Quantitative evaluation for the sources and aging processes of organic aerosols in urban Guangzhou: Insights from a comprehensive method of dual‑carbon isotopes and macro tracers.

Organic carbon aerosol (OC) is a pivotal component of PM in the atmospheric environment, yet its emission sources and atmospheric behaviors remain poorly constrained in many regions. In this study, a comprehensive method based on the combination of dual‑carbon isotopes (C and C) and macro tracers was employed in the PRDAIO campaign performed in the megacity of Guangzhou, China. The C analysis showed that 60 ± 9 % of OC during the sampling campaign was associated with non-fossil sources such as biomass burning activities and biogenic emissions. It should be noted that this non-fossil contribution in OC would significantly decrease when the air masses came from the eastern cities. Overall, we found that non-fossil secondary OC (SOC) was the largest contributor (39 ± 10 %) to OC, followed by fossil secondary OC (SOC: 26 ± 5 %), fossil primary OC (POC: 14 ± 6 %), biomass burning OC (OC: 13 ± 6 %) and cooking OC (OC: 8 ± 5 %). Also, we established the dynamic variation of C as a function of aged OC and the volatile organic compounds (VOCs) oxidized OC to explore the impact of aging processes on OC. Our pilot results showed that atmospheric aging was highly sensitive to the emission sources of seed OC particles, with a higher aging degree (86 ± 4 %) when more non-fossil OC particles were transferred from the northern PRD.