Heavy Metal Levels in the Soils of Riyadh City, Saudi Arabia

Abstract

The metals content (Pb, Zn, Co, Cr, Ni and Li) of surface and
subsurface soils was determined in Riyadh city. A total of 303
surface soils and 303 corresponding subsurface soil samples were
collected at intersection points of a 1 x 1 km grid covering the whole
city. Metal levels were investigated in relation to population density,
prevailing wind direction, land topography and the structure of the
buildings in the city. The levels of Pb, Zn and Cu were found to be
elevated in the urban areas (city centre), which are correlated well
with the population density. Lead, zinc and to a lesser extent copper
distribution in surface soils were affected by the prevailing winds.
Lead levels were attributed to the automobile emission whereas Zn
and Cu were found to be associated more with the industrial locations
than in residential areas. Surface to subsurface ratio results
showed Pb, Zn and Cu were largely concentrated in the upper
surface soils indicating the atmospheric deposition as the main
source of such metals.