Effect of Irrigation with Treated Urban Wastewater on Heavy Metals Accumulation and Distribution in Soil Profile under Corn and Tomato

When good quality water is scarce, application of unconventional water resources is considered in agriculture. One of these sources is treated urban wastewater (TUW). In this research, in which plants were grown in medium-size pots, effect of irrigation with wastewater was evaluated on accumulation and distribution in soil profile of heavy metals (iron, manganese, zinc, copper, arsenic, cadmium, lead, and nickel) under greenhouse conditions of the University of Kurdistan. The factorial experiments were conducted according to complete randomized design with three replications. Also, the effect off three irrigation treatments consisting of TUW, alternating TUW- ordinary water, and ordinary water on the accumulation of heavy metals in the soil cultivated with corn and tomato plant were investigated. Soil samples were taken from four different depths and three horizontal distances from the plant. The results showed that TUW had significantly greater amounts of heavy metals in comparison with ordinary water. Also, the maximum and minimum amounts of heavy metal were observed in TUW and ordinary water, respectively. From the findings, it can be concluded that concentration of heavy metals decreased with increasing depth and horizontal distance from the plant location. Manganese (7.3 mg/kg) had the highest concentration in the soil. Also, Arsenic (5.41 mg/kg), iron (4.21 mg/kg), zinc (3.93 mg/kg) and copper (3.3 mg/kg) ranked from the second to fifth, respectively. Type of plants had a significant effect on the accumulation of manganese, zinc, and arsenic. According to the results of this study, there is a threat to human health of heavy metals contamination in plants such as corn and tomatoes. Therefore, it can recommended that irrigation with treated wastewater is to be limited to non-food crops.