# Seasonal Characteristics of Particulate Matter by Pollution Source Type and Urban Forest Type
## 1 Introduction  
Fossil fuels and various industrial processes release pollutants into the atmosphere, contributing significantly to air pollution. Air pollutants, especially particulate matter (PM), affect diverse regions and generations without distinction. PM exposure is ubiquitous, affecting the health of humans, animals, and plants, thereby posing a significant threat to public health and air quality. Given these challenges, PM has garnered attention as a crucial environmental issue that requires immediate action for reduction. Accordingly, both public and private institutions are actively developing strategies to manage and mitigate PM, with South Korea adopting similar approaches [1, 2]. Effective strategies, such as reducing vehicle exhaust emissions, have led to decreased pollutant concentrations in South Korea over time (National Academy of Environmental Sciences, 2022). However, challenges persist, especially in regions with low wind speeds or stagnantair, where PM concentrations tend to rise [3]. Additionally, rising temperatures in high-latitude regions and a decline in the northwest monsoon could foster conditions favorable for atmospheric stagnation, potentially reversing the trends in reducing PM concentrations, even with ongoing reduction policies [4; 5]. As urbanization progresses globally over the next three decades, all regions are expected to experience heightened urban growth (UN-Habitat Core Team, 2022). Urban residential areas tend to exhibit higher PM levels than rural areas, with urban roadsides experiencing elevated PM exposure from non-exhaust vehicular sources, such as tire and road abrasion, as well as vehicular emissions [6]. Furthermore, industrial emissions from oil combustion, coal burning, and metal processing in urban settings result in higher oxidative output than that in rural areas, exacerbating adverse effects on human health [7; 8]. This confluence of climate change, urbanization, and persistent pollution has resulted in an increasing number of factors contributing to higher particulate matter (PM) concentrations, with their relationships becoming more complex. As such, research into complementary measures to mitigate these trends is essential. The limitations of traditional approaches necessitate complementary strategies, thereby driving the demand for innovative solutions to promote sustainability (National Institute of Forest Science, 2021). Nature-based solutions (NbSs) involve leveraging natural processes to tackle socio-environmental challenges, enhancing sustainability and providing diverse benefits to both society and the environment (National Institute of Forest Science, 2021). NbSs offer adaptive management approaches for complex socio-ecological challenges and may be an effective solution for PM reduction [9]. Particulate matter (PM) can be divided into two types depending on how it is formed: primary PM, which is emitted directly from the source in solid form, and secondary PM, which is formed when gaseous substances from the source undergo chemical reactions with other substances in the air (Ministry of the Environment, Understanding Particulate Matter, 2017). PM refers to particles smaller than 10 \(\upmu\)m, most of which are produced by primary emissions. In 2021, the primary sources of PM emissions in South Korea include manufacturing combustion and production processes (8.22%), road traffic-related pollution (2.39%), and fugitive dust (65.86%) (Korean Statistical Information Service, 2024). In general, the formation of PM varies depending on the source. On roads, PM is released by processes such as fuel combustion in internal combustion engines (exhaust emissions), tire wear, and road surface abrasion (non-exhaust vehicle emissions) [10]. In industrial complexes, PM is generated by the combustion of fossil fuels such as petroleum and coal, metal processing, handling of powdered raw and auxiliary materials in factories, and emissions from incinerators (Ministry of the Environment, Understanding Particulate Matter, 2017).