Chemical and Light-Absorption Properties of Water-Soluble Organic Aerosols in Northern California and Photooxidant Production by Brown Carbon Components
| Autor: | Wenqing Jiang, Lan Ma, Christopher Niedek, Cort Anastasio, Qi Zhang |
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| Rok vydání: | 2023 |
| Předmět: |
Climate Action
Atmospheric Science aqueous-phase reactions oxygenated organic aerosols hydroxyl radical triplet excited state of organic carbon Space and Planetary Science Geochemistry and Petrology biomass burning organic aerosols positive matrix factorization aerosol mass spectrometer singlet oxygen |
| Zdroj: | ACS earth & space chemistry, vol 7, iss 5 |
| Popis: | Atmospheric brown carbon (BrC) can impact the radiative balance of the earth and form photooxidants. However, the light absorption and photochemical properties of BrC from different sources remain poorly understood. To address this gap, dilute water extracts of particulate matter (PM) samples collected at Davis, CA over one year were analyzed using high resolution aerosol mass spectrometry (HR-AMS) and UV-vis spectroscopy. Positive matrix factorization (PMF) on combined AMS and UV-vis data resolved five water-soluble organic aerosol (WSOA) factors with distinct mass spectra and UV-vis spectra: a fresh and an aged water-soluble biomass burning OA (WSBBOAfresh and WSBBOAaged) and three oxygenated OA (WSOOAs). WSBBOAfresh is the most light-absorbing, with a mass absorption coefficient (MAC365nm) of 1.1 m2 g-1, while the WSOOAs are the least (MAC365nm = 0.01-0.1 m2 g-1). These results, together with the high abundance of WSBBOAs (∼52% of the WSOA mass), indicate that biomass burning activities such as residential wood burning and wildfires are an important source of BrC in northern California. The concentrations of aqueous-phase photooxidants, i.e., hydroxyl radical (·OH), singlet molecular oxygen (1O2*), and oxidizing triplet excited states of organic carbon (3C*), were also measured in the PM extracts during illumination. Oxidant production potentials (PPOX) of the five WSOA factors were explored. The photoexcitation of BrC chromophores from BB emissions and in OOAs is a significant source of 1O2* and 3C*. By applying our PPOX values to archived AMS data at dozens of sites, we found that oxygenated organic species play an important role in photooxidant formation in atmospheric waters. |
| Databáze: | OpenAIRE |
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