Atmospheric Brown Carbon on the Tibetan Plateau: Regional Differences in Chemical Composition and Light Absorption Properties

Fine particulate matter (PM2.5) filter samples were collected from two high-altitude remote sites located in the southern (QOMS) and northern (WLG) regions of the Tibetan Plateau (TP) to explore the regional differences in brown carbon (BrC) properties. Chemical differences in BrC composition representative of these two areas were inferred from molecular-level analysis of the PM2.5 samples using high-performance liquid chromatography coupled with photodiode array and high-resolution mass spectrometry detectors. The results show that more polar BrC chromophores were abundant in QOMS samples, while contributions from polar and less polar chromophores were comparable in WLG samples. A higher mass absorption coefficient of BrC was observed at QOMS than at WLG. Strong BrC chromophores in QOMS samples were identified as oxygenated aromatics and nitrophenol compounds, while organosulfate compounds were found in the WLG sample. The results of this study indicate regional differences in BrC chromophores and provide insights into their sources and chemical processes, which should be considered for predictive understanding and modeling of the radiative forcing of aerosol in the TP area.

Automated summary

This study investigates the regional differences in brown carbon (BrC) properties in the southern and northern regions of the Tibetan Plateau through molecular-level analysis of fine particulate matter samples. The results highlight the chemical differences in BrC composition between the two regions, providing insights for predictive understanding of aerosol radiative forcing in the Tibetan Plateau area.