Nowadays engineered nanomaterials (ENM) are widely used in different customer products that lead to their released into the environment. The ENM behavior in aquatic system is influenced by many factors including water chemistry, presence of natural colloids, biota etc. Despite intensive research conducted in this area the fate of ENM in aquatic system isn't clearly understood that poses the threat for leaving organisms and for human health. In our work, by considering cerium(IV) oxide (CeO2) nanoparticles (NPs), we investigated the fate of ENM in aquatic environment. Various physicochemical methods and techniques, such as dynamic light scattering, nanoparticle tracking analysis, scanning electron microscopy, acid-base titration, were used to characterize CeO2 NPs. Then, the influence of the physicochemical properties of aqueous medium, such as variable ionic strengths, pH, and presence of natural polyelectrolytes, on the CeO2 NPs behavior was investigated. We found that natural organic matter and electrolytes are modifying the surface of CeO2 NPs. Such a coating influences their aggregation behavior and stability in pH and ionic strength changing conditions. Our results are important not only for a better understanding ENM fate and transportation in aquatic system but also for their removal in waste water treatment plants.