Chemical characteristics and source apportionment of PM2.5 in a large city in Eastern China during autumn

Rapid economic development and urbanization in China’s Yangtze River Delta region have led to severe air pollution, prompting increasingly stringent control measures and a growing demand for refined, source-specific management strategies. Using Wuxi city in southern Jiangsu Province as a case study, this work conducted hourly resolution ambient monitoring for more than a month (October 28 to November 30) during autumn (the season when particulate matter pollution is typically most severe) to investigate the temporal variations, chemical components, and source apportionment of PM 2.5 . The major chemical components of PM 2.5 , including water-soluble inorganic ions, carbonaceous aerosols, and metal elements, were analyzed. A positive matrix factorization (PMF) model was applied to identify potential sources and quantify their contributions to PM 2.5 . Ground-based aerosol lidar and backward trajectory analysis were used to evaluate the influence of transport processes on local particulate matter mass. The results revealed that the mean PM 2.5 concentration during the sampling period was 34.9 ± 21.7 µg/m 3 , with water-soluble ions and carbonaceous mass as the dominant components accounting for approximately 44.5% and 31.7% of the PM 2.5 mass, respectively. From clean days to pollution days, the chemical components of PM 2.5 underwent a fundamental shift from organic matter dominated to nitrate dominated. The secondary inorganic components, the ratios of organic carbon and elemental carbon indicated a significant secondary pollution phenomenon throughout the sampling period. The PMF model resolved six major sources of PM 2.5 : secondary nitrate (36.1%) > vehicle emission & biomass burning (20.6%) > secondary sulfate (20.1%) > soil dust (11.3%) > metallurgical industry (6.9%) > industrial chlorine & sea salt (4.8%). Secondary inorganic aerosol (nitrate & sulfate totaling 56.2%) was the dominant contributor to PM 2.5 mass, reflecting the combined effect of regional transport and secondary formation during autumn. These findings have important implications for pollution control and science-based emission reduction strategies in large cities.