Heavy Metal Content of Roadside Soils along Ring Road in Riyadh (Saudi Arabia)

Abstract

The metal content (Pb, Zn, Cu, Cr and Ni) of roadside surface

and subsurface soils was determined along the Ring Road in Riyadh

city. Their levels were investigated in relation to traffic loads and

distance from the road edge. Results showed that enhanced levels

of Pb, Zn and Cu correlated well with traffic density. The concentration

of Pb and Zn decreased exponentially with distance from

the road edge and dropped to a background level at about 40 and

30 m respectively. Cr correlated well with Pb indicating the same

source. No evidence of Ni contamination of roadside soils was

obtained. Concentrations of Pb, Zn and Cu showed enrichment in

the upper surface soils, which is attributed to the low rainfall in the

study area. An important source of lead is the combustion of leaded

gasoline used for transportation in Saudi Arabia.