Mapping the spatial distribution of primary and secondary PM in a multi-industrial city by combining monitoring and modeling results.

Industrial cities are strongly influenced by primary emissions of PM from local industries. In addition, gaseous precursors, such as sulfur oxides (SO), nitrogen oxides (NO), and volatile organic compounds (VOCs), emitted from industrial sources, undergo conversion into secondary inorganic and organic aerosols (SIAs and SOAs). In this study, the spatial distributions of primary and secondary PM in Ulsan, the largest industrial city in South Korea, were visualized. PM components (ions, carbons, and metals) and PM precursors (SO, NO, NH, and VOCs) were measured to estimate the concentrations of secondary inorganic ions (SO, NO, and NH) and secondary organic aerosol formation potential (SOAFP). The spatial distributions of SIAs and SOAs were then plotted by combining atmospheric dispersion modeling, receptor modeling, and monitoring data. Spatial distribution maps of primary and secondary PM provide fundamental insights for formulating management policies in different districts of Ulsan. For instance, among the five districts in Ulsan, Nam-gu exhibited the highest levels of primary PM and secondary nitrate. Consequently, controlling both PM and NO emissions becomes essential in this district. The methodology developed in this study successfully identified areas with dominant contributions from both primary emissions and secondary formation. This approach can be further applied to prioritize control measures during periods of elevated PM levels in other industrial cities.