Elucidation of Dissolved Organic Matter Interactions with Model Contaminants of Emerging Concern

Abstract

This study examined the interaction of model cationic, neutral and anionic endocrine disrupting compounds, pharmaceuticals and personal care products (EDC/PPCPs) with bulk and fractionated freshwater and waste water dissolved organic matter (DOM). The chemical composition of the freshwater DOM (Suwannee River, GA, SROM) proved to be rich in plant-derived hydrophobic aromatics, while the wastewater DOM (WWOM) contained a greater proportion of microbial biomolecular products, presumably resulting mainly from human waste. Studies focused on the fluorescence quenching of excitation-emission matrices (EEMs) of WWOM indicated that interaction with bis-phenol A (BPA), carbamazepine (CBZ), and ibuprofen (IBU) occurred preferentially with soluble protein-like and fulvic acid-like constituents. However, upon introduction to bulk SROM, BPA and CBZ were observed to quench humic acid-like regions of the EEMs, while negatively charged ibuprofen preferentially quenched the protein-like and fulvic acid components irrespective of DOM source and/or fraction. Despite this evidence of EDC/PPCP interactions with both DOM types, the strength of bonds formed was generally not sufficient to preclude full recovery and quantification of all three contaminants by liquid chromatography tandem mass spectrometry (LC-MSMS). An important exception, however, was for the hydrophilic acid fraction (HiA) of both DOM types, whose apparent bonding to cationic CBZ and anionic IBU significantly diminished LC-MSMS recovery. Thus, water sources rich in HiA character might produce a concentration underestimation of ionized EDC/PPCPs even with the use of sophisticated instruments such as LC-MSMS.The results of this research are consistent with the evolving ""supramolecular"" theory of natural organic matter, which postulates that organic matter itself is comprised of fragments of partially degraded biomolecules that are aggregated into ""supramolecular"" structures of apparent higher molar mass via relatively weak electrostatic, hydrophobic, and van der Waals interaction. Our findings suggest that EDC/PPCP contaminants, which comprise many of the same functional groups as waste water and freshwater DOM, may be incorporated into such DOM supramolecular structures, likely via the same types of intermolecular bonding, when they are present in natural waters under environmentally-relevant conditions.