Maria Diez Ortiz

The environmental behaviour of ZnO nanoparticles (NPs), their availability to, uptake pathways by, and biokinetics in the earthworm Lumbricus rubellus were investigated using stable isotope labelling. Zinc isotopically enriched to 99.5% in 68Zn (68Zn-E) was used to prepare 68ZnO NPs and a dissolved phase of 68Zn for comparison. These materials enabled tracing of environmentally relevant (below background) NP additions to soil of only 5 mg 68Zn-E kg-1. Uptake routes were isolated by introducing earthworms with sealed and unsealed mouthparts into test soils for up to 72 hours. The Zn isotope compositions of the soils, pore waters and earthworms were then determined using multiple collector inductively coupled plasma mass spectrometry. Detection and quantification of 68Zn-E in earthworm tissue was possible after only 4 hours of dermal exposure, when the uptake of 68Zn-E had increased the total Zn tissue concentration by 0.03‰. The results demonstrate that at these realistic exposure concentrations there is n...

This study aimed at assessing the influence of soil properties on the uptake and toxicity effects of arsenic in the earthworm Eisenia andrei exposed for 4 weeks to seven natural soils spiked with different arsenic concentrations. Water-soluble soil concentrations (AsW) and internal As concentrations in the earthworms (AsE) were greatly different between soils. These two variables were highly correlated and were key factors in earthworm toxicity response. AsW was explained by some soil properties, such as the pH, calcium carbonate content, ionic strength, texture or oxide forms. Toxicity showed a clear variation between soils, in some cases without achieving 50 % adverse effect at the highest As concentration added (600 mg kg⁻¹). Nevertheless, soil properties did not show, in general, a high relation with studied toxicity endpoints, although the high correlation with AsW could greatly reduce indirectly As bioavailability and toxicity risk for earthworms. Obtained results suggest that soil properties should be part of the criteria to establishing thresholds for contaminated soils because they will be key in controlling As availability and thus result in different degrees of toxicity.

Current bioavailability models, such as the free ion activity model and biotic ligand model, explicitly consider that metal exposure will be mainly to the dissolved metal in ionic form. With the rise of nanotechnology products and the increasing release of metal‐based nanoparticles (NPs) to the environment, such models may increasingly be applied to support risk assessment. It is not immediately clear, however, whether the assumption of metal ion exposure will be relevant for NPs. Using an established approach of oral gluing, a toxicokinetics study was conducted to investigate the routes of silver nanoparticles (AgNPs) and Ag⁺ ion uptake in the soil‐dwelling earthworm Lumbricus rubellus. The results indicated that a significant part of the Ag uptake in the earthworms is through oral/gut uptake for both Ag⁺ ions and NPs. Thus, sealing the mouth reduced Ag uptake by between 40% and 75%. An X‐ray analysis of the internal distribution of Ag in transverse sections confirmed the presence of increased Ag concentrations in exposed earthworm tissues. For the AgNPs but not the Ag⁺ ions, high concentrations were associated with the gut wall, liver‐like chloragogenous tissue, and nephridia, which suggest a pathway for AgNP uptake, detoxification, and excretion via these organs. Overall, the results indicate that Ag in the ionic and NP forms is assimilated and internally distributed in earthworms and that this uptake occurs predominantly via the gut epithelium and less so via the body wall. The importance of oral exposure questions the application of current metal bioavailability models, which implicitly consider that the dominant route of exposure is via the soil solution, for bioavailability assessment and modeling of metal‐based NPs. Environ Toxicol Chem 2015;34:2263–2270. © 2015 SETAC

Metal-contaminated soil, from the El Arteal mining district (SE Spain), was remediated with organic (6 % compost) and inorganic amendments (8 % marble sludge) to reduce the mobility of metals and to modify its potential environmental impact. Different measures of metal bioavailability (chemical analysis; survival, growth, reproduction and bioaccumulation in the earthworm Eisenia andrei), were tested in order to evaluate the efficacy of organic and inorganic amendments as immobilizing agents in reducing metal (bio)availability in the contaminated soil. The inorganic amendment reduced water and CaCl₂-extractable concentrations of Cd, Pb, and Zn, while the organic amendment increased these concentrations compared to the untreated soil. The inorganic treatment did not significantly reduce toxicity for the earthworm E. andrei after 28 days exposure. The organic amendment however, made the metal-contaminated soil more toxic to the earthworms, with all earthworms dying in undiluted soil and completely inhibiting reproduction at concentrations higher than 25 %. This may be due to increased available metal concentrations and higher electrical conductivity in the compost-amended soil. No effects of organic and inorganic treatments on metal bioaccumulation in the earthworms were found and metal concentrations in the earthworms increased with increasing total soil concentrations.

To determine how soil properties influence nanoparticle (NP) fate, bioavailability and toxicity, this study compared the toxicity of nano zinc oxide (ZnO NPs), non-nano ZnO and ionic ZnCl₂ to the earthworm Eisenia fetida in a natural soil at three pH levels. NP characterisation indicated that reaction with the soil media greatly controls ZnO properties. Three main conclusions were drawn. First that Zn toxicity, especially for reproduction, was influenced by pH for all Zn forms. This can be linked to the influence of pH on Zn dissolution. Secondly, that ZnO fate, toxicity and bioaccumulation were similar (including relationships with pH) for both ZnO forms, indicating the absence of NP-specific effects. Finally, earthworm Zn concentrations were higher in worms exposed to ZnO compared to ZnCl₂, despite the greater toxicity of the ionic form. This observation suggests the importance of considering the relationship between uptake and toxicity in nanotoxicology studies.