Mineral-leaching chemical transport with runoff and sediment from severely eroded rare-earth tailings in southern China
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...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2017-08-01
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| Series: | Solid Earth |
| Online Access: | https://www.solid-earth.net/8/845/2017/se-8-845-2017.pdf |
| Summary: | 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, NH<sub>4</sub><sup>+</sup> and SO<sub>4</sub><sup>2−</sup> transport via soil erosion was
monitored using runoff and sediment samples collected during natural rainfall
processes. The results demonstrated that the NH<sub>4</sub><sup>+</sup> contents in the
surface sediment deposits increased from the top of the heap
(6.56 mg kg<sup>−1</sup>) to the gully (8.23 mg kg<sup>−1</sup>) and outside the
tailing heap (13.03 mg kg<sup>−1</sup>). The contents of SO<sub>4</sub><sup>2−</sup> in the
different locations of the tailing heaps ranged from 27.71 to
40.33 mg kg<sup>−1</sup>. During typical rainfall events, the absorbed
NH<sub>4</sub><sup>+</sup> concentrations (2.05, 1.26 mg L<sup>−1</sup>) in runoff were
significantly higher than the dissolved concentrations (0.93,
1.04 mg L<sup>−1</sup>), while the absorbed SO<sub>4</sub><sup>2−</sup> concentrations (2.87,
1.92 mg L<sup>−1</sup>) were significantly lower than the dissolved
concentrations (6.55, 7.51 mg L<sup>−1</sup>). The dissolved NH<sub>4</sub><sup>+</sup> and
SO<sub>4</sub><sup>2−</sup> concentrations in runoff displayed an exponentially decreasing
tendency with increasing transport distance (<i>Y</i> = 1. 02 ⋅ exp( − 0. 00312<i>X</i>);
<i>Y</i> = 3. 34 ⋅ exp( − 0. 0185<i>X</i>)). No clear trend with increasing distance was
observed for the absorbed NH<sub>4</sub><sup>+</sup> and SO<sub>4</sub><sup>2−</sup> contents in
transported sediment. The NH<sub>4</sub><sup>+</sup> and SO<sub>4</sub><sup>2−</sup> 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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| ISSN: | 1869-9510 1869-9529 |