The production of manufactured nanomaterials has risen exponentially in recent years. Despite this growth, information regarding the fate and behavior of nanoparticles (NPs) in freshwater and marine aquatic ecosystem is still limited. Whiteness, opacity and being a potent photocatalyst are just some of the features that make TiO2 perfect for a wide range of consumer applications such aspaints, coatings, plastics, papers, printing inks, roofing granules, food, medicine, toothpaste, cosmetics and skin-care products(including topical sunscreens). Studies suggest that anatase and rutile have different photocatalytic properties, being anatase more photocatalytic than rutile. However, the mixture of both is the most photocatalytic form of them. In this research, on one hand we have used anatase/rutile NPs with particle size of ≤100 nm, while on the other hand we have used conventional or bulk TiO2. The aim of the current study was to assess the toxicity of TiO2 in an aqueous solution. Two aspects were studied under laboratory conditions, I) NPs and Bulk TiO2 behavior with and without microalgae and II) quantification of intracellular and extracellular NPs and Bulk TiO2. The experiment was performed for two types of microalgae Phaeodctylum tricornutum and Chamydomonas reinhardtii, seawater and freshwater respectively. Both studies were carried out under light (UV-illumination) and white light. As regards TiO2 behaviour, aggregation was accelerated by UV irradiation and ionic strength due to salinity of sea water. UV irradiation is the cause of the formation of hydroxyl groups, which change surface charge and aggregation. Moreover, the presence of algal cells affects the stability of TiO2suspensions. Both, nano and bulk TiO2 formed aggregates during incubation, but NPs TiO2 formed large aggregates trapped almost completely between algae more than bulk TiO2 did. The dispersion of NPs in seawater is likely to be more difficult than in freshwater. It is reasonable to assume that the mechanisms of toxicity of NPs on marine organisms are more complex. Furthermore, the trend of quantification of intracellular and extracellular TiO2 was similar. Within 72 hours of interaction period under UV and white light conditions, a greater proportion of NPs TiO2 was found in the supernatant compared to the surface and interior of the cell. However, the highest concentration of extracellular and intracellular TiO2 showed up with NPs TiO2 under UV conditions.

Trabajo presentado en la SETAC Europe 25th Annual Meeting (Environmental protection in a multi-stressed world: challenges for science, industry and regulators), celebrada en Barcelona del 3 al 7 de mayo de 2015.

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