Mechanisms of interaction between polycyclic aromatic hydrocarbons and dissolved organic matters

Binding of phenanthrene and fluorene to a number of humic and fulvic substances isolated from various sources as well as a commercially available humic acid, was investigated using a fluorescence quenching approach. The observed fluorescence quenching indicated by linear Stern-Volmer plots and high bimolecular quenching rate constant was induced by a static interaction process. A significant correlation of binding constants with aromaticity and polarity of dissolved organic matter (DOM) was observed. It is hypothesized that the binding of polycyclic aromatic hydrocarbons (PAHs) by DOM is due to both π-π interactions and hydrophobic interactions. In addition, energy transfer from PAHs to DOM occurs because of the significant overlap between the absorbance spectra of DOM and emission spectra of PAHs. Thus, dipole-dipole interaction may also play an important role in the binding mechanism between PAHs and DOM.