1.State Key Laboratory of Soil and Sustainable Agriculture,Institute of Soil Science,Chinese Academy of Sciences;2.University of Chinese Academy of Sciences;3.Institute of Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences;4.State Key Laboratory of Soil and Sustainable Agriculture，Institute of Soil Science , Chinese Academy of Sciences;5.Appraisal Center for Environment and Engineering, Ministry of Ecology and Environment
Supported by the National Key Research and Development Program of China (No. 2018YFC1801801)
离子型稀土开采使用的浸矿剂（硫酸铵）造成土壤铵态氮（NH4+-N）残留，带来严重的氮污染，危及生态环境和人体健康，导致稀土矿开采受限。为明确已开采矿区土壤中NH4+-N的富集特征及其影响因素，选择江西省赣州市龙南县一个已闭矿4年的原地浸矿离子型稀土矿山，在山体不同坡位布点，自土表至矿体底板（土体与基岩交界处，深度为5.5~9.7 m）分层采样，并测定了土体中的NH4+-N及其相关的土壤性质。结果表明，矿区土壤NH4+-N含量范围为2.32~1056.44 mg·kg-1（263.12±301.59 mg·kg-1），是自然和农田土壤的数倍甚至上百倍。从土体分布来看，矿体部分土壤NH4+-N含量高于其上部土壤，不同土层间差异显著。从不同地形部位来看， NH4+-N的平均含量坡顶>坡底>坡中。由于土体中铵过饱和，不同于自然土壤，NH4+-N的分布不受常规土壤理化性质的直接影响，主要受控于浸矿液直接输入的深度、输入量和土体结构带来的渗透性能变化。在降雨的淋洗作用下，开采矿区土体中大量的NH4+-N会不断向周边土壤和水体迁移，对生态环境带来长期的危害。本研究结果对完善离子型稀土矿区土壤氮化物的迁移过程、指导氨氮污染的治理具有重要意义。
【Objective】The leaching agent (ammonium sulfate) causes residues of ammonium nitrogen in the soil of ionic rare earth mining area.This results in serious nitrogen pollution in the soil and water bodies and destroys the ecological environment in the mining area. It also endangers the health of the surrounding residents and restricts the mining of ionic rare earth ore. However, the ammonium nitrogen pollution situation in ionic rare earth tailings and its impact mechanism are still unclear. 【Method】In order to understand the enrichment characteristics of soil ammonium nitrogenin in the mining area and its influencing factors, we chose an in-situ leaching ionic rare earth mining area that has been closed for 4 years in Longnan County, Ganzhou City, Jiangxi Province. We sampled sites located on the different slopes of the hill. Soil samples were chosen from the soil surface to the bottom of the ore body, with a depth of 5.5 to 9.7 m. Ammonium nitrogenin and other soil properties in the soil were determined. 【Result】The results show that soil ammonium nitrogenin content in the mining area ranged from 2.32 to 1056.44 mg·kg-1, and was several times or even hundreds of times higher than in the natural and farmland soils. Ammonium nitrogenin in the mining layers with rare earth was higher than in the upper soil, and with wide the variations among different soil layers in the vertical direction. Also, soil ammonium nitrogenin content in the hill slope followed the sequence of top > bottom > middle slope. The correlation between soil ammonium nitrogen and the physicochemical properties of ionic rare earth tailings was observed to be different from the research conclusions of natural or farmland soil. Due to the supersaturation of ammonium in the soil, the distribution of ammonium nitrogenin is not directly controlled by soil basic physicochemical properties which have an important influence on the ammonium nitrogen adsorption, such as soil clay, cation exchange capacity, etc. 【Conclusion】The major factors observed to influence ammonium nitrogen are the depth and amount of leaching solution inputting, and the permeability changes caused by the soil structure. Mining facilities such as leaching liquid pools, liquid collecting ditch, etc, affect the surrounding soil ammonium nitrogenin content. Due to gravity, ammonium nitrogen will gradually migrates from the top to the middle and the bottom of the slope. This causes ammonium nitrogen to accumulate at the bottom of the slope over time. Under the leaching action of rainfall, a large amount of ammonium nitrogenin in mining area soil will continuously migrate to the surrounding soil and water, which will harm the ecological environment in the long run. The results of this study are of great significance for improving the migration process of soil nitrogen in ionic rare earth mining areas and guiding the treatment of ammonia nitrogen pollution.
许 哲,杨金玲,张甘霖,赵 越,周 俊.离子型稀土闭矿区土壤铵态氮富集特征[J].土壤学报,DOI:10.11766/trxb202104140195,[待发表]
XU Zhe, YANG Jinling, ZHANG Ganlin, ZHAO Yue, ZHOU Jun. Enrichment Characteristics of Soil Ammonium Nitrogen in Ionic Rare Earth Mining Area[J]. Acta Pedologica Sinica, DOI:10.11766/trxb202104140195,[In Press]