Migration and Accumulation Mechanisms of Heavy Metals in Soil from Maoniuping Rare Earth Elements Mining, Southwest China

Sijie He, Yang Li, Liang Tang (), Fang Yang (), Yuan Xie, Xuemin Liu and Lei Xu
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Sijie He: College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu 610059, China
Yang Li: Sichuan Development Environmental Science and Technology Research Institute Co., Ltd., Chengdu 610041, China
Liang Tang: College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu 610059, China
Fang Yang: College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu 610059, China
Yuan Xie: Shaanxi Experimental Center of Geological Survey, Xi’an 710065, China
Xuemin Liu: College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu 610059, China
Lei Xu: College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu 610059, China

Land, 2025, vol. 14, issue 3, 1-26

Abstract: The Maoniuping Rare Earth Elements (REE) deposit, the second largest light REE deposit in the world, has been mined for decades, with serious impacts on the surrounding environment. However, the impact of mining on heavy metals in the downstream area (Nanhe River Basin) has not been systematically documented. To address this issue, this study explored the extent, transport, and accumulation of heavy metal contamination in the Nanhe River Basin through field surveys (2946 topsoil samples and four vertical soil sections) and regional geographic attributes (e.g., mining area, river, and elevation) combined with a variety of methods such as statistics, geostatistics, spatial analysis, geo-accumulation index, and potential ecological risk index. The results showed that soils in the Nanhe River Basin presented different degrees of heavy metal pollution, with Pb and Cd being the most abundant, and the soils as a whole showed moderate-heavy ecological risks. The spatial distribution and correlation of heavy metals exhibited similar distribution patterns and sources. Further analyses revealed that mining of REE in Maoniuping was the main source of heavy metal pollution in the Nanhe River Basin, with heavy metals entering the soil through runoffs. At the same time, mining activities led to the migration of heavy metals in different directions in the Nanhe watershed, i.e., about 1.3 km horizontally, 16 km longitudinally, and more than 1 m vertically. In addition, about 38.1 km 2 of the watershed is contaminated by mine wastes, which is 6.6 times the size of the mining area. In order to mitigate the threat of heavy metals, the local government has implemented water diversion projects and crop conversion in the Nanhe River Basin. This study provides a reference for research on the environmental problems caused by the exploitation of REE mines and other mineral resources.

Keywords: Maoniuping REE deposit; soil; heavy metals contamination; three-dimensional diffusion (search for similar items in EconPapers)
JEL-codes: Q15 Q2 Q24 Q28 Q5 R14 R52 (search for similar items in EconPapers)
Date: 2025
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