Abundance, spatial variation, and sources of rare earth elements in soils around ion-adsorbed rare earth mining areas

Rare earth elements (REEs) concentrated in soils have attracted increasing attention about their impact on soil health as emerging contaminants. However, the sources of REEs enriched in soils are diverse and need to be further investigated. Here, surface soil samples were collected from southern Jiangxi Province, China. REEs contents and soil physicochemical properties were determined, and cerium (Ce) and europium (Eu) anomalies were calculated. Moreover, we established a model to further identify the main sources of REEs accumulation in the studied soils. Results show that the abundance of soil REEs reveals larger spatial variation, suggesting spatially heterogeneous distribution of REEs. The median content of light REEs in soils (154.5 mg kg- 1) of the study area was higher than that of heavy REEs and yttrium (35.8 mg kg- 1). In addition, most of the soil samples present negative Ce anomalies and all the soil samples present negative Eu anomalies implying the combined effect of weathering and potential exogenous inputs on soil REEs. Positive matrix factorization modeling reveals that soil REEs content is primarily influenced by soil parent materials. Potential anthropogenic sources include mining-related leachate, traffic exhaust, and industrial dust. These results demonstrate that the identification of sources of soil REEs is an important starting point for targeted REEs sources management and regulation of excessive and potentially harmful REEs levels in the soil.

Automated summary

The enrichment of rare earth elements (REEs) in soils has been a concern for soil health as emerging contaminants. This study collected surface soil samples from southern Jiangxi Province, China, and determined the REEs content and soil physicochemical properties. A model was established to identify the main sources of REEs in the soils. The results revealed spatial variation in soil REEs abundance and a higher median content of light REEs compared to heavy REEs and yttrium. The negative anomalies of Ce and Eu indicated the combined effect of weathering and potential exogenous inputs on soil REEs. Positive matrix factorization modeling indicated that soil parent materials were the primary influence on soil REEs content, with potential anthropogenic sources including mining-related leachate, traffic exhaust, and industrial dust.