MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, China; Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China.
MOE Key Laboratory of Groundwater Circulation and Environmental Evolution, China University of Geosciences (Beijing), Beijing 100083, China; Beijing Key Laboratory of Water Resources and Environmental Engineering, China University of Geosciences (Beijing), Beijing 100083, China.
Ecotoxicol Environ Saf. 2021 Jan 15;208:111663. doi: 10.1016/j.ecoenv.2020.111663. Epub 2020 Nov 18.
Even after being abandoned for many years, a large number of weathered crust elution-deposited rare earth (WCED-RE) tailings continue to release ammonia nitrogen (AN) pollution into their surrounding environments. However, the influences of particle size distribution and clay minerals on AN pollution caused by these tailings have been insufficiently studied, and its causes are poorly understood. In this study, soil samples at different depths (5, 7, 9, 11 and 14 m) were collected from a rare earth tailing in Ganzhou City, Jiangxi Province, China. Particles were screened by size into six groups (2-1, 1-0.5, 0.5-0.25, 0.25-0.1, 0.1-0.075 and < 0.075 mm), and AN forms were extracted. The results showed that as soil particle size decreases, both soil specific surface area and clay content increase, leading to stronger AN enrichment ability. With increased sampling depth, the distribution of clay across the six particle fractions became more uniform, such that the accumulation of AN in soil with fine particle size was less obvious. Clay minerals with different capacities for AN enrichment vary with sampling depth. This variation is responsible for the profile of AN distribution in the mine, where AN first increases and then decreases as vertical depth is increased. Although AN content was highest at 11 m, water soluble AN content was higher in the upper part of the completely weathered layer (5 and 7 m), which poses a higher environmental risk. This study provides significant information to deepen our understanding of the distribution characteristics of AN and its main influencing factors, as well as a foundation for the prevention and remediation of nitrogen pollution from WCED-RE tailings.
即使已经被废弃多年，大量风化壳淋积型稀土（WCED-RE）尾矿仍在向周围环境中释放氨氮（AN）污染。然而，这些尾矿的粒度分布和粘土矿物对 AN 污染的影响尚未得到充分研究，其原因也知之甚少。本研究在中国江西省赣州市的一处稀土尾矿中，从不同深度（5、7、9、11 和 14 m）采集了土壤样品。通过粒度筛选将颗粒分为六组（2-1、1-0.5、0.5-0.25、0.25-0.1、0.1-0.075 和 < 0.075 mm），并提取了 AN 形态。结果表明，随着土壤颗粒粒径的减小，土壤比表面积和粘土含量增加，导致更强的 AN 富集能力。随着采样深度的增加，六种颗粒级分中粘土的分布变得更加均匀，因此细颗粒土壤中 AN 的积累不那么明显。具有不同 AN 富集能力的粘土矿物随采样深度而变化。这种变化是导致矿山中 AN 分布剖面的原因，随着垂直深度的增加，AN 先增加后减少。尽管 11 m 处的 AN 含量最高，但完全风化层上部（5 和 7 m）的水溶性 AN 含量更高，这构成了更高的环境风险。本研究为深入了解 AN 的分布特征及其主要影响因素提供了重要信息，为 WCED-RE 尾矿氮污染的预防和修复奠定了基础。
