硫酸铵对离子型稀土矿区土壤重金属的释放和形态转化影响

针对离子型稀土矿区浸矿过程导致的土壤氨氮、重金属复合污染问题，研究硫酸铵残留对土壤重金属迁移转化和形态的影响机制。通过土柱淋滤和室内土壤培养考察不同浓度浸矿剂输入土壤后，氨氮、重金属Zn、Cu和Cr的形态和迁移性变化。实验结果表明，与无浸矿剂淋滤对照组相比较，浸矿剂在重金属污染土壤中主要以氨氮形式存在，硝态氮占比低。在培养期间，浸矿剂硫酸铵淋滤降低了土壤pH值和土壤阳离子交换量（CEC），重金属活性增加，当浸矿剂淋滤浓度为5%时，弱酸态Cr、Cu、Zn比例分别提高8.29%、5.21%、4.53%。研究结果表明：硫酸铵加剧了土壤酸化，提高重金属迁移性，促进重金属形态从生物不可利用态向可利用态转化。

Effects of ammonium sulfate on the release and morphological transformation of heavy metals from soil in ionic rare earth mining areas

Due to the combined pollution of ammonia nitrogen and heavy metals in the soil caused by leaching in the ionic rare earth mining areas, the mechanism of the effect of ammonium sulfate residue on the migration, transformation and morphology of heavy metals in the soil was studied. Soil column leaching and indoor soil culture experiments were carried out to investigate the changes in the morphology and mobility of NH₄+-N, Zn, Cu, and Cr after different concentrations of leaching agents were input into the soil. The experimental results showed that the leaching agents mainly existed in the form of NH₄+-N in the contaminated soil, and the proportion of NO₃--N was low. Compared with the control group, after leaching with ammonium sulfate leaching solution, the pH value and cation exchange capacity (CEC) of the soil were reduced, and the activity of heavy metal ions was enhanced during the cultivation period. The contents of weakly acidic Cr, Cu, and Zn increased by 8.29%, 5.21% and 4.53%, respectively. The results showed that ammonium sulfate enhanced soil acidification, promoted heavy metals migration, and transformed the heavy metals form from the bioavailable state to the available one.