John Wiley & Sons, Ltd.

Determination of nanosilver dissolution kinetics and toxicity in an environmentally relevant aqueous medium

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Assessing the dissolution of silver nanoparticles (AgNPs) in laboratory test media and in the aquatic environment is critical for determining toxicity. In the present study, the ion‐release kinetics for 20, 50, and 80 nm AgNPs in environmentally relevant freshwaters with different electrical conductivity values (30 µS/cm, 150 µS/cm) were examined and related to the associated impact on Daphnia magna. The acute toxicity of the AgNPs suspensions to D. magna was assessed after 0 and 7 days interaction time between the particles and test media. When 48‐h lethal median concentrations were expressed as total silver, D. magna was more sensitive to AgNPs suspended in low ionic strength media relative to higher ionic strength media with the exception of 50 nm AgNPs suspended in the 150 µS/cm medium. A 3.3 fold increase in hydrodynamic diameter measured by dynamic light scattering and field flow fractionation was observed over time for 20 nm particles in the150 µS/cm medium but only a small increase in aggregation size for 50 and 80 nm particles (1.4 and 1.2 fold increase, respectively) was observed. At a lower conductivity of 30 µS/cm, a 1.7, 1.0, and 1.2 fold increase in aggregation size was observed in 20, 50 and 80 nm, respectively. Thus, the impact of higher conductivity test media on increased aggregation and decreased toxicity (after 7 days) was relatively greater for the smaller (20 nm) AgNP higher compared to the 50–80 nm AgNPs. Environ Toxicol Chem © 2014 SETAC

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