Sources and atmospheric transformation of PM_2.5 at forest site in southern China revealed by δ¹³C

Suburban forest sites are influenced by both biogenic emissions and anthropogenic pollutants from nearby urban areas. This study investigated PM_2.5 sources and atmospheric transformation processes using chemical components and stable carbon isotopes (δ¹³C) at a suburban forest site in southern China. The average PM_2.5 concentration was 62.72 ± 28.90 μg/m³, dominated by secondary inorganic aerosols and organic matter. SOC contributed about 53% of OC during the sampling period. PMF identified six major sources, including biomass burning, vehicle emissions, coal combustion, dust, industrial dust, and waste incineration. PSCF results showed that PM_2.5 and OC were affected by both local emissions and regional transport in autumn, but mainly by local sources in winter. δ¹³C analysis indicated that carbonaceous aerosols were primarily derived from C3 plant biomass and vehicular emissions. High WSOC/OC and SOC/OC ratios suggested significant aerosol aging and secondary organic carbon formation, which strongly influenced δ¹³C variations in PM_2.5.