Phytoextraction of rare earth elements, germanium and other trace elements as affected by fertilization and liming

Abstract

Trace elements like arsenic, copper, lead, chromium and germanium as well as rare earth elements (REEs) are of interest because environmental safety and raw material extraction reasons, thus studies on enhancing eco-friendly extraction of these elements from soil for resource recovery and remediation reasons are encouraged. In this study we used Lupinus albus , Brassica napus and Zea mays which are of different physiology and morphology as test species, to investigate the effects of soil amendment with fertilizers (cow dung, horse dung, inorganic fertilizer) and lime (inorganic fertilizer + lime) on the phytoextraction of these elements. Effects of fertilization and liming varied according to amendments, elements and test specie except for the decreasing effect of liming on phytoextraction of Ge an REET (sum total of rare earth elements) in all test species. In Z. mays fertilization increased and liming decreased the phytoextraction of PTEs, Ge and REET respectively. In B. napus , organic fertilization mostly decreased phytoextraction of PTEs, Ge and REET (except for As where phytoextraction increased) while in L. albus , organic fertilization mostly increased phytoextraction of PTEs and REET. Common observations in L. albus and B. napus were that liming increased the phytoextraction of Cu and Cr while inorganic fertilization decreased the phytoextraction of most PTEs and increased the phytoextraction of REET. We conclude that liming impedes Ge and REET phytoextraction and that plant characteristics especially Fe acquisition mechanism, soil pH and biological activities play critical roles in the effects observed for soil amendments on phytoextraction of elements from soil. • Fertilization can enhance phytoextraction of Ge, REEs and PTEs in Z. mays . • Liming soils to a pH around 8 can impede phytoextraction of Ge and REEs. • Plant ability to acidify soil can help counteract liming effects & increase phytoextraction of Cu and Cr in the studied forbs. • Inorganic Fertilization can enhance the phytoextraction of REEs and could impede phytoextraction of Ge B. napus and L. albus . • Plant morphology and physiology are critical to phytoextraction of Ge, REEs and PTEs.