In order to characterize the interaction of the pollutants with SOM in more detail, interaction energies between the pollutant molecules and HS functional groups were calculated and plotted for the groups with the highest contributions to the interaction (see Figure ). The negatively charged carboxylate groups exhibit the strongest interaction with SAA in each system. Furthermore, ketone, hydroxyl, phenol, acid anhydride, and aromatic functional groups play an important role. Overall, the preference for these functional groups can be explained by the hydrogen bonding ability of SAA and the hydrophilic character of the sulfonamide group. Conversely, the aromatic nature of SAA is reflected in the attraction to aromatic beads of the HSs, which is the most hydrophobic functional group in Figure that appears for SAA. The overall order for these groups is mostly determined by their abundance within each SOM system. : Time-averaged interaction energies between the pollutant molecules and the beads from different functional groups (x-axis), additionally averaged over the 20 trajectories for each pollutant and each SOM type. Proportions of the sulfonamide group (blue), aromatic ring (gray), and amino group (orange) are depicted for SAA. Green represents the HCB interaction energies. If available for a group, "T" or "S" stands for the Martini size of the bead, namely tiny or small, respectively. In the case of aromatic beads, a distinction is also made between those representing electron-rich regions of a ring, which are denoted by the letter "e".