A TEM–based Study of Individual Aerosol Particles in an Urban Forest Park Across Autumn and Winter

<p indent="0mm">Atmospheric particulate matter has significant impacts on human health, environmental quality, and climate change, making it a key focus in air pollution research. Urban forest parks, as important biological sources, not only contain abundant natural components but are also more susceptible to pollutants from nearby anthropogenic emissions. This study utilized single-particle analysis and backward trajectory analysis to investigate the morphology, sources, and aging of atmospheric single particles in Meiling National Forest Park. The results indicate that the main types of single particles in Meiling National Forest Park are sulfur-rich particles (30.2%) and mixed particles (43.8%), followed by soot particles (13.3%), organic particles (6.6%), mineral particles (4.4%), and metal-rich particles (1.7%). Differences in particle types and sizes were observed between clean and haze days. On clean days, sulfur-rich particles had the highest relative abundance, accounting for 52.7%. Conversely, on haze days, particles underwent heterogeneous reactions increased particle mixing, with mixed particles comprising 49.8% of the total. The core-shell ratio, a marker of particle aging in mixed particles, was found to be smaller on haze days, indicating a higher degree of particle aging. The source of particulate matter was related to airflow transport. Under the influence of winter monsoons, clean days were associated with airflows originating from the northeast, whereas haze days were linked to airflows from the southeast. The aging of particulate matter in Meiling National Forest Park was influenced by both anthropogenic and natural sources.