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Title: New Analytical Paradigm to Determine Concentration of Brown Carbon and Its Sample-by-Sample Mass Absorption Efficiency
Brown carbon (BrC) has a substantial direct radiative effect, but current estimates of its impact on radiative balance are highly uncertain due to a lack of measurements of its light-absorbing properties, such as mass absorption efficiency (MAE). Here, we present a new analytical paradigm based on a Bayesian inference (BI) model that takes multiwavelength aethalometer measurements and total carbon data to resolve the concentrations of black carbon and BrC, and MAEs of BrC on a sample-by-sample basis. Hourly MAEs, unattainable in previous studies, can now be calculated, enabling the first-time observation of the darkening-bleaching dynamics of BrC in response to photochemical transformation. We demonstrate the application of this BI model to analyze measurements collected over one year (2021–2022) in Hong Kong. Diel variations in MAE370 nm of BrC reveal a darkening-to-bleaching transition occurring between 8 and 10 o’clock when the solar irradiance ranges from 30 to 400 W m–2. Furthermore, we consistently observe an increase in MAE370 nm of BrC with nitrogen oxide concentrations, suggesting the enhanced formation of nitrogenous organics. This BI model-based data analysis would bring forth a breakthrough in amassing observation data of BrC and its MAEs in diverse ambient environments and with high time resolution.  more » « less
Award ID(s):
2026824
PAR ID:
10643284
Author(s) / Creator(s):
 ;  ;  ;  ;  ;  
Publisher / Repository:
American Chemical Society
Date Published:
Journal Name:
Environmental Science & Technology
Volume:
58
Issue:
39
ISSN:
0013-936X
Page Range / eLocation ID:
17386 to 17395
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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