and the chemical and mineralogical characterization of brakes pads and tires of common use in Europe.

Road dust sampling campaigns were performed in Athens, Florence and Porto, while in Barcelona previous data from the AIRUSE coordinator were used.Observed road dust levels ranged within 0.2-13.4 mg m−2, well within the range observed in Europe. However a clear difference can be seen from one city to another. Barcelona shows the highest road dust loadings (7.1 mg m−2 in average), followed by Florence (3.6 mg m−2), while much lower values were found in Porto (0.3 mg m−2) and Athens (0.8 mg m−2). As already mentioned, such difference may be explained by local factors, such as the road pavement type; however the Atlantic climate of Porto is believed to play a key role, maintaining high humidity of road surface. Interestingly we found a very good correlation (r2=0.84) between the average level of road dust and the ratio Vehicle non-exhaust/Total traffic contribution at each city, which might be used as a proxy of the road dust emission potential.

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Road dust collection campaign Florence

A road dust sampling campaign was conducted on several streets of Florence between the 21st November, 2014 and the 29th January, 2015. The sampling device developed by IDAEA was used to collect PM10 samples. In every sampling site, 3-4 samples were collected (1 on Teflon and 2-3 on quartz fibre filters) in different points of the right track (asphalted road). Each sample was collected for 15 min. over an area of 0.5 m2. Samples collected on quarts fibre filters have been analysed by a thermal-optical method to obtain their carbonaceous content and by inductively coupled plasma techniques to get the elemental speciation. Samples collected on Teflon filters have been analysed by PIXE to obtain a second quantification of elemental concentrations, especially for soil related elements, which are very well detected by PIXE. The “dust chemical profiles” will be useful to better estimate the contribution of resuspension to ambient PM10 levels.

Road dust campaign Florence photo 1 Road dust campaign Florence photo 2 Road dust campaign Florence photo 3

Road dust collection campaign Athens

A road dust collection campaign was conducted in Athens on August 7th, 2013. These are the first experimental data on road dust chemical profile for the city and they will be used during receptor model application. The campaign was carried out on Stournari street, outside the Ministry of Health, at the city centre. A specially designed dust collector was used for the sampling of PM10 on quartz and teflon filters.  The collector has been developed by IDAEA/CSIC. Training of NCSR “D” staff on the use of the collector and the sampling protocol to be followed was performed by Dr. A. Karanasiou from IDAEA/CSIC. The collected filters were analysed for elemental and organic carbon, ionic species and major and trace elements.

road dust Athens 1 road dust Athens 2 road dust Athens 3   August 2013

Road dust collection campaign Porto

With the collaboration of the Traffic Division of the City Council, as well of the Municipal Police, a road dust sampling campaign was conducted on several streets of Porto and in a road tunnel (Avenida da Liberdade). The sampling device developed by Fulvio Amato was used to collect PM10 samples. These filters have been analysed by a thermal-optical method to obtain their carbonaceous content and by inductively coupled plasma techniques to get the elemental speciation. The “dust chemical profiles” will be useful to better estimate the contribution of resuspension to ambient PM10 levels.

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Training on road dust sampling device

In August 2013 Angeliki Karanasiou from the coordinator IDAEA-CSIC visited the associated partner “NCSR Demokritos” in Athens, for a one day training of the technical staff on the road dust sampling device, designed and developed by the coordinator IDAEA-CSIC.

Demonstration of the device and sampling tests took place at a street near “Demokritos” and 3 of its members assisted: Konstantinos Eleftheriadis; Evangelia Diapouli and Stergios Vratolis.

road dust Athens 6 road dust Athens 5  August 2013