Potency of (doped) rare earth oxide particles and their constituent metals to inhibit algal growth and induce direct toxic effects

Elise Joonas; Villem Aruoja; Kalle Olli; Guttorm Syvertsen-Wiig; Heiki Vija; Anne Kahru

doi:10.1016/j.scitotenv.2017.03.184

Potency of (doped) rare earth oxide particles and their constituent metals to inhibit algal growth and induce direct toxic effects

Sci Total Environ. 2017 Sep 1:593-594:478-486. doi: 10.1016/j.scitotenv.2017.03.184. Epub 2017 Mar 27.

Authors

Elise Joonas¹, Villem Aruoja², Kalle Olli³, Guttorm Syvertsen-Wiig⁴, Heiki Vija², Anne Kahru⁵

Affiliations

¹ Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia; Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia. Electronic address: elise.joonas@kbfi.ee.
² Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia.
³ Institute of Ecology and Earth Sciences, University of Tartu, Lai 40, 51005 Tartu, Estonia.
⁴ Ceramic Powder Technology AS, Kvenildmyra 6, 7093 Tiller, Norway.
⁵ Laboratory of Environmental Toxicology, National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, Tallinn 12618, Estonia; Estonian Academy of Sciences, Kohtu 6, 10130 Tallinn, Estonia.

PMID: 28359999
DOI: 10.1016/j.scitotenv.2017.03.184

Abstract

Use of rare earth elements (REEs) has increased rapidly in recent decades due to technological advances. It has been accompanied by recurring rare earth element anomalies in water bodies. In this work we (i) studied the effects of eight novel doped and one non-doped rare earth oxide (REO) particles (aimed to be used in solid oxide fuel cells and gas separation membranes) on algae, (ii) quantified the individual adverse effects of the elements that constitute the (doped) REO particles and (iii) attempted to find a discernible pattern to relate REO particle physicochemical characteristics to algal growth inhibitory properties. Green algae Raphidocelis subcapitata (formerly Pseudokirchneriella subcapitata) were used as a test species in two different formats: a standard OECD201 algal growth inhibition assay and the algal viability assay (a 'spot test') that avoids nutrient removal effects. In the 24h 'spot' test that demonstrated direct toxicity, algae were not viable at REE concentrations above 1mgmetal/L. 72-hour algal growth inhibition EC₅₀ values for four REE salts (Ce, Gd, La, Pr) were between 1.2 and 1.4mg/L, whereas the EC₅₀ for REO particles ranged from 1 to 98mg/L. The growth inhibition of REEs was presumably the result of nutrient sequestration from the algal growth medium. The adverse effects of REO particles were at least in part due to the entrapment of algae within particle agglomerates. Adverse effects due to the dissolution of constituent elements from (doped) REO particles and the size or specific surface area of particles were excluded, except for La₂NiO₄. However, the structure of the particles and/or the varying effects of oxide composition might have played a role in the observed effects. As the production rates of these REO particles are negligible compared to other forms of REEs, there is presumably no acute risk for aquatic unicellular algae.

Keywords: Agglomeration; Hazard evaluation; Lanthanides; Nanoparticles; Phytoplankton.

MeSH terms

Chlorophyta / drug effects*
Chlorophyta / growth & development
Metals, Rare Earth / toxicity*
Oxides / toxicity*

Substances

Metals, Rare Earth
Oxides