Accumulation and fractionation of rare earth elements (REEs) in the naturally grown Phytolacca americana L. in southern China

Abstract

The widespread use of rare earth elements (REEs) has resulted in problems for soil and human health. Phytolacca americana L. is a herbaceous plant widely distributed in Dingnan county of Jiangxi province, China, which is a REE mining region (ion absorption rare earth mine) and the soil has high levels of REEs. An investigation of REE content of P. americana growing naturally in Dingnan county was conducted. REE concentrations in the roots, stems, and leaves of P. americana and in their rhizospheric soils were determined. Results showed that plant REEs concentrations varied among the sampling sites and can reach 1040 mg/kg in the leaves. Plant REEs concentrations decreased in the order of leaf > root > stem and all tissues were characterized by a light REE enrichment and a heavy REE depletion. However, P. americana exhibited preferential accumulation of light REEs during the absorption process (from soil to root) and preferential accumulation of heavy REEs during the translocation process (from stem to leaf). The ability of P. americana to accumulate high REEs in the shoot makes it a potential candidate for understanding the absorption mechanisms of REEs and for the phytoremediation of REEs contaminated soil.

The accumulation and fractionation of Rare Earth Elements in hydroponically grown Phytolacca americana L.

“…Our previous work has located a natural population of P. americana in Dingnan County, a key REE mining area in the southern province of Jiangxi in China, with a relatively high REE background (Yuan et al 2017). Seeds of P. americana were collected at site P-5 in Yuan et al (2017).…”

“…Moreover, P. americana is a highbiomass plant that is naturalized worldwide, and is able to accumulate REEs up to 623 mg kg −1 in dry leaves, although plant REE concentrations vary substantially among sampling sites (Ichihashi et al 1992). Our recent field survey reported a high abundance of P. americana at an REE mine site in south Jiangxi Province (China) with foliar concentration of REEs as high as 1040 mg kg −1 (Yuan et al 2017). Most research effort to date has focused on the pteridophyte D. dichotoma elucidating REE accumulation, distribution and effects on photosynthesis (Wang et al 1997(Wang et al , 2006Wei et al 2001), in contrast the mechanisms of REE uptake and translocation in the dicot P. americana are largely unknown.…”

“…However, root-to-shoot translocation favored a conspicuous fractionation toward heavy REE (HREE, Gd-Lu), indicating that organic complexation in the xylem vessels may play a role in REE translocation in wheat (Ding et al 2005(Ding et al , 2006, but the specific organic ligands involved remain unknown. Recently, our field survey found that P. americana exhibited a preferential accumulation of LREEs (La-Eu) during soil-to-root assimilation, and a preferential accumulation of HREEs during stem-to-leaf translocation (Yuan et al 2017). However, the accumulation, transport and fractionation mechanisms of REEs in this plant are still inadequately understood.…”

Trend of the research on rare earth elements in environmental science

“…One obvious research area is the investigation of biological effects of REEs using biochemical, cell biological, and toxicological techniques (Pałasz and Czekaj 2000;Jin et al 2017;Joonas et al 2017;Turra 2018;Romero-Freire et al 2019;Dubé et al 2019;Pałasz et al 2019). Another equally important field is the remediation of REEs in the environment (Su 2017;Yuan et al 2018;Wang 2018;Cheng et al 2018;Wei et al 2019;Jalali et al 2019). The findings introduced in this paper will be useful for planning research and education on REEs in environmental or related sciences.…”

“…The recurrent observations of biological toxicity of REEs have invoked another venue of research, which is the remediation of REEs from the environment. This includes phytoremediation (Wei et al 2019;Jalali et al 2019;Yuan et al 2018) and nanoparticle-based remediation (Wang 2018; Su 2017), each of which is specialized for the removal of REEs in soil and water, respectively. In addition, bacteriabased remediation of REEs has been recently investigated (Cheng et al 2018).…”