[Spatial-temporal Distribution， Occurrence Characteristics， and Influencing Factors of Atmospheric Microplastic...

Atmospheric microplastics （MPs） pollution has emerged as a global environmental issue， with growing concerns about its potential risks to ecosystems and human health. However， there is still a lack of systematic comparative studies on the pollution characteristics of atmospheric MPs across different functional zones at a national scale， and their morphological characteristics， polymer composition， and key driving factors remain unclear. Therefore， based on data from 249 deposition sites and 169 suspension sites across China from 2014 to 2024， combined with multi-dimensional environmental parameters including industrial emissions， meteorological conditions， and socio-economic factors， this study systematically analyzed the spatiotemporal distribution and occurrence characteristics of atmospheric MPs in different functional zones in China， and a random forest model was constructed to identify key influencing factors. The results showed that： ① The average deposition flux of MPs exhibited a regional pattern of Central China [3 888 n·（m²·d）^-1] > North China [1 344 n·（m²·d）^-1] > East China [967 n·（m²·d）^-1] > Southwest China [410 n·（m²·d）^-1] > Northwest China [183 n·（m²·d）^-1] > South China [85 n·（m²·d）^-1] > Northeast China [54 n·（m²·d）^-1]， while the highest suspended abundance was found in the eastern coastal area of China （51 n·m^-3）. Both showed a peak in the 28-30°N zone， indicating the central role of human activities. Temporally， the overall deposition flux showed a fluctuating upward trend， while the suspended abundance peaked around 2 022 and then declined， reflecting the combined effects of socio-economic activities and policy interventions. ② Atmospheric MPs were dominated by fibrous and fragmented shapes， with transparent and black being the most common colors. The main polymers were polyethylene terephthalate （PET）， polyethylene （PE）， and polyamide （PA）. Significant differences were observed among functional zones： The highest deposition flux was found in landfills [5 387 n·（m²·d）^-1]， followed by residential [2 352 n·（m²·d）^-1] and industrial areas [2 349 n·（m²·d）^-1]； transportation areas had the highest suspended abundance （57 n·m^-3 ）. Agricultural areas were characterized by a high proportion of small-sized MPs （0-50 μm， 43%） and enrichment of PET polymers （34%）； remote areas were dominated by black MPs （38%） and small suspended particles （91%）， suggesting the influence of long-range transport. ③ The random forest model （R² > 0.71） indicated that industrial emissions， industrial structure， and population density were the fundamental driving factors， while meteorological factors （e.g.， wind speed and precipitation） affected the spatial distribution by regulating the deposition-suspension balance. The integration of multi-source data and machine learning methods at the national scale revealed the pollution characteristics and driving mechanisms of MPs in different functional zones， providing a scientific basis for the targeted management and source control of atmospheric MPs.