Effects of natural water chemistry on nanosilver behavior and toxicity to Ceriodaphnia dubia and Pseudokirchneriella subcapitata

The success of nanotechnology will undoubtedly lead to the increased introduction of nanoparticles (NPs) into natural systems, and aquatic systems will likely act as sinks for these new pollutants. Differences in the chemistry of these aquatic systems will control changes in surface properties of NPs and therefore could impact their environmental fate and toxicity. A series of batch experiments was conducted to determine the effect of natural waters with different solution chemistries on nanosilver (nAg) particle dispersion, stability, and toxicity. Toxicity assays were performed in tested natural waters as well as in traditional growth media. Briefly, nAg suspended in a natural water with a low ionic strength/dissolved organic carbon (DOC) ratio had an average particle size of 76.8 +/- 0.4nm and was less toxic to Ceriodaphnia dubia and Pseudokirchneriella subcapitata (median lethal concentration [LC50]=221ppb and median inhibition concentration [IC50]=1,600ppb, respectively), whereas a natural water with a high ionic strength/DOC ratio had an average particle size of 192 +/- 5.1nm and produced a much higher toxicity response (LC50=0.433ppb and IC50=22.6ppb, respectively). These findings help to establish needed correlations between water-matrix-dependent nAg particle properties and toxicity implications and indicate that the use of traditional growth media in toxicity assays concerning engineered NPs might not always be appropriate. Environ. Toxicol. Chem. 2012;31:168175. (C) 2011 SETAC