Occurrence, Sources, and Export Rates of Ti-Bearing and Ce-Bearing (Nano)particles in the Seine River Where...

This study investigates the occurrence, distribution, and sources of titanium (Ti)-bearing and cerium (Ce)-bearing (nano)particles in the Seine River basin using single particle inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS). Water samples and freshwater mussels (Dreissena polymorpha) were collected during three campaigns (2020, 2021, 2023) to assess colloidal concentrations and bioconcentration patterns. Ti-bearing particle concentrations ranged from 1.18 × 10⁶ to 3.61 × 10⁸ particles·L^-1, while Ce-bearing particles ranged from 5.08 × 10⁶ to 4.58 × 10⁷ particles·L^-1. Calculated export rates were 0.3 - 1.1 kg·year^-1·km^-2 for Ti and 56.5 g·year^-1·km^-2 for Ce. Elemental ratio analysis (Ti:Fe and Ce:La) distinguished engineered from natural particles: approximately 60% of Ti-bearing particles were associated with engineered titanium dioxide (TiO₂), while 40% matched natural hematite-ilmenite minerals; similarly, 65% of Ce-bearing particles were associated with engineered cerium dioxide (CeO₂), while 35% resembled natural monazite. Ti- and Ce-bearing particle sizes ranged from 60 to 500 nm and 20 to 80 nm, respectively, reflecting aggregation and natural mineral contributions. Zebra mussels bioaconcentrated both particle types, with Ti concentrations correlating linearly with water concentrations, suggesting bioindicator potential. These findings demonstrate that engineered nanoparticle concentrations in the Seine River have reached levels comparable to natural colloids, highlighting their significant environmental presence in urbanized watersheds.