Observation-based investigation unveils major local sources of heavy metals associated to fine particulate matters (PM2.5) in an urban area

This study focuses on PM_2.5 pollution in the Taichung Metropolitan Area, Taiwan, with an emphasis on the application of an advanced PMFxPMF method for detailed source identification. Initial Positive Matrix Factorization (PMF) analysis identified six major pollution sources, including regional secondary pollution (41%), carbonaceous aerosols (24%), and Heavy metal-rich industrial processes (8%). To refine the attribution of industrial sources, a second-phase PMFxPMF analysis was employed, specifically targeting heavy metals within the industry factor. By integrating source fingerprints from chimney samples of coal combustion and sintering furnaces, the analysis revealed that these sources contributed 18.4% and 4.9%, respectively, to the total heavy metals in the industry factor. When excluding Fe, the contributions increased to 35.5% and 8.4% for non-Fe heavy metals. The application of the PMFxPMF method was crucial in accurately linking specific industrial activities to heavy metal emissions, offering a more precise understanding of pollution sources. These insights are essential for developing targeted strategies to reduce PM_2.5 levels and mitigate the associated health risks in the Taichung region, particularly through stricter control of emissions from coal combustion and metal processing industries.