Aggregation and ecotoxicity of CeO2 nanoparticles in synthetic and natural waters with variable pH, organic matter concentration and ionic strength

The influence influence of pH (6.0-9.0), natural organic matter (NOM) (0-10 mg C/L) and ionic strength (IS) (1.7-40 mM) on 14 nm CeO2 NP aggregation and ecotoxicity towards the alga Pseudokirchneriella subcapitata was assessed following a central composite design. Mean NP aggregate sizes ranged between 200 and 10000 nm. Increasing pH and IS enhanced aggregation, while increasing NOM decreased mean aggregate sizes. The 48 h-E(r)C20s ranged between 4.7 and 395.8 mg CeO2/L An equation for predicting the 48 h-E(r)C20 (48 h-E(r)C20 = -1626.4 x (pH) + 109.45 x (pH)(2) + 116.49 x ([NOM]) -14.317 x (pH) x ([NOM]) + 6007.2) was developed. In a validation study with natural waters the predicted 48 h-E(r)C20 was a factor 1.08-2.57 lower compared to the experimental values. (C) 2010 Elsevier Ltd. All rights reserved.