Assessment of soil trace metal contamination of an uncontrolled landfill and its vicinity: the case of the city of ‘Targuist’ (Northern Morocco)

Abstract

This study aims to assess, for the first time, soil Trace Metal Elements (TME) contamination level in an uncontrolled landfill and its vicinity of 'Targuist' (town in northern Morocco). Soil samples were collected at two depths (20 and 40cm) from 16 sampling sites. Samples were characterized for their physicochemical parameters (pH, electrical conductivity (EC), organic matter (OM) and total organic carbon (TOC)) and for their TME (copper (Cu), zinc (Zn), cadmium (Cd) and chromium (Cr)) using atomic absorption spectroscopy (ASS). The results show no significant differences between soils sampled at 20cm or 40cm depths regarding the tested parameters. While significant differences between sampling sites In landfill and Out landfill is observed particularly regarding pH, CaCO3, TOC, and Cd. Overall, our results show that soil physicochemical properties follow a spatial variability with decreasing values moving away from the landfill. Regarding TME soil contents, our results show contamination levels in most of the sampling sites of the study area. Furthermore, the total TME concentrations in soils vary according to the type of the studied metal and to the sampling site. Zn, Cu and Cd show significant positive correlations with pH. However, Cd has no correlation with any other trace elements or soil physicochemical properties. Meanwhile, Cr shows a significant negative correlation with Zn and Cu. OM, TOC, CaCO3 and EC are strongly and positively correlated. These results are well illustrated in the outcomes of the Principal Components Analysis and Hierarchical Cluster Analysis.