Nanosized titanium dioxide influences copper‐induced toxicity during aging as a function of environmental conditions

Abstract

Titanium dioxide nanoparticles (TiO2 -NPs) adsorb co-occurring heavy metals in surface waters, modulating their toxicity for freshwater invertebrates. The processes triggering this interaction may be influenced by several environmental parameters; however, their relative importance remains unclear. The present study assessed the implications of aging on the joint acute toxicity of copper (Cu) and TiO2 -NPs for Daphnia magna over a duration of up to 72 h. The influences of aging duration as well as ionic strength, pH, and presence of different qualities of organic matter during aging were assessed. The results indicated that the presence of TiO2 -NPs often reduced the Cu-induced toxicity for daphnids after aging (albeit with varying extent), which was displayed by up to 3-fold higher EC50 (50% effective concentration) values compared to the absence of TiO2 -NPs. Moreover, the Cu speciation, influenced by the ionic composition and the pH as well as the presence of organic additives in the medium, strongly modulated the processes during aging, with partly limited implications of the aging duration on the ecotoxicological response of D. magna. Nonetheless, the present study underpins the potential of TiO2 -NPs to modify toxicity induced by heavy metals in freshwater ecosystems under various environmental conditions. This pattern, however, needs further verification using heavy metal ions with differing properties in combination with further environmental factors, such as ultraviolet irradiation. Environ Toxicol Chem 2016;35:1766-1774. © 2015 SETAC.

Role of graphene oxide in mitigated toxicity of heavy metal ions on Daphnia magna

“…28 In addition, the effect of pH values on the interaction of GO and heavy metal ions was also assessed, because pH determines the surface charge of nanoparticles and ultimately affects the nanoparticles' agglomeration dynamics and the adsorption of metal ions. 29,30 2 Materials and methods…”

Effects of copper in Daphnia are modulated by nanosized titanium dioxide and natural organic matter: what is the impact of aging duration?

“…The discrepancy of NP-induced changes in metal toxicity may depend on the NP concentration (Wang et al 2011) as well as the metal identity or more specifically the metal ion's charge (Rosenfeldt et al 2014). It was, moreover, highlighted that the combined toxicity of metals and NP depends on the environmental conditions triggering their fate and interaction over time (Rosenfeldt et al 2016). Indeed, Rosenfeldt et al (2016) highlighted that Cu toxicity was reduced with increasing aging duration in presence of titanium dioxide (nTiO 2 ) relative to NP's absence.…”

“…It was, moreover, highlighted that the combined toxicity of metals and NP depends on the environmental conditions triggering their fate and interaction over time (Rosenfeldt et al 2016). Indeed, Rosenfeldt et al (2016) highlighted that Cu toxicity was reduced with increasing aging duration in presence of titanium dioxide (nTiO 2 ) relative to NP's absence. While this pattern was observed in medium with ionic strength (9.25 mmol/L), distilled water (ionic strength~0 mmol/L) did not influence Cu toxicity.…”

“…reflecting the 96 h EC 10 and EC 50 of nTiO 2 ( Fig. 1S) for Daphnia as well as the absence of nTiO 2 ) in the presence and absence of NOM (seaweed extract as used in many earlier papers, namely Rosenfeldt et al 2015aRosenfeldt et al , 2016 on Cu toxicity (seven concentrations from the range 0-1536 μg/L; using a spacing factor of 2) were assessed for the model species Daphnia magna. Thereby, two aging scenarios in ASTM reconstituted hard water (ASTM 2007) were realised prior to the toxicity assessment: the first scenario ensured the interaction of nTiO 2 with Cu in presence and absence of NOM during aging.…”

“…The second scenario focused on the aging of nTiO 2 and NOM (presence vs. absence) with Cu being spiked to the test medium just before the introduction of the test species. These aging scenarios simulate the interaction of Cu with fresh nTiO 2 (often in their nanoform) or with aged and thus agglomerated particles, whose average particle size is often in the μm-range (Cupi et al 2015;Seitz et al 2015;Rosenfeldt et al 2016), allowing to assess for the importance of the particle or agglomerate size. The selection of nTiO 2 as model NP is motivated by its high production volume (Jovanović 2015) and widespread application (Baiqi et al 2006;Chen and Mao 2007;Mueller and Nowack 2008).…”