Controlling Soil Erosion of Tailings From Rare Earth Mines With Paspalum wettsteinii and Soil Amendments

Abstract

Rare earth elements are crucial for applications in aerospace, electronics, petrochemicals, and metallurgical industries. However, as rare earth mining expands, their tailings accumulate, leading to severe soil erosion and threatening of the local ecology. This study aimed to investigate the impact of planting Paspalum wettsteinii and soil amendments, including superabsorbent polymers (SAPs), organics, minerals, and urea, in controlling soil erosion. Six treatments, each with four replicates, were implemented on micro‐runoff plots on rare earth tailings: (1) bare slopes, (2) bare slopes repaired with composite soil amendments, (3) grass slopes, (4) grass slopes repaired with SAPs, and grass slopes repaired with (5) low or (6) high amounts of composites. Over 11 months, natural rainfall patterns, vegetation coverage, runoff yield, and sediment yield were monitored on the tailings' slope. Initially, plant growth was slow on bare slopes (56% vegetation coverage at 130 days), but it significantly improved with soil amendments (74% vegetation coverage on grass slopes repaired with SAPs and 97% vegetation coverage on grass slopes repaired with composites at 52 days). Adding composites onto bare slopes marginally reduced runoff and sediment yields by 3% and 16%, respectively. Vegetation, especially when combined with composites, significantly reduced runoff by 77% and sediment by 96%, while supplementing planting with SAPs decreased runoff by 41% and sediment by 88%. Planting without any amendments resulted in lower reductions of 26% in runoff and 81% in sediment. The results of the structural equation model showed that SAPs and fertilizers indirectly reduce sediment yield by increasing vegetation cover, with fertilizers also exercising a positive direct effect on sediment regulation. Our findings highlight how SAPs coupled with organic and inorganic fertilizers promote plant growth and erosion control, as applying these composites alone is less effective in controlling erosion on bare slopes. These results have promising implications for the ecological restoration of rare earth tailings.