Compositions and structures of particulate and colloidal organic matter in aquatic environment by advanced analytical techniques

Colloidal and particulate organic matter (COM and POM) is important in the global carbon cycle, and knowledge of their compositions and structures can be extremely critical to understanding their roles in biogeochemical cycles. We explored the chemical structures of COM and POM samples from typical reservoirs and lake with different trophic states in the Pearl River Basin, China. X-ray photoelectron spectroscopy (XPS), quantitative solid-state ¹³C NMR were employed to characterize the chemical structures of these COM and POM samples. Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) coupled with electrospray ionization (ESI) is used to solve the molecular composition of COM samples. POM contained markedly higher alkyl C and slightly higher COO/NC=O, but lower O-alkyl C relative to COM. In addition, Van Krevelen diagrams revealed that polyphenols and highly unsaturated organic acids were the majority (∼80%) of the compounds in COM, of which, highly unsaturated compounds with high oxygen molecules were 40.5-44.1%. Moreover, compounds containing only C, H, and O (CHO) observed amounts of glycosides. Some of the S-1-containing compounds with high signal magnitudes were tentatively assigned to alkylbenzene sulfonates and their biodegradation and biotransformation derivatives, indicating anthropogenic input in the region.