Effects of in-situ leaching process on spatial distribution of soil properties in ion-type rare earth mines

Abstract

In this study, an abandoned ionic rare-earth mine (MZ) was conducted in southern Ganzhou, China, to investigate the impacts of in-situ leaching mining techniques on the surface soil, with spatial characteristics analyzed from the mine’s bottom (MB), middle (MM), and top (MT) sections. The results revealed that, compared to the control area (CK), the soil in MZ exhibited significant reductions in pH, organic matter, and available potassium levels. Conversely, the concentrations of NH₄⁺-N and SO₄²- in MZ soil were significantly higher than those in CK, being 55.58 and 1.36 times higher, respectively. The distribution pattern of rare-earth elements in MZ soil was consistent with that in CK, but at levels exceeding the background total rare-earth content of Jiangxi Province soils. Significantly lower concentrations of Zn, Pb, Cr, and Cd were observed in MZ soil compared to CK. Spatially, the organic matter content in MM and MT soils was significantly lower than in MB, while the NH₄⁺-N content was significantly higher, being 10.55 and 7.86 times higher than that in MB, respectively. The pH of MT soil was significantly lower than that of MB, indicating the most severe acidification. MT soil also exhibited the lowest comprehensive fertility and the highest Nemerow comprehensive pollution index for non-rare-earth heavy metals. Consequently, the top region of MZ, three years post in-situ leaching mine closure, was identified as the most severely affected area by mining activities, with low soil fertility, residual leaching agents, and soil acidification posing the primary challenges in the abandoned mining area.