Characterization of mercury binding to different molecular weight fractions of dissolved organic matter

Dissolved organic matter (DOM) can strongly complex with various contaminants. Therefore, DOM was deemed as an environmentally friendly substance for controlling the mobility, bioavailability, speciation, toxicity, and fate of metal contaminants in environment. In this study, composting-derived DOM was categorized into three fractions based on different molecular weights (MWs). Furthermore, parallel faction analysis (PARAFAC), two-dimensional correlation spectroscopy (2DCOS), and a complexation model were employed to reveal the contaminate-binding characterization. Two PARAFAC fluorescence components were identified in the MW < 1 kDa and the 1 kDa < MW < 5 kDa fractions, respectively. In the MW > 5 kDa fraction, three PARAFAC components were identified. Protein-like component C5 did not have the Hg²⁺-binding ability. Moreover, the results showed that not all the DOM ligands could bind with contaminants, but a high humification degree of composting DOM ligands could strongly bind Hg²⁺. In addition, DOM ligand with a low humification degree DOM ligands presented a higher Hg²⁺-binding speed. Subsequently, DOM from different MWs DOM could be applied separately to the different pollution forms. With these promising results, the different DOM ligand-Hg²⁺-binding properties were characterized to provide theoretical support for environmental pollution control.