Supported by the National Key Research and Development Program of China (Nos. 2018YFC1801801 and 2016YFD0800301), the Young and Middle Aged Science and Technology Innovation Leaders in the Xinjiang Production and Construction Corps of China (No. 2018CB023)
稀土元素在国家经济、战略上意义重大，随着科学技术快速发展，稀土元素的需求急剧增加，由稀土矿山开采产生的环境污染问题也引起了广泛关注。在南方离子型稀土矿原位浸矿开采过程中大量使用铵盐作为浸矿剂，造成矿区水土环境受到严重化学污染，其中尾矿土壤铵态氮残留尤为严重。然而，稀土矿区土壤中铵态氮沿深层剖面（200 cm以下）变化机制仍不清楚。选择江西赣南足洞矿区典型离子型稀土尾矿矿山（2003年开始采矿，2007年闭矿），对表层土壤、深层土壤进行系统采样，共157件土壤剖面样品，测定了土壤pH、质量含水率和铵态氮含量。结果表明：（1）土壤酸化严重和高浓度铵态氮残留是采矿活动遗留的主要环境污染问题；（2）矿山关闭12年后，尾矿土壤平均pH为3.87，铵态氮浓度为60~204.3 mg·kg-1，是未开矿土壤铵态氮背景值的12倍~40倍。（3）土壤pH和含水率影响铵态氮的吸附和解吸附过程，原位淋洗技术是去除残留铵态氮有效方法。研究成果有望为离子型稀土尾矿土壤中铵态氮迁移转化规律和污染治理提供技术支撑。
[Objective] Rare earths are resources of great strategic significance for national economy. With rapid development of the science and technology, the demand for rare earths is increasing dramatically. However, the environmental pollution caused by mining of rare earth ores has aroused concerns of related countries. In South China, in mining ionic rare earth ores, the technology of in-situ leaching with a large volume of (NH4)2SO4 is commonly used, causing severe chemical pollution of the soil and water environments in the mining areas, especially the pollution of ammonium nitrogen residue in ore tailings. However, the mechanism of ammonium nitrogen changing along with the depth in soil profiles (below 200 cm) of the soil in the rare earth mining areas is still unknown.[Method] Here in this study, a total of 157 soil samples were collected systematically from the upper and down layers of the soil in a hill of ore tailings typical of the Zudong mining area, in South Jiangxi. The mining operation started in 2003 and ended in 2007. The soil samples were analyzed for soil mass moisture content, pH, and ammonium nitrogen content.[Result] Results show:1) serious soil acidification and high concentration of ammonium nitrogen residue were the main environmental pollution problems stemming from the mining activities; 2) after the mining had been closed for 12 years, the mean soil pH followed a decreasing order of raw ore (5.73±0.17) > lower reaches (4.87±0.26) > washing tailing (4.63±0.16) > tailing (3.87±0.32); and the content of soil ammonium nitrogen was 60-204.3 mg·kg-1, about 12-40 times the background value of the virgin soil; 3)The high concentration of soil ammonium nitrogen has posed great environmental risk; and 4)as soil pH and soil water content are two main factors affecting adsorption and desorption of ammonium nitrogen, in-situ washing is an effective method to remove residual ammonium nitrogen. The higher the soil pH and the more the water flowing through the tailings, the more ammonium nitrogen desorbed from the soil.[Conclusion] All the findings in this study are expected to be able to serve as technical support for exploring mechanism of ammonium nitrogen migration in tailings and management of the pollution. However, up to now, little has been reported about soil conditions affecting ammonium nitrogen migration and transformation in the literature. Further study should be done on mechanisms of interactions between soil texture, particle size gradation, porosity, and permeability in the tailing soil.
任富天,张秋英,杨广,柏杨巍,高红杰,李兆,刘山宝,王健祺.离子型稀土尾矿深层土壤剖面铵态氮污染特征及影响因素[J].土壤学报,2022,59(2):517-527. DOI:10.11766/trxb202006190317 REN Futian, ZHANG Qiuying, YANG Guang, BAI Yangwei, GAO Hongjie, LI Zhao, LIU Shanbao, WANG Jianqi. Characteristics of Ammonium Nitrogen Pollution in Deep Soil Profile of Ionic Rare Earth Ore Tailings and Influencing Factors[J]. Acta Pedologica Sinica,2022,59(2):517-527.复制