Single- and Multi-Element Quantification and Characterization of TiO2 Nanoparticles Released From Outdoor Stains and Paints

Abstract

With growing applications of TiO 2 nanoparticles (NPs) in outdoor surface coatings, notably in paints and stains, their release into the environment is inevitable. While NP release has potential ecotoxicological risk, reliable risk assessments are often complicated by the near absence of analytical data on release rates under natural weathering scenarios, and the lack of a chemical characterization of the NPs following their release. This work measured NPs released from painted and stained surfaces and characterized them by size and composition using magnetic sector single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) and SP-ICP-time-of-flight-MS (SP-ICP-TOF-MS). Two in situ experimental plans were examined in which natural precipitation interacted with nano-enhanced surfaces to varying degrees during the fall and winter. Weathering data showed that longer contact times of the precipitation (snow and rain) resulted in greater NP release. Although the stained surfaces had far fewer NPs per unit area, they lost a much higher fraction of their NP load (max 6% leached, as opposed to <10 −4% in paints), over similar exposure times. NP release was particularly enhanced for conditions of frequent rainfall and spring snow melt (i.e., slushy snow). SP-ICP-TOF-MS measurements on the Ti NPs indicated that they were often associated with a secondary metal in both the liquid paint (Al was detected in ∼20% of the Ti NPs; Zr in about ∼1% of the NP) and the liquid stain (Fe was detected in ∼7%, Si in ∼8% and Al in ∼3% of the Ti NPs). In contrast, for the vast majority of Ti NPs being leached out of the painted/stained surfaces, only Ti was detected. Metal interactions in the paint were explained by binding of the TiO 2 within a complex paint matrix; while in the stain, TiO 2 NPs were hypothesized to be found in heteroagglomerates, potentially with aluminosilicates (Fe, Si, and Al). In rain and snow, Ti was the only element detected in about half of the Ti NPs; in the other half, Ti often co-occurred with Fe, Si and Al. The results indicate that single element, likely anthropogenic, Ti NPs are already prevalent in the natural precipitation and that NP release from surface coatings will further increase their presence in the environment.

Measurement of CeO2 Nanoparticles in Natural Waters Using a High Sensitivity, Single Particle ICP-MS

“…The instrument used a segmented reaction cell in which 4-6 cm 3 min −1 of He and ca. Four cm 3 min −1 of H 2 gas was introduced in order to eliminate argon and nitrogen-based interferences for elements such as Si, K, Ca, Cr and Fe [37]. Time of flight mass spectra (23-238 amu) were acquired with a dwell time of 76.5 µs [37].…”

“…Four cm 3 min −1 of H 2 gas was introduced in order to eliminate argon and nitrogen-based interferences for elements such as Si, K, Ca, Cr and Fe [37]. Time of flight mass spectra (23-238 amu) were acquired with a dwell time of 76.5 µs [37]. Total sample acquisition time was 32 s. In some experiments, the instrument was coupled to an Aridus II desolvator (Teledyne Cetac Technologies, Omaha, NE, USA) (Argon was used as the membrane sweep gas (5-6 L min −1 ) and as the nebulizer gas (0.9-1.0 L min −1 )).…”

“…In that case, the algorithm searched for a target isotope, i.e., 140 Ce, using similar smoothing and peak detection parameters as with SF-ICP-MS. Following detection of the Ce-containing peaks, each particle event was assigned start and end timestamps, which were used to integrate peaks for all other isotopes [37]. As above, the criteria to report peak events as NP were based on the FWHM values as well as the standard deviation of the background (for each isotope), which were used to estimate threshold values.…”

Environmental context determines the impact of titanium oxide and silver nanoparticles on the functioning of intertidal microalgal biofilms

“…The mixture of both forms was chosen to mimic natural conditions where NPs will originate from diverse sources. 3,56,57 There are indeed numerous applications that do not require a specific phase of TiO 2 (e.g. painting, photocatalytic applications…).…”

“…TiO 2 -NPs occur commonly as two different crystalline structures, anatase and rutile; a mix of both phases of titanium was chosen in this experiment to take into account the diversity of TiO 2 -NPs arriving on coasts from different sources, 3,56,57 for instance: coatings, paints, sunscreens. Toxicity of TiO 2 -NPs is twofold: a direct physical effect on cells, associating with and shading them, interrupting energy transduction along the membrane and limiting cells access to light.…”