Homoagglomeration and heteroagglomeration of TiO2, in nanoparticle and bulk form, onto freshwater and marine microalgae.
TiO2nanoparticles (TiO2NPs) are employed in many products (paints, personal care products, especially sunscreens, plastics, paper, water potabilization and food products) and are then released into the environment from these products. These nanoparticles present potential risk to freshwater and marine microalgae. The primary toxicity mechanism is adsorption between NPs and microalgae (heteroagglomeration); however, studies of interactions of this kind are scarce. We investigated the heteroagglomeration process that occurs between two forms of TiO2material, nanoparticles and bulk, and three different microalgae species, and under different environmental conditions (freshwater and marine water), in order to assess the influence of pH and ionic strength (IS). The heteroagglomeration process was examined by means of co-settling experiments and the Derjaguin-Landau-Verwey-Overbeek (DLVO) approach. The homoagglomeration process (only NPs to NPs) did not show differences between culture media (freshwater and marine water). However, in the heteroagglomeration process between NPs and cells, IS played an important role. Ions can compress the electro-double layer between NPs and microalgae, allowing a heteroagglomeration process to take place, as shown by settling experiments. TiO2NPs presented a settling rate higher than bulk TiO2. The DLVO theory could only partially explain heteroagglomeration because, in this model, it is not considered that NP-NP and Cell-Cell homoagglomeration co-occur. In this study neither the role of exopolymeric substances in the interaction between NPs and cells nor detoxification are considered. The authors suggest that the interaction between NPs and microalgae could be considered as the first stage in the process by which nanoparticles affect microalgae.
Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain. Electronic address: marta.sendra@icman.csic.es.
M
M
Sendra
Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Sciences, University of Cadiz, E-11510 Puerto Real, Cádiz, Spain.
M P
MP
Yeste
Department of Material Science, Metallurgical Engineering and Inorganic Chemistry, Faculty of Sciences, University of Cadiz, E-11510 Puerto Real, Cádiz, Spain.
J M
JM
Gatica
Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain.
I
I
Moreno-Garrido
Department of Ecology and Coastal Management, Institute of Marine Sciences of Andalusia (CSIC), Campus Río S. Pedro, 11510 Puerto Real, Cádiz, Spain.
J
J
Blasco
D000327:Adsorption; D058086:Microalgae / Q000187:drug effects*; D053758:Nanoparticles / Q000633:toxicity*; D014025:Titanium / Q000633:toxicity*
C009495:titanium dioxide; D014025:Titanium
Bulk TiO(2); Freshwater; Interaction; Marine; Microalgae; Sedimentation; TiO(2) NPs