Stability and Aggregation of Metal Oxide Nanoparticles in Natural Aqueous Matrices Arturo A. Keller Hongtao Wang Dongxu Zhou Hunter S. Lenihan Gary Cherr Bradley J. Cardinale Robert Miller Zhaoxia Ji 10.1021/es902987d.s001 https://acs.figshare.com/articles/journal_contribution/Stability_and_Aggregation_of_Metal_Oxide_Nanoparticles_in_Natural_Aqueous_Matrices/2784541 There is a pressing need for information on the mobility of nanoparticles in the complex aqueous matrices found in realistic environmental conditions. We dispersed three different metal oxide nanoparticles (TiO<sub>2</sub>, ZnO and CeO<sub>2</sub>) in samples taken from eight different aqueous media associated with seawater, lagoon, river, and groundwater, and measured their electrophoretic mobility, state of aggregation, and rate of sedimentation. The electrophoretic mobility of the particles in a given aqueous media was dominated by the presence of natural organic matter (NOM) and ionic strength, and independent of pH. NOM adsorbed onto these nanoparticles significantly reduces their aggregation, stabilizing them under many conditions. The transition from reaction to diffusion limited aggregation occurs at an electrophoretic mobility from around −2 to −0.8 μm s<sup>−1</sup> V<sup>−1</sup> cm. These results are key for designing and interpreting nanoparticle ecotoxicity studies in various environmental conditions. 2010-03-15 00:00:00 Metal Oxide Nanoparticles nanoparticle ecotoxicity studies media aggregation Natural Aqueous MatricesThere NOM electrophoretic mobility metal oxide nanoparticles