Transboundary air pollution in coastal urban area in Japan: Transport model and positive matrix factorization analysis for SPM-PM2.5 and PM2.5

Transboundary air pollutants have raised serious health concerns, particularly in regions with minimal local pollution sources. Distinguishing between local pollution and transboundary contributions is crucial for accurately assessing the health risks to local populations. This study aimed to analyze the differences in coarse and fine particulate matter and develop methods to obtain exposure data for epidemiological studies, thereby providing a scientific basis for public health interventions. We collected SPM-PM2.5 (physically excluded PM2.5 from SPM) and PM2.5 samples in Yonago City, a coastal urban area in Tottori Prefecture, Japan, from 19 October 2015 to 25 July 2016 using a novel slit jet impactor (MCAS-SJ). Positive matrix factorization analysis used heavy metal, ion, and carbon concentrations to identify pollutant sources. This study identified four major air pollution events during the sampling period, primarily attributed to transboundary transport. Episode I was dominated by nitric aerosols, Episodes II and III by Asian dust, and Episode IV by sulfate aerosols. An analysis using global chemical transport models and backward trajectories confirmed that these events verified the contribution of transboundary pollution. In conclusion, identifying the impact of transboundary pollution on local air quality enables an accurate risk assessment of populations. This study provides scientific evidence for developing effective public health strategies and preventive measures. Additionally, the methodology used in this study holds the potential for international contributions and future research applications, helping to address air pollution challenges on a broader scale.