Chunguang Liu

Tire wear particles (TWP), ubiquitously distributed, pose significant risks to ecosystems and human health. Conventional TWP emissions assessment relies on vehicle-type-specific mileage data, but insufficient data on robust vehicle activity statistics limit its applicability globally. Using 2012–2022 comprehensive provincial and national data from mainland China, including vehicle activity, population, and Gross Domestic Product (GDP), we developed an empirical model to estimate TWP emissions via accessible population and GDP indicators. Upon comparison with 2023 mileage-based TWP estimates across 32 Chinese regions and published data sets from 13 countries, our model demonstrated strong predictive performance, characterized by high coefficients of determination (R² = 0.892 and 0.862), low mean absolute error (MAE = 0.107 and 0.196), and low root-mean-square error (RMSE = 0.143 and 0.271). Using this model, we estimated 2022 TWP emissions for 101 eligible countries (vehicle ownership of 35–885 vehicles per 1000 inhabitants), identifying mainland China, the USA, India, Japan, and Brazil as the top five emitters. Globally, TWP emissions are estimated to rise from 3764.6 Kt yr^–1 (median) in 2010 to 4919.2 Kt yr^–1 in 2024, and are projected at 7280.5 Kt yr^–1 by 2050. This work provides a practical tool for large-scale TWP emission risk prediction.

Microplastics (MPs) in the urban atmosphere have been widely reported. However, the distribution of urban atmospheric microplastics (AMPs) under the influence of the East Asia monsoon remains unknown. In this study, total suspended particle (TSP) samples were collected, and polyethene terephthalate (PET) and polycarbonate (PC) MPs concentrations were quantified using a liquid chromatography-tandem mass spectrometry (LC-MS/MS). Higher concentrations of PET and PC were found in the dry season (176.3 ± 22.3 ng/m3 and 41.0 ± 12.6 ng/m3) compared to those in the wet season (49.6 ± 12.0 ng/m3 and 14.7 ± 6.5 ng/m3). Both the concentrations of PET and PC were negatively correlated (p < 0.05) with the frequency of southeast winds, while being positively correlated with the frequency of northwest winds (p < 0.05). Air mass trajectories of the sampling site indicate that during the wet season, a larger number of air masses originate from the oceanic direction, while more air masses come from downtown in the dry season. This further indicates the influence of atmospheric transport on the distribution of PET and PC in the air. In addition, the concentration of PET in the air was significantly correlated with the relative humidity, which may be due to the high proportion of fibrous MPs in PET.

The foliar uptake of Fe₃O₄, Cr₂O₃, CuO, and ZnO nanoparticles (NPs) by maize (Zea mays L.) was studied in a lab-scale experiment. The significant increase of Fe concentrations in leaves exposed to Fe₃O₄ was observed in both stomatal closing and stomatal opening treatments, suggesting the presence of a nonstomatal uptake. In parallel treatments with equal doses of Fe₃O₄ (∼200 nm), Cr₂O₃ (∼300 nm), CuO (∼30 nm), and ZnO (∼40 nm) (20-200 μg), the retention percentage of Fe in the leaves (21.0-69.0%) was higher than that of Cr, Cu, and Zn (0.5-14.0%). The steric hindrance effect seems more important for NPs of >200 nm, while hydrophobic surface and negative charge promote the foliar uptake of NPs smaller than 200 nm. The accumulation of NPs in the cuticle was observed through dark-field hyperspectral microscopy. Cr₂O₃, Fe₃O₄, and CuO NPs were difficult to penetrate the cuticle. In comparison, ZnO further migrated and distributed within the extracellular space of epidermal and mesophyll cells of the exposed leaf, possibly due to its comparatively higher solubility and hydrophilicity. The findings highlight the potential of the nonstomatal uptake, which might be a critical route for metallic oxide NPs to enter the food chain.