title: Size- and composition-dependent toxicity of synthetic and soil-derived Fe oxide colloids for the nematode Caenorhabditis elegans.
abstract: Colloidal iron oxides (FeOx) are increasingly released to the environment due to their use in environmental remediation and biomedical applications, potentially harming living organisms. Size and composition could affect the bioavailability and toxicity of such colloids. Therefore, we investigated the toxicity of selected FeOx with variable aggregate size and variably composed FeOx-associated organic matter (OM) toward the nematode Caenorhabditis elegans. Ferrihydrite colloids containing citrate were taken up by C. elegans with the food and accumulated inside their body. The toxicity of ferrihydrite, goethite, and akaganeite was dependent on aggregate size and specific surface area, with EC50 values for reproduction ranging from 4 to 29 mg Fe L(-1). Experiments with mutant strains lacking mitochondrial superoxide dismutase (sod-2) showed oxidative stress for two FeOx and Fe(3+)-ions, however, revealed that it was not the predominant mechanism of toxicity. The OM composition determined the toxicity of mixed OM-FeOx phases on C. elegans. FeOx associated with humic acids or citrate were less toxic than OM-free FeOx. In contrast, soil-derived ferrihydrite, containing proteins and polysaccharides from mobile OM, was even more toxic than OM-free Fh of similar aggregate size. Consequently, the careful choice of the type of FeOx and the type of associated OM may help in reducing the ecological risks if actively applied to the subsurface.
authors.affiliation: Institute for Biodiversity-Network (IBN) , Nussbergerstr. 6a, 93059 Regensburg, Germany.
authors.forename: Sebastian
authors.initials: S
authors.lastname: Höss
authors.forename: Andreas
authors.initials: A
authors.lastname: Fritzsche
authors.forename: Carolin
authors.initials: C
authors.lastname: Meyer
authors.forename: Julian
authors.initials: J
authors.lastname: Bosch
authors.forename: Rainer U
authors.initials: RU
authors.lastname: Meckenstock
authors.forename: Kai Uwe
authors.initials: KU
authors.lastname: Totsche
mesh_terms: D000818:Animals; D017173:Caenorhabditis elegans / Q000187:drug effects*; D003102:Colloids / Q000633:toxicity*; D004777:Environment; D005290:Ferric Compounds / Q000633:toxicity*; D007501:Iron / Q000032:analysis; D058085:Iron Compounds / Q000633:toxicity; D008903:Minerals / Q000633:toxicity; D010316:Particle Size; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000633:toxicity; D018675:Toxicity Tests
chemical_list: D003102:Colloids; D005290:Ferric Compounds; D058085:Iron Compounds; D008903:Minerals; D012987:Soil; D012989:Soil Pollutants; C473845:akaganeite; C094886:goethite; C092844:ferric oxyhydroxide; D007501:Iron