Uptake and Effects of Six Rare Earth Elements (REEs) on Selected Native and Crop Species Growing in Contaminated Soils

Abstract

Rare earth elements (REEs) have become increasingly important metals used in modern technology. Processes including mining, oil refining, discarding of obsolete equipment containing REEs, and the use of REE-containing phosphate fertilizers may increase the likelihood of environmental contamination. However, there is a scarcity of information on the toxicity and accumulation of these metals to terrestrial primary producers in contaminated soils. The objective of this work was to assess the phytotoxicity and uptake from contaminated soil of six REEs (chloride forms of praseodymium, neodymium, samarium, terbium, dysprosium, and erbium) on three native plants (Asclepias syriaca L., Desmodium canadense (L.) DC., Panicum virgatum L.) and two crop species (Raphanus sativus L., Solanum lycopersicum L.) in separate dose-response experiments under growth chamber conditions. Limited effects of REEs were found on seed germination and speed of germination. Effects on aboveground and belowground biomass were more pronounced, especially for the three native species, which were always more sensitive than the crop species tested. Inhibition concentrations (IC25 and IC50) causing 25 or 50% reductions in plant biomass respectively, were measured. For the native species, the majority of aboveground biomass IC25s (11 out of 18) fell within 100 to 300 mg REE/kg dry soil. In comparison to the native species, IC25s for the crops were always greater than 400 mg REE/kg, with the majority of results (seven out of 12) falling above 700 mg REE/kg. IC50s were often not detected for the crops. Root biomass of native species was also affected at lower doses than in crops. REE uptake by plants was higher in the belowground parts than in the above-ground plant tissues. Results also revealed that chloride may have contributed to the sensitivity of the native species, Desmodium canadense, one of the most sensitive species studied. Nevertheless, these results demonstrated that phytotoxicity may be a concern in contaminated areas.

A book review; "Rare earth elements in human and environmental health; at the crossroads between toxicity and safety"

“…Beneficial effects that have been reported in the literature include weight gains by different livestock (cattle, pigs, chicken, fish, and rabbits) and increases in food production e.g., more milk and eggs (He et al 2001;Pang et al 2002;Redling 2006). However, other studies have extensively investigated REE bioaccumulation and adverse effects to plant growth (Carpenter et al 2015), algae (Goecke et al 2015) and other microorganisms (Wen et al 2011), as discussed in Chapters 4 (by Franca Tommasi and Luigi d'Aquino), 5 (by Luigi d'Aquino and Franca Tommasi), and 6 (by Marco Guida, Antonietta Siciliano, and Giovanni Pagano). In addition to mining and refining activities, worldwide REE manufacturing activities may also raise environmental concerns about REE-polluted wastewater, with consequent bioaccumulation in aquatic biota.…”

Evaluation of Rare Earths viewed from the Occupational Health

“…랫드에 34 mg/kg으로 기관내 투여한 결과에서는 산화란탄 > 산화네오디뮴 > 산화 세륨의 순으로 독성이 높게 나타났고 (Takaya et al, 2005), 마우스에 희토류를 30일간 반복 경구 투여하였 을 때에는 염화세륨 > 염화네오디뮴 > 염화란탄의 순 으로 독성이 높게 나타났다 (Cheng et al, 2014). 해조류 및 식물성장에 있어 희토류의 생체축적 및 부작용이 보고된 반면 (Carpenter et al, 2015), 몇몇 연구에서는 포유동물세포, 해조류 및 미세소기관에 서 희토류와 관련한 촉진 효과가 보고되고 있다 (Jenkins et al, 2011;Liu et al, 2012;Pol et al, 2014;Goecke et al, 2015). …”

Seed Germination Technologies for Helophyte Production Used in Wastewater Treatment

“…Finally, landfill leachate or polluted rivers have been experimentally decontaminated using constructed wetlands with vascular plants as the principal component [1,3]. Uptake of rare earth elements (REEs) from obsolete equipment of modern technologies has also been reported [4].…”

“…Vymazal [1] summarised the most important, and we have taken its publication as a framework. Later references [4][5][6][7][8][9][10][11][12] have also been consulted, and Table 1 shows the helophytes that we have considered most relevant.…”