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Solid Earth An interactive open-access journal of the European Geosciences Union
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Volume 8, issue 4
Solid Earth, 8, 845–855, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Solid Earth, 8, 845–855, 2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 23 Aug 2017

Research article | 23 Aug 2017

Mineral-leaching chemical transport with runoff and sediment from severely eroded rare-earth tailings in southern China

Huizhong Lu1,2, Longxi Cao1, Yin Liang1, Jiuqin Yuan1,2, Yayun Zhu1,2, Yi Wang1,2, Yalan Gu1,2, and Qiguo Zhao1 Huizhong Lu et al.
  • 1State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
  • 2University of Chinese Academy of Sciences, Beijing 100049, China

Abstract. Rare-earth mining has led to severe soil erosion in southern China. Furthermore, the presence of the mineral-leaching chemical ammonium sulfate in runoff and sediment poses a serious environmental threat to downstream water bodies. In this paper, the characteristics of mineral-leaching chemicals in surface soil samples collected in the field were studied. In addition, NH4+ and SO42− transport via soil erosion was monitored using runoff and sediment samples collected during natural rainfall processes. The results demonstrated that the NH4+ contents in the surface sediment deposits increased from the top of the heap (6.56 mg kg−1) to the gully (8.23 mg kg−1) and outside the tailing heap (13.03 mg kg−1). The contents of SO42− in the different locations of the tailing heaps ranged from 27.71 to 40.33 mg kg−1. During typical rainfall events, the absorbed NH4+ concentrations (2.05, 1.26 mg L−1) in runoff were significantly higher than the dissolved concentrations (0.93, 1.04 mg L−1), while the absorbed SO42− concentrations (2.87, 1.92 mg L−1) were significantly lower than the dissolved concentrations (6.55, 7.51 mg L−1). The dissolved NH4+ and SO42− concentrations in runoff displayed an exponentially decreasing tendency with increasing transport distance (Y = 1. 02 ⋅ exp( − 0. 00312X); Y = 3. 34 ⋅ exp( − 0. 0185X)). No clear trend with increasing distance was observed for the absorbed NH4+ and SO42− contents in transported sediment. The NH4+ and SO42− contents had positive correlations with the silt and clay ratio in transported sediment but negative correlations with the sand ratio. These results provide a better understanding of the transport processes and can be used to develop equations to predict the transport of mineral-leaching chemicals in rare-earth tailings, which can provide a scientific foundation for erosion control and soil management in rare-earth tailing regions in southern China.

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