Distribution of heavy metals in soils and plants around a cement factory in Riyadh City, Central of Saudi Arabia.

摘要

Thirty two composite soil and twenty plant samples were collected from area around a cement factory, south of Riyadh City, Central of Saudi Arabia. Soil samples were obtained at two depths, surface (0-10 cm) and subsurface (10-20 cm) and plant samples collected from around cement factory and split into two portions, one washed by distilled water and other is not. Both soils and plants samples were analyzed for its contents of Cd, Cr, Cu, Pb, Zn, Fe and Al metals. Concentrations of Cd, Cr and Zn metals in the soil surface were higher than in subsurface soil samples, while, Cu, Pb and Fe concentrations in subsurface soil were higher. Heavy metals are concentrated on the surface soils due to its chemical and physical soil properties such as high CaCO₃% as well as alkaline pH value. The relatively high soils content Fe, Al, Zn, Cu, Pb, Cr and Cd were related to anthropogenic sources of cement industry. The Enrichment factor (EF) values of heavy metals in soils calculated ranged from 0.25 to 830. Up to 34.3% and 6.25% of soil samples were extremely high enrichment with regard to Cd and Pb, respectively. In addition, 6.3, 9.4, 40.6 and 15.6% of soil samples showed a significant enrichment for Cd, Cu, Pb and Zn, respectively. For Al and Cr metals more than 90% of soil samples showed deficiency to minimal enrichment. Differences in heavy metal uptake rate between Zygophyllum migahidii (Zygophyllaceae) and Conocarpus lancifolius (Combretaceae) plants were observed. High concentrations of some havey metals were determined in the unwashed plant samples as a result of exposure to aerosols. Statistically significant relationships were observed between metals concentration of the studied plants with distance from cement factory. The highest amounts of Pb in plant samples were in leaves with concentration of 14.1 ppm. Zygophyllum migahidii plant accumulated the highest amounts of Cd, Cr, Cu and Al metals. In the other hand, Conocarpus lancifolius plant accumulated the highest amount of Pb and Zn metals for both washed and unwashed plant samples.