Phytoextraction of Cadmium and Zinc By Sedum plumbizincicola Using Different Nitrogen Fertilizers, a Nitrification Inhibitor and a Urease Inhibitor

Cadmium (Cd) and zinc (Zn) phytoavailability and their phytoextraction by Sedum plumbizincicola using different nitrogen fertilizers, nitrification inhibitor (dicyandiamide, DCD) and urease inhibitor (N-(n-Butyl) thiophosphoric triamide, NBPT) were investigated in pot experiments where the soil was contaminated with 0.99mg kg(-1) of Cd and 241mg kg(-1) Zn. The soil solution pH varied between 7.30 and 8.25 during plant growth which was little affected by the type of N fertilizer. The (NH4)(2)SO4+DCD treatment produced higher NH4+-N concentrations in soil solution than the (NH4)(2)SO4 and NaNO3 treatment which indicated that DCD addition inhibited the nitrification process. Shoot Cd and Zn concentrations across all treatments showed ranges of 52.9-88.3 and 2691-4276mg kg(-1), respectively. The (NH4)(2)SO4+DCD treatment produced slightly higher but not significant Cd and Zn concentrations in the xylem sap than the NaNO3 treatment. Plant shoots grown with NaNO3 had higher Cd concentrations than (NH4)(2)SO4+DCD treatment at 24.0 and 15.4mg kg(-1), respectively. N fertilizer application had no significant effect on shoot dry biomass. Total Cd uptake in the urea+DCD treatment was higher than in the control, urea+NBPT, urea+NBPT+DCD, or urea treatments, by about 17.5, 23.3, 10.7, and 25.1%, respectively.