淹水条件对不同土壤中稀土元素钕形态分布的影响

Effect of submersion on the distribution of rare earth Nd in different soils

以旱作条件为参照,研究淹水条件对钕形态分布的影响.结果表明,淹水条件对内源钕B1态(水溶态、可交换态与碳酸盐结合)、B2态(铁锰氧化物结合态)和B3态(有机质及硫化物结合态)的分布无显著影响.对于外源钕,淹水条件使B1和B3态浓度增加,而B2态浓度则因土壤性质而异,中性土壤中浓度稳定,酸性和碱性土壤中浓度分别增高和降低,其机制有待进一步研究;淹水条件对黄红壤和黄褐土中外源钕无显著影响,而砂姜黑土则相反;两种条件下,3种土壤中B2和B3态浓度顺序相同,B2态浓度顺序为:黄红壤>黄褐土>砂姜黑土,B3态浓度顺序为:砂姜黑土>黄褐土>黄红壤,而B1态在黄红壤中浓度最大;外源钕有进入残渣态的趋势,但并不明显,且不同土壤的各形态对残渣态的贡献不同.

The speciation of neodymium（Nd） in submerged soils was compared to that in dry soils.The results showed that the submersion treatments had no significant effects on the B1（including water soluble Nd,exchangeable Nd and carbonate-bound Nd）,B2（Fe/Mn oxide-bound Nd） and B3 forms（organic matter-and sulfide-bound Nd） for endogenous Nd,but if extraneous Nd was added to the soils the proportions of B1 and B3 increased.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 remain unknown.The submersion treatments had no significant effects on speciation of Nd for yellowish red and yellow cinnamon soils,but had significant effects for Vertisol.Whether under submerged or dry conditions,the concentrations in the three soils were in the order： 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 submerged and dry cultivations caused the extraneous Nd to transform into the residual form,with different contributions to the residual form for B1,B2 and B3.