Abstract

This study was conducted to investigate heavy metal accumulation in Melilotus officinalis under crown Olea europaea L forest in Rey town (Tehran, Iran), irrigated with wastewater and well water. Zn, Pb, Cr and Ni were determined at two sites. Heavy metal total concentrations (mg kg^-1) in clay soils of pH 7.95 - 7.93 from site irrigated with wastewater were 187.3 for Zn, 78.4 for Pb, 82.83 for Cr and 46.00 for Ni in the 0 – 15 cm soil depths. The concentrations increased significantly in the forest compared with control soils. Heavy metal concentration in plants increased in site irrigation with wastewater. Zn, Pb and Ni exceeded their permitted limits in soils and Pb, Cr and Ni exceeded their permitted limits in roots of plants irrigated with wastewater. It was concluded that the use of wastewater in urban forest enriched the soils with heavy metals to concentrations that may pose potential environmental and health risks on the long term. 

Key words: Heavy metals, Olea europaea L, Melilotus officinalis, wastewater, irrigation.