Effects of different remediation measures on rare earth elements and non-rare earth toxic elements in rare earth tailings soil and navel orange

Background and Aims

The heap leaching technique causes considerable damage to environment during the mining of ionic rare earth ore in southern China. Restoration of abandoned mining sites into arable land requires determination of the contents of rare earth elements (REEs) and non-rare earth toxic elements in soil and crops.

Methods

In the present study, five treatments, including rare earth tailings without any amendment or navel orange cultivation (RET), biochar and fly ash combined with three organic fertilizers (cow manure organic fertilizer [CF], pig manure organic fertilizer [PF], sugarcane bagasse organic fertilizer [SF]), and a treatment without any amendments (CK) were arranged to explore the effects of different treatments on rare earth and non-rare earth toxic elements contents in soil and crops.

Results

Total EDTA-extractable concentrations of REEs in CF, PF, and SF soils were 42.8%, 26.7%, and 30.5% lower than that those in CK, respectively. Total EDTA-extractable concentrations of non-REEs in the CF, PF, and SF, soils were significantly higher than those in the CK, with the highest in PF, at 337.5%. Compared with CK, all treatments reduced total REEs in navel orange leaves, peel, and pulp. Besides, total rare earth and non-rare earth toxic elements contents in the pulp of the all-treatments navel oranges were all lower than the pollutant limit values for food.

Conclusions

Use of biochar, fly ash, and SF is the optimal strategy for improving ionic rare earth tailings soil, and navel orange cultivation, is a potential strategy for remediating such abandoned mining sites.