n‐Alkanes and PAHs in the Southeastern Tibetan Plateau: Characteristics and Correlations With Brown Carbon Light Absorption

Abstract

The samples of atmospheric total suspended particle (TSP) were obtained at the remote Tibetan site (named Lulang) from November 2015 to November 2016. The seasonal characteristics of n-alkanes, polycyclic aromatic hydrocarbons (PAHs) variations, and their correlations to brown carbon (BrC) light absorption in TSP were investigated. Elevated TSP n-alkanes and PAHs levels were observed in winter (2.8 and 10 times higher than in monsoon, respectively), largely due to the seasonal contributions of wintertime home heating and long-range transport. The total-PAHs was found to correlate strongly with the methanol-soluble BrC (MeS-BrC) light absorption coefficient (b abs) (R = 0.80) compared to water-soluble BrC (WS-BrC) (R = 0.70) at 365 nm. The BrC solar absorptions percentages to those of element carbon (EC) in the range of ultraviolet (300-400 nm) were high in both winter and premonsoon seasons, which can affect the vulnerable environmental radiative balance and atmospheric photochemistry. Until now, the study of TSP BrC chemical components (e.g., PAHs, the important chromophores of atmospheric BrC) and their radiative properties over remote TP is scarce. The sampling site (Lulang, in the ©2020. American Geophysical Union. All Rights Reserved.

Polycyclic Aromatic Carbon: A Key Fraction Determining the Light Absorption Properties of Methanol-Soluble Brown Carbon of Open Biomass Burning Aerosols

“…These observations suggest that PAC is an important fraction determining the light absorption properties of MS-BrC. Recent studies found strong correlations between PAHs and light absorptivity of MS-BrC in remote and urban regions (Tibetan Plateau and urban Xi’an, China). , The priority PAHs are useful tracers of MPAC, as found in the present study. Further studies are required to determine whether there are strong relations between MPAC and the light absorptivity of MS-BrC for ambient aerosols.…”

Collocated Measurements of Light‐Absorbing Organic Carbon in PM2.5: Observation Uncertainty and Organic Tracer‐Based Source Apportionment

“…So, the factor characterized by medium to high MW PAHs were linked with coal combustion. This factor had the second highest average contribution to Abs 365,m (18.5%, Table S6 in the Supporting Information S1), supporting that PAHs could act as one category of water-insoluble BrC chromophores (Huang et al, 2020;Zhu et al, 2020). These three fossil fuel-related primary sources were also identified in urban Denver, USA Xie, Piedrahita et al, 2013;Xie et al, 2014), and had more contributions to Abs 365,m than Abs 365,w (Table S6 in the Supporting Information S1).…”

Brown Carbon From Biomass Burning Reinforces the Himalayas and Tibetan Plateau Warming

“…focused on BC and BrC measured using a seven wavelengths Aethalometer (Zhu et al, 2017(Zhu et al, , 2021, or the correlations between special components (e.g., PAHs) and BrC in the southeastern HTP site (Zhu et al, 2018;Zhu, Li, et al, 2020;Zhu, Zhang et al, 2020). There are high uncertainties in the estimation of BrC radiative forcing and source apportionments due to inadequate observations and constrains in modeling, impeding accurate estimation of its warming effects in the HTP.…”