Heavy Metal Concentrations in Soils and Date Palms Irrigated by Groundwater and Treated Wastewater

Agricultural management of wastewater is a sustainable approach for arid- and semi-arid regions of the world. This research was conducted to evaluate the suitability of treated waste water for irrigating date palms and monitoring the partitioning of some heavy metals (e.g., Cu, Cr, Cd, Pb, Mn, Fe, Zn etc.) among soil, plant and fruits. Soil and plant samples including leaves and fruits were collected from different locations of the date palm plantations at the Sultan Qaboos University, Al-Hamra and izki which have been irrigated with treated water or ground water for seven years. Results showed that the concentrations of heavy metals in both groundwater and treated waste water were within the international standards. There were significant variations in heavy metal concentrations in soil at studied locations. In most of the cases, the concentrations of heavy metals were relatively higher in soils irrigated with treated waste water compared to the soils irrigated with groundwater. Generally, the concentrations of heavy metals in date palm leaves were not significantly different in plants irrigated with treated waste water or groundwater. However, there were significant differences in the concentrations of heavy metals in date fruits irrigated with different sources of water. The concentrations of some metals (Fe, Zn, and Ni) in date fruits were higher in waste water irrigated plants whereas other metals (Cu, Cd, Pb, and B) were higher in ground water treated plants. In all cases the concentration were within the permissible limits. Thus, the long-term effects of treated waste water did not indicate any adverse effects of irrigation using groundwater and waste water on fruit mineral composition, including heavy metals.