Nano Fe-oxide and nano-hydroxyapatite can decrease the Cd uptake by plant in a soil treated with Cd-polluted sewage sludge

Decreasing heavy metal availability has important key factors in environmental studies. This research was done to investigate the effect of nano-Fe oxide and nano-hydroxyapatite (NHAP) on Cd uptake by the plant cultivated in the sewage sludge amended soil. Treatments consisted of applying Cd (0, 10 and 20 mg Cd/kg)-polluted sewage sludge at the rates of 0, 15 and 30 t/ha, nano-Fe oxide (0 and 0.5 ppm) and NHAP (0, 0.5 and 1 % (W/W)). The plant in this experiment was the pinto bean (Cv. Khomein). After 90 days, the plants were harvested and the plant Zn, Cd, and Fe concentrations were measured using atomic absorption spectroscopy. In addition, soil microbial respiration was calculated. Soil application of NHAP significantly increased the Zn and Fe concentration of the plants cultivated in the soil which was amended with 15 t/ha sewage sludge by 12.8 and 14.5%, respectively. However, the Cd concentration was decreased by 17.2%. Using 15 and 30 t/ha sewage sludge significantly increased the plant Zn and Fe by 13.1 and 14.6%, respectively. Foliar application of nano-Fe oxide at the rate of 1 ppm significantly decreased the plant Cd uptake by 18.3%. Using NHAP (0.5 % (W/W)) and sewage sludge (30 t/h) significantly increased the soil microbial respiration by 14.2 and 15.3%, respectively. The results of this study showed that using organic amendments such as NHAP and sewage sludge or foliar application of nano-Fe oxide can affect in decreasing the heavy metal uptake by plants that is a positive point in environmental studies.