Multielement biogeochemistry and lithium isotopic composition of the dominant plants at the Jiajika mine, western Sichuan, China - The largest hard rock-type lithium mine in Asia

Abstract

To comprehensively study the multielement and Li isotope geochemistry at the largest hard rock-type lithium (Li) mine in Asia, a large number of root and shoot (77 sets and 154 pieces) samples of the dominant plants were collected at the Jiajika mine for the first time. The concentrations of 37 trace elements (Li, Be, Nb, Ta, Rb, Cs, Sr, Zr, Hf, Sn, U, Cd, As, Pb, Cu, Cr, Zn, Mn, Co, Ni, Mo, W, Y, and La series without Pm) in 154 plant samples were determined via inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, Li isotopic compositions were determined for 9 groups of soil-root-shoot samples via multicollector inductively coupled plasma mass spectrometry (MC-ICP-MS). The results showed that 1) the dominant plants from mining-related areas had markedly higher mineralization-related element (Li, Be, Nb, Ta, Rb, Cs, Sr, Zr, Hf, Co, Ni, Mo, W, Sn, and U) and rare earth element (REE) (except for Tm and Lu) concentrations than those from non-mining-activity areas; 2) the Cr concentrations of 60 shoot samples exceeded the Chinese hygienic standard for pasture forage by 1.054–19.74 times; 3) based on the BTF (biological translocation factor) values of trace elements, the translocation of trace elements, excluding Ta, Rb, Cs, Sr, Zr, and Cd, was restrained in tailing-affected areas. Furthermore, the excessive accumulation of 31 trace elements (except for Ta, Cs, Sn, U, Cd, and Zn) in the roots could also inhibit the root-shoot translocation of corresponding trace elements; and 4) the δ7Li ranges of the roots, shoots, and corresponding soils of the dominant plants at the Jiajika mine were approximately −6.12 to −0.84‰, approximately −4.84 to 2.02‰, and approximately −5.34 to 3.42‰, respectively. Compared with the roots, the shoots of rhododendron plants showed obvious enrichment in 7Li. The results of this study have some implications: high concentrations of 15 mineralization-related elements and 13 REEs in plants could be regarded as plant indicators of rare metal resources; the Cr concentrations in plants should be given more attention and closely monitored in the future to ensure forage safety; and the mechanism of Li isotope fractionation in plants may be controlled by ambient temperature, but further study and verification are needed.