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Fractionation and fixation of rare earths elements in soils: effect of spiking with lanthanum, cerium, and neodymium chloridesстатья
- Авторы: Rogova Olga B., Fedotov Petr S., Dzhenloda Rustam Kh, Karandashev Vasily K.
- Журнал: Journal of Rare Earths
- Год издания: 2020
- Издательство: The Metallurgical Industry Press
- Местоположение издательства: China
- DOI: 10.1016/j.jre.2020.12.006
- Аннотация: Industrial and agricultural activities lead to the release of rare earth elements (REEs) in wastewater and aquatic ecosystems, their accumulation in soils. However, the behavior of REEs in soils remains somewhat unclear. In the present work the fractionation and fixation of REEs in soddy-podzolic and chernozem soils spiked with La, Ce, and Nd chlorides have been studied using dynamic (continuous flow) extraction, which allows natural conditions to be mimicked and artefacts to be minimised. The eluents applied addressed exchangeable, specifically sorbed, bound to Mn oxides, bound to metal–organic complexes, and bound to amorphous and poorly ordered Fe/Al oxides fractions extractable by 0.05 mol/L Ca(NO3)2, 0.43 mol/L CH3COOH, 0.1 mol/L NH2OH·HCl, 0.1 mol/L K4P2O7 at pH 11, and 0.1 mol/L (NH4)2C2O4 at pH 3.2, respectively. It has been found that the fixations of added La, Ce, and Nd in the form of metal-organic complexes is predominant for both types of soils: 35%–38% in soddy-podzolic soil and 50%–79% in chernozem. The fixation of added elements in the first three fractions (exchangeable, specifically sorbed, and bound to Mn oxides) is significant for soddy-podzolic soil (5%–25%). For chernozem, the relative contents of added Ce and Nd in these fractions are nearly negligible. Only the content of exchangeable La is notable, about 5%. Adding any of three elements (La, Ce, or Nd) at the level of 100 mg/kg to an initial sample results in changing the fractionation and bioaccessibility of other REEs present in soil. Their contents increase in the first three fractions and decrease in fifth (oxalate extractable) fraction for both soddy-podzolic soil and chernozem. The main difference is the behavior of REEs in pyrophosphate extractable fraction. For soddy-podzolic soil, adding La, Ce, or Nd results in decreasing the contents of other REEs associated with organic matter. For chernozem, on the contrary, the contents of REEs in the form of metal-organic complexes slightly increase. These processes may be attributed to competitive binding of elements and soil properties; they must be taken into account when assessing the environmental risks of soil pollution with REEs.
- Добавил в систему: Рогова Ольга Борисовна