High contributions of fossil sources to more volatile organic aerosol

摘要: Abstract. Sources of particulate organic carbon (OC) with different volatility have rarely been investigated, despite the significant importance for better understanding atmospheric processes aerosols. In this study we develop a radiocarbon-based ( 14C ) approach for source apportionment more volatile OC (mvOC) and apply to ambient aerosol samples collected in winter six Chinese megacities. mvOC is isolated by desorbing from filter samples helium (He) at 200  ∘ C custom-made aerosol combustion system analysis. Evaluation new isolation method shows that isolated mvOC amount agrees very well OC1 fraction (also desorbed He) measured by thermal–optical analyzer using the EUSAAR_2 protocol. The mvOC, elemental (EC) of 13 combined PM 2.5 cities are analyzed for investigate their sources formation mechanisms. The relative contribution fossil 59±11  %, consistently larger than 48±16  %) and smaller EC 73±9  %), large differences in fossil contributions different cities. average difference the fossil fractions between 13 % (range 7 %–25 %), similar (13 %, range 4 %–25 %). Secondary OC (SOC) concentrations modeled based on the -apportioned compared sources of mvOC. SOC 15.4±9.0 µ g m −3 are consistently higher those 3.3±2.2 ), indicating only accounted volatile carbon C. is 43 % (10 %–70 %), lower (59 %, 45 %–78 %). Correlation nonfossil (mvOC nf vs. vs. SOC examined further explore formation processes SOC.