Titanium nanoparticles fate in small-sized watersheds under different land-uses

Surface waters from three catchments having contrasting land-uses (forested, agricultural, and urban) were sampled monthly and analysed for nanoparticulate titanium dioxide (NPs-TiO₂) by single particle ICPMS and electron microscopy. We report one-year of data for NPs-TiO₂ having average number and mass concentrations of 9.1 × 10⁸ NPs-TiO₂ particles L^-1 and 11 µg NPs-TiO₂ L^-1 respectively. An increase in concentration during warmer months is observed in the forested and agricultural catchments. Both concentrations of NPs-TiO₂ are within the range of recently reported values using similar analytical approaches. The positive correlations for NPs-TiO₂ mass concentration or particle number with the concentration of some trace elements and DOC in the forested and agricultural catchments suggest the detected NPs-TiO₂ in these two systems are mostly from geogenic origin. Additionally, microscopy imaging confirmed the presence of NPs in the three catchments. Furthermore, the land-area normalized annual flux of NPs-TiO₂ (1.65 kg TiO₂ year^-1 km^-2) was highest for the agricultural catchment, suggesting that agricultural practices have a different impact on the NPs-TiO₂ dynamics and exports than other land-uses (urban or forestry). A similar trend is also found by the reanalysis of recent literature data.