Assessment of Heavy Metal Contamination in Roadside Soils along Irbid-Amman Highway, Jordan by ICP-OES

In this study, the concentrations of selected heavy metals (Al, Cd, Cr, Cu, Mn, Pb, Co, Fe, Ni, V and Zn) in roadside soil samples were determined by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) after microwave digestion. A total of sixty roadside soil samples were collected during July 2018 from seventeen sampling sites (5 km apart) from both sides along Irbid-Amman highway, Jordan. The average concentrations (±SD) of the investigated metals in the analyzed soil samples were found to be 18400 (± 11200), 6.0 (± 4.7), 132 (± 47), 49 (± 26), 695 (± 310), 96 (± 53), 78 (± 32), 31800 (± 12600), 116 (± 67), 141 (± 74) and 129 (± 112) µg/g for Al, Cd, Cr, Cu, Mn, Pb, Co, Fe, Ni, V and Zn, respectively. With exception of Mn, the enrichment factors for the investigated metals in roadside soils were found to be more than 10, indicating anthropogenic sources such as automobile traffic. In the absence of any industrial activities in the sampling sites, the high concentrations of the investigated metals suggest that automobile emissions are the major source of roadside soil pollution. The results obtained in this study showed that metal concentrations in the analyzed soil samples are strongly influenced by the wind direction and traffic density in the investigated area. The higher metal concentrations on the west side of the road were due to the easterly prevailing wind in the studied area. As expected, the concentrations of heavy metals decreased with increasing distance from the edge of the road. The results obtained in this work were compared with the literature values.