Urban plants have been proven to mitigate ambient particulate matter (PM), which can benefit urban planners in their attempts to control urban air pollution. In this study, PM depositions on the leaves of 8 tree species were quantitatively analysed in 7 functional areas of the city of Nanjing, China, over the course of one year. The results demonstrated that leaf PM included different particle size fractions (PM10 and PM2.5), and differed among seasons and species. The highest amounts of total PM, PM10, and PM2.5 were found in the industrial area, and the mean values were 80.24 μg/cm2, 52.14 μg/cm2, and 15.51 μg/cm2, respectively, and the highest accumulation of total PM (60.65 μg/cm2), PM10 (37.29 μg/cm2), and PM2.5 (11.23 μg/cm2) occurred in winter. Significant differences were found between the tree species tested. Cedrus deodara exhibited high amounts of the total PM, PM10, and PM2.5 accumulations. This study examined the mass and quantity distribution of PM among tree species, and identified the particles combined with a scanning electron microscope (SEM). In terms of particle mass, 48% of the identified particles had a diameter of 10 μm, and only 18.3% of them had a diameter of 2.5 μm. In terms of particle number, the results indicated that 73% of them had a diameter of 2.5 μm, and only 5.5% of them had a diameter of 10 μm. To test the relationship between leaf traits and PM2.5 accumulation, results showed that stomata size, density, and hair were significantly related to the PM2.5 capture quantity. As far as we know, this is the first paper to present the mass and quantity distribution of the PM of different tree species in Nanjing. The results not only give comprehensive insights into the dust-retaining capability of tree species but also offer a selection of species for urban green areas where the goal is to mitigate urban airborne PM.

The post-treatment of recycling the fine photocatalyst nanoparticles restricts their application. In this study, a new photocatalytic material was synthesized by immobilizing the N-doped TiO₂ and graphene oxide (GO) composite on polypropylene (PP) (N–TiO₂/GO/PP) fibre sheet, and characterized based on X-ray diffraction spectroscopy (XRD), Raman spectroscopy and Scanning Electron Microscope (SEM). The photocatalytic activity was evaluated using roxithromycin (ROX) as a typical antibiotic pollutant. XRD, Raman spectra and SEM images proved that N–TiO₂/GO/PP fibre sheet was successfully synthesized. The photocatalytic degradation of 10 mg L⁻¹ ROX can reach up to 90% and the degradation rate constant was 0.2299 h⁻¹ in surface water with the application amount of TiO₂/GO/PP fibre sheet of 24.6 cm × 2.7 cm and reaction time of 9 h under the irradiation of simulated sunlight. The application amount of TiO₂/GO/PP fibre sheet, initial concentration of ROX and water matrix significantly affect the degradation of ROX. A low concentration of natural organic matter (NOM) slightly promoted the degradation of ROX, while a high concentration of NOM significantly inhibited the degradation of ROX. Alkaline condition (pH 8–9) is favourable for the photocatalytic degradation of ROX by TiO₂/GO/PP fibre sheet. The photocatalytic reactivity of the TiO₂/GO/PP fibre sheet showed no significant decrease after three runs. Two primary degradation products of ROX were identified and they showed lower ecotoxicity than ROX. The results demonstrate that the new synthesized TiO₂/GO/PP fibre sheet shows promising application prospects in the treatment of antibiotics in wastewater and surface waters. GRAPHICAL ABSTRACT