ASSESSMENT OF METAL TRACE ELEMENT CONTAMINATION OF SURFACE SOILS BY ROAD TRAFFIC (RABAT-SALE HIGHWAY - MOROCCO)

The vehicle emissions cause dangerous metal rejections for environment. Roadside soils can act as long-term reserves of non-biodegradable metals. The overall objective of this research is to study the impact of the metals emitted by vehicles on the roadside soils close to Rabat-Sale high-way and their spatial distribution. This study evaluated the concentration of metal trace element (MTE) in the soils, analyzed the correlation between these metals and land use, as well as with physico-chemical parameters. Samples of roadside soils were collected at precise distances (5, 50 and 100 m), moving away from the road, to analyze spatial distribution of MTE in the soils. The averages of concentrations found in the roadside soils close to Rabat-Sale highway are slightly high, but show an enrichment in some stations. The traffic characteristics are one of the parameters to be considered in the evaluation of the im-pact of the road traffic on the surrounding soils. The age of the highway plays a very important part in the metal enrichment of soil. In fact, Rabat-Sale highway of recent age presents an enrich-ment in elements Mn, Co; elements lately integrated in the field of road traffic. The concentrations of metals recently introduced into automobile technology are higher in the young roads, whereas metals which have been used for several years (Cd, Cu, Pb, Zn) would be higher in the roads of advanced age, confirming the risk of metal deposit in the roadside soils. Significant correlations were found between the concentrations of MTE in the soil.