Size-resolved light-absorbing organic carbon and organic molecular markers in Nanjing, east China: Seasonal variations and sources

Feng, Wei; Shao, Zhijuan; Wang, Qin’geng; Xie, Mingjie

doi:10.1016/j.envpol.2023.122006

Cited by 4 publications

(1 citation statement)

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“…We attempted to assign the known total aerosol properties to BrC using the above parameters, in conjunction with an optical closure study. First, aerosol light absorption was assumed to be solely attributed to absorptive carbonaceous aerosol (BC and BrC) because the dust contribution was much less in Nanjing during this period (Feng et al, 2023). Second, in addition to BrC and BC, the remaining scattering-dominant aerosol (e.g., mainly sulfate and nitrate at our observation site) possess similar optical properties and will therefore be treated together as a non-absorbing type.…”

Section: Aerosol Optical Propertiesmentioning

confidence: 99%

An observation-constrained estimation of brown carbon aerosol direct radiative effects

Cheng,

Liu,

Wang

et al. 2023

Preprint

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Abstract. Brown carbon (BrC) is an organic carbon component with noticeable absorption in the ultraviolet and short visible wavelengths, which influences the global radiative balance. However, the assessment of BrC radiative effects remains a challenging task because of the scarcity of direct BrC observations and uncertainties in their chemical and optical properties. This study proposes a convenient method for estimating BrC radiative effects based on concise observational data. The light-absorbing properties of BrC obtained from aethalometer measurements and an optical separation method were combined with the simulated BrC optical properties to determine their mass concentrations. The aerosol optical depth (AOD) and mass concentration of PM10 were used to constrain the total and other aerosol contents, and the optical properties and concentrations were estimated using an optical closure study. Such a state-of-the-art combination of measurements and numerical models provides the primary variables for radiative transfer simulations to estimate the BrC radiative effects. We use observations over four months (from July 1 to November 18, 2021) in Nanjing (a megacity in East China) as an example. During the observational period, BrC absorption constitutes 8.7–34.1 % of the total aerosol absorption at 370 nm. In the atmosphere, BrC plays a warming role with its average instantaneous radiative forcing (RF) and standard deviation of 6.4 ± 3.4 W m-2, 29.2 % that of black carbon (BC). At the surface, the BrC-induced actinic flux (AF) attenuation was comparable to that caused by BC, accounting for over 40 % of BC effects in the UV range and almost 20 % in the visible range. Furthermore, the photosynthetically active radiation (PAR) caused by BrC is about 34.7 ± 9.7 % that caused by BC. These findings provide valuable insights into the understanding of BrC radiative effects and indicate the importance and necessity of better observation and modeling of BrC properties.

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Section: Aerosol Optical Propertiesmentioning

confidence: 99%