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Title: Mechanism of SOA formation determines magnitude of radiative effects

Secondary organic aerosol (SOA) nearly always exists as an internal mixture and the distribution of this mixture depends on the formation mechanism of SOA. A model is developed to examine the influence of using an internal mixing states based on the mechanism of formation and to estimate the radiative forcing of SOA in the future. For the present day, 66 % of SOA is internally mixed with sulfate, while 34 % is internally mixed with primary soot. When compared with using an external mixture, the direct effect of SOA is decreased, due to the decrease of total aerosol surface area and the increase of absorption efficiency. Aerosol number concentrations are sharply reduced and this is responsible for a large decrease in the cloud albedo effect. In total, internal mixing suppresses the radiative effect of SOA by a factor of >4 compared to treating SOA as an external mixture. The future SOA burden increases by 24% due to CO2 increases and climate change, leading to a total (direct plus cloud albedo) radiative forcing of -0.05 W m-2. When the combined effects of changes in climate, anthropogenic emissions and land use are included, the SOA forcing is -0.07 W m-2, even thoughmore » the SOA burden only increases by 6.8%. This is caused by the substantial increase of SOA associated with sulfate in the Aitken mode. The Aitken mode increase contributes to the enhancement of first indirect radiative forcing, which dominates the total radiative forcing.« less
Authors:
ORCiD logo [1] ;  [1] ;  [2] ;  [1] ;  [3] ;  [4]
  1. Univ. of Michigan, Ann Arbor, MI (United States)
  2. Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
  3. Univ. of California, Irvine, CA (United States)
  4. Nanjing Univ. (China)
Publication Date:
Report Number(s):
PNNL-SA-127631
Journal ID: ISSN 0027-8424; KP1703040
Grant/Contract Number:
AC05-76RL01830
Type:
Accepted Manuscript
Journal Name:
Proceedings of the National Academy of Sciences of the United States of America
Additional Journal Information:
Journal Volume: 114; Journal Issue: 48; Journal ID: ISSN 0027-8424
Publisher:
National Academy of Sciences, Washington, DC (United States)
Research Org:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES
OSTI Identifier:
1430453