Chemical characterization and source apportionment of PM2.5 at an urban site in Gwangju, Korea

It is crucial to investigate the chemical species that cause increases in PM2.5 concentration and to quantitatively estimate source contributions to PM2.5 in urban environments in order to establish strategies to control anthropogenic air pollution. In this study, measurements of 24-hr integrated PM2.5 were performed for 1 year at an urban site in Gwangju, Korea. The collected samples were analyzed for organic and elemental carbon (OC and EC), water-soluble OC (WSOC), eight ionic species, and elemental species, which were used to estimate source contribution of PM2.5 using a positive matrix factorization (PMF) model. The dominant species that contributed to PM2.5 during the study period was organic matter (OM), which accounted for 24% of PM2.5. The major chemical species resulting in PM2.5 pollution episodes (>24-hr Korean PM2.5 standard of 35 mu g/m(3)) depended on the season. For example, PM2.5 increases in winter were strongly associated with increases in secondary nitrate and OM concentrations, while rapid increases in secondary sulfate concentration brought on summertime PM2.5 increases. A total of eight sources of PM2.5 were identified using PMF analysis: secondary nitrate (26%), secondary sulfate (23%), traffic emissions (14%), metallurgical and smelting processes (11%), brake and tire wearing processes (9%), biomass burning emission (8%), crustal source (7%), and industrial sources (1%). The brake and tire wearing processes were a non-negligible contributor to total PM2.5 at the study site, accounting for 7% of PM2.5 in summer and 18% in fall. Metallurgical and smelting processes, which are highly enriched in elements such as Pb, Cu, As, Se, and Zn, were also found to be an important source of PM2.5 at the study site, contributing 7% of PM2.5 in summer and 14% in fall. Moreover, the total contribution of mobile-related emissions, such as vehicles and brake and tire wearing processes, to PM2.5 ranged from 15.2% in summer to 40.0% in winter with an average of 23%. Overall, the results of this study suggest that control of mobile-related sources is crucial to reducing the high PM2.5 levels in the Gwangju metropolitan area.