Stability of Titanium Dioxide Nanoparticle Agglomerates in Transitional Waters and Their Effects Towards Plankton from Lagoon of Venice (Italy)

Abstract

The present study explores the effect of salinity and dissolved organic carbon (DOC) gradients on the stability and reactivity of titanium dioxide nanoparticle (TiO 2 -NP) agglomerates in ambient water from the Lagoon of Venice and their possible effect on nauplii sampled at the same locations. In all ambient water samples, TiO 2 -NPs formed rapidly micrometre-sized agglomerates. The increase in the salinity and concomitant decrease in DOC content induced the formation of larger agglomerates, with z-average hydrodynamic diameter increasing with TiO 2 -NP concentration and exposure duration. Under the studied conditions, f-potential exhibited negative values. In line with agglomeration results, enhancement of the salinity and lower DOC resulted in less negative fpotential with close to 0 values in the dispersions of 100 mg L -1 TiO 2 -NPs in sea water. Two-hour exposure to micrometre-sized agglomerates of TiO 2 -NPs resulted in an increase in the fluorescence of propidium iodide (PI) stained nauplii in comparison with unexposed controls, but had no effect at 24-h exposure. The increase in nauplii-associated PI fluorescence was more noticeable in dispersions containing 100 mg L -1 than those containing 10 mg L -1 TiO 2 -NPs, suggesting membrane permeability alteration in a concentrationdependent manner. However, the PI staining results have to be interpreted with caution because of the possible dye binding to the nauplii surface without penetration of cellular membrane. The effect of TiO 2 -NPs on nauplii was more pronounced at higher salinity and decreased with increasing DOC concentrations at 2 h, while no trends were found at 24-h exposure, as well as exposure to 100 mg L -1 TiO 2 -NPs.

Pro-oxidant effects of nano-TiO2on Chlamydomonas reinhardtii during short-term exposure

“…Thus, large agglomerate subpopulations were possibly removed from the water column, leaving behind smaller subpopulations only for detection by DLS.All in all, particles in the present exposure system were no longer in the nanometer range but much larger sized agglomerates in the micrometer size range. For comparison, C. reinhardtii cells have diameters around 5 -10 µm.These findings are in agreement with earlier observations of nano-TiO 2 forming agglomerates of several hundred nanometers to several micrometers in diameter within minutes at environmentally relevant pH, ionic strengths and dissolved organic matter (DOM) 50,51. A comprehensive study investigating the behavior of nano-TiO 2 in natural matrices at the same concentrations employed here found very low sedimentation rates in freshwater suggesting ecotoxicologically relevant residence times of agglomerated nano-TiO 2 for aquatic organisms in the water column 52.…”

Laura Sigg: Investigating the Speciation, Bioavailability and Ecotoxicology of Trace Metals in Natural Waters

“…5. Ecotoxicology The final two publications of this issue illustrate ongoing research in the new field of nanotoxicology: Behra et al (2015) compare the algal toxicity of gold nanoparticles and gold chloride, and Perstrimaux et al (2015) analyze the effects of titanium dioxide particles on plankton in the Lagoon of Venice.…”