Rare earth element migration and impact of Dicranopteris dichotoma at mines in south China

Abstract

The migration of rare earth elements (REEs) has a major influence on the environment. However, little is known about REEs migration control by Dicranopteris dichotoma at REEs mines. Therefore, this study examined the horizontal and vertical migration of REEs using artificial rainfall and naive soil column experiments, respectively, and the REEs migration control of Dicranopteris dichotoma at REEs mines in south China. The REEs contents in the runoff and sediment were found to be 32.42 μg and 3.39 mg, respectively, in the artificial rainfall experiment. The mean REEs content and amount in the leaching liquor were 0.23 μg L−1 and 7.75 μg, respectively. The REEs content after leaching was significantly lower than that before leaching in the 0–5 cm layer, was significantly higher than that before leaching in the 5–10 cm layer. However, the REEs content of the Fe–Mn oxide form showed significant variation among the sites with different Dicranopteris dichotoma covers. Moreover, the runoff reducing rate rose with increasing Dicranopteris dichotoma cover, and the sediment reducing rate increased to the relatively stable stage when Dicranopteris dichotoma cover was equal or greater than 70%. Thus, REEs migration by sediment is the dominant migration method, and the risk of REEs vertical migration in the soil is low and might have been overestimated. Further, Dicranopteris dichotoma does not control REEs migration by altering the REEs forms, and Dicranopteris dichotoma cover should reach and be maintained at ≥ 70% in order to control REEs migration at REEs mines in south China.