Characterisation of dissolved organic matter using Fourier-transform ion cyclotron resonance mass spectrometry:...

This study investigated the chemodiversity and unique signatures for dissolved organic matter (DOM) from different types of water using high-resolution Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Eight freshwater hydrophobic DOM (HPO) share 10-17% formulas that were mainly lignin-like compounds. Unique signatures were synthesized: unique to the high-humic HPO (Suwannee River and Blavet River) were condensed aromatic and some aliphatic compounds with H/C > 1.5 and O/C < 0.2, which is considered as decisive of these black river water. Medium-humic isolates (Loire River, Seine River, South Platte River, and Ribou Dam) did not show explicit unique signatures. Nonetheless, enhanced chemodiversity was observed for medium-humic isolates extracted from a variety of indigenous environmental conditions. As an example, South Platte River HPO isolated in winter showed signatures similar to low-humic HPO (Colorado River), i.e., predominantly aliphatic CHO (H/C > 1.0). Effluent HPO was mainly aliphatic molecules with 0.2 < O/C < 0.5 and enriched in S-bearing molecules, and molecules unique to glacial DOM (Pony Lake) incorporated N-bearing compounds that were inferiorly oxidized and were considered as microbial-derived. The weight-averaged double bond equivalent and elemental ratio derived from FTICR-MS were compared with SUVA₂₅₄ and the results from elemental analysis. This acts as the first study to synthesize unique chemical compositions that distinguish different types of DOM and determine certain reactivity. It is also a significant reference for future studies using similar types of DOM.