The contamination caused by road traffic not only affects the air, it also seeps under the asphalt and harms the adjacent soil and plants. Jos Antonio Carrero, a chemist at the University of the Basque Country (UPV/EHU), has delved into the subject and studied the extent of the impact of the metals emitted by cars. Likewise, he has analysed their consequences in the short, medium and long term and for this purpose has taken samples from roadsides in Bizkaia (Basque Country) of differing ages; these include the old road connecting Bilbao and Mungia where it passes through Artebakarra (over 60 years old), the motorway that runs parallel with it (over 20 years old), a roundabout in Berango (4-5 years old) and another in Sopelana (1-2 years old). His thesis is entitled Evaluacin del impacto del trfico rodado en suelos y plantas de margen de carretera (Evaluation of the impact of road traffic on roadside soil and plants).
Lead is the most well-known metal among those emitted by road traffic; even though over a decade has passed since leaded petrol was banned, the presence of this contaminant remains on the edges of roads. Nevertheless, Carrero has confirmed that despite its great toxicity, there are other metals that can pose even greater risks for the environment, due to the fact that they can filter through deeper soil layers. Apart from lead, this researcher has studied zinc oxide (produced by tyre wear) and barium, copper and antimony (resulting from brake pad wear), for example.
The older they are, the more there is
Carrero has extracted the metals found in the samples taken and has determined the concentration in which most of them occur. It can be seen that there is a greater accumulation of metals linked to traffic in the upper levels of the soil closest to the veteran roads. "It depends on how long the road has been in use. It is in the older roads that the metals accumulate and a gradient of concentration with
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