Abstract:

Considering the problems of strong soil acidity, severe heavy metal pollution, and poor soil fertility in ion-adsorption rare earth mines, the optimal combination pattern of soil amendments and plants was identified through systematic trials and analyses in this study, with the expectation of providing a useful reference for the ecological remediation of contaminated soil in ion-adsorption rare earth mining areas. This study focused on acidified and Pb-contaminated soil in an ion-adsorption rare earth mining area in northern Guangdong Province, China. Pot experiments were conducted to explore the remediation effect of three soil amendments, limestone, calcium-magnesium-phosphorus fertilizer, and cow manure compost, applied individually or in combination with three plant species, Miscanthus sinensis, Vetiveria zizanioides, and Pennisetum purpureum. The results showed that all treatments effectively increased the pH of the contaminated soil compared to the control group (p<0.05), except for the individual application of limestone after 180 d. Among them, treatment with 1% limestone+1% calcium-magnesium phosphate fertilizer had the most significant effect, increasing soil pH by 3.28-3.49 units. Treatment with 6% individually applied cow manure compost posed the best improvement on soil organic matter content and cation exchange capacity with the mean values of (18.0±0.21) g·kg⁻¹ and (7.83±0.06) cmol·kg⁻¹, respectively, which were 328.0%±5.09% and 54.3%±1.25% higher than those of the control. All amendments, except for the 1% individually applied limestone, reduced the soil Pb content by 15.2%±3.99% compared to the control. In addition, the Pb content in soil was lowest in the treatment with Pennisetum purpureum [(75.0±4.66) mg·kg⁻¹], while those in the soils with Miscanthus sinensis and Vetiveria zizanioides reached [(80.0±7.30) mg·kg⁻¹] and [(77.0±5.93) mg·kg⁻¹], respectively. In conclusion, the combination of 6% cow manure compost and Pennisetum purpureum demonstrated a greater potential for soil improvement and remediation of Pb contamination. Based on previous studies and actual conditions, this study selected the dominant plant species in combination with amendments and developed an optimal solution for the remediation of contaminated soil in rare earth mining areas. The results of this study provide new insights and technical references for the remediation of contaminated soils related to ion-adsorption rare earth mines.

Key words: ion-adsorption rare earth mine, soil amendment, phytoremediation, limestone, calcium-magnesium phosphate fertilizer, cow manure compost

摘要：

针对离子型稀土矿中土壤酸性强、重金属污染严重且肥力低下的问题，通过系统性试验与分析，探寻最佳的改良剂-植物组合方式，以期为离子型稀土矿区污染土壤的生态修复提供有益参考。以粤北某离子型稀土矿区酸化、铅（Pb）污染土壤为对象，通过盆栽实验探讨石灰石、钙镁磷肥和腐熟牛粪等3种改良剂单施或配施，与芒草（Miscanthus sinensis）、香根草（Vetiveria zizanioides）和象草（Pennisetum purpureum）等3种植物的组合修复效果。结果表明：实验180 d后，所有处理组均可显著提升土壤pH值（p<0.05），其中质量分数为1%石灰石+1%钙镁磷肥组合效果最明显，pH值增加3.28－3.49，有效缓解了土壤酸化问题；施加质量分数为6%的腐熟牛粪，其土壤有机质、阳离子交换量含量最高，分别为（18.0±0.21）g·kg⁻¹和（7.83±0.06）cmol·kg⁻¹，比对照组提高328.0%±5.09%和54.3%±1.25%。除单施1%石灰石组外，其他改良剂处理组土壤Pb含量较对照组减少15.2%±3.99%；象草处理组土壤中重金属Pb质量分数[（75.0±4.66）mg·kg⁻¹]低于芒草[（80.0±7.30）mg·kg⁻¹]和香根草[（77.0±5.93）mg·kg⁻¹]，修复效果最佳。综上，利用6%的腐熟牛粪与象草组合处理对离子型稀土矿的土壤改良及Pb污染修复的效果显著，展现出较高的应用潜力。在前期研究的基础上，结合矿区实际情况，因地制宜选取华南地区典型修复植物搭配改良剂，探索出一种针对该稀土矿区污染土壤修复的较优解。研究结果可为离子型稀土矿污染土壤修复提供新的思路和技术参考。

关键词: 离子型稀土矿, 土壤改良, 植物修复, 石灰石, 钙镁磷肥, 腐熟牛粪