Molecular Signatures and Sources of Fluorescent Components in Atmospheric Organic Matter in South China

Abstract

Excitation emission matrix (EEM) spectra coupled with parallel factor analysis (PARAFAC) have been used to characterize brown carbon (BrC). The molecular composition of PARAFAC components is not well understood in atmospheric science, which has impeded the accurate interpretation of the chemical changes and source apportionment of BrC using EEM-PARAFAC methods. We assigned numerous formulas identified by Fourier transform ion cyclotron resonance mass spectrometry (both negative and positive electrospray ionization modes) to each PARAFAC-derived fluorescent component (FC) in atmospheric PM 2.5 samples. Obvious differences in molecular characteristics and sources were observed between atmospheric and hydrospheric FCs, indicating the need for caution in explaining the composition and source of atmospheric FC based on hydrospheric FC. Previously assigned protein-like components (C4) and less-oxidized humic-like FC (C1) were associated mainly with highly saturated photoresistant species and less-polar anthropogenic emissions. Highly oxidized humic-like FCs were associated with aromatic and highly unsaturated/phenolic compounds (high oxygen), which were potentially influenced by biomass burning and related secondary processes. The seasonal variations in light absorption were similar to those of fluorescence intensity and the degree of humification, which were influenced by highly unsaturated/phenolic compounds (high oxygen). These linkages indicated the potential of EEM-PARAFAC for investigating the changes of light absorption, molecular composition, and source of BrC.

Aqueous‐Phase Secondary Processes and Meteorological Change Promote the Brown Carbon Formation and Transformation During Haze Events

“…It is worth noting that the low-oxidized P5 also showed a high contribution in the afternoon compared to other times (Figure 3a). As suggested in our previous study (Jiang et al, 2022),the molecular composition of P5 were mainly composed of low-oxidized and unsaturated nitrogen-containing molecules, which were mainly from primary emissions (e.g., vehicles emission) and aqueous-phase SOA reactions of highly saturated compounds. However, multiphase photolysis and hydrolysis may also lead to the decomposition of these compounds (González-Sánchez et al, 2023).…”

Ultrasensitive and Green Bubbling Extraction Strategies: An Extensible Solvent-Free Re-Enrichment Approach for Ultratrace Pollutants in Aqueous Samples

“…An efficient verification of fluorescent components (FCs) with varying excitation and emission wavelengths, typically classified as dissolved organic matter (DOM) in water, was achieved using the proposed BE method . Organic substances are easily observed in the excitation emission matrix (EEM) spectra, as shown in Figure S14.…”

Supplementary material to "Molecular signatures and formation mechanisms of particulate matter (PM) water-soluble chromophores from Karachi (Pakistan) over South Asia"

“…Therefore, the name and the possible fate of atmospheric fluorescent components were previously referred to as that aquatic DOM. However, multiple studies have shown that the atmospheric chromophores maybe not same as the similar character in other environments (Wu et al, 2021;Jiang et al, 2022), yet direct evidence is lacking. In this study, we examined molecular-level differences between the fluorescent components in the atmosphere and aquatic environment.…”