The heterogenous molecular characteristics of biomass-pyrogenic smoke dissolved organic matters (BPS-DOMs) binding with PAHs: novel insights from combined analysis of FT-ICR MS and fluorescence variation

Biomass-pyrogenic smoke dissolved organic matter (BPS-DOM) can co-deposit with polycyclic aromatic hydrocarbons (PAHs), thereby altering their environmental behavior and fate in surface environments. However, the heterogeneous molecular characteristics of BPS-DOM binding with PAHs remain unclear. This study systematically elucidates the binding characteristics of PAHs (phenanthrene and pyrene), with various molecular compositions in BPS-DOM, utilizing FT-ICR MS and fluorescence variation analysis. CHO compounds in BPS-DOM, characterized by high aromaticity and abundant C=O bonds, significantly enhance PAHs binding by promoting π-π electron donor-acceptor interactions. In contrast, CHON compounds with higher aliphaticity inhibit pyrene binding by competing for binding sites on BPS-DOM. Furthermore, the binding sequence of different fluorescent molecules follows the order of CHO→CHOS→CHON for phenanthrene and CHO→CHON→CHOS for pyrene. This was primarily due to the larger conjugated aromatic structures of CHO compounds, which provide stronger π-π interaction sites for PAHs binding. The difference in binding sequences between phenanthrene and pyrene is primarily attributed to phenanthrene's reliance on π-π electron donor-acceptor interactions induced by -S=O and -N=O, while pyrene binding depended on π-π interactions driven by larger conjugated aromatic structures. These results provide an important theoretical foundation for further understanding the molecular-level interactions between BPS-DOM and PAHs.