[Effect of extraneous rare earths (REs) on form of soil exchangeable REs and heavy metals]

The effects of extraneous rare earths (REs) on the form of exchangeable REs and heavy metals Fe, Mn and Zn in yellow cinnamon soil in different terms were studied through soil culture in both dry and inundated condition. The result showed that the treatments of REs enhanced the contents of soil exchangeable REs (EX-REs) and its distribution coefficients also increased while most still remained under 10%. The contents of EX-REs in inundated condition were higher than that in dry condition, but they decreased with the duration of soil culture. The composition of EX-REs in soil gradually approached that in extraneous REs, and it remained relatively steady over the treatment with 200 mg.kg-1 applied REs. Applying REs raised the contents of exchangeable heavy metals, and the contents of exchangeable Fe, Mn and Zn increased with linear trend, of which the effect of REs on Mn was the strongest one.