06 Apr 2022
06 Apr 2022
Status: a revised version of this preprint is currently under review for the journal ACP.

Chemical properties, sources and size-resolved hygroscopicity of submicron black carbon-containing aerosols in urban Shanghai

Shijie Cui1, Dan Dan Huang2, Yangzhou Wu1,a, Junfeng Wang1, Fuzhen Shen1,b, Jiukun Xian1, Yunjiang Zhang1, Hongli Wang2, Cheng Huang2, Hong Liao1, and Xinlei Ge1 Shijie Cui et al.
  • 1Jiangsu Key Laboratory of Atmospheric Environment Monitoring and Pollution Control, Collaborative Innovation Center of Atmospheric Environment and Equipment Technology, School of Environmental Science and Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China
  • 2Shanghai Academy of Environmental Sciences, Shanghai 200233, China
  • anow at: Department of Atmospheric Sciences, School of Earth Sciences, Zhejiang University, Hangzhou 310027, PR China
  • bnow at: Department of Meteorology, University of Reading, Reading, RG6 6BX, UK

Abstract. Refractory black carbon (rBC) aerosols play an important role in air quality and climate change, yet high time-resolved and detailed investigation on the physicochemical properties of rBC and its associated coating is still scarce. In this work, we used a laser-only Aerodyne soot particle aerosol mass spectrometer (SP-AMS) to exclusively measure the rBC-containing (rBCc) particles, and compared their properties with the total non-refractory submicron particles (NR-PM1) measured in parallel by a high-resolution AMS (HR-AMS) in Shanghai. The observation shows that rBC was overall thickly coated with an average mass ratio of coating to rBC core (RBC) of ~5.0. However, mass of rBC coating species only occupied 19.1 % of those in NR-PM1; sulfate tended to condense preferentially on non-rBC particles therefore its portion on rBC was only 7.4 %, while the majority of primary organic aerosols (POA) were associated with rBC (72.7 %). Positive matrix factorization reveals that cooking emitted organics did not coat on rBC, and a portion of organics coated on rBC was from biomass burning which was unidentifiable in NR-PM1 organics. Small rBCc particles were predominantly from traffic, while large-sized ones were often mixed with secondary components and typically had thick coating. During this campaign, sulfate and secondary organic aerosol (SOA) species were generated mainly through daytime photochemical oxidation (SOA formation likely involved with in-situ chemical conversion of traffic-related POA to SOA), while nocturnal heterogeneous formation was dominant for nitrate; we also estimated the average times of 5~19 hours for those secondary species to coat on rBC. Particles during a short period that was affected by ship emissions, were characterized with a high vanadium concentration (on average 5.8 ng m−3) and a vanadium/nickel mass ratio of 2.0. Furthermore, the size-resolved hygroscopicity parameter (кrBCc) of rBCc particles was obtained based on its fully chemical characterization, and was parameterized as кrBCc(x)= 0.29−0.14 × exp(-0.006 × x) (x is from 150 to 1000 nm). Under critical supersaturations (SSC) of 0.1 % and 0.2 %, the D50 values were 166 ± 16 and 110 ± 5 nm, respectively, and with 16 ± 3 % and 59 ± 4 % of rBCc in number could be activated into cloud condensation nuclei (CCN). Our findings are valuable to advance the understanding of BC chemistry as well as the effective control of atmospheric BC pollution.

Shijie Cui et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-194', Anonymous Referee #2, 29 Apr 2022
  • RC2: 'Comment on acp-2022-194', Anonymous Referee #1, 06 May 2022
  • AC1: 'Reply to comments on acp-2022-194', Xinlei Ge, 23 May 2022

Shijie Cui et al.


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Short summary
Refractory black carbon (rBC) aerosols are important to both air quality and climate change. However, rBC can mix with many other species therefore change its properties significantly. We used a specific set of techniques to exclusively characterize rBC-containing (rBCc) particles in Shanghai. We figured out composition, sources, size distributions and the factors affecting such physicochemical properties. Our findings are valuable to advance the understanding of BC and its pollution control.