Abstract
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.
•Models of nanomaterial release are needed to drive nanomaterial fate models.•Nanomaterial-specific processes are now being included in fate models.•The form and state in which particles are released ...needs to be considered.•There is progress towards process-based modelling at large scales.
Engineered nanomaterials (ENMs, material containing particles with at least one dimension less than 100 nm) are present in a range of consumer products and could be released into the environment from these products during their production, use or end-of-life. The high surface to volume ratio of nanomaterials imparts a high reactivity, which is of interest for novel applications but may raise concern for the environment. In the absence of measurement methods, there is a need for modelling to assess likely concentrations and fate arising from current and future releases. To assess the capability that exists to do such modelling, progress in modelling ENM fate since 2011 is reviewed. ENM-specific processes represented in models are mainly limited to aggregation and, in some instances, dissolution. Transformation processes (e.g. sulphidation), the role of the manufactured coatings, particle size distribution and particle form and state are still usually excluded. Progress is also being made in modelling ENMs at larger scales. Currently, models can give a reasonable assessment of the fate of ENMs in the environment, but a full understanding will likely require fuller inclusion of these ENM-specific processes.
•Can invertebrate body burdens be used to predict ecological effects of metals?•Quantile regression was used to relate body burdens to ecological responses.•Negative relations were observed between ...ecological responses and metal burdens.•Critical body burdens depicting ecological effects could be derived.•Invertebrate body burdens can be used to predict metal-induced ecological effects.
The present study investigated whether invertebrate body burdens can be used to predict metal-induced effects on aquatic invertebrate communities. Total dissolved metal levels and four invertebrate taxa (Leuctra sp., Simuliidae, Rhithrogena sp. and Perlodidae) were sampled in 36 headwater streams located in the north-west part of England. Using the River Invertebrate Prediction and Classification System (RIVPACS) taxonomic completeness of invertebrate communities was assessed. Quantile regression was used to relate invertebrate body burdens to a maximum (90th quantile) ecological response, both for all metals separately and in mixtures. Significant relations between Cu, Zn and Pb burdens in Leuctra sp. (Zn, Pb), Simuliidae (Zn, Pb), Rhithrogena sp. (Cu, Zn, Cu+Zn) and Perlodidae (Zn) and both taxonomic completeness (O/E taxa) and Biological Monitoring Working Party index scores (O/E BMWP) were observed. Correspondingly the obtained Cu–Zn mixture model an acceptable impact of 5% change in taxonomic completeness is expected at Rhithrogena sp. body burdens of 1.9μmolg−1 Cu (121μgg−1 Cu) in case of low Zn bioavailability (Rhithrogena sp. Zn body burden of 2.9μmolg−1 or 190μgg−1), which will drop to 0.30μmolg−1 Cu (19.1μgg−1 Cu) in case of higher Zn bioavailability (Zn body burden of 72.6μmolg−1 or 4747μgg−1). For Zn, 5% change in taxonomic completeness is expected at Rhithrogena sp. body burdens of 76.4μmolg−1 Zn (4995μgg−1 Zn) in case of low Cu bioavailability (Cu body burden of 0.19μmolg−1 or 12.1μgg−1), which will drop to 6.6μmolg−1 Zn (432μgg−1 Zn) at higher Cu bioavailability (Cu body burden of 1.74μmolg−1 or 111μgg−1). Overall, the present study concludes that invertebrate body burdens can be used to (1) predict metal-induced ecological effects and (2) to derive critical burdens for the protection of aquatic invertebrate communities.
Organic matter (OM) and pH may influence nanoparticle fate and effects in soil. This study investigated the influence of soil organic matter content and pH on the toxicity of ZnO–NP and ZnCl2 to ...Folsomia candida in four natural soils, having between 2.37% and 14.7% OM and pHCaCl2 levels between 5.0 and 6.8. Porewater Zn concentrations were much lower in ZnO–NP than in ZnCl2 spiked soils, resulting in higher Freundlich sorption constants for ZnO–NP. For ZnCl2 the porewater Zn concentrations were significantly higher in less organic soils, while for ZnO–NP the highest soluble Zn level (23mgZn/l) was measured in the most organic soil, which had the lowest pH. Free Zn2+ ion concentrations were higher for ZnCl2 than for ZnO–NP and were greatly dependent on pH (pHpw) and dissolved organic carbon content of the pore water. The 28-d EC50 values for the effect of ZnCl2 on the reproduction of F. candida increased with increasing OM content from 356 to 1592mgZn/kg d.w. For ZnO–NP no correlation between EC50 values and OM content was found and EC50 values ranged from 1695 in the most organic soil to 4446mgZn/kg d.w. in the higher pH soil. When based on porewater and free Zn2+ concentrations, EC50 values were higher for ZnCl2 than for ZnO–NP, and consistently decreased with increasing pHpw. This study shows that ZnO–NP toxicity is dependent on soil properties, but is mainly driven by soil pH.
•Toxicity of ZnO–NP and ZnCl2 to Folsomia candida determined in four soils.•Test soils differed in organic matter content (2.37–14.7%) and pH (5.0–6.8).•Higher Zn porewater concentrations and higher toxicity for ZnCl2 than for ZnO–NP.•Zn porewater concentrations were affected by organic matter content and pH.•ZnO–NP and ZnCl2 toxicity more affected by pH than by organic matter content.
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