Effects of copper in Daphnia are modulated by nanosized titanium dioxide and natural organic matter: what is the impact
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RESEARCH ARTICLE
Effects of copper in Daphnia are modulated by nanosized titanium dioxide and natural organic matter: what is the impact of aging duration? Rajdeep Roy 1 & Simon Lüderwald 1 & Asawer Alawi Ahmed Maknoon 1 & George Metreveli 1 & Ralf Schulz 1 & Mirco Bundschuh 1,2 Received: 1 February 2020 / Accepted: 6 November 2020 # The Author(s) 2020
Abstract During its aquatic life cycle, nanosized titanium dioxide (nTiO2) may interact with natural organic matter (NOM) ultimately altering the ecotoxicity of co-occurring chemical stressors such as heavy metals (e.g. copper (Cu)). In this context, the following hypotheses were tested: (1) aging of nTiO2 along with Cu reduces Cu toxicity, (2) nTiO2 agglomerates have a lower potential to reduce Cu toxicity and (3) aging of nTiO2 in presence of NOM reduces Cu toxicity further. A multifactorial test design crossing three nTiO2 levels (0.0, 0.6 and 3.0 mg/L) with two levels of NOM (0 versus 8 mg total organic carbon (TOC)/L) and seven nominal Cu concentrations (ranging from 0 to 1536 μg/L) aged in ASTM medium for 0, 1, 3 and 6 days was realised, while two aging scenarios were applied (type 1: nTiO2 jointly aged with Cu; type 2: Cu added after nTiO2 aging). Subsequently, Cu toxicity was assessed using the immobility of Daphnia magna after 48 h of exposure as response variable. The experiments revealed that neither aging duration nor the extent of agglomeration (type 1 vs. type 2 aging) has a substantial impact on Cu induced toxicity. Moreover, it was confirmed that the presence of NOM substantially reduced Cu induced toxicity, independent of the aging scenario and duration. More importantly, the data suggest the ingestion of Cu loaded nTiO2 as additional exposure pathway contributing to Cu toxicity. In conclusion, it seems unlikely that nTiO2 concentrations currently detected in or predicted for aquatic ecosystems, which are at least one order of magnitude below the concentration tested here, influence Cu toxicity meaningfully. Keywords Aging . Nanomaterials . Natural organic matter . Metal ions . Combined effect . Mixture toxicity
Introduction As a consequence of their small size, nanoparticles (NPs) possess physical and chemical features that are fundamentally different from their water-soluble or bulk counterparts. Those features include a high specific surface area, reactivity in Responsible Editor: Philippe Garrigues * Rajdeep Roy [email protected] * Mirco Bundschuh [email protected] 1
iES Landau, Institute for Environmental Sciences, University of Koblenz-Landau, Fortstrasse 7, 76829 Landau, Germany
2
Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences, Uppsala, Sweden
liquid or gas phase and rapid diffusion (Nowack and Bucheli 2007; Fan et al. 2011) making nanotechnology a multitrillion dollars business involving approximately 6 million employees worldwide (He et al. 2019). Furthermore, the Nanotechnology Consumer Products Inventory (CPI) listed 1814 consumer products from 6222 companies of 32 countries in 2
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