Toxic metal pollution and ecological risk assessment in superficial soils of 'rural-agricultural and coastal-urban' of Monastir region, Eastern Tunisia

摘要

Spatial variability of heavy metal concentrations namely Fe, Pb, Cu, Cd, Ni and Zn, in surface soils of Monastir region showed almost similar trends (an exception made for Fe). The spatial distribution of calculated enrichment factors showed moderate enrichment of superficial soils collected from sites located in both western (rural-agricultural) and eastern (coastal-urban) parts of the region. Contrary, superficial soils collected from sites located in the central part were characterized by a minor enrichment. Adopted chemometric approaches based on principal component analysis and hierarchical cluster analysis highlighted the significant impact of local man-made sources (Traffic road in the costal-urban area and the motorway and railway crossing its western rural-agricultural area). Calculated geoaccumulation index values revealed that mobile source's influence presumed by a moderate contamination in terms of Pb, Zn, Cu, Cd, and Ni. Referring to the coastal-urban area, a significant horizontal extension of contaminated sites in the western part of the region was recognized. Spatial distribution of the integrated pollution index revealed that only site neighboring the busy railway and motorway (approximate to 0.6 km), indicated a high pollution level. Furthermore, it showed a moderate potential ecological risk for all selected metals.