Temporal and Spatial Distributions of Ti‐Containing Nanoparticles and On‐Site Visitor Numbers in Three Recreation Waters in Eastern Taiwan

ABSTRACT The increase in Ti‐containing nanoparticles (NPs) in the environment resulting from the anthropogenic water activities has raised health concerns in recent years. The aim of this study was to differentiate Ti‐containing engineered NPs (ENPs) from natural Ti‐containing NPs (NNPs) in water exposure through water activities. This was achieved by characterizing the temporal and spatial distributions of Ti‐containing NPs in the three recreation waters in Eastern Taiwan, using the Ti/Y elemental ratio method and single‐particle inductively coupled plasma mass spectrometry (sp‐ICPMS). The mass concentration of the Ti‐containing ENPs and the number concentration of NPs were generally higher during the peak season compared with the low season. These concentrations also fluctuated more widely than those of Ti‐containing NNPs. The highest mass and number concentrations, 8.00 ng/mL and 850.5 × 103 particles/mL, were found in the recreation waters of South Nan‐Ao Creek and Lao Creek, respectively. The most frequent particle size ranged from 28 to 60 nm, with no significant variation across sampling seasons and creeks. Furthermore, the number of on‐site visitors was significantly correlated with the mass concentration of Ti‐containing NPs (p = 0.0069), the number concentration of Ti‐containing NPs (p = 0.0023), and estimated TiO2‐ENPs (p = 0.0305). The elemental ratio method allowed for a clearer illustration of the impact of anthropogenic activities on the Ti‐containing ENPs levels in the recreation waters. This method is valuable for future risk assessments regarding potential exposure to TiO2‐ENPs.