Abstract: A pot experiment was conducted to study the influence of different urea fertilization levels (0, 100, 200, 400, and 800 mg·kg^-1) on the speciation distribution of Cd and Pb in rhizospheric and bulk soils and the Cd and Pb concentrations in wheat plants under single (Cd=25 mg·kg^-1, Pb=1000 mg·kg^-1) and combined (Cd+Pb=25+1000 mg·kg^-1) contamination of soil, aimed to provide basis for the control of heavy metals-polluted soils. The results showed that with increasing urea fertilization level, the Cd and Pb concentrations in different parts of wheat improved significantly. The promotion effect of urea fertilization on Cd and Pb uptake by wheat was closely correlated with the influence of urea fertilization on the speciation distribution of Cd and Pb in soil. Urea fertilization decreased soil pH, and increased the contents of soil exchangeable Cd and Pb, the most available speciation for plant uptake, being the main reason of urea fertilization promoted the phytoavailability of soil Cd and Pb. Compared with single contamination, the combined contamination of Cd and Pb restrained the Pb uptake but facilitated the Cd uptake by wheat.

Key words: Land use type, Surface runoff, Heavy metals, Artificial rainstorm