Biogeochemical cycle and residue of extraneous rare earth elements in agricultural ecosystem
Biogeochemical cycle and residue of extraneous rare earth elements in agricultural ecosystem
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发表时间：
2004
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通讯作者：
L. Wang;T. Liang;S. Ding;Chaosheng Zhang;G. L. Zhang;X. L. Wang
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作者：
L. Wang;T. Liang;S. Ding;Chaosheng Zhang;G. L. Zhang;X. L. Wang
在北京市大兴县庞各庄村进行了常规稀土叶面肥、常规稀土土施、三倍稀土土施和对照4组田间试验。利用ICP-MS测定了土壤和植物系统中各种稀土元素的输入和输出通量，结果表明，对照地降雨、雪、灌溉水、复合肥和粉尘携带的稀土元素总量处于很低的水平，每年仅为19.3g中心点nm（-1）左右。施用外源稀土的农田稀土元素输入量明显高于对照。叶面喷施和土施的稀土输入总量分别是对照的9.7倍和106倍。但是，四个试验田中小麦和入渗水对稀土的总输出量却相当接近。小麦的主要输出途径是吸收，各器官中稀土含量的大小顺序为根>叶>茎>皮>籽。计算结果表明，对照地稀土输出量略高于输入量，说明不施稀土肥，稀土难以在土壤中积累。在施用外源稀土的农田中，土壤中的稀土含量随稀土投入量的增加而增加。如果按常规施肥量定期施稀土肥，159年后表层土壤中稀土元素含量可增加一倍。叶面肥对稀土元素的累积速度远低于土施，表层稀土元素浓度增加一倍需要2008年。
Four groups of field experiments including foliage dressing with a regular amount of rare earth elements (REEs), soil dressing with a regular amount of REEs, soil dressing with a triple regular amount of REEs and the control were carried out in Panggezhuang Village, Daxing County, Beijing, where REE fertilizers are widely applied. The input and output fluxes of all kinds of REEs in the soil and plant system were measured using ICP-MS. The results show that the total amount of REEs carried by rain, snow, irrigation water, composite fertilizer and dust is at a very low level in the control field, which is only about 19.3 g center dot nm(-1) per year. The amounts of REE input in the fields with application of extraneous REEs are much higher than that under control. The total amounts of REE input in the fields with foliage dressing and soil dressing are 9.7 and 106 times higher than that under control, respectively. However, the total outputs of REEs via wheat and infiltrated water are quite similar among the four experimental fields. Uptake of wheat is the main way of output and concentrations of REEs in different organs follow a descending order of roots > leaves > stems > crusts > seeds. Based on calculation, the amount of REE output is slightly higher than that of input in the control field, which implies that it is hard for REEs to accumulate in the soils without application of REE fertilizers. In the fields with the application of extraneous REEs, the amount of REEs in soils can increase with the increasing input of REEs. If REE-fertilizers are applied regularly via soil dressing with the ordinary amount, the concentrations of REEs in the surface soils may double in 159 years. The speed of REE accumulation with foliage dressing is much lower than that with soil dressing, and it needs 2008 years to double the concentrations of REEs in surface soils.