Temporal variations of the hygroscopicity and mixing state of black 1 carbon aerosols in a polluted megacity area 2

15 Black carbon (BC) aerosols in the atmosphere strongly affect radiative forcing. They 16 are mainly removed from the air by wet deposition, and their lifetime is controlled by 17 their water uptake ability or hygroscopicity, which is a function of the aerosol mixing 18 states. It is well known that atmospheric aging processes coat various materials on BC 19 aerosols and affect their mixing states and hygroscopicity. However, detailed relations 20 between the aging processes, the hygroscopicity and mixing state of BC aerosol 21 particles in polluted city areas are not well understood. Here, we studied the temporal 22 variation of the hygroscopicity and its correlation with the mixing state of ambient BC 23 particles during 2017 summer in Shanghai, China using a hygroscopicity tandem 24 differential mobility analyzer in-line with a single particle soot photometer 25 (HTDMA-SP2 system) as well as a single particle aerosol mass spectrometer 26 (SPAMS). BC particles with 120 nm, 240 nm and 360 nm dry diameter were 27 Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-602 Manuscript under review for journal Atmos. Chem. Phys. Discussion started: 25 June 2018 c © Author(s) 2018. CC BY 4.0 License.

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