赣南稀土尾矿山土体硝态氮累积
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1.中国科学院南京土壤研究所;2.中国科学院大学;3.中国科学院南京地理与湖泊研究所

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X53;S151

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Accumulation of soil nitrate nitrogen of rare earth tailing in southern Jiangxi
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1.Institute of Soil Science,Chinese Academy of Sciences;2.University of Chinese Academy of Sciences;3.Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences

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    摘要:

    稀土开采会造成大量浸矿剂(硫酸铵)残留在土壤中,高浓度铵态氮(NH4+-N)可能在生物化学作用下转化为硝态氮(NO3--N)。为探明NO3--N在稀土尾矿山土体内的含量及影响因素,明确硝酸盐污染程度,本研究选择赣南地区一个离子型稀土原地浸矿尾矿山,由表土分层采样至基岩面,并分析土壤NO3--N及相关的理化性质。研究结果表明,尾矿山土体NO3--N含量变异范围非常大(2.80~193.99 mg?kg-1),其平均值为46.30±55.16 mg?kg-1,表层土壤NO3--N含量均值为5.16 mg?kg-1,与自然土壤相近;含矿层土壤NO3--N含量均值为48.64 mg?kg-1,是自然土壤的10倍。尾矿山土体深部含矿层土壤NO3--N明显高于表层, NO3--N随深度的分布规律与自然土壤相反,这是矿体部分残留大量浸矿剂造成的。土壤NH4+-N含量主导了NO3--N的产生量,但NO3--N在土体不同深度、山体不同部位的累积量还受降雨淋溶及NO3--N迁移过程的控制。开采结束4年后,尾矿山内累积的NO3--N仍不断向环境中释放。长期来看,尾矿山土壤中富集的NH4+-N将不断转化为NO3--N并随水迁移,持续威胁生态环境及人类健康。本研究可为稀土原地浸矿场地土壤及下游水体污染的评价和治理提供理论基础与科学支撑。

    Abstract:

    【Objective】Rare earth mining excessively increased the content of leaching agents (e.g. ammonium sulfate) in the soil. The high concentration of ammonium nitrogen (NH4+-N) may be converted into nitrate nitrogen (NO3--N) under active biochemical action, resulting in potential environmental risks, especially nitrate pollution of water bodies around tailings. Therefore, it is necessary to evaluate the content of soil NO3--N, explore the influencing factors and understand the nitrate pollution degree of the rare earth tailings. 【Method】We chose an ionic rare earth tailing after in-situ mining in southern Jiangxi province, which used ammonium sulfate as a leaching agent. Up to sampling, this mine had been closed for 4 years. We set three sampling points regularly from the top to bottom of this mine and collected soil profile samples in different layers from the topsoil to the bedrock. Soil samples were divided into two parts. One part was stored at a low temperature to analyze soil nitrate nitrogen and ammonium nitrogen. The other one was used for analyzing relevant physical and chemical properties after air drying. 【Result】The results showed that the variation range of soil NO3--N content in the tailing area was large (2.80 to 193.99 mg?kg-1), with a mean of 46.30±55.16 mg?kg-1. The average content of topsoil NO3--N was 5.16 mg?kg-1, which was similar to that of natural soil. Also, the average content of soil NO3--N in ore-bearing layers was 48.64 mg?kg-1, which was nearly 10 times that in the natural soil. The soil NO3--N of the ore-bearing layer in the deep profile was higher than that of the top layer. Moreover, the distribution of NO3--N with depth was different from that of the natural soil and was mainly caused by a large number of leaching agents remaining in the ore body. NH4+-N content dominated the generation of NO3--N and determined the upper limit of soil NO3--N accumulation. The accumulation degree of NO3--N in different soil layers and different parts of mountains was controlled by rainfall leaching and the NO3--N migration process. However, the soil's physical and chemical properties, including water content, cation exchange capacity and particle composition, had no significant correlation with NO3--N content, and were not the determining factors of NO3--N content. 【Conclusion】The soil NO3--N in the tailing mainly originated from nitrification. Four years after mining, a large amount of NH4+-N remained in the tailing, and the NO3--N generated by nitrification was continuously released into the environment. In the long term, the soil NH4+-N enriched in tailing will be transformed into NO3--N and the NO3--N will migrate with water, threatening the ecological environment and human health. This study can provide a theoretical basis and scientific reference for the assessment and treatment of soil and downstream water pollution in rare earth in-situ leaching sites.

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许 哲,杨金玲,赵越,张甘霖.赣南稀土尾矿山土体硝态氮累积[J].土壤学报,,[待发表]
XU Zhe, YANG Jinling, ZHAO Yue, ZHANG Ganlin. Accumulation of soil nitrate nitrogen of rare earth tailing in southern Jiangxi[J]. Acta Pedologica Sinica,,[In Press]

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  • 收稿日期:2022-07-28
  • 最后修改日期:2022-12-01
  • 录用日期:2023-01-10
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