Soil metal pollution in freeway traffic (Mohammedia-Bouznika section, Morocco)

Freeways and main roads are often potential sources of pollution for the environment, particularly soil, air, and water. This study aims to assess the degree of contamination and metallic pollution of soils along the Mohammedia freeway, focusing on elements such as Lead, Zinc, Nickel, Copper, Chromium, and Cobalt. Eleven soil samples taken along the Mohammedia freeway were analyzed. The results revealed trace metal element concentrations that varied from one aspect to another and from one sampling site to another. Concentrations in milligrams per kilogram mg Kg⁻¹ranged from 25 to 80 for Zinc, from 20 to 44 for Nickel, from 9 to 36 for Copper, from 47 to 93 for Chromium, from less than 10 to 39 for Lead, from 9 to 21 for Cobalt. These results indicate that trace metal contamination in the areas studied is relatively low compared with the AFNOR NF U 44-041 standard. Pollution index analysis reveals moderate to high contamination levels for chromium and copper, with mean pollution index values of 1.37 and 1.42, respectively. In contrast, lead and zinc show low contamination levels, with average pollution index values of 0.87 and 0.81. Cobalt and nickel contamination is negligible, with average pollution index values of 1.05 and 0.86. This contamination depends on several parameters (soil type, distance between sampling point and freeway, number of vehicles using the freeway, etc.).