Figure 4

(Top): ¹H nuclear magnetic resonance (NMR) spectra (800 MHz, CD₃OD) of four DOM derived from “pristine” riverine catchments. (Bottom): Manual overlay difference ¹H NMR spectra (800 MHz, CD₃OD): effluent (red) minus pristine (green) DOM, with positive/negative amplitude referring to elevated abundance in the effluent/pristine DOM.