Lutetium Speciation and Toxicity in a Microbial Bioassay: Testing the Free-Ion Model for Lanthanides

Abstract

The validity of the free-ion model (FIM) for the element lutetium (Lu), a member of the lanthanides, was assessed in experiments with the bacterium Vibrio fischeri. The FIM is mainly based on divalent metals and synthetic ligands and has not yet been validated for the trivalent lanthanides. The bioluminescence response of V. fischeri was studied at different Lu concentrations in the presence and absence of natural and synthetic organic ligands [citrate, malate, oxalate, acetate, ethylenediaminetetraacetate (EDTA), and nitrilotriacetate (NTA)]. All ligands were tested separately to ensure that their concentrations would not cause adverse effects themselves. Free Lu 3+ concentrations were calculated with a speciation program, after extension of its database with the relevant Lu equilibria. The results confirmed the FIM for Lu: that is, in contrast to total dissolved Lu concentrations, free Lu 3+ concentrations had an apparent relationship with the response of V. fischeri. However, a contribution of minor inorganic Lu complexes cannot be ruled out. In the presence of malate and oxalate, the EC 50 for Lu 3+ decreased faster in time than for the other ligands, indicating lower elimination rates. With an EC 50 of 1.57 µM, Lu 3+ is more toxic than La 3+ , Cd 2+ , or Zn 2+ and approximately equally as toxic as Cu 2+ . Although the pH increased slightly during the experiments, it was shown that the influence of pH on Lu speciation was limited.

Lanthanide ecotoxicity: First attempt to measure environmental risk for aquatic organisms

“…4). This result agrees with those obtained in other studies showing that lanthanide toxicity can increase with atomic number (Weltje et al, 2004). When compared with data from the literature on other metals (Table 3), lanthanides showed lower toxicity than Cd, Cu, Pb or Zn (Newman and McCloskey, 1996), but greater toxicity than thallium (Hsieh et al, 2004).…”

Biosorption of metal and salt tolerant microbial isolates from a former uranium mining area. Their impact on changes in rare earth element patterns in acid mine drainage

“…The toxic influence of REE on biota has been known for a long time [24]. With intensified application of fertilizers containing REE [38,41] especially in China the interest on the toxicity of REE increased [40]. In most cases, a stimulating effect of low doses of REE was observed, whereas at higher concentrations REE were found to be toxic.…”

Prosobranch snails as test organisms for the assessment of endocrine active chemicals––an overview and a guideline proposal for a reproduction test with the freshwater mudsnail Potamopyrgus antipodarum

“…non-linear regression according to a reparameterized Weibull model; compare Duft et al 2003a;Weltje et al 2004) in order to estimate the concentration that would cause x% of maximum effects (e.g. EC 10 and EC 50 ), or by testing a statistical hypothesis (e.g.…”