Effect of submersion on the distribution of rare earth Nd in different soils
淹水条件对不同土壤中稀土元素钕形态分布的影响

Speciation of Neodymium (Nd) in soils under submerging condition was studied based on comparison of that under dry condition. The results showed that the submerging treatments had no significant effects on the forms of B1 (including water soluble Nd, exchangeable Nd and carbonate-bound Nd), B2 (Fe/Mn oxide-bound Nd) and B3 (organic matter- and sulfide-bound Nd) for endogenous Nd, but increased the proportions of B1 and B3 if addition of extraneous Nd in soils. The proportion of B2 varied with soil properties, showing stable for neutral soil, and an increase for alkaline soil and a decrease for acidic soil. The mechanisms behind these changes remained unknown. The submerging treatments had no significant effects on speciation of Nd for yellowish red and yellow cinnamon soils, but had significant effects for Vertisol. Whether under submerging or dry conditions, the concentrations in the three soils were all ordered as yellowish red soil > yellow cinnamon soil > Vertisol for B2 and Vertisol > yellow cinnamon soil > yellowish red soil for B3. The concentration of B1 was the greatest in yellowish red soil. Both the submerging and dry cultivations caused the extraneous Nd to transform into residual form, with different contributions to the residual form for B1, B2 and B3.