BACKGROUNDThe Bayan Obo mining area is the main producing area of rare earth elements. During mining and refining, rare earth elements enter plants through migration and enrichment. Study on the distribution characteristics and migration patterns of rare earth elements will provide data support for bioremediation following the closure of the Bayan Obo ore body pit.

OBJECTIVESTo study the distribution characteristics and migration patterns of rare earth elements in soil and plants.

METHODSSeven soil sampling points were set up, and seven plant types including Honeysuckle, Artemisia desertorum, Astragalus Adsurgens Pall, Agriophyllum squarrosum (L.) Moq, Artemisia carvifolia, Populus simonii Carr and Salsola collina Pall were collected. The content of rare earth elements in soil and roots, stems, leaves (or flowers) and whole plants was determined by inductively coupled plasma-mass spectrometry.

RESULTSWith the increase of the distance between the sampling area and the main mining area, the rare earth element content in the soil samples decreased. The rare earth element content of Honeysuckle was the highest in the studied plants, whereas it was the lowest in Artemisia carvifolia. The rare earth element content in whole plant and various parts (root, stems, leaves or flowers) in different plants were analyzed by multiple linear regression analysis. The rare earth element content of leaves (or flowers) accounted for the largest proportion in whole bead plants. In addition, the content of rare earth elements in plants was basically unchanged in different seasons. The rare earth elements with higher content were 0.0035%-0.020%, 0.0012%-0.011%, 0.0010%-0.0094% and 0.00036%-0.0046% for Ce, La, Nd and Pr, respectively.

CONCLUSIONSAccording to the gradual reduction pattern of rare earth elements in soil samples, the rare earth source of the soil around the mining area may be caused by the diffusion of ore during mining and refining. According to the rare earth enrichment ability of plants, Honeysuckle with strong enrichment ability of rare earth can be used for bioremediation of mines, after the mine is closed.