Research on Chemical Components, Seasonal Variation and Sources of Atmospheric PM_2.5 in Taiyuan City

To better understand the chemical composition and sources of fine particulate matter in different seasons in Taiyuan City, we applied online instruments to monitor the major chemical components of PM2.5 (including water-soluble inorganic ions (WSIIs), organic carbon (OC), elemental carbon (EC), and metals) in Taiyuan City during May, July, October, and December 2023. Concentrations of the major chemical components in PM2.5 were measured, and the variation patterns of pollutants in different seasons were analyzed. Furthermore, the Positive Matrix Factorization (PMF) model was used to analyze the sources of PM2.5. The results showed that the average concentration of PM2.5 in Taiyuan was (45.5±41.8) μg/m3 in 2023. And the average concentrations of WSIIs, OC and EC were (20.9±20.4), (5.7±4.4) and (1.1±1.5) μg/m3, respectively. In winter, the concentrations of PM2.5, WSIIs, OC and EC all increased significantly, reaching (76.1±65.9), (34.1±33.5), (9.0±5.9) and (2.7±2.3) μg/m3, respectively. In this study, the Minimum R Squired method (MRS) was used to estimate the concentrations of primary organic carbon (POC) and secondary organic carbon (SOC). The proportion of POC significantly increased in winter, surpassing the proportion of SOC, indicating that the organic carbon components in Taiyuan during winter were mainly from primary sources. Source appointment results indicated that the secondary source, motor vehicles, industry, dust, and combustion were the main contributors to PM 2.5, contributing 47.4%, 16.6%, 16.3%, 11.1%, and 8.6%, respectively. Among them, secondary source was the primary contributor to PM2.5 in Taiyuan across different seasons, accounting for 45%-48%. The contribution of combustion source in spring, autumn, and winter (8.4%-8.7%) was higher than in summer (5.5%). Dust source contributed the most in spring, with a contribution rate of 23.3%.